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Sample records for epr spin labeling

  1. EPR and NMR spectroscopy on spin-labeled proteins

    NARCIS (Netherlands)

    Finiguerra, Michelina Giuseppina

    2011-01-01

    Spin labeling and electron paramagnetic resonance (EPR) have been employed to study structure and dynamics of proteins. The surface polarity of four single cysteine mutants of the Zn-azurin in frozen solution were studied using 275 GHz EPR (J-band), with the advantage compared to 9 GHz (X-band) and

  2. New Developments in Spin Labels for Pulsed Dipolar EPR

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    Alistair J. Fielding

    2014-10-01

    Full Text Available Spin labelling is a chemical technique that enables the integration of a molecule containing an unpaired electron into another framework for study. Given the need to understand the structure, dynamics, and conformational changes of biomacromolecules, spin labelling provides a relatively non-intrusive technique and has certain advantages over X-ray crystallography; which requires high quality crystals. The technique relies on the design of binding probes that target a functional group, for example, the thiol group of a cysteine residue within a protein. The unpaired electron is typically supplied through a nitroxide radical and sterically shielded to preserve stability. Pulsed electron paramagnetic resonance (EPR techniques allow small magnetic couplings to be measured (e.g., <50 MHz providing information on single label probes or the dipolar coupling between multiple labels. In particular, distances between spin labels pairs can be derived which has led to many protein/enzymes and nucleotides being studied. Here, we summarise recent examples of spin labels used for pulse EPR that serve to illustrate the contribution of chemistry to advancing discoveries in this field.

  3. Nuclear spin-lattice relaxation in nitroxide spin-label EPR.

    Science.gov (United States)

    Marsh, Derek

    2016-11-01

    Nuclear relaxation is a sensitive monitor of rotational dynamics in spin-label EPR. It also contributes competing saturation transfer pathways in T 1 -exchange spectroscopy, and the determination of paramagnetic relaxation enhancement in site-directed spin labelling. A survey shows that the definition of nitrogen nuclear relaxation rate W n commonly used in the CW-EPR literature for 14 N-nitroxyl spin labels is inconsistent with that currently adopted in time-resolved EPR measurements of saturation recovery. Redefinition of the normalised 14 N spin-lattice relaxation rate, b=W n /(2W e ), preserves the expressions used for CW-EPR, whilst rendering them consistent with expressions for saturation recovery rates in pulsed EPR. Furthermore, values routinely quoted for nuclear relaxation times that are deduced from EPR spectral diffusion rates in 14 N-nitroxyl spin labels do not accord with conventional analysis of spin-lattice relaxation in this three-level system. Expressions for CW-saturation EPR with the revised definitions are summarised. Data on nitrogen nuclear spin-lattice relaxation times are compiled according to the three-level scheme for 14 N-relaxation: T 1 n =1/W n . Results are compared and contrasted with those for the two-level 15 N-nitroxide system. Copyright © 2016 Elsevier Inc. All rights reserved.

  4. Nuclear spin-lattice relaxation in nitroxide spin-label EPR

    DEFF Research Database (Denmark)

    Marsh, Derek

    2016-01-01

    that the definition of nitrogen nuclear relaxation rate Wn commonly used in the CW-EPR literature for 14N-nitroxyl spin labels is inconsistent with that currently adopted in time-resolved EPR measurements of saturation recovery. Redefinition of the normalised 14N spin-lattice relaxation rate, b = Wn/(2We), preserves...... of spin-lattice relaxation in this three-level system. Expressions for CW-saturation EPR with the revised definitions are summarised. Data on nitrogen nuclear spin-lattice relaxation times are compiled according to the three-level scheme for 14N-relaxation: T1 n = 1/Wn. Results are compared and contrasted...

  5. Peptide-membrane Interactions by Spin-labeling EPR

    Science.gov (United States)

    Smirnova, Tatyana I.; Smirnov, Alex I.

    2016-01-01

    Site-directed spin labeling (SDSL) in combination with Electron Paramagnetic Resonance (EPR) spectroscopy is a well-established method that has recently grown in popularity as an experimental technique, with multiple applications in protein and peptide science. The growth is driven by development of labeling strategies, as well as by considerable technical advances in the field, that are paralleled by an increased availability of EPR instrumentation. While the method requires an introduction of a paramagnetic probe at a well-defined position in a peptide sequence, it has been shown to be minimally destructive to the peptide structure and energetics of the peptide-membrane interactions. In this chapter, we describe basic approaches for using SDSL EPR spectroscopy to study interactions between small peptides and biological membranes or membrane mimetic systems. We focus on experimental approaches to quantify peptide-membrane binding, topology of bound peptides, and characterize peptide aggregation. Sample preparation protocols including spin-labeling methods and preparation of membrane mimetic systems are also described. PMID:26477253

  6. RosettaEPR: rotamer library for spin label structure and dynamics.

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    Nathan S Alexander

    Full Text Available An increasingly used parameter in structural biology is the measurement of distances between spin labels bound to a protein. One limitation to these measurements is the unknown position of the spin label relative to the protein backbone. To overcome this drawback, we introduce a rotamer library of the methanethiosulfonate spin label (MTSSL into the protein modeling program Rosetta. Spin label rotamers were derived from conformations observed in crystal structures of spin labeled T4 lysozyme and previously published molecular dynamics simulations. Rosetta's ability to accurately recover spin label conformations and EPR measured distance distributions was evaluated against 19 experimentally determined MTSSL labeled structures of T4 lysozyme and the membrane protein LeuT and 73 distance distributions from T4 lysozyme and the membrane protein MsbA. For a site in the core of T4 lysozyme, the correct spin label conformation (Χ1 and Χ2 is recovered in 99.8% of trials. In surface positions 53% of the trajectories agree with crystallized conformations in Χ1 and Χ2. This level of recovery is on par with Rosetta performance for the 20 natural amino acids. In addition, Rosetta predicts the distance between two spin labels with a mean error of 4.4 Å. The width of the experimental distance distribution, which reflects the flexibility of the two spin labels, is predicted with a mean error of 1.3 Å. RosettaEPR makes full-atom spin label modeling available to a wide scientific community in conjunction with the powerful suite of modeling methods within Rosetta.

  7. SimLabel: a graphical user interface to simulate continuous wave EPR spectra from site-directed spin labeling experiments.

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    Etienne, E; Le Breton, N; Martinho, M; Mileo, E; Belle, V

    2017-08-01

    Site-directed spin labeling (SDSL) combined with continuous wave electron paramagnetic resonance (cw EPR) spectroscopy is a powerful technique to reveal, at the residue level, structural transitions in proteins. SDSL-EPR is based on the selective grafting of a paramagnetic label on the protein under study, followed by cw EPR analysis. To extract valuable quantitative information from SDSL-EPR spectra and thus give reliable interpretation on biological system dynamics, numerical simulations of the spectra are required. Such spectral simulations can be carried out by coding in MATLAB using functions from the EasySpin toolbox. For non-expert users of MATLAB, this could be a complex task or even impede the use of such simulation tool. We developed a graphical user interface called SimLabel dedicated to run cw EPR spectra simulations particularly coming from SDSL-EPR experiments. Simlabel provides an intuitive way to visualize, simulate, and fit such cw EPR spectra. An example of SDSL-EPR spectra simulation concerning the study of an intrinsically disordered region undergoing a local induced folding is described and discussed. We believe that this new tool will help the users to rapidly obtain reliable simulated spectra and hence facilitate the interpretation of their results. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

  8. EPR spin probe and spin label studies of some low molecular and polymer micelles

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    Wasserman, A. M.; Kasaikin, V. A.; Timofeev, V. P.

    1998-12-01

    The rotational mobility of spin probes of different shape and size in low molecular and polymer micelles has been studied. Several probes having nitroxide fragment localized either in the vicinity of micelle interface or in the hydrocarbon core have been used. Upon increasing the number of carbon atoms in hydrocarbon chain of detergent from 7 to 13 (sodium alkyl sulfate micelles) or from 12 to 16 (alkyltrimethylammonium bromide micelles) the rotational mobility of spin probes is decreased by the factor 1.5-2.0. The spin probe rotational mobility in polymer micelles (the complexes of alkyltrimethylammonium bromides and polymethacrylic or polyacrylic acids) is less than mobility in free micelles of the same surfactants. The study of EPR-spectra of spin labeled polymethacrylic acid (PMA) indicated that formation of water soluble complexes of polymer and alkyltrimethylammonium bromides in alkaline solutions (pH 9) does not affect the polymer segmental mobility. On the other hand, the polymer complexes formation in slightly acidic water solution (pH 6) breaks down the compact PMA conformation, thus increasing the polymer segmental mobility. Possible structures of polymer micelles are discussed.

  9. Ion Channel Conformation and Oligomerization Assessment by Site-Directed Spin Labeling and Pulsed-EPR.

    Science.gov (United States)

    Pliotas, Christos

    2017-01-01

    Mechanosensitive (MS) ion channels are multimeric integral membrane proteins that respond to increased lipid bilayer tension by opening their nonselective pores to release solutes and relieve increased cytoplasmic pressure. These systems undergo major conformational changes during gating and the elucidation of their mechanism requires a deep understanding of the interplay between lipids and proteins. Lipids are responsible for transmitting lateral tension to MS channels and therefore play a key role in obtaining a molecular-detail model for mechanosensation. Site-directed spin labeling combined with electron paramagnetic resonance (EPR) spectroscopy is a powerful spectroscopic tool in the study of proteins. The main bottleneck for its use relates to challenges associated with successful isolation of the protein of interest, introduction of paramagnetic labels on desired sites, and access to specialized instrumentation and expertise. The design of sophisticated experiments, which combine a variety of existing EPR methodologies to address a diversity of specific questions, require knowledge of the limitations and strengths, characteristic of each particular EPR method. This chapter is using the MS ion channels as paradigms and focuses on the application of different EPR techniques to ion channels, in order to investigate oligomerization, conformation, and the effect of lipids on their regulation. The methodology we followed, from the initial strategic selection of mutants and sample preparation, including protein purification, spin labeling, reconstitution into lipid mimics to the complete set-up of the pulsed-EPR experiments, is described in detail. © 2017 Elsevier Inc. All rights reserved.

  10. Electron paramagnetic resonance (EPR spectral components of spin-labeled lipids in saturated phospholipid bilayers: effect of cholesterol

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    Heverton Silva Camargos

    2013-01-01

    Full Text Available Electron paramagnetic resonance (EPR spectroscopy was used to study the main structural accommodations of spin labels in bilayers of saturated phosphatidylcholines with acyl chain lengths ranging from 16 to 22 carbon atoms. EPR spectra allowed the identification of two distinct spectral components in thermodynamic equilibrium at temperatures below and above the main phase transition. An accurate analysis of EPR spectra, using two fitting programs, enabled determination of the thermodynamic profile for these major probe accommodations. Focusing the analysis on two-component EPR spectra of a spin-labeled lipid, the influence of 40 mol % cholesterol in DPPC was studied.

  11. Characterizing Active Pharmaceutical Ingredient Binding to Human Serum Albumin by Spin-Labeling and EPR Spectroscopy.

    Science.gov (United States)

    Hauenschild, Till; Reichenwallner, Jörg; Enkelmann, Volker; Hinderberger, Dariush

    2016-08-26

    Drug binding to human serum albumin (HSA) has been characterized by a spin-labeling and continuous-wave (CW) EPR spectroscopic approach. Specifically, the contribution of functional groups (FGs) in a compound on its albumin-binding capabilities is quantitatively described. Molecules from different drug classes are labeled with EPR-active nitroxide radicals (spin-labeled pharmaceuticals (SLPs)) and in a screening approach CW-EPR spectroscopy is used to investigate HSA binding under physiological conditions and at varying ratios of SLP to protein. Spectral simulations of the CW-EPR spectra allow extraction of association constants (KA ) and the maximum number (n) of binding sites per protein. By comparison of data from 23 SLPs, the mechanisms of drug-protein association and the impact of chemical modifications at individual positions on drug uptake can be rationalized. Furthermore, new drug modifications with predictable protein binding tendency may be envisaged. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Saturation recovery EPR spin-labeling method for quantification of lipids in biological membrane domains.

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    Mainali, Laxman; Camenisch, Theodore G; Hyde, James S; Subczynski, Witold K

    2017-12-01

    The presence of integral membrane proteins induces the formation of distinct domains in the lipid bilayer portion of biological membranes. Qualitative application of both continuous wave (CW) and saturation recovery (SR) electron paramagnetic resonance (EPR) spin-labeling methods allowed discrimination of the bulk, boundary, and trapped lipid domains. A recently developed method, which is based on the CW EPR spectra of phospholipid (PL) and cholesterol (Chol) analog spin labels, allows evaluation of the relative amount of PLs (% of total PLs) in the boundary plus trapped lipid domain and the relative amount of Chol (% of total Chol) in the trapped lipid domain [ M. Raguz, L. Mainali, W. J. O'Brien, and W. K. Subczynski (2015), Exp. Eye Res., 140:179-186 ]. Here, a new method is presented that, based on SR EPR spin-labeling, allows quantitative evaluation of the relative amounts of PLs and Chol in the trapped lipid domain of intact membranes. This new method complements the existing one, allowing acquisition of more detailed information about the distribution of lipids between domains in intact membranes. The methodological transition of the SR EPR spin-labeling approach from qualitative to quantitative is demonstrated. The abilities of this method are illustrated for intact cortical and nuclear fiber cell plasma membranes from porcine eye lenses. Statistical analysis (Student's t -test) of the data allowed determination of the separations of mean values above which differences can be treated as statistically significant ( P ≤ 0.05) and can be attributed to sources other than preparation/technique.

  13. In vivo and ex vivo EPR detection of spin-labelled ovalbumin in mice.

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    Abramović, Zrinka; Brgles, Marija; Habjanec, Lidija; Tomasić, Jelka; Sentjurc, Marjeta; Frkanec, Ruza

    2010-10-01

    In this study, spin-labelled ovalbumin (SL-OVA), free or entrapped in liposomes, was administered to mice subcutaneously (s.c.) or intravenously (i.v.) with the aim to determine the conditions for pharmacokinetic studies of spin-labelled proteins by EPR and to measure the time course of SL-OVA distribution in vivo in live mice and ex vivo in isolated organs. Upon s.c. administration, the decay of the EPR signal was followed for 60min at the site of application using an L-band EPR spectrometer. Within this time period, the signal of free SL-OVA was diminished by about 70%. It was estimated with the help of the oxidizing agent K(3)[(FeCN)(6)] that approximately 30% was a consequence of the spin label reduction to EPR non-visible hydroxylamine and about 40% was due to the SL-OVA elimination from the site of measurement. For liposome encapsulated SL-OVA, the intensity diminished only by approx. 40% in the same period, indicating that liposomes successfully protect the protein from reduction. EPR signal could not be detected directly over live mouse organs within 60min after s.c. application of SL-OVA. With the available L-band EPR spectrometer, the measurements at the site of s.c. application are possible if the amount of SL-OVA applied to a mouse is more than 3mg. For the pharmacokinetic studies of the protein distribution in organs after s.c. or i.v. injection the concentration of the spin-labelled protein should be more than 0.5mmol/kg. After i.v. administration, only ex vivo measurements were possible using an X-band EPR spectrometer, since the total amount of SL-OVA was not sufficient for in vivo detection and also because of rapid reduction of nitroxide. After 2min, the protein was preferentially distributed to liver and, to a smaller extent, to spleen.

  14. Protein rotational dynamics investigated with a dual EPR/optical molecular probe. Spin-labeled eosin.

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    Cobb, C E; Hustedt, E J; Beechem, J M; Beth, A H

    1993-01-01

    An acyl spin-label derivative of 5-aminoeosin (5-SLE) was chemically synthesized and employed in studies of rotational dynamics of the free probe and of the probe when bound noncovalently to bovine serum albumin using the spectroscopic techniques of fluorescence anisotropy decay and electron paramagnetic resonance (EPR) and their long-lifetime counterparts phosphorescence anisotropy decay and saturation transfer EPR. Previous work (Beth, A. H., Cobb, C. E., and J. M. Beechem, 1992. Synthesis and characterization of a combined fluorescence, phosphorescence, and electron paramagnetic resonance probe. Society of Photo-Optical Instrumentation Engineers. Time-Resolved Laser Spectroscopy III. 504-512) has shown that the spin-label moiety only slightly altered the fluorescence and phosphorescence lifetimes and quantum yields of 5-SLE when compared with 5-SLE whose nitroxide had been reduced with ascorbate and with the diamagnetic homolog 5-acetyleosin. In the present work, we have utilized time-resolved fluorescence anisotropy decay and linear EPR spectroscopies to observe and quantitate the psec motions of 5-SLE in solution and the nsec motions of the 5-SLE-bovine serum albumin complex. Time-resolved phosphorescence anisotropy decay and saturation transfer EPR studies have been carried out to observe and quantitate the microseconds motions of the 5-SLE-albumin complex in glycerol/buffer solutions of varying viscosity. These latter studies have enabled a rigorous comparison of rotational correlation times obtained from these complementary techniques to be made with a single probe. The studies described demonstrate that it is possible to employ a single molecular probe to carry out the full range of fluorescence, phosphorescence, EPR, and saturation transfer EPR studies. It is anticipated that "dual" molecular probes of this general type will significantly enhance capabilities for extracting dynamics and structural information from macromolecules and their functional

  15. Site-Directed Spin-Labeling of Nucleic Acids by Click Chemistry. Detection of Abasic Sites in Duplex DNA by EPR Spectroscopy

    DEFF Research Database (Denmark)

    Sigurdsson, Snorri; Vogel, Stefan; Shelke, Sandip

    2010-01-01

    and the nitroxide spin label. The spin label was used to detect, for the first time, abasic sites in duplex DNA by X-band CW-EPR spectroscopy and give information about other structural deformations as well as local conformational changes in DNA. For example, reduced mobility of the spin label in a mismatched pair...... label out of the duplex and toward the solution. Thus, reposition of the spin label, when acting as a mercury(II)-controlled mechanical lever, can be readily detected by EPR spectroscopy. The ease of incorporation and properties of the new spin label make it attractive for EPR studies of nucleic acids...

  16. All-atom molecular dynamics simulations of spin labelled double and single-strand DNA for EPR studies.

    Science.gov (United States)

    Prior, C; Danilāne, L; Oganesyan, V S

    2018-05-16

    We report the first application of fully atomistic molecular dynamics (MD) simulations to the prediction of electron paramagnetic resonance (EPR) spectra of spin labelled DNA. Models for two structurally different DNA spin probes with either the rigid or flexible position of the nitroxide group in the base pair, employed in experimental studies previously, have been developed. By the application of the combined MD-EPR simulation methodology we aimed at the following. Firstly, to provide a test bed against a sensitive spectroscopic technique for the recently developed improved version of the parmbsc1 force field for MD modelling of DNA. The predicted EPR spectra show good agreement with the experimental ones available from the literature, thus confirming the accuracy of the currently employed DNA force fields. Secondly, to provide a quantitative interpretation of the motional contributions into the dynamics of spin probes in both duplex and single-strand DNA fragments and to analyse their perturbing effects on the local DNA structure. Finally, a combination of MD and EPR allowed us to test the validity of the application of the Model-Free (M-F) approach coupled with the partial averaging of magnetic tensors to the simulation of EPR spectra of DNA systems by comparing the resultant EPR spectra with those simulated directly from MD trajectories. The advantage of the M-F based EPR simulation approach over the direct propagation techniques is that it requires motional and order parameters that can be calculated from shorter MD trajectories. The reported MD-EPR methodology is transferable to the prediction and interpretation of EPR spectra of higher order DNA structures with novel types of spin labels.

  17. Toward the fourth dimension of membrane protein structure: insight into dynamics from spin-labeling EPR spectroscopy.

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    McHaourab, Hassane S; Steed, P Ryan; Kazmier, Kelli

    2011-11-09

    Trapping membrane proteins in the confines of a crystal lattice obscures dynamic modes essential for interconversion between multiple conformations in the functional cycle. Moreover, lattice forces could conspire with detergent solubilization to stabilize a minor conformer in an ensemble thus confounding mechanistic interpretation. Spin labeling in conjunction with electron paramagnetic resonance (EPR) spectroscopy offers an exquisite window into membrane protein dynamics in the native-like environment of a lipid bilayer. Systematic application of spin labeling and EPR identifies sequence-specific secondary structures, defines their topology and their packing in the tertiary fold. Long range distance measurements (60 Å-80 Å) between pairs of spin labels enable quantitative analysis of equilibrium dynamics and triggered conformational changes. This review highlights the contribution of spin labeling to bridging structure and mechanism. Efforts to develop methods for determining structures from EPR restraints and to increase sensitivity and throughput promise to expand spin labeling applications in membrane protein structural biology. Copyright © 2011 Elsevier Ltd. All rights reserved.

  18. Characterization of Bifunctional Spin Labels for Investigating the Structural and Dynamic Properties of Membrane Proteins Using EPR Spectroscopy.

    Science.gov (United States)

    Sahu, Indra D; Craig, Andrew F; Dunagum, Megan M; McCarrick, Robert M; Lorigan, Gary A

    2017-10-05

    Site-directed spin labeling (SDSL) coupled with electron paramagnetic resonance (EPR) spectroscopy is a very powerful technique to study structural and dynamic properties of membrane proteins. The most widely used spin label is methanthiosulfonate (MTSL). However, the flexibility of this spin label introduces greater uncertainties in EPR measurements obtained for determining structures, side-chain dynamics, and backbone motion of membrane protein systems. Recently, a newer bifunctional spin label (BSL), 3,4-bis(methanethiosulfonylmethyl)-2,2,5,5-tetramethyl-2,5-dihydro-1H-pyrrol-1-yloxy, has been introduced to overcome the dynamic limitations associated with the MTSL spin label and has been invaluable in determining protein backbone dynamics and inter-residue distances due to its restricted internal motion and fewer size restrictions. While BSL has been successful in providing more accurate information about the structure and dynamics of several proteins, a detailed characterization of the spin label is still lacking. In this study, we characterized BSLs by performing CW-EPR spectral line shape analysis as a function of temperature on spin-labeled sites inside and outside of the membrane for the integral membrane protein KCNE1 in POPC/POPG lipid bilayers and POPC/POPG lipodisq nanoparticles. The experimental data revealed a powder pattern spectral line shape for all of the KCNE1-BSL samples at 296 K, suggesting the motion of BSLs approaches the rigid limit regime for these series of samples. BSLs were further utilized to report for the first time the distance measurement between two BSLs attached on an integral membrane protein KCNE1 in POPC/POPG lipid bilayers at room temperature using dipolar line broadening CW-EPR spectroscopy. The CW dipolar line broadening EPR data revealed a 15 ± 2 Å distance between doubly attached BSLs on KCNE1 (53/57-63/67) which is consistent with molecular dynamics modeling and the solution NMR structure of KCNE1 which yielded a

  19. Elucidating the design principles of photosynthetic electron-transfer proteins by site-directed spin labeling EPR spectroscopy.

    Science.gov (United States)

    Ishara Silva, K; Jagannathan, Bharat; Golbeck, John H; Lakshmi, K V

    2016-05-01

    Site-directed spin labeling electron paramagnetic resonance (SDSL EPR) spectroscopy is a powerful tool to determine solvent accessibility, side-chain dynamics, and inter-spin distances at specific sites in biological macromolecules. This information provides important insights into the structure and dynamics of both natural and designed proteins and protein complexes. Here, we discuss the application of SDSL EPR spectroscopy in probing the charge-transfer cofactors in photosynthetic reaction centers (RC) such as photosystem I (PSI) and the bacterial reaction center (bRC). Photosynthetic RCs are large multi-subunit proteins (molecular weight≥300 kDa) that perform light-driven charge transfer reactions in photosynthesis. These reactions are carried out by cofactors that are paramagnetic in one of their oxidation states. This renders the RCs unsuitable for conventional nuclear magnetic resonance spectroscopy investigations. However, the presence of native paramagnetic centers and the ability to covalently attach site-directed spin labels in RCs makes them ideally suited for the application of SDSL EPR spectroscopy. The paramagnetic centers serve as probes of conformational changes, dynamics of subunit assembly, and the relative motion of cofactors and peptide subunits. In this review, we describe novel applications of SDSL EPR spectroscopy for elucidating the effects of local structure and dynamics on the electron-transfer cofactors of photosynthetic RCs. Because SDSL EPR Spectroscopy is uniquely suited to provide dynamic information on protein motion, it is a particularly useful method in the engineering and analysis of designed electron transfer proteins and protein networks. This article is part of a Special Issue entitled Biodesign for Bioenergetics--the design and engineering of electronic transfer cofactors, proteins and protein networks, edited by Ronald L. Koder and J.L. Ross Anderson. Copyright © 2016. Published by Elsevier B.V.

  20. Combining EPR spectroscopy and X-ray crystallography to elucidate the structure and dynamics of conformationally constrained spin labels in T4 lysozyme single crystals.

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    Consentius, Philipp; Gohlke, Ulrich; Loll, Bernhard; Alings, Claudia; Heinemann, Udo; Wahl, Markus C; Risse, Thomas

    2017-08-09

    Electron paramagnetic resonance (EPR) spectroscopy in combination with site-directed spin labeling is used to investigate the structure and dynamics of conformationally constrained spin labels in T4 lysozyme single crystals. Within a single crystal, the oriented ensemble of spin bearing moieties results in a strong angle dependence of the EPR spectra. A quantitative description of the EPR spectra requires the determination of the unit cell orientation with respect to the sample tube and the orientation of the spin bearing moieties within the crystal lattice. Angle dependent EPR spectra were analyzed by line shape simulations using the stochastic Liouville equation approach developed by Freed and co-workers and an effective Hamiltonian approach. The gain in spectral information obtained from the EPR spectra of single crystalline samples taken at different frequencies, namely the X-band and Q-band, allows us to discriminate between motional models describing the spectra of isotropic solutions similarly well. In addition, it is shown that the angle dependent single crystal spectra allow us to identify two spin label rotamers with very similar side chain dynamics. These results demonstrate the utility of single crystal EPR spectroscopy in combination with spectral line shape simulation techniques to extract valuable dynamic information not readily available from the analysis of isotropic systems. In addition, it will be shown that the loss of electron density in high resolution diffraction experiments at room temperature does not allow us to conclude that there is significant structural disorder in the system.

  1. Membrane docking geometry of GRP1 PH domain bound to a target lipid bilayer: an EPR site-directed spin-labeling and relaxation study.

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    Huai-Chun Chen

    Full Text Available The second messenger lipid PIP(3 (phosphatidylinositol-3,4,5-trisphosphate is generated by the lipid kinase PI3K (phosphoinositide-3-kinase in the inner leaflet of the plasma membrane, where it regulates a broad array of cell processes by recruiting multiple signaling proteins containing PIP(3-specific pleckstrin homology (PH domains to the membrane surface. Despite the broad importance of PIP(3-specific PH domains, the membrane docking geometry of a PH domain bound to its target PIP(3 lipid on a bilayer surface has not yet been experimentally determined. The present study employs EPR site-directed spin labeling and relaxation methods to elucidate the membrane docking geometry of GRP1 PH domain bound to bilayer-embedded PIP(3. The model target bilayer contains the neutral background lipid PC and both essential targeting lipids: (i PIP(3 target lipid that provides specificity and affinity, and (ii PS facilitator lipid that enhances the PIP(3 on-rate via an electrostatic search mechanism. The EPR approach measures membrane depth parameters for 18 function-retaining spin labels coupled to the PH domain, and for calibration spin labels coupled to phospholipids. The resulting depth parameters, together with the known high resolution structure of the co-complex between GRP1 PH domain and the PIP(3 headgroup, provide sufficient constraints to define an optimized, self-consistent membrane docking geometry. In this optimized geometry the PH domain engulfs the PIP(3 headgroup with minimal bilayer penetration, yielding the shallowest membrane position yet described for a lipid binding domain. This binding interaction displaces the PIP(3 headgroup from its lowest energy position and orientation in the bilayer, but the headgroup remains within its energetically accessible depth and angular ranges. Finally, the optimized docking geometry explains previous biophysical findings including mutations observed to disrupt membrane binding, and the rapid lateral

  2. Lesion-induced DNA weak structural changes detected by pulsed EPR spectroscopy combined with site-directed spin labelling.

    Science.gov (United States)

    Sicoli, Giuseppe; Mathis, Gérald; Aci-Sèche, Samia; Saint-Pierre, Christine; Boulard, Yves; Gasparutto, Didier; Gambarelli, Serge

    2009-06-01

    Double electron-electron resonance (DEER) was applied to determine nanometre spin-spin distances on DNA duplexes that contain selected structural alterations. The present approach to evaluate the structural features of DNA damages is thus related to the interspin distance changes, as well as to the flexibility of the overall structure deduced from the distance distribution. A set of site-directed nitroxide-labelled double-stranded DNA fragments containing defined lesions, namely an 8-oxoguanine, an abasic site or abasic site analogues, a nick, a gap and a bulge structure were prepared and then analysed by the DEER spectroscopic technique. New insights into the application of 4-pulse DEER sequence are also provided, in particular with respect to the spin probes' positions and the rigidity of selected systems. The lesion-induced conformational changes observed, which were supported by molecular dynamics studies, confirm the results obtained by other, more conventional, spectroscopic techniques. Thus, the experimental approaches described herein provide an efficient method for probing lesion-induced structural changes of nucleic acids.

  3. Spin entanglement, decoherence and Bohm's EPR paradox

    OpenAIRE

    Cavalcanti, E. G.; Drummond, P. D.; Bachor, H. A.; Reid, M. D.

    2007-01-01

    We obtain criteria for entanglement and the EPR paradox for spin-entangled particles and analyse the effects of decoherence caused by absorption and state purity errors. For a two qubit photonic state, entanglement can occur for all transmission efficiencies. In this case, the state preparation purity must be above a threshold value. However, Bohm's spin EPR paradox can be achieved only above a critical level of loss. We calculate a required efficiency of 58%, which appears achievable with cu...

  4. Spin entanglement, decoherence and Bohm's EPR paradox.

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    Cavalcanti, E G; Drummond, P D; Bachor, H A; Reid, M D

    2009-10-12

    We obtain criteria for entanglement and the EPR paradox for spin-entangled particles and analyse the effects of decoherence caused by absorption and state purity errors. For a two qubit photonic state, entanglement can occur for all transmission efficiencies. In this case, the state preparation purity must be above a threshold value. However, Bohm's spin EPR paradox can be achieved only above a critical level of loss. We calculate a required efficiency of 58%, which appears achievable with current quantum optical technologies. For a macroscopic number of particles prepared in a correlated state, spin entanglement and the EPR paradox can be demonstrated using our criteria for efficiencies eta > 1/3 and eta > 2/3 respectively. This indicates a surprising insensitivity to loss decoherence, in a macroscopic system of ultra-cold atoms or photons.

  5. Spin-Label CW Microwave Power Saturation and Rapid Passage with Triangular Non-Adiabatic Rapid Sweep (NARS) and Adiabatic Rapid Passage (ARP) EPR Spectroscopy

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    Kittell, Aaron W.; Hyde, James S.

    2015-01-01

    Non-adiabatic rapid passage (NARS) electron paramagnetic resonance (EPR) spectroscopy was introduced by Kittell, A.W., Camenisch, T.G., Ratke, J.J. Sidabras, J.W., Hyde, J.S., 2011 as a general purpose technique to collect the pure absorption response. The technique has been used to improve sensitivity relative to sinusoidal magnetic field modulation, increase the range of inter-spin distances that can be measured under near physiological conditions, and enhance spectral resolution in copper (II) spectra. In the present work, the method is extended to CW microwave power saturation of spin-labeled T4 Lysozyme (T4L). As in the cited papers, rapid triangular sweep of the polarizing magnetic field was superimposed on slow sweep across the spectrum. Adiabatic rapid passage (ARP) effects were encountered in samples undergoing very slow rotational diffusion as the triangular magnetic field sweep rate was increased. The paper reports results of variation of experimental parameters at the interface of adiabatic and non-adiabatic rapid sweep conditions. Comparison of the forward (up) and reverse (down) triangular sweeps is shown to be a good indicator of the presence of rapid passage effects. Spectral turning points can be distinguished from spectral regions between turning points in two ways: differential microwave power saturation and differential passage effects. Oxygen accessibility data are shown under NARS conditions that appear similar to conventional field modulation data. However, the sensitivity is much higher, permitting, in principle, experiments at substantially lower protein concentrations. Spectral displays were obtained that appear sensitive to rotational diffusion in the range of rotational correlation times of 10−3 to 10−7 s in a manner that is analogous to saturation transfer spectroscopy. PMID:25917132

  6. Cross relaxation in nitroxide spin labels

    DEFF Research Database (Denmark)

    Marsh, Derek

    2016-01-01

    Cross relaxation, and mI-dependence of the intrinsic electron spin-lattice relaxation rate We, are incorporated explicitly into the rate equations for the electron-spin population differences that govern the saturation behaviour of 14N- and 15N-nitroxide spin labels. Both prove important in spin......-label EPR and ELDOR, particularly for saturation recovery studies. Neither for saturation recovery, nor for CW-saturation EPR and CW-ELDOR, can cross relaxation be described simply by increasing the value of We, the intrinsic spin-lattice relaxation rate. Independence of the saturation recovery rates from...... the hyperfine line pumped or observed follows directly from solution of the rate equations including cross relaxation, even when the intrinsic spin-lattice relaxation rate We is mI-dependent....

  7. EPR spin trapping of protein radicals

    DEFF Research Database (Denmark)

    Davies, Michael Jonathan; Hawkins, Clare Louise

    2004-01-01

    Electron paramagnetic resonance (EPR) spin trapping was originally developed to aid the detection of low-molecular-mass radicals formed in chemical systems. It has subsequently found widespread use in biology and medicine for the direct detection of radical species formed during oxidative stress...... tumbling radicals are often broad and relatively poor in distinctive features, a number of techniques have been developed that allow a wealth of information to be obtained about the nature, site, and reactions of such radicals. This article summarizes recent developments in this area and reviews selected...... examples of radical formation on proteins....

  8. Spin labels. Applications in biology

    International Nuclear Information System (INIS)

    Frangopol, T.P.; Frangopol, M.; Ionescu, S.M.; Pop, I.V.; Benga, G.

    1980-11-01

    The main applications of spin labels in the study of biomembranes, enzymes, nucleic acids, in pharmacology, spin immunoassay are reviewed along with the fundamentals of the spin label method. 137 references. (author)

  9. Technological advances in site-directed spin labeling of proteins.

    Science.gov (United States)

    Hubbell, Wayne L; López, Carlos J; Altenbach, Christian; Yang, Zhongyu

    2013-10-01

    Molecular flexibility over a wide time range is of central importance to the function of many proteins, both soluble and membrane. Revealing the modes of flexibility, their amplitudes, and time scales under physiological conditions is the challenge for spectroscopic methods, one of which is site-directed spin labeling EPR (SDSL-EPR). Here we provide an overview of some recent technological advances in SDSL-EPR related to investigation of structure, structural heterogeneity, and dynamics of proteins. These include new classes of spin labels, advances in measurement of long range distances and distance distributions, methods for identifying backbone and conformational fluctuations, and new strategies for determining the kinetics of protein motion. Copyright © 2013 Elsevier Ltd. All rights reserved.

  10. EPR Studies of Spin-Spin Exchange Processes: A Physical Chemistry Experiment.

    Science.gov (United States)

    Eastman, Michael P.

    1982-01-01

    Theoretical background, experimental procedures, and analysis of experimental results are provided for an undergraduate physical chemistry experiment on electron paramagnetic resonance (EPR) linewidths. Source of line broadening observed in a spin-spin exchange process between radicals formed in aqueous solutions of potassium peroxylamine…

  11. Characterization of beer flavour stability (EPR - spin trapping)

    International Nuclear Information System (INIS)

    Stasko, A.; Liptakova, M.; Malik, F.

    1999-01-01

    The beer flavour stability is coupled with free radical degradation processes. Probably, aldehydes produced during the brewery but also generated by stalling are responsible for beer flavour as well as for its breaking down. The storing beer at the lower temperatures and in the dark place inhibits, and otherwise the rising temperature and illumination accelerate the rate of such radical processes. Beers contain naturally occurring radical scavengers - antioxidants which inhibit such unwanted reactions. Then depleting of scavengers results in the breaking down of the beer stability. EPR spin trapping technique was used as monitor such processes and for characterising so the flavour stability of beer. The probe was temperated at 60 grad C in the cavity of EPR spectrometer in the presence of spin trapping agent, N-tert.-butyl-α-phenyl nitrone (PBN) and EPR spectra were recorded for few hours. After beer antioxidants become depleted, free radicals formed by the beer degradation are scavenged by PBN spin trap and this point is characterised with a dramatically increased concentration of the free radicals trapped

  12. Comparison of continuous wave, spin echo, and rapid scan EPR of irradiated fused quartz

    International Nuclear Information System (INIS)

    Mitchell, Deborah G.; Quine, Richard W.; Tseitlin, Mark; Meyer, Virginia; Eaton, Sandra S.; Eaton, Gareth R.

    2011-01-01

    The E' defect in irradiated fused quartz has spin lattice relaxation times (T 1 ) about 100-300 μs and spin-spin relaxation times (T 2 ) up to about 200 μs, depending on the concentration of defects and other species in the sample. These long relaxation times make it difficult to record an unsaturated continuous wave (CW) electron paramagnetic resonance (EPR) signal that is free of passage effects. Signals measured at X-band (∼9.5 GHz) by three EPR methods: conventional slow-scan field-modulated EPR, rapid scan EPR, and pulsed EPR, were compared. To acquire spectra with comparable signal-to-noise, both pulsed and rapid scan EPR require less time than conventional CW EPR. Rapid scan spectroscopy does not require the high power amplifiers that are needed for pulsed EPR. The pulsed spectra, and rapid scan spectra obtained by deconvolution of the experimental data, are free of passage effects.

  13. High-frequency EPR on high-spin transition-metal sites

    NARCIS (Netherlands)

    Mathies, Guinevere

    2012-01-01

    The electronic structure of transition-metal sites can be probed by electron-paramagnetic-resonance (EPR) spectroscopy. The study of high-spin transition-metal sites benefits from EPR spectroscopy at frequencies higher than the standard 9.5 GHz. However, high-frequency EPR is a developing field. In

  14. Resolution of the EPR Paradox for Fermion Spin Correlations

    Science.gov (United States)

    Close, Robert

    2011-10-01

    The EPR paradox addresses the question of whether a physical system can have a definite state independent of its measurement. Bell's Theorem places limits on correlations between local measurements of particles whose properties are established prior to measurement. Experimental violation of Bell's theorem has been regarded as evidence against the existence of a definite state prior to measurement. We model fermions as having a spatial distribution of spin values, so that a Stern-Gerlach device samples the spin distribution differently at different orientations. The computed correlations agree with quantum mechanical predictions and experimental observations. Bell's Theorem is not applicable because for any sampling of angles, different points on the sphere have different density of states.

  15. Advances in the synthesis of nitroxide radicals for use in biomolecule spin labelling.

    Science.gov (United States)

    Haugland, Marius M; Lovett, Janet E; Anderson, Edward A

    2018-02-05

    EPR spectroscopy is an increasingly useful analytical tool to probe biomolecule structure, dynamic behaviour, and interactions. Nitroxide radicals are the most commonly used radical probe in EPR experiments, and many methods have been developed for their synthesis, as well as incorporation into biomolecules using site-directed spin labelling. In this Tutorial Review, we discuss the most practical methods for the synthesis of nitroxides, focusing on the tunability of their structures, the manipulation of their sidechains into spin labelling handles, and their installation into biomolecules.

  16. Use of rapid-scan EPR to improve detection sensitivity for spin-trapped radicals.

    Science.gov (United States)

    Mitchell, Deborah G; Rosen, Gerald M; Tseitlin, Mark; Symmes, Breanna; Eaton, Sandra S; Eaton, Gareth R

    2013-07-16

    The short lifetime of superoxide and the low rates of formation expected in vivo make detection by standard continuous wave (CW) electron paramagnetic resonance (EPR) challenging. The new rapid-scan EPR method offers improved sensitivity for these types of samples. In rapid-scan EPR, the magnetic field is scanned through resonance in a time that is short relative to electron spin relaxation times, and data are processed to obtain the absorption spectrum. To validate the application of rapid-scan EPR to spin trapping, superoxide was generated by the reaction of xanthine oxidase and hypoxanthine with rates of 0.1-6.0 μM/min and trapped with 5-tert-butoxycarbonyl-5-methyl-1-pyrroline-N-oxide (BMPO). Spin trapping with BMPO to form the BMPO-OOH adduct converts the very short-lived superoxide radical into a more stable spin adduct. There is good agreement between the hyperfine splitting parameters obtained for BMPO-OOH by CW and rapid-scan EPR. For the same signal acquisition time, the signal/noise ratio is >40 times higher for rapid-scan than for CW EPR. Rapid-scan EPR can detect superoxide produced by Enterococcus faecalis at rates that are too low for detection by CW EPR. Copyright © 2013 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  17. Stearic acid spin labels in lipid bilayers :  insight through atomistic simulations

    NARCIS (Netherlands)

    Stimson, L.M.; Dong, L.; Karttunen, M.E.J.; Wisniewska, A.; Dutka, M.; Róg, T.

    2007-01-01

    Spin-labeled stearic acid species are commonly used for electron paramagnetic resonance (EPR) studies of cell membranes to investigate phase transitions, fluidity, and other physical properties. In this paper, we use large-scale molecular dynamics simulations to investigate the position and behavior

  18. Conformational change of spin labelled myoglobin

    International Nuclear Information System (INIS)

    Wajnberg, E.; Ribeiro, P.C.; Nascimento, O.R.; Bemski, G.

    1978-01-01

    A conformational change of spin labelled myoglobin have been followed by measuring the spin label's (isothiocyanate) correlation time for temperatures between 18 0 C and 44 0 C. The correlation time was calculated from Electrom Paramagnetic Ressonance Spectra using the components of the espectroscopic and hiperfine tensors obtained by fitting the powder spectra using Lefebvre and Maruani's program- [pt

  19. Investigations on resolution enhancement in EPR by means of electron spin echoes

    International Nuclear Information System (INIS)

    Merks, R.P.J.

    1979-01-01

    The electron spin echo technique has been applied in four types of experiments: the measurement of electric field induced shifts of the EPR line; the detection of electron spin echo ENDOR; a relaxation measurement and the measurement of hyperfine interactions via the nuclear modulation effect. (Auth.)

  20. Trichloroethylene Radicals: An EPR/SPIN Trapping Study

    National Research Council Canada - National Science Library

    Steel-Goodwin, Linda

    1995-01-01

    .... As part of the process to develop environmental and health effects criteria for base clean-up the initial radicals produced by TCE were studied by electron paramagnetic resonance spectroscopy (EPR...

  1. Detection and characterisation of radicals using electron paramagnetic resonance (EPR) spin trapping and related methods

    DEFF Research Database (Denmark)

    Davies, Michael Jonathan

    2016-01-01

    Electron paramagnetic resonance (EPR) spectroscopy (also known as electron spin resonance, ESR, or electron magnetic resonance, EMR, spectroscopy) is often described as the “gold standard” for the detection and characterisation of radicals in chemical, biological and medical systems. The article...... reviews aspects of EPR spectroscopy and discusses how this methodology and related techniques can be used to obtain useful information from biological systems. Consideration is given to the direct detection of radicals, the use of spin traps and the detection of nitric oxide, and the advantages...

  2. Spin states of reduced fullerenes (C60 and C120O) by CW and pulsed EPR

    International Nuclear Information System (INIS)

    Boas, J.F.; Drew, S.C.; Pilbrow, J.R.; Boyd, P.D.W.; Paul, P.; Reed, C.A.; Sun, D.

    2003-01-01

    Full text: The ESTN (Electron Spin Transient Nutation) EPR (Electron Paramagnetic Resonance) experiments reported at Wagga 2002 showed that the spin states of the reduced fullerenes C 120 O (2-), C 120 O (3-) and C 120 O (4-) were S = 1, S = 1/2 and S = 1 respectively. Further experiments using CW (Continuous Wave) EPR have confirmed the results of Paul et al. and have now shown that these states are the ground states of these anions. In the case of C 60 (3-), the recent CW and ESTN EPR experiments have shown that the electronic ground state of this anion is S = 1/2. The observation of ground states of low multiplicity for these anions is contrary to expectations based on MO calculations and the application of Hund's rules. A series of CW EPR experiments on C 60 (3-) have shown that some previous results may need to be re-interpreted. This arises from the delineation of the effects of microwave power, modulation amplitude and frequency, sample temperature and freezing rate on the EPR spectrum which is the combination of a broad line, attributed to C 60 (3-), and a 'spike' attributed to C 120 O impurities and other oxygen related species. Our results cast doubt on the existence of Jahn-Teller effects at low temperatures and of a low-lying spin quartet excited state

  3. Study of dipole-dipole interactions between iron and spin labelled centre in cytochrome C by means of ESR; Badanie oddzialywan dipolowo-dipolowych pomiedzy zelazem a znacznikiem spinowym w cytochromie C metoda SF EPR

    Energy Technology Data Exchange (ETDEWEB)

    Blicharski, W; Froncisz, W; Kostrzewa, A; Osyczka, A; Turyna, B [Inst. Biologii Molekularnej, Uniwersytet Jagiellonski, Cracow (Poland)

    1994-12-31

    The influence of dipole-dipole interactions between two different spins localized in the same molecule on spin-lattice relaxation time have been discussed on the base of measured spectra by means of pulsed ESR. The structural conclusions, the distance between interacting paramagnetic centers, for molecules of three derivatives of cytochrome C have been presented. 8 refs, 2 figs, 1 tab.

  4. Use of spin traps to detect superoxide production in living cells by electron paramagnetic resonance (EPR) spectroscopy.

    Science.gov (United States)

    Abbas, Kahina; Babić, Nikola; Peyrot, Fabienne

    2016-10-15

    Detection of superoxide produced by living cells has been an on-going challenge in biology for over forty years. Various methods have been proposed to address this issue, among which spin trapping with cyclic nitrones coupled to EPR spectroscopy, the gold standard for detection of radicals. This technique is based on the nucleophilic addition of superoxide to a diamagnetic cyclic nitrone, referred to as the spin trap, and the formation of a spin adduct, i.e. a persistent radical with a characteristic EPR spectrum. The first application of spin trapping to living cells dates back 1979. Since then, considerable improvements of the method have been achieved both in the structures of the spin traps, the EPR methodology, and the design of the experiments including appropriate controls. Here, we will concentrate on technical aspects of the spin trapping/EPR technique, delineating recent breakthroughs, inherent limitations, and potential artifacts. Copyright © 2016 Elsevier Inc. All rights reserved.

  5. Spin labeled amino acid nitrosourea derivatives--synthesis and antitumour activity.

    Science.gov (United States)

    Zheleva, A; Raikov, Z; Ilarionova, M; Todorov, D

    1995-01-01

    The synthesis of three spin labeled derivatives of N-[N'-(chloroethyl)-N'-nitrosocarbamoyl] amino acids is reported. The new nitrosoureas are obtained by condensation of the corresponding N-[N'-(2-chloroethyl)-N'-nitrosocarbamoyl] amino acid with 2,2,6,6-tetramethyl-1-oxyl-4-aminopiperidine using dicyclohexylcarbodiimide. Their chemical structures are confirmed by elemental analysis, IR, MS, and EPR spectroscopy. All newly synthesized compounds showed high antitumour activity against the lymphoid leukemia L1210 in BDF1 mice.

  6. Spin labelling of human erythrocytes with nitroxide radicals

    International Nuclear Information System (INIS)

    Chagalj, C.; DePaoli, T.C.P.; Hager, A.A.; Palaoro, L.A.; Rubin de Celis, E.; Farach, H.A.; Poole, C.P. jr

    1984-01-01

    Human erythrocytes were labelled with nitroxide, the spin label SYNVAR 101, under various experimantal conditions. A study was made of the influence of antireductants on the labelling efficiency and the kinetics of the radical decay during the labelling process

  7. Nanosecond time-resolved EPR in pulse radiolysis via the spin echo method

    International Nuclear Information System (INIS)

    Trifunac, A.D.; Norris, J.R.; Lawler, R.G.

    1979-01-01

    The design and operation of a time-resolved electron spin echo spectrometer suitable for detecting transient radicals produced by 3 MeV electron radiolysis is described. Two modes of operation are available: Field swept mode which generates a normal EPR spectrum and kinetic mode in which the time dependence of a single EPR line is monitored. Techniques which may be used to minimize the effects of nonideal microwave pulses and overlapping sample tube signals are described. The principal advantages of the spin echo method over other time-resolved EPR methods are: (1) Improved time resolution (presently approx.30--50 nsec) allows monitoring of fast changes in EPR signals of transient radicals, (2) Lower susceptibility to interference between the EPR signal and the electron beam pulse at short times, and (3) Lack of dependence of transient signals on microwave field amplitude or static field inhomogeneity at short times. The performance of the instrument is illustrated using CIDEP from acetate radical formed in pulsed radiolysis of aqueous solutions of potassium acetate. The relaxation time and CIDEP enhancement factor obtained for this radical using the spin echo method compare favorably with previous determinations using direct detection EPR. Radical decay rates yield estimates of initial radical concentrations of 10 -4 10 -3 M per electron pulse. The Bloch equations are solved to give an expression for the echo signal for samples exhibiting CIDEP using arbitrary microwave pulse widths and distributions of Larmor frequencies. Conditions are discussed under which the time-dependent signal would be distorted by deviations from an ideal nonselective 90 0 --tau--180 0 pulse sequence

  8. Structure and dynamics of spin-labeled insulin entrapped in a silica matrix by the sol-gel method.

    Science.gov (United States)

    Vanea, E; Gruian, C; Rickert, C; Steinhoff, H-J; Simon, V

    2013-08-12

    The structure and conformational dynamics of insulin entrapped into a silica matrix was monitored during the sol to maturated-gel transition by electron paramagnetic resonance (EPR) spectroscopy. Insulin was successfully spin-labeled with iodoacetamide and the bifunctional nitroxide reagent HO-1944. Room temperature continuous wave (cw) EPR spectra of insulin were recorded to assess the mobility of the attached spin labels. Insulin conformation and its distribution within the silica matrix were studied using double electron-electron resonance (DEER) and low-temperature cw-EPR. A porous oxide matrix seems to form around insulin molecules with pore diameters in the order of a few nanometers. Secondary structure of the encapsulated insulin investigated by Fourier transform infrared spectroscopy proved a high structural integrity of insulin even in the dried silica matrix. The results show that silica encapsulation can be used as a powerful tool to effectively isolate and functionally preserve biomolecules during preparation, storage, and release.

  9. Isolation of EPR spectra and estimation of spin-states in two-component mixtures of paramagnets.

    Science.gov (United States)

    Chabbra, Sonia; Smith, David M; Bode, Bela E

    2018-04-26

    The presence of multiple paramagnetic species can lead to overlapping electron paramagnetic resonance (EPR) signals. This complication can be a critical obstacle for the use of EPR to unravel mechanisms and aid the understanding of earth abundant metal catalysis. Furthermore, redox or spin-crossover processes can result in the simultaneous presence of metal centres in different oxidation or spin states. In this contribution, pulse EPR experiments on model systems containing discrete mixtures of Cr(i) and Cr(iii) or Cu(ii) and Mn(ii) complexes demonstrate the feasibility of the separation of the EPR spectra of these species by inversion recovery filters and the identification of the relevant spin states by transient nutation experiments. We demonstrate the isolation of component spectra and identification of spin states in a mixture of catalyst precursors. The usefulness of the approach is emphasised by monitoring the fate of the chromium species upon activation of an industrially used precatalyst system.

  10. The evaluation of new and isotopically labeled isoindoline nitroxides and an azaphenalene nitroxide for EPR oximetry

    Science.gov (United States)

    Khan, Nadeem; Blinco, James P.; Bottle, Steven E.; Hosokawa, Kazuyuki; Swartz, Harold M.; Micallef, Aaron S.

    2011-01-01

    Isoindoline nitroxides are potentially useful probes for viable biological systems, exhibiting low cytotoxicity, moderate rates of biological reduction and favorable Electron Paramagnetic Resonance (EPR) characteristics. We have evaluated the anionic (5-carboxy-1,1,3,3-tetramethylisoindolin-2-yloxyl; CTMIO), cationic (5-(N,N,N-trimethylammonio)-1,1,3,3-tetramethylisoindolin-2-yloxyl iodide, QATMIO) and neutral (1,1,3,3-tetramethylisoindolin-2-yloxyl; TMIO) nitroxides and their isotopically labeled analogues (2H12- and/or 2H12-15N-labeled) as potential EPR oximetry probes. An active ester analogue of CTMIO, designed to localize intracellularly, and the azaphenalene nitroxide 1,1,3,3-tetramethyl-2,3-dihydro-2-azaphenalen-2-yloxyl (TMAO) were also studied. While the EPR spectra of the unlabeled nitroxides exhibit high sensitivity to O2 concentration, deuteration resulted in a loss of superhyperfine features and a subsequent reduction in O2 sensitivity. Labeling the nitroxides with 15N increased the signal intensity and this may be useful in decreasing the detection limits for in vivo measurements. The active ester nitroxide showed approximately 6% intracellular localization and low cytotoxicity. The EPR spectra of TMAO nitroxide indicated an increased rigidity in the nitroxide ring, due to dibenzo-annulation. PMID:21665499

  11. Orientation of spin-labeled light chain 2 of myosin heads in muscle fibers.

    Science.gov (United States)

    Arata, T

    1990-07-20

    Electron paramagnetic resonance (e.p.r.) spectroscopy has been used to monitor the orientation of spin labels attached rigidly to a reactive SH residue on the light chain 2 (LC2) of myosin heads in muscle fibers. e.p.r. spectra from spin-labeled myosin subfragment-1 (S1), allowed to diffuse into unlabeled rigor (ATP-free) fibers, were roughly approximated by a narrow angular distribution of spin labels centered at 66 degrees relative to the fiber axis, indicating a uniform orientation of S1 bound to actin. On the other hand, spectra from spin-labeled heavy meromyosin (HMM) were roughly approximated by two narrow angular distributions centered at 42 degrees and 66 degrees, suggesting that the LC2 domains of the two HMM heads have different orientations. In contrast to S1 or HMM, the spectra from rigor fibers, in which LC2 of endogenous myosin heads was labeled, showed a random orientation which may be due to distortion imposed by the structure of the filament lattice and the mismatch of the helical periodicities of the thick and thin filaments. However, spectra from the fibers in the presence of ATP analog 5'-adenylyl imidodiphosphate (AMPPNP) were approximated by two narrow angular distributions similar to those obtained with HMM. Thus, AMPPNP may cause the LC2 domain to be less flexible and/or the S2 portion to be more flexible, so as to release the distortion of the LC2 domain and make it return to its natural position. At high ionic strength, AMPPNP disoriented the spin labels as ATP did under relaxing conditions, suggesting that the myosin head is detached from and/or weakly (flexibly) attached to a thin filament.

  12. Sequence- and structure-dependent DNA base dynamics: Synthesis, structure, and dynamics of site and sequence specifically spin-labeled DNA

    International Nuclear Information System (INIS)

    Spaltenstein, A.; Robinson, B.H.; Hopkins, P.B.

    1989-01-01

    A nitroxide spin-labeled analogue of thymidine (1a), in which the methyl group is replaced by an acetylene-tethered nitroxide, was evaluated as a probe for structural and dynamics studies of sequence specifically spin-labeled DNA. Residue 1a was incorporated into synthetic deoxyoligonucleotides by using automated phosphite triester methods. 1 H NMR, CD, and thermal denaturation studies indicate that 1a (T) does not significantly alter the structure of 5'-d(CGCGAATT*CGCG) from that of the native dodecamer. EPR studies on monomer, single-stranded, and duplexed DNA show that 1a readily distinguishes environments of different rigidity. Comparison of the general line-shape features of the observed EPR spectra of several small duplexes (12-mer, 24-mer) with simulated EPR spectra assuming isotropic motion suggests that probe 1a monitors global tumbling of small duplexes. Increasing the length of the DNA oligomers results in significant deviation from isotropic motion, with line-shape features similar to those of calculated spectra of objects with isotropic rotational correlation times of 20-100 ns. EPR spectra of a spin-labeled GT mismatch and a T bulge in long DNAs are distinct from those of spin-labeled Watson-Crick paired DNAs, further demonstrating the value of EPR as a tool in the evaluation of local dynamic and structural features in macromolecules

  13. An EPR spin-probe and spin-trap study of the free radicals produced by plant plasma membranes

    Directory of Open Access Journals (Sweden)

    GORAN BACIC

    2005-02-01

    Full Text Available Plant plasma membranes are known to produce superoxide radicals, while the production of hydroxyl radical is thought to occur only in the cell wall. In this work it was demonstrated using combined spin-trap and spin-probe EPR spectroscopic techniques, that plant plasma membranes do produce superoxide and hydroxyl radicals but by kinetically different mechanisms. The results show that superoxide and hydroxyl radicals can be detected by DMPO spin-trap and that the mechanisms and location of their production can be differentiated using the reduction of spin-probes Tempone and 7-DS. It was shown that the mechanism of production of oxygen reactive species is NADH dependent and diphenylene iodonium inhibited. The kinetics of the reduction of Tempone, combined with scavengers or the absence of NADH indicates that hydroxyl radicals are produced by a mechanism independent of that of superoxide production. It was shown that a combination of the spin-probe and spin-trap technique can be used in free radical studies of biological systems, with a number of advantages inherent to them.

  14. Temperature-induced variation in the intrinsic hyperfine separation of a tightly bound nitroxide spin label

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, M.E.

    1979-01-01

    Recently there has been increasing interest in studying the rotational motion of biological molecules by monitoring the electron paramagnetic resonance (EPR) spectra of spin labels which are tightly bound to the molecule of interest. Theoretical studies have shown that in the slow motion region the correlation time may be determined by comparing the apparent hyperfine separation (HFS) in the presence of rotational motion with the rigid limit HFS in the absence of rotational motion. The majority of work to date has assumed the tightly bound nitroxide label to act simply as a reporter group for molecular motion, exhibiting little or no intrinsic environmental or temperature sensitivity. However, we have demonstrated that the rigid limit EPR spectra exhibit a substantial intrinsic temperature dependence, with the rigid limit HFS of MAL-6-labelled carboxyhemoglobin (HbCO) decreasing by nearly 10G over the temperature range -196/sup 0/C to +45/sup 0/C. The steepest temperature dependence was also found to occur over the 0 to 40/sup 0/C temperature range where most biological measurements are made. This strong temperature dependence in the intrinsic HFS was shown to produce substantial errors in correlation time calculations if it was not explicitly recognized and appropriate corrections made. This detailed behavior of this intrinsic temperature dependence suggests that it is most probably produced by equilibrium hydrogen bonding between the nitroxide NO/sup ./ group and an unidentified proton donor within the spin label binding site. (RJC)

  15. Use of EPR to Solve Biochemical Problems

    Science.gov (United States)

    Sahu, Indra D.; McCarrick, Robert M.; Lorigan, Gary A.

    2013-01-01

    EPR spectroscopy is a very powerful biophysical tool that can provide valuable structural and dynamic information on a wide variety of biological systems. The intent of this review is to provide a general overview for biochemists and biological researchers on the most commonly used EPR methods and how these techniques can be used to answer important biological questions. The topics discussed could easily fill one or more textbooks; thus, we present a brief background on several important biological EPR techniques and an overview of several interesting studies that have successfully used EPR to solve pertinent biological problems. The review consists of the following sections: an introduction to EPR techniques, spin labeling methods, and studies of naturally occurring organic radicals and EPR active transition metal systems which are presented as a series of case studies in which EPR spectroscopy has been used to greatly further our understanding of several important biological systems. PMID:23961941

  16. Introduction to Spin Label Electron Paramagnetic Resonance Spectroscopy of Proteins

    Science.gov (United States)

    Melanson, Michelle; Sood, Abha; Torok, Fanni; Torok, Marianna

    2013-01-01

    An undergraduate laboratory exercise is described to demonstrate the biochemical applications of electron paramagnetic resonance (EPR) spectroscopy. The beta93 cysteine residue of hemoglobin is labeled by the covalent binding of 3-maleimido-proxyl (5-MSL) and 2,2,5,5-tetramethyl-1-oxyl-3-methyl methanethiosulfonate (MTSL), respectively. The excess…

  17. Application of nonlinear EPR and NMR responses on spin systems in structure and relaxation structures

    International Nuclear Information System (INIS)

    Polyakov, A.I.; Ryabikin, Yu.A.; Bitenbaev, M.M.

    2004-01-01

    Full text: In this work results of investigation of paramagnetic systems (irradiated polymers and crystals, plastic-deformed metals, systems with strong exchange interaction, etc.) by methods of nonlinear relaxation spectroscopy (NRS) are presented. The NRS theoretical grounds were developed in the earlier works. Later the technique was applied successfully to relaxation studies and when analyzing magnetic resonance complicated overlapping spectra. As in course of polymer system irradiation, basically, several type of paramagnetic defects are formed with close values of the g factors, these materials can be used to exemplify NRS capabilities. In this work we use samples of irradiated PMMA copolymers. Analysis of the PMMA spectra shows that several types of paramagnetic defects strongly differing in the spin-lattice relaxation times are formed in irradiated PMMA-based polymer composites. It is found that degradation of the composite physical and engineering characteristics is caused, mainly, by radiation-induced disintegration of macromolecules, following the chain reaction, which can be revealed by occurring lattice radical states. Another portion of work is devoted to NRS application to deterring influence of structural defects (impurity, dislocation, etc.) on variation in times of nuclear spin-lattice relaxation in metal systems. At this stage we managed, for the first time, to separate the distribution functions for spin-lattice relaxation (T l ) and relaxation of nuclear spin dipole-dipole interaction (T d ). It is shown that one can assess an extent of crystal defect by the dependence of T d =f(c). Also in this work the NRS methods are applied to analyze EPR spectra of polycrystalline solid systems where exchange interaction is strong. It is shown that these systems, as a rule, contain a complete set of spin assemblies having different relaxation times, and the spin assembly distribution over the relaxation time depends on the defect number and type in solid

  18. Entanglement, EPR steering, and Bell-nonlocality criteria for multipartite higher-spin systems

    International Nuclear Information System (INIS)

    He, Q. Y.; Drummond, P. D.; Reid, M. D.

    2011-01-01

    We develop criteria to detect three classes of nonlocality that have been shown by Wiseman et al. [Phys. Rev. Lett. 98, 140402 (2007)] to be nonequivalent: entanglement, EPR steering, and the failure of local hidden-variable theories. We use the approach of Cavalcanti et al. [Phys. Rev. Lett. 99, 210405 (2007)] for continuous variables to develop the nonlocality criteria for arbitrary spin observables defined on a discrete Hilbert space. The criteria thus apply to multisite qudits, i.e., systems of fixed dimension d, and take the form of inequalities. We find that the spin moment inequalities that test local hidden variables (Bell inequalities) can be violated for arbitrary d by optimized highly correlated nonmaximally entangled states provided the number of sites N is high enough. On the other hand, the spin inequalities for entanglement are violated and thus detect entanglement for such states, for arbitrary d and N, and with a violation that increases with N. We show that one of the moment entanglement inequalities can detect the entanglement of an arbitrary generalized multipartite Greenberger-Horne-Zeilinger state. Because they involve the natural observables for atomic systems, the relevant spin-operator correlations should be readily observable in trapped ultracold atomic gases and ion traps.

  19. Antioxidant pool in beer and kinetics of EPR spin-trapping.

    Science.gov (United States)

    Kocherginsky, Nikolai M; Kostetski, Yuri Yu; Smirnov, Alex I

    2005-08-24

    The kinetics of spin-trap adduct formation in beer oxidation exhibits an induction period if the reaction is carried out at elevated temperatures and in the presence of air. This lag period lasts until the endogenous antioxidants are almost completely depleted, and its duration is used as an indicator of the flavor stability and shelf life of beer. This paper demonstrates that the total kinetics of the process can be characterized by three parameters-the lag period, the rate of spin-trap adduct formation, and, finally, the steady-state spin-adduct concentration. A steady-state chain reaction mechanism is described, and quantitative estimates of the main kinetic parameters such as the initiation rate, antioxidant pool, effective content of organic molecules participating in the chain reactions, and the rate constant of the 1-hydroxyethyl radical EtOH(*) spin-adduct disappearance are given. An additional new dimensionless parameter is suggested to characterize the antioxidant pool-the product of the lag time and the rate of spin-trap radical formation immediately after the lag time, normalized by the steady-state concentration of the adducts. The results of spin-tapping EPR experiments are compared with the nitroxide reduction kinetics measured in the same beer samples. It is shown that although the kinetics of nitroxide reduction in beer can be used to evaluate the reducing power of beer, the latter parameter does not correlate with the antioxidant pool. The relationship of free radical processes, antioxidant pool, reducing power, and beer staling is discussed.

  20. Communication: Orientational self-ordering of spin-labeled cholesterol analogs in lipid bilayers in diluted conditions

    Energy Technology Data Exchange (ETDEWEB)

    Kardash, Maria E.; Dzuba, Sergei A., E-mail: dzuba@kinetics.nsc.ru [Voevodsky Institute of Chemical Kinetics and Combustion, 630090 Novosibirsk, Russia, and Novosibirsk State University, 630090 Novosibirsk (Russian Federation)

    2014-12-07

    Lipid-cholesterol interactions are responsible for different properties of biological membranes including those determining formation in the membrane of spatial inhomogeneities (lipid rafts). To get new information on these interactions, electron spin echo (ESE) spectroscopy, which is a pulsed version of electron paramagnetic resonance (EPR), was applied to study 3β-doxyl-5α-cholestane (DCh), a spin-labeled analog of cholesterol, in phospholipid bilayer consisted of equimolecular mixture of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine and 1,2-dioleoyl-sn-glycero-3-phosphocholine. DCh concentration in the bilayer was between 0.1 mol.% and 4 mol.%. For comparison, a reference system containing a spin-labeled 5-doxyl-stearic acid (5-DSA) instead of DCh was studied as well. The effects of “instantaneous diffusion” in ESE decay and in echo-detected (ED) EPR spectra were explored for both systems. The reference system showed good agreement with the theoretical prediction for the model of spin labels of randomly distributed orientations, but the DCh system demonstrated remarkably smaller effects. The results were explained by assuming that neighboring DCh molecules are oriented in a correlative way. However, this correlation does not imply the formation of clusters of cholesterol molecules, because conventional continuous wave EPR spectra did not show the typical broadening due to aggregation of spin labels and the observed ESE decay was not faster than in the reference system. So the obtained data evidence that cholesterol molecules at low concentrations in biological membranes can interact via large distances of several nanometers which results in their orientational self-ordering.

  1. Inter-spin distance determination using L-band (1-2 GHz) non-adiabatic rapid sweep electron paramagnetic resonance (NARS EPR)

    Science.gov (United States)

    Kittell, Aaron W.; Hustedt, Eric J.; Hyde, James S.

    2014-01-01

    Site-directed spin-labeling electron paramagnetic resonance (SDSL EPR) provides insight into the local structure and motion of a spin probe strategically attached to a molecule. When a second spin is introduced to the system, macromolecular information can be obtained through measurement of inter-spin distances either by continuous wave (CW) or pulsed electron double resonance (ELDOR) techniques. If both methodologies are considered, inter-spin distances of 8 to 80 Å can be experimentally determined. However, there exists a region at the upper limit of the conventional X-band (9.5 GHz) CW technique and the lower limit of the four-pulse double electron-electron resonance (DEER) experiment where neither method is particularly reliable. The work presented here utilizes L-band (1.9 GHz) in combination with non-adiabatic rapid sweep (NARS) EPR to address this opportunity by increasing the upper limit of the CW technique. Because L-band linewidths are three to seven times narrower than those at X-band, dipolar broadenings that are small relative to the X-band inhomogeneous linewidth become observable, but the signal loss due to the frequency dependence of the Boltzmann factor, has made L-band especially challenging. NARS has been shown to increase sensitivity by a factor of five, and overcomes much of this loss, making L-band distance determination more feasible [1]. Two different systems are presented and distances of 18–30 Å have been experimentally determined at physiologically relevant temperatures. Measurements are in excellent agreement with a helical model and values determined by DEER. PMID:22750251

  2. Molecular order and T1-relaxation, cross-relaxation in nitroxide spin labels

    Science.gov (United States)

    Marsh, Derek

    2018-05-01

    Interpretation of saturation-recovery EPR experiments on nitroxide spin labels whose angular rotation is restricted by the orienting potential of the environment (e.g., membranes) currently concentrates on the influence of rotational rates and not of molecular order. Here, I consider the dependence on molecular ordering of contributions to the rates of electron spin-lattice relaxation and cross relaxation from modulation of N-hyperfine and Zeeman anisotropies. These are determined by the averages and , where θ is the angle between the nitroxide z-axis and the static magnetic field, which in turn depends on the angles that these two directions make with the director of uniaxial ordering. For saturation-recovery EPR at 9 GHz, the recovery rate constant is predicted to decrease with increasing order for the magnetic field oriented parallel to the director, and to increase slightly for the perpendicular field orientation. The latter situation corresponds to the usual experimental protocol and is consistent with the dependence on chain-labelling position in lipid bilayer membranes. An altered dependence on order parameter is predicted for saturation-recovery EPR at high field (94 GHz) that is not entirely consistent with observation. Comparisons with experiment are complicated by contributions from slow-motional components, and an unexplained background recovery rate that most probably is independent of order parameter. In general, this analysis supports the interpretation that recovery rates are determined principally by rotational diffusion rates, but experiments at other spectral positions/field orientations could increase the sensitivity to order parameter.

  3. Spin Label Studies of the Hemoglobin-Membrane Interaction During Sickle Hemoglobin Polymerization

    International Nuclear Information System (INIS)

    Falcon Dieguez, Jose E.; Rodi, Pablo; Lores Guevara, Manuel A.; Gennaro, Ana Maria

    2009-12-01

    An enhanced hemoglobin-membrane association has been previously documented in Sickle Cell Anemia. However, it is not known how this interaction is modified during the hemoglobin S polymerization process. In this work, we use a model of reconstituted erythrocytes from ghost membranes whose cytoskeleton proteins had been previously labeled with the 4-maleimido Tempo spin label, and that were subsequently resealed with hemoglobin S or A solutions. Using EPR spectroscopy, we studied the time dependence of the spectral W/S parameter, indicative of the conformational state of cytoskeleton proteins (mainly spectrin) under spontaneous deoxygenation, with the aim of detecting the eventual effects due to hemoglobin S polymerization. The differences observed in the temporal behaviour of W/S in erythrocytes reconstituted with both hemoglobins were considered as experimental evidence of an increment in hemoglobin S-membrane interaction, as a result of the polymerization process of hemoglobin S under spontaneous deoxygenation. (author)

  4. Application of nonlinear EPR and NMR responses on spin systems in structure and relaxation structures

    Energy Technology Data Exchange (ETDEWEB)

    Polyakov, A I; Ryabikin, Yu A; Bitenbaev, M M [Inst. of Physics and Technology, Almaty (Kazakhstan)

    2004-07-01

    Full text: In this work results of investigation of paramagnetic systems (irradiated polymers and crystals, plastic-deformed metals, systems with strong exchange interaction, etc.) by methods of nonlinear relaxation spectroscopy (NRS) are presented. The NRS theoretical grounds were developed in the earlier works. Later the technique was applied successfully to relaxation studies and when analyzing magnetic resonance complicated overlapping spectra. As in course of polymer system irradiation, basically, several type of paramagnetic defects are formed with close values of the g factors, these materials can be used to exemplify NRS capabilities. In this work we use samples of irradiated PMMA copolymers. Analysis of the PMMA spectra shows that several types of paramagnetic defects strongly differing in the spin-lattice relaxation times are formed in irradiated PMMA-based polymer composites. It is found that degradation of the composite physical and engineering characteristics is caused, mainly, by radiation-induced disintegration of macromolecules, following the chain reaction, which can be revealed by occurring lattice radical states. Another portion of work is devoted to NRS application to deterring influence of structural defects (impurity, dislocation, etc.) on variation in times of nuclear spin-lattice relaxation in metal systems. At this stage we managed, for the first time, to separate the distribution functions for spin-lattice relaxation (T{sub l}) and relaxation of nuclear spin dipole-dipole interaction (T{sub d}). It is shown that one can assess an extent of crystal defect by the dependence of T{sub d}=f(c). Also in this work the NRS methods are applied to analyze EPR spectra of polycrystalline solid systems where exchange interaction is strong. It is shown that these systems, as a rule, contain a complete set of spin assemblies having different relaxation times, and the spin assembly distribution over the relaxation time depends on the defect number and

  5. Probing Nuclear Spin Effects on Electronic Spin Coherence via EPR Measurements of Vanadium(IV) Complexes.

    Science.gov (United States)

    Graham, Michael J; Krzyaniak, Matthew D; Wasielewski, Michael R; Freedman, Danna E

    2017-07-17

    Quantum information processing (QIP) has the potential to transform numerous fields from cryptography, to finance, to the simulation of quantum systems. A promising implementation of QIP employs unpaired electronic spins as qubits, the fundamental units of information. Though molecular electronic spins offer many advantages, including chemical tunability and facile addressability, the development of design principles for the synthesis of complexes that exhibit long qubit superposition lifetimes (also known as coherence times, or T 2 ) remains a challenge. As nuclear spins in the local qubit environment are a primary cause of shortened superposition lifetimes, we recently conducted a study which employed a modular spin-free ligand scaffold to place a spin-laden propyl moiety at a series of fixed distances from an S = 1 / 2 vanadium(IV) ion in a series of vanadyl complexes. We found that, within a radius of 4.0(4)-6.6(6) Å from the metal center, nuclei did not contribute to decoherence. To assess the generality of this important design principle and test its efficacy in a different coordination geometry, we synthesized and investigated three vanadium tris(dithiolene) complexes with the same ligand set employed in our previous study: K 2 [V(C 5 H 6 S 4 ) 3 ] (1), K 2 [V(C 7 H 6 S 6 ) 3 ] (2), and K 2 [V(C 9 H 6 S 8 ) 3 ] (3). We specifically interrogated solutions of these complexes in DMF-d 7 /toluene-d 8 with pulsed electron paramagnetic resonance spectroscopy and electron nuclear double resonance spectroscopy and found that the distance dependence present in the previously synthesized vanadyl complexes holds true in this series. We further examined the coherence properties of the series in a different solvent, MeCN-d 3 /toluene-d 8 , and found that an additional property, the charge density of the complex, also affects decoherence across the series. These results highlight a previously unknown design principle for augmenting T 2 and open new pathways for the

  6. EPR spin probe investigation of irradiated wheat, rice and sunflower seeds

    Energy Technology Data Exchange (ETDEWEB)

    Paktas, Dilek Dadayl [Department of Physics, Faculty of Art and Science, Zonguldak Karaelmas University, 67100 Zonguldak (Turkey)]. E-mail: dadayli@karaelmas.edu.tr; Suennetcioglu, M. Maral [Department of Physics Engineering, Hacettepe University, 06532 Beytepe, Ankara (Turkey)

    2007-01-15

    TEMPO and 4-nitro-TEMPO spin probes were used to monitor dose-dependent changes in the EPR spectra of irradiated wheat and rice embryos and sunflower embryo parts. Rice embryos were studied in the 233-293 K temperature range using 4-nitro-TEMPO. TEMPAMINE, TEMPYO and DTBN spin probes were also studied for their applicability in the determination of irradiated seeds. All the recorded spectra were simulated, and spectral parameters and partition of the probes among various domains were determined. Despite the contribution of the signal from extracellular regions, it was possible to detect the changes in the water/lipid ratios with dose. The hydrophilic character of the probe alone was not sufficient to distinguish the different doses of irradiation. Line widths and rotational correlation times of various domains within embryo also play an important role. Partition after dehydration was another measure in the selection of the suitable probes for irradiation studies. Better results were obtained in dehydrated embryos for the probes preferring lipid bodies.

  7. EPR-based distance measurements at ambient temperature

    Science.gov (United States)

    Krumkacheva, Olesya; Bagryanskaya, Elena

    2017-07-01

    Pulsed dipolar (PD) EPR spectroscopy is a powerful technique allowing for distance measurements between spin labels in the range of 2.5-10.0 nm. It was proposed more than 30 years ago, and nowadays is widely used in biophysics and materials science. Until recently, PD EPR experiments were limited to cryogenic temperatures (T biomolecules, the influence of a linker between the spin probe and biomolecule, and future opportunities.

  8. EPR spectroscopy of a family of Cr(III) 7M(II) (M = Cd, Zn, Mn, Ni) "wheels": studies of isostructural compounds with different spin ground states

    DEFF Research Database (Denmark)

    Piligkos, Stergios; Weihe, Høgni; Bill, Eckhard

    2009-01-01

    examples of high nuclearity polymetallic systems where detailed information on the spin-Hamiltonian parameters of the ground and excited spin states is observed. We interpret the EPR spectra by use of restricted size effective subspaces obtained by the rigorous solution of spin-Hamiltonians of dimension up...

  9. Insight into the labeling mechanism of acceleration selective arterial spin labeling

    DEFF Research Database (Denmark)

    Schmid, Sophie; Petersen, Esben T; Van Osch, Matthias J P

    2017-01-01

    OBJECTIVES: Acceleration selective arterial spin labeling (AccASL) is a spatially non-selective labeling technique, used in traditional ASL methods, which labels spins based on their flow acceleration rather than spatial localization. The exact origin of the AccASL signal within the vasculature......-ASL, combined AccASL and VS-ASL signal, and signal from one module with crushing from the other. RESULTS: The label created with AccASL has an overlap of approximately 50% in the vascular region with VS-ASL, but also originates from smaller vessels closer to the capillaries. CONCLUSION: AccASL is able to label...

  10. Consensus structures of the Mo(v) sites of sulfite-oxidizing enzymes derived from variable frequency pulsed EPR spectroscopy, isotopic labelling and DFT calculations.

    Science.gov (United States)

    Enemark, John H

    2017-10-10

    Sulfite-oxidizing enzymes from eukaryotes and prokaryotes have five-coordinate distorted square-pyramidal coordination about the molybdenum atom. The paramagnetic Mo(v) state is easily generated, and over the years four distinct CW EPR spectra have been identified, depending upon enzyme source and the reaction conditions, namely high and low pH (hpH and lpH), phosphate inhibited (P i ) and sulfite (or blocked). Extensive studies of these paramagnetic forms of sulfite-oxidizing enzymes using variable frequency pulsed electron spin echo (ESE) spectroscopy, isotopic labeling and density functional theory (DFT) calculations have led to the consensus structures that are described here. Errors in some of the previously proposed structures are corrected.

  11. α-Tocopherol impact on oxy-radical induced free radical decomposition of DMSO: Spin trapping EPR and theoretical studies

    International Nuclear Information System (INIS)

    Jerzykiewicz, Maria; Cwielag-Piasecka, Irmina; Witwicki, Maciej; Jezierski, Adam

    2011-01-01

    Graphical abstract: α-Tocopherol inhibits the oxidation of ·CH 3 to ·OCH 3 . Display Omitted Highlights: → α-Tocopherol does not inhibit the oxidation of DMSO to ·CH 3 . → α-Tocopherol inhibits the oxidation of ·CH 3 to ·OCH 3 . → α-Tocopherol does not inhibit the oxidation of PBN. → The structures of observed spin adducts were theoretically confirmed. - Abstract: EPR spin trapping and theoretical methods such as density functional theory (DFT) as well as combined DFT and quadratic configuration interaction approach (DFT/QCISD) were used to identify the radicals produced in the reaction of oxy-radicals and dimethyl sulfoxide (DMSO) in the presence and absence of α-tocopherol. Additionally, the mixtures of α-tocopherol with linolenic acid and glyceryl trilinoleate as well as bioglycerols (glycerol fractions from biodiesel production) were tested. α-Tocopherol inhibited oxidation of the main decomposition product of DMSO, ·CH 3 to ·OCH 3 but did not prevent the transformation process of N-t-butyl-α-phenylnitrone (PBN) into 2-methyl-2-nitrosopropane (MNP). Theoretical investigations confirmed the structures of proposed spin adducts and allowed to correlate the EPR parameters observed in the experiment with the spin adducts electronic structure.

  12. {alpha}-Tocopherol impact on oxy-radical induced free radical decomposition of DMSO: Spin trapping EPR and theoretical studies

    Energy Technology Data Exchange (ETDEWEB)

    Jerzykiewicz, Maria, E-mail: Mariaj@wchuwr.pl [Faculty of Chemistry, Wroclaw University, 14 F. Joliot-Curie St., 50-383 Wroclaw (Poland); Cwielag-Piasecka, Irmina; Witwicki, Maciej; Jezierski, Adam [Faculty of Chemistry, Wroclaw University, 14 F. Joliot-Curie St., 50-383 Wroclaw (Poland)

    2011-05-26

    Graphical abstract: {alpha}-Tocopherol inhibits the oxidation of {center_dot}CH{sub 3} to {center_dot}OCH{sub 3}. Display Omitted Highlights: {yields} {alpha}-Tocopherol does not inhibit the oxidation of DMSO to {center_dot}CH{sub 3}. {yields} {alpha}-Tocopherol inhibits the oxidation of {center_dot}CH{sub 3} to {center_dot}OCH{sub 3}. {yields} {alpha}-Tocopherol does not inhibit the oxidation of PBN. {yields} The structures of observed spin adducts were theoretically confirmed. - Abstract: EPR spin trapping and theoretical methods such as density functional theory (DFT) as well as combined DFT and quadratic configuration interaction approach (DFT/QCISD) were used to identify the radicals produced in the reaction of oxy-radicals and dimethyl sulfoxide (DMSO) in the presence and absence of {alpha}-tocopherol. Additionally, the mixtures of {alpha}-tocopherol with linolenic acid and glyceryl trilinoleate as well as bioglycerols (glycerol fractions from biodiesel production) were tested. {alpha}-Tocopherol inhibited oxidation of the main decomposition product of DMSO, {center_dot}CH{sub 3} to {center_dot}OCH{sub 3} but did not prevent the transformation process of N-t-butyl-{alpha}-phenylnitrone (PBN) into 2-methyl-2-nitrosopropane (MNP). Theoretical investigations confirmed the structures of proposed spin adducts and allowed to correlate the EPR parameters observed in the experiment with the spin adducts electronic structure.

  13. The rotational mobility of spin labels in wool creatine depending on temperature, humidity and deformation

    International Nuclear Information System (INIS)

    Bobodzhanov, P.Kh.; Yusupov, I.Kh.; Marupov, R.

    2001-01-01

    Present article is devoted to study of rotational mobility of spin labels in wool creatine depending on temperature, humidity and deformation. The experimental data of study of structure and molecular mobility of wool creatine modified by spin labels was considered.

  14. Free radical generation induced by ultrasound in red wine and model wine: An EPR spin-trapping study

    OpenAIRE

    Zhang, Quing An; Shen, Yuan; Fan, Xue-Hui; García-Martín, Juan Francisco; Wang, Xi; Song, Yun

    2015-01-01

    © 2015 Published by Elsevier B.V. Direct evidence for the formation of 1-hydroxylethyl radicals by ultrasound in red wine and air-saturated model wine is presented in this paper. Free radicals are thought to be the key intermediates in the ultrasound processing of wine, but their nature has not been established yet. Electron paramagnetic resonance (EPR) spin trapping with 5,5-dimethyl-l-pyrrolin N-oxide (DMPO) was used for the detection of hydroxyl free radicals and 1-hydroxylethyl free radic...

  15. Circular dichroism and site-directed spin labeling reveal structural and dynamical features of high-pressure states of myoglobin

    Science.gov (United States)

    Lerch, Michael T.; Horwitz, Joseph; McCoy, John; Hubbell, Wayne L.

    2013-01-01

    Excited states of proteins may play important roles in function, yet are difficult to study spectroscopically because of their sparse population. High hydrostatic pressure increases the equilibrium population of excited states, enabling their characterization [Akasaka K (2003) Biochemistry 42:10875–85]. High-pressure site-directed spin-labeling EPR (SDSL-EPR) was developed recently to map the site-specific structure and dynamics of excited states populated by pressure. To monitor global secondary structure content by circular dichroism (CD) at high pressure, a modified optical cell using a custom MgF2 window with a reduced aperture is introduced. Here, a combination of SDSL-EPR and CD is used to map reversible structural transitions in holomyoglobin and apomyoglobin (apoMb) as a function of applied pressure up to 2 kbar. CD shows that the high-pressure excited state of apoMb at pH 6 has helical content identical to that of native apoMb, but reversible changes reflecting the appearance of a conformational ensemble are observed by SDSL-EPR, suggesting a helical topology that fluctuates slowly on the EPR time scale. Although the high-pressure state of apoMb at pH 6 has been referred to as a molten globule, the data presented here reveal significant differences from the well-characterized pH 4.1 molten globule of apoMb. Pressure-populated states of both holomyoglobin and apoMb at pH 4.1 have significantly less helical structure, and for the latter, that may correspond to a transient folding intermediate. PMID:24248390

  16. Electron spin relaxation governed by Raman processes both for Cu2+ ions and carbonate radicals in KHCO3 crystals: EPR and electron spin echo studies

    Science.gov (United States)

    Hoffmann, Stanislaw K.; Goslar, Janina; Lijewski, Stefan

    2012-08-01

    EPR studies of Cu2+ and two free radicals formed by γ-radiation were performed for KHCO3 single crystal at room temperature. From the rotational EPR results we concluded that Cu2+ is chelated by two carbonate molecules in a square planar configuration with spin-Hamiltonian parameters g|| = 2.2349 and A|| = 18.2 mT. Free radicals were identified as neutral HOCOrad with unpaired electron localized on the carbon atom and a radical anion CO3·- with unpaired electron localized on two oxygen atoms. The hyperfine splitting of the EPR lines by an interaction with a single hydrogen atom of HOCOrad was observed with isotropic coupling constants ao = 0.31 mT. Two differently oriented radical sites were identified in the crystal unit cell. Electron spin-lattice relaxation measured by electron spin echo methods shows that both Cu2+ and free radicals relax via two-phonon Raman processes with almost the same relaxation rate. The temperature dependence of the relaxation rate 1/T1 is well described with the effective Debye temperature ΘD = 175 K obtained from a fit to the Debye-type phonon spectrum. We calculated a more realistic Debye temperature value from available elastic constant values of the crystal as ΘD = 246 K. This ΘD-value and the Debye phonon spectrum approximation give a much worse fit to the experimental results. Possible contributions from a local mode or an optical mode are considered and it is suggested that the real phonon spectrum should be used for the relaxation data interpretation. It is unusual that free radicals in KHCO3 relax similarly to the well localized Cu2+ ions, which suggests a small destruction of the host crystal lattice by the ionizing irradiation allowing well coupling between radical and lattice dynamics.

  17. EPR-based distance measurements at ambient temperature.

    Science.gov (United States)

    Krumkacheva, Olesya; Bagryanskaya, Elena

    2017-07-01

    Pulsed dipolar (PD) EPR spectroscopy is a powerful technique allowing for distance measurements between spin labels in the range of 2.5-10.0nm. It was proposed more than 30years ago, and nowadays is widely used in biophysics and materials science. Until recently, PD EPR experiments were limited to cryogenic temperatures (TEPR as well as other approaches based on EPR (e.g., relaxation enhancement; RE). In this paper, we review the features of PD EPR and RE at ambient temperatures, in particular, requirements on electron spin phase memory time, ways of immobilization of biomolecules, the influence of a linker between the spin probe and biomolecule, and future opportunities. Copyright © 2017 Elsevier Inc. All rights reserved.

  18. DNA with Parallel Strand Orientation: A Nanometer Distance Study with Spin Labels in the Watson-Crick and the Reverse Watson-Crick Double Helix.

    Science.gov (United States)

    Wunnicke, Dorith; Ding, Ping; Yang, Haozhe; Seela, Frank; Steinhoff, Heinz-Jürgen

    2015-10-29

    Parallel-stranded (ps) DNA characterized by its sugar-phosphate backbones pointing in the same direction represents an alternative pairing system to antiparallel-stranded (aps) DNA with the potential to inhibit transcription and translation. 25-mer oligonucleotides were selected containing only dA·dT base pairs to compare spin-labeled nucleobase distances over a range of 10 or 15 base pairs in ps DNA with those in aps DNA. By means of the copper(I)-catalyzed Huisgen-Meldal-Sharpless alkyne-azide cycloaddition, the spin label 4-azido-2,2,6,6-tetramethylpiperidine-1-oxyl was clicked to 7-ethynyl-7-deaza-2'-deoxyadenosine or 5-ethynyl-2'-deoxyuridine to yield 25-mer oligonucleotides incorporating two spin labels. The interspin distances between spin labeled residues were determined by pulse EPR spectroscopy. The results reveal that in ps DNA these distances are between 5 and 10% longer than in aps DNA when the labeled DNA segment is located near the center of the double helix. The interspin distance in ps DNA becomes shorter compared with aps DNA when one of the spin labels occupies a position near the end of the double helix.

  19. Electron Spin Resonance Studies of Carbonic Anhydrase: Transition Metal Ions and Spin-Labeled Sulfonamides*

    Science.gov (United States)

    Taylor, June S.; Mushak, Paul; Coleman, Joseph E.

    1970-01-01

    Electron spin resonance (esr) spectra of Cu(II) and Co(II) carbonic anhydrase, and a spin-labeled sulfonamide complex of the Zn(II) enzyme, are reported. The coordination geometry of Cu(II) bound in the enzyme appears to have approximately axial symmetry. Esr spectra of enzyme complexes with metal-binding anions also show axial symmetry and greater covalency, in the order ethoxzolamide cyanide complex suggests the presence of two, and probably three, equivalent nitrogen ligands from the protein. Esr spectra of the Co(II) enzyme and its complexes show two types of Co(II) environment, one typical of the native enzyme and the 1:1 CN- complex, and one typical of a 2:1 CN- complex. Co(II) in the 2:1 complex appears to be low-spin and probably has a coordination number of 5. Binding of a spin-labeled sulfonamide to the active center immobilizes the free radical. The similarity of the esr spectra of spin-labeled Zn(II) and Co(II) carbonic anhydrases suggests that the conformation at the active center is similar in the two metal derivatives. PMID:4320976

  20. N-tert-butylmethanimine N-oxide is an efficient spin-trapping probe for EPR analysis of glutathione thiyl radical

    Science.gov (United States)

    Scott, Melanie J.; Billiar, Timothy R.; Stoyanovsky, Detcho A.

    2016-01-01

    The electron spin resonance (EPR) spin-trapping technique allows detection of radical species with nanosecond half-lives. This technique is based on the high rates of addition of radicals to nitrones or nitroso compounds (spin traps; STs). The paramagnetic nitroxides (spin-adducts) formed as a result of reactions between STs and radical species are relatively stable compounds whose EPR spectra represent “structural fingerprints” of the parent radical species. Herein we report a novel protocol for the synthesis of N-tert-butylmethanimine N-oxide (EBN), which is the simplest nitrone containing an α-H and a tertiary α′-C atom. We present EPR spin-trapping proof that: (i) EBN is an efficient probe for the analysis of glutathione thiyl radical (GS•); (ii) β-cyclodextrins increase the kinetic stability of the spin-adduct EBN/•SG; and (iii) in aqueous solutions, EBN does not react with superoxide anion radical (O2−•) to form EBN/•OOH to any significant extent. The data presented complement previous studies within the context of synthetic accessibility to EBN and efficient spin-trapping analysis of GS•. PMID:27941944

  1. Pulsed EPR Spin-probe study of intracellular glasses in seed and pollen

    NARCIS (Netherlands)

    Buitink, J.; Dzuba, S.A.; Hoekstra, F.A.; Tsvetkov, Y.D.

    2000-01-01

    EPR spectra of 3-carboxy-proxyl (CP) in dry biological tissues exhibited a temperature-dependent change in the principal value A′zz of the hyperfine interaction tensor. The A′zz value changed sharply at a particular temperature that was dependent on water content. At elevated water contents, the

  2. In Vivo EPR Resolution Enhancement Using Techniques Known from Quantum Computing Spin Technology.

    Science.gov (United States)

    Rahimi, Robabeh; Halpern, Howard J; Takui, Takeji

    2017-01-01

    A crucial issue with in vivo biological/medical EPR is its low signal-to-noise ratio, giving rise to the low spectroscopic resolution. We propose quantum hyperpolarization techniques based on 'Heat Bath Algorithmic Cooling', allowing possible approaches for improving the resolution in magnetic resonance spectroscopy and imaging.

  3. Pulsed EPR study of spin coherence time of P donors in isotopically controlled Si

    International Nuclear Information System (INIS)

    Abe, Eisuke; Isoya, Junichi; Itoh, Kohei M.

    2006-01-01

    We investigate spin coherence time of electrons bound to phosphorus donors in silicon single crystals. The samples are isotopically controlled so that they may possess various concentrations (from 4.7% to 99.2%) of 29 Si, which is the only non-zero-spin stable isotope of silicon. The orientation dependence of electron-spin coherence times are presented, and electron spin echo envelope modulation is analyzed in time-frequency space

  4. Factors affecting the line-shape of the EPR signal of high-spin Fe(III) in soybean lipoxygenase-1

    NARCIS (Netherlands)

    Slappendel, S.; Aasa, R.; Malmström, B.G.; Verhagen, J.; Veldink, G.A.; Vliegenthart, J.F.G.

    1982-01-01

    The yellow form of soybean lipoxygenase-1 (linoleate:oxygen oxidoreductase, EC 1.13.11.12), obtained upon addition of one molar equivalent of acid (13--HPOD) to the native enzyme, shows a complex EPR signal around g 6 which results from contributions of different high-spin Fe(III) species with

  5. Spin-locking and cross-polarization under magic-angle spinning of uniformly labeled solids.

    Science.gov (United States)

    Hung, Ivan; Gan, Zhehong

    2015-07-01

    Spin-locking and cross-polarization under magic-angle spinning are investigated for uniformly (13)C and (15)N labeled solids. In particular, the interferences from chemical shift anisotropy, and (1)H heteronuclear and (13)C homonuclear dipolar couplings are identified. The physical origin of these interferences provides guidelines for selecting the best (13)C and (15)N polarization transfer rf fields. Optimal settings for both the zero- and double-quantum cross-polarization transfer mechanisms are recommended. Copyright © 2015 Elsevier Inc. All rights reserved.

  6. Demonstration using EPR spin-trapping of an oxygen-dependent, carbon-centered free radical generated by soybean lipoxygenase

    International Nuclear Information System (INIS)

    Carpenter, M.F.; Smith, F.L.

    1986-01-01

    Purified prostaglandin synthase produces a carbon-centered, oxygen-dependent free radical which they have shown forms a spin-trapped adduct with 4-POBN and has characteristic hyperfine spin coupling constants (hfsc). As production of this radical is cyclooxygenase-dependent, additional studies on radical production were done using soybean lipoxygenase. The latter generates a lipid substrate-derived free radical trapped by the EPR spin trap 4-POBN [α-(4-pyridyl 1-oxide)N-tert-butyl nitrone]. With linoleate as substrate, the hfsc are a/sub N/ = 15.5 G, a/sub β//sup H/ = 2.7 G. This signal is inhibited by ETYA, various antioxidants and heat inactivation of the enzyme. Additional hfsc are not seen when the enzyme is incubated in an 17 O 2 atmosphere, but the signal is inhibited by anaerobeosis. Substitution of 13 C 18 carbon free fatty acids from Chlorella pyrenoisdosa for linoleate produces 2 new lines for each of the original 6 observed with 12 C substrate; the new spectrum has hfsc of a/sub N/ = 16.0 G, a/sub β//sup H/ = 2.4 G, a/sub β/ 13 C = 4.2 G. This demonstrates that the radical is carbon centered and oxygen-dependent and appears not to be the same radical formed by enzymic hydrogen abstraction from the lipid substrate. This radical and the prostaglandin synthase-dependent radical appear to be nearly identical

  7. Free radical generation induced by ultrasound in red wine and model wine: An EPR spin-trapping study.

    Science.gov (United States)

    Zhang, Qing-An; Shen, Yuan; Fan, Xue-Hui; Martín, Juan Francisco García; Wang, Xi; Song, Yun

    2015-11-01

    Direct evidence for the formation of 1-hydroxylethyl radicals by ultrasound in red wine and air-saturated model wine is presented in this paper. Free radicals are thought to be the key intermediates in the ultrasound processing of wine, but their nature has not been established yet. Electron paramagnetic resonance (EPR) spin trapping with 5,5-dimethyl-l-pyrrolin N-oxide (DMPO) was used for the detection of hydroxyl free radicals and 1-hydroxylethyl free radicals. Spin adducts of hydroxyl free radicals were detected in DMPO aqueous solution after sonication while 1-hydroxylethyl free radical adducts were observed in ultrasound-processed red wine and model wine. The latter radical arose from ethanol oxidation via the hydroxyl radical generated by ultrasound in water, thus providing the first direct evidence of the formation of 1-hydroxylethyl free radical in red wine exposed to ultrasound. Finally, the effects of ultrasound frequency, ultrasound power, temperature and ultrasound exposure time were assessed on the intensity of 1-hydroxylethyl radical spin adducts in model wine. Copyright © 2015 Elsevier B.V. All rights reserved.

  8. Spin-labelled derivatives of cardiotonic steroids as tools for characterization of the extracellular entrance to the Na+ ,K+ -ATPase binding site.

    Science.gov (United States)

    Guo, Jin-Hua; Jiang, Ren-Wang; Andersen, Jacob Lauwring; Esmann, Mikael; Fedosova, Natalya U

    2018-04-24

    The information obtained from crystallized complexes of the Na + ,K + -ATPase with cardiotonic steroids (CTS) is not sufficient to explain differences in the inhibitory properties of CTS such as stereoselectivity of CTS-binding or effect of glycosylation on the preference to enzyme isoforms. The uncertainty is related to the spacial organization of the hydrophilic cavity at the entrance of the CTS-binding site. Therefore, there is a need to supplement the crystallographic description with data obtained in aqueous solution, where molecules have significant degree of flexibility. This work addresses the applicability of the electron paramagnetic resonance (EPR) method for the purpose. We have designed and synthesized spin-labelled compounds based on the cinobufagin steroid core. The length of the spacer arms between the steroid core and the nitroxide group determines the position of the reporting group (N-O) confined to the binding site. High affinity to Na + ,K + -ATPase is inferred from their ability to inhibit enzymatic activity. The differences between the EPR spectra in the absence and presence of high ouabain concentrations identify the signature peaks originating from the fraction of the spin-labels bound within the ouabain site. The degree of perturbations of the EPR spectra depends on the length of the spacer arm. Docking of the compounds into the CTS-site suggests which elements of the protein structure might be responsible for interference with the spin-label (e.g. steric clashes or immobilization). Thus, the method is suitable for gathering information on the cavity leading to the CTS-binding site in Na + ,K + -ATPase in all conformations with high affinity to CTS. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

  9. Classical and quantum 'EPR'-spin correlations in the triplet state

    International Nuclear Information System (INIS)

    Barut, A.O.; Bozic, M.

    1987-01-01

    Quantum correlations and joint probabilities in the triplet state as well as the correlations of components of two correlated classical spin vectors, are evaluated. Correlations in the states with |S tot z |=1 are different from correlations in the state with S tot z =0 which may serve to distinguish different states of the triplet. As in the singlet case, we can reproduce quantum correlations by correlated classical spin vectors which also provide a precision of the notion of ''parallel spins''. Triplet state correlations could in principle be measured, for example, in the decay reaction J/ψ → e + e - for which there is a sufficiently large branching ratio. (author). 12 refs

  10. Superselective pseudo-continuous arterial spin labeling angiography

    Energy Technology Data Exchange (ETDEWEB)

    Jensen-Kondering, Ulf [Department of Radiology and Neuroradiology, University Medical Center Schleswig-Holstein, Kiel (Germany); Lindner, Thomas, E-mail: thomas.lindner@uksh.de [Department of Radiology and Neuroradiology, University Medical Center Schleswig-Holstein, Kiel (Germany); Osch, Matthias J.P. van [C. J. Gorter Center for High Field MRI, Department of Radiology, Leiden University Medical Center, Leiden (Netherlands); Rohr, Axel; Jansen, Olav [Department of Radiology and Neuroradiology, University Medical Center Schleswig-Holstein, Kiel (Germany); Helle, Michael [Department of Radiology and Neuroradiology, University Medical Center Schleswig-Holstein, Kiel (Germany); Now with Philips GmbH Innovative Technologies, Research Laboratories, Hamburg (Germany)

    2015-09-15

    Highlights: • Superselective arterial spin labeling was capable of acquiring angiograms of individually selected arteries. • Image quality was similar compared with a routinely used time-of-flight angiography. • Superselective arterial spin labeling was utilized in patients with arterio-venous malformations and made it possible to visualize individual feeding vessels in a complete non-invasive way - Abstract: Purpose: To evaluate the utility of a novel non-contrast enhanced, vessel-selective magnetic resonance angiography (MRA) approach based on superselective pseudo-continuous arterial spin labeling (ASL) for the morphologic assessment of intracranial arteries when compared to a clinically used time-of-flight (TOF) MRA. Materials and methods: Three sets of selective ASL angiographies (right and left internal carotid artery, basilar artery) as well as one TOF data set were obtained from each of the five volunteers included in this study on a clinical 1.5T system. The depiction of arterial segments as well as their delineation was evaluated and independently analyzed by two radiologists. Additionally, the ASL angiography approach was performed in two patients suffering from arterio-venous malformations (AVM) in order to illustrate potential applications in a clinical setting. Results: In both angiography techniques, intracranial arteries and their segments (distal branches up to A5 segments of the anterior cerebral arteries, M8 segments of the middle cerebral arteries, and P5 segments of the posterior cerebral arteries) were continuously depicted with excellent inter-reader agreement (κ > 0.81). In AVM patients, reconstructed images of the TOF angiography presented similar information about the size and shape of the AVM as did superselective ASL angiography. In addition, the acquired ASL angiograms of selected vessels allowed assessing the blood supply of individually labeled arteries to the AVM which could also be confirmed by digital subtraction angiography

  11. Superselective pseudo-continuous arterial spin labeling angiography

    International Nuclear Information System (INIS)

    Jensen-Kondering, Ulf; Lindner, Thomas; Osch, Matthias J.P. van; Rohr, Axel; Jansen, Olav; Helle, Michael

    2015-01-01

    Highlights: • Superselective arterial spin labeling was capable of acquiring angiograms of individually selected arteries. • Image quality was similar compared with a routinely used time-of-flight angiography. • Superselective arterial spin labeling was utilized in patients with arterio-venous malformations and made it possible to visualize individual feeding vessels in a complete non-invasive way - Abstract: Purpose: To evaluate the utility of a novel non-contrast enhanced, vessel-selective magnetic resonance angiography (MRA) approach based on superselective pseudo-continuous arterial spin labeling (ASL) for the morphologic assessment of intracranial arteries when compared to a clinically used time-of-flight (TOF) MRA. Materials and methods: Three sets of selective ASL angiographies (right and left internal carotid artery, basilar artery) as well as one TOF data set were obtained from each of the five volunteers included in this study on a clinical 1.5T system. The depiction of arterial segments as well as their delineation was evaluated and independently analyzed by two radiologists. Additionally, the ASL angiography approach was performed in two patients suffering from arterio-venous malformations (AVM) in order to illustrate potential applications in a clinical setting. Results: In both angiography techniques, intracranial arteries and their segments (distal branches up to A5 segments of the anterior cerebral arteries, M8 segments of the middle cerebral arteries, and P5 segments of the posterior cerebral arteries) were continuously depicted with excellent inter-reader agreement (κ > 0.81). In AVM patients, reconstructed images of the TOF angiography presented similar information about the size and shape of the AVM as did superselective ASL angiography. In addition, the acquired ASL angiograms of selected vessels allowed assessing the blood supply of individually labeled arteries to the AVM which could also be confirmed by digital subtraction angiography

  12. EPR investigation of zinc/iodine exchange between propargyl iodides and diethylzinc: detection of propargyl radical by spin trapping.

    Science.gov (United States)

    Maury, Julien; Jammi, Suribabu; Vibert, François; Marque, Sylvain R A; Siri, Didier; Feray, Laurence; Bertrand, Michèle

    2012-10-19

    The production of propargyl radicals in the reaction of dialkylzincs with propargyl iodides in nondegassed medium was investigated by EPR using tri-tert-butylnitrosobenzene (TTBNB) as a spin trap. The radical mechanism and the nature of the observed species were confirmed by the trapping of propargyl radicals generated by an alternative pathway: i.e., upon irradiation of propargyl iodides in the presence of hexa-n-butyldistannane. In dialkylzinc-mediated experiments a high concentration of adduct was instantaneously observed, whereas no spontaneous production of spin adduct was detected in a blank experiment performed with the propargylic iodide and TTBNB in the absence of diethylzinc. Under irradiation in the presence of distannane, two different species were observed at the very beginning of the irradiation; the nitroxide resulting from the trapping of propargyl radical at the propargyl carbon remained the only species detected after irradiating for several minutes. The absence of adducts resulting from the trapping of allenyl canonical forms was supported by DFT calculations and by the preparation of an authentic sample.

  13. Identification of mitochondrial electron transport chain-mediated NADH radical formation by EPR spin-trapping techniques.

    Science.gov (United States)

    Matsuzaki, Satoshi; Kotake, Yashige; Humphries, Kenneth M

    2011-12-20

    The mitochondrial electron transport chain (ETC) is a major source of free radical production. However, due to the highly reactive nature of radical species and their short lifetimes, accurate detection and identification of these molecules in biological systems is challenging. The aim of this investigation was to determine the free radical species produced from the mitochondrial ETC by utilizing EPR spin-trapping techniques and the recently commercialized spin-trap, 5-(2,2-dimethyl-1,3-propoxycyclophosphoryl)-5-methyl-1-pyrroline N-oxide (CYPMPO). We demonstrate that this spin-trap has the preferential quality of having minimal mitochondrial toxicity at concentrations required for radical detection. In rat heart mitochondria and submitochondrial particles supplied with NADH, the major species detected under physiological pH was a carbon-centered radical adduct, indicated by markedly large hyperfine coupling constant with hydrogen (a(H) > 2.0 mT). In the presence of the ETC inhibitors, the carbon-centered radical formation was increased and exhibited NADH concentration dependency. The same carbon-centered radical could also be produced with the NAD biosynthesis precursor, nicotinamide mononucleotide, in the presence of a catalytic amount of NADH. The results support the conclusion that the observed species is a complex I derived NADH radical. The formation of the NADH radical could be blocked by hydroxyl radical scavengers but not SOD. In vitro experiments confirmed that an NADH-radical is readily formed by hydroxyl radical but not superoxide anion, further implicating hydroxyl radical as an upstream mediator of NADH radical production. These findings demonstrate the identification of a novel mitochondrial radical species with potential physiological significance and highlight the diverse mechanisms and sites of production within the ETC.

  14. Kinetics of rapid covalent bond formation of aniline with humic acid: ESR investigations with nitroxide spin labels

    Science.gov (United States)

    Glinka, Kevin; Matthies, Michael; Theiling, Marius; Hideg, Kalman; Steinhoff, Heinz-Jürgen

    2016-04-01

    Sulfonamide antibiotics used in livestock farming are distributed to farmland by application of slurry as fertilizer. Previous work suggests rapid covalent binding of the aniline moiety to humic acids found in soil. In the current work, kinetics of this binding were measured in X-band EPR spectroscopy by incubating Leonardite humic acid (LHA) with a paramagnetic aniline spin label (anilino-NO (2,5,5-Trimethyl-2-(3-aminophenyl)pyrrolidin-1-oxyl)). Binding was detected by a pronounced broadening of the spectral lines after incubation of LHA with anilino-NO. The time evolution of the amplitude of this feature was used for determining the reaction kinetics. Single- and double-exponential models were fitted to the data obtained for modelling one or two first-order reactions. Reaction rates of 0.16 min-1 and 0.012 min-1, were found respectively. Addition of laccase peroxidase did not change the kinetics but significantly enhanced the reacting fraction of anilino-NO. This EPR-based method provides a technically simple and effective method for following rapid binding processes of a xenobiotic substance to humic acids.

  15. EPR-spin probe studies of model polymers: separation of covalent cross-linking effects from hydrogen bonding effects in swelled Argonne Premium Coal samples

    Energy Technology Data Exchange (ETDEWEB)

    Spears, D.R.; Sady, W.; Tucker, D.; Kispert, L.D. (University of Alabama, Tuscaloosa, AL (United States). Chemistry Dept.)

    The swelling behaviour of 2-12% cross-linked polystyrene-divinylbenzene (PSDVB) copolymers was examined by an EPR-spin probe technique. It was observed that the mechanism of spin probe inclusion was the intercalation into the matrix rather than diffusion into the pores. The disruption of van der Waals forces between adjacent aromatic rings appeared to be the primary mechanism for pyridine swelling of PSDVB. By comparing the data to results from coal swelling studies it was also inferred that the extent of hydrogen bonding in coal will have a much greater impact on its swelling properties than its covalently cross-linked character. 24 refs., 6 figs.

  16. Vessel encoded arterial spin labeling with cerebral perfusion: preliminary study

    International Nuclear Information System (INIS)

    Wu Bing; Xiao Jiangxi; Xie Cheng; Wang Xiaoying; Jiang Xuexiang; Wong, E.C.; Wang Jing; Guo Jia; Zhang Beiru; Zhang Jue; Fang Jing

    2008-01-01

    Objective: To evaluate a noninvasive vessel encoded imaging for selective mapping of the flow territories of the left and fight internal carotid arteries and vertebral-basilar arteries. Methods: Seven volunteers [(33.5 ± 4.1) years; 3 men, 4 women] and 6 patients [(55.2 ± 3.2) years; 2 men, 4 women] were given written informed consent approved by the institutional review board before participating in the study. A pseudo-continuous tagging pulse train is modified to encode all vessels of interest. The selectivity of this method was demonstrated. Regional perfusion imaging was developed on the same arterial spin labeling sequence. Perfusion-weighted images of the selectively labeled cerebral arteries were obtained by subtraction of the labeled from control images. The CBF values of hemisphere, white matter, and gray matter of volunteers were calculated. The vessel territories on patients were compared with DSA. The low perfusion areas were compared with high signal areas on T 2 -FLAIR. Results: High SNR maps of left carotid, right carotid, and basilar territories were generated in 8 minutes of scan time. Cerebral blood flow values measured with regional perfusion imaging in the complete hemisphere (32.6 ± 4.3) ml·min -1 · 100 g -1 , white matter (10.8 ± 0.9) ml·min -1 ·100 g -1 , and gray matter (55.6±2.9) ml·min -1 · 100 g -1 were in agreement with data in the literature. Vessel encoded imaging in patients had a good agreement with DSA. The low perfusion areas were larger than high signal areas on T 2 -FLAIR. Conclusion: We present a new method capable of evaluating both quantitatively and qualitatively the individual brain- feeding arteries in vivo. (authors)

  17. Spin transition diagram of (2Me-5Et-PyH)[Fe(Th-5Cl-Sa)2] studied by EPR

    International Nuclear Information System (INIS)

    Krupska, A.; Augustyniak-Jablokow, M.A.; Yablokov, V.Yu.; Zelentsov, V.V.

    2005-01-01

    The high-spin - low-spin transition in (2Me-5Et-PyH)[Fe(Th-5Cl-Sa) 2 ] was studied by EPR under hydrostatic pressure in the temperature range of 80-310 K. Two modifications of the low-spin complexes: low-pressure (LS-1) and high-pressure (S-2) ones were observed. The low-spin complexes are associated in domains. Under atmospheric pressure LS-1 appears or disappears at 220 K. The hydrostatic pressure shifts the transition to high temperatures. Above 410 MPa the abrupt changes of the g-factor and width ΔB of the EPR line is observed. The pressure-induced transition LS-1 - LS-2 is almost independent of T up to 275 K where under pressure 420 MPa a triple point is observed. When the pressure has been decreased the reverse transition from LS-2 to LS-1 or to high spin phase (at T > 260 K) occurs with a large hysteresis about 95 MPa. (author)

  18. A spin labelling study of immunomodulating peptidoglycan monomer and adamantyltripeptides entrapped into liposomes.

    Science.gov (United States)

    Frkanec, Ruza; Noethig-Laslo, Vesna; Vranesić, Branka; Mirosavljević, Krunoslav; Tomasić, Jelka

    2003-04-01

    The interaction of immunostimulating compounds, the peptidoglycan monomer (PGM) and structurally related adamantyltripeptides (AdTP1 and AdTP2), respectively, with phospholipids in liposomal bilayers were investigated by electron paramagnetic resonance spectroscopy. (1). The fatty acids bearing the nitroxide spin label at different positions along the acyl chain were used to investigate the interaction of tested compounds with negatively charged multilamellar liposomes. Electron spin resonance (ESR) spectra were studied at 290 and 310 K. The entrapment of the adamantyltripeptides affected the motional properties of all spin labelled lipids, while the entrapment of PGM had no effect. (2). Spin labelled PGM was prepared and the novel compound bearing the spin label attached via the amino group of diaminopimelic acid was chromatographically purified and chemically characterized. The rotational correlation time of the spin labelled molecule dissolved in buffer at pH 7.4 was studied as a function of temperature. The conformational change was observed above 300 K. The same effect was observed with the spin labelled PGM incorporated into liposomes. Such effect was not observed when the spin labelled PGM was studied at alkaline pH, probably due to the hydrolysis of PGM molecule. The study of possible interaction with liposomal membrane is relevant to the use of tested compounds incorporated into liposomes, as adjuvants in vivo.

  19. Pulse Double-Resonance EPR Techniques for the Study of Metallobiomolecules.

    Science.gov (United States)

    Cox, Nicholas; Nalepa, Anna; Pandelia, Maria-Eirini; Lubitz, Wolfgang; Savitsky, Anton

    2015-01-01

    Electron paramagnetic resonance (EPR) spectroscopy exploits an intrinsic property of matter, namely the electron spin and its related magnetic moment. This can be oriented in a magnetic field and thus, in the classical limit, acts like a little bar magnet. Its moment will align either parallel or antiparallel to the field, giving rise to different energies (termed Zeeman splitting). Transitions between these two quantized states can be driven by incident microwave frequency radiation, analogous to NMR experiments, where radiofrequency radiation is used. However, the electron Zeeman interaction alone provides only limited information. Instead, much of the usefulness of EPR is derived from the fact that the electron spin also interacts with its local magnetic environment and thus can be used to probe structure via detection of nearby spins, e.g., NMR-active magnetic nuclei and/or other electron spin(s). The latter is exploited in spin labeling techniques, an exciting new area in the development of noncrystallographic protein structure determination. Although these interactions are often smaller than the linewidth of the EPR experiment, sophisticated pulse EPR methods allow their detection. A number of such techniques are well established today and can be broadly described as double-resonance methods, in which the electron spin is used as a reporter. Below we give a brief description of pulse EPR methods, particularly their implementation at higher magnetic fields, and how to best exploit them for studying metallobiomolecules. © 2015 Elsevier Inc. All rights reserved.

  20. Application of Arterial Spin Labelling in Detecting Retinal Ischemia

    Directory of Open Access Journals (Sweden)

    Ehsan Vaghefi

    2017-12-01

    Full Text Available Purpose: Here, we have tried to quantify the chorioretinal blood perfusion in patients who are clinically identified to be suffering from retinal ischemia using arterial spin labelling (ASL MRI. Method: Four participants, diagnosed with retinal ischemia based on their structural OCT and angiography test, were then scanned using anatomical MRI as well as ASL. We optimized MR parameters to maximize resolution and target fixation, blinking, and breathing ques to minimize motion artifacts. Results: Participants had a maximum of ∼50 mL/100 mL/min of blood perfusion, which is below the normal values of ∼200 mL/100 mL/min. It also appeared that thinning of the choroid contributes more to the measured decreased chorioretinal perfusion, compared to slowed arterial filling time. Conclusion: Decreased chorioretinal perfusion is a multifactorial event and has been implicated in several posterior eye pathologies. Based on our current results, it seems that ischemia of the eye could be due to anatomy (tissue volume and/or functionality (arterial flow.

  1. Arterial spin-labeling MR imaging of cerebral hemorrhages

    International Nuclear Information System (INIS)

    Noguchi, Tomoyuki; Nishihara, Masashi; Egashira, Yoshiaki; Azama, Shinya; Hirai, Tetsuyoshi; Kitano, Isao; Irie, Hiroyuki; Yakushiji, Yusuke; Kawashima, Masatou

    2015-01-01

    The purpose of this study is to identify the characteristics of brain perfusion measured by arterial spin-labeling magnetic resonance imaging (ASL-MRI) in cerebral hemorrhages. Brain blood flow values (CBF-ASL values) for cerebral and cerebellar hemispheres and segmented cerebral regions were measured by ASL-MRI in 19 putaminal hemorrhage patients and 20 thalamic hemorrhage patients in acute or subacute stages. We assessed the lateralities of CBF-ASL values and the relationships between CBF-ASL values and other imaging findings and clinical manifestations. Both the 19 putaminal hemorrhage patients and the 20 thalamic hemorrhage patients had significantly low CBF-ASL values of the contralateral cerebellum in subacute stage, suggesting that ASL-MRI might delineate crossed cerebellar diaschisis (CCD). Ipsilateral low CBF-ASL values were observed in frontal lobes and thalami with a putaminal hemorrhage and lentiform nuclei, temporal lobes, and parietal lobes with a thalamic hemorrhage, suggesting that ASL-MRI showed the ipsilateral cerebral diaschisis (ICD). In the putaminal hemorrhage patients, the hematoma volume negatively affected both the bilateral cerebellar and cerebral hemispheric CBF-ASL values. In the thalamic hemorrhage patients, a concomitant intraventricular hemorrhage caused low cerebral hemispheric CBF-ASL values. The use of ASL-MRI is sensitive to the perfusion abnormalities and could thus be helpful to estimate functional abnormalities in cerebral hemorrhage patients. (orig.)

  2. Arterial spin-labeling MR imaging of cerebral hemorrhages

    Energy Technology Data Exchange (ETDEWEB)

    Noguchi, Tomoyuki [Department of Radiology, National Center for Global Health and Medicine, Tokyo (Japan); Saga University, Department of Radiology, Faculty of Medicine and Graduate School of Medicine, Saga (Japan); Nishihara, Masashi; Egashira, Yoshiaki; Azama, Shinya; Hirai, Tetsuyoshi; Kitano, Isao; Irie, Hiroyuki [Saga University, Department of Radiology, Faculty of Medicine and Graduate School of Medicine, Saga (Japan); Yakushiji, Yusuke [Saga University, Department of Neurology, Faculty of Medicine and Graduate School of Medicine, Saga (Japan); Kawashima, Masatou [Saga University, Department of Neurosurgery, Faculty of Medicine and Graduate School of Medicine, Saga (Japan)

    2015-11-15

    The purpose of this study is to identify the characteristics of brain perfusion measured by arterial spin-labeling magnetic resonance imaging (ASL-MRI) in cerebral hemorrhages. Brain blood flow values (CBF-ASL values) for cerebral and cerebellar hemispheres and segmented cerebral regions were measured by ASL-MRI in 19 putaminal hemorrhage patients and 20 thalamic hemorrhage patients in acute or subacute stages. We assessed the lateralities of CBF-ASL values and the relationships between CBF-ASL values and other imaging findings and clinical manifestations. Both the 19 putaminal hemorrhage patients and the 20 thalamic hemorrhage patients had significantly low CBF-ASL values of the contralateral cerebellum in subacute stage, suggesting that ASL-MRI might delineate crossed cerebellar diaschisis (CCD). Ipsilateral low CBF-ASL values were observed in frontal lobes and thalami with a putaminal hemorrhage and lentiform nuclei, temporal lobes, and parietal lobes with a thalamic hemorrhage, suggesting that ASL-MRI showed the ipsilateral cerebral diaschisis (ICD). In the putaminal hemorrhage patients, the hematoma volume negatively affected both the bilateral cerebellar and cerebral hemispheric CBF-ASL values. In the thalamic hemorrhage patients, a concomitant intraventricular hemorrhage caused low cerebral hemispheric CBF-ASL values. The use of ASL-MRI is sensitive to the perfusion abnormalities and could thus be helpful to estimate functional abnormalities in cerebral hemorrhage patients. (orig.)

  3. Characterizing Resting-State Brain Function Using Arterial Spin Labeling

    Science.gov (United States)

    Jann, Kay; Wang, Danny J.J.

    2015-01-01

    Abstract Arterial spin labeling (ASL) is an increasingly established magnetic resonance imaging (MRI) technique that is finding broader applications in studying the healthy and diseased brain. This review addresses the use of ASL to assess brain function in the resting state. Following a brief technical description, we discuss the use of ASL in the following main categories: (1) resting-state functional connectivity (FC) measurement: the use of ASL-based cerebral blood flow (CBF) measurements as an alternative to the blood oxygen level-dependent (BOLD) technique to assess resting-state FC; (2) the link between network CBF and FC measurements: the use of network CBF as a surrogate of the metabolic activity within corresponding networks; and (3) the study of resting-state dynamic CBF-BOLD coupling and cerebral metabolism: the use of dynamic CBF information obtained using ASL to assess dynamic CBF-BOLD coupling and oxidative metabolism in the resting state. In addition, we summarize some future challenges and interesting research directions for ASL, including slice-accelerated (multiband) imaging as well as the effects of motion and other physiological confounds on perfusion-based FC measurement. In summary, this work reviews the state-of-the-art of ASL and establishes it as an increasingly viable MRI technique with high translational value in studying resting-state brain function. PMID:26106930

  4. Reaction between peroxynitrite and boronates: EPR spin-trapping, HPLC analyses, and quantum mechanical study of the free radical pathway

    Science.gov (United States)

    Sikora, Adam; Zielonka, Jacek; Lopez, Marcos; Dybala-Defratyka, Agnieszka; Joseph, Joy; Marcinek, Andrzej; Kalyanaraman, Balaraman

    2013-01-01

    Recently we showed that peroxynitrite (ONOO−) reacts directly and rapidly with aromatic and aliphatic boronic acids (k ≈ 106 M−1s−1). Product analyses and substrate consumption data indicated that ONOO− reacts stoichiometrically with boronates, yielding the corresponding phenols as the major product (~85–90%), and the remaining products (10–15%) were proposed to originate from free radical intermediates (phenyl and phenoxyl radicals). Here we investigated in detail the minor, free radical pathway of boronate reaction with ONOO−. The electron paramagnetic resonance (EPR) spin-trapping technique was used to characterize the free radical intermediates formed from the reaction between boronates and ONOO−. Using 2-methyl-2-nitrosopropane (MNP) and 5-diethoxyphosphoryl-5-methyl-1-pyrroline-N-oxide (DEPMPO) spin traps, phenyl radicals were trapped and detected. Although phenoxyl radicals were not detected, the positive effects of molecular oxygen, and inhibitory effects of hydrogen atom donors (acetonitrile, and 2-propanol) and general radical scavengers (GSH, NADH, ascorbic acid and tyrosine) on the formation of phenoxyl radical-derived nitrated product, suggest that phenoxyl radical was formed as the secondary species. We propose that the initial step of the reaction involves the addition of ONOO− to the boron atom in boronates. The anionic intermediate undergoes both heterolytic (major pathway) and homolytic (minor pathway) cleavage of the peroxy (O-O) bond to form phenol and nitrite as a major product (via a non-radical mechanism), or a radical pair PhB(OH)2O•−…•NO2 as a minor product. It is conceivable that phenyl radicals are formed by the fragmentation of PhB(OH)2O•− radical anion. According to the DFT quantum mechanical calculations, the energy barrier for the dissociation of PhB(OH)2O•− radical anion to form phenyl radicals is only a few kcal/mol, suggesting rapid and spontaneous fragmentation of PhB(OH)2O•− radical anion

  5. Conformational changes of plasma fibronectin detected upon adsorption to solid substrates: A spin-label study

    International Nuclear Information System (INIS)

    Narasimhan, C.; Lai, Chingsan

    1989-01-01

    Changes in local environment of the free sulfhydryl groups in plasma fibronectin upon adsorption of the protein to polystyrene beads have been examined by electron spin resonance (ESR) spin-label spectroscopy. The two free sulfhydryl groups per subunit of plasma fibronectin were modified chemically with an [ 15 N, 2 H]maleimide spin-label. For soluble fibronectin, both free sulfhydryl groups shown to be in confined environments as evidenced from the labeled protein exhibiting a strongly immobilized ESR spectrum as described previously using [ 14 N, 1 H]maleimide spin-labels. When the labeled protein was adsorbed to the beads, half of the strongly immobilized component was found to convert into a weakly immobilized component, a result indicating that one of the two labeled sites becomes exposed and exhibits a fast tumbling motion. Experiments conducted using various spin-labeled fibronectin fragments suggest that the newly exposed labeled site is located between the DNA-binding and the cell-binding regions of the molecule. The data obtained indicate that, upon adsorption to polystyrene beads, plasma fibronectin undergoes a conformational change through which the buried free sulfhydryl group near the cell-binding region of the molecule is exposed. This observation may have important implications regarding the expression of cell adhesive properties of the fibronectin molecule

  6. Coherence transfer and electron T1-, T2-relaxation in nitroxide spin labels

    DEFF Research Database (Denmark)

    Marsh, Derek

    2017-01-01

    -hyperfine anisotropies of isolated nitroxide spin labels. Results compatible with earlier treatments by Redfield theory are obtained without specifically evaluating matrix elements. Extension to single-transition operators for isolated nitroxides predicts electron coherence transfer by pseudosecular electron...

  7. The nature of the exchange coupling between high-spin Fe(III) heme o3 and CuBII in Escherichia coli quinol oxidase, cytochrome bo3: MCD and EPR studies.

    Science.gov (United States)

    Cheesman, Myles R; Oganesyan, Vasily S; Watmough, Nicholas J; Butler, Clive S; Thomson, Andrew J

    2004-04-07

    Fully oxidized cytochrome bo3 from Escherichia coli has been studied in its oxidized and several ligand-bound forms using electron paramagnetic resonance (EPR) and magnetic circular dichroism (MCD) spectroscopies. In each form, the spin-coupled high-spin Fe(III) heme o3 and CuB(II) ion at the active site give rise to similar fast-relaxing broad features in the dual-mode X-band EPR spectra. Simulations of dual-mode spectra are presented which show that this EPR can arise only from a dinuclear site in which the metal ions are weakly coupled by an anisotropic exchange interaction of J 1 cm-1. A variable-temperature and magnetic field (VTVF) MCD study is also presented for the cytochrome bo3 fluoride and azide derivatives. New methods are used to extract the contribution to the MCD of the spin-coupled active site in the presence of strong transitions from low-spin Fe(III) heme b. Analysis of the MCD data, independent of the EPR study, also shows that the spin-coupling within the active site is weak with J approximately 1 cm-1. These conclusions overturn a long-held view that such EPR signals in bovine cytochrome c oxidase arise from an S' = 2 ground state resulting from strong exchange coupling (J > 10(2) cm-1) within the active site.

  8. Electron spin dynamics of Ce.sup.3+./sup. ions in YAG crystals studied by pulse-EPR and pump-probe Faraday rotation

    Czech Academy of Sciences Publication Activity Database

    Azamat, Dmitry; Belykh, V.V.; Yakovlev, D.R.; Fobbe, F.; Feng, D.H.; Evers, E.; Jastrabík, Lubomír; Dejneka, Alexandr; Bayer, M.

    2017-01-01

    Roč. 96, č. 7 (2017), s. 1-10, č. článku 075160. ISSN 2469-9950 R&D Projects: GA MŠk LO1409; GA ČR GA16-22092S Institutional support: RVO:68378271 Keywords : electron spin dynamics * Ce 3+ ions * YAG crystals * pulse-EPR * Faraday rotation Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 3.836, year: 2016

  9. Biomolecular EPR spectroscopy

    CERN Document Server

    Hagen, Wilfred Raymond

    2008-01-01

    Comprehensive, Up-to-Date Coverage of Spectroscopy Theory and its Applications to Biological SystemsAlthough a multitude of books have been published about spectroscopy, most of them only occasionally refer to biological systems and the specific problems of biomolecular EPR (bioEPR). Biomolecular EPR Spectroscopy provides a practical introduction to bioEPR and demonstrates how this remarkable tool allows researchers to delve into the structural, functional, and analytical analysis of paramagnetic molecules found in the biochemistry of all species on the planet. A Must-Have Reference in an Intrinsically Multidisciplinary FieldThis authoritative reference seamlessly covers all important bioEPR applications, including low-spin and high-spin metalloproteins, spin traps and spin lables, interaction between active sites, and redox systems. It is loaded with practical tricks as well as do's and don'ts that are based on the author's 30 years of experience in the field. The book also comes with an unprecedented set of...

  10. Analysis of spin-Hamiltonian and molecular orbital coefficients of Cu2+ doped C8H11KO8 single crystal through EPR technique

    Science.gov (United States)

    Juliet sheela, K.; Krishnan, S. Radha; Shanmugam, V. M.; Subramanian, P.

    2018-04-01

    Electron paramagnetic resonance (EPR) studies have been investigated at X-band microwave frequency on Cu2+ ion incorporated into the single crystal of potassium succinate-succinic acid (KSSA) at room temperature. The angular variation of the EPR spectra has shown two magnetically in-equivalent Cu2+ sites in the KSSA single crystal system. The spin Hamiltonian parameters g and A are determined which reveals that the site I and site II occupied in rhombic and axial local field symmetry around the impurity ion. Among the two paramagnetic impurity ions, sites one occupies at substituitional position in the place of monovalent cation (K+) in the crystal whereas the other enters in its lattice interstitially by the correlation of EPR and crystal structure data. From the calculated principle values gxx, gyy, gzz and Axx, Ayy, Azz of both the sites, the admixture coefficients and molecular orbital coefficients were evaluated which gives the information of ground state wave function and types of bonding of impurity ions with the ligands.

  11. Electron paramagnetic resonance spin label titration: a novel method to investigate random and site-specific immobilization of enzymes onto polymeric membranes with different properties

    International Nuclear Information System (INIS)

    Butterfield, D. Allan; Colvin, Joshua; Liu Jiangling; Wang Jianquan; Bachas, Leonidas; Bhattacharrya, Dibakar

    2002-01-01

    The immobilization of biological molecules onto polymeric membranes to produce biofunctional membranes is used for selective catalysis, separation, analysis, and artificial organs. Normally, random immobilization of enzymes onto polymeric membranes leads to dramatic reduction in activity due to chemical reactions involved in enzyme immobilization, multiple-point binding, etc., and the extent of activity reduction is a function of membrane hydrophilicity (e.g. activity in cellulosic membrane >> polysulfone membrane). We have used molecular biology to effect site-specific immobilization of enzymes in a manner that orients the active site away from the polymeric membrane surface, thus resulting in higher enzyme activity that approaches that in solution and in increased stability of the enzyme relative to the enzyme in solution. A prediction of this site-specific method of enzyme immobilization, which in this study with subtilisin and organophosphorus hydrolase consists of a fusion tag genetically added to these enzymes and subsequent immobilization via the anti-tag antibody and membrane-bound protein A, is that the active site conformation will more closely resemble that of the enzyme in solution than is the case for random immobilization. This hypothesis was confirmed using a new electron paramagnetic resonance (EPR) spin label active site titration method that determines the amount of spin label bound to the active site of the immobilized enzyme. This value nearly perfectly matched the enzyme activity, and the results suggested: (a) a spectroscopic method for measuring activity and thus the extent of active enzyme immobilization in membrane, which may have advantages in cases where optical methods can not be used due to light scattering interference; (b) higher spin label incorporation (and hence activity) in enzymes that had been site-specifically immobilized versus random immobilization; (c) higher spin label incorporation in enzymes immobilized onto hydrophilic

  12. Characterization of KCNE1 inside Lipodisq Nanoparticles for EPR Spectroscopic Studies of Membrane Proteins.

    Science.gov (United States)

    Sahu, Indra D; Zhang, Rongfu; Dunagan, Megan M; Craig, Andrew F; Lorigan, Gary A

    2017-06-01

    EPR spectroscopic studies of membrane proteins in a physiologically relevant native membrane-bound state are extremely challenging due to the complexity observed in inhomogeneity sample preparation and dynamic motion of the spin-label. Traditionally, detergent micelles are the most widely used membrane mimetics for membrane proteins due to their smaller size and homogeneity, providing high-resolution structure analysis by solution NMR spectroscopy. However, it is often difficult to examine whether the protein structure in a micelle environment is the same as that of the respective membrane-bound state. Recently, lipodisq nanoparticles have been introduced as a potentially good membrane mimetic system for structural studies of membrane proteins. However, a detailed characterization of a spin-labeled membrane protein incorporated into lipodisq nanoparticles is still lacking. In this work, lipodisq nanoparticles were used as a membrane mimic system for probing the structural and dynamic properties of the integral membrane protein KCNE1 using site-directed spin labeling EPR spectroscopy. The characterization of spin-labeled KCNE1 incorporated into lipodisq nanoparticles was carried out using CW-EPR titration experiments for the EPR spectral line shape analysis and pulsed EPR titration experiment for the phase memory time (T m ) measurements. The CW-EPR titration experiment indicated an increase in spectral line broadening with the addition of the SMA polymer which approaches close to the rigid limit at a lipid to polymer weight ratio of 1:1, providing a clear solubilization of the protein-lipid complex. Similarly, the T m titration experiment indicated an increase in T m values with the addition of SMA polymer and approaches ∼2 μs at a lipid to polymer weight ratio of 1:2. Additionally, CW-EPR spectral line shape analysis was performed on six inside and six outside the membrane spin-label probes of KCNE1 in lipodisq nanoparticles. The results indicated significant

  13. Frequency bandwidth extension by use of multiple Zeeman field offsets for electron spin-echo EPR oxygen imaging of large objects

    Science.gov (United States)

    Seifi, Payam; Epel, Boris; Sundramoorthy, Subramanian V.; Mailer, Colin; Halpern, Howard J.

    2011-01-01

    Purpose: Electron spin-echo (ESE) oxygen imaging is a new and evolving electron paramagnetic resonance (EPR) imaging (EPRI) modality that is useful for physiological in vivo applications, such as EPR oxygen imaging (EPROI), with potential application to imaging of multicentimeter objects as large as human tumors. A present limitation on the size of the object to be imaged at a given resolution is the frequency bandwidth of the system, since the location is encoded as a frequency offset in ESE imaging. The authors’ aim in this study was to demonstrate the object size advantage of the multioffset bandwidth extension technique.Methods: The multiple-stepped Zeeman field offset (or simply multi-B) technique was used for imaging of an 8.5-cm-long phantom containing a narrow single line triaryl methyl compound (trityl) solution at the 250 MHz imaging frequency. The image is compared to a standard single-field ESE image of the same phantom.Results: For the phantom used in this study, transverse relaxation (T2e) electron spin-echo (ESE) images from multi-B acquisition are more uniform, contain less prominent artifacts, and have a better signal to noise ratio (SNR) compared to single-field T2e images.Conclusions: The multi-B method is suitable for imaging of samples whose physical size restricts the applicability of the conventional single-field ESE imaging technique. PMID:21815379

  14. EPR of some low-spin dsup(5) tris-chelate complexes of Fe(3), Ru(3), Os(3) in liquid-crystal matrix

    International Nuclear Information System (INIS)

    Domracheva, N.E.; Konstantinov, V.N.; Luchkona, S.A.; Ovchinnikov, I.V.

    1985-01-01

    Using the EPR method low-spin trischelate complexes of Fe, Ru, Os with 8-mercaptoquinoline and 8-oxyquinoline in oriented vitrified liquid-crystal matrix have been studied. Analtysis of angular dependences of EPR spectra of the complexes permitted to correlate the main axes of g-tensor with molecular axes and, consequently, to determine unambiguously the main electron states of the systems, as well as the value of crystal splittings. It is shown that in the complexes studied the splitting of energy levels is mainly determined by spin-orbital interaction, and not by axial or rhombic components of crystal field. However, rhombic distortion is responsible for anisotropy of g-tensor in xy plane and anisotropy of x- and y-axes orientation. The way to orient complexes in liquid-crystal matrix is substantiated; symmetry axis of the third order C 3 (Z) is mainly oriented along the director. Parameters of the function of orientational distribution of the complex axes are obtained

  15. Quantitative EPR A Practitioners Guide

    CERN Document Server

    Eaton, Gareth R; Barr, David P; Weber, Ralph T

    2010-01-01

    This is the first comprehensive yet practical guide for people who perform quantitative EPR measurements. No existing book provides this level of practical guidance to ensure the successful use of EPR. There is a growing need in both industrial and academic research to provide meaningful and accurate quantitative EPR results. This text discusses the various sample, instrument and software related aspects required for EPR quantitation. Specific topics include: choosing a reference standard, resonator considerations (Q, B1, Bm), power saturation characteristics, sample positioning, and finally, putting all the factors together to obtain an accurate spin concentration of a sample.

  16. Na+/substrate Coupling in the Multidrug Antiporter NorM Probed with a Spin-labeled Substrate

    Science.gov (United States)

    Steed, P. Ryan; Stein, Richard A.; Mishra, Smriti; Goodman, Michael C.; Mchaourab, Hassane S.

    2013-01-01

    NorM of the multidrug and toxic compound extrusion (MATE) family of transporters couples the efflux of a broad range of hydrophobic molecules to an inward Na+ gradient across the cell membrane. Several crystal structures of MATE transporters revealed distinct substrate binding sites leading to differing models of the mechanism of ion-coupled substrate extrusion. In the experiments reported here, we observed that a spin-labeled derivative of daunorubicin, Ruboxyl, is transported by NorM from Vibrio cholerae. It is therefore ideal to characterize mechanistically relevant binding interactions with NorM and to directly address the coupling of ion and drug binding. Fluorescence and EPR experiments revealed that Ruboxyl binds to NorM with micromolar affinity and becomes immobilized upon binding, even in the presence of Na+. Using double electron-electron resonance (DEER) spectroscopy, we determined that Ruboxyl binds to a single site on the periplasmic side of the protein. The presence of Na+ did not translocate the substrate to a second site as previously proposed. These experiments surprisingly show that Na+ does not affect the affinity or location of the substrate binding site on detergent-solubilized NorM, thus suggesting that additional factors beyond simple mutual exclusivity of binding, such as the presence of a Na+ gradient across the native membrane, govern Na+/drug coupling during antiport. PMID:23902581

  17. Effect of temperature on thermal oxidation of palmitic acid studied by combination of EPR spin trapping technique and SPME-GC-MS/MS.

    Science.gov (United States)

    Chen, Hongjian; Wang, Yong; Cao, Peirang; Liu, Yuanfa

    2017-11-01

    Effect of temperatures on thermal oxidation of palmitic acid was studied by the combination of EPR and GC-MS/MS. DMPO was used as the spin trap. The experimental spectrum was simulated with alkyl and alkoxyl spin adducts. Total amount of spins, a parameter to indicate radical concentrations, detected at 180°C was nearly 10 times higher than that at 175°C. Besides, total amounts of spins detected at 180°C decreased rapidly because of the reaction between radical adducts and newly formed radicals. Signal intensities of alkyl radical adducts increased rapidly from 0.405 to 4.785 from 175°C to 180°C. Besides, more palmitic acid degraded to oxidized compounds from 175°C to 180°C than that of other temperature ranges. The C-C linkages between carbons 2 to 6 were easier to be oxidized at 180°C. The results all implied that oxidation rates of palmitic acid samples increased rapidly from 175°C to 180°C. Copyright © 2017 Elsevier Ltd. All rights reserved.

  18. Pulse EPR distance measurements to study multimers and multimerisation

    Science.gov (United States)

    Ackermann, Katrin; Bode, Bela E.

    2018-06-01

    Pulse dipolar electron paramagnetic resonance (PD-EPR) has become a powerful tool for structural biology determining distances on the nanometre scale. Recent advances in hardware, methodology, and data analysis have widened the scope to complex biological systems. PD-EPR can be applied to systems containing lowly populated conformers or displaying large intrinsic flexibility, making them all but intractable for cryo-electron microscopy and crystallography. Membrane protein applications are of particular interest due to the intrinsic difficulties for obtaining high-resolution structures of all relevant conformations. Many drug targets involved in critical cell functions are multimeric channels or transporters. Here, common approaches for introducing spin labels for PD-EPR cause the presence of more than two electron spins per multimeric complex. This requires careful experimental design to overcome detrimental multi-spin effects and to secure sufficient distance resolution in presence of multiple distances. In addition to obtaining mere distances, PD-EPR can also provide information on multimerisation degrees allowing to study binding equilibria and to determine dissociation constants.

  19. Spin label evidence for the role of lysoglycerophosphatides in cellular membranes of hibernating mammals

    Energy Technology Data Exchange (ETDEWEB)

    Keith, A D [Pennsylvania State Univ., University Park; Aloia, R C; Lyons, J; Snipes, W; Pengelley, E T

    1975-01-01

    The phospholipid composition of ground squirrel heart muscle changes during hibernation: more lysoglycerophosphatides are found in the hibernating state than in the active state. Phase transitions inferred from spin label motion occur in the usual manner typical of mammalian mitochondria for the mitochondria and mitochondrial lipids from active squirrels. However, a conspicuous absence of a spin label-detectable phase transition is observed in equivalent preparations from hibernating animals. The addition of lysolecithin to preparations from active squirrels removes the break and induces a straight line in the Arrhenius plot. The lack of a spin label-detectable phase transition in hibernating animals, therefore, is attributed to an increased content of lysoglycerophosphatides present in the phospholipids during hibernation.

  20. Spin-labeled 1-alkyl-1-nitrosourea synergists of antitumor antibiotics.

    Science.gov (United States)

    Gadjeva, V; Koldamova, R

    2001-01-01

    A new method for synthesis of four spin-labeled structural analogues of the antitumor drug 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU), using ethyl nitrite for nitrosation of the intermediate spin-labeled ureas has been described. In vitro synergistic effects of 1-ethyl-3-[4-(2,2,6,6-tetramethylpiperidine-1-oxyl)]-1-nitrosourea (3b) on the cytotoxicity of bleomycin and farmorubicin were found in human lymphoid leukemia tumor cells. We measured the tissue distribution of 3b in organ homogenates of C57BL mice by an electron paramagnetic resonance method. The spin-labeled nitrosourea was mainly localized in the lungs. Our results strongly support the development and validation of a new approach for synthesis of less toxic nitrosourea derivatives as potential synergists of antitumor drugs.

  1. Water accessibility in a membrane-inserting peptide comparing Overhauser DNP and pulse EPR methods

    Energy Technology Data Exchange (ETDEWEB)

    Segawa, Takuya F., E-mail: takuya.segawa@alumni.ethz.ch; Doppelbauer, Maximilian; Garbuio, Luca; Doll, Andrin; Polyhach, Yevhen O.; Jeschke, Gunnar, E-mail: gjeschke@ethz.ch [Laboratory of Physical Chemistry, ETH Zurich, Vladimir-Prelog-Weg 2, CH-8093 Zurich (Switzerland)

    2016-05-21

    Water accessibility is a key parameter for the understanding of the structure of biomolecules, especially membrane proteins. Several experimental techniques based on the combination of electron paramagnetic resonance (EPR) spectroscopy with site-directed spin labeling are currently available. Among those, we compare relaxation time measurements and electron spin echo envelope modulation (ESEEM) experiments using pulse EPR with Overhauser dynamic nuclear polarization (DNP) at X-band frequency and a magnetic field of 0.33 T. Overhauser DNP transfers the electron spin polarization to nuclear spins via cross-relaxation. The change in the intensity of the {sup 1}H NMR spectrum of H{sub 2}O at a Larmor frequency of 14 MHz under a continuous-wave microwave irradiation of the nitroxide spin label contains information on the water accessibility of the labeled site. As a model system for a membrane protein, we use the hydrophobic α-helical peptide WALP23 in unilamellar liposomes of DOPC. Water accessibility measurements with all techniques are conducted for eight peptides with different spin label positions and low radical concentrations (10–20 μM). Consistently in all experiments, the water accessibility appears to be very low, even for labels positioned near the end of the helix. The best profile is obtained by Overhauser DNP, which is the only technique that succeeds in discriminating neighboring positions in WALP23. Since the concentration of the spin-labeled peptides varied, we normalized the DNP parameter ϵ, being the relative change of the NMR intensity, by the electron spin concentration, which was determined from a continuous-wave EPR spectrum.

  2. Perfusion by Arterial Spin labelling following Single dose Tadalafil In Small vessel disease (PASTIS)

    DEFF Research Database (Denmark)

    Pauls, Mathilde M H; Clarke, Natasha; Trippier, Sarah

    2017-01-01

    vascular territories. The aim of this trial is to test the hypothesis that tadalafil increases cerebral blood flow in older people with small vessel disease. METHODS/DESIGN: Perfusion by Arterial Spin labelling following Single dose Tadalafil In Small vessel disease (PASTIS) is a phase II randomised double......-blind crossover trial. In two visits, 7-30 days apart, participants undergo arterial spin labelling to measure cerebral blood flow and a battery of cognitive tests, pre- and post-dosing with oral tadalafil (20 mg) or placebo. SAMPLE SIZE: 54 participants are required to detect a 15% increase in cerebral blood...

  3. Resting quantitative cerebral blood flow in schizophrenia measured by pulsed arterial spin labeling perfusion MRI

    OpenAIRE

    Pinkham, Amy; Loughead, James; Ruparel, Kosha; Wu, Wen-Chau; Overton, Eve; Gur, Raquel; Gur, Ruben

    2011-01-01

    Arterial spin labeling imaging (ASL) perfusion MRI is a relatively novel technique that can allow for quantitative measurement of cerebral blood flow (CBF) by using magnetically labeled arterial blood water as an endogenous tracer. Available data on resting CBF in schizophrenia primarily comes from invasive and expensive nuclear medicine techniques that are often limited to small samples and yield mixed results. The noninvasive nature of ASL offers promise for larger-scale studies. The utilit...

  4. Physiological and pathophysiological reactive oxygen species as probed by EPR spectroscopy: the underutilized research window on muscle ageing.

    Science.gov (United States)

    A Abdel-Rahman, Engy; Mahmoud, Ali M; Khalifa, Abdulrahman M; Ali, Sameh S

    2016-08-15

    Reactive oxygen and nitrogen species (ROS and RNS) play crucial roles in triggering, mediating and regulating physiological and pathophysiological signal transduction pathways within the cell. Within the cell, ROS efflux is firmly controlled both spatially and temporally, making the study of ROS dynamics a challenging task. Different approaches have been developed for ROS assessment; however, many of these assays are not capable of direct identification or determination of subcellular localization of different ROS. Here we highlight electron paramagnetic resonance (EPR) spectroscopy as a powerful technique that is uniquely capable of addressing questions on ROS dynamics in different biological specimens and cellular compartments. Due to their critical importance in muscle functions and dysfunction, we discuss in some detail spin trapping of various ROS and focus on EPR detection of nitric oxide before highlighting how EPR can be utilized to probe biophysical characteristics of the environment surrounding a given stable radical. Despite the demonstrated ability of EPR spectroscopy to provide unique information on the identity, quantity, dynamics and environment of radical species, its applications in the field of muscle physiology, fatiguing and ageing are disproportionately infrequent. While reviewing the limited examples of successful EPR applications in muscle biology we conclude that the field would greatly benefit from more studies exploring ROS sources and kinetics by spin trapping, protein dynamics by site-directed spin labelling, and membrane dynamics and global redox changes by spin probing EPR approaches. © 2016 The Authors. The Journal of Physiology © 2016 The Physiological Society.

  5. Exploring the local conformational space of a membrane protein by site-directed spin labeling

    NARCIS (Netherlands)

    Stopar, D.; Strancar, J.; Spruijt, R.B.; Hemminga, M.A.

    2005-01-01

    Molecular modeling based on a hybrid evolutionary optimization and an information condensation algorithm, called GHOST, of spin label ESR spectra was applied to study the structure and dynamics of membrane proteins. The new method is capable of providing detailed molecular information about the

  6. Improved calculation of the equilibrium magnetization of arterial blood in arterial spin labeling

    DEFF Research Database (Denmark)

    Ahlgren, André; Wirestam, Ronnie; Knutsson, Linda

    2018-01-01

    PURPOSE: To propose and assess an improved method for calculating the equilibrium magnetization of arterial blood ( M0a), used for calibration of perfusion estimates in arterial spin labeling. METHODS: Whereas standard M0a calculation is based on dividing a proton density-weighted image by an ave...

  7. Effect of some radiosensitising drugs on human erythrocyte membrane - - spin label study

    Energy Technology Data Exchange (ETDEWEB)

    Mishra, K P [Bhabha Atomic Research Centre, Bombay (India). Biology and Agriculture Div.

    1982-02-01

    Electron spin resonance and spin label techniques have been employed to study the effects of local anaesthetic drugs, procaine and tetracaine, on human erythrocyte membrane. Both the drugs altered the protein and lipid arrangements in the membrane and these changes were reversible. Procaine had greater effect on the labels attached to proteins while tetracaine fluidized interior of lipid bilayer to a greater extent. The differential effects of these drugs on the protein and lipid labels have been interpreted in terms of their relative penetrability in the membrane. Present results have explained that radiation induced enhanced killing of cells in the presence of these drugs might be due to the alterations in membrane, particularly proteins both structural and enzymatic. In addition, these results indicate a possible relationship between drug-induced structural changes in membrane and their anaesthetic potency.

  8. EPR-Spin Trapping and Flow Cytometric Studies of Free Radicals Generated Using Cold Atmospheric Argon Plasma and X-Ray Irradiation in Aqueous Solutions and Intracellular Milieu.

    Directory of Open Access Journals (Sweden)

    Hidefumi Uchiyama

    Full Text Available Electron paramagnetic resonance (EPR-spin trapping and flow cytometry were used to identify free radicals generated using argon-cold atmospheric plasma (Ar-CAP in aqueous solutions and intracellularly in comparison with those generated by X-irradiation. Ar-CAP was generated using a high-voltage power supply unit with low-frequency excitation. The characteristics of Ar-CAP were estimated by vacuum UV absorption and emission spectra measurements. Hydroxyl (·OH radicals and hydrogen (H atoms in aqueous solutions were identified with the spin traps 5,5-dimethyl-1-pyrroline N-oxide (DMPO, 3,3,5,5-tetramethyl-1-pyrroline-N-oxide (M4PO, and phenyl N-t-butylnitrone (PBN. The occurrence of Ar-CAP-induced pyrolysis was evaluated using the spin trap 3,5-dibromo-4-nitrosobenzene sulfonate (DBNBS in aqueous solutions of DNA constituents, sodium acetate, and L-alanine. Human lymphoma U937 cells were used to study intracellular oxidative stress using five fluorescent probes with different affinities to a number of reactive species. The analysis and quantification of EPR spectra revealed the formation of enormous amounts of ·OH radicals using Ar-CAP compared with that by X-irradiation. Very small amounts of H atoms were detected whereas nitric oxide was not found. The formation of ·OH radicals depended on the type of rare gas used and the yield correlated inversely with ionization energy in the order of krypton > argon = neon > helium. No pyrolysis radicals were detected in aqueous solutions exposed to Ar-CAP. Intracellularly, ·OH, H2O2, which is the recombination product of ·OH, and OCl- were the most likely formed reactive oxygen species after exposure to Ar-CAP. Intracellularly, there was no practical evidence for the formation of NO whereas very small amounts of superoxides were formed. Despite the superiority of Ar-CAP in forming ·OH radicals, the exposure to X-rays proved more lethal. The mechanism of free radical formation in aqueous solutions and

  9. Arterial spin labelling in imaging of renal diseases and renal allograft pathology; MRT-Perfusionsmessung mit Arterial Spin Labelling. Anwendung fuer die Niere und Transplantatniere

    Energy Technology Data Exchange (ETDEWEB)

    Hueper, Katja; Gutberlet, Marcel [Medizinische Hochschule Hannover (Germany). Inst. fuer Diagnostische und Interventionelle Radiologie; Kuehn, Bernd [Siemens AG/Siemens Healthcare GmbH, Erlangen (Germany)

    2016-06-15

    Arterial Spin Labelling (ASL) is a technique for non-invasive and contrast-free assessment of perfusion with MRI. Renal ASL allows examination of renal pathophysiology, evaluation of the course of renal disease and therapy effects by longitudinal measurements as well as characterization of renal tumors. In this article, techniques of ASL will be explained and challenges of renal ASL will be emphasized. In addition, examples for clinical application of ASL for diagnosis of renal disease and renal allograft pathology will be given.

  10. Spin-labelling study of interactions of ovalbumin with multilamellar liposomes and specific anti-ovalbumin antibodies.

    Science.gov (United States)

    Brgles, Marija; Mirosavljević, Krunoslav; Noethig-Laslo, Vesna; Frkanec, Ruza; Tomasić, Jelka

    2007-03-10

    Ovalbumin (OVA) has been used continuously as the model antigen in numerous studies of immune reactions and antigen processing, very often encapsulated into liposomes. The purpose of this work was to study the possible interactions of spin-labelled OVA and lipids in liposomal membranes using electron spin resonance (ESR) spectroscopy. OVA was covalently spin-labelled with 4-maleimido-2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO-maleimide), characterized and encapsulated into multilamellar, negatively charged liposomes. ESR spectra of this liposomal preparation gave evidence for the interaction of OVA with the lipid bilayers. Such an interaction was also evidenced by the ESR spectra of liposomal preparation containing OVA, where liposomes were spin-labelled with n-doxyl stearic acids. The spin-labelled OVA retains its property to bind specific anti-OVA antibodies, as shown by ESR spectroscopy, but also in ELISA for specific anti-OVA IgG.

  11. Dynamic nuclear polarization of membrane proteins: covalently bound spin-labels at protein–protein interfaces

    International Nuclear Information System (INIS)

    Wylie, Benjamin J.; Dzikovski, Boris G.; Pawsey, Shane; Caporini, Marc; Rosay, Melanie; Freed, Jack H.; McDermott, Ann E.

    2015-01-01

    We demonstrate that dynamic nuclear polarization of membrane proteins in lipid bilayers may be achieved using a novel polarizing agent: pairs of spin labels covalently bound to a protein of interest interacting at an intermolecular interaction surface. For gramicidin A, nitroxide tags attached to the N-terminal intermolecular interface region become proximal only when bimolecular channels forms in the membrane. We obtained signal enhancements of sixfold for the dimeric protein. The enhancement effect was comparable to that of a doubly tagged sample of gramicidin C, with intramolecular spin pairs. This approach could be a powerful and selective means for signal enhancement in membrane proteins, and for recognizing intermolecular interfaces

  12. Estimation of perfusion properties with MR Fingerprinting Arterial Spin Labeling.

    Science.gov (United States)

    Wright, Katherine L; Jiang, Yun; Ma, Dan; Noll, Douglas C; Griswold, Mark A; Gulani, Vikas; Hernandez-Garcia, Luis

    2018-03-12

    In this study, the acquisition of ASL data and quantification of multiple hemodynamic parameters was explored using a Magnetic Resonance Fingerprinting (MRF) approach. A pseudo-continuous ASL labeling scheme was used with pseudo-randomized timings to acquire the MRF ASL data in a 2.5 min acquisition. A large dictionary of MRF ASL signals was generated by combining a wide range of physical and hemodynamic properties with the pseudo-random MRF ASL sequence and a two-compartment model. The acquired signals were matched to the dictionary to provide simultaneous quantification of cerebral blood flow, tissue time-to-peak, cerebral blood volume, arterial time-to-peak, B 1 , and T 1. A study in seven healthy volunteers resulted in the following values across the population in grey matter (mean ± standard deviation): cerebral blood flow of 69.1 ± 6.1 ml/min/100 g, arterial time-to-peak of 1.5 ± 0.1 s, tissue time-to-peak of 1.5 ± 0.1 s, T 1 of 1634 ms, cerebral blood volume of 0.0048 ± 0.0005. The CBF measurements were compared to standard pCASL CBF estimates using a one-compartment model, and a Bland-Altman analysis showed good agreement with a minor bias. Repeatability was tested in five volunteers in the same exam session, and no statistical difference was seen. In addition to this validation, the MRF ASL acquisition's sensitivity to the physical and physiological parameters of interest was studied numerically. Copyright © 2018 Elsevier Inc. All rights reserved.

  13. Measurement of brain perfusion in newborns: Pulsed arterial spin labeling (PASL) versus pseudo-continuous arterial spin labeling (pCASL)

    Science.gov (United States)

    Boudes, Elodie; Gilbert, Guillaume; Leppert, Ilana Ruth; Tan, Xianming; Pike, G. Bruce; Saint-Martin, Christine; Wintermark, Pia

    2014-01-01

    Background Arterial spin labeling (ASL) perfusion-weighted imaging (PWI) by magnetic resonance imaging (MRI) has been shown to be useful for identifying asphyxiated newborns at risk of developing brain injury, whether or not therapeutic hypothermia was administered. However, this technique has been only rarely used in newborns until now, because of the challenges to obtain sufficient signal-to-noise ratio (SNR) and spatial resolution in newborns. Objective To compare two methods of ASL-PWI (i.e., single inversion-time pulsed arterial spin labeling [single TI PASL], and pseudo-continuous arterial spin labeling [pCASL]) to assess brain perfusion in asphyxiated newborns treated with therapeutic hypothermia and in healthy newborns. Design/methods We conducted a prospective cohort study of term asphyxiated newborns meeting the criteria for therapeutic hypothermia; four additional healthy term newborns were also included as controls. Each of the enrolled newborns was scanned at least once during the first month of life. Each MRI scan included conventional anatomical imaging, as well as PASL and pCASL PWI-MRI. Control and labeled images were registered separately to reduce the effect of motion artifacts. For each scan, the axial slice at the level of the basal ganglia was used for comparisons. Each scan was scored for its image quality. Quantification of whole-slice cerebral blood flow (CBF) was done afterwards using previously described formulas. Results A total number of 61 concomitant PASL and pCASL scans were obtained in nineteen asphyxiated newborns treated with therapeutic hypothermia and four healthy newborns. After discarding the scans with very poor image quality, 75% (46/61) remained for comparison between the two ASL methods. pCASL images presented a significantly superior image quality score compared to PASL images (p newborns. However, pCASL might be a better choice over PASL in newborns, as pCASL perfusion maps had a superior image quality that allowed a

  14. Convenient biosynthetic preparation of isomeric spin-labelled radioactive phosphatidic acids

    Energy Technology Data Exchange (ETDEWEB)

    Stuhne, L.; Stanacev, N.Z. (Toronto Univ., Ontario (Canada). Dept. of Clinical Biochemistry)

    1982-11-01

    A convenient method for the enzymatic preparation of sn-3-(2-/sup 3/H)phosphatidic acids carrying also 5-, 12-, or 16-nitroxide stearic acids, from sn-3-(2-/sup 3/H) glycerophosphate and isolated guinea pig liver microsomes, is described in detail. The procedure allows a simultaneous preparation of three spin-labelled sn-3-(2-/sup 3/H)phosphatidic acids of yields 3-3.5..mu..mol of each compound which is >99% pure in respect to the radioactivity and which contains 25 mol% of spin-labelled fatty acids. These phosphatidic acids were approximately equally distributed between the primary and the secondary hydroxyl when 12- or 16-nitroxide stearic acids were used or predominantly (75%) associated with the secondary hydroxyl of sn-3-(2-/sup 3/H)phosphatidic acid when 5-nitroxide stearic acid was present in the incubation mixture.

  15. Potentials and Challenges for Arterial Spin Labeling in Pharmacological Magnetic Resonance Imaging

    OpenAIRE

    Wang, Danny J. J.; Chen, Yufen; Fernández-Seara, María A.; Detre, John A.

    2011-01-01

    Pharmacological magnetic resonance imaging (phMRI) is increasingly being used in drug discovery and development to speed the translation from the laboratory to the clinic. The two primary methods in phMRI include blood-oxygen-level-dependent (BOLD) contrast and arterial spin-labeled (ASL) perfusion MRI. BOLD contrast has been widely applied in existing phMRI studies. However, because of the lack of absolute quantification and poor reproducibility over time scales longer than hours or across s...

  16. Intersubunit distances in full-length, dimeric, bacterial phytochrome Agp1, as measured by pulsed electron-electron double resonance (PELDOR) between different spin label positions, remain unchanged upon photoconversion.

    Science.gov (United States)

    Kacprzak, Sylwia; Njimona, Ibrahim; Renz, Anja; Feng, Juan; Reijerse, Edward; Lubitz, Wolfgang; Krauss, Norbert; Scheerer, Patrick; Nagano, Soshichiro; Lamparter, Tilman; Weber, Stefan

    2017-05-05

    Bacterial phytochromes are dimeric light-regulated histidine kinases that convert red light into signaling events. Light absorption by the N-terminal photosensory core module (PCM) causes the proteins to switch between two spectrally distinct forms, Pr and Pfr, thus resulting in a conformational change that modulates the C-terminal histidine kinase region. To provide further insights into structural details of photoactivation, we investigated the full-length Agp1 bacteriophytochrome from the soil bacterium Agrobacterium fabrum using a combined spectroscopic and modeling approach. We generated seven mutants suitable for spin labeling to enable application of pulsed EPR techniques. The distances between attached spin labels were measured using pulsed electron-electron double resonance spectroscopy to probe the arrangement of the subunits within the dimer. We found very good agreement of experimental and calculated distances for the histidine-kinase region when both subunits are in a parallel orientation. However, experimental distance distributions surprisingly showed only limited agreement with either parallel- or antiparallel-arranged dimer structures when spin labels were placed into the PCM region. This observation indicates that the arrangements of the PCM subunits in the full-length protein dimer in solution differ significantly from that in the PCM crystals. The pulsed electron-electron double resonance data presented here revealed either no or only minor changes of distance distributions upon Pr-to-Pfr photoconversion. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

  17. Intra-albumin migration of bound fatty acid probed by spin label ESR

    International Nuclear Information System (INIS)

    Gurachevsky, Andrey; Shimanovitch, Ekaterina; Gurachevskaya, Tatjana; Muravsky, Vladimir

    2007-01-01

    Conventional ESR spectra of 16-doxyl-stearic acid bound to bovine and human serum albumin were recorded at different temperatures in order to investigate the status of spin-labeled fatty acid in the interior of the protein globule. A computer spectrum simulation of measured spectra, performed by non-linear least-squares fits, clearly showed two components corresponding to strongly and weakly immobilized fatty acid molecules. The two-component model was verified on spectra measured at different pH. Thermodynamic parameters of the spin probe exchange between two spin probe states were analyzed. It was concluded that at physiological conditions, fatty acid molecules permanently migrate in the globule interior between the specific binding sites and a space among albumin domains

  18. Temperature-induced changes in lecithin model membranes detected by novel covalent spin-labelled phospholipids.

    Science.gov (United States)

    Stuhne-Sekalec, L; Stanacev, N Z

    1977-02-01

    Several spin-labelled phospholipids carrying covalently bound 5-doxylstearic acid (2-(3-carboxydecyl)-2-hexyl-4,4-dimethyl-3-oxazolidinoxyl) were intercalated in liposomes of saturated and unsaturated lecithins. Temperature-induced changes of these liposomes, detected by the spin-labelled phospholipids, were found to be in agreement with the previously described transitions of hydrocarbon chains of host lecithins detected by different probes and different techniques, establishing that spin-labelled phosopholipids are sensitive probes for the detection of temperature-induced changes in lecithin model membranes. In addition to the detection of already-known transitions in lecithin liposomes, the coexistence of two distinctly different enviroments was observed above the characteristic transition temperature. This phenomenon was tentatively attributed to the influence of the lecithin polar group on the fluidity of fatty acyl chains near the polar group. Combined with other results from the literature, the coexistence of two environments could be associated with the coexistence of two conformational isomers of lecithin, differing in the orientation of the polar head group with respect to the plane of bilayer. These findings have been discussed in view of the present state of knowledge regarding temperature-induced changes in model membranes.

  19. Comparison of selective arterial spin labeling using 1D and 2D tagging RF pulses

    Energy Technology Data Exchange (ETDEWEB)

    Konstandin, Simon; Heiler, Patrick M.; Schad, Lothar R. [Heidelberg Univ., Mannheim (Germany). Computer Assisted Clinical Medicine; Scharf, Johann [Heidelberg Univ., Mannheim (Germany). Dept. of Neuroradiology

    2011-07-01

    Generic arterial spin labeling (ASL) techniques label all brain feeding arteries. In this work, we used two different selective ASL (SASL) methods to show the perfusion of one single artery. A slice selective inversion of an area including the desired vessel was compared to a multidimensional RF pulse with Gaussian profile to label only the artery of interest. Perfusion images with a resolution of 2 x 2 x 5 mm{sup 3} are shown that were acquired after tagging only the internal carotid artery of healthy volunteers. In addition, both techniques were applied to a patient with an extra-intracranial bypass to illustrate its perfusion territory. These perfusion images are consistent with a standard angiography. SASL imaging with a resolution of 2 x 2 x 5 mm{sup 3} is possible in a total scan time of 5 min. The presented MR techniques may in part replace the assessment of revascularization success by conventional angiography. (orig.)

  20. Comparison of selective arterial spin labeling using 1D and 2D tagging RF pulses

    International Nuclear Information System (INIS)

    Konstandin, Simon; Heiler, Patrick M.; Schad, Lothar R.; Scharf, Johann

    2011-01-01

    Generic arterial spin labeling (ASL) techniques label all brain feeding arteries. In this work, we used two different selective ASL (SASL) methods to show the perfusion of one single artery. A slice selective inversion of an area including the desired vessel was compared to a multidimensional RF pulse with Gaussian profile to label only the artery of interest. Perfusion images with a resolution of 2 x 2 x 5 mm 3 are shown that were acquired after tagging only the internal carotid artery of healthy volunteers. In addition, both techniques were applied to a patient with an extra-intracranial bypass to illustrate its perfusion territory. These perfusion images are consistent with a standard angiography. SASL imaging with a resolution of 2 x 2 x 5 mm 3 is possible in a total scan time of 5 min. The presented MR techniques may in part replace the assessment of revascularization success by conventional angiography. (orig.)

  1. On the search for new anticancer drugs 14: the plasma pharmacokinetics and tissue distribution of spin-labeled thio-TEPA (SL-O-TT).

    Science.gov (United States)

    Gutierrez, P L; Cohen, B E; Sosnovsky, G; Davis, T A; Egorin, M J

    1985-01-01

    We defined the plasma and tissue concentrations and pharmacokinetics of SL-O-TT, a spin-labeled analog of thio-TEPA, in 35-44-g male Swiss Webster mice that had received spin-labeled thio-TEPA at a dosage of 10 mg/kg. Concentrations of spin-labeled thio-TEPA in ethyl acetate extracts of tissue and plasma were determined by gas-liquid chromatography and electron spin resonance spectroscopy. Plasma concentrations of spin-labeled thio-TEPA declined in a biexponential fashion that was well described by the equation: Ct = 21.5e-0.276t + 2.30e-0.026t indicating a half-life alpha of 2.5 min and a half-life beta of 26.6 min. After 2 h there was still spin-labeled thio-TE-PA in plasma, but not in tissues. In tissues, no spin-labeled thio-TEPA was detected with gas-liquid chromatography 15 min after injection, but with electron-spin resonance label was found in lung and skeletal muscle. The main metabolite of spin-labeled thio-TEPA is spin-labeled TEPA, where oxidative desulfurization is invoked as the main metabolic mechanism. Reduction of the spin label to the hydroxylamine was also observed with time.

  2. Potential of EPR spin-trapping to investigate in situ free radicals generation from skin allergens in reconstructed human epidermis: cumene hydroperoxide as proof of concept.

    Science.gov (United States)

    Kuresepi, Salen; Vileno, Bertrand; Turek, Philippe; Lepoittevin, Jean-Pierre; Giménez-Arnau, Elena

    2018-02-01

    The first step in the development of skin sensitisation to a chemical, and in the elicitation of further allergic contact dermatitis (ACD), is the binding of the allergen to skin proteins after penetrating into the epidermis. The so-formed antigenic adduct is then recognised by the immune system as foreign to the body. Sensitising organic hydroperoxides derived from autoxidation of natural terpenes are believed to form antigens through radical-mediated mechanisms, although this has not yet been established. So far, in vitro investigations on reactive radical intermediates derived from these skin sensitisers have been conducted in solution, yet with experimental conditions being far away from real-life sensitisation. Herein, we report for the first time, the potential use of EPR spin-trapping to study the in situ generation of free radicals derived from cumene hydroperoxide CumOOH in a 3D reconstructed human epidermis (RHE) model, thus much closer to what may happen in vivo. Among the undesirable effects associated with dermal exposure to CumOOH, it is described to cause allergic and irritant dermatitis, being reported as a significant sensitiser. We considered exploiting the usage of spin-trap DEPMPO as an extensive view of all sort of radicals derived from CumOOH were observed all at once in solution. We showed that in the Episkin TM RHE model, both by incubating in the assay medium and by topical application, carbon radicals are mainly formed by redox reactions suggesting the key role of CumOOH-derived carbon radicals in the antigen formation process.

  3. Perfusion deficits detected by arterial spin-labeling in patients with TIA with negative diffusion and vascular imaging.

    Science.gov (United States)

    Qiao, X J; Salamon, N; Wang, D J J; He, R; Linetsky, M; Ellingson, B M; Pope, W B

    2013-01-01

    A substantial portion of clinically diagnosed TIA cases is imaging-negative. The purpose of the current study is to determine if arterial spin-labeling is helpful in detecting perfusion abnormalities in patients presenting clinically with TIA. Pseudocontinuous arterial spin-labeling with 3D background-suppressed gradient and spin-echo was acquired on 49 patients suspected of TIA within 24 hours of symptom onset. All patients were free of stroke history and had no lesion-specific findings on general MR, DWI, and MRA sequences. The calculated arterial spin-labeling CBF maps were scored from 1-3 on the basis of presence and severity of perfusion disturbance by 3 independent observers blinded to patient history. An age-matched cohort of 36 patients diagnosed with no cerebrovascular events was evaluated as a control. Interobserver agreement was assessed by use of the Kendall concordance test. Scoring of perfusion abnormalities on arterial spin-labeling scans of the TIA cohort was highly concordant among the 3 observers (W = 0.812). The sensitivity and specificity of arterial spin-labeling in the diagnosis of perfusion abnormalities in TIA was 55.8% and 90.7%, respectively. In 93.3% (70/75) of the arterial spin-labeling CBF map readings with positive scores (≥2), the brain regions where perfusion abnormalities were identified by 3 observers matched with the neurologic deficits at TIA onset. In this preliminary study, arterial spin-labeling showed promise in the detection of perfusion abnormalities that correlated with clinically diagnosed TIA in patients with otherwise normal neuroimaging results.

  4. New loophole for the EPR paradox

    OpenAIRE

    Feldmann, Michel

    1999-01-01

    We exhibit a classical model free from any paradox which exactly simulates the spin EPR test. We conclude that Bell's inequality violation is a strictly classical phenomenon, contrary to a general belief.

  5. The EPR reactor

    International Nuclear Information System (INIS)

    Lacoste, A.C.; Dupuy, Ph.; Gupta, O.; Perez, J.R.; Emond, D.; Cererino, G.; Rousseau, J.M.; Jeffroy, F.; Evrard, J.M.; Seiler, J.M.; Azarian, G.; Chaumont, B.; Dubail, A.; Fischer, M.; Tiippana, P.; Hyvarinen, J.; Zaleski, C.P.; Meritet, S.; Iglesias, F.; Vincent, C.; Massart, S.; Graillat, G.; Esteve, B.; Mansillon, Y.; Gatinol, C.; Carre, F.

    2005-01-01

    This document reviews economical and environmental aspects of the EPR project. The following topics are discussed: role and point of view of the French Nuclear Safety Authority on EPR, control of design and manufacturing of EPR by the French Nuclear Safety Authority, assessment by IRSN of EPR safety, research and development in support of EPR, STUK safety review of EPR design, standpoint on EPR, the place of EPR in the French energy policy, the place of EPR in EDF strategy, EPR spearhead of nuclear rebirth, the public debate, the local stakes concerning the building of EPR in France at Flamanville (Manche) and the research on fourth generation reactors. (A.L.B.)

  6. Reduction in cerebral perfusion after heroin administration: a resting state arterial spin labeling study.

    Directory of Open Access Journals (Sweden)

    Niklaus Denier

    Full Text Available Heroin dependence is a chronic relapsing brain disorder, characterized by the compulsion to seek and use heroin. Heroin itself has a strong potential to produce subjective experiences characterized by intense euphoria, relaxation and release from craving. The neurofunctional foundations of these perceived effects are not well known. In this study, we have used pharmacological magnetic resonance imaging (phMRI in 15 heroin-dependent patients from a stable heroin-assisted treatment program to observe the steady state effects of heroin (60 min after administration. Patients were scanned in a cross-over and placebo controlled design. They received an injection of their regular dose of heroin or saline (placebo before or after the scan. As phMRI method, we used a pulsed arterial spin labeling (ASL sequence based on a flow-sensitive alternating inversion recovery (FAIR spin labeling scheme combined with a single-shot 3D GRASE (gradient-spin echo readout on a 3 Tesla scanner. Analysis was performed with Statistical Parametric Mapping (SPM 8, using a general linear model for whole brain comparison between the heroin and placebo conditions. We found that compared to placebo, heroin was associated with reduced perfusion in the left anterior cingulate cortex (ACC, the left medial prefrontal cortex (mPFC and in the insula (both hemispheres. Analysis of extracted perfusion values indicate strong effect sizes and no gender related differences. Reduced perfusion in these brain areas may indicate self- and emotional regulation effects of heroin in maintenance treatment.

  7. Comparison of 250 MHz electron spin echo and continuous wave oxygen EPR imaging methods for in vivo applications

    Science.gov (United States)

    Epel, Boris; Sundramoorthy, Subramanian V.; Barth, Eugene D.; Mailer, Colin; Halpern, Howard J.

    2011-01-01

    Purpose: The authors compare two electron paramagnetic resonance imaging modalities at 250 MHz to determine advantages and disadvantages of those modalities for in vivo oxygen imaging. Methods: Electron spin echo (ESE) and continuous wave (CW) methodologies were used to obtain three-dimensional images of a narrow linewidth, water soluble, nontoxic oxygen-sensitive trityl molecule OX063 in vitro and in vivo. The authors also examined sequential images obtained from the same animal injected intravenously with trityl spin probe to determine temporal stability of methodologies. Results: A study of phantoms with different oxygen concentrations revealed a threefold advantage of the ESE methodology in terms of reduced imaging time and more precise oxygen resolution for samples with less than 70 torr oxygen partial pressure. Above∼100 torr, CW performed better. The images produced by both methodologies showed pO2 distributions with similar mean values. However, ESE images demonstrated superior performance in low pO2 regions while missing voxels in high pO2 regions. Conclusions: ESE and CW have different areas of applicability. ESE is superior for hypoxia studies in tumors. PMID:21626937

  8. Selectively dispersed isotope labeling for protein structure determination by magic angle spinning NMR

    Energy Technology Data Exchange (ETDEWEB)

    Eddy, Matthew T. [Massachusetts Institute of Technology, Department of Chemistry (United States); Belenky, Marina [Brandeis University, Department of Chemistry (United States); Sivertsen, Astrid C. [Massachusetts Institute of Technology, Francis Bitter Magnet Laboratory (United States); Griffin, Robert G. [Massachusetts Institute of Technology, Department of Chemistry (United States); Herzfeld, Judith, E-mail: herzfeld@brandeis.edu [Brandeis University, Department of Chemistry (United States)

    2013-10-15

    The power of nuclear magnetic resonance spectroscopy derives from its site-specific access to chemical, structural and dynamic information. However, the corresponding multiplicity of interactions can be difficult to tease apart. Complimentary approaches involve spectral editing on the one hand and selective isotope substitution on the other. Here we present a new 'redox' approach to the latter: acetate is chosen as the sole carbon source for the extreme oxidation numbers of its two carbons. Consistent with conventional anabolic pathways for the amino acids, [1-{sup 13}C] acetate does not label {alpha} carbons, labels other aliphatic carbons and the aromatic carbons very selectively, and labels the carboxyl carbons heavily. The benefits of this labeling scheme are exemplified by magic angle spinning spectra of microcrystalline immunoglobulin binding protein G (GB1): the elimination of most J-couplings and one- and two-bond dipolar couplings provides narrow signals and long-range, intra- and inter-residue, recoupling essential for distance constraints. Inverse redox labeling, from [2-{sup 13}C] acetate, is also expected to be useful: although it retains one-bond couplings in the sidechains, the removal of CA-CO coupling in the backbone should improve the resolution of NCACX spectra.

  9. Studies on the clinical application of MR perfusion image using arterial spin labeling method

    International Nuclear Information System (INIS)

    Miyasaka, Kenji

    1999-01-01

    A new technique for imaging brain perfusion, arterial spin labeling method was applied in clinic. Brain perfusion was imaged by FAIR and EPISTAR both of which using arterial spin labeling (ASL) method. Suitable parameters for small contamination were examined using a imaging phantom. Then normal volunteers were examined for imaging timing. Suitable time between labeling pulse and imaging pulse for brain capillary and parenchyma was 1.0 sec. For clinical application study, total 48 patients with brain diseases were examined by FAIR and/or EPISTAR. A lesion/white matter signal intensity ratio was calculated in all clinical cases. Average of signal intensity ratio in infarction, tumor and arteriovenous malformation (AVM) were 0.8, 2.2 and 18.6 at FAIR, and 0.6, 2.2 and 12.8 at EPISTAR, respectively. Low perfusion diseases such as cerebral infarction have low signal intensity ratio and high perfusion diseases such as AVM have high signal intensity ratio in both FAIR and EPISTAR. Brain lesions were imaged similarly in FAIR and EPISTAR, and no remarkable difference was found between FAIR and EPISTAR. As a result of diagnostic trial by signal intensity ratio in operated tumor, hemorrhagic cases could be diagnosed by accuracies of 75% in FAIR and 100% in EPISTAR, respectively. (author)

  10. Computational and instrumental methods in EPR

    CERN Document Server

    Bender, Christopher J

    2006-01-01

    Computational and Instrumental Methods in EPR Prof. Bender, Fordham University Prof. Lawrence J. Berliner, University of Denver Electron magnetic resonance has been greatly facilitated by the introduction of advances in instrumentation and better computational tools, such as the increasingly widespread use of the density matrix formalism. This volume is devoted to both instrumentation and computation aspects of EPR, while addressing applications such as spin relaxation time measurements, the measurement of hyperfine interaction parameters, and the recovery of Mn(II) spin Hamiltonian parameters via spectral simulation. Key features: Microwave Amplitude Modulation Technique to Measure Spin-Lattice (T1) and Spin-Spin (T2) Relaxation Times Improvement in the Measurement of Spin-Lattice Relaxation Time in Electron Paramagnetic Resonance Quantitative Measurement of Magnetic Hyperfine Parameters and the Physical Organic Chemistry of Supramolecular Systems New Methods of Simulation of Mn(II) EPR Spectra: Single Cryst...

  11. How can EPR spectroscopy help to unravel molecular mechanisms of flavin-dependent photoreceptors?

    Directory of Open Access Journals (Sweden)

    Daniel eNohr

    2015-09-01

    Full Text Available Electron paramagnetic resonance (EPR spectroscopy is a well-established spectroscopic method for the examination of paramagnetic molecules. Proteins can contain paramagnetic moieties in form of stable cofactors, transiently formed intermediates, or spin labels artificially introduced to cysteine sites. The focus of this review is to evaluate potential scopes of application of EPR to the emerging field of optogenetics. The main objective for EPR spectroscopy in this context is to unravel the complex mechanisms of light-active proteins, from their primary photoreaction to downstream signal transduction. An overview of recent results from the family of flavin-containing, blue-light dependent photoreceptors is given. In detail, mechanistic similarities and differences are condensed from the three classes of flavoproteins, the cryptochromes, LOV (Light-oxygen-voltage, and BLUF (blue-light using FAD domains. Additionally, a concept that includes spin-labeled proteins and examination using modern pulsed EPR is introduced, which allows for a precise mapping of light-induced conformational changes.

  12. How can EPR spectroscopy help to unravel molecular mechanisms of flavin-dependent photoreceptors?

    Science.gov (United States)

    Nohr, Daniel; Rodriguez, Ryan; Weber, Stefan; Schleicher, Erik

    2015-01-01

    Electron paramagnetic resonance (EPR) spectroscopy is a well-established spectroscopic method for the examination of paramagnetic molecules. Proteins can contain paramagnetic moieties in form of stable cofactors, transiently formed intermediates, or spin labels artificially introduced to cysteine sites. The focus of this review is to evaluate potential scopes of application of EPR to the emerging field of optogenetics. The main objective for EPR spectroscopy in this context is to unravel the complex mechanisms of light-active proteins, from their primary photoreaction to downstream signal transduction. An overview of recent results from the family of flavin-containing, blue-light dependent photoreceptors is given. In detail, mechanistic similarities and differences are condensed from the three classes of flavoproteins, the cryptochromes, LOV (Light-oxygen-voltage), and BLUF (blue-light using FAD) domains. Additionally, a concept that includes spin-labeled proteins and examination using modern pulsed EPR is introduced, which allows for a precise mapping of light-induced conformational changes.

  13. A Short Introduction to Arterial Spin Labeling and its Application to Flow Territory Mapping.

    Science.gov (United States)

    Lindner, T; Helle, M; Jansen, O

    2015-10-01

    Arterial spin labeling (ASL) is an emerging method for the assessment of perfusion in various diseases of the brain. In ASL, the magnetization of arterial blood water spins is manipulated in a complete non-invasive way before flowing into the tissue of interest. This allows absolute quantification of cerebral blood flow, thereby, presenting an alternative to contrast-enhanced methods based on computed tomography or magnetic resonance imaging. Furthermore, its potential application for flow territory mapping can provide additional information of the individual configuration of intracerebral blood flow. This article gives a brief overview of the basic ASL methodology and its approaches to image individual perfusion territories. Additionally, the utilization of ASL in a variety of cerebrovascular diseases is presented to provide examples of potential applications of (territorial) ASL in clinical routine.

  14. Characterisation and vapour sensing properties of spin coated thin films of anthracene labelled PMMA polymer

    Energy Technology Data Exchange (ETDEWEB)

    Capan, I., E-mail: inci.capan@gmail.com [Balikesir University, Faculty of Art and Sciences, Department of Physics, Cagis Campus, 10145 Balikesir (Turkey); Tarimci, C., E-mail: Celik.Tarimci@eng.ankara.edu.tr [Ankara University, Faculty of Engineering, Department of Engineering Physics, 06100, Ankara (Turkey); Erdogan, M., E-mail: merdogan@balikesir.edu.tr [Balikesir University, Faculty of Art and Sciences, Department of Physics, Cagis Campus, 10145 Balikesir (Turkey); Hassan, A.K., E-mail: A.Hassan@shu.ac.uk [Materials and Engineering Research Institute, Sheffield Hallam University, Sheaf Building, Pond Street, Sheffield S1 1WB (United Kingdom)

    2009-05-05

    In the present article thin films of poly (methyl methacrylate) (PMMA) polymer labelled with anthracene (Ant-PMMA) prepared by spin coating are characterised by UV-visible spectroscopy, surface plasmon resonance (SPR), spectroscopic ellipsometry (SE) and Atomic Force Microscopy (AFM) and their organic vapour sensing properties are investigated. Ant-PMMA films' thickness are determined by performing theoretical fitting to experimental data measured using SPR and SE. Results obtained show that the spin-cast films are of good uniformity with an average thickness of 6-8 nm. Organic vapour sensing properties are studied using SPR technique during exposures to different volatile organic compounds (VOCs). Ant-PMMA films' response to the selected VOCs has been examined in terms of solubility parameters and molar volumes of the solvents, and the films were found to be largely sensitive to benzene vapour compared to other studied analytes.

  15. Characterisation and vapour sensing properties of spin coated thin films of anthracene labelled PMMA polymer

    International Nuclear Information System (INIS)

    Capan, I.; Tarimci, C.; Erdogan, M.; Hassan, A.K.

    2009-01-01

    In the present article thin films of poly (methyl methacrylate) (PMMA) polymer labelled with anthracene (Ant-PMMA) prepared by spin coating are characterised by UV-visible spectroscopy, surface plasmon resonance (SPR), spectroscopic ellipsometry (SE) and Atomic Force Microscopy (AFM) and their organic vapour sensing properties are investigated. Ant-PMMA films' thickness are determined by performing theoretical fitting to experimental data measured using SPR and SE. Results obtained show that the spin-cast films are of good uniformity with an average thickness of 6-8 nm. Organic vapour sensing properties are studied using SPR technique during exposures to different volatile organic compounds (VOCs). Ant-PMMA films' response to the selected VOCs has been examined in terms of solubility parameters and molar volumes of the solvents, and the films were found to be largely sensitive to benzene vapour compared to other studied analytes.

  16. Interactions of the spin-labeled chloroethylnitrosourea SLCNUgly with electrode-supported lipid films

    International Nuclear Information System (INIS)

    Tacheva, Bilyana; Georgieva, Radostina; Karabaliev, Miroslav

    2016-01-01

    The spin-labeled chloroethylnitrosourea containig glycine SLCNUgly is an analogue of the clinically used nitrosourea drug lomustine (1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea, CCNU), showing promising properties and features in vitro as well as in vivo. In this work the interaction of SLCNUgly with a lipid model membrane is investigated. The presented results indicate penetration of the drug in the membranes without causing defects of the lipid structure and reveal the potential of both SLCNUgly and electrode-supported lipid films as models for investigating nitrosourea drugs-membrane interactions.

  17. Arterial Spin Labeling and Blood Oxygen Level-Dependent MRI Cerebrovascular Reactivity in Cerebrovascular Disease

    DEFF Research Database (Denmark)

    Smeeing, Diederik P J; Hendrikse, Jeroen; Petersen, Esben T

    2016-01-01

    BACKGROUND: The cerebrovascular reactivity (CVR) results of blood oxygen level-dependent (BOLD) and arterial spin labeling (ASL) MRI studies performed in patients with cerebrovascular disease (steno-occlusive vascular disease or stroke) were systematically reviewed. SUMMARY: Thirty-one articles...... found a significant lower ASL CVR in the ipsilateral hemispheres of patients compared to controls. KEY MESSAGES: This review brings support for a reduced BOLD and ASL CVR in the ipsilateral hemisphere of patients with cerebrovascular disease. We suggest that future studies will be performed in a uniform...... way so reference values can be established and could be used to guide treatment decisions in patients with cerebrovascular disease....

  18. EPR correlations and EPW distributions

    International Nuclear Information System (INIS)

    Bell, J.S.

    1995-01-01

    In the case of two free spin-zero particles, the wave function originally considered by Einstein, Podolsky and Rosen to exemplify EPR correlations has a non-negative Wigner distribution. This distribution gives an explicitly local account of the correlations. For an irreducible non-locality, more elaborate wave functions are required, with Wigner distributions which are not non-negative. (author)

  19. EPR measurements in irradiated polyacetylene

    International Nuclear Information System (INIS)

    Hola, O.; Foeldesova, M.

    1990-01-01

    The influence of γ-irradiation on the paramagnetic properties of polyacetylene, and the dependence of the EPR spectra on the radiation dose in samples of irradiated polyacetylene were studied. The measurements show that no essential changes of the spin mobility occurred during irradiation. (author) 3 refs.; 2 figs

  20. EPR studies of melanin from Cladosporium cladosporioides

    International Nuclear Information System (INIS)

    Pilawa, B.; Buszman, E.; Latocha, M.; Wilczok, T.

    1996-01-01

    Free radical properties of Cladosporium cladosporioides mycelium and melanin, and synthetic eumelanin and pheomelanin were studied by electron paramagnetic resonance method. Single EPR line and complex EPR spectrum with hyperfine splitting were measured for model DOPA-melanin and cysteinyldopa-melanin, respectively. EPR spectra of Cladosporium cladosporioides samples and pheomelanin show the same character. The concentration of paramagnetic centers in melanins isolated from Cladosporium cladosporioides is considerably higher than that of crude mycelium, whereas the EPR line widths are lower for mycelium than for melanin samples. For all analyzed samples the increase of EPR signals intensity with the increase of microwave power, and the decrease of intensities after saturation were observed the low values of microwave power sufficient for EPR lines saturation demonstrate that the spin-lattice relaxation times of unpaired electrons in melanins are long. (author)

  1. Homogeneity and EPR metrics for assessment of regular grids used in CW EPR powder simulations.

    Science.gov (United States)

    Crăciun, Cora

    2014-08-01

    CW EPR powder spectra may be approximated numerically using a spherical grid and a Voronoi tessellation-based cubature. For a given spin system, the quality of simulated EPR spectra depends on the grid type, size, and orientation in the molecular frame. In previous work, the grids used in CW EPR powder simulations have been compared mainly from geometric perspective. However, some grids with similar homogeneity degree generate different quality simulated spectra. This paper evaluates the grids from EPR perspective, by defining two metrics depending on the spin system characteristics and the grid Voronoi tessellation. The first metric determines if the grid points are EPR-centred in their Voronoi cells, based on the resonance magnetic field variations inside these cells. The second metric verifies if the adjacent Voronoi cells of the tessellation are EPR-overlapping, by computing the common range of their resonance magnetic field intervals. Beside a series of well known regular grids, the paper investigates a modified ZCW grid and a Fibonacci spherical code, which are new in the context of EPR simulations. For the investigated grids, the EPR metrics bring more information than the homogeneity quantities and are better related to the grids' EPR behaviour, for different spin system symmetries. The metrics' efficiency and limits are finally verified for grids generated from the initial ones, by using the original or magnetic field-constraint variants of the Spherical Centroidal Voronoi Tessellation method. Copyright © 2014 Elsevier Inc. All rights reserved.

  2. Homogeneity and EPR metrics for assessment of regular grids used in CW EPR powder simulations

    Science.gov (United States)

    Crăciun, Cora

    2014-08-01

    CW EPR powder spectra may be approximated numerically using a spherical grid and a Voronoi tessellation-based cubature. For a given spin system, the quality of simulated EPR spectra depends on the grid type, size, and orientation in the molecular frame. In previous work, the grids used in CW EPR powder simulations have been compared mainly from geometric perspective. However, some grids with similar homogeneity degree generate different quality simulated spectra. This paper evaluates the grids from EPR perspective, by defining two metrics depending on the spin system characteristics and the grid Voronoi tessellation. The first metric determines if the grid points are EPR-centred in their Voronoi cells, based on the resonance magnetic field variations inside these cells. The second metric verifies if the adjacent Voronoi cells of the tessellation are EPR-overlapping, by computing the common range of their resonance magnetic field intervals. Beside a series of well known regular grids, the paper investigates a modified ZCW grid and a Fibonacci spherical code, which are new in the context of EPR simulations. For the investigated grids, the EPR metrics bring more information than the homogeneity quantities and are better related to the grids’ EPR behaviour, for different spin system symmetries. The metrics’ efficiency and limits are finally verified for grids generated from the initial ones, by using the original or magnetic field-constraint variants of the Spherical Centroidal Voronoi Tessellation method.

  3. In the search for new anticancer drugs XII. Synthesis and biological evaluation of spin labeled nitrosoureas.

    Science.gov (United States)

    Sosnovsky, G; Li, S W

    1985-04-15

    The spin labeled nitrosourea 1-(2-chloroethyl)-3-(1-oxyl-2,2,6,6- tetramethyl-piperidinyl)-1-nitrosourea (SLCNU, 4) and its analogues 5-7 were synthesized either by a regio-selective method or by a conventional route via the nitrosation of the spin labeled intermediates (11a-e). Nitrosation of the ureas 11a-e with dinitrogen tetraoxide resulted in better yields than those obtained with sodium nitrite. The nitrosoureas 4-8 were tested for their anticancer activity against the lymphocytic leukemia P388 in mice. Thus, either at the equal molar dose or at the dose of equal toxicity level, the SLCNU (4) was found to be more active than the clinically used CCNU (1). Unlike CCNU (1) whose LD50 is 56 mg/kg, the SLCNU (4) possesses a low toxicity (LD50 123 mg/kg). Therefore, SLCNU (4) is a promising new entry into the nitrosourea class of anticancer drugs.

  4. EPR and development of quantum electronics

    International Nuclear Information System (INIS)

    Manenkov, A A

    2011-01-01

    A role of electron paramagnetic resonance in development of quantum electronics is discussed. Basic principles and history of masers are briefly described. Spin-levels of paramagnetic ions in crystals as a very suitable object for active media of solid-state masers (called as EPR-masers) and physical processes in EPR-masers (population inversion of energy states) are analyzed. This analysis demonstrates a significant role of relaxation processes in multi-level spin-systems for efficient maser action. In this context peculiarities of spin-lattice and spin-spin cross relaxation processes in multi-level systems are analyzed. Development of EPR-masers and their application in radioastronomy and far-space communication systems are briefly described.

  5. Spin labelled nitrosoureas and triazenes and their non-labelled clinically used analogues--a comparative study on their physicochemical properties and antimelanomic effects.

    Science.gov (United States)

    Zheleva, A M; Gadjeva, V G

    2001-01-16

    Physicochemical properties, such as half life time (tau0.5), alkylating and carbamoylating activity and in vivo antimelanomic effects against B16 melanoma of spin labeled (containing nitroxyl free radical moiety) amino acid nitrosoureas, synthesized in our laboratory, have been studied and compared to those of the antitumor drug N'-cyclohexyl-N-(2-chloroethyl)-N-nitrosourea (lomustine, CCNU). We have shown that the introduction of amino acid moieties and the replacement of cyclohexylamine with nitroxyl moiety leads to a faster decomposition, higher alkylating, lower carbamoylating activity, better antimelanomic activity and lower general toxicity, when compared to those of CCNU. It was also established that spin labeled triazenes, previously synthesized by us, were more stable in phosphate saline than their nonlabeled analogue, 5-(3,3-dimethyltriazene-1-yl)-imidazole-4-carboxamide (dacarbazine, DTIC). A higher cytotoxicity to B16 melanoma cells than to YAC-1 and lymphocytes was demonstrated for all spin labeled triazenes, in comparison with DTIC. An assumption has been made to explain the lower general toxicity of the spin labeled nitrosoureas compared to that of CCNU. Based on the results presented, we accept that a new trend for synthesis of more selective and less toxic nitrosourea and triazene derivatives as potential antimelanomic drugs might be developed.

  6. Spin probes of chemistry in zeolites

    International Nuclear Information System (INIS)

    Werst, D.W.; Trifunac, A.D.

    1997-09-01

    Electron spin resonance (EPR) studies in zeolites are reviewed in which radiolysis was used to ionize the zeolite lattice, create reactive intermediates, spin label reaction products and to provide a window onto chemistry and transport of adsorbates and matrix control of chemistry. The review examines reactions of radical cations and the influence of the geometry constraints inside the zeolite, explores how zeolite model systems can be used to learn about energy and charge transfer in solids and illustrates the use of radiolysis and EPR for in situ spectroscopic studies of solid-acid catalysis. The various spin probes created inside the zeolite pores report on properties of the zeolites as well as shed light on radiolytic processes

  7. High-field EPR on membrane proteins - crossing the gap to NMR.

    Science.gov (United States)

    Möbius, Klaus; Lubitz, Wolfgang; Savitsky, Anton

    2013-11-01

    quantities of sample molecules have become sufficient to characterize stable and transient reaction intermediates of complex molecular systems - offering highly interesting applications for chemists, biochemists and molecular biologists. In three case studies, representative examples of advanced EPR spectroscopy are reviewed: (I) High-field PELDOR and ENDOR structure determination of cation-anion radical pairs in reaction centers from photosynthetic purple bacteria and cyanobacteria (Photosystem I); (II) High-field ENDOR and ELDOR-detected NMR spectroscopy on the oxygen-evolving complex of Photosystem II; and (III) High-field electron dipolar spectroscopy on nitroxide spin-labelled bacteriorhodopsin for structure-function studies. An extended conclusion with an outlook to further developments and applications is also presented. Copyright © 2013 Elsevier B.V. All rights reserved.

  8. Improving perfusion quantification in arterial spin labeling for delayed arrival times by using optimized acquisition schemes

    International Nuclear Information System (INIS)

    Kramme, Johanna; Diehl, Volker; Madai, Vince I.; Sobesky, Jan; Guenther, Matthias

    2015-01-01

    The improvement in Arterial Spin Labeling (ASL) perfusion quantification, especially for delayed bolus arrival times (BAT), with an acquisition redistribution scheme mitigating the T1 decay of the label in multi-TI ASL measurements is investigated. A multi inflow time (TI) 3D-GRASE sequence is presented which adapts the distribution of acquisitions accordingly, by keeping the scan time constant. The MR sequence increases the number of averages at long TIs and decreases their number at short TIs and thus compensating the T1 decay of the label. The improvement of perfusion quantification is evaluated in simulations as well as in-vivo in healthy volunteers and patients with prolonged BATs due to age or steno-occlusive disease. The improvement in perfusion quantification depends on BAT. At healthy BATs the differences are small, but become larger for longer BATs typically found in certain diseases. The relative error of perfusion is improved up to 30% at BATs > 1500 ms in comparison to the standard acquisition scheme. This adapted acquisition scheme improves the perfusion measurement in comparison to standard multi-TI ASL implementations. It provides relevant benefit in clinical conditions that cause prolonged BATs and is therefore of high clinical relevance for neuroimaging of steno-occlusive diseases.

  9. Noninvasive measurements of regional cerebral perfusion in preterm and term neonates by magnetic resonance arterial spin labeling

    DEFF Research Database (Denmark)

    Miranda Gimenez-Ricco, Maria Jo; Olofsson, K; Sidaros, Karam

    2006-01-01

    Magnetic resonance arterial spin labeling (ASL) at 3 Tesla has been investigated as a quantitative technique for measuring regional cerebral perfusion (RCP) in newborn infants. RCP values were measured in 49 healthy neonates: 32 preterm infants born before 34 wk of gestation and 17 term-born neon......Magnetic resonance arterial spin labeling (ASL) at 3 Tesla has been investigated as a quantitative technique for measuring regional cerebral perfusion (RCP) in newborn infants. RCP values were measured in 49 healthy neonates: 32 preterm infants born before 34 wk of gestation and 17 term...

  10. Algorithm for selection of optimized EPR distance restraints for de novo protein structure determination

    Science.gov (United States)

    Kazmier, Kelli; Alexander, Nathan S.; Meiler, Jens; Mchaourab, Hassane S.

    2010-01-01

    A hybrid protein structure determination approach combining sparse Electron Paramagnetic Resonance (EPR) distance restraints and Rosetta de novo protein folding has been previously demonstrated to yield high quality models (Alexander et al., 2008). However, widespread application of this methodology to proteins of unknown structures is hindered by the lack of a general strategy to place spin label pairs in the primary sequence. In this work, we report the development of an algorithm that optimally selects spin labeling positions for the purpose of distance measurements by EPR. For the α-helical subdomain of T4 lysozyme (T4L), simulated restraints that maximize sequence separation between the two spin labels while simultaneously ensuring pairwise connectivity of secondary structure elements yielded vastly improved models by Rosetta folding. 50% of all these models have the correct fold compared to only 21% and 8% correctly folded models when randomly placed restraints or no restraints are used, respectively. Moreover, the improvements in model quality require a limited number of optimized restraints, the number of which is determined by the pairwise connectivities of T4L α-helices. The predicted improvement in Rosetta model quality was verified by experimental determination of distances between spin labels pairs selected by the algorithm. Overall, our results reinforce the rationale for the combined use of sparse EPR distance restraints and de novo folding. By alleviating the experimental bottleneck associated with restraint selection, this algorithm sets the stage for extending computational structure determination to larger, traditionally elusive protein topologies of critical structural and biochemical importance. PMID:21074624

  11. Optimization of bicelle lipid composition and temperature for EPR spectroscopy of aligned membranes.

    Science.gov (United States)

    McCaffrey, Jesse E; James, Zachary M; Thomas, David D

    2015-01-01

    We have optimized the magnetic alignment of phospholipid bilayered micelles (bicelles) for EPR spectroscopy, by varying lipid composition and temperature. Bicelles have been extensively used in NMR spectroscopy for several decades, in order to obtain aligned samples in a near-native membrane environment and take advantage of the intrinsic sensitivity of magnetic resonance to molecular orientation. Recently, bicelles have also seen increasing use in EPR, which offers superior sensitivity and orientational resolution. However, the low magnetic field strength (less than 1 T) of most conventional EPR spectrometers results in homogeneously oriented bicelles only at a temperature well above physiological. To optimize bicelle composition for magnetic alignment at reduced temperature, we prepared bicelles containing varying ratios of saturated (DMPC) and unsaturated (POPC) phospholipids, using EPR spectra of a spin-labeled fatty acid to assess alignment as a function of lipid composition and temperature. Spectral analysis showed that bicelles containing an equimolar mixture of DMPC and POPC homogeneously align at 298 K, 20 K lower than conventional DMPC-only bicelles. It is now possible to perform EPR studies of membrane protein structure and dynamics in well-aligned bicelles at physiological temperatures and below. Copyright © 2014 Elsevier Inc. All rights reserved.

  12. Novelties in radiology: arterial spin labeling, the gadolinium-free MR perfusion

    International Nuclear Information System (INIS)

    Goncalves, Fabricio Guimaraes; Maldjian, Joseph A.

    2011-01-01

    Arterial spin labeling (ASL) is a recently developed magnetic resonance (MR) technique that assesses cerebral blood flow. This method has been mainly used for investigative purposes with very few centers in the world performing it on a routine clinical basis. ASL has already been validated and proven to be useful in the assessment of a growing number of diseases and conditions. As with any recently established technique, ASL has some limitations that need to be overcome to become more widely used and to be part of the daily routine of the neuroimaging specialist. Currently, four major current ASL techniques are available: pulsed ASL (PASL), continuous ASL (CASL), pseudo-continuous ASL (PCASL) and velocity-selective ASL (VSASL). This article describe these techniques

  13. Arterial spin-labeling perfusion imaging of childhood meningitis: a case series.

    Science.gov (United States)

    Wong, Alex Mun-Ching; Yeh, Chih-Hua; Liu, Ho-Ling; Lin, Kuang-Lin; Wang, Huei-Shyong; Toh, Cheng-Hong

    2016-03-01

    Conventional magnetic resonance imaging (MRI), which is mainly used to detect complications, is ineffective in determining the neurological status of patients with meningitis. Hemodynamic change in the brain may be more indicative of the neurological status but few imaging studies have verified this. Arterial spin-labeling (ASL) perfusion, a noninvasive MR method requiring no contrast agent injection, can be used to measure cerebral blood flow (CBF). We describe three pediatric patients with meningitis, who all showed regions of increased CBF on perfusion imaging. One patient, presenting with headache and conscious disturbance, had CBF changes in the frontal, temporal, and occipital regions. The other two patients, presenting with hallucinations, memory deficits, and seizures, had CBF changes in the frontal and temporal regions. ASL perfusion imaging may be helpful in assessing patients with meningitis, demonstrating CBF changes more strongly correlating with the neurological status, and detecting active brain abnormalities.

  14. Arterial Spin Labeling (ASL) fMRI: advantages, theoretical constrains, and experimental challenges in neurosciences.

    Science.gov (United States)

    Borogovac, Ajna; Asllani, Iris

    2012-01-01

    Cerebral blood flow (CBF) is a well-established correlate of brain function and therefore an essential parameter for studying the brain at both normal and diseased states. Arterial spin labeling (ASL) is a noninvasive fMRI technique that uses arterial water as an endogenous tracer to measure CBF. ASL provides reliable absolute quantification of CBF with higher spatial and temporal resolution than other techniques. And yet, the routine application of ASL has been somewhat limited. In this review, we start by highlighting theoretical complexities and technical challenges of ASL fMRI for basic and clinical research. While underscoring the main advantages of ASL versus other techniques such as BOLD, we also expound on inherent challenges and confounds in ASL perfusion imaging. In closing, we expound on several exciting developments in the field that we believe will make ASL reach its full potential in neuroscience research.

  15. Arterial spin labeling blood flow magnetic resonance imaging for evaluation of renal injury.

    Science.gov (United States)

    Liu, Yupin P; Song, Rui; Liang, Chang hong; Chen, Xin; Liu, Bo

    2012-08-15

    A multitude of evidence suggests that iodinated contrast material causes nephrotoxicity; however, there have been no previous studies that use arterial spin labeling (ASL) blood flow functional magnetic resonance imaging (fMRI) to investigate the alterations in effective renal plasma flow between normointensive and hypertensive rats following injection of contrast media. We hypothesized that FAIR-SSFSE arterial spin labeling MRI may enable noninvasive and quantitative assessment of regional renal blood flow abnormalities and correlate with disease severity as assessed by histological methods. Renal blood flow (RBF) values of the cortex and medulla of rat kidneys were obtained from ASL images postprocessed at ADW4.3 workstation 0.3, 24, 48, and 72 h before and after injection of iodinated contrast media (6 ml/kg). The H&E method for morphometric measurements was used to confirm the MRI findings. The RBF values of the outer medulla were lower than those of the cortex and the inner medulla as reported previously. Iodinated contrast media treatment resulted in decreases in RBF in the outer medulla and cortex in spontaneously hypertensive rats (SHR), but only in the outer medulla in normotensive rats. The iodinated contrast agent significantly decreased the RBF value in the outer medulla and the cortex in SHR compared with normotensive rats after injection of the iodinated contrast media. Histological observations of kidney morphology were also consistent with ASL perfusion changes. These results demonstrate that the RBF value can reflect changes of renal perfusion in the cortex and medulla. ASL-MRI is a feasible and accurate method for evaluating nephrotoxic drugs-induced kidney damage.

  16. Rapid-scan EPR imaging.

    Science.gov (United States)

    Eaton, Sandra S; Shi, Yilin; Woodcock, Lukas; Buchanan, Laura A; McPeak, Joseph; Quine, Richard W; Rinard, George A; Epel, Boris; Halpern, Howard J; Eaton, Gareth R

    2017-07-01

    In rapid-scan EPR the magnetic field or frequency is repeatedly scanned through the spectrum at rates that are much faster than in conventional continuous wave EPR. The signal is directly-detected with a mixer at the source frequency. Rapid-scan EPR is particularly advantageous when the scan rate through resonance is fast relative to electron spin relaxation rates. In such scans, there may be oscillations on the trailing edge of the spectrum. These oscillations can be removed by mathematical deconvolution to recover the slow-scan absorption spectrum. In cases of inhomogeneous broadening, the oscillations may interfere destructively to the extent that they are not visible. The deconvolution can be used even when it is not required, so spectra can be obtained in which some portions of the spectrum are in the rapid-scan regime and some are not. The technology developed for rapid-scan EPR can be applied generally so long as spectra are obtained in the linear response region. The detection of the full spectrum in each scan, the ability to use higher microwave power without saturation, and the noise filtering inherent in coherent averaging results in substantial improvement in signal-to-noise relative to conventional continuous wave spectroscopy, which is particularly advantageous for low-frequency EPR imaging. This overview describes the principles of rapid-scan EPR and the hardware used to generate the spectra. Examples are provided of its application to imaging of nitroxide radicals, diradicals, and spin-trapped radicals at a Larmor frequency of ca. 250MHz. Copyright © 2017 Elsevier Inc. All rights reserved.

  17. Modulating effect of new potential antimelanomic agents, spin-labeled triazenes and nitrosoureas on the DOPA-oxidase activity of tyrosinase.

    Science.gov (United States)

    Gadjeva, V; Zheleva, A; Raikova, E

    1999-07-01

    The modulating effect of newly synthesized alkylating spin labeled triazene and spin labeled nitrosourea derivatives on the DOPA-oxidase activity of mushroom tyrosinase has been investigated by Bumett's spectrophotometric method (Burnett et al., 1967). All spin labeled triazenes have exhibited activating effect on DOPA-oxidase activity of tyrosinase, whereas clinically used triazene (DTIC), which does not contain nitroxide moiety, have showed inhibiting effect. At the same experimental conditions the spin labeled aminoacid nitrosoureas have showed dual effect - activating, in the beginning of the enzyme reaction and inhibiting later on. It is deduced that the activating effect of the spin labeled compounds is due to the nitroxide moiety and the inhibiting effect of all compounds depends on their half-life time. This study might contribute to make more clear the mechanism of action of the new compounds and on the other hand would come in quite useful as a preliminary prognosis for their antimelanomic activity.

  18. Quantification of renal allograft perfusion using arterial spin labeling MRI: initial results.

    Science.gov (United States)

    Lanzman, Rotem S; Wittsack, Hans-Jörg; Martirosian, Petros; Zgoura, Panagiota; Bilk, Philip; Kröpil, Patric; Schick, Fritz; Voiculescu, Adina; Blondin, Dirk

    2010-06-01

    To quantify renal allograft perfusion in recipients with stable allograft function and acute decrease in allograft function using nonenhanced flow-sensitive alternating inversion recovery (FAIR)-TrueFISP arterial spin labeling (ASL) MR imaging. Following approval of the local ethics committee, 20 renal allograft recipients were included in this study. ASL perfusion measurement and an anatomical T2-weighted single-shot fast spin-echo (HASTE) sequence were performed on a 1.5-T scanner (Magnetom Avanto, Siemens, Erlangen, Germany). T2-weighted MR urography was performed in patients with suspected ureteral obstruction. Patients were assigned to three groups: group a, 6 patients with stable allograft function over the previous 4 months; group b, 7 patients with good allograft function who underwent transplantation during the previous 3 weeks; group c, 7 allograft recipients with an acute deterioration of renal function. Mean cortical perfusion values were 304.8 +/- 34.4, 296.5 +/- 44.1, and 181.9 +/- 53.4 mg/100 ml/min for groups a, b and c, respectively. Reduction in cortical perfusion in group c was statistically significant. Our results indicate that ASL is a promising technique for nonenhanced quantification of cortical perfusion of renal allografts. Further studies are required to determine the clinical value of ASL for monitoring renal allograft recipients.

  19. Quantification of renal allograft perfusion using arterial spin labeling MRI: initial results

    International Nuclear Information System (INIS)

    Lanzman, Rotem S.; Wittsack, Hans-Joerg; Bilk, Philip; Kroepil, Patric; Blondin, Dirk; Martirosian, Petros; Schick, Fritz; Zgoura, Panagiota; Voiculescu, Adina

    2010-01-01

    To quantify renal allograft perfusion in recipients with stable allograft function and acute decrease in allograft function using nonenhanced flow-sensitive alternating inversion recovery (FAIR)-TrueFISP arterial spin labeling (ASL) MR imaging. Following approval of the local ethics committee, 20 renal allograft recipients were included in this study. ASL perfusion measurement and an anatomical T2-weighted single-shot fast spin-echo (HASTE) sequence were performed on a 1.5-T scanner (Magnetom Avanto, Siemens, Erlangen, Germany). T2-weighted MR urography was performed in patients with suspected ureteral obstruction. Patients were assigned to three groups: group a, 6 patients with stable allograft function over the previous 4 months; group b, 7 patients with good allograft function who underwent transplantation during the previous 3 weeks; group c, 7 allograft recipients with an acute deterioration of renal function. Mean cortical perfusion values were 304.8 ± 34.4, 296.5 ± 44.1, and 181.9 ± 53.4 mg/100 ml/min for groups a, b and c, respectively. Reduction in cortical perfusion in group c was statistically significant. Our results indicate that ASL is a promising technique for nonenhanced quantification of cortical perfusion of renal allografts. Further studies are required to determine the clinical value of ASL for monitoring renal allograft recipients. (orig.)

  20. Early-stage differentiation between presenile Alzheimer’s disease and frontotemporal dementia using arterial spin labeling MRI

    NARCIS (Netherlands)

    R.M.E. Steketee (Rebecca); E.E. Bron (Esther); R. Meijboom (Rozanna); G.C. Houston (Gavin); S. Klein (Stefan); H.J.M.M. Mutsaerts (Henri J. M.); C. Méndez Orellana (Carolina); F.J. De Jong (Frank J.); J.C. van Swieten (John); A. van der Lugt (Aad); M. Smits (Marion)

    2016-01-01

    textabstractObjective: To investigate arterial spin labeling (ASL)-MRI for the early diagnosis of and differentiation between the two most common types of presenile dementia: Alzheimer’s disease (AD) and frontotemporal dementia (FTD), and for distinguishing age-related from pathological perfusion

  1. Early-stage differentiation between presenile Alzheimer’s disease and frontotemporal dementia using arterial spin labeling MRI

    NARCIS (Netherlands)

    R.M.E. Steketee (Rebecca); E.E. Bron (Esther); Meijboom, R. (Rozanna); Houston, G.C. (Gavin C.); Klein, S. (Stefan); H.J.M.M. Mutsaerts (Henri J. M.); Orellana, C.P.M. (Carolina P. Mendez); F.J. de Jong (Fransina); J.C. van Swieten (John); A. van der Lugt (Aad); M. Smits (Marion)

    2015-01-01

    textabstractObjective: To investigate arterial spin labeling (ASL)-MRI for the early diagnosis of and differentiation between the two most common types of presenile dementia: Alzheimer’s disease (AD) and frontotemporal dementia (FTD), and for distinguishing age-related from pathological perfusion

  2. Effect of thiol reactive reagents and ionizing radiation on the permeability of erythrocyte membrane for non-electrolyte spin labels

    International Nuclear Information System (INIS)

    Gwozdzinski, K.

    1986-01-01

    The paper presents some results on the effect of PCMB and NEM on the transport of non-electrolyte spin labels: TEMPO and TEMPOL across non-irradiated and irradiated porcine erythrocyte. Irradiated erythrocytes exhibited increased inhibitory effect of thiol reactive compounds in the TEMPO and TEMPOL transport compared to non-irradiated erythrocytes. (orig.)

  3. Conformational change in full-length mouse prion: A site-directed spin-labeling study

    International Nuclear Information System (INIS)

    Inanami, Osamu; Hashida, Shukichi; Iizuka, Daisuke; Horiuchi, Motohiro; Hiraoka, Wakako; Shimoyama, Yuhei; Nakamura, Hideo; Inagaki, Fuyuhiko; Kuwabara, Mikinori

    2005-01-01

    The structure of the mouse prion (moPrP) was studied using site-directed spin-labeling electron spin resonance (SDSL-ESR). Since a previous NMR study by Hornemanna et al., [Hornemanna, Korthb, Oeschb, Rieka, Widera, Wuethricha, Glockshubera, Recombinant full-length murine prion protein, mPrP (23-231): purification and spectroscopic characterization, FEBS Lett. 413 (1997) 277-281] has indicated that N96, D143, and T189 in moPrP are localized in a Cu 2+ binding region, Helix1 and Helix2, respectively, three recombinant moPrP mutations (N96C, D143C, and T189C) were expressed in an Escherichia coli system, and then refolded by dialysis under low pH and purified by reverse-phase HPLC. By using the preparation, we succeeded in preserving a target cystein residue without alteration of the α-helix structure of moPrP and were able to apply SDSL-ESR with a methane thiosulfonate spin label to the full-length prion protein. The rotational correlation times (τ) of 1.1, 3.3, and 4.8 ns were evaluated from the X-band ESR spectra at pH 7.4 and 20 deg C for N96R1, D143R1, and T189R1, respectively. τ reflects the fact that the Cu 2+ binding region is more flexible than Helix1 or Helix2. ESR spectra recorded at various temperatures revealed two phases together with a transition point at around 20 deg C in D143R1 and T189R1, but not in N96R1. With the variation of pH from 4.0 to 7.8, ESR spectra of T189R1 at 20 deg C showed a gradual increase of τ from 2.9 to 4.8 ns. On the other hand, the pH-dependent conformational changes in N96R1 and D143R1 were negligible. These results indicated that T189 located in Helix2 possessed a structure sensitive to physiological pH changes; simultaneously, N96 in the Cu 2+ binding region and D143 in Helix1 were conserved

  4. Comparing model-based and model-free analysis methods for QUASAR arterial spin labeling perfusion quantification.

    Science.gov (United States)

    Chappell, Michael A; Woolrich, Mark W; Petersen, Esben T; Golay, Xavier; Payne, Stephen J

    2013-05-01

    Amongst the various implementations of arterial spin labeling MRI methods for quantifying cerebral perfusion, the QUASAR method is unique. By using a combination of labeling with and without flow suppression gradients, the QUASAR method offers the separation of macrovascular and tissue signals. This permits local arterial input functions to be defined and "model-free" analysis, using numerical deconvolution, to be used. However, it remains unclear whether arterial spin labeling data are best treated using model-free or model-based analysis. This work provides a critical comparison of these two approaches for QUASAR arterial spin labeling in the healthy brain. An existing two-component (arterial and tissue) model was extended to the mixed flow suppression scheme of QUASAR to provide an optimal model-based analysis. The model-based analysis was extended to incorporate dispersion of the labeled bolus, generally regarded as the major source of discrepancy between the two analysis approaches. Model-free and model-based analyses were compared for perfusion quantification including absolute measurements, uncertainty estimation, and spatial variation in cerebral blood flow estimates. Major sources of discrepancies between model-free and model-based analysis were attributed to the effects of dispersion and the degree to which the two methods can separate macrovascular and tissue signal. Copyright © 2012 Wiley Periodicals, Inc.

  5. Accelerated territorial arterial spin labeling based on shared rotating control acquisition: an observer study for validation

    International Nuclear Information System (INIS)

    Kamano, Hironori; Yoshiura, Takashi; Hiwatashi, Akio; Yamashita, Koji; Takayama, Yukihisa; Nagao, Eiki; Sagiyama, Koji; Honda, Hiroshi; Zimine, Ivan

    2012-01-01

    Shared rotating control acquisition can shorten the imaging time of territorial arterial spin labeling (tASL) by 33% compared with the normal control acquisition scheme but potentially results in an inaccurate estimate of vascular territories due to imperfect magnetization transfer compensation. Our purpose was to validate the accuracy of the shared rotating control acquisition method in evaluation of vascular territories. Twenty-four patients underwent tASL at a 3.0-T MRI with the conventional normal control acquisition method. Composite vascular territory maps, in which the blood flows from the right and left internal carotid arteries and the posterior circulation were encoded in red-green-blue, were generated as a normal averaged control-label scheme and as a simulated shared rotating control scheme. Two observers independently reported the most dominant territorial flow in 26 brain regions corresponding to the arterial segments at three post-labeling time points. Inter-reader and inter-method agreements were analyzed using κ statistics. Overall inter-reader agreements were excellent for both the normal control and the shared rotating control methods (κ = 0.98, respectively). Overall inter-method agreement was also excellent (κ = 0.98), although relatively low agreement was noted in the bilateral posterior cerebral artery territories (κ = 0.79 to 0.93). Our results suggested that tASL using shared rotating control acquisition can provide information on the vascular territories comparable to that obtained using the normal control acquisition while substantially shortening the imaging time. (orig.)

  6. Demonstration of pulmonary perfusion heterogeneity induced by gravity and lung inflation using arterial spin labeling

    Energy Technology Data Exchange (ETDEWEB)

    Fan Li [Department of Radiology, ChangZheng Hospital, Second Military Medical University, Shanghai 200003 (China)], E-mail: fanli0930@163.com; Liu Shiyuan [Department of Radiology, ChangZheng Hospital, Second Military Medical University, Shanghai 200003 (China)], E-mail: fanli7938@chinaren.com; Xiao Xiangsheng [Department of Radiology, ChangZheng Hospital, Second Military Medical University, Shanghai 200003 (China)], E-mail: lizhaobin79@163.com; Sun Fei [GE Healthcare (China)], E-mail: Fei.sun@med.ge.com

    2010-02-15

    Objective: To evaluate the effect of gravity and lung inflation on pulmonary perfusion heterogeneity in human lung using an arterial spin labeling (ASL) sequence called flow sensitive alternating inversion recovery (FAIR). Materials and methods: Magnetic resonance imaging of lung perfusion using arterial spin labeling sequence was performed in supine position in ten healthy volunteers on a 1.5 T whole body scanner (GE Healthcare). Five coronal slices at an interval of 3 cm from dorsal to ventral (labeled as P3, P6, P9, P12, P15, sequently) were obtained when the volunteers performed breath holding on end expiration and the relative pulmonary blood flow (rPBF) was measured. Then, another coronal perfusion-weighted image of P3 slice was obtained on end inspiration. Tagging efficiency of pulmonary parenchyma with IR ({delta}SI), rPBF and area of the P3 slice were analyzed. Results: (1) Along the direction of gravity, a gradient was visually perceived as a vertical increase in rPBF. There were significant statistic differences in rPBF between any two coronal planes except that between P12 and P15. In supine position, regression coefficients of right and left lung were -4.98 and -5.16, respectively. This means that rPBF decreased 4.98 (right) and 5.16 (left) for each centimeter above the dorsal. No statistical difference was seen between ROIs placed along iso-gravitational plane. (2) For a same slice, there were significant statistic differences in {delta}SI, rPBF and area at different respiratory phases (P < 0.05). Greater {delta}SI and more perfusion were observed on end expiration than on end inspiration. The area was larger on end inspiration than on end expiration. Conclusion: Both gravity and respiratory phase are important determinants of pulmonary perfusion heterogeneity. FAIR is sensitive to demonstrate gravity- and respiratory phase-dependent differences in lung perfusion. Positioning the patient so that the area of interest is down-gravity and asking patient

  7. Location of the higher affinity copper site on human hemoglobin by the use of the spin label technique

    International Nuclear Information System (INIS)

    Tabak, M.; Louro, S.R.W.

    1983-11-01

    Addition of copper (II) ions to Cys β-93 maleimide spin-labelled human hemoglobin A produces a dramatic decrease in the amplitude of the spin-label ESR spectra. This effect was analyzed in the framework of Leigh's theory which permits interspin distances to be deduced from the effect of dipolar coupling on the ESR spectra and led to an estimate of 9A as the distance between the label and the higher affinity copper site. Taking into account the previous results which suggest that four nitrogen atoms coordinate with copper, and that the N terminal val β-1 and His β-2 residues are involved, the location of the higher affinity copper site is proposed to be at the β 1 β 2 interface of the hemoglobin molecule, involving the N terminal of one β subunit and the C terminal of the other. (Author) [pt

  8. Applications of EPR in radiation research

    CERN Document Server

    Lund, Anders

    2014-01-01

    Applications of EPR in Radiation Research is a multi-author contributed volume presented in eight themes: I. Elementary radiation processes (in situ and low temperature radiolysis, quantum solids); II: Solid state radiation chemistry (crystalline, amorphous and heterogeneous systems); III: Biochemistry, biophysics and biology applications (radicals in biomaterials, spin trapping, free-radical-induced DNA damage); IV: Materials science (polymeric and electronic materials, materials for treatment of nuclear waste, irradiated food); V: Radiation metrology (EPR-dosimetry, retrospective and medical

  9. A novel microfluidic rapid freeze-quench device for trapping reactions intermediates for high field EPR analysis.

    Science.gov (United States)

    Kaufmann, Royi; Yadid, Itamar; Goldfarb, Daniella

    2013-05-01

    Rapid freeze quench electron paramagnetic resonance (RFQ)-EPR is a method for trapping short lived intermediates in chemical reactions and subjecting them to EPR spectroscopy investigation for their characterization. Two (or more) reacting components are mixed at room temperature and after some delay the mixture is sprayed into a cold trap and transferred into the EPR tube. A major caveat in using commercial RFQ-EPR for high field EPR applications is the relatively large amount of sample needed for each time point, a major part of which is wasted as the dead volume of the instrument. The small sample volume (∼2μl) needed for high field EPR spectrometers, such as W-band (∼3.5T, 95GHz), that use cavities calls for the development of a microfluidic based RFQ-EPR apparatus. This is particularly important for biological applications because of the difficulties often encountered in producing large amounts of intrinsically paramagnetic proteins and spin labeled nucleic acid and proteins. Here we describe a dedicated microfluidic based RFQ-EPR apparatus suitable for small volume samples in the range of a few μl. The device is based on a previously published microfluidic mixer and features a new ejection mechanism and a novel cold trap that allows collection of a series of different time points in one continuous experiment. The reduction of a nitroxide radical with dithionite, employing the signal of Mn(2+) as an internal standard was used to demonstrate the performance of the microfluidic RFQ apparatus. Copyright © 2013 Elsevier Inc. All rights reserved.

  10. Relativistic Nonlocality and the EPR Paradox

    Science.gov (United States)

    Chamberlain, Thomas

    2014-03-01

    The exact violation of Bell's Inequalities is obtained with a local realistic model for spin. The model treats one particle that comprises a quantum ensemble and simulates the EPR data one coincidence at a time as a product state. Such a spin is represented by operators σx , iσy ,σz in its body frame rather than the usual set of σX ,σY ,σZ in the laboratory frame. This model, assumed valid in the absence of a measuring probe, contains both quantum polarizations and coherences. Each carries half the EPR correlation, but only half can be measured using coincidence techniques. The model further predicts the filter angles that maximize the spin correlation in EPR experiments.

  11. EPR of impurity ions in disordered solids

    International Nuclear Information System (INIS)

    Kliava, J.

    1986-01-01

    The state of the art in the EPR spectroscopy of disordered solids is reviewed and theoretical aspects of the EPR shape in disordered systems are discussed. Emphasis is placed on the concept of the joint probability density of the spin Hamiltonian parameters. A survey of experimental data is provided on distributions of spin Hamiltonian parametes obtained using computer simulation techniques. A quantitative information is given on the short-range ordering in disordered materials available from EPR studies. A procedure of extracting such type of data which consists in a transformation from the distribution of the spin Hamiltonian parameters to that of atomic coordinates in the surrounding of a paramagnetic center is outlined. Numerical estimates of the degree of continuous disorder are reviewed

  12. Site directed spin labeling studies of Escherichia coli dihydroorotate dehydrogenase N-terminal extension

    Energy Technology Data Exchange (ETDEWEB)

    Couto, Sheila G. [Instituto de Fisica de Sao Carlos, Universidade de Sao Paulo, Av. Trabalhador Sao-carlense 400, C.P. 369, 13560-970, Sao Carlos, SP (Brazil); Grupo de Biofisica e Fisica Aplicada a Medicina, Instituto de Fisica, Universidade Federal de Goias, Campus Samambaia, C.P. 131, 74001-970, Goiania, GO (Brazil); Cristina Nonato, M. [Laboratorio de Cristalografia de Proteinas, Faculdade de Ciencias Farmaceuticas de Ribeirao Preto, Universidade de Sao Paulo, Av. do Cafe S/N, 14040-903, Ribeirao Preto, SP (Brazil); Costa-Filho, Antonio J., E-mail: ajcosta@ffclrp.usp.br [Instituto de Fisica de Sao Carlos, Universidade de Sao Paulo, Av. Trabalhador Sao-carlense 400, C.P. 369, 13560-970, Sao Carlos, SP (Brazil); Departamento de Fisica, Faculdade de Filosofia, Ciencias e Letras de Ribeirao Preto, Av. Bandeirantes 3900, 14040-901, Ribeirao Preto, SP (Brazil)

    2011-10-28

    Highlights: Black-Right-Pointing-Pointer EcDHODH is a membrane-associated enzyme and a promising target for drug design. Black-Right-Pointing-Pointer Enzyme's N-terminal extension is responsible for membrane association. Black-Right-Pointing-Pointer N-terminal works as a molecular lid regulating access to the protein interior. -- Abstract: Dihydroorotate dehydrogenases (DHODHs) are enzymes that catalyze the fourth step of the de novo synthesis of pyrimidine nucleotides. In this reaction, DHODH converts dihydroorotate to orotate, using a flavine mononucleotide as a cofactor. Since the synthesis of nucleotides has different pathways in mammals as compared to parasites, DHODH has gained much attention as a promising target for drug design. Escherichia coli DHODH (EcDHODH) is a family 2 DHODH that interacts with cell membranes in order to promote catalysis. The membrane association is supposedly made via an extension found in the enzyme's N-terminal. In the present work, we used site directed spin labeling (SDSL) to specifically place a magnetic probe at positions 2, 5, 19, and 21 within the N-terminal and thus monitor, by using Electron Spin Resonance (ESR), dynamics and structural changes in this region in the presence of a membrane model system. Overall, our ESR spectra show that the N-terminal indeed binds to membranes and that it experiences a somewhat high flexibility that could be related to the role of this region as a molecular lid controlling the entrance of the enzyme's active site and thus allowing the enzyme to give access to quinones that are dispersed in the membrane and that are necessary for the catalysis.

  13. EPR study of the low-spin state of Ru.sup.3+./sup. in the YAl.sub.3./sub.(BO.sub.4./sub.).sub.3./sub. and EuAl.sub.3./sub.(BO.sub.3./sub.).sub.4./sub. aluminum borates

    Czech Academy of Sciences Publication Activity Database

    Prokhorov, Andriy; Chernush, L.F.; Dyakonov, V.P.; Szymczak, H.; Prokhorov, A.D.

    2016-01-01

    Roč. 420, Dec (2016), s. 285-289 ISSN 0304-8853 R&D Projects: GA MŠk LO1409; GA MŠk LM2015088 Institutional support: RVO:68378271 Keywords : EPR spectra * rare-earth * aluminum borates * spin Hamiltonian parameters * superposition model * low-spin state Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.630, year: 2016

  14. EPR of exchange coupled systems

    CERN Document Server

    Bencini, Alessandro

    2012-01-01

    From chemistry to solid state physics to biology, the applications of Electron Paramagnetic Resonance (EPR) are relevant to many areas. This unified treatment is based on the spin Hamiltonian approach and makes extensive use of irreducible tensor techniques to analyze systems in which two or more spins are magnetically coupled. This edition contains a new Introduction by coauthor Dante Gatteschi, a pioneer and scholar of molecular magnetism.The first two chapters review the foundations of exchange interactions, followed by examinations of the spectra of pairs and clusters, relaxation in oligon

  15. EPR and Bell Locality

    OpenAIRE

    Norsen, Travis

    2004-01-01

    A new formulation of the EPR argument is presented, one which uses John Bell's mathematically precise local causality condition in place of the looser locality assumption which was used in the original EPR paper and on which Niels Bohr seems to have based his objection to the EPR argument. The new formulation of EPR bears a striking resemblance to Bell's derivation of his famous inequalities. The relation between these two arguments -- in particular, the role of EPR as part one of Bell's two-...

  16. EPR of uranium ions

    International Nuclear Information System (INIS)

    Ursu, I.; Lupei, V.

    1984-02-01

    A review of the electron paramagnetic resonance data on the uranium ions is given. After a general account of the electronic structure of the uranium free atoms and ions, the influence of the external fields (magnetic field, crystal fields) is discussed. The main information obtained from EPR studies on the uranium ions in crystals are emphasized: identification of the valence and of the ground electronic state, determination of the structure of the centers, crystal field effects, role of the intermediate coupling and of the J-mixing, role of the covalency, determination of the nuclear spin, maqnetic dipole moment and electric quadrupole moment of the odd isotopes of uranium. These data emphasize the fact that the actinide group has its own identity and this is accutely manifested at the beginning of the 5fsup(n) series encompassed by the uranium ions. (authors)

  17. Quantifying Cerebellum Grey Matter and White Matter Perfusion Using Pulsed Arterial Spin Labeling

    Directory of Open Access Journals (Sweden)

    Xiufeng Li

    2014-01-01

    Full Text Available To facilitate quantification of cerebellum cerebral blood flow (CBF, studies were performed to systematically optimize arterial spin labeling (ASL parameters for measuring cerebellum perfusion, segment cerebellum to obtain separate CBF values for grey matter (GM and white matter (WM, and compare FAIR ASST to PICORE. Cerebellum GM and WM CBF were measured with optimized ASL parameters using FAIR ASST and PICORE in five subjects. Influence of volume averaging in voxels on cerebellar grey and white matter boundaries was minimized by high-probability threshold masks. Cerebellar CBF values determined by FAIR ASST were 43.8 ± 5.1 mL/100 g/min for GM and 27.6 ± 4.5 mL/100 g/min for WM. Quantitative perfusion studies indicated that CBF in cerebellum GM is 1.6 times greater than that in cerebellum WM. Compared to PICORE, FAIR ASST produced similar CBF estimations but less subtraction error and lower temporal, spatial, and intersubject variability. These are important advantages for detecting group and/or condition differences in CBF values.

  18. Quantifying cerebellum grey matter and white matter perfusion using pulsed arterial spin labeling.

    Science.gov (United States)

    Li, Xiufeng; Sarkar, Subhendra N; Purdy, David E; Briggs, Richard W

    2014-01-01

    To facilitate quantification of cerebellum cerebral blood flow (CBF), studies were performed to systematically optimize arterial spin labeling (ASL) parameters for measuring cerebellum perfusion, segment cerebellum to obtain separate CBF values for grey matter (GM) and white matter (WM), and compare FAIR ASST to PICORE. Cerebellum GM and WM CBF were measured with optimized ASL parameters using FAIR ASST and PICORE in five subjects. Influence of volume averaging in voxels on cerebellar grey and white matter boundaries was minimized by high-probability threshold masks. Cerebellar CBF values determined by FAIR ASST were 43.8 ± 5.1 mL/100 g/min for GM and 27.6 ± 4.5 mL/100 g/min for WM. Quantitative perfusion studies indicated that CBF in cerebellum GM is 1.6 times greater than that in cerebellum WM. Compared to PICORE, FAIR ASST produced similar CBF estimations but less subtraction error and lower temporal, spatial, and intersubject variability. These are important advantages for detecting group and/or condition differences in CBF values.

  19. Quantifying Cerebellum Grey Matter and White Matter Perfusion Using Pulsed Arterial Spin Labeling

    Science.gov (United States)

    Li, Xiufeng; Sarkar, Subhendra N.; Purdy, David E.; Briggs, Richard W.

    2014-01-01

    To facilitate quantification of cerebellum cerebral blood flow (CBF), studies were performed to systematically optimize arterial spin labeling (ASL) parameters for measuring cerebellum perfusion, segment cerebellum to obtain separate CBF values for grey matter (GM) and white matter (WM), and compare FAIR ASST to PICORE. Cerebellum GM and WM CBF were measured with optimized ASL parameters using FAIR ASST and PICORE in five subjects. Influence of volume averaging in voxels on cerebellar grey and white matter boundaries was minimized by high-probability threshold masks. Cerebellar CBF values determined by FAIR ASST were 43.8 ± 5.1 mL/100 g/min for GM and 27.6 ± 4.5 mL/100 g/min for WM. Quantitative perfusion studies indicated that CBF in cerebellum GM is 1.6 times greater than that in cerebellum WM. Compared to PICORE, FAIR ASST produced similar CBF estimations but less subtraction error and lower temporal, spatial, and intersubject variability. These are important advantages for detecting group and/or condition differences in CBF values. PMID:24949416

  20. Sequences of 12 monoclonal anti-dinitrophenyl spin-label antibodies for NMR studies

    International Nuclear Information System (INIS)

    Leahy, D.J.; Rule, G.S.; Whittaker, M.M.; McConnell, H.M.

    1988-01-01

    Eleven monoclonal antibodies specific for a spin-labeled dinitrophenyl hapten (DNP-SL) have been produces for use in NMR studies. They have been named AN01 and ANO3-AN12. The stability constants for the association of these antibodies with DNP-SL and related haptens were measured by fluorescence quenching. cDNA clones coding for the heavy and light chains of each antibody and of an additional anti-DNP-SL monoclonal antibody, ANO2, have been isolated. The nucleic acid sequence of the 5' end of each clone has been determined, and the amino acid sequence of the variable regions of each antibody has been deduced from the cDNA sequence. The sequences are relatively heterogeneous, but both the heavy and the light chains of ANO1 and ANO3 are derived from the same variable-region gene families as those of the ANO2 antibody. ANO7 has a heavy chain that is related to that of ANO2, and ANO9 has a related light chain. ANO5 and ANO6 are unrelated to ANO2 but share virtually identical heavy and light chains. Preliminary NMR difference spectra comparing related antibodies show that sequence-specific assignment of resonances is possible. Such spectra also provide a measure of structural relatedness

  1. Arterial spin-labelling perfusion MRI and outcome in neonates with hypoxic-ischemic encephalopathy

    International Nuclear Information System (INIS)

    Vis, Jill B. de; Hendrikse, Jeroen; Petersen, Esben T.; Vries, Linda S. de; Bel, Frank van; Alderliesten, Thomas; Negro, Simona; Groenendaal, Floris; Benders, Manon J.N.L.

    2015-01-01

    Hyperperfusion may be related to outcome in neonates with hypoxic-ischemic encephalopathy (HIE). The purpose of this study was to evaluate whether arterial spin labelling (ASL) perfusion is associated with outcome in neonates with HIE and to compare the predictive value of ASL MRI to known MRI predictive markers. Twenty-eight neonates diagnosed with HIE and assessed with MR imaging (conventional MRI, diffusion-weighted MRI, MR spectroscopy [MRS], and ASL MRI) were included. Perfusion in the basal ganglia and thalami was measured. Outcome at 9 or 18 months of age was scored as either adverse (death or cerebral palsy) or favourable. The median (range) perfusion in the basal ganglia and thalami (BGT) was 63 (28-108) ml/100 g/min in the neonates with adverse outcome and 28 (12-51) ml/100 g/min in the infants with favourable outcome (p 2 = 0.86, p < 0.001). Higher ASL perfusion values in neonates with HIE are associated with a worse neurodevelopmental outcome. A combination of the MRS and ASL MRI information is the best predictor of outcome. (orig.)

  2. Arterial spin-labelling perfusion MRI and outcome in neonates with hypoxic-ischemic encephalopathy

    Energy Technology Data Exchange (ETDEWEB)

    Vis, Jill B. de; Hendrikse, Jeroen [University Medical Center Utrecht, Department of Radiology, HP E 01.132, P.O. Box 85500, Utrecht (Netherlands); Petersen, Esben T. [University Medical Center Utrecht, Department of Radiology, HP E 01.132, P.O. Box 85500, Utrecht (Netherlands); University Medical Center Utrecht, Department of Radiotherapy, Utrecht (Netherlands); Vries, Linda S. de; Bel, Frank van; Alderliesten, Thomas; Negro, Simona; Groenendaal, Floris; Benders, Manon J.N.L. [Wilhelmina Children' s Hospital/University Medical Center Utrecht, Department of Neonatology, Utrecht (Netherlands)

    2015-01-15

    Hyperperfusion may be related to outcome in neonates with hypoxic-ischemic encephalopathy (HIE). The purpose of this study was to evaluate whether arterial spin labelling (ASL) perfusion is associated with outcome in neonates with HIE and to compare the predictive value of ASL MRI to known MRI predictive markers. Twenty-eight neonates diagnosed with HIE and assessed with MR imaging (conventional MRI, diffusion-weighted MRI, MR spectroscopy [MRS], and ASL MRI) were included. Perfusion in the basal ganglia and thalami was measured. Outcome at 9 or 18 months of age was scored as either adverse (death or cerebral palsy) or favourable. The median (range) perfusion in the basal ganglia and thalami (BGT) was 63 (28-108) ml/100 g/min in the neonates with adverse outcome and 28 (12-51) ml/100 g/min in the infants with favourable outcome (p < 0.01). The area-under-the-curve was 0.92 for ASL MRI, 0.97 for MRI score, 0.96 for Lac/NAA and 0.92 for ADC in the BGT. The combination of Lac/NAA and ASL MRI results was the best predictor of outcome (r {sup 2} = 0.86, p < 0.001). Higher ASL perfusion values in neonates with HIE are associated with a worse neurodevelopmental outcome. A combination of the MRS and ASL MRI information is the best predictor of outcome. (orig.)

  3. Enhancement of automated blood flow estimates (ENABLE) from arterial spin-labeled MRI.

    Science.gov (United States)

    Shirzadi, Zahra; Stefanovic, Bojana; Chappell, Michael A; Ramirez, Joel; Schwindt, Graeme; Masellis, Mario; Black, Sandra E; MacIntosh, Bradley J

    2018-03-01

    To validate a multiparametric automated algorithm-ENhancement of Automated Blood fLow Estimates (ENABLE)-that identifies useful and poor arterial spin-labeled (ASL) difference images in multiple postlabeling delay (PLD) acquisitions and thereby improve clinical ASL. ENABLE is a sort/check algorithm that uses a linear combination of ASL quality features. ENABLE uses simulations to determine quality weighting factors based on an unconstrained nonlinear optimization. We acquired a set of 6-PLD ASL images with 1.5T or 3.0T systems among 98 healthy elderly and adults with mild cognitive impairment or dementia. We contrasted signal-to-noise ratio (SNR) of cerebral blood flow (CBF) images obtained with ENABLE vs. conventional ASL analysis. In a subgroup, we validated our CBF estimates with single-photon emission computed tomography (SPECT) CBF images. ENABLE produced significantly increased SNR compared to a conventional ASL analysis (Wilcoxon signed-rank test, P Wilcoxon signed-rank test, P < 0.0001) and this similarity was strongly related to ASL SNR (t = 24, P < 0.0001). These findings suggest that ENABLE improves CBF image quality from multiple PLD ASL in dementia cohorts at either 1.5T or 3.0T, achieved by multiparametric quality features that guided postprocessing of dementia ASL. 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:647-655. © 2017 International Society for Magnetic Resonance in Medicine.

  4. Resting state cerebral blood flow with arterial spin labeling MRI in developing human brains.

    Science.gov (United States)

    Liu, Feng; Duan, Yunsuo; Peterson, Bradley S; Asllani, Iris; Zelaya, Fernando; Lythgoe, David; Kangarlu, Alayar

    2018-07-01

    The development of brain circuits is coupled with changes in neurovascular coupling, which refers to the close relationship between neural activity and cerebral blood flow (CBF). Studying the characteristics of CBF during resting state in developing brain can be a complementary way to understand the functional connectivity of the developing brain. Arterial spin labeling (ASL), as a noninvasive MR technique, is particularly attractive for studying cerebral perfusion in children and even newborns. We have collected pulsed ASL data in resting state for 47 healthy subjects from young children to adolescence (aged from 6 to 20 years old). In addition to studying the developmental change of static CBF maps during resting state, we also analyzed the CBF time series to reveal the dynamic characteristics of CBF in differing age groups. We used the seed-based correlation analysis to examine the temporal relationship of CBF time series between the selected ROIs and other brain regions. We have shown the developmental patterns in both static CBF maps and dynamic characteristics of CBF. While higher CBF of default mode network (DMN) in all age groups supports that DMN is the prominent active network during the resting state, the CBF connectivity patterns of some typical resting state networks show distinct patterns of metabolic activity during the resting state in the developing brains. Copyright © 2018 European Paediatric Neurology Society. All rights reserved.

  5. ASAP (Automatic Software for ASL Processing): A toolbox for processing Arterial Spin Labeling images.

    Science.gov (United States)

    Mato Abad, Virginia; García-Polo, Pablo; O'Daly, Owen; Hernández-Tamames, Juan Antonio; Zelaya, Fernando

    2016-04-01

    The method of Arterial Spin Labeling (ASL) has experienced a significant rise in its application to functional imaging, since it is the only technique capable of measuring blood perfusion in a truly non-invasive manner. Currently, there are no commercial packages for processing ASL data and there is no recognized standard for normalizing ASL data to a common frame of reference. This work describes a new Automated Software for ASL Processing (ASAP) that can automatically process several ASL datasets. ASAP includes functions for all stages of image pre-processing: quantification, skull-stripping, co-registration, partial volume correction and normalization. To assess the applicability and validity of the toolbox, this work shows its application in the study of hypoperfusion in a sample of healthy subjects at risk of progressing to Alzheimer's disease. ASAP requires limited user intervention, minimizing the possibility of random and systematic errors, and produces cerebral blood flow maps that are ready for statistical group analysis. The software is easy to operate and results in excellent quality of spatial normalization. The results found in this evaluation study are consistent with previous studies that find decreased perfusion in Alzheimer's patients in similar regions and demonstrate the applicability of ASAP. Copyright © 2015 Elsevier Inc. All rights reserved.

  6. Skull metastases detecting on arterial spin labeling perfusion: Three case reports and review of literature.

    Science.gov (United States)

    Ryu, Kyeong H; Baek, Hye J; Cho, Soo B; Moon, Jin I; Choi, Bo H; Park, Sung E; An, Hyo J

    2017-11-01

    Detection of skull metastases is as important as detection of brain metastases because early diagnosis of skull metastases is a crucial determinant of treatment. However, the skull can be a blind spot for assessing metastases on routine brain magnetic resonance imaging (MRI). To the best of our knowledge, the finding of skull metastases on arterial spin labeling (ASL) has not been reported. ASL is a specific MRI sequence for evaluating cerebral blood flow using magnetized endogenous inflow blood. This study uses ASL as a routine sequence of brain MRI protocol and describes 3 clinical cases of skull metastases identified by ASL. The study also highlights the clinical usefulness of ASL in detecting skull metastases. Three patients with known malignancy underwent brain MRI to evaluate for brain metastases. All of the skull metastases were conspicuously depicted on routine ASL images, and the lesions correlated well with other MRI sequences. Three patients received palliative chemotherapy. Three patients are being followed up regularly at the outpatient department. The routine use of ASL may help to detect lesions in blind spots, such as skull metastases, and to facilitate the evaluation of intracranial pathologies without the use of contrast materials in exceptional situations.

  7. Effect of polysaccharide capsule of the microalgae Staurastrum iversenii var. americanum on diffusion of charged and uncharged molecules, using EPR technique

    International Nuclear Information System (INIS)

    Freire-Nordi, Cristina S.; Nascimento, Otaciro R.; Vieira, Armando A.H.; Nakaie, Clovis R.

    2006-01-01

    The existence of a mucilaginous envelope, sheath or capsule is usual in many desmids, but few data concerning its function are available. Previous studies of the transport function and permeation of molecules through the algae capsules were done using the algae Spondylosium panduriforme and Nephrocytium lunatum, the Electron Paramagnetic Resonance (EPR) technique, and different spin labels. The results suggested that the capsule functions as a selective diffusion medium. In the present work charged and uncharged molecules (spin labels group A) and Staurastrum iversenii var. americanum (Desmids),whose alga presents a great mucilaginous capsule, were used. Charged nitroxide molecules similar to amino acids (spin labels group B) were also used allowing a better understanding of the electrostatic effect in the permeation process across the capsule. The role of the cell capsule in the solute diffusion was evaluated by determining the capsulated and decapsulated cell permeation times. The permeation times for all spin labels tested in the cells lacking capsules were always shorter than those containing this physical barrier. The decay times of spin labels group A observed for S. iversenii were compared to other studied algae. The results regarding the diffusion of charged spin labels group B suggested that the interaction of cell capsule occurs more strongly with negatively charged molecules than with positively charged ones. The results obtained in this work with spin labels group A confirm that the capsule is an essential structure for the cell, and that due to the polar interactions with the spin labels, it plays an important role in the selection of small molecules. Several parameters, mainly those of electrostatic nature, seem to control the permeation across the algal capsules of spin labels group B, showing that structures which are similar to amino acids could diffuse across the interior of the algal cell. (author)

  8. EPR study of the low-spin state of Ru{sup 3+}in the YAl{sub 3}(BO{sub 3}){sub 4} and EuAl{sub 3}(BO{sub 3}){sub 4} aluminum borates

    Energy Technology Data Exchange (ETDEWEB)

    Prokhorov, A.A., E-mail: andaprokhorov@gmail.com [Institute of Physics AS CR, Na Slovance 2, Praha 8 18221 (Czech Republic); Chernush, L.F. [A.A. Galkin Donetsk Physico-Technical Institute, 72, R. Luxembourg Str., Donetsk 83114 (Ukraine); Dyakonov, V.P.; Szymczak, H. [Institute of Physics, PAS, al. Lotników 32/46, Warsaw 02-668 (Poland); Prokhorov, A.D. [A.A. Galkin Donetsk Physico-Technical Institute, 72, R. Luxembourg Str., Donetsk 83114 (Ukraine)

    2016-12-15

    New data on the ground state of impurity Ru{sup 3+} ions in the crystals of YAl{sub 3}(BO{sub 3}){sub 4} and EuAl{sub 3}(BO{sub 3}){sub 4} aluminum borates were obtained. It was shown that Ru{sup 3+} ion replaces trivalent rare-earth ions without breaking the symmetry of the site. The crystal field acting on 4d{sup 5} ions forms an EPR spectrum, which is described by the spin Hamiltonian with S=1/2. The spin-Hamiltonian parameters determined are equal to g{sub II}=1.963, g{sub ⊥}=3.796, A{sub II}=43.03*10{sup −4} cm{sup −1}, A{sub ⊥}=84.86*10{sup −4} cm{sup −1} in the YAl{sub 3}(BO{sub 3}){sub 4} crystal (at T=15 K) and g{sub II}=2.016, g{sub ⊥}=3.796 in the EuAl{sub 3}(BO{sub 3}){sub 4} crystal (at T=15 K). It is found that the value of ∆g=g{sub II}-g{sub ⊥} is an indicator of distortions of nearest environment of Ru{sup 3+} ion. The angle between the C{sub 3} axis and the direction into nearest oxygen ion was determined. The EPR linewidth of Ru{sup 3+} ion increases with increasing temperature due to the dipole-dipole and exchange interactions with the excited states of the host lattice Ru{sup 3+} ion.

  9. Mobility of TOAC spin-labelled peptides binding to the Src SH3 domain studied by paramagnetic NMR

    Energy Technology Data Exchange (ETDEWEB)

    Lindfors, Hanna E. [Leiden University, Leiden Institute of Chemistry, Gorlaeus Laboratories (Netherlands); Koning, Peter E. de; Wouter Drijfhout, Jan [Leiden University Medical Centre, Department of Immunohematology and Blood Transfusion (Netherlands); Venezia, Brigida; Ubbink, Marcellus [Leiden University, Leiden Institute of Chemistry, Gorlaeus Laboratories (Netherlands)], E-mail: m.ubbink@chem.leidenuniv.nl

    2008-07-15

    Paramagnetic relaxation enhancement provides a tool for studying the dynamics as well as the structure of macromolecular complexes. The application of side-chain coupled spin-labels is limited by the mobility of the free radical. The cyclic, rigid amino acid spin-label TOAC (2,2,6,6-Tetramethylpiperidine-1-oxyl-4-amino-4-carboxylic acid), which can be incorporated straightforwardly by peptide synthesis, provides an attractive alternative. In this study, TOAC was incorporated into a peptide derived from focal adhesion kinase (FAK), and the interaction of the peptide with the Src homology 3 (SH3) domain of Src kinase was studied, using paramagnetic NMR. Placing TOAC within the binding motif of the peptide has a considerable effect on the peptide-protein binding, lowering the affinity substantially. When the TOAC is positioned just outside the binding motif, the binding constant remains nearly unaffected. Although the SH3 domain binds weakly and transiently to proline-rich peptides from FAK, the interaction is not very dynamic and the relative position of the spin-label to the protein is well-defined. It is concluded that TOAC can be used to generate reliable paramagnetic NMR restraints.

  10. Mobility of TOAC spin-labelled peptides binding to the Src SH3 domain studied by paramagnetic NMR

    International Nuclear Information System (INIS)

    Lindfors, Hanna E.; Koning, Peter E. de; Wouter Drijfhout, Jan; Venezia, Brigida; Ubbink, Marcellus

    2008-01-01

    Paramagnetic relaxation enhancement provides a tool for studying the dynamics as well as the structure of macromolecular complexes. The application of side-chain coupled spin-labels is limited by the mobility of the free radical. The cyclic, rigid amino acid spin-label TOAC (2,2,6,6-Tetramethylpiperidine-1-oxyl-4-amino-4-carboxylic acid), which can be incorporated straightforwardly by peptide synthesis, provides an attractive alternative. In this study, TOAC was incorporated into a peptide derived from focal adhesion kinase (FAK), and the interaction of the peptide with the Src homology 3 (SH3) domain of Src kinase was studied, using paramagnetic NMR. Placing TOAC within the binding motif of the peptide has a considerable effect on the peptide-protein binding, lowering the affinity substantially. When the TOAC is positioned just outside the binding motif, the binding constant remains nearly unaffected. Although the SH3 domain binds weakly and transiently to proline-rich peptides from FAK, the interaction is not very dynamic and the relative position of the spin-label to the protein is well-defined. It is concluded that TOAC can be used to generate reliable paramagnetic NMR restraints

  11. Nitrogen ligation to manganese in the photosynthetic oxygen-evolving complex: Continuous-wave and pulsed EPR studies of Photosystem II particles containing 14N or 15N

    International Nuclear Information System (INIS)

    DeRose, V.J.; Yachandra, V.K.; McDermott, A.E.; Britt, R.D.; Sauer, K.; Klein, M.P.

    1991-01-01

    The possibility of nitrogen ligation to the Mn in the oxygen-evolving complex from photosystem II was investigated with electron paramagnetic resonance (EPR) and electron spin echo envelope modulation (ESEEM) spectroscopies using 14 N- and 15 N-labeled preparations. Oxygen-evolving preparations were isolated from a thermophilic cyanobacterium, Synechococcus sp., grown on a medium containing either 14 NO 3 - or 15 NO - 3 as the sole source of nitrogen. The substructure on the multiline EPR signal, which arises from Mn in the S 2 state of the enzyme, was measured with continuous-wave EPR. No changes were detected in the substructure peak positions upon substitution of 15 N for 14 N, indicating that this substructure is not due to superhyperfine coupling from nitrogen ligands. To detect potential nitrogen ligands with superhyperfine couplings of lesser magnitude than could be observed with conventional EPR methods, electron spin-echo envelope modulation experiments were also performed on the multiline EPR signal. The Fourier transform of the light-minus-dark time domain ESEEM data shows a peak at 4.8 MHz in 14 N samples which is absent upon substitution with 15 N. This gives unambiguous evidence for weak hyperfine coupling of nitrogen to the Mn of the oxygen-evolving complex. Possible origins of this nitrogen interaction are discussed

  12. Improving the Grading Accuracy of Astrocytic Neoplasms Noninvasively by Combining Timing Information with Cerebral Blood Flow: A Multi-TI Arterial Spin-Labeling MR Imaging Study.

    Science.gov (United States)

    Yang, S; Zhao, B; Wang, G; Xiang, J; Xu, S; Liu, Y; Zhao, P; Pfeuffer, J; Qian, T

    2016-12-01

    Systematic and accurate glioma grading has clinical significance. We present the utility of multi-TI arterial spin-labeling imaging and provide the bolus arrival time maps for grading astrocytomas. Forty-three patients with astrocytomas (21 men; mean age, 51 years) were recruited. The classification abilities of conventional MR imaging features, normalized CBF value derived from multi-TI arterial spin-labeling imaging, normalized bolus arrival time, and normalized CBF derived from single-TI arterial spin-labeling were compared in patients with World Health Organization (WHO) grade II, III, and IV astrocytomas. The normalized CBF value derived from multi-TI arterial spin-labeling imaging was higher in patients with higher grade astrocytoma malignancies compared with patients with lower grade astrocytomas, while the normalized bolus arrival time showed the opposite tendency. The normalized CBF value derived from the multi-TI arterial spin-labeling imaging showed excellent performance with areas under the receiver operating characteristic curve of 0.813 (WHO II versus III), 0.964 (WHO II versus IV), 0.872 (WHO III versus IV), and 0.883 (low-grade-versus-high-grade gliomas). The normalized CBF value derived from single-TI arterial spin-labeling imaging could statistically differentiate the WHO II and IV groups (area under the receiver operating characteristic curve = 0.826). The normalized bolus arrival time effectively identified the WHO grades II and III with an area under the receiver operating characteristic curve of 0.836. Combining the normalized CBF value derived from multi-TI arterial spin-labeling imaging and normalized bolus arrival time improved the diagnostic accuracy from 65.10% to 72.10% compared with the normalized CBF value derived from multi-TI arterial spin-labeling imaging being applied independently. The combination of multi-TI arterial spin-labeling imaging and conventional MR imaging had the best performance, with a diagnostic accuracy of 81

  13. Correlation between the rate of bioreduction of nitroxide spin label by human tumor cells and their low-dose radiation response

    International Nuclear Information System (INIS)

    Halpern, H.J.; Peric, M.; Nguyen, T.D.; Spencer, D.P.; Bowman, M.K.; Beckett, M.; Weichselbaum, R.R.

    1988-01-01

    The authors discuss a correlation observed between the bioreduction of nitroxide spin label by four human tumor cell lines and a normal tissue fibroblast clone and their low-dose radiation response, specifically their D Q . In measurements of the bioreduction rate of several other cell lines, this correlation appears to persist. In order to define the mechanism of this correlation, they have begun by subtly altering the measurement conditions. The original conditions for measurement involved adding the spin label to cells whose culture medium had been changed (the label was added to the new medium). By delaying the addition of the label to the culture medium, they substantially reduced the variation of the bioreduction rate between the cell lines. This implies that the fresh medium provides a nonspecific irritant or disequilibrium to the cultured cell system to which they response variably by accelerating, among other things, the metabolic process responsible for spin label bioreduction

  14. A web-based database for EPR centers in semiconductors

    International Nuclear Information System (INIS)

    Umeda, T.; Hagiwara, S.; Katagiri, M.; Mizuochi, N.; Isoya, J.

    2006-01-01

    We develop a web-based database system for electron paramagnetic resonance (EPR) centers in semiconductors. This database is available to anyone at http://www.kc.tsukuba.ac.jp/div-media/epr/. It currently has more than 300 records of the spin-Hamiltonian parameters for major known EPR centers. One can upload own new records to the database or can use simulation tools powered by EPR-NMR(C). Here, we describe the features and objectives of this database, and mention some future plans

  15. Arterial spin labelling perfusion MRI of breast cancer using FAIR TrueFISP: Initial results

    International Nuclear Information System (INIS)

    Buchbender, S.; Obenauer, S.; Mohrmann, S.; Martirosian, P.; Buchbender, C.; Miese, F.R.; Wittsack, H.J.; Miekley, M.; Antoch, G.; Lanzman, R.S.

    2013-01-01

    Aim: To assess the feasibility of an unenhanced, flow-sensitive, alternating inversion recovery-balanced steady-state free precession (FAIR TrueFISP) arterial spin labelling (ASL) magnetic resonance imaging (MRI) technique for quantification of breast cancer perfusion. Materials and methods: Eighteen untreated breast tumour patients (mean age 53 ± 17 years, range 30–68 years) and four healthy controls (mean age 51 ± 14 years, range 33–68 years) were enrolled in this study and were imaged using a clinical 1.5 T MRI machine. Perfusion measurements were performed using a coronal single-section ASL FAIR TrueFISP technique in addition to a routine breast MRI examination. T1 relaxation time of normal breast parenchyma was determined in four healthy volunteers using the variable flip angle approach. The definitive diagnosis was obtained at histology after biopsy or surgery and was available for all patients. Results: ASL perfusion was successfully acquired in 13 of 18 tumour patients and in all healthy controls. The mean ASL perfusion of invasive ductal carcinoma tissue was significantly higher (88.2 ± 39.5 ml/100 g/min) compared to ASL perfusion of normal breast parenchyma (24.9 ± 12.7 ml/100 g/min; p < 0.05) and invasive lobular carcinoma (30.5 ± 4.3 ml/100 g/min; p < 0.05). No significant difference was found between the mean ASL perfusion of normal breast parenchyma and invasive lobular carcinoma tissue (p = 0.97). Conclusion: ASL MRI enables quantification of breast cancer perfusion without the use of contrast material. However, its impact on diagnosis and therapy management of breast tumours has to be evaluated in larger patient studies

  16. Transit time corrected arterial spin labeling technique aids to overcome delayed transit time effect

    International Nuclear Information System (INIS)

    Yun, Tae Jin; Sohn, Chul-Ho; Yoo, Roh-Eul; Kang, Kyung Mi; Choi, Seung Hong; Kim, Ji-hoon; Park, Sun-Won; Hwang, Moonjung; Lebel, R.M.

    2018-01-01

    This study aimed to evaluate the usefulness of transit time corrected cerebral blood flow (CBF) maps based on multi-phase arterial spin labeling MR perfusion imaging (ASL-MRP). The Institutional Review Board of our hospital approved this retrospective study. Written informed consent was waived. Conventional and multi-phase ASL-MRPs and dynamic susceptibility contrast MR perfusion imaging (DSC-MRP) were acquired for 108 consecutive patients. Vascular territory-based volumes of interest were applied to CBF and time to peak (TTP) maps obtained from DSC-MRP and CBF maps obtained from conventional and multi-phase ASL-MRPs. The concordances between normalized CBF (nCBF) from DSC-MRP and nCBF from conventional and transition time corrected CBF maps from multi-phase ASL-MRP were evaluated using Bland-Altman analysis. In addition, the dependence of difference between nCBF (ΔnCBF) values obtained from DSC-MRP and conventional ASL-MRP (or multi-phase ASL-MRP) on TTP obtained from DSC-MRP was also analyzed using regression analysis. The values of nCBFs from conventional and multi-phase ASL-MRPs had lower values than nCBF based on DSC-MRP (mean differences, 0.08 and 0.07, respectively). The values of ΔnCBF were dependent on TTP values from conventional ASL-MRP technique (F = 5.5679, P = 0.0384). No dependency of ΔnCBF on TTP values from multi-phase ASL-MRP technique was revealed (F = 0.1433, P > 0.05). The use of transit time corrected CBF maps based on multi-phase ASL-MRP technique can overcome the effect of delayed transit time on perfusion maps based on conventional ASL-MRP. (orig.)

  17. Arterial spin labelling shows functional depression of non-lesion tissue in chronic Wernicke's aphasia.

    Science.gov (United States)

    Robson, Holly; Specht, Karsten; Beaumont, Helen; Parkes, Laura M; Sage, Karen; Lambon Ralph, Matthew A; Zahn, Roland

    2017-07-01

    Behavioural impairment post-stroke is a consequence of structural damage and altered functional network dynamics. Hypoperfusion of intact neural tissue is frequently observed in acute stroke, indicating reduced functional capacity of regions outside the lesion. However, cerebral blood flow (CBF) is rarely investigated in chronic stroke. This study investigated CBF in individuals with chronic Wernicke's aphasia (WA) and examined the relationship between lesion, CBF and neuropsychological impairment. Arterial spin labelling CBF imaging and structural MRIs were collected in 12 individuals with chronic WA and 13 age-matched control participants. Joint independent component analysis (jICA) investigated the relationship between structural lesion and hypoperfusion. Partial correlations explored the relationship between lesion, hypoperfusion and language measures. Joint ICA revealed significant differences between the control and WA groups reflecting a large area of structural lesion in the left posterior hemisphere and an associated area of hypoperfusion extending into grey matter surrounding the lesion. Small regions of remote cortical hypoperfusion were observed, ipsilateral and contralateral to the lesion. Significant correlations were observed between the neuropsychological measures (naming, repetition, reading and semantic association) and the jICA component of interest in the WA group. Additional ROI analyses found a relationship between perfusion surrounding the core lesion and the same neuropsychological measures. This study found that core language impairments in chronic WA are associated with a combination of structural lesion and abnormal perfusion in non-lesioned tissue. This indicates that post-stroke impairments are due to a wider disruption of neural function than observable on structural T1w MRI. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

  18. Transit time corrected arterial spin labeling technique aids to overcome delayed transit time effect

    Energy Technology Data Exchange (ETDEWEB)

    Yun, Tae Jin; Sohn, Chul-Ho; Yoo, Roh-Eul; Kang, Kyung Mi; Choi, Seung Hong; Kim, Ji-hoon [Seoul National University Medical Research Center, Institute of Radiation Medicine, Seoul (Korea, Republic of); Seoul National University Hospital, Department of Radiology, Seoul (Korea, Republic of); Park, Sun-Won [Seoul National University Medical Research Center, Institute of Radiation Medicine, Seoul (Korea, Republic of); Seoul National University Boramae Medical Center, Department of Radiology, Seoul (Korea, Republic of); Hwang, Moonjung [GE Healthcare Korea, Seoul (Korea, Republic of); Lebel, R.M. [GE Healthcare Canada, Calgary (Canada)

    2018-03-15

    This study aimed to evaluate the usefulness of transit time corrected cerebral blood flow (CBF) maps based on multi-phase arterial spin labeling MR perfusion imaging (ASL-MRP). The Institutional Review Board of our hospital approved this retrospective study. Written informed consent was waived. Conventional and multi-phase ASL-MRPs and dynamic susceptibility contrast MR perfusion imaging (DSC-MRP) were acquired for 108 consecutive patients. Vascular territory-based volumes of interest were applied to CBF and time to peak (TTP) maps obtained from DSC-MRP and CBF maps obtained from conventional and multi-phase ASL-MRPs. The concordances between normalized CBF (nCBF) from DSC-MRP and nCBF from conventional and transition time corrected CBF maps from multi-phase ASL-MRP were evaluated using Bland-Altman analysis. In addition, the dependence of difference between nCBF (ΔnCBF) values obtained from DSC-MRP and conventional ASL-MRP (or multi-phase ASL-MRP) on TTP obtained from DSC-MRP was also analyzed using regression analysis. The values of nCBFs from conventional and multi-phase ASL-MRPs had lower values than nCBF based on DSC-MRP (mean differences, 0.08 and 0.07, respectively). The values of ΔnCBF were dependent on TTP values from conventional ASL-MRP technique (F = 5.5679, P = 0.0384). No dependency of ΔnCBF on TTP values from multi-phase ASL-MRP technique was revealed (F = 0.1433, P > 0.05). The use of transit time corrected CBF maps based on multi-phase ASL-MRP technique can overcome the effect of delayed transit time on perfusion maps based on conventional ASL-MRP. (orig.)

  19. Stability of MR brain-perfusion measurement using arterial spin labeling

    Energy Technology Data Exchange (ETDEWEB)

    Petr, Jan; Hofheinz, Frank; Platzek, Ivan; Schramm, Georg; Van Den Hoff, Jorg [Helmholtz-Center Dresden-Rossendorf, PET Center, Institute of Radiopharmaceutical Cancer Research (Germany)

    2015-05-18

    Arterial spin labeling (ASL) is an MR technique for assessment of cerebral blood flow (CBF) that does not require use of contrast agents which makes it a less invasive alternative to the 15O-H2O-PET measurement. The repeatability of ASL has been studied extensively but mainly in young healthy volunteers. We have tested repeatability of ASL under realistic clinical conditions in elderly brain tumor patients acquired with a Philips Ingenuity TF PET/MR in the context of an ongoing 11C-Methionine PET/MR study. Twenty three patients (age 54.8±13.0 y) were scanned on two or more session. The patients underwent 6 weeks of concurrent radiochemotherapy with Temozolomide between the first session and second measurement. The mean relative difference of gray matter CBF was 18.6% between the first two session and 13.0% for the second session and further on. The mean gray matter CBF was 46.6±7.2 mL/min/100 g on the first sessions and there was a significant decrease of 9.8% between first and second session (p=0.027). In summary, the ASL presents measurement of CBF with reasonable repeatability also in elderly patients under clinical conditions when it is not possible to control for all sources of variation. Significant decrease of CBF in healthy tissue was observed after the radiochemotherapy. Prospectively, the ASL data together with the also acquired 11C-Methionine PET will be evaluated regarding their separate and combined ability to predict patient outcome and effectiveness of the performed radiochemotherapy.

  20. High accuracy of arterial spin labeling perfusion imaging in differentiation of pilomyxoid from pilocytic astrocytoma

    Energy Technology Data Exchange (ETDEWEB)

    Nabavizadeh, S.A.; Assadsangabi, R.; Hajmomenian, M.; Vossough, A. [Perelman School of Medicine of the University of Pennsylvania, Department of Radiology, Children' s Hospital of Philadelphia, Philadelphia, PA (United States); Santi, M. [Perelman School of Medicine of the University of Pennsylvania, Department of Pathology, Children' s Hospital of Philadelphia, Philadelphia, PA (United States)

    2015-05-01

    Pilomyxoid astrocytoma (PMA) is a relatively new tumor entity which has been added to the 2007 WHO Classification of tumors of the central nervous system. The goal of this study is to utilize arterial spin labeling (ASL) perfusion imaging to differentiate PMA from pilocytic astrocytoma (PA). Pulsed ASL and conventional MRI sequences of patients with PMA and PA in the past 5 years were retrospectively evaluated. Patients with history of radiation or treatment with anti-angiogenic drugs were excluded. A total of 24 patients (9 PMA, 15 PA) were included. There were statistically significant differences between PMA and PA in mean tumor/gray matter (GM) cerebral blood flow (CBF) ratios (1.3 vs 0.4, p < 0.001) and maximum tumor/GM CBF ratio (2.3 vs 1, p < 0.001). Area under the receiver operating characteristic (ROC) curves for differentiation of PMA from PA was 0.91 using mean tumor CBF, 0.95 using mean tumor/GM CBF ratios, and 0.89 using maximum tumor/GM CBF. Using a threshold value of 0.91, the mean tumor/GM CBF ratio was able to diagnose PMA with 77 % sensitivity, 100 % specificity, and a threshold value of 0.7, provided 88 % sensitivity and 86 % specificity. There was no statistically significant difference between the two tumors in enhancement pattern (p = 0.33), internal architecture (p = 0.15), or apparent diffusion coefficient (ADC) values (p = 0.07). ASL imaging has high accuracy in differentiating PMA from PA. The result of this study may have important applications in prognostication and treatment planning especially in patients with less accessible tumors such as hypothalamic-chiasmatic gliomas. (orig.)

  1. A neuroradiologist's guide to arterial spin labeling MRI in clinical practice

    International Nuclear Information System (INIS)

    Grade, M.; Hernandez Tamames, J.A.; Pizzini, F.B.; Achten, E.; Golay, X.; Smits, M.

    2015-01-01

    Arterial spin labeling (ASL) is a non-invasive MRI technique to measure cerebral blood flow (CBF). This review provides a practical guide and overview of the clinical applications of ASL of the brain, as well its potential pitfalls. The technical and physiological background is also addressed. At present, main areas of interest are cerebrovascular disease, dementia and neuro-oncology. In cerebrovascular disease, ASL is of particular interest owing to its quantitative nature and its capability to determine cerebral arterial territories. In acute stroke, the source of the collateral blood supply in the penumbra may be visualised. In chronic cerebrovascular disease, the extent and severity of compromised cerebral perfusion can be visualised, which may be used to guide therapeutic or preventative intervention. ASL has potential for the detection and follow-up of arteriovenous malformations. In the workup of dementia patients, ASL is proposed as a diagnostic alternative to PET. It can easily be added to the routinely performed structural MRI examination. In patients with established Alzheimer's disease and frontotemporal dementia, hypoperfusion patterns are seen that are similar to hypometabolism patterns seen with PET. Studies on ASL in brain tumour imaging indicate a high correlation between areas of increased CBF as measured with ASL and increased cerebral blood volume as measured with dynamic susceptibility contrast-enhanced perfusion imaging. Major advantages of ASL for brain tumour imaging are the fact that CBF measurements are not influenced by breakdown of the blood-brain barrier, as well as its quantitative nature, facilitating multicentre and longitudinal studies. (orig.)

  2. Arterial spin labelling reveals prolonged arterial arrival time in idiopathic Parkinson's disease.

    Science.gov (United States)

    Al-Bachari, Sarah; Parkes, Laura M; Vidyasagar, Rishma; Hanby, Martha F; Tharaken, Vivek; Leroi, Iracema; Emsley, Hedley C A

    2014-01-01

    Idiopathic Parkinson's disease (IPD) is the second most common neurodegenerative disease, yet effective disease modifying treatments are still lacking. Neurodegeneration involves multiple interacting pathological pathways. The extent to which neurovascular mechanisms are involved is not well defined in IPD. We aimed to determine whether novel magnetic resonance imaging (MRI) techniques, including arterial spin labelling (ASL) quantification of cerebral perfusion, can reveal altered neurovascular status (NVS) in IPD. Fourteen participants with IPD (mean ± SD age 65.1 ± 5.9 years) and 14 age and cardiovascular risk factor matched control participants (mean ± SD age 64.6 ± 4.2 years) underwent a 3T MRI scan protocol. ASL images were collected before, during and after a 6 minute hypercapnic challenge. FLAIR images were used to determine white matter lesion score. Quantitative images of cerebral blood flow (CBF) and arterial arrival time (AAT) were calculated from the ASL data both at rest and during hypercapnia. Cerebrovascular reactivity (CVR) images were calculated, depicting the change in CBF and AAT relative to the change in end-tidal CO2. A significant (p = 0.005) increase in whole brain averaged baseline AAT was observed in IPD participants (mean ± SD age 1532 ± 138 ms) compared to controls (mean ± SD age 1335 ± 165 ms). Voxel-wise analysis revealed this to be widespread across the brain. However, there were no statistically significant differences in white matter lesion score, CBF, or CVR between patients and controls. Regional CBF, but not AAT, in the IPD group was found to correlate positively with Montreal cognitive assessment (MoCA) scores. These findings provide further evidence of alterations in NVS in IPD.

  3. Quantifying fluctuations of resting state networks using arterial spin labeling perfusion MRI.

    Science.gov (United States)

    Dai, Weiying; Varma, Gopal; Scheidegger, Rachel; Alsop, David C

    2016-03-01

    Blood oxygen level dependent (BOLD) functional magnetic resonance imaging (fMRI) has been widely used to investigate spontaneous low-frequency signal fluctuations across brain resting state networks. However, BOLD only provides relative measures of signal fluctuations. Arterial Spin Labeling (ASL) MRI holds great potential for quantitative measurements of resting state network fluctuations. This study systematically quantified signal fluctuations of the large-scale resting state networks using ASL data from 20 healthy volunteers by separating them from global signal fluctuations and fluctuations caused by residual noise. Global ASL signal fluctuation was 7.59% ± 1.47% relative to the ASL baseline perfusion. Fluctuations of seven detected resting state networks vary from 2.96% ± 0.93% to 6.71% ± 2.35%. Fluctuations of networks and residual noise were 6.05% ± 1.18% and 6.78% ± 1.16% using 4-mm resolution ASL data applied with Gaussian smoothing kernel of 6mm. However, network fluctuations were reduced by 7.77% ± 1.56% while residual noise fluctuation was markedly reduced by 39.75% ± 2.90% when smoothing kernel of 12 mm was applied to the ASL data. Therefore, global and network fluctuations are the dominant structured noise sources in ASL data. Quantitative measurements of resting state networks may enable improved noise reduction and provide insights into the function of healthy and diseased brain. © The Author(s) 2015.

  4. A neuroradiologist's guide to arterial spin labeling MRI in clinical practice

    Energy Technology Data Exchange (ETDEWEB)

    Grade, M. [Queen Square, UCL Institute of Neurology, London (United Kingdom); Stanford School of Medicine, Stanford, CA (United States); Hernandez Tamames, J.A. [Rey Juan Carlos University, Medical Image Analysis and Biometry Laboratory, Madrid (Spain); Erasmus MC - University Medical Centre Rotterdam, Department of Radiology, PO Box 2040, Rotterdam (Netherlands); Pizzini, F.B. [Queen Square, UCL Institute of Neurology, London (United Kingdom); Verona University Hospital, Neuroradiology, Department of Diagnostics and Pathology, Verona (Italy); Achten, E. [Ghent University Hospital, Neuroradiology, Department of Radiology, Ghent (Belgium); Golay, X. [Queen Square, UCL Institute of Neurology, London (United Kingdom); Smits, M. [Erasmus MC - University Medical Centre Rotterdam, Department of Radiology, PO Box 2040, Rotterdam (Netherlands)

    2015-12-15

    Arterial spin labeling (ASL) is a non-invasive MRI technique to measure cerebral blood flow (CBF). This review provides a practical guide and overview of the clinical applications of ASL of the brain, as well its potential pitfalls. The technical and physiological background is also addressed. At present, main areas of interest are cerebrovascular disease, dementia and neuro-oncology. In cerebrovascular disease, ASL is of particular interest owing to its quantitative nature and its capability to determine cerebral arterial territories. In acute stroke, the source of the collateral blood supply in the penumbra may be visualised. In chronic cerebrovascular disease, the extent and severity of compromised cerebral perfusion can be visualised, which may be used to guide therapeutic or preventative intervention. ASL has potential for the detection and follow-up of arteriovenous malformations. In the workup of dementia patients, ASL is proposed as a diagnostic alternative to PET. It can easily be added to the routinely performed structural MRI examination. In patients with established Alzheimer's disease and frontotemporal dementia, hypoperfusion patterns are seen that are similar to hypometabolism patterns seen with PET. Studies on ASL in brain tumour imaging indicate a high correlation between areas of increased CBF as measured with ASL and increased cerebral blood volume as measured with dynamic susceptibility contrast-enhanced perfusion imaging. Major advantages of ASL for brain tumour imaging are the fact that CBF measurements are not influenced by breakdown of the blood-brain barrier, as well as its quantitative nature, facilitating multicentre and longitudinal studies. (orig.)

  5. EPR in non-doped irradiated polyacetylene

    International Nuclear Information System (INIS)

    Hola, O.; Stasko, A.; Foeldesova, M.

    1993-01-01

    The influence of γ-irradiation on the paramagnetic properties of non-doped polyacetylene at low and high radiation doses has been studied and summarized. The dependence of the EPR spectra on the radiation dose in irradiated polyacetylene has been measured. No essential changes of the spin mobility as a consequence of irradiation were observed. The measurements of spin concentration confirm the high resistivity of non-doped polyacetylene to radiation. (author) 9 refs

  6. Computing distance distributions from dipolar evolution data with overtones: RIDME spectroscopy with Gd(iii)-based spin labels.

    Science.gov (United States)

    Keller, Katharina; Mertens, Valerie; Qi, Mian; Nalepa, Anna I; Godt, Adelheid; Savitsky, Anton; Jeschke, Gunnar; Yulikov, Maxim

    2017-07-21

    Extraction of distance distributions between high-spin paramagnetic centers from relaxation induced dipolar modulation enhancement (RIDME) data is affected by the presence of overtones of dipolar frequencies. As previously proposed, we account for these overtones by using a modified kernel function in Tikhonov regularization analysis. This paper analyzes the performance of such an approach on a series of model compounds with the Gd(iii)-PyMTA complex serving as paramagnetic high-spin label. We describe the calibration of the overtone coefficients for the RIDME kernel, demonstrate the accuracy of distance distributions obtained with this approach, and show that for our series of Gd-rulers RIDME technique provides more accurate distance distributions than Gd(iii)-Gd(iii) double electron-electron resonance (DEER). The analysis of RIDME data including harmonic overtones can be performed using the MATLAB-based program OvertoneAnalysis, which is available as open-source software from the web page of ETH Zurich. This approach opens a perspective for the routine use of the RIDME technique with high-spin labels in structural biology and structural studies of other soft matter.

  7. Structural Characterization of Polymer-Clay Nanocomposites Prepared by Co-Precipitation Using EPR Techniques

    Directory of Open Access Journals (Sweden)

    Udo Kielmann

    2014-02-01

    Full Text Available Polymer-clay nanocomposites (PCNCs containing either a rubber or an acrylate polymer were prepared by drying or co-precipitating polymer latex and nanolayered clay (synthetic and natural suspensions. The interface between the polymer and the clay nanoparticles was studied by electron paramagnetic resonance (EPR techniques by selectively addressing spin probes either to the surfactant layer (labeled stearic acid or the clay surface (labeled catamine. Continuous-wave (CW EPR studies of the surfactant dynamics allow to define a transition temperature T* which was tentatively assigned to the order-disorder transition of the surfactant layer. CW EPR studies of PCNC showed that completely exfoliated nanoparticles coexist with agglomerates. HYSCORE spectroscopy in PCNCs showed couplings within the probe −assigned with DFT computations− and couplings with nuclei of the environment, 1H and 23Na for the surfactant layer probe, and 29Si, 7Li, 19F and 23Na for the clay surface probe. Analysis of these couplings indicates that the integrity of the surfactant layer is conserved and that there are sizeable ionic regions containing sodium ions directly beyond the surfactant layer. Simulations of the very weak couplings demonstrated that the HYSCORE spectra are sensitive to the composition of the clay and whether or not clay platelets stack.

  8. Perfusion magnetic resonance imaging with continuous arterial spin labeling: methods and clinical applications in the central nervous system

    Energy Technology Data Exchange (ETDEWEB)

    Detre, John A. E-mail: detre@mail.med.upenn.edu; Alsop, David C

    1999-05-01

    Several methods are now available for measuring cerebral perfusion and related hemodynamic parameters using magnetic resonance imaging (MRI). One class of techniques utilizes electromagnetically labeled arterial blood water as a noninvasive diffusible tracer for blood flow measurements. The electromagnetically labeled tracer has a decay rate of T1, which is sufficiently long to allow perfusion of the tissue and microvasculature to be detected. Alternatively, electromagnetic arterial spin labeling (ASL) may be used to obtain qualitative perfusion contrast for detecting changes in blood flow, similar to the use of susceptibility contrast in blood oxygenation level dependent functional MRI (BOLD fMRI) to detect functional activation in the brain. The ability to obtain blood flow maps using a non-invasive and widely available modality such as MRI should greatly enhance the utility of blood flow measurement as a means of gaining further insight into the broad range of hemodynamically related physiology and pathophysiology. This article describes the biophysical considerations pertaining to the generation of quantitative blood flow maps using a particular form of ASL in which arterial blood water is continuously labeled, termed continuous arterial spin labeling (CASL). Technical advances permit multislice perfusion imaging using CASL with reduced sensitivity to motion and transit time effects. Interpretable cerebral perfusion images can now be reliably obtained in a variety of clinical settings including acute stroke, chronic cerebrovascular disease, degenerative diseases and epilepsy. Over the past several years, the technical and theoretical foundations of CASL perfusion MRI techniques have evolved from feasibility studies into practical usage. Currently existing methodologies are sufficient to make reliable and clinically relevant observations which complement structural assessment using MRI. Future technical improvements should further reduce the acquisition times

  9. Arterial Transit Time-corrected Renal Blood Flow Measurement with Pulsed Continuous Arterial Spin Labeling MR Imaging.

    Science.gov (United States)

    Shimizu, Kazuhiro; Kosaka, Nobuyuki; Fujiwara, Yasuhiro; Matsuda, Tsuyoshi; Yamamoto, Tatsuya; Tsuchida, Tatsuro; Tsuchiyama, Katsuki; Oyama, Nobuyuki; Kimura, Hirohiko

    2017-01-10

    The importance of arterial transit time (ATT) correction for arterial spin labeling MRI has been well debated in neuroimaging, but it has not been well evaluated in renal imaging. The purpose of this study was to evaluate the feasibility of pulsed continuous arterial spin labeling (pcASL) MRI with multiple post-labeling delay (PLD) acquisition for measuring ATT-corrected renal blood flow (ATC-RBF). A total of 14 volunteers were categorized into younger (n = 8; mean age, 27.0 years) and older groups (n = 6; 64.8 years). Images of pcASL were obtained at three different PLDs (0.5, 1.0, and 1.5 s), and ATC-RBF and ATT were calculated using a single-compartment model. To validate ATC-RBF, a comparative study of effective renal plasma flow (ERPF) measured by 99m Tc-MAG3 scintigraphy was performed. ATC-RBF was corrected by kidney volume (ATC-cRBF) for comparison with ERPF. The younger group showed significantly higher ATC-RBF (157.68 ± 38.37 mL/min/100 g) and shorter ATT (961.33 ± 260.87 ms) than the older group (117.42 ± 24.03 mL/min/100 g and 1227.94 ± 226.51 ms, respectively; P renal ASL-MRI as debated in brain imaging.

  10. Reliability of Three Dimentional Pseudo-continuous Arterial Spin Labeling: A Volumetric Cerebral Perfusion Imaging with Different Post-labeling Time and Functional State in Health Adults.

    Science.gov (United States)

    Liu, Meng-Qi; Chen, Zhi-Ye; Ma, Lin

    2018-03-30

    Objective To evaluate the reliability of three dimensional spiral fast spin echo pseudo-continuous arterial spin labeling (3D pc-ASL) in measuring cerebral blood flow (CBF) with different post-labeling delay time (PLD) in the resting state and the right finger taping state. Methods 3D pc-ASL and three dimensional T1-weighted fast spoiled gradient recalled echo (3D T1-FSPGR) sequence were applied to eight healthy subjects twice at the same time each day for one week interval. ASL data acquisition was performed with post-labeling delay time (PLD) 1.5 seconds and 2.0 seconds in the resting state and the right finger taping state respectively. CBF mapping was calculated and CBF value of both the gray matter (GM) and white matter (WM) was automatically extracted. The reliability was evaluated using the intraclass correlation coefficient (ICC) and Bland and Altman plot. Results ICC of the GM (0.84) and WM (0.92) was lower at PLD 1.5 seconds than that (GM, 0.88; WM, 0.94) at PLD 2.0 seconds in the resting state, and ICC of GM (0.88) was higher in the right finger taping state than that in the resting state at PLD 1.5 seconds. ICC of the GM and WM was 0.71 and 0.78 for PLD 1.5 seconds and PLD 2.0 seconds in the resting state at the first scan, and ICC of the GM and WM was 0.83 and 0.79 at the second scan, respectively. Conclusion This work demonstrated that 3D pc-ASL might be a reliable imaging technique to measure CBF over the whole brain at different PLD in the resting state or controlled state.

  11. Noise Reduction in Arterial Spin Labeling Based Functional Connectivity Using Nuisance Variables.

    Science.gov (United States)

    Jann, Kay; Smith, Robert X; Rios Piedra, Edgar A; Dapretto, Mirella; Wang, Danny J J

    2016-01-01

    Arterial Spin Labeling (ASL) perfusion image series have recently been utilized for functional connectivity (FC) analysis in healthy volunteers and children with autism spectrum disorders (ASD). Noise reduction by using nuisance variables has been shown to be necessary to minimize potential confounding effects of head motion and physiological signals on BOLD based FC analysis. The purpose of the present study is to systematically evaluate the effectiveness of different noise reduction strategies (NRS) using nuisance variables to improve perfusion based FC analysis in two cohorts of healthy adults using state of the art 3D background-suppressed (BS) GRASE pseudo-continuous ASL (pCASL) and dual-echo 2D-EPI pCASL sequences. Five different NRS were performed in healthy volunteers to compare their performance. We then compared seed-based FC analysis using 3D BS GRASE pCASL in a cohort of 12 children with ASD (3f/9m, age 12.8 ± 1.3 years) and 13 typically developing (TD) children (1f/12m; age 13.9 ± 3 years) in conjunction with NRS. Regression of different combinations of nuisance variables affected FC analysis from a seed in the posterior cingulate cortex (PCC) to other areas of the default mode network (DMN) in both BOLD and pCASL data sets. Consistent with existing literature on BOLD-FC, we observed improved spatial specificity after physiological noise reduction and improved long-range connectivity using head movement related regressors. Furthermore, 3D BS GRASE pCASL shows much higher temporal SNR compared to dual-echo 2D-EPI pCASL and similar effects of noise reduction as those observed for BOLD. Seed-based FC analysis using 3D BS GRASE pCASL in children with ASD and TD children showed that noise reduction including physiological and motion related signals as nuisance variables is crucial for identifying altered long-range connectivity from PCC to frontal brain areas associated with ASD. This is the first study that systematically evaluated the effects of

  12. Noise reduction in Arterial Spin Labeling based Functional Connectivity using nuisance variables

    Directory of Open Access Journals (Sweden)

    Kay Jann

    2016-08-01

    Full Text Available Arterial Spin Labeling (ASL perfusion image series have recently been utilized for functional connectivity (FC analysis in healthy volunteers and children with autism spectrum disorders (ASD. Noise reduction by using nuisance variables has been shown to be necessary to minimize potential confounding effects of head motion and physiological signals on BOLD based FC analysis. The purpose of the present study is to systematically evaluate the effectiveness of different noise reduction strategies using nuisance variables to improve perfusion based FC analysis in two cohorts of healthy adults using state of the art 3D background-suppressed (BS GRASE pseudo-continuous ASL (pCASL and dual-echo 2D-EPI pCASL sequences. Five different noise reduction strategies (NRS were performed in healthy volunteers to compare their performance. We then compared seed-based FC analysis using 3D BS GRASE pCASL in a cohort of 12 children with ASD (3f/9m, age 12.8±1.3y and 13 typically developing (TD children (1f/12m; age 13.9±3years in conjunction with noise reduction strategies. Regression of different combinations of nuisance variables affected FC analysis from a seed in the posterior cingulate cortex (PCC to other areas of the default mode network (DMN in both BOLD and pCASL data sets. Consistent with existing literature on BOLD-FC, we observed improved spatial specificity after physiological noise reduction and improved long-range connectivity using head movement related regressors. Furthermore, 3D BS GRASE pCASL shows much higher temporal SNR compared to dual-echo 2D-EPI pCASL and similar effects of noise reduction as those observed for BOLD. Seed-based FC analysis using 3D BS GRASE pCASL children with ASD and TD children showed that noise reduction including physiological and motion related signals as nuisance variables is crucial for identifying altered long-range connectivity from PCC to frontal brain areas associated with ASD. This is the first study that

  13. Combining crystallography and EPR: crystal and solution structures of the multidomain cochaperone DnaJ

    Energy Technology Data Exchange (ETDEWEB)

    Barends, Thomas R. M., E-mail: thomas.barends@mpimf-heidelberg.mpg.de [MPI for Medical Research, Heidelberg (Germany); Brosi, Richard W. W. [Freie Universitat Berlin, Berlin (Germany); Steinmetz, Andrea; Scherer, Anna; Hartmann, Elisabeth; Eschenbach, Jessica; Lorenz, Thorsten [MPI for Medical Research, Heidelberg (Germany); Seidel, Ralf [MPI for Molecular Physiology, Dortmund (Germany); Shoeman, Robert L.; Zimmermann, Sabine [MPI for Medical Research, Heidelberg (Germany); Bittl, Robert [Freie Universitat Berlin, Berlin (Germany); Schlichting, Ilme; Reinstein, Jochen [MPI for Medical Research, Heidelberg (Germany)

    2013-08-01

    The crystal structure of the N-terminal part of T. thermophilus DnaJ unexpectedly showed an ordered GF domain and guided the design of a construct enabling the first structure determination of a complete DnaJ cochaperone molecule. By combining the crystal structures with spin-labelling EPR and cross-linking in solution, a dynamic view of this flexible molecule was developed. Hsp70 chaperones assist in a large variety of protein-folding processes in the cell. Crucial for these activities is the regulation of Hsp70 by Hsp40 cochaperones. DnaJ, the bacterial homologue of Hsp40, stimulates ATP hydrolysis by DnaK (Hsp70) and thus mediates capture of substrate protein, but is also known to possess chaperone activity of its own. The first structure of a complete functional dimeric DnaJ was determined and the mobility of its individual domains in solution was investigated. Crystal structures of the complete molecular cochaperone DnaJ from Thermus thermophilus comprising the J, GF and C-terminal domains and of the J and GF domains alone showed an ordered GF domain interacting with the J domain. Structure-based EPR spin-labelling studies as well as cross-linking results showed the existence of multiple states of DnaJ in solution with different arrangements of the various domains, which has implications for the function of DnaJ.

  14. QUANTITATIVE CHANGES IN REGIONAL CEREBRAL BLOOD FLOW INDUCED BY COLD, HEAT AND ISCHEMIC PAIN: A CONTINUOUS ARTERIAL SPIN LABELING STUDY

    Science.gov (United States)

    Frölich, Michael A.; Deshpande, Hrishikesh; Ness, Timothy; Deutsch, Georg

    2012-01-01

    Background The development of arterial spin labeling methods, has allowed measuring regional cerebral blood flow (rCBF) quantitatively and to show the pattern of cerebral activity associated with any state such as a sustained pain state or changes due to a neurotropic drug. Methods We studied the differential effects of three pain conditions in ten healthy subjects on a 3T scanner during resting baseline, heat, cold and ischemic pain using continuous arterial spin labeling. Results Cold pain showed the greatest absolute rCBF increases in left anterior cingulate cortex, left amygdala, left angular gyrus, and Brodmann Area 6, and a significant rCBF decrease in the cerebellum. Changes in rCBF were characteristic of the type of pain condition: cold and heat pain showed increases, while the ischemic condition showed a reduction in mean absolute gray matter flow compared to rest. An association of subjects’ pain tolerance and cerebral blood flow was noted. Conclusions The observation that quantitative rCBF changes are characteristic of the pain task employed and that there is a consistent rCBF change in Brodman area 6, an area responsible for the integration of a motor response to pain, should provide extremely useful information in the quest to develop an imaging biomarker of pain. Conceivably, response in BA6 may serve as an objective measure of analgesic efficacy. PMID:22913924

  15. Quantitative changes in regional cerebral blood flow induced by cold, heat and ischemic pain: a continuous arterial spin labeling study.

    Science.gov (United States)

    Frölich, Michael A; Deshpande, Hrishikesh; Ness, Timothy; Deutsch, Georg

    2012-10-01

    The development of arterial spin labeling methods has allowed measuring regional cerebral blood flow (rCBF) quantitatively and to show the pattern of cerebral activity associated with any state such as a sustained pain state or changes due to a neurotropic drug. The authors studied the differential effects of three pain conditions in 10 healthy subjects on a 3 Tesla scanner during resting baseline, heat, cold, and ischemic pain using continuous arterial spin labeling. Cold pain showed the greatest absolute rCBF increases in left anterior cingulate cortex, left amygdala, left angular gyrus, and Brodmann area 6, and a significant rCBF decrease in the cerebellum. Changes in rCBF were characteristic of the type of pain condition: cold and heat pain showed increases, whereas the ischemic condition showed a reduction in mean absolute gray matter flow compared with rest. An association of subjects' pain tolerance and cerebral blood flow was noted. The observation that quantitative rCBF changes are characteristic of the pain task used and that there is a consistent rCBF change in Brodman area 6, an area responsible for the integration of a motor response to pain, should provide extremely useful information in the quest to develop an imaging biomarker of pain. Conceivably, response in BA6 may serve as an objective measure of analgesic efficacy.

  16. Spin dynamics of light-induced charge separation in composites of semiconducting polymers and PC60BM revealed using Q-band pulse EPR.

    Science.gov (United States)

    Lukina, E A; Suturina, E; Reijerse, E; Lubitz, W; Kulik, L V

    2017-08-23

    Light-induced processes in composites of semiconducting polymers and fullerene derivatives have been widely studied due to their usage as active layers of organic solar cells. However the process of charge separation under light illumination - the key process of an organic solar cell is not well understood yet. Here we report a Q-band pulse electron paramagnetic resonance study of composites of the fullerene derivative PC 60 BM ([6,6]-phenyl-C 61 -butyric acid methyl ester) with different p-type semiconducting polymers regioregular and regiorandom P3HT (poly(3-hexylthiophene-2,5-diyl), MEH-PPV (poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene]), PCDTBT (poly[N-9'-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)]), PTB7 (poly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl}))), resulting in a detailed description of the in-phase laser flash-induced electron spin echo (ESE) signal. We found that in organic donor-acceptor composites the laser flash simultaneously induces species of two types: a polymer˙ + /fullerene˙ - spin-correlated polaron pair (SCPP) with an initial singlet spin state and (nearly) free polymer˙ + and fullerene˙ - species with non-equilibrium spin polarization. Species of the first type (SCPP) are well-known for polymer/fullerene blends and are usually associated with a charge-separated state. Also, spin polarization of long-living free species (polarons in deep traps) is affected by the laser flash, which is the third contribution to the flash-induced ESE signal. A protocol for extracting the in-phase ESE signal of the SCPP based on the dependence of the microwave nutation frequency on the strength of the spin coupling within the polaron pair was developed. Nutation experiments revealed an unusual pattern of the SCPP in RR-P3HT/PC 60 BM composites, from which the strength of the exchange interaction between the polymer

  17. Photochemical sensitization by azathioprine and its metabolites. Part 3. A direct EPR and spin-trapping study of light-induced free radicals from 6-mercaptopurine and its oxidation products.

    Science.gov (United States)

    Moore, D E; Sik, R H; Bilski, P; Chignell, C F; Reszka, K J

    1994-12-01

    Sunlight has been implicated in the high incidence of skin cancer found in patients receiving 6-mercaptopurine (PSH) in the form of its pro-drug azathioprine. In this study we have used EPR spectroscopy in conjunction with the spin-trapping technique to determine whether PSH and its metabolic or photochemical oxidation products generate highly reactive free radicals upon UV irradiation. When an aqueous anaerobic solution (pH 5 or 9) of PSH (pKa = 7.7) and either 2-methyl-2-nitrosopropane (MNP) or nitromethane (NM) were irradiated (lambda > 300 nm) with a Xe arc lamp, the corresponding purine-6-thiyl (PS.) radical adduct and the reduced form of the spin trap (MNP/H. or CH3NO2.-) were observed. However, no radical adducts were detected when PSH and 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) were irradiated (lambda = 320 nm) in oxygen-free buffer. These findings suggest that PSH does not photoionize but that instead MNP and NM are reduced by direct electron transfer from excited state PSH, 1.3(PSH)*. In aerobic solution, oxygen can act as an electron acceptor and the O2.- and PS. radicals are formed and trapped by DMPO. 6-Mercaptopurine did photoionize when irradiated with a Nd:YAG laser at 355 nm as evidenced by the appearance of the DMPO/H.(eq- + H+) adduct, which decreased in intensity in the presence of N2O. 1.3(6-Mercaptopurine)* oxidized ascorbate, formate and reduced glutathione to the corresponding ascorbyl, CO2.- or glutathiyl radicals. The photochemical behavior of 6-thioxanthine and 6-thiouric acid was similar to PSH. However, the excited states of these metabolic oxidation products exhibited stronger reducing properties than 1.3(PSH)*.(ABSTRACT TRUNCATED AT 250 WORDS)

  18. Intra-arterial high signals on arterial spin labeling perfusion images predict the occluded internal carotid artery segment

    International Nuclear Information System (INIS)

    Sogabe, Shu; Satomi, Junichiro; Tada, Yoshiteru; Kanematsu, Yasuhisa; Kuwayama, Kazuyuki; Yagi, Kenji; Yoshioka, Shotaro; Mizobuchi, Yoshifumi; Mure, Hideo; Yamaguchi, Izumi; Kitazato, Keiko T.; Nagahiro, Shinji; Abe, Takashi; Harada, Masafumi; Yamamoto, Nobuaki; Kaji, Ryuji

    2017-01-01

    Arterial spin labeling (ASL) involves perfusion imaging using the inverted magnetization of arterial water. If the arterial arrival times are longer than the post-labeling delay, labeled spins are visible on ASL images as bright, high intra-arterial signals (IASs); such signals were found within occluded vessels of patients with acute ischemic stroke. The identification of the occluded segment in the internal carotid artery (ICA) is crucial for endovascular treatment. We tested our hypothesis that high IASs on ASL images can predict the occluded segment. Our study included 13 patients with acute ICA occlusion who had undergone angiographic and ASL studies within 48 h of onset. We retrospectively identified the high IAS on ASL images and angiograms and recorded the occluded segment and the number of high IAS-positive slices on ASL images. The ICA segments were classified as cervical (C1), petrous (C2), cavernous (C3), and supraclinoid (C4). Of seven patients with intracranial ICA occlusion, five demonstrated high IASs at C1-C2, suggesting that high IASs could identify stagnant flow proximal to the occluded segment. Among six patients with extracranial ICA occlusion, five presented with high IASs at C3-C4, suggesting that signals could identify the collateral flow via the ophthalmic artery. None had high IASs at C1-C2. The mean number of high IAS-positive slices was significantly higher in patients with intra- than extracranial ICA occlusion. High IASs on ASL images can identify slow stagnant and collateral flow through the ophthalmic artery in patients with acute ICA occlusion and help to predict the occlusion site. (orig.)

  19. Arterial spin-labeling assessment of normalized vascular intratumoral signal intensity as a predictor of histologic grade of astrocytic neoplasms.

    Science.gov (United States)

    Furtner, J; Schöpf, V; Schewzow, K; Kasprian, G; Weber, M; Woitek, R; Asenbaum, U; Preusser, M; Marosi, C; Hainfellner, J A; Widhalm, G; Wolfsberger, S; Prayer, D

    2014-03-01

    Pulsed arterial spin-labeling is a noninvasive MR imaging perfusion method performed with the use of water in the arterial blood as an endogenous contrast agent. The purpose of this study was to determine the inversion time with the largest difference in normalized intratumoral signal intensity between high-grade and low-grade astrocytomas. Thirty-three patients with gliomas, histologically classified as low-grade (n = 7) or high-grade astrocytomas (n = 26) according to the World Health Organization brain tumor classification, were included. A 3T MR scanner was used to perform pulsed arterial spin-labeling measurements at 8 different inversion times (370 ms, 614 ms, 864 ms, 1114 ms, 1364 ms, 1614 ms, 1864 ms, and 2114 ms). Normalized intratumoral signal intensity was calculated, which was defined by the signal intensity ratio of the tumor and the contralateral normal brain tissue for all fixed inversion times. A 3-way mixed ANOVA was used to reveal potential differences in the normalized vascular intratumoral signal intensity between high-grade and low-grade astrocytomas. The difference in normalized vascular intratumoral signal intensity between high-grade and low-grade astrocytomas obtained the most statistically significant results at 370 ms (P = .003, other P values ranged from .012-.955). The inversion time by which to differentiate high-grade and low-grade astrocytomas by use of normalized vascular intratumoral signal intensity was 370 ms in our study. The normalized vascular intratumoral signal intensity values at this inversion time mainly reflect the labeled intra-arterial blood bolus and therefore could be referred to as normalized vascular intratumoral signal intensity. Our data indicate that the use of normalized vascular intratumoral signal intensity values allows differentiation between low-grade and high-grade astrocytomas and thus may serve as a new, noninvasive marker for astrocytoma grading.

  20. Intra-arterial high signals on arterial spin labeling perfusion images predict the occluded internal carotid artery segment

    Energy Technology Data Exchange (ETDEWEB)

    Sogabe, Shu; Satomi, Junichiro; Tada, Yoshiteru; Kanematsu, Yasuhisa; Kuwayama, Kazuyuki; Yagi, Kenji; Yoshioka, Shotaro; Mizobuchi, Yoshifumi; Mure, Hideo; Yamaguchi, Izumi; Kitazato, Keiko T.; Nagahiro, Shinji [Tokushima University Graduate School, Department of Neurosurgery, Tokushima (Japan); Abe, Takashi; Harada, Masafumi [Tokushima University Graduate School, Department of Radiology, Tokushima (Japan); Yamamoto, Nobuaki; Kaji, Ryuji [Tokushima University Graduate School, Department of Clinical Neurosciences, Institute of Biomedical Biosciences, Tokushima (Japan)

    2017-06-15

    Arterial spin labeling (ASL) involves perfusion imaging using the inverted magnetization of arterial water. If the arterial arrival times are longer than the post-labeling delay, labeled spins are visible on ASL images as bright, high intra-arterial signals (IASs); such signals were found within occluded vessels of patients with acute ischemic stroke. The identification of the occluded segment in the internal carotid artery (ICA) is crucial for endovascular treatment. We tested our hypothesis that high IASs on ASL images can predict the occluded segment. Our study included 13 patients with acute ICA occlusion who had undergone angiographic and ASL studies within 48 h of onset. We retrospectively identified the high IAS on ASL images and angiograms and recorded the occluded segment and the number of high IAS-positive slices on ASL images. The ICA segments were classified as cervical (C1), petrous (C2), cavernous (C3), and supraclinoid (C4). Of seven patients with intracranial ICA occlusion, five demonstrated high IASs at C1-C2, suggesting that high IASs could identify stagnant flow proximal to the occluded segment. Among six patients with extracranial ICA occlusion, five presented with high IASs at C3-C4, suggesting that signals could identify the collateral flow via the ophthalmic artery. None had high IASs at C1-C2. The mean number of high IAS-positive slices was significantly higher in patients with intra- than extracranial ICA occlusion. High IASs on ASL images can identify slow stagnant and collateral flow through the ophthalmic artery in patients with acute ICA occlusion and help to predict the occlusion site. (orig.)

  1. Interpretation of the parameters of the EPR spectra of transition metal complexes

    International Nuclear Information System (INIS)

    Murav'ev, V.I.

    2005-01-01

    The calculated parameters of the EPR spectra of complexes of d 1 and d 9 ions, inclusive of MoOX 5 (X = Cl, Br), are reviewed. The covalent bond parameters used in the calculations were determined from EPR and experimental optical data (inverse problem of EPR spectroscopy). Various contributions to the expressions for the EPR parameters were compared. The observed abnormal values of the EPR parameters were discussed. The effects of charge-transfer states and the vibronic coupling on the components of g, A, and A L tensors were considered. Mechanisms of spin density transfer to ligands in paramagnetic complexes were proposed [ru

  2. Medical application of EPR

    International Nuclear Information System (INIS)

    Eichhoff, Uwe; Hoefer, Peter

    2015-01-01

    Selected applications of continuous-wave EPR in medicine are reviewed. This includes detection of reactive oxygen and nitrogen species, pH measurements and oxymetry. Applications of EPR imaging are demonstrated on selected examples and future developments to faster imaging methods are discussed

  3. Free radical generation by non-equilibrium atmospheric pressure plasma in alcohol-water mixtures: an EPR-spin trapping study

    Science.gov (United States)

    Uchiyama, Hidefumi; Ishikawa, Kenji; Zhao, Qing-Li; Andocs, Gabor; Nojima, Nobuyuki; Takeda, Keigo; Krishna, Murali C.; Ishijima, Tatsuo; Matsuya, Yuji; Hori, Masaru; Noguchi, Kyo; Kondo, Takashi

    2018-03-01

    Free radical species in aqueous solution—various alcohol-water reaction mixtures—by exposure to non-equilibrium cold atmospheric pressure Ar plasma (CAP), were monitored using electron paramagnetic resonance spin-trapping techniques with 3, 5-dibromo-4-nitrosobenzene sulfonate as a water soluble nitroso spin trap. The major radical species were formed by H-abstraction from alcohol molecules due to ·OH radicals. In the ethanol-water mixture ·CH2CH2OH produced by H abstraction from CH3 group of the ethanol and ·CH3 radicals were detected. The latter was due to the decomposition of unstable CH3·CHOH to form the ·CH3 radicals and the stable formaldehyde by C-C bond fission. These intermediates are similar to those observed by reaction with ·OH radicals generation in the H2O2-UV photolysis of the reaction mixtures. The evidence of ·CH3 radical formation in the pyrolytic decomposition of the reaction mixtures by exposure to ultrasound or in methane irradiated with microwave plasma have been reported previously. However, the pyrolytic ·CH3 radicals were not found in both plasma and H2O2-UV photolysis condition. These results suggests that free radicals produced by Ar-CAP are most likely due to the reaction between abundant ·OH radicals and alcohol molecules.

  4. Head-to-Head Visual Comparison between Brain Perfusion SPECT and Arterial Spin-Labeling MRI with Different Postlabeling Delays in Alzheimer Disease.

    Science.gov (United States)

    Kaneta, T; Katsuse, O; Hirano, T; Ogawa, M; Yoshida, K; Odawara, T; Hirayasu, Y; Inoue, T

    2017-08-01

    Arterial spin-labeling MR imaging has been recently developed as a noninvasive technique with magnetically labeled arterial blood water as an endogenous contrast medium for the evaluation of CBF. Our aim was to compare arterial spin-labeling MR imaging and SPECT in the visual assessment of CBF in patients with Alzheimer disease. In 33 patients with Alzheimer disease or mild cognitive impairment due to Alzheimer disease, CBF images were obtained by using both arterial spin-labeling-MR imaging with a postlabeling delay of 1.5 seconds and 2.5 seconds (PLD 1.5 and PLD 2.5 , respectively) and brain perfusion SPECT. Twenty-two brain regions were visually assessed, and the diagnostic confidence of Alzheimer disease was recorded. Among all arterial spin-labeling images, 84.9% of PLD 1.5 and 9% of PLD 2.5 images showed the typical pattern of advanced Alzheimer disease (ie, decreased CBF in the bilateral parietal, temporal, and frontal lobes). PLD 1.5 , PLD 2.5 , and SPECT imaging resulted in obviously different visual assessments. PLD 1.5 showed a broad decrease in CBF, which could have been due to an early perfusion. In contrast, PLD 2.5 did not appear to be influenced by an early perfusion but showed fewer pathologic findings than SPECT. The distinctions observed by us should be carefully considered in the visual assessments of Alzheimer disease. Further studies are required to define the patterns of change in arterial spin-labeling-MR imaging associated with Alzheimer disease. © 2017 by American Journal of Neuroradiology.

  5. Cerebral blood flow measured by arterial spin labeling MRI at resting state in normal aging and Alzheimer's disease.

    Science.gov (United States)

    Zhang, Nan; Gordon, Marc L; Goldberg, Terry E

    2017-01-01

    Arterial spin labeling (ASL) magnetic resonance imaging uses arterial blood water as an endogenous tracer to measure cerebral blood flow (CBF). In this review, based on ASL studies in the resting state, we discuss state-of-the-art technical and data processing improvements in ASL, and ASL CBF changes in normal aging, mild cognitive impairment (MCI), Alzheimer's disease (AD), and other types of dementia. We propose that vascular and AD risk factors should be considered when evaluating CBF changes in aging, and that other validated biomarkers should be used as inclusion criteria or covariates when evaluating CBF changes in MCI and AD. With improvements in hardware and experimental design, ASL is proving to be an increasingly promising tool for exploring pathogenetic mechanisms, early detection, monitoring disease progression and pharmacological response, and differential diagnosis of AD. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

  6. Localization of dexamethasone within dendritic core-multishell (CMS) nanoparticles and skin penetration properties studied by multi-frequency electron paramagnetic resonance (EPR) spectroscopy.

    Science.gov (United States)

    Saeidpour, S; Lohan, S B; Anske, M; Unbehauen, M; Fleige, E; Haag, R; Meinke, M C; Bittl, R; Teutloff, C

    2017-07-01

    The skin and especially the stratum corneum (SC) act as a barrier and protect epidermal cells and thus the whole body against xenobiotica of the external environment. Topical skin treatment requires an efficient drug delivery system (DDS). Polymer-based nanocarriers represent novel transport vehicles for dermal application of drugs. In this study dendritic core-multishell (CMS) nanoparticles were investigated as promising candidates. CMS nanoparticles were loaded with a drug (analogue) and were applied to penetration studies of skin. We determined by dual-frequency electron paramagnetic resonance (EPR) how dexamethasone (Dx) labelled with 3-carboxy-2,2,5,5-tetramethyl-1-pyrrolidinyloxy (PCA) is associated with the CMS. The micro-environment of the drug loaded to CMS nanoparticles was investigated by pulsed high-field EPR at cryogenic temperature, making use of the fact that magnetic parameters (g-, A-matrices, and spin-lattice relaxation time) represent specific probes for the micro-environment. Additionally, the rotational correlation time of spin-labelled Dx was probed by continuous wave EPR at ambient temperature, which provides independent information on the drug environment. Furthermore, the penetration depth of Dx into the stratum corneum of porcine skin after different topical applications was investigated. The location of Dx in the CMS nanoparticles is revealed and the function of CMS as penetration enhancers for topical application is shown. Copyright © 2016 Elsevier B.V. All rights reserved.

  7. EPR Test with Photons and Kaons Analogies

    CERN Document Server

    Gisin, Nicolas

    2001-01-01

    We present a unified formalism describing EPR test using spin 1/2 particles, photons and kaons. This facilitates the comparison between existing experiments using photons and kaons. It underlines the similarities between birefringence and polarization dependent losses that affects experiments using optical fibers and mixing and decay that are intrinsic to the kaons. We also discuss the limitation these two characteristics impose on the testing of Bell's inequality.

  8. One-way EPR steering and genuine multipartite EPR steering

    Science.gov (United States)

    He, Qiongyi; Reid, Margaret D.

    2012-11-01

    We propose criteria and experimental strategies to realise the Einstein-Podolsky-Rosen (EPR) steering nonlocality. One-way steering can be obtained where there is asymmetry of thermal noise on each system. We also present EPR steering inequalities that act as signatures and suggest how to optimise EPR correlations in specific schemes so that the genuine multipartite EPR steering nonlocality (EPR paradox) can also possibly be realised. The results presented here also apply to the spatially separated macroscopic atomic ensembles.

  9. Mononitroxides and proximate dinitroxides derived by oxidation of 2,2,4,4,5,5-hexasubstituted imidazolidines. A new series of nitroxide and dinitroxide spin labels

    International Nuclear Information System (INIS)

    Keana, J.F.W.; Norton, R.S.; Morello, M.; Van Engen, D.; Clardy, J.

    1978-01-01

    The synthesis and some properties of two members of a new series of rigid dinitroxides in which the nitroxide groups are separated from each other by only one carbon atom are reported. The synthesis of reverse intermediate imidazolidine mononitroxides which may have potential as new spin labels is also reported

  10. Do "good" food products make others look "bad"? Spin-off effects of labels for sustainable food production in the consumer perception

    NARCIS (Netherlands)

    Binnekamp, M.H.A.; Ingenbleek, P.T.M.

    2008-01-01

    Abstract Purpose ¿ The objective of this study is to examine whether sustainability labels like Fair Trade have a spin-off effect to mainstream products in the consumer perception: do consumers perceive mainstream products and brands more negatively in the presence of a product with a sustainability

  11. EPR: Evidence and fallacy.

    Science.gov (United States)

    Nichols, Joseph W; Bae, You Han

    2014-09-28

    The enhanced permeability and retention (EPR) of nanoparticles in tumors has long stood as one of the fundamental principles of cancer drug delivery, holding the promise of safe, simple and effective therapy. By allowing particles preferential access to tumors by virtue of size and longevity in circulation, EPR provided a neat rationale for the trend toward nano-sized drug carriers. Following the discovery of the phenomenon by Maeda in the mid-1980s, this rationale appeared to be well justified by the flood of evidence from preclinical studies and by the clinical success of Doxil. Clinical outcomes from nano-sized drug delivery systems, however, have indicated that EPR is not as reliable as previously thought. Drug carriers generally fail to provide superior efficacy to free drug systems when tested in clinical trials. A closer look reveals that EPR-dependent drug delivery is complicated by high tumor interstitial fluid pressure (IFP), irregular vascular distribution, and poor blood flow inside tumors. Furthermore, the animal tumor models used to study EPR differ from clinical tumors in several key aspects that seem to make EPR more pronounced than in human patients. On the basis of this evidence, we believe that EPR should only be invoked on a case-by-case basis, when clinical evidence suggests the tumor type is susceptible. Copyright © 2014 Elsevier B.V. All rights reserved.

  12. Labelling by deuteration and nitroxide radicals of mono-, oligo- and polysaccharides (cellulose and amylose)

    Energy Technology Data Exchange (ETDEWEB)

    Odier, L

    1975-01-01

    The application of NMR and deuteration labelling to the investigation of polysaccharides has led to considerable progress in recent years in the knowledge of these compounds. Although far more recent, the introduction of spin labelling techniques in the investigation of polymers, has given rise to interesting EPR studies of synthetic and natural macromolecules, but nothing appears to have been accomplished in the area of spin labelling of polysaccharides. This work was aimed at applying these two techniques to the study of glucose derivatives and of some of its oligomers (low molecular weight polymers): cellobiose, maltose and cyclodextrins; and its polymers: cellulose and amylose. Irrespective of the technique employed, the complexity of the polymers and problems connected with handling them always require the same procedure: an initial study of a model compound generally prepared from the monomer or an oligomer (dimer), followed by the oligomers, and finally the polymer. Part 1 is devoted to the deuteration labelling of mono- and oligosaccharides. Part 2 concerns spin labelling of cellulose acetate. In part 3, an attempt is made to apply the spin labelling technique to the determination of conformations of two disaccharides of different glycosidic configurations: cellobiose and maltose. Part 4 is devoted to spin and deuteration labelling of ..cap alpha.. and ..beta.. cyclodextrins.

  13. A Local Realistic Reconciliation of the EPR Paradox

    Science.gov (United States)

    Sanctuary, Bryan

    2014-03-01

    The exact violation of Bell's Inequalities is obtained with a local realistic model for spin. The model treats one particle that comprises a quantum ensemble and simulates the EPR data one coincidence at a time as a product state. Such a spin is represented by operators σx , iσy ,σz in its body frame rather than the usual set of σX ,σY ,σZ in the laboratory frame. This model, assumed valid in the absence of a measuring probe, contains both quantum polarizations and coherences. Each carries half the EPR correlation, but only half can be measured using coincidence techniques. The model further predicts the filter angles that maximize the spin correlation in EPR experiments.

  14. The QUASAR reproducibility study, Part II: Results from a multi center Arterial Spin Labeling test-retest Study

    Science.gov (United States)

    Petersen, Esben Thade; Mouridsen, Kim; Golay, Xavier

    2009-01-01

    Arterial Spin Labeling (ASL) is a method to measure perfusion using magnetically labeled blood water as an endogenous tracer. Being fully non-invasive, this technique is attractive for longitudinal studies of cerebral blood flow in healthy and diseased individuals, or as a surrogate marker of metabolism. So far, ASL has been restricted mostly to specialist centers due to a generally low SNR of the method and potential issues with user-dependent analysis needed to obtain quantitative measurement of cerebral blood flow (CBF). Here, we evaluated a particular implementation of ASL (called Quantitative STAR labeling of Arterial Regions or QUASAR), a method providing user independent quantification of CBF in a large test-retest study across sites from around the world, dubbed “The QUASAR reproducibility study”. Altogether, 28 sites located in Asia, Europe and North America participated and a total of 284 healthy volunteers were scanned. Minimal operator dependence was assured by using an automatic planning tool and its accuracy and potential usefulness in multi-center trials was evaluated as well. Accurate repositioning between sessions was achieved with the automatic planning tool showing mean displacements of 1.87±0.95mm and rotations of 1.56±0.66°. Mean gray matter CBF was 47.4±7.5 [ml/100g/min] with a between subject standard variation SDb = 5.5 [ml/100g/min] and a within subject standard deviation SDw = 4.7 [ml/100g/min]. The corresponding repeatability was 13.0 [ml/100g/min] and was found to be within the range of previous studies. PMID:19660557

  15. The QUASAR reproducibility study, Part II: Results from a multi-center Arterial Spin Labeling test-retest study.

    Science.gov (United States)

    Petersen, Esben Thade; Mouridsen, Kim; Golay, Xavier

    2010-01-01

    Arterial Spin Labeling (ASL) is a method to measure perfusion using magnetically labeled blood water as an endogenous tracer. Being fully non-invasive, this technique is attractive for longitudinal studies of cerebral blood flow in healthy and diseased individuals, or as a surrogate marker of metabolism. So far, ASL has been restricted mostly to specialist centers due to a generally low SNR of the method and potential issues with user-dependent analysis needed to obtain quantitative measurement of cerebral blood flow (CBF). Here, we evaluated a particular implementation of ASL (called Quantitative STAR labeling of Arterial Regions or QUASAR), a method providing user independent quantification of CBF in a large test-retest study across sites from around the world, dubbed "The QUASAR reproducibility study". Altogether, 28 sites located in Asia, Europe and North America participated and a total of 284 healthy volunteers were scanned. Minimal operator dependence was assured by using an automatic planning tool and its accuracy and potential usefulness in multi-center trials was evaluated as well. Accurate repositioning between sessions was achieved with the automatic planning tool showing mean displacements of 1.87+/-0.95 mm and rotations of 1.56+/-0.66 degrees . Mean gray matter CBF was 47.4+/-7.5 [ml/100 g/min] with a between-subject standard variation SD(b)=5.5 [ml/100 g/min] and a within-subject standard deviation SD(w)=4.7 [ml/100 g/min]. The corresponding repeatability was 13.0 [ml/100 g/min] and was found to be within the range of previous studies.

  16. EPR spectral investigation of radiation-induced radicals of gallic acid

    International Nuclear Information System (INIS)

    Tuner, Hasan

    2017-01-01

    In the present work, spectroscopic features of the radiation-induced radicals of gallic acid compounds were investigated using electron paramagnetic resonance (EPR) spectroscopy. While un-irradiated samples presented no EPR signal, irradiated samples exhibited an EPR spectrum consisting of an intense resonance line at the center and weak lines on both sides. Detailed microwave saturation investigations were carried out to determine the origin of the experimental EPR lines. It is concluded that the two side lines of the triplet satellite originate from forbidden ''spin-flip'' transitions. The spectroscopic and structural features of the radiation-induced radicals were determined using EPR spectrum fittings. The experimental EPR spectra of the two gallic acid compounds were consistent with the calculated EPR spectroscopic features of the proposed radicals. It is concluded that the most probable radicals are the cyclohexadienyl-type, O(OH) 2 C 6 H 2 COOH radicals for both compounds. (orig.)

  17. EPR spectral investigation of radiation-induced radicals of gallic acid.

    Science.gov (United States)

    Tuner, Hasan

    2017-11-01

    In the present work, spectroscopic features of the radiation-induced radicals of gallic acid compounds were investigated using electron paramagnetic resonance (EPR) spectroscopy. While un-irradiated samples presented no EPR signal, irradiated samples exhibited an EPR spectrum consisting of an intense resonance line at the center and weak lines on both sides. Detailed microwave saturation investigations were carried out to determine the origin of the experimental EPR lines. It is concluded that the two side lines of the triplet satellite originate from forbidden "spin-flip" transitions. The spectroscopic and structural features of the radiation-induced radicals were determined using EPR spectrum fittings. The experimental EPR spectra of the two gallic acid compounds were consistent with the calculated EPR spectroscopic features of the proposed radicals. It is concluded that the most probable radicals are the cyclohexadienyl-type, [Formula: see text] radicals for both compounds.

  18. Conformation and dynamics of nucleotides in bulges and symmetric internal loops in duplex DNA studied by EPR and fluorescence spectroscopies

    International Nuclear Information System (INIS)

    Cekan, Pavol; Sigurdsson, Snorri Th.

    2012-01-01

    Highlights: ► Bulges and loops were studied by both EPR and fluorescence spectroscopies using the probe Ç/Ç f . ► One-base bulge was in a temperature-dependent equilibrium between looped-out and stacked states. ► Bases in two- and three-base bulges were stacked at all temperatures, resulting in DNA bending. ► Bases were stacked in symmetrical two- to five-base internal loops, according to EPR data. ► Unexpectedly high fluorescence for the smaller loops indicated local structural perturbations. -- Abstract: The dynamics and conformation of base bulges and internal loops in duplex DNA were studied using the bifunctional spectroscopic probe Ç, which becomes fluorescent (Ç f ) upon reduction of the nitroxide functional group, along with EPR and fluorescence spectroscopies. A one-base bulge was in a conformational equilibrium between looped-out and stacked states, the former favored at higher temperature and the latter at lower temperature. Stacking of bulge bases was favored in two- and three-base bulges, independent of temperature, resulting in DNA bending as evidenced by increased fluorescence of Ç f . EPR spectra of Ç-labeled three-, four- and five-base symmetrical interior DNA bulges at 20 °C showed low mobility, indicating that the spin-label was stacked within the loop. The spin-label mobility at 37 °C increased as the loops became larger. A considerable variation in fluorescence between different loops was observed, as well as a temperature-dependence within constructs. Fluorescence unexpectedly increased as the size of the loop decreased at 2 °C. Fluorescence of the smallest loops, where a single T·T mismatch was located between the stem region and the probe, was even larger than for the single strand, indicating a considerable local structural deformation of these loops from regular B-DNA. These results show the value of combining EPR and fluorescence spectroscopy to study non-helical regions of nucleic acids.

  19. The EPR paradox revisited

    International Nuclear Information System (INIS)

    Cantrell, C.D.; Scully, M.O.

    1978-01-01

    Einstein, Podolsky and Rosen (EPR) argued in 1935 that quantum mechanics fails to give an adequate description of physical reality, and also cannot give a consistent wave-function description of certain phenomena. The authors show that a calculation based upon the reduced density matrix removes the formal inconsistency pointed out by EPR. The spirit of the present paper is that of a pedagogical review. (Auth.)

  20. EPR paradox revisited

    Energy Technology Data Exchange (ETDEWEB)

    Cantrell, C.D.; Scully, M.O.

    1978-07-01

    Einstein, Podolsky, and Rosen (EPR) argued in 1935 that quantum mechanics fails to give an adequate description of physical reality, and also cannot give a consistent wave-function description of certain phenomena. It is shown that a calculation based upon the reduced density matrix removes the formal inconsistency pointed out by EPR. The spirit of the present paper is that of a pedagogical review.

  1. EPR of photochromic Mo3+ in SrTiO3

    NARCIS (Netherlands)

    Kool, Th.W.

    2010-01-01

    In single crystals of SrTiO_3, a paramagnetic center, characterized by S = 3/2 and hyperfine interaction with an I = 5/2 nuclear spin has been observed in the temperature range 4.2K-77K by means of EPR. The impurity center is attributed to Mo3+. No additional line splitting in the EPR spectrum due

  2. Membrane remodeling by amyloidogenic and non-amyloidogenic proteins studied by EPR.

    Science.gov (United States)

    Varkey, Jobin; Langen, Ralf

    2017-07-01

    The advancement in site-directed spin labeling of proteins has enabled EPR studies to expand into newer research areas within the umbrella of protein-membrane interactions. Recently, membrane remodeling by amyloidogenic and non-amyloidogenic proteins has gained a substantial interest in relation to driving and controlling vital cellular processes such as endocytosis, exocytosis, shaping of organelles like endoplasmic reticulum, Golgi and mitochondria, intracellular vesicular trafficking, formation of filopedia and multivesicular bodies, mitochondrial fusion and fission, and synaptic vesicle fusion and recycling in neurotransmission. Misregulation in any of these processes due to an aberrant protein (mutation or misfolding) or alteration of lipid metabolism can be detrimental to the cell and cause disease. Dissection of the structural basis of membrane remodeling by proteins is thus quite necessary for an understanding of the underlying mechanisms, but it remains a formidable task due to the difficulties of various common biophysical tools in monitoring the dynamic process of membrane binding and bending by proteins. This is largely since membranes generally complicate protein structure analysis and this problem is amplified for structural analysis in the presence of different types of membrane curvatures. Recent EPR studies on membrane remodeling by proteins show that a significant structural information can be generated to delineate the role of different protein modules, domains and individual amino acids in the generation of membrane curvature. These studies also show how EPR can complement the data obtained by high resolution techniques such as X-ray and NMR. This perspective covers the application of EPR in recent studies for understanding membrane remodeling by amyloidogenic and non-amyloidogenic proteins that is useful for researchers interested in using or complimenting EPR to gain better understanding of membrane remodeling. We also discuss how a single

  3. Membrane remodeling by amyloidogenic and non-amyloidogenic proteins studied by EPR

    Science.gov (United States)

    Varkey, Jobin; Langen, Ralf

    2017-07-01

    The advancement in site-directed spin labeling of proteins has enabled EPR studies to expand into newer research areas within the umbrella of protein-membrane interactions. Recently, membrane remodeling by amyloidogenic and non-amyloidogenic proteins has gained a substantial interest in relation to driving and controlling vital cellular processes such as endocytosis, exocytosis, shaping of organelles like endoplasmic reticulum, Golgi and mitochondria, intracellular vesicular trafficking, formation of filopedia and multivesicular bodies, mitochondrial fusion and fission, and synaptic vesicle fusion and recycling in neurotransmission. Misregulation in any of these processes due to an aberrant protein (mutation or misfolding) or alteration of lipid metabolism can be detrimental to the cell and cause disease. Dissection of the structural basis of membrane remodeling by proteins is thus quite necessary for an understanding of the underlying mechanisms, but it remains a formidable task due to the difficulties of various common biophysical tools in monitoring the dynamic process of membrane binding and bending by proteins. This is largely since membranes generally complicate protein structure analysis and this problem is amplified for structural analysis in the presence of different types of membrane curvatures. Recent EPR studies on membrane remodeling by proteins show that a significant structural information can be generated to delineate the role of different protein modules, domains and individual amino acids in the generation of membrane curvature. These studies also show how EPR can complement the data obtained by high resolution techniques such as X-ray and NMR. This perspective covers the application of EPR in recent studies for understanding membrane remodeling by amyloidogenic and non-amyloidogenic proteins that is useful for researchers interested in using or complimenting EPR to gain better understanding of membrane remodeling. We also discuss how a single

  4. The effects of general anesthetics on ESR spectra of spin labels in phosphatidylcholine vesicles containing purified Na,K-ATPase or microsomal protein

    Energy Technology Data Exchange (ETDEWEB)

    Shibuya, Makiko, E-mail: shibu@den.hokudai.ac.jp [Department of Dental Anesthesiology, Graduate School of Dental Medicine, Hokkaido University (Japan); Hiraoki, Toshifumi [Division of Applied Physics, Graduate School of Engineering, Hokkaido University (Japan); Kimura, Kunie; Fukushima, Kazuaki [Department of Dental Anesthesiology, Graduate School of Dental Medicine, Hokkaido University (Japan); Suzuki, Kuniaki [Department of Molecular Cell Pharmacology, Graduate School of Dental Medicine, Hokkaido University (Japan)

    2012-12-01

    Highlights: Black-Right-Pointing-Pointer We studied the effects of general anesthetics on liposome using ESR spectra. Black-Right-Pointing-Pointer Two spin labels, 5-DSA and 16-DSA, were located in different position in liposome. Black-Right-Pointing-Pointer Anesthetics did not change the environment around the spin labels in the liposome. Black-Right-Pointing-Pointer Anesthetics remained on the surface of the lipid bilayer of liposome. Black-Right-Pointing-Pointer Proteins in the liposome did not change the effects of anesthetics on liposome. - Abstract: We investigated the effects of general anesthetics on liposome containing spin labels, 5-doxyl stearic acid (5-DSA) and 16-doxyl stearic acid (16-DSA), and purified Na,K-ATPase or membrane protein of microsome using an electron spin resonance (ESR) spectroscopy. The spectra of 16-DSA in liposomes with both proteins showed three sharp signals compared with 5-DSA. The difference in the order parameter S value of 5-DSA and 16-DSA suggested that the nitroxide radical location of 5-DSA and 16-DSA were different in the membrane bilayer. The results were almost the same as those obtained in liposomes without proteins. The addition of sevoflurane, isoflurane, halothane, ether, ethanol and propofol increased the intensity of the signals, but the clinical concentrations of anesthetics did not significantly alter the S and {tau} values, which are indices of the fluidity of the membrane. These results suggest that anesthetics remain on the surface of the lipid bilayer and do not act on both the inside hydrophobic area and the relatively hydrophilic area near the surface. These results and others also suggest that the existence of Na,K-ATPase and microsomal proteins did not affect the environment around the spin labels in the liposome and the effects of anesthetics on liposome as a model membrane.

  5. Assessment of glioma response to radiotherapy using 3D pulsed-continuous arterial spin labeling and 3D segmented volume

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Peng; Li, Jianrui; Diao, Qiang; Lin, YuanKai; Zhang, Jun; Li, Lin; Yang, Gang; Fang, Xiaokun; Li, Xie; Chen, YingQi; Zheng, Ling, E-mail: lingzheng1989@yeah.net; Lu, Guangming, E-mail: guangminglu1905@163.com

    2016-11-15

    Background: Gliomas are the most common primary brain tumors in adults, in some cases, radiotherapy may be the preferred treatment option especially for elderly people who cannot endure surgery. Therefore, it is necessary to evaluate the effects of radiotherapy on glioma. Arterial spin labeling (ASL) is an MR imaging technique that allows for a quantitative determination of cerebral blood flow (CBF) noninvasively. Tumor volume is still an important determinant for evaluating treatment response. The purpose of this study was to investigate the relationship between the tumor perfusion parameters and tumor volume and assess the effects of radiotherapy on glioma using pulsed-continuous arterial spin labeling (pcASL) technique. Methods: 35 patients with gliomas, histologically classified as low-grade group (n = 16) and high-grade group (n = 19), treated with radiotherapy only or before using other therapies were included in this study. MR examinations, including T1 weighted image and pcASL, were performed before and 4, 8, 12, 16 weeks after radiotherapy. Regional CBF of normal tissue, mean tumor blood flow (TBF{sub mean}), maximum tumor blood flow (TBF{sub max}), and tumor volume were evaluated at each time point. Both the percentage change in CBF (CBF ratio), TBF{sub mean} (TBF{sub mean} ratio), TBF{sub max} (TBF{sub max} ratio) and the percentage change in tumor volume (volume ratio) were calculated using values obtained before and after radiotherapy. The correlation between the volume ratio and CBF ratio, TBF{sub mean} ratio, TBF{sub max} ratio was assessed using linear regression analysis and Pearson’s correlation. Results: The TBF{sub mean} and TBF{sub max} of high-grade gliomas were significantly higher than that of low-grade group. In high-grade group, a strong correlation was demonstrated between the tumor volume and the TBF{sub max} before radiotherapy (R{sup 2} = 0.35, r{sub s} = 0.59, p < 0.05). There was also a significant correlation between the TBF

  6. Arterial spin labeling MR imaging for characterisation of renal masses in patients with impaired renal function: initial experience

    International Nuclear Information System (INIS)

    Pedrosa, Ivan; Rafatzand, Khashayar; Robson, Philip; Alsop, David C.; Wagner, Andrew A.; Atkins, Michael B.; Rofsky, Neil M.

    2012-01-01

    To retrospectively evaluate the feasibility of arterial spin labeling (ASL) magnetic resonance imaging (MRI) for the assessment of vascularity of renal masses in patients with impaired renal function. Between May 2007 and November 2008, 11/67 consecutive patients referred for MRI evaluation of a renal mass underwent unenhanced ASL-MRI due to moderate-to-severe chronic or acute renal failure. Mean blood flow in vascularised and non-vascularised lesions and the relation between blood flow and final diagnosis of malignancy were correlated with a 2-sided homogeneous variance t-test and the Fisher Exact Test, respectively. A p value 2 (range 7-39). The average blood flow of 11 renal masses interpreted as ASL-positive (134 +/- 85.7 mL/100 g/min) was higher than that of 6 renal masses interpreted as ASL-negative (20.5 +/- 8.1 mL/100 g/min)(p = 0.015). ASL-positivity correlated with malignancy (n = 3) or epithelial atypia (n = 1) at histopathology or progression at follow up (n = 7). ASL detection of vascularity in renal masses in patients with impaired renal function is feasible and seems to indicate neoplasia although the technique requires further evaluation. (orig.)

  7. Evaluation of Renal Blood Flow in Chronic Kidney Disease Using Arterial Spin Labeling Perfusion Magnetic Resonance Imaging.

    Science.gov (United States)

    Li, Lu-Ping; Tan, Huan; Thacker, Jon M; Li, Wei; Zhou, Ying; Kohn, Orly; Sprague, Stuart M; Prasad, Pottumarthi V

    2017-01-01

    Chronic kidney disease (CKD) is known to be associated with reduced renal blood flow. However, data to-date in humans is limited. In this study, non-invasive arterial spin labeling (ASL) MRI data was acquired in 33 patients with diabetes and stage-3 CKD, and 30 healthy controls. A significantly lower renal blood flow both in cortex (108.4±36.4 vs . 207.3±41.8; pblood flow were correlated with eGFR, and cortical blood flow was found to be confounded by age and BMI. However, in a subset of subjects that were matched for age and BMI (n=6), the differences between CKD and control subjects remained significant both in cortex (107.4±42.8 vs . 187.51±20.44; p=0.002) and medulla (15.43±8.43 vs . 39.18±11.13; p=0.002). A threshold value to separate healthy and CKD was estimated to be Cor_BF=142.9 and Med_BF=24.1. These results support the use of ASL in the evaluation of renal blood flow in patients with moderate level of CKD. Whether these measurements can identify subjects at risk of progressive CKD requires further longitudinal follow-up.

  8. Arterial spin labeling MR imaging for characterisation of renal masses in patients with impaired renal function: initial experience

    Energy Technology Data Exchange (ETDEWEB)

    Pedrosa, Ivan [Beth Israel Deaconess Medical Center and Harvard Medical School, Department of Radiology, Boston, MA (United States); UT Southwestern Medical Center, Department of Radiology, Dallas, TX (United States); Rafatzand, Khashayar; Robson, Philip; Alsop, David C. [Beth Israel Deaconess Medical Center and Harvard Medical School, Department of Radiology, Boston, MA (United States); Wagner, Andrew A. [Beth Israel Deaconess Medical Center and Harvard Medical School, Surgery, Division of Urology, Boston, MA (United States); Atkins, Michael B. [Beth Israel Deaconess Medical Center and Harvard Medical School, Hematology/Oncology, Boston, MA (United States); Rofsky, Neil M. [University of Texas Southwestern Medical Center, Departments of Radiology, Dallas, TX (United States)

    2012-02-15

    To retrospectively evaluate the feasibility of arterial spin labeling (ASL) magnetic resonance imaging (MRI) for the assessment of vascularity of renal masses in patients with impaired renal function. Between May 2007 and November 2008, 11/67 consecutive patients referred for MRI evaluation of a renal mass underwent unenhanced ASL-MRI due to moderate-to-severe chronic or acute renal failure. Mean blood flow in vascularised and non-vascularised lesions and the relation between blood flow and final diagnosis of malignancy were correlated with a 2-sided homogeneous variance t-test and the Fisher Exact Test, respectively. A p value <0.05 was considered statistically significant. Seventeen renal lesions were evaluated in 11 patients (8 male; mean age = 70 years) (range 57-86). The median eGFR was 24 mL/min/1.73 m{sup 2} (range 7-39). The average blood flow of 11 renal masses interpreted as ASL-positive (134 +/- 85.7 mL/100 g/min) was higher than that of 6 renal masses interpreted as ASL-negative (20.5 +/- 8.1 mL/100 g/min)(p = 0.015). ASL-positivity correlated with malignancy (n = 3) or epithelial atypia (n = 1) at histopathology or progression at follow up (n = 7). ASL detection of vascularity in renal masses in patients with impaired renal function is feasible and seems to indicate neoplasia although the technique requires further evaluation. (orig.)

  9. Perfusion imaging of brain gliomas using arterial spin labeling: correlation with histopathological vascular density in MRI-guided biopsies

    Energy Technology Data Exchange (ETDEWEB)

    Di, Ningning; Pang, Haopeng; Ren, Yan; Yao, Zhenwei; Feng, Xiaoyuan [Huashan Hospital Fudan University, Department of Radiology, Shanghai (China); Dang, Xuefei [Shang Hai Gamma Knife Hospital, Shanghai (China); Cheng, Wenna [Binzhou Medical University Affiliated Hospital, Department of Pharmacy, Binzhou (China); Wu, Jingsong; Yao, Chengjun [Huashan Hospital Fudan University, Department of Neurosurgery, Shanghai (China)

    2017-01-15

    This study was designed to determine if cerebral blood flow (CBF) derived from arterial spin labeling (ASL) perfusion imaging could be used to quantitatively evaluate the microvascular density (MVD) of brain gliomas on a ''point-to-point'' basis by matching CBF areas and surgical biopsy sites as accurate as possible. The study enrolled 47 patients with treatment-naive brain gliomas who underwent preoperative ASL, 3D T1-weighted imaging with gadolinium contrast enhancement (3D T1C+), and T2 fluid acquisition of inversion recovery (T2FLAIR) sequences before stereotactic surgery. We histologically quantified MVD from CD34-stained sections of stereotactic biopsies and co-registered biopsy locations with localized CBF measurements. The correlation between CBF and MVD was determined using Spearman's correlation coefficient. P ≤.05 was considered statistically significant. Of the 47 patients enrolled in the study, 6 were excluded from the analysis because of brain shift or poor co-registration and localization of the biopsy site during surgery. Finally, 84 biopsies from 41 subjects were included in the analysis. CBF showed a statistically significant positive correlation with MVD (ρ = 0.567; P =.029). ASL can be a useful noninvasive perfusion MR method for quantitative evaluation of the MVD of brain gliomas. (orig.)

  10. Noninvasive measurements of regional cerebral perfusion in preterm and term neonates by magnetic resonance arterial spin labeling.

    Science.gov (United States)

    Miranda, Maria J; Olofsson, Kern; Sidaros, Karam

    2006-09-01

    Magnetic resonance arterial spin labeling (ASL) at 3 Tesla has been investigated as a quantitative technique for measuring regional cerebral perfusion (RCP) in newborn infants. RCP values were measured in 49 healthy neonates: 32 preterm infants born before 34 wk of gestation and 17 term-born neonates. Examinations were performed on unsedated infants at postmenstrual age of 39-40 wk in both groups. Due to motion, reliable data were obtained from 23 preterm and 6 term infants. Perfusion in the basal ganglia (39 and 30 mL/100 g/min for preterm and term neonates, respectively) was significantly higher (p neonates at term-equivalent age and in term neonates. Perfusion was significantly higher (p = 0.01) in the preterm group than in the term infants, indicating that RCP may be influenced by developmental and postnatal ages. This study demonstrates, for the first time, that noninvasive ASL at 3T may be used to measure RCP in healthy unsedated preterm and term neonates. ASL is, therefore, a viable tool that will allow serial studies of RCP in high-risk neonates.

  11. Comparing kidney perfusion using noncontrast arterial spin labeling MRI and microsphere methods in an interventional swine model.

    Science.gov (United States)

    Artz, Nathan S; Wentland, Andrew L; Sadowski, Elizabeth A; Djamali, Arjang; Grist, Thomas M; Seo, Songwon; Fain, Sean B

    2011-02-01

    The purpose of this study was to assess the ability of a flow-sensitive alternating inversion recovery-arterial spin labeling (FAIR-ASL) technique to track renal perfusion changes during pharmacologic and physiologic alterations in renal blood flow using microspheres as a gold standard. Fluorescent microsphere and FAIR-ASL perfusion were compared in the cortex of the kidney for 11 swine across 4 interventional time points: (1) under baseline conditions, (2) during an acetylcholine and fluid bolus challenge to increase perfusion, (3) initially after switching to isoflurane anesthesia, and (4) after 2 hours of isoflurane anesthesia. In 10 of the 11 swine, a bag of ice was placed on the hilum of 1 kidney at the beginning of isoflurane administration to further reduce perfusion in 1 kidney. Both ASL and microspheres tracked the expected cortical perfusion changes (P values were systematically lower compared with microsphere perfusion. Very good correlation (r = 0.81, P values in the expected physiologic range (microsphere perfusion values saturated for perfusion >550 mL/min/100 g. Cortical perfusion measured with ASL correlated with microspheres and reliably detected changes in renal perfusion in response to physiologic challenge.

  12. Estimation of arterial arrival time and cerebral blood flow from QUASAR arterial spin labeling using stable spline.

    Science.gov (United States)

    Castellaro, Marco; Peruzzo, Denis; Mehndiratta, Amit; Pillonetto, Gianluigi; Petersen, Esben Thade; Golay, Xavier; Chappell, Michael A; Bertoldo, Alessandra

    2015-12-01

    QUASAR arterial spin labeling (ASL) permits the application of deconvolution approaches for the absolute quantification of cerebral perfusion. Currently, oscillation index regularized singular value decomposition (oSVD) combined with edge-detection (ED) is the most commonly used method. Its major drawbacks are nonphysiological oscillations in the impulse response function and underestimation of perfusion. The aim of this work is to introduce a novel method to overcome these limitations. A system identification method, stable spline (SS), was extended to address ASL peculiarities such as the delay in arrival of the arterial blood in the tissue. The proposed framework was compared with oSVD + ED in both simulated and real data. SS was used to investigate the validity of using a voxel-wise tissue T1 value instead of using a single global value (of blood T1 ). SS outperformed oSVD + ED in 79.9% of simulations. When applied to real data, SS exhibited a physiologically realistic range for perfusion and a higher mean value with respect to oSVD + ED (55.5 ± 9.5 SS, 34.9 ± 5.2 oSVD + ED mL/100 g/min). SS can represent an alternative to oSVD + ED for the quantification of QUASAR ASL data. Analysis of the retrieved impulse response function revealed that using a voxel wise tissue T1 might be suboptimal. © 2014 Wiley Periodicals, Inc.

  13. Perfusion imaging of parotid gland tumours: usefulness of arterial spin labeling for differentiating Warthin's tumours

    Energy Technology Data Exchange (ETDEWEB)

    Kato, Hiroki; Watanabe, Haruo [Gifu University School of Medicine, Department of Radiology, Gifu (Japan); Kanematsu, Masayuki [Gifu University School of Medicine, Department of Radiology, Gifu (Japan); Gifu University Hospital, High-level Imaging Diagnosis Center, Gifu (Japan); Kajita, Kimihiro [Gifu University Hospital, High-level Imaging Diagnosis Center, Gifu (Japan); Mizuta, Keisuke; Aoki, Mitsuhiro [Gifu University School of Medicine, Department of Otolaryngology, Gifu (Japan); Okuaki, Tomoyuki [Philips Healthcare, Tokyo (Japan)

    2015-11-15

    To assess prospectively the efficacy of arterial spin labelling (ASL) against conventional and diffusion-weighted (DW) MR imaging for differentiating parotid gland tumours. We included 10 pleomorphic adenomas, 12 Warthin's tumours, and nine malignant tumours of the parotid glands. Only tumours larger than 10 mm were included in this study. All parotid gland tumours underwent T1-weighted, T2-weighted, DW, and ASL imaging. Tumour-to-parotid gland signal intensity ratios (SIRs) and apparent diffusion coefficients (ADCs) of solid components were correlated with these pathologies. SIRs on T2-weighted images and ADCs were higher in pleomorphic adenomas than in Warthin's tumours (p <.01) and malignant tumours (p <.01). SIRs on ASL were higher in Warthin's tumours than in pleomorphic adenomas (p <.01) and malignant tumours (p <.05). Az value of SIRs on ASL for differentiating Warthin's tumours from the other pathologies was 0.982. The sensitivity, specificity, and accuracy of SIRs on ASL for the diagnosis of Warthin's tumours at an optimal SIR threshold of over 8.70 were 91.7 %, 94.7 %, and 93.5 %, respectively. ASL with SIR measurements could non-invasively evaluate tumour blood flow of parotid gland tumours and differentiate Warthin's tumours from pleomorphic adenomas and malignant tumours. (orig.)

  14. Arterial spin labelling MRI for detecting pseudocapsule defects and predicting renal capsule invasion in renal cell carcinoma.

    Science.gov (United States)

    Zhang, H; Wu, Y; Xue, W; Zuo, P; Oesingmann, N; Gan, Q; Huang, Z; Wu, M; Hu, F; Kuang, M; Song, B

    2017-11-01

    To evaluate prospectively the performance of combining morphological and arterial spin labelling (ASL) magnetic resonance imaging (MRI) for detecting pseudocapsule defects in renal cell carcinoma (RCC), and to predict renal capsule invasion confirmed histopathologically. Twenty consecutive patients with suspicious renal tumours underwent MRI. Renal ASL imaging was performed and renal blood flow was measured quantitatively. The diagnostic performance of T2-weighted images alone, and a combination of T2-weighted and ASL images for predicting renal capsule invasion were assessed. Twenty renal lesions were evaluated in 20 patients. All lesions were clear cell RCCs (ccRCCs) confirmed at post-surgical histopathology. Fifteen ccRCCs showed pseudocapsule defects on T2-weighted images, of which 12 cases showed existing blood flow in defect areas on perfusion images. To predict renal capsule invasion, the sensitivity, specificity, positive predictive value, and negative predictive value were 100%, 71.4%, 86.7%, 100%, respectively, for T2-weighted images alone, and 92.3%, 100%, 100%, 87.5%, respectively, for the combination of T2-weighted and ASL images. ASL images can reflect the perfusion of pseudocapsule defects and as such, the combination of T2-weighted and ASL images produces promising diagnostic accuracy for predicting renal capsule invasion. Copyright © 2017 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.

  15. Early-stage differentiation between presenile Alzheimer's disease and frontotemporal dementia using arterial spin labeling MRI

    Energy Technology Data Exchange (ETDEWEB)

    Steketee, Rebecca M.E.; Meijboom, Rozanna; Lugt, Aad van der; Smits, Marion [Erasmus MC - University Medical Center, Department of Radiology, PO Box 2040, Rotterdam (Netherlands); Bron, Esther E.; Klein, Stefan [Erasmus MC - University Medical Center, Biomedical Imaging Group Rotterdam, Departments of Medical Informatics and Radiology, PO Box 2040, Rotterdam (Netherlands); Houston, Gavin C. [GE Healthcare, Hatfield (United Kingdom); Mutsaerts, Henri J.M.M. [Academic Medical Center, Department of Radiology, PO Box 22660, Amsterdam (Netherlands); Mendez Orellana, Carolina P. [Erasmus MC - University Medical Center, Department of Radiology, PO Box 2040, Rotterdam (Netherlands); Erasmus MC - University Medical Center, Department of Neurology, PO Box 2040, Rotterdam (Netherlands); Jong, Frank Jan de; Swieten, John C. van [Erasmus MC - University Medical Center, Department of Neurology, PO Box 2040, Rotterdam (Netherlands)

    2016-01-15

    To investigate arterial spin labeling (ASL)-MRI for the early diagnosis of and differentiation between the two most common types of presenile dementia: Alzheimer's disease (AD) and frontotemporal dementia (FTD), and for distinguishing age-related from pathological perfusion changes. Thirteen AD and 19 FTD patients, and 25 age-matched older and 22 younger controls underwent 3D pseudo-continuous ASL-MRI at 3 T. Gray matter (GM) volume and cerebral blood flow (CBF), corrected for partial volume effects, were quantified in the entire supratentorial cortex and in 10 GM regions. Sensitivity, specificity and diagnostic performance were evaluated in regions showing significant CBF differences between patient groups or between patients and older controls. AD compared with FTD patients had hypoperfusion in the posterior cingulate cortex, differentiating these with a diagnostic performance of 74 %. Compared to older controls, FTD patients showed hypoperfusion in the anterior cingulate cortex, whereas AD patients showed a more widespread regional hypoperfusion as well as atrophy. Regional atrophy was not different between AD and FTD. Diagnostic performance of ASL to differentiate AD or FTD from controls was good (78-85 %). Older controls showed global hypoperfusion compared to young controls. ASL-MRI contributes to early diagnosis of and differentiation between presenile AD and FTD. (orig.)

  16. Improving quality of arterial spin labeling MR imaging at 3 Tesla with a 32-channel coil and parallel imaging.

    Science.gov (United States)

    Ferré, Jean-Christophe; Petr, Jan; Bannier, Elise; Barillot, Christian; Gauvrit, Jean-Yves

    2012-05-01

    To compare 12-channel and 32-channel phased-array coils and to determine the optimal parallel imaging (PI) technique and factor for brain perfusion imaging using Pulsed Arterial Spin labeling (PASL) at 3 Tesla (T). Twenty-seven healthy volunteers underwent 10 different PASL perfusion PICORE Q2TIPS scans at 3T using 12-channel and 32-channel coils without PI and with GRAPPA or mSENSE using factor 2. PI with factor 3 and 4 were used only with the 32-channel coil. Visual quality was assessed using four parameters. Quantitative analyses were performed using temporal noise, contrast-to-noise and signal-to-noise ratios (CNR, SNR). Compared with 12-channel acquisition, the scores for 32-channel acquisition were significantly higher for overall visual quality, lower for noise and higher for SNR and CNR. With the 32-channel coil, artifact compromise achieved the best score with PI factor 2. Noise increased, SNR and CNR decreased with PI factor. However mSENSE 2 scores were not always significantly different from acquisition without PI. For PASL at 3T, the 32-channel coil at 3T provided better quality than the 12-channel coil. With the 32-channel coil, mSENSE 2 seemed to offer the best compromise for decreasing artifacts without significantly reducing SNR, CNR. Copyright © 2012 Wiley Periodicals, Inc.

  17. Early-stage differentiation between presenile Alzheimer's disease and frontotemporal dementia using arterial spin labeling MRI

    International Nuclear Information System (INIS)

    Steketee, Rebecca M.E.; Meijboom, Rozanna; Lugt, Aad van der; Smits, Marion; Bron, Esther E.; Klein, Stefan; Houston, Gavin C.; Mutsaerts, Henri J.M.M.; Mendez Orellana, Carolina P.; Jong, Frank Jan de; Swieten, John C. van

    2016-01-01

    To investigate arterial spin labeling (ASL)-MRI for the early diagnosis of and differentiation between the two most common types of presenile dementia: Alzheimer's disease (AD) and frontotemporal dementia (FTD), and for distinguishing age-related from pathological perfusion changes. Thirteen AD and 19 FTD patients, and 25 age-matched older and 22 younger controls underwent 3D pseudo-continuous ASL-MRI at 3 T. Gray matter (GM) volume and cerebral blood flow (CBF), corrected for partial volume effects, were quantified in the entire supratentorial cortex and in 10 GM regions. Sensitivity, specificity and diagnostic performance were evaluated in regions showing significant CBF differences between patient groups or between patients and older controls. AD compared with FTD patients had hypoperfusion in the posterior cingulate cortex, differentiating these with a diagnostic performance of 74 %. Compared to older controls, FTD patients showed hypoperfusion in the anterior cingulate cortex, whereas AD patients showed a more widespread regional hypoperfusion as well as atrophy. Regional atrophy was not different between AD and FTD. Diagnostic performance of ASL to differentiate AD or FTD from controls was good (78-85 %). Older controls showed global hypoperfusion compared to young controls. ASL-MRI contributes to early diagnosis of and differentiation between presenile AD and FTD. (orig.)

  18. Radicals as EPR probes of magnetization of gadolinium stearate Langmuir-Blodgett film

    DEFF Research Database (Denmark)

    Koksharov, Y.A.; Bykov, I.V.; Malakho, A.P.

    2002-01-01

    In the present work we have applied the method of the EPR spin probes which allows performing simultaneously EPR and magnetization measurements to the investigation of magnetism of the Cid stearate Langmuir-Blodgett (LB) films. For this purpose we have prepared and studied by the EPR technique...... the Gd and Y stearate LB films. Placing the small BDPA crystal on the film surface we have found that for the Gd LB sample the effective g-value of the radical's resonance depends on the film orientation in respect to the external magnetic field direction. The relative shift of the EPR signal...

  19. Host material induced hyperfine structure of F{sup +} centres EPR spectra in CaS

    Energy Technology Data Exchange (ETDEWEB)

    Seeman, Viktor, E-mail: viktor.seeman@ut.ee; Dolgov, Sergei; Maaroos, Aarne

    2017-05-15

    The hyperfine structure (HFS) of F{sup +} centres in CaS single crystals due to the interaction with {sup 33}S and {sup 43}Ca nuclei was observed in EPR spectra for the first time. Angular variations of the HFS were measured for rotation of magnetic field in {100} and {110} crystallographic planes. Using measured orientation-dependent EPR spectra and the EPR NMR program, the parameters of the spin Hamiltonian were determined. In case of {sup 33}S nucleus there is a strong dependence of the F{sup +} centre EPR spectrum on the quadrupole term whereas for {sup 43}Ca nucleus this dependence is insignificant.

  20. Study of growth of polyaniline chain by EPR method

    Energy Technology Data Exchange (ETDEWEB)

    Kulikov, A V [Inst. of Chemical Physics, Chernogolovka (Russian Federation); Kogan, Ya L [Inst. of Chemical Physics, Chernogolovka (Russian Federation); Fokeeva, L S [Inst. of Chemical Physics, Chernogolovka (Russian Federation)

    1993-03-22

    Chemical aniline polymerization has been studied by the EPR method. After a long delay a weak EPR signal I is appeared and transformed rapidly into a strong Lorentzian line. Constants of spin exchange of signals I and II with paramagnetic probes Fe(CN)[sub 6][sup 3-], Co[sup 2+] and O[sub 2], freely diffusing in solution, have been determined. Effect of ferricyanide ions and urea, a breaker of hydrogen bonds, has been measured for signals I and II. Data obtained show the formation of an array of positive charges in PANI at early stage of doping. Constants of spin exchange depend on prehistory of samples. Averaging of EPR line widths of different paramagnetic centers in polyaniline was found. (orig.)

  1. Full cycle rapid scan EPR deconvolution algorithm.

    Science.gov (United States)

    Tseytlin, Mark

    2017-08-01

    Rapid scan electron paramagnetic resonance (RS EPR) is a continuous-wave (CW) method that combines narrowband excitation and broadband detection. Sinusoidal magnetic field scans that span the entire EPR spectrum cause electron spin excitations twice during the scan period. Periodic transient RS signals are digitized and time-averaged. Deconvolution of absorption spectrum from the measured full-cycle signal is an ill-posed problem that does not have a stable solution because the magnetic field passes the same EPR line twice per sinusoidal scan during up- and down-field passages. As a result, RS signals consist of two contributions that need to be separated and postprocessed individually. Deconvolution of either of the contributions is a well-posed problem that has a stable solution. The current version of the RS EPR algorithm solves the separation problem by cutting the full-scan signal into two half-period pieces. This imposes a constraint on the experiment; the EPR signal must completely decay by the end of each half-scan in order to not be truncated. The constraint limits the maximum scan frequency and, therefore, the RS signal-to-noise gain. Faster scans permit the use of higher excitation powers without saturating the spin system, translating into a higher EPR sensitivity. A stable, full-scan algorithm is described in this paper that does not require truncation of the periodic response. This algorithm utilizes the additive property of linear systems: the response to a sum of two inputs is equal the sum of responses to each of the inputs separately. Based on this property, the mathematical model for CW RS EPR can be replaced by that of a sum of two independent full-cycle pulsed field-modulated experiments. In each of these experiments, the excitation power equals to zero during either up- or down-field scan. The full-cycle algorithm permits approaching the upper theoretical scan frequency limit; the transient spin system response must decay within the scan

  2. EPR paradox revisited

    Energy Technology Data Exchange (ETDEWEB)

    Klippert, R. [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil)

    1999-07-01

    In a seminal paper from 1935 Einstein, Podolsky and Rosen produced one of the most powerful weapon against the unpredictability of the world ensured by quantum mechanics. The recent production of entangled states, with all its possible future applications in quantum computation, re-open the possibility of testing EPR states on physical grounds. The present intends to present a challenge to the wedding of classical (special) relativity with quantum mechanics, the so called relativistic quantum mechanics. Making use of the same apparatus devised in EPR, it is shown that non local quantum states are incompatible with either their possibility of being measured or else with Lorentz invariance (or even with both). (author)

  3. Free-radical probes for functional in vivo EPR imaging

    Science.gov (United States)

    Subramanian, S.; Krishna, M. C.

    2007-02-01

    Electron paramagnetic resonance imaging (EPRI) is one of the recent functional imaging modalities that can provide valuable in vivo physiological information on its own merit and aids as a complimentary imaging technique to MRI and PET of tissues especially with respect to in vivo pO II (oxygen partial pressure), redox status and pharmacology. EPR imaging mainly deals with the measurement of distribution and in vivo dynamics and redox changes using special nontoxic paramagnetic spin probes that can be infused into the object of investigation. These spin probes should be characterized by simple EPR spectra, preferably with narrow EPR lines. The line width should be reversibly sensitive to the concentration of in vivo pO II with a linear dependence. Several non-toxic paramagnetic probes, some particulate and insoluble and others water-soluble and infusible (by intravenous or intramuscular injection) have been developed which can be effectively used to quantitatively assess tissue redox status, and tumor hypoxia. Quantitative assessment of the redox status of tissue in vivo is important in investigating oxidative stress, and that of tissue pO II is very important in radiation oncology. Other areas in which EPR imaging and oxymetry may help are in the investigation of tumorangiogenesis, wound healing, oxygenation of tumor tissue by the ingestion of oxygen-rich gases, etc. The correct choice of the spin probe will depend on the modality of measurement (whether by CW or time-domain EPR imaging) and the particular physiology interrogated. Examples of the available spin probes and some EPR imaging applications employing them are presented.

  4. Medial Occipital Lobe Hyperperfusion Identified by Arterial Spin-Labeling: A Poor Prognostic Sign in Patients with Hypoxic-Ischemic Encephalopathy.

    Science.gov (United States)

    de Havenon, A; Sultan-Qurraie, A; Tirschwell, D; Cohen, W; Majersik, J; Andre, J B

    2015-12-01

    Hypoxic-ischemic encephalopathy carries an uncertain prognosis. We sought to retrospectively assess the prognostic value of arterial spin-labeling MR imaging in 22 adult patients diagnosed with hypoxic-ischemic encephalopathy. Quantitative CBF maps were generated from the M0 map, and arterial spin-labeling data on a per-voxel basis were regionally interrogated via visual inspection and ROI placement. Hyperperfusion was defined as regional increases in CBF of >20% (relative to global CBF) and/or >100 mL/100 g/min. Eleven of 22 patients had prominent bilateral medial occipital lobe hyperperfusion, all of whom died before hospital discharge. One patient who had nondistinct arterial spin-labeling hyperperfusion and restricted diffusion survived. Medial occipital lobe hyperperfusion is a distinctive pattern that merits prospective investigation in a cohort of patients with moderate hypoxic-ischemic encephalopathy to determine its predictive ability in patients with a higher likelihood of survival. © 2015 by American Journal of Neuroradiology.

  5. Recent progress in synchrotron-based frequency-domain Fourier-transform THz-EPR.

    Science.gov (United States)

    Nehrkorn, Joscha; Holldack, Karsten; Bittl, Robert; Schnegg, Alexander

    2017-07-01

    We describe frequency-domain Fourier-transform THz-EPR as a method to assign spin-coupling parameters of high-spin (S>1/2) systems with very large zero-field splittings. The instrumental foundations of synchrotron-based FD-FT THz-EPR are presented, alongside with a discussion of frequency-domain EPR simulation routines. The capabilities of this approach is demonstrated for selected mono- and multinuclear HS systems. Finally, we discuss remaining challenges and give an outlook on the future prospects of the technique. Copyright © 2017 Elsevier Inc. All rights reserved.

  6. EPR: the nuclear impasse

    International Nuclear Information System (INIS)

    Marillier, F.

    2008-01-01

    The questions relative to the climatic change constitute crucial challenges for the next ten years. In this context the author aims to show how the EPR project illustrates the nuclear french ''autism''. He presents and analyzes the international and environmental impacts of this obsolete technology, as a project useless and dangerous. (A.L.B.)

  7. Perfusion MRI of brain tumours: a comparative study of pseudo-continuous arterial spin labelling and dynamic susceptibility contrast imaging

    Energy Technology Data Exchange (ETDEWEB)

    Jaernum, Hanna; Steffensen, Elena G.; Simonsen, Carsten Wiberg; Jensen, Finn Taagehoej [Aalborg Hospital/Aarhus University Hospital, Department of Radiology, Aalborg (Denmark); Knutsson, Linda [Lund University, Department of Medical Radiation Physics, Lund (Sweden); Fruend, Ernst-Torben [Aalborg Hospital/Aarhus University Hospital, Department of Radiology, Aalborg (Denmark); GE Healthcare - Applied Science Lab Europe, Aalborg (Denmark); Lundbye-Christensen, Soeren [Aalborg Hospital/Aarhus University Hospital, Department of Cardiology, Center for Cardiovascular Research, Aalborg (Denmark); Shankaranarayanan, Ajit [Global Applied Science Lab, GE Healthcare, Menlo Park, CA (United States); Alsop, David C. [Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA (United States); Larsson, Elna-Marie [Aalborg Hospital/Aarhus University Hospital, Department of Radiology, Aalborg (Denmark); Uppsala University Hospital, Department of Radiology, Uppsala (Sweden)

    2010-04-15

    The purpose of this study was to compare the non-invasive 3D pseudo-continuous arterial spin labelling (PC ASL) technique with the clinically established dynamic susceptibility contrast perfusion magnetic resonance imaging (DSC-MRI) for evaluation of brain tumours. A prospective study of 28 patients with contrast-enhancing brain tumours was performed at 3 T using DSC-MRI and PC ASL with whole-brain coverage. The visual qualitative evaluation of signal enhancement in tumour was scored from 0 to 3 (0 = no signal enhancement compared with white matter, 3 = pronounced signal enhancement with equal or higher signal intensity than in grey matter/basal ganglia). The extent of susceptibility artefacts in the tumour was scored from 0 to 2 (0 = no susceptibility artefacts and 2 = extensive susceptibility artefacts (maximum diameter > 2 cm)). A quantitative analysis was performed with normalised tumour blood flow values (ASL nTBF, DSC nTBF): mean value for region of interest (ROI) in an area with maximum signal enhancement/the mean value for ROIs in cerebellum. There was no difference in total visual score for signal enhancement between PC ASL and DSC relative cerebral blood flow (p = 0.12). ASL had a lower susceptibility-artefact score than DSC-MRI (p = 0.03). There was good correlation between DSC nTBF and ASL nTBF values with a correlation coefficient of 0.82. PC ASL is an alternative to DSC-MRI for the evaluation of perfusion in brain tumours. The method has fewer susceptibility artefacts than DSC-MRI and can be used in patients with renal failure because no contrast injection is needed. (orig.)

  8. MDMA ‘ecstasy’ increases cerebral cortical perfusion determined by bolus-tracking arterial spin labelling (btASL) MRI

    Science.gov (United States)

    Rouine, J; Gobbo, O L; Campbell, M; Gigliucci, V; Ogden, I; McHugh Smith, K; Duffy, P; Behan, B; Byrne, D; Kelly, M E; Blau, C W; Kerskens, C M; Harkin, A

    2013-01-01

    Background and Purpose The purpose of this study was to assess cerebral perfusion changes following systemic administration of the recreational drug 3,4-methylendioxymethamphetamine (MDMA ‘ecstasy’) to rats. Experimental Approach Cerebral perfusion was quantified using bolus-tracking arterial spin labelling (btASL) MRI. Rats received MDMA (20 mg·kg−1; i.p.) and were assessed 1, 3 or 24 h later. Rats received MDMA (5 or 20 mg·kg−1; i.p.) and were assessed 3 h later. In addition, rats received MDMA (5 or 10 mg·kg−1; i.p.) or saline four times daily over 2 consecutive days and were assessed 8 weeks later. Perfusion-weighted images were generated in a 7 tesla (7T) MRI scanner and experimental data was fitted to a quantitative model of cerebral perfusion to generate mean transit time (MTT), capillary transit time (CTT) and signal amplitude. Key Results MDMA reduces MTT and CTT and increases amplitude in somatosensory and motor cortex 1 and 3 h following administration, indicative of an increase in perfusion. Prior exposure to MDMA provoked a long-term reduction in cortical 5-HT concentration, but did not produce a sustained effect on cerebral cortical perfusion. The response to acute MDMA challenge (20 mg·kg−1; i.p.) was attenuated in these animals indicating adaptation in response to prior MDMA exposure. Conclusions and Implications MDMA provokes changes in cortical perfusion, which are quantifiable by btASL MRI, a neuroimaging tool with translational potential. Future studies are directed towards elucidation of the mechanisms involved and correlating changes in cerebrovascular function with potential behavioural deficits associated with drug use. PMID:23517012

  9. Temporal and extra-temporal hypoperfusion in medial temporal lobe epilepsy evaluated by arterial-spin-labeling based MRI

    International Nuclear Information System (INIS)

    Shen Lianfang; Zhang Zhiqiang; Lu Guangming; Yuan Cuiping; Wang Zhengge; Wang Haoxue; Huang Wei; Wei Fangyuan; Chen Guanghui; Tan Qifu

    2012-01-01

    Objective: To evaluate the feasibility of the lateralization of unilateral medial temporal lobe epilepsy (mTLE) by using arterial-spin-labeling (ASL) based perfusion MR imaging and investigate the changes of perfusion in the regions related to mTLE network and the relationship between the perfusion and the clinical status. Methods: Twenty-five patients with left-sided and 23 with right-sided mTLE were enrolled, and 30 healthy volunteers were recruited. The cerebral blood flow (CBF) of related region was measured based on pulsed-ASL sequence on Siemens 3 T scanner. The CBF of the mTLE group were compared with that in the controls by using ANOVA analysis. The asymmetric indices of CBF in the medial temporal lobe were calculated as the lesion side compared with the normal side in matched region in mTLE group. Results: Compared with the volunteers, the patients with mTLE showed the decrease of CBF in the bilateral medial and lateral temporal, the frontal and parietal regions relating to the default-mode network and more serious in lesion side. The CBF values of the medial temporal lobe were negatively correlated with the epilepsy duration (r=-0.51, P<0.01). The asymmetric index of CBF as-0.01 has a 76.0% (19/25) sensitivity and a 78.3% (18/23) specificity to distinguish the lesion side. Conclusions: The decrease of CBF in the temporal and extra-temporal region by ASL-based MRI suggests the functional abnormalities in the network involved by mTLE. The ASL technique is a useful tool for lateralizing the unilateral mTLE. (authors)

  10. Task Related Cerebral Blood Flow Changes of Patients with Chronic Fatigue Syndrome: An Arterial Spin Labeling Study.

    Science.gov (United States)

    Staud, Roland; Boissoneault, Jeff; Craggs, Jason G; Lai, Song; Robinson, Michael E

    2018-01-01

    One hallmark of chronic fatigue syndrome (ME/CFS) is task related worsening of fatigue. Global brain hypoperfusion, abnormal regional activation, and altered functional connectivity of brain areas associated with cognition and memory have been reported but remain controversial. We enrolled 17 female participants fulfilling the CDC Criteria for ME/CFS and 16 matched healthy controls (HC). Using a 3T-Phillips Achieva MRI-scanner, pseudo-continuous arterial spin-labeling (pCASL), was used to study the dynamics of regional cerebral blood flow (rCBF) and their relationship to mental fatigue in ME/CFS patients and HC during a demanding cognitive task, i.e. modified Paced-Auditory-Serial-Addition-Testing (PASAT). ME/CFS subjects reported more fatigue than HC at baseline (p fatigue in ME/CFS participants and HC. Although not different between groups, overall CBF significantly increased over the first 3 min of the PASAT and then decreased thereafter. Regional CBF (rCBF) changes were significantly different between groups during the post-task recovery period. Whereas improvement of fatigue of ME/CFS subjects was associated with decreased rCBF in both superior temporal gyri (STG), precuneus, and fusiform gyrus, it was associated with increased rCBF in the same areas in HC. Our results suggest that ME/CFS is associated with normal global CBF at rest and during a strenuous task (PASAT); however rCBF of several brain regions associated with memory, goal-oriented attention, and visual function was differentially associated with recovery from fatigue in ME/CFS patients and HC.

  11. Contribution of tryptophan residues to the combining site of a monoclonal anti dinitrophenyl spin-label antibody

    International Nuclear Information System (INIS)

    Anglister, J.; Bond, M.W.; Frey, T.; Leahy, D.; Levitt, M.; McConnell, H.M.; Rule, G.S.; Tomasello, J.; Whittaker, M.

    1987-01-01

    Two Fab fragments of the monoclonal anti dinitrophenyl (DNP) spin-label antibody AN02 were prepared by recombination of specifically deuterated heavy and light chains. In the recombinant H(I)L(II) all the tyrosines and phenylalanines were perdeuterated as were the tryptophan residues of the heavy chain. In the recombinant H(II)L(I) all the tyrosines and phenylalanines were perdeuterated as were the tryptophan residues of the light chain. Saturation of three resonances of H(I)L(II), assigned to tryptophan protons of the light chain, resulted in magnetization transfer to the aromatic proton at position 6 of the DNP ring and to the CH2 protons of the glycines linked to the DNP in a diamagnetic hapten (DNP-DG). Saturation of three resonances of H(II)L(I) assigned to tryptophan protons of the heavy chain resulted in magnetization transfer to the CH2 protons of the glycines in DNP-DG. From the dependence of the magnetization transfer on the irradiation time, the cross relaxation rates between the involved protons were estimated. The inferred distances between these protons of the hapten and certain tryptophan protons are 3-4 A. It is concluded that in the combining site of AN02 there is one tryptophan from the light chain and one tryptophan from the heavy chain that are very near the hapten. When all tyrosines and phenylalanines were perdeuterated and all tryptophan aromatic protons were deuterated except for the protons at positions 2 and 5, titration of the Fab fragments with variable amounts of paramagnetic hapten showed that one proton from the light chain tryptophan is near (less than 7 A) the unpaired electron and that three other protons are significantly closer than 15 A

  12. Contribution of tryptophan residues to the combining site of a monoclonal anti dinitrophenyl spin-label antibody

    Energy Technology Data Exchange (ETDEWEB)

    Anglister, J.; Bond, M.W.; Frey, T.; Leahy, D.; Levitt, M.; McConnell, H.M.; Rule, G.S.; Tomasello, J.; Whittaker, M.

    1987-09-22

    Two Fab fragments of the monoclonal anti dinitrophenyl (DNP) spin-label antibody AN02 were prepared by recombination of specifically deuterated heavy and light chains. In the recombinant H(I)L(II) all the tyrosines and phenylalanines were perdeuterated as were the tryptophan residues of the heavy chain. In the recombinant H(II)L(I) all the tyrosines and phenylalanines were perdeuterated as were the tryptophan residues of the light chain. Saturation of three resonances of H(I)L(II), assigned to tryptophan protons of the light chain, resulted in magnetization transfer to the aromatic proton at position 6 of the DNP ring and to the CH2 protons of the glycines linked to the DNP in a diamagnetic hapten (DNP-DG). Saturation of three resonances of H(II)L(I) assigned to tryptophan protons of the heavy chain resulted in magnetization transfer to the CH2 protons of the glycines in DNP-DG. From the dependence of the magnetization transfer on the irradiation time, the cross relaxation rates between the involved protons were estimated. The inferred distances between these protons of the hapten and certain tryptophan protons are 3-4 A. It is concluded that in the combining site of AN02 there is one tryptophan from the light chain and one tryptophan from the heavy chain that are very near the hapten. When all tyrosines and phenylalanines were perdeuterated and all tryptophan aromatic protons were deuterated except for the protons at positions 2 and 5, titration of the Fab fragments with variable amounts of paramagnetic hapten showed that one proton from the light chain tryptophan is near (less than 7 A) the unpaired electron and that three other protons are significantly closer than 15 A.

  13. Arterial spin labelling MRI for assessment of cerebral perfusion in children with moyamoya disease: comparison with dynamic susceptibility contrast MRI

    Energy Technology Data Exchange (ETDEWEB)

    Goetti, Robert [University Children' s Hospital Zurich, Department of Diagnostic Imaging, Zurich (Switzerland); University Hospital Zurich, Department of Diagnostic and Interventional Radiology, Zurich (Switzerland); O' Gorman, Ruth [University Children' s Hospital Zurich, Center for MR Research, Zurich (Switzerland); Khan, Nadia [University Children' s Hospital Zurich, Moyamoya Center, Division of Neurosurgery, Department of Surgery, Zurich (Switzerland); Kellenberger, Christian J.; Scheer, Ianina [University Children' s Hospital Zurich, Department of Diagnostic Imaging, Zurich (Switzerland)

    2013-05-15

    This study seeks to evaluate the diagnostic accuracy of cerebral perfusion imaging with arterial spin labelling (ASL) MR imaging in children with moyamoya disease compared to dynamic susceptibility contrast (DSC) imaging. Ten children (7 females; age, 9.2 {+-} 5.4 years) with moyamoya disease underwent cerebral perfusion imaging with ASL and DSC on a 3-T MRI scanner in the same session. Cerebral perfusion images were acquired with ASL (pulsed continuous 3D ASL sequence, 32 axial slices, TR = 5.5 s, TE = 25 ms, FOV = 24 cm, matrix = 128 x 128) and DSC (gradient echo EPI sequence, 35 volumes of 28 axial slices, TR = 2,000 ms, TE = 36 ms, FOV = 24 cm, matrix = 96 x 96, 0.2 ml/kg Gd-DOTA). Cerebral blood flow maps were generated. ASL and DSC images were qualitatively assessed regarding perfusion of left and right ACA, MCA, and PCA territories by two independent readers using a 3-point-Likert scale and quantitative relative cerebral blood flow (rCBF) was calculated. Correlation between ASL and DSC for qualitative and quantitative assessment and the accuracy of ASL for the detection of reduced perfusion per territory with DSC serving as the standard of reference were calculated. With a good interreader agreement ({kappa} = 0.62) qualitative perfusion assessment with ASL and DSC showed a strong and significant correlation ({rho} = 0.77; p < 0.001), as did quantitative rCBF (r = 0.79; p < 0.001). ASL showed a sensitivity, specificity and accuracy of 94 %, 93 %, and 93 % for the detection of reduced perfusion per territory. In children with moyamoya disease, unenhanced ASL enables the detection of reduced perfusion per vascular territory with a good accuracy compared to contrast-enhanced DSC. (orig.)

  14. Chemistry of artemisinin: an EPR study and nucleobases interaction

    Energy Technology Data Exchange (ETDEWEB)

    Mustafa, Damra Elhaj [Department of Chemistry, Faculty of Education, University of Khartoum, Khartoum (Sudan)

    2000-10-01

    In the present, the radical transformations of artemisinin, a potent antimalarial drug have been examined using EPR and EPR spin trapping techniques. The effect of light on artemisinin has been investigated at 77 K as well as with the use of phenyl butyl nitrone (PBN) spin trapping agent. While no EPR signal was observed at 77 K, intense light irradiation of artemisinin/PBN gave EPR signal characteristic of radical transformation of the PBN. The reactions of artemisinin with iron (II), manganese (II), hemin and ferrocyanide ion have been investigated by spin trapping techniques. Artemisinin/iron (II) formed spin adducts with nitrosobenzene, nitroso-t-butane and PBN. The hypertine splittings of the spin adducts were a{sub N}=1.08 mT/a{sub N}=1.25 mT/a{sub N}=0.09 mT and a{sub N}=1.56 mT/a{sub N}=0.29 mT respectively. PBN trapping of artemether/iron (II) gave similar result to artemisinin/iron (II). These results are indicative of secondary carbon-centered radical formation. While artemisinin/hemin/PBN gave very weak EPR signal, ferrocyanide under the same condition gave no signal. Incubation of artemisinin with RNA at different reaction conditions, including irradiation with light, heat and mild acidic media, revealed no RNA damage when examined by agarose electrophoresis. However, artemisinin/iron (II) caused RNA damage in pH-dependant manner. In contrast, hemin did not show the same effect when it was used instead of iron (II). (Author)

  15. Chemistry of artemisinin: an EPR study and nucleobases interaction

    International Nuclear Information System (INIS)

    Mustafa, Damra Elhaj

    2000-10-01

    In the present, the radical transformations of artemisinin, a potent antimalarial drug have been examined using EPR and EPR spin trapping techniques. The effect of light on artemisinin has been investigated at 77 K as well as with the use of phenyl butyl nitrone (PBN) spin trapping agent. While no EPR signal was observed at 77 K, intense light irradiation of artemisinin/PBN gave EPR signal characteristic of radical transformation of the PBN. The reactions of artemisinin with iron (II), manganese (II), hemin and ferrocyanide ion have been investigated by spin trapping techniques. Artemisinin/iron (II) formed spin adducts with nitrosobenzene, nitroso-t-butane and PBN. The hypertine splittings of the spin adducts were a N =1.08 mT/a N =1.25 mT/a N =0.09 mT and a N =1.56 mT/a N =0.29 mT respectively. PBN trapping of artemether/iron (II) gave similar result to artemisinin/iron (II). These results are indicative of secondary carbon-centered radical formation. While artemisinin/hemin/PBN gave very weak EPR signal, ferrocyanide under the same condition gave no signal. Incubation of artemisinin with RNA at different reaction conditions, including irradiation with light, heat and mild acidic media, revealed no RNA damage when examined by agarose electrophoresis. However, artemisinin/iron (II) caused RNA damage in pH-dependant manner. In contrast, hemin did not show the same effect when it was used instead of iron (II). (Author)

  16. Morpholino spin-labeling for base-pair sequencing of a 3'-terminal RNA stem by proton homonuclear Overhauser enhancements: yeast ribosomal 5S RNA

    International Nuclear Information System (INIS)

    Lee, K.M.; Marshall, A.G.

    1987-01-01

    Base-pair sequences for 5S and 5.8S RNAs are not readily extracted from proton homonuclear nuclear Overhauser enhancement (NOE) connectivity experiments alone, due to extensive peak overlap in the downfield (11-15 ppm) proton NMR spectrum. In this paper, we introduce a new method for base-pair proton peak assignment for ribosomal RNAs, based upon the distance-dependent broadening of the resonances of base-pair protons spatially proximal to a paramagnetic group. Introduction of a nitroxide spin-label covalently attached to the 3'-terminal ribose provides an unequivocal starting point for base-pair hydrogen-bond proton NMR assignment. Subsequent NOE connectivities then establish the base-pair sequence for the terminal stem of a 5S RNA. Periodate oxidation of yeast 5S RNA, followed by reaction with 4-amino-2,2,6,6-tetramethylpiperidinyl-1-oxy (TEMPO-NH2) and sodium borohydride reduction, produces yeast 5S RNA specifically labeled with a paramagnetic nitroxide group at the 3'-terminal ribose. Comparison of the 500-MHz 1H NMR spectra of native and 3'-terminal spin-labeled yeast 5S RNA serves to identify the terminal base pair (G1 . C120) and its adjacent base pair (G2 . U119) on the basis of their proximity to the 3'-terminal spin-label. From that starting point, we have then identified (G . C, A . U, or G . U) and sequenced eight of the nine base pairs in the terminal helix via primary and secondary NOE's

  17. The effects of general anesthetics on ESR spectra of spin labels in phosphatidylcholine vesicles containing purified Na,K-ATPase or microsomal protein

    Science.gov (United States)

    Shibuya, Makiko; Hiraoki, Toshifumi; Kimura, Kunie; Fukushima, Kazuaki; Suzuki, Kuniaki

    2012-12-01

    We investigated the effects of general anesthetics on liposome containing spin labels, 5-doxyl stearic acid (5-DSA) and 16-doxyl stearic acid (16-DSA), and purified Na,K-ATPase or membrane protein of microsome using an electron spin resonance (ESR) spectroscopy. The spectra of 16-DSA in liposomes with both proteins showed three sharp signals compared with 5-DSA. The difference in the order parameter S value of 5-DSA and 16-DSA suggested that the nitroxide radical location of 5-DSA and 16-DSA were different in the membrane bilayer. The results were almost the same as those obtained in liposomes without proteins. The addition of sevoflurane, isoflurane, halothane, ether, ethanol and propofol increased the intensity of the signals, but the clinical concentrations of anesthetics did not significantly alter the S and τ values, which are indices of the fluidity of the membrane. These results suggest that anesthetics remain on the surface of the lipid bilayer and do not act on both the inside hydrophobic area and the relatively hydrophilic area near the surface. These results and others also suggest that the existence of Na,K-ATPase and microsomal proteins did not affect the environment around the spin labels in the liposome and the effects of anesthetics on liposome as a model membrane.

  18. EPR of divalent manganese in non-Kramers hosts

    Energy Technology Data Exchange (ETDEWEB)

    Lech, J.; Slezak, A. [Institute of Physics, Technical University of Czestochowa, Czestochowa (Poland)

    1997-12-31

    Various interactions which lead to the observation of sharp EPR spectra of the high half-integer spin impurity Mn{sup 2+} (S=5/2) in paramagnetic hosts with integer spins S=1 and S=2 have been studied. Studies have been carried out on the basis of data extracted from experimental EPR spectra of Mn{sup 2+} in single crystal of divalent nickel Ni{sup 2+} (S=1) and Fe{sup 2+} (S=1) perchlorate hexahydrates. It has been shown that dipolar host-host and host-guest couplings broaden resonance lines of Mn{sup 2+}. Narrowing of the lines in the both crystals can be mainly attributed to the host-guest exchange interactions and quenching of the host spins. 19 refs, 3 figs, 1 tab.

  19. EPR and UV spectrometry investigation of sucrose irradiated with carbon particles

    International Nuclear Information System (INIS)

    Karakirova, Yordanka; Yordanov, Nicola D.

    2010-01-01

    Solid state/EPR (SS/EPR) dosimeters of carbon ions irradiated sucrose are studied with EPR, and their water solutions - with UV spectroscopy. Doses between 20 and 200 Gy are used with linear energy transfer (LET) values for carbon ions of 63, 77, 96 and 230 keV μm -1 . After irradiation all samples show typical for irradiated sucrose EPR and UV spectra. The obtained data are compared with those previously reported for nitrogen particles and gamma rays irradiated sucrose. The identical shape of both the EPR and UV spectra of irradiated with various type radiation samples suggests that generated free radicals are not influenced by the nature of radiation. The lack of difference in the line width of the separate lines or the whole EPR spectrum, obtained for gamma and heavy particles irradiation, suggests negligible spin-spin interaction among the radiation-generated free radicals in the samples. The linear dependence of the EPR response on the absorbed dose radiation is found to be higher when generated by gamma rays, than by the same absorbed dose of heavy particles. In addition, the EPR response for carbon ions is higher than that for nitrogen ions. Water solutions of irradiated sucrose exhibit UV spectrum with absorption maximum at 267 nm, attributed to the recombination products of free radicals. The UV band intensity depends on the absorbed dose radiation. The UV spectra obtained for carbon, nitrogen and gamma rays irradiated sucrose are also compared.

  20. EPR (European Pressurized Reactor)

    International Nuclear Information System (INIS)

    2015-01-01

    This document presents the EPR (European Pressurized Reactor), a modernised version of PWRs which uses nuclear fission. It indicates to which category it belongs (third generation). It briefly describes its operation: recalls on nuclear fission, electricity production in a nuclear reactor. It presents and comments its characteristics: power, thermal efficiency, redundant systems for safety control, double protective enclosure, expected lifetime, use of MOX fuel, modular design. It discusses economic stakes (expected higher nuclear electricity competitiveness, but high construction costs), and safety challenges (design characteristics, critics by nuclear safety authorities about the safety data processing system). It presents the main involved actors (Areva, EDF) and competitors in the field of advanced reactors (Rosatom with its VVER 1200, General Electric with its ABWR and its ESBWR, Mitsubishi with its APWR, Westinghouse with its AP100) while outlining the importance of certifications and delays to obtain them. After having evoked key data on EPR fuel consumption, it indicates reactors under construction, evokes potential markets and perspectives

  1. SU-G-IeP1-15: Towards Accurate Cerebral Blood Flow Quantification with Distortion- Corrected Pseudo-Continuous Arterial Spin Labeling

    Energy Technology Data Exchange (ETDEWEB)

    Hoff, M; Rane-Levandovsky, S; Andre, J [University of Washington, Seattle, WA (United States)

    2016-06-15

    Purpose: Traditional arterial spin labeling (ASL) acquisitions with echo planar imaging (EPI) readouts suffer from image distortion due to susceptibility effects, compromising ASL’s ability to accurately quantify cerebral blood flow (CBF) and assess disease-specific patterns associated with CBF abnormalities. Phase labeling for additional coordinate encoding (PLACE) can remove image distortion; our goal is to apply PLACE to improve the quantitative accuracy of ASL CBF in humans. Methods: Four subjects were imaged on a 3T Philips Ingenia scanner using a 16-channel receive coil with a 21/21/10cm (frequency/phase/slice direction) field-of-view. An ASL sequence with a pseudo-continuous ASL (pCASL) labeling scheme was employed to acquire thirty dynamics of single-shot EPI data, with control and label datasets for all dynamics, and PLACE gradients applied on odd dynamics. Parameters included a post-labeling delay = 2s, label duration = 1.8s, flip angle = 90°, TR/TE = 5000/23.5ms, and 2.9/2.9/5.0mm (frequency/phase/slice direction) voxel size. “M0” EPI-reference images and T1-weighted spin-echo images with 0.8/1.0/3.3mm (frequency/phase/slice directions) voxel size were also acquired. Complex conjugate image products of pCASL odd and even dynamics were formed, a linear phase ramp applied, and data expanded and smoothed. Data phase was extracted to map control, label, and M0 magnitude image pixels to their undistorted locations, and images were rebinned to original size. All images were corrected for motion artifacts in FSL 5.0. pCASL images were registered to M0 images, and control and label images were subtracted to compute quantitative CBF maps. Results: pCASL image and CBF map distortions were removed by PLACE in all subjects. Corrected images conformed well to the anatomical T1-weighted reference image, and deviations in corrected CBF maps were evident. Conclusion: Eliminating pCASL distortion with PLACE can improve CBF quantification accuracy using minimal

  2. SU-G-IeP1-15: Towards Accurate Cerebral Blood Flow Quantification with Distortion- Corrected Pseudo-Continuous Arterial Spin Labeling

    International Nuclear Information System (INIS)

    Hoff, M; Rane-Levandovsky, S; Andre, J

    2016-01-01

    Purpose: Traditional arterial spin labeling (ASL) acquisitions with echo planar imaging (EPI) readouts suffer from image distortion due to susceptibility effects, compromising ASL’s ability to accurately quantify cerebral blood flow (CBF) and assess disease-specific patterns associated with CBF abnormalities. Phase labeling for additional coordinate encoding (PLACE) can remove image distortion; our goal is to apply PLACE to improve the quantitative accuracy of ASL CBF in humans. Methods: Four subjects were imaged on a 3T Philips Ingenia scanner using a 16-channel receive coil with a 21/21/10cm (frequency/phase/slice direction) field-of-view. An ASL sequence with a pseudo-continuous ASL (pCASL) labeling scheme was employed to acquire thirty dynamics of single-shot EPI data, with control and label datasets for all dynamics, and PLACE gradients applied on odd dynamics. Parameters included a post-labeling delay = 2s, label duration = 1.8s, flip angle = 90°, TR/TE = 5000/23.5ms, and 2.9/2.9/5.0mm (frequency/phase/slice direction) voxel size. “M0” EPI-reference images and T1-weighted spin-echo images with 0.8/1.0/3.3mm (frequency/phase/slice directions) voxel size were also acquired. Complex conjugate image products of pCASL odd and even dynamics were formed, a linear phase ramp applied, and data expanded and smoothed. Data phase was extracted to map control, label, and M0 magnitude image pixels to their undistorted locations, and images were rebinned to original size. All images were corrected for motion artifacts in FSL 5.0. pCASL images were registered to M0 images, and control and label images were subtracted to compute quantitative CBF maps. Results: pCASL image and CBF map distortions were removed by PLACE in all subjects. Corrected images conformed well to the anatomical T1-weighted reference image, and deviations in corrected CBF maps were evident. Conclusion: Eliminating pCASL distortion with PLACE can improve CBF quantification accuracy using minimal

  3. EPR, kvantemekanik og Bohr

    OpenAIRE

    Nielsen, Morten Klockmann

    2007-01-01

    Dette projekt omhandler området hvor filosofi og fysik smelter sammen. Kvantemekanikkens tilblivelse fik en hård medfart hvilket diskussionerne mellem især Albert Einstein og Niels Bohr vidner om. De var hovedpersoner i striden om hvordan kvantemekanikken skulle fortolkes, og diskussionen kulminerede i 1935 hvor Einstein sammen med kollegerne Podolsky og Rosen offentliggjorde en artikel med titlen “Can Quantum-Mechanical Description of Physical Reality Be Considered Complete?” (EPR-artiklen)....

  4. EPR a strategic choice

    International Nuclear Information System (INIS)

    2003-01-01

    How can we answer to the increasing demand of electric power, resulting of the demographic evolution and needed to the economic development, without exhausting the fossil resources? The answers are function of the countries and imply an optimization of the production and the consumption. This document published by the Areva Group aims to show the advantages of the nuclear energy: economical and environmental advantages. A special chapter is devoted to the European Pressurized Reactor, EPR. (A.L.B.)

  5. EPR spectroscopy of spices

    Directory of Open Access Journals (Sweden)

    R. T. Тimakova

    2016-01-01

    Full Text Available From 01 January 2017 you enter the interstate standard GOST 33271-2015 “Dry Spices, herbs and vegetable seasonings. Manual exposure in order to combat pathogens and other microorganisms” which States that the absorbed dose of radiation to the spices should be from 3 to 30 kGy. The study found that before the introduction of permissive legislative framework in the consumer market of Russia there are irradiated food products (chili, ground chili, ground spicy chili, black pepper. For radiation monitoring of food safety, we used the method of electron paramagnetic resonance (EPR, which allows quickly and with a high degree of reliability to establish the fact of irradiation. It is established that all samples of spices irradiated with dose of 12 kGy (technology radappertization gave typical spectra of the signals established by the method of electron paramagnetic resonance in the domestic EPR spectrometer, the intensity, amplitude and peak width of the EPR signal of samples of spices with the increase of irradiation dose increases. It is proven that repeated exposure no effect accumulation. Integration with 2017 Russia in the global practi ce of using radiation technologies of processing of food products and food raw materials with the purpose of extending shelf life confirms the need for a data Bank on the radiation sensitivity of various food products to determine the optimal doses and the eff ect of radiation doses on the shelf life and quality of products.

  6. Arterial spin labeling in patients with chic cerebral artery steno-occlusive disease - Correlation with 15O-PET

    International Nuclear Information System (INIS)

    Kamano, Hironori; Yoshiura, Takashi; Hiwatashi, Akio; Abe, Koichiro; Yamashita, Koji; Honda, Hiroshi; Togao, Osamu

    2013-01-01

    Background: Heterogeneity of arterial transit time due to cerebral artery steno-occlusive lesions hampers accurate regional cerebral blood flow measurement by arterial spin labeling (ASL). Purpose: To assess the feasibility of regional cerebral blood flow measurement by ASL with multiple-delay time sampling in patients with steno-occlusive diseases by comparing with positron emission tomography (PET), and to determine whether regional arterial transit time measured by this ASL technique is correlated with regional mean transit time, a PET index of perfusion pressure. Material and Methods: Sixteen patients with steno-occlusive diseases received both ASL and 15 O-PET. The mean regional cerebral blood flow measured by ASL and PET, regional arterial transit time by ASL, and regional mean transit time by PET were obtained by a region-of-interest analysis. Correlation between regional cerebral blood flow by ASL and that by PET, and correlation between regional arterial transit time by ASL and regional mean transit time by PET were tested using Pearson's correlation coefficient for both absolute and relative values. A multivariate regression analysis was performed to test whether regional arterial transit time by ASL was a significant contributor in modeling regional mean transit time by PET after controlling the effect of regional cerebral blood flow by ASL. Results: A significant positive correlation was found between regional cerebral blood flow by ASL and that by PET for both absolute (r = 0.520, P < 0.0001) and relative (r = 0.691, P < 0.0001) values. A significant positive correlation was found between regional arterial transit time by ASL and regional mean transit time by PET both for absolute (r = 0.369, P = 0.0002) and relative (r = 0.443, P < 0.0001) values. The regression analysis revealed that regional arterial transit time by ASL was a significant contributor in modeling regional mean transit time by PET after controlling regional cerebral blood flow by ASL

  7. Differentiating Primary CNS Lymphoma from Malignant Glioma using 123I-IMP SPECT and Arterial Spin labeling

    International Nuclear Information System (INIS)

    Ito, Tamio; Sato, Kenichi; Ozaki, Yoshimaru; Asanome, Taku; Nakamura, Hirohiko; Ono, Hidetoshi

    2016-01-01

    Using conventional CT or MRI methods, the differentiation of primary central nervous system lymphoma (PCNSL) and malignant glioma (MG) is difficult because of overlapping imaging characteristics. Pretreatment differentiation between PCNSL and MG is essential for therapeutic decision making because post operative adjuvant therapy is extremely different. We examined the utility of N-isopropyl-p-[ 123 I]iodoamphetamine SPECT (IMP SPECT) and arterial spin labeling (ASL) in differentiating PCNSL from MG. Twenty PCNSL and ten MG patients underwent IMP SPECT and ASL. Early SPECT image (E) was initiated 20 min after intravenous injection of 222 MBq 123 I-IMP, and delayed image (D) and ultrade-layed image (UD) were initiated 3 h and 24 h, respectively, after the injection. SPECT images were visually analyzed with a color-grading scale (low, iso, and high), and the tumor-to-normal activity ratio (T/N) was calculated for all three images. The pulsed ASL was performed using a 3-T system. We set regions of interest in the tumor and symmetrically in the contralateral white matter on the cerebral blood flow (CBF) map and estimated tumor blood flow (TBF)/CBF ratio (TBF/CBF). 1) IMP SPECT: (1) Visual image analysis of PCNSL cases showed high accumulation of 123 I-IMP up-take on D and UD, whereas most MG cases showed low accumulation. (2) T/Ns of PCNSL were significantly higher than those of MG on D and UD (E: 1.13 vs. 0.95, p>0.05; D: 1.23 vs. 0.86, p<0.01; UD: 1.40 vs. 0.86, p<0.01). 2) ASL: TBF/CBFs of MG were higher than those of PCNSL, particularly in glioblastoma patients [1.84 vs. 6.22 (III; 1.51, IV; 8.58)]. IMP SPECT and ASL are helpful tools for differentiating primary CNS lymphoma from MG. Using these examinations, we could perform adjuvant therapy without biopsy in deep-seated tumors. (author)

  8. Effects of global signal regression and subtraction methods on resting-state functional connectivity using arterial spin labeling data.

    Science.gov (United States)

    Silva, João Paulo Santos; Mônaco, Luciana da Mata; Paschoal, André Monteiro; Oliveira, Ícaro Agenor Ferreira de; Leoni, Renata Ferranti

    2018-05-16

    Arterial spin labeling (ASL) is an established magnetic resonance imaging (MRI) technique that is finding broader applications in functional studies of the healthy and diseased brain. To promote improvement in cerebral blood flow (CBF) signal specificity, many algorithms and imaging procedures, such as subtraction methods, were proposed to eliminate or, at least, minimize noise sources. Therefore, this study addressed the main considerations of how CBF functional connectivity (FC) is changed, regarding resting brain network (RBN) identification and correlations between regions of interest (ROI), by different subtraction methods and removal of residual motion artifacts and global signal fluctuations (RMAGSF). Twenty young healthy participants (13 M/7F, mean age = 25 ± 3 years) underwent an MRI protocol with a pseudo-continuous ASL (pCASL) sequence. Perfusion-based images were obtained using simple, sinc and running subtraction. RMAGSF removal was applied to all CBF time series. Independent Component Analysis (ICA) was used for RBN identification, while Pearson' correlation was performed for ROI-based FC analysis. Temporal signal-to-noise ratio (tSNR) was higher in CBF maps obtained by sinc subtraction, although RMAGSF removal had a significant effect on maps obtained with simple and running subtractions. Neither the subtraction method nor the RMAGSF removal directly affected the identification of RBNs. However, the number of correlated and anti-correlated voxels varied for different subtraction and filtering methods. In an ROI-to-ROI level, changes were prominent in FC values and their statistical significance. Our study showed that both RMAGSF filtering and subtraction method might influence resting-state FC results, especially in an ROI level, consequently affecting FC analysis and its interpretation. Taking our results and the whole discussion together, we understand that for an exploratory assessment of the brain, one could avoid removing RMAGSF to

  9. Electron paramagnetic resonance (EPR) biodosimetry

    International Nuclear Information System (INIS)

    Desrosiers, Marc; Schauer, David A.

    2001-01-01

    Radiation-induced electron paramagnetic resonance (EPR) signals were first reported by Gordy et al. [Proc. Natl. Acad. Sci. USA 41 (1955) 983]. The application of EPR spectroscopy to ionizing radiation dosimetry was later proposed by Brady et al. [Health Phys. 15 (1968) 43]. Since that time EPR dosimetry has been applied to accident and epidemiologic dose reconstruction, radiation therapy, food irradiation, quality assurance programs and archaeological dating. Materials that have been studied include bone, tooth enamel, alanine and quartz. This review paper presents the fundamentals and applications of EPR biodosimetry. Detailed information regarding sample collection and preparation, EPR measurements, dose reconstruction, and data analysis and interpretation will be reviewed for tooth enamel. Examples of EPR biodosimetry application in accidental overexposures, radiopharmaceutical dose assessment and retrospective epidemiologic studies will also be presented

  10. EPR spectroscopy at DNP conditions

    International Nuclear Information System (INIS)

    Heckmann, J.; Goertz, St.; Meyer, W.; Radtke, E.; Reicherz, G.

    2004-01-01

    In terms of dynamic nuclear polarization (DNP) studies and systematic target material research it is crucial to know the EPR lineshape of the DNP relevant paramagnetic centers. Therefore in Bochum an EPR spectrometer has been implemented into the 4 He evaporation DNP facility in order to perform EPR studies at DNP conditions (B=2.5 T, T=1 K). The spectrometer hardware and performance as well as first results are presented

  11. Probing Microenvironment in Ionic Liquids by Time-Resolved EPR of Photoexcited Triplets.

    Science.gov (United States)

    Ivanov, M Yu; Veber, S L; Prikhod'ko, S A; Adonin, N Yu; Bagryanskaya, E G; Fedin, M V

    2015-10-22

    Unusual physicochemical properties of ionic liquids (ILs) open vistas for a variety of new applications. Herewith, we investigate the influence of microviscosity and nanostructuring of ILs on spin dynamics of the dissolved photoexcited molecules. We use two most common ILs [Bmim]PF6 and [Bmim]BF4 (with its close analogue [C10mim]BF4) as solvents and photoexcited Zn tetraphenylporphyrin (ZnTPP) as a probe. Time-resolved electron paramagnetic resonance (TR EPR) is employed to investigate spectra and kinetics of spin-polarized triplet ZnTPP in the temperature range 100-270 K. TR EPR data clearly indicate the presence of two microenvironments of ZnTPP in frozen ILs at 100-200 K, being manifested in different spectral shapes and different spin relaxation rates. For one of these microenvironments TR EPR data is quite similar to those obtained in common frozen organic solvents (toluene, glycerol, N-methyl-2-pyrrolidone). However, the second one favors the remarkably slow relaxation of spin polarization, being much longer than in the case of common solvents. Additional experiments using continuous wave EPR and stable nitroxide as a probe confirmed the formation of heterogeneities upon freezing of ILs and complemented TR EPR results. Thus, TR EPR of photoexcited triplets can be effectively used for probing heterogeneities and nanostructuring in frozen ILs. In addition, the increase of polarization lifetime in frozen ILs is an interesting finding that might allow investigation of short-lived intermediates inaccessible otherwise.

  12. Skew Projection of Echo-Detected EPR Spectra for Increased Sensitivity and Resolution

    Science.gov (United States)

    Bowman, Michael K.; Krzyaniak, Matthew D.; Cruce, Alex A.; Weber, Ralph T.

    2013-01-01

    The measurement of EPR spectra during pulsed EPR experiments is commonly accomplished by recording the integral of the electron spin echo as the applied magnetic field is stepped through the spectrum. This approach to echo-detected EPR spectral measurement (ED-EPR) limits sensitivity and spectral resolution and can cause gross distortions in the resulting spectra because some of the information present in the electron spin echo is discarded in such measurements. However, Fourier Transformation of echo shapes measured at a series of magnetic field values followed by skew projection onto either a magnetic field or resonance frequency axis can increase both spectral resolution and sensitivity without the need to trade one against the other. Examples of skew-projected spectra with single crystals, glasses and powders show resolution improvements as large as a factor of seven with sensitivity increases of as much as a factor of five. PMID:23644351

  13. EPR design for maintenance

    International Nuclear Information System (INIS)

    Krugmann, U.

    1998-01-01

    Preventive maintenance is very important in achieving high plant availability. For the European Pressurized Reactor (EPR) preventive maintenance has been carefully addressed in the design stage. This is particularly necessary because of the traditionally different maintenance strategies employed in France and Germany. This paper emphasizes the following features introduced in the ERP design to minimize the duration of the refueling outage: (1) containment accessibility during power operation; (2) overall plant layout to facilitate inspections and maintenances within the containment; and (3) safety system design for enabling preventive maintenance during power operation. (author)

  14. Longitudinal Assessment of Renal Perfusion and Oxygenation in Transplant Donor-Recipient Pairs Using Arterial Spin Labeling and Blood Oxygen Level-Dependent Magnetic Resonance Imaging.

    Science.gov (United States)

    Niles, David J; Artz, Nathan S; Djamali, Arjang; Sadowski, Elizabeth A; Grist, Thomas M; Fain, Sean B

    2016-02-01

    The aims of this study were to assess renal function in kidney transplant recipients and their respective donors over 2 years using arterial spin labeling (ASL) and blood oxygen level-dependent (BOLD) magnetic resonance imaging (MRI) and to prospectively evaluate the effect of losartan on functional MRI measures in recipients. The study included 15 matched pairs of renal transplant donors and recipients. Arterial spin labeling and BOLD MRI of the kidneys were performed on donors before transplant surgery (baseline) and on both donors and recipients at 3 months, 1 year, and 2 years after transplant. After 3 months, 7 of the 15 recipients were prescribed 25 to 50 mg/d losartan for the remainder of the study. A linear mixed-effects model was used to evaluate perfusion, R2*, estimated glomerular filtration rate, and fractional excretion of sodium for changes across time or associated with losartan treatment. In donors, cortical perfusion in the remaining kidney decreased by 50 ± 19 mL/min per 100 g (11.8%) between baseline and 2 years (P donors and to 14.6 ± 4.3 mL/min per 1.73 m (33.3%; P donors, and they indicate a potentially beneficial effect of losartan in recipients.

  15. Identification of pH-sensitive regions in the mouse prion by the cysteine-scanning spin-labeling ESR technique

    International Nuclear Information System (INIS)

    Watanabe, Yasuko; Inanami, Osamu; Horiuchi, Motohiro; Hiraoka, Wakako; Shimoyama, Yuhei; Inagaki, Fuyuhiko; Kuwabara, Mikinori

    2006-01-01

    We analyzed the pH-induced mobility changes in moPrP C α-helix and β-sheets by cysteine-scanning site-directed spin labeling (SDSL) with ESR. Nine amino acid residues of α-helix1 (H1, codon 143-151), four amino acid residues of β-sheet1 (S1, codon 127-130), and four amino acid residues of β-sheet2 (S2, codon 160-163) were substituted for by cysteine residues. These recombinant mouse PrP C (moPrP C ) mutants were reacted with a methane thiosulfonate sulfhydryl-specific spin labeling reagent (MTSSL). The 1/δH of the central ( 14 N hyperfine) component (M I = 0) in the ESR spectrum of spin-labeled moPrP C was measured as a mobility parameter of nitroxide residues (R1). The mobilities of E145R1 and Y149R1 at pH 7.4, which was identified as a tertiary contact site by a previous NMR study of moPrP, were lower than those of D143R1, R147R1, and R150R1 reported on the helix surface. Thus, the mobility in the H1 region in the neutral solution was observed with the periodicity associated with a helical structure. On the other hand, the values in the S2 region, known to be located in the buried side, were lower than those in the S1 region located in the surface side. These results indicated that the mobility parameter of the nitroxide label was well correlated with the 3D structure of moPrP. Furthermore, the present study clearly demonstrated three pH-sensitive sites in moPrP, i.e. (1) the N-terminal tertiary contact site of H1 (2) the C-terminal end of H1, and (3) the S2 region. In particular, among these pH-sensitive sites, the N-terminal tertiary contact region of H1 was found to be the most pH-sensitive one and was easily converted to a flexible structure by a slight decrease of pH in the solution. These data provided molecular evidence to explain the cellular mechanism for conversion from PrP C to PrP Sc in acidic organelles such as the endosome

  16. Bimolecular encounters and re-encounters (cage effect) of a spin-labeled analogue of cholestane in a series of n-alkanes: effect of anisotropic exchange integral.

    Science.gov (United States)

    Vandenberg, Andrew D; Bales, Barney L; Salikhov, K M; Peric, Miroslav

    2012-12-27

    Electron paramagnetic resonance (EPR) spectra of the nitroxide spin probe 3β-doxyl-5α-cholestane (CSL) are studied as functions of the molar concentration, c, and the temperature, T, in a series of n-alkanes. The results are compared with a similar study of a much smaller spin probe, perdeuterated 2,2,6,6-tetramethyl-4-oxopiperidine-1-oxyl (pDT). The Heisenberg spin exchange (HSE) rate constants, K(ex), of CSL are similar in hexane, octane, and decane and are about one-half of those for pDT in the same solvents. They are also about one-half of the Stokes-Einstein-Perrin prediction. This reduction in HSE efficiency is attributed to an effective steric factor, f(eff), which was evaluated by comparing the results with the Stokes-Einstein-Perrin prediction or with pDT, and it is equal to 0.49 ± 0.03, independent of temperature. The unpaired spin density in CSL is localized near one end of the long molecule, so the exchange integral, J, leading to HSE, is expected to be large in some collisions and small in others; thus, J is modeled by an ideal distribution of values of J = J(0) with probability f and J = 0 with probability (1 - f). Because of rotational and translation diffusion during contact and between re-encounters of the probe, the effective steric factor is predicted to be f(eff) = f(1/2). Estimating the fraction of the surface of CSL with rich spin density yields a theoretical estimate of f(eff) = 0.59 ± 0.08, in satisfactory agreement with experiment. HSE is well described by simple hydrodynamic theory, with only a small dependence on solvent-probe relative sizes at the same value of T/η, where η is the viscosity of the solvent. This result is probably due to a fortuitous interplay between long- and short-range effects that describe diffusion processes over relatively large distances. In contrast, dipole-dipole interactions (DD) as measured by the line broadening, B(dip), and the mean time between re-encounters within the cage, τ(RE), vary significantly

  17. Medical reference dosimetry using EPR measurements of alanine

    DEFF Research Database (Denmark)

    Helt-Hansen, Jakob; Rosendal, F.; Kofoed, I.M.

    2009-01-01

    Background. Electron spin resonance (EPR) is used to determine the absorbed dose of alanine dosimeters exposed to clinical photon beams in a solid-water phantom. Alanine is potentially suitable for medical reference dosimetry, because of its near water equivalence over a wide energy spectrum, low...... methods the proposed algorithm can be applied without normalisation of phase shifts caused by changes in the g-value of the cavity. The study shows that alanine dosimetry is a suitable candidate for medical reference dosimetry especially for quality control applications.......Background. Electron spin resonance (EPR) is used to determine the absorbed dose of alanine dosimeters exposed to clinical photon beams in a solid-water phantom. Alanine is potentially suitable for medical reference dosimetry, because of its near water equivalence over a wide energy spectrum, low...

  18. Spatially distributed multipartite entanglement enables EPR steering of atomic clouds

    Science.gov (United States)

    Kunkel, Philipp; Prüfer, Maximilian; Strobel, Helmut; Linnemann, Daniel; Frölian, Anika; Gasenzer, Thomas; Gärttner, Martin; Oberthaler, Markus K.

    2018-04-01

    A key resource for distributed quantum-enhanced protocols is entanglement between spatially separated modes. However, the robust generation and detection of entanglement between spatially separated regions of an ultracold atomic system remain a challenge. We used spin mixing in a tightly confined Bose-Einstein condensate to generate an entangled state of indistinguishable particles in a single spatial mode. We show experimentally that this entanglement can be spatially distributed by self-similar expansion of the atomic cloud. We used spatially resolved spin read-out to reveal a particularly strong form of quantum correlations known as Einstein-Podolsky-Rosen (EPR) steering between distinct parts of the expanded cloud. Based on the strength of EPR steering, we constructed a witness, which confirmed genuine 5-partite entanglement.

  19. Three-dimensional whole-brain perfusion quantification using pseudo-continuous arterial spin labeling MRI at multiple post-labeling delays: accounting for both arterial transit time and impulse response function.

    Science.gov (United States)

    Qin, Qin; Huang, Alan J; Hua, Jun; Desmond, John E; Stevens, Robert D; van Zijl, Peter C M

    2014-02-01

    Measurement of the cerebral blood flow (CBF) with whole-brain coverage is challenging in terms of both acquisition and quantitative analysis. In order to fit arterial spin labeling-based perfusion kinetic curves, an empirical three-parameter model which characterizes the effective impulse response function (IRF) is introduced, which allows the determination of CBF, the arterial transit time (ATT) and T(1,eff). The accuracy and precision of the proposed model were compared with those of more complicated models with four or five parameters through Monte Carlo simulations. Pseudo-continuous arterial spin labeling images were acquired on a clinical 3-T scanner in 10 normal volunteers using a three-dimensional multi-shot gradient and spin echo scheme at multiple post-labeling delays to sample the kinetic curves. Voxel-wise fitting was performed using the three-parameter model and other models that contain two, four or five unknown parameters. For the two-parameter model, T(1,eff) values close to tissue and blood were assumed separately. Standard statistical analysis was conducted to compare these fitting models in various brain regions. The fitted results indicated that: (i) the estimated CBF values using the two-parameter model show appreciable dependence on the assumed T(1,eff) values; (ii) the proposed three-parameter model achieves the optimal balance between the goodness of fit and model complexity when compared among the models with explicit IRF fitting; (iii) both the two-parameter model using fixed blood T1 values for T(1,eff) and the three-parameter model provide reasonable fitting results. Using the proposed three-parameter model, the estimated CBF (46 ± 14 mL/100 g/min) and ATT (1.4 ± 0.3 s) values averaged from different brain regions are close to the literature reports; the estimated T(1,eff) values (1.9 ± 0.4 s) are higher than the tissue T1 values, possibly reflecting a contribution from the microvascular arterial blood compartment

  20. High-frequency EPR of surface impurities on nanodiamond

    Science.gov (United States)

    Peng, Zaili; Stepanov, Viktor; Takahashi, Susumu

    Diamond is a fascinating material, hosting nitrogen-vacancy (NV) defect centers with unique magnetic and optical properties. There have been many reports that suggest the existence of paramagnetic impurities near surface of various kinds of diamonds. Electron paramagnetic resonance (EPR) investigation of mechanically crushed nanodiamonds (NDs) as well as detonation NDs revealed g 2 like signals that are attributed to structural defects and dangling bonds near the diamond surface. In this presentation, we investigate paramagnetic impurities in various sizes of NDs using high-frequency (HF) continuous wave (cw) and pulsed EPR spectroscopy. Strong size dependence on the linewidth of HF cw EPR spectra reveals the existence of paramagnetic impurities in the vicinity of the diamond surface. We also study the size dependence of the spin-lattice and spin-spin relaxation times (T1 and T2) of single substitutional nitrogen defects in NDs Significant deviations from the temperature dependence of the phonon-assisted T1 process were observed in the ND samples, and were attributed to the contribution from the surface impurities. This work was supported by the Searle Scholars Program and the National Science Foundation (DMR-1508661 and CHE-1611134).

  1. Measurement of cerebral white matter perfusion using pseudocontinuous arterial spin labeling 3T magnetic resonance imaging--an experimental and theoretical investigation of feasibility.

    Directory of Open Access Journals (Sweden)

    Wen-Chau Wu

    Full Text Available PURPOSE: This study was aimed to experimentally and numerically investigate the feasibility of measuring cerebral white matter perfusion using pseudocontinuous arterial spin labeling (PCASL 3T magnetic resonance imaging (MRI at a relatively fine resolution to mitigate partial volume effect from gray matter. MATERIALS AND METHODS: The Institutional Research Ethics Committee approved this study. On a clinical 3T MR system, ten healthy volunteers (5 females, 5 males, age = 28 ± 3 years were scanned after providing written informed consent. PCASL imaging was performed with varied combinations of labeling duration (τ = 1000, 1500, 2000, and 2500 ms and post-labeling delay (PLD = 1000, 1400, 1800, and 2200 ms, at a spatial resolution (1.56 x 1.56 x 5 mm(3 finer than commonly used (3.5 x 3.5 mm(2, 5-8 mm in thickness. Computer simulations were performed to calculate the achievable perfusion-weighted signal-to-noise ratio at varied τ, PLD, and transit delay. RESULTS: Based on experimental and numerical data, the optimal τ and PLD were found to be 2000 ms and 1500-1800 ms, respectively, yielding adequate SNR (~2 to support perfusion measurement in the majority (~60% of white matter. The measurement variability was about 9% in a one-week interval. The measured white matter perfusion and perfusion ratio of gray matter to white matter were 15.8-27.5 ml/100ml/min and 1.8-4.0, respectively, depending on spatial resolution as well as the amount of deep white matter included. CONCLUSION: PCASL 3T MRI is able to measure perfusion in the majority of cerebral white matter at an adequate signal-to-noise ratio by using appropriate tagging duration and post-labeling delay. Although pixel-wise comparison may not be possible, region-of-interest based flow quantification is feasible.

  2. WE-FG-206-05: New Arterial Spin Labeling Method for Simultaneous Estimation of Arterial Cerebral Blood Volume, Cerebral Blood Flow and Arterial Transit Time

    Energy Technology Data Exchange (ETDEWEB)

    Johnston, M; Whitlow, C; Jung, Y [Wake Forest School of Medicine, Winston-Salem, NC (United States); Liu, H [UT MD Anderson Cancer Center, Houston, TX (United States)

    2016-06-15

    Purpose: To demonstrate the feasibility of a novel Arterial Spin Labeling (ASL) method for simultaneously measuring cerebral blood flow (CBF), arterial transit time (ATT), and arterial cerebral blood volume (aCBV) without the use of a contrast agent. Methods: A series of multi-TI ASL images were acquired from one healthy subject on a 3T Siemens Skyra, with the following parameters: PCASL labeling with variable TI [300, 400, 500, 600, 700, 800, 900, 1000, 1500, 2000, 2500, 3000, 3500, 4000] ms, labeling bolus 1400 ms when TI allows, otherwise 100 ms less than TI, TR was minimized for each TI, two sinc shaped pre-saturation pulses were applied in the imaging plane immediately before 2D EPI acquisition. 64×64×24 voxels, 5 mm slice thickness, 1 mm gap, full brain coverage, 6 averages per TI, no crusher gradients, 11 ms TE, scan time of 4:56. The perfusion weighted time-series was created for each voxel and fit to a novel model. The model has two components: 1) the traditional model developed by Buxton et al., accounting for CBF and ATT, and 2) a box car function characterizing the width of the labeling bolus, with variable timing and height in proportion to the aCBV. All three parameters were fit using a nonlinear fitting routine that constrained all parameters to be positive. The main purpose of the high-temporal resolution TI sampling for the first second of data acquisition was to precisely estimate the blood volume component for better detection of arrival time and magnitude of signal. Results: Whole brain maps of CBF, ATT, and aCBV were produced, and all three parameters maps are consistent with similar maps described in the literature. Conclusion: Simultaneous mapping of CBF, ATT, and aCBV is feasible with a clinically tractable scan time (under 5 minutes).

  3. Solid-support Electron Paramagnetic Resonance (EPR) Studies of Aβ40 Monomers Reveal a Structured State with Three Ordered Segments*

    Science.gov (United States)

    Gu, Lei; Ngo, Sam; Guo, Zhefeng

    2012-01-01

    Alzheimer disease is associated with the pathological accumulation of amyloid-β peptide (Aβ) in the brain. Soluble Aβ oligomers formed during early aggregation process are believed to be neurotoxins and causative agents in Alzheimer disease. Aβ monomer is the building block for amyloid assemblies. A comprehensive understanding of the structural features of Aβ monomer is crucial for delineating the mechanism of Aβ oligomerization. Here we investigated the structures of Aβ40 monomer using a solid-support approach, in which Aβ40 monomers are tethered on the solid support via an N-terminal His tag to prevent further aggregation. EPR spectra of tethered Aβ40 with spin labels at 18 different positions show that Aβ40 monomers adopt a completely disordered structure under denaturing conditions. Under native conditions, however, EPR spectra suggest that Aβ40 monomers adopt both a disordered state and a structured state. The structured state of Aβ40 monomer has three more ordered segments at 14–18, 29–30, and 38–40. Interactions between these segments may stabilize the structured state, which likely plays an important role in Aβ aggregation. PMID:22277652

  4. The structural flexibility of the human copper chaperone Atox1: Insights from combined pulsed EPR studies and computations.

    Science.gov (United States)

    Levy, Ariel R; Turgeman, Meital; Gevorkyan-Aiapetov, Lada; Ruthstein, Sharon

    2017-08-01

    Metallochaperones are responsible for shuttling metal ions to target proteins. Thus, a metallochaperone's structure must be sufficiently flexible both to hold onto its ion while traversing the cytoplasm and to transfer the ion to or from a partner protein. Here, we sought to shed light on the structure of Atox1, a metallochaperone involved in the human copper regulation system. Atox1 shuttles copper ions from the main copper transporter, Ctr1, to the ATP7b transporter in the Golgi apparatus. Conventional biophysical tools such as X-ray or NMR cannot always target the various conformational states of metallochaperones, owing to a requirement for crystallography or low sensitivity and resolution. Electron paramagnetic resonance (EPR) spectroscopy has recently emerged as a powerful tool for resolving biological reactions and mechanisms in solution. When coupled with computational methods, EPR with site-directed spin labeling and nanoscale distance measurements can provide structural information on a protein or protein complex in solution. We use these methods to show that Atox1 can accommodate at least four different conformations in the apo state (unbound to copper), and two different conformations in the holo state (bound to copper). We also demonstrate that the structure of Atox1 in the holo form is more compact than in the apo form. Our data provide insight regarding the structural mechanisms through which Atox1 can fulfill its dual role of copper binding and transfer. © 2017 The Protein Society.

  5. EPR Flamanville 3, Site Management

    International Nuclear Information System (INIS)

    Menager, Antoine

    2014-01-01

    Antoine Menager, the EPR Flamanville 3 Site Manager described the organization and the management of the Flamanville site during the construction phase. He placed emphasis on Health and Safety, Environmental and Social Responsibility and on Nuclear Safety and Quality

  6. Validating and analyzing EPR hyperfine coupling constants with density functional theory

    DEFF Research Database (Denmark)

    Hedegård, Erik D.; Kongsted, Jacob; Sauer, Stephan P. A.

    2013-01-01

    Electron Paramagnetic Resonance (EPR) is a central spectroscopic technique for compounds with non-zero spin. The effective parameters from the EPR spin-Hamiltonian can today be calculated from rst principles using quantum chemical methods. We focus here on the hyperne coupling tensor, A, which....... Unfortunately both organometallic and traditional coordination complexes show a completely different behavior, where the core contributions to AKiso either are comparable (“class 2”) or far exceed (“class 3”) the contributions from the frontier orbitals. Agreement with experiment can for these complexes only...

  7. Probing topology and dynamics of the second transmembrane domain (M2δ) of the acetyl choline receptor using magnetically aligned lipid bilayers (bicelles) and EPR spectroscopy.

    Science.gov (United States)

    Sahu, Indra D; Mayo, Daniel J; Subbaraman, Nidhi; Inbaraj, Johnson J; McCarrick, Robert M; Lorigan, Gary A

    2017-08-01

    Characterizing membrane protein structure and dynamics in the lipid bilayer membrane is very important but experimentally challenging. EPR spectroscopy offers a unique set of techniques to investigate a membrane protein structure, dynamics, topology, and distance constraints in lipid bilayers. Previously our lab demonstrated the use of magnetically aligned phospholipid bilayers (bicelles) for probing topology and dynamics of the membrane peptide M2δ of the acetyl choline receptor (AchR) as a proof of concept. In this study, magnetically aligned phospholipid bilayers and rigid spin labels were further utilized to provide improved dynamic information and topology of M2δ peptide. Seven TOAC-labeled AchR M2δ peptides were synthesized to demonstrate the utility of a multi-labeling amino acid substitution alignment strategy. Our data revealed the helical tilts to be 11°, 17°, 9°, 17°, 16°, 11°, 9°±4° for residues I7TOAC, Q13TOAC, A14TOAC, V15TOAC, C16TOAC, L17TOAC, and L18TOAC, respectively. The average helical tilt of the M2δ peptide was determined to be ∼13°. This study also revealed that the TOAC labels were attached to the M2δ peptide with different dynamics suggesting that the sites towards the C-terminal end are more rigid when compared to the sites towards the N-terminus. The dynamics of the TOAC labeled sites were more resolved in the aligned samples when compared to the randomly disordered samples. This study highlights the use of magnetically aligned lipid bilayer EPR technique to determine a more accurate helical tilt and more resolved local dynamics of AchR M2δ peptide. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. Towards EPR (European pressurized reactor)

    International Nuclear Information System (INIS)

    Anon.

    2003-01-01

    According to the French industry minister, it is nonsense continuing delaying the construction of an EPR prototype because France needs it in order to renew timely its park of nuclear reactors. The renewing is expected to begin in 2020 and will be assured with third generation reactors like EPR. A quick launching of the EPR prototype is necessary to have it being in service by 2012, the feedback operating experience that will be accumulated over the 8 years that will follow will be necessary to optimize the industrial version and to have it ready by 2020. The EPR reactor has indisputable assets: modern, safer, more competitive and it will produce less wastes than present nuclear reactors. The construction cost of an EPR prototype is estimated to 3 milliard Euros and the nuclear industry operators propose to finance it completely. The EPR prototype does not jeopardize the ambitious French program about renewable energy sources, France is committed to produce 21% of its electricity from renewable energies by 2010 and 10 milliard Euros will be invested over this period on wind energy. Nuclear energy and alternative energies must be considered as 2 aspects of a diversified energy policy. (A.C.)

  9. EPR analysis of biomaterials

    International Nuclear Information System (INIS)

    Sukhodub, L.

    2001-01-01

    There is the review of electron spin resonance application for paramagnetic individual investigation in biomaterials. Especially the bone tissue and tooth enamel can be taken into account. The material composition (e.g. Mn 2+ and Cr 3+ ions) can be measured, also after irradiation (X, γ radiations) when paramagnetic signal appears as a result of physical radiation effects

  10. Renal blood flow using arterial spin labelling MRI and calculated filtration fraction in healthy adult kidney donors pre-nephrectomy and post-nephrectomy

    Energy Technology Data Exchange (ETDEWEB)

    Cutajar, Marica; Clark, Christopher A.; Gordon, Isky [University College London, Imaging and Biophysics Unit, Institute of Child Health, London (United Kingdom); Hilton, Rachel; Olsburgh, Jonathon [Renal Unit, Guy' s and St Thomas' NHS Foundation Trust, London (United Kingdom); Marks, Stephen D. [Great Ormond Street Hospital for Children NHS Foundation Trust, Department of Paediatric Nephrology, London (United Kingdom); Thomas, David L. [University College London, Department of Brain Repair and Rehabilitation, Institute of Neurology, London (United Kingdom); Banks, Tina [Great Ormond Street Hospital for Children NHS Foundation Trust, Department of Radiology, London (United Kingdom)

    2015-08-15

    Renal plasma flow (RPF) (derived from renal blood flow, RBF) and glomerular filtration rate (GFR) allow the determination of the filtration fraction (FF), which may have a role as a non-invasive renal biomarker. This is a hypothesis-generating pilot study assessing the effect of nephrectomy on renal function in healthy kidney donors. Eight living kidney donors underwent arterial spin labelling (ASL) magnetic resonance imaging (MRI) and GFR measurement prior to and 1 year after nephrectomy. Chromium-51 labelled ethylenediamine tetraacetic acid ({sup 51}Cr-EDTA) with multi-blood sampling was undertaken and GFR calculated. The RBF and GFR obtained were used to calculate FF. All donors showed an increase in single kidney GFR of 24 - 75 %, and all but two showed an increase in FF (-7 to +52 %) after nephrectomy. The increase in RBF, and hence RPF, post-nephrectomy was not as great as the increase in GFR in seven out of eight donors. As with any pilot study, the small number of donors and their relatively narrow age range are potential limiting factors. The ability to measure RBF, and hence RPF, non-invasively, coupled with GFR measurement, allows calculation of FF, a biomarker that might provide a sensitive indicator of loss of renal reserve in potential donors. (orig.)

  11. Renal blood flow using arterial spin labelling MRI and calculated filtration fraction in healthy adult kidney donors Pre-nephrectomy and post-nephrectomy.

    Science.gov (United States)

    Cutajar, Marica; Hilton, Rachel; Olsburgh, Jonathon; Marks, Stephen D; Thomas, David L; Banks, Tina; Clark, Christopher A; Gordon, Isky

    2015-08-01

    Renal plasma flow (RPF) (derived from renal blood flow, RBF) and glomerular filtration rate (GFR) allow the determination of the filtration fraction (FF), which may have a role as a non-invasive renal biomarker. This is a hypothesis-generating pilot study assessing the effect of nephrectomy on renal function in healthy kidney donors. Eight living kidney donors underwent arterial spin labelling (ASL) magnetic resonance imaging (MRI) and GFR measurement prior to and 1 year after nephrectomy. Chromium-51 labelled ethylenediamine tetraacetic acid ((51)Cr-EDTA) with multi-blood sampling was undertaken and GFR calculated. The RBF and GFR obtained were used to calculate FF. All donors showed an increase in single kidney GFR of 24 - 75 %, and all but two showed an increase in FF (-7 to +52 %) after nephrectomy. The increase in RBF, and hence RPF, post-nephrectomy was not as great as the increase in GFR in seven out of eight donors. As with any pilot study, the small number of donors and their relatively narrow age range are potential limiting factors. The ability to measure RBF, and hence RPF, non-invasively, coupled with GFR measurement, allows calculation of FF, a biomarker that might provide a sensitive indicator of loss of renal reserve in potential donors. • Non-invasive MRI measured renal blood flow and calculated renal plasma flow. • Effect of nephrectomy on blood flow and filtration in donors is presented. • Calculated filtration fraction may be a useful new kidney biomarker.

  12. Renal blood flow using arterial spin labelling MRI and calculated filtration fraction in healthy adult kidney donors pre-nephrectomy and post-nephrectomy

    International Nuclear Information System (INIS)

    Cutajar, Marica; Clark, Christopher A.; Gordon, Isky; Hilton, Rachel; Olsburgh, Jonathon; Marks, Stephen D.; Thomas, David L.; Banks, Tina

    2015-01-01

    Renal plasma flow (RPF) (derived from renal blood flow, RBF) and glomerular filtration rate (GFR) allow the determination of the filtration fraction (FF), which may have a role as a non-invasive renal biomarker. This is a hypothesis-generating pilot study assessing the effect of nephrectomy on renal function in healthy kidney donors. Eight living kidney donors underwent arterial spin labelling (ASL) magnetic resonance imaging (MRI) and GFR measurement prior to and 1 year after nephrectomy. Chromium-51 labelled ethylenediamine tetraacetic acid ( 51 Cr-EDTA) with multi-blood sampling was undertaken and GFR calculated. The RBF and GFR obtained were used to calculate FF. All donors showed an increase in single kidney GFR of 24 - 75 %, and all but two showed an increase in FF (-7 to +52 %) after nephrectomy. The increase in RBF, and hence RPF, post-nephrectomy was not as great as the increase in GFR in seven out of eight donors. As with any pilot study, the small number of donors and their relatively narrow age range are potential limiting factors. The ability to measure RBF, and hence RPF, non-invasively, coupled with GFR measurement, allows calculation of FF, a biomarker that might provide a sensitive indicator of loss of renal reserve in potential donors. (orig.)

  13. A fast analysis method for non-invasive imaging of blood flow in individual cerebral arteries using vessel-encoded arterial spin labelling angiography

    Science.gov (United States)

    Chappell, Michael A.; Okell, Thomas W.; Payne, Stephen J.; Jezzard, Peter; Woolrich, Mark W.

    2012-01-01

    Arterial spin labelling (ASL) MRI offers a non-invasive means to create blood-borne contrast in vivo for dynamic angiographic imaging. By spatial modulation of the ASL process it is possible to uniquely label individual arteries over a series of measurements, allowing each to be separately identified in the resulting angiographic images. This separation requires appropriate analysis for which a general Bayesian framework has previously been proposed. Here this framework is adapted for clinical dynamic angiographic imaging. This specifically addresses the issues of computational speed of the algorithm and the robustness required to deal with real patient data. An algorithm is proposed that can incorporate planning information about the arteries being imaged whilst adapting for subsequent patient movement. A fast maximum a posteriori solution is adopted and shown to be only marginally less accurate than Monte Carlo sampling under simulation. The final algorithm is demonstrated on in vivo data with analysis on a time scale of the order of 10 min, from both a healthy control and a patient with a vertebro-basilar occlusion. PMID:22322066

  14. Pulsed EPR analysis of tooth enamel samples exposed to UV and {gamma}-radiations

    Energy Technology Data Exchange (ETDEWEB)

    Marrale, M., E-mail: marrale@unipa.it [Dipartimento di Fisica, Universita di Palermo, Viale delle Scienze, Edificio 18, 90128 Palermo (Italy); Gruppo V Sezione INFN, Catania, Italy and Unita CNISM, Palermo (Italy); Longo, A.; Brai, M. [Dipartimento di Fisica, Universita di Palermo, Viale delle Scienze, Edificio 18, 90128 Palermo (Italy); Gruppo V Sezione INFN, Catania (Italy) and Unita CNISM, Palermo (Italy); Barbon, A.; Brustolon, M. [Dipartimento di Scienze Chimiche, Universita degli Studi di Padova, Via Marzolo 1, 35131 Padova (Italy); Fattibene, P. [Istituto Superiore di Sanita, Viale Regina Elena 299, 00161 Rome (Italy)

    2011-09-15

    The electron paramagnetic resonance (EPR) spectroscopy is widely applied for retrospective dosimetric purposes by means of quantitative detection of radicals in tooth enamel and bone samples. In this work we report a study by cw and pulsed EPR on two samples of human tooth enamel respectively irradiated by UV (254 nm) and {gamma}-exposed. The continuous wave (cw) EPR spectra have shown the usual presence in both samples of two types of CO{sub 2}{sup -} radicals, with axial and orthorombic g tensors. We have obtained the electron spin echo detected EPR (ED-EPR) spectra at 80 K of the two samples, and we have shown that they are suitable to mark the difference between the effects produced by the different irradiations. At low temperature the contribution to the ED-EPR spectrum of the mobile radical with the axial g tensor is still present in the UV irradiated sample, but not in the {gamma}-irradiated one, where its dynamics is too slow to average the g tensor. We have moreover studied the two-pulse electron spin echo decay on varying the microwave power, a well established method for measuring the Instantaneous Diffusion. We have found that the spectral diffusion parameter is almost the same for both radiation types, whereas the Instantaneous Diffusion is significantly larger for {gamma}-exposed samples than for UV irradiated ones. This difference is due to a higher local microscopic concentration of free radicals for samples irradiated with {gamma} photons.

  15. EPR by Areva. EPR the 1600+ MWe reactor

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2008-07-01

    This brochure presents the GEN III+ EPR reactor designed by the Areva and Siemens consortium. The EPR reactor is a direct descendent of the well-proven N4 and KONVOI reactors, the most modern reactors in France and Germany. The EPR was designed by teams from KWU/Siemens and Framatome, EDF in France and the major German utilities, working in collaboration with both French and German safety authorities. The EPR integrates the results of decades of R and D programs, in particular those performed by the CEA (French Atomic Energy Commission) and the Karlsruhe Research Center in Germany. The EPR benefits from the experience of several thousand reactor-years of operation of pressurized water reactor technology. This experience has put 87 AREVA PWRs online throughout the world. Innovative Features: - An outer shell covering the reactor building, the spent fuel building and two of the four safeguard buildings provides protection against large commercial or military aircraft crash. - A heavy neutron reflector that surrounds the reactor core lowers uranium consumption. - An axial economizer inside the steam generator allows a high level of steam pressure and therefore high plant efficiency. - A core catcher allows passive collection and retention of the molten core should the reactor vessel fail in the highly unlikely event of a core melt. - A digital technology and a fully computerized control room with an operator friendly man-machine interface improve the reactor protection system.

  16. EPR by Areva. EPR the 1600+ MWe reactor

    International Nuclear Information System (INIS)

    2008-01-01

    This brochure presents the GEN III+ EPR reactor designed by the Areva and Siemens consortium. The EPR reactor is a direct descendent of the well-proven N4 and KONVOI reactors, the most modern reactors in France and Germany. The EPR was designed by teams from KWU/Siemens and Framatome, EDF in France and the major German utilities, working in collaboration with both French and German safety authorities. The EPR integrates the results of decades of R and D programs, in particular those performed by the CEA (French Atomic Energy Commission) and the Karlsruhe Research Center in Germany. The EPR benefits from the experience of several thousand reactor-years of operation of pressurized water reactor technology. This experience has put 87 AREVA PWRs online throughout the world. Innovative Features: - An outer shell covering the reactor building, the spent fuel building and two of the four safeguard buildings provides protection against large commercial or military aircraft crash. - A heavy neutron reflector that surrounds the reactor core lowers uranium consumption. - An axial economizer inside the steam generator allows a high level of steam pressure and therefore high plant efficiency. - A core catcher allows passive collection and retention of the molten core should the reactor vessel fail in the highly unlikely event of a core melt. - A digital technology and a fully computerized control room with an operator friendly man-machine interface improve the reactor protection system

  17. Active cancellation - A means to zero dead-time pulse EPR.

    Science.gov (United States)

    Franck, John M; Barnes, Ryan P; Keller, Timothy J; Kaufmann, Thomas; Han, Songi

    2015-12-01

    The necessary resonator employed in pulse electron paramagnetic resonance (EPR) rings after the excitation pulse and creates a finite detector dead-time that ultimately prevents the detection of signal from fast relaxing spin systems, hindering the application of pulse EPR to room temperature measurements of interesting chemical or biological systems. We employ a recently available high bandwidth arbitrary waveform generator (AWG) to produce a cancellation pulse that precisely destructively interferes with the resonant cavity ring-down. We find that we can faithfully detect EPR signal at all times immediately after, as well as during, the excitation pulse. This is a proof of concept study showcasing the capability of AWG pulses to precisely cancel out the resonator ring-down, and allow for the detection of EPR signal during the pulse itself, as well as the dead-time of the resonator. However, the applicability of this approach to conventional EPR experiments is not immediate, as it hinges on either (1) the availability of low-noise microwave sources and amplifiers to produce the necessary power for pulse EPR experiment or (2) the availability of very high conversion factor micro coil resonators that allow for pulse EPR experiments at modest microwave power. Copyright © 2015 Elsevier Inc. All rights reserved.

  18. EPR spectral investigation of radiation-induced radicals of gallic acid

    Energy Technology Data Exchange (ETDEWEB)

    Tuner, Hasan [Balikesir University, Department of Physics, Faculty of Art and Science, Balikesir (Turkey)

    2017-11-15

    In the present work, spectroscopic features of the radiation-induced radicals of gallic acid compounds were investigated using electron paramagnetic resonance (EPR) spectroscopy. While un-irradiated samples presented no EPR signal, irradiated samples exhibited an EPR spectrum consisting of an intense resonance line at the center and weak lines on both sides. Detailed microwave saturation investigations were carried out to determine the origin of the experimental EPR lines. It is concluded that the two side lines of the triplet satellite originate from forbidden ''spin-flip'' transitions. The spectroscopic and structural features of the radiation-induced radicals were determined using EPR spectrum fittings. The experimental EPR spectra of the two gallic acid compounds were consistent with the calculated EPR spectroscopic features of the proposed radicals. It is concluded that the most probable radicals are the cyclohexadienyl-type, O(OH){sub 2}C{sub 6}H{sub 2}COOH radicals for both compounds. (orig.)

  19. High field high frequency EPR techniques and their application to single molecule magnets

    International Nuclear Information System (INIS)

    Edwards, R.S.; Hill, S.; Goy, P.; Wylde, R.; Takahashi, S.

    2004-01-01

    We present details of a new high-field/high-frequency EPR technique, and its application to measurements of single-molecule magnets (SMMs). By using a quasi-optical set-up and microwave sources covering a continuous frequency range from 170 to 600 GHz, in conjunction with a millimetre-wave vector network analyser, we are able to measure EPR to high magnetic fields. For example, a g=2 system will exhibit EPR at about 14 T at a frequency of 400 GHz. We illustrate the technique by presenting details of recent high-frequency experiments on several SMMs which are variations of the well-known SMM Mn 12 -Ac. This material has a spin ground state of S=10 and large uniaxial anisotropy, hence frequencies above 300 GHz are required in order to observe EPR from the ground state

  20. EPR investigations of silicon carbide nanoparticles functionalized by acid doped polyaniline

    Science.gov (United States)

    Karray, Fekri; Kassiba, Abdelhadi

    2012-06-01

    Nanocomposites (SiC-PANI) based on silicon carbide nanoparticles (SiC) encapsulated in conducting polyaniline (PANI) are synthesized by direct polymerization of PANI on the nanoparticle surfaces. The conductivity of PANI and the nanocomposites was modulated by several doping levels of camphor sulfonic acid (CSA). Electron paramagnetic resonance (EPR) investigations were carried out on representative SiC-PANI samples over the temperature range [100-300 K]. The features of the EPR spectra were analyzed taking into account the paramagnetic species such as polarons with spin S=1/2 involved in two main environments realized in the composites as well as their thermal activation. A critical temperature range 200-225 K was revealed through crossover changes in the thermal behavior of the EPR spectral parameters. Insights on the electronic transport properties and their thermal evolutions were inferred from polarons species probed by EPR and the electrical conductivity in doped nanocomposites.

  1. EPR investigations of silicon carbide nanoparticles functionalized by acid doped polyaniline

    Energy Technology Data Exchange (ETDEWEB)

    Karray, Fekri [Laboratoire des materiaux Ceramiques Composites et Polymeres, Faculte des Sciences de Sfax, BP 802, 3018 Sfax (Tunisia); Kassiba, Abdelhadi, E-mail: kassiba@univ-lemans.fr [Institute of Molecules and Materials of Le Mans (I3M), UMR-CNRS 6283, Universite du Maine, 72085 Le Mans (France)

    2012-06-15

    Nanocomposites (SiC-PANI) based on silicon carbide nanoparticles (SiC) encapsulated in conducting polyaniline (PANI) are synthesized by direct polymerization of PANI on the nanoparticle surfaces. The conductivity of PANI and the nanocomposites was modulated by several doping levels of camphor sulfonic acid (CSA). Electron paramagnetic resonance (EPR) investigations were carried out on representative SiC-PANI samples over the temperature range [100-300 K]. The features of the EPR spectra were analyzed taking into account the paramagnetic species such as polarons with spin S=1/2 involved in two main environments realized in the composites as well as their thermal activation. A critical temperature range 200-225 K was revealed through crossover changes in the thermal behavior of the EPR spectral parameters. Insights on the electronic transport properties and their thermal evolutions were inferred from polarons species probed by EPR and the electrical conductivity in doped nanocomposites.

  2. Quantitative Interpretation of Multifrequency Multimode EPR Spectra of Metal Containing Proteins, Enzymes, and Biomimetic Complexes.

    Science.gov (United States)

    Petasis, Doros T; Hendrich, Michael P

    2015-01-01

    Electron paramagnetic resonance (EPR) spectroscopy has long been a primary method for characterization of paramagnetic centers in materials and biological complexes. Transition metals in biological complexes have valence d-orbitals that largely define the chemistry of the metal centers. EPR spectra are distinctive for metal type, oxidation state, protein environment, substrates, and inhibitors. The study of many metal centers in proteins, enzymes, and biomimetic complexes has led to the development of a systematic methodology for quantitative interpretation of EPR spectra from a wide array of metal containing complexes. The methodology is now contained in the computer program SpinCount. SpinCount allows simulation of EPR spectra from any sample containing multiple species composed of one or two metals in any spin state. The simulations are quantitative, thus allowing determination of all species concentrations in a sample directly from spectra. This chapter will focus on applications to transition metals in biological systems using EPR spectra from multiple microwave frequencies and modes. © 2015 Elsevier Inc. All rights reserved.

  3. The QUASAR reproducibility study, Part II: Results from a multi-center Arterial Spin Labeling test-retest study

    DEFF Research Database (Denmark)

    Petersen, Esben Thade; Mouridsen, Kim; Golay, Xavier

    2010-01-01

    Quantitative STAR labeling of Arterial Regions or QUASAR), a method providing user independent quantification of CBF in a large test-retest study across sites from around the world, dubbed "The QUASAR reproducibility study". Altogether, 28 sites located in Asia, Europe and North America participated...... and a total of 284 healthy volunteers were scanned. Minimal operator dependence was assured by using an automatic planning tool and its accuracy and potential usefulness in multi-center trials was evaluated as well. Accurate repositioning between sessions was achieved with the automatic planning tool showing...

  4. The QUASAR reproducibility study, Part II: Results from a multi-center Arterial Spin Labeling test-retest study

    DEFF Research Database (Denmark)

    Petersen, Esben; Mouridsen, Kim; Golay, Xavier

    2009-01-01

    Quantitative STAR labeling of Arterial Regions or QUASAR), a method providing user independent quantification of CBF in a large test-retest study across sites from around the world, dubbed "The QUASAR reproducibility study". Altogether, 28 sites located in Asia, Europe and North America participated...... and a total of 284 healthy volunteers were scanned. Minimal operator dependence was assured by using an automatic planning tool and its accuracy and potential usefulness in multi-center trials was evaluated as well. Accurate repositioning between sessions was achieved with the automatic planning tool showing...

  5. The EPR layout design

    International Nuclear Information System (INIS)

    Mast, U.; Le Carrer, P.Y.

    2001-01-01

    General: The European Pressurised Water Reactor (EPR) is a French - German development for the next generation of Pressurised Water Reactor. The new reactor design is based on the experiences of operation and design of nuclear power plants in both countries. The EPR fulfils enhanced safety standards, higher availability and a longer service life. Utilities aspects: For the Utilities one important requirement is the reduction of personnel exposure during maintenance and in-service inspection. The other significant requirement is of economic nature. The main points influencing costs, which have also impact on the layout, are: outage times, accessibility of the reactor building and the available maintenance and set down areas. The Utilities have also required to load the spent fuel assemblies into the shipping cask from the bottom of the fuel pool, because of the exclusion of the drop of the cask and in order to avoid contamination at the outer cask shell. Layout and safety aspects: All safety relevant Nuclear Island (NI) buildings are designed against design earthquake as well as explosion pressure wave. The protection against Airplane Crash (APC) is realised by civil and layout dispositions. The Reactor Building, the Safeguard Buildings division 2 and 3 and the Fuel Building are protected by concrete structures. The other safety relevant nuclear buildings are protected by geographical separation. Important safety requirements are the further reduction of the probability of severe accidents and the mitigation of such an accident on the plant area. For that, a spreading area for molten corium, a channel from the reactor pit to the spreading area and the In Containment Refuelling Water Storage Tank (IRWST) for flooding and initial cooling of the corium, were implemented in the design of the Reactor Building. Layout results: The following buildings are arranged on a common raft to protect them against design earthquake: Reactor Building (RB), Safeguard Buildings (SAB

  6. CW- and pulsed-EPR of carbonaceous matter in primitive meteorites: solving a lineshape paradox.

    Science.gov (United States)

    Delpoux, Olivier; Gourier, Didier; Binet, Laurent; Vezin, Hervé; Derenne, Sylvie; Robert, François

    2008-05-01

    Insoluble organic matter (IOM) of Orgueil and Tagish Lake meteorites are studied by CW-EPR and pulsed-EPR spectroscopies. The EPR line is due to polycyclic paramagnetic moieties concentrated in defect-rich regions of the IOM, with concentrations of the order of 4x10(19) spin/g. CW-EPR reveals two types of paramagnetic defects: centres with S=1/2, and centres with S=0 ground state and thermally accessible triple state S=1. In spite of the Lorentzian shape of the EPR and its narrowing upon increasing the spin concentration, the EPR line is not in the exchange narrowing regime as previously deduced from multi-frequency CW-EPR [L. Binet, D. Gourier, Appl. Magn. Reson. 30 (2006) 207-231]. It is inhomogeneously broadened as demonstrated by the presence of nuclear modulations in the spin-echo decay. The line narrowing, similar to an exchange narrowing effect, is the result of an increasing contribution of the narrow line of the triplet state centres in addition to the broader line of doublet states. Hyperfine sublevel correlation spectroscopy (HYSCORE) of hydrogen and (13)C nuclei indicates that IOM* centres are small polycyclic moieties that are moderately branched with aliphatic chains, as shown by the presence of aromatic hydrogen atoms. On the contrary the lack of such aromatic hydrogen in triplet states suggests that these radicals are most probably highly branched. Paramagnetic centres are considerably enriched in deuterium, with D/H approximately 1.5+/-0.5x10(-2) of the order of values existing in interstellar medium.

  7. CW- and pulsed-EPR of carbonaceous matter in primitive meteorites: Solving a lineshape paradox

    Science.gov (United States)

    Delpoux, Olivier; Gourier, Didier; Binet, Laurent; Vezin, Hervé; Derenne, Sylvie; Robert, François

    2008-05-01

    Insoluble organic matter (IOM) of Orgueil and Tagish Lake meteorites are studied by CW-EPR and pulsed-EPR spectroscopies. The EPR line is due to polycyclic paramagnetic moieties concentrated in defect-rich regions of the IOM, with concentrations of the order of 4 × 10 19 spin/g. CW-EPR reveals two types of paramagnetic defects: centres with S = 1/2, and centres with S = 0 ground state and thermally accessible triple state S = 1. In spite of the Lorentzian shape of the EPR and its narrowing upon increasing the spin concentration, the EPR line is not in the exchange narrowing regime as previously deduced from multi-frequency CW-EPR [L. Binet, D. Gourier, Appl. Magn. Reson. 30 (2006) 207-231]. It is inhomogeneously broadened as demonstrated by the presence of nuclear modulations in the spin-echo decay. The line narrowing, similar to an exchange narrowing effect, is the result of an increasing contribution of the narrow line of the triplet state centres in addition to the broader line of doublet states. Hyperfine sublevel correlation spectroscopy (HYSCORE) of hydrogen and 13C nuclei indicates that IOM rad centres are small polycyclic moieties that are moderately branched with aliphatic chains, as shown by the presence of aromatic hydrogen atoms. On the contrary the lack of such aromatic hydrogen in triplet states suggests that these radicals are most probably highly branched. Paramagnetic centres are considerably enriched in deuterium, with D/H ≈ 1.5 ± 0.5 × 10 -2 of the order of values existing in interstellar medium.

  8. EPR Evidence of Liquid Water in Ice: An Intrinsic Property of Water or a Self-Confinement Effect?

    Science.gov (United States)

    Thangswamy, Muthulakshmi; Maheshwari, Priya; Dutta, Dhanadeep; Rane, Vinayak; Pujari, Pradeep K

    2018-06-01

    Liquid water (LW) existence in pure ice below 273 K has been a controversial aspect primarily because of the lack of experimental evidence. Recently, electron paramagnetic resonance (EPR) has been used to study deeply supercooled water in a rapidly frozen polycrystalline ice. The same technique can also be used to probe the presence of LW in polycrystalline ice that has formed through a more conventional, slow cooling one. In this context, the present study aims to emphasize that in case of an external probe involving techniques such as EPR, the results are influenced by the binary phase (BP) diagram of the probe-water system, which also predicts the existence of LW domains in ice, up to the eutectic point. Here we report the results of our such EPR spin-probe studies on water, which demonstrate that smaller the concentration of the probe stronger is the EPR evidence of liquid domains in polycrystalline ice. We used computer simulations based on stochastic Liouville theory to analyze the lineshapes of the EPR spectra. We show that the presence of the spin probe modifies the BP diagram of water, at very low concentrations of the spin probe. The spin probe thus acts, not like a passive reporter of the behavior of the solvent and its environment, but as an active impurity to influence the solvent. We show that there exists a lower critical concentration, below which BP diagram needs to be modified, by incorporating the effect of confinement of the spin probe. With this approach, we demonstrate that the observed EPR evidence of LW domains in ice can be accounted for by the modified BP diagram of the probe-water system. The present work highlights the importance of taking cognizance of the possibility of spin probes affecting the host systems, when interpreting the EPR (or any other probe based spectroscopic) results of phase transitions of host, as its ignorance may lead to serious misinterpretations.

  9. Copper ESEEM and HYSCORE through ultra-wideband chirp EPR spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Segawa, Takuya F.; Doll, Andrin; Pribitzer, Stephan; Jeschke, Gunnar, E-mail: gjeschke@ethz.ch [ETH Zurich, Laboratory of Physical Chemistry, Vladimir-Prelog-Weg 2, CH-8093 Zurich (Switzerland)

    2015-07-28

    The main limitation of pulse electron paramagnetic resonance (EPR) spectroscopy is its narrow excitation bandwidth. Ultra-wideband (UWB) excitation with frequency-swept chirp pulses over several hundreds of megahertz overcomes this drawback. This allows to excite electron spin echo envelope modulation (ESEEM) from paramagnetic copper centers in crystals, whereas up to now, only ESEEM of ligand nuclei like protons or nitrogens at lower frequencies could be detected. ESEEM spectra are recorded as two-dimensional correlation experiments, since the full digitization of the electron spin echo provides an additional Fourier transform EPR dimension. Thus, UWB hyperfine-sublevel correlation experiments generate a novel three-dimensional EPR-correlated nuclear modulation spectrum.

  10. Detection and identification of nitrogen defects in nanodiamond as studied by EPR

    Energy Technology Data Exchange (ETDEWEB)

    Soltamova, A.A.; Ilyin, I.V. [Ioffe Physical Technical Institute, Politechnicheskaya, 26, St. Petersburg 194021 (Russian Federation); Baranov, P.G., E-mail: pavel.baranov@mail.ioffe.r [Ioffe Physical Technical Institute, Politechnicheskaya, 26, St. Petersburg 194021 (Russian Federation); Vul' , A.Ya.; Kidalov, S.V.; Shakhov, F.M. [Ioffe Physical Technical Institute, Politechnicheskaya, 26, St. Petersburg 194021 (Russian Federation); Mamin, G.V.; Orlinskii, S.B.; Silkin, N.I.; Salakhov, M.Kh. [Kazan State University, Federal Center of Shared Usage for Physicochemical Measurements, Kazan 420008 (Russian Federation)

    2009-12-15

    Electron paramagnetic resonance (EPR) and electron spin echo (ESE) at X-band and at high-frequency W-band (95 GHz) have been used to study defects in natural diamond nanocrystals, detonation nanodiamond (ND) with a size of approx4.5 nm and detonation ND after high-temperature, high-pressure sintering with a size of approx8.5 nm. Atomic nitrogen centers N{sup 0} and nitrogen pairs N{sub 2}{sup +} have been detected and identified and their structure has been unambiguously determined by means of the high frequency EPR and ESE in natural diamond nanocrystals. In detonation ND and detonation ND after sintering atomic nitrogen centers N{sup 0} have been discovered in nanodiamond core. In addition EPR signal of multi-vacancy centers with spin 3/2 seems to be observed in diamond core of detonation ND.

  11. A high-resolution EPR-CT microscope using cavity-resonators equipped with small field gradient coils

    International Nuclear Information System (INIS)

    Miki, T.; Murata, T.; Kumai, H.; Yamashiro, A.

    1996-01-01

    Cylindrical cavity resonators equipped with field gradient coils were developed for two-dimensional EPR-CT microscope systems. The field gradient coils lie in four (or six) thin metal tubes placed along the direction of the microwave magnetic field in the cavity to minimize impact on the resonator's quality factor. Two pairs of the tubes carry a 100 kHz current for magnetic field modulation. This cavity has high spin-detection sensitivity and can provide EPR images with submillimeter resolution. In order to reconstruct better images from fewer projections, we used an algebraic reconstruction technique (ART) for the two-dimensional image reconstruction. The ART method may be suitable for not only spectral-spatial two-dimensional EPR imaging, but also spatio-temporal EPR imaging in dynamic spin systems. (author)

  12. Time-resolved EPR study of singlet oxygen in the gas phase.

    Science.gov (United States)

    Ruzzi, Marco; Sartori, Elena; Moscatelli, Alberto; Khudyakov, Igor V; Turro, Nicholas J

    2013-06-27

    X-band EPR spectra of singlet O2((1)Δg) and triplet O2((3)Σg(-)) were observed in the gas phase under low molecular-oxygen pressures PO2 = 0.175-0.625 Torr, T = 293-323 K. O2((1)Δg) was produced by quenching of photogenerated triplet sensitizers naphthalene C8H10, perdeuterated naphthalene, and perfluoronaphthalene in the gas phase. The EPR spectrum of O2((1)Δg) was also observed under microwave discharge. Integrated intensities and line widths of individual components of the EPR spectrum of O2((3)Σg(-)) were used as internal standards for estimating the concentration of O2 species and PO2 in the EPR cavity. Time-resolved (TR) EPR experiments of C8H10 were the main focus of this Article. Pulsed irradiation of C8H10 in the presence of O2((3)Σg(-)) allowed us to determine the kinetics of formation and decay for each of the four components of the O2((1)Δg) EPR signal, which lasted for only a few seconds. We found that the kinetics of EPR-component decay fit nicely to a biexponential kinetics law. The TR EPR 2D spectrum of the third component of the O2((1)Δg) EPR spectrum was examined in experiments using C8H10. This spectrum vividly presents the time evolution of an EPR component. The largest EPR signal and the longest lifetime of O2((1)Δg), τ = 0.4 s, were observed at medium pressure PO2 = 0.4 Torr, T = 293 K. The mechanism of O2((1)Δg) decay in the presence of photosensitizers is discussed. EPR spectra of O2((1)Δg) evidence that the spin-rotational states of O2((1)Δg) are populated according to Boltzmann distribution in the studied time range of 10-100 ms. We believe that this is the first report dealing with the dependence of O2((1)Δg) EPR line width on PO2 and T.

  13. CW EPR parameters reveal cytochrome P450 ligand binding modes.

    Science.gov (United States)

    Lockart, Molly M; Rodriguez, Carlo A; Atkins, William M; Bowman, Michael K

    2018-06-01

    Cytochrome P450 (CYP) monoxygenses utilize heme cofactors to catalyze oxidation reactions. They play a critical role in metabolism of many classes of drugs, are an attractive target for drug development, and mediate several prominent drug interactions. Many substrates and inhibitors alter the spin state of the ferric heme by displacing the heme's axial water ligand in the resting enzyme to yield a five-coordinate iron complex, or they replace the axial water to yield a nitrogen-ligated six-coordinate iron complex, which are traditionally assigned by UV-vis spectroscopy. However, crystal structures and recent pulsed electron paramagnetic resonance (EPR) studies find a few cases where molecules hydrogen bond to the axial water. The water-bridged drug-H 2 O-heme has UV-vis spectra similar to nitrogen-ligated, six-coordinate complexes, but are closer to "reverse type I" complexes described in older liteature. Here, pulsed and continuous wave (CW) EPR demonstrate that water-bridged complexes are remarkably common among a range of nitrogenous drugs or drug fragments that bind to CYP3A4 or CYP2C9. Principal component analysis reveals a distinct clustering of CW EPR spectral parameters for water-bridged complexes. CW EPR reveals heterogeneous mixtures of ligated states, including multiple directly-coordinated complexes and water-bridged complexes. These results suggest that water-bridged complexes are under-represented in CYP structural databases and can have energies similar to other ligation modes. The data indicates that water-bridged binding modes can be identified and distinguished from directly-coordinated binding by CW EPR. Copyright © 2018 Elsevier Inc. All rights reserved.

  14. The EPR in a few words: all you need to know about the EPR nuclear reactor

    International Nuclear Information System (INIS)

    2009-01-01

    After a brief presentation of the EPR (European - or Evolutionary - Pressurized Reactor) type nuclear reactor, this paper, proposed by the collective group 'Stop EPR', develops the following points: EPR is as dangerous as other reactors; EPR flouts democracy; France's energy demand do not need the construction of EPRs; the construction of EPRs is not a factor of economical and social development; EPR should not be constructed neither in France nor elsewhere and the present building sites should be cancelled; the EPR will not help France to increase its energy independence and protect itself from oil price increases; choosing the EPR is incompatible with the large investments to be made in energy conservation and renewable energies; the EPR is not a solution to climate change; the VHV line corridor that will starts at Flamanville is not justified and poses risks to the environment and public health

  15. Simultaneous PET/MR imaging of the brain: feasibility of cerebral blood flow measurements with FAIR-TrueFISP arterial spin labeling MRI.

    Science.gov (United States)

    Stegger, Lars; Martirosian, Petros; Schwenzer, Nina; Bisdas, Sotirios; Kolb, Armin; Pfannenberg, Christina; Claussen, Claus D; Pichler, Bernd; Schick, Fritz; Boss, Andreas

    2012-11-01

    Hybrid positron emission tomography/magnetic resonance imaging (PET/MRI) with simultaneous data acquisition promises a comprehensive evaluation of cerebral pathophysiology on a molecular, anatomical, and functional level. Considering the necessary changes to the MR scanner design the feasibility of arterial spin labeling (ASL) is unclear. To evaluate whether cerebral blood flow imaging with ASL is feasible using a prototype PET/MRI device. ASL imaging of the brain with Flow-sensitive Alternating Inversion Recovery (FAIR) spin preparation and true fast imaging in steady precession (TrueFISP) data readout was performed in eight healthy volunteers sequentially on a prototype PET/MRI and a stand-alone MR scanner with 128 × 128 and 192 × 192 matrix sizes. Cerebral blood flow values for gray matter, signal-to-noise and contrast-to-noise ratios, and relative signal change were compared. Additionally, the feasibility of ASL as part of a clinical hybrid PET/MRI protocol was demonstrated in five patients with intracerebral tumors. Blood flow maps showed good delineation of gray and white matter with no discernible artifacts. The mean blood flow values of the eight volunteers on the PET/MR system were 51 ± 9 and 51 ± 7 mL/100 g/min for the 128 × 128 and 192 × 192 matrices (stand-alone MR, 57 ± 2 and 55 ± 5, not significant). The value for signal-to-noise (SNR) was significantly higher for the PET/MRI system using the 192 × 192 matrix size (P change (δS) was significantly lower for the 192 × 192 matrix size (P = 0.02). ASL imaging as part of a clinical hybrid PET/MRI protocol could successfully be accomplished in all patients in diagnostic image quality. ASL brain imaging is feasible with a prototype hybrid PET/MRI scanner, thus adding to the value of this novel imaging technique.

  16. Non-contrast-enhanced 4D MR angiography with STAR spin labeling and variable flip angle sampling: a feasibility study for the assessment of Dural Arteriovenous Fistula

    Energy Technology Data Exchange (ETDEWEB)

    Jang, Jinhee; Kim, Bom-yi; Choi, Hyun Seok; Jung, So-Lyung; Ahn, Kook-Jin; Kim, Bum-soo [The Catholic University of Korea, Department of Radiology, Seoul St. Mary' s Hospital, College of Medicine, Seoul (Korea, Republic of); Schmitt, Peter [Siemens AG, Healthcare Sector, Erlangen (Germany); Kim, Inseong; Paek, Munyoung [Siemens AG, Healthcare, Seoul (Korea, Republic of)

    2014-04-15

    This study aimed to evaluate the feasibility of non-contrast-enhanced 4D magnetic resonance angiography (NCE 4D MRA) with signal targeting with alternative radiofrequency (STAR) spin labeling and variable flip angle (VFA) sampling in the assessment of dural arteriovenous fistula (DAVF) in the transverse sinus. Nine patients underwent NCE 4D MRA for the evaluation of DAVF in the transverse sinus at 3 T. One patient was examined twice, once before and once after the interventional treatment. All patients also underwent digital subtraction angiography (DSA) and/or contrast-enhanced magnetic resonance angiography (CEMRA). For the acquisition of NCE 4D MRA, a STAR spin tagging method was used, and a VFA sampling was applied in the data readout module instead of a constant flip angle. Two readers evaluated the NCE 4D MRA data for the diagnosis of DAVF and its type with consensus. The results were compared with those from DSA and/or CEMRA. All patients underwent NCE 4D MRA without any difficulty. Among seven patients with patent DAVFs, all cases showed an early visualization of the transverse sinus on NCE 4D MRA. Except for one case, the type of DAVF of NCE 4D MRA was agreed with that of reference standard study. Cortical venous reflux (CVR) was demonstrated in two cases out of three patients with CVR. NCE 4D MRA with STAR tagging and VFA sampling is technically and clinically feasible and represents a promising technique for assessment of DAVF in the transverse sinus. Further technical developments should aim at improvements of spatial and temporal coverage. (orig.)

  17. Non-contrast-enhanced 4D MR angiography with STAR spin labeling and variable flip angle sampling: a feasibility study for the assessment of Dural Arteriovenous Fistula

    International Nuclear Information System (INIS)

    Jang, Jinhee; Kim, Bom-yi; Choi, Hyun Seok; Jung, So-Lyung; Ahn, Kook-Jin; Kim, Bum-soo; Schmitt, Peter; Kim, Inseong; Paek, Munyoung

    2014-01-01

    This study aimed to evaluate the feasibility of non-contrast-enhanced 4D magnetic resonance angiography (NCE 4D MRA) with signal targeting with alternative radiofrequency (STAR) spin labeling and variable flip angle (VFA) sampling in the assessment of dural arteriovenous fistula (DAVF) in the transverse sinus. Nine patients underwent NCE 4D MRA for the evaluation of DAVF in the transverse sinus at 3 T. One patient was examined twice, once before and once after the interventional treatment. All patients also underwent digital subtraction angiography (DSA) and/or contrast-enhanced magnetic resonance angiography (CEMRA). For the acquisition of NCE 4D MRA, a STAR spin tagging method was used, and a VFA sampling was applied in the data readout module instead of a constant flip angle. Two readers evaluated the NCE 4D MRA data for the diagnosis of DAVF and its type with consensus. The results were compared with those from DSA and/or CEMRA. All patients underwent NCE 4D MRA without any difficulty. Among seven patients with patent DAVFs, all cases showed an early visualization of the transverse sinus on NCE 4D MRA. Except for one case, the type of DAVF of NCE 4D MRA was agreed with that of reference standard study. Cortical venous reflux (CVR) was demonstrated in two cases out of three patients with CVR. NCE 4D MRA with STAR tagging and VFA sampling is technically and clinically feasible and represents a promising technique for assessment of DAVF in the transverse sinus. Further technical developments should aim at improvements of spatial and temporal coverage. (orig.)

  18. Collateral circulation via the circle of Willis in patients with carotid artery steno-occlusive disease: evaluation on 3-T 4D MRA using arterial spin labelling

    International Nuclear Information System (INIS)

    Iryo, Yasuhiko; Hirai, Toshinori; Nakamura, Masanobu; Inoue, Yasuteru; Watanabe, Masaki; Ando, Yukio; Azuma, Minako; Nishimura, Shinichiro; Shigematsu, Yoshinori; Kitajima, Mika; Yamashita, Yasuyuki

    2015-01-01

    Aim: To evaluate whether 3-T four-dimensional (4D) arterial spin-labelling (ASL) -based magnetic resonance angiography (MRA) is useful for assessing the collateral circulation via the circle of Willis in patients with carotid artery steno-occlusive disease. Materials and methods: Institutional review board approval and prior written informed consent from all patients were obtained. The inclusion criteria were fulfilled by 13 patients with carotid artery steno-occlusive disease. All underwent 4D-ASL MRA at 3 T and digital subtraction angiography (DSA). The flow-sensitive alternating inversion recovery (FAIR) preparation scheme with look-locker sampling was used for spin labeling. At 300-ms intervals seven dynamic scans were obtained with a spatial resolution of 0.5×0.5×0.6 mm 3 . The collateral flow via the circle of Willis was read on 4D-ASL MRA and DSA images by two sets of two independent readers each. κ statistics were used to assess interobserver and intermodality agreement. Results: On DSA, collateral flow via the anterior communicating artery (AcomA) was observed in six patients, via the posterior communicating artery (PcomA) in four patients, and via both the AcomA and PcomA in three patients. With respect to the qualitative evaluation of 4D-ASL MRA images, interobserver agreement was excellent for all items (κ=1). 4D-ASL MRA and DSA consensus readings agreed on the type of collateral flow pattern in 10 of the 13 patients (77%). Intermodality agreement was good (κ=0.606; 95% confidence interval (CI): 0.215–0.997). Conclusion: 3 T 4D-ASL MRA may be a useful tool for the evaluation of the collateral circulation in patients with carotid artery steno-occlusive disease. -- Highlights: •3-T 4D-ASL MRA has high spatial and temporal resolution. •There is no need for the use of contrast agents in this technique. •4D-ASL MRA is useful for assessing the collateral flow associated with carotid artery stenosis. •Intermodality agreement between 4D

  19. EPR: Some History and Clarification

    Science.gov (United States)

    Fine, Arthur

    2002-04-01

    Locality, separation and entanglement 1930s style. We’ll explore the background to the 1935 paper by Einstein, Podolsky and Rosen, how it was composed, the actual argument of the paper, the principles used, and how the paper was received by Schroedinger, and others.We’ll also look at Bohr’s response: the extent to which Bohr connects with what Einstein was after in EPR and the extent to EPR marks a shift in Bohr’s thinking about the quantum theory.

  20. Some ideas on the EPR

    International Nuclear Information System (INIS)

    2003-01-01

    Facing the debate and controversial between partisans and opponents of the European Pressurized Reactor construction, the SFP energy Group aims to offer some reflexions. In this framework the following topics are discussed: the french nuclear park and its replacement, the energy costs, the nuclear reactors profitability, the generation IV reactors. The paper examines then the EPR technology and its cost to conclude on the advantage of an EPR construction, in the case of an energy policy based on the nuclear. This last point seems to be the real challenge of the problem. (A.L.B.)

  1. EPR in B physics and elsewhere

    International Nuclear Information System (INIS)

    Lipkin, H.J.; Tel Aviv Univ.; Argonne National Lab., IL

    1997-01-01

    The application of Einstein-Podolsky-Rosen correlations in Υ(4s) → B anti B decays to research in CP violation is the first and probably only use of EPR as a technique for research in new physics. Elsewhere highly sophisticated EPR projects question EPR and test its predictions to look for violations of quantum mechanics, hidden variables, Bell''s inequalities, etc

  2. The analogy in the formation of hardness salts and gallstones according to the EPR study

    Science.gov (United States)

    Pichugina, Alina; Tsyro, Larisa; Unger, Felix

    2017-11-01

    The article shows that the hardness salts contain the same crystalline phases as the bile stone pigment. The identity of EPR spectra of hardness salts and pigment of gallstones containing calcium carbonate was established. An analogy between the processes of formation of hardness salts and gallstones is played, in which particles with open spin-orbitals (fermions) play a decisive role.

  3. EPR of free radicals in solids I trends in methods and applications

    CERN Document Server

    Lund, Anders; Lund, Anders

    2012-01-01

    In its updated 2nd edition, this book surveys methods and applications of EPR in the study of free radical processes in solids. The focus is on trends in methods for extracting structural and dynamical properties of radicals and spin probes in solid matrices.

  4. EPR: the nuclear impasse; EPR: l'impasse nucleaire

    Energy Technology Data Exchange (ETDEWEB)

    Marillier, F [Association Ecologiste Greenpeace (France)

    2008-07-01

    The questions relative to the climatic change constitute crucial challenges for the next ten years. In this context the author aims to show how the EPR project illustrates the nuclear french ''autism''. He presents and analyzes the international and environmental impacts of this obsolete technology, as a project useless and dangerous. (A.L.B.)

  5. EPR: the nuclear impasse; EPR: l'impasse nucleaire

    Energy Technology Data Exchange (ETDEWEB)

    Marillier, F. [Association Ecologiste Greenpeace (France)

    2008-07-01

    The questions relative to the climatic change constitute crucial challenges for the next ten years. In this context the author aims to show how the EPR project illustrates the nuclear french ''autism''. He presents and analyzes the international and environmental impacts of this obsolete technology, as a project useless and dangerous. (A.L.B.)

  6. Global Structure of a Three-Way Junction in a Phi29 Packaging RNA Dimer Determined Using Site-Directed Spin Labeling

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xiaojun; Tung, Chang-Shung; Sowa, Glenna; Hatmal, Ma' mon M.; Haworth, Ian S.; Qin, Peter Z.

    2012-02-08

    The condensation of bacteriophage phi29 genomic DNA into its preformed procapsid requires the DNA packaging motor, which is the strongest known biological motor. The packaging motor is an intricate ring-shaped protein/RNA complex, and its function requires an RNA component called packaging RNA (pRNA). Current structural information on pRNA is limited, which hinders studies of motor function. Here, we used site-directed spin labeling to map the conformation of a pRNA three-way junction that bridges binding sites for the motor ATPase and the procapsid. The studies were carried out on a pRNA dimer, which is the simplest ring-shaped pRNA complex and serves as a functional intermediate during motor assembly. Using a nucleotide-independent labeling scheme, stable nitroxide radicals were attached to eight specific pRNA sites without perturbing RNA folding and dimer formation, and a total of 17 internitroxide distances spanning the three-way junction were measured using Double Electron-Electron Resonance spectroscopy. The measured distances, together with steric chemical constraints, were used to select 3662 viable three-way junction models from a pool of 65 billion. The results reveal a similar conformation among the viable models, with two of the helices (HT and HL) adopting an acute bend. This is in contrast to a recently reported pRNA tetramer crystal structure, in which HT and HL stack onto each other linearly. The studies establish a new method for mapping global structures of complex RNA molecules, and provide information on pRNA conformation that aids investigations of phi29 packaging motor and developments of pRNA-based nanomedicine and nanomaterial.

  7. Effects of clary sage oil and its main components, linalool and linalyl acetate, on the plasma membrane of Candida albicans: an in vivo EPR study.

    Science.gov (United States)

    Blaskó, Ágnes; Gazdag, Zoltán; Gróf, Pál; Máté, Gábor; Sárosi, Szilvia; Krisch, Judit; Vágvölgyi, Csaba; Makszin, Lilla; Pesti, Miklós

    2017-02-01

    The effects of clary sage (Salvia sclarea L.) oil (CS-oil), and its two main components, linalool (Lol) and linalyl acetate (LA), on cells of the eukaryotic human pathogen yeast Candida albicans were studied. Dynamic and thermodynamic properties of the plasma membrane were investigated by electron paramagnetic resonance (EPR) spectroscopy, with 5-doxylstearic acid (5-SASL) and 16-SASL as spin labels. The monitoring of the head group regions with 5-SASL revealed break-point frequency decrease in a temperature dependent manner of the plasma membrane between 9.55 and 13.15 °C in untreated, in CS-oil-, Lol- and LA-treated membranes. The results suggest a significant increase in fluidity of the treated plasma membranes close to the head groups. Comparison of the results observed with the two spin labels demonstrated that CS-oil and LA induced an increased level of fluidization at both depths of the plasma membrane. Whereas Lol treatment induced a less (1 %) ordered bilayer organization in the superficial regions and an increased (10 %) order of the membrane leaflet in deeper layers. Acute toxicity tests and EPR results indicated that both the apoptotic and the effects exerted on the plasma membrane fluidity depended on the composition and chemical structure of the examined materials. In comparison with the control, treatment with CS-oil, Lol or LA induced 13.0, 12.3 and 26.4 % loss respectively, of the metabolites absorbing at 260 nm, as a biological consequence of the plasma membrane fluidizing effects. Our results confirmed that clary sage oil causes plasma membrane perturbations which leads to cell apoptosis process.

  8. Enhanced accuracy of the microwave field strength measurement in a CW-EPR by pulsed modulation technique

    Science.gov (United States)

    Rakvin, B.; Carić, D.; Kveder, M.

    2018-02-01

    The microwave magnetic field strength, B1, in the cavity of a conventional continuous wave electron paramagnetic resonance, CW-EPR, spectrometer was measured by employing modulation sidebands, MS, in the EPR spectrum. MS spectrum in CW-EPR is produced by applying the modulation frequency, ωrf, which exceeds the linewidth, δB, given in frequency units. An amplitude-modulated CW-EPR, AM-CW-EPR, was selected as detection method. Theoretical description of AM-CW-EPR spectrum was modified by adding Bloch-Siegert-like shift obtained by taking into account the cumulative effect of the non-resonant interactions between the driving fields and the spin system. This approach enables to enhance the precision of B1 measurement. In order to increase the sensitivity of the method when saturation effects, due to higher intensity of B1, decrease the resolution of AM-CW-EPR spectrum, detection at the second harmonic of CW-EPR has been employed.

  9. Enhanced accuracy of the microwave field strength measurement in a CW-EPR by pulsed modulation technique.

    Science.gov (United States)

    Rakvin, B; Carić, D; Kveder, M

    2018-02-01

    The microwave magnetic field strength, B 1 , in the cavity of a conventional continuous wave electron paramagnetic resonance, CW-EPR, spectrometer was measured by employing modulation sidebands, MS, in the EPR spectrum. MS spectrum in CW-EPR is produced by applying the modulation frequency, ω rf , which exceeds the linewidth, δB, given in frequency units. An amplitude-modulated CW-EPR, AM-CW-EPR, was selected as detection method. Theoretical description of AM-CW-EPR spectrum was modified by adding Bloch-Siegert-like shift obtained by taking into account the cumulative effect of the non-resonant interactions between the driving fields and the spin system. This approach enables to enhance the precision of B 1 measurement. In order to increase the sensitivity of the method when saturation effects, due to higher intensity of B 1 , decrease the resolution of AM-CW-EPR spectrum, detection at the second harmonic of CW-EPR has been employed. Copyright © 2018 Elsevier Inc. All rights reserved.

  10. Interaction of spin-labeled HPMA-based nanoparticles with human blood plasma proteins - the introduction of protein-corona-free polymer nanomedicine

    Czech Academy of Sciences Publication Activity Database

    Klepac, Damir; Kostková, Hana; Petrova, Svetlana; Chytil, Petr; Etrych, Tomáš; Kereiche, S.; Raška, I.; Weitz, D. A.; Filippov, Sergey K.

    2018-01-01

    Roč. 10, č. 13 (2018), s. 6194-6204 ISSN 2040-3364 R&D Projects: GA MŠk(CZ) LH15213; GA ČR(CZ) GA17-07164S Institutional support: RVO:61389013 Keywords : EPR * nanoparticles * protein s Subject RIV: CD - Macromolecular Chemistry OBOR OECD: Polymer science Impact factor: 7.367, year: 2016

  11. Evaluation of the applicability of territorial arterial spin labeling in meningiomas for presurgical assessments compared with 3-dimensional time-of-flight magnetic resonance angiography

    International Nuclear Information System (INIS)

    Lu, Yiping; Wen, Jianbo; Geng, Daoying; Yin, Bo; Luan, Shihai; Liu, Li; Xiong, Ji; Qu, Jianxun

    2017-01-01

    To prospectively evaluate the application of territorial arterial spin labelling (t-ASL) in comparison with unenhanced three-dimensional time-of-flight magnetic resonance angiography (3D-TOF-MRA) in the identification of the feeding vasculature of meningiomas. Thirty consecutive patients with suspected meningiomas underwent conventional MR imaging, unenhanced 3D-TOF-MRA and t-ASL scanning. Four experienced neuro-radiologists assessed the feeding vessels with different techniques separately. For the identification of the origin of the feeding arteries on t-ASL, the inter-observer agreement was excellent (κ = 0.913), while the inter-observer agreement of 3D-TOF-MRA was good (κ = 0.653). The inter-modality agreement between t-ASL and 3D-TOF-MRA for the feeding arteries was moderate (κ = 0.514). All 8 patients with motor or sensory disorders proved to have meningiomas supplied completely or partially by the internal carotid arteries, while all 14 patients with meningiomas supplied by the external carotid arteries or basilar arteries didn't show any symptoms concerning motor or sensory disorders (p = 0.003). T-ASL could complement unenhanced 3D-TOF-MRA and increase accuracy in the identification of the supplying arteries of meningiomas in a safe, intuitive, non-radioactive manner. The information about feeding arteries was potentially related to patients' symptoms and pathology, making it more crucial for neurosurgeons in planning surgery as well as evaluating prognosis. (orig.)

  12. Evaluation of the applicability of territorial arterial spin labeling in meningiomas for presurgical assessments compared with 3-dimensional time-of-flight magnetic resonance angiography

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Yiping; Wen, Jianbo; Geng, Daoying; Yin, Bo [Fudan University, Department of Radiology, Huashan Hospital, Shanghai (China); Luan, Shihai [Fudan University, Department of Neurosurgery, Huashan Hospital, Shanghai (China); Liu, Li [Fudan University, Department of Radiology, Shanghai Cancer Center, Shanghai (China); Xiong, Ji [Fudan University, Department of Pathology, Huashan Hospital, Shanghai (China); Qu, Jianxun [GE Healthcare, Department of MR Research, Shanghai (China)

    2017-10-15

    To prospectively evaluate the application of territorial arterial spin labelling (t-ASL) in comparison with unenhanced three-dimensional time-of-flight magnetic resonance angiography (3D-TOF-MRA) in the identification of the feeding vasculature of meningiomas. Thirty consecutive patients with suspected meningiomas underwent conventional MR imaging, unenhanced 3D-TOF-MRA and t-ASL scanning. Four experienced neuro-radiologists assessed the feeding vessels with different techniques separately. For the identification of the origin of the feeding arteries on t-ASL, the inter-observer agreement was excellent (κ = 0.913), while the inter-observer agreement of 3D-TOF-MRA was good (κ = 0.653). The inter-modality agreement between t-ASL and 3D-TOF-MRA for the feeding arteries was moderate (κ = 0.514). All 8 patients with motor or sensory disorders proved to have meningiomas supplied completely or partially by the internal carotid arteries, while all 14 patients with meningiomas supplied by the external carotid arteries or basilar arteries didn't show any symptoms concerning motor or sensory disorders (p = 0.003). T-ASL could complement unenhanced 3D-TOF-MRA and increase accuracy in the identification of the supplying arteries of meningiomas in a safe, intuitive, non-radioactive manner. The information about feeding arteries was potentially related to patients' symptoms and pathology, making it more crucial for neurosurgeons in planning surgery as well as evaluating prognosis. (orig.)

  13. Controlling T2 blurring in 3D RARE arterial spin labeling acquisition through optimal combination of variable flip angles and k-space filtering.

    Science.gov (United States)

    Zhao, Li; Chang, Ching-Di; Alsop, David C

    2018-02-09

    To improve the SNR efficiency and reduce the T 2 blurring of 3D rapid acquisition with relaxation enhancement stack-of-spiral arterial spin labeling imaging by using variable refocusing flip angles and k-space filtering. An algorithm for determining the optimal combination of variable flip angles and filtering correction is proposed. The flip angles are designed using extended phase graph physical simulations in an analytical and global optimization framework, with an optional constraint on deposited power. Optimal designs for correcting to Hann and Fermi window functions were compared with conventional constant amplitude or variable flip angle only designs on 6 volunteers. With the Fermi window correction, the proposed optimal designs provided 39.8 and 27.3% higher SNR (P variable flip angle designs. Even when power deposition was limited to 50% of the constant amplitude design, the proposed method outperformed the SNR (P variable flip angles can be derived as the output of an optimization problem. The combined design of variable flip angle and k-space filtering provided superior SNR to designs primarily emphasizing either approach singly. © 2018 International Society for Magnetic Resonance in Medicine.

  14. Evaluation of the degree of arteriovenous shunting in intracranial arteriovenous malformations using pseudo-continuous arterial spin labeling magnetic resonance imaging

    Energy Technology Data Exchange (ETDEWEB)

    Sunwoo, Leonard; Park, Sun-Won [Seoul Metropolitan Government - Seoul National University Boramae Medical Center, Department of Radiology, Seoul (Korea, Republic of); Seoul National University College of Medicine, Department of Radiology, Seoul (Korea, Republic of); Sohn, Chul-Ho; Yun, Tae Jin; Choi, Seung Hong; Cho, Young Dae; Kim, Ji-hoon; Han, Moon Hee [Seoul National University College of Medicine, Department of Radiology, Seoul (Korea, Republic of); Seoul National University Hospital, Department of Radiology, Seoul (Korea, Republic of); Lee, Jong Young [Kangdong Sacred Heart Hospital, Department of Neurosurgery, Seoul (Korea, Republic of); Yi, Kyung Sik [Chungbuk National University Hospital, Department of Radiology, Cheongju (Korea, Republic of); Paek, Sun Ha; Kim, Yong Hwy; Kim, Jin Wook; Chung, Hyun-Tai; Kim, Dong Gyu [Seoul National University Hospital, Department of Neurosurgery, Seoul (Korea, Republic of)

    2015-08-15

    Intracranial arteriovenous malformations (AVMs) display venous signals on arterial spin labeling (ASL) magnetic resonance (MR) imaging due to the presence of arteriovenous shunting. Our aim was to quantitatively correlate AVM signal intensity on ASL with the degree of arteriovenous shunting estimated on digital subtraction angiography (DSA) in AVMs. MR imaging including pseudo-continuous ASL at 3 T and DSA were obtained on the same day in 40 patients with intracranial AVMs. Two reviewers assessed the nidus and venous signal intensities on ASL images to determine the presence of arteriovenous shunting. Interobserver agreement on ASL between the reviewers was determined. ASL signal intensity of the AVM lesion was correlated with AVM size and the time difference between normal and AVM venous transit times measured from the DSA images. Interobserver agreement between two reviewers for nidus and venous signal intensities was excellent (κ = 0.80 and 1.0, respectively). Interobserver agreement regarding the presence of arteriovenous shunting was perfect (κ = 1.0). AVM signal intensity showed a positive relationship with the time difference between normal and AVM venous transit times (r = 0.638, P < 0.001). AVM signal intensity also demonstrated a positive relationship with AVM size (r = 0.561, P < 0.001). AVM signal intensity on ASL in patients with AVM correlates well with the degree of early vein opacification on DSA, which corresponds to the degree of arteriovenous shunting. (orig.)

  15. Thyroid perfusion imaging as a diagnostic tool in Graves' disease. Arterial spin labeling magnetic resonance imaging vs. colour-coded Doppler ultrasound

    Energy Technology Data Exchange (ETDEWEB)

    Muessig, K. [University Hospital of Duesseldorf (Germany). Dept. of Metabolic Diseases; Leibniz Center for Diabetes Research, Duesseldorf (Germany). Inst. for Clinical Diabetology; University Hospital of Tuebingen (Germany). Div. of Endocrinology, Diabetes, Nephrology, Angiology, and Clinical Chemistry; Schraml, C.; Schwenzer, N.F. [University Hospital of Tuebingen (Germany). Dept. of Radiology, Section on Experimental Radiology; University Hospital of Tuebingen (Germany). Dept. of Radiology, Diagnostic and Interventional Radiology; Rietig, R.; Balletshofer, B. [University Hospital of Tuebingen (Germany). Div. of Endocrinology, Diabetes, Nephrology, Angiology, and Clinical Chemistry; Martirosian, P.; Haering, H.U.; Schick, F. [University Hospital of Tuebingen (Germany). Dept. of Radiology, Section on Experimental Radiology; Claussen, C.D. [University Hospital of Tuebingen (Germany). Dept. of Radiology, Diagnostic and Interventional Radiology

    2012-12-15

    Purpose: Though increased thyroid perfusion assessed by colour-coded Doppler ultrasound (CDUS) is characteristic of Graves' disease (GD), sometimes perfusion assessment by CDUS is not possible. In these cases, arterial spin labelling (ASL), a novel magnetic resonance imaging (MRI) technique allowing non-invasive thyroid perfusion quantification, may have additional diagnostic value. We aimed to evaluate the potential of ASL-MRI for assessment of increased blood perfusion in patients with GD compared to CDUS. Materials and Methods: Thyroid perfusion was measured by CDUS (volume flow rate calculated from pulsed wave Doppler signals and vessel diameter) and ASL-MRI at 1.5 T in 7 patients with GD and 10 healthy controls. Results: In patients with GD, average perfusion in both thyroid lobes was markedly increased compared to controls. Both techniques applied for volume related perfusion as well as absolute volume flow in thyroid feeding vessels provided similar results (all p = 0.0008). Using a cut-off value of 22 ml/min for the volume flow rate assessed by CDUS in the four feeding vessels allowed discrimination between patients with GD and controls in all cases. After adjusting thyroid perfusion for the differences in organ volume, both CDUS and ASL revealed also complete discrimination between health and disease. Conclusion: Thyroid perfusion measurement by ASL-MRI reliably discriminate GD from normal thyroid glands. In patients in whom thyroid arteries cannot be depicted by CDUS for technical or anatomical reasons, ASL-MRI may have additional diagnostic value. (orig.)

  16. A two-stage model for in vivo assessment of brain tumor perfusion and abnormal vascular structure using arterial spin labeling.

    Directory of Open Access Journals (Sweden)

    Patrick W Hales

    Full Text Available The ability to assess brain tumor perfusion and abnormalities in the vascular structure in vivo could provide significant benefits in terms of lesion diagnosis and assessment of treatment response. Arterial spin labeling (ASL has emerged as an increasingly viable methodology for non-invasive assessment of perfusion. Although kinetic models have been developed to describe perfusion in healthy tissue, the dynamic behaviour of the ASL signal in the brain tumor environment has not been extensively studied. We show here that dynamic ASL data acquired in brain tumors displays an increased level of 'biphasic' behaviour, compared to that seen in healthy tissue. A new two-stage model is presented which more accurately describes this behaviour, and provides measurements of perfusion, pre-capillary blood volume fraction and transit time, and capillary bolus arrival time. These biomarkers offer a novel contrast in the tumor and surrounding tissue, and provide a means for measuring tumor perfusion and vascular structural abnormalities in a fully non-invasive manner.

  17. Spectral fitting for signal assignment and structural analysis of uniformly {sup 13}C-labeled solid proteins by simulated annealing based on chemical shifts and spin dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Matsuki, Yoh; Akutsu, Hideo; Fujiwara, Toshimichi [Osaka University, Institute for Protein Research (Japan)], E-mail: tfjwr@protein.osaka-u.ac.jp

    2007-08-15

    We describe an approach for the signal assignment and structural analysis with a suite of two-dimensional {sup 13}C-{sup 13}C magic-angle-spinning solid-state NMR spectra of uniformly {sup 13}C-labeled peptides and proteins. We directly fit the calculated spectra to experimental ones by simulated annealing in restrained molecular dynamics program CNS as a function of atomic coordinates. The spectra are calculated from the conformation dependent chemical shift obtained with SHIFTX and the cross-peak intensities computed for recoupled dipolar interactions. This method was applied to a membrane-bound 14-residue peptide, mastoparan-X. The obtained C', C{sup {alpha}} and C{sup {beta}} chemical shifts agreed with those reported previously at the precisions of 0.2, 0.7 and 0.4 ppm, respectively. This spectral fitting program also provides backbone dihedral angles with a precision of about 50 deg. from the spectra even with resonance overlaps. The restraints on the angles were improved by applying protein database program TALOS to the obtained chemical shifts. The peptide structure provided by these restraints was consistent with the reported structure at the backbone RMSD of about 1 A.

  18. Quantitative assessment of cerebral hemodynamic parameters by QUASAR arterial spin labeling in Alzheimer's disease and cognitively normal Elderly adults at 3-tesla.

    Science.gov (United States)

    Mak, Henry K F; Chan, Queenie; Zhang, Zhipeng; Petersen, Esben T; Qiu, Deqiang; Zhang, Linda; Yau, Kelvin K W; Chu, Leung-Wing; Golay, Xavier

    2012-01-01

    QUASAR arterial spin labeling (ASL) was used to investigate the role of vascular impairment in Alzheimer's disease (AD). We hypothesized that the hemodynamic parameters monitoring cerebrovascular integrity, i.e., cerebral blood flow (CBF), arterial blood volume (aBV), and arterial transit time (aTT), would be affected. 13 AD patients and 15 healthy control (HC) subjects underwent 3T MRI scanning. Two separate blood flow acquisitions were obtained with 1 slice overlap for whole brain coverage. CBF, aBV, and aTT maps were calculated using in-house software. Preprocessing and statistical analyses were performed on SPM5. Region-of-interest (ROI) studies of ten selected cerebral regions were also conducted. There were significant differences in mini mental status exam (MMSE) (AD: 16.3 ± 4.55, HC: 28.5 ± 2.00) and Alzheimer's disease assessment scale-cognitive subscale (ADAS-cog) scores (AD: 25.25 ± 9.64, HC: 5.51 ± 2.62) between the 2 groups (p QUASAR ASL, we found patterns of regional hemodynamic impairment typical of moderate AD, suggesting underlying vascular abnormality. As potential biomarkers, these hemodynamic parameters could differentiate patients from volunteers, and possibly indicate the conversion from healthy aging to mild cognitive impairment to AD.

  19. The role of magnetic resonance diffusion-weighted imaging and three-dimensional arterial spin labelling perfusion imaging in the differentiation of parasellar meningioma and cavernous haemangioma.

    Science.gov (United States)

    Xiao, Hua-Feng; Lou, Xin; Liu, Meng-Yu; Wang, Yu-Lin; Wang, Yan; Chen, Zhi-Ye; Shi, Kai-Ning; Ma, Lin

    2014-08-01

    To evaluate the diagnostic value of magnetic resonance diffusion-weighted imaging (DWI) and three-dimensional arterial spin labelling perfusion imaging (3D-ASL) in distinguishing cavernous haemangioma from parasellar meningioma, using histological data as a reference standard. Patients with parasellar meningioma or parasellar cavernous haemangioma underwent conventional T1- and T2-weighted magnetic resonance imaging (MRI) followed by DWI and 3D-ASL using a 3.0 Tesla MRI. The minimum apparent diffusion coefficient (minADC) from DWI and the maximal normalized cerebral blood flow (nCBF) from 3D-ASL were measured in each tumour. Diagnosis was confirmed by histology. MinADC was significantly lower and nCBF significantly higher in meningioma (n = 19) than cavernous haemangioma (n = 15). There was a significant negative correlation between minADC and nCBF (r = -0.605). DWI and 3D-ASL are useful in differentiating cavernous haemangiomas from parasellar meningiomas, particularly in situations when the appearance on conventional MRI sequences is otherwise ambiguous. © The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

  20. Arterial spin labeling-based Z-maps have high specificity and positive predictive value for neurodegenerative dementia compared to FDG-PET

    Energy Technology Data Exchange (ETDEWEB)

    Faellmar, David; Larsson, Elna-Marie [Uppsala University, Department of Surgical Sciences, Radiology, Uppsala (Sweden); Haller, Sven [Uppsala University, Department of Surgical Sciences, Radiology, Uppsala (Sweden); University Medical Center Freiburg, Department of Neuroradiology, Freiburg (Germany); University of Geneva, Faculty of Medicine, Geneva (Switzerland); Affidea CDRC - Centre Diagnostique Radiologique de Carouge, Carouge (Switzerland); Lilja, Johan [Uppsala University, Department of Surgical Sciences, Nuclear Medicine and PET, Uppsala (Sweden); Hermes Medical Solutions, Stockholm (Sweden); Danfors, Torsten [Uppsala University, Department of Surgical Sciences, Nuclear Medicine and PET, Uppsala (Sweden); Kilander, Lena [Uppsala University, Department of Public Health and Caring Sciences, Geriatrics, Uppsala (Sweden); Tolboom, Nelleke; Croon, Philip M.; Berckel, Bart N.M. van [VU University Medical Center, Department of Radiology and Nuclear Medicine, Amsterdam (Netherlands); Egger, Karl [University Medical Center Freiburg, Department of Neuroradiology, Freiburg (Germany); Kellner, Elias [Medical Center University of Freiburg, Department of Radiology, Medical Physics, Faculty of Medicine, Freiburg (Germany); Verfaillie, Sander C.J.; Ossenkoppele, Rik [VU University Medical Center, Department of Neurology, Alzheimer Center Amsterdam, Amsterdam (Netherlands); Barkhof, Frederik [VU University Medical Center, Department of Radiology and Nuclear Medicine, Amsterdam (Netherlands); UCL, Institutes of Neurology and Healthcare Engineering, London (United Kingdom)

    2017-10-15

    Cerebral perfusion analysis based on arterial spin labeling (ASL) MRI has been proposed as an alternative to FDG-PET in patients with neurodegenerative disease. Z-maps show normal distribution values relating an image to a database of controls. They are routinely used for FDG-PET to demonstrate disease-specific patterns of hypometabolism at the individual level. This study aimed to compare the performance of Z-maps based on ASL to FDG-PET. Data were combined from two separate sites, each cohort consisting of patients with Alzheimer's disease (n = 18 + 7), frontotemporal dementia (n = 12 + 8) and controls (n = 9 + 29). Subjects underwent pseudocontinuous ASL and FDG-PET. Z-maps were created for each subject and modality. Four experienced physicians visually assessed the 166 Z-maps in random order, blinded to modality and diagnosis. Discrimination of patients versus controls using ASL-based Z-maps yielded high specificity (84%) and positive predictive value (80%), but significantly lower sensitivity compared to FDG-PET-based Z-maps (53% vs. 96%, p < 0.001). Among true-positive cases, correct diagnoses were made in 76% (ASL) and 84% (FDG-PET) (p = 0.168). ASL-based Z-maps can be used for visual assessment of neurodegenerative dementia with high specificity and positive predictive value, but with inferior sensitivity compared to FDG-PET. (orig.)

  1. Combination of MRI hippocampal volumetry and arterial spin labeling MR perfusion at 3-Tesla improves the efficacy in discriminating Alzheimer's disease from cognitively normal elderly adults.

    Science.gov (United States)

    Mak, Henry Ka-Fung; Qian, Wenshu; Ng, Kwok Sing; Chan, Queenie; Song, You-Qiang; Chu, Leung Wing; Yau, Kelvin Kai-Wing

    2014-01-01

    Structural magnetic resonance imaging has been employed for evaluation of medial temporal atrophy in patients with Alzheimer's disease (AD). Arterial spin labeling (ASL) technique could detect cerebral perfusion abnormalities in AD. We hypothesized that combination of hippocampal volumetry and cerebral blood flow yield higher accuracy than either method alone in discriminating AD patients from cognitively normal elderly adults. 13 AD patients and 15 healthy controls were studied using a 3-tesla scanner. Standardized T1W 3D volumetric Fast Field Echo and QUASAR ASL sequences were employed for cerebral volumetry and perfusion respectively. Manual Right and left hippocampal volumetry was performed manually by ANALYZE software, with total intracranial volume normalization. ASL data were analyzed by institutional specially-design software to calculate cerebral blood flow of region-of-interests placed at the middle and posterior cingulate gyri. Right and left hippocampal volumes and middle and posterior cingulate gyri cerebral blood flows were significantly lower in the patients than in the controls (independent-samples t-tests, p volumetry and cerebral perfusion has improved efficacy in discriminating AD patients from cognitively normal elderly adults.

  2. Magnetic resonance imaging in children presenting migraine with aura: Association of hypoperfusion detected by arterial spin labelling and vasospasm on MR angiography findings.

    Science.gov (United States)

    Cadiot, Domitille; Longuet, Romain; Bruneau, Bertrand; Treguier, Catherine; Carsin-Vu, Aline; Corouge, Isabelle; Gomes, Constantin; Proisy, Maïa

    2018-04-01

    Objective A child presenting with a first attack of migraine with aura usually undergoes magnetic resonance imaging (MRI) to rule out stroke. The purpose of this study was to report vascular and brain perfusion findings in children suffering from migraine with aura on time-of-flight MR angiography (TOF-MRA) and MR perfusion imaging using arterial spin labelling (ASL). Methods We retrospectively included all children who had undergone an emergency MRI examination with ASL and TOF-MRA sequences for acute neurological deficit and were given a final diagnosis of migraine with aura. The ASL perfusion maps and TOF-MRA images were independently assessed by reviewers blinded to clinical data. A mean cerebral blood flow (CBF) value was obtained for each cerebral lobe after automatic data post-processing. Results Seventeen children were finally included. Hypoperfusion was identified in one or more cerebral lobes on ASL perfusion maps by visual assessment in 16/17 (94%) children. Vasospasm was noted within the intracranial vasculature on the TOF-MRA images in 12/17 (71%) children. All (100%) of the abnormal TOF-MRA images were associated with homolateral hypoperfusion. Mean CBF values were significantly lower ( P < 0.05) in visually hypoperfused lobes than in normally perfused lobes. Conclusion ASL and TOF-MRA are two totally non-invasive, easy-to-use MRI sequences for children in emergency settings. Hypoperfusion associated with homolateral vasospasm may suggest a diagnosis of migraine with aura.

  3. EPR study of human hair

    Czech Academy of Sciences Publication Activity Database

    Křížová, Jana; Káfuňková, Eva; Stopka, Pavel

    2005-01-01

    Roč. 99, č. 14 (2005), s. 217-218 ISSN 0009-2770 R&D Projects: GA MZd(CZ) NL7567; GA MZd(CZ) NB7377 Institutional research plan: CEZ:AV0Z40320502 Keywords : EPR Subject RIV: CA - Inorganic Chemistry Impact factor: 0.445, year: 2005

  4. SPIDYAN, a MATLAB library for simulating pulse EPR experiments with arbitrary waveform excitation.

    Science.gov (United States)

    Pribitzer, Stephan; Doll, Andrin; Jeschke, Gunnar

    2016-02-01

    Frequency-swept chirp pulses, created with arbitrary waveform generators (AWGs), can achieve inversion over a range of several hundreds of MHz. Such passage pulses provide defined flip angles and increase sensitivity. The fact that spectra are not excited at once, but single transitions are passed one after another, can cause new effects in established pulse EPR sequences. We developed a MATLAB library for simulation of pulse EPR, which is especially suited for modeling spin dynamics in ultra-wideband (UWB) EPR experiments, but can also be used for other experiments and NMR. At present the command line controlled SPin DYnamics ANalysis (SPIDYAN) package supports one-spin and two-spin systems with arbitrary spin quantum numbers. By providing the program with appropriate spin operators and Hamiltonian matrices any spin system is accessible, with limits set only by available memory and computation time. Any pulse sequence using rectangular and linearly or variable-rate frequency-swept chirp pulses, including phase cycling can be quickly created. To keep track of spin evolution the user can choose from a vast variety of detection operators, including transition selective operators. If relaxation effects can be neglected, the program solves the Liouville-von Neumann equation and propagates spin density matrices. In the other cases SPIDYAN uses the quantum mechanical master equation and Liouvillians for propagation. In order to consider the resonator response function, which on the scale of UWB excitation limits bandwidth, the program includes a simple RLC circuit model. Another subroutine can compute waveforms that, for a given resonator, maintain a constant critical adiabaticity factor over the excitation band. Computational efficiency is enhanced by precomputing propagator lookup tables for the whole set of AWG output levels. The features of the software library are discussed and demonstrated with spin-echo and population transfer simulations. Copyright © 2016

  5. EPR and IR spectral investigations on some leafy vegetables of Indian origin

    Science.gov (United States)

    Prasuna, C. P. Lakshmi; Chakradhar, R. P. S.; Rao, J. L.; Gopal, N. O.

    2009-09-01

    EPR spectral investigations have been carried out on four edible leafy vegetables of India, which are used as dietary component in day to day life. In Rumex vesicarius leaf sample, EPR spectral investigations at different temperatures indicate the presence of anti-ferromagnetically coupled Mn(IV)-Mn(IV) complexes. EPR spectra of Trigonella foenum graecum show the presence of Mn ions in multivalent state and Fe 3+ ions in rhombic symmetry. EPR spectra of Basella rubra indicate the presence of Mn(IV)-O-Mn(IV) type complexes. The EPR spectra of Basella rubra have been studied at different temperatures. It is found that the spin population for the resonance signal at g = 2.06 obeys the Boltzmann distribution law. The EPR spectra of Moringa oliefera leaves show the presence of Mn 2+ ions. Radiation induced changes in free radical of this sample have also been studied. The FT-IR spectra of Basella rubra and Moringa oliefera leaves show the evidences for the protein matrix bands and those corresponding to carboxylic C dbnd O bonds.

  6. Multi-photon transitions and Rabi resonance in continuous wave EPR.

    Science.gov (United States)

    Saiko, Alexander P; Fedaruk, Ryhor; Markevich, Siarhei A

    2015-10-01

    The study of microwave-radiofrequency multi-photon transitions in continuous wave (CW) EPR spectroscopy is extended to a Rabi resonance condition, when the radio frequency of the magnetic-field modulation matches the Rabi frequency of a spin system in the microwave field. Using the non-secular perturbation theory based on the Bogoliubov averaging method, the analytical description of the response of the spin system is derived for all modulation frequency harmonics. When the modulation frequency exceeds the EPR linewidth, multi-photon transitions result in sidebands in absorption EPR spectra measured with phase-sensitive detection at any harmonic. The saturation of different-order multi-photon transitions is shown to be significantly different and to be sensitive to the Rabi resonance. The noticeable frequency shifts of sidebands are found to be the signatures of this resonance. The inversion of two-photon lines in some spectral intervals of the out-of-phase first-harmonic signal is predicted under passage through the Rabi resonance. The inversion indicates the transition from absorption to stimulated emission or vice versa, depending on the sideband. The manifestation of the primary and secondary Rabi resonance is also demonstrated in the time evolution of steady-state EPR signals formed by all harmonics of the modulation frequency. Our results provide a theoretical framework for future developments in multi-photon CW EPR spectroscopy, which can be useful for samples with long spin relaxation times and extremely narrow EPR lines. Copyright © 2015 Elsevier Inc. All rights reserved.

  7. EPR invastigation of glasses on the base of the oxides of vanadium and tellurium

    International Nuclear Information System (INIS)

    Imanov, L.M; Ibragimov, Z.A.

    1978-01-01

    The results of investigation of EPR spectra of the nV 2 O 5 (100-n)TeO 2 binary system in the range from 95 to 5 mol % V 2 O 5 with the 5 mol % step on the DRON-2 installation (X-ray diffraction measurements) are presented. The EPR spectra were read out on the RE-1301 spectrometer at liquid nitrogen and room temperatures. The concentration of the EPR centres was determined by comparing it with the signal from the known number of Cu 2+ ions in the CuSO 4 x5H 2 O crystal. It is established that the VO 2+ complexes were the EPR centres. In all prepared samples the EPR spectra were observed, and at n=70 the SFS components were revealed both in the crystalline (with the TeO 2 content up to 30 mol %) and in amorphous states. The singularities of the EPR spectrum are discussed on the basis of the spin-hamiltonian with axial asymmetry. The dependence of the spin-hamiltonian components on the content was revealed and the P=670 value characterizing the average value of the distance between the nucleus and noncoupled electron is found. Observation of the line with well resoluted SFS components in the amorphous samples is explained by 'a great freedom'' of paramagnetic ions in the choice of close environment, and consequently the field of ligand atoms localizing in the paramagnetic ion produces the ''strong field'' effect (D, E>>GβH, G=1.985+-0.005) and removes degeneration due to the presence of the I=7/2 nuclear momentum of the V 4+ ion. Conservation of the SFS lines even at room temperature is connected with great scattering of the spin-lattice relaxation time

  8. EPR-technical codes - a common basis for the EPR

    International Nuclear Information System (INIS)

    Zaiss, W.; Appell, B.

    1997-01-01

    The design and construction of Nuclear Power Plants implies a full set of codes and standards to define the construction rules of components and equipment. Rules are existing and are currently implemented, respectively in France and Germany (mainly RCCs and KTA safety standards). In the frame of the EPR-project, the common objective requires an essential industrial work programme between engineers from both countries to elaborate a common set of codes and regulations. These new industrial rules are called the ETCs (EPR Technical Codes). In the hierarchy the ETCs are - in case of France - on the common level of basic safety rules (RFS), design and construction rules (RCC) and - in Germany - belonging to RSK guidelines and KTA safety standards. A set of six ETCs will be elaborated to cover: safety and process, mechanical components, electrical equipment, instrumentation and control, civil works, fire protection. (orig.)

  9. The Flamanville 3 EPR reactor; Le reacteur EPR Flamanville 3

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2007-07-01

    On April 10. 2007, the french government authorized EDF to create on the site of Flamanville ( La Manche) a nuclear base installation containing a pressurized water EPR type reactor. This nuclear reactor, conceived by AREVA NP and EDF, is the first copy of a generation susceptible to replace later, at least partly, the French nuclear reactors at present in operation.Within the framework of its mission of technical support of the Authority of Nuclear Safety ( A.S.N.), the I.R.S.N. widely contributed successively: to define the general objectives of safety assigned to this new generation of pressurized water nuclear reactors; to analyze the options of safety proposed by EDF for the EPR project; To deepen, upstream to the authorization of creation, the evaluation of the step of safety and the measures of conception retained by EDF that have to allow to respect the objectives of safety which were notified to it. (N.C.)

  10. Investigating the dynamic nature of the ABC transporters: ABCB1 and MsbA as examples for the potential synergies of MD theory and EPR applications.

    Science.gov (United States)

    Stockner, Thomas; Mullen, Anna; MacMillan, Fraser

    2015-10-01

    ABC transporters are primary active transporters found in all kingdoms of life. Human multidrug resistance transporter ABCB1, or P-glycoprotein, has an extremely broad substrate spectrum and confers resistance against chemotherapy drug treatment in cancer cells. The bacterial ABC transporter MsbA is a lipid A flippase and a homolog to the human ABCB1 transporter, with which it partially shares its substrate spectrum. Crystal structures of MsbA and ABCB1 have been solved in multiple conformations, providing a glimpse into the possible conformational changes the transporter could be going through during the transport cycle. Crystal structures are inherently static, while a dynamic picture of the transporter in motion is needed for a complete understanding of transporter function. Molecular dynamics (MD) simulations and electron paramagnetic resonance (EPR) spectroscopy can provide structural information on ABC transporters, but the strength of these two methods lies in the potential to characterise the dynamic regime of these transporters. Information from the two methods is quite complementary. MD simulations provide an all atom dynamic picture of the time evolution of the molecular system, though with a narrow time window. EPR spectroscopy can probe structural, environmental and dynamic properties of the transporter in several time regimes, but only through the attachment sites of an exogenous spin label. In this review the synergistic effects that can be achieved by combining the two methods are highlighted, and a brief methodological background is also presented. © 2015 Authors; published by Portland Press Limited.

  11. Dynamic nuclear spin polarization

    Energy Technology Data Exchange (ETDEWEB)

    Stuhrmann, H B [GKSS-Forschungszentrum Geesthacht GmbH (Germany)

    1996-11-01

    Polarized neutron scattering from dynamic polarized targets has been applied to various hydrogenous materials at different laboratories. In situ structures of macromolecular components have been determined by nuclear spin contrast variation with an unprecedented precision. The experiments of selective nuclear spin depolarisation not only opened a new dimension to structural studies but also revealed phenomena related to propagation of nuclear spin polarization and the interplay of nuclear polarisation with the electronic spin system. The observation of electron spin label dependent nuclear spin polarisation domains by NMR and polarized neutron scattering opens a way to generalize the method of nuclear spin contrast variation and most importantly it avoids precontrasting by specific deuteration. It also likely might tell us more about the mechanism of dynamic nuclear spin polarisation. (author) 4 figs., refs.

  12. EPR compared to international requirements (Mainly EUR)

    International Nuclear Information System (INIS)

    Broecker, B.

    1996-01-01

    A number of European Utilities have entered an agreement to write common requirements dedicated to future light water nuclear power plants to be built in Europe. The activities are known under the sign EUR (European Utilities Requirements). EPR, the future European Pressurized water Reactor, is the first installation of this type which will be operational from the year 2000 onwards, must fulfill the European requirements. EPR will serve as a test whether these requirements are realistic and well balanced. At the basic design stage of EPR, this paper concentrates on four main topics: the requirements which are new compared with existing reactors and which put a major challenge to the designer; the requirements today still open and the way they can be met by the EPR or not; the points for which already today the EPR special requirements exceed the EUR; the examples where the design of the EPR has given feedback which has led to a change of the EUR. EPR and EUR are different approaches to the reactor of the future. EUR is a set of requirements which leaves a flexibility to the designer while EPR is a real project which defines the technical solutions. EPR will fulfill the EUR and will at the same time serve as a test whether these requirements are realistic. EPR will also fulfill international requirements with minor changes. (J.S.). 7 figs

  13. Hydrogen Analyses in the EPR

    International Nuclear Information System (INIS)

    Worapittayaporn, S.; Eyink, J.; Movahed, M.

    2008-01-01

    In severe accidents with core melting large amounts of hydrogen may be released into the containment. The EPR provides a combustible gas control system to prevent hydrogen combustion modes with the potential to challenge the containment integrity due to excessive pressure and temperature loads. This paper outlines the approach for the verification of the effectiveness and efficiency of this system. Specifically, the justification is a multi-step approach. It involves the deployment of integral codes, lumped parameter containment codes and CFD codes and the use of the sigma criterion, which provides the link to the broad experimental data base for flame acceleration (FA) and deflagration to detonation transition (DDT). The procedure is illustrated with an example. The performed analyses show that hydrogen combustion at any time does not lead to pressure or temperature loads that threaten the containment integrity of the EPR. (authors)

  14. SU-G-IeP1-12: Size Selective Arterial Cerebral Blood Volume Mapping Using Multiple Inversion Time Arterial Spin Labeling

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Y; Johnston, M; Whitlow, C [Wake Forest School of Medicine, Winston-salem, NC (United States); Liu, H [UT MD Anderson Cancer Center, Houston, TX (United States)

    2016-06-15

    Purpose: To demonstrate the feasibility of a novel method for size specific arterial cerebral blood volume (aCBV) mapping using pseudo-continuous arterial spin labeling (PCASL), with multiple TI. Methods: Multiple PCASL images were obtained from a subject with TI of [300, 400, 500, 600, 700, 800, 900, 1000, 1500, 2000, 2500, 3000, 3500, 4000] ms. Each TI pair was averaged six times. Two scans were performed: one without a flow crusher gradient and the other with a crusher gradient (10cm/s in three directions) to remove signals from large arteries. Scan times were 5min. without a crusher gradient and 5.5 min with a crusher gradient. Non-linear fitting algorithm finds the minimum mean squared solution of per-voxel based aCBV, cerebral blood flow, and arterial transit time, and fits the data into a hemodynamic model that represents superposition of blood volume and flow components within a single voxel. Results: aCBV maps with a crusher gradient represent signals from medium and small sized arteries, while those without a crusher gradient represent signals from all sized arteries, indicating that flow crusher gradients can be effectively employed to achieve size-specific aCBV mapping. Regardless of flow crusher, the CBF and ATT maps are very similar in appearance. Conclusion: Quantitative size selective blood volume mapping controlled by a flow crusher is feasible without additional information because the ASL quantification process doesn’t require an arterial input function measured from a large artery. The size specific blood volume mapping is not interfered by sSignals from large arteries do not interfere with size specific aCBV mapping in the applications of interest in for applications in which only medium or small arteries are of interest.

  15. Assessment of tumor blood flow and its correlation with histopathologic features in skull base meningiomas and schwannomas by using pseudo-continuous arterial spin labeling images

    International Nuclear Information System (INIS)

    Yamamoto, Tatsuya; Takeuchi, Hiroaki; Kinoshita, Kazuyuki; Kosaka, Nobuyuki; Kimura, Hirohiko

    2014-01-01

    Objective: We aimed to investigate whether pseudo-continuous arterial spin labeling (pcASL)-MRI can adequately evaluate tumor perfusion even if the tumors are located in the skull base region and evaluate the correlation between tumor blood flow (TBF) and the histopathologic features of skull base meningiomas and schwannomas. Materials and methods: We enrolled 31 patients with skull base meningioma (n = 14) and schwannoma (n = 17) who underwent surgical resection. TBF was calculated from pcASL. Tissue sections were stained with CD34 to evaluate microvessel area (MVA). TBF and MVA ratio were compared between meningiomas and schwannomas using Mann–Whitney U-test. The correlations between MVA ratio and TBF were evaluated in each tumor by using single linear regression analysis and Spearman's rank correlation coefficients (r s ). Results: MVA ratio and TBF were significantly higher in meningioma than in schwannoma (both p < 0.01). Correlation analyses revealed significant positive correlations between MVA ratio and both mean and max TBF for meningiomas (r s = 0.89, 0.81, both p < 0.01). There was a weak positive correlation between MVA ratio and mean TBF for schwannomas (r s = 0.43, p = 0.04). However, no significant correlation was found between MVA ratio and max TBF for schwannoma. Conclusions: pcASL-MRI is useful for evaluating tumor perfusion even if the tumors are located in the skull base region. Moreover, pcASL-TBF was significantly higher in most meningiomas compared to schwannomas, which can help in the differential diagnosis of the 2 tumor types even without the use of contrast material

  16. Origins of intersubject variability of blood oxygenation level dependent and arterial spin labeling fMRI: implications for quantification of brain activity.

    Science.gov (United States)

    Gaxiola-Valdez, Ismael; Goodyear, Bradley G

    2012-12-01

    Accurate localization of brain activity using blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) has been challenged because of the large BOLD signal within distal veins. Arterial spin labeling (ASL) techniques offer greater sensitivity to the microvasculature but possess low temporal resolution and limited brain coverage. In this study, we show that the physiological origins of BOLD and ASL depend on whether percent change or statistical significance is being considered. For BOLD and ASL fMRI data collected during a simple unilateral hand movement task, we found that in the area of the contralateral motor cortex the centre of gravity (CoG) of the intersubject coefficient of variation (CV) of BOLD fMRI was near the brain surface for percent change in signal, whereas the CoG of the intersubject CV for Z-score was in close proximity of sites of brain activity for both BOLD and ASL. These findings suggest that intersubject variability of BOLD percent change is vascular in origin, whereas the origin of inter-subject variability of Z-score is neuronal for both BOLD and ASL. For longer duration tasks (12 s or greater), however, there was a significant correlation between BOLD and ASL percent change, which was not evident for short duration tasks (6 s). These findings suggest that analyses directly comparing percent change in BOLD signal between pre-defined regions of interest using short duration stimuli, as for example in event-related designs, may be heavily weighted by large-vessel responses rather than neuronal responses. Copyright © 2012 Elsevier Inc. All rights reserved.

  17. Comparative study of pulsed-continuous arterial spin labeling and dynamic susceptibility contrast imaging by histogram analysis in evaluation of glial tumors.

    Science.gov (United States)

    Arisawa, Atsuko; Watanabe, Yoshiyuki; Tanaka, Hisashi; Takahashi, Hiroto; Matsuo, Chisato; Fujiwara, Takuya; Fujiwara, Masahiro; Fujimoto, Yasunori; Tomiyama, Noriyuki

    2018-06-01

    Arterial spin labeling (ASL) is a non-invasive perfusion technique that may be an alternative to dynamic susceptibility contrast magnetic resonance imaging (DSC-MRI) for assessment of brain tumors. To our knowledge, there have been no reports on histogram analysis of ASL. The purpose of this study was to determine whether ASL is comparable with DSC-MRI in terms of differentiating high-grade and low-grade gliomas by evaluating the histogram analysis of cerebral blood flow (CBF) in the entire tumor. Thirty-four patients with pathologically proven glioma underwent ASL and DSC-MRI. High-signal areas on contrast-enhanced T 1 -weighted images or high-intensity areas on fluid-attenuated inversion recovery images were designated as the volumes of interest (VOIs). ASL-CBF, DSC-CBF, and DSC-cerebral blood volume maps were constructed and co-registered to the VOI. Perfusion histogram analyses of the whole VOI and statistical analyses were performed to compare the ASL and DSC images. There was no significant difference in the mean values for any of the histogram metrics in both of the low-grade gliomas (n = 15) and the high-grade gliomas (n = 19). Strong correlations were seen in the 75th percentile, mean, median, and standard deviation values between the ASL and DSC images. The area under the curve values tended to be greater for the DSC images than for the ASL images. DSC-MRI is superior to ASL for distinguishing high-grade from low-grade glioma. ASL could be an alternative evaluation method when DSC-MRI cannot be used, e.g., in patients with renal failure, those in whom repeated examination is required, and in children.

  18. Correlation between arterial spin labeling MRI and dynamic FDG on PET-MR in Alzheimer’s disease and non-Alzhiemer’s disease patients

    Energy Technology Data Exchange (ETDEWEB)

    Douglas, David; Goubran, Maged; Wilson, Eugene; Xu, Guofan; Tripathi, Pragya; Holley, Dawn; Chao, Steven; Wintermark, Max; Quon, Andrew; Zeineh, Michael; Vasanawala, Minal; Zaharchuk, Greg [Stanford University, California (United States)

    2015-05-18

    Regional hypoperfusion on Arterial Spin Labeling (ASL) MRI and corresponding regions of hypometabolism on FDG PET have been reported in Alzheimer’s Disease (AD). To our knowledge these correlations have not been studied under simultaneous acquisition. The purpose of this study is to investigate the correlation of ASL with FDG PET under simultaneous acquisition on PET-MR and to explore this correlation as a possible biomarker for AD. Dynamic FDG and ASL imaging was performed using a simultaneous TOF-enabled PET-MR scanner in 7 subjects without AD and 3 subjects with AD. Average age was 68±5 years. Automated atlas-based segmentation was performed using T2 MRI using the Talairach atlas. Quantitative analysis of ASL and FDG (delayed 45-75 minute scan) was performed in five regions using the pons as a reference region for both perfusion and metabolism. Statistical analyses included Spearman’s correlation and student’s t-test. Significant correlation of relative perfusion and metabolism was found in two of the five brain regions including the putamen (p = 0.018) and the hippocampus (p = 0.031). In addition, there was significant difference between the relative perfusion and metabolism of the thalamus (p = 0.04). No difference was seen between the AD and non-AD groups. Simultaneous PET-MR demonstrates a positive correlation of perfusion of ASL with metabolism on FDG PET in the hippocampus and putamen. The putamen correlation has previously been reported in the literature on a non-simultaneous ASL and FDG imaging. The thalamus was noted to have a difference in the relative perfusion and metabolism representing a perfusion-metabolism mismatch. Future studies should explore the correlation in additional brain regions and the meaning of perfusion-metabolism mismatches as potential imaging biomarkers for patients with and without AD.

  19. Non-invasive assessment of intratumoral vascularity using arterial spin labeling: A comparison to susceptibility-weighted imaging for the differentiation of primary cerebral lymphoma and glioblastoma

    International Nuclear Information System (INIS)

    Furtner, J.; Schöpf, V.; Preusser, M.; Asenbaum, U.; Woitek, R.; Wöhrer, A.; Hainfellner, J.A.; Wolfsberger, S.; Prayer, D.

    2014-01-01

    Using conventional MRI methods, the differentiation of primary cerebral lymphomas (PCNSL) and other primary brain tumors, such as glioblastomas, is difficult due to overlapping imaging characteristics. This study was designed to discriminate tumor entities using normalized vascular intratumoral signal intensity values (nVITS) obtained from pulsed arterial spin labeling (PASL), combined with intratumoral susceptibility signals (ITSS) from susceptibility-weighted imaging (SWI). Thirty consecutive patients with glioblastoma (n = 22) and PCNSL (n = 8), histologically classified according to the WHO brain tumor classification, were included. MRIs were acquired on a 3 T scanner, and included PASL and SWI sequences. nVITS was defined by the signal intensity ratio between the tumor and the contralateral normal brain tissue, as obtained by PASL images. ITSS was determined as intratumoral low signal intensity structures detected on SWI sequences and were divided into four different grades. Potential differences in the nVITS and ITSS between glioblastomas and PCNSLs were revealed using statistical testing. To determine sensitivity, specificity, and diagnostic accuracy, as well as an optimum cut-off value for the differentiation of PCNSL and glioblastoma, a receiver operating characteristic analysis was used. We found that nVITS (p = 0.011) and ITSS (p = 0.001) values were significantly higher in glioblastoma than in PCNSL. The optimal cut-off value for nVITS was 1.41 and 1.5 for ITSS, with a sensitivity, specificity, and accuracy of more than 95%. These findings indicate that nVITS values have a comparable diagnostic accuracy to ITSS values in differentiating glioblastoma and PCNSL, offering a completely non-invasive and fast assessment of tumoral vascularity in a clinical setting

  20. Non-invasive assessment of intratumoral vascularity using arterial spin labeling: A comparison to susceptibility-weighted imaging for the differentiation of primary cerebral lymphoma and glioblastoma.

    Science.gov (United States)

    Furtner, J; Schöpf, V; Preusser, M; Asenbaum, U; Woitek, R; Wöhrer, A; Hainfellner, J A; Wolfsberger, S; Prayer, D

    2014-05-01

    Using conventional MRI methods, the differentiation of primary cerebral lymphomas (PCNSL) and other primary brain tumors, such as glioblastomas, is difficult due to overlapping imaging characteristics. This study was designed to discriminate tumor entities using normalized vascular intratumoral signal intensity values (nVITS) obtained from pulsed arterial spin labeling (PASL), combined with intratumoral susceptibility signals (ITSS) from susceptibility-weighted imaging (SWI). Thirty consecutive patients with glioblastoma (n=22) and PCNSL (n=8), histologically classified according to the WHO brain tumor classification, were included. MRIs were acquired on a 3T scanner, and included PASL and SWI sequences. nVITS was defined by the signal intensity ratio between the tumor and the contralateral normal brain tissue, as obtained by PASL images. ITSS was determined as intratumoral low signal intensity structures detected on SWI sequences and were divided into four different grades. Potential differences in the nVITS and ITSS between glioblastomas and PCNSLs were revealed using statistical testing. To determine sensitivity, specificity, and diagnostic accuracy, as well as an optimum cut-off value for the differentiation of PCNSL and glioblastoma, a receiver operating characteristic analysis was used. We found that nVITS (p=0.011) and ITSS (p=0.001) values were significantly higher in glioblastoma than in PCNSL. The optimal cut-off value for nVITS was 1.41 and 1.5 for ITSS, with a sensitivity, specificity, and accuracy of more than 95%. These findings indicate that nVITS values have a comparable diagnostic accuracy to ITSS values in differentiating glioblastoma and PCNSL, offering a completely non-invasive and fast assessment of tumoral vascularity in a clinical setting. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

  1. Changes in cerebral blood flow after transjugular intrahepatic portosystemic shunt can help predict the development of hepatic encephalopathy: An arterial spin labeling MR study

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Gang [Department of Medical Imaging, Jinling Hospital, Clinical School of Medical College, Nanjing University, Nanjing, Jiangsu 210002 (China); College of Civil Aviation, Nanjing University of Aeronautics and Astronautics, Nanjing, Jiangsu 210016 (China); Zhang, Long Jiang [Department of Medical Imaging, Jinling Hospital, Clinical School of Medical College, Nanjing University, Nanjing, Jiangsu 210002 (China); Wang, Ze [Department of Psychiatry, Perelman School of Medicine, University of Pennsylvania, 3900 Chestnut St., Philadelphia, PA 19104 (United States); Qi, Rong Feng; Shi, Donghong [Department of Medical Imaging, Jinling Hospital, Clinical School of Medical College, Nanjing University, Nanjing, Jiangsu 210002 (China); Wang, Li [Department of Medical Imaging, Jinling Hospital, Clinical School of Medical College, Nanjing University, Nanjing, Jiangsu 210002 (China); College of Civil Aviation, Nanjing University of Aeronautics and Astronautics, Nanjing, Jiangsu 210016 (China); Fan, Xinxin [Research Institute of General Surgery, Jinling Hospital, Clinical School of Medical College, Nanjing University, Nanjing, Jiangsu 210002 (China); Lu, Guang Ming, E-mail: kevinzhanglongjiang@yahoo.com.cn [Department of Medical Imaging, Jinling Hospital, Clinical School of Medical College, Nanjing University, Nanjing, Jiangsu 210002 (China)

    2012-12-15

    Background and purpose: Cerebral blood flow (CBF) changes after transjugular intrahepatic portosystemic shunt (TIPS) are still unclear. Our aim is to assess the TIPS-induced CBF changes and their potential clinical significance using the arterial spin labeling (ASL) perfusion magnetic resonance imaging. Materials and methods: Nine cirrhotic patients underwent ASL 1–8 days before and 4–7 days after TIPS. CBF was calculated at each voxel and mean CBF values were computed in the whole brain, gray matter and white matter. Changes of CBFs before and after TIPS were compared by paired t-test. Results: Voxel-wise results showed CBF diffusely increased in patients after TIPS, but no region with significant decrease in CBF was found, nor was any significant mean CBF difference detected in the whole brain, gray matter and white matter. Six patients out of nine showed a global CBF increase of 9–39%; one patient presented a global CBF decrease of 6%; another two showed a global CBF decrease of 16% and 31% respectively. Follow-up studies showed that the two patients with greatly decreased global CBF suffered from multiple episodes of overt hepatic encephalopathy (OHE) after TIPS and one died of OHE. Conclusions: CBF derived from noninvasive ASL MRI could be used as a useful biomarker to predict the development of OHE through consecutively tracking CBF changes in patients with inserted TIPS. Increased CBFs in many cortical regions could be common effects of the TIPS procedure, while decreased global CBF following TIPS might indicate the development of OHE.

  2. Differentiation of residual/recurrent gliomas from postradiation necrosis with arterial spin labeling and diffusion tensor magnetic resonance imaging-derived metrics

    Energy Technology Data Exchange (ETDEWEB)

    Abdel Razek, Ahmed Abdel Khalek; El-Serougy, Lamiaa; Gaballa, Gada; Talaat, Mona [Mansoura Faculty of Medicine, Department of Diagnostic Radiology, Mansoura (Egypt); Abdelsalam, Mohamed [Mansoura Faculty of Medicine, Department of Neurology, Mansoura (Egypt)

    2018-02-15

    The aim of this study is to differentiate recurrent/residual gliomas from postradiation changes using arterial spin labeling (ASL) perfusion and diffusion tensor imaging (DTI)-derived metrics. Prospective study was conducted upon 42 patients with high-grade gliomas after radiotherapy only or prior to other therapies that underwent routine MR imaging, ASL, and DTI. The tumor blood flow (TBF), fractional anisotropy (FA), and mean diffusivity (MD) of the enhanced lesion and related edema were calculated. The lesion was categorized as recurrence/residual or postradiation changes. There was significant differences between residual/recurrent gliomas and postradiation changes of TBF (P = 0.001), FA (P = 0.001 and 0.04), and MD (P = 0.001) of enhanced lesion and related edema respectively. The area under the curve (AUC) of TBF of enhanced lesion and related edema used to differentiate residual/recurrent gliomas from postradiation changes were 0.95 and 0.93 and of MD were 0.95 and 0.81 and of FA were 0.81 and 0.695, respectively. Combined ASL and DTI metrics of the enhanced lesion revealed AUC of 0.98, accuracy of 95%, sensitivity of 93.8%, specificity of 95.8%, positive predictive value (PPV) of 93.8%, and negative predictive value (NPV) of 95.8%. Combined metrics of ASL and DTI of related edema revealed AUC of 0.97, accuracy of 92.5%, sensitivity of 93.8%, specificity of 91.7%, PPV of 88.2%, and NPV of 95.7. Combined ASL and DTI metrics of enhanced lesion and related edema are valuable noninvasive tools in differentiating residual/recurrent gliomas from postradiation changes. (orig.)

  3. Astrocytic tumour grading: a comparative study of three-dimensional pseudocontinuous arterial spin labelling, dynamic susceptibility contrast-enhanced perfusion-weighted imaging, and diffusion-weighted imaging

    International Nuclear Information System (INIS)

    Xiao, Hua-Feng; Chen, Zhi-Ye; Wang, Yu-Lin; Wang, Yan; Ma, Lin; Lou, Xin; Gui, Qiu-Ping; Shi, Kai-Ning; Zhou, Zhen-Yu; Zheng, Dan-Dan

    2015-01-01

    We hypothesized that three-dimensional pseudocontinuous arterial spin labelling (pCASL) may have similar efficacy in astrocytic tumour grading as dynamic susceptibility contrast-enhanced perfusion-weighted imaging (DSC-PWI), and the grading accuracy may be further improved when combined with apparent diffusion coefficient (ADC) values. Forty-three patients with astrocytic tumours were studied using diffusion weighted imaging (DWI), pCASL, and DSC-PWI. Histograms of ADC and normalized tumour cerebral blood flow values (nCBF on pCASL and nrCBF on DSC-PWI) were measured and analyzed. The mean 10 % ADC value was the DWI parameter that provided the best differentiation between low-grade astrocytoma (LGA) and high-grade astrocytoma (HGA). The nCBF and nrCBF (1.810 ± 0.979 and 2.070 ± 1.048) in LGA were significantly lower than those (4.505 ± 2.270 and 5.922 ± 2.630) in HGA. For differentiation between LGA and HGA, the cutoff values of 0.764 x 10 -3 mm 2 /s for mean 10 % ADC, 2.374 for nCBF, and 3.464 for nrCBF provided the optimal accuracy (74.4 %, 86.1 %, and 88.6 %, respectively). Combining the ADC values with nCBF or nrCBF could further improve the grading accuracy to 97.7 % or 95.3 %, respectively. pCASL is an alternative to DSC-PWI for astrocytic tumour grading. The combination of DWI and contrast-free pCASL offers a valuable choice in patients with risk factors. (orig.)

  4. Astrocytic tumour grading: a comparative study of three-dimensional pseudocontinuous arterial spin labelling, dynamic susceptibility contrast-enhanced perfusion-weighted imaging, and diffusion-weighted imaging

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Hua-Feng [302 Hospital of Chinese People' s Liberation Army, Department of Radiology, Beijing (China); Chen, Zhi-Ye; Wang, Yu-Lin; Wang, Yan; Ma, Lin [People' s Liberation Army General Hospital, Department of Radiology, Beijing (China); Lou, Xin [People' s Liberation Army General Hospital, Department of Radiology, Beijing (China); University of California, Department of Neurology, Los Angeles, CA (United States); Gui, Qiu-Ping [People' s Liberation Army General Hospital, Department of Pathology, Beijing (China); Shi, Kai-Ning; Zhou, Zhen-Yu; Zheng, Dan-Dan [General Electric Healthcare (China) Co., Ltd., Beijing; Wang, Danny J.J. [University of California, Department of Neurology, Los Angeles, CA (United States)

    2015-12-15

    We hypothesized that three-dimensional pseudocontinuous arterial spin labelling (pCASL) may have similar efficacy in astrocytic tumour grading as dynamic susceptibility contrast-enhanced perfusion-weighted imaging (DSC-PWI), and the grading accuracy may be further improved when combined with apparent diffusion coefficient (ADC) values. Forty-three patients with astrocytic tumours were studied using diffusion weighted imaging (DWI), pCASL, and DSC-PWI. Histograms of ADC and normalized tumour cerebral blood flow values (nCBF on pCASL and nrCBF on DSC-PWI) were measured and analyzed. The mean 10 % ADC value was the DWI parameter that provided the best differentiation between low-grade astrocytoma (LGA) and high-grade astrocytoma (HGA). The nCBF and nrCBF (1.810 ± 0.979 and 2.070 ± 1.048) in LGA were significantly lower than those (4.505 ± 2.270 and 5.922 ± 2.630) in HGA. For differentiation between LGA and HGA, the cutoff values of 0.764 x 10{sup -3} mm{sup 2}/s for mean 10 % ADC, 2.374 for nCBF, and 3.464 for nrCBF provided the optimal accuracy (74.4 %, 86.1 %, and 88.6 %, respectively). Combining the ADC values with nCBF or nrCBF could further improve the grading accuracy to 97.7 % or 95.3 %, respectively. pCASL is an alternative to DSC-PWI for astrocytic tumour grading. The combination of DWI and contrast-free pCASL offers a valuable choice in patients with risk factors. (orig.)

  5. Effects of resting state condition on reliability, trait specificity, and network connectivity of brain function measured with arterial spin labeled perfusion MRI.

    Science.gov (United States)

    Li, Zhengjun; Vidorreta, Marta; Katchmar, Natalie; Alsop, David C; Wolf, Daniel H; Detre, John A

    2018-06-01

    Resting state fMRI (rs-fMRI) provides imaging biomarkers of task-independent brain function that can be associated with clinical variables or modulated by interventions such as behavioral training or pharmacological manipulations. These biomarkers include time-averaged regional brain function as manifested by regional cerebral blood flow (CBF) measured using arterial spin labeled (ASL) perfusion MRI and correlated temporal fluctuations of function across brain networks with either ASL or blood oxygenation level dependent (BOLD) fMRI. Resting-state studies are typically carried out using just one of several prescribed state conditions such as eyes closed (EC), eyes open (EO), or visual fixation on a cross-hair (FIX), which may affect the reliability and specificity of rs-fMRI. In this study, we collected test-retest ASL MRI data during 4 resting-state task conditions: EC, EO, FIX and PVT (low-frequency psychomotor vigilance task), and examined the effects of these task conditions on reliability and reproducibility as well as trait specificity of regional brain function. We also acquired resting-state BOLD fMRI under FIX and compared the network connectivity reliabilities between the four ASL conditions and the BOLD FIX condition. For resting-state ASL data, EC provided the highest CBF reliability, reproducibility, trait specificity, and network connectivity reliability, followed by EO, while FIX was lowest on all of these measures. PVT demonstrated lower CBF reliability, reproducibility and trait specificity than EO and EC. Overall network connectivity reliability was comparable between ASL and BOLD. Our findings confirm ASL CBF as a reliable, stable, and consistent measure of resting-state regional brain function and support the use of EC or EO over FIX and PVT as the resting-state condition. Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

  6. Non-invasive assessment of intratumoral vascularity using arterial spin labeling: A comparison to susceptibility-weighted imaging for the differentiation of primary cerebral lymphoma and glioblastoma

    Energy Technology Data Exchange (ETDEWEB)

    Furtner, J., E-mail: julia.furtner@meduniwien.ac.at [Department of Biomedical Imaging und Image-guided Therapy, Medical University of Vienna (Austria); Comprehensive Cancer Center-Central Nervous System Tumors Unit (CCC-CNS), Medical University of Vienna (Austria); Schöpf, V., E-mail: veronika.schoepf@meduniwien.ac.at [Department of Biomedical Imaging und Image-guided Therapy, Medical University of Vienna (Austria); Preusser, M., E-mail: matthias.preusser@meduniwien.ac.at [Department of Medicine I, Division of Oncology, Medical University of Vienna (Austria); Comprehensive Cancer Center-Central Nervous System Tumors Unit (CCC-CNS), Medical University of Vienna (Austria); Asenbaum, U., E-mail: ulrika.asenbaum@meduniwien.ac.at [Department of Biomedical Imaging und Image-guided Therapy, Medical University of Vienna (Austria); Woitek, R., E-mail: ramona.woitek@meduniwien.ac.at [Department of Biomedical Imaging und Image-guided Therapy, Medical University of Vienna (Austria); Wöhrer, A., E-mail: adelheid.woehrer@meduniwien.ac.at [Institute of Neurology, Medical University of Vienna (Austria); Comprehensive Cancer Center-Central Nervous System Tumors Unit (CCC-CNS), Medical University of Vienna (Austria); Hainfellner, J.A., E-mail: johannes.hainfellner@meduniwien.ac.at [Institute of Neurology, Medical University of Vienna (Austria); Comprehensive Cancer Center-Central Nervous System Tumors Unit (CCC-CNS), Medical University of Vienna (Austria); Wolfsberger, S., E-mail: stefan.wolfsberger@meduniwien.ac.at [Department of Neurosurgery, Medical University of Vienna (Austria); Comprehensive Cancer Center-Central Nervous System Tumors Unit (CCC-CNS), Medical University of Vienna (Austria); Prayer, D., E-mail: daniela.prayer@meduniwien.ac.at [Department of Biomedical Imaging und Image-guided Therapy, Medical University of Vienna (Austria); Comprehensive Cancer Center-Central Nervous System Tumors Unit (CCC-CNS), Medical University of Vienna (Austria)

    2014-05-15

    Using conventional MRI methods, the differentiation of primary cerebral lymphomas (PCNSL) and other primary brain tumors, such as glioblastomas, is difficult due to overlapping imaging characteristics. This study was designed to discriminate tumor entities using normalized vascular intratumoral signal intensity values (nVITS) obtained from pulsed arterial spin labeling (PASL), combined with intratumoral susceptibility signals (ITSS) from susceptibility-weighted imaging (SWI). Thirty consecutive patients with glioblastoma (n = 22) and PCNSL (n = 8), histologically classified according to the WHO brain tumor classification, were included. MRIs were acquired on a 3 T scanner, and included PASL and SWI sequences. nVITS was defined by the signal intensity ratio between the tumor and the contralateral normal brain tissue, as obtained by PASL images. ITSS was determined as intratumoral low signal intensity structures detected on SWI sequences and were divided into four different grades. Potential differences in the nVITS and ITSS between glioblastomas and PCNSLs were revealed using statistical testing. To determine sensitivity, specificity, and diagnostic accuracy, as well as an optimum cut-off value for the differentiation of PCNSL and glioblastoma, a receiver operating characteristic analysis was used. We found that nVITS (p = 0.011) and ITSS (p = 0.001) values were significantly higher in glioblastoma than in PCNSL. The optimal cut-off value for nVITS was 1.41 and 1.5 for ITSS, with a sensitivity, specificity, and accuracy of more than 95%. These findings indicate that nVITS values have a comparable diagnostic accuracy to ITSS values in differentiating glioblastoma and PCNSL, offering a completely non-invasive and fast assessment of tumoral vascularity in a clinical setting.

  7. Effects of acute levodopa challenge on resting cerebral blood flow in Parkinson’s Disease patients assessed using pseudo-continuous arterial spin labeling

    Directory of Open Access Journals (Sweden)

    Yufen Chen

    2015-11-01

    Full Text Available Introduction. Levodopa is the gold-standard for treatment of Parkinson’s disease (PD related motor symptoms. In this study, we used pseudo-continuous arterial spin labeling (pCASL to quantify changes in cerebral blood flow (CBF after acute oral administration of levodopa in PD patients.Materials and Methods. Thirteen patients (3 females, age 66.2 ± 8.7 years with moderately advanced PD (Hoehn and Yahr stage >2 (median 2.5, disease duration >3 years were scanned on a 3T Siemens MR scanner before and after oral levodopa administration. Statistical parametric mapping was used to detect drug-induced changes in CBF and its correlation to clinical severity scales. Images were normalized and flipped in order to examine effects on the more affected (left and less affected (right cerebral hemispheres across the cohort.Results. Levodopa did not change global CBF but increased regional CBF in dorsal midbrain, precuneus/cuneus, more affected inferior frontal pars opercularis and triangularis, bilateral pre- and postcentral gyri, more affected inferior parietal areas, as well as less affected putamen/globus pallidus by 27–74% (p < 0.05, FWE corrected for multiple comparisons. CBF change was negatively correlated with improvement in bradykinesia UPDRS-III subscore in the more affected precentral gyrus, and total predrug UPDRS-III score in the mid-cingulate region. Drug-induced CBF change in a widespread network of regions including parietal and postcentral areas was also negatively correlated with the predrug rigidity UPDRS-III subscore.Conclusion. These findings are in line with prior reports of abnormal activity in the nigrostriatal pathway of PD patients and demonstrate the feasibility of pCASL as a neuroimaging tool for investigating in vivo physiological effects of acute drug administration in PD.

  8. Application of EPR spectroscopy to the examination of pro-oxidant activity of coffee.

    Science.gov (United States)

    Krakowian, Daniel; Skiba, Dominik; Kudelski, Adam; Pilawa, Barbara; Ramos, Paweł; Adamczyk, Jakub; Pawłowska-Góral, Katarzyna

    2014-05-15

    Free radicals present in coffee may be responsible for exerting toxic effects on an organism. The objectives of this work were to compare free radicals properties and concentrations in different commercially available coffees, in solid and liquid states, and to determine the effect of roasting on the formation of free radicals in coffee beans of various origins. The free radicals content of 15 commercially available coffees (solid and liquid) was compared and the impact of processing examined using electron paramagnetic resonance (EPR) spectroscopy at X-band (9.3 GHz). First derivative EPR spectra were measured at microwave power in the range of 0.7-70 mW. The following parameters were calculated for EPR spectra: amplitude (A), integral intensity (I), and line-width (ΔBpp); g-Factor was obtained from resonance condition. Our study showed that free radicals exist in green coffee beans (10(16) spin/g), roasted coffee beans (10(18) spin/g), and in commercially available coffee (10(17)-10(18) spin/g). Free radical concentrations were higher in solid ground coffee than in instant or lyophilised coffee. Continuous microwave saturation indicated homogeneous broadening of EPR lines from solid and liquid commercial coffee samples as well as green and roasted coffee beans. Slow spin-lattice relaxation processes were found to be present in all coffee samples tested, solid and liquid commercial coffees as well as green and roasted coffee beans. Higher free radicals concentrations were obtained for both the green and roasted at 240 °C coffee beans from Peru compared with those originating from Ethiopia, Brazil, India, or Colombia. Moreover, more free radicals occurred in Arabica coffee beans roasted at 240 °C than Robusta. EPR spectroscopy is a useful method of examining free radicals in different types of coffee. Copyright © 2013 Elsevier Ltd. All rights reserved.

  9. Pulsed EPR for studying silver clusters

    International Nuclear Information System (INIS)

    Michalik, J.; Wasowicz, T.; Sadlo, J.; Reijerse, E.J.; Kevan, L.

    1996-01-01

    The cationic silver clusters of different nuclearity have been produced by radiolysis of zeolite A and SAPO molecular sieves containing Ag + as exchangeable cations. The pulsed EPR spectroscopy has been applied for studying the local environment of silver cluster in order to understand the mechanism of cluster formation and stabilization. the electron spin echo modulation (ESEM) results on Ag 6 n+ cluster in dehydration zeolite A indicate that the hexameric silver is stabilized only in sodalite cages which are surrounded by α-cages containing no water molecules. Trimeric silver clusters formed in hydrated A zeolites strongly interact with water, thus the paramagnetic center can be considered as a cluster-water adduct. In SAPO-molecular sieves, silver clusters are formed only in the presence of adsorbed alcohol molecules. From ESEM it is determined that Ag 4 n+ in SAPO-42 is stabilized in α cages, where it is directly coordinated by two methanol molecules. Dimeric silver, Ag 2 + in SAPO-5 and SAPO-11 is located in 6-ring channels and interacts with three CH 3 OH molecules, each in different 10 ring or 12 ring channels. The differences of Ag 2 + stability in SAPO-5 and SAPO-11 are also discussed. (Author)

  10. EPR dosimetry of irradiated human teeth

    International Nuclear Information System (INIS)

    Rodas Duran, J.E.; Panzeri, H.; Mascarenhas, S.

    1985-01-01

    The determination of the absorbed radiation dose in man may be made by Electron Paramagnetic Resonance (EPR) spectroscopy of dental enamel. We analysed the EPR signals for dental enamel submitted to gamma radiation in doses between 1 Gy and 25 Gy. We conclude that independent of the type of tooth analysed there exists a linear relation between the EPR signals and the absorbed doses. These studies were extended to enamel irradiated with gamma rays and with X rays in doses between 0.1 Gy and 0.6 Gy. The graph of the intensity of the EPR signals as a function of the dose has a slope of 0.22. This calibration may be used to calculate the absorbed dose for humans from a measurement of the EPR signal from small samples of enamel taken from any permanent tooth. Finally we comment on some EPR studies of effects of radiation of milk teeth. (author)

  11. Spectroscopic Evidence for Covalent Binding of Sulfadiazine to Natural Soils via 1,4-nucleophilic addition (Michael Type Addition) studied by Spin Labeling ESR

    Science.gov (United States)

    Aleksandrova, Olga

    2015-04-01

    Among different classes of veterinary pharmaceuticals, Sulfadiazine (SDZ) is widely used in animal husbandry. Its residues were detected in different environmental compartments. However, soil is a hot spot for SDZ as it receives a large portion of excreted compounds through the application of manure during soil fertilization. Ample studies on the fate of SDZ in soils showed that a large portion forms nonextractable residues (NER) along with transformation products and a low mineralization (Mueller et al., 2013). A common observation was an initially fast formation of NER up to 10% of the applied amount promptly after the application of SDZ to soil, and this portion increased up to 50% within a few days (Mueller et al., 2013; Nowak et al., 2011). A common finding for SDZ, as for other sulfonamides, was biphasic kinetics of the formation of NER, which was attributed to the occurrence of two reaction processes: a rapid, often reversible process and a slower, irreversible process (Weber et al., 1996). A single-phase reaction process was also established under anaerobic treatment (Gulkowska et al., 2014). A major focus of this work is to elucidate a reaction mechanism of covalent binding of SDZ to soil that is currently required to estimate a risk of NER formed by SDZ in soils for human health. Taking into account a key role of the amine functional groups of SDZ on its reactivity in soil, nitroxide radicals with the sewed aromatic or aliphatic amines labeled soil samples and then, were investigated by means of ESR spectroscopy. 2,5,5-Trimethyl-2-(3-aminophenyl)pyrrolidin-1-yloxy and 4-amino-2,2,6,6-Tetramethylpiperidin-1-oxyl modeled decomposition products of SDZ with the aromatic and aliphatic amines, respectively. The application of the defined combination of both spin labels (SL) to different soils well simulated a change of a paramagnetic signal of soil organic radicals interacted with SDZ. After their application to soil, SL were found in soil sites characterized

  12. Pharmaceutical applications of in vivo EPR

    International Nuclear Information System (INIS)

    Maeder, K.

    1998-01-01

    The aim of this article is to discuss the applications of in vivo EPR in the field of pharmacy. In addition to direct detection of free radical metabolites and measurement of oxygen, EPR can be used to characterize the mechanisms of drug release from biodegradable polymers. Unique information about drug concentration, the microenvironment (viscosity, polarity, pH) and biodistribution (by localized measurement or EPR Imaging) can be obtained. (author)

  13. EPR-based material modelling of soils

    Science.gov (United States)

    Faramarzi, Asaad; Alani, Amir M.

    2013-04-01

    In the past few decades, as a result of the rapid developments in computational software and hardware, alternative computer aided pattern recognition approaches have been introduced to modelling many engineering problems, including constitutive modelling of materials. The main idea behind pattern recognition systems is that they learn adaptively from experience and extract various discriminants, each appropriate for its purpose. In this work an approach is presented for developing material models for soils based on evolutionary polynomial regression (EPR). EPR is a recently developed hybrid data mining technique that searches for structured mathematical equations (representing the behaviour of a system) using genetic algorithm and the least squares method. Stress-strain data from triaxial tests are used to train and develop EPR-based material models for soil. The developed models are compared with some of the well-known conventional material models and it is shown that EPR-based models can provide a better prediction for the behaviour of soils. The main benefits of using EPR-based material models are that it provides a unified approach to constitutive modelling of all materials (i.e., all aspects of material behaviour can be implemented within a unified environment of an EPR model); it does not require any arbitrary choice of constitutive (mathematical) models. In EPR-based material models there are no material parameters to be identified. As the model is trained directly from experimental data therefore, EPR-based material models are the shortest route from experimental research (data) to numerical modelling. Another advantage of EPR-based constitutive model is that as more experimental data become available, the quality of the EPR prediction can be improved by learning from the additional data, and therefore, the EPR model can become more effective and robust. The developed EPR-based material models can be incorporated in finite element (FE) analysis.

  14. Spin dynamics of paramagnetic centers with anisotropic g tensor and spin of 1/2

    Science.gov (United States)

    Maryasov, Alexander G.; Bowman, Michael K.

    2012-08-01

    The influence of g tensor anisotropy on spin dynamics of paramagnetic centers having real or effective spin of 1/2 is studied. The g anisotropy affects both the excitation and the detection of EPR signals, producing noticeable differences between conventional continuous-wave (cw) EPR and pulsed EPR spectra. The magnitudes and directions of the spin and magnetic moment vectors are generally not proportional to each other, but are related to each other through the g tensor. The equilibrium magnetic moment direction is generally parallel to neither the magnetic field nor the spin quantization axis due to the g anisotropy. After excitation with short microwave pulses, the spin vector precesses around its quantization axis, in a plane that is generally not perpendicular to the applied magnetic field. Paradoxically, the magnetic moment vector precesses around its equilibrium direction in a plane exactly perpendicular to the external magnetic field. In the general case, the oscillating part of the magnetic moment is elliptically polarized and the direction of precession is determined by the sign of the g tensor determinant (g tensor signature). Conventional pulsed and cw EPR spectrometers do not allow determination of the g tensor signature or the ellipticity of the magnetic moment trajectory. It is generally impossible to set a uniform spin turning angle for simple pulses in an unoriented or 'powder' sample when g tensor anisotropy is significant.

  15. Electron paramagnetic resonance (EPR) in medical dosimetry

    International Nuclear Information System (INIS)

    Schauer, David A.; Iwasaki, Akinori; Romanyukha, Alexander A.; Swartz, Harold M.; Onori, Sandro

    2006-01-01

    This paper describes the fundamentals of electron paramagnetic resonance (EPR) and its application to retrospective measurements of clinically significant doses of ionizing radiation. X-band is the most widely used in EPR dosimetry because it represents a good compromise between sensitivity, sample size and water content in the sample. Higher frequency bands (e.g., W and Q) provide higher sensitivity, but they are also greatly influenced by water content. L and S bands can be used for EPR measurements in samples with high water content but they are less sensitive than X-band. Quality control for therapeutic radiation facilities using X-band EPR spectrometry of alanine is also presented

  16. EFFECT OF CADMIUM(II) ON FREE RADICALS IN DOPA-MELANIN TESTED BY EPR SPECTROSCOPY.

    Science.gov (United States)

    Zdybel, Magdalena; Pilawa, Barbara; Chodurek, Ewa

    2015-01-01

    Electron paramagnetic resonance (EPR) spectroscopy may be applied to examine interactions of melanin with metal ions and drugs. In this work EPR method was used to examination of changes in free radical system of DOPA-melanin--the model eumelanin after complexing with diamagnetic cadmium(II) ions. Cadmium(II) may affect free radicals in melanin and drugs binding by this polymer, so the knowledge of modification of properties and free radical concentration in melanin is important to pharmacy. The effect of cadmium(II) in different concentrations on free radicals in DOPA-melanin was determined. EPR spectra of DOPA-melanin, and DOPA-melanin complexes with cadmium(II) were measured by an X-band (9.3 GHz) EPR spectrometer produced by Radiopan (Poznań, Poland) and the Rapid Scan Unit from Jagmar (Krak6w, Poland). The DOPA (3,4-dihydroxyphenylalanine) to metal ions molar ratios in the reaction mixtures were 2:1, 1:1, and 1: 2. High concentrations of o-semiquinone (g ~2.0040) free radicals (~10(21)-10(22) spin/g) characterize DOPA-melanin and its complexes with cadmium(II). Formation of melanin complexes with cadmium(II) increase free radical concentration in DOPA-melanin. The highest free radical concentration was obtained for DOPA-melanin-cadmium(II) (1:1) complexes. Broad EPR lines with linewidths: 0.37-0.73 mT, were measured. Linewidths increase after binding of cadmium(II) to melanin. Changes of integral intensities and linewidths with increasing microwave power indicate the homogeneous broadening of EPR lines, independently on the metal ion concentration. Slow spin-lattice relaxation processes existed in all the tested samples, their EPR lines saturated at low microwave powers. Cadmium(II) causes fastening of spin-lattice relaxation processes in DOPA-melanin. The EPR results bring to light the effect of cadmium(II) on free radicals in melanin, and probably as the consequence on drug binding to eumelanin.

  17. EPR and optical absorption studies of Cr3+ ions in potassium sodium dl-tartrate tetrahydrate

    International Nuclear Information System (INIS)

    Kripal, Ram; Singh, Pragya; Shukla, Santwana

    2011-01-01

    EPR spectra of Cr 3+ ions doped in potassium sodium dl-tartrate tetrahydrate single crystals are recorded at 77 K. The spin Hamiltonian and zero field parameters g, |D| and |E| are measured from the resonance lines obtained at various rotations of the magnetic field. The values obtained are: g x =1.9257±0.0002, g y =1.9720±0.0002, g z =2.0102±0.0002, |D|=313±2 (x10 -4 ) cm -1 and |E|=101±2 (x10 -4 ) cm -1 . From the results of EPR study, the site symmetry of Cr 3+ ion in the crystal is discussed. The optical absorption at room temperature is also studied. From the observed band positions, the crystal field splitting parameter (D q ) and the Racah inter-electronic repulsion parameters (B and C) are evaluated. The bonding parameters are obtained by correlating optical and EPR data and the nature of bonding in the crystal is discussed. -- Research Highlights: → EPR spectra of Cr 3+ ions doped in potassium sodium dl-tartrate tetrahydrate single crystals are done at 77 K. → The spin Hamiltonian and zero field parameters g, |D| and |E| are measured. From the results of EPR study, the site symmetry of Cr 3+ ion in the crystal is discussed. → The optical absorption at room temperature is also studied and the crystal field splitting parameter (D q ) as well as the Racah inter-electronic repulsion parameters (B and C) is evaluated. → The bonding parameters are obtained by correlating optical and EPR data and the nature of bonding in the crystal is discussed.

  18. EPR and optical study of Mn{sup 2+} doped monohydrated dipotassium stannic chloride

    Energy Technology Data Exchange (ETDEWEB)

    Kripal, Ram, E-mail: ram_kripal2001@rediffmail.com; Singh, Manju

    2014-11-15

    Highlights: • EPR study of Mn{sup 2+}: DPSC crystal is done at room temperature. • The spin Hamiltonian parameters for two Mn{sup 2+} sites are determined. • The optical absorption study is also done. • The nature of metal–ligand bonding is discussed on the basis of EPR and optical data. • Theoretical zero-field splitting parameters match well with the experimental values. - Abstract: Electron paramagnetic resonance (EPR) study at room temperature (RT) is used to investigate the property of Mn{sup 2+} doped monohydrated dipotassium stannic chloride (K{sub 2}SnCl{sub 4}⋅H{sub 2}O) single crystal. EPR spectra show that there exist two substitutional sites, the spin Hamiltonian parameters for which are determined. The optical absorption study is also done at room temperature in the wavelength range 195–1100 nm. The observed bands are assigned as transitions from {sup 6}A{sub 1g}(S) ground state to various excited states. These bands are fitted with four parameters, namely Racah inter-electronic repulsion parameters B = 792 cm{sup −1}, C = 2278 cm{sup −1}; cubic crystal field splitting parameter Dq = 700 cm{sup −1} and Trees correction α = 76 cm{sup −1}. The nature of metal–ligand bonding is discussed on the basis of EPR and optical data. Superposition model (SPM) is used to find out the crystal field (CF) parameters and the perturbation formulae are used to obtain zero-field splitting (ZFS) parameters. Theoretically calculated ZFS parameters match well with the experimental values obtained from EPR study.

  19. Stern-Gerlach experiment, electron spin and intermediate quantum mechanics

    Energy Technology Data Exchange (ETDEWEB)

    Mackintosh, A.R. (Copenhagen Univ. (Denmark). H.C. Oersted Inst.)

    1983-01-01

    The paper deals with the theory of electron spin. The Stern-Gerlach experiment, the anticommutation relations and the properties of spin operators are discussed. The Pauli theory, Dirac transformation theory, the double Stern-Gerlach experiment, the EPR paradox and Bell's inequality are also covered.

  20. Rabi oscillation and electron-spin-echo envelope modulation of the photoexcited triplet spin system in silicon

    Science.gov (United States)

    Akhtar, Waseem; Sekiguchi, Takeharu; Itahashi, Tatsumasa; Filidou, Vasileia; Morton, John J. L.; Vlasenko, Leonid; Itoh, Kohei M.

    2012-09-01

    We report on a pulsed electron paramagnetic resonance (EPR) study of the photoexcited triplet state (S=1) of oxygen-vacancy centers in silicon. Rabi oscillations between the triplet sublevels are observed using coherent manipulation with a resonant microwave pulse. The Hahn echo and stimulated echo decay profiles are superimposed with strong modulations known as electron-spin-echo envelope modulation (ESEEM). The ESEEM spectra reveal a weak but anisotropic hyperfine coupling between the triplet electron spin and a 29Si nuclear spin (I=1/2) residing at a nearby lattice site, that cannot be resolved in conventional field-swept EPR spectra.

  1. EPR project construction cost control

    International Nuclear Information System (INIS)

    Duflo, D.; Pouget-Abadie, X.; Dufour, A.; Kauffmann, G.

    2001-01-01

    The EPR project is now managed by EDF in cooperation with the German Utilities. The main engineering activities for this period are related to the preparation of construction project management, deepening of some safety issues, definition of the project technical reference. The EPR project concerns the so-called reference unit, that is an isolated first-off unit, with unit electrical power of about 1500 MW. The construction costs evaluated are those of the nuclear island, the conventional island, site facilities, installation work and the administrative buildings. The EPR project construction cost evaluation method applies to all the equipment installed and commissioned. It requires the availability of a preliminary project detailed enough to identify the bill of quantities. To these quantities are then assigned updated unit prices that are based either on cost bases for similar and recent facilities or taken from request for quotation for similar equipment or result from gains due to contractual conditions benefiting from simplifications in the functional and technical specifications. The input and output data are managed in a model that respects the breakdown on which the evaluation method is based. The structural organization of this method reflects a functional breakdown on the one hand (nuclear island, conventional island, common site elements) and on the other hand a breakdown according to equipment or activity (civil engineering, mechanics, electricity, instrumentation and control). This paper discusses the principle and the method of construction cost evaluation carried out, the cost data base and input and output parameters as well as results and oncoming cost analysis tasks. (author)

  2. EPR Dosimetry in Irradiated Fingernails

    International Nuclear Information System (INIS)

    Spinella, M.R.; Dubner, D.L.; Bof, E.

    2010-01-01

    The Electron Paramagnetic Resonance (EPR) is being transformed in a complementary tool of biologically-based methods for evaluation of dose after accidental radiation exposure. Many efforts are being carried out in laboratories to evaluate the performance of different materials for its use in EPR doses measurements and for improving the current methods for spectrum analysis and calibration curves determinations. In our country the EPR techniques have been used in different areas with dosimetric (alanine) and non dosimetric purposes. Now we are performing the first studies to obtain properly dose response curves to be used for accidental dose assessments through irradiated fingernails. It is by now well known that the fingernails present two types of signals, a background one (BKS), originated in elastic and inelastic mechanical deformations and the radio induced one (RIS), object of interest (I). In this work we will present some of the previous studies performed to characterize the fingernail samples and we analyse the additive dose method for data obtained employing the technique of the substraction of the spectrum recorded at two different microwave powers in order to reduce the BKS signal. Fingernail samples collected from different donors were treated by soaking in water during 10 min and 5 min drying on paper towel and the BKS signals were studied previously its irradiation. The statistical analysis (R statistics) show a distribution with a Standard Deviation of 24% respects to its media. During these studies we also conserved in freezer for more than 6 months irradiated fingernails that, were periodically measured and the statistical analysis of the peak to peak amplitude show a normal distribution through the Quantile correlation test with a SD 11% respected to its median. (authors)

  3. EPR of free radicals in solids II trends in methods and applications

    CERN Document Server

    Lund, Anders; Lund, Anders

    2012-01-01

    EPR of Free Radicals in Solids: Trends in Methods and Applications, 2nd ed. presents a critical two volume review of the methods and applications of EPR (ESR) for the study of free radical processes in solids. Emphasis is on the progress made in the developments in EPR technology, in the application of sophisticated matrix isolation techniques and in the advancement in quantitative EPR that have occurred since the 1st edition was published. Improvements have been made also at theoretical level, with the development of methods based on first principles and their application to the calculation of magnetic properties as well as in spectral simulations. EPR of Free Radicals in Solids II focuses on the trends in applications of experimental and theoretical methods to extract structural and dynamical properties of radicals and spin probes in solid matrices by continuous wave (CW) and pulsed techniques in nine chapters written by experts in the field. It examines the studies involving radiation- and photo-induced in...

  4. Differentiating primary CNS lymphoma from glioblastoma multiforme: assessment using arterial spin labeling, diffusion-weighted imaging, and {sup 18}F-fluorodeoxyglucose positron emission tomography

    Energy Technology Data Exchange (ETDEWEB)

    Yamashita, Koji; Yoshiura, Takashi; Hiwatashi, Akio; Togao, Osamu; Abe, Koichiro; Kikuchi, Kazufumi; Maruoka, Yasuhiro; Honda, Hiroshi [Kyushu University, Department of Clinical Radiology, Graduate School of Medical Sciences, Fukuoka (Japan); Yoshimoto, Koji; Mizoguchi, Masahiro [Kyushu University, Department of Neurosurgery, Graduate School of Medical Sciences, Fukuoka (Japan); Suzuki, Satoshi O.; Iwaki, Toru [Kyushu University, Department of Neuropathology, Graduate School of Medical Sciences, Fukuoka (Japan)

    2013-02-15

    Our purpose was to evaluate the diagnostic performance of arterial spin labeling (ASL) perfusion imaging, diffusion-weighted imaging (DWI), and {sup 18}F-fluorodeoxyglucose positron emission tomography (FDG-PET) in differentiating primary central nervous system lymphomas (PCNSLs) from glioblastoma multiformes (GBMs). Fifty-six patients including 19 with PCNSL and 37 with GBM were retrospectively studied. From the ASL data, an absolute tumor blood flow (aTBF) and a relative tumor blood flow (rTBF) were obtained within the enhancing portion of each tumor. In addition, the minimum apparent diffusion coefficient (ADCmin) and the maximum standard uptake value (SUVmax) were obtained from DWI and FDG-PET data, respectively. Each of the four parameters was compared between PCNSLs and GBMs using Kruskal-Wallis test. The performance in discriminating between PCNSLs and GBMs was evaluated using the receiver-operating characteristics analysis. Area-under-the-curve (AUC) values were compared among the four parameters using a nonparametric method. The aTBF, rTBF, and ADCmin were significantly higher in GBMs (mean aTBF {+-} SD = 91.6 {+-} 56.0 mL/100 g/min, mean rTBF {+-} SD = 2.61 {+-} 1.61, mean ADCmin {+-} SD = 0.78 {+-} 0.19 x 10{sup -3} mm{sup 2}/s) than in PCNSLs (mean aTBF {+-} SD = 37.3 {+-} 10.5 mL/100 g/min, mean rTBF {+-} SD = 1.24 {+-} 0.37, mean ADCmin {+-} SD = 0.61 {+-} 0.13 x 10{sup -3} mm{sup 2}/s) (p < 0.005, respectively). In addition, SUVmax was significantly lower in GBMs (mean {+-} SD = 13.1 {+-} 6.34) than in PCNSLs (mean {+-} SD = 22.5 {+-} 7.83) (p < 0.005). The AUC for aTBF (0.888) was higher than those for rTBF (0.810), ADCmin (0.768), and SUVmax (0.848), although their difference was not statistically significant. ASL perfusion imaging is useful for differentiating PCNSLs from GBMs as well as DWI and FDG-PET. (orig.)

  5. Grading and outcome prediction of pediatric diffuse astrocytic tumors with diffusion and arterial spin labeling perfusion MRI in comparison with 18F-DOPA PET

    Energy Technology Data Exchange (ETDEWEB)

    Morana, Giovanni; Tortora, Domenico; Severino, Mariasavina; Rossi, Andrea [Istituto Giannina Gaslini, Neuroradiology Unit, Genoa (Italy); Piccardo, Arnoldo; Cabria, Manlio [Ente Ospedaliero Ospedali Galliera, Nuclear Medicine Unit, Genoa (Italy); Puntoni, Matteo [Ente Ospedaliero Ospedali Galliera, Clinical Trial Unit, Scientific Directorate, Genoa (Italy); Nozza, Paolo [Istituto Giannina Gaslini, Pathology Unit, Genoa (Italy); Ravegnani, Marcello; Consales, Alessandro; Mascelli, Samantha; Raso, Alessandro [Istituto Giannina Gaslini, Neurosurgery Unit, Genoa (Italy); Verrico, Antonio; Milanaccio, Claudia [Istituto Giannina Gaslini, Neuro-oncology Unit, Genoa (Italy)

    2017-11-15

    The aim of this study was to investigate MRI-derived diffusion weighted imaging (DWI) and arterial spin labeling (ASL) perfusion imaging in comparison with {sup 18}F-dihydroxyphenylalanine (DOPA) PET with respect to diagnostic performance in tumor grading and outcome prediction in pediatric patients with diffuse astrocytic tumors (DAT). We retrospectively analyzed 26 children with histologically proven treatment naive low and high grade DAT who underwent ASL and DWI performed within 2 weeks of {sup 18}F-DOPA PET. Relative ASL-derived cerebral blood flow max (rCBF max) and DWI-derived minimum apparent diffusion coefficient (rADC min) were compared with {sup 18}F-DOPA uptake tumor/normal tissue (T/N) and tumor/striatum (T/S) ratios, and correlated with World Health Organization (WHO) tumor grade and progression-free survival (PFS). Statistics included Pearson's chi-square and Mann-Whitney U tests, Spearman's rank correlation, receiver operating characteristic (ROC) analysis, discriminant function analysis (DFA), Kaplan-Meier survival curve, and Cox analysis. A significant correlation was demonstrated between rCBF max, rADC min, and {sup 18}F-DOPA PET data (p < 0.001). Significant differences in terms of rCBF max, rADC min, and {sup 18}F-DOPA uptake were found between low- and high-grade DAT (p ≤ 0.001). ROC analysis and DFA demonstrated that T/S and T/N values were the best parameters for predicting tumor progression (AUC 0.93, p < 0.001). On univariate analysis, all diagnostic tools correlated with PFS (p ≤ 0.001); however, on multivariate analysis, only {sup 18}F-DOPA uptake remained significantly associated with outcome (p ≤ 0.03), while a trend emerged for rCBF max (p = 0.09) and rADC min (p = 0.08). The combination of MRI and PET data increased the predictive power for prognosticating tumor progression (AUC 0.97, p < 0.001). DWI, ASL and {sup 18}F-DOPA PET provide useful complementary information for pediatric DAT grading. {sup 18}F-DOPA uptake

  6. Cerebral blood flow measured by arterial-spin labeling MRI: A useful biomarker for characterization of minimal hepatic encephalopathy in patients with cirrhosis

    International Nuclear Information System (INIS)

    Zheng, Gang; Zhang, Long Jiang; Zhong, Jianhui; Wang, Ze; Qi, Rongfeng; Shi, Donghong; Lu, Guang Ming

    2013-01-01

    Purpose: To investigate the role of arterial-spin labeling (ASL) MRI to non-invasively characterize the patterns of cerebral blood flow (CBF) changes in cirrhotic patients and to assess the potential of ASL MRI to characterize minimal hepatic encephalopathy (MHE). Materials and methods: This study was approved by the local ethics committee, and written informed consent was obtained from all participants. Thirty six cirrhosis patients without overt hepatic encephalopathy (16 MHE patients and 20 non hepatic encephalopathy (non-HE) patients) and 25 controls underwent ASL MRI, and CBF was measured for each subject. One-way ANOCOVA test with age and gender as covariences was used to compare CBF difference among three groups, and post hoc analysis was performed between each two groups. Region-based correlation analysis was applied between Child–Pugh score, venous blood ammonia level, neuropsychological tests and CBF values in cirrhosis patients. Receiver operator characteristic (ROC) analysis was used for assessing CBF measurements in ASL MRI to differentiate MHE from non-HE patients. Results: The gray matter CBF of MHE patients (71.09 ± 11.88 mL min −1 100 g −1 ) was significantly higher than that of non-HE patients (55.28 ± 12.30 mL min −1 100 g −1 , P < 0.01) and controls (52.09 ± 9.27 mL min −1 100 g −1 , P < 0.001). Voxel-wise ANOCOVA results showed that CBFs were significantly different among three groups in multiple gray matter areas (P < 0.05, Bonferroni corrected). Post hoc comparisons showed that CBF of these brain regions was increased in MHE patients compared with controls and non-HE patients (P < 0.05, Bonferroni corrected). CBF of the right putamen was of the highest sensitivity (93.8%) and moderate specificity (75.0%) for characterization of MHE when using the cutoff value of 50.57 mL min −1 100 g −1 . CBFs in the bilateral median cingulate gyri, left supramarginal gyrus, right angular gyrus, right heschl gyrus and right superior

  7. Cerebral blood flow measured by arterial-spin labeling MRI: A useful biomarker for characterization of minimal hepatic encephalopathy in patients with cirrhosis

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Gang [Department of Medical Imaging, Jinling Hospital, Clinical School of Medical College, Nanjing University, Nanjing, Jiangsu, 210002 (China); College of Civil Aviation, Nanjing University of Aeronautics and Astronautics, Nanjing, Jiangsu, 210016 (China); Zhang, Long Jiang, E-mail: kevinzhlj@163.com [Department of Medical Imaging, Jinling Hospital, Clinical School of Medical College, Nanjing University, Nanjing, Jiangsu, 210002 (China); Zhong, Jianhui [Department of Imaging Sciences, University of Rochester School of Medicine and Dentistry, Box648, 601 Elmwood Avenue, Rochester, NY 14642-8648 (United States); Wang, Ze [Department of Psychiatry, Perelman School of Medicine, University of Pennsylvania, 3900 Chestnut St., Philadelphia, PA 19104 (United States); Qi, Rongfeng; Shi, Donghong [Department of Medical Imaging, Jinling Hospital, Clinical School of Medical College, Nanjing University, Nanjing, Jiangsu, 210002 (China); Lu, Guang Ming, E-mail: cjr.luguangming@vip.163.com [Department of Medical Imaging, Jinling Hospital, Clinical School of Medical College, Nanjing University, Nanjing, Jiangsu, 210002 (China)

    2013-11-01

    Purpose: To investigate the role of arterial-spin labeling (ASL) MRI to non-invasively characterize the patterns of cerebral blood flow (CBF) changes in cirrhotic patients and to assess the potential of ASL MRI to characterize minimal hepatic encephalopathy (MHE). Materials and methods: This study was approved by the local ethics committee, and written informed consent was obtained from all participants. Thirty six cirrhosis patients without overt hepatic encephalopathy (16 MHE patients and 20 non hepatic encephalopathy (non-HE) patients) and 25 controls underwent ASL MRI, and CBF was measured for each subject. One-way ANOCOVA test with age and gender as covariences was used to compare CBF difference among three groups, and post hoc analysis was performed between each two groups. Region-based correlation analysis was applied between Child–Pugh score, venous blood ammonia level, neuropsychological tests and CBF values in cirrhosis patients. Receiver operator characteristic (ROC) analysis was used for assessing CBF measurements in ASL MRI to differentiate MHE from non-HE patients. Results: The gray matter CBF of MHE patients (71.09 ± 11.88 mL min{sup −1} 100 g{sup −1}) was significantly higher than that of non-HE patients (55.28 ± 12.30 mL min{sup −1} 100 g{sup −1}, P < 0.01) and controls (52.09 ± 9.27 mL min{sup −1} 100 g{sup −1}, P < 0.001). Voxel-wise ANOCOVA results showed that CBFs were significantly different among three groups in multiple gray matter areas (P < 0.05, Bonferroni corrected). Post hoc comparisons showed that CBF of these brain regions was increased in MHE patients compared with controls and non-HE patients (P < 0.05, Bonferroni corrected). CBF of the right putamen was of the highest sensitivity (93.8%) and moderate specificity (75.0%) for characterization of MHE when using the cutoff value of 50.57 mL min{sup −1} 100 g{sup −1}. CBFs in the bilateral median cingulate gyri, left supramarginal gyrus, right angular gyrus, right

  8. Cerebral perfusion characteristics show differences in younger versus older children with sickle cell anaemia: Results from a multiple-inflow-time arterial spin labelling study.

    Science.gov (United States)

    Kawadler, Jamie M; Hales, Patrick W; Barker, Simon; Cox, Timothy C S; Kirkham, Fenella J; Clark, Chris A

    2018-03-30

    Sickle cell anaemia (SCA) is associated with chronic anaemia and oxygen desaturation, which elevate cerebral blood flow (CBF) and increase the risk of neurocognitive complications. Arterial spin labelling (ASL) provides a methodology for measuring CBF non-invasively; however, ASL techniques using only a single inflow time are not sufficient to fully characterize abnormal haemodynamic behaviour in SCA. This study investigated haemodynamic parameters from a multi-inflow-time ASL acquisition in younger (8-12 years) and older (13-18 years) children with SCA with and without silent cerebral infarction (SCI+/-) (n = 20 and 19 respectively, 6 and 4 SCI+ respectively) and healthy controls (n = 9 and 7 respectively). Compared with controls, CBF was elevated globally in both groups of patients. In the younger SCA patients, blood oxygen content was negatively correlated with CBF in the middle and posterior cerebral artery territories and significantly positively correlated with bolus arrival time (BAT) in the anterior and middle cerebral artery territories. In older children, SCA patients had significantly shorter BAT than healthy controls and there was a significant negative correlation between CBF and oxygen content only in the territory of the posterior cerebral artery, with a trend for a correlation in the anterior cerebral artery but no relationship for the middle cerebral artery territory. In the younger group, SCI+ patients had significantly higher CBF in the posterior cerebral artery territory (SCI+ mean = 92.78 ml/100 g/min; SCI- mean = 72.71 ml/100 g/min; F = 4.28, p = 0.04), but this no longer reached significance when two children with abnormal transcranial Doppler and one with haemoglobin SC disease were excluded, and there were no significant differences between patients with and without SCI in the older children. With age, there appears to be increasing disparity between patients and controls in terms of the relationship between CBF and oxygen

  9. EPR investigations on technetium compounds

    International Nuclear Information System (INIS)

    Abram, U.; Munze, R.; Kirmse, R.; Stach, J.

    1986-01-01

    Stimulated by the widespread use of the isotope /sup 99m/Tc in the field of nuclear medicine, there has been a substantial growth of interest in the chemistry of this man-made element. A particular need emerges for analytical methods allowing solution investigations of coordination compounds of technetium with low substance use. Considering these facts, Electron Paramagnetic Resonance Spectroscopy (EPR) appears to be a very suitable method because only very small amounts of the compounds are needed (lower than 1 mg). The resulting spectra give information regarding the valence state, symmetry and bonding properties of the compounds under study

  10. EPR spectroscopic investigation of psoriatic finger nails.

    Science.gov (United States)

    Nakagawa, Kouichi; Minakawa, Satoko; Sawamura, Daisuke

    2013-11-01

    Nail lesions are common features of psoriasis and found in almost half of the patients. However, there is no feasible spectroscopic method evaluating changes and severity of nail psoriasis. EPR (electron paramagnetic resonance) might be feasible for evaluating nail conditions in the patients of psoriasis. Finger nails of five cases with nail psoriasis, (three females and two males) were examined. Nail samples were subjected to the EPR assay. The small piece of the finger nail (1.5 × 5 mm(2)) was incubated in ~50 μM 5-DSA (5-doxylstearic acid) aqueous solutions for about 60 min at 37°C. After rinsing and wiping off the excess 5-DSA solution, the nail samples were measured by EPR. EPR spectra were analyzed using the intensity ratio (Fast/Slow) of the two motions at the peaks of the lower magnetic field. We observed two distinguishable sites on the basis of the EPR results. In addition, the modern EPR calculation was performed to analyze the spectra obtained. The nail psoriasis-related region is 2~3 times higher than that of the control. The present EPR results show that there are two distinguishable sites in the nail. In the case of nail psoriasis, the fragile components are 2~3 times more than those of the control. Thus, the EPR method is thought to be a novel and reliable method of evaluating the nail psoriasis. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  11. EPR STUDIES OF THERMALLY STERILIZED VASELINUM ALBUM.

    Science.gov (United States)

    Ramos, Paweł; Pilawa, Barbara

    2015-01-01

    Electron paramagnetic resonance (EPR) spectroscopy was used for examination of free radicals in thermally treated vaselinum album (VA). Thermal treatment in hot air as sterilization process was tested. Conditions of thermal sterilization were chosen according to the pharmaceutical norms. Vaselinum album was heated at the following conditions (T--temperature, t--time): T = 160°C and t = 120 min, T = 170°C and t = 60 min and T = 180°C and t = 30 min. The aim of this work was to determine concentration and free radical properties of thermally sterilized VA. EPR analysis for VA was done 15 min after sterilization. EPR measurements were done at room temperature. EPR spectra were recorded in the range of microwave power of 2.2-70 mW. g-Factor, amplitudes (A) and line width (ΔBpp) of the spectra were determined. The shape of the EPR spectra was analyzed. Free radical concentration (N) in the heated samples was determined. EPR spectra were not obtained for the non heated VA. EPR spectra were detected for all thermally sterilized samples. The spectra revealed complex character, their asymmetry depends on microwave power. The lowest free radicals concentration was found for the VA sterilized at 180°C during 30 min. EPR spectroscopy is proposed as the method useful for optimization of sterilization process of drugs.

  12. Overview of LBB implementation for the EPR

    International Nuclear Information System (INIS)

    Cauquelin, C.

    1997-01-01

    This paper presents an overview of the use of leak-before-break (LBB) analysis for EPR reactors. EPR is an evolutionary Nuclear Island of the 4 loop x 1500 Mwe class currently in the design phase. Application of LBB to the main coolant lines and resulting design impacts are summarized. Background information on LBB analysis in France and Germany is also presented

  13. Overview of LBB implementation for the EPR

    Energy Technology Data Exchange (ETDEWEB)

    Cauquelin, C.

    1997-04-01

    This paper presents an overview of the use of leak-before-break (LBB) analysis for EPR reactors. EPR is an evolutionary Nuclear Island of the 4 loop x 1500 Mwe class currently in the design phase. Application of LBB to the main coolant lines and resulting design impacts are summarized. Background information on LBB analysis in France and Germany is also presented.

  14. EPR dosimetry with tooth enamel: A review

    International Nuclear Information System (INIS)

    Fattibene, Paola; Callens, Freddy

    2010-01-01

    When tooth enamel is exposed to ionizing radiation, radicals are formed, which can be detected using electron paramagnetic resonance (EPR) techniques. EPR dosimetry using tooth enamel is based on the (presumed) correlation between the intensity or amplitude of some of the radiation-induced signals with the dose absorbed in the enamel. In the present paper a critical review is given of this widely applied dosimetric method. The first part of the paper is fairly fundamental and deals with the main properties of tooth enamel and some of its model systems (e.g., synthetic apatites). Considerable attention is also paid to the numerous radiation-induced and native EPR signals and the radicals responsible for them. The relevant methods for EPR detection, identification and spectrum analyzing are reviewed from a general point of view. Finally, the needs for solid-state modelling and studies of the linearity of the dose response are investigated. The second part is devoted to the practical implementation of EPR dosimetry using enamel. It concerns specific problems of preparation of samples, their irradiation and spectrum acquisition. It also describes how the dosimetric signal intensity and dose can be retrieved from the EPR spectra. Special attention is paid to the energy dependence of the EPR response and to sources of uncertainties. Results of and problems encountered in international intercomparisons and epidemiological studies are also dealt with. In the final section the future of EPR dosimetry with tooth enamel is analyzed.

  15. EPR meeting international safety standards with margin

    International Nuclear Information System (INIS)

    Mazurkiewicz, S.M.; Brauns, J.; Blombach, J.

    2005-01-01

    The EPR provides technology that offers a solution to the market's need for safe, economic power. The EPR was originally developed through a joint effort between Framatome ANP and Siemens by incorporating the best technological features from the French and German nuclear reactor fleets into a cost-competitive product capable of international licensing. As such, the EPR is a global product with commercial units currently being built in Finland at the Olkiluoto site, and planned for France, at the Flamanville site. Framatome ANP has recently proposed four EPR units to China in response to a request for vendor bids. In addition, Framatome ANP has announced their intent to pursue design certification with the United States Nuclear Regulatory Commission (NRC). This paper discusses how EPR's innovative safety philosophy ensures compliance with international safety standards for advanced light-water reactors (ALWRs). (author)

  16. EPR meeting international safety standards with margin

    International Nuclear Information System (INIS)

    Mazurkiewicz, S.M.; Brauns, J.; Blombach, J.

    2005-01-01

    The EPR provides technology that offers a solution to the market's need for safe, economic power. The EPR was originally developed through a joint effort between Framatome ANP and Siemens by incorporating the best technological features from the French and German nuclear reactor fleets into a cost-competitive product capable of international licensing. As such, the EPR is a global product with commercial units currently being built in Finland at the Olkiluoto site, and planned for France, at the Flamanville site. Framatome ANP has recently proposed four EPR units to China in response to a request for vendor bids. In addition, Framatome ANP has announced their intent to pursue design certification in with the United States Nuclear Regulatory Commission (NRC). This paper discusses how EPR's innovative safety philosophy ensures compliance with international safety standards for advanced light-water reactors (ALWRs). (author)

  17. EPR-study of reversible oxygenation process of coordination compounds of cobalt(II) with S-substituted N1,N4-di(salicylidene)-isothiosemicarbazides

    International Nuclear Information System (INIS)

    Gerbeleu, N.V.; Revenko, M.D.; Rusu, V.G.; Shames, A.T.

    1987-01-01

    The reaction between molecular oxygen and coordination compounds of cobalt(II) with S-substituted N 1 ,N 4 -di(salicylidene)isothiosemicarbazides in dimethyl sulfoxide solution was studied by the EPR method. It was found that paramagnetic monomeric adducts and diamagnetic μ-peroxo-dimers are formed. The spin-Hamiltonian parameters of the EPR spectra of the initial cobalt complexes, as well as of the paramagnetic adducts were determined. The nature of the Co-O 2 bond is discussed

  18. Electronic Structure of ZnO Quantum Dots studied by High-frequency EPR, ESE, ENDOR and ODMR Spectroscopy

    NARCIS (Netherlands)

    Baranov, P.G.; Romanov, N.G.; Bundakova, A.P.; de Mello-Donega, Celso; Schmidt, J.

    2016-01-01

    High-frequency electron paramagnetic resonance (EPR), electron spin echo (ESE), electron-nuclear double resonance (ENDOR) and optically detected magnetic resonance (ODMR) were applied for the investigation of the electronic properties of ZnO colloidal quantum dots (QDs) which consist of a ZnO

  19. EPR dosimetry - present and future

    International Nuclear Information System (INIS)

    Regulla, D.F.

    1999-01-01

    In the past, IAEA has played a central role in stipulating research and development in EPR high-dose standardisation as well as co-ordinating and organising international dose intercomparison programs, within the Member States of the United Nations from the mid-seventies till today. The future tasks of EPR dosimetry seem to tend towards different subjects such as biomarkers, biological radiation effects, post-accident dose reconstruction in the environment, and retrospective human dosimetry. The latter may be considered a promising tool for epidemiology on the way to re-define radiation risk of man for chronicle radiation exposures, based on e.g. South Ural civil population and radiation workers. There are on-going international activities in the field of standardising high-level dosimetry by the American Standards on Testing and Materials (ASTM), and the International Organisation of Standards (ISO) as well as those of the International Commission on Radiation Units and Measurements (ICRU) considering the establishment of relevant recommendations concerning industrial radiation processing, but also human dose reconstruction. (author)

  20. EPR Dosimetry - Present and Future

    Energy Technology Data Exchange (ETDEWEB)

    Regulla, D.F. [GSF - National Research Centre for Environment and Health, Institute of Radiation Protection, 85764 Neuherberg (Germany)

    1999-07-01

    In the past, IAEA has played a central role in stipulating research and development in EPR high-dose standardisation as well as in coordinating and organising international dose intercomparison programs, within the Member States of the United Nations from the mid-seventies till today. The future tasks of EPR dosimetry seem to tend towards different subjects such as bio markers, biological radiation effects, post-accident dose reconstruction in the environment, and retrospective human dosimetry. The latter may be considered a promising tool for epidemiology on the way to re-define radiation risk of man for chronicle radiation exposures, based on e.g. South Ural civil population and radiation workers. There are on-going international activities in the field of standardising high-level dosimetry by the American Standards on Testing and Materials (Astm), and by the International Organisation of Standards (ISO). The International Commission on Radiation Units and Measurements (ICRU) is considering the establishment of relevant recommendations concerning industrial radiation processing, but also human dose reconstruction. (Author)

  1. EPR Dosimetry - Present and Future

    International Nuclear Information System (INIS)

    Regulla, D.F.

    1999-01-01

    In the past, IAEA has played a central role in stipulating research and development in EPR high-dose standardisation as well as in coordinating and organising international dose intercomparison programs, within the Member States of the United Nations from the mid-seventies till today. The future tasks of EPR dosimetry seem to tend towards different subjects such as bio markers, biological radiation effects, post-accident dose reconstruction in the environment, and retrospective human dosimetry. The latter may be considered a promising tool for epidemiology on the way to re-define radiation risk of man for chronicle radiation exposures, based on e.g. South Ural civil population and radiation workers. There are on-going international activities in the field of standardising high-level dosimetry by the American Standards on Testing and Materials (Astm), and by the International Organisation of Standards (ISO). The International Commission on Radiation Units and Measurements (ICRU) is considering the establishment of relevant recommendations concerning industrial radiation processing, but also human dose reconstruction. (Author)

  2. Monitoring sequential electron transfer with EPR

    International Nuclear Information System (INIS)

    Thurnauer, M.C.; Feezel, L.L.; Snyder, S.W.; Tang, J.; Norris, J.R.; Morris, A.L.; Rustandi, R.R.

    1989-01-01

    A completely general model which treats electron spin polarization (ESP) found in a system in which radical pairs with different magnetic interactions are formed sequentially has been described. This treatment has been applied specifically to the ESP found in the bacterial reaction center. Test cases show clearly how parameters such as structure, lifetime, and magnetic interactions within the successive radical pairs affect the ESP, and demonstrate that previous treatments of this problem have been incomplete. The photosynthetic bacterial reaction center protein is an ideal system for testing the general model of ESP. The radical pair which exhibits ESP, P 870 + Q - (P 870 + is the oxidized, primary electron donor, a bacteriochlorophyll special pair and Q - is the reduced, primary quinone acceptor) is formed via sequential electron transport through the intermediary radical pair P 870 + I - (I - is the reduced, intermediary electron acceptor, a bacteriopheophytin). In addition, it is possible to experimentally vary most of the important parameters, such as the lifetime of the intermediary radical pair and the magnetic interactions in each pair. It has been shown how selective isotopic substitution ( 1 H or 2 H) on P 870 , I and Q affects the ESP of the EPR spectrum of P 870 + Q - , observed at two different microwave frequencies, in Fe 2+ -depleted bacterial reaction centers of Rhodobacter sphaeroides R26. Thus, the relative magnitudes of the magnetic properties (nuclear hyperfine and g-factor differences) which influence ESP development were varied. The results support the general model of ESP in that they suggest that the P 870 + Q - radical pair interactions are the dominant source of ESP production in 2 H bacterial reaction centers

  3. EPR investigation of Ti2+ in SrCl2 single crystals.

    Science.gov (United States)

    Herrington, J. R.; Estle, T. L.; Boatner, L. A.

    1972-01-01

    The observation of 'double quantum' transitions which made it possible to determine the charge state of Ti as 2+ is reported. The EPR spectrum observed at 1.2 K is presented in a graph. The first derivative of the absorption is shown vs the magnetic field. The hyperfine patterns for the Ti-47 and Ti-49 isotopes are identified. Spin-Hamiltonian parameters for Ti(2+) in various cubic hosts are listed.

  4. The Effects of Acutely Administered 3,4-Methylenedioxymethamphetamine on Spontaneous Brain Function in Healthy Volunteers Measured with Arterial Spin Labeling and Blood Oxygen Level–Dependent Resting State Functional Connectivity

    Science.gov (United States)

    Carhart-Harris, Robin L.; Murphy, Kevin; Leech, Robert; Erritzoe, David; Wall, Matthew B.; Ferguson, Bart; Williams, Luke T.J.; Roseman, Leor; Brugger, Stefan; De Meer, Ineke; Tanner, Mark; Tyacke, Robin; Wolff, Kim; Sethi, Ajun; Bloomfield, Michael A.P.; Williams, Tim M.; Bolstridge, Mark; Stewart, Lorna; Morgan, Celia; Newbould, Rexford D.; Feilding, Amanda; Curran, H. Val; Nutt, David J.

    2015-01-01

    Background The compound 3,4-methylenedioxymethamphetamine (MDMA) is a potent monoamine releaser that produces an acute euphoria in most individuals. Methods In a double-blind, placebo-controlled, balanced-order study, MDMA was orally administered to 25 physically and mentally healthy individuals. Arterial spin labeling and seed-based resting state functional connectivity (RSFC) were used to produce spatial maps displaying changes in cerebral blood flow (CBF) and RSFC after MDMA administration. Participants underwent two arterial spin labeling and two blood oxygen level–dependent scans in a 90-minute scan session; MDMA and placebo study days were separated by 1 week. Results Marked increases in positive mood were produced by MDMA. Decreased CBF only was observed after MDMA, and this was localized to the right medial temporal lobe (MTL), thalamus, inferior visual cortex, and the somatosensory cortex. Decreased CBF in the right amygdala and hippocampus correlated with ratings of the intensity of global subjective effects of MDMA. The RSFC results complemented the CBF results, with decreases in RSFC between midline cortical regions, the medial prefrontal cortex, and MTL regions, and increases between the amygdala and hippocampus. There were trend-level correlations between these effects and ratings of intense and positive subjective effects. Conclusions The MTLs appear to be specifically implicated in the mechanism of action of MDMA, but further work is required to elucidate how the drug’s characteristic subjective effects arise from its modulation of spontaneous brain activity. PMID:24495461

  5. The Effects of Acutely Administered 3,4-Methylenedioxymethamphetamine on Spontaneous Brain Function in Healthy Volunteers Measured with Arterial Spin Labeling and Blood Oxygen Level-Dependent Resting State Functional Connectivity.

    Science.gov (United States)

    Carhart-Harris, Robin L; Murphy, Kevin; Leech, Robert; Erritzoe, David; Wall, Matthew B; Ferguson, Bart; Williams, Luke T J; Roseman, Leor; Brugger, Stefan; De Meer, Ineke; Tanner, Mark; Tyacke, Robin; Wolff, Kim; Sethi, Ajun; Bloomfield, Michael A P; Williams, Tim M; Bolstridge, Mark; Stewart, Lorna; Morgan, Celia; Newbould, Rexford D; Feilding, Amanda; Curran, H Val; Nutt, David J

    2015-10-15

    The compound 3,4-methylenedioxymethamphetamine (MDMA) is a potent monoamine releaser that produces an acute euphoria in most individuals. In a double-blind, placebo-controlled, balanced-order study, MDMA was orally administered to 25 physically and mentally healthy individuals. Arterial spin labeling and seed-based resting state functional connectivity (RSFC) were used to produce spatial maps displaying changes in cerebral blood flow (CBF) and RSFC after MDMA administration. Participants underwent two arterial spin labeling and two blood oxygen level-dependent scans in a 90-minute scan session; MDMA and placebo study days were separated by 1 week. Marked increases in positive mood were produced by MDMA. Decreased CBF only was observed after MDMA, and this was localized to the right medial temporal lobe (MTL), thalamus, inferior visual cortex, and the somatosensory cortex. Decreased CBF in the right amygdala and hippocampus correlated with ratings of the intensity of global subjective effects of MDMA. The RSFC results complemented the CBF results, with decreases in RSFC between midline cortical regions, the medial prefrontal cortex, and MTL regions, and increases between the amygdala and hippocampus. There were trend-level correlations between these effects and ratings of intense and positive subjective effects. The MTLs appear to be specifically implicated in the mechanism of action of MDMA, but further work is required to elucidate how the drug's characteristic subjective effects arise from its modulation of spontaneous brain activity. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

  6. Thermal induced EPR signals in tooth enamel

    International Nuclear Information System (INIS)

    Fattibene, P.; Aragno, D.; Onori, S.; Pressello, M.C.

    2000-01-01

    Electron paramagnetic resonance (EPR) spectroscopy was used to detect the effects of temperature on powdered human tooth enamel, not irradiated in the laboratory. Samples were heated at temperature between 350 and 450, at 600 and at 1000 deg. C, for different heating times, between 6 min and 39 h. Changes in the EPR spectra were detected, with the formation of new signals. Possible correlation between the changes in EPR spectra and modifications in the enamel and in the mineral phase of bone detected with other techniques is discussed. The implications for dosimetric applications of signals induced by overheating due to mechanical friction during sample preparation are underlined

  7. Nitrosyl hemoglobins: EPR above 80 K

    Energy Technology Data Exchange (ETDEWEB)

    Wajnberg, E.; Bemski, G.; El-Jaick, L.J.; Alves, O.C.

    1995-03-01

    The EPR spectra of nitrosyl hemoglobin and myoglobin in different conditions (native, denatured and lyophilized), as well as of hematin-NO were obtained in the temperature range of 80 K-280 K. There is a substantial and reversible.decrease of the areas of the EPR spectra of all the hemoglobin samples above 150 K. The interpretation of the results implies the existence of two conformational states in thermal equilibrium only one of which is EPR detectable. Thermodynamical parameters are determined for the hexa and penta-coordinated cases. (author). 25 refs, 3 figs.

  8. Nitrosyl hemoglobins: EPR above 80 K

    International Nuclear Information System (INIS)

    Wajnberg, E.; Bemski, G.; El-Jaick, L.J.; Alves, O.C.

    1995-03-01

    The EPR spectra of nitrosyl hemoglobin and myoglobin in different conditions (native, denatured and lyophilized), as well as of hematin-NO were obtained in the temperature range of 80 K-280 K. There is a substantial and reversible.decrease of the areas of the EPR spectra of all the hemoglobin samples above 150 K. The interpretation of the results implies the existence of two conformational states in thermal equilibrium only one of which is EPR detectable. Thermodynamical parameters are determined for the hexa and penta-coordinated cases. (author). 25 refs, 3 figs

  9. EPR ohmic heating energy storage

    International Nuclear Information System (INIS)

    Heck, F.M.; Stillwagon, R.E.; King, E.I.

    1977-01-01

    The Ohmic Heating (OH) Systems for all the Experimental Power Reactor (EPR) designs to date have all used temporary energy storage to assist in providing the OH current charge required to build up the plasma current. The energies involved (0.8 x 10 9 J to 1.9 x 10 9 J) are so large as to make capacitor storage impractical. Two alternative approaches are homopolar dc generators and ac generators. Either of these can be designed for pulse duty and can be made to function in a manner similar to a capacitor in the OH circuit and are therefore potential temporary energy storage devices for OH systems for large tokamaks. This study compared total OH system costs using homopolar and ac generators to determine their relative merits. The total system costs were not significantly different for either type of machine. The added flexibility and the lower maintenance of the ac machine system make it the more attractive approach

  10. Detection of Redox Imbalance in Normal Lymphocytes with Induced Mitochondrial Dysfunction - EPR Study.

    Science.gov (United States)

    Georgieva, Ekaterina; Zhelev, Zhivko; Aoki, Ichio; Bakalova, Rumiana; Higashi, Tatsuya

    2016-10-01

    The present study describes a new approach for direct imaging of redox status in live cells using paramagnetic spin-probes, which allows evaluation of the level of oxidative stress due to overproduction of superoxide. The method is based on redox cycling of cell/mitochondria-penetrating nitroxide radicals (e.g. mito-TEMPO) and their electron-paramagnetic resonance (EPR) contrast, which makes them useful molecular sensors for analysis of redox status and oxidative stress in cells and tissues. Oxidative stress was induced in normal human lymphocytes by treatment with 2-methoxyestradiol and rotenone (ME/Rot) at different concentrations. This combination provokes mitochondrial dysfunction, which is accompanied by overproduction of superoxide. The EPR measurements were performed in dynamics on X-Band spectrometer after addition of mito-TEMPO to cell suspensions. The intensity of the EPR signal in untreated cells decreased significantly, which indicates a conversion of paramagnetic mito-TEMPO to its non-contrast diamagnetic form (hydroxylamine - mito-TEMPOH) due to reduction. In ME/Rot-treated cells, the signal decreased more slowly and to a lower level with increasing the concentration of ME/Rot. These data indicate an induction of oxidative stress in the cells in a concentration-dependent manner. A very good positive correlation between the intensity of EPR signal of mito-TEMPO and the intracellular level of superoxide was found, analyzed by conventional dihydroethidium test (R=0.9143, pEPR imaging of the superoxide level in live cells, as well as for EPR imaging of mitochondrial dysfunction and metabolic activity, accompanied by superoxide imbalance. Copyright© 2016 International Institute of Anticancer Research (Dr. John G. Delinassios), All rights reserved.

  11. Using rapid scan EPR to improve the detection limit of quantitative EPR by more than one order of magnitude

    OpenAIRE

    Möser, J.; Lips, K.; Tseytlin, M.; Eaton, G.; Eaton, S.; Schnegg, A

    2017-01-01

    X band rapid scan EPR was implemented on a commercially available Bruker ELEXSYS E580 spectrometer. Room temperature rapid scan and continuous wave EPR spectra were recorded for amorphous silicon powder samples. By comparing the resulting signal intensities the feasibility of performing quantitative rapid scan EPR is demonstrated. For different hydrogenated amorphous silicon samples, rapid scan EPR results in signal to noise improvements by factors between 10 and 50. Rapid scan EPR is thus ca...

  12. Perspectives of shaped pulses for EPR spectroscopy

    Science.gov (United States)

    Spindler, Philipp E.; Schöps, Philipp; Kallies, Wolfgang; Glaser, Steffen J.; Prisner, Thomas F.

    2017-07-01

    This article describes current uses of shaped pulses, generated by an arbitrary waveform generator, in the field of EPR spectroscopy. We show applications of sech/tanh and WURST pulses to dipolar spectroscopy, including new pulse schemes and procedures, and discuss the more general concept of optimum-control-based pulses for applications in EPR spectroscopy. The article also describes a procedure to correct for experimental imperfections, mostly introduced by the microwave resonator, and discusses further potential applications and limitations of such pulses.

  13. EPR Spectroscopy in Environmental Lichen-Indication

    Science.gov (United States)

    Bondarenko, P. V.; Nguyet, Le Thi Bich; Zhuravleva, S. E.; Trukhan, E. M.

    2017-09-01

    The paramagnetic properties of lichens were investigated using EPR spectroscopy and Xanthoria parietina (L.) Th. Fr. as a case study. It was found that the concentration of paramagnetic centers in lichen thalli increased as the air-pollution level increased. Possible formation mechanisms of the paramagnetic centers in lichens were discussed. The efficiency of using EPR spectroscopy to study lichens as environmental quality indicators was demonstrated.

  14. EPR of alanine irradiated by neutrons

    International Nuclear Information System (INIS)

    Pivovarov, S.P.; Seredavina, T.A.; Zhdanov, S.V.; Mul'gin, S.I.; Zhakparov, R.K.

    2001-01-01

    In the work the first results of EPR studies of alanine, irradiated with diverse doses at neutron cyclotron generator different conditions and on the critical reactor stand are presented. A dose linearity dependence of EPR signal is observing, the methods of γ-background contribution separation are discussed. Obtain results is giving the basis to recommendation of alanine as an effective detector irradiation. However it is demanded the farther study on clarification of radiation sensitivity value dependence on the neutron energy spectrum form

  15. Investigation of anisotropy in EPR spectra of radiation defects in irradiated beryllium ceramics

    International Nuclear Information System (INIS)

    Polyakov, A.I.; Ryabikin, Yu.A.; Zashkvara, O. V.; Bitenbaev, M.I.; Petukhov, Yu. V.

    2004-01-01

    Full text: In this work results of analysis of anisotropy and hyperfine structure in EPR spectra of paramagnetic defects in irradiated samples of beryllium ceramics are presented. To explain peculiarities in a shape and parameters of the EPR spectrum hyperfine structure in beryllium ceramics, we have analyzed several versions of model representations for the radiation-induced paramagnetic defects uniformly distributed in a sample as well as for cluster defects which hyperfine structure is determined by interactions between electrons and nuclei of impurity atoms (S=1/2) and which are characterized by anisotropy in the g factors. Calculations of a shape of the uniformly widened EPR spectra are carried out by the model of random interactions between electron spins. The EPR spectra, widened at the expense of anisotropy in the g factors, are calculated by the following equation: g(Δ)=[2(ω-ω 0 )+α] -1/2 , where ω 0 =γH 0 , α is the quantify proportional to the anisotropy shift. To describe wings of spectral lines, where the equation doesn't work, we use the Gaussian function. To determine the frequency of precession of electron spins packages with local concentration N loc , the following expression is used: ω=ω 0 +1/2α(3cos 2 θ-1), where θ is an angle between the symmetry axis and the direction of the external magnetic field. It is shown that the best agreement between the calculated and experimental EPR spectra is observed with the following computational model: paramagnetic radiation defects are distributed uniformly over a ceramics sample, and the g factors of its EPR spectra have the anisotropy typical for dipole-dipole interaction in powder samples. By results of the data we obtained, it's clear that in future we'll need in more detailed information than that published in scientific journals about formation of the paramagnetic defect EPR spectra structure in beryllium oxides and ceramics at the expense of resonance line hyperfine splitting on atoms of

  16. Investigation of anisotropy in EPR spectra of radiation defects in irradiated beryllium ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Polyakov, A I; Ryabikin, Yu A; Zashkvara, O V; Bitenbaev, M I; Petukhov, Yu V [Inst. of Physics and Technology, Almaty (Kazakhstan)

    2004-07-01

    Full text: In this work results of analysis of anisotropy and hyperfine structure in EPR spectra of paramagnetic defects in irradiated samples of beryllium ceramics are presented. To explain peculiarities in a shape and parameters of the EPR spectrum hyperfine structure in beryllium ceramics, we have analyzed several versions of model representations for the radiation-induced paramagnetic defects uniformly distributed in a sample as well as for cluster defects which hyperfine structure is determined by interactions between electrons and nuclei of impurity atoms (S=1/2) and which are characterized by anisotropy in the g factors. Calculations of a shape of the uniformly widened EPR spectra are carried out by the model of random interactions between electron spins. The EPR spectra, widened at the expense of anisotropy in the g factors, are calculated by the following equation: g({delta})=[2({omega}-{omega}{sub 0})+{alpha}]{sup -1/2}, where {omega}{sub 0}={gamma}H{sub 0}, {alpha} is the quantify proportional to the anisotropy shift. To describe wings of spectral lines, where the equation doesn't work, we use the Gaussian function. To determine the frequency of precession of electron spins packages with local concentration N{sub loc}, the following expression is used: {omega}={omega}{sub 0}+1/2{alpha}(3cos{sup 2}{theta}-1), where {theta} is an angle between the symmetry axis and the direction of the external magnetic field. It is shown that the best agreement between the calculated and experimental EPR spectra is observed with the following computational model: paramagnetic radiation defects are distributed uniformly over a ceramics sample, and the g factors of its EPR spectra have the anisotropy typical for dipole-dipole interaction in powder samples. By results of the data we obtained, it's clear that in future we'll need in more detailed information than that published in scientific journals about formation of the paramagnetic defect EPR spectra structure in

  17. EPR and optical absorption studies of VO2+ doped L-alanine (C3H7NO2) single crystals

    International Nuclear Information System (INIS)

    Biyik, Recep

    2009-01-01

    VO 2+ doped L-alanine (C 3 H 7 NO 2 ) single crystals and powders are examined by electron paramagnetic resonance (EPR) and optical absorption spectroscopy. Three magnetically different sites are resolved from angular variations of L-alanine single crystal EPR spectra. In some specific orientations each VO 2+ line splits into three superhyperfine lines with intensities of 1:2:1 and maximum splitting value of 2.23 mT. The local symmetries of VO 2+ complex sites are nearly axial. The optical absorption spectra show three bands. Spin Hamiltonian parameters are measured and molecular orbital coefficients are calculated by correlating EPR and optical absorption data for the central vanadyl ion.

  18. Sonoporation enhances liposome accumulation and penetration in tumors with low EPR.

    Science.gov (United States)

    Theek, Benjamin; Baues, Maike; Ojha, Tarun; Möckel, Diana; Veettil, Seena Koyadan; Steitz, Julia; van Bloois, Louis; Storm, Gert; Kiessling, Fabian; Lammers, Twan

    2016-06-10

    The Enhanced Permeability and Retention (EPR) effect is a highly variable phenomenon. To enhance EPR-mediated passive drug targeting to tumors, several different pharmacological and physical strategies have been evaluated over the years, including e.g. TNFα-treatment, vascular normalization, hyperthermia and radiotherapy. Here, we systematically investigated the impact of sonoporation, i.e. the combination of ultrasound (US) and microbubbles (MB), on the tumor accumulation and penetration of liposomes. Two different MB formulations were employed, and their ability to enhance liposome accumulation and penetration was evaluated in two different tumor models, which are both characterized by relatively low levels of EPR (i.e. highly cellular A431 epidermoid xenografts and highly stromal BxPC-3 pancreatic carcinoma xenografts). The liposomes were labeled with two different fluorophores, enabling in vivo computed tomography/fluorescence molecular tomography (CT-FMT) and ex vivo two-photon laser scanning microscopy (TPLSM). In both models, in spite of relatively high inter- and intra-individual variability, a trend towards improved liposome accumulation and penetration was observed. In treated tumors, liposome concentrations were up to twice as high as in untreated tumors, and sonoporation enhanced the ability of liposomes to extravasate out of the blood vessels into the tumor interstitium. These findings indicate that sonoporation may be a useful strategy for improving drug targeting to tumors with low EPR. Copyright © 2016 Elsevier B.V. All rights reserved.

  19. EPR Dosimetry for ageing effect in NPP

    International Nuclear Information System (INIS)

    Choi, Hoon; Lim, Young Ki; Kim, Jong Seog; Jung, Sun Chul

    2005-01-01

    As one of the retrospective dosimetry method, EPR spectroscopy has been studied by many research up to theses days. As a dosimeter for EPR spectroscopy, Alanine is already a well known dosimeter in the field of radiation therapy and dose assessment in radiological accident by its characteristics as good linearity in a wide range of energy level and extremely low signal fading on time. Through technical document of IAEA, the EPR dosimetry method using alanine sample was published in 2000 after research by coordinated project on management of ageing of in-containment I and C cables. Although alanine sample is regarded as a good EPR dosimeter like above ageing assessment field, actually the assessment of radiation should be done at least for two fuel cycles, because of its relatively low irradiation environment in almost all spots in power plant. So, for getting more accurate detection value of radiation, another material is tested for being put in simultaneously inside the power plant with alanine. The test result for lithium formate monohydrate (HCO 2 LiH 2 0) was presented below for checking its possibility for being applied as EPR dosimeter for this project

  20. Disentangling overlapping high-field EPR spectra of organic radicals: Identification of light-induced polarons in the record fullerene-free solar cell blend PBDB-T:ITIC

    Science.gov (United States)

    Van Landeghem, Melissa; Maes, Wouter; Goovaerts, Etienne; Van Doorslaer, Sabine

    2018-03-01

    We present a combined high-field EPR and DFT study of light-induced radicals in the bulk heterojunction blend of PBDB-T:ITIC, currently one of the highest efficiency non-fullerene donor:acceptor combinations in organic photovoltaics. We demonstrate two different approaches for disentangling the strongly overlapping high-field EPR spectra of the positive and negative polarons after charge separation: (1) relaxation-filtered field-swept EPR based on the difference in T1 spin-relaxation times and (2) field-swept EDNMR-induced EPR by exploiting the presence of 14N hyperfine couplings in only one of the radical species, the small molecule acceptor radical. The approach is validated by light-induced EPR spectra on related blends and the spectral assignment is underpinned by DFT computations. The broader applicability of the spectral disentangling methods is discussed.

  1. Disentangling overlapping high-field EPR spectra of organic radicals: Identification of light-induced polarons in the record fullerene-free solar cell blend PBDB-T:ITIC.

    Science.gov (United States)

    Van Landeghem, Melissa; Maes, Wouter; Goovaerts, Etienne; Van Doorslaer, Sabine

    2018-03-01

    We present a combined high-field EPR and DFT study of light-induced radicals in the bulk heterojunction blend of PBDB-T:ITIC, currently one of the highest efficiency non-fullerene donor:acceptor combinations in organic photovoltaics. We demonstrate two different approaches for disentangling the strongly overlapping high-field EPR spectra of the positive and negative polarons after charge separation: (1) relaxation-filtered field-swept EPR based on the difference in T 1 spin-relaxation times and (2) field-swept EDNMR-induced EPR by exploiting the presence of 14 N hyperfine couplings in only one of the radical species, the small molecule acceptor radical. The approach is validated by light-induced EPR spectra on related blends and the spectral assignment is underpinned by DFT computations. The broader applicability of the spectral disentangling methods is discussed. Copyright © 2018 Elsevier Inc. All rights reserved.

  2. Magnetic, catalytic, EPR and electrochemical studies on binuclear ...

    Indian Academy of Sciences (India)

    Magnetic, catalytic, EPR and electrochemical studies on binuclear copper(II) complexes ... to the oxidation of 3,5-di--butylcatechol to the corresponding quinone. ... EPR spectral studies in methanol solvent show welldefined four hyperfine ...

  3. Investigation of radical locations in various sesame seeds by CW EPR and 9-GHz EPR imaging.

    Science.gov (United States)

    Nakagawa, K; Hara, H

    2015-01-01

    We investigated the location of radical in various sesame seeds using continuous-wave (CW) electron paramagnetic resonance (EPR) and 9-GHz EPR imaging. CW EPR detected persistent radicals (single line) for various sesame seeds. The EPR linewidth of black sesame seeds was narrower than that of the irradiated white sesame seeds. A very small signal was detected for the white sesame seeds. Two-dimensional (2D) imaging using a 9-GHz EPR imager showed that radical locations vary for various sesame seeds. The paramagnetic species in black sesame seeds were located on the seed coat (skin) and in the hilum region. The signal with the highest intensity was obtained from the hilum part. A very low-intensity image was observed for the white sesame seeds. In addition, the 2D imaging of the irradiated white sesame seeds showed that free radicals were located throughout the entire seed. For the first time, CW EPR and 9-GHz EPR imaging showed the exact location of radical species in various sesame seeds.

  4. Selfcalibrated alanine/EPR dosimeters. A new generation of solid state/EPR dosimeters

    International Nuclear Information System (INIS)

    Yordanov, N.D.; Gancheva, V.

    1999-01-01

    Alanine/EPR dosimeters are well established as secondary, reference dosimeters for high-energy radiation. However, there are various sources of uncertainty in the evaluation of absorbed dose. This arises primarily from the necessity to calibrate each EPR spectrometer and each batch of dosimeters before their use. In order to overcome this disadvantage, a new generation alanine/EPR dosimeter has been developed, and its possibilities as a radiation detector are reported. Principally, it is a mixture of alanine, some quantity of EPR active substance, and a binding material. The EPR active substance, acting as an internal EPR standard, is chosen to have EPR parameters which are independent of the irradiation dose. The simultaneous recording of the spectra of both the sample and the standard under the same experimental conditions and the estimation of the ratio I alanine /I Mn as a function of the absorbed dose strongly reduces the uncertainties. The response of these dosimeters for 60 Co γ-radiation exhibits excellent linearity and reproducibility in the range of absorbed dose, 10 2 - 5 x 10 4 Gy. (author)

  5. Optical and EPR studies of barium alumino borate glasses containing Cu2+ ions

    Science.gov (United States)

    Ahmed, Mohamad Raheem; Phani, A. V. Lalitha; Narsimha Chary, M.; Shareefuddin, Md.

    2018-05-01

    Glass containing Cu2+ ions in (30-x) BaO-xAl2O3-69.5B2O3-0.5CuO (0 ≤ x ≤ 15 mol %) were prepared by the conventional melt quenching technique. Peak free X-ray diffractograms confirmed the amorphous nature of the glass samples. Spectroscopic studies such as optical absorption, EPR were studied to understand the effect of modifier oxide and CuO dopant. From EPR spectra the spin-Hamiltonian parameter were evaluated. The ground state of Cu2+ is dx2-y2 (2B1g state) and the site symmetry around Cu2+ is tetragonally distorted octahedral. A broad optical absorption band was observed for all the glasses containing Cu2+ ions corresponding to the 2B1g → 2B2g transition. The optical band gap and Urbach energy values are calculated.

  6. EPR, optical and superposition model study of Mn2+ doped L+ glutamic acid

    Science.gov (United States)

    Kripal, Ram; Singh, Manju

    2015-12-01

    Electron paramagnetic resonance (EPR) study of Mn2+ doped L+ glutamic acid single crystal is done at room temperature. Four interstitial sites are observed and the spin Hamiltonian parameters are calculated with the help of large number of resonant lines for various angular positions of external magnetic field. The optical absorption study is also done at room temperature. The energy values for different orbital levels are calculated, and observed bands are assigned as transitions from 6A1g(s) ground state to various excited states. With the help of these assigned bands, Racah inter-electronic repulsion parameters B = 869 cm-1, C = 2080 cm-1 and cubic crystal field splitting parameter Dq = 730 cm-1 are calculated. Zero field splitting (ZFS) parameters D and E are calculated by the perturbation formulae and crystal field parameters obtained using superposition model. The calculated values of ZFS parameters are in good agreement with the experimental values obtained by EPR.

  7. Braked rotation of CH3 group in L-alanine monocrystals: temperature transformation of EPR spectrum

    International Nuclear Information System (INIS)

    Lemanov, V.V.; Sochava, L.S.

    2003-01-01

    EPR spectra temperature transformation of the irradiated alanine crystals is used for studying rotation of CH 3 methyl group in L-alamine monocrystals. 60 Co (2 x 10 4 Gy dose) was applied as a γ-radiation source. The simple method of experimental data processing which is reduced to obtaining the resonance lines width dependence on the temperature is used for the quantitative analysis of the spectrum temperature transformation. Temperature dependence of the CH 3 group rotation frequency is identified on the basis of these data. Activation energy U = 0.18 eV and pre-exponential multiplier ω 0 = 10 13 s -1 are determined from the EPR spectra temperature transformation which are in good agreement with values obtained earlier from the measurements of the proton spin-lattice relaxation in alanine polycrystal samples [ru

  8. Operator spin foam models

    International Nuclear Information System (INIS)

    Bahr, Benjamin; Hellmann, Frank; Kaminski, Wojciech; Kisielowski, Marcin; Lewandowski, Jerzy

    2011-01-01

    The goal of this paper is to introduce a systematic approach to spin foams. We define operator spin foams, that is foams labelled by group representations and operators, as our main tool. A set of moves we define in the set of the operator spin foams (among other operations) allows us to split the faces and the edges of the foams. We assign to each operator spin foam a contracted operator, by using the contractions at the vertices and suitably adjusted face amplitudes. The emergence of the face amplitudes is the consequence of assuming the invariance of the contracted operator with respect to the moves. Next, we define spin foam models and consider the class of models assumed to be symmetric with respect to the moves we have introduced, and assuming their partition functions (state sums) are defined by the contracted operators. Briefly speaking, those operator spin foam models are invariant with respect to the cellular decomposition, and are sensitive only to the topology and colouring of the foam. Imposing an extra symmetry leads to a family we call natural operator spin foam models. This symmetry, combined with assumed invariance with respect to the edge splitting move, determines a complete characterization of a general natural model. It can be obtained by applying arbitrary (quantum) constraints on an arbitrary BF spin foam model. In particular, imposing suitable constraints on a spin(4) BF spin foam model is exactly the way we tend to view 4D quantum gravity, starting with the BC model and continuing with the Engle-Pereira-Rovelli-Livine (EPRL) or Freidel-Krasnov (FK) models. That makes our framework directly applicable to those models. Specifically, our operator spin foam framework can be translated into the language of spin foams and partition functions. Among our natural spin foam models there are the BF spin foam model, the BC model, and a model corresponding to the EPRL intertwiners. Our operator spin foam framework can also be used for more general spin

  9. EPR spectra of some irradiated polycrystalline perrhenate

    International Nuclear Information System (INIS)

    Zaitseva, N.G.; Constantinescu, M.; Georgescu, R.; Constantinescu, O.

    1978-10-01

    An EPR study of the paramagnetic centers formed by γ, electron and neutron irradiation of the NaReO 4 and KReO 4 was made. In the EPR spectra of the powder samples irradiated γ, with electrons and neutrons, the presence of three types of paramagnetic centers was observed. From the EPR parameters, the centers were attributed to the ReOsub(4)sup(.), ReOsub(3)sup(.) and ReOsub(2)sup(.) radicals respectively. The lower intensity of the spectra observed by KReO 4 samples irradiation showed a higher radioresistance of the KReO 4 than that of NaReO 4 . A radiolitical scheme taking into account the paramagnetic centers formation was proposed. (author)

  10. Pressurized water reactors: the EPR project

    International Nuclear Information System (INIS)

    Py, J.P.; Yvon, M.

    2007-01-01

    EPR (originally 'European pressurized water reactor', and now 'evolutionary power reactor') is a model of reactor initially jointly developed by French and German engineers which fulfills the particular safety specifications of both countries but also the European utility requirements jointly elaborated by the main European power companies under the initiative of Electricite de France (EdF). Today, two EPR-based reactors are under development: one is under construction in Finland and the other, Flamanville 3 (France), received its creation permit decree on April 10, 2007. This article presents, first, the main objectives of the EPR, and then, describes the Flamanville 3 reactor: reactor type and general conditions, core and conditions of operation, primary and secondary circuits with their components, main auxiliary and recovery systems, man-machine interface and instrumentation and control system, confinement and serious accidents, arrangement of buildings. (J.S.)

  11. EPR study of free radicals in bread

    Science.gov (United States)

    Yordanov, Nicola D.; Mladenova, Ralitsa

    2004-05-01

    The features of the recorded EPR spectra of paramagnetic species formed in bread and rusk are reported. The appearance of free radicals in them is only connected with their thermal treatment since the starting materials (flour and grains) exhibit very weak EPR signal. The obtained EPR spectra are complex and indicate that: (i) the relative number of paramagnetic species depends on the temperature and treating time of the raw product; (ii) the g-values are strongly temperature dependent with a tendency to coincide at t≥220 °C. Because of the relatively low (150-220 °C) temperature of thermal treatment, the studied free radicals can be assumed to appear in the course of the browning (Maillard) reaction and not to the carbonization of the material.

  12. Application of EPR spectroscopy to examine free radicals evolution during storage of the thermally sterilized Ungentum ophthalmicum.

    Science.gov (United States)

    Ramos, Paweł; Pilawa, Barbara

    2016-06-24

    Free radicals formed during thermal sterilization of the Ungentum ophthalmicum were examined by an X-band EPR spectroscopy. The influence of storage time (15 min; 1, 2 and 3 days after heating) on free radical properties and concentrations in this sample was determined. Thermal sterilization was done according to the pharmaceutical norms. The first-derivative EPR spectra with g-values about 2 were measured with magnetic modulation of 100 kHz in the range of microwave power 2.2-70 mW. The changes of amplitudes (A) and linewidths (ΔB pp ) with microwave powers were evaluated. Free radicals in concentration ∼10 17 spin/g were formed during heating of the tested Ungentum. Free radical concentration decreased with increase in storage time, and reached values ∼10 17 spin/g after 3 days from sterilization. The tested U. ophthalmicum should not be sterilized at a temperature of 160 °C because of the free radicals formation, or it should be used 3 days after heating, when free radicals were considerably quenched. Free radical properties remain unchanged during storage of the Ungentum. The EPR lines of the U. ophthalmicum were homogeneously broadened and their linewidths (ΔB pp ) increased with increase in microwave power. EPR spectroscopy is useful to examine free radicals to optimize sterilization process and storage conditions of ophthalmologic samples.

  13. Can EPR non-locality be geometrical?

    International Nuclear Information System (INIS)

    Ne'eman, Y.

    1995-01-01

    The presence in Quantum Mechanics of non-local correlations is one of the two fundamentally non-intuitive features of that theory. The non-local correlations themselves fall into two classes: EPR and Geometrical. The non-local characteristics of the geometrical type are well-understood and are not suspected of possibly generating acausal features, such as faster-than-light propagation of information. This has especially become true since the emergence of a geometrical treatment for the relevant gauge theories, i.e. Fiber Bundle geometry, in which the quantum non-localities are seen to correspond to pure homotopy considerations. This aspect is reviewed in section 2. Contrary-wise, from its very conception, the EPR situation was felt to be paradoxical. It has been suggested that the non-local features of EPR might also derive from geometrical considerations, like all other non-local characteristics of QM. In[7], one of the authors was able to point out several plausibility arguments for this thesis, emphasizing in particular similarities between the non-local correlations provided by any gauge field theory and those required by the preservation of the quantum numbers of the original EPR state-vector, throughout its spatially-extended mode. The derivation was, however, somewhat incomplete, especially because of the apparent difference between, on the one hand, the closed spatial loops arising in the analysis of the geometrical non-localities, from Aharonov-Bohm and Berry phases to magnetic monopoles and instantons, and on the other hand, in the EPR case, the open line drawn by the positions of the two moving decay products of the disintegrating particle. In what follows, the authors endeavor to remove this obstacle and show that as in all other QM non-localities, EPR is somehow related to closed loops, almost involving homotopy considerations. They develop this view in section 3

  14. Using rapid-scan EPR to improve the detection limit of quantitative EPR by more than one order of magnitude.

    Science.gov (United States)

    Möser, J; Lips, K; Tseytlin, M; Eaton, G R; Eaton, S S; Schnegg, A

    2017-08-01

    X-band rapid-scan EPR was implemented on a commercially available Bruker ELEXSYS E580 spectrometer. Room temperature rapid-scan and continuous-wave EPR spectra were recorded for amorphous silicon powder samples. By comparing the resulting signal intensities the feasibility of performing quantitative rapid-scan EPR is demonstrated. For different hydrogenated amorphous silicon samples, rapid-scan EPR results in signal-to-noise improvements by factors between 10 and 50. Rapid-scan EPR is thus capable of improving the detection limit of quantitative EPR by at least one order of magnitude. In addition, we provide a recipe for setting up and calibrating a conventional pulsed and continuous-wave EPR spectrometer for rapid-scan EPR. Copyright © 2017 Elsevier Inc. All rights reserved.

  15. Nano-Mole Scale Side-Chain Signal Assignment by 1H-Detected Protein Solid-State NMR by Ultra-Fast Magic-Angle Spinning and Stereo-Array Isotope Labeling

    KAUST Repository

    Wang, Songlin

    2015-04-09

    We present a general approach in 1H-detected 13C solid-state NMR (SSNMR) for side-chain signal assignments of 10-50 nmol quantities of proteins using a combination of a high magnetic field, ultra-fast magic-angle spinning (MAS) at ~80 kHz, and stereo-array-isotope-labeled (SAIL) proteins [Kainosho M. et al., Nature 440, 52–57, 2006]. First, we demonstrate that 1H indirect detection improves the sensitivity and resolution of 13C SSNMR of SAIL proteins for side-chain assignments in the ultra-fast MAS condition. 1H-detected SSNMR was performed for micro-crystalline ubiquitin (~55 nmol or ~0.5mg) that was SAIL-labeled at seven isoleucine (Ile) residues. Sensitivity was dramatically improved by 1H-detected 2D 1H/13C SSNMR by factors of 5.4-9.7 and 2.1-5.0, respectively, over 13C-detected 2D 1H/13C SSNMR and 1D 13C CPMAS, demonstrating that 2D 1H-detected SSNMR offers not only additional resolution but also sensitivity advantage over 1D 13C detection for the first time. High 1H resolution for the SAIL-labeled side-chain residues offered reasonable resolution even in the 2D data. A 1H-detected 3D 13C/13C/1H experiment on SAIL-ubiquitin provided nearly complete 1H and 13C assignments for seven Ile residues only within ~2.5 h. The results demonstrate the feasibility of side-chain signal assignment in this approach for as little as 10 nmol of a protein sample within ~3 days. The approach is likely applicable to a variety of proteins of biological interest without any requirements of highly efficient protein expression systems.

  16. Nano-Mole Scale Side-Chain Signal Assignment by 1H-Detected Protein Solid-State NMR by Ultra-Fast Magic-Angle Spinning and Stereo-Array Isotope Labeling

    KAUST Repository

    Wang, Songlin; Parthasarathy, Sudhakar; Nishiyama, Yusuke; Endo, Yuki; Nemoto, Takahiro; Yamauchi, Kazuo; Asakura, Tetsuo; Takeda, Mitsuhiro; Terauchi, Tsutomu; Kainosho, Masatsune; Ishii, Yoshitaka

    2015-01-01

    We present a general approach in 1H-detected 13C solid-state NMR (SSNMR) for side-chain signal assignments of 10-50 nmol quantities of proteins using a combination of a high magnetic field, ultra-fast magic-angle spinning (MAS) at ~80 kHz, and stereo-array-isotope-labeled (SAIL) proteins [Kainosho M. et al., Nature 440, 52–57, 2006]. First, we demonstrate that 1H indirect detection improves the sensitivity and resolution of 13C SSNMR of SAIL proteins for side-chain assignments in the ultra-fast MAS condition. 1H-detected SSNMR was performed for micro-crystalline ubiquitin (~55 nmol or ~0.5mg) that was SAIL-labeled at seven isoleucine (Ile) residues. Sensitivity was dramatically improved by 1H-detected 2D 1H/13C SSNMR by factors of 5.4-9.7 and 2.1-5.0, respectively, over 13C-detected 2D 1H/13C SSNMR and 1D 13C CPMAS, demonstrating that 2D 1H-detected SSNMR offers not only additional resolution but also sensitivity advantage over 1D 13C detection for the first time. High 1H resolution for the SAIL-labeled side-chain residues offered reasonable resolution even in the 2D data. A 1H-detected 3D 13C/13C/1H experiment on SAIL-ubiquitin provided nearly complete 1H and 13C assignments for seven Ile residues only within ~2.5 h. The results demonstrate the feasibility of side-chain signal assignment in this approach for as little as 10 nmol of a protein sample within ~3 days. The approach is likely applicable to a variety of proteins of biological interest without any requirements of highly efficient protein expression systems.

  17. Alanine EPR dosimetry of therapeutic irradiators

    International Nuclear Information System (INIS)

    Bugay, O.; Bartchuk, V.; Kolesnik, S.; Mazin, M.; Gaponenko, H.

    1999-01-01

    The high-dose alanine EPR dosimetry is a very precise method in the dose range 1-100 kGy. The system is used generally as the standard high-dose transfer dosimetry in many laboratories. This is comparatively expensive technique so it is important to use it as a more universal dosimetry system also in the middle and low dose ranges. The problems of the middle-dose alanine dosimetry are discussed and the solution of several problems is proposed. The alanine EPR dosimetry has been applied to the dose measurements of medical irradiators in the Kiev City Oncology Center. (author)

  18. Identification of irradiated crab using EPR

    Energy Technology Data Exchange (ETDEWEB)

    Maghraby, A. [Radiation Dosimetry Department, National Institute for Standards (NIS), Ministry of Scientific Research, Haram, 12211- Giza, P.O. Box: 136 (Egypt)]. E-mail: maghrabism@yahoo.com

    2007-02-15

    EPR spectroscopy is a fast and powerful technique for the identification of irradiated food. Crab exoskeleton was divided into six parts: dactyl, cheliped, carapace, apron, swimming legs, and walking legs. Samples of the exoskeleton were prepared and irradiated to Cs-137 gamma radiation in the range (1.156-5.365 kGy). EPR spectra of unirradiated as well as irradiated samples were recorded and analyzed. Response to gamma radiation was plotted for each part of the exoskeleton, dactyl was found to be the most sensitive part, followed by the apron (38%), cheliped (37%), walking legs (30%), swimming legs (24%), and carapace (21%) relative to the dactyl response.

  19. Krótka (prehistoria argumentu EPR

    Directory of Open Access Journals (Sweden)

    Tadeusz Pabjan

    2010-12-01

    Full Text Available The 1935 thought experiment of Einstein, Podolsky and Rosen is one of the most important episodes in the history of the dispute about the correct interpretation of quantum mechanics. The present paper deals with the origin of the EPR paper and discusses some other thought experiments that preceded the formulation of the Einstein-Podolsky-Rosen argument. Special attention is paid to the evolution of a simply photon-box experiment, which was devised by Einstein in 1930 and then modified by him several times before 1935. It is argued that the scheme of the original EPR argument is in fact contained in these few seminal experiments.

  20. Biophysical EPR Studies Applied to Membrane Proteins

    Science.gov (United States)

    Sahu, Indra D; Lorigan, Gary A

    2015-01-01

    Membrane proteins are very important in controlling bioenergetics, functional activity, and initializing signal pathways in a wide variety of complicated biological systems. They also represent approximately 50% of the potential drug targets. EPR spectroscopy is a very popular and powerful biophysical tool that is used to study the structural and dynamic properties of membrane proteins. In this article, a basic overview of the most commonly used EPR techniques and examples of recent applications to answer pertinent structural and dynamic related questions on membrane protein systems will be presented. PMID:26855825

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