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Sample records for dichroism

  1. Dichroism in spinach chloroplasts

    NARCIS (Netherlands)

    Thomas, J.B.; Lierop, J.H. van; Ham, M. ten

    1967-01-01

    In spinach chloroplasts oriented at steel-water interfaces parallel to the light beam a distinct dichroism is measured at about 680 nm. This dichroism is minimal upon addition of sucrose up to a final concentration of 0.18 M to the medium, the dichroic ratio amounting to 1.02. It is concluded that

  2. Magnetoelectric Jones dichroism

    International Nuclear Information System (INIS)

    Andrews, D L; Daniels, G J; Stedman, G E

    2003-01-01

    Recent work on liquids has verified a novel magnetoelectrical birefringence predicted by Jones. Co-present static electric and magnetic fields generate a differential response to optical polarizations positively or negatively tilted against a plane orthogonal to the one containing the static field vectors. Reports indicated a dichroic counterpart; establishing its theory is the present aim. Results are trilinearly dependent on the irradiance, and the static electric and magnetic fields. For isotropic fluids a scalar quantifies propensity for Jones dichroism. In field-polarized fluids a second scalar also contributes; temperature dependence enables determination of both parameters. (letter to the editor)

  3. Nuclear spin circular dichroism

    International Nuclear Information System (INIS)

    Vaara, Juha; Rizzo, Antonio; Kauczor, Joanna; Norman, Patrick; Coriani, Sonia

    2014-01-01

    Recent years have witnessed a growing interest in magneto-optic spectroscopy techniques that use nuclear magnetization as the source of the magnetic field. Here we present a formulation of magnetic circular dichroism (CD) due to magnetically polarized nuclei, nuclear spin-induced CD (NSCD), in molecules. The NSCD ellipticity and nuclear spin-induced optical rotation (NSOR) angle correspond to the real and imaginary parts, respectively, of (complex) quadratic response functions involving the dynamic second-order interaction of the electron system with the linearly polarized light beam, as well as the static magnetic hyperfine interaction. Using the complex polarization propagator framework, NSCD and NSOR signals are obtained at frequencies in the vicinity of optical excitations. Hartree-Fock and density-functional theory calculations on relatively small model systems, ethene, benzene, and 1,4-benzoquinone, demonstrate the feasibility of the method for obtaining relatively strong nuclear spin-induced ellipticity and optical rotation signals. Comparison of the proton and carbon-13 signals of ethanol reveals that these resonant phenomena facilitate chemical resolution between non-equivalent nuclei in magneto-optic spectra

  4. Magnetic circular dichroism in electron microscopy

    Czech Academy of Sciences Publication Activity Database

    Rusz, Ján; Novák, Pavel; Rubino, S.; Hébert, C.; Schattschneider, P.

    2008-01-01

    Roč. 113, č. 1 (2008), s. 599-604 ISSN 0587-4246. [CSMAG'07. Košice, 09.07.2007-12.07.2007] EU Projects: European Commission(XE) 508971 - CHIRALTEM Institutional research plan: CEZ:AV0Z10100521 Keywords : magnetic circular dichroism * electron microscopy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.321, year: 2008

  5. Chiral surface waves for enhanced circular dichroism

    Science.gov (United States)

    Pellegrini, Giovanni; Finazzi, Marco; Celebrano, Michele; Duò, Lamberto; Biagioni, Paolo

    2017-06-01

    We present a novel chiral sensing platform that combines a one-dimensional photonic crystal design with a birefringent surface defect. The platform sustains simultaneous transverse electric and transverse magnetic surface modes, which are exploited to generate chiral surface waves. The present design provides homogeneous and superchiral fields of both handednesses over arbitrarily large areas in a wide spectral range, resulting in the enhancement of the circular dichroism signal by more than two orders of magnitude, thus paving the road toward the successful combination of surface-enhanced spectroscopies and electromagnetic superchirality.

  6. Porphyrin Protonation Studied by Magnetic Circular Dichroism

    Czech Academy of Sciences Publication Activity Database

    Štěpánek, Petr; Andrushchenko, Valery; Ruud, K.; Bouř, Petr

    2012-01-01

    Roč. 116, č. 1 (2012), s. 778-783 ISSN 1089-5639 R&D Projects: GA ČR GAP208/11/0105; GA ČR GA203/09/2037; GA ČR GAP208/10/0559; GA MŠk(CZ) LH11033 Institutional research plan: CEZ:AV0Z40550506 Keywords : magnetic circular dichroism ( MCD ) * TPPS * spectra simulations * porphyrin protonation Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.771, year: 2012

  7. Energy-loss magnetic chiral dichroism (EMCD): magnetic chiral dichroism in the electron microscope

    Czech Academy of Sciences Publication Activity Database

    Rubino, S.; Schattschneider, P.; Stöger-Pollach, M.; Hébert, S.; Rusz, Ján; Calmels, L.; Warot-Fonrose, B.; Houdellier, F.; Serin, V.; Novák, Pavel

    2008-01-01

    Roč. 23, č. 10 (2008), s. 2582-2590 ISSN 0884-2914 EU Projects: European Commission(XE) 508971 - CHIRALTEM Institutional research plan: CEZ:AV0Z10100521 Keywords : magnetic circular dichroism * transmission electron microscopy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.743, year: 2008

  8. Photoexcitation circular dichroism in chiral molecules

    Science.gov (United States)

    Beaulieu, S.; Comby, A.; Descamps, D.; Fabre, B.; Garcia, G. A.; Géneaux, R.; Harvey, A. G.; Légaré, F.; Mašín, Z.; Nahon, L.; Ordonez, A. F.; Petit, S.; Pons, B.; Mairesse, Y.; Smirnova, O.; Blanchet, V.

    2018-05-01

    Chiral effects appear in a wide variety of natural phenomena and are of fundamental importance in science, from particle physics to metamaterials. The standard technique of chiral discrimination—photoabsorption circular dichroism—relies on the magnetic properties of a chiral medium and yields an extremely weak chiral response. Here, we propose and demonstrate an orders of magnitude more sensitive type of circular dichroism in neutral molecules: photoexcitation circular dichroism. This technique does not rely on weak magnetic effects, but takes advantage of the coherent helical motion of bound electrons excited by ultrashort circularly polarized light. It results in an ultrafast chiral response and the efficient excitation of a macroscopic chiral density in an initially isotropic ensemble of randomly oriented chiral molecules. We probe this excitation using linearly polarized laser pulses, without the aid of further chiral interactions. Our time-resolved study of vibronic chiral dynamics opens a way to the efficient initiation, control and monitoring of chiral chemical change in neutral molecules at the level of electrons.

  9. Conformational effects in photoelectron circular dichroism

    Science.gov (United States)

    Turchini, S.

    2017-12-01

    Photoelectron circular dichroism (PECD) is a novel type of spectroscopy, which presents surprising sensitivity to conformational effects in chiral systems. While classical photoelectron spectroscopy mainly responds to conformational effects in terms of energy level shifts, PECD provides a rich and detailed response to tiny changes in electronic and structural properties by means of the intensity dispersion of the circular dichroism as a function of photoelectron kinetic energy. In this work, the basics of PECD will be outlined, emphasizing the role of interference from the l,l+/- 1 outgoing partial wave of the photoelectron in the PECD transition matrix element, which is responsible for the extreme sensitivity to conformational effects. Examples using molecular systems and interfaces will shed light on the powerful application of PECD to classical conformational effects such as group substitution, isomerism, conformer population and clustering. Moreover, the PECD results will be reported in challenging new fields where conformations play a key role, such as vibrational effects, transient chirality and time- resolved experiments. To date, PECD has mostly been based on synchrotron radiation facilities, but it also has a future as a table-top lab experiment by means of multiphoton ionization. An important application of PECD as an analytical tool will be reported. The aim of this review is to illustrate that in PECD, the presence of conformational effects is essential for understanding a wide range of effects from a new perspective, making it different from classical spectroscopy.

  10. Optical dichroism: E1-M1 integral relations

    International Nuclear Information System (INIS)

    Marri, Ivan; Carra, Paolo; Bertoni, C M

    2006-01-01

    The present paper discusses optical dichroism in noncentrosymmetric systems. The cases of circular and linear polarizations are considered. Integrated spectra are interpreted using effective two-electron operators, which are derived within a localized (atomic) model. As a consequence, our theory is not suitable for quantitative predictions; nevertheless, it identifies microscopic origins of natural, nonreciprocal and Jones' dichroisms

  11. PCDDB: the Protein Circular Dichroism Data Bank, a repository for circular dichroism spectral and metadata.

    Science.gov (United States)

    Whitmore, Lee; Woollett, Benjamin; Miles, Andrew John; Klose, D P; Janes, Robert W; Wallace, B A

    2011-01-01

    The Protein Circular Dichroism Data Bank (PCDDB) is a public repository that archives and freely distributes circular dichroism (CD) and synchrotron radiation CD (SRCD) spectral data and their associated experimental metadata. All entries undergo validation and curation procedures to ensure completeness, consistency and quality of the data included. A web-based interface enables users to browse and query sample types, sample conditions, experimental parameters and provides spectra in both graphical display format and as downloadable text files. The entries are linked, when appropriate, to primary sequence (UniProt) and structural (PDB) databases, as well as to secondary databases such as the Enzyme Commission functional classification database and the CATH fold classification database, as well as to literature citations. The PCDDB is available at: http://pcddb.cryst.bbk.ac.uk.

  12. Circular dichroism beamline B23 at the Diamond Light Source.

    Science.gov (United States)

    Hussain, Rohanah; Jávorfi, Tamás; Siligardi, Giuliano

    2012-01-01

    Synchrotron radiation circular dichroism (SRCD) is a well established technique in structural biology. The first UV-VIS beamline, dedicated to circular dichroism, at Diamond Light Source Ltd, a third-generation synchrotron facility in south Oxfordshire, UK, has recently become operational and it is now available for the user community. Herein the main characteristics of the B23 SRCD beamline, the ancillary facilities available for users, and some of the recent advances achieved are summarized.

  13. Dichroism in resonant inelastic soft X-ray scattering

    International Nuclear Information System (INIS)

    Braicovich, L.

    2004-01-01

    Full text: The dichroism (and in particular the magnetic dichroism) has emerged in the last decade as a key method in the study of electronic states in solids. This has been largely due to the exploitation of the modern sources of Synchrotron Radiation. This approach has been extensively used in X ray Absorption Spectroscopy i.e. in a first order process giving a straightforward access, trough sum rules, to the ground state properties of the sample. On the other hand the studies of dichroism in second order processes as the photon scattering experiments has been up to now relatively limited probably due to experimental difficulties. This is too bad because, at least in principle, the scattering experiments offer unique opportunities typical of second order processes, beyond the possibilities offered by absorption spectroscopy. This requires specific scattering experiments able to give information that cannot be obtained in the absorption mode. A typical example is the circular magnetic dichroism in resonant inelastic scattering in perpendicular geometry i.e. with the light incident perpendicular to the magnetisation. In this case the circular dichroism in absorption is zero by symmetry while the detection of the scattered photons at an angle breaks the left-right symmetry and allows a dichroism to be observed. The aim of the present talk is to review critically the dichroism in resonant X-ray scattering and to show the potential of this approach. In particular it will be shown how to recover, in magnetic samples, the ground state information up to the moments of order four. In this connection original results will be presented including the demonstration of a new experimental approach. The perspectives of the field will be also discussed

  14. Employing Theories Far beyond Their Limits - Linear Dichroism Theory.

    Science.gov (United States)

    Mayerhöfer, Thomas G

    2018-05-15

    Using linear polarized light, it is possible in case of ordered structures, such as stretched polymers or single crystals, to determine the orientation of the transition moments of electronic and vibrational transitions. This not only helps to resolve overlapping bands, but also assigning the symmetry species of the transitions and to elucidate the structure. To perform spectral evaluation quantitatively, a sometimes "Linear Dichroism Theory" called approach is very often used. This approach links the relative orientation of the transition moment and polarization direction to the quantity absorbance. This linkage is highly questionable for several reasons. First of all, absorbance is a quantity that is by its definition not compatible with Maxwell's equations. Furthermore, absorbance seems not to be the quantity which is generally compatible with linear dichroism theory. In addition, linear dichroism theory disregards that it is not only the angle between transition moment and polarization direction, but also the angle between sample surface and transition moment, that influences band shape and intensity. Accordingly, the often invoked "magic angle" has never existed and the orientation distribution influences spectra to a much higher degree than if linear dichroism theory would hold strictly. A last point that is completely ignored by linear dichroism theory is the fact that partially oriented or randomly-oriented samples usually consist of ordered domains. It is their size relative to the wavelength of light that can also greatly influence a spectrum. All these findings can help to elucidate orientation to a much higher degree by optical methods than currently thought possible by the users of linear dichroism theory. Hence, it is the goal of this contribution to point out these shortcomings of linear dichroism theory to its users to stimulate efforts to overcome the long-lasting stagnation of this important field. © 2018 Wiley-VCH Verlag GmbH & Co. KGa

  15. Direct surface magnetometry with photoemission magnetic x-ray dichroism

    Energy Technology Data Exchange (ETDEWEB)

    Tobin, J.G.; Goodman, K.W. [Lawrence Berkeley National Lab., CA (United States); Schumann, F.O. [Pennsylvania State Univ., University Park, PA (United States)] [and others

    1997-04-01

    Element specific surface magnetometry remains a central goal of synchrotron radiation based studies of nanomagnetic structures. One appealing possibility is the combination of x-ray absorption dichroism measurements and the theoretical framework provided by the {open_quotes}sum rules.{close_quotes} Unfortunately, sum rule analysis are hampered by several limitations including delocalization of the final state, multi-electronic phenomena and the presence of surface dipoles. An alternative experiment, Magnetic X-Ray Dichroism in Photoelectron Spectroscopy, holds out promise based upon its elemental specificity, surface sensitivity and high resolution. Computational simulations by Tamura et al. demonstrated the relationship between exchange and spin orbit splittings and experimental data of linear and circular dichroisms. Now the authors have developed an analytical framework which allows for the direct extraction of core level exchange splittings from circular and linear dichroic photoemission data. By extending a model initially proposed by Venus, it is possible to show a linear relation between normalized dichroism peaks in the experimental data and the underlying exchange splitting. Since it is reasonable to expect that exchange splittings and magnetic moments track together, this measurement thus becomes a powerful new tool for direct surface magnetometry, without recourse to time consuming and difficult spectral simulations. The theoretical derivation will be supported by high resolution linear and circular dichroism data collected at the Spectromicroscopy Facility of the Advanced Light Source.

  16. Structure analysis of biomolecules using synchrotron radiation circular dichroism spectrophotometer

    International Nuclear Information System (INIS)

    Gekko, Kunihiko; Matsuo, Koichi

    2004-01-01

    We constructed the vacuum-ultraviolet circular dichroism (VUVCD) spectrophotometer, which is capable of measuring circular dichroism spectra to 140 nm for aqueous solutions at temperature from -30 to 70degC, using a small-scale SR source at Hiroshima Synchrotron Radiation Center (HiSOR). This spectrophotometer was used for structural analyses of amino acids, saccharides, and proteins in water. The obtained results demonstrate that a synchrotron radiation VUVCD spectroscopy provides more detailed and new information on the structures of biomolecules, based on the high energy transitions of chromophores such as hydroxyl, acetal, and peptide groups. (author)

  17. The protein circular dichroism data bank, a Web-based site for access to circular dichroism spectroscopic data.

    Science.gov (United States)

    Whitmore, Lee; Woollett, Benjamin; Miles, Andrew J; Janes, Robert W; Wallace, B A

    2010-10-13

    The Protein Circular Dichroism Data Bank (PCDDB) is a newly released resource for structural biology. It is a web-accessible (http://pcddb.cryst.bbk.ac.uk) data bank for circular dichroism (CD) and synchrotron radiation circular dichroism (SRCD) spectra and their associated experimental and secondary metadata, with links to protein sequence and structure data banks. It is designed to provide a public repository for CD spectroscopic data on macromolecules, to parallel the Protein Data Bank (PDB) for crystallographic, electron microscopic, and nuclear magnetic resonance spectroscopic data. Similarly to the PDB, it includes validation checking procedures to ensure good practice and the integrity of the deposited data. This paper reports on the first public release of the PCDDB, which provides access to spectral data that comprise standard reference datasets. Copyright © 2010 Elsevier Ltd. All rights reserved.

  18. Direct access to polyisocyanide screw sense using vibrational circular dichroism

    NARCIS (Netherlands)

    Schwartz, E.; Domingos, S.R.; Vdovin, A.; Koepf, M.; Buma, W.J.; Cornelissen, J.J.L.M.; Rowan, A.E.; Nolte, R.J.M.; Woutersen, S.

    2010-01-01

    We show that the screw sense of polyisocyanide helices can be determined in a simple manner from the vibrational circular dichroism (VCD) of their CN-stretching mode. The relation between VCD and molecular structure is obtained using the coupled-oscillator approximation. It is shown that since the

  19. Magnetic circular dichroism of chlorofullerenes: Experimental and computational study

    Czech Academy of Sciences Publication Activity Database

    Štěpánek, Petr; Straka, Michal; Šebestík, Jaroslav; Bouř, Petr

    2016-01-01

    Roč. 647, Mar (2016), s. 117-121 ISSN 0009-2614 R&D Projects: GA ČR GA13-03978S; GA ČR(CZ) GA14-03564S Institutional support: RVO:61388963 Keywords : chlorofullerenes * magnetic circular dichroism * density functional theory Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.815, year: 2016

  20. Magnetic x-ray dichroism in ultrathin epitaxial films

    Energy Technology Data Exchange (ETDEWEB)

    Tobin, J.G.; Goodman, K.W. [Lawrence Berkeley National Lab., CA (United States); Cummins, T.R. [Univ. of Missouri, Rolla, MO (United States)] [and others

    1997-04-01

    The authors have used Magnetic X-ray Linear Dichroism (MXLD) and Magnetic X-ray Circular Dichroism (MXCD) to study the magnetic properties of epitaxial overlayers in an elementally specific fashion. Both MXLD and MXCD Photoelectron Spectroscopy were performed in a high resolution mode at the Spectromicroscopy Facility of the ALS. Circular Polarization was obtained via the utilization of a novel phase retarder (soft x-ray quarter wave plate) based upon transmission through a multilayer film. The samples were low temperature Fe overlayers, magnetic alloy films of NiFe and CoNi, and Gd grown on Y. The authors results include a direct comparison of high resolution angle resolved Photoelectron Spectroscopy performed in MXLD and MXCD modes as well as structural studies with photoelectron diffraction.

  1. Electronic and vibrational circular dichroism spectra of (R)-(-)-apomorphine

    Energy Technology Data Exchange (ETDEWEB)

    Abbate, Sergio, E-mail: abbate@med.unibs.it [Dipartimento di Scienze Biomediche e Biotecnologie, Universita di Brescia, Viale Europa 11, 25123 Brescia (Italy); CNISM, Consorzio Interuniversitario Scienze Fisiche della Materia, Via della Vasca Navale 84, 00146 Roma (Italy); Longhi, Giovanna; Lebon, France [Dipartimento di Scienze Biomediche e Biotecnologie, Universita di Brescia, Viale Europa 11, 25123 Brescia (Italy); CNISM, Consorzio Interuniversitario Scienze Fisiche della Materia, Via della Vasca Navale 84, 00146 Roma (Italy); Tommasini, Matteo [Dipartimento di Chimica, Materiali e Ingegneria Chimica ' G. Natta' , Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano (Italy); Consorzio Interuniversitario per la Scienza e Tecnologia dei Materiali (INSTM), Unita di Ricerca del Politecnico di Milano (Dip. CMIC), Piazza Leonardo da Vinci 32, 20133 Milano (Italy)

    2012-09-11

    Highlights: Black-Right-Pointing-Pointer ECD and VCD Spectra of (R)-(-)-apomorphine measured in various solvents. Black-Right-Pointing-Pointer DFT calculations allow to study the protonation state and conformations. Black-Right-Pointing-Pointer Contributions from catechol OH vibrations to the VCD spectra is studied. -- Abstract: Apomorphine is a chiral drug molecule; notwithstanding its extraordinary importance, little attention has been paid to the characterization of its chiroptical properties. Here we report on its electronic circular dichroism (ECD) spectra, recorded in methanol and water, and vibrational circular dichroism (VCD) in methanol and dimethyl sulfoxide (DMSO) solutions. Density functional theory (DFT) calculations have allowed us to interpret the spectra and to evaluate the role of possible conformations, charge-states and interactions with counter ions.

  2. Magnetic x-ray dichroism in ultrathin epitaxial films

    International Nuclear Information System (INIS)

    Tobin, J.G.; Goodman, K.W.; Cummins, T.R.

    1997-01-01

    The authors have used Magnetic X-ray Linear Dichroism (MXLD) and Magnetic X-ray Circular Dichroism (MXCD) to study the magnetic properties of epitaxial overlayers in an elementally specific fashion. Both MXLD and MXCD Photoelectron Spectroscopy were performed in a high resolution mode at the Spectromicroscopy Facility of the ALS. Circular Polarization was obtained via the utilization of a novel phase retarder (soft x-ray quarter wave plate) based upon transmission through a multilayer film. The samples were low temperature Fe overlayers, magnetic alloy films of NiFe and CoNi, and Gd grown on Y. The authors results include a direct comparison of high resolution angle resolved Photoelectron Spectroscopy performed in MXLD and MXCD modes as well as structural studies with photoelectron diffraction

  3. Modeling Electronic Circular Dichroism within the Polarizable Embedding Approach

    DEFF Research Database (Denmark)

    Nørby, Morten S; Olsen, Jógvan Magnus Haugaard; Steinmann, Casper

    2017-01-01

    We present a systematic investigation of the key components needed to model single chromophore electronic circular dichroism (ECD) within the polarizable embedding (PE) approach. By relying on accurate forms of the embedding potential, where especially the inclusion of local field effects...... are in focus, we show that qualitative agreement between rotatory strength parameters calculated by full quantum mechanical calculations and the more efficient embedding calculations can be obtained. An important aspect in the computation of reliable absorption parameters is the need for conformational...... sampling. We show that a significant number of snapshots are needed to avoid artifacts in the calculated electronic circular dichroism parameters due to insufficient configurational sampling, thus highlighting the efficiency of the PE model....

  4. Magnetic Circular Dichroism of Porphyrin Lanthanide M3+ Complexes

    Czech Academy of Sciences Publication Activity Database

    Andrushchenko, Valery; Padula, Daniele; Zhivotova, E.; Yamamoto, S.; Bouř, Petr

    2014-01-01

    Roč. 26, č. 10 (2014), s. 655-662 ISSN 0899-0042 R&D Projects: GA ČR GA13-03978S; GA ČR GAP208/11/0105; GA MŠk(CZ) LH11033 Grant - others:GA AV ČR(CZ) M200550902 Institutional support: RVO:61388963 Keywords : magnetic circular dichroism * lanthanides * porphyrin complexes * density functional theory * sum over state computations Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.886, year: 2014

  5. Magnetic circular dichroism of CdTe nanoparticles

    Science.gov (United States)

    Malakhovskii, A. V.; Sokolov, A. E.; Tsipotan, A. S.; Zharkov, S. M.; Zabluda, V. N.

    2018-04-01

    Magnetic circular dichroism (MCD) of water-soluble CdTe nanoparticles was observed in the visible spectral range for the first time. Diameter of nanoparticles varied from 2.3 to 4.5 nm. Absorption and photoluminescence spectra were also recorded. Absorption line at 19400 cm-1 and luminescent line at 18200 cm-1 were observed. Splitting of value 960 cm-1 was revealed in the MCD spectrum. Approximately the same splitting was extracted from the absorption spectrum. The MCD was identified as the temperature independent paramagnetic mixing effect. Nature of the absorption line and of its splitting are discussed.

  6. Modeling magnetic circular dichroism within the polarizable embedding approach

    DEFF Research Database (Denmark)

    Nørby, Morten Steen; Coriani, Sonia; Kongsted, Jacob

    2018-01-01

    Magnetic circular dichroism (MCD) is defined as the differential absorption of left and right circularly polarized light in a sample subjected to an external magnetic field. In order to interpret the results of MCD measurements, theoretical predictions of key MCD parameters can be of utmost...... importance. From an experimental point of view, MCD spectra of molecules are often measured in an environment and most notably in a solution. Thus, it may be very important that the method used to predict the MCD parameters is able to correctly account for medium effects. In this paper, we investigate...

  7. Twisting dirac fermions: circular dichroism in bilayer graphene

    Science.gov (United States)

    Suárez Morell, E.; Chico, Leonor; Brey, Luis

    2017-09-01

    Twisted bilayer graphene is a chiral system which has been recently shown to present circular dichroism. In this work we show that the origin of this optical activity is the rotation of the Dirac fermions’ helicities in the top and bottom layer. Starting from the Kubo formula, we obtain a compact expression for the Hall conductivity that takes into account the dephasing of the electromagnetic field between the top and bottom layers and gathers all the symmetries of the system. Our results are based in both a continuum and a tight-binding model, and they can be generalized to any two-dimensional Dirac material with a chiral stacking between layers.

  8. Understanding electron magnetic circular dichroism in a transition potential approach

    Science.gov (United States)

    Barthel, J.; Mayer, J.; Rusz, J.; Ho, P.-L.; Zhong, X. Y.; Lentzen, M.; Dunin-Borkowski, R. E.; Urban, K. W.; Brown, H. G.; Findlay, S. D.; Allen, L. J.

    2018-04-01

    This paper introduces an approach based on transition potentials for inelastic scattering to understand the underlying physics of electron magnetic circular dichroism (EMCD). The transition potentials are sufficiently localized to permit atomic-scale EMCD. Two-beam and three-beam systematic row cases are discussed in detail in terms of transition potentials for conventional transmission electron microscopy, and the basic symmetries which arise in the three-beam case are confirmed experimentally. Atomic-scale EMCD in scanning transmission electron microscopy (STEM), using both a standard STEM probe and vortex beams, is discussed.

  9. PCDDB: new developments at the Protein Circular Dichroism Data Bank.

    Science.gov (United States)

    Whitmore, Lee; Miles, Andrew John; Mavridis, Lazaros; Janes, Robert W; Wallace, B A

    2017-01-04

    The Protein Circular Dichroism Data Bank (PCDDB) has been in operation for more than 5 years as a public repository for archiving circular dichroism spectroscopic data and associated bioinformatics and experimental metadata. Since its inception, many improvements and new developments have been made in data display, searching algorithms, data formats, data content, auxillary information, and validation techniques, as well as, of course, an increase in the number of holdings. It provides a site (http://pcddb.cryst.bbk.ac.uk) for authors to deposit experimental data as well as detailed information on methods and calculations associated with published work. It also includes links for each entry to bioinformatics databases. The data are freely available to accessors either as single files or as complete data bank downloads. The PCDDB has found broad usage by the structural biology, bioinformatics, analytical and pharmaceutical communities, and has formed the basis for new software and methods developments. © The Author(s) 2016. Published by Oxford University Press on behalf of Nucleic Acids Research.

  10. Circular dichroism probed by two-photon fluorescence microscopy in enantiopure chiral polyfluorene thin films

    NARCIS (Netherlands)

    Savoini, M.; Wu, Xiaofei; Celebrano, M.; Ziegler, J.; Biagioni, P.; Meskers, S.C.J.; Duo, L.; Hecht, B.; Finazzi, M.

    2012-01-01

    Two-photon fluorescence scanning confocal microscopy sensitive to circular dichroism with a diffraction-limited resolution well below 500 nm is demonstrated. With this method, the spatial variation of the circular dichroism of thermally annealed chiral polyfluorene thin films has been imaged. We

  11. X-ray dichroism of rare earth materials

    International Nuclear Information System (INIS)

    Goedkoop, J.B.

    1989-01-01

    The theme of this thesis is the investigation of the strong polarization dependende, or dichroism, that occur in the X-ray absorption spectra of rare earth materials. The rare earth elements distinguish themselves from the other elements through the behaviour of the 4f electrons which form the valence shell. This shell lies deep inside the atom, with the result that influences from the surrounding solid are well screened off by the outer electrons, so that even in the solid the 4f shell behaves very much like a in free atom or ion, and is almost completely spherically symmetric. Perturbations from the solid environment however always disturb this symmetry to some extend, with the result that the absorption spectrum becomes dependent on the mutual orientation of the polarization vector of the radiation and the ion. Earlier the existence of a strong magnetic X-ray dichroism (MXD) in the 3d→4f transitions of rare earths. In this thesis this work is extended, to a small degree theoretically but mainly experimentally. MXD is used in experiments on bulk sample, terbium iron garnet, and on rare earth overlayers on a ferromagnetic surface, Ni(110). The results of the latter study show unequivocally the potential of the MXD technique. The second theme of the thesis concerns experimental developments in soft X-ray spectroscopy. A description is given of a double crystal monochromator beamline that was constructed by our group at LURE, France. Results of the use of an organic crystal - multilayer comination in such a monochromator is described. Also a method is described for the characterization of the resolution of soft X-ray monochromators. Finally a contribution to the characterization of the electron yield technique in the soft X-ray range is given. (author). 296 refs.; 64 figs.; 59 schemes; 9 tabs

  12. Second-harmonic generation circular dichroism spectroscopy from tripod-like chiral molecular films

    International Nuclear Information System (INIS)

    Wang Xiao-Ou; Chen Li-An; Chen Li-Xue; Sun Xiu-Dong; Li Jun-Qing; Li Chun-Fei

    2010-01-01

    The second-harmonic generation (SHG) circular dichroism in the light of reflection from chiral films of tripod-like chiral molecules is investigated. The expressions of the second-harmonic generation circular dichroism are derived from our presented three-coupled-oscillator model for the tripod-like chiral molecules. Spectral dependence of the circular dichroism of SHG from film surface composed of tripod-like chiral molecules is simulated numerically and analysed. Influence of chiral parameters on the second-harmonic generation circular dichroism spectrum in chiral films is studied. The result shows that the second-harmonic generation circular dichroism is a sensitive method of detecting chirality compared with the ordinary circular dichroism in linear optics. All of our work indicates that the classical molecular models are very effective to explain the second-harmonic generation circular dichroism of chiral molecular system. The classical molecular model theory can give us a clear physical picture and brings us very instructive information about the link between the molecular configuration and the nonlinear processes

  13. Vacuum-ultraviolet circular dichroism spectrophotometer using synchrotron radiation

    International Nuclear Information System (INIS)

    Matsuo, K.; Fukuyama, T.; Yonehara, R.; Namatame, H.; Taniguchi, M.; Gekko, K.

    2005-01-01

    We have constructed a vacuum-ultraviolet circular dichroism (VUVCD) spectrophotometer using a synchrotron radiation and an assembled-type MgF 2 cell endurable under a high vacuum, to measure the CD spectra of biomaterials in aqueous solutions from 310 to 140 nm. To avoid the absorption of light by air and water vapor, all optical devices of the spectrophotometer were set up under a high vacuum (10 -4 Pa). A path length of the optical cell can be adjusted by various Teflon spacers in the range from 1.3 to 50 μm and its temperature can be controlled to an accuracy of ±1 deg. C over the range from -30 to 70 deg. C by a temperature-control unit using a Peltier thermoelectric element. The performance of the spectrophotometer and the optical cell constructed was tested by measuring the CD spectra of ammonium d-camphor-10-sulfonate, D- and L-isomers of amino acids, and myoglobin in aqueous solutions. The spectra obtained demonstrate that the optical system and the sample cell constructed operate normally under a high vacuum and provide useful information on the structure of biomolecules based on the higher energy chromophores

  14. The magnitude of linear dichroism of biological tissues as a result of cancer changes

    Science.gov (United States)

    Bojchuk, T. M.; Yermolenko, S. B.; Fedonyuk, L. Y.; Petryshen, O. I.; Guminetsky, S. G.; Prydij, O. G.

    2011-09-01

    The results of studies of linear dichroism values of different types of biological tissues (human prostate, esophageal epithelial human muscle tissue in rats) both healthy and infected tumor at different stages of development are shown here. The significant differences in magnitude of linear dichroism and its spectral dependence in the spectral range λ = 330 - 750 nm both among the objects of study, and between biotissues: healthy (or affected by benign tumors) and cancer patients are established. It is researched that in all cases in biological tissues (prostate gland, esophagus, human muscle tissue in rats) with cancer the linear dichroism arises, the value of which depends on the type of tissue and time of the tumor process. As for healthy tissues linear dichroism is absent, the results may have diagnostic value for detecting and assessing the degree of development of cancer.

  15. DNA electronic circular dichroism on the inter-base pair scale

    DEFF Research Database (Denmark)

    Di Meo, Florent; Nørby, Morten Steen; Rubio-Magnieto, Jenifer

    2015-01-01

    A successful elucidation of the near-ultraviolet electronic circular dichroism spectrum of a short double-stranded DNA is reported. Time-dependent density functional theory methods are shown to accurately predict spectra and assign bands on the microscopic base-pair scale, a finding that opens...... the field for using circular dichroism spectroscopy as a sensitive nanoscale probe of DNA to reveal its complex interactions with the environment. (Chemical Equation Presented)....

  16. Vacuum-ultraviolet circular dichroism spectrophotometer using synchrotron radiation

    International Nuclear Information System (INIS)

    Matsu, K.; Yonehara, R.; Gekko, K.

    2004-01-01

    Full text: Circular dichroism (CD) spectroscopy is powerful for analyzing the structure of optically active materials such as biopolymers. However, no commercial CD spectrophotometer is capable of measuring the CD in the vacuum ultraviolet (VUV) region below 190 nm because of technical difficulties involved in the light source, optical device, and sample cell. CD measurements extended to the VUV region can provide more detailed and new information on the structure of biopolymers based on the higher energy transition of chromophores such as hydroxyl and acetal groups. We have constructed a VUVCD spectrophotometer to measure the CD spectra of biomaterials in aqueous solutions in the 310-140 nm wavelength region under a high vacuum, using a small-scale SR source (0.7 GeV) at Hiroshima Synchrotron Radiation Center (HiSOR). All optical devices of the spectrophotometer were set up under a high vacuum (10 -6 Torr), to avoid the absorption of light by air and water vapor. The SR light is separated into two orthogonal linearly polarized light beams by a linear polarizer and then modulated to circularly polarized light at 50 kHz by a photo-elastic modulator (PEM). In order to control PEM accurately and to stabilize the lock-in amplifier under a high vacuum, we used the optical servo-control system. Also, an assembled-type MgF 2 cell with a temperature-control unit was constructed using a Peltier thermoelectric element. Its path length can be adjusted by various Tefron spacers in the range from 1.3 to 50 μm and its temperature can be controlled within an accuracy of ± 1 deg C in the range from -30 to 70 deg C. The performance of the spectrophotometer and MgF 2 cell constructed was tested by monitoring the CD spectra of ammonium d-camphor-10-sulfonate (ACS), D- and L-isomers of amino acids. These obtained results demonstrate that the optical system and the sample cell constructed normally operate under a high vacuum to provide useful information on the structure analysis of

  17. Soft x-ray circular dichroism of biomolecules

    International Nuclear Information System (INIS)

    Nakagawa, Kazumichi; Tanaka, Makoto; Agui, Akane

    2005-01-01

    We succeeded to observe natural circular dichroism NCD for biomolecules in soft X-ray region for the first time. Evaporated films of amino acids, phenylalanine (phe) and serine (ser) were prepared in vacuum with the thickness of about 300 nm. Measurement was carried out at the soft X-ray undulator beamline BL23SU of the Spring-8, where left- and right-circularly polarized light (LCPL and RCPL) was available from an APPLE-2 undulator. Difference spectra DA(hν) was plotted as a function of photon energy hν of soft X-ray to be the difference between absorption coefficient A L for LCPL and absorption coefficient A R for RCPL, namely, DA(hν) ≡ A L (hν) - A R (hν). Values of A L and A R were determined by means of the photoelectric drain current measurement. In the DA(hν) spectra for L-phe films, negative peak was observed at 407 eV. On the contrary, for D-phe films, positive peak was observed at 407 eV with the same magnitude but opposite sign. Moreover, no signal was observed for racemic phenylalanine (DL-phe). In the wavelength region of visible to ultraviolet, there is well-known general law in which NCD signals for D- and L-enantiomers are the same magnitude but opposite sign and racemic compound does not show NCD spectra. Characteristic features in DA(hν) spectra of the L-phe, D-phe and DL-phe were of good agreement with this well-known general law. Based on this good agreement, we concluded that peaks at 407 eV in the DA(hν) spectra are true NCD peaks. For ser films, we assigned peaks at 540 eV and 548 eV to be NCD peaks in the same manner. We hope that our first observation of NCD for biomolecules at soft X-ray region will open new science and technologies such as basic science including elucidation of fundamental mechanism of NCD and application to manipulate biomolecules using circularly polarized soft X-ray beams. (author)

  18. Magnetoelectric Jones birefringence and dichroism in a medium of free atoms

    International Nuclear Information System (INIS)

    Mironova, P V; Ovsiannikov, V D; Chernushkin, V V

    2006-01-01

    Theoretical treatment of the magnetoelectric Jones birefringence and dichroism is developed through the bilinearity in static electric and magnetic field dipole-forbidden corrections to the amplitude of Rayleigh scattering. In particular cases of orientation of the static fields relative to the polarization and wave vectors of monochromatic radiation, the amplitude determines corrections to the refractive index of atomic gas responsible for (i) the Jones birefringence and dichroism (ii) linear birefringence and dichroism and (iii) directional anisotropy for the monochromatic wave. The analytical equations and numerical data for the indicated corrections, calculated for alkaline-earth-like atoms, determine optimal conditions for observing the effects in vapours. For resonance on 1 D 2 state essential enhancement is discovered in the frequency dependence for the ratio of refractive index anisotropy of the Jones effect to the square-root product of corresponding anisotropies determining the Kerr and Cotton-Mouton effects

  19. Magnetic x-ray linear dichroism of ultrathin Fe-Ni alloy films

    Energy Technology Data Exchange (ETDEWEB)

    Schumann, F.O.; Willis, R.F. [Pennsylvania State Univ., University Park, PA (United States); Goodman, K.W. [Lawrence Berkeley National Lab., CA (United States)] [and others

    1997-04-01

    The authors have studied the magnetic structure of ultrathin Fe-Ni alloy films as a function of Fe concentration by measuring the linear dichroism of the 3p-core levels in angle-resolved photoemission spectroscopy. The alloy films, grown by molecular-beam epitaxy on Cu(001) surfaces, were fcc and approximately four monolayers thick. The intensity of the Fe dichroism varied with Fe concentration, with larger dichroisms at lower Fe concentrations. The implication of these results to an ultrathin film analogue of the bulk Invar effect in Fe-Ni alloys will be discussed. These measurements were performed at the Spectromicroscopy Facility (Beamline 7.0.1) of the Advanced Light Source.

  20. Giant Circular Dichroism in Individual Carbon Nanotubes Induced by Extrinsic Chirality

    Directory of Open Access Journals (Sweden)

    A. Yokoyama

    2014-01-01

    Full Text Available Circular dichroism is widely used for characterizing organic and biological materials, but measurements at a single-molecule level are challenging because differences in absorption for opposite helicities are small. Here, we show that extrinsic chirality can induce giant circular dichroism in individual carbon nanotubes, with the degree of polarization reaching 65%. The signal has a large dependence on the incidence angle, consistent with extrinsic-chirality-induced effects in which symmetry is broken by the optical wave vector. We propose that the field-induced charge distribution on the substrate results in an efficient polarization conversion, giving rise to the giant dichroism. Our results highlight the possibility of polarization manipulation at the nanoscale for applications in integrated photonics and novel metamaterial designs.

  1. Magnetic dichroism in UV photoemission at off-normal emission: Study of the valence bands

    International Nuclear Information System (INIS)

    Venus, D.; Kuch, W.; Lin, M.; Schneider, C.M.; Ebert, H.; Kirschner, J.

    1997-01-01

    Magnetic dichroism of angle-resolved UV photoemission from fcc Co/Cu(001) thin films has been measured using linearly p-polarized light, and a coplanar geometry where the light and photoelectron wave vectors are antiparallel, and both are perpendicular to the in-plane sample magnetization. This geometry emphasizes information about state dispersion due to the crystalline symmetry. An orderly dispersion of the features in the magnetic dichroism over a wide range of off-normal angles of electron emission is related in detail to the bulk band structure of fcc Co. The measurements confirm the practical utility of magnetic dichroism experiments as a relatively simple complement to spin-resolved photoemission. copyright 1997 The American Physical Society

  2. Near shot-noise limited time-resolved circular dichroism pump-probe spectrometer

    Science.gov (United States)

    Stadnytskyi, Valentyn; Orf, Gregory S.; Blankenship, Robert E.; Savikhin, Sergei

    2018-03-01

    We describe an optical near shot-noise limited time-resolved circular dichroism (TRCD) pump-probe spectrometer capable of reliably measuring circular dichroism signals in the order of μdeg with nanosecond time resolution. Such sensitivity is achieved through a modification of existing TRCD designs and introduction of a new data processing protocol that eliminates approximations that have caused substantial nonlinearities in past measurements and allows the measurement of absorption and circular dichroism transients simultaneously with a single pump pulse. The exceptional signal-to-noise ratio of the described setup makes the TRCD technique applicable to a large range of non-biological and biological systems. The spectrometer was used to record, for the first time, weak TRCD kinetics associated with the triplet state energy transfer in the photosynthetic Fenna-Matthews-Olson antenna pigment-protein complex.

  3. DichroMatch at the protein circular dichroism data bank (DM@PCDDB): A web-based tool for identifying protein nearest neighbors using circular dichroism spectroscopy.

    Science.gov (United States)

    Whitmore, Lee; Mavridis, Lazaros; Wallace, B A; Janes, Robert W

    2018-01-01

    Circular dichroism spectroscopy is a well-used, but simple method in structural biology for providing information on the secondary structure and folds of proteins. DichroMatch (DM@PCDDB) is an online tool that is newly available in the Protein Circular Dichroism Data Bank (PCDDB), which takes advantage of the wealth of spectral and metadata deposited therein, to enable identification of spectral nearest neighbors of a query protein based on four different methods of spectral matching. DM@PCDDB can potentially provide novel information about structural relationships between proteins and can be used in comparison studies of protein homologs and orthologs. © 2017 The Authors Protein Science published by Wiley Periodicals, Inc. on behalf of The Protein Society.

  4. Conformational analysis and circular dichroism of bilirubin, the yellow pigment of jaundice

    Science.gov (United States)

    Lightner, David A.; Person, Richard; Peterson, Blake; Puzicha, Gisbert; Pu, Yu-Ming; Bojadziev, Stefan

    1991-06-01

    Conformational analysis of (4Z, 15Z)-bilirubin-IX(alpha) by molecular mechanics computations reveals a global energy minimum folded conformation. Powerful added stabilization is achieved through intramolecular hydrogen bonding. Theoretical treatment of bilirubin as a molecular exciton predicts an intense bisignate circular dichroism spectrum for the folded conformation: (Delta) (epsilon) is congruent to 270 L (DOT) mole-1 (DOT) cm-1 for the $OM450 nm electronic transition(s). Synthesis of bilirubin analogs with propionic acid groups methylated at the (alpha) or (beta) position introduces an allosteric effect that allows for an optical resolution of the pigments, with enantiomers exhibiting the theoretically predicted circular dichroism.

  5. Circular dichroism spectral data and metadata in the Protein Circular Dichroism Data Bank (PCDDB): a tutorial guide to accession and deposition.

    Science.gov (United States)

    Janes, Robert W; Miles, A J; Woollett, B; Whitmore, L; Klose, D; Wallace, B A

    2012-09-01

    The Protein Circular Dichroism Data Bank (PCDDB) is a web-based resource containing circular dichroism (CD) and synchrotron radiation circular dichroism spectral and associated metadata located at http://pcddb.cryst.bbk.ac.uk. This resource provides a freely available, user-friendly means of accessing validated CD spectra and their associated experimental details and metadata, thereby enabling broad usage of this material and new developments across the structural biology, chemistry, and bioinformatics communities. The resource also enables researchers utilizing CD as an experimental technique to have a means of storing their data at a secure site from which it is easily retrievable, thereby making their results publicly accessible, a current requirement of many grant-funding agencies world-wide, as well as meeting the data-sharing requirements for journal publications. This tutorial provides extensive information on searching, accessing, and downloading procedures for those who wish to utilize the data available in the data bank, and detailed information on deposition procedures for creating and validating entries, including comprehensive explanations of their contents and formats, for those who wish to include their data in the data bank. Copyright © 2012 Wiley Periodicals, Inc.

  6. A Simple Spreadsheet Program to Simulate and Analyze the Far-UV Circular Dichroism Spectra of Proteins

    Science.gov (United States)

    Abriata, Luciano A.

    2011-01-01

    A simple algorithm was implemented in a spreadsheet program to simulate the circular dichroism spectra of proteins from their secondary structure content and to fit [alpha]-helix, [beta]-sheet, and random coil contents from experimental far-UV circular dichroism spectra. The physical basis of the method is briefly reviewed within the context of…

  7. Optical absorption and magnetic circular dichroism spectra of thiouracils: a quantum mechanical study in solution

    DEFF Research Database (Denmark)

    Martínez-Fernández, L.; Fahleson, Tobias; Norman, Patrick

    2017-01-01

    The excited electronic states of 2-thiouracil, 4-thiouracil and 2,4-dithiouracil, the analogues of uracil where the carbonyl oxygens are substituted by sulphur atoms, have been investigated by computing the magnetic circular dichroism (MCD) and one-photon absorption (OPA) spectra at the time-depe...

  8. Circular dichroism as a means to follow DNA gymnastics: on the shoulders of giants

    Directory of Open Access Journals (Sweden)

    H.H. Klump

    2010-01-01

    Full Text Available This is the first report of DNA stem-loops self-assembled by ‘foot-loop’ interactions into either two-dimensional strings or three-dimensional spirals, distinguished by circular dichroism spectroscopy. All subunits are linked by cooperative Watson-Crick hydrogen bonds.

  9. Protein Circular Dichroism Data Bank (PCDDB): data bank and website design.

    Science.gov (United States)

    Whitmore, Lee; Janes, Robert W; Wallace, B A

    2006-06-01

    The Protein Circular Dichroism Data Bank (PCDDB) is a new deposition data bank for validated circular dichroism spectra of biomacromolecules. Its aim is to be a resource for the structural biology and bioinformatics communities, providing open access and archiving facilities for circular dichroism and synchrotron radiation circular dichroism spectra. It is named in parallel with the Protein Data Bank (PDB), a long-existing valuable reference data bank for protein crystal and NMR structures. In this article, we discuss the design of the data bank structure and the deposition website located at http://pcddb.cryst.bbk.ac.uk. Our aim is to produce a flexible and comprehensive archive, which enables user-friendly spectral deposition and searching. In the case of a protein whose crystal structure and sequence are known, the PCDDB entry will be linked to the appropriate PDB and sequence data bank files, respectively. It is anticipated that the PCDDB will provide a readily accessible biophysical catalogue of information on folded proteins that may be of value in structural genomics programs, for quality control and archiving in industrial and academic labs, as a resource for programs developing spectroscopic structural analysis methods, and in bioinformatics studies. Copyright 2006 Wiley-Liss, Inc.

  10. Chirality Transfer in Magnetic Coordination Complexes Monitored by Vibrational and Electronic Circular Dichroism

    Czech Academy of Sciences Publication Activity Database

    Wu, T.; Zhang, X. P.; You, X. Z.; Li, Y. Z.; Bouř, Petr

    2014-01-01

    Roč. 79, č. 5 (2014), s. 698-707 ISSN 2192-6506 Institutional support: RVO:61388963 Keywords : chirality * circular dichroism * iron * magnetic properties * Schiff bases Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.997, year: 2014

  11. Probing electronic coupling between adenine bases in RNA strands from synchrotron radiation circular dichroism experiments

    DEFF Research Database (Denmark)

    Nielsen, Lisbeth Munksgård; Hoffmann, Søren Vrønning; Nielsen, Steen Brøndsted

    2012-01-01

    Circular dichroism spectra (176–330 nm) of RNA adenine oligomers, (rA)n (n = 1–10, 12, 15, and 20), reveal electronic coupling between two bases in short strands. The number of interacting bases in long strands is more and larger than that reported previously for the corresponding DNA strands....

  12. SUM-RULES FOR MAGNETIC DICHROISM IN RARE-EARTH 4F-PHOTOEMISSION

    NARCIS (Netherlands)

    THOLE, BT; VANDERLAAN, G

    1993-01-01

    We present new sum rules for magnetic dichroism in spin polarized photoemission from partly filled shells which give the expectation values of the orbital and spin magnetic moments and their correlations in the ground state. We apply this to the 4f photoemission of rare earths, where the

  13. Near infrared magnetic circular dichroism of uranium borohydride, U(BH4)4

    International Nuclear Information System (INIS)

    Keiderling, T.A.; Schulz, W.C.

    1980-01-01

    The magnetic circular dichroism of U(BH 4 ) 4 in Hf(BH 4 ) 4 at low temperatures has been measured in the near. The A terms resulting can be interpreted to confirm the E symmetry ground state and three excited state assignments. (orig.)

  14. Magnetic dichroism and spin structure of antiferromagnetic NiO(001) films

    NARCIS (Netherlands)

    Altieri, S; Finazzi, M; Hsieh, HH; Lin, HJ; Chen, CT; Hibma, T; Valeri, S; Sawatzky, GA

    2003-01-01

    We find that Ni L-2 edge x-ray magnetic linear dichroism is fully reversed for NiO(001) films on materials with reversed lattice mismatch. We relate this phenomenon to a preferential stabilization of magnetic S domains with main spin component either in or out of the plane, via dipolar interactions.

  15. Vibrational and electronic circular dichroism as powerful tools for the conformational analysis of cationic antimicrobial peptides

    Czech Academy of Sciences Publication Activity Database

    Kocourková, L.; Novotná, P.; Šťovíčková-Habartová, L.; Čujová, Sabína; Čeřovský, Václav; Urbanová, M.; Setnička, V.

    2016-01-01

    Roč. 147, č. 8 (2016), s. 1439-1445 ISSN 0026-9247 Institutional support: RVO:61388963 Keywords : conformation * circular dichroism * antimicrobial peptides * liposomes * infrared spectroscopy Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 1.282, year: 2016

  16. Interpretation of synchrotron radiation circular dichroism spectra of anionic, cationic, and zwitterionic dialanine forms

    Czech Academy of Sciences Publication Activity Database

    Šebek, Jiří; Gyurcsik, B.; Šebestík, Jaroslav; Kejík, Z.; Bednárová, Lucie; Bouř, Petr

    2007-01-01

    Roč. 111, č. 14 (2007), s. 2750-2760 ISSN 1089-5639 R&D Projects: GA ČR GA203/06/0420; GA AV ČR IAA400550702 Institutional research plan: CEZ:AV0Z40550506 Keywords : synchrotron radiation * circular dichroism * TD DFT Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.918, year: 2007

  17. A complex-polarization-propagator protocol for magneto-chiral axial dichroism and birefringence dispersion

    DEFF Research Database (Denmark)

    Cukras, Janusz; Kauczor, Joanna; Norman, Patrick

    2016-01-01

    A computational protocol for magneto-chiral dichroism and magneto-chiral birefringence dispersion is presented within the framework of damped response theory, also known as complex polarization propagator theory, at the level of time-dependent Hartree–Fock and time-dependent density functional th...

  18. Magnetic x-ray linear dichroism in resonant and non-resonant Gd 4f photoemission

    Energy Technology Data Exchange (ETDEWEB)

    Mishra, S.; Gammon, W.J.; Pappas, D.P. [Virginia Commonwealth Univ., Richmond, VA (United States)] [and others

    1997-04-01

    The enhancement of the magnetic linear dichroism in resonant 4f photoemission (MLDRPE) is studied from a 50 monolayer film of Gd/Y(0001). The ALS at beamline 7.0.1 provided the source of linearly polarized x-rays used in this study. The polarized light was incident at an angle of 30 degrees relative to the film plane, and the sample magnetization was perpendicular to the photon polarization. The linear dichroism of the 4f core levels is measured as the photon energy is tuned through the 4d-4f resonance. The authors find that the MLDRPE asymmetry is strongest at the resonance. Near the threshold the asymmetry has several features which are out of phase with the fine structure of the total yield.

  19. Circular dichroism in a three-dimensional semiconductor chiral photonic crystal

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, S.; Ota, Y.; Tatebayashi, J. [Institute of Nano Quantum Information Electronics, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan); Tajiri, T. [Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan); Iwamoto, S.; Arakawa, Y. [Institute of Nano Quantum Information Electronics, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan); Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan)

    2014-08-04

    Circular dichroism covering the telecommunication band is experimentally demonstrated in a semiconductor-based three-dimensional chiral photonic crystal (PhC). We design a rotationally stacked woodpile PhC structure where neighboring layers are rotated by 60° and three layers construct a single helical unit. The mirror-asymmetric PhC made from GaAs with sub-micron periodicity is fabricated by a micro-manipulation technique. Due to the large contrast of refractive indices between GaAs and air, the experimentally obtained circular dichroism extends over a wide wavelength range, with the transmittance of right-handed circularly polarized incident light being 85% and that of left-handed light being 15% at a wavelength of 1.3 μm. The obtained results show good agreement with numerical simulations.

  20. Magnetic x-ray linear dichroism in resonant and non-resonant Gd 4f photoemission

    International Nuclear Information System (INIS)

    Mishra, S.; Gammon, W.J.; Pappas, D.P.

    1997-01-01

    The enhancement of the magnetic linear dichroism in resonant 4f photoemission (MLDRPE) is studied from a 50 monolayer film of Gd/Y(0001). The ALS at beamline 7.0.1 provided the source of linearly polarized x-rays used in this study. The polarized light was incident at an angle of 30 degrees relative to the film plane, and the sample magnetization was perpendicular to the photon polarization. The linear dichroism of the 4f core levels is measured as the photon energy is tuned through the 4d-4f resonance. The authors find that the MLDRPE asymmetry is strongest at the resonance. Near the threshold the asymmetry has several features which are out of phase with the fine structure of the total yield

  1. Electronic and vibrational circular dichroism spectra of (R)-(−)-apomorphine

    International Nuclear Information System (INIS)

    Abbate, Sergio; Longhi, Giovanna; Lebon, France; Tommasini, Matteo

    2012-01-01

    Highlights: ► ECD and VCD Spectra of (R)-(−)-apomorphine measured in various solvents. ► DFT calculations allow to study the protonation state and conformations. ► Contributions from catechol OH vibrations to the VCD spectra is studied. -- Abstract: Apomorphine is a chiral drug molecule; notwithstanding its extraordinary importance, little attention has been paid to the characterization of its chiroptical properties. Here we report on its electronic circular dichroism (ECD) spectra, recorded in methanol and water, and vibrational circular dichroism (VCD) in methanol and dimethyl sulfoxide (DMSO) solutions. Density functional theory (DFT) calculations have allowed us to interpret the spectra and to evaluate the role of possible conformations, charge-states and interactions with counter ions.

  2. A new X-ray detector for magnetic circular dichroism experiments

    CERN Document Server

    Bateman, J E; Dudzik, E; Laan, G V D; Lipp, J D; Smith, A D; Stephenson, R

    2001-01-01

    X-ray magnetic circular dichroism (XMCD) studies of magnetic 3d transition metal samples require the recording of high quality absorption scans in high magnetic fields using circularly polarised soft X-rays of energies in the range 0.5-1 keV. A Gas Microstrip Detector is described which permits the option of using the X-ray fluorescence signal instead of the usual electron yield signal.

  3. On the magnetic circular dichroism of benzene. A density-functional study

    Czech Academy of Sciences Publication Activity Database

    Kaminský, Jakub; Kříž, Jan; Bouř, Petr

    2017-01-01

    Roč. 146, č. 14 (2017), č. článku 144301. ISSN 0021-9606 R&D Projects: GA ČR GA13-03978S; GA ČR(CZ) GA16-05935S Institutional support: RVO:61388963 Keywords : magnetic circular dichroism * benzene * DFT Subject RIV: CF - Physical ; Theoretical Chemistry OBOR OECD: Physical chemistry Impact factor: 2.965, year: 2016

  4. Soft X-ray magnetic circular dichroism study of UFe2

    International Nuclear Information System (INIS)

    Okane, T.; Takeda, Y.; Fujimori, S.-I.; Terai, K.; Saitoh, Y.; Muramatsu, Y.; Fujimori, A.; Haga, Y.; Yamamoto, E.; Onuki, Y.

    2006-01-01

    Soft X-ray magnetic circular dichroism has been measured at the U N 4,5 and Fe L 2,3 absorption edges of ferromagnetic UFe 2 . The orbital and spin magnetic moments of U 5f and Fe 3d electrons are evaluated by a sum-rule analysis of the XMCD data. It is confirmed that the U 5f orbital moment is parallel to the Fe 3d spin moment

  5. MICROFLUIDIC MIXERS FOR THE INVESTIGATION OF PROTEIN FOLDING USING SYNCHROTRON RADIATION CIRCULAR DICHROISM SPECTROSCOPY

    International Nuclear Information System (INIS)

    Kane, A; Hertzog, D; Baumgartel, P; Lengefeld, J; Horsley, D; Schuler, B; Bakajin, O

    2006-01-01

    The purpose of this study is to design, fabricate and optimize microfluidic mixers to investigate the kinetics of protein secondary structure formation with Synchrotron Radiation Circular Dichroism (SRCD) spectroscopy. The mixers are designed to rapidly initiate protein folding reaction through the dilution of denaturant. The devices are fabricated out of fused silica, so that they are transparent in the UV. We present characterization of mixing in the fabricated devices, as well as the initial SRCD data on proteins inside the mixers

  6. Circular Dichroism is Sensitive to Monovalent Cation Binding in Monensin Complexes

    Czech Academy of Sciences Publication Activity Database

    Nedzhib, A.; Kessler, Jiří; Bouř, Petr; Gyurcsik, B.; Pantcheva, I.

    2016-01-01

    Roč. 28, č. 5 (2016), s. 420-428 ISSN 0899-0042 R&D Projects: GA ČR GA15-09072S; GA ČR(CZ) GA16-05935S Institutional support: RVO:61388963 Keywords : monovalent polyether ionophore * metal complexes * synchrotron radiation circular dichroism * time-dependent density functional theory Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.956, year: 2016

  7. Vibrational Structure in Magnetic Circular Dichroism Spectra of Polycyclic Aromatic Hydrocarbons

    Czech Academy of Sciences Publication Activity Database

    Kaminský, Jakub; Chalupský, Jakub; Štěpánek, P.; Kříž, Jan; Bouř, Petr

    2017-01-01

    Roč. 121, č. 47 (2017), s. 9064-9073 ISSN 1089-5639 R&D Projects: GA ČR GA15-19143S; GA ČR(CZ) GA16-05935S; GA ČR(CZ) GA16-00270S Institutional support: RVO:61388963 Keywords : magnetic circular dichroism * polycyclic aromatic hydrocarbons * DFT Subject RIV: CF - Physical ; Theoretical Chemistry OBOR OECD: Physical chemistry Impact factor: 2.847, year: 2016

  8. Resolving Electronic Transitions in Synthetic Fluorescent Protein Chromophores by Magnetic Circular Dichroism

    Czech Academy of Sciences Publication Activity Database

    Štěpánek, P.; Cowie, T. Y.; Šafařík, Martin; Šebestík, Jaroslav; Pohl, Radek; Bouř, Petr

    2016-01-01

    Roč. 17, č. 15 (2016), s. 2348-2354 ISSN 1439-4235 R&D Projects: GA ČR GA13-03978S; GA ČR(CZ) GA16-05935S Institutional support: RVO:61388963 Keywords : density functional calculations * fluorescence protein chromophores * magnetic circular dichroism * organic synthesis * spectral simulations Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.075, year: 2016

  9. Circular magnetic dichroism of the Fa center adsorption in KCl doped with Li and Na

    International Nuclear Information System (INIS)

    Baldacchini, G.; Botti, S.; Grassano, U.M.

    1990-01-01

    The spin-orbit structure of F A in KCl:Li and KCl:Na have been studied by means of the magnetic circular dichroism. Due to their C 4V , symmetry the F A centers have two different spin-orbit parameters, Δ * and Δ * , which only in the KCl:Li case follow the relation: Δ * F A centers have been determined using the method of moment

  10. Dichroism in the photoionisation of atoms at XUV free-electron lasers

    Energy Technology Data Exchange (ETDEWEB)

    Mazza, T., E-mail: tommaso.mazza@xfel.eu [European XFEL GmbH, Albert-Einstein-Ring 19, D-22761 Hamburg (Germany); Gryzlova, E.V.; Grum-Grzhimailo, A.N. [Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Moscow 119991 (Russian Federation); Kazansky, A.K. [Departamento de Fisica de Materiales, UPV/EHU, E-20018 San Sebastian/Donostia (Spain); IKERBASQUE, Basque Foundation for Science, E-48011 Bilbao (Spain); Donostia International Physics Center (DIPC), E-20018 San Sebastian/Donostia (Spain); Kabachnik, N.M. [European XFEL GmbH, Albert-Einstein-Ring 19, D-22761 Hamburg (Germany); Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Moscow 119991 (Russian Federation); Donostia International Physics Center (DIPC), E-20018 San Sebastian/Donostia (Spain); Meyer, M., E-mail: michael.meyer@xfel.eu [European XFEL GmbH, Albert-Einstein-Ring 19, D-22761 Hamburg (Germany)

    2015-10-15

    Highlights: • We studied 2-color photoionization of He by angle-resolved electron spectroscopy. • Beta-parameters contain information about the symmetry of outgoing electron waves. • Experiments are compared to strong field approximation and perturbation theory. • 2-Photon measurements can be used to characterize FEL radiation properties. • Non-dipole contributions are predicted to produce new features in the dichroism. - Abstract: Two-color photoionization of atomic He has been investigated by angle-integrated and angle-resolved electron spectroscopy. The combined action of intense radiation pulses from the XUV free-electron laser (FEL), FERMI or FLASH, and a synchronized optical laser on the target atom gives rise to a rich sideband structure in the photoemission spectrum. Measurements of the angular distribution parameters and the determination of the circular and linear dichroism for the two-color photoionization enable a detailed analysis of the symmetry of the outgoing electron waves and of the dynamics underlying the multi-photon processes. The experimental results are in excellent agreement with theoretical results obtained using perturbation theory (low intensity regime) and the strong field approximation. For the particular case of two-photon ionization the measurements represent an ideal tool for characterizing certain FEL parameters, here for example the degree and the sign of circular polarization. Finally, new features of the dichroism are theoretically predicted originating from the non-dipole contribution into the photoionization amplitudes.

  11. Electronic states of model hydrocarbon chromophores investigated by Synchrotron Radiation Linear Dichroism (SRLD) spectroscopy on aligned samples

    DEFF Research Database (Denmark)

    Nguyen, Duy Duc; Hoffmann, Søren Vrønning; Jones, Nykola

    2010-01-01

    Conventional UV-VIS absorption spectroscopy provides information on transition energies and intensities. Linear dichroism (LD) spectroscopy on aligned molecular samples yields additional information on transition moment directions, thereby frequently leading to resolution of otherwise overlapping...

  12. Structure of human Rad51 protein filament from molecular modeling and site-specific linear dichroism spectroscopy

    KAUST Repository

    Reymer, A.; Frykholm, K.; Morimatsu, K.; Takahashi, M.; Norden, B.

    2009-01-01

    for central and N-terminal parts of pure (uncomplexed) Rad51 protein by aid of linear dichroism spectroscopy, providing angular orientations of substituted tyrosine residues of Rad51-dsDNA filaments in solution. The structure, validated by comparison

  13. Protein fiber linear dichroism for structure determination and kinetics in a low-volume, low-wavelength couette flow cell

    OpenAIRE

    Dafforn, Tim; Rajendra, Jacindra; Halsall, David J.; Serpell, Louise C.; Rodger, Alison

    2004-01-01

    High-resolution structure determination of soluble globular proteins relies heavily on x-ray crystallography techniques. Such an approach is often ineffective for investigations into the structure of fibrous proteins as these proteins generally do not crystallize. Thus investigations into fibrous protein structure have relied on less direct methods such as x-ray fiber diffraction and circular dichroism. Ultraviolet linear dichroism has the potential to provide additional information on the st...

  14. Element selective X-ray magnetic circular and linear dichroisms in ferrimagnetic yttrium iron garnet films

    Energy Technology Data Exchange (ETDEWEB)

    Rogalev, A. [European Synchrotron Radiation Facility (ESRF), B.P. 220, F-38043 Grenoble Cedex (France); Goulon, J. [European Synchrotron Radiation Facility (ESRF), B.P. 220, F-38043 Grenoble Cedex (France)], E-mail: goulon@esrf.fr; Wilhelm, F. [European Synchrotron Radiation Facility (ESRF), B.P. 220, F-38043 Grenoble Cedex (France); Brouder, Ch. [Institut de Mineralogie et de Physique des Milieux Condenses, UMR-CNRS 7590, Universite Paris VI-VII, 4 place Jussieu, F-75252 Paris Cedex 05 (France); Yaresko, A. [Max Planck Institute for Solid State Research, Heisenbergstrasse 1, 70569 Stuttgart (Germany); Ben Youssef, J.; Indenbom, M.V. [Laboratoire de Magnetisme de Bretagne, CNRS FRE 2697, UFR Sciences et Techniques, F-29328 Brest Cedex (France)

    2009-12-15

    X-ray magnetic circular dichroism (XMCD) was used to probe the existence of induced magnetic moments in yttrium iron garnet (YIG) films in which yttrium is partly substituted with lanthanum, lutetium or bismuth. Spin polarization of the 4d states of yttrium and of the 5d states of lanthanum or lutetium was clearly demonstrated. Angular momentum resolved d-DOS of yttrium and lanthanun was shown to be split by the crystal field, the two resolved substructures having opposite magnetic polarization. The existence of a weak orbital moment involving the 6p states of bismuth was definitely established with the detection of a small XMCD signal at the Bi M{sub 1}-edge. Difference spectra also enhanced the visibility of subtle changes in the Fe K-edge XMCD spectra of YIG and {l_brace}Y, Bi{r_brace}IG films. Weak natural X-ray linear dichroism signatures were systematically observed with all iron garnet films and with a bulk YIG single crystal cut parallel to the (1 1 1) plane: this proved that, at room temperature, the crystal cannot satisfy all requirements of perfect cubic symmetry (space group: Ia3-bar d), crystal distortions preserving at best trigonal symmetry (R3-bar or R3m). For the first time, a very weak X-ray magnetic linear dichroism (XMLD) was also measured in the iron K-edge pre-peak of YIG and revealed the presence of a tiny electric quadrupole moment in the ground-state charge distribution of iron atoms. Band-structure calculations carried out with fully relativistic LMTO-LSDA methods support our interpretation that ferrimagnetically coupled spins at the iron sites induce a spin polarization of the yttrium d-DOS and reproduce the observed crystal field splitting of the XMCD signal.

  15. X-ray magnetic circular dichroism in (Ge,Mn) compounds: Experiments and modeling

    International Nuclear Information System (INIS)

    Tardif, Samuel; Titov, Andrey; Arras, Emmanuel; Slipukhina, Ivetta; Hlil, El-Kébir; Cherifi, Salia; Joly, Yves; Jamet, Matthieu; Barski, André; Cibert, Joël; Kulatov, Erkin; Uspenskii, Yurii A.; Pochet, Pascal

    2014-01-01

    X-ray absorption (XAS) and x-ray magnetic circular dichroism (XMCD) spectra at the L 2,3 edges of Mn in (Ge,Mn) compounds have been measured and are compared to the results of first principles calculation. Early ab initio studies show that the Density Functional Theory (DFT) can very well describe the valence band electronic properties but fails to reproduce a characteristic change of sign in the L 3 XMCD spectrum of Mn in Ge 3 Mn 5 , which is observed in experiments. In this work we demonstrate that this disagreement is partially related to an underestimation of the exchange splitting of Mn 2p core states within the local density approximation. It is shown that the change in sign experimentally observed is reproduced if the exchange splitting is accurately calculated within the Hartree–Fock approximation, while the final states can be still described by the DFT. This approach is further used to calculate the XMCD in different (Ge,Mn) compounds. It demonstrates that the agreement between experimental and theoretical spectra can be improved by combining state of the art calculations for the core and valence states respectively. - Highlights: • X-ray absorption and magnetic circular dichroism spectra are measured and compared to first principles calculations in (Ge,Mn) compounds. • Standard density functional theory fails in properly describing peculiar features observed in the experiment. • A new approach to calculate theoretical X-ray absorption and magnetic circular dichroism spectra is proposed. • Improved modeling of the core levels splitting using the Hartree–Fock approximation allows for a better matching with the experiment. • This new method could be generalized to any 3d metallic-like system

  16. Element selective X-ray magnetic circular and linear dichroisms in ferrimagnetic yttrium iron garnet films

    International Nuclear Information System (INIS)

    Rogalev, A.; Goulon, J.; Wilhelm, F.; Brouder, Ch.; Yaresko, A.; Ben Youssef, J.; Indenbom, M.V.

    2009-01-01

    X-ray magnetic circular dichroism (XMCD) was used to probe the existence of induced magnetic moments in yttrium iron garnet (YIG) films in which yttrium is partly substituted with lanthanum, lutetium or bismuth. Spin polarization of the 4d states of yttrium and of the 5d states of lanthanum or lutetium was clearly demonstrated. Angular momentum resolved d-DOS of yttrium and lanthanun was shown to be split by the crystal field, the two resolved substructures having opposite magnetic polarization. The existence of a weak orbital moment involving the 6p states of bismuth was definitely established with the detection of a small XMCD signal at the Bi M 1 -edge. Difference spectra also enhanced the visibility of subtle changes in the Fe K-edge XMCD spectra of YIG and {Y, Bi}IG films. Weak natural X-ray linear dichroism signatures were systematically observed with all iron garnet films and with a bulk YIG single crystal cut parallel to the (1 1 1) plane: this proved that, at room temperature, the crystal cannot satisfy all requirements of perfect cubic symmetry (space group: Ia3-bar d), crystal distortions preserving at best trigonal symmetry (R3-bar or R3m). For the first time, a very weak X-ray magnetic linear dichroism (XMLD) was also measured in the iron K-edge pre-peak of YIG and revealed the presence of a tiny electric quadrupole moment in the ground-state charge distribution of iron atoms. Band-structure calculations carried out with fully relativistic LMTO-LSDA methods support our interpretation that ferrimagnetically coupled spins at the iron sites induce a spin polarization of the yttrium d-DOS and reproduce the observed crystal field splitting of the XMCD signal.

  17. Molecular photoionisation using synchrotron radiation. Photoelectron photoion coincidence and circular dichroism

    International Nuclear Information System (INIS)

    Garcia-Macias, Gustavo Adolfo

    2002-01-01

    The first ionisation potential of the CF 3 radical has been determined in this work from the appearance potential of the CF 3 + fragment, formed in the photofragmentation of CF 3 Br. In obtaining this value special care has been taken in removing the contributions from second order light and internal energy of the fragmenting parent ion. The resulting ionisation potential was found to be in very good agreement with a number of recent theoretical calculations. The valence photoelectron spectra of three monoterpenes such as limonene, carvone and camphor have been recorded along with their mass spectra taken in coincidence with energy selected photoelectrons, providing information about state selected parent ion fragmentation channels. A new photoelectron spectrometer based on the Alien box design has been studied by ray-tracing simulations. It will include a two dimensional position sensitive detector system consisting in two micro channel plates in a chevron stack and a delay-line anode to encode the impact position. It is currently under construction and it is expected to be commissioned by summer 2002. Continuum molecular scattering calculations have been performed in the optically active carvone. We have looked for circular dichroism in the angular distributions of core and valence photoelectron spectra. The values have been found to be of at least four orders of magnitude bigger than the normal circular dichroism in absorption. Experimental results have been obtained for the circular dichroism in the valence and inner shells of camphor and carvone as a function of photon energy. The experiments were performed in the BESSY II and SACO storage rings in Berlin and Orsay respectively. The core results on camphor show a definite difference between the partial cross-sections of the carbonyl carbon Is orbital when switching the helicity of either the light or the enantiomer. The core results on carvone have yet to be properly analysed and are noisier but the circular

  18. Assignment of absolute stereostructures through quantum mechanics electronic and vibrational circular dichroism calculations.

    Science.gov (United States)

    Dai, Peng; Jiang, Nan; Tan, Ren-Xiang

    2016-01-01

    Elucidation of absolute configuration of chiral molecules including structurally complex natural products remains a challenging problem in organic chemistry. A reliable method for assigning the absolute stereostructure is to combine the experimental circular dichroism (CD) techniques such as electronic and vibrational CD (ECD and VCD), with quantum mechanics (QM) ECD and VCD calculations. The traditional QM methods as well as their continuing developments make them more applicable with accuracy. Taking some chiral natural products with diverse conformations as examples, this review describes the basic concepts and new developments of QM approaches for ECD and VCD calculations in solution and solid states.

  19. Vacuum-ultraviolet circular dichroism of amino acids as revealed by synchrotron radiation spectrophotometer

    International Nuclear Information System (INIS)

    Matsuo, Koichi; Matsushima, Yosuke; Fukuyama, Takayuki; Gekko, Kunihiko; Senba, Shinya

    2002-01-01

    We succeeded in constructing a vacuum-ultraviolet circular dichroism (VUVCD) spectrophotometer with a small-scale synchrotron radiation source (0.7 GeV) at Hiroshima Synchrotron Radiation Center (HiSOR). This VUVCD system revealed for the first time the CD spectra of amino acids in aqueous media in the 310-140 nm region under high vacuum. These data, which cannot be observed by any types of existing CD spectrophotometers, now open a new field in the structural analysis of biomaterials on a basis of the higher energy transition of chromophores. (author)

  20. Enhanced Circular Dichroism of Gold Bilayered Slit Arrays Embedded with Rectangular Holes.

    Science.gov (United States)

    Zhang, Hao; Wang, Yongkai; Luo, Lina; Wang, Haiqing; Zhang, Zhongyue

    2017-01-01

    Gold bilayered slit arrays with rectangular holes embedded into the metal surface are designed to enhance the circular dichroism (CD) effect of gold bilayered slit arrays. The rectangular holes in these arrays block electric currents and generate localized surface plasmons around these holes, thereby strengthening the CD effect. The CD enhancement factor depends strongly on the rotational angle and the structural parameters of the rectangular holes; this factor can be enhanced further by drilling two additional rectangular holes into the metal surfaces of the arrays. These results help facilitate the design of chiral structures to produce a strong CD effect and large electric fields.

  1. Synchrotron radiation linear dichroism (SRLD) investigation of the electronictransitions of quinizarin, chrysazin, and anthrarufin

    DEFF Research Database (Denmark)

    Nguyen, Duy Duc; Jones, Nykola C.; Hoffmann, Søren Vrønning

    2010-01-01

    The electronic transitions of the three , (alpha), (alphaPrime) -dihydroxy derivatives of anthraquinone, 1,4-dihydroxy-, 1,8-dihydroxy-, and 1,5-dihydroxy-9,10-anthraquinone (quinizarin, chrysazin, and anthrarufin), were investigated by synchrotron radiation linear dichroism (SRLD) spectroscopy...... the investigated region (15,000-58,000cm-1), essentially similar wavenumbers, intensities, and transition moment directions were determined for chrysazin and anthrarufin, while the spectrum of quinizarin deviated significantly. The results of time-dependent density functional theory (TD-DFT) calculations were...

  2. Structure and Absolute Configuration of Nyasol and Hinokiresinol via Synthesis and Vibrational Circular Dichroism Spectroscopy

    DEFF Research Database (Denmark)

    Lassen, Peter Rygaard

    2005-01-01

    The absolute configuration of the norlignan (+)-nyasol was determined to be S by comparison of the experimental vibrational circular dichroism data with first-principle calculations taking into account the eight lowest energy conformations. The established absolute configuration of (+)-nyasol...... enables establishment of the absolute configuration of (-)-hinokiresinol, which is concluded to be S. A total synthesis and resolution of hinokiresinol has been performed to resolve the conflicting reports of the coupling constant of the vinylic protons of the disubstituted double bond in this molecule...

  3. Linear and circular dichroism in angle resolved Fe 3p photomission. Revision 1

    International Nuclear Information System (INIS)

    Tamura, E.; Waddill, G.D.; Tobin, J.G.; Sterne, P.A.

    1994-01-01

    Using a recently developed spin-polarized, fully relativistic, multiple scattering approach based on the layer KKR Green function method, we have reproduced the Fe 3p angle-resolved soft x-ray photoemission spectra and analyzed the associated large magnetic dichroism effects for excitation with both linearly and circularly polarized light. Comparison between theory and experiment yields a spin-orbit splitting of 1.0--1.2 eV and an exchange splitting of 0.9-- 1.0 eV for Fe 3p. These values are 50--100% larger than those hitherto obtained experimentally

  4. Imaging photoelectron circular dichroism of chiral molecules by femtosecond multiphoton coincidence detection

    Energy Technology Data Exchange (ETDEWEB)

    Lehmann, C. Stefan; Ram, N. Bhargava; Janssen, Maurice H. M., E-mail: m.h.m.janssen@vu.nl [LaserLaB Amsterdam, VU University Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam (Netherlands); Powis, Ivan [School of Chemistry, University of Nottingham, Nottingham NG7 2RD (United Kingdom)

    2013-12-21

    Here, we provide a detailed account of novel experiments employing electron-ion coincidence imaging to discriminate chiral molecules. The full three-dimensional angular scattering distribution of electrons is measured after photoexcitation with either left or right circular polarized light. The experiment is performed using a simplified photoelectron-photoion coincidence imaging setup employing only a single particle imaging detector. Results are reported applying this technique to enantiomers of the chiral molecule camphor after three-photon ionization by circularly polarized femtosecond laser pulses at 400 nm and 380 nm. The electron-ion coincidence imaging provides the photoelectron spectrum of mass-selected ions that are observed in the time-of-flight mass spectra. The coincident photoelectron spectra of the parent camphor ion and the various fragment ions are the same, so it can be concluded that fragmentation of camphor happens after ionization. We discuss the forward-backward asymmetry in the photoelectron angular distribution which is expressed in Legendre polynomials with moments up to order six. Furthermore, we present a method, similar to one-photon electron circular dichroism, to quantify the strength of the chiral electron asymmetry in a single parameter. The circular dichroism in the photoelectron angular distribution of camphor is measured to be 8% at 400 nm. The electron circular dichroism using femtosecond multiphoton excitation is of opposite sign and about 60% larger than the electron dichroism observed before in near-threshold one-photon ionization with synchrotron excitation. We interpret our multiphoton ionization as being resonant at the two-photon level with the 3s and 3p Rydberg states of camphor. Theoretical calculations are presented that model the photoelectron angular distribution from a prealigned camphor molecule using density functional theory and continuum multiple scattering X alpha photoelectron scattering calculations

  5. Computation of magnetic circular dichroism by sum-over-states summations

    Czech Academy of Sciences Publication Activity Database

    Štěpánek, Petr; Bouř, Petr

    2013-01-01

    Roč. 34, č. 18 (2013), s. 1531-1539 ISSN 0192-8651 R&D Projects: GA ČR GAP208/11/0105; GA MŠk(CZ) LH11033; GA ČR GA13-03978S Grant - others:AV ČR(CZ) M200551205 Institutional support: RVO:61388963 Keywords : time-dependent * density functional theory * sum over states * spectroscopy * magnetic circular dichroism * origin dependence Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.601, year: 2013

  6. Ab initio calculations of anharmonic vibrational circular dichroism intensities of trans-2,3-dideuteriooxirane

    DEFF Research Database (Denmark)

    Bak, KL; Bludsky, O.; Jorgensen, P

    1995-01-01

    A priori theory is derived for anharmonic calculations of vibrational circular dichroism (VCD). The anharmonic VCD expression is gauge origin independent and reduce to the magnetic field perturbation theory expression in the double-harmonic approximation. The theory has been implemented using...... for the atomic axial tensors and using second-order Moller-Plesset theory for the atomic polar tensors and the force fields, The changes of the vibrational rotatory strengths from anharmonicities are small, and do not explain the previously observed large discrepancies between the double-harmonic results...

  7. Scaling of the L2,3 circular magnetic x-ray dichroism of Fe nitrides

    International Nuclear Information System (INIS)

    Alouani, M.; Wills, J.M.; Wilkins, J.W.

    1998-01-01

    We have implemented the calculation of the x-ray-absorption cross section for left- and right-circularly polarized x-ray beams within the local-density approximation by means of our all-electron full-relativistic and spin-polarized full-potential linear muffin-tin orbital method. We show that the L 2,3 circular magnetic x-ray dichroism of Fe, Fe 3 N, and Fe 4 N compounds scales to a single curve when divided by the local magnetic moment. Sum rules determine the spin and orbital magnetic moment of iron atoms in these ordered iron nitrides. copyright 1998 The American Physical Society

  8. Time-resolved circular dichroism: Application to the study of conformal changes in biomolecules

    Science.gov (United States)

    Hache, F.

    2010-06-01

    Circular dichroism (CD) is known to be a very sensitive probe of the conformation of molecules and biomolecules. It is therefore tempting to implement CD in a pump-probe experiment in order to measure ultrarapid conformational changes which occur in photochemical processes. We present two technical developments of such time-resolved CD experiments. The first one relies on the modulation of the probe polarization from left to right circular whereas the second one measures the pump-induced ellipticity of the probe with a Babinet-Soleil compensator. Some applications are described and extension of these techniques towards the study of elementary protein folding processes is discussed.

  9. Time-resolved circular dichroism: Application to the study of conformal changes in biomolecules

    Directory of Open Access Journals (Sweden)

    Hache F.

    2010-06-01

    Full Text Available Circular dichroism (CD is known to be a very sensitive probe of the conformation of molecules and biomolecules. It is therefore tempting to implement CD in a pump-probe experiment in order to measure ultrarapid conformational changes which occur in photochemical processes. We present two technical developments of such time-resolved CD experiments. The first one relies on the modulation of the probe polarization from left to right circular whereas the second one measures the pump-induced ellipticity of the probe with a Babinet-Soleil compensator. Some applications are described and extension of these techniques towards the study of elementary protein folding processes is discussed.

  10. Dichroism, chirality, and polarization eigenstates in Babinet nanoslot-dimer membrane metamaterials

    Science.gov (United States)

    Zhukovsky, Sergei V.; Chigrin, Dmitry N.; Kremers, Christian; Lavrinenko, Andrei V.

    2013-11-01

    We present a detailed theoretical description of the optical properties of planar metamaterials comprising a metal membrane patterned with openings (microslots) arranged in closely located couples (dimers). Using the covariant coupled-dipole approach, the effective material tensors of such a metamaterial are recovered, and contributions responsible for elliptical dichroism and optical activity are identified. Polarization conversion properties of II-shaped and V-shaped dimers are determined and explained in terms of elliptically polarized eigenmodes of the metamaterial. Good agreement with direct numerical simulations is demonstrated. The results obtained are promising for the design of thin-film frequency selective polarization shapers for terahertz waves.

  11. Predicting near-UV electronic circular dichroism in nucleosomal DNA by means of DFT response theory.

    Science.gov (United States)

    Norman, Patrick; Parello, Joseph; Polavarapu, Prasad L; Linares, Mathieu

    2015-09-14

    It is demonstrated that time-dependent density functional theory (DFT) calculations can accurately predict changes in near-UV electronic circular dichroism (ECD) spectra of DNA as the structure is altered from the linear (free) B-DNA form to the supercoiled N-DNA form found in nucleosome core particles. At the DFT/B3LYP level of theory, the ECD signal response is reduced by a factor of 6.7 in going from the B-DNA to the N-DNA form, and it is illustrated how more than 90% of the individual base-pair dimers contribute to this strong hypochromic effect. Of the several inter-base pair parameters, an increase in twist angles is identified as to strongly contribute to a reduced ellipticity. The present work provides first evidence that first-principles calculations can elucidate changes in DNA dichroism due to the supramolecular organization of the nucleoprotein particle and associates these changes with the local structural features of nucleosomal DNA.

  12. DichroCalc: Improvements in Computing Protein Circular Dichroism Spectroscopy in the Near-Ultraviolet.

    Science.gov (United States)

    Jasim, Sarah B; Li, Zhuo; Guest, Ellen E; Hirst, Jonathan D

    2017-12-16

    A fully quantitative theory connecting protein conformation and optical spectroscopy would facilitate deeper insights into biophysical and simulation studies of protein dynamics and folding. The web server DichroCalc (http://comp.chem.nottingham.ac.uk/dichrocalc) allows one to compute from first principles the electronic circular dichroism spectrum of a (modeled or experimental) protein structure or ensemble of structures. The regular, repeating, chiral nature of secondary structure elements leads to intense bands in the far-ultraviolet (UV). The near-UV bands are much weaker and have been challenging to compute theoretically. We report some advances in the accuracy of calculations in the near-UV, realized through the consideration of the vibrational structure of the electronic transitions of aromatic side chains. The improvements have been assessed over a set of diverse proteins. We illustrate them using bovine pancreatic trypsin inhibitor and present a new, detailed analysis of the interactions which are most important in determining the near-UV circular dichroism spectrum. Copyright © 2018. Published by Elsevier Ltd.

  13. A Reference Database for Circular Dichroism Spectroscopy Covering Fold and Secondary Structure Space

    International Nuclear Information System (INIS)

    Lees, J.; Miles, A.; Wien, F.; Wallace, B.

    2006-01-01

    Circular Dichroism (CD) spectroscopy is a long-established technique for studying protein secondary structures in solution. Empirical analyses of CD data rely on the availability of reference datasets comprised of far-UV CD spectra of proteins whose crystal structures have been determined. This article reports on the creation of a new reference dataset which effectively covers both secondary structure and fold space, and uses the higher information content available in synchrotron radiation circular dichroism (SRCD) spectra to more accurately predict secondary structure than has been possible with existing reference datasets. It also examines the effects of wavelength range, structural redundancy and different means of categorizing secondary structures on the accuracy of the analyses. In addition, it describes a novel use of hierarchical cluster analyses to identify protein relatedness based on spectral properties alone. The databases are shown to be applicable in both conventional CD and SRCD spectroscopic analyses of proteins. Hence, by combining new bioinformatics and biophysical methods, a database has been produced that should have wide applicability as a tool for structural molecular biology

  14. Sensing site-specific structural characteristics and chirality using vibrational circular dichroism of isotope labeled peptides.

    Science.gov (United States)

    Keiderling, Timothy A

    2017-12-01

    Isotope labeling has a long history in chemistry as a tool for probing structure, offering enhanced sensitivity, or enabling site selection with a wide range of spectroscopic tools. Chirality sensitive methods such as electronic circular dichroism are global structural tools and have intrinsically low resolution. Consequently, they are generally insensitive to modifications to enhance site selectivity. The use of isotope labeling to modify vibrational spectra with unique resolvable frequency shifts can provide useful site-specific sensitivity, and these methods have been recently more widely expanded in biopolymer studies. While the spectral shifts resulting from changes in isotopic mass can provide resolution of modes from specific parts of the molecule and can allow detection of local change in structure with perturbation, these shifts alone do not directly indicate structure or chirality. With vibrational circular dichroism (VCD), the shifted bands and their resultant sign patterns can be used to indicate local conformations in labeled biopolymers, particularly if multiple labels are used and if their coupling is theoretically modeled. This mini-review discusses selected examples of the use of labeling specific amides in peptides to develop local structural insight with VCD spectra. © 2017 Wiley Periodicals, Inc.

  15. Plications of extended ultra-violet circular dichroism spectroscopy in biology and medicine.

    Science.gov (United States)

    Jones, Gareth R; Clarke, David T

    2004-01-01

    Deep ultra-violet circular dichroism is fast becoming an important technique in structural biology. The exponential increase in the number of protein structures deposited in the Protein Data Bank together with programs that extract protein secondary structure from atomic coordinates and the advancement of the software to analyse circular dichroic spectra, have revolutionised the technique. In addition, the extended short wavelength data afforded by synchrotron radiation is set to have a major impact on the development of the area. We have selected three diverse areas of research and development in the biomedical sciences to illustrate the ubiquity of the technique for future applications in the area of biomedical research. For example, the high flux of synchrotron radiation has provided a gold standard for the assay of the lipoprotein HDL in serum which has been proven to reverse the effects of coronary heart disease. In a second example, the high flux of synchrotron radiation enables the recording of millisecond data during the conformational changes in proteins over their spectrum, mapping out changes to protein secondary structure and thus providing absolute structural measurements in the millisecond time regime. In the third example, subtle conformational changes are interpreted from the extended CD spectra on protein drug binding, distinguishing between induced binding effects and the conformational changes in the target protein. The strengths and weaknesses of extended ultra-violet circular dichroism using synchrotron radiation are discussed using these examples as a template.

  16. Circular dichroism of magnetically induced transitions for D2 lines of alkali atoms

    Science.gov (United States)

    Tonoyan, A.; Sargsyan, A.; Klinger, E.; Hakhumyan, G.; Leroy, C.; Auzinsh, M.; Papoyan, A.; Sarkisyan, D.

    2018-03-01

    In this letter we study magnetic circular dichroism in alkali atoms exhibiting asymmetric behaviour of magnetically induced transitions. The magnetic field \\textbf{B}\\parallel\\textbf{k} induces transitions between Δ F = +/-2 hyperfine levels of alkali atoms and in the range of ∼0.1{\\text{--}}3 \\text{kG} magnetic field, the intensities of these transitions experience significant enhancement. We have inferred a general rule applicable for the D 2 lines of all alkali atoms, that is the transition intensity enhancement is around four times larger for the case of σ+ than for σ- excitation for Δ F = +2 , whereas it is several hundreds of thousand times larger in the case of σ- than that for σ+ polarization for Δ F = -2 . This asymmetric behaviour results in circular dichroism. For experimental verification we employed half-wavelength-thick atomic vapor nanocells using a derivative of the selective reflection technique, which provides a sub-Doppler spectroscopic linewidth (∼50 \\text{MHz} ). The presented theoretical curves well describe the experimental results. This effect can find applications particularly in parity violation experiments.

  17. A molecular dynamics and circular dichroism study of a novel synthetic antimicrobial peptide

    International Nuclear Information System (INIS)

    Rodina, N P; Yudenko, A N; Terterov, I N; Eliseev, I E

    2013-01-01

    Antimicrobial peptides are a class of small, usually positively charged amphiphilic peptides that are used by the innate immune system to combat bacterial infection in multicellular eukaryotes. Antimicrobial peptides are known for their broad-spectrum antimicrobial activity and thus can be used as a basis for a development of new antibiotics against multidrug-resistant bacteria. The most challengeous task on the way to a therapeutic use of antimicrobial peptides is a rational design of new peptides with enhanced activity and reduced toxicity. Here we report a molecular dynamics and circular dichroism study of a novel synthetic antimicrobial peptide D51. This peptide was earlier designed by Loose et al. using a linguistic model of natural antimicrobial peptides. Molecular dynamics simulation of the peptide folding in explicit solvent shows fast formation of two antiparallel beta strands connected by a beta-turn that is confirmed by circular dichroism measurements. Obtained from simulation amphipatic conformation of the peptide is analysed and possible mechanism of it's interaction with bacterial membranes together with ways to enhance it's antibacterial activity are suggested

  18. Bright circularly polarized soft X-ray high harmonics for X-ray magnetic circular dichroism.

    Science.gov (United States)

    Fan, Tingting; Grychtol, Patrik; Knut, Ronny; Hernández-García, Carlos; Hickstein, Daniel D; Zusin, Dmitriy; Gentry, Christian; Dollar, Franklin J; Mancuso, Christopher A; Hogle, Craig W; Kfir, Ofer; Legut, Dominik; Carva, Karel; Ellis, Jennifer L; Dorney, Kevin M; Chen, Cong; Shpyrko, Oleg G; Fullerton, Eric E; Cohen, Oren; Oppeneer, Peter M; Milošević, Dejan B; Becker, Andreas; Jaroń-Becker, Agnieszka A; Popmintchev, Tenio; Murnane, Margaret M; Kapteyn, Henry C

    2015-11-17

    We demonstrate, to our knowledge, the first bright circularly polarized high-harmonic beams in the soft X-ray region of the electromagnetic spectrum, and use them to implement X-ray magnetic circular dichroism measurements in a tabletop-scale setup. Using counterrotating circularly polarized laser fields at 1.3 and 0.79 µm, we generate circularly polarized harmonics with photon energies exceeding 160 eV. The harmonic spectra emerge as a sequence of closely spaced pairs of left and right circularly polarized peaks, with energies determined by conservation of energy and spin angular momentum. We explain the single-atom and macroscopic physics by identifying the dominant electron quantum trajectories and optimal phase-matching conditions. The first advanced phase-matched propagation simulations for circularly polarized harmonics reveal the influence of the finite phase-matching temporal window on the spectrum, as well as the unique polarization-shaped attosecond pulse train. Finally, we use, to our knowledge, the first tabletop X-ray magnetic circular dichroism measurements at the N4,5 absorption edges of Gd to validate the high degree of circularity, brightness, and stability of this light source. These results demonstrate the feasibility of manipulating the polarization, spectrum, and temporal shape of high harmonics in the soft X-ray region by manipulating the driving laser waveform.

  19. Femtosecond X-ray magnetic circular dichroism absorption spectroscopy at an X-ray free electron laser

    Energy Technology Data Exchange (ETDEWEB)

    Higley, Daniel J., E-mail: dhigley@stanford.edu; Yuan, Edwin [SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025 (United States); Department of Applied Physics, Stanford University, Stanford, California 94305 (United States); Hirsch, Konstantin; Dakovski, Georgi L.; Jal, Emmanuelle; Lutman, Alberto A.; Coslovich, Giacomo; Hart, Philip; Hoffmann, Matthias C.; Mitra, Ankush; Moeller, Stefan; Ohldag, Hendrik; Seaberg, Matthew; Stöhr, Joachim; Nuhn, Heinz-Dieter; Reid, Alex H.; Dürr, Hermann A.; Schlotter, William F. [SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025 (United States); Liu, Tianmin; MacArthur, James P. [SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025 (United States); Department of Physics, Stanford University, Stanford, California 94305 (United States); and others

    2016-03-15

    X-ray magnetic circular dichroism spectroscopy using an X-ray free electron laser is demonstrated with spectra over the Fe L{sub 3,2}-edges. The high brightness of the X-ray free electron laser combined with high accuracy detection of incident and transmitted X-rays enables ultrafast X-ray magnetic circular dichroism studies of unprecedented sensitivity. This new capability is applied to a study of all-optical magnetic switching dynamics of Fe and Gd magnetic sublattices in a GdFeCo thin film above its magnetization compensation temperature.

  20. Enantioselective semi-preparative HPLC separation of PCB metabolites and their absolute structures determined by electronic and vibrational circular dichroism

    Energy Technology Data Exchange (ETDEWEB)

    Tuan, H.P.; Larsson, C.; Huehnerfuss, H. [Hamburg Univ. (Germany). Inst. fuer Organische Chemie; Hoffmann, F.; Froeba, M. [Giessen Univ. (Germany). Inst. fuer Anorganische und Analytische Chemie; Bergmann, Aa. [Stockholm Univ. (Sweden). Dept. of Environmental Chemistry

    2004-09-15

    The present paper represents a first result of an ongoing systematic study of atropisomeric methylsulfonyl, methylthionyl, hydroxy, and methoxy metabolites of environmentally most relevant PCBs. This involves semi-preparative enantioselective HPLC separation to obtain pure atropisomers from synthesized PCB metabolite standards, their configuration estimation using the electronic circular dichroism (UV-CD) method and the determination / confirmation of these absolute configurations applying the combined vibrational circular dichroism (VCD) / ab initio approach. The following substances have been investigated: 4-HO-, 4-MeO-, 4-MeS-, 4-MeSO2-, 3-MeS- and 3-MeSO{sub 2}-CB149.

  1. Vitamin E Circular Dichroism Studies: Insights into Conformational Changes Induced by the Solvent’s Polarity

    Directory of Open Access Journals (Sweden)

    Drew Marquardt

    2016-12-01

    Full Text Available We used circular dichroism (CD to study differences in CD spectra between α-, δ-, and methylated-α-tocopherol in solvents with different polarities. CD spectra of the different tocopherol structures differ from each other in intensity and peak locations, which can be attributed to chromanol substitution and the ability to form hydrogen bonds. In addition, each structure was examined in different polarity solvents using the Reichardt index—a measure of the solvent’s ionizing ability, and a direct measurement of solvent–solute interactions. Differences across solvents indicate that hydrogen bonding is a key contributor to CD spectra at 200 nm. These results are a first step in examining the hydrogen bonding abilities of vitamin E in a lipid bilayer.

  2. Origin of DNA-Induced Circular Dichroism in a Minor-Groove Binder.

    Science.gov (United States)

    Holmgaard List, Nanna; Knoops, Jérémie; Rubio-Magnieto, Jenifer; Idé, Julien; Beljonne, David; Norman, Patrick; Surin, Mathieu; Linares, Mathieu

    2017-10-25

    Induced circular dichroism (ICD) of DNA-binding ligands is well known to be strongly influenced by the specific mode of binding, but the relative importance of the possible mechanisms has remained undetermined. With a combination of molecular dynamics simulations, CD response calculations, and experiments on an AT-sequence, we show that the ICD of minor-groove-bound 4',6-diamidino-2-phenylindole (DAPI) originates from an intricate interplay between the chiral imprint of DNA, off-resonant excitonic coupling to nucleobases, charge-transfer, and resonant excitonic coupling between DAPIs. The significant contributions from charge-transfer and the chiral imprint to the ICD demonstrate the inadequacy of a standard Frenkel exciton theory of the DAPI-DNA interactions.

  3. Effects of Trehalose on Thermodynamic Properties of Alpha-synuclein Revealed through Synchrotron Radiation Circular Dichroism

    Directory of Open Access Journals (Sweden)

    Paolo Ruzza

    2015-05-01

    Full Text Available Many neurodegenerative diseases, including Huntington’s, Alzheimer’s and Parkinson’s diseases, are characterized by protein misfolding and aggregation. The capability of trehalose to interfere with protein misfolding and aggregation has been recently evaluated by several research groups. In the present work, we studied, by means of synchrotron radiation circular dichroism (SRCD spectroscopy, the dose-effect of trehalose on α-synuclein conformation and/or stability to probe the capability of this osmolyte to interfere with α-synuclein’s aggregation. Our study indicated that a low trehalose concentration stabilized α-synuclein folding much better than at high concentration by blocking in vitro α-synuclein’s polymerisation. These results suggested that trehalose could be associated with other drugs leading to a new approach for treating Parkinson’s and other brain-related diseases.

  4. Fano resonance assisting plasmonic circular dichroism from nanorice heterodimers for extrinsic chirality

    Science.gov (United States)

    Hu, Li; Huang, Yingzhou; Fang, Liang; Chen, Guo; Wei, Hua; Fang, Yurui

    2015-11-01

    In this work, the circular dichroisms (CD) of nanorice heterodimers consisting of two parallel arranged nanorices with the same size but different materials are investigated theoretically. Symmetry-breaking is introduced by using different materials and oblique incidence to achieve strong CD at the vicinity of Fano resonance peaks. We demonstrate that all Au-Ag heterodimers exhibit multipolar Fano resonances and strong CD effect. A simple quantitative analysis shows that the structure with larger Fano asymmetry factor has stronger CD. The intensity and peak positions of the CD effect can be flexibly tuned in a large range by changing particle size, shape, the inter-particle distance and surroundings. Furthermore, CD spectra exhibit high sensitivity to ambient medium in visible and near infrared regions. Our results here are beneficial for the design and application of high sensitive CD sensors and other related fields.

  5. Interpretation of magnetic circular dichroism of X-ray emission spectra

    International Nuclear Information System (INIS)

    Takayama, Yasuhiro; Yoshida, Tetsuo; Nakamura, Satoshi; Sasaki, Naoya; Ishii, Hiroyoshi; Miyahara, Tsuneaki

    2006-01-01

    We have measured the dependence of the magnetic circular dichroism (MCD) of the X-ray emission spectra (XES) on the temperature and incident angle for a Gd thin film. The energy of the incident photon for the XES was 138.25eV, which corresponded to the resonant excitation to the 8 D 9/2 intermediate state. The dependence of the observed MCD on the temperature and incident angle was quite different from that of the magnetic moment estimated with a SQUID magnetometer. By considering the reflection, saturation effect, self-absorption effect and magnetic anisotropy of the thin film, the agreement of the two behaviors was considerably improved. This result shows that the revisions of the MCD of the XES are extremely important for the quantitative estimation of the magnetic moment from the MCD of the XES. (author)

  6. Conformational effects on the circular dichroism of Human Carbonic Anhydrase II: a multilevel computational study.

    Directory of Open Access Journals (Sweden)

    Tatyana G Karabencheva-Christova

    Full Text Available Circular Dichroism (CD spectroscopy is a powerful method for investigating conformational changes in proteins and therefore has numerous applications in structural and molecular biology. Here a computational investigation of the CD spectrum of the Human Carbonic Anhydrase II (HCAII, with main focus on the near-UV CD spectra of the wild-type enzyme and it seven tryptophan mutant forms, is presented and compared to experimental studies. Multilevel computational methods (Molecular Dynamics, Semiempirical Quantum Mechanics, Time-Dependent Density Functional Theory were applied in order to gain insight into the mechanisms of interaction between the aromatic chromophores within the protein environment and understand how the conformational flexibility of the protein influences these mechanisms. The analysis suggests that combining CD semi empirical calculations, crystal structures and molecular dynamics (MD could help in achieving a better agreement between the computed and experimental protein spectra and provide some unique insight into the dynamic nature of the mechanisms of chromophore interactions.

  7. Chirality sensing of bioactive compounds with amino alcohol unit via circular dichroism.

    Science.gov (United States)

    Górecki, Marcin; Groszek, Grażyna; Frelek, Jadwiga

    2017-10-01

    The aim of the present work was to test various chiroptical techniques, including in particular the in situ dirhodium methodology, to assign the absolute configuration of 1,2- and 1,3-amino alcohols. As models, we selected mainly compounds that have both an additional strongly absorbing and interfering chromophoric system and application in medicinal chemistry. Determination of the absolute configuration (AC) of the tested molecules such as cinchona alkaloids, Tamiflu, and others was carried out using a combination of electronic and vibrational circular dichroism (ECD, VCD) spectroscopy. It has been demonstrated that both 1,2- and 1,3-aminol moieties are subject to the same sector rule correlating stereostructure of formed Rh 2 -complex with chiroptical properties, and that the changes in the position of the stereogenic center do not affect its proper use. © 2017 Wiley Periodicals, Inc.

  8. Fe/Rh (100) multilayer magnetism probed by x-ray magnetic circular dichroism

    Science.gov (United States)

    Tomaz, M. A.; Ingram, D. C.; Harp, G. R.; Lederman, D.; Mayo, E.; O'brien, W. L.

    1997-09-01

    We report the layer-averaged magnetic moments of both Fe and Rh in sputtered Fe/Rh (100) multilayer thin films as measured by x-ray magnetic circular dichroism. We observe two distinct regimes in these films. The first is characterized by Rh moments of at least 1μB, Fe moments enhanced as much as 30% above bulk, and a bct crystal structure. The second regime is distinguished by sharp declines of both Fe and Rh moments accompanied by a transition to an fct crystal lattice. The demarcation between the two regions is identified as the layer thickness for which both bct and fct phases first coexist, which we term the critical thickness tcrit. We attribute the change in magnetic behavior to the structural transformation.

  9. Magnetic circular dichroism study of electron-irradiation induced defects in InP

    International Nuclear Information System (INIS)

    Gislason, H.P.

    1989-01-01

    A strong magnetic circular dichroism (MCD) absorption band centered at 1.07 eV in electron irradiated InP is reported. Temperature and magnetic field dependence of the signal reveal that the centre giving rise to this band is a spin triplet. By simulating neutral and reverse bias conditions of junction measurements through a careful choice of irradiation dose and starting material, the MCD band is shown to have an annealing behaviour closely resembling that of the majority carrier traps which control the Fermi level position in n- and p-type InP. The 1.07 eV MCD band represents the first magneto-optical signal connected with this family of complex irradiation-induced defects in InP. (author) 19 refs., 5 figs., 1 tab

  10. Relativistic effects on magnetic circular dichroism studied by GUHF/SECI method

    Science.gov (United States)

    Honda, Y.; Hada, M.; Ehara, M.; Nakatsuji, H.; Downing, J.; Michl, J.

    2002-04-01

    Quasi-relativistic formulation of the Magnetic circular dichroism (MCD) Faraday terms are presented using the generalized unrestricted Hartree-Fock (GUHF)/single excitation configuration interaction (SECI) method combined with the finite perturbation method and applied to the MCD of the three n-σ ∗ states ( 3Q1, 3Q0, 1Q1) of CH 3I. The Faraday B term for the 1Q1 state was 0.1976( Debye) 2( Bohr magneton )/(10 3 cm-1) in the non-relativistic theory, but was dramatically improved by the relativistic effect and became 0.0184 in agreement with the experimental values, 0.014 and 0.0257. This change was mainly due to the one-electron spin-orbit (SO1) term rather than the spin-free relativistic (SFR) and the two-electron spin-orbit (SO2) terms.

  11. Characterization of dry globular proteins and protein fibrils by synchrotron radiation vacuum UV circular dichroism

    DEFF Research Database (Denmark)

    Nesgaard, Lise W.; Hoffmann, Søren Vrønning; Andersen, Christian Beyschau

    2008-01-01

    Circular dichroism using synchrotron radiation (SRCD) can extend the spectral range down to approximately 130 nm for dry proteins, potentially providing new structural information. Using a selection of dried model proteins, including alpha-helical, beta-sheet, and mixed-structure proteins, we...... with previously published theoretical calculations related to pi-orbital transitions. We also show that drying does not lead to large changes in the secondary structure and does not induce orientational artifacts. In combination with principal component analysis, our SRCD data allow us to distinguish between two...... different types of protein fibrils, highlighting that bona fide fibrils formed by lysozyme are structurally more similar to the nonclassical fibrillar aggregates formed by the SerADan peptide than with the amyloid formed by alpha-synuclein. Thus, despite the lack of direct structural conclusions...

  12. Sizeable magnetic circular dichroism of artificially precipitated Co clusters in amorphous carbon

    Directory of Open Access Journals (Sweden)

    H. S. Hsu

    2012-09-01

    Full Text Available This study examines sizeable magnetic circular dichroism (MCD in Co(20%-doped amorphous carbon (a-C films. While as-grown films exhibit a non-detectable MCD signal, films that undergo rapid thermal annealing (RTA at 600°C in a vacuum yield broad MCD spectra with a large amplitude of ∼3.9 × 104 deg/cm in saturation field 0.78 T at the σ-σ* gap transition (∼5.5 eV. In such films after RTA, the metastable Co-C bonding is decomposed and suitable Co nanoparticles/a-C interfaces are thus formed. Our results indicate that the large change in MCD is contributed from Co nanoparticles and associated with the spin-dependent electronic structure at the Co/a-C interfaces.

  13. Intrinsic transmission magnetic circular dichroism spectra of GaMnAs

    Science.gov (United States)

    Terada, Hiroshi; Ohya, Shinobu; Tanaka, Masaaki

    2018-03-01

    Transmission magnetic circular dichroism (MCD) spectroscopy has been widely used to reveal the spin-dependent band structure of ferromagnetic semiconductors. In these previous studies, some band pictures have been proposed from the spectral shapes observed in transmission MCD; however, extrinsic signals originating from optical interference have not been appropriately considered. In this study, we calculate the MCD spectra taking into account the optical interference of the layered structure of samples and show that the spectral shape of MCD is strongly influenced by optical interference. To correctly understand the transmission MCD, we also calculate the intrinsic MCD spectra of GaMnAs that are not influenced by the optical interference. The spectral shape of the intrinsic MCD can be explained by the characteristic band structure of GaMnAs, that is, the spin-polarized valence band and the impurity band existing above the valence band top.

  14. Large circular dichroism and optical rotation in titanium doped chiral silver nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Titus, Jitto; Perera, A.G. Unil [Department of Physics and Astronomy, Optoelectronics Laboratory, GSU, Atlanta, GA (United States); Larsen, George; Zhao, Yiping [Department of Physics and Astronomy, Nanolab, UGA, Athens, GA (United States)

    2016-10-15

    The circular dichroism of titanium-doped silver chiral nanorod arrays grown using the glancing angle deposition (GLAD) method is investigated in the visible and near infrared ranges using transmission ellipsometry and spectroscopy. These films are found to have significant circular polarization effects across broad ranges of the visible to NIR spectrum, including large values for optical rotation. The characteristics of these circular polarization effects are strongly influenced by the morphology of the deposited arrays. Thus, the morphological control of the optical activity in these nanostructures demonstrates significant optimization capability of the GLAD technique for fabricating chiral plasmonic materials. (copyright 2016 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  15. Experimental study of linear magnetic dichroism in photoionization satellite transitions of atomic rubidium

    International Nuclear Information System (INIS)

    Jaenkaelae, K.; Alagia, M.; Feyer, V.; Richter, R.; Prince, K. C.

    2011-01-01

    Laser orientation in the initial state has been used to study the properties of satellite transitions in inner-shell photoionization of rubidium atoms. The linear magnetic dichroism in the angular distribution (LMDAD) has been utilized to probe the continuum waves of orbital angular momentum conserving monopole, and angular momentum changing conjugate satellites, accompanying the 4p ionization of atomic Rb. We show experimentally that LMDAD of both types of satellite transitions is nonzero and that LMDAD of monopole satellites, measured as a function of photon energy, mimics the LMDAD of direct photoionization, whereas the LMDAD of conjugate transitions deviates drastically from that trend. The results indicate that conjugate transitions cannot be described theoretically without explicit inclusion of electron-electron interaction. The present data can thus be used as a very precise test of current models for photoionization.

  16. Stability of some Cactaceae proteins based on fluorescence, circular dichroism, and differential scanning calorimetry measurements.

    Science.gov (United States)

    Gorinstein, S; Zemser, M; Vargas-Albores, F; Ochoa, J L; Paredes-Lopez, O; Scheler, C; Aksu, S; Salnikow, J

    1999-02-01

    Characterization of three cactus proteins (native and denatured) from Machaerocereus gummosus (Pitahaya agria), Lophocereu schottii (Garambullo), and Cholla opuntia (Cholla), was based on electrophoretic, fluorescence, CD (circular dichroism), DSC (differential scanning calorimetry), and FT-IR (Fourier transform infrared) measurements. The obtained results of intrinsic fluorescence, DSC, and CD were dissimilar for the three species of cactus, providing evidence of differences in secondary and tertiary structures. Cactus proteins may be situated in the following order corresponding to their relative stability: Machaerocereus gummosus (Pitahaya agria) > Cholla opuntia (Cholla) > Lophocereu schottii (Garambullo). Thermodynamic properties of proteins and their changes upon denaturation (temperature of denaturation, enthalphy, and the number of ruptured hydrogen bonds) were correlated with the secondary structure of proteins and disappearance of alpha-helix.

  17. Birefringence and dichroism of poly(vinyl-alcohol) foils containing phthalazinium ylids

    Science.gov (United States)

    Rogojanu, Alina; Dascalu, Carmen Felicia; Zelinschi, Beatrice Carmen; Caprosu, Maria; Dorohoi, Dana Ortansa

    2011-10-01

    Pure and colored with phthalazinium ylids poly(vinyl-alcohol) (PVA) foils were stretched under gentile heating. The birefringence of the thin foils was determined with a Babinet compensator standardized for yellow radiation of a Sodium lamp. The determined birefringence of the colored PVA foils is higher than that of the pure PVA foils. This fact indicates that the phthalazinium ylids facilitate the increase in the anisotropy of the stretched foils. The visible absorption electronic band of phthalazinium ylids was used to estimate the dichroic ratio and the degree of order of the ylid molecules in the stretched PVA foils. An increase in dichroism and birefringence with the degree of stretching has been evidenced for uncolored and colored PVA foils.

  18. Irreversible denaturation of maltodextrin glucosidase studied by differential scanning calorimetry, circular dichroism, and turbidity measurements.

    Science.gov (United States)

    Goyal, Megha; Chaudhuri, Tapan K; Kuwajima, Kunihiro

    2014-01-01

    Thermal denaturation of Escherichia coli maltodextrin glucosidase was studied by differential scanning calorimetry, circular dichroism (230 nm), and UV-absorption measurements (340 nm), which were respectively used to monitor heat absorption, conformational unfolding, and the production of solution turbidity. The denaturation was irreversible, and the thermal transition recorded at scan rates of 0.5-1.5 K/min was significantly scan-rate dependent, indicating that the thermal denaturation was kinetically controlled. The absence of a protein-concentration effect on the thermal transition indicated that the denaturation was rate-limited by a mono-molecular process. From the analysis of the calorimetric thermograms, a one-step irreversible model well represented the thermal denaturation of the protein. The calorimetrically observed thermal transitions showed excellent coincidence with the turbidity transitions monitored by UV-absorption as well as with the unfolding transitions monitored by circular dichroism. The thermal denaturation of the protein was thus rate-limited by conformational unfolding, which was followed by a rapid irreversible formation of aggregates that produced the solution turbidity. It is thus important to note that the absence of the protein-concentration effect on the irreversible thermal denaturation does not necessarily means the absence of protein aggregation itself. The turbidity measurements together with differential scanning calorimetry in the irreversible thermal denaturation of the protein provided a very effective approach for understanding the mechanisms of the irreversible denaturation. The Arrhenius-equation parameters obtained from analysis of the thermal denaturation were compared with those of other proteins that have been reported to show the one-step irreversible thermal denaturation. Maltodextrin glucosidase had sufficiently high kinetic stability with a half-life of 68 days at a physiological temperature (37°C).

  19. Magnetic dichroism in photoemission: a new element-specific magnetometer with atomic-layer resolution

    International Nuclear Information System (INIS)

    Starke, K.; Arenholz, E.; Kaindl, G.

    1998-01-01

    Full text: Magnetic coupling in layered metallic structures has become a key issue in thin-film magnetism since the observation of oscillatory exchange coupling across non-ferromagnetic spacer layers. Although this phenomenon was discovered in rare earths (RE) superlattices, mostly transition-metal systems have been studied and are now applied in data-storage industry. An understanding of the coupling mechanisms has been reached after a fabrication of high-quality interfaces became possible. It allowed, in particular, the experimental finding of induced ferromagnetic order in 'nonmagnetic' atomic layers near an interface, using element-specific probes such as magnetic circular dichroism in x-ray absorption. - In layered RE systems, by contrast, the well known intermiscibility has prevented a preparation of atomically sharp interfaces, and all RE superlattices studied so far showed interdiffusion zones of several atomic layers. In the present overview, we report the first fabrication of atomically flat heteromagnetic RE interfaces, their structural characterization and their magnetic analysis using magnetic dichroism in photoemission (MDPE). This new tool gives access to the magnetization of individual atomic layers near interfaces in favourite cases. Merits of MDPE as a magnetometer are demonstrated at the example of Eu/Gd(0001), where chemical shifts of core-level photoemission lines allow to spectroscopically separate up to four different atomic layers. The high surface sensitivity of MDPE, together with the well known dependence of the core-level binding energies on the coordination number of the photo emitting atom, opens the door to future site-specific studies of magnetism in sub-monolayer systems such as 'nanowires'

  20. Synthesis and vibrational circular dichroism of enantiopure chiral oxorhenium(V) complexes containing the hydrotris(1-pyrazolyl)borate ligand

    DEFF Research Database (Denmark)

    Lassen, Peter Rygaard

    2006-01-01

    The infrared and vibrational circular dichroism (VCD) spectra of six chiral oxorhenium(V) complexes, bearing a hydrotris(1-pyrazolyl)borate (Tp) ligand, have been investigated. These complexes are promising candidates for observation of parity violation (symmetry breaking due to the weak nuclear...

  1. Circular Dichroism of G-Quadruplex: A Laboratory Experiment for the Study of Topology and Ligand Binding

    Science.gov (United States)

    Carvalho, Josue´; Queiroz, João A.; Cruz, Carla

    2017-01-01

    Circular dichroism (CD) has emerged as one of the standard biophysical techniques for the study of guaninequadruplex (G4) folding, cation effect, and ligand binding. The utility of this technique is based on its robustness, ease of use, and requirement of only small quantities of nucleic acid. This experiment is also extendable to the classroom…

  2. Effect of Coulomb interaction on the X-ray magnetic circular dichroism spin sum rule in rare earths

    NARCIS (Netherlands)

    Teramura, Y; Tanaka, A; Thole, BT; Jo, T

    A deviation from the spin sum rule, which relates the integrated intensity of the X-ray magnetic circular dichroism (MCD) signal to the expectation value of the spin operator S-z ((S-z)), is numerically calculated in the case of the 3d --> 4f absorption for rare earths from the trivalent Ce to Tm.

  3. Protein fiber linear dichroism for structure determination and kinetics in a low-volume, low-wavelength couette flow cell.

    Science.gov (United States)

    Dafforn, Timothy R; Rajendra, Jacindra; Halsall, David J; Serpell, Louise C; Rodger, Alison

    2004-01-01

    High-resolution structure determination of soluble globular proteins relies heavily on x-ray crystallography techniques. Such an approach is often ineffective for investigations into the structure of fibrous proteins as these proteins generally do not crystallize. Thus investigations into fibrous protein structure have relied on less direct methods such as x-ray fiber diffraction and circular dichroism. Ultraviolet linear dichroism has the potential to provide additional information on the structure of such biomolecular systems. However, existing systems are not optimized for the requirements of fibrous proteins. We have designed and built a low-volume (200 microL), low-wavelength (down to 180 nm), low-pathlength (100 microm), high-alignment flow-alignment system (couette) to perform ultraviolet linear dichroism studies on the fibers formed by a range of biomolecules. The apparatus has been tested using a number of proteins for which longer wavelength linear dichroism spectra had already been measured. The new couette cell has also been used to obtain data on two medically important protein fibers, the all-beta-sheet amyloid fibers of the Alzheimer's derived protein Abeta and the long-chain assemblies of alpha1-antitrypsin polymers.

  4. TD-DFT Investigation of the Magnetic Circular Dichroism Spectra of Some Purine and Pyrimidine Bases of Nucleic Acids

    DEFF Research Database (Denmark)

    Fahleson, Tobias; Kauczor, Joanna; Norman, Patrick

    2015-01-01

    We present a computational study of the magnetic circular dichroism (MCD) spectra in the 200–300 nm wavelength region of purine and its derivative hypoxanthine, as well as of the pyrimidine bases of nucleic acids uracil, thymine, and cytosine, using the B3LYP and CAM–B3LYP functionals. Solvent...

  5. Crystal field multiplet calculations and the Magnetic circular dichroism of CrO2 in Resonant inelastic Xray scattering

    NARCIS (Netherlands)

    Zimmermann, P.

    2018-01-01

    X-ray spectroscopy is an effective tool to investigate the properties of a broad range of systems. With the advent of modern light sources and high resolution detection techniques, the X-ray Magnetic Circular Dichroism has since its early days evolved into a powerful method to study the magnetic

  6. Calculations of magnetic x-ray dichroism in the 3d absorption spectra of rare-earth compounds

    NARCIS (Netherlands)

    GOEDKOOP, JB; THOLE, BT; VANDERLAAN, G; SAWATZKY, GA; DEGROOT, FMF; FUGGLE, JC; de Groot, Frank|info:eu-repo/dai/nl/08747610X

    1988-01-01

    We present atomic calculations for the recently discovered magnetic x-ray dichroism (MXD) displayed by the 3d x-ray-absorption spectra of rare-earth compounds. The spectral shapes expected at T=0 K for linear polarization parallel and normal to the local magnetic field is given, together with the

  7. A computational protocol for the study of circularly polarized phosphorescence and circular dichroism in spin-forbidden absorption

    DEFF Research Database (Denmark)

    Kaminski, Maciej; Cukras, Janusz; Pecul, Magdalena

    2015-01-01

    We present a computational methodology to calculate the intensity of circular dichroism (CD) in spinforbidden absorption and of circularly polarized phosphorescence (CPP) signals, a manifestation of the optical activity of the triplet–singlet transitions in chiral compounds. The protocol is based...

  8. Stokes-Mueller matrix polarimetry technique for circular dichroism/birefringence sensing with scattering effects.

    Science.gov (United States)

    Phan, Quoc-Hung; Lo, Yu-Lung

    2017-04-01

    A surface plasmon resonance (SPR)-enhanced method is proposed for measuring the circular dichroism (CD), circular birefringence (CB), and degree of polarization (DOP) of turbid media using a Stokes–Mueller matrix polarimetry technique. The validity of the analytical model is confirmed by means of numerical simulations. The simulation results show that the proposed detection method enables the CD and CB properties to be measured with a resolution of 10 ? 4 refractive index unit (RIU) and 10 ? 5 ?? RIU , respectively, for refractive indices in the range of 1.3 to 1.4. The practical feasibility of the proposed method is demonstrated by detecting the CB/CD/DOP properties of glucose–chlorophyllin compound samples containing polystyrene microspheres. It is shown that the extracted CB value decreases linearly with the glucose concentration, while the extracted CD value increases linearly with the chlorophyllin concentration. However, the DOP is insensitive to both the glucose concentration and the chlorophyllin concentration. Consequently, the potential of the proposed SPR-enhanced Stokes–Mueller matrix polarimetry method for high-resolution CB/CD/DOP detection is confirmed. Notably, in contrast to conventional SPR techniques designed to detect relative refractive index changes, the SPR technique proposed in the present study allows absolute measurements of the optical properties (CB/CD/DOP) to be obtained.

  9. Tchebichef image moment approach to the prediction of protein secondary structures based on circular dichroism.

    Science.gov (United States)

    Li, Sha Sha; Li, Bao Qiong; Liu, Jin Jin; Lu, Shao Hua; Zhai, Hong Lin

    2018-04-20

    Circular dichroism (CD) spectroscopy is a widely used technique for the evaluation of protein secondary structures that has a significant impact for the understanding of molecular biology. However, the quantitative analysis of protein secondary structures based on CD spectra is still a hard work due to the serious overlap of the spectra corresponding to different structural motifs. Here, Tchebichef image moment (TM) approach is introduced for the first time, which can effectively extract the chemical features in CD spectra for the quantitative analysis of protein secondary structures. The proposed approach was applied to analyze reference set. and the obtained results were evaluated by the strict statistical parameters such as correlation coefficient, cross-validation correlation coefficient and root mean squared error. Compared with several specialized prediction methods, TM approach provided satisfactory results, especially for turns and unordered structures. Our study indicates that TM approach can be regarded as a feasible tool for the analysis of the secondary structures of proteins based on CD spectra. An available TMs package is provided and can be used directly for secondary structures prediction. This article is protected by copyright. All rights reserved. © 2018 Wiley Periodicals, Inc.

  10. Heterogeneous bilayer films NiFe (Fe)-Dy: magnetic circular dichroism and Dy spin ordering

    Energy Technology Data Exchange (ETDEWEB)

    Markov, V.V. E-mail: ise@iph.krasn.ruise@iph.krasnoyarsk.su; Kesler, V.G.; Khudyakov, A.E.; Edelman, I.S.; Bondarenko, G.V

    2001-08-01

    Results of the magnetic circular dichroism (MCD) and Auger electron spectroscopy (AES) investigations in the 3d transition metal-Dy bi-layer films are presented. It is shown that even at room temperature the Dy layer makes a contribution to MCD of the bi-layer film, which corresponds to the MCD value in the single-layer Dy film measured below T{sub C}=85 K. According to the AES data there is no sharp interface between 3d and Dy layers in these films. Some amount of Ni and Fe atoms is dispersed in the Dy layer and some amount of Dy atoms is dispersed in the 3d layer. The comparison of the MCD and AES data allows one to suppose the Dy layer in the bi-layer films to be magnetically ordered at room temperature under the influence of the 3d-layer spin system. The influence spreads to long distances inside Dy layer through the 3d-ions dispersed in it.

  11. Circular dichroism studies of low molecular weight hydrogelators: The use of SRCD and addressing practical issues.

    Science.gov (United States)

    Sitsanidis, Efstratios D; Piras, Carmen C; Alexander, Bruce D; Siligardi, Giuliano; Jávorfi, Tamás; Hall, Andrew J; Edwards, Alison A

    2018-04-12

    Circular dichroism (CD) spectroscopy has been used extensively for the investigation of the conformation and configuration of chiral molecules, but its use for evaluating the mode of self-assembly in soft materials has been limited. Herein, we report a protocol for the study of such materials by electronic CD spectroscopy using commercial/benchtop instruments and synchrotron radiation (SR) using the B23 beamline available at Diamond Light Source. The use of the B23 beamtime for SRCD was advantageous because of the unique enhanced spatial resolution achieved because of its highly collimated and small beamlight cross section (ca. 250 μm) and higher photon flux in the far UV region (175-250 nm) enhancing the signal-to-noise ratio relative to benchtop CD instruments. A set of low molecular weight (LMW) hydrogelators, comprising two Fmoc-protected enantiomeric monosaccharides and one Fmoc dipeptide (Fmoc-FF), were studied. The research focused on the optimization of sample preparation and handling, which then enabled the characterization of sample conformational homogeneity and thermal stability. CD spectroscopy, in combination with other spectroscopic techniques and microscopy, will allow a better insight into the self-assembly of chiral building blocks into higher order structural architectures. © 2018 Wiley Periodicals, Inc.

  12. Characterization of Glutaredoxin Fe-S Cluster-Binding Interactions Using Circular Dichroism Spectroscopy.

    Science.gov (United States)

    Albetel, Angela-Nadia; Outten, Caryn E

    2018-01-01

    Monothiol glutaredoxins (Grxs) with a conserved Cys-Gly-Phe-Ser (CGFS) active site are iron-sulfur (Fe-S) cluster-binding proteins that interact with a variety of partner proteins and perform crucial roles in iron metabolism including Fe-S cluster transfer, Fe-S cluster repair, and iron signaling. Various analytical and spectroscopic methods are currently being used to monitor and characterize glutaredoxin Fe-S cluster-dependent interactions at the molecular level. The electronic, magnetic, and vibrational properties of the protein-bound Fe-S cluster provide a convenient handle to probe the structure, function, and coordination chemistry of Grx complexes. However, some limitations arise from sample preparation requirements, complexity of individual techniques, or the necessity for combining multiple methods in order to achieve a complete investigation. In this chapter, we focus on the use of UV-visible circular dichroism spectroscopy as a fast and simple initial approach for investigating glutaredoxin Fe-S cluster-dependent interactions. © 2018 Elsevier Inc. All rights reserved.

  13. Vertical-type chiroptical spectrophotometer (I): instrumentation and application to diffuse reflectance circular dichroism measurement.

    Science.gov (United States)

    Harada, Takunori; Hayakawa, Hiroshi; Kuroda, Reiko

    2008-07-01

    We have designed and built a novel universal chiroptical spectrophotometer (UCS-2: J-800KCMF), which can carry out in situ chirality measurement of solid samples without any pretreatment, in the UV-vis region and with high relative efficiency. The instrument was designed to carry out transmittance and diffuse reflectance (DR) circular dichroism (CD) measurements simultaneously, thus housing two photomultipliers. It has a unique feature that light impinges on samples vertically so that loose powders can be measured by placing them on a flat sample holder in an integrating sphere. As is our first universal chiroptical spectrophotometer, UCS-1, two lock-in amplifiers are installed to remove artifact signals arising from macroscopic anisotropies which are unique to solid samples. High performance was achieved by theoretically analyzing and experimentally proven the effect of the photoelastic modulator position on the CD base line shifts, and by selecting high-quality optical and electric components. Measurement of microcrystallines of both enantiomers of ammonium camphorsulfonate by the DRCD mode gave reasonable results.

  14. Frenkel-exciton decomposition analysis of circular dichroism and circularly polarized luminescence for multichromophoric systems.

    Science.gov (United States)

    Shiraogawa, Takafumi; Ehara, Masahiro; Jurinovich, Sandro; Cupellini, Lorenzo; Mennucci, Benedetta

    2018-06-15

    Recently, a method to calculate the absorption and circular dichroism (CD) spectra based on the exciton coupling has been developed. In this work, the method was utilized for the decomposition of the CD and circularly polarized luminescence (CPL) spectra of a multichromophoric system into chromophore contributions for recently developed through-space conjugated oligomers. The method which has been implemented using rotatory strength in the velocity form and therefore it is gauge-invariant, enables us to evaluate the contribution from each chromophoric unit and locally excited state to the CD and CPL spectra of the total system. The excitonic calculations suitably reproduce the full calculations of the system, as well as the experimental results. We demonstrate that the interactions between electric transition dipole moments of adjacent chromophoric units are crucial in the CD and CPL spectra of the multichromophoric systems, while the interactions between electric and magnetic transition dipole moments are not negligible. © 2018 Wiley Periodicals, Inc. © 2018 Wiley Periodicals, Inc.

  15. Dichroism and resonant diffraction in x-ray scattering by complex materials

    International Nuclear Information System (INIS)

    Collins, S P; Lovesey, S W; Balcar, E

    2007-01-01

    We survey universal concepts that influence dichroism and resonant Bragg diffraction, aiming to reach across the range of scientific disciplines that benefit from x-ray techniques, namely, chemistry, physics, life-sciences, and the science of materials. To this end, we adopt a top down discussion of the aspects of symmetry and concomitant selection rules. Starting from selection rules that can be deduced from the global condition that an observable quantity is unchanged on reversing the directions of both space and time separately, to selection rules that flow from bulk symmetry properties of electrons imposed by elements of a point group or crystal class to, finally, atomic selection rules that emerge from the details of the electronic structure. As a motivation for the latter we discuss, with a new calculation of the x-ray scattering length, E 1-M 1 absorption and scattering events that particularly interest scientists studying the chirality of life. In the main text there is modest use of mathematics, with appropriate details relegated to a few appendices. (topical review)

  16. Circular dichroism measured on single chlorosomal light-harvesting complexes of green photosynthetic bacteria

    KAUST Repository

    Furumaki, Shu

    2012-12-06

    We report results on circular dichroism (CD) measured on single immobilized chlorosomes of a triple mutant of green sulfur bacterium Chlorobaculum tepidum. The CD signal is measured by monitoring chlorosomal bacteriochlorphyll c fluorescence excited by alternate left and right circularly polarized laser light with a fixed wavelength of 733 nm. The excitation wavelength is close to a maximum of the negative CD signal of a bulk solution of the same chlorosomes. The average CD dissymmetry parameter obtained from an ensemble of individual chlorosomes was gs = -0.025, with an intrinsic standard deviation (due to variations between individual chlorosomes) of 0.006. The dissymmetry value is about 2.5 times larger than that obtained at the same wavelength in the bulk solution. The difference can be satisfactorily explained by taking into account the orientation factor in the single-chlorosome experiments. The observed distribution of the dissymmetry parameter reflects the well-ordered nature of the mutant chlorosomes. © 2012 American Chemical Society.

  17. Introducing DInaMo: A Package for Calculating Protein Circular Dichroism Using Classical Electromagnetic Theory

    Directory of Open Access Journals (Sweden)

    Igor V. Uporov

    2015-09-01

    Full Text Available The dipole interaction model is a classical electromagnetic theory for calculating circular dichroism (CD resulting from the π-π* transitions of amides. The theoretical model, pioneered by J. Applequist, is assembled into a package, DInaMo, written in Fortran allowing for treatment of proteins. DInaMo reads Protein Data Bank formatted files of structures generated by molecular mechanics or reconstructed secondary structures. Crystal structures cannot be used directly with DInaMo; they either need to be rebuilt with idealized bond angles and lengths, or they need to be energy minimized to adjust bond lengths and bond angles because it is common for crystal structure geometries to have slightly short bond lengths, and DInaMo is sensitive to this. DInaMo reduces all the amide chromophores to points with anisotropic polarizability and all nonchromophoric aliphatic atoms including hydrogens to points with isotropic polarizability; all other atoms are ignored. By determining the interactions among the chromophoric and nonchromophoric parts of the molecule using empirically derived polarizabilities, the rotational and dipole strengths are determined leading to the calculation of CD. Furthermore, ignoring hydrogens bound to methyl groups is initially explored and proves to be a good approximation. Theoretical calculations on 24 proteins agree with experiment showing bands with similar morphology and maxima.

  18. The Role of Heme Chirality in the Circular Dichroism of Heme Proteins

    Science.gov (United States)

    Woody, Robert W.; Pescitelli, Gennaro

    2014-07-01

    The rotational strength (R) of the Soret transition in sperm-whale myoglobin (SW Mb), the hemoglobin from Chironomus thummi thummi (CTT Hb), and human hemoglobin (hHb) has been calculated using 20 high-resolution ( Raro > Rpep. For CTT Hb and hHB, the orders were, respectively, Rint > Rpep > Raro and Rint > Raro ≈ Rpep. Human Hb ɑ chains showed the same trend as CTT Hb. Only in the hHb β chains did Raro predominate, with the order Raro > Rint > Rpep. The total predicted Rtot for SW Mb, CTT Hb, and hHb averaged +0.77±0.10 (0.56 - 0.80), -0.37±0.12 (-0.5), and +0.31±0.17 DBM (0.23 - 0.50), respectively. (Values in parentheses are experimental values.) Thus, contrary to the currently accepted view, coupling with aromatic side-chain or peptide transitions is not the dominant factor in the Soret circular dichroism (CD) of these proteins. The Soret CD is dominated by intrinsic CD of the heme chromophore, of which vinyl torsion is the major determinant. This result suggests an explanation for the large effect of heme isomerism on the Soret CD of Mb and Hb. Rotation about the ɑ-γ axis may be associated with large changes in vinyl torsion and thus substantially alter the intrinsic CD, even reversing its sign.

  19. Circular dichroism measurements at an x-ray free-electron laser with polarization control

    Energy Technology Data Exchange (ETDEWEB)

    Hartmann, G.; Shevchuk, I.; Walter, P.; Viefhaus, J. [Deutsches Elektronen-Synchrotron, Notkestraße 85, 22607 Hamburg (Germany); Lindahl, A. O. [PULSE at Stanford, 2575 Sand Hill Road, Menlo Park, California 94025 (United States); Knie, A. [Institut für Physik, University of Kassel, Heinrich-Plett-Str. 40, 34132 Kassel (Germany); Hartmann, N.; Lutman, A. A.; MacArthur, J. P.; Glownia, J. M.; Helml, W.; Huang, Z.; Marinelli, A.; Nuhn, H.-D.; Moeller, S.; Coffee, R. N.; Ilchen, M., E-mail: markus.ilchen@xfel.eu [SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025 (United States); Buck, J.; Galler, A.; Liu, J. [European XFEL GmbH, Albert-Einstein-Ring 19, 22761 Hamburg (Germany); and others

    2016-08-15

    A non-destructive diagnostic method for the characterization of circularly polarized, ultraintense, short wavelength free-electron laser (FEL) light is presented. The recently installed Delta undulator at the LCLS (Linac Coherent Light Source) at SLAC National Accelerator Laboratory (USA) was used as showcase for this diagnostic scheme. By applying a combined two-color, multi-photon experiment with polarization control, the degree of circular polarization of the Delta undulator has been determined. Towards this goal, an oriented electronic state in the continuum was created by non-resonant ionization of the O{sub 2} 1s core shell with circularly polarized FEL pulses at hν ≃ 700 eV. An also circularly polarized, highly intense UV laser pulse with hν ≃ 3.1 eV was temporally and spatially overlapped, causing the photoelectrons to redistribute into so-called sidebands that are energetically separated by the photon energy of the UV laser. By determining the circular dichroism of these redistributed electrons using angle resolving electron spectroscopy and modeling the results with the strong-field approximation, this scheme allows to unambiguously determine the absolute degree of circular polarization of any pulsed, ultraintense XUV or X-ray laser source.

  20. Circular dichroism and Raman optical activity in antiferromagnetic transition metal fluorides

    International Nuclear Information System (INIS)

    Hoffman, K.R.; Lockwood, D.J.; Yen, W.M.

    2005-01-01

    The Raman optical activity (ROA) of magnons in rutile-structure antiferromagnetic FeF 2 (T N = 78 K) has been studied as a function of temperature and applied magnetic field. For exciting light incident along the c axis, ROA is observed for magnons but not for phonons. In zero field, a small splitting (0.09 cm -1 ) of the two acoustic-magnon branches is observed for the first time by inelastic light scattering. The splitting in applied magnetic field is found to reduce with increasing temperature in accordance with theory. No ROA was detected for two-magnon excitations. In optical absorption measurements performed over thirty years ago, a very small circular dichroism (CD) was observed in the magnon sidebands of other simple rutile antiferromagnetic fluorides (MnF 2 and CoF 2 ). The origin of this CD was not understood at the time. The Raman studies of the one-magnon Raman scattering in FeF 2 have demonstrated that in zero field the degeneracy of the antiferromagnetic magnon branches is lifted by a weak magnetic dipole-dipole interaction, as predicted by Pincus and Loudon and by White four decades ago. The source of the observed CD in the magnon sidebands can now be traced to this same magnetic-dipole induced splitting

  1. Circular dichroism measured on single chlorosomal light-harvesting complexes of green photosynthetic bacteria

    KAUST Repository

    Furumaki, Shu; Yabiku, Yu; Habuchi, Satoshi; Tsukatani, Yusuke; Bryant, Donald A.; Vá cha, Martin

    2012-01-01

    We report results on circular dichroism (CD) measured on single immobilized chlorosomes of a triple mutant of green sulfur bacterium Chlorobaculum tepidum. The CD signal is measured by monitoring chlorosomal bacteriochlorphyll c fluorescence excited by alternate left and right circularly polarized laser light with a fixed wavelength of 733 nm. The excitation wavelength is close to a maximum of the negative CD signal of a bulk solution of the same chlorosomes. The average CD dissymmetry parameter obtained from an ensemble of individual chlorosomes was gs = -0.025, with an intrinsic standard deviation (due to variations between individual chlorosomes) of 0.006. The dissymmetry value is about 2.5 times larger than that obtained at the same wavelength in the bulk solution. The difference can be satisfactorily explained by taking into account the orientation factor in the single-chlorosome experiments. The observed distribution of the dissymmetry parameter reflects the well-ordered nature of the mutant chlorosomes. © 2012 American Chemical Society.

  2. X-ray magnetic circular dichroism used to image magnetic domains

    CERN Document Server

    Fischer, P; Kalchgruber, R; Schütz, G M; Schmahl, G; Guttmann, P; Bayreuther, G

    1999-01-01

    A new technique to image magnetic domain structures has been established by the combination of the high resolution transmission X- ray microscope (TXM) at BESSY I based on the zone plate technique with the X-ray magnetic circular $9 dichroism (X-MCD) providing a huge magnetic contrast. A lateral spatial resolution down to 30 nm could be achieved. Basic features of X-MCD are the inherent element- specificity and the potential to gain information on the local spin $9 and orbital moments of the absorbing species applying magneto-optical sum rules. Key results at the Fe L/sub 3,2/ edges of Fe in a layered GdFe system and at the Co L/sub 3/ edge of a PtCo layered system demonstrate the potential of $9 this microscopy. The images can be recorded in varying magnetic fields which allows to study the evolution of magnetic domains within a complete hysteresis loop. (8 refs).

  3. Applications of Circular Dichroism for Structural Analysis of Gelatin and Antimicrobial Peptides

    Directory of Open Access Journals (Sweden)

    Yoonkyung Park

    2012-03-01

    Full Text Available Circular dichroism (CD is a useful technique for monitoring changes in the conformation of antimicrobial peptides or gelatin. In this study, interactions between cationic peptides and gelatin were observed without affecting the triple helical content of the gelatin, which was more strongly affected by anionic surfactant. The peptides did not adopt a secondary structure in the presence of aqueous solution or Tween 80, but a peptide secondary structure formed upon the addition of sodium dodecyl sulfate (SDS. The peptides bound to the phosphate group of lipopolysaccharide (LPS and displayed an alpha-helical conformation while (KW4 adopted a folded conformation. Further, the peptides did not specifically interact with the fungal cell wall components of mannan or laminarin. Tryptophan blue shift assay indicated that these peptides interacted with SDS, LPS, and gelatin but not with Tween 80, mannan, or laminarin. The peptides also displayed antibacterial activity against P. aeruginosa without cytotoxicity against HaCaT cells at MIC, except for HPA3NT3-analog peptide. In this study, we used a CD spectroscopic method to demonstrate the feasibility of peptide characterization in numerous environments. The CD method can thus be used as a screening method of gelatin-peptide interactions for use in wound healing applications.

  4. Circular dichroism measurements at an x-ray free-electron laser with polarization control

    Science.gov (United States)

    Hartmann, G.; Lindahl, A. O.; Knie, A.; Hartmann, N.; Lutman, A. A.; MacArthur, J. P.; Shevchuk, I.; Buck, J.; Galler, A.; Glownia, J. M.; Helml, W.; Huang, Z.; Kabachnik, N. M.; Kazansky, A. K.; Liu, J.; Marinelli, A.; Mazza, T.; Nuhn, H.-D.; Walter, P.; Viefhaus, J.; Meyer, M.; Moeller, S.; Coffee, R. N.; Ilchen, M.

    2016-08-01

    A non-destructive diagnostic method for the characterization of circularly polarized, ultraintense, short wavelength free-electron laser (FEL) light is presented. The recently installed Delta undulator at the LCLS (Linac Coherent Light Source) at SLAC National Accelerator Laboratory (USA) was used as showcase for this diagnostic scheme. By applying a combined two-color, multi-photon experiment with polarization control, the degree of circular polarization of the Delta undulator has been determined. Towards this goal, an oriented electronic state in the continuum was created by non-resonant ionization of the O2 1s core shell with circularly polarized FEL pulses at hν ≃ 700 eV. An also circularly polarized, highly intense UV laser pulse with hν ≃ 3.1 eV was temporally and spatially overlapped, causing the photoelectrons to redistribute into so-called sidebands that are energetically separated by the photon energy of the UV laser. By determining the circular dichroism of these redistributed electrons using angle resolving electron spectroscopy and modeling the results with the strong-field approximation, this scheme allows to unambiguously determine the absolute degree of circular polarization of any pulsed, ultraintense XUV or X-ray laser source.

  5. Near-infrared dichroism of a mesogenic transition metal complex and its solubility in nematic hosts

    International Nuclear Information System (INIS)

    Marshall, K.L.; Jacobs, S.D.

    1987-01-01

    A transition metal complex possessing the nematic phase, bis (p-n-butylstyryl-1, 2-dithiolato) nickel, was synthesized and its optical properties and solubility in the nematic hosts K15 and MBBA were investigated. The metal complex displayed a high solubility in both host materials (up to 10% wt/wt) and a strong near-infrared absorption band centered at 860 nm. A blocking extinction of greater than OD = 3 was obtained with a 100 micron pathlength of a 0.5% wt/wt mixture of the nematic metal complex in K15, suggesting its usefulness for passive blocking of near infrared radiation. A 24 micron thick, homogeneously aligned guest-host cell containing a 1% wt/wt mixture of the metal complex in K15 possessed a contrast ratio of nearly 5:1 and a blocking extinction of OD = 3.5 at 860 nm, demonstrating for the first time the existence of near-infrared dichroism in this class of materials. The solubility and blocking extinction of the mesogenic metal complex in K15 was considerably superior to the non-mesogenic near ir laser dye bis(dimethylaminodithiobenzil) nickel in the same host. An interaction of the nematic metal complex in mixtures with MBBA which resulted in the creation of a new absorption band at 1050 nm was also observed. 21 refs., 9 figs

  6. Detection of a weak ring current in a nonaromatic porphyrin nanoring using magnetic circular dichroism.

    Science.gov (United States)

    Kowalska, Patrycja; Peeks, Martin D; Roliński, Tomasz; Anderson, Harry L; Waluk, Jacek

    2017-12-13

    We compare the absorption and magnetic circular dichroism (MCD) spectra of a series of porphyrin oligomers - dimer, tetramer, and hexamer - bound in a linear or cyclic fashion. The MCD signal is extremely weak for low energy transitions in the linear oligomers, but it is amplified when the cyclic porphyrin hexamer binds a template, restricting rotational freedom. The appearance of Faraday A terms in the MCD spectra demonstrates the presence of a magnetic moment, and thus, uncompensated electronic current. The value of the excited state magnetic moment estimated from the A term is very low compared with those of monomeric porphyrins, which confirms the nonaromatic character of the cyclic array and the lack of a global ring current in the ground state of the neutral nanoring. DFT calculations predict the absorption and MCD patterns reasonably well, but fail to reproduce the MCD sign inversion observed in substituted monomeric zinc porphyrins ("soft" chromophores). Interestingly, a correct sign pattern is predicted by INDO/S calculations. Analysis of the MCD spectra of the monomeric porphyrin unit allowed us to distinguish between two close-lying lowest energy transitions, which some previous assignments placed further apart. The present results prove the usefulness of MCD not only for deconvolution and assignment of electronic transitions, but also as a sensitive tool for detecting electronic ring currents.

  7. Heterogeneous bilayer films NiFe (Fe)-Dy: magnetic circular dichroism and Dy spin ordering

    International Nuclear Information System (INIS)

    Markov, V.V.; Kesler, V.G.; Khudyakov, A.E.; Edelman, I.S.; Bondarenko, G.V.

    2001-01-01

    Results of the magnetic circular dichroism (MCD) and Auger electron spectroscopy (AES) investigations in the 3d transition metal-Dy bi-layer films are presented. It is shown that even at room temperature the Dy layer makes a contribution to MCD of the bi-layer film, which corresponds to the MCD value in the single-layer Dy film measured below T C =85 K. According to the AES data there is no sharp interface between 3d and Dy layers in these films. Some amount of Ni and Fe atoms is dispersed in the Dy layer and some amount of Dy atoms is dispersed in the 3d layer. The comparison of the MCD and AES data allows one to suppose the Dy layer in the bi-layer films to be magnetically ordered at room temperature under the influence of the 3d-layer spin system. The influence spreads to long distances inside Dy layer through the 3d-ions dispersed in it

  8. Theory of Kerr and Faraday rotations and linear dichroism in Topological Weyl Semimetals.

    Science.gov (United States)

    Kargarian, Mehdi; Randeria, Mohit; Trivedi, Nandini

    2015-08-03

    We consider the electromagnetic response of a topological Weyl semimetal (TWS) with a pair of Weyl nodes in the bulk and corresponding Fermi arcs in the surface Brillouin zone. We compute the frequency-dependent complex conductivities σαβ(ω) and also take into account the modification of Maxwell equations by the topological θ-term to obtain the Kerr and Faraday rotations in a variety of geometries. For TWS films thinner than the wavelength, the Kerr and Faraday rotations, determined by the separation between Weyl nodes, are significantly larger than in topological insulators. In thicker films, the Kerr and Faraday angles can be enhanced by choice of film thickness and substrate refractive index. We show that, for radiation incident on a surface with Fermi arcs, there is no Kerr or Faraday rotation but the electric field develops a longitudinal component inside the TWS, and there is linear dichroism signal. Our results have implications for probing the TWS phase in various experimental systems.

  9. Holographic Reconstruction of Photoelectron Diffraction and Its Circular Dichroism for Local Structure Probing

    Science.gov (United States)

    Matsui, Fumihiko; Matsushita, Tomohiro; Daimon, Hiroshi

    2018-06-01

    The local atomic structure around a specific element atom can be recorded as a photoelectron diffraction pattern. Forward focusing peaks and diffraction rings around them indicate the directions and distances from the photoelectron emitting atom to the surrounding atoms. The state-of-the-art holography reconstruction algorithm enables us to image the local atomic arrangement around the excited atom in a real space. By using circularly polarized light as an excitation source, the angular momentum transfer from the light to the photoelectron induces parallax shifts in these diffraction patterns. As a result, stereographic images of atomic arrangements are obtained. These diffraction patterns can be used as atomic-site-resolved probes for local electronic structure investigation in combination with spectroscopy techniques. Direct three-dimensional atomic structure visualization and site-specific electronic property analysis methods are reviewed. Furthermore, circular dichroism was also found in valence photoelectron and Auger electron diffraction patterns. The investigation of these new phenomena provides hints for the development of new techniques for local structure probing.

  10. Absolute Configuration of 3-METHYLCYCLOHEXANONE by Chiral Tag Rotational Spectroscopy and Vibrational Circular Dichroism

    Science.gov (United States)

    Evangelisti, Luca; Holdren, Martin S.; Mayer, Kevin J.; Smart, Taylor; West, Channing; Pate, Brooks

    2017-06-01

    The absolute configuration of 3-methylcyclohexanone was established by chiral tag rotational spectroscopy measurements using 3-butyn-2-ol as the tag partner. This molecule was chosen because it is a benchmark measurement for vibrational circular dichroism (VCD). A comparison of the analysis approaches of chiral tag rotational spectroscopy and VCD will be presented. One important issue in chiral analysis by both methods is the conformational flexibility of the molecule being analyzed. The analysis of conformational composition of samples will be illustrated. In this case, the high spectral resolution of molecular rotational spectroscopy and potential for spectral simplification by conformational cooling in the pulsed jet expansion are advantages for chiral tag spectroscopy. The computational chemistry requirements for the two methods will also be discussed. In this case, the need to perform conformer searches for weakly bound complexes and to perform reasonably high level quantum chemistry geometry optimizations on these complexes makes the computational time requirements less favorable for chiral tag rotational spectroscopy. Finally, the issue of reliability of the determination of the absolute configuration will be considered. In this case, rotational spectroscopy offers a "gold standard" analysis method through the determination of the ^{13}C-subsitution structure of the complex between 3-methylcyclohexanone and an enantiopure sample of the 3-butyn-2-ol tag.

  11. Measuring circular dichroism in a capillary cell using the b23 synchrotron radiation CD beamline at diamond light source.

    Science.gov (United States)

    Jávorfi, Tamás; Hussain, Rohanah; Myatt, Daniel; Siligardi, Giuliano

    2010-01-01

    Synchrotron radiation circular dichroism (SRCD) is a well-established method in structural biology. The first UV-VIS beamline dedicated to circular dichroism at Diamond Light Source, a third generation synchrotron facility in South Oxfordshire, has recently become operational and it is now available for the user community. Herein we present an important application of SRCD: the CD measurement of protein solutions in fused silica rectangular capillary cells. This was achieved without the use of any lens between the photoelastic modulator and the photomultiplier tube detectors by exploiting the high photon flux of the collimated beam that can be as little as half a millimeter squared. Measures to minimize or eliminate vacuum-UV protein denaturation effects are discussed. The CD spectra measured in capillaries is a proof of principle to address CD measurements in microdevice systems using the new B23 SRCD beamline. © 2010 Wiley-Liss, Inc.

  12. Interaction of fisetin with human serum albumin by fluorescence, circular dichroism spectroscopy and DFT calculations: binding parameters and conformational changes

    International Nuclear Information System (INIS)

    Matei, Iulia; Ionescu, Sorana; Hillebrand, Mihaela

    2011-01-01

    The interaction between fisetin, an antioxidant and neuroprotective flavonoid, and human serum albumin (HSA) is investigated by means of fluorescence (steady-state, synchronous, time-resolved) and circular dichroism (CD) spectroscopy. The formation of a 1:1 complex with a constant of about 10 5 M -1 was evidenced. Foerster's resonance energy transfer and competitive binding with site markers warfarin and ibuprofen were considered and discussed. Changes in the CD band of HSA indicate a decrease in the α-helix content upon binding. An induced CD signal for bound fisetin was observed and rationalized in terms of density functional theory calculations. - Highlights: → Fisetin-BSA system was studied by fluorescence spectroscopy. → Binding parameters, association constant and number of sites were estimated. → Binding site of fisetin was identified by competitive experiments. → Conformational changes in HSA and fisetin were evidenced by circular dichroism. → TDDFT calculated CD spectra supported the experimental data.

  13. Interaction of fisetin with human serum albumin by fluorescence, circular dichroism spectroscopy and DFT calculations: binding parameters and conformational changes

    Energy Technology Data Exchange (ETDEWEB)

    Matei, Iulia; Ionescu, Sorana [Department of Physical Chemistry, Faculty of Chemistry, University of Bucharest, Bd. Regina Elisabeta 4-12, 030018 Bucharest (Romania); Hillebrand, Mihaela, E-mail: mihh@gw-chimie.math.unibuc.ro [Department of Physical Chemistry, Faculty of Chemistry, University of Bucharest, Bd. Regina Elisabeta 4-12, 030018 Bucharest (Romania)

    2011-08-15

    The interaction between fisetin, an antioxidant and neuroprotective flavonoid, and human serum albumin (HSA) is investigated by means of fluorescence (steady-state, synchronous, time-resolved) and circular dichroism (CD) spectroscopy. The formation of a 1:1 complex with a constant of about 10{sup 5} M{sup -1} was evidenced. Foerster's resonance energy transfer and competitive binding with site markers warfarin and ibuprofen were considered and discussed. Changes in the CD band of HSA indicate a decrease in the {alpha}-helix content upon binding. An induced CD signal for bound fisetin was observed and rationalized in terms of density functional theory calculations. - Highlights: > Fisetin-BSA system was studied by fluorescence spectroscopy. > Binding parameters, association constant and number of sites were estimated. > Binding site of fisetin was identified by competitive experiments. > Conformational changes in HSA and fisetin were evidenced by circular dichroism. > TDDFT calculated CD spectra supported the experimental data.

  14. Magnetic linear dichroism in x-ray emission spectroscopy: Yb in Yb3 Fe5 O12

    NARCIS (Netherlands)

    Groot, F.M.F. de; Krisch, M.H.; Sette, F.; Vogel, J.

    2000-01-01

    A magnetic linear dichroism MLD effect of up to 5% has been observed in the 2p 1/2 4d x-ray emission spectrum of Yb in Yb 3 Fe 5 O 12 . The spectral shape is well reproduced with an atomic multiplet calculation of the 4d to 2p decay. It is shown that the details of the spectral shapes are

  15. Flexible bent rod model with a saturating induced dipole moment to study the electric linear dichroism of DNA fragments

    Science.gov (United States)

    Bertolotto, Jorge A.; Umazano, Juan P.

    2016-06-01

    In the present work we make a theoretical study of the steady state electric linear dichroism of DNA fragments in aqueous solution. The here developed theoretical approach considers a flexible bent rod model with a saturating induced dipole moment. The electric polarizability tensor of bent DNA fragments is calculated considering a phenomenological model which theoretical and experimental backgroung is presented here. The model has into account the electric polarizability longitudinal and transversal to the macroion. Molecular flexibility is described using an elastic potential. We consider DNA fragments originally bent with bending fluctuations around an average bending angle. The induced dipole moment is supposed constant once the electric field strength grows up at critical value. To calculate the reduced electric linear dichroism we determine the optical factor considering the basis of the bent DNA perpendicular to the molecular axis. The orientational distribution function has into account the anisotropic electric properties and the molecule flexibility. We applied the present theoretical background to fit electric dichroism experimental data of DNA fragments reported in the bibliography in a wide range of molecular weight and electric field. From these fits, values of DNA physical properties are estimated. We compare and discuss the results here obtained with the theoretical and experimental data presented by other authors. The original contributions of this work are: the inclusion of the transversal electric polarizability saturating with the electric field, the description of the electric properties with an electric polarizability tensor dependant on the bending angle and the use of an arc model originally bent.

  16. Molecular and vibrational structure of diphenylether and its 4,4' -dibromo derivative. Infrared linear dichroism spectroscopy and density functional theory calculations

    DEFF Research Database (Denmark)

    Eriksen, Troels K; Karlsen, Eva; Spanget-Larsen, Jens

    2015-01-01

    The title compounds were investigated by means of Linear Dichroism (LD) IR spectroscopy on samples partially aligned in uniaxially stretched low-density polyethylene and by density functional theory calculations. Satisfactory overall agreement between observed and calculated vibrational wavenumbers...

  17. Origin-Independent Sum Over States Simulations of Magnetic and Electronic Circular Dichroism Spectra via the Localized Orbital/Local Origin Method

    Czech Academy of Sciences Publication Activity Database

    Štěpánek, Petr; Bouř, Petr

    2015-01-01

    Roč. 36, č. 10 (2015), s. 723-730 ISSN 0192-8651 R&D Projects: GA ČR GA13-03978S; GA ČR GAP208/11/0105 Grant - others:GA AV ČR(CZ) M200551205 Institutional support: RVO:61388963 Keywords : density functional theory * electronic circular dichroism * magnetic circular dichroism * origin-dependence Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.648, year: 2015

  18. Synchrotron radiation circular dichroism spectroscopy study of recombinant T β4 folding

    Science.gov (United States)

    Huang, Yung-Chin; Chu, Hsueh-Liang; Chen, Peng-Jen; Chang, Chia-Ching

    Thymosin beta 4 (T β4) is a 43-amino acid small peptide, has been demonstrated that it can promote cardiac repair, wound repair, tissue protection, and involve in the proliferation of blood cell precursor stem cells of bone marrow. Moreover, T β4 has been identified as a multifunction intrinsically disordered protein, which is lacking the stable tertiary structure. Owing to the small size and disordered character, the T β4 protein degrades rapidly and the storage condition is critical. Therefore, it is not easy to reveal its folding mechanism of native T β4. However, recombinant T β4 protein (rT β4), which fused with a 5-kDa peptide in its amino-terminal, is stable and possesses identical function of T β4. Therefore, rT β4 can be used to study its folding mechanism. By using over-critical folding process, stable folding intermediates of rT β4 can be obtained. Structure analysis of folding intermediates by synchrotron radiation circular dichroism (SRCD) and fluorescence spectroscopies indicate that rT β4 is a random coli major protein and its hydrophobic region becomes compact gradually. Moreover, the rT β4 folding is a two state transition. Thermal denaturation analysis indicates that rT β4 lacks stable tertiary structure. These results indicated that rT β4, similar to T β4, is an intrinsically disordered protein. Research is supported by MOST, Taiwan. MOST 103-2112-M-009-011-MY3. Corresponding author: Chia-Ching Chang; ccchang01@faculty.nctu.edu.tw.

  19. Detection of electron magnetic circular dichroism signals under zone axial diffraction geometry

    Energy Technology Data Exchange (ETDEWEB)

    Song, Dongsheng [National Center for Electron Microscopy in Beijing, Key Laboratory of Advanced Materials (MOE) and The State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Rusz, Jan [Department of Physics and Astronomy, Uppsala University, Box 516, S-751 20 Uppsala (Sweden); Cai, Jianwang [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Zhu, Jing, E-mail: jzhu@mail.tsinghua.edu.cn [National Center for Electron Microscopy in Beijing, Key Laboratory of Advanced Materials (MOE) and The State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China)

    2016-10-15

    EMCD (electron magnetic circular dichroism) technique provides us a new opportunity to explore magnetic properties in the transmission electron microscope. However, specific diffraction geometry is the major limitation. Only the two-beam and three-beam case are demonstrated in the experiments until now. Here, we present the more general case of zone axial (ZA) diffraction geometry through which the EMCD signals can be detected even with the very strong sensitivity to dynamical diffraction conditions. Our detailed calculations and well-controlled diffraction conditions lead to experiments in agreement with theory. The effect of dynamical diffraction conditions on EMCD signals are discussed both in theory and experiments. Moreover, with the detailed analysis of dynamical diffraction effects, we experimentally obtain the separate EMCD signals for each crystallographic site in Y{sub 3}Fe{sub 5}O{sub 12}, which is also applicable for other materials and cannot be achieved by site-specific EMCD and XMCD technique directly. Our work extends application of more general diffraction geometries and will further promote the development of EMCD technique. - Highlights: • The zone axial (ZA) diffraction geometry is presented for EMCD technique. • The detailed calculations for EMCD signals under ZA case are conducted. • The EMCD signals are obtained under the ZA case in the experiments. • The effect of dynamical effect on EMCD signals under ZA case is discussed. • Site-specific EMCD signals of Fe in Y{sub 3}Fe{sub 5}O{sub 12} are obtained by specific ZA conditions.

  20. X-ray magnetic circular dichroism strongly influenced by non-magnetic cover layers

    International Nuclear Information System (INIS)

    Zafar, K.; Audehm, P.; Schütz, G.; Goering, E.; Pathak, M.; Chetry, K.B.; LeClair, P.R.; Gupta, A.

    2013-01-01

    Highlights: •Energy filtering gives much larger sampling depth and escape length as expected. •XMCD sum rules could be dramatically altered by this effect. •Strong enhanced effective escape length for buried layers. •A “universal curve” model gives semi quantitative understanding. •Buried layers are more sensitive to self-absorption phenomena. -- Abstract: Total electron yield (TEY) is the dominating measurement mode in soft X-ray absorption spectroscopy (XAS), where the sampling depth is generally assumed to be quite small and constant, and the related self-absorption or saturation phenomena are about to be negligible at normal incidence conditions. From the OK edge to CrL 2,3 edge XAS ratio we determined a strong change in the effective electron escape length between an uncovered and a RuO 2 covered CrO 2 sample. This effect has been explained by a simple electron energy filtering model, providing a semi quantitative description. In addition, this simple model can quantitatively describe the unexpected reduced and positive CrL 2,3 X-ray magnetic circular dichroism (XMCD) signal of a RuO 2 /CrO 2 bilayer, while previous results have identified a clear negative Cr magnetization at the RuO 2 /CrO 2 interface. In our case this escape length enhancement has strong impact on the XMCD sum rule results and in general it provides much deeper sampling depth, but also larger self-absorption or saturation effects

  1. Magnetic circular Dichroism and Faraday rotation of cesium-argon excimers and cesium dimers

    International Nuclear Information System (INIS)

    Islam, M.A.

    1981-01-01

    Magnetic Circular Dichroism (MCD) and Faraday Rotation (FR) of excimer absorption bands in gases are measured to obtain the first direct information about the angular momentum quantum numbers and the angular momentum coupling schemes of excimer molecules. So far, there has been no experimental method to obtain information about the axial angular momentum and the angular momentum coupling schemes of excimer molecules. In this experiment, the MCD and the FR of cesium-argon excimer and cesium dimer absorption bands between 5000 A and 10,000 A are measured for the range of temperature from 116 0 to 355 0 C. Of particular interest is the blue wing of D 2 line in cesium which has been the subject of vigorous investigation. The measured MCD data at the blue wing of D 2 line clearly shows that the assignment of 2 μ/sub 1/2/ to this excited state assuming Hund's case (b) is a poor approximation. By a simple inspection of the MCD data, it is found that the coupling scheme is more nearly Hund's case (c) than Hynd's case (b). Several other new and interesting results are obtained. The blue wing associated with 5D transition in atomic cesium is devoid of MCD and exhibits strong MCD in the red wings. Thus, the assignment of 2 μ/sub 1/2/ and 2 π to the blue and red wings, respectively, assuming Hund's case (a) and (b), is a very good approximation. Again the yellow-green band associated with 7s-6s transition in atomic cesium shows no MCD. It is therefore also a good approximation to assign 2 μ/sub 1/2/ to the upper state assuming Hund's case (b). Much more information can be obtained by a detailed analysis of the MCD data

  2. Magnetic circular dichroism studies on microsomal aryl hydrocarbon hydroxylase: comparison with cytochrome b/sub 5/ and cytochrome P-450/sub cam/

    Energy Technology Data Exchange (ETDEWEB)

    Vickery, L; Salmon, A; Sauer, K

    1975-01-01

    Magnetic circular dichroism spectra are reported for the visible and near ultraviolet spectral regions of liver microsomes from dimethylbenzanthracene-treated rats. The sequential addition of NADH, dithionite, and carbon monoxide enables us to determine contributions to the magnetic circular dichroism by cytochromes b/sub 5/ and P-450, which dominate the spectra. The magnetic circular dichroism of the microsomal preparation is compared with that of purified oxidized and reduced cytochrome b/sub 5/ from pig liver and with the camphor-complexed and camphor-free oxidized, reduced, and reduced carbonmonoxy cytochrome P-450/sub cam/ from Pseudomonas putida. The magnetic circular dichroism spectra of the membrane bound cytochrome b/sub 5/ are similar to those of the purified protein, indicating that little or no alteration in the environment of the heme occurs during the isolation procedure. The soluble bacterial cytochrome P-450/sub cam/ also appears to be a suitable model for microsomal P-450, although differences in the magnetic circular dichroism intensity are observed for the two enzymes. No effect of dimethylbenzanthracene on the magnetic circular dichroism spectra of induced compared to control rat microsomes could be observed.

  3. Flexible bent rod model with a saturating induced dipole moment to study the electric linear dichroism of DNA fragments

    Directory of Open Access Journals (Sweden)

    Jorge A. Bertolotto

    2016-06-01

    Full Text Available In the present work we make a theoretical study of the steady state electric linear dichroism of DNA fragments in aqueous solution. The here developed theoretical approach considers a flexible bent rod model with a saturating induced dipole moment. The electric polarizability tensor of bent DNA fragments is calculated considering a phenomenological model which theoretical and experimental backgroung is presented here. The model has into account the electric polarizability longitudinal and transversal to the macroion. Molecular flexibility is described using an elastic potential. We consider DNA fragments originally bent with bending fluctuations around an average bending angle. The induced dipole moment is supposed constant once the electric field strength grows up at critical value. To calculate the reduced electric linear dichroism we determine the optical factor considering the basis of the bent DNA perpendicular to the molecular axis. The orientational distribution function has into account the anisotropic electric properties and the molecule flexibility. We applied the present theoretical background to fit electric dichroism experimental data of DNA fragments reported in the bibliography in a wide range of molecular weight and electric field. From these fits, values of DNA physical properties are estimated. We compare and discuss the results here obtained with the theoretical and experimental data presented by other authors. The original contributions of this work are: the inclusion of the transversal electric polarizability saturating with the electric field, the description of the electric properties with an electric polarizability tensor dependant on the bending angle and the use of an arc model originally bent.

  4. Upper limits for the circular dichroism for the C 1s and O 1s core excitation of methyl oxirane

    International Nuclear Information System (INIS)

    Pruemper, G; Lischke, T; Fukuzawa, H; Reinkoester, A; Ueda, K

    2007-01-01

    The circular dichroism (CD) in the total and partial ion yields of methyl-oxirane C 3 H 6 O was measured at the C 1s and O 1s edges. The difference of the response of the chiral molecule to circularly polarized light with opposite handedness was found to be less than 0.2% for the total ion yield and less than 0.5% for the partial ion yield. Additionally we tried to find a dipole allowed molecular orientation CD effect by analysing the fragmentation in the forward and backward direction. For this effect we found an upper limit of 1-2% for all abundant ionic fragments

  5. Determination of the absolute configurations of natural products via density functional theory calculations of optical rotation, electronic circular dichroism, and vibrational circular dichroism: the cytotoxic sesquiterpene natural products quadrone, suberosenone, suberosanone, and suberosenol A acetate.

    Science.gov (United States)

    Stephens, P J; McCann, D M; Devlin, F J; Smith, A B

    2006-07-01

    The determination of the absolute configurations (ACs) of chiral molecules using the chiroptical techniques of optical rotation (OR), electronic circular dichroism (ECD), and vibrational circular dichroism (VCD) has been revolutionized by the development of density functional theory (DFT) methods for the prediction of these properties. Here, we demonstrate the significance of these advances for the stereochemical characterization of natural products. Time-dependent DFT (TDDFT) calculations of the specific rotations, [alpha](D), of four cytotoxic natural products, quadrone (1), suberosenone (2), suberosanone (3), and suberosenol A acetate (4), are used to assign their ACs. TDDFT calculations of the ECD of 1 are used to assign its AC. The VCD spectrum of 1 is reported and also used, together with DFT calculations, to assign its AC. The ACs of 1 derived from its [alpha](D), ECD, and VCD are identical and in agreement with the AC previously determined via total synthesis. The previously undetermined ACs of 2-4, derived from their [alpha](D) values, have absolute configurations of their tricyclic cores identical to that of 1. Further studies of the ACs of these molecules using ECD and, especially, VCD are recommended to establish more definitively this finding. Our studies of the OR, ECD, and VCD of quadrone are the first to utilize DFT calculations of all three properties for the determination of the AC of a chiral natural product molecule.

  6. Electron magnetic chiral dichroism in CrO2 thin films using monochromatic probe illumination in a transmission electron microscope

    International Nuclear Information System (INIS)

    Loukya, B.; Zhang, X.; Gupta, A.; Datta, R.

    2012-01-01

    Electron magnetic chiral dichroism (EMCD) has been studied in CrO 2 thin films (with (100) and (110) growth orientations on TiO 2 substrates) using a gun monochromator in an aberration corrected transmission electron microscope operating at 300 kV. Excellent signal-to-noise ratio is obtained at spatial resolution ∼10 nm using a monochromatic probe as compared to conventional parallel illumination, large area convergent beam electron diffraction and scanning transmission electron microscopy techniques of EMCD. Relatively rapid exposure using mono probe illumination enables collection of EMCD spectra in total of 8–9 min in energy filtered imaging mode for a given Cr L 2,3 energy scan (energy range ∼35 eV). We compared the EMCD signal obtained by extracting the Cr L 2,3 spectra under three beam diffraction geometry of two different reciprocal vectors (namely g=110 and 200) and found that the g=200 vector enables acquisition of excellent EMCD signal from relatively thicker specimen area due to the associated larger extinction distance. Orbital to spin moment ratio has been calculated using EMCD sum rules for 3d elements and dichroic spectral features associated with CrO 2 are compared and discussed with XMCD theoretical spectra. - Highlights: ► Electron magnetic circular dichroism (EMCD) of CrO 2 thin film with two different orientations. ► Improved EMCD signal with Gun monochromator illumination. ► Improved EMCD signal with higher g vector.

  7. Magnetic properties of Co/Rh (001) multilayers studied by x-ray magnetic-circular dichroism

    Science.gov (United States)

    Tomaz, M. A.; Mayo, E.; Lederman, D.; Hallin, E.; Sham, T. K.; O'brien, W. L.; Harp, G. R.

    1998-11-01

    The layer-averaged magnetic moments of Co and Rh have been measured in sputter deposited Co/Rh (001) multilayer thin films using the x-ray magnetic circular dichroism. The Rh moments were measured at both the L and M absorption edges, where we find that the Rh moment decreases as a function of increasing Rh layer thickness (tRh). The decline of the layer-averaged Rh moment is well described in terms of a simple dilution, implying that the Rh moment is confined to the interfacial region. We find that the Co moment remains largely unaffected, maintaining a bulklike value of 1.7μB in the region preceding the first antiferromagnetic coupling peak where tRh ranges from 0 to 4 Å. We also find, via application of the dichroism sum rules, that the ratio / for Co increases ~10% for this same region. Finally, we contrast the magnetic behavior of the Co/Rh (001) and Fe/Rh (001) multilayer systems.

  8. Magnetometry of buried layers—Linear magnetic dichroism and spin detection in angular resolved hard X-ray photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Gloskovskii, Andrei; Stryganyuk, Gregory; Fecher, Gerhard H.; Felser, Claudia; Thiess, Sebastian; Schulz-Ritter, Heiko; Drube, Wolfgang; Berner, Götz; Sing, Michael; Claessen, Ralph; Yamamoto, Masafumi

    2012-01-01

    Highlights: ► Newly commissioned HAXPES instrument at P09 beamline of the PETRA III ring at DESY. ► We report HAXPES studies on buried magnetic nanolayers in a multi-layer sample. ► Linear magnetic dichroism of photoelectrons from buried CoFe–Ir 78 Mn 22 layers. ► Spin-resolved HAXPES measurements on buried magnetic multilayers using Mott detector. - Abstract: The electronic properties of buried magnetic nano-layers were studied using the linear magnetic dichroism in the angular distribution of photoemitted Fe, Co, and Mn 2p electrons from a CoFe–Ir 78 Mn 22 multi-layered sample. The buried layers were probed using hard X-ray photoelectron spectroscopy, HAXPES, at the undulator beamline P09 of the 3rd generation storage ring PETRA III. The results demonstrate that this magnetometry technique can be used as a sensitive element specific probe for magnetic properties suitable for application to buried ferromagnetic and antiferromagnetic magnetic materials and multilayered spintronics devices. Using the same instrument, spin-resolved Fe 2p HAXPES spectra were obtained from the buried layer with good signal quality.

  9. Combining sequence-based prediction methods and circular dichroism and infrared spectroscopic data to improve protein secondary structure determinations

    Directory of Open Access Journals (Sweden)

    Lees Jonathan G

    2008-01-01

    Full Text Available Abstract Background A number of sequence-based methods exist for protein secondary structure prediction. Protein secondary structures can also be determined experimentally from circular dichroism, and infrared spectroscopic data using empirical analysis methods. It has been proposed that comparable accuracy can be obtained from sequence-based predictions as from these biophysical measurements. Here we have examined the secondary structure determination accuracies of sequence prediction methods with the empirically determined values from the spectroscopic data on datasets of proteins for which both crystal structures and spectroscopic data are available. Results In this study we show that the sequence prediction methods have accuracies nearly comparable to those of spectroscopic methods. However, we also demonstrate that combining the spectroscopic and sequences techniques produces significant overall improvements in secondary structure determinations. In addition, combining the extra information content available from synchrotron radiation circular dichroism data with sequence methods also shows improvements. Conclusion Combining sequence prediction with experimentally determined spectroscopic methods for protein secondary structure content significantly enhances the accuracy of the overall results obtained.

  10. Preliminary Understanding of Surface Plasmon-Enhanced Circular Dichroism Spectroscopy by Single Particle Imaging

    Science.gov (United States)

    Zhan, Kangshu

    evaluated. Full spectrum reconstruction using a set of selected optical filters was carried out and data visualization using a Matlab based 3D mapping method was demonstrated. The third chapter describes the introduction of biomolecules in chiral particle studies. By measuring the circular dichroism spectrum and image of nanorods during lysozyme adsorption and denaturation, I was able to monitor the conformation change of proteins on large gapped nanorods. Experiment results suggested that the conformational change of absorbed protein could lead to the change of chiral signal of nanoparticles, suggesting the potentials of detecting biomolecular structural changes at the single nanoparticle level, though much uncertainty still present. The inherent high background of large, gapped nanoparticles when they interact with biomolecules led to the research described in the 4th chapter where I studied small palladium-silver coreshell nanoparticle properties and its interaction with proteins. SEM was used to characterize particles structures; UV-Vis and darkfield microscopy was used to capture particles' optical responses; and the finite-difference time-domain (FDTD) method was used to simulate resulting spectra and to compare with experimental outcomes. Lysozyme and bovine serum albumin (BSA) were used as the model molecules to study their conformational changes after being adsorbed onto particles. Last but the least, the 5th chapter is dedicated to FDTD simulation of a pair of perfectly shaped triangle nanoprisms to illustrate possible CD responses to be expected from extreme particles with sharp corners and much concentrated local EM field. Different coupling modes of triangle nanoprism were analyzed. It is found that many factors, such as particle orientation, spacing, and their relative position, could lead to significantly different coupling efficient, for both homodimers and heterodimers. The modeling data suggested interesting potentials of nanoparticles of extreme geometric

  11. Magnetism of unconventional nanoscaled materials. An X-ray circular dichroism and muon spin rotation study

    International Nuclear Information System (INIS)

    Tietze, Thomas Hermann

    2014-01-01

    The physical properties of nanoparticles deviate strongly from its bulk counterparts. In particular, the magnetic properties change strongly due to an elevated number of surface compared to bulk atoms. As a consequence the orbital magnetic moment in nanoparticles as well as the magnetic anisotropy is enhanced. Therefore, such nanoparticles have great potential in e.g. next generation high density data storage devices. A promising way to realize such devices is to deposit nanoparticles on graphene. Depending on the preparation conditions the templated growth of nanocluster arrays with different particle size and shape is possible. Since graphene possesses outstanding properties as well it is congruous to combine the advantages of both systems and to investigate its principle properties in more detail. Thus, one part of this work is dedicated to the size and shape dependence of electronic and magnetic properties of Ni nanoclusters on graphene. The magnetic properties were investigated using X-ray Magnetic Circular Dichroism (XMCD). From the corresponding absorption spectra, the electronic structure and the nanoparticle substrate interaction could be determined. Two sets of nanoparticles were investigated, with triangular and spherical shape. For each set the size was varied. Nonmagnetic absorption spectra indicate a strong interaction between the Ni nanoclusters and the graphene substrate. The integrated absorption signal which is a measure of the number of unoccupied states in the Ni d shell decreases strongly with decreasing cluster size. This means an enhanced occupancy of the Ni d states, most likely caused by charge transfer at the Ni nanocluster/graphene interface. As a consequence the magnetic moment was much smaller than expected for nanoclusters for all samples investigated. The smallest value obtained was only 50% of the respective bulk magnetic moment. The magnetic moment increases disproportionally and converges towards bulk properties above 2 ML. No

  12. Wavelength dependent photoelectron circular dichroism of limonene studied by femtosecond multiphoton laser ionization and electron-ion coincidence imaging

    Science.gov (United States)

    Rafiee Fanood, Mohammad M.; Janssen, Maurice H. M.; Powis, Ivan

    2016-09-01

    Enantiomers of the monoterpene limonene have been investigated by (2 + 1) resonance enhanced multiphoton ionization and photoelectron circular dichroism employing tuneable, circularly polarized femtosecond laser pulses. Electron imaging detection provides 3D momentum measurement while electron-ion coincidence detection can be used to mass-tag individual electrons. Additional filtering, by accepting only parent ion tagged electrons, can be then used to provide discrimination against higher energy dissociative ionization mechanisms where more than three photons are absorbed to better delineate the two photon resonant, one photon ionization pathway. The promotion of different vibrational levels and, tentatively, different electronic ion core configurations in the intermediate Rydberg states can be achieved with different laser excitation wavelengths (420 nm, 412 nm, and 392 nm), in turn producing different state distributions in the resulting cations. Strong chiral asymmetries in the lab frame photoelectron angular distributions are quantified, and a comparison made with a single photon (synchrotron radiation) measurement at an equivalent photon energy.

  13. Local X-ray magnetic circular dichroism study of Fe/Cu(111) using a tunneling smart tip

    Energy Technology Data Exchange (ETDEWEB)

    DiLullo, Andrew; Shirato, Nozomi; Cummings, Marvin [Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States); Kersell, Heath; Chang, Hao [Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States); Ohio University, Athens, OH 45701 (United States); Rosenmann, Daniel; Miller, Dean; Freeland, John W. [Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States); Hla, Saw-Wai [Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States); Ohio University, Athens, OH 45701 (United States); Rose, Volker, E-mail: vrose@anl.gov [Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States); Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States)

    2016-01-28

    A tunneling smart tip of a synchrotron X-ray scanning tunneling microscope provides simultaneously localized topographic, elemental and magnetic information. Localized spectroscopy with simultaneous topographic, elemental and magnetic information is presented. A synchrotron X-ray scanning tunneling microscope has been employed for the local study of the X-ray magnetic circular dichroism at the Fe L{sub 2,3}-edges of a thin iron film grown on Cu(111). Polarization-dependent X-ray absorption spectra have been obtained through a tunneling smart tip that serves as a photoelectron detector. In contrast to conventional spin-polarized scanning tunneling microscopy, X-ray excitations provide magnetic contrast even with a non-magnetic tip. Intensity variations in the photoexcited tip current point to chemical variations within a single magnetic Fe domain.

  14. Live cell linear dichroism imaging reveals extensive membrane ruffling within the docking structure of natural killer cell immune synapses

    DEFF Research Database (Denmark)

    Benninger, Richard K P; Vanherberghen, Bruno; Young, Stephen

    2009-01-01

    We have applied fluorescence imaging of two-photon linear dichroism to measure the subresolution organization of the cell membrane during formation of the activating (cytolytic) natural killer (NK) cell immune synapse (IS). This approach revealed that the NK cell plasma membrane is convoluted...... into ruffles at the periphery, but not in the center of a mature cytolytic NK cell IS. Time-lapse imaging showed that the membrane ruffles formed at the initial point of contact between NK cells and target cells and then spread radialy across the intercellular contact as the size of the IS increased, becoming...... absent from the center of the mature synapse. Understanding the role of such extensive membrane ruffling in the assembly of cytolytic synapses is an intriguing new goal....

  15. Investigation of binding behaviour of procainamide hydrochloride with human serum albumin using synchronous, 3D fluorescence and circular dichroism

    Directory of Open Access Journals (Sweden)

    Kirthi Byadagi

    2017-04-01

    Full Text Available Interaction of procainamide hydrochloride (PAH with human serum albumin (HSA is of great significance in understanding the pharmacokinetic and pharmacodynamic mechanisms of the drug. Multi-spectroscopic techniques were used to investigate the binding mode of PAH to HSA and results revealed the presence of static type of quenching mechanism. The number of binding sites, binding constants and thermodynamic parameters were calculated. The results showed a spontaneous binding of PAH to HSA and hydrophobic interactions played a major role. In addition, the distance between PAH and the Trp–214 was estimated employing the Förster's theory. Site marker competitive experiments indicated that the binding of PAH to HSA primarily took place in subdomain IIA (Sudlow's site I. The influence of interference of some common metal ions on the binding of PAH to HSA was studied. Synchronous fluorescence spectra (SFS, 3D fluorescence spectra and circular dichroism (CD results indicated the conformational changes in the structure of HSA.

  16. On the interplay between chirality and exciton coupling: a DFT calculation of the circular dichroism in π-stacked ethylene.

    Science.gov (United States)

    Norman, Patrick; Linares, Mathieu

    2014-09-01

    The chirality of stacked weakly interacting π-systems was interpreted in terms of Frenkel exciton states and the formation of excitonic circular dichroism (CD) bands was monitored for ethylene stacks of varying sizes. Convergence of CD bands with respect to the system size was observed for stacks involving around 10 molecules. By means of rotation around the C-C double bond in ethylene, chirality was induced in the monomeric system and which was shown to dominate the spectral responses, even for polymer aggregates. In helical assemblies of chiral entities, there will always be a mix of excitonic and monomeric contributions to the CD signal and it is demonstrated that the complex polarization propagator approach in combination with Density Functional Theory is a suitable method to address this situation. © 2014 Wiley Periodicals, Inc.

  17. Thermolysis of (1R,2R)-1,2-dideuteriocyclobutane. An application of vibrational circular dichroism to kinetic analysis

    International Nuclear Information System (INIS)

    Chickos, J.S.; Annamalai, A.; Keiderling, T.A.

    1986-01-01

    The relative rates of geometric isomerization to racemization have been studied for the title compound by using a combination of infrared (IR) and vibrational circular dichroism (VCD) spectroscopies, respectively. The results are interpreted with a kinetic and mechanistic scheme which parallels that used by Berson, Pedersen, and Carpenter on a similar study of chiral cyclopropane-d 2 thermolysis. Relative rates of isomerization to stereomutation of 1.5 +/- 0.4 were obtained which can be interpreted to be consistent with a mechanism best described by random methylene rotation in tetramethylene-d 2 . This is the first application of VCD to kinetic analysis, and the advantages of IR techniques over the more usually employed UV spectroscopies to this type of basic mechanistic problem are illustrated

  18. Conformational analysis of quinine and its pseudo enantiomer quinidine: a combined jet-cooled spectroscopy and vibrational circular dichroism study.

    Science.gov (United States)

    Sen, Ananya; Bouchet, Aude; Lepère, Valeria; Le Barbu-Debus, Katia; Scuderi, D; Piuzzi, F; Zehnacker-Rentien, A

    2012-08-16

    Laser-desorbed quinine and quinidine have been studied in the gas phase by combining supersonic expansion with laser spectroscopy, namely, laser-induced fluorescence (LIF), resonance-enhanced multiphoton ionization (REMPI), and IR-UV double resonance experiments. Density funtional theory (DFT) calculations have been done in conjunction with the experimental work. The first electronic transition of quinine and quinidine is of π-π* nature, and the studied molecules weakly fluoresce in the gas phase, in contrast to what was observed in solution (Qin, W. W.; et al. J. Phys. Chem. C2009, 113, 11790). The two pseudo enantiomers quinine and quinidine show limited differences in the gas phase; their main conformation is of open type as it is in solution. However, vibrational circular dichroism (VCD) experiments in solution show that additional conformers exist in condensed phase for quinidine, which are not observed for quinine. This difference in behavior between the two pseudo enantiomers is discussed.

  19. Intrinsic and Extrinsic Ferromagnetism in Co-Doped Indium Tin Oxide Revealed Using X-Ray Magnetic Circular Dichroism

    Directory of Open Access Journals (Sweden)

    A. M. H. R. Hakimi

    2017-01-01

    Full Text Available The effects of high-temperature annealing on ferromagnetic Co-doped Indium Tin Oxide (ITO thin films have been investigated using X-ray diffraction (XRD, magnetometry, and X-Ray Magnetic Circular Dichroism (XMCD. Following annealing, the magnetometry results indicate the formation of Co clusters with a significant increase in the saturation magnetization of the thin films arising from defects introduced during cluster formation. However, sum rule analysis of the element-specific XMCD results shows that the magnetic moment at the Co sites is reduced after annealing. The effects of annealing demonstrate that the ferromagnetism observed in the as-deposited Co-doped ITO films arises from intrinsic defects and cannot be related to the segregation of metallic Co clusters.

  20. How and How Much Molecular Conformation Affects Electronic Circular Dichroism: The Case of 1,1-Diarylcarbinols

    Directory of Open Access Journals (Sweden)

    Daniele Padula

    2018-01-01

    Full Text Available Chiroptical spectra such as electronic circular dichroism (ECD are said to be much more sensitive to conformation than their non-chiroptical counterparts, however, it is difficult to demonstrate such a common notion in a clear-cut way. We run DFT and TDDFT calculations on two closely related 1,1-diarylmethanols which show mirror-image ECD spectra for the same absolute configuration. We demonstrate that the main reason for the different chiroptical response of the two compounds lies in different conformational ensembles, caused by a single hydrogen-to-methyl substitution. We conclude that two compounds, having the same configuration but different conformation, may exhibit mirror-image ECD signals, stressing the importance and impact of conformational factors on ECD spectra.

  1. How and How Much Molecular Conformation Affects Electronic Circular Dichroism: The Case of 1,1-Diarylcarbinols.

    Science.gov (United States)

    Padula, Daniele; Pescitelli, Gennaro

    2018-01-09

    Chiroptical spectra such as electronic circular dichroism (ECD) are said to be much more sensitive to conformation than their non-chiroptical counterparts, however, it is difficult to demonstrate such a common notion in a clear-cut way. We run DFT and TDDFT calculations on two closely related 1,1-diarylmethanols which show mirror-image ECD spectra for the same absolute configuration. We demonstrate that the main reason for the different chiroptical response of the two compounds lies in different conformational ensembles, caused by a single hydrogen-to-methyl substitution. We conclude that two compounds, having the same configuration but different conformation, may exhibit mirror-image ECD signals, stressing the importance and impact of conformational factors on ECD spectra.

  2. Wideband giant optical activity and negligible circular dichroism of near-infrared chiral metamaterial based on a complementary twisted configuration

    International Nuclear Information System (INIS)

    Zhu, Weiren; Rukhlenko, Ivan D; Premaratne, Malin; Huang, Yongjun; Wen, Guangjun

    2013-01-01

    We theoretically analyze the near-infrared properties of a chiral metamaterial constituting an array of twisted crosses and complementary crosses made of silver. Through rigorous full-wave numerical simulations, we demonstrate that this type of metamaterial exhibits wideband giant optical activity, with a polarization azimuth rotation angle reaching values as large as 1900 ∘ per wavelength. Owing to the negligible loss at optical frequencies in the dielectric (magnesium fluoride) making up the metamaterial, we observe negligible circular dichroism and low dispersion of the polarization azimuth rotation angle over a wide frequency band. We envision that this type of chiral metamaterial will find extensive applications in optical communication systems and biological sensing. (paper)

  3. Kaempferol-human serum albumin interaction: Characterization of the induced chirality upon binding by experimental circular dichroism and TDDFT calculations

    Science.gov (United States)

    Matei, Iulia; Ionescu, Sorana; Hillebrand, Mihaela

    2012-10-01

    The experimental induced circular dichroism (ICD) and absorption spectra of the achiral flavonoid kaempferol upon binding to human serum albumin (HSA) were correlated to electronic CD and UV-vis spectra theoretically predicted by time-dependent density functional theory (TDDFT). The neutral and four anionic species of kaempferol in various conformations were considered in the calculations. The appearance of the experimental ICD signal was rationalized in terms of kaempferol binding to HSA in a distorted, chiral, rigid conformation. The comparison between the experimental and simulated spectra allowed for the identification of the kaempferol species that binds to HSA, namely the anion generated by deprotonation of the hydroxyl group in position 7. This approach constitutes a convenient method for evidencing the binding species and for determining its conformation in the binding pocket of the protein. Its main advantage over the UV-vis absorption method lays in the fact that only the bound ligand species gives an ICD signal.

  4. Mechanical design and analysis of an eight-pole superconducting vector magnet for soft x-ray magnetic dichroism measurements

    Energy Technology Data Exchange (ETDEWEB)

    Arbelaez, D.; Black, A.; Prestemon, S.O.; Wang, S.; Chen, J.; Arenholz, E.

    2010-01-13

    An eight-pole superconducting magnet is being developed for soft x-ray magnetic dichroism (XMD) experiments at the Advanced Light Source, Lawrence Berkley National Laboratory (LBNL). Eight conical Nb{sub 3}Sn coils with Holmium poles are arranged in octahedral symmetry to form four dipole pairs that provide magnetic fields of up to 5 T in any direction relative to the incoming x-ray beam. The dimensions of the magnet yoke as well as pole taper, diameter, and length were optimized for maximum peak field in the magnet center using the software package TOSCA. The structural analysis of the magnet is performed using ANSYS with the coil properties derived using a numerical homogenization scheme. It is found that the use of orthotropic material properties for the coil has an important influence in the design of the magnet.

  5. Gigantic transverse x-ray magnetic circular dichroism in ultrathin Co in Au/Co/Au(001)

    International Nuclear Information System (INIS)

    Koide, T; Mamiya, K; Asakura, D; Osatune, Y; Fujimori, A; Suzuki, Y; Katayama, T; Yuasa, S

    2014-01-01

    Transverse-geometry x-ray magnetic circular dichroism (TXMCD) measurements on Au/Co-staircase/Au(001) reveal the orbital origin of intrinsic in-plane magnetic anisotropy A gigantic TXMCD was successfully observed at the Co L 3,2 edges for Co thickness (t C0 ) in the 2-monolayer regime. A TXMCD-sum-rule analysis shows a remarkable enhancement of an orbital-moment anisotropy (Δm orb ) and of an in-plane magnetic dipole moment (m || T ). Both Δm orb and m || T exhibit close similarity in t Co dependence, reflecting the in-plane magnetic anisotropy These observations evidence that extremely strong, intrinsic, in-plane magnetic anisotropy originates from the anisotropic orbital part of the wave function, dominating the dipole-dipole-interaction-derived, extrinsic, in-plane magnetic anisotropy.

  6. Gigantic transverse x-ray magnetic circular dichroism in ultrathin Co in Au/Co/Au(001)

    Science.gov (United States)

    Koide, T.; Mamiya, K.; Asakura, D.; Osatune, Y.; Fujimori, A.; Suzuki, Y.; Katayama, T.; Yuasa, S.

    2014-04-01

    Transverse-geometry x-ray magnetic circular dichroism (TXMCD) measurements on Au/Co-staircase/Au(001) reveal the orbital origin of intrinsic in-plane magnetic anisotropy A gigantic TXMCD was successfully observed at the Co L3,2 edges for Co thickness (tC0) in the 2-monolayer regime. A TXMCD-sum-rule analysis shows a remarkable enhancement of an orbital-moment anisotropy (Δmorb) and of an in-plane magnetic dipole moment (m||T). Both Δmorb and m||T exhibit close similarity in tCo dependence, reflecting the in-plane magnetic anisotropy These observations evidence that extremely strong, intrinsic, in-plane magnetic anisotropy originates from the anisotropic orbital part of the wave function, dominating the dipole-dipole-interaction-derived, extrinsic, in-plane magnetic anisotropy.

  7. X-ray magnetic circular dichroism and small angle neutron scattering studies of thiol capped gold nanoparticles

    International Nuclear Information System (INIS)

    de la Venta, J.; Bouzas, V.; Pucci, A.; Laguna-Marco, M.A.; Haskel, D.; te Velthuis, S.G.E; Hoffmann, A.; Lal, J.; Bleuel, M.; Ruggeri, G.; de Julian Fernandez, C.; Garcia, M.A.

    2009-01-01

    X-ray magnetic circular dichroism (XMCD) and Small Angle Neutron Scattering (SANS) measurements were performed on thiol capped Au nanoparticles (NPs) embedded into polyethylene. An XMCD signal of 0.8 · 10 -4 was found at the Au L 3 edge of thiol capped Au NPs embedded in a polyethylene matrix for which Superconducting Quantum Interference Device (SQUID) magnetometry yielded a saturation magnetization, M s , of 0.06 emu/g Au . SANS measurements showed that the 3.2 nm average-diameter nanoparticles are 28% polydispersed, but no detectable SANS magnetic signal was found with the resolution and sensitivity accessible with the neutron experiment. A comparison with previous experiments carried out on Au NPs and multilayers, yield to different values between XMCD signals and magnetization measured by SQUID magnetometer. We discuss the origin of those differences

  8. Non-Steroidal Biphenyl Gelators: Correlation of Xerogel Structure with Solid-State Structure and Circular Dichroism Spectroscopy

    Directory of Open Access Journals (Sweden)

    H. Cristina Geiger

    2018-04-01

    Full Text Available Because the factors favoring the formation of well-formed single crystals are dissimilar to those conducive to gel formation, few examples of single-crystal structural characterizations of organogelators are found in the literature. A series of biphenyl methyl and ethyl diester derivatives of varying chain length were synthesized and their gelation abilities explored. X-ray diffraction of single crystals of one of the gelators reveals a columnar extended structure. Based on XRD results for xerogels obtained from the reported organogelators, the members of the series are isostructural and so also adopt a columnar superstructure. Scanning electron microscopy (SEM was used for the investigation of the morphology of the xerogels, which display either platelet-like morphologies or more typical entangled twisted ribbon-like aggregates. The gels exhibit chirality, which depends on the sol-gel transition history, as observed by induced circular dichroism (ICD spectroscopy.

  9. X-ray magnetic circular dichroism and small angle neutron scattering studies of thiol capped gold nanoparticles.

    Energy Technology Data Exchange (ETDEWEB)

    de la Venta, J.; Bouzas, V.; Pucci, A.; Laguna-Marco, M. A.; Haskel, D.; te Velthuis, S. G. E; Hoffmann, A.; Lal, J.; Bleuel, M.; Ruggeri, G.; de Julian Fernandez, C.; Garcia, M. A.; Univ.Complutense de Madrid; Inst. de Magnetismo Aplicado; Univ. of Pisa; Lab. di Magnetismo Molecolare

    2009-01-01

    X-ray magnetic circular dichroism (XMCD) and Small Angle Neutron Scattering (SANS) measurements were performed on thiol capped Au nanoparticles (NPs) embedded into polyethylene. An XMCD signal of 0.8 {center_dot} 10{sup -4} was found at the Au L{sub 3} edge of thiol capped Au NPs embedded in a polyethylene matrix for which Superconducting Quantum Interference Device (SQUID) magnetometry yielded a saturation magnetization, M{sub s}, of 0.06 emu/g{sub Au}. SANS measurements showed that the 3.2 nm average-diameter nanoparticles are 28% polydispersed, but no detectable SANS magnetic signal was found with the resolution and sensitivity accessible with the neutron experiment. A comparison with previous experiments carried out on Au NPs and multilayers, yield to different values between XMCD signals and magnetization measured by SQUID magnetometer. We discuss the origin of those differences.

  10. X-ray magnetic circular dichroism and small angle neutron scattering study of thiol capped gold nanoparticles.

    Energy Technology Data Exchange (ETDEWEB)

    de la Venta, J.; Bouzas, V.; Pucci, A.; Laguna-Marco, M. A.; Haskel, D.; Pinel, E. F.; te Velthuis, S. G. E.; Hoffmann, A.; Lal, J.; Bleuel, M.; Ruggeri, G.; de Julian, C.; Garcia, M. A.; Univ. Complutense de Madrid; Inst. de Magnetismo Aplicado UCM; Univ. Pisa; Univ. di Padova

    2009-11-01

    X-ray magnetic circular dichroism (XMCD) and Small Angle Neutron Scattering (SANS) measurements were performed on thiol capped Au nanoparticles (NPs) embedded into polyethylene. An XMCD signal of 0.8 {center_dot} 10{sup -4} was found at the Au L{sub 3} edge of thiol capped Au NPs embedded in a polyethylene matrix for which Superconducting Quantum Interference Device (SQUID) magnetometry yielded a saturation magnetization, M{sub s}, of 0.06 emu/g{sub Au}. SANS measurements showed that the 3.2 nm average-diameter nanoparticles are 28% polydispersed, but no detectable SANS magnetic signal was found with the resolution and sensitivity accessible with the neutron experiment. A comparison with previous experiments carried out on Au NPs and multilayers, yield to different values between XMCD signals and magnetization measured by SQUID magnetometer. We discuss the origin of those differences.

  11. Circular dichroism study of the interaction between mutagens and bilirubin bound to different binding sites of serum albumins

    Science.gov (United States)

    Orlov, Sergey; Goncharova, Iryna; Urbanová, Marie

    Although recent investigations have shown that bilirubin not only has a negative role in the organism but also exhibits significant antimutagenic properties, the mechanisms of interactions between bilirubin and mutagens are not clear. In this study, interaction between bilirubin bound to different binding sites of mammalian serum albumins with structural analogues of the mutagens 2-aminofluorene, 2,7-diaminofluorene and mutagen 2,4,7-trinitrofluorenone were investigated by circular dichroism and absorption spectroscopy. Homological human and bovine serum albumins were used as chiral matrices, which preferentially bind different conformers of bilirubin in the primary binding sites and make it observable by circular dichroism. These molecular systems approximated a real system for the study of mutagens in blood serum. Differences between the interaction of bilirubin bound to primary and to secondary binding sites of serum albumins with mutagens were shown. For bilirubin bound to secondary binding sites with low affinity, partial displacement and the formation of self-associates were observed in all studied mutagens. The associates of bilirubin bound to primary binding sites of serum albumins are formed with 2-aminofluorene and 2,4,7-trinitrofluorenone. It was proposed that 2,7-diaminofluorene does not interact with bilirubin bound to primary sites of human and bovine serum albumins due to the spatial hindrance of the albumins binding domains. The spatial arrangement of the bilirubin bound to serum albumin along with the studied mutagens was modelled using ligand docking, which revealed a possibility of an arrangement of the both bilirubin and 2-aminofluorene and 2,4,7-trinitrofluorenone in the primary binding site of human serum albumin.

  12. X-ray circular magnetic dichroism as a probe of spin reorientation transitions in Nd2Fe14B and Er2Fe14B systems

    International Nuclear Information System (INIS)

    Chaboy, J.; Marcelli, A.; Garcia, L.M.; Bartolome, J.; Kuz'min, M.D.; Maruyama, H.; Kobayashi, K.; Kawata, H.; Iwazumi, T.

    1995-01-01

    We present the first experimental observation of spin reorientation phase transitions (SRT) with the X-Ray circular magnetic dichroism (XCMD) technique. Both the first-order SRT in Er 2 Fe 14 B and the second-order one in Nd 2 Fe 14 B have been clearly detected, demonstrating the feasibility of this technique for studying SRTs. ((orig.))

  13. X-Ray Magnetic Dichroism of Antiferromagnet Fe2O3 : The Orientation of Magnetic Moments Observed by Fe 2p X-Ray Absorption Spectroscopy

    NARCIS (Netherlands)

    Kuiper, Pieter; Searle, Barry G.; Rudolf, Petra; Tjeng, L.H.; Chen, C.T.

    1993-01-01

    We report strong magnetic linear dichroism at the Fe L2,3 edge of the antiferromagnet Fe2O3 (hematite). The relative difference in absorption for light polarized parallel and perpendicular to the magnetic moment is as high as 40% at the Fe L2 edge. The spectra are in excellent agreement with

  14. X-ray magnetic dichroism: from quantitative determination of magnetic moments to imaging of magnetization dynamics; Dichroisme magnetique des rayons X: de la determination quantitative des moments magnetiques a l'imagerie de la dynamique de l'aimantation

    Energy Technology Data Exchange (ETDEWEB)

    Vogel, J

    2006-03-15

    In this document, I use some results of my research activities of the last ten years to show the power of x-ray magnetic dichroism for determining magnetic properties of thin layers, multilayers and nano-structures. The use of sum rules for x-ray dichroism allows a quantitative determination of the spin and orbital contributions to the magnetic moment, for each element of a heterogeneous material separately. Used in a qualitative way, x-ray dichroism allows monitoring the magnetization of the different layers in a multilayer material as a function of applied field. In combination with the temporal structure of synchrotron radiation, it is possible to study fast magnetization reversal with element selectivity, which is important for devices like spin valves and magnetic tunnel junctions. Adding the spatial resolution of a photoelectron emission microscope (PEEM), it becomes possible to study all the details of the fast magnetization reversal in complex magnetic systems. (author)

  15. Direct evidence of Ni magnetic moment in TbNi{sub 2}Mn—X-ray magnetic circular dichroism

    Energy Technology Data Exchange (ETDEWEB)

    Yu, D.H., E-mail: dyu@ansto.gov.au [Bragg Institute, Australian Nuclear Science and Technology Organisation, Lucas Heights, Sydney, NSW 2234 (Australia); Huang, Meng-Jie [National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu Science Park, Hsinchu 30076, Taiwan (China); Wang, J.L. [Bragg Institute, Australian Nuclear Science and Technology Organisation, Lucas Heights, Sydney, NSW 2234 (Australia); School of Physical, Environmental and Mathematical Sciences, University of New South Wales, Canberra at the Australian Defense Force Academy, Sydney, ACT 2600 (Australia); Institute for Superconductivity and Electronic Materials, University of Wollongong, Wollongong, NSW 2522 (Australia); Su, Hui-Chia; Lin, Hong-Ji; Chen, Chien-Te [National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu Science Park, Hsinchu 30076, Taiwan (China); Campbell, S.J. [School of Physical, Environmental and Mathematical Sciences, University of New South Wales, Canberra at the Australian Defense Force Academy, Sydney, ACT 2600 (Australia)

    2014-12-15

    We have investigated the individual magnetic moments of Ni, Mn and Tb atoms in the intermetallic compound TbNi{sub 2}Mn in the Laves phase (magnetic phase transition temperature T{sub C} ∼131 K) by X-ray magnetic circular dichroism (XMCD) studies at 300 K, 80 K and 20 K. Analyses of the experimental results reveal that Ni atoms at 20 K in an applied magnetic field of 1 T carry an intrinsic magnetic moment of spin and orbital magnetic moment contributions 0.53±0.01 μ{sub B} and 0.05±0.01 μ{sub B}, respectively. These moment values are similar to those of the maximum saturated moment of Ni element. A very small magnetic moment of order <0.1 μ{sub B} has been measured for Mn. This suggests that Mn is antiferromagnetically ordered across the two nearly equally occupied sites of 16d and 8a. A magnetic moment of up to ∼0.3 μ{sub B} has been observed for the Tb atoms. Identification of a magnetic moment on the Ni atoms has provided further evidence for the mechanism of enhancement of the magnetic phase transition temperature in TbNi{sub 2}Mn compared with TbNi{sub 2} (T{sub C}∼37.5 K) and TbMn{sub 2} (T{sub C}∼54 K) due to rare earth–transition metal (R–T) and transition metal–transition metal (T–T) interactions. The behaviour of the X-ray magnetic circular dichroism spectra of TbNi{sub 2}Mn at 300 K, 80 K and 20 K – above and below the magnetic ordering temperature T{sub C} ∼131 K – is discussed. - Highlights: • We study the magnetic moment of TbNi{sub 2}Mn with XMCD. • We observe directly the Ni intrinsic magnetic moment in TbNi{sub 2}Mn. • We find that Mn ordered antiferromagnetically across the 16d and 8a sites. • We confirm the mechanism for increasing the magnetic phase transition temperature.

  16. X-ray magnetic circular dichroism study of epitaxial magnetite ultrathin film on MgO(100)

    Energy Technology Data Exchange (ETDEWEB)

    Liu, W. Q.; Xu, Y. B., E-mail: yongbing.xu@york.ac.uk, E-mail: rzhang@nju.edu.cn [York-Nanjing International Center for Spintronics (YNICS), School of Electronics Science and Engineering, Nanjing University, Nanjing 210093 (China); Spintronics and Nanodevice Laboratory, Department of Electronics, University of York, York YO10 5DD (United Kingdom); Song, M. Y.; Lin, J. G. [Center for Condensed Matter Sciences, National Taiwan University, Taipei 106, Taiwan (China); Maltby, N. J.; Li, S. P. [Spintronics and Nanodevice Laboratory, Department of Electronics, University of York, York YO10 5DD (United Kingdom); Samant, M. G.; Parkin, S. S. P. [IBM Research Division, Almaden Research Center, San Jose, California 95120 (United States); Bencok, P.; Steadman, Paul; Dobrynin, Alexey [Diamond Light Source, Didcot OX11 0DE (United Kingdom); Zhang, R., E-mail: yongbing.xu@york.ac.uk, E-mail: rzhang@nju.edu.cn [York-Nanjing International Center for Spintronics (YNICS), School of Electronics Science and Engineering, Nanjing University, Nanjing 210093 (China)

    2015-05-07

    The spin and orbital magnetic moments of the Fe{sub 3}O{sub 4} epitaxial ultrathin film synthesized by plasma assisted simultaneous oxidization on MgO(100) have been studied with X-ray magnetic circular dichroism. The ultrathin film retains a rather large total magnetic moment, i.e., (2.73 ± 0.15) μ{sub B}/f.u., which is ∼70% of that for the bulk-like Fe{sub 3}O{sub 4}. A significant unquenched orbital moment up to 0.54 ± 0.05 μ{sub B}/f.u. was observed, which could come from the symmetry breaking at the Fe{sub 3}O{sub 4}/MgO interface. Such sizable orbital moment will add capacities to the Fe{sub 3}O{sub 4}-based spintronics devices in the magnetization reversal by the electric field.

  17. Conformational study of bovine lactoferricin in membrane-micking conditions by molecular dynamics simulation and circular dichroism.

    Science.gov (United States)

    Daidone, Isabella; Magliano, Alessandro; Di Nola, Alfredo; Mignogna, Giuseppina; Clarkson, Matilda Manuela; Lizzi, Anna Rita; Oratore, Arduino; Mazza, Fernando

    2011-04-01

    Lactoferricins are potent antimicrobial peptides released by pepsin cleavage of Lactoferrins. Bovine Lactoferricin (LfcinB) has higher activity than the intact bovine Lactoferrin, and is the most active among the other Lactoferricins of human, murine and caprine origin. In the intact protein the fragment corresponding to LfcinB is in an helical conformation, while in water LfcinB adopts an amphipathic β-hairpin structure. However, whether any of these structural motifs is the antibacterial active conformation, i.e., the one interacting with bacterial membrane components, remains to be seen. Here we present Circular Dichroism (CD) spectra and Molecular Dynamics (MD) simulations indicating that in membrane-mimicking solvents the LfcinB adopts an amphipathic β-hairpin structure similar to that observed in water, but differing in the dynamic behavior of the side-chains of the two tryptophan residues. In the membrane-mimicking solvent these side-chains show a high propensity to point towards the hydrophobic environment, rather than being in the hydrophobic core as seen in water, while the backbone preserves the hairpin conformation as found in water. These results suggest that the tryptophans might act as anchors pulling the stable, solvent-invariant hairpin structure into the membrane.

  18. An atomic orbital based real-time time-dependent density functional theory for computing electronic circular dichroism band spectra

    Energy Technology Data Exchange (ETDEWEB)

    Goings, Joshua J.; Li, Xiaosong, E-mail: xsli@uw.edu [Department of Chemistry, University of Washington, Seattle, Washington 98195 (United States)

    2016-06-21

    One of the challenges of interpreting electronic circular dichroism (ECD) band spectra is that different states may have different rotatory strength signs, determined by their absolute configuration. If the states are closely spaced and opposite in sign, observed transitions may be washed out by nearby states, unlike absorption spectra where transitions are always positive additive. To accurately compute ECD bands, it is necessary to compute a large number of excited states, which may be prohibitively costly if one uses the linear-response time-dependent density functional theory (TDDFT) framework. Here we implement a real-time, atomic-orbital based TDDFT method for computing the entire ECD spectrum simultaneously. The method is advantageous for large systems with a high density of states. In contrast to previous implementations based on real-space grids, the method is variational, independent of nuclear orientation, and does not rely on pseudopotential approximations, making it suitable for computation of chiroptical properties well into the X-ray regime.

  19. Laser mass spectrometry with circularly polarized light: circular dichroism of cold molecules in a supersonic gas beam.

    Science.gov (United States)

    Titze, Katharina; Zollitsch, Tilo; Heiz, Ulrich; Boesl, Ulrich

    2014-09-15

    An experiment on chiral molecules that combines circular dichroism (CD) spectroscopy, mass-selective detection by laser mass spectrometry (MS), and cooling of molecules by using a supersonic beam is presented. The combination of the former two techniques (CD-laser-MS) is a new method to investigate chiral molecules and is now used by several research groups. Cooling in a supersonic beam supplies a substantial increase in spectroscopic resolution, a feature that has not yet been used in CD spectroscopy. In the experiments reported herein, a large variation in the electronic CD of carbonyl 3-methylcyclopentanone was observed depending on the excited vibrational modes in the n → π* transition. This finding should be of interest for the detection of chiral molecules and for the theoretical understanding of the CD of vibronic bands. It is expected that this effect will show up in other chiral carbonyls because the n → π* transition is typical for the carbonyl group. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Probing Magnetism in the Vortex Phase of PuCoGa_{5} by X-Ray Magnetic Circular Dichroism.

    Science.gov (United States)

    Magnani, N; Eloirdi, R; Wilhelm, F; Colineau, E; Griveau, J-C; Shick, A B; Lander, G H; Rogalev, A; Caciuffo, R

    2017-10-13

    We measure x-ray magnetic circular dichroism (XMCD) spectra at the Pu M_{4,5} absorption edges from a newly prepared high-quality single crystal of the heavy-fermion superconductor ^{242}PuCoGa_{5}, exhibiting a critical temperature T_{c}=18.7  K. The experiment probes the vortex phase below T_{c} and shows that an external magnetic field induces a Pu 5f magnetic moment at 2 K equal to the temperature-independent moment measured in the normal phase up to 300 K by a superconducting quantum interference device. This observation is in agreement with theoretical models claiming that the Pu atoms in PuCoGa_{5} have a nonmagnetic singlet ground state resulting from the hybridization of the conduction electrons with the intermediate-valence 5f electronic shell. Unexpectedly, XMCD spectra show that the orbital component of the 5f magnetic moment increases significantly between 30 and 2 K; the antiparallel spin component increases as well, leaving the total moment practically constant. We suggest that this indicates a low-temperature breakdown of the complete Kondo-like screening of the local 5f moment.

  1. Vibrational circular dichroism from ab initio molecular dynamics and nuclear velocity perturbation theory in the liquid phase

    Energy Technology Data Exchange (ETDEWEB)

    Scherrer, Arne [Martin-Luther-Universität Halle-Wittenberg, Institut für Chemie, von-Danckelmann-Platz 4, 06120 Halle (Germany); Département de Chimie, École Normale supérieure, PSL Research University, UPMC Univ Paris 06, CNRS, PASTEUR, 24 rue Lhomond, 75005 Paris (France); Sorbonne Universités, UPMC Univ Paris 06, ENS, CNRS, PASTEUR, 75005 Paris (France); Vuilleumier, Rodolphe, E-mail: rodolphe.vuilleumier@ens.fr [Département de Chimie, École Normale supérieure, PSL Research University, UPMC Univ Paris 06, CNRS, PASTEUR, 24 rue Lhomond, 75005 Paris (France); Sorbonne Universités, UPMC Univ Paris 06, ENS, CNRS, PASTEUR, 75005 Paris (France); Sebastiani, Daniel, E-mail: daniel.sebastiani@chemie.uni-halle.de [Martin-Luther-Universität Halle-Wittenberg, Institut für Chemie, von-Danckelmann-Platz 4, 06120 Halle (Germany)

    2016-08-28

    We report the first fully ab initio calculation of dynamical vibrational circular dichroism spectra in the liquid phase using nuclear velocity perturbation theory (NVPT) derived electronic currents. Our approach is rigorous and general and thus capable of treating weak interactions of chiral molecules as, e.g., chirality transfer from a chiral molecule to an achiral solvent. We use an implementation of the NVPT that is projected along the dynamics to obtain the current and magnetic dipole moments required for accurate intensities. The gauge problem in the liquid phase is resolved in a twofold approach. The electronic expectation values are evaluated in a distributed origin gauge, employing maximally localized Wannier orbitals. In a second step, the gauge invariant spectrum is obtained in terms of a scaled molecular moments, which allows to systematically include solvent effects while keeping a significant signal-to-noise ratio. We give a thorough analysis and discussion of this choice of gauge for the liquid phase. At low temperatures, we recover the established double harmonic approximation. The methodology is applied to chiral molecules ((S)-d{sub 2}-oxirane and (R)-propylene-oxide) in the gas phase and in solution. We find an excellent agreement with the theoretical and experimental references, including the emergence of signals due to chirality transfer from the solute to the (achiral) solvent.

  2. Determination of the Absolute Configurations Using Exciton Chirality Method for Vibrational Circular Dichroism: Right Answers for the Wrong Reasons?

    Science.gov (United States)

    Covington, Cody L; Nicu, Valentin P; Polavarapu, Prasad L

    2015-10-22

    Quantum chemical (QC) predictions of vibrational circular dichroism (VCD) spectra for the keto form of 3-benzoylcamphor and conformationally flexible diacetates of spiroindicumide A and B are presented. The exciton chirality (EC) model has been briefly reviewed, and a procedure to evaluate the relevance of the EC model has been presented. The QC results are compared with literature experimental VCD spectra as well as with those obtained using the EC model for VCD. These comparisons reveal that the EC contributions to bisignate VCD couplets associated with the C═O stretching vibrations of benzoylcamphor, spiroindicumide A diacetate, and spiroindicumide B diacetate are only ∼30%, ∼3%, and ∼15%, respectively. With such meager EC contributions, the correct absolute configurations (ACs) suggested in the literature for spiroindicumide A diacetate and spiroindicumide B diacetate molecules using the EC concepts can be considered fortuitous. The possibilities for obtaining wrong AC predictions using the EC concepts for VCD are identified, and guidelines for the future use of this model are presented.

  3. Normal and reversed supramolecular chirality of insulin fibrils probed by vibrational circular dichroism at the protofilament level of fibril structure.

    Science.gov (United States)

    Kurouski, Dmitry; Dukor, Rina K; Lu, Xuefang; Nafie, Laurence A; Lednev, Igor K

    2012-08-08

    Fibrils are β-sheet-rich aggregates that are generally composed of several protofibrils and may adopt variable morphologies, such as twisted ribbons or flat-like sheets. This polymorphism is observed for many different amyloid associated proteins and polypeptides. In a previous study we proposed the existence of another level of amyloid polymorphism, namely, that associated with fibril supramolecular chirality. Two chiral polymorphs of insulin, which can be controllably grown by means of small pH variations, exhibit opposite signs of vibrational circular dichroism (VCD) spectra. Herein, using atomic force microscopy (AFM) and scanning electron microscopy (SEM), we demonstrate that indeed VCD supramolecular chirality is correlated not only by the apparent fibril handedness but also by the sense of supramolecular chirality from a deeper level of chiral organization at the protofilament level of fibril structure. Our microscopic examination indicates that normal VCD fibrils have a left-handed twist, whereas reversed VCD fibrils are flat-like aggregates with no obvious helical twist as imaged by atomic force microscopy or scanning electron microscopy. A scheme is proposed consistent with observed data that features a dynamic equilibrium controlled by pH at the protofilament level between left- and right-twist fibril structures with distinctly different aggregation pathways for left- and right-twisted protofilaments. Copyright © 2012 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  4. The amide III vibrational circular dichroism band as a probe to detect conformational preferences of alanine dipeptide in water.

    Science.gov (United States)

    Mirtič, Andreja; Merzel, Franci; Grdadolnik, Jože

    2014-07-01

    The conformational preferences of blocked alanine dipeptide (ADP), Ac-Ala-NHMe, in aqueous solution were studied using vibrational circular dichroism (VCD) together with density functional theory (DFT) calculations. DFT calculations of three most representative conformations of ADP surrounded by six explicit water molecules immersed in a dielectric continuum have proven high sensitivity of amide III VCD band shape that is characteristic for each conformation of the peptide backbone. The polyproline II (PII ) and αR conformation of ADP are associated with a positive VCD band while β conformation has a negative VCD band in amide III region. Knowing this spectral characteristic of each conformation allows us to assign the experimental amide III VCD spectrum of ADP. Moreover, the amide III region of the VCD spectrum was used to determine the relative populations of conformations of ADP in water. Based on the interpretation of the amide III region of VCD spectrum we have shown that dominant conformation of ADP in water is PII which is stabilized by hydrogen bonded water molecules between CO and NH groups on the peptide backbone. Copyright © 2014 Wiley Periodicals, Inc.

  5. Optical and structural properties of plasma-treated Cordyceps bassiana spores as studied by circular dichroism, absorption, and fluorescence spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Geon Joon, E-mail: gjlee@kw.ac.kr; Sim, Geon Bo; Choi, Eun Ha [Plasma Bioscience Research Center/Department of Electrical and Biological Physics, Kwangwoon University, Seoul 139-701 (Korea, Republic of); Kwon, Young-Wan [KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul 136-701 (Korea, Republic of); Kim, Jun Young; Jang, Siun; Kim, Seong Hwan, E-mail: piceae@naver.com [Department of Microbiology and Institute of Basic Sciences, Dankook University, Cheonan 330-714 (Korea, Republic of)

    2015-01-14

    To understand the killing mechanism of fungal spores by plasma treatment, the optical, structural, and biological properties of the insect pathogenic fungus Cordyceps bassiana spores were studied. A nonthermal atmospheric-pressure plasma jet (APPJ) was used to treat the spores in aqueous solution. Optical emission spectra of the APPJ acquired in air indicated emission peaks corresponding to hydroxyl radicals and atomic oxygen. When the APPJ entered the aqueous solution, additional reactive species were derived from the interaction of plasma radicals with the aqueous solution. Fluorescence and absorption spectroscopy confirmed the generation of hydroxyl radicals and hydrogen peroxide in the plasma-activated water (PAW). Spore counting showed that plasma treatment significantly reduced spore viability. Absorption spectroscopy, circular dichroism (CD) spectroscopy, and agarose gel electrophoresis of the DNA extracted from plasma-treated spores showed a reduction in spore DNA content. The magnitude of the dip in the CD spectrum was lower in the plasma-treated spores than in the control, indicating that plasma treatment causes structural modifications and/or damage to cellular components. Tryptophan fluorescence intensity was lower in the plasma-treated spores than in the control, suggesting that plasma treatment modified cell wall proteins. Changes in spore viability and DNA content were attributed to structural modification of the cell wall by reactive species coming from the APPJ and the PAW. Our results provided evidence that the plasma radicals and the derived reactive species play critical roles in fungal spore inactivation.

  6. A new highly adaptable design of shear-flow device for orientation of macromolecules for Linear Dichroism (LD) measurement

    KAUST Repository

    Lundahl, P. Johan; Kitts, Catherine C.; Nordé n, Bengt

    2011-01-01

    This article presents a new design of flow-orientation device for the study of bio-macromolecules, including DNA and protein complexes, as well as aggregates such as amyloid fibrils and liposome membranes, using Linear Dichroism (LD) spectroscopy. The design provides a number of technical advantages that should make the device inexpensive to manufacture, easier to use and more reliable than existing techniques. The degree of orientation achieved is of the same order of magnitude as that of the commonly used concentric cylinders Couette flow cell, however, since the device exploits a set of flat strain-free quartz plates, a number of problems associated with refraction and birefringence of light are eliminated, increasing the sensitivity and accuracy of measurement. The device provides similar shear rates to those of the Couette cell but is superior in that the shear rate is constant across the gap. Other major advantages of the design is the possibility to change parts and vary sample volume and path length easily and at a low cost. © 2011 The Royal Society of Chemistry.

  7. TD-DFT investigation of the magnetic circular dichroism spectra of some purine and pyrimidine bases of nucleic acids.

    Science.gov (United States)

    Fahleson, Tobias; Kauczor, Joanna; Norman, Patrick; Santoro, Fabrizio; Improta, Roberto; Coriani, Sonia

    2015-05-28

    We present a computational study of the magnetic circular dichroism (MCD) spectra in the 200-300 nm wavelength region of purine and its derivative hypoxanthine, as well as of the pyrimidine bases of nucleic acids uracil, thymine, and cytosine, using the B3LYP and CAM-B3LYP functionals. Solvent effects are investigated within the polarizable continuum model and by inclusion of explicit water molecules. In general, the computed spectra are found to be in good agreement with the experimental ones, apart from some overall blue shifts. Both the pseudo-A term shape of the MCD spectra of the purines and the B term shape of the spectra of pyrimidine bases are reproduced. Our calculations also correctly reproduce the reversed phase of the MCD bands in purine compared to that of its derivatives present in nucleic acids. Solvent effects are sizable and system specific, but they do not in general alter the qualitative shape of the spectra. The bands are dominated by the bright π → π* transitions, and our calculations in solution nicely reproduce their energy differences, improving the estimates obtained in the gas phase. Shoulders are predicted for purine and uracil due to n → π* excitations, but they are too weak to be observed in the experiment.

  8. Measurement of electron-spin transports in GaAs quantum wells using a transmission-grating-sampled circular dichroism absorption spectroscopy

    International Nuclear Information System (INIS)

    Yu, Hua-Liang; Fang, Shaoyin; Wen, Jinhui; Lai, Tianshu

    2014-01-01

    A transmission-grating-sampled circular dichroism absorption spectroscopy (TGS-CDAS) and its theoretical model are developed sensitively to measure decay dynamics of a transient spin grating (TSG). A binary transmission grating with the same period as TSG is set behind TSG. It allows only a same small part of each period in TSG measured by circular dichroism absorption effect of a probe. In this way, the zero average of spin-dependent effects measured over a whole period in TSG is avoided so that TGS-CDAS has a high sensitivity to spin evolution in TSG. Spin transport experiments are performed on GaAs/AlGaAs quantum wells. Experimental results prove the feasibility and reliability of TGS-CDAS

  9. X-ray magnetic circular dichroism and hard X-ray photoelectron spectroscopy of tetragonal Mn72Ge28 epitaxial thin film

    Science.gov (United States)

    Kim, Jinhyeok; Mizuguchi, Masaki; Inami, Nobuhito; Ueno, Tetsuro; Ueda, Shigenori; Takanashi, Koki

    2018-04-01

    An epitaxially grown Mn72Ge28 film with a tetragonal crystal structure was fabricated. It was clarified that the film had a perpendicular magnetization and a high perpendicular magnetic anisotropy energy of 14.3 Merg/cm3. The electronic structure was investigated by X-ray magnetic circular dichroism and hard X-ray photoelectron spectroscopy. The obtained X-ray magnetic circular dichroism spectrum revealed that the Mn orbital magnetic moment governed the magnetocrystalline anisotropy of the Mn72Ge28 film. A doublet structure was observed for the Mn 2p3/2 peak of hard X-ray photoelectron spectrum, indicating the spin exchange interaction between the 2p core-hole and 3d valence electrons.

  10. Tight beta-turns in peptides. DFT-based study of infrared absorption and vibrational circular dichroism for various conformers including solvent effects

    Czech Academy of Sciences Publication Activity Database

    Kim, J.; Kapitán, Josef; Lakhani, A.; Bouř, Petr; Keiderling, T. A.

    2008-01-01

    Roč. 119, 1/3 (2008), s. 81-97 ISSN 1432-881X R&D Projects: GA ČR GA203/06/0420 Grant - others:NSF(US) CHE03-16014 Institutional research plan: CEZ:AV0Z40550506 Keywords : peptide beta -turn * density functional theory * infrared absorption * vibrational circular dichroism Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.370, year: 2008

  11. The polarization-angular structure and elliptical dichroism of the cross sections for three-photon bound-bound transitions in atoms

    International Nuclear Information System (INIS)

    Manakov, N.L.; Merem'yanin, A.V.

    1997-01-01

    Using the electric dipole approximation, we present, in invariant form, the cross section of an arbitrary three-photon transition between the discrete states of an atom with total angular momenta J i and J f . The cross section contains scalar and mixed products of the photon polarization vectors, and invariant atomic parameters dependent only on the photon frequencies. We determine the number of independent atomic parameters at fixed values of J i and J f and obtain their explicit expressions in terms of the reduced composite dipole matrix elements. The polarization dependence of the cross sections is expressed in terms of the degrees l and ξ of linear and circular photon polarizations. We analyze the phenomenon of dissipation-induced circular dichroism in three-photon processes, i.e., the difference Δ of the cross sections for opposite signs of the degree of circular polarization of all the photons. We study in detail the case of two identical photons and the phenomenon of elliptical dichroism, when Δ∼lξ holds and dichroism occurs only when the photons are elliptically polarized, with 0< vertical bar ξ vertical bar <1. Finally, we discuss the dissipation-induced effects of atom polarization in three-photon processes involving linearly polarized or unpolarized photons

  12. X-ray magnetic circular dichroism in d and f ferromagnetic materials: recent theoretical progress. Part II

    International Nuclear Information System (INIS)

    Antonov, V.N.; Shpak, A.P.; Yares'ko, A.N.

    2008-01-01

    The present state of theoretical understanding of the x-ray magnetic circular dichroism (XMCD) of 4f and 5f compounds is reviewed. Energy band theory based upon the local spin-density approximation (LSDA) describes the XMCD spectra of transition metal compounds with high accuracy. However, the LSDA does not suffice for lanthanide compounds which have a correlated 4f shell. A satisfactory description of the XMCD spectra could be obtained by using a generalization of the LSDA, in which explicitly f electron Coulomb correlations are taken into account (LSDA+U approach). As examples of this group we consider the compound GdN. We also consider uranium 5f compounds. In those compounds where the 5f electrons are rather delocalized, the LSDA describes the XMCD spectra reasonably well. As an example of this group we consider UFe 2 . Particular differences occur for uranium compounds in which the 5f electrons are neither delocalized nor localized, but more or less semilocalized. Typical examples are UXAl (X=Co, Rh, and Pt), and UX (X=S, Se, Te). However, the semilocalized 5f's are not inert, but their interaction with conduction electrons plays an important role. We also consider the electronic structure and XMCD spectra of the heavy-fermion compounds UPt 3 , URu 2 Si 2 , UPd 2 Al 3 , UNi 2 Al 3 , and UBe 13 , where the degree of the 5f localization is increased in comparison with other uranium compounds. The electronic structure and XMCD spectra of UGe 2 which possesses simultaneously ferromagnetism and superconductivity also presented. Recently achieved improvements for describing 5f compounds are discussed

  13. Ag(I)-mediated homo and hetero pairs of guanosine and cytidine: monitoring by circular dichroism spectroscopy.

    Science.gov (United States)

    Goncharova, Iryna

    2014-01-24

    Ag(I)-containing compounds are attractive as antibacterial and antifungal agents. The renewed interest in the application of silver(I) compounds has led to the need for detailed knowledge of the mechanism of their action. One of the possible ways is the coordination of Ag(I) to G-C pairs of DNA, where Ag(+) ions form Ag(I)-mediated base pairs and inhibit the transcription. Herein, a systematic chiroptical study on silver(I)-mediated homo and mixed pairs of the C-G complementary-base derivatives cytidine(C) and 5'-guanosine monophosphate(G) in water is presented. Ag(I)-mediated homo and hetero pairs of G and C and their self-assembled species were studied under two pH levels (7.0 and 10.0) by vibrational (VCD) and electronic circular dichroism(ECD). VCD was used for the first time in this field and showed itself to be a powerful method for obtaining specific structural information in solution. Based on results of the VCD experiments, the different geometries of the homo pairs were proposed under pH 7.0 and 10.0. ECD was used as a diagnostic tool to characterize the studied systems and as a contact point between the previously defined structures of the metal or proton mediated pairs of nucleobases and the systems studied here. On the basis of the obtained data, the formation of the self-assembled species of cytidine with a structure similar to the i-motif structure in DNA was proposed at pH 10.0. Copyright © 2013 Elsevier B.V. All rights reserved.

  14. Structure of human Rad51 protein filament from molecular modeling and site-specific linear dichroism spectroscopy

    KAUST Repository

    Reymer, A.

    2009-07-08

    To get mechanistic insight into the DNA strand-exchange reaction of homologous recombination, we solved a filament structure of a human Rad51 protein, combining molecular modeling with experimental data. We build our structure on reported structures for central and N-terminal parts of pure (uncomplexed) Rad51 protein by aid of linear dichroism spectroscopy, providing angular orientations of substituted tyrosine residues of Rad51-dsDNA filaments in solution. The structure, validated by comparison with an electron microscopy density map and results from mutation analysis, is proposed to represent an active solution structure of the nucleo-protein complex. An inhomogeneously stretched double-stranded DNA fitted into the filament emphasizes the strategic positioning of 2 putative DNA-binding loops in a way that allows us speculate about their possibly distinct roles in nucleo-protein filament assembly and DNA strand-exchange reaction. The model suggests that the extension of a single-stranded DNA molecule upon binding of Rad51 is ensured by intercalation of Tyr-232 of the L1 loop, which might act as a docking tool, aligning protein monomers along the DNA strand upon filament assembly. Arg-235, also sitting on L1, is in the right position to make electrostatic contact with the phosphate backbone of the other DNA strand. The L2 loop position and its more ordered compact conformation makes us propose that this loop has another role, as a binding site for an incoming double-stranded DNA. Our filament structure and spectroscopic approach open the possibility of analyzing details along the multistep path of the strand-exchange reaction.

  15. Ultraviolet magnetic circular dichroism study and x-ray absorption spectroscopy of zinc-blende type CrAs multilayer

    International Nuclear Information System (INIS)

    Mizuguchi, M.; Manago, T.; Akinaga, H.; Yamada, T.; Yagi-Watanabe, K.; Yuri, M.; Chen, C.T.; Shirai, M.

    2004-01-01

    Full text: Half-metallic ferromagnets such as CrO 2 and Heusler alloys have attracted a great deal of attention due to its application to spin-dependent device. We have predicted by first principle calculations that zinc-blende (zb) type CrAs, which normally exists in a MnP type, shows a half-metallic band structure, and succeeded in fabrication of this film. However, the epitaxial growth with maintaining a zb structure was limited up to around the nominal thickness of 3 nm. In this contribution, ultraviolet magnetic circular dichroism (MCD) and x-ray absorption spectroscopy (XAS) of CrAs multilayers are reported. These multilayers include zb-CrAs layers and low-temperature GaAs layers stacked alternately, and total thicknesses of zb- CrAs are thicker than 3 nm. Incident beam with the photon energy from 4 to 8 eV were used, and samples were attached on a magnet with the magnetic field of 1.0 T for the MCD measurements. Strong signal with the peak top at 6.5 eV is observed in the MCD spectrum. It can be seen that the experimental spectrum has a good agreement with the theoretical one, which indicates the formation of a superstructure as designed. It was also clarified by the XAS measurement using incident beam from 560 to 600 eV that peak positions of these multilayers shift systematically according to the thickness of each layer. The CrAs/GaAs multilayer is also expected to possess a half-metallic property by the theoretical calculation, therefore, the present result shows the multilayer will be the promising candidate as the spin electronics material

  16. 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

  17. Vibrational circular dichroism of a 2,5-diketopiperazine (DKP) peptide: Evidence for dimer formation in cyclo LL or LD diphenylalanine in the solid state.

    Science.gov (United States)

    Pérez-Mellor, Ariel; Zehnacker, Anne

    2017-02-01

    The diastereomer diketopiperazine (DKP) peptides built on phenylalanine, namely, cyclo diphenylalanine LPhe-LPhe and LPhe-DPhe, were studied in the solid phase by vibrational circular dichroism (VCD) coupled to quantum chemical calculations. The unit structure of cyclo LPhe-LPhe in KBr pellets is a dimer bridged by two strong NH…O hydrogen bonds. The intense bisignate signature in the CO stretch region is interpreted in terms of two contributions arising from the free COs of the dimer and the antisymmetrical combination of the bound COs. In contrast, cyclo LPhe-DPhe shows no VCD signal in relation to its symmetric nature. © 2017 Wiley Periodicals, Inc.

  18. Structural and magnetic properties of Co-doped (La,Sr)TiO{sub 3} epitaxial thin films probed using x-ray magnetic circular dichroism

    Energy Technology Data Exchange (ETDEWEB)

    Copie, O; Mattana, R; Bibes, M; Cros, V; Herranz, G; Anane, A; Ranchal, R; Jacquet, E; Bouzehouane, K; Petroff, F; Barthelemy, A [Unite Mixte de Physique CNRS/Thales, Campus de l' Ecole Polytechnique, 1 Avenue A Fresnel, 91767 Palaiseau, France and Universite Paris-Sud 11, 91405 Orsay (France); Rode, K [Center for Research on Adaptative Nanostructures and Nanodevices, Trinity College Dublin, Dublin 2, Republic of Ireland (Ireland); Arrio, M-A [Institut de Mineralogie et de Physique des Milieux Condenses CNRS, Universite Pierre et Marie Curie, 140 rue de Lourmel 75015 Paris (France); Bencok, P; Brookes, N B, E-mail: agnes.barthelemy@thalesgroup.co [European Synchrotron Radiation Facility, 6 rue Horowitz, 38083 Grenoble (France)

    2009-10-07

    We report a study of Co-doped La{sub 0.37}Sr{sub 0.63}TiO{sub 3-delta} thin films grown by pulsed laser deposition in various oxygen pressure conditions. X-ray absorption spectroscopy and magnetic circular dichroism measurements at the Co L{sub 2,3} edges reveal that the cobalt mainly substitutes for the titanium and is in an ionic state. Nevertheless, in some films, indications of additional cobalt metallic impurities were found, suggesting that the intrinsic character of this magnetic system remains questionable.

  19. Lanthanide tris(β-diketonates) as useful probes for chirality determination of biological amino alcohols in vibrational circular dichroism: ligand to ligand chirality transfer in lanthanide coordination sphere.

    Science.gov (United States)

    Miyake, Hiroyuki; Terada, Keiko; Tsukube, Hiroshi

    2014-06-01

    A series of lanthanide tris(β-diketonates) functioned as useful chirality probes in the vibrational circular dichroism (VCD) characterization of biological amino alcohols. Various chiral amino alcohols induced intense VCD signals upon ternary complexation with racemic lanthanide tris(β-diketonates). The VCD signals observed around 1500 cm(-1) (β-diketonate IR absorption region) correlated well with the stereochemistry and enantiomeric purity of the targeted amino alcohol, while the corresponding monoalcohol, monoamine, and diol substrates induced very weak VCD signals. The high-coordination number and dynamic property of the lanthanide complex offer an effective chirality VCD probing of biological substrates. © 2014 Wiley Periodicals, Inc.

  20. Perpendicular magnetic anisotropy at the interface between ultrathin Fe film and MgO studied by angular-dependent x-ray magnetic circular dichroism

    Energy Technology Data Exchange (ETDEWEB)

    Okabayashi, J. [Research Center for Spectrochemistry, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033 (Japan); Koo, J. W.; Mitani, S. [National Institute for Materials Science (NIMS), Tsukuba 305-0047 (Japan); Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8577 (Japan); Sukegawa, H. [National Institute for Materials Science (NIMS), Tsukuba 305-0047 (Japan); Takagi, Y.; Yokoyama, T. [Institute of Molecular Science, Okazaki, Aichi 444-8585 (Japan)

    2014-09-22

    Interface perpendicular magnetic anisotropy (PMA) in ultrathin Fe/MgO (001) has been investigated using angular-dependent x-ray magnetic circular dichroism (XMCD). We found that anisotropic orbital magnetic moments deduced from the analysis of XMCD contribute to the large PMA energies, whose values depend on the annealing temperature. The large PMA energies determined from magnetization measurements are related to those estimated from the XMCD and the anisotropic orbital magnetic moments through the spin-orbit interaction. The enhancement of anisotropic orbital magnetic moments can be explained mainly by the hybridization between the Fe 3d{sub z}{sup 2} and O 2p{sub z} states.

  1. Quantitatively analyzing the mechanism of giant circular dichroism in extrinsic plasmonic chiral nanostructures by tracking the interplay of electric and magnetic dipoles.

    Science.gov (United States)

    Hu, Li; Tian, Xiaorui; Huang, Yingzhou; Fang, Liang; Fang, Yurui

    2016-02-14

    Plasmonic chirality has drawn much attention because of tunable circular dichroism (CD) and the enhancement for chiral molecule signals. Although various mechanisms have been proposed to explain the plasmonic CD, a quantitative explanation like the ab initio mechanism for chiral molecules, is still unavailable. In this study, a mechanism similar to the mechanisms associated with chiral molecules was analyzed. The giant extrinsic circular dichroism of a plasmonic splitting rectangle ring was quantitatively investigated from a theoretical standpoint. The interplay of the electric and magnetic modes of the meta-structure is proposed to explain the giant CD. We analyzed the interplay using both an analytical coupled electric-magnetic dipole model and a finite element method model. The surface charge distributions showed that the circular current yielded by the splitting rectangle ring causes the ring to behave like a magneton at some resonant modes, which then interact with the electric modes, resulting in a mixing of the two types of modes. The strong interplay of the two mode types is primarily responsible for the giant CD. The analysis of the chiral near-field of the structure shows potential applications for chiral molecule sensing.

  2. Quantitative magnetic-moment mapping of a permanent-magnet material by X-ray magnetic circular dichroism nano-spectroscopy

    Directory of Open Access Journals (Sweden)

    Tetsuro Ueno

    2017-05-01

    Full Text Available We demonstrate the quantitative mapping of magnetic moments in a permanent-magnet material by X-ray magnetic circular dichroism nano-spectroscopy. An SmCo5 specimen was prepared from the bulk material by using a micro-fabrication technique. Scanning transmission X-ray microscopy images were obtained around the Sm M4,5 absorption edges. By applying the magneto-optical sum rules to these images, we obtained quantitative maps of the orbital and spin magnetic moments as well as their ratio. We found that the magnitudes of the orbital and spin magnetic moments and their ratio do not depend on thickness of the specimen.

  3. Magnetic and structural properties of Fe/Pd multilayers studied by magnetic x-ray dichroism and x-ray absorption spectroscopy

    International Nuclear Information System (INIS)

    Mini, S.M.; Fullerton, E.E.; Sowers, C.H.; Fontaine, A.; Pizzini, S.; Bommannavar, A.S.; Traverse, A.; Baudelet, F.

    1994-12-01

    The results of magnetic circular x-ray dichroism (MCXD) measurements and extended x-ray absorption fine structure measurements (EXAFS) of the Fe K-edges of textured Fe(110)/Pd(111) multilayers are reported. The EXAFS results indicates that the iron in the system goes from bcc to a more densely packed system as the thickness of the iron layer is decreased. The magnetic properties were measured by SQUID magnetometry from 5-350 K. For all the samples, the saturation magnetization was significantly enhanced over the bulk values indicating the interface Pd atoms are polarized by the Fe layer. The enhancement corresponds to a moment of ∼2.5μ B per interface Pd atom

  4. A rapid alternative to X-ray crystallography for chiral determination: case studies of vibrational circular dichroism (VCD) to advance drug discovery projects.

    Science.gov (United States)

    Wesolowski, Steven S; Pivonka, Don E

    2013-07-15

    The absolute stereochemistry of chiral drugs is usually established via X-ray crystallography. However, vibrational circular dichroism (VCD) spectroscopy coupled with quantum mechanics simulations offers a rapid alternative to crystallography and is readily applied to both crystalline and non-crystalline samples. VCD is an effective complement to X-ray analysis of drug candidates, and it can be used as a high-throughput means of assessing absolute stereochemistry at all phases of the discovery process (hundreds of assignments per year). The practical implementation (or fee-for-service outsourcing) of VCD and selected case studies are illustrated with an emphasis on providing utility and impact to pharmaceutical discovery programs. Copyright © 2013 Elsevier Ltd. All rights reserved.

  5. Transfer of chirality from adsorbed chiral molecules to the substrates highlighted by circular dichroism in angle-resolved valence photoelectron spectroscopy

    DEFF Research Database (Denmark)

    Contini, G.; Turchini, S.; Sanna, Simone

    2012-01-01

    Studies of self-assembled chiral molecules on achiral metallic surfaces have mostly focused on the determination of the geometry of adsorbates and their electronic structure. The aim of this paper is to provide direct information on the chirality character of the system and on the chirality...... transfer from molecules to substrate by means of circular dichroism in the angular distribution of valence photoelectrons for the extended domain of the chiral self-assembled molecular structure, formed by alaninol adsorbed on Cu(100). We show, by the dichroic behavior of a mixed molecule–copper valence...... state, that the presence of molecular chiral domains induces asymmetry in the interaction with the substrate and locally transfers the chiral character to the underlying metal atoms participating in the adsorption process; combined information related to the asymmetry of the initial electronic state...

  6. Spin reorientation transitions of Fe/Ni/Cu(001) studied by using the depth-resolved X-ray magnetic circular dichroism technique

    International Nuclear Information System (INIS)

    Abe, Hitoshi; Amemiya, Kenta; Matsumura, Daiju; Kitagawa, Soichiro; Watanabe, Hirokazu; Yokoyama, Toshihiko; Ohta, Toshiaki

    2006-01-01

    The spin reorientation transition (SRT) of Ni/Cu(001) induced by Fe deposition was investigated using the X-ray magnetic circular dichroism (XMCD) method. In-plane magnetized Ni films (= =10ML) also exhibit a transition to in-plane by 1-2ML Fe deposition. A precise magnetic anisotropy phase diagram was obtained using a combination of wedge-shaped Ni samples and stepwise Fe deposition. Magnetic anisotropy energies in the bulk, surface and interface layers of Ni films were separately determined using the depth-resolved XMCD technique, while values in the 1ML and 2ML portions of the Fe films were obtained from the conventional XMCD measurements. The origin of the SRTs is successfully explained with a simple phenomenological layer model using the obtained magnetic anisotropy energies. es

  7. Direct observation of high-spin states in manganese dimer and trimer cations by x-ray magnetic circular dichroism spectroscopy in an ion trap

    Energy Technology Data Exchange (ETDEWEB)

    Zamudio-Bayer, V. [Physikalisches Institut, Universität Freiburg, Stefan-Meier-Straße 21, 79104 Freiburg (Germany); Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Straße 15, 12489 Berlin (Germany); Hirsch, K.; Langenberg, A.; Kossick, M. [Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Straße 15, 12489 Berlin (Germany); Institut für Optik und Atomare Physik, Technische Universität Berlin, Hardenbergstraße 36, 10623 Berlin (Germany); Ławicki, A.; Lau, J. T., E-mail: tobias.lau@helmholtz-berlin.de [Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Straße 15, 12489 Berlin (Germany); Terasaki, A. [Cluster Research Laboratory, Toyota Technological Institute, 717-86 Futamata, Ichikawa, Chiba 272-0001 (Japan); Department of Chemistry, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581 (Japan); Issendorff, B. von [Physikalisches Institut, Universität Freiburg, Stefan-Meier-Straße 21, 79104 Freiburg (Germany)

    2015-06-21

    The electronic structure and magnetic moments of free Mn{sub 2}{sup +} and Mn{sub 3}{sup +} are characterized by 2p x-ray absorption and x-ray magnetic circular dichroism spectroscopy in a cryogenic ion trap that is coupled to a synchrotron radiation beamline. Our results directly show that localized magnetic moments of 5 μ{sub B} are created by 3d{sup 5}({sup 6}S) states at each ionic core, which are coupled ferromagnetically to form molecular high-spin states via indirect exchange that is mediated in both cases by a delocalized valence electron in a singly occupied 4s derived antibonding molecular orbital with an unpaired spin. This leads to total magnetic moments of 11 μ{sub B} for Mn{sub 2}{sup +} and 16 μ{sub B} for Mn{sub 3}{sup +}, with no contribution of orbital angular momentum.

  8. Magnetic circular dichroism of LaMn sub 1 sub - sub x Al sub x O sub 3 sub + subdelta series of samples

    CERN Document Server

    Banerjee, A; Krishnan, R V; Dasannacharya, B A; Muro, T; Saitoh, Y; Imada, S; Suga, S

    2003-01-01

    We report magnetic circular dichroism (MCD) studies on the polycrystalline LaMn sub 1 sub - sub x Al sub x O sub 3 sub + subdelta series with x=0-0.2. The Mn-2p MCD was recorded in the temperature range from 45 to 300 K for samples with x=0, 0.075, 0.1 and 0.15. It was seen that unlike ac-susceptibility no second transition in MCD was observed at lower temperatures in the samples with x>=0.075 indicating that it is not intrinsic to the samples but arise out of the dynamics of ferromagnetic clusters in the polycrystalline sample. More significantly, the MCD signal persists even 100 K above the ferromagnetic T sub C confirming that the observation of the magnetic correlation above T sub C in bulk measurement is intrinsic to this type of systems.

  9. A high-performance liquid chromatography-electronic circular dichroism online method for assessing the absolute enantiomeric excess and conversion ratio of asymmetric reactions

    Science.gov (United States)

    Zhang, Xiang; Wang, Mingchao; Li, Li; Yin, Dali

    2017-03-01

    Asymmetric reactions often need to be evaluated during the synthesis of chiral compounds. However, traditional evaluation methods require the isolation of the individual enantiomer, which is tedious and time-consuming. Thus, it is desirable to develop simple, practical online detection methods. We developed a method based on high-performance liquid chromatography-electronic circular dichroism (HPLC-ECD) that simultaneously analyzes the material conversion ratio and absolute optical purity of each enantiomer. In particular, only a reverse-phase C18 column instead of a chiral column is required in our method because the ECD measurement provides a g-factor that describes the ratio of each enantiomer in the mixtures. We used our method to analyze the asymmetric hydrosilylation of β-enamino esters, and we discussed the advantage, feasibility, and effectiveness of this new methodology.

  10. Magnetic Circular X-ray Dichroism Study of Paramagnetic and Anti-Ferromagnetic States in SrFeO3 Using a 10-T Superconducting Magnet

    International Nuclear Information System (INIS)

    Okamoto, J.; Mamiya, K.; Fujimori, S.-I.; Okane, T.; Saitoh, Y.; Muramatsu, Y.; Fujimori, A.; Ishiwata, S.; Takano, M.

    2004-01-01

    Magnetic circular x-ray dichroism (MCXD) measurements in Fe 2p absorption have been done on SrFeO3, which shows a spiral anti-ferromagnetism, by using a 10-T superconducting magnet. Finite MCXD structures have been observed under magnetic field of 8 T even in the paramagnetic and anti-ferromagnetic states. The intensity of the MCXD structure at hv ∼ 710 eV increases linearly as magnetic field increases linearly and the total magnetic moments estimated by MCXD sum rules roughly corresponds to the magnetization measured by SQUID measurements. MCXD study of paramagnetic and/or anti-ferromagnetic samples can be done by using a superconducting magnet that generates a strong magnetic field enough to induce finite magnetization

  11. Effects of dynamic diffraction conditions on magnetic parameter determination in a double perovskite Sr_2FeMoO_6 using electron energy-loss magnetic chiral dichroism

    International Nuclear Information System (INIS)

    Wang, Z.C.; Zhong, X.Y.; Jin, L.; Chen, X.F.; Moritomo, Y.; Mayer, J.

    2017-01-01

    Electron energy-loss magnetic chiral dichroism (EMCD) spectroscopy, which is similar to the well-established X-ray magnetic circular dichroism spectroscopy (XMCD), can determine the quantitative magnetic parameters of materials with high spatial resolution. One of the major obstacles in quantitative analysis using the EMCD technique is the relatively poor signal-to-noise ratio (SNR), compared to XMCD. Here, in the example of a double perovskite Sr_2FeMoO_6, we predicted the optimal dynamical diffraction conditions such as sample thickness, crystallographic orientation and detection aperture position by theoretical simulations. By using the optimized conditions, we showed that the SNR of experimental EMCD spectra can be significantly improved and the error of quantitative magnetic parameter determined by EMCD technique can be remarkably lowered. Our results demonstrate that, with enhanced SNR, the EMCD technique can be a unique tool to understand the structure-property relationship of magnetic materials particularly in the high-density magnetic recording and spintronic devices by quantitatively determining magnetic structure and properties at the nanometer scale. - Highlights: • We demonstrate how to choose the optimal experimental conditions by using dynamical diffraction calculations in Sr_2FeMoO_6. • With optimized diffraction conditions, the signal-to-noise ratio of experimental EMCD spectra has been significantly improved. • We have determined orbital to spin magnetic moment ratio of Sr_2FeMoO_6 quantitatively. • We have discussed the effects of dynamical diffraction conditions on the error bar of quantitative magnetic parameters.

  12. Linear-dichroism measurements on the LH2 antenna complex of Rhodopseudomonas Acidophila strain 10050 show that the transition dipole moment of the Carotenoid Rhodopin Glucoside us nit collinair with the long molecular axis

    NARCIS (Netherlands)

    Georgakopoulou, S.; Gogdell, R.J.; Grondelle, van R.; Amerongen, van H.

    2003-01-01

    We have applied linear-dichroism experiments to determine the orientation of the transition dipole moment, corresponding to the main absorption band of the carotenoid, rhodopin glucoside, in the light-harvesting complex LH2 from Rhodopseudomonas acidophila strain 10050. The crystal structure of this

  13. A circular dichroism sensor for Ni{sup 2+} and Co{sup 2+} based on L-cysteine capped cadmium sulfide quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Tedsana, Wimonsiri [Materials Chemistry Research Center, Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Khon Kaen University, Khon Kaen 40002 (Thailand); Tuntulani, Thawatchai [Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330 (Thailand); Ngeontae, Wittaya, E-mail: wittayange@kku.ac.th [Materials Chemistry Research Center, Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Khon Kaen University, Khon Kaen 40002 (Thailand)

    2015-03-31

    Highlights: • Demonstrated a new efficient sensor platform based quantum dots. • Used chiral quantum dots as CD sensor for the detection of heavy metal ions for the first time. • The proposed CD sensor showed highest selectivity towards Ni{sup 2+} and Co{sup 2+}. • Low detection limits of 7.33 μM and 1.13 μM for Ni{sup 2+} and Co{sup 2+}, respectively. • Can be used in real water samples comparing with ICP-OES. - Abstract: A new circular dichroism sensor for detecting Ni{sup 2+} and Co{sup 2+} was proposed for the first time using chiral chelating quantum dots. The detection principle was based on changing of circular dichroism signals of the chiral quantum dots when forming a chiral complex with Ni{sup 2+} or Co{sup 2+}. L-Cysteine capped cadmium sulfide quantum dots (L-Cyst-CdS QDs) were proposed as a chiral probe. The CD spectrum of L-Cyst-CdS QDs was significantly changed in the presence of Ni{sup 2+} and Co{sup 2+}. On the other hand, other studied cations did not alter the original CD spectrum. Moreover, when increasing the concentration of Ni{sup 2+} or Co{sup 2+}, the intensity of the CD spectrum linearly increased as a function of concentration and could be useful for the quantitative analysis. The proposed CD sensor showed linear working concentration ranges of 10–60 μM and 4–80 μM with low detection limits of 7.33 μM and 1.13 μM for the detection of Ni{sup 2+} and Co{sup 2+}, respectively. Parameters possibly affected the detection sensitivity such as solution pH and incubation time were studied and optimized. The proposed sensor was applied to detect Ni{sup 2+} and Co{sup 2+} in real water samples, and the results agreed well with the analysis using the standard ICP-OES.

  14. Rapid analysis of NSAIDs binding to β-cyclodextrin using the simultaneous measurement of absorption and circular dichroism with a novel multi-cell low-volume device.

    Science.gov (United States)

    Aboel Dahab, Ali; El-Hag, Dhia

    2012-10-01

    One of the relatively recent and most widely used approaches to reduce side effects associated with the use of nonsteroidal anti-inflammatory drugs (NSAIDs) is the complexation of NSAIDs with Cyclodextrins (CyD). So far, CyD interaction with drugs is not well understood. There have been many reports along these lines; however, rarely do these studies exploit the full potential of optical techniques. The purpose of this work is to produce a versatile, compact, low-volume, routine apparatus for the simultaneous measurements of absorbance and circular dichroism (CD) which allows for the concurrent use of three different pathlengths for binding studies of NSAIDs/CyD as a function of pH. A new rotating multi-cell holder which holds four cells was designed and manufactured. The work was achieved using an effective novel method for binding titration employing four separate flow cells connected in series in a flow system involving a titration flask and a pump. The pK(a), binding constants, stoichiometry and structural co-conformations of NSAIDs/β-CyD complexes were elucidated and determined with accuracy. The system proved to be efficient and the analysis time was reduced to less than or equal to one fourth of total analysis time used in one-cell systems, with possible automation for high-throughput analysis.

  15. Element-specific observation of the ferromagnetic ordering process in UCoAl via soft x-ray magnetic circular dichroism

    Science.gov (United States)

    Takeda, Yukiharu; Saitoh, Yuji; Okane, Tetsuo; Yamagami, Hiroshi; Matsuda, Tatsuma D.; Yamamoto, Etsuji; Haga, Yoshinori; Ōnuki, Yoshichika

    2018-05-01

    We have performed soft x-ray magnetic circular dichroism (XMCD) experiments on the itinerant-electron metamagnet UCoAl at the U 4 d -5 f (N4 ,5) and Co 2 p -3 d (L2 ,3) absorption edges in order to investigate the magnetic properties of the U 5 f and Co 3 d electrons separately. From the line shape of the XMCD spectrum, it is deduced that the orbital magnetic moment of the Co 3 d electrons is unusually large. Through the systematic temperature (T )- and magnetic field (H )-dependent XMCD measurements, we have obtained two types of the magnetization curve as a function of H and T (M-H curve and M-T curve, respectively). The metamagnetic transition from a paramagnetic state to a field-induced ferromagnetic state was clearly observed under 15 K at HM. The value of the HM and its T dependence agree well between the U and Co sites, and the bulk magnetization. Whereas, we have discovered the remarkable differences in the M-H and M-T curves between the U and Co sites. The present findings clearly show that the role of the Co 3 d electrons should be considered more carefully in order to understand the origin of the magnetic ordering in UCoAl.

  16. First-principles approach to the dynamic magnetoelectric couplings for the non-reciprocal directional dichroism in BiFeO3

    International Nuclear Information System (INIS)

    Lee, Jun Hee; Fishman, Randy S; Kézsmáki, István

    2016-01-01

    Due to the complicated magnetic and crystallographic structures of BiFeO 3 , its magnetoelectric (ME) couplings and microscopic model Hamiltonian remain poorly understood. By employing a first-principles approach, we uncover all possible ME couplings associated with the spin-current (SC) and exchange-striction (ES) polarizations, and construct an appropriate Hamiltonian for the long-range spin-cycloid in BiFeO 3 . First-principles calculations are used to understand the microscopic origins of the ME couplings. We find that inversion symmetries broken by ferroelectric and antiferroelectric distortions induce the SC and the ES polarizations, which cooperatively produce the dynamic ME effects in BiFeO 3 . A model motivated by first principles reproduces the absorption difference of counter-propagating light beams called non-reciprocal directional dichroism. The current paper focuses on the spin-driven (SD) polarizations produced by a dynamic electric field, i.e. the dynamic ME couplings. Due to the inertial properties of Fe, the dynamic SD polarizations differ significantly from the static SD polarizations. Our systematic approach can be generally applied to any multiferroic material, laying the foundation for revealing hidden ME couplings on the atomic scale and for exploiting optical ME effects in the next generation of technological devices such as optical diodes. (paper)

  17. Effect of urea on bovine serum albumin in aqueous and reverse micelle environments investigated by small angle X-ray scattering, fluorescence and circular dichroism

    International Nuclear Information System (INIS)

    Itri, Rosangela; Caetano, Wilker; Barbosa, Leandro R.S.; Baptista, Mauricio S.

    2004-01-01

    The influence that urea has on the conformation of water-soluble globular protein, bovine serum albumin (BSA), exposed directly to the aqueous solution as compared to the condition where the macromolecule is confined in the Aerosol-OT (AOT - sodium bis-2-ethylhexyl sulfosuccinate)/n-hexane/water reverse micelle (RM) is addressed. Small angle X-ray scattering (SAXS), tryptophan (Trp) fluorescence emission and circular dichroism (CD) spectra of aqueous BSA solution in the absence and in the presence of urea (3M and 5M) confirm the known denaturing effect of urea in proteins. The loss of the globular native structure is observed by the increase in the protein maximum dimension and gyration radius, through the Trp emission increase and maximum red-shift as well as the decrease in helix content. In RMs, the Trp fluorescence and CD spectra show that BSA is mainly located in its interfacial region independently of the micellar size. Addition of urea in this BSA/RM system also causes changes in the Trp fluorescence (emission decrease and maximum red-shift) and in the BSA CD spectra (decrease in helix content), which are compatible with the denaturation of the protein and Trp exposition to a more apolar environment in the RM. The fact that urea causes changes in the protein structure when it is located in the interfacial region (evidenced by CD) is interpreted as an indication that the direct interaction of urea with the protein is the major factor to explain its denaturing effect. (author)

  18. Photo-physics study of an hydroxy-quinoline derivative as inhibitor of Pim-1 kinase: ultraviolet-visible linear dichroism spectroscopy and quantum chemical calculations.

    Science.gov (United States)

    Lamhasni, T; Ait Lyazidi, S; Hnach, M; Haddad, M; Desmaële, D; Spanget-Larsen, J; Nguyen, D D; Ducasse, L

    2013-09-01

    The photophysical properties of the antiviral 7-nicotinoyl-styrylquinoline (MB96) were investigated by means of UV-Vis linear dichroism (LD) spectroscopy on molecular samples aligned in stretched polyvinylalcohol (PVA), supported by time dependent density functional theory (TD-DFT) calculations. Experimentally, the directions of the transitions moments with respect to the long axis of the molecule were deduced from the orientation K factors, determined by means of "trial-and-error" procedure. The absorption spectrum presents two parts. The main transition in the lowest energy part, observed around 365 nm and showing the highest K value 0.8, is longitudinally in-plane polarized. The highest energy part which is extended between 230 and 320 nm, large, diffuse, and of weak intensity, shows estimated K values between 0.2 and 0.5. This complex structure is transversally polarized with some contamination by the longitudinal character of the first strong band. The TD-DFT results agree fairly well with the LD measurements. Copyright © 2013 Elsevier B.V. All rights reserved.

  19. Intra- versus Intermolecular Hydrogen Bonding: Solvent-Dependent Conformational Preferences of a Common Supramolecular Binding Motif from 1 H NMR and Vibrational Circular Dichroism Spectra.

    Science.gov (United States)

    Demarque, Daniel P; Merten, Christian

    2017-12-19

    When predicting binding properties of small molecules or larger supramolecular aggregates, intra- and intermolecular hydrogen bonds are often considered the most important factor. Spectroscopic techniques such as 1 H NMR spectroscopy are typically utilized to characterize such binding events, but interpretation is often qualitative and follows chemical intuition. In this study, we compare the effects of intramolecular hydrogen bonding and solvation on two chiral 2,6-pyridinediyl-dialkylamides. In comparison with 1 H NMR spectroscopy, vibrational circular dichroism (VCD) spectroscopy proved to be more sensitive to conformational changes. In fact, the change of the solvent from CDCl 3 to [D 6 ]DMSO generates mirror-image VCD spectra for the same enantiomer. Here, the common sense that the sterically less hindered group is more prone to solvation proved to be wrong according predicted VCD spectra, which clearly show that both asymmetric amide hydrogens are equally likely to be solvated, but never simultaneously. The competition between intra- and intermolecular hydrogen bonding and their importance for a correct prediction of spectral properties are discussed. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Oriented circular dichroism analysis of chiral surface-anchored metal-organic frameworks grown by liquid-phase epitaxy and upon loading with chiral guest compounds

    KAUST Repository

    Gu, Zhigang

    2014-06-17

    Oriented circular dichroism (OCD) is explored and successfully applied to investigate chiral surface-anchored metal-organic frameworks (SURMOFs) based on camphoric acid (D- and Lcam) with the composition [Cu2(Dcam) 2x(Lcam)2-2x(dabco)]n (dabco=1,4-diazabicyclo- [2.2.2]-octane). The three-dimensional chiral SURMOFs with high-quality orientation were grown on quartz glass plates by using a layer-by-layer liquid-phase epitaxy method. The growth orientation, as determined by X-ray diffraction (XRD), could be switched between the [001] and [110] direction by using either OH- or COOH-terminated substrates. These SURMOFs were characterized by using OCD, which confirmed the ratio as well as the orientation of the enantiomeric linker molecules. Theoretical computations demonstrate that the OCD band intensities of the enantiopure [Cu2(Dcam)2(dabco)] n grown in different orientations are a direct result of the anisotropic nature of the chiral SURMOFs. Finally, the enantiopure [Cu 2(Dcam)2(dabco)]n and [Cu2(Lcam) 2(dabco)]n SURMOFs were loaded with the two chiral forms of ethyl lactate [(+)-ethyl-D-lactate and (-)-ethyl-L-lactate)]. An enantioselective enrichment of >60 % was observed by OCD when the chiral host scaffold was loaded from the racemic mixture. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Ratio of ellipticities between 192 and 208 nm (R1 ): An effective electronic circular dichroism parameter for characterization of the helical components of proteins and peptides.

    Science.gov (United States)

    Banerjee, Raja; Sheet, Tridip

    2017-11-01

    Circular dichroism (CD) spectroscopy represents an important tool for characterization of the peptide and protein secondary structures that mainly arise from the conformational disposition of the peptide backbone in solution. In 1991 Manning and Woody proposed that, in addition to the signal intensity, the ratio between [θ]nπ* and [θ]ππ*ǁ ((R 2 ) ≅ [θ] 222 /[θ] 208 ), along with [θ]ππ*⊥ and [θ]ππ*ǁ ((R 1 ) ≅ [θ] 192 /[θ] 208 ), may be utilized towards identifying the peptide/protein conformation (especially 3 10 - and α-helices). However, till date the use of the ratiometric ellipticity component for helical structure analysis of peptides and proteins has not been reported. We studied a series of temperature dependent CD spectra of a thermally stable, model helical peptide and its related analogs in water as a function of added 2,2,2-trifluoroethanol (TFE) in order to explore their landscape of helicity. For the first time, we have experimentally shown here that the R 1 parameter can characterize better the individual helices, while the other parameter R 2 and the signal intensity do not always converge. We emphasize the use of the R 1 ratio of ellipticities for helical characterization because of the common origin of these two bands (exciton splitting of the amide π→ π* transition in a helical polypeptide). This approach may become worthwhile and timely with the increasing accessibility of CD synchrotron sources. © 2017 Wiley Periodicals, Inc.

  2. Valley Zeeman splitting of monolayer MoS2 probed by low-field magnetic circular dichroism spectroscopy at room temperature

    Science.gov (United States)

    Wu, Y. J.; Shen, C.; Tan, Q. H.; Shi, J.; Liu, X. F.; Wu, Z. H.; Zhang, J.; Tan, P. H.; Zheng, H. Z.

    2018-04-01

    The valley Zeeman splitting of monolayer two-dimensional (2D) materials in the magnetic field plays an important role in the valley and spin manipulations. In general, a high magnetic field (6-65 T) and low temperature (2-30 K) were two key measurement conditions to observe the resolvable valley Zeeman splitting of monolayer 2D materials in current reported experiments. In this study, we experimentally demonstrate an effective measurement scheme by employing magnetic circular dichroism (MCD) spectroscopy, which enables us to distinguish the valley Zeeman splitting under a relatively low magnetic field of 1 T at room temperature. MCD peaks related to both A and B excitonic transitions in monolayer MoS2 can be clearly observed. Based on the MCD spectra under different magnetic fields (-3 to 3 T), we obtained the valley Zeeman splitting energy and the g-factors of A and B excitons, respectively. Our results show that MCD spectroscopy is a high-sensitive magneto-optical technique to explore the valley and spin manipulation in 2D materials.

  3. Dzyaloshinskii-Moriya interaction in α -Fe2O3 measured by magnetic circular dichroism in resonant inelastic soft x-ray scattering

    Science.gov (United States)

    Miyawaki, Jun; Suga, Shigemasa; Fujiwara, Hidenori; Urasaki, Masato; Ikeno, Hidekazu; Niwa, Hideharu; Kiuchi, Hisao; Harada, Yoshihisa

    2017-12-01

    Fe L2 ,3-edge x-ray absorption spectra (XAS) and magnetic circular dichroism (MCD) in resonant inelastic x-ray scattering (RIXS) of α -Fe2O3 were measured to identify the electronic structure responsible for its weak ferromagnetism caused by the Dzyaloshinskii-Moriya interaction (DMI) at room temperature. In contrast to negligible MCD in XAS, MCD in RIXS (RIXS-MCD) was clearly observed in the d d excitation at 1.8 eV via excitation to charge-transfer states. Furthermore, RIXS-MCD showed a crystal orientation dependence, indicating that the observed RIXS-MCD originated from DMI. The observed RIXS-MCD is well described by ab initio charge-transfer multiplet calculations, revealing that the RIXS-MCD derives from spin flip excitations at delocalized eg orbitals. By the combination of the experiments and calculations, RIXS-MCD has unraveled that the origin of DMI in α -Fe2O3 is the eg orbitals, which are strongly hybridized with the 2 p orbitals of oxygen atoms. The results demonstrate the importance of RIXS-MCD for identifying the electronic structure related to DMI.

  4. Magnetocrystalline Anisotropy of Magnetic Grains in Co80Pt20:Oxide Thin Films Probed by X-ray Magnetic Circular Dichroism

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, W.; Morton, S. A.; Wong, P. K. J.; Arenholz, E.; Lu, B.; Cheng, T. Y.; Xu, Y. B.; Laan, G. van der; Hu, X.F

    2011-01-12

    Using angle-dependent x-ray magnetic circular dichroism, we have measured magnetic hysteresis loops at the Co L2,3 edges of oxide-doped Co80Pt20 thin films. The magnetocrystalline anisotropy energy (MAE) of the Co atoms, which is the main source of the magnetocrystalline anisotropy of the CoPt magnetic grains, has been determined directly from these element-specific hysteresis loops. When the oxide volume fraction (OVF) is increased from 16.6% to 20.7%, the Co MAE has been found to decrease from 0.117 meV/atom to 0.076 meV/atom. While a larger OVF helps one to achieve a smaller grain size, it reduces the magnetocrystalline anisotropy, as demonstrated unambiguously from the direct Co MAE measurements. Our results suggest that those Co80Pt20:oxide films with an OVF between 19.1% and 20.7% are suitable candidates for high-density magnetic recording.

  5. Oriented circular dichroism analysis of chiral surface-anchored metal-organic frameworks grown by liquid-phase epitaxy and upon loading with chiral guest compounds

    KAUST Repository

    Gu, Zhigang; Bü rck, Jochen; Bihlmeier, Angela; Liu, Jinxuan; Shekhah, Osama; Weidler, Peter G.; Azucena, Carlos; Wang, Zhengbang; Heiß ler, Stefan; Gliemann, Hartmut; Klopper, Wim; Ulrich, Anne S.; Wö ll, Christof H.

    2014-01-01

    Oriented circular dichroism (OCD) is explored and successfully applied to investigate chiral surface-anchored metal-organic frameworks (SURMOFs) based on camphoric acid (D- and Lcam) with the composition [Cu2(Dcam) 2x(Lcam)2-2x(dabco)]n (dabco=1,4-diazabicyclo- [2.2.2]-octane). The three-dimensional chiral SURMOFs with high-quality orientation were grown on quartz glass plates by using a layer-by-layer liquid-phase epitaxy method. The growth orientation, as determined by X-ray diffraction (XRD), could be switched between the [001] and [110] direction by using either OH- or COOH-terminated substrates. These SURMOFs were characterized by using OCD, which confirmed the ratio as well as the orientation of the enantiomeric linker molecules. Theoretical computations demonstrate that the OCD band intensities of the enantiopure [Cu2(Dcam)2(dabco)] n grown in different orientations are a direct result of the anisotropic nature of the chiral SURMOFs. Finally, the enantiopure [Cu 2(Dcam)2(dabco)]n and [Cu2(Lcam) 2(dabco)]n SURMOFs were loaded with the two chiral forms of ethyl lactate [(+)-ethyl-D-lactate and (-)-ethyl-L-lactate)]. An enantioselective enrichment of >60 % was observed by OCD when the chiral host scaffold was loaded from the racemic mixture. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. 1s2p Resonant Inelastic X-ray Scattering Magnetic Circular Dichroism as a probe for the local and non-local orbitals in CrO 2

    NARCIS (Netherlands)

    Zimmermann, Patric; Bouldi, Nadejda; Hunault, Myrtille O.j.y.; Sikora, Marcin; Ablett, James M.; Rueff, Jean Pascal; Lebert, Blair; Sainctavit, Philippe; De Groot, Frank M.f.; Juhin, Amélie

    2018-01-01

    We have determined the magnetic ground state of the half-metal CrO2 based on 1s2p Resonant Inelastic X-ray Scattering Magnetic Circular Dichroism (RIXS-MCD) experiments. The two-dimensional RIXS-MCD map displays the 1s X-ray absorption spectrum combined with the 1s2p X-ray emission decay, where

  7. Structure and function of cytochrome c2 in electron transfer complexes with the photosynthetic reaction center of Rhodobacter sphaeroides: optical linear dichroism and EPR.

    Science.gov (United States)

    Drepper, F; Mathis, P

    1997-02-11

    The photosynthetic reaction center (RC) and its secondary electron donor the water-soluble cytochrome (cyt) c2 from the purple bacterium Rhodobacter sphaeroides have been used in cross-linked and non-cross-linked complexes, oriented in compressed gels or partially dried multilayers, to study the respective orientation of the primary donor P (BChl dimer) and of cyt c2. Three methods were used: (i) Polarized optical absorption spectra at 295 and 10 K were measured and the linear dichroism of the two individual transitions (Qx, Qy), which are nearly degenerate within the alpha-band of reduced cyt c2, was determined. Attribution of the polarization directions to the molecular axes within the heme plane yielded the average cyt orientation in the complexes. (ii) Time-resolved flash absorption measurements using polarized light allowed determination of the orientation of cyt c2 in complexes which differ in their kinetics of electron transfer. (iii) EPR spectroscopy of ferricyt c2 in cross-linked RC-cyt c2 complexes was used to determine the angle between the heme and the membrane plane. The results suggest the following structural properties for the docking of cyt c2 to the RC: (i) In cross-linked complexes, the two cytochromes displaying half-lives of 0.7 and 60 micros for electron transfer to P+ are similarly oriented (difference plane is parallel to the symmetry axis of the RC (0 degrees +/- 10 degrees). Moreover, the Qy transition, which is assumed to be polarized within the ring III-ring I direction of the heme plane, makes an angle of 56 degrees +/- 1 degree with the symmetry axis. (iii) The dichroism spectrum for the fast phase (0.7 micros) for the non-cross-linked cyt c2-RC complex suggests an orientation similar to that of cross-linked cyt c2, but the heme plane is tilted about 20 degrees closer to the membrane. An alternative model is that two or more bound states of cyt c2 with heme plane tilt angles between 0 degrees and 30 degrees allow the fast electron

  8. Combination of acoustic levitation with small angle scattering techniques and synchrotron radiation circular dichroism. Application to the study of protein solutions.

    Science.gov (United States)

    Cristiglio, Viviana; Grillo, Isabelle; Fomina, Margarita; Wien, Frank; Shalaev, Evgenyi; Novikov, Alexey; Brassamin, Séverine; Réfrégiers, Matthieu; Pérez, Javier; Hennet, Louis

    2017-01-01

    The acoustic levitation technique is a useful sample handling method for small solid and liquids samples, suspended in air by means of an ultrasonic field. This method was previously used at synchrotron sources for studying pharmaceutical liquids and protein solutions using x-ray diffraction and small angle x-ray scattering (SAXS). In this work we combined for the first time this containerless method with small angle neutron scattering (SANS) and synchrotron radiation circular dichroism (SRCD) to study the structural behavior of proteins in solutions during the water evaporation. SANS results are also compared with SAXS experiments. The aggregation behavior of 45μl droplets of lysozyme protein diluted in water was followed during the continuous increase of the sample concentration by evaporating the solvent. The evaporation kinetics was followed at different drying stage by SANS and SAXS with a good data quality. In a prospective work using SRCD, we also studied the evolution of the secondary structure of the myoglobin protein in water solution in the same evaporation conditions. Acoustic levitation was applied for the first time with SANS and the high performances of the used neutron instruments made it possible to monitor fast container-less reactions in situ. A preliminary work using SRCD shows the potentiality of its combination with acoustic levitation for studying the evolution of the protein structure with time. This multi-techniques approach could give novel insights into crystallization and self-assembly phenomena of biological compound with promising potential applications in pharmaceutical, food and cosmetics industry. This article is part of a Special Issue entitled "Science for Life" Guest Editor: Dr. Austen Angell, Dr. Salvatore Magazù and Dr. Federica Migliardo. Copyright © 2016 Elsevier B.V. All rights reserved.

  9. Biomolecular and structural analyses of cauliflower-like DNAs by ultraviolet, circular dichroism, and fluorescence spectroscopies in comparison with natural DNA.

    Science.gov (United States)

    Gill, Pooria; Ranjbar, Bijan; Saber, Reza; Khajeh, Khosro; Mohammadian, Mehdi

    2011-07-01

    Cauliflower-like DNAs are stem-loop DNAs that are fabricated periodically in inverted repetitions from deoxyribonucleic acid phosphates (dNTPs) by loop-mediated isothermal amplification (LAMP). Cauliflower-like DNAs have ladder-shape behaviors on gel electrophoresis, and increasing the time of LAMP leads to multiplying the repetitions, stem-loops, and electrophoretic bands. Cauliflower-like DNAs were fabricated via LAMP using two loop primers, two bumper primers, dNTPs, a λ-phage DNA template, and a Bst DNA polymerase in 75- and 90-min periods. These times led to manufacturing two types of cauliflower-like DNAs with different contents of inverted repetitions and stem-loops, which were clearly indicated by two comparable electrophoresis patterns in agarose gel. LAMP-fabricated DNAs and natural dsB-DNA (salmon genomic DNA) were dialyzed in Gomori phosphate buffer (10 mM, pH 7.4) to be isolated from salts, nucleotides, and primers. Dialyzed DNAs were studied using UV spectroscopy, circular dichroism spectropolarimetry, and fluorescence spectrophotometry. Structural analyses indicated reduction of the molecular ellipticity and extinction coefficients in comparison with B-DNA. Also, cauliflower-like DNAs demonstrated less intrinsic and more extrinsic fluorescence in comparison with natural DNA. The overwinding and lengthening of the cauliflower-like configurations of LAMP DNAs led to changes in physical parameters of this type of DNA in comparison with natural DNA. The results obtained introduced new biomolecular characteristics of DNA macromolecules fabricated within a LAMP process and show the effects of more inverted repeats and stem-loops, which are manufactured by lengthening the process.

  10. First-principles approach to the dynamic magnetoelectric couplings for the non-reciprocal directional dichroism in BiFeO3

    Science.gov (United States)

    Lee, Jun Hee; Kézsmáki, István; Fishman, Randy S.

    2016-04-01

    Due to the complicated magnetic and crystallographic structures of BiFeO3, its magnetoelectric (ME) couplings and microscopic model Hamiltonian remain poorly understood. By employing a first-principles approach, we uncover all possible ME couplings associated with the spin-current (SC) and exchange-striction (ES) polarizations, and construct an appropriate Hamiltonian for the long-range spin-cycloid in BiFeO3. First-principles calculations are used to understand the microscopic origins of the ME couplings. We find that inversion symmetries broken by ferroelectric and antiferroelectric distortions induce the SC and the ES polarizations, which cooperatively produce the dynamic ME effects in BiFeO3. A model motivated by first principles reproduces the absorption difference of counter-propagating light beams called non-reciprocal directional dichroism. The current paper focuses on the spin-driven (SD) polarizations produced by a dynamic electric field, i.e. the dynamic ME couplings. Due to the inertial properties of Fe, the dynamic SD polarizations differ significantly from the static SD polarizations. Our systematic approach can be generally applied to any multiferroic material, laying the foundation for revealing hidden ME couplings on the atomic scale and for exploiting optical ME effects in the next generation of technological devices such as optical diodes. This manuscript has been written by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the US Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan.

  11. Protocol for the Solid-phase Synthesis of Oligomers of RNA Containing a 2'-O-thiophenylmethyl Modification and Characterization via Circular Dichroism.

    Science.gov (United States)

    Francis, Andrew J; Resendiz, Marino J E

    2017-07-28

    Solid-phase synthesis has been used to obtain canonical and modified polymers of nucleic acids, specifically of DNA or RNA, which has made it a popular methodology for applications in various fields and for different research purposes. The procedure described herein focuses on the synthesis, purification, and characterization of dodecamers of RNA 5'-[CUA CGG AAU CAU]-3' containing zero, one, or two modifications located at the C2'-O-position. The probes are based on 2-thiophenylmethyl groups, incorporated into RNA nucleotides via standard organic synthesis and introduced into the corresponding oligonucleotides via their respective phosphoramidites. This report makes use of phosphoramidite chemistry via the four canonical nucleobases (Uridine (U), Cytosine (C), Guanosine (G), Adenosine (A)), as well as 2-thiophenylmethyl functionalized nucleotides modified at the 2'-O-position; however, the methodology is amenable for a large variety of modifications that have been developed over the years. The oligonucleotides were synthesized on a controlled-pore glass (CPG) support followed by cleavage from the resin and deprotection under standard conditions, i.e., a mixture of ammonia and methylamine (AMA) followed by hydrogen fluoride/triethylamine/N-methylpyrrolidinone. The corresponding oligonucleotides were purified via polyacrylamide electrophoresis (20% denaturing) followed by elution, desalting, and isolation via reversed-phase chromatography (Sep-pak, C18-column). Quantification and structural parameters were assessed via ultraviolet-visible (UV-vis) and circular dichroism (CD) photometric analysis, respectively. This report aims to serve as a resource and guide for beginner and expert researchers interested in embarking in this field. It is expected to serve as a work-in-progress as new technologies and methodologies are developed. The description of the methodologies and techniques within this document correspond to a DNA/RNA synthesizer (refurbished and purchased in

  12. Mimicking the membrane-mediated conformation of dynorphin A-(1-13)-peptide: Circular dichroism and nuclear magnetic resonance studies in methanolic solution

    International Nuclear Information System (INIS)

    Lancaster, C.R.D.; Hughes, D.W.; Epand, R.M.; Mishra, P.K.; Bothner-By, A.A.; St Pierre, S.A.

    1991-01-01

    The structural requirements for the binding of dynorphin to the κ-opioid receptor are of profound clinical interest in the search for a powerful nonaddictive analgesic. These requirements are thought to be met by the membrane-mediated conformation of the opioid peptide dynorphin A-(1-13)-peptide, Tyr 1 -Gly 2 -Gly 3 -Phe 4 -Leu 5 -Arg 6 -Arg 7 -Ile 8 -Arg 9 -Pro 10 -Lys 11 -Leu 12 -Lys 13 . Schwyzer has proposed an essentially α-helical membrane-mediated conformation of the 13 amino acid peptide. In the present study, circular dichroism (CD) studies on dynorphin A-(1-13)-peptide bound to an anionic phospholipid signified negligible helical content of the peptide. CD studies also demonstrated that the aqueous-membraneous interphase may be mimicked by methanol. The 500- and 620-MHz 1 H nuclear magnetic resonance (NMR) spectra of dynorphin A-(1-13)-peptide in methanolic solution were sequence-specifically assigned with the aid of correlated spectroscopy (COSY), double-quantum filtered phase-sensitive COSY (DQF-COSY), relayed COSY (RELAY), and nuclear Overhauser enhancement spectroscopy (NOESY). 2-D CAMELSPIN/ROESY experiments indicated that at least the part of the molecule from Arg 7 to Arg 9 was in an extended or β-strand conformation, which agreed with deuterium-exchange and temperature-dependence studies of the amide protons and analysis of the vicinal spin-spin coupling constants 3 J HNα . The results clearly demonstrated the absence of extensive α-helix formation. χ 1 rotamer analysis of the 3 J αβ demonstrated no preferred side-chain conformations

  13. The shape of the electronic circular dichroism spectrum of (2,6-dimethylphenyl)(phenyl)methanol: interplay between conformational equilibria and vibronic effects.

    Science.gov (United States)

    Padula, Daniele; Cerezo, Javier; Pescitelli, Gennaro; Santoro, Fabrizio

    2017-12-13

    Comparison between chiroptical spectra and theoretical predictions is the method of choice for the assignment of the absolute configuration of chiral compounds in solution. Here we report the case of an apparently simple biarylcarbinol, whose electronic circular dichroism (ECD) in the 1 L b region exhibits a peculiar alternation of negative and positive bands. Adopting Density Functional Theory, and describing solvent effects with implicit methods, we found three stable conformers in ethanol, each of them with two close lying states corresponding to similar local 1 L b excitations on the two phenyls. We computed the corresponding vibronic ECD spectra in harmonic approximation, including Duschinsky mixings as well as both Franck Condon (FC) and Herzberg Teller (HT) effects. Exploiting a recently developed mixed quantum/classical method, we further investigated the contribution of the vibronic spectra of out-of-equilibrium structures along the interconversion path connecting the different conformers. In this way, we achieved a reasonable agreement with experiment and attributed the alternating signs of the bands to the existence of different conformers. The remaining discrepancies with experiment indicate that specific solute-solvent interactions modulate the relative conformers' stabilities, calling for new methods able to combine Molecular Dynamics explorations and vibronic calculations. Moreover, the poor performance of HT approaches and the existence of two closely-lying states suggest the necessity of an improved fully-nonadiabatic vibronic approach. These findings demonstrate that even for such a simple system as the biarylcarbinol investigated here, a full reproduction of the fine details of the ECD spectrum requires the development of new improved methods.

  14. The influence of carbon nanotubes on enzyme activity and structure: investigation of different immobilization procedures through enzyme kinetics and circular dichroism studies

    International Nuclear Information System (INIS)

    Cang-Rong, Jason Teng; Pastorin, Giorgia

    2009-01-01

    In the last decade, many environmental organizations have devoted their efforts to identifying renewable biosystems, which could provide sustainable fuels and thus enhance energy security. Amidst the myriad of possibilities, some biofuels make use of different types of waste biomasses, and enzymes are often employed to hydrolyze these biomasses and produce sugars that will be subsequently converted into ethanol. In this project, we aimed to bridge nanotechnology and biofuel production: here we report on the activity and structure of the enzyme amyloglucosidase (AMG), physically adsorbed or covalently immobilized onto single-walled carbon nanotubes (SWNTs) and multi-walled carbon nanotubes (MWNTs). In fact, carbon nanotubes (CNTs) present several properties that render them ideal support systems, without the diffusion limitations displayed by porous material and with the advantage of being further functionalizable at their surface. Chemical ligation was achieved both on oxidized nanotubes (via carbodiimide chemistry), as well as on amino-functionalized nanotubes (via periodate-oxidized AMG). Results showed that AMG retained a certain percentage of its specific activity for all enzyme-carbon nanotubes complexes prepared, with the physically adsorbed samples displaying better catalytic efficiency than the covalently immobilized samples. Analysis of the enzyme's structure through circular dichroism (CD) spectroscopy revealed significant structural changes in all samples, the degree of change being consistent with the activity profiles. This study proves that AMG interacts differently with carbon nanotubes depending on the method employed. Due to the higher activity reported by the enzyme physically adsorbed onto CNTs, these samples demonstrated a vast potential for further development. At the same time, the possibility of inducing magnetic properties into CNTs offers the opportunity to easily separate them from the original solution. Hence, substances to which they

  15. Towards an exact theory of linear absorbance and circular dichroism of pigment-protein complexes: Importance of non-secular contributions

    International Nuclear Information System (INIS)

    Dinh, Thanh-Chung; Renger, Thomas

    2015-01-01

    A challenge for the theory of optical spectra of pigment-protein complexes is the equal strength of the pigment-pigment and the pigment-protein couplings. Treating both on an equal footing so far can only be managed by numerically costly approaches. Here, we exploit recent results on a normal mode analysis derived spectral density that revealed the dominance of the diagonal matrix elements of the exciton-vibrational coupling in the exciton state representation. We use a cumulant expansion technique that treats the diagonal parts exactly, includes an infinite summation of the off-diagonal parts in secular and Markov approximations, and provides a systematic perturbative way to include non-secular and non-Markov corrections. The theory is applied to a model dimer and to chlorophyll (Chl) a and Chl b homodimers of the reconstituted water-soluble chlorophyll-binding protein (WSCP) from cauliflower. The model calculations reveal that the non-secular/non-Markov effects redistribute oscillator strength from the strong to the weak exciton transition in absorbance and they diminish the rotational strength of the exciton transitions in circular dichroism. The magnitude of these corrections is in a few percent range of the overall signal, providing a quantitative explanation of the success of time-local convolution-less density matrix theory applied earlier. A close examination of the optical spectra of Chl a and Chl b homodimers in WSCP suggests that the opening angle between Q y transition dipole moments in Chl b homodimers is larger by about 9 ∘ than for Chl a homodimers for which a crystal structure of a related WSCP complex exists. It remains to be investigated whether this change is due to a different mutual geometry of the pigments or due to the different electronic structures of Chl a and Chl b

  16. Towards an exact theory of linear absorbance and circular dichroism of pigment-protein complexes: Importance of non-secular contributions

    Energy Technology Data Exchange (ETDEWEB)

    Dinh, Thanh-Chung; Renger, Thomas, E-mail: thomas.renger@jku.at [Institut für Theoretische Physik, Johannes Kepler University Linz, Altenberger Str. 69, 4040 Linz (Austria)

    2015-01-21

    A challenge for the theory of optical spectra of pigment-protein complexes is the equal strength of the pigment-pigment and the pigment-protein couplings. Treating both on an equal footing so far can only be managed by numerically costly approaches. Here, we exploit recent results on a normal mode analysis derived spectral density that revealed the dominance of the diagonal matrix elements of the exciton-vibrational coupling in the exciton state representation. We use a cumulant expansion technique that treats the diagonal parts exactly, includes an infinite summation of the off-diagonal parts in secular and Markov approximations, and provides a systematic perturbative way to include non-secular and non-Markov corrections. The theory is applied to a model dimer and to chlorophyll (Chl) a and Chl b homodimers of the reconstituted water-soluble chlorophyll-binding protein (WSCP) from cauliflower. The model calculations reveal that the non-secular/non-Markov effects redistribute oscillator strength from the strong to the weak exciton transition in absorbance and they diminish the rotational strength of the exciton transitions in circular dichroism. The magnitude of these corrections is in a few percent range of the overall signal, providing a quantitative explanation of the success of time-local convolution-less density matrix theory applied earlier. A close examination of the optical spectra of Chl a and Chl b homodimers in WSCP suggests that the opening angle between Q{sub y} transition dipole moments in Chl b homodimers is larger by about 9{sup ∘} than for Chl a homodimers for which a crystal structure of a related WSCP complex exists. It remains to be investigated whether this change is due to a different mutual geometry of the pigments or due to the different electronic structures of Chl a and Chl b.

  17. Real time observation of proteolysis with Fourier transform infrared (FT-IR) and UV-circular dichroism spectroscopy: Watching a protease eat a protein

    Science.gov (United States)

    Güler, Günnur; Džafić, Enela; Vorob'ev, Mikhail M.; Vogel, Vitali; Mäntele, Werner

    2011-06-01

    Fourier transform infrared (FT-IR)- and UV-circular dichroism (UV-CD) spectroscopy have been used to study real-time proteolytic digestion of β-lactoglobulin (β-LG) and β-casein (β-CN) by trypsin at various substrate/enzyme ratios in D 2O-buffer at 37 °C. Both techniques confirm that protein substrate looses its secondary structure upon conversion to the peptide fragments. This perturbation alters the backbone of the protein chain resulting in conformational changes and degrading of the intact protein. Precisely, the most significant spectral changes which arise from digestion take place in the amide I and amide II regions. The FT-IR spectra for the degraded β-LG show a decrease around 1634 cm -1, suggesting a decrease of β-sheet structure in the course of hydrolysis. Similarly, the intensity around the 1654 cm -1 band decreases for β-CN digested by trypsin, indicating a reduction in the α-helical part. On the other hand, the intensity around ˜1594 cm -1 and ˜1406 cm -1 increases upon enzymatic breakdown of both substrates, suggesting an increase in the antisymmetric and symmetric stretching modes of free carboxylates, respectively, as released digestion products. Observation of further H/D exchange in the course of digestion manifests the structural opening of the buried groups and accessibility to the core of the substrate. On the basis of the UV-CD spectra recorded for β-LG and β-CN digested by trypsin, the unordered structure increases concomitant with a decrease in the remaining structure, thus, revealing breakdown of the intact protein into smaller fragments. This model study in a closed reaction system may serve as a basis for the much more complex digestion processes in an open reaction system such as the stomach.

  18. K-edge x-ray dichroism investigation of Fe1−xCoxSi: Experimental evidence for spin polarization crossover

    International Nuclear Information System (INIS)

    Hearne, G.R.; Diguet, G.; Baudelet, F.; Itié, J.-P.; Manyala, N.

    2015-01-01

    Both Fe and Co K-edge x-ray magnetic circular dichroism (XMCD) have been employed as element-specific probes of the magnetic moments in the composition series of the disordered ferromagnet Fe 1−x Co x Si (for x=0.2, 0.3, 0.4, 0.5). A definitive single peaked XMCD profile occurs for all compositions at both Fe and Co K-edges. The Fe 4p orbital moment, deduced from the integral of the XMCD signal, has a steep dependence on x at low doping levels and evolves to a different (weaker) dependence at x≥0.3, similar to the behavior of the magnetization in the Co composition range studied here. It is systematically higher, by at least a factor of two, than the corresponding Co orbital moment for most of the composition series. Fine structure beyond the K-edge absorption (limited range EXAFS) suggests that the local order (atomic environment) is very similar across the series, from the perspective of both the Fe and Co absorbing atom. The variation in the XMCD integral across the Co composition range has two regimes, that which occurs below x=0.3 and then evolves to different behavior at higher doping levels. This is more conspicuously present in the Fe contribution. This is rationalized as the evolution from a half-metallic ferromagnet at low Co doping to that of a strong ferromagnet at x>0.3 and as such, spin polarization crossover occurs. The Fermi level is tuned from the majority spin band for x<0.3 where a strongly polarized majority spin electron gas prevails, to a regime where minority spin carriers dominate at higher doping. The evolution of the Fe-derived spin polarized (3d) bands, indirectly probed here via the 4p states, is the primary determinant of the doping dependence of the magnetism in this alloy series. - Highlights: • Element-specific probing of the electronic structure of the Fe 1−x Co x Si series. • XMCD at the level of 10 −4 at the K-edge in such low-moment systems. • Element-specific probing of magnetic contributions from both Fe and Co

  19. Theoretical analysis of the influence of chelate-ring size and vicinal effects on electronic circular dichroism spectra of cobalt(III) EDDA-type complexes.

    Science.gov (United States)

    Wang, Ai; Wang, Yuekui; Jia, Jie; Feng, Lixia; Zhang, Chunxia; Liu, Linlin

    2013-06-20

    To assess the contributions of configurational and vicinal effects as well as chelate-ring size to rotational strengths, the geometries of a series of cobalt(III) complexes [Co(EDDA-type)(L)](±) with the tetradentate EDDA-type ligands, EDDA (ethylenediamine-N,N'-diacetate), DMEDDA (N,N'-dimethylethylenediamine-N,N'-diacetate), DEEDDA (N,N'-diethylethylenediamine-N,N'-diacetate), and a bidentate ancillary ligand L (L = ethylenediamine, oxalate, carbonate, (S)-alanine, and malonate) in aqueous solution have been optimized at the DFT/B3LYP/6-311++G(2d,p) level of theory. Based on the optimized geometries, the excitation energies and oscillator and rotational strengths have been calculated using the time-dependent density functional theory (TDDFT) method with the same functional and basis set. The calculated circular dichroism (CD) curves are in excellent agreement with the observed ones except for some small red or blue shifts in peak wavelengths. For the influence of chelate-ring size of the bidentate ligands on the CD intensities, a qualitative analysis together with the quantitative TDDFT calculation reveal that it depends on the symmetry of the cobalt-EDDA backbone. For the s-cis-isomers, the influence is negligible due to the perturbation is symmetric. For the uns-cis-isomers, the perturbation is unsymmetric. Since a small ring size means a large perturbation, this leads to the integral CD intensities decreasing with increasing the chelate ring size. The vicinal effects of asymmetric nitrogens incorporate both the substitutent effects and conformational relaxation effects, with the former being dominant. By analyzing the contributions of chiral arrays to rotational strengths, we found that the part of contributions dominated by the S-type chiral nitrogens could be considered as a good measure for the vicinal effects of chiral nitrogens. In addition, we found that the twist form (δ/λ) of the backbone ethylenediamine ring (E-ring) of the coordinated EDDA

  20. Study on the interaction of phthalate esters to human serum albumin by steady-state and time-resolved fluorescence and circular dichroism spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Xiaoyun [National Key Laboratory of Organic Chemistry, Lanzhou University, Lanzhou 730000 (China); College of Earth and Environmental Sciences, Lanzhou University, Lanzhou 730000 (China); Wang, Zhaowei [College of Earth and Environmental Sciences, Lanzhou University, Lanzhou 730000 (China); Zhou, Ximin; Wang, Xiaoru [National Key Laboratory of Organic Chemistry, Lanzhou University, Lanzhou 730000 (China); Chen, Xingguo, E-mail: chenxg@lzu.edu.cn [National Key Laboratory of Organic Chemistry, Lanzhou University, Lanzhou 730000 (China); Department of Chemistry, Lanzhou University, Lanzhou 730000 (China)

    2011-09-15

    Highlights: {center_dot} Molecular docking revealed PAEs to be located in the hydrophobic pocket of HSA. {center_dot} HSA-DMP had one class of binding sites while HSA-BBP and HSA-DEHP had two types. {center_dot} Hydrophobic and hydrogen interactions dominated in the association of HSA-PAEs. {center_dot} The lifetime of Trp residue of HSA decreased after the addition of PAEs. {center_dot} The presences of PAEs could alter the second structure of HSA. - Abstract: Phthalate esters (PAEs) are globally pervasive contaminants that are considered to be endocrine disruptor chemicals and toxic environmental priority pollutants. In this paper, the interactions between PAEs and human serum albumin (HSA) were examined by molecular modelling, steady state and time-resolved fluorescence, ultraviolet-visible spectroscopy (UV-vis) and circular dichroism spectroscopy (CD). The association constants between PAEs and HSA were determined using the Stern-Volmer and Scatchard equations. The binding of dimethyl phthalate (DMP) to HSA has a single class of binding site and its binding constants (K) are 4.08 x 10{sup 3}, 3.97 x 10{sup 3}, 3.45 x 10{sup 3}, and 3.20 x 10{sup 3} L mol{sup -1} at 289, 296, 303, and 310 K, respectively. The Stern-Volmer and Scatchard plots both had two regression curves for HSA-butylbenzyl phthalate (BBP) and HSA-di-2-ethylhexyl phthalate (DEHP), which indicated that these bindings were via two types of binding sites: the numbers of binding site for the first type were lower than for the second type. The binding constants of the first type binding site were higher than those of the second type binding site at corresponding temperatures, the results suggesting that the first type of binding site had high affinity and the second binding site involved other sites with lower binding affinity and selectivity. The thermodynamic parameters of the binding reactions ({Delta}G{sup o}, {Delta}H{sup o} and {Delta}S{sup o}) were measured, and they indicated the presences

  1. Investigation of a Spin Transition in a LaCoO3 Single Crystal by the Method of X-Ray Magnetic Circular Dichroism at the Cobalt K- and L 2,3-Edges

    Science.gov (United States)

    Sikolenko, V. V.; Troyanchuk, I. O.; Karpinsky, D. V.; Rogalev, A.; Wilhelm, F.; Rosenberg, R.; Prabhakaran, D.; Efimova, E. A.; Efimov, V. V.; Tiutiunnikov, S. I.; Bobrikov, I. A.

    2018-02-01

    Spin transitions of cobalt ions in LaCoO3 single crystals have been studied by the method of X-ray magnetic circular dichroism (XMCD) at the K- and L 2,3-edges of Co3+ ions. The orbital momentum of cobalt ions obtained for the K-edge at the 3 d level in the region of the spin transition in the temperature range from 25 to 120 K increases by a factor of approximately 1.6, whereas the slope of the magnetization curve value in the same temperature range and magnetic field increases by a factor of more than 10. XMCD experiments at the cobalt L 2,3-edges demonstrate gradual growth of the ratio of the orbital momentum to the spin one L/ S from 0.48 to 0.53 in the temperature range from 60 K to 120 K.

  2. Itinerant ferromagnetism in the As 4p conduction band of Ba_{0.6}K_{0.4}Mn_{2}As_{2} identified by X-ray magnetic circular dichroism.

    Science.gov (United States)

    Ueland, B G; Pandey, Abhishek; Lee, Y; Sapkota, A; Choi, Y; Haskel, D; Rosenberg, R A; Lang, J C; Harmon, B N; Johnston, D C; Kreyssig, A; Goldman, A I

    2015-05-29

    X-ray magnetic circular dichroism (XMCD) measurements on single-crystal and powder samples of Ba_{0.6}K_{0.4}Mn_{2}As_{2} show that the ferromagnetism below T_{C}≈100  K arises in the As 4p conduction band. No XMCD signal is observed at the Mn x-ray absorption edges. Below T_{C}, however, a clear XMCD signal is found at the As K edge which increases with decreasing temperature. The XMCD signal is absent in data taken with the beam directed parallel to the crystallographic c axis indicating that the orbital magnetic moment lies in the basal plane of the tetragonal lattice. These results show that the previously reported itinerant ferromagnetism is associated with the As 4p conduction band and that distinct local-moment antiferromagnetism and itinerant ferromagnetism with perpendicular easy axes coexist in this compound at low temperature.

  3. Effects of dynamic diffraction conditions on magnetic parameter determination in a double perovskite Sr{sub 2}FeMoO{sub 6} using electron energy-loss magnetic chiral dichroism

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Z.C. [National Center for Electron Microscopy in Beijing, Key Laboratory of Advanced Materials (MOE), The State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Zhong, X.Y., E-mail: xyzhong@mail.tsinghua.edu.cn [National Center for Electron Microscopy in Beijing, Key Laboratory of Advanced Materials (MOE), The State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Jin, L. [Peter Grünberg Institute and Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons (ER-C), Forschungszentrum Jülich, 52425 Jülich (Germany); Chen, X.F. [National Center for Electron Microscopy in Beijing, Key Laboratory of Advanced Materials (MOE), The State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Moritomo, Y. [Graduate School of Pure & Applied Science and Faculty of Pure & Applied Science, University of Tsukuba, Tennodai 1-1-1, Tsukuba, Ibaraki 305-7571 (Japan); Mayer, J. [Peter Grünberg Institute and Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons (ER-C), Forschungszentrum Jülich, 52425 Jülich (Germany); Central Facility for Electron Microscopy, RWTH Aachen University, 52074 Aachen (Germany)

    2017-05-15

    Electron energy-loss magnetic chiral dichroism (EMCD) spectroscopy, which is similar to the well-established X-ray magnetic circular dichroism spectroscopy (XMCD), can determine the quantitative magnetic parameters of materials with high spatial resolution. One of the major obstacles in quantitative analysis using the EMCD technique is the relatively poor signal-to-noise ratio (SNR), compared to XMCD. Here, in the example of a double perovskite Sr{sub 2}FeMoO{sub 6}, we predicted the optimal dynamical diffraction conditions such as sample thickness, crystallographic orientation and detection aperture position by theoretical simulations. By using the optimized conditions, we showed that the SNR of experimental EMCD spectra can be significantly improved and the error of quantitative magnetic parameter determined by EMCD technique can be remarkably lowered. Our results demonstrate that, with enhanced SNR, the EMCD technique can be a unique tool to understand the structure-property relationship of magnetic materials particularly in the high-density magnetic recording and spintronic devices by quantitatively determining magnetic structure and properties at the nanometer scale. - Highlights: • We demonstrate how to choose the optimal experimental conditions by using dynamical diffraction calculations in Sr{sub 2}FeMoO{sub 6}. • With optimized diffraction conditions, the signal-to-noise ratio of experimental EMCD spectra has been significantly improved. • We have determined orbital to spin magnetic moment ratio of Sr{sub 2}FeMoO{sub 6} quantitatively. • We have discussed the effects of dynamical diffraction conditions on the error bar of quantitative magnetic parameters.

  4. Modified spectrophotometer for multi-dimensional circular dichroism/fluorescence data acquisition in titration experiments: application to the pH and guanidine-HCI induced unfolding of apomyoglobin.

    Science.gov (United States)

    Ramsay, G; Ionescu, R; Eftink, M R

    1995-01-01

    In a previous paper (Ramsay and Eftink, Biophys. J. 66:516-523) we reported the development of a modified spectrophotometer that can make nearly simultaneous circular dichroism (CD) and fluorescence measurements. This arrangement allows multiple data sets to be collected during a single experiment, resulting in a saving of time and material, and improved correlation between the different types of measurements. The usefulness of the instrument was shown by thermal melting experiments on several different protein systems. This CD/fluorometer spectrophotometer has been further modified by interfacing with a syringe pump and a pH meter. This arrangement allows ligand, pH, and chemical denaturation titration experiments to be performed while monitoring changes in the sample's CD, absorbance, fluorescence, and light scattering properties. Our data acquisition program also has an ability to check whether the signals have approached equilibrium before the data is recorded. For performing pH titrations we have developed a procedure which uses the signal from a pH meter in a feedback circuit in order to collect data at evenly spaced pH intervals. We demonstrate the use of this instrument with studies of the unfolding of sperm whale apomyoglobin, as induced by acid pH and by the addition of guanidine-HCI. Images FIGURE 2 PMID:8527683

  5. Cluster model calculation for X-ray magnetic circular dichroism at rare-earth (R) L sub 2 sub , sub 3 absorption edges in R sub 2 Fe sub 1 sub 4 B

    CERN Document Server

    Asakura, K; Harada, I; Ogasawara, H; Fukui, K; Kotani, A

    2002-01-01

    X-ray magnetic circular dichroism (MCD) at the L sub 2 sub , sub 3 absorption edges for the entire series of rare-earth (RE) elements in R sub 2 Fe sub 1 sub 4 B (R=RE) is studied based on a cluster model including 10 RE and 16 Fe atoms. The cluster model takes into account band effects of RE 5d states, to which the electric dipole transition occurs from the core 2p states, as well as spin polarization of the 5d states due to the interatomic hybridization with the spin polarized Fe 3d states. We also take into account spin and orbital polarization of the 5d states due to the 5d-4f intra-atomic exchange interaction, and the 2p to 4f quadrupole transition. The calculated results are in satisfactory agreement with experimental ones, suggesting that the cluster model calculation provides a new method to calculate quantitatively MCD spectra of RE systems with complicated atomic arrangements. (author)

  6. Determination of the ground state of an Au-supported FePc film based on the interpretation of Fe K - and L -edge x-ray magnetic circular dichroism measurements

    Science.gov (United States)

    Natoli, Calogero R.; Krüger, Peter; Bartolomé, Juan; Bartolomé, Fernando

    2018-04-01

    We determine the magnetic ground state of the FePc molecule on Au-supported thin films based on the observed values of orbital anisotropy and spectroscopic x-ray magnetic circular dichroism (XMCD) measurements at the Fe K and L edges. Starting from ab initio molecular orbital multiplet calculations for the isolated molecule, we diagonalize the spin-orbit interaction in the subspace spanned by the three lowest spin triplet states of 3A2 g and 3Eg symmetry in the presence of a saturating magnetic field at a polar angle θ with respect to the normal to the plane of the film, plus an external perturbation representing the effect of the molecules in the stack on the FePc molecule under consideration. We find that the orbital moment of the ground state strongly depends on the magnetic field direction in agreement with the sum rule analysis of the L23-edge XMCD data. We calculate integrals over the XMCD spectra at the Fe K and L23 edges as used in the sum rules and explicitly show that they agree with the expectation values of the orbital moment and effective spin moment of the ground state. On the basis of this analysis, we can rule out alternative candidates proposed in the literature.

  7. Photoproduction of long-lived holes and electronic processes in intrinsic electric fields seen through photoinduced absorption and dichroism in Ca sub 3 Ga sub 2 sub - sub x Mn sub x Ge sub 3 O sub 1 sub 2 garnets

    CERN Document Server

    Eremenko, V V; Kachur, I S; Piryatinskaya, V G; Ratner, A M; Kosmyna, M B; Nazarenko, B P; Puzikov, V M

    2003-01-01

    Long-lived photoinduced absorption and dichroism in the Ca sub 3 Ga sub 2 sub - sub x Mn sub x Ge sub 3 O sub 1 sub 2 garnets with x < 0.06 were examined versus temperature and pumping intensity. Unusual features of the kinetics of photoinduced phenomena are indicative of the underlying electronic processes. The comparison with the case of Ca sub 3 Mn sub 2 Ge sub 3 O sub 1 sub 2 , explored earlier by the authors, permits one to finally establish the main common mechanisms of photoinduced absorption and dichroism caused by random electric fields of photoproduced charges (hole polarons). The rate of their diffusion and relaxation through recombination is strongly influenced by the same fields, whose large statistical straggling is responsible for a broad continuous set of relaxation components (observed in the relaxation time range from 1 to about 1000 min). For Ca sub 3 Ga sub 2 sub - sub x Mn sub x Ge sub 3 O sub 1 sub 2 , the time and temperature dependences of photoinduced absorption and dichroism bear ...

  8. Circular dichroism and fluorescence spectroscopy of cysteinyl-tRNA synthetase from Halobacterium salinarum ssp. NRC-1 demonstrates that group I cations are particularly effective in providing structure and stability to this halophilic protein.

    Directory of Open Access Journals (Sweden)

    Christopher J Reed

    Full Text Available Proteins from extremophiles have the ability to fold and remain stable in their extreme environment. Here, we investigate the presence of this effect in the cysteinyl-tRNA synthetase from Halobacterium salinarum ssp. NRC-1 (NRC-1, which was used as a model halophilic protein. The effects of salt on the structure and stability of NRC-1 and of E. coli CysRS were investigated through far-UV circular dichroism (CD spectroscopy, fluorescence spectroscopy, and thermal denaturation melts. The CD of NRC-1 CysRS was examined in different group I and group II chloride salts to examine the effects of the metal ions. Potassium was observed to have the strongest effect on NRC-1 CysRS structure, with the other group I salts having reduced strength. The group II salts had little effect on the protein. This suggests that the halophilic adaptations in this protein are mediated by potassium. CD and fluorescence spectra showed structural changes taking place in NRC-1 CysRS over the concentration range of 0-3 M KCl, while the structure of E. coli CysRS was relatively unaffected. Salt was also shown to increase the thermal stability of NRC-1 CysRS since the melt temperature of the CysRS from NRC-1 was increased in the presence of high salt, whereas the E. coli enzyme showed a decrease. By characterizing these interactions, this study not only explains the stability of halophilic proteins in extremes of salt, but also helps us to understand why and how group I salts stabilize proteins in general.

  9. Pulsed laser induced heat transfer from a phthalocyanine-based thin film to a Bi, Al-substituted DyIG substrate: photothermal demagnetization observed by magnetic circular dichroism and numerical analysis.

    Science.gov (United States)

    Karasawa, Masanobu; Ishii, Kazuyuki

    2018-05-03

    We have investigated the demagnetization of a ferrimagnetic substrate, Bi, Al-substituted dysprosium iron garnet (Bi0.8Dy2.2Fe4.3Al0.7O12), based on selective pulsed laser irradiation of a molecular thin film consisting of μ-oxo-bis[hydroxyl{2,9(or 10),16(or 17),23(or 24)-tetra-tert-butylphthalocyanato}silicon] ((SiPc)2) and poly(vinylidene fluoride), and succeeded in reproducing photothermal energy transfer from a molecular thin film to an inorganic magnetic substrate in a submicrometer-order and a submicrosecond time scale using numerical analysis. After the instant temperature rise due to nanosecond pulsed laser irradiation of the (SiPc)2-based film, followed by heat transfer from the film to the neighboring magnetic substrate, demagnetization of the magnetic substrate was spectroscopically monitored by the decrease in its magnetic circular dichroism (MCD) intensity. The MCD intensity decreased with increasing pulsed laser energy, which reflects the fact that the submicrometer-order region of the substrate was demagnetized as a result of temperature rise reaching high Curie temperature. This heat transfer phenomenon resulting in the demagnetization of the magnetic substrate was numerically analyzed in a submicrometer-order and a submicrosecond time scale using the finite difference method: the demagnetized regions were calculated to be the same order of magnitude as those experimentally evaluated. These results would provide a more detailed understanding of photothermal energy transfer in organic-inorganic hybrid materials, which would be useful for developing photofunctional materials.

  10. Coordination modes of tyrosinate-ligated catalase-type heme enzymes: magnetic circular dichroism studies of Plexaura homomalla allene oxide synthase, Mycobacterium avium ssp. paratuberculosis protein-2744c, and bovine liver catalase in their ferric and ferrous states.

    Science.gov (United States)

    Bandara, D M Indika; Sono, Masanori; Bruce, Grant S; Brash, Alan R; Dawson, John H

    2011-12-01

    Bovine liver catalase (BLC), catalase-related allene oxide synthase (cAOS) from Plexaura homomalla, and a recently isolated protein from the cattle pathogen Mycobacterium avium ssp. paratuberculosis (MAP-2744c (MAP)) are all tyrosinate-ligated heme enzymes whose crystal structures have been reported. cAOS and MAP have low (enzymes in their ferric and ferrous states using magnetic circular dichroism and UV-visible absorption spectroscopy. The MAP protein shows remarkable spectral similarities to cAOS and BLC in its native Fe(III) state, but clear differences from ferric proximal heme ligand His93Tyr Mb (myoglobin) mutant, which may be attributed to the presence of an Arg(+)-N(ω)-H···¯O-Tyr (proximal heme axial ligand) hydrogen bond in the first three heme proteins. Furthermore, the spectra of Fe(III)-CN¯, Fe(III)-NO, Fe(II)-NO (except for five-coordinate MAP), Fe(II)-CO, and Fe(II)-O(2) states of cAOS and MAP, but not H93Y Mb, are also similar to the corresponding six-coordinate complexes of BLC, suggesting that a tyrosinate (Tyr-O¯) is the heme axial ligand trans to the bound ligands in these complexes. The Arg(+)-N(ω)-H to ¯O-Tyr hydrogen bond would be expected to modulate the donor properties of the proximal tyrosinate oxyanion and, combined with the subtle differences in the catalytic site structures, affect the activities of cAOS, MAP and BLC. Copyright © 2011 Elsevier Inc. All rights reserved.

  11. Valence states and occupation sites in (Fe,Mn){sub 3}O{sub 4} spinel oxides investigated by soft x-ray absorption spectroscopy and magnetic circular dichroism

    Energy Technology Data Exchange (ETDEWEB)

    Lee, H J; Kim, G; Kim, D H; Kang, J-S [Department of Physics, Catholic University of Korea (CUK), Bucheon 420-743 (Korea, Republic of); Zhang, C L; Cheong, S-W [Rutgers Center for Emergent Materials and Department of Physics, Rutgers University, Piscataway, NJ 08854 (United States); Shim, J H; Lee, Soonchil [Department of Physics, KAIST, Daejeon 305-701 (Korea, Republic of); Lee, Hangil; Kim, J-Y [Pohang Accelerator Laboratory (PAL), POSTECH, Pohang 790-784 (Korea, Republic of); Kim, B H; Min, B I [Department of Physics, POSTECH, Pohang 790-784 (Korea, Republic of)], E-mail: kangjs@catholic.ac.kr

    2008-07-23

    The electronic structures of (Fe,Mn){sub 3}O{sub 4} spinel oxides have been investigated by employing soft-x-ray absorption spectroscopy (XAS) and soft x-ray magnetic circular dichroism (XMCD). We have determined the valence states as well as the occupation sites of Mn and Fe ions in Fe{sub 0.9}Mn{sub 2.1}O{sub 4} and MnFe{sub 2}O{sub 4}. Fe{sub 0.9}Mn{sub 2.1}O{sub 4} is found to be close to the inverse spinel (the inversion parameter y{approx}0.85), while MnFe{sub 2}O{sub 4} is close to the normal spinel (y{approx}0.2). In Fe{sub 0.9}Mn{sub 2.1}O{sub 4}, Fe ions are mainly trivalent and the majority of Fe{sup 3+} ions occupy the octahedral B sites, while Mn ions are mixed-valent with approximately 45% Mn{sub A}{sup 2+} at the tetrahedral A sites and 55% Mn{sub B}{sup 3+} ions at the octahedral B sites. In MnFe{sub 2}O{sub 4}, Mn ions are mainly divalent and the majority of Mn{sup 2+} ions occupy the tetrahedral A sites, while Fe ions are mainly trivalent and the majority of Fe{sup 3+} ions occupy the octahedral B sites.

  12. Utilization of circular dichroism and electrospray ionization mass spectrometry to understand the formation and conversion of G-quadruplex DNA at the human c-myb proto-oncogene.

    Science.gov (United States)

    Fu, Hengqing; Yang, Pengfei; Hai, Jinhui; Li, Huihui

    2018-10-05

    G-quadruplex DNAs are involved in a number of key biological processes, including gene expression, transcription, and apoptosis. The c-myb oncogene contains a number of GGA repeats in its promoter which forms G-quadruplex, thus it could be used as a target in cancer therapeutics. Several in-vitro studies have used Circular Dichroism (CD) spectroscopy or electrospray ionization mass spectrometry (ESI-MS) to demonstrate formation and stability of G-quadruplex DNA structure in the promoter region of human c-myb oncogene. The factors affecting the c-myb G-quadruplex structures were investigated, such as cations (i.e. K + , NH 4 + and Na + ) and co-solutes (methanol and polyethylene glycol). The results indicated that the presence of cations and co-solutes could change the G-quadruplex structural population and promote its thermodynamic stabilization as indicated by CD melting curves. It indicated that the co-solutes preferentially stabilize the c-myb G-quadruplex structure containing both homo- and hetero-stacking. In addition, protopine was demonstrated as a binder of c-myb G-quadruplex as screened from a library of natural alkaloids using ESI-MS method. CD spectra showed that it could selectively stabilize the c-myb G-quadruplex structure compared to other six G-quadruplexes from tumor-related G-rich sequences and the duplex DNAs (both long and short-chain ones). The binding of protopine could induce the change in the G-quadruplex structural populations. Therefore, protopine with its high binding specificity could be considered as a precursor for the design of drugs to target and regulate c-myb oncogene transcription. Copyright © 2018 Elsevier B.V. All rights reserved.

  13. Color and dichroism of silver-stained glasses

    International Nuclear Information System (INIS)

    Molina, Gloria; Murcia, Sonia; Molera, Judit; Roldan, Clodoaldo; Crespo, Daniel; Pradell, Trinitat

    2013-01-01

    Yellow decorations in glasses have been produced since the beginning of the fourteenth century by incorporating metallic silver nanoparticles into the glass (from a few to some tens of nanometers). The optical response of the glass-particles composite is determined by the surface plasmon resonance absorption and scattering of the nanometric metallic particles. Generally, the same color is perceived in reflection and in transmission although dichroic effects are occasionally observed. As silver-stained glasses were designed to be observed in transmission, tuning the transmission color from yellow to red was of technological interest. The relationship between the color observed both in transmission and reflection and the composition and nanostructure of regular (yellow) and dichroic (yellow and red) silver stains from the Renaissance (late fifteenth and sixteenth century, respectively) is related to the presence of a layer (of about 10–20 μm thick) of metallic silver nanoparticles (from few to 100 nm in size). The correlation between the colors observed and the silver stain nanostructure is studied with particular emphasis on the origin of the dichroic behavior. The optical response is computed and compared to the experimental data. Differences in the synthesis parameters responsible for the colors and for the dichroic behavior of the silver stain glasses are proposed. This is essential for the replication of the glass pieces which are required as replacements in the restoration/conservation of the windows but is also of broader interest

  14. Color and dichroism of silver-stained glasses

    Energy Technology Data Exchange (ETDEWEB)

    Molina, Gloria [Universitat Politecnica de Catalunya, Center for Research in NanoEngineering (Spain); Murcia, Sonia [Universidad de Valencia, Instituto de Ciencia de los Materiales (Spain); Molera, Judit [Universitat de Vic, GRTD, Escola Politecnica Superior (Spain); Roldan, Clodoaldo [Universidad de Valencia, Instituto de Ciencia de los Materiales (Spain); Crespo, Daniel; Pradell, Trinitat, E-mail: Trinitat.Pradell@upc.edu [Universitat Politecnica de Catalunya, Center for Research in NanoEngineering (Spain)

    2013-09-15

    Yellow decorations in glasses have been produced since the beginning of the fourteenth century by incorporating metallic silver nanoparticles into the glass (from a few to some tens of nanometers). The optical response of the glass-particles composite is determined by the surface plasmon resonance absorption and scattering of the nanometric metallic particles. Generally, the same color is perceived in reflection and in transmission although dichroic effects are occasionally observed. As silver-stained glasses were designed to be observed in transmission, tuning the transmission color from yellow to red was of technological interest. The relationship between the color observed both in transmission and reflection and the composition and nanostructure of regular (yellow) and dichroic (yellow and red) silver stains from the Renaissance (late fifteenth and sixteenth century, respectively) is related to the presence of a layer (of about 10-20 {mu}m thick) of metallic silver nanoparticles (from few to 100 nm in size). The correlation between the colors observed and the silver stain nanostructure is studied with particular emphasis on the origin of the dichroic behavior. The optical response is computed and compared to the experimental data. Differences in the synthesis parameters responsible for the colors and for the dichroic behavior of the silver stain glasses are proposed. This is essential for the replication of the glass pieces which are required as replacements in the restoration/conservation of the windows but is also of broader interest.

  15. Communication: Fullerene resolution by the magnetic circular dichroism

    Czech Academy of Sciences Publication Activity Database

    Štěpánek, Petr; Straka, Michal; Andrushchenko, Valery; Bouř, Petr

    2013-01-01

    Roč. 138, č. 15 (2013), 151103/1-151103/4 ISSN 0021-9606 R&D Projects: GA ČR GAP208/11/0105; GA MŠk(CZ) LH11033; GA ČR GA13-03978S Grant - others:AV ČR(CZ) M200551205 Institutional support: RVO:61388963 Keywords : density-functional theory * minor isomers * B-term * C-60 * spectra Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.122, year: 2013

  16. Structural characterization of chiral molecules using vibrational circular dichroism spectroscopy

    DEFF Research Database (Denmark)

    Lassen, Peter Rygaard

    2006-01-01

    comparison of experimental and calculated spectra. Theoretical structures of the sample molecules were constructed and optimized using molecular mechanical force fields followed by the quantum mechanical method density functional theory (DFT). Calculations of IR absorption and VCD spectra were then carried...... out using the same DFT methods. Here, VCD has the advantage over CD that time-independent DFT calculations are sufficient. During the course of this project, the above methodology has been applied to a range of molecules. Some of them (nyasol, curcuphenol dimers and ginkgolide) are purely organic...... or as flexible as the curcuphenol dimer with 11 variable dihedral angles. This illustrates the capabilities of the method, which are primarily limited by the duration of DFT calculations. In the case of metal complexes, they have only recently become within reach of DFT, which opens new possibilities...

  17. Transfer of Frequency-Dependent Polarizabilities: A Tool To Simulate Absorption and Circular Dichroism Molecular Spectra

    Czech Academy of Sciences Publication Activity Database

    Kessler, Jiří; Bouř, Petr

    2015-01-01

    Roč. 11, č. 5 (2015), s. 2210-2220 ISSN 1549-9618 R&D Projects: GA ČR GAP208/11/0105; GA ČR GA13-03978S; GA ČR GA15-09072S Grant - others:GA AV ČR(CZ) M200551205; GA MŠk(CZ) ED3.2.00/08.0144; GA MŠk(CZ) LM2010005 Institutional support: RVO:61388963 Keywords : Raman optical activity * density functional theory * charge-transfer transitions Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 5.301, year: 2015

  18. Relation between molecular electronic structure and nuclear spin-induced circular dichroism

    DEFF Research Database (Denmark)

    Štěpánek, Petr; Coriani, Sonia; Sundholm, Dage

    2017-01-01

    with spatially localized, high-resolution information. To survey the factors relating the molecular and electronic structure to the NSCD signal, we theoretically investigate NSCD of twenty structures of the four most common nucleic acid bases (adenine, guanine, thymine, cytosine). The NSCD signal correlates...... with the spatial distribution of the excited states and couplings between them, reflecting changes in molecular structure and conformation. This constitutes a marked difference to the nuclear magnetic resonance (NMR) chemical shift, which only reflects the local molecular structure in the ground electronic state....... The calculated NSCD spectra are rationalized by means of changes in the electronic density and by a sum-over-states approach, which allows to identify the contributions of the individual excited states. Two separate contributions to NSCD are identified and their physical origins and relative magnitudes...

  19. Insight into vibrational circular dichroism of proteins by density functional modeling

    Czech Academy of Sciences Publication Activity Database

    Kessler, Jiří; Andrushchenko, Valery; Kapitán, J.; Bouř, Petr

    2018-01-01

    Roč. 20, č. 7 (2018), s. 4926-4935 ISSN 1463-9076 R&D Projects: GA MŠk(CZ) LTC17012; GA ČR(CZ) GA16-05935S; GA ČR(CZ) GA16-04902S Institutional support: RVO:61388963 Keywords : Raman optical activity * molecular property tensors * coupled oscillator model Subject RIV: CF - Physical ; Theoretical Chemistry OBOR OECD: Physical chemistry Impact factor: 4.123, year: 2016

  20. X-RAY CIRCULAR-DICHROISM AND LOCAL MAGNETIC-FIELDS

    NARCIS (Netherlands)

    CARRA, P; THOLE, BT; ALTARELLI, M; WANG, XD

    1993-01-01

    Sum rules are derived for the circular dichroic response of a core line (CMXD). They relate the intensity of the CMXD signal to the ground-state expectation value of the magnetic field operators (orbital, spin, and magnetic dipole) of the valence electrons. The results obtained are discussed and

  1. Flow Linear Dichroism Spectroscopic Studies of the Natural Product Curcumin and Double Stranded DNA

    DEFF Research Database (Denmark)

    Leth, Rasmus; Thulstrup, Peter Waaben

    2011-01-01

    Curcumin is a polyphenol found in the rhizomes of the plant Curcuma Longa, commonly known as turmeric. Curcumin has a bright yellow color, and in turmeric, curcumin exists along with two other curcuminoids: desmethoxy curcumin and bisdesmethoxy curcumin [1]. Curcumin has shown multiple biological...... effect, including antibacterial effects [2], antioxidant activities [1], antidepressant effects [3] and anticarcinogenic effects among others as reviewed by [4]. Importantly, it is known that curcumin can bind to and cross cellular membranes [5]....

  2. Experimental Demonstration of the Microscopic Origin of Circular Dichroism in Two dimensional Metamaterials

    Science.gov (United States)

    2016-06-22

    White dashed lines in b,c outline the geometry of the structure. BS, beam splitter ; Det, pseudoeheterodyne detection; P, linear polarizer; PM...planar-chiral metasurface, along with its chiral enantiomer, was designed to maximize the CDA in mid-infrared wavelength range21. The CDA gives rise to...illumination. Results Design and theoretical analysis of the metasurface. The specific plasmonic metasurface shown in Fig. 1a consists of a square array

  3. Application of magnetic circular dichroism spectroscopy to the optical spectra of natural and irradiated diamonds

    International Nuclear Information System (INIS)

    Douglas, I.N.; Ruciman, W.A.; Australian National Univ., Canberra. Research School of Physical Sciences)

    1977-01-01

    The MCD spectra of natural type Ia and electron-irradiated type Ia and type IIa diamonds have been measured. The information obtained from MCD spectroscopy complements that obtained from absorption spectroscopy and can be helpful in the assignment of electronic transitions. (orig.) [de

  4. Relation between molecular electronic structure and nuclear spin-induced circular dichroism

    Czech Academy of Sciences Publication Activity Database

    Štěpánek, Petr; Coriani, S.; Sundholm, D.; Ovchinnikov, V. A.; Vaara, J.

    2017-01-01

    Roč. 7, Apr 24 (2017), č. článku 46617. ISSN 2045-2322 R&D Projects: GA ČR GA13-03978S Institutional support: RVO:61388963 Keywords : induced optical rotation * NMR spectroscopy * magnetic field Subject RIV: CF - Physical ; Theoretical Chemistry OBOR OECD: Physical chemistry Impact factor: 4.259, year: 2016 https://www.nature.com/articles/srep46617

  5. Circular dichroism spectroscopy of conformers of (guanine + adenine) repeat strands of DNA

    Czech Academy of Sciences Publication Activity Database

    Kejnovská, Iva; Kypr, Jaroslav; Vorlíčková, Michaela

    2003-01-01

    Roč. 15, č. 7 (2003), s. 584-592 ISSN 0899-0042 R&D Projects: GA AV ČR IAA4004201; GA ČR GA204/01/0561 Institutional research plan: CEZ:AV0Z5004920 Keywords : DNA conformation * (guanine + adenine) repeats * homoduplexes Subject RIV: BO - Biophysics Impact factor: 1.793, year: 2003

  6. Performances and first experimental results of BACH, the beamline for dichroism and scattering experiments at ELETTRA

    International Nuclear Information System (INIS)

    Zangrando, M.; Zacchigna, M.; Bondino, F.; Finazzi, M.; Pardini, T.; Plate, M.; Rochow, R.; Cocco, D.; Parmigiani, F.

    2004-01-01

    BACH, the new soft x-ray beamline for polarization dependent experiments at the Italian synchrotron radiation facility ELETTRA, has been commissioned, characterized and opened to external users. Based on two APPLE II undulators, it covers an energy range between 35 eV and 1600 eV with the control of the light polarization. The monochromator works either in high resolution or high flux mode. Resolving powers of 16000 at 50 eV, 12000 at 90 eV, more than 12000 at 400 eV, 15000 at 534 eV and 6600 at 867 eV have been achieved with the three high resolution gratings. The resolving powers of the high flux grating, which covers the 290 - 1600 eV range, have been measured reaching 7000 at 400 eV and 2200 at 867 eV. The fluxes, in the high resolution mode, range between 4·1011 photons/s at 125 eV and 2·1010 photons/s at about 1100 eV. Using the high flux grating with the best resolution achievable 1.7·1011 photons/s impinge on the sample at 900 eV. Two branches are installed after the monochromator allowing the set-up of two different experimental stations. One of them, besides several facilities for surface preparation and analysis, hosts a compact inelastic soft x-ray spectrometer (ComIXS) dedicated to x-ray emission experiments exploiting the small spot (10 μm in the vertical direction) on the sample. The other branch hosts a liquid helium cryostat equipped with a superconducting coil to perform absorption and transmission experiments with temperatures down to 2 K and magnetic field up to ±7 T

  7. Strong Intermolecular Exciton Couplings in Solid-State Circular Dichroism of Aryl Benzyl Sulfoxides

    Czech Academy of Sciences Publication Activity Database

    Padula, Daniele; Di Pietro, S.; Capozzi, M. A. M.; Cardellicchio, C.; Pescitelli, G.

    2014-01-01

    Roč. 26, č. 9 (2014), s. 462-470 ISSN 0899-0042 Institutional support: RVO:61388963 Keywords : organic crystals * TDDFT CD calculations * pairwise additive approximation * two-body effects * intermolecular forces in crystal lattices Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.886, year: 2014

  8. Magnetic circular dichroism spectroscopy of weakly exchange coupled transition metal dimers: A model study

    DEFF Research Database (Denmark)

    Piligkos, S.; Slep, L.D.; Weyhermuller, T.

    2009-01-01

    bands of the minority spin Ni(II) ligand field bands were observed to change sign relative to the parent complex 2. This behavior has been analyzed. The present work hence provides a benchmark study for the application of MCD spectroscopy to weakly interacting transition metal dinners. (C) 2008 Elsevier...

  9. Electronic Circular Dichroism of the Chiral Rigid Tricyclic Dilactam with Nonplanar Tertiary Amide Groups

    Czech Academy of Sciences Publication Activity Database

    Pazderková, Markéta; Profant, V.; Seidlerová, Beata; Dlouhá, Helena; Hodačová, J.; Javorfi, T.; Siligardi, G.; Baumruk, V.; Bednárová, Lucie; Maloň, P.

    2014-01-01

    Roč. 118, č. 38 (2014), s. 11100-11108 ISSN 1520-6106 R&D Projects: GA ČR GAP205/10/1276 Institutional support: RVO:61388963 Keywords : Gaussian basis sets * correlated molecular calculations * density functional calculations Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.302, year: 2014

  10. X-ray magnetic circular dichroism experiments and theory of transuranium Laves phase compounds

    Czech Academy of Sciences Publication Activity Database

    Wilhelm, F.; Eloirdi, R.; Rusz, Ján; Springell, R.; Colineau, E.; Griveau, J.C.; Oppeneer, P. M.; Caciuffo, R.; Rogalev, A.; Lander, G.H.

    2013-01-01

    Roč. 88, č. 2 (2013), "024424-1"-"024424-14" ISSN 1098-0121 Institutional support: RVO:68378271 Keywords : electronic-structure * uranium-compounds * self -absorption * moments Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.664, year: 2013

  11. The design of the beamline for magnetic circular dichroism study at HNSRL

    CERN Document Server

    ShengWeiFan; Li Da Shi; Yan Yong Lia

    2000-01-01

    A synchrotron radiation beamline for MCD study is being developed at Hefei National Synchrotron Radiation Laboratory (HNSRL) in the P. R. China. As a key component on the beamline, the varied line-spacing plane grating (VLSPG) monochromator is designed to cover a broad photon energy range from 100 to 1000 eV with a medium energy resolving power of 2000. The design is analyzed and optimized to meet the high requirements of MCD studying.

  12. Magnetic Dichroism of Potassium Atoms on the Surface of Helium Nanodroplets

    International Nuclear Information System (INIS)

    Nagl, Johann; Auboeck, Gerald; Callegari, Carlo; Ernst, Wolfgang E.

    2007-01-01

    The population ratio of Zeeman sublevels of atoms on the surface of superfluid helium droplets (T=0.37 K) has been measured. Laser induced fluorescence spectra of K atoms are measured in the presence of a moderately strong magnetic field (2.9 kG). The relative difference between the two states of circular polarization of the exciting laser is used to determine the electron spin polarization of the ensemble. Equal fluorescence levels indicate that the two spin sublevels of the ground-state K atom are equipopulated, within 1%. Thermalization to 0.37 K would give a population ratio of 0.35. We deduce that the rate of spin relaxation induced by the droplet must be 2 triplet dimer we find instead full thermalization of the spin

  13. Green Oxidation of Menthol Enantiomers and Analysis by Circular Dichroism Spectroscopy: An Advanced Organic Chemistry Laboratory

    Science.gov (United States)

    Geiger, H. Cristina; Donohoe, James S.

    2012-01-01

    Green chemistry addresses environmental concerns associated with chemical processes and increases awareness of possible harmful effects of chemical reagents. Efficient reactions that eliminate or reduce the use of organic solvents or toxic reagents are increasingly available. A two-week experiment is reported that entails the calcium hypochlorite…

  14. The PVLAS experiment: measuring vacuum magnetic birefringence and dichroism with a birefringent Fabry-Perot cavity

    Energy Technology Data Exchange (ETDEWEB)

    Della Valle, Federico; Milotti, Edoardo [INFN, Trieste (Italy); Universita di Trieste, Dipt. di Fisica, Trieste (Italy); Ejlli, Aldo; Messineo, Giuseppe; Zavattini, Guido [INFN, Ferrara (Italy); Universita di Ferrara, Dipt. di Fisica e Scienze della Terra, Ferrara (Italy); Gastaldi, Ugo [INFN, Ferrara (Italy); Pengo, Ruggero; Ruoso, Giuseppe [INFN, Lab. Nazionale di Legnaro, Legnaro (Italy)

    2016-01-15

    Vacuum magnetic birefringence was predicted long time ago and is still lacking a direct experimental confirmation. Several experimental efforts are striving to reach this goal, and the sequence of results promises a success in the next few years. This measurement generally is accompanied by the search for hypothetical light particles that couple to two photons. The PVLAS experiment employs a sensitive polarimeter based on a high finesse Fabry-Perot cavity. In this paper we report on the latest experimental results of this experiment. The data are analysed taking into account the intrinsic birefringence of the dielectric mirrors of the cavity. Besides a new limit on the vacuum magnetic birefringence, the measurements also allow the model-independent exclusion of new regions in the parameter space of axion-like and milli-charged particles. In particular, these last limits hold also for all types of neutrinos, resulting in a laboratory limit on their charge. (orig.)

  15. Soft X-ray magnetic dichroism and Faraday rotation measured with linearly polarised light

    Czech Academy of Sciences Publication Activity Database

    Mertins, H. Ch.; Schäfers, F.; Gaupp, A.; Gudat, W.; Kuneš, Jan; Oppeneer, P. M.

    467-468, - (2001), s. 1407-1410 ISSN 0168-9002 Grant - others:ERBFM(XX) GECT 980105; SFB(XX) 463 Institutional research plan: CEZ:AV0Z1010914 Keywords : Faraday-effect * magneto-optical effects * optical properties of consensed matter * synchrotron radiation * X-ray Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.026, year: 2001

  16. Magnetic x-ray circular dichroism in spin-polarized photoelectron diffraction

    International Nuclear Information System (INIS)

    Waddill, G.D.; Tobin, J.G.

    1994-01-01

    The first structural determination with spin-polarized, energy-dependent photoelectron diffraction using circularly-polarized x-rays is reported for Fe films on Cu(001). Circularly-polarized x-rays produced spin-polarized photoelectrons from the Fe 2p doublet, and intensity asymmetries in the 2p 3/2 level are observed. Fully spin-specific multiple scattering calculations reproduced the experimentally-determined energy and angular dependences. A new analytical procedure which focuses upon intensity variations due to spin-dependent diffraction is introduced. A sensitivity to local geometric and magnetic structure is demonstrated

  17. Systematic study of magnetic linear dichroism and birefringence in (Ga,Mn)As

    Czech Academy of Sciences Publication Activity Database

    Tesařová, N.; Ostatnický, T.; Novák, Vít; Olejník, Kamil; Šubrt, J.; Reichlová, Helena; Ellis, C.T.; Mukherjee, A.; Lee, J.; Sipahi, G.M.; Sinova, Jairo; Hamrle, J.; Jungwirth, Tomáš; Němec, P.; Cerne, J.; Výborný, Karel

    2014-01-01

    Roč. 89, č. 8 (2014), , , "085203-1"-"085203-14" ISSN 1098-0121 R&D Projects: GA MŠk(CZ) LM2011026 EU Projects: European Commission(XE) 268066 - 0MSPIN Grant - others:AV ČR(CZ) AP0801 Program:Akademická prémie - Praemium Academiae Institutional support: RVO:68378271 Keywords : ferromagnetic semiconductors * magneto-optics Subject RIV: BH - Optics, Masers, Lasers Impact factor: 3.736, year: 2014

  18. Sexual dichroism and pigment localization in the wing scales of Pieris rapae butterflies

    NARCIS (Netherlands)

    Giraldo, M. A.; Stavenga, D. G.

    2007-01-01

    The beads in the wing scales of pierid butterflies play a crucially important role in wing coloration as shown by spectrophotometry and scanning electron microscopy (SEM). The beads contain pterin pigments, which in Pieris rapae absorb predominantly in the ultraviolet (UV). SEM demonstrates that in

  19. Dichroism, chirality, and polarization eigenstates in Babinet nanoslot-dimer membrane metamaterials

    DEFF Research Database (Denmark)

    Zhukovsky, Sergei; Chigrin, Dmitry N.; Kremers, Christian

    2013-01-01

    We present a detailed theoretical description of the optical properties of planar metamaterials comprising a metal membrane patterned with openings (microslots) arranged in closely located couples (dimers). Using the covariant coupled-dipole approach, the effective material tensors of such a meta...

  20. An Energy-Stabilized Varied-Line-Space-Monochromator Undulator Beam Line for PEEM Illumination and Magnetic Circular Dichroism

    International Nuclear Information System (INIS)

    Warwick, Tony; McKinney, Wayne; Domning, Ed; Doran, Andrew; Padmore, Howard

    2006-01-01

    A new undulator beam line has been built and commissioned at the Advanced Light Source for illumination of the PEEM3 microscope. The beam line delivers high flux beams over an energy range from C1s through the transition metals to include the M edges of the magnetic rare earth elements. We present details of the optical design, and data on the performance of the zero-order tracking of the photon energy

  1. Arrangement of Fibril Side Chains Studied by Molecular Dynamics and Simulated Infrared and Vibrational Circular Dichroism Spectra

    Czech Academy of Sciences Publication Activity Database

    Kessler, Jiří; Kiederling, T. A.; Bouř, Petr

    2014-01-01

    Roč. 118, č. 24 (2014), s. 6937-6945 ISSN 1520-6106 R&D Projects: GA ČR GAP208/11/0105; GA MŠk(CZ) LH11033 Grant - others:MŠMT(CZ) LM2010005; AV ČR(CZ) M200550902; MŠMT(CZ) ED3.2.00/08.0144 Institutional support: RVO:61388963 Keywords : insulin amyloid superstructures * DFT * VCD * molecular dynamics Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.302, year: 2014

  2. Magneto-optical detection of the relaxation dynamics of alloy nanoparticles with a high-stability magnetic circular dichroism setup

    Energy Technology Data Exchange (ETDEWEB)

    Cavigli, L. [L.E.N.S. University of Florence, via N. Carrara 1, I-50019 Sesto F.no (Italy); INSTM Department of Chemistry, University of Florence, via della Lastruccia 5, I-50019 Sesto F.no (Italy); Julian Fernandez, C. de [Department of Physics, University of Padua, via Marzolo 8, I-35131 Padova (Italy); Gatteschi, D. [INSTM Department of Chemistry, University of Florence, via della Lastruccia 5, I-50019 Sesto F.no (Italy); Gurioli, M. [L.E.N.S. University of Florence, via N. Carrara 1, I-50019 Sesto F.no (Italy); Sangregorio, C. [INSTM Department of Chemistry, University of Florence, via della Lastruccia 5, I-50019 Sesto F.no (Italy)]. E-mail: claudio.sangregorio@unifi.it; Mattei, G. [Department of Physics, University of Padua, via Marzolo 8, I-35131 Padova (Italy); Mazzoldi, P. [Department of Physics, University of Padua, via Marzolo 8, I-35131 Padova (Italy); Bogani, L. [L.E.N.S. University of Florence, via N. Carrara 1, I-50019 Sesto F.no (Italy); INSTM Department of Chemistry, University of Florence, via della Lastruccia 5, I-50019 Sesto F.no (Italy)

    2007-09-15

    We present a versatile high-stability and high-sensitivity magneto-optical setup that allows transmission and reflection measurements at high fields and low temperatures. We apply the technique to measure the decay in time of the magnetization of highly monodisperse 3.3nm Co{sub 33}Ni{sub 67} alloy nanoparticles embedded in a silica host. We demonstrate the possibility of observing the dynamics of the magnetization over a macroscopic timescale in dilute samples, where other techniques are unavailable.

  3. Magneto-optical detection of the relaxation dynamics of alloy nanoparticles with a high-stability magnetic circular dichroism setup

    International Nuclear Information System (INIS)

    Cavigli, L.; Julian Fernandez, C. de; Gatteschi, D.; Gurioli, M.; Sangregorio, C.; Mattei, G.; Mazzoldi, P.; Bogani, L.

    2007-01-01

    We present a versatile high-stability and high-sensitivity magneto-optical setup that allows transmission and reflection measurements at high fields and low temperatures. We apply the technique to measure the decay in time of the magnetization of highly monodisperse 3.3nm Co 33 Ni 67 alloy nanoparticles embedded in a silica host. We demonstrate the possibility of observing the dynamics of the magnetization over a macroscopic timescale in dilute samples, where other techniques are unavailable

  4. Probing the structure of glucan lyases – the lytic members of GH31 - by sequence analysis, circular dichroism and proteolysis

    DEFF Research Database (Denmark)

    Ernst, Heidi; Lo Leggio, Leila; Yu, Shukun

    2005-01-01

    Glucan lyase (GL) is a polysaccharide lyase with unique characteristics. It is involved in an alternative pathway for the degradation of alpha-glucans, the anhydrofructose pathway. Sequence similarity suggests that this lytic enzyme belongs to glycoside hydrolase family 31, for which until very r...

  5. Electronic states of the fluorophore 9,10-bis(phenylethynyl)anthracene (BPEA). A synchrotron radiation linear dichroism investigation

    DEFF Research Database (Denmark)

    Thulstrup, Peter Waaben; Jones, Nykola; Hoffmann, Søren Vrønning

    2013-01-01

    temperature spectroscopy and by quantum chemical calculations in the LCOAO and TD-DFT models. The combined experimental and theoretical evidence leads to characterization of several previously unobserved transitions and provides a revised polarization analysis of the visible absorption band of BPEA....

  6. Remnant magnetization of Fe8 high-spin molecules: X-ray magnetic circular dichroism at 300 mK

    Science.gov (United States)

    Letard, Isabelle; Sainctavit, Philippe; dit Moulin, Christophe Cartier; Kappler, Jean-Paul; Ghigna, Paolo; Gatteschi, Dante; Doddi, Bruno

    2007-06-01

    Fe8 high-spin molecules exhibit quantum spin tunneling at very low temperatures. Eight Fe3+ ions are sixfold coordinated and magnetically coupled through oxygen bridges. The net magnetization (MS=20 μB per molecule) results from competing antiferromagnetic interactions between the various Fe3+ ions (S =5/2). Because of the structural anisotropy of these molecules, the magnetization curve presents a hysteresis loop with staircases below 2 K. The staircases of the hysteresis loop are due to the quantum spin tunneling, which is temperature dependent for 400 mKmolecule. It has been possible to register an XMCD remnant signal, without magnetic field applied, at the iron L2,3 edges. XMCD coupled with ligand field multiplet calculations has allowed to determine the spin and orbit contributions to the magnetization of the Fe3+ ions.

  7. Direct determination of absolute configuration: a vibrational circular dichroism study on dimethyl-substituted phenyloxiranes synthesized by Shi epoxidation

    DEFF Research Database (Denmark)

    Fristrup, Peter; Lassen, Peter Rygaard; Tanner, David Ackland

    2008-01-01

    obtained using DFT/B3LYP calculations, and the differences between experiment and theory are discussed. The absolute configuration at the benzylic position was established as being (R), (S) and (R) for the cis, trans and geminal dimethylsubstituted phenyloxiranes, respectively. In all three cases...

  8. Magneto-optical detection of the relaxation dynamics of alloy nanoparticles with a high-stability magnetic circular dichroism setup

    Science.gov (United States)

    Cavigli, L.; de Julián Fernández, C.; Gatteschi, D.; Gurioli, M.; Sangregorio, C.; Mattei, G.; Mazzoldi, P.; Bogani, L.

    2007-09-01

    We present a versatile high-stability and high-sensitivity magneto-optical setup that allows transmission and reflection measurements at high fields and low temperatures. We apply the technique to measure the decay in time of the magnetization of highly monodisperse 3.3 nm Co33Ni67 alloy nanoparticles embedded in a silica host. We demonstrate the possibility of observing the dynamics of the magnetization over a macroscopic timescale in dilute samples, where other techniques are unavailable.

  9. Influence of plural scattering on the quantitative determination of spin and orbital moments in electron magnetic chiral dichroism measurements

    Czech Academy of Sciences Publication Activity Database

    Rusz, Ján; Lidbaum, H.; Rubino, S.; Hjörvarsson, B.; Oppeneer, P.M.; Eriksson, O.; Leifer, K.

    2011-01-01

    Roč. 83, č. 13 (2011), "132402-1"-"132402-4" ISSN 1098-0121 Institutional research plan: CEZ:AV0Z10100521 Keywords : EMCD experiments Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.691, year: 2011

  10. Inversed linear dichroism in F K-edge NEXAFS spectra of fluorinated planar aromatic molecules

    DEFF Research Database (Denmark)

    de Oteyza, D. G.; Sakko, A.; El-Sayed, A.

    2012-01-01

    The symmetry and energy distribution of unoccupied molecular orbitals is addressed in this work by means of NEXAFS and density functional theory calculations for planar, fluorinated organic semiconductors (perfluorinated copper phthalocyanines and perfluoropentacene). We demonstrate how molecular...

  11. Characterization of the crystal orientation in mono-oriented films of HDPE/LLDPE blends by IR dichroism

    Energy Technology Data Exchange (ETDEWEB)

    Canevarolo, Sebastião V., E-mail: caneva@ufscar.br; Ravazzi, Camila; Silva, Jorge, E-mail: jorge.silva@ufscar.br [Departamento de Engenharia de Materiais, Universidade Federal de São Carlos Rod. Washington Luiz Km 235, 13565-905, SãoCarlos, SP - Brazil (Brazil); Elias, Marcelo [Motechfilm Produtos Plásticos, Estrada Municipal do Bonfim, 100, Pinhal, Cabreúva, SP - Brazil (Brazil)

    2016-03-09

    Polyethylene films are a common packaging material. The level and type of chain orientation in these films are a very important property which is of great care and concern of the converter personnel during the conformation process. Usually bi-orientation is the conventional procedure but when easy tear in one direction is needed mono-orientation is sought. This paper deal with the characterization of the crystalline orientation in films of polyethylene blends (HDPE/LLDPE) which have being oriented in two steps: initially the polymer was bi-oriented via extrusion-blown, cooled, and then in a second process hot stretched along the machine direction in order to produce mono-oriented films. In order to evaluate the orientation of the film, the polarization of the FT-IR beam was rotated 360° in steps of 5° by rotating the polarizer. In each step the absorbance spectrum was recorded and the corresponding dichroic ratio (DR) calculated after subtracting the baseline. With differential scanning calorimetry (DSC) was possible to infer about the changes in the morphology caused by the stretching.

  12. Chirality in Magnetic Multilayers Probed by the Symmetry and the Amplitude of Dichroism in X-Ray Resonant Magnetic Scattering

    Science.gov (United States)

    Chauleau, Jean-Yves; Legrand, William; Reyren, Nicolas; Maccariello, Davide; Collin, Sophie; Popescu, Horia; Bouzehouane, Karim; Cros, Vincent; Jaouen, Nicolas; Fert, Albert

    2018-01-01

    Chirality in condensed matter has recently become a topic of the utmost importance because of its significant role in the understanding and mastering of a large variety of new fundamental physical mechanisms. Versatile experimental approaches, capable to reveal easily the exact winding of order parameters, are therefore essential. Here we report x-ray resonant magnetic scattering as a straightforward tool to reveal directly the properties of chiral magnetic systems. We show that it can straightforwardly and unambiguously determine the main characteristics of chiral magnetic distributions: i.e., its chiral nature, the quantitative winding sense (clockwise or counterclockwise), and its type, i.e., Néel [cycloidal] or Bloch [helical]. This method is model independent, does not require a priori knowledge of the magnetic parameters, and can be applied to any system with magnetic domains ranging from a few nanometers (wavelength limited) to several microns. By using prototypical multilayers with tailored magnetic chiralities driven by spin-orbit-related effects at Co |Pt interfaces, we illustrate the strength of this method.

  13. Deflection gating for time-resolved x-ray magnetic circular dichroism-photoemission electron microscopy using synchrotron radiation

    Science.gov (United States)

    Wiemann, C.; Kaiser, A. M.; Cramm, S.; Schneider, C. M.

    2012-06-01

    In this paper, we present a newly developed gating technique for a time-resolving photoemission microscope. The technique makes use of an electrostatic deflector within the microscope's electron optical system for fast switching between two electron-optical paths, one of which is used for imaging, while the other is blocked by an aperture stop. The system can be operated with a switching time of 20 ns and shows superior dark current rejection. We report on the application of this new gating technique to exploit the time structure in the injection bunch pattern of the synchrotron radiation source BESSY II at Helmholtz-Zentrum Berlin for time-resolved measurements in the picosecond regime.

  14. Synchrotron Radiation Linear Dichroism (SRLD) and Time Dependent Density Functional Theory (TD-DFT) Calculations on Dihydroxy-Anthraquinones

    DEFF Research Database (Denmark)

    Nguyen, Duy Duc; Spanget-Larsen, Jens

    SRLD spectra of Quinizarin, Anthrarufin, and Chrysazin partially aligned in stretched polyethylene were measured at the ASTRID synchrotron UV1 beamline (ISA, Aarhus University), yielding absorbance and polarization data up to 57000 cm-1. The observed absorption bands were assigned to electronic t...

  15. Fluorescence-Detected Linear Dichroism of Wood Cell Walls in Juvenile Serbian Spruce: Estimation of Compression Wood Severity

    Czech Academy of Sciences Publication Activity Database

    Savić, A.; Mitrović, A.; Donaldson, L.; Radosavljević, J.S.; Pristov, J.B.; Steinbach, Gabor; Garab, G.; Radotić, K.

    2016-01-01

    Roč. 22, č. 2 (2016), s. 361-367 ISSN 1431-9276 R&D Projects: GA MŠk EE2.3.30.0059; GA MŠk ED2.1.00/03.0110; GA MŠk(CZ) LO1416 Institutional support: RVO:61388971 Keywords : cell wall * cellulose fibrils * compression wood severity Subject RIV: EE - Microbiology, Virology Impact factor: 1.891, year: 2016

  16. Magnetic circular dichroism and computational study of mononuclear and dinuclear iron(iv) complexes† †Electronic supplementary information (ESI) available: VT MCD spectra, VT and VTVH MCD intensity analysis of complex 1, energies, S x, S z values and Boltzmann populations of S = 1 magnetic sublevels as a function of the applied magnetic field, derivation of the excited states arising from the 1b2 → 2b1 transition, determination of the C-term sign of band 1 and the E(2e → 2a1) transitions for complex 1, VTVH MCD spectra, VTVH simulations and the computed MCD spectrum of complex 2. See DOI: 10.1039/c4sc03268c Click here for additional data file.

    Science.gov (United States)

    Xue, Genqiang; Krivokapic, Itana; Petrenko, Taras

    2015-01-01

    High-valent iron(iv)-oxo species are key intermediates in the catalytic cycles of a range of O2-activating iron enzymes. This work presents a detailed study of the electronic structures of mononuclear ([FeIV(O)(L)(NCMe)]2+, 1, L = tris(3,5-dimethyl-4-methoxylpyridyl-2-methyl)amine) and dinuclear ([(L)FeIV(O)(μ-O)FeIV(OH)(L)]3+, 2) iron(iv) complexes using absorption (ABS), magnetic circular dichroism (MCD) spectroscopy and wave-function-based quantum chemical calculations. For complex 1, the experimental MCD spectra at 2–10 K are dominated by a broad positive band between 12 000 and 18 000 cm–1. As the temperature increases up to ∼20 K, this feature is gradually replaced by a derivative-shaped signal. The computed MCD spectra are in excellent agreement with experiment, which reproduce not only the excitation energies and the MCD signs of key transitions but also their temperature-dependent intensity variations. To further corroborate the assignments suggested by the calculations, the individual MCD sign for each transition is independently determined from the corresponding electron donating and accepting orbitals. Thus, unambiguous assignments can be made for the observed transitions in 1. The ABS/MCD data of complex 2 exhibit ten features that are assigned as ligand-field transitions or oxo- or hydroxo-to-metal charge transfer bands, based on MCD/ABS intensity ratios, calculated excitation energies, polarizations, and MCD signs. In comparison with complex 1, the electronic structure of the FeIV 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000

  17. Contribution to the study of TRH (thyrotropin-releasing hormone) conformation using circular dichroism. Physico-chemical studies, radioactive labelling and biological applications

    International Nuclear Information System (INIS)

    Pradelles, Philippe.

    1977-01-01

    In an attempt to reach a better understanding at the molecular level of phenomena connected with the action of TRF the conformation and radioactive labelling of this hormone were investigated. The specific detection of a hormone at its action site is only possible if labelled substances of very high specific activity are used. TRF was tritium labelled by three methods: direct catalytic exchange; catalytic dehalogenation of mono- and di-iodo TRF; catalytic denitrogenation of mono-azo-TRF. Whatever the method used the tritiated TRF has a very high specific activity and keeps all its biological properties. Biological activity measurements carried out on labelled TRF, in vivo in rats and in vitro on a TRF-sensitive prolactine cell clone, are described. TRF tritiated by the above methods is shown to have the same biological activity as standard TRF. Some results are given concerning the application of labelled TRF to research on the hormone action mechanism. The tritiated TRF distribution kinetics were examined in vivo and in vitro. The kinetics of hormone fixation on the antehypophysary tissue match those of in vivo release of the plasma thyreotropic hormone, confirming the relationships between the hormone fixation on its target tissue and its biological effect. Finally an outline is given of work on the interaction of tritiated TRF with prolactine cell receptors and on the penetration of intact tritiated TRF into these cells. In addition the radioimmunological analysis of TRF was developed by the use of 125 I-mono-iodo-TRF at high specific activity (above 2000 Ci/mmole) [fr

  18. Biomolecular and Structural Analyses of Cauliflower-like DNAs by Ultraviolet, Circular Dichroism, and Fluorescence Spectroscopies in Comparison with Natural DNA

    OpenAIRE

    Gill, Pooria; Ranjbar, Bijan; Saber, Reza; Khajeh, Khosro; Mohammadian, Mehdi

    2011-01-01

    Cauliflower-like DNAs are stem-loop DNAs that are fabricated periodically in inverted repetitions from deoxyribonucleic acid phosphates (dNTPs) by loop-mediated isothermal amplification (LAMP). Cauliflower-like DNAs have ladder-shape behaviors on gel electrophoresis, and increasing the time of LAMP leads to multiplying the repetitions, stem-loops, and electrophoretic bands. Cauliflower-like DNAs were fabricated via LAMP using two loop primers, two bumper primers, dNTPs, a λ-phage DNA template...

  19. Magneto-optical measurement of spin-lattice relaxation time in KBr and in the Na and Cs halogenetes and Co++ ion magnetic circular dichroism study in KCl

    International Nuclear Information System (INIS)

    Carvalho, R.A.

    1977-01-01

    A magnetic circular dicroism spectrometer is described, which was used in the following experiments: 1) The spin-lattice relaxation time (T 1 ) for F centers in NaCl, NaBr, CsBr and CsCl, at 1,8 0 K in magnetic fields up to 15000Gs is described. The suitability of the theory of ref. (08) to explain the differences observed for halides of differents alkali ions as well as for different structures is verified proves that the hyperfine interaction is the most important mechanism for this kind of centers. It is also verified that, for temperatures between 6 0 K and 15 0 K, T 1 experimental values fits the theory of ref. (21) reasonably well, for F centers in KBr. This theory us an extension of that of ref. (8). 2) The MCD spectra for KCl:Co ++ and Caf 2 :Co ++ in different magnetic fields up to 56KGs, and in temperature range between 1,8 0 K and 4,2 0 K is obtained. The results are consistent with the assumption that Co ++ centers are intersticial in KCl lattice [pt

  20. Characterization of the 1st and 2nd EF-hands of NADPH oxidase 5 by fluorescence, isothermal titration calorimetry, and circular dichroism

    Directory of Open Access Journals (Sweden)

    Wei Chin-Chuan

    2012-04-01

    Full Text Available Abstract Background Superoxide generated by non-phagocytic NADPH oxidases (NOXs is of growing importance for physiology and pathobiology. The calcium binding domain (CaBD of NOX5 contains four EF-hands, each binding one calcium ion. To better understand the metal binding properties of the 1st and 2nd EF-hands, we characterized the N-terminal half of CaBD (NCaBD and its calcium-binding knockout mutants. Results The isothermal titration calorimetry measurement for NCaBD reveals that the calcium binding of two EF-hands are loosely associated with each other and can be treated as independent binding events. However, the Ca2+ binding studies on NCaBD(E31Q and NCaBD(E63Q showed their binding constants to be 6.5 × 105 and 5.0 × 102 M-1 with ΔHs of -14 and -4 kJ/mol, respectively, suggesting that intrinsic calcium binding for the 1st non-canonical EF-hand is largely enhanced by the binding of Ca2+ to the 2nd canonical EF-hand. The fluorescence quenching and CD spectra support a conformational change upon Ca2+ binding, which changes Trp residues toward a more non-polar and exposed environment and also increases its α-helix secondary structure content. All measurements exclude Mg2+-binding in NCaBD. Conclusions We demonstrated that the 1st non-canonical EF-hand of NOX5 has very weak Ca2+ binding affinity compared with the 2nd canonical EF-hand. Both EF-hands interact with each other in a cooperative manner to enhance their Ca2+ binding affinity. Our characterization reveals that the two EF-hands in the N-terminal NOX5 are Ca2+ specific. Graphical abstract

  1. Reflection of circularly polarized light and the effect of particle distribution on circular dichroism in evaporation induced self-assembled cellulose nanocrystal thin films

    Directory of Open Access Journals (Sweden)

    D. Hewson

    2017-06-01

    Full Text Available Evaporation induced self-assembled (EISA thin films of cellulose nanocrystals (CNCs have shown great potential for displaying structural colour across the visible spectrum. They are believed primarily to reflect left handed circularly polarised (LCP light due to their natural tendency to form structures comprising left handed chirality. Accordingly the fabrication of homogenously coloured CNC thin films is challenging. Deposition of solid material towards the edge of a dried droplet, via the coffee-stain effect, is one such difficulty in achieving homogenous colour across CNC films. These effects are most easily observed in films prepared from droplets where observable reflection of visible light is localised around the edge of the dry film. We report here, the observation of both left and right hand circularly polarised (LCP/RCP light in reflection from distinct separate regions of CNC EISA thin films and we elucidate how these reflections are dependent on the distribution of CNC material within the EISA thin film. Optical models of reflection are presented which are based on structures revealed using high resolution transmission electron microscopy (TEM images of film cross sections. We have also employed spectroscopic characterisation techniques to evaluate the distribution of solid CNC material within a selection of CNC EISA thin films and we have correlated this distribution with polarised light spectra collected from each film. We conclude that film regions from which RCP light was reflected were associated with lower CNC concentrations and thicker film regions.

  2. Conformational Plasticity of the Cell-Penetrating Peptide SAP As Revealed by Solid-State 19F-NMR and Circular Dichroism Spectroscopies.

    Science.gov (United States)

    Afonin, Sergii; Kubyshkin, Vladimir; Mykhailiuk, Pavel K; Komarov, Igor V; Ulrich, Anne S

    2017-07-13

    The cell-penetrating peptide SAP, which was designed as an amphipathic poly-l-proline helix II (PPII), was suggested to self-assemble into regular fibrils that are relevant for its internalization. Herein we have analyzed the structure of SAP in the membrane-bound state by solid-state 19 F-NMR, which revealed other structural states, in addition to the expected surface-aligned PPII. Trifluoromethyl-bicyclopentyl-glycine (CF 3 -Bpg) and two rigid isomers of trifluoromethyl-4,5-methanoprolines (CF 3 -MePro) were used as labels for 19 F-NMR analysis. The equilibria between different conformations of SAP were studied and were found to be shifted by the substituents at Pro-11. Synchrotron-CD results suggested that substituting Pro-11 by CF 3 -MePro governed the coil-to-PPII equilibrium in solution and in the presence of a lipid bilayer. Using CD and 19 F-NMR, we examined the slow kinetics of the association of SAP with membranes and the dependence of the SAP conformational dynamics on the lipid composition. The peptide did not bind to lipids in the solid ordered phase and aggregated only in the liquid ordered "raft"-like bilayers. Self-association could not be detected in solution or in the presence of liquid disordered membranes. Surface-bound amphipathic SAP in a nonaggregated state was structured as a mixture of nonideal extended conformations reflecting the equilibrium already present in solution, i.e., before binding to the membrane.

  3. Probing magnetism in the vortex phase of PuCoGa.sub.5./sub. by X-ray magnetic circular dichroism

    Czech Academy of Sciences Publication Activity Database

    Magnani, N.; Eloirdi, R.; Wilhelm, F.; Colineau, E.; Griveau, J.C.; Shick, Alexander; Lander, G.H.; Rogalev, A.; Caciuffo, R.

    2017-01-01

    Roč. 119, č. 15 (2017), s. 1-6, č. článku 157204. ISSN 0031-9007 R&D Projects: GA ČR GA15-07172S Institutional support: RVO:68378271 Keywords : XMCD * superconductivity * strong electron correlations Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 8.462, year: 2016

  4. Structures, vibrational absorption and vibrational circular dichroism spectra of L-alanine in aqueous solution: a density functional theory and RHF study

    DEFF Research Database (Denmark)

    Frimand, Kenneth; Bohr, Henrik; Jalkanen, Karl J.

    2000-01-01

    at the density functional theory level using the B3LYP functional with the 6-31G* basis set. The Hessians and atomic polar tensors and atomic axial tensors were all calculated at the B3LYP/6-31G* level of theory. An important result is the method of treating solvent effects by both adding explicit water...

  5. Vibrational circular dichroism spectroscopy of a spin-triplet bis-(biuretato) cobaltate(III) coordination compound with low-lying electronic transitions

    DEFF Research Database (Denmark)

    Johannessen, Christian; Thulstrup, Peter W.

    2007-01-01

    . The spectroscopic results were compared to measurements performed on the free ligand and to theoretical calculations using density functional theory (B3LYP/TZVP). The results of the VCD analysis of the coordination compound identified an electronic, dipole-forbidden, magnetic dipole-allowed low-lying d-d transition...

  6. The vibrational structure of (E,E’)-1,4-diphenyl-1,3-butadiene. Linear dichroism FTIR spectroscopy and quantum chemical calculations

    DEFF Research Database (Denmark)

    Hansen, Bjarke Knud Vilster; Møller, Søren; Spanget-Larsen, Jens

    2006-01-01

    than 40 vibrational transitions. The observed IR wavenumbers, relative intensities, and polarization directions were generally well reproduced by the results of a harmonic analysis based on B3LYP/cc-pVTZ density functional theory (DFT). The combined experimental and theoretical results led to proposal...... of a nearly complete assignment of the IR active fundamentals of DPB, involving reassignment of a number of transitions. In addition, previously published Raman spectra of DPB were well predicted by the B3LYP/cc-pVTZ calculations....

  7. 3ircular dichroism simulation shows a site-II-to-site-I displacement of human serum albumin-bound diclofenac by ibuprofen

    OpenAIRE

    Yamasaki, Keishi; Rahman, Mohammed Hablbur; Tsutsumi, Yasuhiro; Maruyama, Toru; Ahmed, Shamim; Kragh-Hansen; Otagiri, Masaki

    2000-01-01

    Purpose: The purpose of this study was to confirm the hypothesis that a site-II-to-site-I displacement takes place when some nonsteroidal anti-inflammatory drugs are displaced by another drug from their high-affinity binding site to a site of lower affinity on human serum albumin (HSA).Methods: Diclofenac, sodium salt, was used as a representative example because of its prominent reversal of the Cotton effect. Effects of site-specific drugs on the free fraction of diclofenac were determined b...

  8. Vibrational analysis of various irotopes of L-alanyl-L-alanine in aqueous solution: Vibrational Absorption (VA), Vibrational Circular Dichroism (VCD), Raman and Raman Optical Activity (ROA) Spectra

    DEFF Research Database (Denmark)

    Jalkanen, Karl J.; Nieminen, R.M.; Knapp-Mohammady, M.

    2003-01-01

    . DFT Becke3LYP/6-31G* theory has been used to determine the geometry, Hessian, atomic polar tensors (APT), and atomic axial tensors (AAT), and the electric dipole-electric dipole polarizability derivatives (EDEDPD), which are required for us to simulate the VA, VCD, and Raman spectra. The electric...

  9. Two-photon absorption and two-photon circular dichroism of hexahelicene derivatives: a study of the effect of the nature of intramolecular charge transfer

    Czech Academy of Sciences Publication Activity Database

    Díaz, C.; Vesga, Y.; Echevarria, L.; Stará, Irena G.; Starý, Ivo; Anger, E.; Shen, C.; Moussa, M. E. S.; Vanthuyne, N.; Crassous, J.; Rizzo, A.; Hernández, F. E.

    2015-01-01

    Roč. 5, č. 23 (2015), s. 17429-17437 ISSN 2046-2069 Institutional support: RVO:61388963 Keywords : [6]helicene * two photon absorption * two photon CD Subject RIV: CC - Organic Chemistry Impact factor: 3.289, year: 2015

  10. Electrochemical and circular dichroism spectroscopic evidence of two types of interaction between [Ru(NH3)(6)](3+) and an elongated thrombin binding aptamer G-quadruplex

    Czech Academy of Sciences Publication Activity Database

    De Rache, A.; Kejnovská, Iva; Buess-Herman, C.; Doneux, T.

    2015-01-01

    Roč. 179, OCT 2015 (2015), s. 84-92 ISSN 0013-4686 Institutional support: RVO:68081707 Keywords : Biosensors * Thrombin binding aptamer * Hexaammineruthenium Subject RIV: BO - Biophysics Impact factor: 4.803, year: 2015

  11. X-ray magnetic circular dichroism at IrL2,3 edges in Fe100−xIrx and ...

    Indian Academy of Sciences (India)

    2Japan Synchrotron Radiation Institute, SPring8, 1-1-1 Kouto, Mikazuki,. Hyogo 679-5198, Japan. ∗. Email: krishna@postman.riken.go.jp. Abstract. The formation of induced 5d magnetic moment on Ir in Fe100−x Irx (x=3, 10 and 17) and. Co100−x Irx (x =5, 17, 25 and 32) alloys has been investigated by X-ray magnetic ...

  12. Absorption Linear Dichroism Measured Directly on a Single Light-Harvesting System: The Role of Disorder in Chlorosomes of Green Photosynthetic Bacteria

    Czech Academy of Sciences Publication Activity Database

    Furumaki, S.; Vácha, František; Habuchi, S.; Tsukatani, Y.; Bryant, D.A.; Vácha, M.

    2011-01-01

    Roč. 133, č. 17 (2011), s. 6703-6710 ISSN 0002-7863 R&D Projects: GA ČR GA206/09/0375 Institutional research plan: CEZ:AV0Z50510513 Keywords : CHLOROBIUM-TEPIDUM * BACTERIOCHLOROPHYLL-C * SUPRAMOLECULAR ORGANIZATION Subject RIV: EF - Botanics Impact factor: 9.907, year: 2011

  13. Nonlinear Dichroism in Back-to-Back Double Ionization of He by an Intense Elliptically Polarized Few-Cycle Extreme Ultraviolet Pulse.

    Science.gov (United States)

    Ngoko Djiokap, J M; Manakov, N L; Meremianin, A V; Hu, S X; Madsen, L B; Starace, Anthony F

    2014-11-28

    Control of double ionization of He by means of the polarization and carrier-envelope phase (CEP) of an intense, few-cycle extreme ultraviolet (XUV) pulse is demonstrated numerically by solving the six-dimensional two-electron, time-dependent Schrödinger equation for He interacting with an elliptically polarized XUV pulse. Guided by perturbation theory (PT), we predict the existence of a nonlinear dichroic effect (∝I^{3/2}) that is sensitive to the CEP, ellipticity, peak intensity I, and temporal duration of the pulse. This dichroic effect (i.e., the difference of the two-electron angular distributions for opposite helicities of the ionizing XUV pulse) originates from interference of first- and second-order PT amplitudes, allowing one to probe and control S- and D-wave channels of the two-electron continuum. We show that the back-to-back in-plane geometry with unequal energy sharing is an ideal one for observing this dichroic effect that occurs only for an elliptically polarized, few-cycle attosecond pulse.

  14. Development of new radioactive labelling methods (3H and 11C) in luteizing hormone (LH) and its releasing hormone (LRF). Study of physico-chemical properties of LRF by circular dichroism and emission spectroscopy

    International Nuclear Information System (INIS)

    Marche, Pierre.

    1975-01-01

    After a brief review of present knowledge on the hypothalamus-hypophysis this thesis falls into three parts. The first situates the peptide hormones studied in their biological context. Research on the radioactive labelling of hormonal peptides is dealt with in part two which includes, besides the application of already known tritiation methods to particular problems, the description of a new tritium labelling method and the use of carbon 11 for the kinetic distribution study of a hormone. Part three concerns the physico-chemical study of a hypothalamic hormone. As a contribution towards research on the hypophysary gonadotrophic function regulation, the work involved in all the above three sections was directed towards the luteinising hormone (LH) and its hypothalamic release factor (LRF). During the study of this latter the problem of peptides containing tryptophane arose and was consequently investigated [fr

  15. Expression, Purification, and Monitoring of Conformational Changes of hCB2 TMH67H8 in Different Membrane-Mimetic Lipid Mixtures Using Circular Dichroism and NMR Techniques

    Directory of Open Access Journals (Sweden)

    Elvis K. Tiburu

    2017-02-01

    Full Text Available This work was intended to develop self-assembly lipids for incorporating G-protein coupled receptors (GPCRs in order to improve the success rate for nuclear magnetic resonance spectroscopy (NMR structural elucidation. We hereby report the expression and purification of uniformly 15N-labeled human cannabinoid receptor-2 domain in insect cell media. The domain was refolded by screening several membrane mimetic environments. Different q ratios of isotropic bicelles were screened for solubilizing transmembrane helix 6, 7 and 8 (TMH67H8. As the concentration of dimyristoylphosphocholine (DMPC was increased such that the q ratio was between 0.16 and 0.42, there was less crowding in the cross peaks with increasing q ratio. In bicelles of q = 0.42, the maximum number of cross peaks were obtained and the cross peaks were uniformly dispersed. The receptor domain in bicelles beyond q = 0.42 resulted in peak crowding. These studies demonstrate that GPCRs folding especially in bicelles is protein-specific and requires the right mix of the longer chain and shorter chain lipids to provide the right environment for proper folding. These findings will allow further development of novel membrane mimetics to provide greater diversity of lipid mixtures than those currently being employed for GPCR stability and folding, which are critical for both X-ray and NMR studies of GPCRs.

  16. Theoretical Prediction of Vibrational Circular Dichroism Spectra of R- Glyceraldehyde, R-Erythrose, and R-Threose. 2. Development of a Procedure to Scale the Force Constant Matrix Expressed in Terms of Internal Coordinates

    Science.gov (United States)

    1993-11-01

    IS PROGRAM NUMBER 1 OF THE COMPLETE VIBRATIONAL PACKAGE. C C BMAT ... WIL.riON B MATRIX ELDEMETS FOR INTERNAL COORDINATES C iVERSIONO JUL 28, 1977) C...MATRIX ISCAN=ISCAN+ 1 IER=O GO TO 30 210 WRITE(6,1120) STOP 1000 FORMAT(20A4/20A4/214) 1010 FORMAT(’l’,20A4,24X.’ BMAT (VERSIONO JUL 28. 1977)’/1X,20A4

  17. Transverse magneto-optical anisotropy in bidisperse ferrofluids with long range particle correlations

    Energy Technology Data Exchange (ETDEWEB)

    Elfimova, E.A.; Ivanov, A.O. [Ural Federal University, ul. Lenina 51, Yekaterinburg 620000 (Russian Federation); Popescu, L.B. [Institute for Space Sciences, Atomistilor 409, Magurele RO-077125 (Romania); Socoliuc, V., E-mail: vsocoliuc@acad-tim.tm.edu.ro [Romanian Academy-Timisoara Branch, Center for Fundamental and Advanced Technical Research, Lab. Magnetic Fluids, Bv.M. Viteazu 24, Timisoara RO-300223 (Romania)

    2017-06-01

    A comparative study between experiment and the predictions of a theoretical model developed for the description of magnetically induced dichroism in ferrofluids with long range interacting bidisperse spherical nanoparticles is presented. Magnetically induced dichroism in dilution series of two ferrofluids with different surfactant thickness was measured. Both ferrofluids show a concave solid volume fraction dependence of the specific dichroism, whose characteristics are very well qualitatively explained by the theoretical model. The theory fails to satisfactorily explain the magnetic field dependence of the highly concentrated samples specific dichroism, due to inherent approximations in the virial expansion of the pair correlation function.

  18. Denaturation/Renaturation of Organophosphorus Acid Anhydrolase (OPAA) Using Guanidinium Hydrochloride and Urea

    National Research Council Canada - National Science Library

    Ong, K. K; Sun, Z; Cheng, T. C; Wei, Y; Yuan, J. M; Yin, R

    2004-01-01

    ...; thereby indicating conformational changes. Similar results were obtained with circular dichroism as the peak representing the alpha-helix conformation decreased as denaturant concentration was increased...

  19. Resolution and Determination of the Absolute Configuration of a Twisted Bis-Lactam Analogue of Troger's Base: A Comparative Spectroscopic and Computational Study

    DEFF Research Database (Denmark)

    Rúnarsson, Ögmundur Vidar; Benkhäuser, Christian; Christensen, Niels Johan

    2015-01-01

    ) and electronic circular dichroism (ECD) spectra. The absolute configuration of (-)-2 was determined by comparing experimental and calculated electronic circular dichroism (ECD) spectra. The corresponding theoretical spectra were calculated using the lowest energy conformation of (R,R)-2 and (S,S)-2 at the B3LYP...

  20. The quantitative relationship between structure and polarized spectroscopy in the FMO complex of Prosthecochloris aestuarii: refining experiments and simulations

    NARCIS (Netherlands)

    Wendling, Markus; Przyjalgowski, Milosz A.; Gülen, Demet; Vulto, Simone I. E.; Aartsma, Thijs J.; van Grondelle, Rienk; van Amerongen, Herbert

    2002-01-01

    New absorption, linear dichroism (LD) and circular dichroism (CD) measurements at low temperatures on the Fenna-Matthews-Olson complex from Prosthecochloris aestuarii are presented. Furthermore, the anisotropy of fluorescence excitation spectra is measured and used to determine absolute LD spectra,

  1. Purification and Characterization of Tryptophan Hydroxylase

    DEFF Research Database (Denmark)

    Haahr, Lærke Tvedebrink

    be concluded that Glu363, which is an iron ligand, is essential for activity, while Tyr358 affects the activity, but is not absolutely required. Circular dichroism and magnetic circular dichroism results on chTPH2 clearly demonstrated that the active site iron changes conformation from 6 to 5 coordinated only...

  2. Boundaries for efficient use of electron vortex beams to measure magnetic properties

    Czech Academy of Sciences Publication Activity Database

    Rusz, Ján; Bhowmick, S.

    2013-01-01

    Roč. 111, č. 10 (2013), "105504-1"-"105504-5" ISSN 0031-9007 Institutional support: RVO:68378271 Keywords : orbital angular-momentum * circular-dichroism * chiral dichroism * microscope * resolution Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 7.728, year: 2013

  3. Vibrační optická aktivita: Experimentální zázemí a počítačové simulace

    Czech Academy of Sciences Publication Activity Database

    Hudecová, Jana; Bouř, Petr

    2014-01-01

    Roč. 108, č. 4 (2014), s. 285-292 ISSN 0009-2770 Institutional support: RVO:61388963 Keywords : vibrational optical activity * circular dichroism * DFT calculations Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 0.272, year: 2014

  4. Vibrationally induced inversion of photoelectron forward-backward asymmetry in chiral molecule photoionization by circularly polarized light

    Science.gov (United States)

    Garcia, Gustavo A.; Nahon, Laurent; Daly, Steven; Powis, Ivan

    2013-01-01

    Electron–nuclei coupling accompanying excitation and relaxation processes is a fascinating phenomenon in molecular dynamics. A striking and unexpected example of such coupling is presented here in the context of photoelectron circular dichroism measurements on randomly oriented, chiral methyloxirane molecules, unaffected by any continuum resonance. Here, we report that the forward-backward asymmetry in the electron angular distribution, with respect to the photon axis, which is associated with photoelectron circular dichroism can surprisingly reverse direction according to the ion vibrational mode excited. This vibrational dependence represents a clear breakdown of the usual Franck–Condon assumption, ascribed to the enhanced sensitivity of photoelectron circular dichroism (compared with other observables like cross-sections or the conventional anisotropy parameter-β) to the scattering phase off the chiral molecular potential, inducing a dependence on the nuclear geometry sampled in the photoionization process. Important consequences for the interpretation of such dichroism measurements within analytical contexts are discussed. PMID:23828557

  5. A physico-chemical study of some areas of fundamental significance to biophysics

    International Nuclear Information System (INIS)

    McGlynn, S.P.; Kumar, D.

    1992-01-01

    This report discusses the following topics: Radiation signatures; photoelectron spectroscopy of biologically active molecules; laser optogalvanic effect; magnetic circular dichroism; photochemistry of halogenated molecules; and density effects on high-n rydbergs

  6. Low resolution solution structure of the Apo form of Escherichia coli haemoglobin protease Hbp.

    NARCIS (Netherlands)

    scott, D.J.; Grossman, J.G.; Tame, J.R.H.; Byron, O.; Wilson, K.S.; Otto, B.R.

    2002-01-01

    We have studied the solution properties of the apo form of the haemoglobin protease or "haemoglobinase", Hbp, a principal component of an important iron acquisition system in pathogenic Escherichia coli. Experimental determination of secondary structure content from circular dichroism (CD)

  7. [Formation of purple membranes during salt bacteria cultivation].

    Science.gov (United States)

    Chekulaeva, L N; Korolev, Iu N; Telegin, N L; Rikhireva, G T

    1975-01-01

    Experiments have been carried out on cultivation of halophile with probe selection in the interval of 1--2 hours to record the spectra of repeated disturbed completed inner reflection. Periodicity in the changes of spectral characteristics of the culture with the interval of 20--24 hours is revealed. A clearly expressed dichroism of the amid II band of the membrane complex is found, the absence of this dichroism in the protein isolated from the membrane complex is stated. It is suggested that dichroism revealed is a specific feature of the presence of purpuric membranes in the cells. Spontaneous plane orientation of protein macromolecules in purpuric membranes is established. The level of dichroism of amid II band is shown to depend on fermentation conditions of salt bacteria.

  8. Interaction between sodium dodecyl sulfate and membrane reconstituted aquaporins: A comparative study of spinach SoPIP2;1 and E. coli AqpZ

    DEFF Research Database (Denmark)

    Hansen, Jesper Schmidt; Vararattanavech, Ardcharaporn; Plasencia, Inés

    2011-01-01

    This study describes the interaction between sodium dodecyl sulfate (SDS) and membrane proteins reconstituted into large unilamellar lipid vesicles and detergent micelles studied by circular dichroism (CD) and polarity sensitive probe labeling. Specifically, we carried out a comparative study of ...

  9. Electronic transitions of fluorene, dibenzofuran, carbazole, and dibenzothiophene

    DEFF Research Database (Denmark)

    Nguyen, Duy Duc; Trunk, John; Nakhimovsky, Lina

    2010-01-01

    A comparative study of the electronic transitions of fluorene and its hetero-analogues dibenzofuran, carbazole, and dibenzothiophene was performed in a wide energy range. Gas phase, crystal phase, and linear dichroism electronic transmittance spectra were measured with synchrotron radiation...

  10. Kerr ellipticity effect in a birefringent optical fiber

    International Nuclear Information System (INIS)

    Ishiekwene, G.C.; Mensah, S.Y.; Brown, C.S.

    2004-09-01

    An intensity-dependent change in the ellipticity of an input light beam leads to a characteristic shift in polarization instability. Dichroism gives rise to a self-induced ellipticity effect in the polarization state of an intense input light oriented along the fast axis of a birefringent optical fiber. The critical power at which the fiber effective beat length becomes infinite is reduced considerably in the presence of dichroism. (author)

  11. Magnetoplasmonic Nanomaterials: A Route to Predictive Photocatalytic, Light-Harvesting and Ferrofluidic Properties

    Science.gov (United States)

    2013-10-01

    circular dichroism ( MCD )] techniques. Because MCD is inherently sensitive to oxidation and spin state, we will be able to use this technique in the future...have developed femtosecond time-resolved magnetic circular dichroism ( MCD ) capabilities. MCD data are highly sensitive to the electronic structure of...molecules and nanoclusters. In light of this, we currently employ time-resolved MCD to investigate the interplay between nanoscale structure and

  12. Investigation of rare earth complexes with pyridoxalydenamino acids by optical methods. Structure of complexes on basis of hydrophobic amino acids

    International Nuclear Information System (INIS)

    Zolin, V.F.; Koreneva, L.G.; Serbinova, T.A.; Tsaryuk, V.I.

    1975-01-01

    The structure of pyridoxalidene amino acid complexes was studied by circular dichroism, magnetic circular dichroism and luminescence spectroscopy. It was shown that these are two-ligand complexes, whereby in the case of those based on valine, leucine and isoleucine the chromophores are almost perpendicular to one another. In the case of complexes based on glycine and alanine the co-ordination sphere is strongly deformed. (author)

  13. Imaging differential polarization microscope with electronic readout

    International Nuclear Information System (INIS)

    Mickols, W.; Tinoco, I.; Katz, J.E.; Maestre, M.F.; Bustamante, C.

    1985-01-01

    A differential polarization microscope forms two images: one of the transmitted intensity and the other due to the change in intensity between images formed when different polarizations of light are used. The interpretation of these images for linear dichroism and circular dichroism are described. The design constraints on the data acquisition systems and the polarization modulation are described. The advantage of imaging several biological systems which contain optically anisotropic structures are described

  14. Two-color above-threshold ionization of atoms and ions in XUV Bessel beams and intense laser light

    Science.gov (United States)

    Seipt, D.; Müller, R. A.; Surzhykov, A.; Fritzsche, S.

    2016-11-01

    The two-color above-threshold ionization (ATI) of atoms and ions is investigated for a vortex Bessel beam in the presence of a strong near-infrared (NIR) light field. While the photoionization is caused by the photons from the weak but extreme ultraviolet (XUV) vortex Bessel beam, the energy and angular distribution of the photoelectrons and their sideband structure are affected by the plane-wave NIR field. We here explore the energy spectra and angular emission of the photoelectrons in such two-color fields as a function of the size and location of the target atoms with regard to the beam axis. In addition, analog to the circular dichroism in typical two-color ATI experiments with circularly polarized light, we define and discuss seven different dichroism signals for such vortex Bessel beams that arise from the various combinations of the orbital and spin angular momenta of the two light fields. For localized targets, it is found that these dichroism signals strongly depend on the size and position of the atoms relative to the beam. For macroscopically extended targets, in contrast, three of these dichroism signals tend to zero, while the other four just coincide with the standard circular dichroism, similar as for Bessel beams with a small opening angle. Detailed computations of the dichroism are performed and discussed for the 4 s valence-shell photoionization of Ca+ ions.

  15. Zen and the art of dichroic photoemission

    Energy Technology Data Exchange (ETDEWEB)

    Laan, Gerrit van der, E-mail: gerrit.vanderlaan@diamond.ac.uk

    2015-04-15

    Highlights: • General theory for angle and spin dependence of dichroic core-level photoemission. • Fundamental spectra give correlation between spin and orbital moments. • Interference term between emission channels results in MLDAD and CDAD. • Core-hole polarization is probed by resonant photoemission. - Abstract: The discovery of magnetic dichroism in photoemission is celebrating its 25th anniversary this year. Here a review of the underlying general theory for the angular and spin dependence of dichroic core-level photoemission is presented using both a single-particle model and a many-body approach. The established methods of angular momentum coupling offer an elegant and powerful way to analyse the magnetic dichroism and spin polarization in photoemission from core and localized valence levels. In the presence of core-valence interactions one can distinguish different fundamental spectra, which via sum rules are related to physical properties described by coupled tensor operators for spin and orbital moments. By separating the angular dependence from the physical information, different geometries can be distinguished to measure the magnetic circular dichroism (MCD), linear dichroism (LD), circular dichroism in the angular dependence (CDAD), and magnetic linear dichroism in the angular dependence (MLDAD). Various ways to probe the core-hole polarization are discussed, such as using the angular dependence, moment analysis of the spectral distribution, and resonant photoemission decay.

  16. Azimuthally invariant Mueller-matrix mapping of biological optically anisotropic network

    Science.gov (United States)

    Ushenko, Yu. O.; Vanchuliak, O.; Bodnar, G. B.; Ushenko, V. O.; Grytsyuk, M.; Pavlyukovich, N.; Pavlyukovich, O. V.; Antonyuk, O.

    2017-09-01

    A new technique of Mueller-matrix mapping of polycrystalline structure of histological sections of biological tissues is suggested. The algorithms of reconstruction of distribution of parameters of linear and circular dichroism of histological sections liver tissue of mice with different degrees of severity of diabetes are found. The interconnections between such distributions and parameters of linear and circular dichroism of liver of mice tissue histological sections are defined. The comparative investigations of coordinate distributions of parameters of amplitude anisotropy formed by Liver tissue with varying severity of diabetes (10 days and 24 days) are performed. The values and ranges of change of the statistical (moments of the 1st - 4th order) parameters of coordinate distributions of the value of linear and circular dichroism are defined. The objective criteria of cause of the degree of severity of the diabetes differentiation are determined.

  17. Design of planar chiral metamaterials for near-infrared regime

    Science.gov (United States)

    Kaya, Sabri; Turkmen, Mustafa; Topaktas, Omer

    2017-01-01

    Planar chiral metamaterials (PCMs) comprising double-layer dielectric-metal-dielectric resonant structures in the shape of a windmill are presented for near-infrared regime. The circular dichroism is retrieved from transmission spectra. Effects of used materials on circular dichroism characteristics of PCM arrays are investigated for the first time. The dependence of spectral characteristics on the geometrical parameters of the PCMs is analyzed by the finite-difference time-domain method. The observations indicated that the circular dichroism characteristics of the proposed PCM arrays are strongly dependent on the type of metal and dielectric materials. Due to the enhanced chiroptical near-field response and tunable spectral behavior, proposed PCM arrays may have potential for biosensing applications of chiral biomolecules.

  18. Spectropolarimetric analysis. Communication 14. Determination of uranyl with d-tartaric acid

    Energy Technology Data Exchange (ETDEWEB)

    Bakalov, V D; Dunina, V V; Potapov, V M [Moskovskij Gosudarstvennyj Univ. (USSR)

    1982-02-01

    The possibility has been shown of improving the sensitivity and precision of determination of uranium (6) in the form of its tartrate complex by using spectropolarimetry instead of polarimetry and circular dichroism instead of optical rotatory dispersion. The method makes it possible to reduce reagent consumption, to expand a range of uranium(6) concentration, which could be determined, due to changes of the cell length and reading range. On the basis of the circular dichroism spectrum of the uranyl-tartrate complex, its symmetry has been estimated to be Dsub(4h) with the coordination number of four on the equatorial plane.

  19. Testing chameleon theories with light propagating through a magnetic field

    International Nuclear Information System (INIS)

    Brax, Philippe; Bruck, Carsten van de; Davis, Anne-Christine; Mota, David F.; Shaw, Douglas

    2007-01-01

    It was recently argued that the observed PVLAS anomaly can be explained by chameleon field theories in which large deviations from Newton's law can be avoided. Here we present the predictions for the dichroism and the birefringence induced in the vacuum by a magnetic field in these models. We show that chameleon particles behave very differently from standard axionlike particles (ALPs). We find that, unlike ALPs, the chameleon particles are confined within the experimental setup. As a consequence, the birefringence is always bigger than the dichroism in PVLAS-type experiments

  20. Spectropolarimetric analysis

    International Nuclear Information System (INIS)

    Bakalov, V.D.; Dunina, V.V.; Potapov, V.M.

    1982-01-01

    The possibility has been shown of improving the sensitivity and precision of determination of uranium (6) in the form of its tartrate complex by using spectropolarimetry instead of polarimetry and circular dichroism instead of optical rotatory dispersion. The method makes it possible to reduce reagent consumption, to expand a range of uranium(6) concentration, which could be determined, due to changes of the cell length and reading range. On the basis of the circular dichroism spectrum of the uranyl-tartrate complex, its symmetry has been estimated to be Dsub(4h) with the coordination number of four on the equatorial plane

  1. In-Situ Measurement of Chirality of Molecules and Molecular Assemblies with Surface Nonlinear Spectroscopy

    International Nuclear Information System (INIS)

    Wang, Hongfei

    2012-01-01

    Developments in quantitative measurement and analysis in nonlinear surface spectroscopy, namely, second harmonic generation linear dichroism (SHG-LD) and sum frequency generation vibrational spectroscopy linear dichroism (SFG-VS-LD), provide new opportunities for probing the surface chirality of monolayers and thin films. In this book chapter, the up-to-date theoretical background and experimental methodology, as well as examples and future perspectives on the developments with surface nonlinear spectroscopy in surface chirality studies are to be summarized and outlined for general readers.

  2. Fifth Annual Meeting of the Advanced Light Source User`s Association

    Energy Technology Data Exchange (ETDEWEB)

    1993-10-01

    This report discusses the following topics: ALS Project Status; Accelerator Commissioning; Experimental Systems: Supersmooth Optics and Ultra-Precise Undulators; Planning for Users and User Services; ALS Scientific Program; High Resolution Core-Level Photoemission; Photoelectron Diffraction and Holography; Soft X-Ray Emission Spectroscopy of Solids at the NSLS and the ALS; Gas-Phase Spectrometry; Spectromicroscopy; X-Ray Dichroism Experiments Using Circular Polarization; Magnetic Circular X-Ray Dichroism and MCXD Microscopy; Applications of Soft X-Ray Optics to Sub-Micron Silicon Device Technology; Bend Magnet Microprobe; Protein Crystallography: Recent Developments and Plans for the ALS; and Applications of High-Brightness Synchrotron Radiation to Protein Crystallography.

  3. Scanning differential polarization microscope: Its use to image linear and circular differential scattering

    International Nuclear Information System (INIS)

    Mickols, W.; Maestre, M.F.

    1988-01-01

    A differential polarization microscope that couples the sensitivity of single-beam measurement of circular dichroism and circular differential scattering with the simultaneous measurement of linear dichroism and linear differential scattering has been developed. The microscope uses a scanning microscope stage and single-point illumination to give the very shallow depth of field found in confocal microscopy. This microscope can operate in the confocal mode as well as in the near confocal condition that can allow one to program the coherence and spatial resolution of the microscope. This microscope has been used to study the change in the structure of chromatin during the development of sperm in Drosophila

  4. Fifth Annual Meeting of the Advanced Light Source User's Association

    International Nuclear Information System (INIS)

    1993-10-01

    This report discusses the following topics: ALS Project Status; Accelerator Commissioning; Experimental Systems: Supersmooth Optics and Ultra-Precise Undulators; Planning for Users and User Services; ALS Scientific Program; High Resolution Core-Level Photoemission; Photoelectron Diffraction and Holography; Soft X-Ray Emission Spectroscopy of Solids at the NSLS and the ALS; Gas-Phase Spectrometry; Spectromicroscopy; X-Ray Dichroism Experiments Using Circular Polarization; Magnetic Circular X-Ray Dichroism and MCXD Microscopy; Applications of Soft X-Ray Optics to Sub-Micron Silicon Device Technology; Bend Magnet Microprobe; Protein Crystallography: Recent Developments and Plans for the ALS; and Applications of High-Brightness Synchrotron Radiation to Protein Crystallography

  5. Spektroskopický výzkum fullerenů a počítačové simulace

    Czech Academy of Sciences Publication Activity Database

    Straka, Michal; Bouř, Petr

    2016-01-01

    Roč. 110, č. 5 (2016), s. 344-353 ISSN 0009-2770 R&D Projects: GA ČR(CZ) GA14-03564S; GA ČR GA13-03978S Institutional support: RVO:61388963 Keywords : fullerenes * nuclear magnetic resonance * magnetic circular dichroism * nuclear spin circular dichroism * density functional theory Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 0.387, year: 2016 http://www.chemicke-listy.cz/docs/full/2016_05_344-353.pdf

  6. Linear birefringence and optical ativity in a magnetized plasma

    International Nuclear Information System (INIS)

    Vuolo, J.H.; Galvao, R.M.O.

    1982-02-01

    Linear birefringence and optical activity are considered separately to electromagnetic wave propagation in magnetized cold plasma, using frequency approximation much bigger than plasma frequency. It's showen that in some interesting cases, those phenomena could be independents. Explicit expressions are obtained for refraction indices to linear birefringency and optical activity. The correspondents indices attenuation aRe obtained in first orden of attenuation. It's showen that the characteristic states for linear dichroism coincide with the characteristic states for linear birefringence. The characteristic states for elliptic dichroism are obtained. (M.A.F.) [pt

  7. Electronic states of emodin and its conjugate base

    DEFF Research Database (Denmark)

    Nguyen, Son Chi; Hansen, Bjarke Knud Vilster; Hoffmann, Søren Vrønning

    2008-01-01

    The electronic transitions of emodin (1,3,8-trihydroxy-6-methyl-9,10-anthraquinone, E) and its conjugate base (3-oxido-6-methyl-1,8-dihydroxy-9,10-anthraquinone, Ecb) were investigated by UV-Vis linear dichroism (LD) spectroscopy on molecular samples aligned in stretched poly(vinylalcohol). The e......The electronic transitions of emodin (1,3,8-trihydroxy-6-methyl-9,10-anthraquinone, E) and its conjugate base (3-oxido-6-methyl-1,8-dihydroxy-9,10-anthraquinone, Ecb) were investigated by UV-Vis linear dichroism (LD) spectroscopy on molecular samples aligned in stretched poly...

  8. Two dimensional electron gas confined over a spherical surface: Magnetic moment

    International Nuclear Information System (INIS)

    Hernando, A; Crespo, P; Garcia, M A

    2011-01-01

    Magnetism of capped nanoparticles, NPs, of non-magnetic substances as Au and ZnO is briefly reviewed. The source of the magnetization is discussed on the light of recent X-ray magnetic circular dichroism experiments. As magnetic dichroism analysis has pointed out impurity atoms bonded to the surface act as donor or acceptor of electrons that occupy the surface states. It is proposed that mesoscopic collective orbital magnetic moments induced at the surface states can account for the experimental magnetism characteristic of these nanoparticles. The total magnetic moment of the surface originated at the unfilled Fermi level can reach values as large as 10 2 or 10 3 Bohr magnetons.

  9. T Ishikawa

    Indian Academy of Sciences (India)

    Home; Journals; Pramana – Journal of Physics. T Ishikawa. Articles written in Pramana – Journal of Physics. Volume 58 Issue 5-6 May-June 2002 pp 761-767 Strongly Correlated Electron Systems. X-ray magnetic circular dichroism at IrL2,3 edges in Fe100-Ir and Co100-Ir alloys: Magnetism of 5d electronic states.

  10. Identification of the upper exciton component of the B850 bacteriochlorophylls of the LH2 antenna complex, using a B800-free mutant of Rhodobacter sphaeroides.

    NARCIS (Netherlands)

    Koolhaas, M.H.C.; Frese, R.N.; Fowler, G.J.S.; Bibby, T.S.; Georgakopoulou, S.; van der Zwan, G.; Hunter, C.N.; van Grondelle, R.

    1998-01-01

    In this paper, we report the circular dichroism (CD) spectra of two types of LH2 -only mutants of Rhodobacter sphaeroides. In the first, only the wild type LH2 is present, while in the second, the B800 binding site of LH2 has been either destabilized or removed. For the first time, we have

  11. Spontaneous Formation of left- and right-handed cholesterically ordered domains in an enantioppure chiral polyfluorene film

    NARCIS (Netherlands)

    Savoini, M.; Biagioni, P.; Meskers, S.C.J.; Duò, L.; Hecht, B.; Finazzi, M.

    2011-01-01

    Thermally annealed chiral polyfluorene films are studied by circular differential optical microscopy. We observe the presence of micrometer-sized domains displaying circular dichroism of opposite sign. Our findings suggest the spontaneous occurrence of left- and right-handed cholesterically ordered

  12. Electronic states of 1,4-bis(phenylethynyl)benzene

    DEFF Research Database (Denmark)

    Nguyen, Duy Duc; Jones, Nykola; Hoffmann, Søren Vrønning

    2012-01-01

    The electronic transitions of 1,4-bis(phenylethynyl)benzene (BPEB) were investigated by UV synchrotron radiation linear dichroism (SRLD) spectroscopy in the range 25,000 – 58,000 cm–1 (400 – 170 nm) on molecular samples aligned in stretched polyethylene. The investigation was supported by variable...

  13. The pro region required for folding of carboxypeptidase Y is a partially folded domain with little regular structural core

    DEFF Research Database (Denmark)

    Sørensen, P; Winther, Jakob R.; Kaarsholm, N C

    1993-01-01

    The pro region of carboxypeptidase Y (CPY) from yeast is necessary for the correct folding of the enzyme [Winther, J. R., & Sørensen P. (1991) Proc. Natl. Acad. Sci. U.S.A. 88, 9330-9334]. Using fluorescence, circular dichroism, and heteronuclear NMR analyses, it is demonstrated that the isolated...

  14. DNA homoduplexes containing no pyrimidine nucleotide

    Czech Academy of Sciences Publication Activity Database

    Kypr, Jaroslav; Kejnovská, Iva; Vorlíčková, Michaela

    2003-01-01

    Roč. 32, č. 2 (2003), s. 154-158 ISSN 0175-7571 R&D Projects: GA ČR GA301/01/0590; GA AV ČR IAA4004201 Institutional research plan: CEZ:AV0Z5004920 Keywords : adenine * base pairing * circular dichroism spectroscopy Subject RIV: BO - Biophysics Impact factor: 1.769, year: 2003

  15. Artificial proteins as allosteric modulators of PDZ3 and SH3 in two-domain constructs: A computational characterization of novel chimeric proteins

    Czech Academy of Sciences Publication Activity Database

    Palani, K.; Pfeiferová, L.; Boušová, Kristýna; Bednárová, L.; Obšilová, Veronika; Vondrášek, J.

    2016-01-01

    Roč. 84, č. 10 (2016), s. 1358-1374 ISSN 0887-3585 Institutional support: RVO:67985823 Keywords : protein design * fusion proteins * PDZ3 * SH3 * Trp-cage * two domain proteins * molecular dynamics simulation * circular dichroism Subject RIV: BO - Biophysics Impact factor: 2.289, year: 2016

  16. Antimicrobial Peptide from the Eusocial Bee Halictus sexcinctus Interacting with Model Membranes

    Czech Academy of Sciences Publication Activity Database

    Pazderková, Markéta; Kočišová, E.; Pazderka, T.; Maloň, Petr; Kopecký ml., V.; Monincová, Lenka; Čeřovský, Václav; Bednárová, Lucie

    2012-01-01

    Roč. 27, 5-6 (2012), s. 497-502 ISSN 0712-4813 R&D Projects: GA ČR GAP208/10/0376 Institutional research plan: CEZ:AV0Z40550506 Keywords : antibacterial peptides * halictine * micelle * liposome * phospholipid * circular dichroism * fluorescence * infrared spectroscopy Subject RIV: CC - Organic Chemistry Impact factor: 0.530, year: 2012

  17. The novel antimicrobial peptide from the venom of solitary bee Macropis fulvipes and its analogs

    Czech Academy of Sciences Publication Activity Database

    Monincová, Lenka; Slaninová, Jiřina; Fučík, Vladimír; Bednárová, Lucie; Voburka, Zdeněk; Straka, J.; Čeřovský, Václav

    2012-01-01

    Roč. 106, - (2012), s724-s724 ISSN 0009-2770. [EuCheMS Chemistry Congress /4./. 26.08.2012-30.08.2012, Prague] Institutional research plan: CEZ:AV0Z40550506 Keywords : peptides * circular dichroism * biological activity Subject RIV: CC - Organic Chemistry

  18. Absolute Configuration Determination of a Taxol Precursor Based on Raman Optical Activity Spectra

    Czech Academy of Sciences Publication Activity Database

    Profant, V.; Jegorov, A.; Bouř, Petr; Baumruk, V.

    2017-01-01

    Roč. 121, č. 7 (2017), s. 1544-1551 ISSN 1520-6106 R&D Projects: GA ČR(CZ) GA16-05935S Institutional support: RVO:61388963 Keywords : vibrational circular dichroism * polarized light * molecules Subject RIV: CF - Physical ; Theoretical Chemistry OBOR OECD: Physical chemistry Impact factor: 3.177, year: 2016

  19. Wavelength dependence of the magnetic resolution of the magneto-optical near-field scanning tunneling microscope

    NARCIS (Netherlands)

    Schad, R.; Jordan, S.M.; Stoelinga, M.J.P.; Prins, M.W.J.; Groeneveld, R.H.M.; Kempen, van H.; Kesteren, van H.W.

    1998-01-01

    A magneto-optical near-field scanning tunneling microscope is used to image the prewritten magnetic domain structure of a Pt/Co multilayer. A semiconducting tip acts as a local photodetector to measure the magnetic circular dichroism signal coming from the magnetic sample. The resolution of the

  20. Journal of Biosciences | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    We investigated the interaction of six 18-residue peptides derived from amphipathic helical segments of globular proteins with model membranes. The net charge of the peptides at neutral pH varies from –1 to +6. Circular dichroism spectra indicate that peptides with a high net positive charge tend to fold into a helical ...

  1. Photo-physics study of an hydroxy-quinoline derivative as inhibitor of Pim-1 kinase

    DEFF Research Database (Denmark)

    Lamhasni, T.; Aitlyazidi, S.; Hnach, M.

    2013-01-01

    The photophysical properties of the antiviral 7-nicotinoyl-styrylquinoline (MB96) were investigated by means of UV-Vis linear dichroism (LD) spectroscopy on molecular samples aligned in stretched polyvinylalcohol (PVA), supported by Time Dependent Density Functional Theory (TD-DFT) calculations...

  2. New potent antimicrobial peptides from the venom of Polistinae wasps and their analogs

    Czech Academy of Sciences Publication Activity Database

    Čeřovský, Václav; Slaninová, Jiřina; Fučík, Vladimír; Hulačová, Hana; Borovičková, Lenka; Ježek, Rudolf; Bednárová, Lucie

    2008-01-01

    Roč. 29, č. 6 (2008), s. 992-1003 ISSN 0196-9781 Institutional research plan: CEZ:AV0Z40550506 Keywords : antimicrobial peptides * wasp venom * circular dichroism * hemolytic activity Subject RIV: CC - Organic Chemistry Impact factor: 2.565, year: 2008

  3. Transition dipole coupling modeling of optical activity enhancements in macromolecular protein systems

    Czech Academy of Sciences Publication Activity Database

    Průša, Jiří; Bouř, Petr

    2018-01-01

    Roč. 30, č. 1 (2018), s. 55-64 ISSN 0899-0042 R&D Projects: GA ČR GA15-09072S; GA MŠk(CZ) LTC17012 Institutional support: RVO:61388963 Keywords : optical activity * vibrational circular dichroism * protein fibrils Subject RIV: BO - Biophysics OBOR OECD: Biophysics Impact factor: 1.956, year: 2016

  4. Voltammetric and chronopotentiometric protein structure-sensitive analysis

    Czech Academy of Sciences Publication Activity Database

    Černocká, Hana; Paleček, Emil

    2017-01-01

    Roč. 224, JAN2017 (2017), s. 211-219 ISSN 0013-4686 R&D Projects: GA ČR(CZ) GA15-15479S Institutional support: RVO:68081707 Keywords : circular-dichroism spectroscopy * catalytic hydrogen evolution * mercury-electrodes Subject RIV: BO - Biophysics Impact factor: 4.798, year: 2016

  5. Photoinduced Circular Anisotropy in Side-Chain Azobenzene Polyesters

    DEFF Research Database (Denmark)

    Nikolova, L.; Todorov, T.; Ivanov, M.

    1997-01-01

    We report for the first time the inducing of large circular anisotropy in previously unoriented films of side-chain azobenzene polyesters on illumination with circularly polarized light at a wavelength of 488 nm. The circular dichroism and optical activity are measured simultaneously in real time...

  6. Calcium-induced stabilization of -amylase against guanidine ...

    African Journals Online (AJOL)

    Guanidine hydrochloride (GdnHCl) denaturation of native and Ca- depleted Bacillus licheniformis α-amylase (BLA) was investigated both in the absence and presence of 2 mM calcium chloride (CaCl2) using circular dichroism, fluorescence spectroscopy and biological activity. In both states (Cadepleted and native form), ...

  7. Journal of Chemical Sciences | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    Size and structure of cytochrome c (Cyt C) bound to gold nano-clusters (AuNC) were studied using fluorescence correlation spectroscopy (FCS) and circular dichroism (CD) spectroscopy. The CD spectra of Cyt C indicate that the ellipticity is almost completely lost on binding to AuNC which indicates unfolding.Addition of ...

  8. On the interaction between [Ru(NH3)(6)](3+) and the G-quadruplex forming thrombin binding aptamer sequence

    Czech Academy of Sciences Publication Activity Database

    De Rache, A.; Doneux, T.; Kejnovská, Iva; Buess-Herman, C.

    2013-01-01

    Roč. 126, SEP 2013 (2013), s. 84-90 ISSN 0162-0134 Institutional support: RVO:68081707 Keywords : SELF-ASSEMBLED MONOLAYERS * DNA-MODIFIED SURFACES * CIRCULAR-DICHROISM Subject RIV: BO - Biophysics Impact factor: 3.274, year: 2013

  9. Driving Unidirectional Molecular Rotary Motors with Visible Light by Intra- And Intermolecular Energy Transfer from Palladium Porphyrin

    NARCIS (Netherlands)

    Cnossen, Arjen; Hou, Lili; Pollard, Michael M.; Wesenhagen, Philana V.; Browne, Wesley R.; Feringa, Ben L.

    2012-01-01

    Driving molecular rotary motors using visible light (530-550 nm) instead of UV light was achieved using palladium tetraphenylporphyrin as a triplet sensitizer. Visible light driven rotation was confirmed by UV/vis absorption, circular dichroism and H-1 NMR spectroscopy and the rotation was confirmed

  10. UV-Vis spectroscopy of tyrosine side-groups in studies of protein structure. Part 2: selected applications.

    Science.gov (United States)

    Antosiewicz, Jan M; Shugar, David

    2016-06-01

    In Part 2 we discuss application of several different types of UV-Vis spectroscopy, such as normal, difference, and second-derivative UV absorption spectroscopy, fluorescence spectroscopy, linear and circular dichroism spectroscopy, and Raman spectroscopy, of the side-chain of tyrosine residues in different molecular environments. We review the ways these spectroscopies can be used to probe complex protein structures.

  11. UV-Vis spectroscopy of tyrosine side-groups in studies of protein structure. Part 1: basic principles and properties of tyrosine chromophore.

    Science.gov (United States)

    Antosiewicz, Jan M; Shugar, David

    2016-06-01

    Spectroscopic properties of tyrosine residues may be employed in structural studies of proteins. Here we discuss several different types of UV-Vis spectroscopy, like normal, difference and second-derivative UV absorption spectroscopy, fluorescence spectroscopy, linear and circular dichroism spectroscopy, and Raman spectroscopy, and corresponding optical properties of the tyrosine chromophore, phenol, which are used to study protein structure.

  12. Photoorientation of a liquid crystalline polyester with azobenzene side groups

    DEFF Research Database (Denmark)

    Zebger, I; Rutloh, M; Hoffmann, U

    2002-01-01

    segments in the side- and main-chain. The very high values of the normalized linear dichroism up to 0.8 and the birefringence (above 0.3) are due to the interaction of photoorientation and thermotropic self-organization. The induction of anisotropy shows a pronounced dependence on the power density...

  13. The characterization of a novel S100A1 binding site in the N-terminus of TRPM1

    Czech Academy of Sciences Publication Activity Database

    Jirků, M.; Lánský, Z.; Bednárová, Lucie; Šulc, M.; Monincová, Lenka; Majer, Pavel; Vyklický, L.; Vondrášek, Jiří; Teisinger, J.; Boušová, Kristýna

    2016-01-01

    Roč. 78, Sep (2016), s. 186-193 ISSN 1357-2725 Institutional support: RVO:61388963 Keywords : TRPM1 channel * binding site * calcium-binding protein S100A1 * steady-state fluorescence anisotropy * molecular modeling * circular dichroism Subject RIV: CE - Biochemistry Impact factor: 3.505, year: 2016

  14. Cation-pi interaction of Ag+ with [6]helicene: An experimental and theoretical study

    Czech Academy of Sciences Publication Activity Database

    Makrlík, E.; Jaklová Dytrtová, Jana; Vaňura, P.; Sýkora, Jan; Církva, Vladimír; Storch, Jan

    2015-01-01

    Roč. 633, Jul 16 (2015), s. 105-108 ISSN 0009-2614 R&D Projects: GA ČR GP13-21409P; GA ČR GAP207/10/1124 Institutional support: RVO:61388963 ; RVO:67985858 Keywords : circular dichroism * amino acids * gas-phase Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.860, year: 2015

  15. Uranyl complexes of glutathione

    Energy Technology Data Exchange (ETDEWEB)

    Marzotto, A [Consiglio Nazionale delle Ricerche, Padua (Italy). Lab. di Chimica e Tecnologia dei Radioelementi

    1977-01-01

    Dioxouranium(VI) complexes of the tripeptide glutathione having different molar ratios were prepared and studied by IR, PMR, electronic absorption and circular dichroism spectra. The results indicate that coordination occurs at the carboxylato groups, acting as monodentate ligands, whereas no significant interaction with the amino and sulfhydrylic groups takes place.

  16. Cooperative use of VCD and XRD for the determination of tetrahydrobenzoisoquinolines absolute configuration: a reliable proof of memory of chirality and retention of configuration in enediyne rearrangements.

    Science.gov (United States)

    Mondal, Shovan; Naubron, Jean-Valère; Campolo, Damien; Giorgi, Michel; Bertrand, Michéle P; Nechab, Malek

    2013-12-01

    The absolute configurations (AC) of azaheterocylic compounds resulting from the cascade rearrangement of enediynes involving only light atoms were unambiguously assigned by the joint use of vibrational circular dichroism (VCD) and copper radiation single crystal X-ray diffraction (XRD). These AC determinations proved that the rearrangements of enediynes proceeded with memory of chirality and retention of configuration. © 2013 Wiley Periodicals, Inc.

  17. Sensitive Electrochemical Detection of Native and Aggregated x-Synuclein Protein Involved in Parkinson's Disease

    NARCIS (Netherlands)

    Masarik, Michal; Stobiecka, Agata; Kizek, René; Jelen, Frantisek; Pechan, Zdenk; Hoyer, Wolfgang; Subramaniam, Vinod; Palecek, Emil

    2004-01-01

    The aggregation of α-synuclein, a 14 kDa protein, is involved in several human neurodegenerative disorders, including Parkinson's disease. We studied native and in vitro aggregated α-synuclein by circular dichroism (CD), atomic force microscopy (AFM) and electrochemical methods. We used constant

  18. Optical properties of helical cylindrical molecular aggregates : the homogeneous limit

    NARCIS (Netherlands)

    Didraga, C.; Klugkist, J.A.; Knoester, J.

    2002-01-01

    Using a Frenkel exciton model, we study the optical absorption spectrum and linear and circular dichroism (CD) spectra of cylindrical molecular aggregates. We demonstrate that such aggregates can always be described as a stack of molecular rings with nearest-neighbor rings rotated relative to each

  19. Characterization of linear forms of the circular enterocin AS-48 obtained by limited proteolysis

    NARCIS (Netherlands)

    Montalbán-López, Manuel; Spolaore, Barbara; Pinato, Odra; Martínez-Bueno, Manuel; Valdivia, Eva; Maqueda, Mercedes; Fontana, Angelo

    2008-01-01

    AS-48 is a 70-residue circular peptide from Enterococcus faecalis with a broad antibacterial activity. Here, we produced by limited proteolysis a protein species carrying a single nicking and fragments of 55 and 38 residues. Nicked AS-48 showed a lower helicity by far-ultraviolet circular dichroism

  20. Enforcing multifunctionality: a pressure-induced spin-crossover photomagnet

    Czech Academy of Sciences Publication Activity Database

    Pinkowicz, D.; Rams, M.; Míšek, Martin; Kamenev, K. V.; Tomkowiak, H.; Katrusiak, A.; Sieklucka, B.

    2015-01-01

    Roč. 137, č. 27 (2015), 8795-8802 ISSN 0002-7863 Institutional support: RVO:68378271 Keywords : single-molecule magnet * electron-transfer * chiral dichroism * rational design * light * complex * transition * cyanide * magnet ization * absorption Subject RIV: BM - Solid Matter Physics ; Magnet ism Impact factor: 13.038, year: 2015

  1. Preparation and characterization of insulin-surfactant complexes for loading into lipid-based drug delivery systems

    DEFF Research Database (Denmark)

    Li, Ping; Nielsen, Hanne Mørck; Fano, Mathias

    2013-01-01

    of surfactants, but also a nonnative secondary structure in the solid state. Finally, circular dichroism analysis of rehydrated complexes showed that the processing did not irreversibly alter the secondary structure of insulin. In short, the present study demonstrates changes in the secondary structure...

  2. Photochromism and polarization spectroscopy of p-methylthiobenzoylacetone

    DEFF Research Database (Denmark)

    Gorski, Alexander; Posokhov, Yevgen; Hansen, Bjarke Knud Vilster

    2006-01-01

    achieved by using irradiation wavelengths corresponding to differently polarized electronic transitions. This was followed by measurements of linear dichroism (LD) in the IR region. The analysis of the IR spectra, combined with the results of DFT B3LYP/cc-pVDZ calculations enabled determining...

  3. A configurational and conformational study of aframodial and its diasteriomers via experimental and theoretical VA and VCD spectroscopies

    DEFF Research Database (Denmark)

    Jalkanen, Karl J.; Gale, J.D.; Lassen, Peter Rygaard

    2008-01-01

    In this work we present the experimental and theoretical vibrational absorption (VA) and the theoretical vibrational circular dichroism (VCD) spectra for aframodial. In addition, we present the theoretical VA and VCD spectra for the diasteriomers of aframodial. Aframodial has four chiral centers ...

  4. Conformational studies of peptides representing a segment of TM7 from Vo-H+-V-ATPase in SDS micelles

    NARCIS (Netherlands)

    Duarte, A.M.; Jong, de E.R.; Koehorst, R.B.M.; Hemminga, M.A.

    2010-01-01

    The conformation of a transmembrane peptide, sMTM7, encompassing the cytoplasmic hemi-channel domain of the seventh transmembrane section of subunit a from V-ATPase from Saccharomyces cerevisiae solubilized in SDS solutions was studied by circular dichroism (CD) spectroscopy and fluorescence

  5. Local magnetism in rare-earth metals encapsulated in fullerenes

    NARCIS (Netherlands)

    De Nadai, C; Mirone, A; Dhesi, SS; Bencok, P; Brookes, NB; Marenne, [No Value; Rudolf, P; Tagmatarchis, N; Shinohara, H; Dennis, TJS; Marenne, I.; Nadaï, C. De

    Local magnetic properties of rare-earth (RE) atoms encapsulated in fullerenes have been characterized using x-ray magnetic circular dichroism and x-ray absorption spectroscopy (XAS). The orbital and spin contributions of the magnetic moment have been determined through sum rules and theoretical

  6. DNA psi-condensation and reentrant decondensation: Effect of the PEG degree of polymerization

    NARCIS (Netherlands)

    Ramos, J.E.B.; Vries, de R.J.; Neto, J.R.

    2005-01-01

    ¿-Condensation of DNA fragments of about 4 kbp was induced by poly(ethylene glycol) (PEG), with degrees of polymerization ranging from 45 to 182, and univalent salt (NaCl). Using circular dichroism spectroscopy, we were able to accurately determine the critical amount of PEG needed to induce

  7. CD spectroscopy of proteins adsorbed at flat hydrophilic quartz and hydrophobic Teflon surfaces

    NARCIS (Netherlands)

    Vermeer, AWP; Norde, W

    2000-01-01

    Spectroscopic methods provide a powerful tool for studying the properties of proteins at interfaces. The protein accumulated in one adsorbed layer is frequently less than the minimum mass of protein required by a detection method. In such a case las is the case in circular dichroism spectroscopy)

  8. Reciprocal and real space maps for EMCD experiments

    Czech Academy of Sciences Publication Activity Database

    Lidbaum, H.; Rusz, Ján; Rubino, S.; Liebig, A.; Hjörvarsson, B.; Oppeneer, P.M.; Eriksson, A.; Leifer, K.

    2010-01-01

    Roč. 110, č. 11 (2010), s. 1380-1389 ISSN 0304-3991 Institutional research plan: CEZ:AV0Z10100520 Keywords : magnetic circular dichroism * electron energy-loss spectra * transmission electron microscopy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.061, year: 2010

  9. A new amyloidosis caused by fibrillar aggregates of mutated corneodesmosin

    DEFF Research Database (Denmark)

    Caubet, Cécile; Bousset, Luc; Clemmensen, Ole

    2010-01-01

    with circular dichroism measurements. This identifies HSS as a human amyloidosis related to the aggregation of natively unfolded (mut)CDSN polypeptides into amyloid fibrils.-Caubet, C., Bousset, L., Clemmensen, O., Sourigues, Y., Bygum, A., Chavanas, S., Coudane, F., Hsu, C.-Y., Betz, R. C., Melki, R., Simon, M...

  10. Functional and Structural Characterization of Novel Type of Linker Connecting Capsid and Nucleocapsid Protein Domains in Murine Leukemia Virus

    Czech Academy of Sciences Publication Activity Database

    Doležal, Michal; Hadravová, Romana; Kožíšek, Milan; Bednárová, Lucie; Langerová, H.; Ruml, T.; Rumlová, Michaela

    2016-01-01

    Roč. 291, č. 39 (2016), s. 20630-20642 ISSN 0021-9258 R&D Projects: GA ČR(CZ) GA14-15326S; GA MŠk LO1302 Institutional support: RVO:61388963 Keywords : circular dichroism (CD) * electron microscopy (EM) * nuclear magnetic resonance (NMR) * retrovirus * virus assembly Subject RIV: CE - Biochemistry Impact factor: 4.125, year: 2016

  11. A comparative study of MP2, B3LYP, RHF and SCC-DFTB force fields in predicting the vibrational spectra of N-acetyl-L-alanine-N'-methyl amide: VA and VCD spectra

    DEFF Research Database (Denmark)

    Bohr, Henrik; Jalkanen, Karl J.; Elstner, M.

    1999-01-01

    dichroism (VCD) spectra of NALANMA. We have utilised MP2/6-31G*, B3LYP/6-31G*, RHF/6-31G* and SCC-DFTB level theory to determine the geometries and Hessians, atomic polar tensors (APT) and atomic axial tensors (AAT) which are required for simulating the VA and VCD spectra. We have also calculated the AAT...

  12. Exciton modeling of energy-transfer dynamics in the LHCII complex of higher plants: a Redfield theory approach

    NARCIS (Netherlands)

    Novoderezhkin, V.; Salverda, J.M.; Amerongen, van H.; Grondelle, van R.

    2003-01-01

    We propose an exciton model for the peripheral plant light-harvesting complex LHCII that allows us to explain the absorption (OD) and linear dichroism (LD) spectra, the superradiance (SR), the pump-probe transient absorption (TA), the three-pulse photon echo peak shift (3PEPS), and transient grating

  13. Exciton modeling of energy-transfer dynamics in the LHCII complex of higher plants: A redfield theory approach

    NARCIS (Netherlands)

    Novoderezhkin, V.; Salverda, J.M.; van Amerongen, H.; van Grondelle, R.

    2003-01-01

    We propose an exciton model for the peripheral plant light-harvesting complex LHCII that allows us to explain the absorption (OD) and linear dichroism (LD) spectra, the superradiance (SR), the pump-probe transient absorption (TA), the three-pulse photon echo peak shift (3PEPS), and transient grating

  14. A Combined Experimental-Computational Investigation to Uncover the Puzzling (Chiro-)optical Response of Pyridocyclophanes: One- and Two-Photon Spectra

    Czech Academy of Sciences Publication Activity Database

    Padula, Daniele; Lahoz, I. R.; Díaz, C.; Hernández, F. E.; Di Bari, L.; Rizzo, A.; Santoro, F.; Cid, M. M.

    2015-01-01

    Roč. 21, č. 34 (2015), s. 12136-12147 ISSN 0947-6539 Institutional support: RVO:61388963 Keywords : chirality * conformation analysis * circular dichroism * density functional calculations * quantum chemistry Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 5.771, year: 2015

  15. Anisotropy of Wood in the Microwave Region

    Science.gov (United States)

    Ziherl, Sasa; Bajc, Jurij; Urankar, Bernarda; Cepic, Mojca

    2010-01-01

    Wood is transparent for microwaves and due to its anisotropic structure has anisotropic dielectric properties. A laboratory experiment that allows for the qualitative demonstration and quantitative measurements of linear dichroism and birefringence in the microwave region is presented. As the proposed experiments are based on the anisotropy (of…

  16. The chiroptical properties of chiral substituted poly[3-((3S)-3,7-dimethyloctyl)thiophene] as a function of film thickness

    NARCIS (Netherlands)

    Lakhwani, G.; Koeckelberghs, G.; Meskers, S.C.J.; Janssen, R.A.J.

    2007-01-01

    Circular dichroism (CD) and circular polarization of the luminescence (CPL) of spin coated films of chiral, regioregular poly[3-((3S)-3,7-dimethyloctyl)thiophene] are investigated as a function of their thickness (50–500 nm). The dissymmetry factors for absorption (gabs) and emission (glum) do not

  17. Multimerization rules for G-quadruplexes

    Czech Academy of Sciences Publication Activity Database

    Kolesnikova, Sofia; Hubálek, Martin; Bednárová, Lucie; Cvačka, Josef; Curtis, Edward A.

    2017-01-01

    Roč. 45, č. 15 (2017), s. 8684-8696 ISSN 0305-1048 Institutional support: RVO:61388963 Keywords : tetramolecular G-quadruplexes * RNA G-quadruplexes * circular dichroism Subject RIV: CE - Biochemistry OBOR OECD: Biochemistry and molecular biology Impact factor: 10.162, year: 2016 https://academic.oup.com/nar/article/45/15/8684/4002725/Multimerization-rules-for-Gquadruplexes

  18. On the nature of non-covalent interactions in isomers of 2,5-dichloro-1,4-benzoquinone dimers - ground- and excited-state properties

    Czech Academy of Sciences Publication Activity Database

    Pandiyan, B. V.; Deepa, Palanisamy; Kolandaivel, P.

    2014-01-01

    Roč. 16, č. 37 (2014), s. 19928-19940 ISSN 1463-9076 Institutional support: RVO:61388963 Keywords : hydrogen bonding interactions * density functional theory * circular dichroism Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 4.493, year: 2014

  19. Effects of PEG size on structure, function and stability of PEGylated BSA

    DEFF Research Database (Denmark)

    Plesner, Bitten; Fee, Conan J.; Westh, Peter

    2011-01-01

    The effects of PEGylation on the structural, thermal and functional stability of bovine serum albumin (BSA) were investigated using BSA and 6 linear mono-PEGylated BSA compounds. The secondary and tertiary structure of BSA measured by circular dichroism (CD) was independent of PEGylation. In cont...

  20. New algorithm for efficient Bloch-waves calculations of orientation-sensitive ELNES

    Czech Academy of Sciences Publication Activity Database

    Rusz, Ján; Muto, S.; Tatsumi, K.

    2013-01-01

    Roč. 125, Feb (2013), s. 81-88 ISSN 0304-3991 Institutional support: RVO:68378271 Keywords : transmission electron microscopy * density functional theory * dynamical diffraction theory * Bloch waves * electron magnetic circular dichroism Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.745, year: 2013

  1. Electronic Transitions in Conformationally Controlled Peralkylated Hexasilanes

    Czech Academy of Sciences Publication Activity Database

    Kanazawa, Y.; Tsuji, H.; Ehara, M.; Fukuda, R.; Casher, D. L.; Tamao, K.; Nakatsuji, H.; Michl, Josef

    2016-01-01

    Roč. 17, č. 19 (2016), s. 3010-3022 ISSN 1439-4235 Institutional support: RVO:61388963 Keywords : configuration interaction * density functional calculations * magnetic circular dichroism * oligosilanes * UV/Vis spectroscopy Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.075, year: 2016

  2. Measurements of temperature dependence of 'localized susceptibility'

    CERN Document Server

    Shiozawa, H; Ishii, H; Takayama, Y; Obu, K; Muro, T; Saitoh, Y; Matsuda, T D; Sugawara, H; Sato, H

    2003-01-01

    The magnetic susceptibility of some rare-earth compounds is estimated by measuring magnetic circular dichroism (MCD) of rare-earth 3d-4f absorption spectra. The temperature dependence of the magnetic susceptibility obtained by the MCD measurement is remarkably different from the bulk susceptibility in most samples, which is attributed to the strong site selectivity of the core MCD measurement.

  3. The VA and VCD spectra of various isotopomers of L-alanine in aqueous solution

    DEFF Research Database (Denmark)

    Abdali, Salim; Jalkanen, Karl J.; Bohr, Henrik

    2002-01-01

    Density functional theory (DFT) at the Becke 3LYP level has been used to calculate the vibrational absorption (VA) and vibrational circular dichroism (VCD) spectra of various deuterated species Of L-alanine. The effect of replacing the methine hydrogen, CH1, the methyl group, CH3, and both...

  4. Optical spectroscopic studies of L-alanyl-L-alanine

    Czech Academy of Sciences Publication Activity Database

    Šebek, Jiří; Gyurcsik, B.; Kapitán, Josef; Šebestík, Jaroslav; Bouř, Petr

    2007-01-01

    Roč. 14, č. 1 (2007), s. 45-45 ISSN 1211-5894. [Discussions in Structural Molecular Biology /6./. 29.03.2007-31.03.2007, Nové Hrady] Institutional research plan: CEZ:AV0Z40550506 Keywords : Ala-Ala * vibrational circular dichroism * Raman optical activity * peptides Subject RIV: CF - Physical ; Theoretical Chemistry

  5. Cationic oligopeptides with the repeating sequence L-Lysyl-L-alanyl-L-alanine: conformational and thermal stability stuydy using optical spectroscopic methods

    Czech Academy of Sciences Publication Activity Database

    Setnička, V.; Hlaváček, Jan; Urbanová, J.

    2009-01-01

    Roč. 15, č. 8 (2009), s. 533-539 ISSN 1075-2617 Institutional research plan: CEZ:AV0Z40550506 Keywords : cationic peptides * conformation * thermal stability * vibrational circular dichroism Subject RIV: CC - Organic Chemistry Impact factor: 1.807, year: 2009

  6. Linear response properties required to simulate vibrational spectra of biomolecules in various media: (R)-phenyloxirane (A comparative theoretical and spectroscopic vibrational study)

    DEFF Research Database (Denmark)

    Jalkanen, Karl J.; Jürgensen, Vibeke Würtz; Degtyarenko, I.M.

    2005-01-01

    We here present a combined VA, VCD, Raman and ROA vibrational study of phenyloxirane. We have simulated the vibrational absorption (VA), also called IR, vibrational circular dichroism (VCD), Raman scattering and Raman optical activity (ROA) intensities utilizing the density functional theory (DFT...

  7. Investigation of the effects of different carotenoids on the absorption and CD signals of light harvesting 1 complexes

    NARCIS (Netherlands)

    Georgakopoulou, S.; van der Zwan, G.; Olsen, J.D.; Hunter, C.N.; Niederman, R.A.; van Grondelle, R.

    2006-01-01

    Absorption and circular dichroism (CD) spectra of light-harvesting (LH)1 complexes from the purple bacteria Rhodobacter (Rba.) sphaeroides and Rhodospirillum (Rsp.) rubrum are presented. The complexes exhibit very low intensity, highly nonconservative, near-infrared (NIR) CD spectra. Absorption and

  8. Conformational study of melectin and antapin antimicrobial peptides in model membrane environments

    Czech Academy of Sciences Publication Activity Database

    Kocourková, L.; Novotná, P.; Čujová, Sabína; Čeřovský, Václav; Urbanová, M.; Setnička, V.

    2017-01-01

    Roč. 170, Jan 5 (2017), s. 247-255 ISSN 1386-1425 Institutional support: RVO:61388963 Keywords : antimicrobial peptides * conformation * liposomes * model membranes * circular dichroism * infrared spectroscopy Subject RIV: CB - Analytical Chemistry, Separation OBOR OECD: Analytical chemistry Impact factor: 2.536, year: 2016

  9. Intramolecular hydrogen bonding

    DEFF Research Database (Denmark)

    Hansen, Bjarke Knud Vilster; Winther, Morten; Spanget-Larsen, Jens

    2006-01-01

    The vibrational structure of the title compound (DBM) was investigated by FTIR spectroscopy in liquid solutions, by FTIR linear dichroism (LD) measurements, and by Raman spectroscopy. The results were supported by the application of theoretical model calculations and analyzed with particular atte...

  10. Ultrathin Limit of Exchange Bias Coupling at Oxide Multiferroic/Ferromagnetic Interfaces

    NARCIS (Netherlands)

    Huijben, Mark; Yu, P.; Martin, L.W.; Molegraaf, Hajo; Chu, Y.H.; Holcomb, M.B.; Balke, N.; Rijnders, Augustinus J.H.M.; Ramesh, R.

    2013-01-01

    Exchange bias coupling at the multiferroic- ferromagnetic interface in BiFeO3/La0.7Sr0.3MnO3 heterostructures exhibits a critical thickness for ultrathin BiFeO3 layers of 5 unit cells (2 nm). Linear dichroism measurements demonstrate the dependence on the BiFeO3 layer thickness with a strong

  11. A partially folded intermediate species of the β-sheet protein apo-pseudoazurin ism trapped during proline-limited folding

    NARCIS (Netherlands)

    Reader, J.S.; van Nuland, N.A.J.; Thompson, G.S.; Ferguson, S.J.; Dobson, C.M.; Radford, S.E.

    2001-01-01

    The folding of apo-pseudoazurin, a 123-residue, predominantly -sheet protein with a complex Greek key topology, has been investigated using several biophysical techniques. Kinetic analysis of refolding using farand near-ultraviolet circular dichroism (UV CD) shows that the protein folds slowly to

  12. Orientation of the pigment molecules in the chloroplast

    NARCIS (Netherlands)

    Goedheer, J.C.

    1955-01-01

    Dichroism, absorption anisotropy, and anomal dispersion of birefringence were measured in the big lamellate chloroplasts of Mougeotia. The results of these measurements indicate a certain orientation of the chlorophyll molecules, and to a smaller extent, of the carotenoids in the chloroplast. In

  13. Nonplanar Tertiary Amides in Rigid Chiral Tricyclic Dilactams. Peptide Group Distortions and Vibrational Optical Activity

    Czech Academy of Sciences Publication Activity Database

    Pazderková, Markéta; Profant, V.; Hodačová, J.; Šebestík, Jaroslav; Pazderka, T.; Novotná, P.; Urbanová, M.; Šafařík, Martin; Buděšínský, Miloš; Tichý, Miloš; Bednárová, Lucie; Baumruk, V.; Maloň, Petr

    2013-01-01

    Roč. 117, č. 33 (2013), s. 9626-9642 ISSN 1520-6106 R&D Projects: GA ČR GAP205/10/1276 Institutional support: RVO:61388963 Keywords : spirodilactams * amide bond * vibrational circular dichroism * non-planarity * Raman optical activity Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.377, year: 2013

  14. Optical Properties of Helical Cylindrical Molecular Aggregates : The Homogeneous Limit

    NARCIS (Netherlands)

    Didraga, Cătălin; Klugkist, Joost A.; Knoester, Jasper

    2002-01-01

    Using a Frenkel exciton model, we study the optical absorption spectrum and linear and circular dichroism (CD) spectra of cylindrical molecular aggregates. We demonstrate that such aggregates can always be described as a stack of molecular rings with nearest-neighbor rings rotated relative to each

  15. Gauge-Origin Independent Formulation and Implementation of Magneto-Optical Activity within Atomic-Orbital-Density Based Hartree-Fock and Kohn-Sham Response Theories

    DEFF Research Database (Denmark)

    Kjærgaard, Thomas; Jørgensen, Poul; Thorvaldsen, Andreas

    2009-01-01

    A Lagrangian approach has been used to derive gauge-origin independent expressions for two properties that rationalize magneto-optical activity, namely the Verdet constant V(ω) of the Faraday effect and the B term of magnetic circular dichroism. The approach is expressed in terms of an atomic-orb...

  16. The role of albumin conformation in the binding of diazepam to human serum albumin

    NARCIS (Netherlands)

    Wilting, J.; Hart, B.J. 't; Gier, J.J. de

    2006-01-01

    The effect of hydrogen, chloride and calcium ions on the binding of diazepare to human serum albumin has been studied by circular dichroism and equilibrium dialysis. In all cases the molar ellipticity of the diazepam-albumin complex increases with pH over the pH range 5 to 9. Under these

  17. Journal of Chemical Sciences | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    Interaction of cyclodextrins (CDs) with the two most abundant proteins, namely human serum albumin (HSA) and bovine serum albumin (BSA), has been investigated using steady-state and time-resolved fluorometric techniques, circular dichroism measurements and molecular docking simulation. The study reveals that the ...

  18. Location and characterization of the warfarin binding site of human serum albumin A comparative study of two large fragments

    NARCIS (Netherlands)

    Bos, O.J.M.; Remijn, J.P.M.; Fischer, M.J.E.; Wilting, J.; Janssen, L.H.M.

    1988-01-01

    The warfarin binding behaviour of a large tryptic fragment (residues 198–585 which comprise domains two and three) and of a large peptic fragment (residues 1–387 which comprise domains one and two) of human serum albumin has been studied by circular dichroism and equilibrium dialysis in order to

  19. Enhanced thermal stability of the thylakoid membranes from spruce. A comparison with selected angiosperms

    Czech Academy of Sciences Publication Activity Database

    Karlický, Václav; Kurasová, Irena; Ptáčková, B.; Večeřová, Kristýna; Urban, Otmar; Špunda, Vladimír

    2016-01-01

    Roč. 130, 1-3 (2016), s. 357-371 ISSN 0166-8595 R&D Projects: GA MŠk(CZ) LO1415; GA ČR GA13-28093S Institutional support: RVO:67179843 Keywords : Norway spruce * Thermal stability * Circular dichroism * Photosystem II organization * Thylakoid membrane Subject RIV: ED - Physiology Impact factor: 3.864, year: 2016

  20. Local electronic structure information contained in energy-filtered diffraction patterns

    Czech Academy of Sciences Publication Activity Database

    Rusz, Ján; Rubino, S.; Eriksson, O.; Oppeneer, P.M.; Leifer, K.

    2011-01-01

    Roč. 84, č. 6 (2011), "064444-1"-"064444-7" ISSN 1098-0121 Institutional research plan: CEZ:AV0Z10100521 Keywords : ray circular-dichroism * microscope Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.691, year: 2011

  1. Dipole-Assisted Self-Assembly of Light-Emitting p-nP Needles on Mica

    DEFF Research Database (Denmark)

    Balzer, Frank; Rubahn, Horst-Günter

    2001-01-01

    molecules oriented along the direction of microscopic dipoles on the mica surface. They have submicrometer cross-sectional dimensions and lengths as large as millimeters. Moreover, due to the strong dipole confinement of individual molecules, the needles form large domains with parallel oriented entities....... A pronounced optical dichroism agrees with the findings from LEED....

  2. The fragile X chromosome (GCC) repeat folds into a DNA tetraplex at neutral pH

    Czech Academy of Sciences Publication Activity Database

    Fojtík, Petr; Vorlíčková, Michaela

    2001-01-01

    Roč. 29, č. 22 (2001), s. 4684-4690 ISSN 0305-1048 R&D Projects: GA ČR GA204/01/0561 Institutional research plan: CEZ:AV0Z5004920 Keywords : Parallel-stranded DNA * circular dichroism spectroscopy Subject RIV: BO - Biophysics Impact factor: 6.373, year: 2001

  3. Response function for the characterization of photo-induced anisotropy in azobenzene containing polymers

    DEFF Research Database (Denmark)

    Sajti, S.; Kerekes, Á.; Ramanujam, P.S.

    2002-01-01

    A response function is derived for the description of photo-induced birefringence and dichroism in case of materials where the underlying process is photo-isomerization. Our result explains the usefulness of the theoretical formulae derived earlier by Kakichashvili for photo-anisotropic materials...

  4. Enantiomeric resolution and X-ray optical activity of a tricobalt extended metal atom chain† †Electronic supplementary information (ESI) available: Bond distances and angles for 2 and 3, thermal ellipsoid plots, packing diagrams, PXRD data, magnetization curves, thermogravimetric analysis, and additional XNCD and XMCD plots and CD spectra. CCDC 1574514–1574516 and 1588703. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c7sc04131d

    Science.gov (United States)

    Srinivasan, Anandi; Cortijo, Miguel; Bulicanu, Vladimir; Naim, Ahmad; Clérac, Rodolphe; Rogalev, Andrei; Wilhelm, Fabrice; Rosa, Patrick

    2017-01-01

    A simple procedure based on anion exchange was employed for the enantiomeric resolution of the extended metal atom chain (EMAC) [Co3(dpa)4(MeCN)2]2+. Use of the chiral salt (NBu4)2[As2(tartrate)2], (Λ-1 or Δ-1), resulted in the selective crystallization of the EMAC enantiomers as [Δ-Co3(dpa)4(MeCN)2](NBu4)2[Λ-As2(tartarte)2]2, (Δ-2) and [Λ-Co3(dpa)4(MeCN)2](NBu4)2[Δ-As2(tartrate)2]2 (Λ-2), respectively, in the P4212 space group, whereas a racemic mixture of 1 yielded [Co3(dpa)4(MeCN)2][As2(tartrate)2]·2MeCN (rac-3), which crystallized in the C2/c space group. The local electronic and magnetic structure of the EMAC enantiomers was studied, exploiting a variety of dichroisms in single crystals. A strong linear dichroism at the Co K-edge was observed in the orthoaxial configuration, whereas it vanished in the axial orientation, thus spectroscopically confirming the D4 crystal symmetry. Compounds Δ-2 and Λ-2 are shown to be enantiopure materials as evidenced by mirror-image natural circular dichroism spectra in the UV/vis in solution and in the X-ray range at the Co K-edge in single crystals. The surprising absence of detectable X-ray magnetic circular dichroism or X-ray magnetochiral dichroism signals at the Co K-edge, even at low temperature (3 K) and a high magnetic field (17 T), is ascribed to a strongly delocalized spin density on the tricobalt core. PMID:29675158

  5. Determination of the Fe magnetic anisotropies and the CoO frozen spins in epitaxial CoO/Fe/Ag(001)

    Energy Technology Data Exchange (ETDEWEB)

    Meng, J. Li, Y.; Park, J. S.; Jenkins, C. A.; Arenholz, E.; Scholl, A.; Tan, A.; Son, H.; Zhao, H. W.; Hwang, Chanyong; Qiu, Z. Q.

    2011-04-28

    CoO/Fe/Ag(001) films were grown epitaxially and studied by X-ray Magnetic Circular Dichroism (XMCD) and X-ray Magnetic Linear Dichroism (XMLD). After field cooling along the Fe[100] axis to 80 K, exchange bias, uniaxial anisotropy, and 4-fold anisotropy of the films were determined by hysteresis loop and XMCD measurements by rotating the Fe magnetization within the film plane. The CoO frozen spins were determined by XMLD measurement as a function of CoO thickness.We find that among the exchange bias, uniaxial anisotropy, and 4-fold anisotropy, only the uniaxial magnetic anisotropy follows thickness dependence of the CoO frozen spins.

  6. Absorption spectra of adenocarcinoma and squamous cell carcinoma cervical tissues

    Science.gov (United States)

    Ivashko, Pavlo; Peresunko, Olexander; Zelinska, Natalia; Alonova, Marina

    2014-08-01

    We studied a methods of assessment of a connective tissue of cervix in terms of specific volume of fibrous component and an optical density of staining of connective tissue fibers in the stroma of squamous cancer and cervix adenocarcinoma. An absorption spectra of blood plasma of the patients suffering from squamous cancer and cervix adenocarcinoma both before the surgery and in postsurgical periods were obtained. Linear dichroism measurements transmittance in polarized light at different orientations of the polarization plane relative to the direction of the dominant orientation in the structure of the sample of biotissues of stroma of squamous cancer and cervix adenocarcinoma were carried. Results of the investigation of the tumor tissues showed that the magnitude of the linear dichroism Δ is insignificant in the researched spectral range λ=280-840 nm and specific regularities in its change observed short-wave ranges.

  7. Searching for Models Exhibiting High Circularly Polarized Luminescence: the Electroactive Inherently Chiral Oligothiophenes.

    Science.gov (United States)

    Benincori, Tiziana; Appoloni, Giulio; Mussini, Patrizia Romana; Arnaboldi, Serena; Cirilli, Roberto; Quartapelle Procopio, Elsa; Panigati, Monica; Abbate, Sergio; Mazzeo, Giuseppe; Longhi, Giovanna

    2018-05-02

    Two new inherently chiral oligothiophenes characterized by the atropisomeric 3,3'-bithianaphtene scaffold functionalized with fused ring bithiophene derivatives, namely 4H-cyclopenta [2,1-b3:4b']dithiophene (CPDT) and dithieno[3,3-b:2',3'-d]pyrrole (DTP), were synthesized. The racemates were fully characterized and resolved into antipodes by enantioselective HPLC. The enantiomers were analyzed through different chiroptical techniques: electronic circular dichroism (ECD) and vibrational circular dichroism (VCD) were employed to attribute the absolute configuration (AC). Comparison of experimental and calculated VCD spectra confirmed the DFT calculated conformational characteristics. The compound functionalized with two CPDT units was oxidized with FeCl3 and ECD and CPL of the resulting material were measured. Circularly Polarized Luminescence (CPL) was measured in order to verify if inherently chiral oligothiophenes could be promising systems for chiral photonics applications. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Competing effects in the magnetic polarization of non-magnetic atoms

    International Nuclear Information System (INIS)

    Boada, R; Piquer, C; Chaboy, J; Laguna-Marco, M A

    2013-01-01

    The magnetic polarization of the Lu 5d states through the Ho 1-x Lu x (Fe 1-y Al y ) 2 series has been studied by means of x-ray magnetic circular dichroism. A combined study of the dichroic signals performed at the Fe K-, Ho L 2 - and Lu L 2,3 -edges gives a complete picture of the polarization scheme at the conduction band. The results show that in the presence of competing localized magnetic moments, μ Fe (3d) and μ Ho (4f), the dichroic signal at the Lu site is mainly due to the Fe atoms, the effect of the magnetic rare-earth being negligible. Estimation of the spin and orbital components of the Lu(5d) induced magnetic moment have been obtained by applying the magneto-optical sum rules derived for x-ray magnetic circular dichroism.

  9. A Single Chiroptical Spectroscopic Method May Not Be Able To Establish the Absolute Configurations of Diastereomers: Dimethylesters of Hibiscus and Garcinia Acids

    Science.gov (United States)

    Polavarapu, Prasad L.; Donahue, Emily A.; Shanmugam, Ganesh; Scalmani, Giovanni; Hawkins, Edward K.; Rizzo, Carmelo; Ibnusaud, Ibrahim; Thomas, Grace; Habel, Deenamma; Sebastian, Dellamol

    2013-01-01

    Electronic circular dichroism (ECD), optical rotatory dispersion (ORD), and vibrational circular dichroism (VCD) spectra of hibiscus acid dimethyl ester have been measured and analyzed in combination with quantum chemical calculations of corresponding spectra. These results, along with those reported previously for garcinia acid dimethyl ester, reveal that none of these three (ECD, ORD, or VCD) spectroscopic methods, in isolation, can unequivocally establish the absolute configurations of diastereomers. This deficiency is eliminated when a combined spectral analysis of either ECD and VCD or ORD and VCD methods is used. It is also found that the ambiguities in the assignment of absolute configurations of diastereomers may also be overcome when unpolarized vibrational absorption is included in the spectral analysis. PMID:21568330

  10. High-resolution magnetic-domain imaging by Fourier transform holography at 21 nm wavelength

    International Nuclear Information System (INIS)

    Schaffert, Stefan; Pfau, Bastian; Günther, Christian M; Schneider, Michael; Korff Schmising, Clemens von; Eisebitt, Stefan; Geilhufe, Jan

    2013-01-01

    Exploiting x-ray magnetic circular dichroism at the L-edges of 3d transition metals, Fourier transform holography has become a standard technique to investigate magnetic samples with sub-100 nm spatial resolution. Here, magnetic imaging in the 21 nm wavelength regime using M-edge circular dichroism is demonstrated. Ultrafast pulses in this wavelength regime are increasingly available from both laser- and accelerator-driven soft x-ray sources. We explain the adaptations concerning sample preparation and data evaluation compared to conventional holography in the 1 nm wavelength range. We find the correction of the Fourier transform hologram to in-plane Fourier components to be critical for high-quality reconstruction and demonstrate 70 nm spatial resolution in magnetization imaging with this approach. (paper)

  11. Intense Vibronic Modulation of the Chiral Photoelectron Angular Distribution Generated by Photoionization of Limonene Enantiomers with Circularly Polarized Synchrotron Radiation.

    Science.gov (United States)

    Rafiee Fanood, Mohammad M; Ganjitabar, Hassan; Garcia, Gustavo A; Nahon, Laurent; Turchini, Stefano; Powis, Ivan

    2018-04-17

    Photoionization of the chiral monoterpene limonene has been investigated using polarized synchrotron radiation between the adiabatic ionization threshold, 8.505 and 23.5 eV. A rich vibrational structure is seen in the threshold photoelectron spectrum and is interpreted using a variety of computational methods. The corresponding photoelectron circular dichroism-measured in the photoelectron angular distribution as a forward-backward asymmetry with respect to the photon direction-was found to be strongly dependent on the vibronic structure appearing in the photoelectron spectra, with the observed asymmetry even switching direction in between the major vibrational peaks. This effect can be ultimately attributed to the sensitivity of this dichroism to small phase shifts between adjacent partial waves of the outgoing photoelectron. These observations have implications for potential applications of this chiroptical technique, where the enantioselective analysis of monoterpene components is of particular interest. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Azimuthally invariant Mueller-matrix mapping of optically anisotropic layers of biological networks of blood plasma in the diagnosis of liver disease

    Science.gov (United States)

    Ushenko, A. G.; Dubolazov, A. V.; Ushenko, V. A.; Ushenko, Yu. A.; Sakhnovskiy, M. Y.; Pavlyukovich, O.; Pavlyukovich, N.; Novakovskaya, O.; Gorsky, M. P.

    2016-09-01

    The model of Mueller-matrix description of mechanisms of optical anisotropy that typical for polycrystalline layers of the histological sections of biological tissues and fluids - optical activity, birefringence, as well as linear and circular dichroism - is suggested. Within the statistical analysis distributions quantities of linear and circular birefringence and dichroism the objective criteria of differentiation of myocardium histological sections (determining the cause of death); films of blood plasma (liver pathology); peritoneal fluid (endometriosis of tissues of women reproductive sphere); urine (kidney disease) were determined. From the point of view of probative medicine the operational characteristics (sensitivity, specificity and accuracy) of the method of Mueller-matrix reconstruction of optical anisotropy parameters were found.

  13. Conformational alteration in alpha-toxin from Staphylococcus aureus concomitant with the transformation of the water-soluble monomer to the membrane oligomer.

    Science.gov (United States)

    Ikigai, H; Nakae, T

    1985-07-16

    The membrane-damaging alpha-toxin aggregate of Staphylococcus aureus was characterized physicochemically. The aggregate weight of the toxin formed by various methods appeared to be 6 times higher than the molecular weight of the monomer as determined by the laser light scattering technique, suggesting the presence of a hexamer in the membrane. The aggregates fluoresced 20 to 50% more than the monomer at 336 nm. Circular dichroism measurements revealed that both the monomer and the oligomer showed essentially beta-sheet structure with the maximum ellipticity about -8,400 deg.cm2.dmol-1 at 215 nm. Circular dichroism spectrum of the oligomers showed ellipticity difference of -6,600, -44 and +84 deg.cm2.dmol-1, at 200, 250 and 280 nm, respectively, compared with the monomer. All these results suggest that the conformational change in the toxin molecule occurs concomitant with the transformation of the water-soluble monomer to the membrane-embedded hexamer.

  14. Characterization of Chiral Carbonaceous Nanotubes Prepared from Four Coiled Tubular 4,4'-biphenylene-silica Nanoribbons

    Directory of Open Access Journals (Sweden)

    Shuwei Lin

    2014-04-01

    Full Text Available Four dipeptides derived from phenylalanine were synthesized, which can self-assemble into twisted nanoribbon in deionized water. The handedness of the organic self-assemblies was controlled by the chirality of the phenylalanine at the terminals. Coiled 4,4'-biphenylene bridged polybissilsesquioxane tubular nanoribbons were prepared using the organic self-assemblies as the templates. The circular dichroism spectra indicated that the biphenylene rings preferred to twist in one-handedness within the walls of the samples. After carbonization and removal of silica, single-handed coiled carbonaceous tubular nanoribbons were obtained. The Raman spectra indicated that the carbon was amorphous. The diffuse reflectance circular dichroism spectra indicated the tubular carbonaceous nanoribbons exhibited optical activity.

  15. Chirality detection of enantiomers using twisted optical metamaterials

    Science.gov (United States)

    Zhao, Yang; Askarpour, Amir N.; Sun, Liuyang; Shi, Jinwei; Li, Xiaoqin; Alù, Andrea

    2017-01-01

    Many naturally occurring biomolecules, such as amino acids, sugars and nucleotides, are inherently chiral. Enantiomers, a pair of chiral isomers with opposite handedness, often exhibit similar physical and chemical properties due to their identical functional groups and composition, yet show different toxicity to cells. Detecting enantiomers in small quantities has an essential role in drug development to eliminate their unwanted side effects. Here we exploit strong chiral interactions with plasmonic metamaterials with specifically designed optical response to sense chiral molecules down to zeptomole levels, several orders of magnitude smaller than what is typically detectable with conventional circular dichroism spectroscopy. In particular, the measured spectra reveal opposite signs in the spectral regime directly associated with different chiral responses, providing a way to univocally assess molecular chirality. Our work introduces an ultrathin, planarized nanophotonic interface to sense chiral molecules with inherently weak circular dichroism at visible and near-infrared frequencies. PMID:28120825

  16. Solvent polarity effects on supramolecular chirality of a polyfluorene-thiophene copolymer.

    Science.gov (United States)

    Hirahara, Takashi; Yoshizawa-Fujita, Masahiro; Takeoka, Yuko; Rikukawa, Masahiro

    2018-06-01

    This study demonstrates the supramolecular chirality control of a conjugated polymer via solvent polarity. We designed and synthesized a chiral polyfluorene-thiophene copolymer having two different chiral side chains at the 9-position of the fluorene unit. Chiral cyclic and alkyl ethers with different polarities were selected as the chiral side chains. The sign of the circular dichroism spectra in the visible wavelength region was affected by the solvent system, resulting from the change of supramolecular structure. The estimation of the solubility parameter revealed that the solubility difference of the side chains contributed to the change of the circular dichroism sign, which was also observed in spin-coated films prepared from good solvents having different polarities. © 2018 Wiley Periodicals, Inc.

  17. Design and finite element simulation of vacuum systems for insertion devices in Indus-2 storage ring

    International Nuclear Information System (INIS)

    Yadav, D.P.; Bais, Vijay; Sridhar, R.; Dhimole, Vivek K.; Nitesh, Suthar; Rawal, B.R.; Chogaonkar, Swati

    2015-01-01

    Indus-2 is a 2.5 GeV, 300 mA, Synchrotron Radiation Source (SRS) located at Raja Ramanna Centre for Advanced Technology, Indore. As part of insertion device (ID) development programme two new devices namely, APPLE-2 (Advanced Planar Polarized Light Emitter) type Undulator (also known as U-3 Undulator) and 5 Tesla superconducting wavelength shifter (SWLS) are being developed. APPLE-2 will generate variably polarized synchrotron radiation (SR) required for carrying out magnetic circular dichroism (MCD) and magnetic linear dichroism (MLD) experiments and SWLS will generate synchrotron radiation (SR) with critical photon energy of about 20.8 keV for Energy Dispersive XRD beam line. This paper describes design details and finite element analysis results of various simulations carried out for the vacuum systems of these IDs

  18. Mueller-matrix mapping of biological tissues in differential diagnosis of optical anisotropy mechanisms of protein networks

    Energy Technology Data Exchange (ETDEWEB)

    Ushenko, V A; Sidor, M I [Yuriy Fedkovych Chernivtsi National University, Chernivtsi (Ukraine); Marchuk, Yu F; Pashkovskaya, N V; Andreichuk, D R [Bukovinian State Medical University, Chernivtsi (Ukraine)

    2015-03-31

    We report a model of Mueller-matrix description of optical anisotropy of protein networks in biological tissues with allowance for the linear birefringence and dichroism. The model is used to construct the reconstruction algorithms of coordinate distributions of phase shifts and the linear dichroism coefficient. In the statistical analysis of such distributions, we have found the objective criteria of differentiation between benign and malignant tissues of the female reproductive system. From the standpoint of evidence-based medicine, we have determined the operating characteristics (sensitivity, specificity and accuracy) of the Mueller-matrix reconstruction method of optical anisotropy parameters and demonstrated its effectiveness in the differentiation of benign and malignant tumours. (laser applications and other topics in quantum electronics)

  19. Double photoionization of helium at an excess energy of 60 eV using left- and right-elliptically-polarized light

    International Nuclear Information System (INIS)

    Collins, S.A.; Cvejanovic, S.; Dawson, C.; Reddish, T.J.; Seccombe, D.P.; Huetz, A.; Malegat, L.; Selles, P.; Kazansky, A.K.; Danjo, A.; Soejima, K.; Okuno, K.; Yagishita, A.

    2002-01-01

    Helium double photoionization (γ,2e) triple differential cross sections (TDCSs) were measured at an excess energy of 60 eV using a dual toroidal spectrometer and synchrotron radiation from a helical undulator (BL-28A, Photon Factory, Japan). Energy-sharing ratios (R=E 2 /E 1 ) for the two ejected electrons of 5 and 11 are studied with both right- and left-handed elliptically polarized light. The TDCSs are found to be in good agreement with those obtained using the hyperspherical R matrix with semiclassical outgoing waves theory. The circular dichroism for a limited mutual angular range (φ 12 ≅110 deg. -200 deg.) is determined from the experimental data for both R=5 and 11, and compared to theoretical calculations performed over the complete range of mutual angles. No dynamic nodes are found in either the experimental (within the explored φ 12 range) or theoretical circular dichroism for these R values at this excess energy

  20. Active control of chirality in nonlinear metamaterials

    International Nuclear Information System (INIS)

    Zhu, Yu; Chai, Zhen; Yang, Hong; Hu, Xiaoyong; Gong, Qihuang

    2015-01-01

    An all-optical tunabe chirality is realized in a photonic metamaterial, the metamolecule of which consists of a nonlinear nano-Au:polycrystalline indium-tin oxide layer sandwiched between two L-shaped gold nano-antennas twisted 90° with each other. The maximum circular dichroism reached 30%. Under excitation of a 40 kW/cm 2 weak pump light, the peak in the circular dichroism shifts 45 nm in the short-wavelength direction. An ultrafast response time of 35 ps is maintained. This work not only opens up the possibility for the realization of ultralow-power and ultrafast all-optical tunable chirality but also offers a way to construct ultrahigh-speed on-chip biochemical sensors

  1. Neolignan and phenylpropanoid compounds from the fruits of Illicium simonsii Maxim.

    Science.gov (United States)

    Zhuang, Peng-Yu; Chen, Ming-Hua; Wang, Ya-Nan; Wang, Xiao-Xia; Feng, Ya-Jing; Zhang, Dan-Yang

    2018-01-04

    One new sesqui-neolignan compound, namely, sesqui-illisimonan A (1), one new neolignan, illisimonan A (2), and one new phenylpropanoid compound, illisimoid A (3) were isolated from the fruits of Illicium simonsii Maxim. The structures and absolute configurations of these compounds were determined by extensive spectroscopic, including NMR, circular dichroism and calculated electronic circular dichroism methods. The antioxidant activities of compounds 1-3 were also evaluated. Vitamin E was selected as the positive control (IC 50  = 49.73 ± 0.88 μM). Compounds 1 and 2 exhibited in vitro antioxidant activity with an IC 50 value of 55.76 ± 1.30 and 59.36 ± 0.50 μM, respectively. However, the compound 3 didn't show obvious antioxidant activity.

  2. Element Specific Versus Integral Structural and Magnetic Properties of Co:ZnO and Gd:GaN Probed with Hard X-ray Absorption Spectroscopy

    Directory of Open Access Journals (Sweden)

    Andreas Ney

    2010-06-01

    Full Text Available Dilute magnetic semiconductors (DMS are envisioned as sources of spin-polarized carriers for future semiconductor devices which simultaneously utilize spin and charge of the carriers. The hope of discovering a DMS with ferromagnetic order up to room temperature still motivates research on suitable DMS materials. Two candidate wide-band gap DMS are Gd:GaN and Co:ZnO. We have used hard X-ray absorption spectroscopy (XAS and in particular X-ray linear dichroism (XLD and X-ray magnetic circular dichroism (XMCD to study both DMS materials with element specificity and compare these findings with results from integral SQUID magnetometry as well as electron paramagnetic resonance (EPR.

  3. Interaction studies of resistomycin from Streptomyces aurantiacus AAA5 with calf thymus DNA and bovine serum albumin

    Science.gov (United States)

    Vijayabharathi, R.; Sathyadevi, P.; Krishnamoorthy, P.; Senthilraja, D.; Brunthadevi, P.; Sathyabama, S.; Priyadarisini, V. Brindha

    2012-04-01

    Resistomycin, a secondary metabolite produced by Streptomyces aurantiacus AAA5. The binding interaction of resistomycin with calf thymus DNA (CT DNA) and bovine serum albumin (BSA) was investigated by spectrophotometry, spectrofluorimetry, circular dichroism (CD) and synchronous fluorescence techniques under physiological conditions in vitro. Absorption spectral studies along with the fluorescence competition with ethidium bromide measurements and circular dichroism clearly suggest that the resistomycin bind with CT DNA relatively strong via groove binding. BSA interaction results revealed that the drug was found to quench the fluorescence intensity of the protein through a static quenching mechanism. The number of binding sites 'n' and apparent binding constant 'K' calculated according to the Scatchard equation exhibit a good binding property to bovine serum albumin protein. In addition, the results observed from synchronous fluorescence measurements clearly demonstrate the occurrence of conformational changes of BSA upon addition of the test compound.

  4. Photo-Acoustic Spectroscopy Reveals Extrinsic Optical Chirality in GaAs-Based Nanowires Partially Covered with Gold

    Science.gov (United States)

    Petronijevic, E.; Leahu, G.; Belardini, A.; Centini, M.; Li Voti, R.; Hakkarainen, T.; Koivusalo, E.; Rizzo Piton, M.; Suomalainen, S.; Guina, M.; Sibilia, C.

    2018-04-01

    We report on the extrinsic chirality behavior of GaAs-based NWs asymmetrically hybridized with Au. The samples are fabricated by a recently developed, lithography-free self-organized GaAs growth, with the addition of AlGaAs shell and GaAs supershell. The angled Au flux is then used to cover three-out-of-six sidewalls with a thin layer of Au. Oblique incidence and proper sample orientation can lead to circular dichroism. We characterize this chiral behavior at 532 {nm} and 980 {nm} by means of photo-acoustic spectroscopy, which directly measures the difference in absorption for the circularly polarized light of the opposite headedness. For the first time to our knowledge, circular dichroism is observed in both the amplitude and the phase of the photo-acoustic signal. We strongly believe that such samples can be used for chiral applications, spanning from circularly polarized light emission, to the enantioselectivity applications.

  5. 3-hydroxyflavone-bovine serum albumin interaction in Dextran medium

    Directory of Open Access Journals (Sweden)

    Voicescu Mariana

    2015-01-01

    Full Text Available Spectroscopic analysis of a bioactive flavonol, 3-Hydroxyflavone (3-HF, in systems based on Dextran 70 (Dx70 (an important bio-relevant polysacharide and Bovine Serum Albumin (BSA (a carrier protein, have been studied by fluorescence and circular dichroism. Changes produced by different concentrations of Dx70 on the fluorescent characteristics of 3-HF, and on the excited - state intramolecular proton transfer (ESIPT process were studied. The influence of 3-HF binding and of Dx70 on the secondary structure of BSA were investigated by circular dichroism spectroscopy. The influence of temperature (30-80°C range on the intrinsic Tryptophan fluorescence in 3-HF/BSA/Dx70 systems, was investigated. The results are discussed with relevance to 3-HF as a sensitive fluorescence probe for exploring flavone-protein interaction in plasma expander media and also for its biological evaluation.

  6. Binding of caffeine, theophylline, and theobromine with human serum albumin: A spectroscopic study

    Science.gov (United States)

    Zhang, Hong-Mei; Chen, Ting-Ting; Zhou, Qiu-Hua; Wang, Yan-Qing

    2009-12-01

    The interaction between three purine alkaloids (caffeine, theophylline, and theobromine) and human serum albumin (HSA) was investigated using UV/vis absorption, circular dichroism (CD), fluorescence, synchronous fluorescence, and three-dimensional fluorescence spectra techniques. The results revealed that three alkaloids caused the fluorescence quenching of HSA by the formation of alkaloid-HSA complex. The binding site number n and apparent binding constant KA, corresponding thermodynamic parameters the free energy change (Δ G), enthalpy change (Δ H), and entropy change (Δ S) at different temperatures were calculated. The hydrophobic interaction plays a major role in stabilizing the complex. The distance r between donor (HSA) and acceptor (alkaloids) was obtained according to fluorescence resonance energy transfer. The effect of alkaloids on the conformation of HSA was analyzed using circular dichroism (CD), UV/vis absorption, synchronous fluorescence and three-dimensional fluorescence spectra techniques.

  7. Comparison of absorption spectra of adenocarcinoma and squamous cell carcinoma cervical tissue

    Science.gov (United States)

    Peresunko, O. P.; Zelinska, N. V.; Prydij, O. G.; Zymnyakov, D. A.; Ushakova, O. V.

    2013-12-01

    We studied a methods of assessment of a connective tissue of cervix in terms of specific volume of fibrous component and an optical density of staining of connective tissue fibers in the stroma of squamous cancer and cervix adenocarcinoma. An absorption spectra of blood plasma of the patients suffering from squamous cancer and cervix adenocarcinoma both before the surgery and in postsurgical periods were obtained. Linear dichroism measurements transmittance in polarized light at different orientations of the polarization plane relative to the direction of the dominant orientation in the structure of the sample of biotissues of stroma of squamous cancer and cervix adenocarcinoma were carried. Results of the investigation of the tumor tissues showed that the magnitude of the linear dichroism Δ is insignificant in the researched spectral range λ=280-840 nm and specific regularities in its change observed short-wave ranges.

  8. Interaction of nogalamycin and analogs with DNA and other biopolymers

    Energy Technology Data Exchange (ETDEWEB)

    Krueger, W C [Univ. of Minnesota, Minneapolis; Pschigoda, L M; Schpok, S L.F.; Moscowitz, A.; McGovren, J P; Neta, P; Merritt, M V; Li, L H

    1981-01-01

    The interaction with calf thymus DNA of the anthracycline antibiotics, nogalamycin and its analogs, was studied by electronic absorption, circular dichroism (CD), thermal denaturation, solvent partition and pulse radiolysis techniques. The Scatchard, thermal denaturation (..delta..T/sub m/), difference circular dichroism (..delta..CD) and solvent partition binding parameters gave the same order of relative binding on a given lot of DNA, but some parameters were DNA-lot-dependent. In general, molecules containing the sugar moiety nogalose at C-7 or those having the natural or dis stereochemistry of nogalamycin at C-7 bound more strongly to DNA than did the molecules lacking nogalose or those with the opposite configuration at C-7 (con stereochemistry). This stereochemical-binding correlation differs from that found for adriamycin which has the con stereochemistry, but which binds strongly to DNA. Scatchard binding parameters could not be obtained from the pulse radiolysis or solvent partition techniques because of solubility difficulties.

  9. Analysis of aggregate optical spectra using moments. Application to the purple membrane of halobacterium halobium

    International Nuclear Information System (INIS)

    Hemenger, R.P.

    1978-01-01

    The problem of extracting structural information from the optical spectra of aggregates of molecules interacting through their electronic transitions is studied. One serious difficulty common to all approaches to this problem is that of properly taking into account the effects of molecular vibrations. A series of exact relations derived previously which are correct with regard to molecular vibrations provide a number of independent, explicit connections between aggregate geometrical parameters and moments of experimental spectra. It is shown that, by applying these moment relations to the optical absorption and circular dichroism spectra of simple aggregates, a complete set of equations can be found, i.e., enough equations can be found to solve for all of the geometrical parameters which enter into the expressions for absorption and circular dichroism spectra. This procedure is applied in some detail to the purple membrane of Halobacterium halobium. The results are completely consistent with what is known about its structure

  10. Structural studies on serum albumins under green light irradiation.

    Science.gov (United States)

    Comorosan, Sorin; Polosan, Silviu; Popescu, Irinel; Ionescu, Elena; Mitrica, Radu; Cristache, Ligia; State, Alina Elena

    2010-10-01

    This paper presents two new experimental results: the protective effect of green light (GL) on ultraviolet (UV) denaturation of proteins, and the effect of GL on protein macromolecular structures. The protective effect of GL was revealed on two serum albumins, bovine (BSA) and human (HSA), and recorded by electrophoresis, absorption, and circular dichroism spectra. The effect of GL irradiation on protein structure was recorded by using fluorescence spectroscopy and electrophoresis. These new effects were modeled by quantum-chemistry computation using Gaussian 03 W, leading to good fit between theoretical and experimental absorption and circular dichroism spectra. A mechanism for these phenomena is suggested, based on a double-photon absorption process. This nonlinear effect may lead to generation of long-lived Rydberg macromolecular systems, capable of long-range interactions. These newly suggested systems, with macroscopic quantum coherence behaviors, may block the UV denaturation processes.

  11. Spectropolarimetry biopsies of the cervix at an early cancer and dysplasia

    Science.gov (United States)

    Yermolenko, S. B.; Peresunko, O. P.; Babechko, N. J.

    2015-11-01

    The analysis of the spectral anisotropic properties of layers of oncologic modified biological tissues with precancerous condition (CIN) and with cancer formation (G) of cervix according to linear dichroism determined in the wavelength range 300-800 nm was conducted. Comparison of results of animal testing of samples of biological samples oncologic modified human tissue was conducted, introduction of differentiation criterion spectropolarimetric precancerous condition and the stage cancer formation in the spectral band of 390-410 nm was proposed. Appropriate diagnostically important changes in the value ranges of linear dichroism at each stage of cancer formation (high- and low-grade dysplasia, high and low-grade adenocarcinoma) was determined. A differential method for diagnosis of epithelial cells in the above diseases was suggested.

  12. Synthesis of the natural product building block 5-(3-bromophenyl)-4-hydroxy-5-methylhexan-2-one and its chiral characterization by using chiroptical spectroscopy.

    Science.gov (United States)

    De Gussem, Ewoud; Cornelus, Jelle; Pieters, Sam; Van den Bossche, Dries; Van der Eycken, Johan; Herrebout, Wouter; Bultinck, Patrick

    2013-10-07

    The absolute configuration of 5-(3-bromophenyl)-4-hydroxy-5-methylhexan-2-one, an intermediate in the synthesis of various natural products, is assigned by using vibrational circular dichroism (VCD), electronic circular dichroism (ECD), and optical rotatory dispersion (ORD). Experimental spectra were compared to density functional theory (DFT) calculations of the molecule with known configuration. These three techniques independently confirm that the absolute configuration is (S)-5-(3-bromophenyl)-4-hydroxy-5-methylhexan-2-one, thus enabling us to assign the absolute configuration with high reliability. The reliability of the VCD analysis was assessed quantitatively by using the CompareVOA program. We found that, in cases in which the agreement between theory and experiment was very good, a value of 10 cm(-1) for the triangular weighting function gave a more-realistic discriminative power between enantiomers than the default value of 20 cm(-1). Copyright © 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Two dimensional electron gas confined over a spherical surface: Magnetic moment

    Energy Technology Data Exchange (ETDEWEB)

    Hernando, A; Crespo, P [Instituto de Magnetismo Aplicado, UCM-CSIC-ADIF, Las Rozas. P. O. Box 155, Madrid 28230 (Spain) and Dpto. Fisica de Materiales, Universidad Complutense (Spain); Garcia, M A, E-mail: antonio.hernando@adif.es [Instituto de Ceramica y Vidrio, CSIC c/Kelsen, 5 Madrid 28049 (Spain)

    2011-04-01

    Magnetism of capped nanoparticles, NPs, of non-magnetic substances as Au and ZnO is briefly reviewed. The source of the magnetization is discussed on the light of recent X-ray magnetic circular dichroism experiments. As magnetic dichroism analysis has pointed out impurity atoms bonded to the surface act as donor or acceptor of electrons that occupy the surface states. It is proposed that mesoscopic collective orbital magnetic moments induced at the surface states can account for the experimental magnetism characteristic of these nanoparticles. The total magnetic moment of the surface originated at the unfilled Fermi level can reach values as large as 10{sup 2} or 10{sup 3} Bohr magnetons.

  14. Fine tuning of the catalytic activity of colicin E7 nuclease domain by systematic N-terminal mutations

    Czech Academy of Sciences Publication Activity Database

    Németh, E.; Körtvélyesi, T.; Thulstrup, P. W.; Christensen, H. E. M.; Kožíšek, Milan; Nagata, K.; Czene, A.; Gyurcsik, B.

    2014-01-01

    Roč. 23, č. 8 (2014), s. 1113-1122 ISSN 0961-8368 Grant - others:Seventh Framework Programme of the European Union(XE) FP7-312284; OPPC(CZ) CZ.2.16/3.1.00/24016 Institutional support: RVO:61388963 Keywords : DNA cleavage * flow linear dichroism * isothermal calorimetry * positively charged N-terminal residues * Zn2+ binding Subject RIV: CE - Biochemistry Impact factor: 2.854, year: 2014

  15. Vitamin k3 inhibits protein aggregation: Implication in the treatment of amyloid diseases

    OpenAIRE

    Parvez Alam; Sumit Kumar Chaturvedi; Mohammad Khursheed Siddiqi; Ravi Kant Rajpoot; Mohd Rehan Ajmal; Masihuz Zaman; Rizwan Hasan Khan

    2016-01-01

    Protein misfolding and aggregation have been associated with several human diseases such as Alzheimer?s, Parkinson?s and familial amyloid polyneuropathy etc. In this study, anti-fibrillation activity of vitamin k3 and its effect on the kinetics of amyloid formation of hen egg white lysozyme (HEWL) and A?-42 peptide were investigated. Here, in combination with Thioflavin T (ThT) fluorescence assay, circular dichroism (CD), transmission electron microscopy and cell cytotoxicity assay, we demons...

  16. Two Furanosesterterpenoids from the Sponge Luffariella variabilis

    Directory of Open Access Journals (Sweden)

    Peni Ahmadi

    2017-08-01

    Full Text Available Two new sesterterpenoids, 1 and 2, were isolated from the sponge Luffariella variabilis. Their planar structures were characterized with spectroscopic analyses. The sole chiral center of compound 1 was elucidated as 12R by comparing observed and calculated optical rotation values. The configurations of compound 2 were determined by NMR and electronic circular dichroism (ECD studies. Furthermore, compound 2 showed cytotoxicity at IC50 1.0 µM against NBT-T2 cells.

  17. Gaussian sum rules for optical functions

    International Nuclear Information System (INIS)

    Kimel, I.

    1981-12-01

    A new (Gaussian) type of sum rules (GSR) for several optical functions, is presented. The functions considered are: dielectric permeability, refractive index, energy loss function, rotatory power and ellipticity (circular dichroism). While reducing to the usual type of sum rules in a certain limit, the GSR contain in general, a Gaussian factor that serves to improve convergence. GSR might be useful in analysing experimental data. (Author) [pt

  18. Numerical computer methods part D

    CERN Document Server

    Johnson, Michael L

    2004-01-01

    The aim of this volume is to brief researchers of the importance of data analysis in enzymology, and of the modern methods that have developed concomitantly with computer hardware. It is also to validate researchers' computer programs with real and synthetic data to ascertain that the results produced are what they expected. Selected Contents: Prediction of protein structure; modeling and studying proteins with molecular dynamics; statistical error in isothermal titration calorimetry; analysis of circular dichroism data; model comparison methods.

  19. Structural Characterization of Monomeric/Dimeric State of p59fyn SH2 Domain.

    Science.gov (United States)

    Huculeci, Radu; Kieken, Fabien; Garcia-Pino, Abel; Buts, Lieven; van Nuland, Nico; Lenaerts, Tom

    2017-01-01

    Src homology 2 (SH2) domains are key modulators in various signaling pathways allowing the recognition of phosphotyrosine sites of different proteins. Despite the fact that SH2 domains acquire their biological functions in a monomeric state, a multitude of reports have shown their tendency to dimerize. Here, we provide a technical description on how to isolate and characterize by gel filtration, circular dichroism (CD), and nuclear magnetic resonance (NMR) each conformational state of p59 fyn SH2 domain.

  20. Through-space transfer of chiral information mediated by a plasmonic nanomaterial

    Czech Academy of Sciences Publication Activity Database

    Pour, S. O.; Rocks, L.; Faulds, K.; Graham, D.; Parchaňský, Václav; Bouř, Petr; Blanch, E. W.

    2015-01-01

    Roč. 7, č. 7 (2015), s. 591-596 ISSN 1755-4330 R&D Projects: GA ČR GAP208/11/0105; GA ČR GA13-03978S Grant - others:GA AV ČR(CZ) M200551205 Institutional support: RVO:61388963 Keywords : Raman optical activity * bis(zinc porphyrin) * circular dichroism Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 27.893, year: 2015

  1. (CGA)4: parallel, anti-parallel, right-handed and left-handed homoduplexes of a trinucleotide repeat DNA

    Czech Academy of Sciences Publication Activity Database

    Kejnovská, Iva; Tůmová, Marcela; Vorlíčková, Michaela

    2001-01-01

    Roč. 1527, 1-2 (2001), s. 73-80 ISSN 0304-4165 R&D Projects: GA ČR GA204/98/1027; GA ČR GA204/01/0561 Institutional research plan: CEZ:AV0Z5004920 Keywords : DNA conformational polymorphism * circular dichroism * Z-DNA Subject RIV: BO - Biophysics Impact factor: 1.849, year: 2000

  2. Tracking of protein folding by chiral spectroscopic methods

    Czech Academy of Sciences Publication Activity Database

    Krupová, Monika; Andrushchenko, Valery; Bouř, Petr

    2016-01-01

    Roč. 23, č. 1 (2016), s. 36 ISSN 1211-5894. [Discussions in Structural Molecular Biology /14./. 17.03.2016-19.03.2016, Nové Hrady] R&D Projects: GA ČR(CZ) GA16-04902S; GA ČR GA15-09072S Institutional support: RVO:61388963 Keywords : proteins * fibrils * lanthanides * vibrational circular dichroism * circularly polarised luminescence Subject RIV: CF - Physical ; Theoretical Chemistry

  3. Studies on interaction between flavonoids and bovine serum albumin by spectral methods

    International Nuclear Information System (INIS)

    Shi Xiaolei; Li Xuwen; Gui Mingyu; Zhou Hongyu; Yang Ruijie; Zhang Hanqi; Jin Yongri

    2010-01-01

    The interaction between three kinds of flavonoids and bovine serum albumin (BSA) was investigated by fluorescence and UV-vis absorption spectrometry. The results indicated that flavonoids have strong ability to quench the intrinsic fluorescence of BSA by forming complexes. The binding constants, number of binding sites, thermodynamic parameters and energy transfer mechanisms were also investigated. Conformation change of BSA was observed from synchronous, three-dimensional fluorescence and circular dichroism spectrum.

  4. Absolute Configuration of a Cyclic Dipeptide Reflected in Vibrational Optical Activity: Ab Initio and Experimental Investigation

    Czech Academy of Sciences Publication Activity Database

    Li, X.; Hopmann, K. H.; Hudecová, Jana; Stensen, W.; Novotná, J.; Urbanová, M.; Svendsen, J. S.; Bouř, Petr; Ruud, K.

    2012-01-01

    Roč. 116, č. 10 (2012), s. 2554-2563 ISSN 1089-5639 R&D Projects: GA ČR GAP208/11/0105; GA MŠk(CZ) LH11033 Grant - others:AV ČR(CZ) M200550902 Institutional research plan: CEZ:AV0Z40550506 Keywords : cyclic dipeptide * vibrational otpical activity * density functional theory * dispersion * electronic circular dichroism Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.771, year: 2012

  5. Chirality sensing with stereodynamic copper(I) complexes.

    Science.gov (United States)

    De Los Santos, Zeus A; Legaux, Nicholas M; Wolf, Christian

    2017-11-01

    Three Cu(I) complexes derived from stereodynamic diphosphine ligands were synthesized and used for chirality sensing. The coordination of diamines and amino acids to these complexes generates distinct circular dichroism signals. The chiroptical sensor response allows determination of the absolute configuration and the enantiomeric excess of the analyte at low concentrations. This method is operationally simple, fast, and attractive for high-throughput sensing applications. © 2017 Wiley Periodicals, Inc.

  6. Deracemization of bilirubin as the marker of the chirality of micellar aggregates.

    Science.gov (United States)

    Sorrenti, Alessandro; Altieri, Barbara; Ceccacci, Francesca; Di Profio, Pietro; Germani, Raimondo; Giansanti, Luisa; Savelli, Gianfranco; Mancini, Giovanna

    2012-01-01

    The deracemization of bilirubin in micellar aggregates of structurally correlated chiral surfactants was studied by circular dichroism experiments and exploited as the marker of the expression of chirality of the aggregates. The obtained results suggest that the hydrophobic interactions control the transfer of chirality from the monomers to the aggregates, and that different regions of the same aggregate might feature opposite enantiorecognition capabilities. Copyright © 2011 Wiley-Liss, Inc.

  7. AFRRI Reports, July-September 1990

    Science.gov (United States)

    1990-10-01

    Geacintov, N. E. Linear dichroism characteristics of 0 ethidium- and proflavine-supercoiled DNA complexes. SR90-24: Weiss, J. F., Kumar, K. S...forming units per milliliter, based on colony count within contain 10% fetal bovine serum (HyClone, Logan, UT), plus 10% the linear part of the dilution...dps Press. Hyalomers und des Granulomers . Acta Haemat. 6, 207- BLASCHKO, H., FIREMARK, H., SMITH, A. D. & WINKLFR, 12. H. (1967) Lipids of the adrenal

  8. Mapping the Local Organization of Cell Membranes Using Excitation-Polarization-Resolved Confocal Fluorescence Microscopy

    OpenAIRE

    Kress, Alla; Wang, Xiao; Ranchon, Hubert; Savatier, Julien; Rigneault, Hervé; Ferrand, Patrick; Brasselet, Sophie

    2013-01-01

    International audience; Fluorescence anisotropy and linear dichroism imaging have been widely used for imaging biomolecular orientational distributions in protein aggregates, fibrillar structures of cells, and cell membranes. However, these techniques do not give access to complete orientational order information in a whole image, because their use is limited to parts of the sample where the average orientation of molecules is known a priori. Fluorescence anisotropy is also highly sensitive t...

  9. Electronic states of myricetin

    DEFF Research Database (Denmark)

    Vojta, Danijela; Karlsen, Eva; Spanget-Larsen, Jens

    2017-01-01

    Myricetin (3,3',4',5,5',7'-hexahydroxyflavone) was investigated by linear dichroism spectroscopy on molecular samples partially aligned in stretched poly(vinyl alcohol) (PVA). At least five electronic transitions in the range 40000 – 20000 cm–1 were characterized with respect to their wavenumbers......, relative intensities, and transition moment directions. The observed bands were assigned to electronic transitions predicted with TD-B3LYP/6-31+G(d,p)....

  10. Resonant Impulsive Stimulated Raman Scattering

    Energy Technology Data Exchange (ETDEWEB)

    Mokhtari, A; Chesnoy, J

    1988-03-15

    Using a femtosecond dye laser, we observe in real-time vibrational oscillations excited by impulsive stimulated Raman scattering (ISRS) close to an electronic resonance. We perform single-beam Raman excitation and probe the driven coherence by a polarization-sensitive detection. We demonstrate for the first time impulsively Raman-induced dichroism, birefringence as well as frequency and time delay shifts. We analyse the characteristics of resonant ISRS on a vibrational mode of a dye molecule (malachite green) in solution.

  11. Rotenoids from Tephrosia toxicaria with larvicidal activity against Aedes aegypti, the main vector of dengue fever

    International Nuclear Information System (INIS)

    Vasconcelos, Jackson Nunes e; Santiago, Gilvandete Maria Pinheiro; Lima, Jefferson Queiroz; Arriaga, Angela Martha Campos

    2012-01-01

    In the search for new larvicides from plants, we have investigated the potential activity of the rotenoids deguelin (1), 12a-hydroxy-a-toxicarol (2) and tephrosin (3), isolated from the bioactive ethanol extract of roots of Tephrosia toxicaria Pers., against Aedes aegypti, the main vector of dengue. The absolute configuration of these compounds was determined by circular dichroism (CD) spectra. The LC50 values of the compounds evaluated justify the potential of T. toxicaria as a new natural larvicide. (author)

  12. CH Stretching Region: Computational Modeling of Vibrational Optical Activity

    Czech Academy of Sciences Publication Activity Database

    Hudecová, Jana; Profant, V.; Novotná, P.; Baumruk, V.; Urbanová, M.; Bouř, Petr

    2013-01-01

    Roč. 9, č. 7 (2013), s. 3096-3108 ISSN 1549-9618 R&D Projects: GA ČR GAP208/11/0105; GA MŠk(CZ) LH11033 Grant - others:AV ČR(CZ) M200550902 Institutional support: RVO:61388963 Keywords : density-functional theory * circular-dichroism spectra * N-methyl acetamide * alpha-pinene * Raman Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 5.310, year: 2013

  13. Transferability of Various Molecular Property Tensors in Vibrational Spectroscopy

    Czech Academy of Sciences Publication Activity Database

    Yamamoto, Shigeki; Li, X.; Ruud, K.; Bouř, Petr

    2012-01-01

    Roč. 8, č. 3 (2012), s. 977-985 ISSN 1549-9618 R&D Projects: GA MŠk(CZ) LH11033; GA ČR GAP208/11/0105 Grant - others:AV ČR(CZ) M200550902 Institutional research plan: CEZ:AV0Z40550506 Keywords : raman optical-activity * circular-dichroism * polypeptides * conformational determination * density-functional theory Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 5.389, year: 2012

  14. A New Terminal Cyano Group-containing Benzodiazepine Alkaloid from the Mangrove Endophytic Fungus Penicillium sp. .

    Science.gov (United States)

    Li, Jing; Zhong, Yi-sheng; Yuan, Jie; Zhu, Xun; Lu, Yong-jun; Lin, Yong-cheng; Liu, Lan

    2015-09-01

    A new benzodiazepine alkaloid containing terminal cyano group has been isolated from a mangrove endophytic fungus, Penicillium 299#. Structure elucidation was determined by 1D and 2D NMR spectroscopy and the absolute configuration was determined by electronic circular dichroism (ECD). The new compound showed no cytotoxic activities in vitro against human cancer lines MDA-MB-435, HepG2, HCT-116, and Calu-3.

  15. Thermal E/ Z Isomerization in First Generation Molecular Motors.

    Science.gov (United States)

    Kuwahara, Shunsuke; Suzuki, Yuri; Sugita, Naoya; Ikeda, Mari; Nagatsugi, Fumi; Harada, Nobuyuki; Habata, Yoichi

    2018-04-20

    Determination of a thermal E/ Z isomerization barrier of first generation molecular motors is reported. Stable ( E)-1a directly converts to stable ( Z)-1c without photochemical E/ Z isomerization. The activation Gibbs energy of the isomerization was determined to be 123 kJ mol -1 by circular dichroism spectral changes. Density functional theory calculations show that ( Z)-1c is ∼11.4 kJ mol -1 more stable than ( E)-1a.

  16. Cocaine Hydrochloride Structure in Solution Revealed by Three Chiroptical Methods

    Czech Academy of Sciences Publication Activity Database

    Fagan, P.; Kocourková, L.; Tatarkovič, M.; Králík, F.; Kuchař, M.; Setnička, V.; Bouř, Petr

    2017-01-01

    Roč. 18, č. 16 (2017), s. 2258-2265 ISSN 1439-4235 R&D Projects: GA ČR(CZ) GA16-05935S; GA MŠk(CZ) LTC17012 Institutional support: RVO:61388963 Keywords : analytical methods * circular dichroism * density functional calculations * Raman spectroscopy * structure elucidation Subject RIV: CF - Physical ; Theoretical Chemistry OBOR OECD: Physical chemistry Impact factor: 3.075, year: 2016

  17. Flow-alignment of bicellar lipid mixtures: orientations of probe molecules and membrane-associated biomacromolecules in lipid membranes studied with polarized light

    KAUST Repository

    Kogan, Maxim; Beke-Somfai, Tamá s; Nordé n, Bengt

    2011-01-01

    Bicelles are excellent membrane-mimicking hosts for a dynamic and structural study of solutes with NMR, but the magnetic fields required for their alignment are hard to apply to optical conditions. Here we demonstrate that bicellar mixtures can be aligned by shear forces in a Couette flow cell, to provide orientation of membrane-bound retinoic acid, pyrene and cytochrome c (cyt c) protein, conveniently studied with linear dichroism spectroscopy. © 2011 The Royal Society of Chemistry.

  18. Conformational Diversity of Single-Stranded DNA from Bacterial Repetitive Extragenic Palindromes: Implications for the DNA Recognition Elements of Transposases

    Czech Academy of Sciences Publication Activity Database

    Charnavets, Tatsiana; Nunvář, Jaroslav; Nečasová, Iva; Voelker, J.; Breslauer, K.J.; Schneider, Bohdan

    2015-01-01

    Roč. 103, č. 10 (2015), s. 585-596 ISSN 0006-3525 R&D Projects: GA MŠk(CZ) ED1.1.00/02.0109; GA ČR GAP305/12/1801; GA MŠk(CZ) EE2.3.30.0020 Institutional support: RVO:86652036 Keywords : bacterial repetitive extragenic palindromes (REP) * circular dichroism spectroscopy * REP associated tyrosine transposases (RAYTs) Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 2.248, year: 2015

  19. Contrasting Binding of Fisetin and daidzein in γ-Cyclodextrin Nanocavity

    OpenAIRE

    Pahari, Biswapathik; Sengupta, Bidisha; Chakraborty, Sandipan; Thomas, Briannica; McGowan, Dyffreyon; Sengupta, Pradeep K.

    2012-01-01

    Steady state and time resolved fluorescence along with anisotropy and induced circular dichroism (ICD) spectroscopy provide useful tools to observe and understand the behavior of the therapeutically important plant flavonoids fisetin and daidzein in γ-cyclodextrin (γ-CDx) nanocavity. Benesi-Hildebrand plots indicated 1:1 stoichiometry for both the supramolecular complexes. However the mode of the binding of fisetin significantly differs from daidzein in γ-CDx, as is observed from ICD spectra ...

  20. Vortex-Induced Alignment of a Water Soluble Supramolecular Nanofiber Composed of an Amphiphilic Dendrimer

    Directory of Open Access Journals (Sweden)

    Akihiko Tsuda

    2013-06-01

    Full Text Available We have synthesized a novel amphiphilic naphthalene imide bearing a cationic dendrimer wedge (NID. NID molecules in water self-assemble to form a two-dimensional ribbon, which further coils to give a linear supramolecular nanofiber. The sample solution showed linear dichroism (LD upon stirring of the solution, where NID nanofibers dominantly align at the center of vortex by hydrodynamic interaction with the downward torsional flows.