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Sample records for substituent chemical shifts

  1. Substituent Chemical Shifts of (E)-1-Aryl-3-thienylpropen-1-ones

    Energy Technology Data Exchange (ETDEWEB)

    Lee, In-Sook Han; Jeon, Hyun Ju; Yu, Ji Sook; Lee, Chang Kiu [Kangwon National University, Chuncheon (Korea, Republic of)

    2010-06-15

    Substituent chemical shifts were examined for the 2- and 3-thiophene derivatives of chalcone and compared to the thiophene series of derivatives with the phenyl series. The chemical shift values for the α-carbons of the enones showed and inverse correlation with the Hammett σ values, but the correlation coefficients were moderate (r = 0.836 - 0.878). On the other hand, the β-carbons showed a normal correlation with excellent correlation coefficients (r = 0.994). The absolute magnitude of the ρ values for the α-carbon are about half of those of the β-carbon. The observation may be the result of a through-space transition of the electronic effect of the substituents in addition to the through bond transition.

  2. {sup 1}H and {sup 13}C NMR Data on Hydroxy/methoxy Flavonoids and the Effects of Substituents on Chemical Shifts

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Hyuk; Eom, Sung Lock; Hyun, Ji Ye; Jo, Geun Hyeong; Hwang, Do Seok; Lee, Sun Hee; Yong, Yeon Joong; Lee, Young Han; Lim, Yoong Ho [Konkuk University, Seoul (Korea, Republic of); Park, Jun Cheol [National Institute of Animal Science, Rural Development Administration, Suwon (Korea, Republic of)

    2011-06-15

    Polyphenols have recently been examined for such applications, and they are classified based on their carbon skeletons: phenolic acids with C6-C1 skeleton, hydrocinammates with C6-C{sub 3} skeleton, stilbenes with C6-C2-C6 skeleton, and flavonoids with C6-C{sub 3}-C6 skeleton.2 Of these compounds, flavonoids are ubiquitously found in most plants. Since flavonoids belong to polyphenols, they have many hydroxy groups. From a bioavailability point of view, hydroxy groups prevent cell membrane transport, and hydroxyflavonoids can be metabolized by O-methyltransferases. However, methoxylated flavonoids may not have these problems. Hydroxylated or methoxylated flavonoids are found from natural sources. Nuclear magnetic resonance (NMR) spectroscopy is widely used to identify different compounds including hydroxylated or methoxylated flavonoids. Because the position and the number of substituted hydroxy or/and methoxy groups will change the {sup 1}H and {sup 13}C chemical shifts, it is important to understand these changes so that the structures of newly isolated hydroxy/methoxy-flavonoids can be easily identified.

  3. E-2-Benzylidenebenzocycloalkanones. IV. Studies on transmission of substituent effects on 13C NMR chemical shifts of E-2-(X-benzylidene)-1-tetralones, and -benzosuberones. Comparison with the 13C NMR data of chalcones and E-2-(X-benzylidene)-1-indanones

    Science.gov (United States)

    Perjési, Pál; Linnanto, Juha; Kolehmainen, Erkki; Ősz, Erzsébet; Virtanen, Elina

    2005-04-01

    Single substituent parameter (SSP) and dual substituent parameter (DSP) analyses were applied to study the transmission of substituent effects on selected 13C NMR chemical shifts of the cyclic chalcone analogues, E-2-(4'-X-benzylidene)-1-tetralones ( 2) and E-2-(4'-X-benzylidene)-1-benzosuberones ( 3). In order to study how the geometry of the cyclic chalcone analogues affects the transmission of substituent effects similar investigations with the respective chalcones ( 4) were also performed. The results obtained earlier with the five-membered analogue E-2-(4'-X-benzylidene)-1-indanones ( 1) were also involved in the comparisons. Geometry optimization of the unsubstituted 1a, 2a, 3a and 4a as well as the substituted 2 and 3 was performed by ab initio quantum chemical calculations. Both SSP and DSP analyses reflected that resonance effects contribute more to the chemical shift of C-α (C2), while inductive effects primarily affect that of C-β (C10) of the enone moiety of all the four series. This latter effect, however, is far not as pronounced as that of the former one. It was found that DSP analysis data ( ρF and ρR values) of transmission of substituent effects on the δC2 data can serve as a measure of choice to study the conformation (planarity) of the investigated enones in the four series.

  4. Protein Chemical Shift Prediction

    CERN Document Server

    Larsen, Anders S

    2014-01-01

    The protein chemical shifts holds a large amount of information about the 3-dimensional structure of the protein. A number of chemical shift predictors based on the relationship between structures resolved with X-ray crystallography and the corresponding experimental chemical shifts have been developed. These empirical predictors are very accurate on X-ray structures but tends to be insensitive to small structural changes. To overcome this limitation it has been suggested to make chemical shift predictors based on quantum mechanical(QM) calculations. In this thesis the development of the QM derived chemical shift predictor Procs14 is presented. Procs14 is based on 2.35 million density functional theory(DFT) calculations on tripeptides and contains corrections for hydrogen bonding, ring current and the effect of the previous and following residue. Procs14 is capable at performing predictions for the 13CA, 13CB, 13CO, 15NH, 1HN and 1HA backbone atoms. In order to benchmark Procs14, a number of QM NMR calculatio...

  5. Chemical shift and coupling constant analysis of dibenzyloxy disulfides.

    Science.gov (United States)

    Stoutenburg, Eric G; Gryn'ova, Ganna; Coote, Michelle L; Priefer, Ronny

    2015-02-05

    Dialkoxy disulfides have found applications in the realm of organic synthesis as an S2 or alkoxy donor, under thermal and photolytic decompositions conditions, respectively. Spectrally, dibenzyloxy disulfides possess an ABq in the (1)H NMR, which can shift by over 1.1ppm depending on the substituents present on the aromatic ring, as well as the solvent employed. The effect of the said substituents and solvent were analyzed and compared to the center of the ABq, geminal coupling, and the differences in chemical shifts of the individual doublets. Additionally, quantum-chemical calculations demonstrated the intramolecular H-bonding arrangement, found within the dibenzyloxy disulfides. Copyright © 2014 Elsevier B.V. All rights reserved.

  6. Calculations of proton chemical shifts in olefins and aromatics

    CERN Document Server

    Escrihuela, M C

    2000-01-01

    induced reagents on alpha,beta unsaturated ketones has also been investigated in order to deduce molecular structures and to obtain the assignment of the spectra of these molecules. A semi-empirical calculation of the partial atomic charges in organic compounds based on molecular dipole moments (CHARGE3) was developed into a model capable of predicting proton chemical shifts in a wide variety of organic compounds to a reasonable degree of accuracy. The model has been modified to include condensed aromatic hydrocarbons and substituted benzenes, alkenes, halo-monosubstituted benzenes and halo-alkenes. Within the aromatic compounds the influence of the pi electron densities and the ring current have been investigated, along with the alpha, beta and gamma effects. The model gives the first accurate calculation of the proton chemical shifts of condensed aromatic compounds and the proton substituent chemical shifts (SCS) in the benzene ring. For the data set of 55 proton chemical shifts spanning 3 ppm the rms error...

  7. Charge-Shift Corrected Electronegativities and the Effect of Bond Polarity and Substituents on Covalent-Ionic Resonance Energy.

    Science.gov (United States)

    James, Andrew M; Laconsay, Croix J; Galbraith, John Morrison

    2017-07-13

    Bond dissociation energies and resonance energies for HnA-BHm molecules (A, B = H, C, N, O, F, Cl, Li, and Na) have been determined in order to re-evaluate the concept of electronegativity in the context of modern valence bond theory. Following Pauling's original scheme and using the rigorous definition of the covalent-ionic resonance energy provided by the breathing orbital valence bond method, we have derived a charge-shift corrected electronegativity scale for H, C, N, O, F, Cl, Li, and Na. Atomic charge shift character is defined using a similar approach resulting in values of 0.42, 1.06, 1.43, 1.62, 1.64, 1.44, 0.46, and 0.34 for H, C, N, O, F, Cl, Li, and Na, respectively. The charge-shift corrected electronegativity values presented herein follow the same general trends as Pauling's original values with the exception of Li having a smaller value than Na (1.57 and 1.91 for Li and Na respectively). The resonance energy is then broken down into components derived from the atomic charge shift character and polarization effects. It is then shown that most of the resonance energy in the charge-shift bonds H-F, H3C-F, and Li-CH3 and borderline charge-shift H-OH is associated with polarity rather than the intrinsic atomic charge-shift character of the bonding species. This suggests a rebranding of these bonds as "polar charge-shift" rather than simply "charge-shift". Lastly, using a similar breakdown method, it is shown that the small effect the substituents -CH3, -NH2, -OH, and -F have on the resonance energy (bonding atom.

  8. Elucidation of the substitution pattern of 9,10-anthraquinones through the chemical shifts of peri-hydroxyl protons

    DEFF Research Database (Denmark)

    Schripsema, Jan; Danigno, Denise

    1996-01-01

    In 9,10-anthraquinones the chemical shift of a peri-hydroxyl proton is affected by the substituents in the other benzenoid ring. These effects are additive. They are useful for the determination of substitution patterns and have been used to revise the structures of six previously reported...... anthraquinones containing methoxyl, hydroxyl, methylenedioxy and beta-methyl substituents. Because the chemical shifts of the other protons are hardly affected by substitutions in the other ring, the characteristic chemical shifts for a wide variety of substitution patterns could be derived....

  9. Effect analysis of quantum chemical descriptors and substituent characteristics on Henry's law constants of polybrominated diphenyl ethers at different temperatures.

    Science.gov (United States)

    Long, Jiang; Youli, Qiu; Yu, Li

    2017-11-01

    Twelve substituent descriptors, 17 quantum chemical descriptors and 1/T were selected to establish a quantitative structure-property relationship (QSPR) model of Henry's law constants for 7 polybrominated diphenyl ethers (PBDEs) at five different temperatures. Then, the lgH of 202 congeners at different temperatures were predicted. The variation rule and regulating mechanism of lgH was studied from the perspectives of both quantum chemical descriptors and substituent characteristics. The R2 for modeling and testing sets of the final QSPR model are 0.977 and 0.979, respectively, thus indicating good fitness and predictive ability for Henry' law constants of PBDEs at different temperatures. The favorable hydrogen binding sites are the 5,5',6,6'-positions for high substituent congeners and the O atom of the ether bond for low substituent congeners, which affects the interaction between PBDEs and water molecules. lgH is negatively and linearly correlated with 1/T, and the variation trends of lgH with temperature are primarily regulated by individual substituent characteristics, wherein: the more substituents involved, the smaller the lgH. The significant sequence for the main effect of substituent positions is para>meta>ortho, where the ortho-positions are mainly involved in second-order interaction effect (64.01%). Having two substituents in the same ring also provides a significant effect, with 81.36% of second-order interaction effects, particularly where there is an adjacent distribution (55.02%). Copyright © 2017 Elsevier Inc. All rights reserved.

  10. Protein Structure Determination Using Chemical Shifts

    DEFF Research Database (Denmark)

    Christensen, Anders Steen

    In this thesis, a protein structure determination using chemical shifts is presented. The method is implemented in the open source PHAISTOS protein simulation framework. The method combines sampling from a generative model with a coarse-grained force field and an energy function that includes...... chemical shifts. The method is benchmarked on folding simulations of five small proteins. In four cases the resulting structures are in excellent agreement with experimental data, the fifth case fail likely due to inaccuracies in the energy function. For the Chymotrypsin Inhibitor protein, a structure...... is determined using only chemical shifts recorded and assigned through automated processes. The CARMSD to the experimental X-ray for this structure is 1.1. Å. Additionally, the method is combined with very sparse NOE-restraints and evolutionary distance restraints and tested on several protein structures >100...

  11. Topological Substituent Descriptors

    Directory of Open Access Journals (Sweden)

    Mircea V. DIUDEA

    2002-12-01

    Full Text Available Motivation. Substituted 1,3,5-triazines are known as useful herbicidal substances. In view of reducing the cost of biological screening, computational methods are carried out for evaluating the biological activity of organic compounds. Often a class of bioactives differs only in the substituent attached to a basic skeleton. In such cases substituent descriptors will give the same prospecting results as in case of using the whole molecule description, but with significantly reduced computational time. Such descriptors are useful in describing steric effects involved in chemical reactions. Method. Molecular topology is the method used for substituent description and multi linear regression analysis as a statistical tool. Results. Novel topological descriptors, XLDS and Ws, based on the layer matrix of distance sums and walks in molecular graphs, respectively, are proposed for describing the topology of substituents linked on a chemical skeleton. They are tested for modeling the esterification reaction in the class of benzoic acids and herbicidal activity of 2-difluoromethylthio-4,6-bis(monoalkylamino-1,3,5-triazines. Conclusions. Ws substituent descriptor, based on walks in graph, satisfactorily describes the steric effect of alkyl substituents behaving in esterification reaction, with good correlations to the Taft and Charton steric parameters, respectively. Modeling the herbicidal activity of the seo of 1,3,5-triazines exceeded the models reported in literature, so far.

  12. Random coil chemical shift for intrinsically disordered proteins

    DEFF Research Database (Denmark)

    Kjærgaard, Magnus; Brander, Søren; Poulsen, Flemming Martin

    2011-01-01

    Secondary chemical shift analysis is the main NMR method for detection of transiently formed secondary structure in intrinsically disordered proteins. The quality of the secondary chemical shifts is dependent on an appropriate choice of random coil chemical shifts. We report random coil chemical....... Temperature has a non-negligible effect on the (13)C random coil chemical shifts, so temperature coefficients are reported for the random coil chemical shifts to allow extrapolation to other temperatures. The pH dependence of the histidine random coil chemical shifts is investigated in a titration series...... shifts and sequence correction factors determined for a GGXGG peptide series following the approach of Schwarzinger et al. (J Am Chem Soc 123(13):2970-2978, 2001). The chemical shifts are determined at neutral pH in order to match the conditions of most studies of intrinsically disordered proteins...

  13. Delocalization does not always stabilize : a quantum chemical analysis of -substituent effects on 54 alkyl and vinyl cations

    NARCIS (Netherlands)

    Alem, van K.; Lodder, G.; Zuilhof, H.

    2002-01-01

    The effects of -substituents on alkyl and vinyl cations are studied using high-level ab initio calculations. The geometries, stabilities, and electronic properties of 27 alkyl cations and 27 vinyl cations with -substituents are computed at the B3LYP/6-311 G(d,p), MP2/6-311 G(d,p), and CBS-Q levels.

  14. Identifying Stereoisomers by ab-initio Calculation of Secondary Isotope Shifts on NMR Chemical Shieldings

    Directory of Open Access Journals (Sweden)

    Karl-Heinz Böhm

    2014-04-01

    Full Text Available We present ab-initio calculations of secondary isotope effects on NMR chemical shieldings. The change of the NMR chemical shift of a certain nucleus that is observed if another nucleus is replaced by a different isotope can be calculated by computing vibrational corrections on the NMR parameters using electronic structure methods. We demonstrate that the accuracy of the computational results is sufficient to even distinguish different conformers. For this purpose, benchmark calculations for fluoro(2-2Hethane in gauche and antiperiplanar conformation are carried out at the HF, MP2 and CCSD(T level of theory using basis sets ranging from double- to quadruple-zeta quality. The methodology is applied to the secondary isotope shifts for 2-fluoronorbornane in order to resolve an ambiguity in the literature on the assignment of endo- and exo-2-fluoronorbornanes with deuterium substituents in endo-3 and exo-3 positions, also yielding insight into mechanistic details of the corresponding synthesis.

  15. Spectroscopic and quantum chemical investigations of substituent effects on the azo-hydrazone tautomerism and acid-base properties of arylazo pyridone dyes.

    Science.gov (United States)

    Dostanić, J; Mijin, D; Ušćumlić, G; Jovanović, D M; Zlatar, M; Lončarević, D

    2014-04-05

    A series of 5-(4-substituted arylazo)-6-hydroxy-4-methyl-3-cyano-2-pyridone dyes was synthesized and the structure of the dyes was confirmed by UV-Vis, FT-IR, (1)H NMR and (13)C NMR spectroscopic techniques. The azo-hydrazone tautomeric equilibrium was found to depend on the substituents as well as on the acidity and basicity of the media. Ionization constant, pKa, of the dyes was determined by UV-Vis spectroscopy and correlated with the Hammett substituent constants, σp and σI. The interpretation of the effect of different substituent in phenyl ring of arylazo pyridone dyes on their spectroscopic and structural properties was based on quantum chemical calculations performed by the density functional theory (DFT/M06-2X) method. The DFT calculations confirmed the existence of two forms in water solution: hydrazone form in acidic and neutral media and anionic form in basic media. The different contribution of azo and hydrazone canonical forms of anionic form is observed for dyes with electron-donating and dyes with electron-withdrawing groups. The dependence of absorption spectra and determined pKa values to the substituent type seems to be mostly due to azo/hydrazone canonical structure ratio in their anionic form. Copyright © 2013 Elsevier B.V. All rights reserved.

  16. Improving 3D structure prediction from chemical shift data

    NARCIS (Netherlands)

    van der Schot, G.; Zhang, Z.; Vernon, R.; Shen, Y.; Vranken, W.F.; Baker, D.; Bonvin, A.M.J.J.|info:eu-repo/dai/nl/113691238; Lange, O.F.

    2013-01-01

    We report advances in the calculation of protein structures from chemical shift nuclear magnetic resonance data alone. Our previously developed method, CSRosetta, assembles structures from a library of short protein fragments picked from a large library of protein structures using chemical shifts

  17. Rapid and reliable protein structure determination via chemical shift threading.

    Science.gov (United States)

    Hafsa, Noor E; Berjanskii, Mark V; Arndt, David; Wishart, David S

    2017-12-01

    Protein structure determination using nuclear magnetic resonance (NMR) spectroscopy can be both time-consuming and labor intensive. Here we demonstrate how chemical shift threading can permit rapid, robust, and accurate protein structure determination using only chemical shift data. Threading is a relatively old bioinformatics technique that uses a combination of sequence information and predicted (or experimentally acquired) low-resolution structural data to generate high-resolution 3D protein structures. The key motivations behind using NMR chemical shifts for protein threading lie in the fact that they are easy to measure, they are available prior to 3D structure determination, and they contain vital structural information. The method we have developed uses not only sequence and chemical shift similarity but also chemical shift-derived secondary structure, shift-derived super-secondary structure, and shift-derived accessible surface area to generate a high quality protein structure regardless of the sequence similarity (or lack thereof) to a known structure already in the PDB. The method (called E-Thrifty) was found to be very fast (often structure) and to significantly outperform other shift-based or threading-based structure determination methods (in terms of top template model accuracy)-with an average TM-score performance of 0.68 (vs. 0.50-0.62 for other methods). Coupled with recent developments in chemical shift refinement, these results suggest that protein structure determination, using only NMR chemical shifts, is becoming increasingly practical and reliable. E-Thrifty is available as a web server at http://ethrifty.ca .

  18. A study of substituent effects on the NH bond in alkyl and aryl 4,6-disubstituted-3-cyano-2-pyridones

    Directory of Open Access Journals (Sweden)

    MILICA MISIC–VUKOVIC

    2007-12-01

    Full Text Available Substituent effects on the IR stretching frequencies and 1H-NMR chemical shifts of the pyridone NH group in 4- and 6-disubstituted alkyl and aryl 3-cyano-2-pyridones were investigated. The bands most sensitive to substituent effects from the broad and multiple IR NH band for each compound were selected by a computer calculation. The selected values of the IR frequencies and the determined 1H-NMR chemical shifts were subjected to LFER analysis, by correlations with the Hamett σm/p and Swain–Lupton F and R substituent constants.

  19. Unraveling the meaning of chemical shifts in protein NMR.

    Science.gov (United States)

    Berjanskii, Mark V; Wishart, David S

    2017-11-01

    Chemical shifts are among the most informative parameters in protein NMR. They provide wealth of information about protein secondary and tertiary structure, protein flexibility, and protein-ligand binding. In this report, we review the progress in interpreting and utilizing protein chemical shifts that has occurred over the past 25years, with a particular focus on the large body of work arising from our group and other Canadian NMR laboratories. More specifically, this review focuses on describing, assessing, and providing some historical context for various chemical shift-based methods to: (1) determine protein secondary and super-secondary structure; (2) derive protein torsion angles; (3) assess protein flexibility; (4) predict residue accessible surface area; (5) refine 3D protein structures; (6) determine 3D protein structures and (7) characterize intrinsically disordered proteins. This review also briefly covers some of the methods that we previously developed to predict chemical shifts from 3D protein structures and/or protein sequence data. It is hoped that this review will help to increase awareness of the considerable utility of NMR chemical shifts in structural biology and facilitate more widespread adoption of chemical-shift based methods by the NMR spectroscopists, structural biologists, protein biophysicists, and biochemists worldwide. This article is part of a Special Issue entitled: Biophysics in Canada, edited by Lewis Kay, John Baenziger, Albert Berghuis and Peter Tieleman. Copyright © 2017 Elsevier B.V. All rights reserved.

  20. NightShift: NMR shift inference by general hybrid model training - a framework for NMR chemical shift prediction

    Science.gov (United States)

    2013-01-01

    Background NMR chemical shift prediction plays an important role in various applications in computational biology. Among others, structure determination, structure optimization, and the scoring of docking results can profit from efficient and accurate chemical shift estimation from a three-dimensional model. A variety of NMR chemical shift prediction approaches have been presented in the past, but nearly all of these rely on laborious manual data set preparation and the training itself is not automatized, making retraining the model, e.g., if new data is made available, or testing new models a time-consuming manual chore. Results In this work, we present the framework NightShift (NMR Shift Inference by General Hybrid Model Training), which enables automated data set generation as well as model training and evaluation of protein NMR chemical shift prediction. In addition to this main result – the NightShift framework itself – we describe the resulting, automatically generated, data set and, as a proof-of-concept, a random forest model called Spinster that was built using the pipeline. Conclusion By demonstrating that the performance of the automatically generated predictors is at least en par with the state of the art, we conclude that automated data set and predictor generation is well-suited for the design of NMR chemical shift estimators. The framework can be downloaded from https://bitbucket.org/akdehof/nightshift. It requires the open source Biochemical Algorithms Library (BALL), and is available under the conditions of the GNU Lesser General Public License (LGPL). We additionally offer a browser-based user interface to our NightShift instance employing the Galaxy framework via https://ballaxy.bioinf.uni-sb.de/. PMID:23496927

  1. NightShift: NMR shift inference by general hybrid model training--a framework for NMR chemical shift prediction.

    Science.gov (United States)

    Dehof, Anna Katharina; Loew, Simon; Lenhof, Hans-Peter; Hildebrandt, Andreas

    2013-03-16

    NMR chemical shift prediction plays an important role in various applications in computational biology. Among others, structure determination, structure optimization, and the scoring of docking results can profit from efficient and accurate chemical shift estimation from a three-dimensional model.A variety of NMR chemical shift prediction approaches have been presented in the past, but nearly all of these rely on laborious manual data set preparation and the training itself is not automatized, making retraining the model, e.g., if new data is made available, or testing new models a time-consuming manual chore. In this work, we present the framework NightShift (NMR Shift Inference by General Hybrid Model Training), which enables automated data set generation as well as model training and evaluation of protein NMR chemical shift prediction.In addition to this main result - the NightShift framework itself - we describe the resulting, automatically generated, data set and, as a proof-of-concept, a random forest model called Spinster that was built using the pipeline. By demonstrating that the performance of the automatically generated predictors is at least en par with the state of the art, we conclude that automated data set and predictor generation is well-suited for the design of NMR chemical shift estimators.The framework can be downloaded from https://bitbucket.org/akdehof/nightshift. It requires the open source Biochemical Algorithms Library (BALL), and is available under the conditions of the GNU Lesser General Public License (LGPL). We additionally offer a browser-based user interface to our NightShift instance employing the Galaxy framework via https://ballaxy.bioinf.uni-sb.de/.

  2. 15N Chemical Shifts in Energetic Materials: CP/MAS and ab Initio Studies of Aminonitropyridines, Aminonitropyrimidines, and Their N-Oxides

    Directory of Open Access Journals (Sweden)

    Julio C. Facelli

    2002-08-01

    Full Text Available Abstract: Solid state 15N NMR chemical shift measurements have been performed on a series of nitro- and amino-substituted nitrogen-containing heterocycles that are of interest as potential new insensitive explosives. Due to low solubilities, many of these compounds are not amenable to study by solution state methods. Theoretical calculations of 15N chemical shift parameters have been performed on the structures of interest and are reported herein. The calculated and experimental values are in good agreement. The use of a model that includes intermolecular effects and allows the proton positions of the nearest neighbors to be optimized leads to the best agreement between calculated and experimental values. The theoretical models accurately predict the effects of nitro and amino substituents on ringnitrogen chemical shifts, explaining a seeming reversal in trend that is noted in the pyridine and pyridine-1-oxide chemical shifts of the highly substituted compounds.

  3. Counterion influence on chemical shifts in strychnine salts

    Energy Technology Data Exchange (ETDEWEB)

    Metaxas, Athena E.; Cort, John R.

    2013-05-01

    The highly toxic plant alkaloid strychnine is often isolated in the form of the anion salt of its protonated tertiary amine. Here we characterize the relative influence of different counterions on 1H and 13C chemical shifts in several strychnine salts in D2O, methanol-d4 (CD3OD) and chloroform-d (CDCl3) solvents. In organic solvents, but not in water, substantial variation in chemical shifts of protons near the tertiary amine was observed among different salts. These secondary shifts reveal differences in the way each anion influences electronic structure within the protonated amine. The distributions of secondary shifts allow salts to be easily distinguished from each other as well as from the free base form. The observed effects are much greater in organic solvents than in water. Slight concentration-dependence in chemical shifts of some protons near the amine was observed for two salts in CDCl3, but this effect is small compared to the influence of the counterion. Distinct chemical shifts in different salt forms of the same compound may be useful as chemical forensic signatures for source attribution and sample matching of alkaloids such as strychnine and possibly other organic acid and base salts.

  4. Bayesian inference of protein structure from chemical shift data

    DEFF Research Database (Denmark)

    Bratholm, Lars Andersen; Christensen, Anders Steen; Hamelryck, Thomas Wim

    2015-01-01

    Protein chemical shifts are routinely used to augment molecular mechanics force fields in protein structure simulations, with weights of the chemical shift restraints determined empirically. These weights, however, might not be an optimal descriptor of a given protein structure and predictive model...... Monte Carlo simulations of three small proteins (ENHD, Protein G and the SMN Tudor Domain) using the PROFASI force field and the chemical shift predictor CamShift. Using a clustering-criterion for identifying the best structure, together with the addition of a solvent exposure scoring term......, result in overall better convergence to the native fold, suggesting that both types of distribution might be useful in different aspects of the protein structure prediction....

  5. [Shift-work and cardiovascular diseases among chemical industry workers].

    Science.gov (United States)

    Meloni, M; Marchi, R; Broi, M; Avataneo, G; Sanna Randaccio, F

    2003-01-01

    In order to assess the prevalence of cardiovascular abnormalities among shift workers, who were free from such abnormalities at the time of hiring, compared to day workers and ex-shift workers, we studied the QTc interval and several cardiovascular risk factors in 61 chemical workers, including 40 shift workers, 11 day workers, and 10 ex-shift workers. We found a high prevalence rate of ischemic heart disease and conduction abnormalities among ex-shift workers (5/10, 50%). We did not observe variations in the QTc interval among the three groups. The occurrence of cardiovascular disease is a reason for moving workers to day work. Therefore, the shift workers group in our study might have been selected among subjects with a healthier lifestyle preventing side effects on their cardiovascular system.

  6. Evaluating amber force fields using computed NMR chemical shifts.

    Science.gov (United States)

    Koes, David R; Vries, John K

    2017-10-01

    NMR chemical shifts can be computed from molecular dynamics (MD) simulations using a template matching approach and a library of conformers containing chemical shifts generated from ab initio quantum calculations. This approach has potential utility for evaluating the force fields that underlie these simulations. Imperfections in force fields generate flawed atomic coordinates. Chemical shifts obtained from flawed coordinates have errors that can be traced back to these imperfections. We use this approach to evaluate a series of AMBER force fields that have been refined over the course of two decades (ff94, ff96, ff99SB, ff14SB, ff14ipq, and ff15ipq). For each force field a series of MD simulations are carried out for eight model proteins. The calculated chemical shifts for the 1 H, 15 N, and 13 Ca atoms are compared with experimental values. Initial evaluations are based on root mean squared (RMS) errors at the protein level. These results are further refined based on secondary structure and the types of atoms involved in nonbonded interactions. The best chemical shift for identifying force field differences is the shift associated with peptide protons. Examination of the model proteins on a residue by residue basis reveals that force field performance is highly dependent on residue position. Examination of the time course of nonbonded interactions at these sites provides explanations for chemical shift differences at the atomic coordinate level. Results show that the newer ff14ipq and ff15ipq force fields developed with the implicitly polarized charge method perform better than the older force fields. © 2017 Wiley Periodicals, Inc.

  7. Quantum chemical investigation of thermal cis-to-trans isomerization of azobenzene derivatives: substituent effects, solvent effects, and comparison to experimental data.

    Science.gov (United States)

    Dokić, Jadranka; Gothe, Marcel; Wirth, Jonas; Peters, Maike V; Schwarz, Jutta; Hecht, Stefan; Saalfrank, Peter

    2009-06-18

    Quantum chemical calculations of various azobenzene (AB) derivatives have been carried out with the goal to describe the energetics and kinetics of their thermal cis --> trans isomerization. The effects of substituents, in particular their type, number, and positioning, on activation energies have been systematically studied with the ultimate goal to tailor the switching process. Trends observed for mono- and disubstituted species are discussed. A polarizable continuum model is used to study, in an approximate fashion, the cis --> trans isomerization of azobenzenes in solution. The nature of the transition state(s) and its dependence on substituents and the environment is discussed. In particular for push-pull azobenzenes, the reaction mechanism is found to change from inversion in nonpolar solvents to rotation in polar solvents. Concerning kinetics, calculations based on the Eyring transition state theory give usually reliable activation energies and enthalpies when compared to experimentally determined values. Also, trends in the resulting rate constants are correct. Other computed properties such as activation entropies and thus preexponential rate factors are in only moderate agreement with experiment.

  8. 13C nuclear magnetic resonance data of lanosterol derivatives—Profiling the steric topology of the steroid skeleton via substituent effects on its 13C NMR

    Science.gov (United States)

    Dias, Jerry Ray; Gao, Hongwu

    2009-12-01

    The 13C NMR spectra of over 24 tetracyclic triterpenoid derivatives have been structurally analyzed. The 13C NMR chemical shifts allow one to probe the steric topology of the rigid steroid skeleton and inductive effects of its substituents. Use of deuterium labeling in chemical shift assignment and B-ring aromatic terpenoids are also featured.

  9. Chemical shift of UL 3 edges in different uranium compounds ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 37; Issue 3. Chemical shift of U L3 edges in different uranium compounds obtained by X-ray absorption spectroscopy with synchrotron radiation. D Joseph C Nayak P Venu Babu S N Jha D Bhattacharyya. Volume 37 Issue 3 May 2014 pp 643-647 ...

  10. Ligand binding analysis and screening by chemical denaturation shift.

    Science.gov (United States)

    Schön, Arne; Brown, Richard K; Hutchins, Burleigh M; Freire, Ernesto

    2013-12-01

    The identification of small molecule ligands is an important first step in drug development, especially drugs that target proteins with no intrinsic activity. Toward this goal, it is important to have access to technologies that are able to measure binding affinities for a large number of potential ligands in a fast and accurate way. Because ligand binding stabilizes the protein structure in a manner dependent on concentration and binding affinity, the magnitude of the protein stabilization effect elicited by binding can be used to identify and characterize ligands. For example, the shift in protein denaturation temperature (Tm shift) has become a popular approach to identify potential ligands. However, Tm shifts cannot be readily transformed into binding affinities, and the ligand rank order obtained at denaturation temperatures (≥60°C) does not necessarily coincide with the rank order at physiological temperature. An alternative approach is the use of chemical denaturation, which can be implemented at any temperature. Chemical denaturation shifts allow accurate determination of binding affinities with a surprisingly wide dynamic range (high micromolar to sub nanomolar) and in situations where binding changes the cooperativity of the unfolding transition. In this article, we develop the basic analytical equations and provide several experimental examples. Copyright © 2013 Elsevier Inc. All rights reserved.

  11. Relationships between geometrical and electronic structures and optical properties of 1,8-naphthosultam substituents and derivatives: TDDFT study

    Science.gov (United States)

    Fedorov, M. S.; Giricheva, N. I.; Lapykina, E. A.; Suvorova, O. A.

    2017-08-01

    Geometrical and electronic structure and optical properties of several substituents and derivatives of 1,8-naphthosultam are studied by quantum-chemical DFT and TDDFT. It is found that the substituents -NO2, -CF3, and -N(CH3)2 affect the geometrical and electronic structure the most. It is shown that the Stokes shift is greatest (≈260 nm) for compounds with the strong donor substituent -N(CH3)2, while strong acceptor substituents provide a quite small Stokes shift. The dependence of the Stokes shift on the difference in energies of the frontier orbitals of the ground and excited states of molecules is found. Of the 1,8-naphthosultam substituents considered, compounds with -N(CH3)2 substituent, which emit in the biological window region, can be advised for use in optical bioimaging. The results can be used as a basis for the development and creation of new functional materials and biologically active compounds.

  12. IR and NMR spectral studies of 4-bromo-1-naphthyl chalcones-assessment of substituent effects

    Science.gov (United States)

    Thirunarayanan, G.; Gopalakrishnan, M.; Vanangamudi, G.

    2007-07-01

    Infrared νCO (cm -1) of s-cis and s-trans frequencies and nuclear magnetic resonance chemical shifts δ1H (ppm) of H-α and H-β, δ13C (ppm) of C-α and C-β data were assigned from their respective spectra of a series of various substituted styryl 4-bromo-1-naphthyl chalcones. These values are correlated with various Hammett substituent constants. From the results of statistical analysis, the effect of substituents can be explained.

  13. Pressure-induced red shift and broadening of the Qy absorption of main light-harvesting antennae chlorosomes from green photosynthetic bacteria and their dependency upon alkyl substituents of the composite bacteriochlorophylls.

    Science.gov (United States)

    Mizoguchi, Tadashi; Kim, Tae-Yeun; Sawamura, Seiji; Tamiaki, Hitoshi

    2008-12-25

    When pressure was applied to the main light-harvesting apparatus (chlorosomes) isolated from several green photosynthetic bacteria (up to 128 MPa), the Qy-absorption band in an aqueous solution was shifted to longer wavelengths. The shift, deltav, was completely reversible for (de)compression and also showed a linear relation as a function of the applied pressure. The pressure-sensitivity in the deltav was dependent upon the bacterial species. The pressure coefficient, deltav/deltaP, was -565 to -535 cm(-1) GPa(-1) for the chlorosomes from several green sulfur bacteria (Chlorobium species), which have several bacteriochlorophyll(BChl) homologues at the 8- and 12-positions as the antenna pigments. In contrast, a smaller value (-445 cm(-1) GPa(-1)) was estimated for the chlorosomes from the green nonsulfur bacterium (Chloroflexus aurantiacus), which has a single homologue with 8-ethyl and 12-methyl groups. These results were confirmed by the similar pressure dependency of in vitro self-aggregates of isolated BChls-c having various alkyl substituents at the 8- and 12-positions. The present pressurization study enables us to discuss a physiological meaning of a variety of antenna pigments in green photosynthetic bacteria.

  14. Computational Protocols for Prediction of Solute NMR Relative Chemical Shifts

    DEFF Research Database (Denmark)

    Eriksen, Janus Juul; Olsen, Jógvan Magnus Haugaard; Aidas, Kestutis

    2011-01-01

    In this study, we have applied two different spanning protocols for obtaining the molecular conformations of L-tryptophan in aqueous solution, namely a molecular dynamics simulation and a molecular mechanics conformational search with subsequent geometry re-optimization of the stable conformers...... using a quantum mechanically based method. These spanning protocols represent standard ways of obtaining a set of conformations on which NMR calculations may be performed. The results stemming from the solute–solvent configurations extracted from the MD simulation at 300 K are found to be inferior...... to the results stemming from the conformations extracted from the MM conformational search in terms of replicating an experimental reference as well as in achieving the correct sequence of the NMR relative chemical shifts of L-tryptophan in aqueous solution. We find this to be due to missing conformations...

  15. Theoretical Modeling of 99 Tc NMR Chemical Shifts

    Energy Technology Data Exchange (ETDEWEB)

    Hall, Gabriel B.; Andersen, Amity; Washton, Nancy M.; Chatterjee, Sayandev; Levitskaia, Tatiana G.

    2016-09-06

    Technetium (Tc) displays a rich chemistry due to the wide range of oxidation states (from -I to +VII) and ability to form coordination compounds. Determination of Tc speciation in complex mixtures is a major challenge, and 99Tc NMR spec-troscopy is widely used to probe chemical environments of Tc in odd oxidation states. However interpretation of the 99Tc NMR data is hindered by the lack of reference compounds. DFT computations can help fill this gap, but to date few com-putational studies have focused on 99Tc NMR of compounds and complexes. This work systematically evaluates the inclu-sion small percentages of Hartree-Fock exchange correlation and relativistic effects in DFT computations to support in-terpretation of the 99Tc NMR spectra. Hybrid functionals are found to perform better than their pure GGA counterparts, and non-relativistic calculations have been found to generally show a lower mean absolute deviation from experiment. Overall non-relativistic PBE0 and B3PW91 calculations are found to most accurately predict 99Tc NMR chemical shifts.

  16. Macrocycle and substituent vibrational modes of nonplanar nickel (II) octaethyltetraphenylporphyrin from its resonance Raman, near-infrared-excited FT Raman, and FT-IR spectra and deuterium isotope shifts

    Energy Technology Data Exchange (ETDEWEB)

    Stichternath, A.; Schweitzer-Stenner, R.; Dreybrodt, W. (Univ. of Bremen (Germany)); Mak, R.S.W.; Li, X.Y. (Hong Kong Univ. of Science and Technology (Hong Kong)); Sparks, L.D.; Shelnutt, J.A. (Sandia National Lab., Albuquerque, NM (United States) Univ. of New Mexico, Albuquerque (United States)); Medforth, C.J.; Smith, K.M. (Univ. of California, Davis (United States))

    1993-04-15

    We have employed Raman dispersion, FT Raman, and FT-IR spectroscopy to identify a large number of resonance Raman lines of Ni(II) octaethyltetraphenylporphyrin dissolved in CS[sub 2]. The Raman depolarization dispersion technique was used to derive the symmetry of the normal modes giving rise to the observed Raman lines. By combining this information and the already available normal coordinates of Ni(II) tetraphenylporphyrin and Ni(II) octaethylporphyrin, many of the Raman-modes of the macrocycle could be assigned. Some resonance-enhanced Raman lines were found to arise from vibrations of the ethyl and phenyl substituents. They were identified by comparing resonance Raman, FT Raman, and FT infrared spectra of the Ni(II) octaethyltetraphenylporphyrin and its d[sub 20] isotopomer. All Raman lines normally referred to as core-size markers are found to be significantly shifted to lower frequencies with respect to their positions in Ni(II) octaethylporphyrin, in accordance with earlier findings (Shelnutt et al., J. Am. Chem. Soc. 113, 4077, 1991). This suggests that the molecule is in a highly nonplanar conformation. This notion is further corroborated by the strong dispersion of the depolarization ratio observed for nearly all A[sub 1g] and A[sub 2g] modes of the macrocycle. 27 refs., 13 figs., 2 tabs.

  17. Stereoelectronic Substituent Effects

    DEFF Research Database (Denmark)

    Bols, Mikael; Jensen, Henrik Helligsø

    2006-01-01

    An investigation was carried Out on the influence of the stereo-chemistry of substituents, particularly hydroxyl groups, on their electronic effects in piperidines, carbohydrates (pyranosides), and related compounds. Polar groups, such as OH, OR, and F, were found in the 3 and 4 position to be much...... to explain why stereoisomeric glycosides hydrolyze with different rates. The conformational changes of hydroxylated piperidines and related compounds as a function of pH were likewise explained from the different substituent effects of axial and equatorial OH groups....... more electron-withdrawing when positioned equatorially rather than axially. In contrast, little difference in electronic effects was observed from apolar groups as a result of epimerization. These observations were believed to be caused by differences in charge-dipole interactions and were used...

  18. Chemical shift encoded imaging of hyperpolarized (13) C pyruvate.

    Science.gov (United States)

    Wiens, Curtis N; Friesen-Waldner, Lanette J; Wade, Trevor P; Sinclair, Kevin J; McKenzie, Charles A

    2015-12-01

    To demonstrate a reconstruction technique for separating signal from different hyperpolarized carbon-13 metabolites. A reconstruction method is described for chemical shift encoded separation of the signal from pyruvate and its downstream metabolites. This method uses consistency of the data with the signal model rather than an additional free-induction decay (FID) acquisition to estimate the B0 offset. Compressed sensing was also integrated into the reconstruction allowing reconstruction of metabolite images from undersampled datasets. The performance of the reconstruction was assessed using thermal phantoms, digital phantoms, and in vivo hyperpolarized [1-(13) C] pyruvate experiments. Thermal and digital phantoms indicate that metabolite separation is feasible given Signal-to-noise ratio > 5 and an initial B0 offset estimate within -105 Hz to 90 Hz of the actual B0 offset. In vivo comparisons to an existing FID calibrated reconstruction show improved fidelity in regions with significant field map inhomogeneity provided that these field map variations are accounted for using an additional proton acquisition. Prospectively and retrospectively undersampled studies show acceleration factors of 2 are feasible using compressed sensing. A reconstruction framework for the separation of signal from pyruvate and its downstream metabolites is shown. This reconstruction eliminates the need to acquire additional calibration FID acquisition and allows acceleration through compressed sensing. © 2014 Wiley Periodicals, Inc.

  19. Diagnostic value of chemical shift artifact in distinguishing benign lymphadenopathy

    Energy Technology Data Exchange (ETDEWEB)

    Farshchian, Nazanin, E-mail: farshchian.n@gmail.com [Department of Radiology, Kermanshah University of Medical Sciences, Kermanshah (Iran, Islamic Republic of); Tamari, Saghar; Farshchian, Negin [Department of Radiology, Kermanshah University of Medical Sciences, Kermanshah (Iran, Islamic Republic of); Madani, Hamid [Department of Pathology, Imam-Reza Hospital, Kermanshah University of Medical Sciences, Kermanshah (Iran, Islamic Republic of); Rezaie, Mansour [Department of Biostatistics, Kermanshah University of Medical Sciences, Kermanshah (Iran, Islamic Republic of); Mohammadi-Motlagh, Hamid-Reza, E-mail: mohammadimotlagh@gmail.com [Medical Biology Research Center, Kermanshah University of Medical Sciences, Kermanshah (Iran, Islamic Republic of)

    2011-11-15

    Purpose: Today, distinguishing metastatic lymph nodes from secondary benign inflammatory ones via using non-invasive methods is increasingly favorable. In this study, the diagnostic value of chemical shift artifact (CSA) in magnetic resonance imaging (MRI) was evaluated to distinguish benign lymphadenopathy. Subjects and methods: A prospective intraindividual internal review board-approved study was carried out on 15 men and 15 women having lymphadenopathic lesions in different locations of the body who underwent contrast-enhanced dynamic MR imaging at 1.5 T. Then, the imaging findings were compared with pathology reports, using the statistics analyses. Results: Due to the findings of the CSA existence in MRI, a total of 56.7% of the studied lesions (17 of 30) were identified as benign lesions and the rest were malignant, whereas the pathology reports distinguished twelve malignant and eighteen benign cases. Furthermore, the CSA findings comparing the pathology reports indicated that CSA, with confidence of 79.5%, has a significant diagnostic value to differentiate benign lesions from malignant ones. Conclusion: Our study demonstrated that CSA in MR imaging has a suitable diagnostic potential nearing readiness for clinical trials. Furthermore, CSA seems to be a feasible tool to differentiate benign lymph nodes from malignant ones; however, further studies including larger numbers of patients are required to confirm our results.

  20. The PROSECCO server for chemical shift predictions in ordered and disordered proteins.

    Science.gov (United States)

    Sanz-Hernández, Máximo; De Simone, Alfonso

    2017-11-08

    The chemical shifts measured in solution-state and solid-state nuclear magnetic resonance (NMR) are powerful probes of the structure and dynamics of protein molecules. The exploitation of chemical shifts requires methods to correlate these data with the protein structures and sequences. We present here an approach to calculate accurate chemical shifts in both ordered and disordered proteins using exclusively the information contained in their sequences. Our sequence-based approach, protein sequences and chemical shift correlations (PROSECCO), achieves the accuracy of the most advanced structure-based methods in the characterization of chemical shifts of folded proteins and improves the state of the art in the study of disordered proteins. Our analyses revealed fundamental insights on the structural information carried by NMR chemical shifts of structured and unstructured protein states.

  1. Temperature dependence of 1H NMR chemical shifts and its influence on estimated metabolite concentrations.

    Science.gov (United States)

    Wermter, Felizitas C; Mitschke, Nico; Bock, Christian; Dreher, Wolfgang

    2017-07-06

    Temperature dependent chemical shifts of important brain metabolites measured by localised 1H MRS were investigated to test how the use of incorrect prior knowledge on chemical shifts impairs the quantification of metabolite concentrations. Phantom measurements on solutions containing 11 metabolites were performed on a 7 T scanner between 1 and 43 °C. The temperature dependence of the chemical shift differences was fitted by a linear model. Spectra were simulated for different temperatures and analysed by the AQSES program (jMRUI 5.2) using model functions with chemical shift values for 37 °C. Large differences in the temperature dependence of the chemical shift differences were determined with a maximum slope of about ±7.5 × 10-4 ppm/K. For 32-40 °C, only minor quantification errors resulted from using incorrect chemical shifts, with the exception of Cr and PCr. For 1-10 °C considerable quantification errors occurred if the temperature dependence of the chemical shifts was neglected. If 1H MRS measurements are not performed at 37 °C, for which the published chemical shift values have been determined, the temperature dependence of chemical shifts should be considered to avoid systematic quantification errors, particularly for measurements on animal models at lower temperatures.

  2. Empirical correlation between protein backbone 15N and 13C secondary chemical shifts and its application to nitrogen chemical shift re-referencing.

    Science.gov (United States)

    Wang, Liya; Markley, John L

    2009-06-01

    The linear analysis of chemical shifts (LACS) has provided a robust method for identifying and correcting 13C chemical shift referencing problems in data from protein NMR spectroscopy. Unlike other approaches, LACS does not require prior knowledge of the three-dimensional structure or inference of the secondary structure of the protein. It also does not require extensive assignment of the NMR data. We report here a way of extending the LACS approach to 15N NMR data from proteins, so as to enable the detection and correction of inconsistencies in chemical shift referencing for this nucleus. The approach is based on our finding that the secondary 15N chemical shift of the backbone nitrogen atom of residue i is strongly correlated with the secondary chemical shift difference (experimental minus random coil) between the alpha and beta carbons of residue i-1. Thus once alpha and beta 13C chemical shifts are available (their difference is referencing error-free), the 15N referencing can be validated, and an appropriate offset correction can be derived. This approach can be implemented prior to a structure determination and can be used to analyze potential referencing problems in database data not associated with three-dimensional structure. Application of the LACS algorithm to the current BMRB protein chemical shift database, revealed that nearly 35% of the BMRB entries have delta 15N values mis-referenced by over 0.7 ppm and over 25% of them have delta 1HN values mis-referenced by over 0.12 ppm. One implication of the findings reported here is that a backbone 15N chemical shift provides a better indicator of the conformation of the preceding residue than of the residue itself.

  3. Detection of initiation sites in protein folding of the four helix bundle ACBP by chemical shift analysis

    DEFF Research Database (Denmark)

    Modig, K.; Jürgensen, Vibeke Würtz; Lindorff-Larsen, K.

    2007-01-01

    A simple alternative method for obtaining "random coil" chemical shifts by intrinsic referencing using the protein's own peptide sequence is presented. These intrinsic random coil backbone shifts were then used to calculate secondary chemical shifts, that provide important information on the resi......A simple alternative method for obtaining "random coil" chemical shifts by intrinsic referencing using the protein's own peptide sequence is presented. These intrinsic random coil backbone shifts were then used to calculate secondary chemical shifts, that provide important information...

  4. NMR chemical shift data and ab initio shielding calculations : emerging tools for protein structure determination

    NARCIS (Netherlands)

    Mulder, Frans A. A.; Filatov, Michael

    2010-01-01

    In this tutorial review, we discuss the utilization of chemical shift information as well as ab initio calculations of nuclear shieldings for protein structure determination. Both the empirical and computational aspects of the chemical shift are reviewed and the role of molecular dynamics and the

  5. Fluorine Chemical Shift Imaging by Nuclear Magnetic Resonance

    Science.gov (United States)

    Lee, Heung Kyu

    1990-01-01

    One of the difficulties encountered in ^{19}F NMR imaging of fluorinated blood substitutes is that these compounds often exhibit complex multi-peak spectra. These peaks result in chemical shift artifacts along the readout direction (mis-registration). In addition, each peak excites a different slice (mis-selection) when a slice selection gradient is applied. Another difficulty is due to its low concentration in the human body. Even after injecting a fluorinated compound into a living system up to the safest level, the concentration still does not appear to be enough to give a sufficient SNR. To solve the inherent problem of mis-selection, a simultaneous multislice method has been developed. The essence of this method is to use the two strongest peaks of the spectrum to excite different multiple slices simultaneously in a controlled fashion, with or without a slice gap. The images corresponding to the two spectral lines are then separated from in and out of phase images (Dixon method). A signed magnitude method is proposed in conjunction with the simultaneous multislice method. Corrected images are obtained from the magnitude of the measured images using the sign determined from the phase images. The method was tested in the presence of phase error, such as static magnetic field inhomogeneity. As alternatives, two deconvolution methods have been devised to eliminate the mis-registration artifacts and utilize the multiple spectral lines. The reblurring deconvolution method, an iterative deconvolution method, is utilized without serious noise amplifications. A pseudo parametric Wiener filter, a variation of the Wiener filter combined with a constrained least square filter, is also devised. Since the point spread function and 2D or 3D object data are already available in the time domain as the FID data, the computational overhead for either method is negligible. To enhance the signal to noise ratio and solve the problems of mis-registration and mis

  6. Tuning Conductance in Aromatic Molecules: Constructive and Counteractive Substituent Effects

    DEFF Research Database (Denmark)

    Garner, Marc H.; Solomon, Gemma C.; Strange, Mikkel

    2016-01-01

    Destructive quantum interference in aromatic hydrocarbons can be tuned using chemical substituents; however, classical chemical intuition is not enough to explain the effects on electron transport. Using Huckel theory and density functional theory calculations, in combination with the Landauer....... This insight should be useful when substituents are to be used for tuning destructive quantum interference features in the transmission relative to the Fermi energy of the electrodes....

  7. Ab Initio Calculation of Nuclear Magnetic Resonance Chemical Shift Anisotropy Tensors 1. Influence of Basis Set on the Calculation of 31P Chemical Shifts

    Energy Technology Data Exchange (ETDEWEB)

    Alam, T.M.

    1998-09-01

    The influence of changes in the contracted Gaussian basis set used for ab initio calculations of nuclear magnetic resonance (NMR) phosphorous chemical shift anisotropy (CSA) tensors was investigated. The isotropic chemical shitl and chemical shift anisotropy were found to converge with increasing complexity of the basis set at the Hartree-Fock @IF) level. The addition of d polarization function on the phosphorous nucIei was found to have a major impact of the calculated chemical shi~ but diminished with increasing number of polarization fimctions. At least 2 d polarization fimctions are required for accurate calculations of the isotropic phosphorous chemical shift. The introduction of density fictional theory (DFT) techniques through tie use of hybrid B3LYP methods for the calculation of the phosphorous chemical shift tensor resulted in a poorer estimation of the NMR values, even though DFT techniques result in improved energy and force constant calculations. The convergence of the W parametem with increasing basis set complexity was also observed for the DFT calculations, but produced results with consistent large deviations from experiment. The use of a HF 6-31 l++G(242p) basis set represents a good compromise between accuracy of the simulation and the complexity of the calculation for future ab initio calculations of 31P NMR parameters in larger complexes.

  8. Deuterium isotope effects on 13C chemical shifts of 10-Hydroxybenzo[h]quinolines

    DEFF Research Database (Denmark)

    Hansen, Poul Erik; Kamounah, Fadhil S.; Gryko, Daniel T.

    2013-01-01

    Deuterium isotope effects on 13C-NMR chemical shifts are investigated in a series of 10-hydroxybenzo[h]quinolines (HBQ’s) The OH proton is deuteriated. The isotope effects on 13C chemical shifts in these hydrogen bonded systems are rather unusual. The formal four-bond effects are found to be nega...... with calculated OH stretching frequencies. Isotope effects on chemical shifts are calculated for systems with OH exchanged by OD. Hydrogen bond potentials are discussed. New and more soluble nitro derivatives are synthesized.......Deuterium isotope effects on 13C-NMR chemical shifts are investigated in a series of 10-hydroxybenzo[h]quinolines (HBQ’s) The OH proton is deuteriated. The isotope effects on 13C chemical shifts in these hydrogen bonded systems are rather unusual. The formal four-bond effects are found...... to be negative, indicating transmission via the hydrogen bond. In addition unusual long-range effects are seen. Structures, NMR chemical shifts and changes in nuclear shieldings upon deuteriation are calculated using DFT methods. Two-bond deuterium isotope effects on 13C chemical shifts are correlated...

  9. Correlation of chemical shifts predicted by molecular dynamics simulations for partially disordered proteins

    Energy Technology Data Exchange (ETDEWEB)

    Karp, Jerome M.; Erylimaz, Ertan; Cowburn, David, E-mail: cowburn@cowburnlab.org, E-mail: David.cowburn@einstein.yu.edu [Albert Einstein College of Medicine of Yeshiva University, Department of Biochemistry (United States)

    2015-01-15

    There has been a longstanding interest in being able to accurately predict NMR chemical shifts from structural data. Recent studies have focused on using molecular dynamics (MD) simulation data as input for improved prediction. Here we examine the accuracy of chemical shift prediction for intein systems, which have regions of intrinsic disorder. We find that using MD simulation data as input for chemical shift prediction does not consistently improve prediction accuracy over use of a static X-ray crystal structure. This appears to result from the complex conformational ensemble of the disordered protein segments. We show that using accelerated molecular dynamics (aMD) simulations improves chemical shift prediction, suggesting that methods which better sample the conformational ensemble like aMD are more appropriate tools for use in chemical shift prediction for proteins with disordered regions. Moreover, our study suggests that data accurately reflecting protein dynamics must be used as input for chemical shift prediction in order to correctly predict chemical shifts in systems with disorder.

  10. Correlation of chemical shifts predicted by molecular dynamics simulations for partially disordered proteins.

    Science.gov (United States)

    Karp, Jerome M; Eryilmaz, Ertan; Erylimaz, Ertan; Cowburn, David

    2015-01-01

    There has been a longstanding interest in being able to accurately predict NMR chemical shifts from structural data. Recent studies have focused on using molecular dynamics (MD) simulation data as input for improved prediction. Here we examine the accuracy of chemical shift prediction for intein systems, which have regions of intrinsic disorder. We find that using MD simulation data as input for chemical shift prediction does not consistently improve prediction accuracy over use of a static X-ray crystal structure. This appears to result from the complex conformational ensemble of the disordered protein segments. We show that using accelerated molecular dynamics (aMD) simulations improves chemical shift prediction, suggesting that methods which better sample the conformational ensemble like aMD are more appropriate tools for use in chemical shift prediction for proteins with disordered regions. Moreover, our study suggests that data accurately reflecting protein dynamics must be used as input for chemical shift prediction in order to correctly predict chemical shifts in systems with disorder.

  11. Empirical Correlation Between Protein Backbone 15N And 13C Secondary Chemical Shifts and its Application to Nitrogen Chemical Shift Re-referencing

    OpenAIRE

    Wang, Liya; Markley, John L.

    2009-01-01

    The linear analysis of chemical shifts (LACS) has provided a robust method for identifying and correcting 13C chemical shift referencing problems in data from protein NMR spectroscopy. Unlike other approaches, LACS does not require prior knowledge of the three-dimensional structure or inference of the secondary structure of the protein. It also does not require extensive assignment of the NMR data. We report here a way of extending the LACS approach to 15N NMR data from proteins, so as to ena...

  12. Determination of Water Content in THF Based on Chemical Shift Differences in Solution NMR

    Energy Technology Data Exchange (ETDEWEB)

    Jun, Jae Kyung; Park, Hey Rhee; Lee, Yunhee; Choi, Myung Gil; Chang, Suk-Kyu; Ahn, Sangdoo [Chung-Ang University, Seoul (Korea, Republic of)

    2016-03-15

    In this study, H NMR chemical shift differences were used as a probe for water content in organic solvents. Changes in chemical shift differences reflecting the competition for hydrogen bondings between fluoride ions and water were linearly proportional to water content within certain ranges. Comparison between the results obtained using the developed sensor and Karl Fischer showed that this method could be useful to understand water sensing mechanisms of dye and that the probes were sensitive to water content in organic solvents. NMR spectroscopy is one of the most powerful and versatile analytical techniques for the analysis of molecular structures and properties. Chemical shifts can be regarded as the most important information that can be obtained from NMR in regard to molecular structures. Changes in chemical and/or physical environments affecting electronic distributions result in alterations in the chemical shifts of the nuclei involved.

  13. Stereospecific assignment of the asparagine and glutamine sidechain amide protons in proteins from chemical shift analysis

    Energy Technology Data Exchange (ETDEWEB)

    Harsch, Tobias; Schneider, Philipp; Kieninger, Bärbel; Donaubauer, Harald; Kalbitzer, Hans Robert, E-mail: hans-robert.kalbitzer@biologie.uni-regensburg.de [University of Regensburg, Institute of Biophysics and Physical Biochemistry and Centre of Magnetic Resonance in Chemistry and Biomedicine (Germany)

    2017-02-15

    Side chain amide protons of asparagine and glutamine residues in random-coil peptides are characterized by large chemical shift differences and can be stereospecifically assigned on the basis of their chemical shift values only. The bimodal chemical shift distributions stored in the biological magnetic resonance data bank (BMRB) do not allow such an assignment. However, an analysis of the BMRB shows, that a substantial part of all stored stereospecific assignments is not correct. We show here that in most cases stereospecific assignment can also be done for folded proteins using an unbiased artificial chemical shift data base (UACSB). For a separation of the chemical shifts of the two amide resonance lines with differences ≥0.40 ppm for asparagine and differences ≥0.42 ppm for glutamine, the downfield shifted resonance lines can be assigned to H{sup δ21} and H{sup ε21}, respectively, at a confidence level >95%. A classifier derived from UASCB can also be used to correct the BMRB data. The program tool AssignmentChecker implemented in AUREMOL calculates the Bayesian probability for a given stereospecific assignment and automatically corrects the assignments for a given list of chemical shifts.

  14. Theoretical Study of the NMR Chemical Shift of Xe in Supercritical Condition

    DEFF Research Database (Denmark)

    Lacerda Junior, Evanildo Gomes; Sauer, Stephan P. A.; Mikkelsen, Kurt Valentin

    2018-01-01

    In this work we investigate the level of theory necessary for reproducing the non-linear variation of the 129Xe nuclear magnetic resonance (NMR) chemical shift with the density of Xe in supercritical conditions. In detail we study how the 129Xe chemical shift depends under these conditions...... on electron correlation, relativistic and many-body effects. The latter are included using a sequential-QM/MM methodology, in which a classical MD simulation is performed first and the chemical shift is then obtained as an average of quantum calculations of 250 MD snapshots conformations carried out for Xen...... this approach we obtain very good agreement with the experimental data, showing that the chemical shift of 129Xe in supercritical conditions is very well described by cluster calculations at the HF level, with small contributions from relativistic and electron correlation effects....

  15. Combined Effects of Noise and Shift Work on Workers’ Physiological Parameters in a Chemical Industry

    OpenAIRE

    M. Motamedzade; S. Ghazaiee

    2003-01-01

    This study was conducted to determine the combined effects of noise and shift work on physiological parameters including body temperature, heart rate and blood pressure. This study was performed in a chemical industry in Tehran in 1993. The workers’ physiological parameters was recorded at the beginning and at the end of all work shifts. Groups under study included : day workers (n=115) , day workers with continuous noise exposure (n=44) , two-shift workers without...

  16. Supramolecular chemical shift reagents inducing conformational transitions: NMR analysis of carbohydrate homooligomer mixtures

    DEFF Research Database (Denmark)

    Beeren, Sophie; Meier, Sebastian

    2015-01-01

    We introduce the concept of supramolecular chemical shift reagents as a tool to improve signal resolution for the NMR analysis of homooligomers. Non-covalent interactions with the shift reagent can constrain otherwise flexible analytes inducing a conformational transition that results in signal...

  17. Prediction of hydrogen and carbon chemical shifts from RNA using database mining and support vector regression.

    Science.gov (United States)

    Brown, Joshua D; Summers, Michael F; Johnson, Bruce A

    2015-09-01

    The Biological Magnetic Resonance Data Bank (BMRB) contains NMR chemical shift depositions for over 200 RNAs and RNA-containing complexes. We have analyzed the (1)H NMR and (13)C chemical shifts reported for non-exchangeable protons of 187 of these RNAs. Software was developed that downloads BMRB datasets and corresponding PDB structure files, and then generates residue-specific attributes based on the calculated secondary structure. Attributes represent properties present in each sequential stretch of five adjacent residues and include variables such as nucleotide type, base-pair presence and type, and tetraloop types. Attributes and (1)H and (13)C NMR chemical shifts of the central nucleotide are then used as input to train a predictive model using support vector regression. These models can then be used to predict shifts for new sequences. The new software tools, available as stand-alone scripts or integrated into the NMR visualization and analysis program NMRViewJ, should facilitate NMR assignment and/or validation of RNA (1)H and (13)C chemical shifts. In addition, our findings enabled the re-calibration a ring-current shift model using published NMR chemical shifts and high-resolution X-ray structural data as guides.

  18. Chemical shift MRI can aid in the diagnosis of indeterminate skeletal lesions of the spine

    Energy Technology Data Exchange (ETDEWEB)

    Douis, H. [University Hospital Birmingham, Department of Radiology, Birmingham (United Kingdom); Royal Orthopaedic Hospital, Department of Radiology, Birmingham (United Kingdom); Davies, A.M. [Royal Orthopaedic Hospital, Department of Radiology, Birmingham (United Kingdom); Jeys, L. [Royal Orthopaedic Hospital, Department of Orthopaedic Oncology, Birmingham (United Kingdom); Sian, P. [Royal Orthopaedic Hospital, Department of Spinal Surgery and Spinal Oncology, Birmingham (United Kingdom)

    2016-04-15

    To evaluate the role of chemical shift MRI in the characterisation of indeterminate skeletal lesions of the spine as benign or malignant. Fifty-five patients (mean age 54.7 years) with 57 indeterminate skeletal lesions of the spine were included in this retrospective study. In addition to conventional MRI at 3 T which included at least sagittal T1WI and T2WI/STIR sequences, patients underwent chemical shift MRI. A cut-off value with a signal drop-out of 20 % was used to differentiate benign lesions from malignant lesions (signal drop-out <20 % being malignant). There were 45 benign lesions and 12 malignant lesions. Chemical shift imaging correctly diagnosed 33 of 45 lesions as benign and 11 of 12 lesions as malignant. In contrast, there were 12 false positive cases and 1 false negative case based on chemical shift MRI. This yielded a sensitivity of 91.7 %, a specificity of 73.3 %, a negative predictive value of 97.1 %, a positive predictive value of 47.8 % and a diagnostic accuracy of 82.5 %. Chemical shift MRI can aid in the characterisation of indeterminate skeletal lesions of the spine in view of its high sensitivity in diagnosing malignant lesions. Chemical shift MRI can potentially avoid biopsy in a considerable percentage of patients with benign skeletal lesions of the spine. (orig.)

  19. Errors in the Calculation of 27Al Nuclear Magnetic Resonance Chemical Shifts

    Directory of Open Access Journals (Sweden)

    Hui Zhao

    2012-11-01

    Full Text Available Computational chemistry is an important tool for signal assignment of 27Al nuclear magnetic resonance spectra in order to elucidate the species of aluminum(III in aqueous solutions. The accuracy of the popular theoretical models for computing the 27Al chemical shifts was evaluated by comparing the calculated and experimental chemical shifts in more than one hundred aluminum(III complexes. In order to differentiate the error due to the chemical shielding tensor calculation from that due to the inadequacy of the molecular geometry prediction, single-crystal X-ray diffraction determined structures were used to build the isolated molecule models for calculating the chemical shifts. The results were compared with those obtained using the calculated geometries at the B3LYP/6-31G(d level. The isotropic chemical shielding constants computed at different levels have strong linear correlations even though the absolute values differ in tens of ppm. The root-mean-square difference between the experimental chemical shifts and the calculated values is approximately 5 ppm for the calculations based on the X-ray structures, but more than 10 ppm for the calculations based on the computed geometries. The result indicates that the popular theoretical models are adequate in calculating the chemical shifts while an accurate molecular geometry is more critical.

  20. Further conventions for NMR shielding and chemical shifts IUPAC recommendations 2008.

    Science.gov (United States)

    Harris, Robin K; Becker, Edwin D; Cabral De Menezes, Sonia M; Granger, Pierre; Hoffman, Roy E; Zilm, Kurt W

    2008-03-01

    IUPAC has published a number of recommendations regarding the reporting of nuclear magnetic resonance (NMR) data, especially chemical shifts. The most recent publication [Pure Appl. Chem. 73, 1795 (2001)] recommended that tetramethylsilane (TMS) serve as a universal reference for reporting the shifts of all nuclides, but it deferred recommendations for several aspects of this subject. This document first examines the extent to which the (1)H shielding in TMS itself is subject to change by variation in temperature, concentration, and solvent. On the basis of recently published results, it has been established that the shielding of TMS in solution [along with that of sodium-3-(trimethylsilyl)propanesulfonate, DSS, often used as a reference for aqueous solutions] varies only slightly with temperature but is subject to solvent perturbations of a few tenths of a part per million (ppm). Recommendations are given for reporting chemical shifts under most routine experimental conditions and for quantifying effects of temperature and solvent variation, including the use of magnetic susceptibility corrections and of magic-angle spinning (MAS). This document provides the first IUPAC recommendations for referencing and reporting chemical shifts in solids, based on high-resolution MAS studies. Procedures are given for relating (13)C NMR chemical shifts in solids to the scales used for high-resolution studies in the liquid phase. The notation and terminology used for describing chemical shift and shielding tensors in solids are reviewed in some detail, and recommendations are given for best practice.

  1. Further conventions for NMR shielding and chemical shifts (IUPAC Recommendations 2008).

    Science.gov (United States)

    Harris, Robin K; Becker, Edwin D; De Menezes, Sonia M Cabral; Granger, Pierre; Hoffman, Roy E; Zilm, Kurt W

    2008-06-01

    IUPAC has published a number of recommendations regarding the reporting of nuclear magnetic resonance (NMR) data, especially chemical shifts. The most recent publication [Pure Appl. Chem. 73, 1795 (2001)] recommended that tetramethylsilane (TMS) serve as a universal reference for reporting the shifts of all nuclides, but it deferred recommendations for several aspects of this subject. This document first examines the extent to which the (1)H shielding in TMS itself is subject to change by variation in temperature, concentration, and solvent. On the basis of recently published results, it has been established that the shielding of TMS in solution [along with that of sodium-3-(trimethylsilyl)propanesulfonate, DSS, often used as a reference for aqueous solutions] varies only slightly with temperature but is subject to solvent perturbations of a few tenths of a part per million (ppm). Recommendations are given for reporting chemical shifts under most routine experimental conditions and for quantifying effects of temperature and solvent variation, including the use of magnetic susceptibility corrections and of magic-angle spinning (MAS). This document provides the first IUPAC recommendations for referencing and reporting chemical shifts in solids, based on high-resolution MAS studies. Procedures are given for relating (13)C NMR chemical shifts in solids to the scales used for high-resolution studies in the liquid phase. The notation and terminology used for describing chemical shift and shielding tensors in solids are reviewed in some detail, and recommendations are given for best practice. Copyright (c) 2008 John Wiley & Sons, Ltd

  2. Error assessment in molecular dynamics trajectories using computed NMR chemical shifts.

    Science.gov (United States)

    Koes, David R; Vries, John K

    2017-01-01

    Accurate chemical shifts for the atoms in molecular mechanics (MD) trajectories can be obtained from quantum mechanical (QM) calculations that depend solely on the coordinates of the atoms in the localized regions surrounding atoms of interest. If these coordinates are correct and the sample size is adequate, the ensemble average of these chemical shifts should be equal to the chemical shifts obtained from NMR spectroscopy. If this is not the case, the coordinates must be incorrect. We have utilized this fact to quantify the errors associated with the backbone atoms in MD simulations of proteins. A library of regional conformers containing 169,499 members was constructed from 6 model proteins. The chemical shifts associated with the backbone atoms in each of these conformers was obtained from QM calculations using density functional theory at the B3LYP level with a 6-311+G(2d,p) basis set. Chemical shifts were assigned to each backbone atom in each MD simulation frame using a template matching approach. The ensemble average of these chemical shifts was compared to chemical shifts from NMR spectroscopy. A large systematic error was identified that affected the 1H atoms of the peptide bonds involved in hydrogen bonding with water molecules or peptide backbone atoms. This error was highly sensitive to changes in electrostatic parameters. Smaller errors affecting the 13Ca and 15N atoms were also detected. We believe these errors could be useful as metrics for comparing the force-fields and parameter sets used in MD simulation because they are directly tied to errors in atomic coordinates.

  3. Proof of ion-pair structures in ammonium-based protic ionic liquids using combined NMR and DFT/PCM-based chemical shift calculations.

    Science.gov (United States)

    Lozynski, M; Pernak, J; Gdaniec, Z; Gorska, B; Béguin, F

    2017-09-20

    The self-assembly of triethylammonium bis(trifluoromethylsulfonyl)imide, i.e. [(C 2 H 5 ) 3 NH][TFSI], in chloroform and aqueous solutions has been investigated using 1 H NMR spectroscopy and computational (DFT/PCM prediction) methods. We have examined a number of ion pairs formed between the [(C 2 H 5 ) 3 NH] + cation with different conformations of alkyl substituents as well as various dispositions of the multi-site [TFSI] - anion. Based on the agreement between the calculated (DFT) and observed 1 H NMR chemical shifts, [(C 2 H 5 ) 3 NH][TFSI] in chloroform formed lipophilic complexes with effective N + -HN or N + -HO hydrogen bonding, whereas hydrophilic complexes with C α -HO and C α -HF hydrogen bonding are found in aqueous solutions. This study provides a new insight into the self-aggregation of ammonium PILs incorporating the widely used [TFSI] - anion and demonstrates the importance of solvent effects on chemical shifts. The simulations with explicit and implicit dielectric continuum solvents are found to be the most realistic method, yielding a representative ensemble of structures.

  4. Prediction algorithm for amino acid types with their secondary structure in proteins (PLATON) using chemical shifts.

    Science.gov (United States)

    Labudde, D; Leitner, D; Krüger, M; Oschkinat, H

    2003-01-01

    The algorithm PLATON is able to assign sets of chemical shifts derived from a single residue to amino acid types with its secondary structure (amino acid species). A subsequent ranking procedure using optionally two different penalty functions yields predictions for possible amino acid species for the given set of chemical shifts. This was demonstrated in the case of the alpha-spectrin SH3 domain and applied to 9 further protein data sets taken from the BioMagRes database. A database consisting of reference chemical shift patterns (reference CSPs) was generated from assigned chemical shifts of proteins with known 3D-structure. This reference CSP database is used in our approach for extracting distributions of amino acid types with their most likely secondary structure elements (namely alpha-helix, beta-sheet, and coil) for single amino acids by comparison with query CSPs. Results obtained for the 10 investigated proteins indicates that the percentage of correct amino acid species in the first three positions in the ranking list, ranges from 71.4% to 93.2% for the more favorable penalty function. Where only the top result of the ranking list for these 10 proteins is considered, 36.5% to 83.1% of the amino acid species are correctly predicted. The main advantage of our approach, over other methods that rely on average chemical shift values is the ability to increase database content by incorporating newly derived CSPs, and therefore to improve PLATON's performance over time.

  5. Prediction of Xaa-Pro peptide bond conformation from sequence and chemical shifts

    Energy Technology Data Exchange (ETDEWEB)

    Shen Yang; Bax, Ad, E-mail: bax@nih.go [National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Laboratory of Chemical Physics (United States)

    2010-03-15

    We present a program, named Promega, to predict the Xaa-Pro peptide bond conformation on the basis of backbone chemical shifts and the amino acid sequence. Using a chemical shift database of proteins of known structure together with the PDB-extracted amino acid preference of cis Xaa-Pro peptide bonds, a cis/trans probability score is calculated from the backbone and {sup 13}C{sup {beta}} chemical shifts of the proline and its neighboring residues. For an arbitrary number of input chemical shifts, which may include Pro-{sup 13}C{sup {gamma}}, Promega calculates the statistical probability that a Xaa-Pro peptide bond is cis. Besides its potential as a validation tool, Promega is particularly useful for studies of larger proteins where Pro-{sup 13}C{sup {gamma}} assignments can be challenging, and for on-going efforts to determine protein structures exclusively on the basis of backbone and {sup 13}C{sup {beta}} chemical shifts.

  6. Consistent porphyrin force field. 2. Nickel octaethylporphyrin skeletal and substituent mode assignments from sup 15 N, meso-d sub 4 , and methylene-d sub 16 Raman and infrared isotope shifts

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xiaoyuan; Czernuszewicz, R.S.; Spiro, T.G. (Princeton Univ., NJ (USA)); Kincaid, J.R. (Marquette Univ., Milwaukee, WI (USA)); Stein, P. (Duquesne Univ., Pittsburgh, PA (USA))

    1990-01-11

    Resonance Raman spectra with variable-wavelength excitation are reported for nickel octaethylporphyrin and its isotopomers containing {sup 15}N, and {sup 2}H at the methine (meso-d{sub 4}) and methylene (methylene-d{sub 16}) carbon atoms. The {sup 15}N, meso-d{sub 4} double isotopomer is also examined. The infrared spectrum of the methylene-d{sub 16} isotopomer is reported, and the frequencies are combined with recently published infrared results for the other isotopomers. Essentially all of the porphyrin skeletal modes have been assigned and have been allocated to local coordinates which recognize the pyrrole rings as cooperative vibrational units. The assignments are supported by a normal-coordinate analysis with a valence force field involving standard ethyl force constants and porphyrin in-plane force constants which are transferred nearly intact from Ni porphine and Ni tetraphenylporphine. Many vibrational modes of the NiOEP ethyl substituents have also been located in the spectra and assigned. Bands assignable to ethyl C-C stretching and C-H bending modes are surprisingly strong in the resonance Raman spectra and suggest appreciable involvement of the ethyl groups in the porphyrin {pi}-{pi}{sup *} excited states. The conformations of the ethyl substituents have a marked influence on the low-frequency vibrational spectra.

  7. Density functional calculations of {sup 15}N chemical shifts in solvated dipeptides

    Energy Technology Data Exchange (ETDEWEB)

    Cai Ling; Fushman, David, E-mail: fushman@umd.edu; Kosov, Daniel S. [University of Maryland, Department of Chemistry and Biochemistry (United States)], E-mail: dkosov@umd.edu

    2008-06-15

    We performed density functional calculations to examine the effects of solvation, hydrogen bonding, backbone conformation, and the side chain on {sup 15}N chemical shielding in proteins. We used N-methylacetamide (NMA) and N-formyl-alanyl-X (with X being one of the 19 naturally occurring amino acids excluding proline) as model systems. In addition, calculations were performed for selected fragments from protein GB3. The conducting polarizable continuum model was employed to include the effect of solvent in the density functional calculations. Our calculations for NMA show that the augmentation of the polarizable continuum model with the explicit water molecules in the first solvation shell has a significant influence on isotropic {sup 15}N chemical shift but not as much on the chemical shift anisotropy. The difference in the isotropic chemical shift between the standard {beta}-sheet and {alpha}-helical conformations ranges from 0.8 to 6.2 ppm depending on the residue type, with the mean of 2.7 ppm. This is in good agreement with the experimental chemical shifts averaged over a database of 36 proteins containing >6100 amino acid residues. The orientation of the {sup 15}N chemical shielding tensor as well as its anisotropy and asymmetry are also in the range of values experimentally observed for peptides and proteins.

  8. 1H NMR spectra. Part 30(+): 1H chemical shifts in amides and the magnetic anisotropy, electric field and steric effects of the amide group.

    Science.gov (United States)

    Abraham, Raymond J; Griffiths, Lee; Perez, Manuel

    2013-03-01

    The (1)H spectra of 37 amides in CDCl(3) solvent were analysed and the chemical shifts obtained. The molecular geometries and conformational analysis of these amides were considered in detail. The NMR spectral assignments are of interest, e.g. the assignments of the formamide NH(2) protons reverse in going from CDCl(3) to more polar solvents. The substituent chemical shifts of the amide group in both aliphatic and aromatic amides were analysed using an approach based on neural network data for near (≤3 bonds removed) protons and the electric field, magnetic anisotropy, steric and for aromatic systems π effects of the amide group for more distant protons. The electric field is calculated from the partial atomic charges on the N.C═O atoms of the amide group. The magnetic anisotropy of the carbonyl group was reproduced with the asymmetric magnetic anisotropy acting at the midpoint of the carbonyl bond. The values of the anisotropies Δχ(parl) and Δχ(perp) were for the aliphatic amides 10.53 and -23.67 (×10(-6) Å(3)/molecule) and for the aromatic amides 2.12 and -10.43 (×10(-6) Å(3)/molecule). The nitrogen anisotropy was 7.62 (×10(-6) Å(3)/molecule). These values are compared with previous literature values. The (1)H chemical shifts were calculated from the semi-empirical approach and also by gauge-independent atomic orbital calculations with the density functional theory method and B3LYP/6-31G(++) (d,p) basis set. The semi-empirical approach gave good agreement with root mean square error of 0.081 ppm for the data set of 280 entries. The gauge-independent atomic orbital approach was generally acceptable, but significant errors (ca. 1 ppm) were found for the NH and CHO protons and also for some other protons. Copyright © 2013 John Wiley & Sons, Ltd.

  9. Deuterium isotope effects on 13C chemical shifts of negatively charged NH.N systems

    DEFF Research Database (Denmark)

    Hansen, Poul Erik; Pietrzak, Mariusz; Grech, Eugeniusz

    2013-01-01

    ” and equilibrium cases. NMR assignments of the former have been revised. The NH proton is deuteriated. The isotope effects on 13C chemical shifts are rather unusual in these strongly hydrogen bonded systems between a NH and a negatively charged nitrogen atom. The formal four-bond effects are found to be negative......Deuterium isotope effects on 13C chemical shifts are investigated in anions of 1,8-bis(4-toluenesulphonamido)naphthalenes together with N,N-(naphthalene-1,8-diyl)bis(2,2,2-trifluoracetamide) all with bis(1,8-dimethylamino)napthaleneH+ as counter ion. These compounds represent both “static...... indicating transmission via the hydrogen bond. In addition, unusual long range effects are seen. Structures, 1H and 13C NMR chemical shifts and changes in nuclear shieldings upon deuteriation are calculated using density functional theory methods...

  10. Protein structure validation and refinement using amide proton chemical shifts derived from quantum mechanics

    DEFF Research Database (Denmark)

    Christensen, Anders Steen; Linnet, Troels Emtekær; Borg, Mikael

    2013-01-01

    that the structural sensitivity of the QM-based amide proton chemical shift predictions is needed to obtain this agreement. The ProCS method thus offers a powerful new tool for refining the structures of hydrogen bonding networks to high accuracy with many potential applications such as protein flexibility in ligand......We present the ProCS method for the rapid and accurate prediction of protein backbone amide proton chemical shifts - sensitive probes of the geometry of key hydrogen bonds that determine protein structure. ProCS is parameterized against quantum mechanical (QM) calculations and reproduces high level......-based structural refinements, starting from high-resolution X-ray structures of Protein G, ubiquitin, and SMN Tudor Domain, result in average chemical shifts, hydrogen bond geometries, and trans-hydrogen bond ((h3) JNC' ) spin-spin coupling constants that are in excellent agreement with experiment. We show...

  11. Isotope effects on chemical shifts in the study of intramolecular hydrogen bonds.

    Science.gov (United States)

    Hansen, Poul Erik

    2015-01-30

    The paper deals with the use of isotope effects on chemical shifts in characterizing intramolecular hydrogen bonds. Both so-called resonance-assisted (RAHB) and non-RAHB systems are treated. The importance of RAHB will be discussed. Another very important issue is the borderline between "static" and tautomeric systems. Isotope effects on chemical shifts are particularly useful in such studies. All kinds of intramolecular hydrogen bonded systems will be treated, typical hydrogen bond donors: OH, NH, SH and NH+, typical acceptors C=O, C=N, C=S C=N-. The paper will be deal with both secondary and primary isotope effects on chemical shifts. These two types of isotope effects monitor the same hydrogen bond, but from different angles.

  12. Isotope effects on chemical shifts in the study of intramolecular hydrogen bonds

    DEFF Research Database (Denmark)

    Hansen, Poul Erik

    2015-01-01

    The paper deals with the use of isotope effects on chemical shifts in characterizing intramolecular hydrogen bonds. Both so-called resonance-assisted (RAHB) and non-RAHB systems are treated. The importance of RAHB will be discussed. Another very important issue is the borderline between “static......” and tautomeric systems. Isotope effects on chemical shifts are particularly useful in such studies. All kinds of intramolecular hydrogen bonded systems will be treated, typical hydrogen bond donors: OH, NH, SH and NH+, typical acceptors C=O, C=N, C=S C=N−. The paper will be deal with both secondary and primary...... isotope effects on chemical shifts. These two types of isotope effects monitor the same hydrogen bond, but from different angles...

  13. 13C-detection in RNA bases: revealing structure-chemical shift relationships.

    Science.gov (United States)

    Farès, Christophe; Amata, Irene; Carlomagno, Teresa

    2007-12-26

    The chemical shifts of the unprotonated carbons in the proton-deficient nucleobases of RNA are rarely reported, despite the valuable information that they contain about base-pairing and base-stacking. We have developed 13C-detected 2D-experiments to identify the unprotonated 13C in the RNA bases and have assigned all the base nuclei of uniformly 13C,15N-labeled HIV-2 TAR-RNA. The 13C chemical shift distributions revealed perturbations correlated with the base-pairing and base-stacking properties of all four base-types. From this work, we conclude that the information contained in the chemical shift perturbations within the base rings can provide valuable restraint information for solving RNA structures, especially in conformational averaged regions, where NOE-based information is not available.

  14. Solar energy absorption in norbornadiene-quadricyclane system through electron donating or withdrawing substituents1

    Science.gov (United States)

    Edjlali, L.; Vessally, E.; Abbasian, M.

    2011-05-01

    An attempt is made to maximize the solar energy absorption in norbornadiene ( 1)-quadricyclane ( 2) system, through direct attachment of substituents at C1, C2, or C7 atoms of 1; calculating the corresponding energies at B3LYP/6-311++G** level of theory. The electron donating and electron withdrawing substituents of 1 n-X, attached at C2, were suitable for both solar absorption bands and solar energy storage. DFT calculations indicate that the solar absorption bands of 12-X were shifted to the visible spectrum region through the electron withdrawing substituents more than through electron donating substituents.

  15. CSI 2.0: a significantly improved version of the Chemical Shift Index.

    Science.gov (United States)

    Hafsa, Noor E; Wishart, David S

    2014-11-01

    Protein chemical shifts have long been used by NMR spectroscopists to assist with secondary structure assignment and to provide useful distance and torsion angle constraint data for structure determination. One of the most widely used methods for secondary structure identification is called the Chemical Shift Index (CSI). The CSI method uses a simple digital chemical shift filter to locate secondary structures along the protein chain using backbone (13)C and (1)H chemical shifts. While the CSI method is simple to use and easy to implement, it is only about 75-80% accurate. Here we describe a significantly improved version of the CSI (2.0) that uses machine-learning techniques to combine all six backbone chemical shifts ((13)Cα, (13)Cβ, (13)C, (15)N, (1)HN, (1)Hα) with sequence-derived features to perform far more accurate secondary structure identification. Our tests indicate that CSI 2.0 achieved an average identification accuracy (Q3) of 90.56% for a training set of 181 proteins in a repeated tenfold cross-validation and 89.35% for a test set of 59 proteins. This represents a significant improvement over other state-of-the-art chemical shift-based methods. In particular, the level of performance of CSI 2.0 is equal to that of standard methods, such as DSSP and STRIDE, used to identify secondary structures via 3D coordinate data. This suggests that CSI 2.0 could be used both in providing accurate NMR constraint data in the early stages of protein structure determination as well as in defining secondary structure locations in the final protein model(s). A CSI 2.0 web server (http://csi.wishartlab.com) is available for submitting the input queries for secondary structure identification.

  16. Protein Structure Validation and Refinement Using Chemical Shifts Derived from Quantum Mechanics

    DEFF Research Database (Denmark)

    Bratholm, Lars Andersen

    In this thesis, my work involving dierent aspects of protein structure determination by computer modeling is presented. Determination of several protein's native fold were carried out with Markov chain Monte Carlo simulations in the PHAISTOS protein structure simulation framework, utilizing...... to within 3 A. Furthermore, a fast quantum mechanics based chemical shift predictor was developed together with methodology for using chemical shifts in structure simulations. The developed predictor was used for renement of several protein structures and for reducing the computational cost of quantum...

  17. Using chemical shifts to assess transient secondary structure and generate ensemble structures of intrinsically disordered proteins.

    Science.gov (United States)

    Kashtanov, Stepan; Borcherds, Wade; Wu, Hongwei; Daughdrill, Gary W; Ytreberg, F Marty

    2012-01-01

    The chemical shifts of backbone atoms in polypeptides are sensitive to the dihedral angles phi and psi and can be used to estimate transient secondary structure and to generate structural ensembles of intrinsically disordered proteins (IDPs). In this chapter, several of the random coil reference databases used to estimate transient secondary structure are described, and the procedure is outlined for using these databases to estimate transient secondary structure. A new protocol is also presented for generating a diverse ensemble of structures for an IDP and reweighting these structures to optimize the fit between simulated and experimental chemical shift values.

  18. Sequential nearest-neighbor effects on computed {sup 13}C{sup {alpha}} chemical shifts

    Energy Technology Data Exchange (ETDEWEB)

    Vila, Jorge A. [Cornell University, Baker Laboratory of Chemistry and Chemical Biology (United States); Serrano, Pedro; Wuethrich, Kurt [The Scripps Research Institute, Department of Molecular Biology (United States); Scheraga, Harold A., E-mail: has5@cornell.ed [Cornell University, Baker Laboratory of Chemistry and Chemical Biology (United States)

    2010-09-15

    To evaluate sequential nearest-neighbor effects on quantum-chemical calculations of {sup 13}C{sup {alpha}} chemical shifts, we selected the structure of the nucleic acid binding (NAB) protein from the SARS coronavirus determined by NMR in solution (PDB id 2K87). NAB is a 116-residue {alpha}/{beta} protein, which contains 9 prolines and has 50% of its residues located in loops and turns. Overall, the results presented here show that sizeable nearest-neighbor effects are seen only for residues preceding proline, where Pro introduces an overestimation, on average, of 1.73 ppm in the computed {sup 13}C{sup {alpha}} chemical shifts. A new ensemble of 20 conformers representing the NMR structure of the NAB, which was calculated with an input containing backbone torsion angle constraints derived from the theoretical {sup 13}C{sup {alpha}} chemical shifts as supplementary data to the NOE distance constraints, exhibits very similar topology and comparable agreement with the NOE constraints as the published NMR structure. However, the two structures differ in the patterns of differences between observed and computed {sup 13}C{sup {alpha}} chemical shifts, {Delta}{sub ca,i}, for the individual residues along the sequence. This indicates that the {Delta}{sub ca,i} -values for the NAB protein are primarily a consequence of the limited sampling by the bundles of 20 conformers used, as in common practice, to represent the two NMR structures, rather than of local flaws in the structures.

  19. Combined Effects of Noise and Shift Work on Workers’ Physiological Parameters in a Chemical Industry

    Directory of Open Access Journals (Sweden)

    M. Motamedzade

    2003-04-01

    Full Text Available This study was conducted to determine the combined effects of noise and shift work on physiological parameters including body temperature, heart rate and blood pressure. This study was performed in a chemical industry in Tehran in 1993. The workers’ physiological parameters was recorded at the beginning and at the end of all work shifts. Groups under study included : day workers (n=115 , day workers with continuous noise exposure (n=44 , two-shift workers without noise exposure (n=180 , three-shift workers without noise exposure and three-shift workers with continous noise exposure (n=216. In workers with continuous noise exposure, noise dosimetry was performed using B & K noise dose meter type 4428. The results showed that noise and shift work hove more effects on systolic and diastolic blood pressure than body temperature. The statistical analysis showed that in 3-shift workers, combined effects of noise and shift work on systolic and diastolic blood pressure caused considerable differences between exposed and control group. In general, regarding research design of this study to determine probable combined effects of noise and shiftwork on physiological parameters, our findings confirmed the additive effects of noise and shiftwork on systolic and diastolic blood pressure in which the effect of noise was more significant. Our findings showed that combined exposure to shiftwork and noise may be regarded as a risk factor for cardiovascular diseases because it is responsible for increasing blood pressure in exposed workers.

  20. Substituent Effect in Benzene Dication

    NARCIS (Netherlands)

    Palusiak, M.; Domagala, M.; Dominikowska, J.E.; Bickelhaupt, F.M.

    2014-01-01

    It was recently postulated that the benzene ring and its 4n + 2 π-electron analogues are resistant to the substituent effect due to the fact that such systems tend to retain their delocalized character. Therefore, the 4n π-electron dicationic form of benzene should appear to be less resistant to the

  1. Investigation of DOTA-Metal Chelation Effects on the Chemical Shift of 129 Xe

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, K; Slack, CC; Vassiliou, CC; Dao, P; Gomes, MD; Kennedy, DJ; Truxal, AE; Sperling, LJ; Francis, MB; Wemmer, DE; Pines, A

    2015-09-17

    Recent work has shown that xenon chemical shifts in cryptophane-cage sensors are affected when tethered chelators bind to metals. Here in this paper, we explore the xenon shifts in response to a wide range of metal ions binding to diastereomeric forms of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) linked to cryptophane-A. The shifts induced by the binding of Ca2+, Cu2+, Ce3+, Zn2+, Cd2+, Ni2+, Co2+, Cr2+, Fe3+, and Hg2+ are distinct. In addition, the different responses of the diastereomers for the same metal ion indicate that shifts are affected by partial folding with a correlation between the expected coordination number of the metal in the DOTA complex and the chemical shift of 129Xe. Lastly, these sensors may be used to detect and quantify many important metal ions, and a better understanding of the basis for the induced shifts could enhance future designs.

  2. Parameter-free calculation of K alpha chemical shifts for Al, Si, and Ge oxides

    DEFF Research Database (Denmark)

    Lægsgaard, Jesper

    2001-01-01

    The chemical shifts of the K alpha radiation line from Al, Si, and Ge ions between their elemental and oxide forms are calculated within the framework of density functional theory using ultrasoft pseudopotentials. It is demonstrated that this theoretical approach yields quantitatively accurate...

  3. Automated assignment of NMR chemical shifts based on a known structure and 4D spectra

    Energy Technology Data Exchange (ETDEWEB)

    Trautwein, Matthias; Fredriksson, Kai [Eberhard Karls Universität Tübingen, Institute of Pharmacy (Germany); Möller, Heiko M. [University of Potsdam, Institute of Chemistry (Germany); Exner, Thomas E., E-mail: thomas.exner@uni-konstanz.de [Eberhard Karls Universität Tübingen, Institute of Pharmacy (Germany)

    2016-08-15

    Apart from their central role during 3D structure determination of proteins the backbone chemical shift assignment is the basis for a number of applications, like chemical shift perturbation mapping and studies on the dynamics of proteins. This assignment is not a trivial task even if a 3D protein structure is known and needs almost as much effort as the assignment for structure prediction if performed manually. We present here a new algorithm based solely on 4D [{sup 1}H,{sup 15}N]-HSQC-NOESY-[{sup 1}H,{sup 15}N]-HSQC spectra which is able to assign a large percentage of chemical shifts (73–82 %) unambiguously, demonstrated with proteins up to a size of 250 residues. For the remaining residues, a small number of possible assignments is filtered out. This is done by comparing distances in the 3D structure to restraints obtained from the peak volumes in the 4D spectrum. Using dead-end elimination, assignments are removed in which at least one of the restraints is violated. Including additional information from chemical shift predictions, a complete unambiguous assignment was obtained for Ubiquitin and 95 % of the residues were correctly assigned in the 251 residue-long N-terminal domain of enzyme I. The program including source code is available at https://github.com/thomasexner/4Dassign https://github.com/thomasexner/4Dassign .

  4. Skeletal and chlorine effects on 13C-NMR chemical shifts of chlorinated polycyclic systems

    Directory of Open Access Journals (Sweden)

    Costa V.E.U.

    1999-01-01

    Full Text Available In order to establish a comparative analysis of chemical shifts caused by ring compression effects or by the presence of a chlorine atom on strained chlorinated carbons, a series of the chlorinated and dechlorinated polycyclic structures derived from "aldrin" (5 and "isodrin" (14 was studied. Compounds were classified in four different groups, according to their conformation and number of ring such as: endo-exo and endo-endo tetracyclics, pentacyclics and hexacyclics. The 13C chemical shift comparison between the chlorinated and dechlorinated compounds showed that when C-9 and C-10 are olefinic carbons, it occurs a shielding of 0.5-2.4 ppm for endo-endo tetracyclics and of 4.7-7.6 ppm for endo-exo tetracyclic. The chemical shift variation for C-11 reaches 49-53 ppm for endo-exo and endo-endo tetracyclics, 54 ppm for pentacyclic and 56-59 ppm for hexacyclic compounds. From these data, it was possible to observe the influence of ring compression on the chemical shifts.

  5. Identify Beta-Hairpin Motifs with Quadratic Discriminant Algorithm Based on the Chemical Shifts.

    Directory of Open Access Journals (Sweden)

    Feng YongE

    Full Text Available Successful prediction of the beta-hairpin motif will be helpful for understanding the of the fold recognition. Some algorithms have been proposed for the prediction of beta-hairpin motifs. However, the parameters used by these methods were primarily based on the amino acid sequences. Here, we proposed a novel model for predicting beta-hairpin structure based on the chemical shift. Firstly, we analyzed the statistical distribution of chemical shifts of six nuclei in not beta-hairpin and beta-hairpin motifs. Secondly, we used these chemical shifts as features combined with three algorithms to predict beta-hairpin structure. Finally, we achieved the best prediction, namely sensitivity of 92%, the specificity of 94% with 0.85 of Mathew's correlation coefficient using quadratic discriminant analysis algorithm, which is clearly superior to the same method for the prediction of beta-hairpin structure from 20 amino acid compositions in the three-fold cross-validation. Our finding showed that the chemical shift is an effective parameter for beta-hairpin prediction, suggesting the quadratic discriminant analysis is a powerful algorithm for the prediction of beta-hairpin.

  6. NMR Nomenclature: Nuclear Spin Properties and Conventions for Chemical Shifts. IUPAC Recommendations 2001.

    Science.gov (United States)

    Harris, Robin K.; Becker, Edwin D.; Cabral de Menezes, Sonia M.; Goodfellow, Robin; Granger, Pierre

    2002-12-01

    A unified scale is recommended for reporting the NMR chemical shifts of all nuclei relative to the (1)H resonance of tetramethylsilane. The unified scale is designed to provide a precise ratio, Xi, of the resonance frequency of a given nuclide to that of the primary reference, the (1)H resonance of tetramethylsilane (TMS) in dilute solution (volume fraction, varphi<1%) in chloroform. Referencing procedures are discussed, including matters of practical application of the unified scale. Special attention is paid to recommended reference samples, and values of Xi for secondary references on the unified scale are listed, many of which are the results of new measurements. Some earlier recommendations relating to the reporting of chemical shifts are endorsed. The chemical shift, delta, is redefined to avoid previous ambiguities but to leave practical usage unchanged. Relations between the unified scale and recently published recommendations for referencing in aqueous solutions (for specific use in biochemical work) are discussed, as well as the special effects of working in the solid state with magic-angle spinning. In all, nine new recommendations relating to chemical shifts are made. Standardised nuclear spin data are also presented in tabular form for the stable (and some unstable) isotopes of all elements with non-zero quantum numbers. The information given includes quantum numbers, isotopic abundances, magnetic moments, magnetogyric ratios, and receptivities, together with quadrupole moments and line-width factors (where appropriate).

  7. H-1 chemical shift imaging characterization of human brain tumor and edema

    NARCIS (Netherlands)

    Sijens, PE; Oudkerk, M

    Longitudinal (T1) and transverse (T2) relaxation times of metabolites in human brain tumor, peritumoral edema, and unaffected brain tissue were assessed from point resolved spectroscopy (PRESS) H-1 chemical shift imaging results at different repetition times (TR = 1500 and 5000 ms; T1: n = 19) and

  8. Rapid chemical shift encoding with single-acquisition single-slab 3D GRASE.

    Science.gov (United States)

    Kim, Hahnsung; Kim, Dong-Hyun; Sohn, Chul-Ho; Park, Jaeseok

    2017-11-01

    To investigate the feasibility of chemical shift encoded, single-slab 3D GRASE for rapid fat-water separation within a single acquisition. The proposed method incorporates signal-to-noise-ratio-optimal chemical shift encoding into single-slab 3D GRASE with variable flip angles. Chemical shift induced phase information was encoded in succession to different positions in k-space by inserting phase encoding blips between adjacent lobes of the oscillating readout gradients. To enhance imaging efficiency, signal prescription-based variable flip angles were used in the long refocusing pulse train. After echo-independent phase correction, missing signals in k-echo space were interpolated using convolution kernels that span over all echoes. Fat-water separation in a single acquisition was performed using both multi-echo fast spin echo and GRASE as compared to conventional multiacquisition fast spin echo with echo shifts. The proposed single-slab 3D GRASE shows superior performance in accurately delineating cartilage structures compared to its counterpart, multi-echo 3D fast spin echo. Compared with multiacquisition fast spin echo with three echo shifts (63 min), the proposed method substantially speeds up imaging time (7 min), and achieves 0.6 mm isotropic resolution in knee imaging with reduced artifacts and noise. We successfully demonstrated the feasibility of rapid chemical shift encoding and separation using the proposed, single-acquisition single-slab 3D GRASE for high resolution isotropic imaging within clinically acceptable time. Magn Reson Med 78:1852-1861, 2017. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

  9. Rapid calculation of protein chemical shifts using bond polarization theory and its application to protein structure refinement.

    Science.gov (United States)

    Jakovkin, Igor; Klipfel, Marco; Muhle-Goll, Claudia; Ulrich, Anne S; Luy, Burkhard; Sternberg, Ulrich

    2012-09-21

    Although difficult to analyze, NMR chemical shifts provide detailed information on protein structure. We have adapted the semi-empirical bond polarization theory (BPT) to protein chemical shift calculation and chemical shift driven protein structure refinement. A new parameterization for BPT amide nitrogen chemical shift calculation has been derived from MP2 ab initio calculations and successfully evaluated using crystalline tripeptides. We computed the chemical shifts of the small globular protein ubiquitin, demonstrating that BPT calculations can match the results obtained at the DFT level of theory at very low computational cost. In addition to the calculation of chemical shift tensors, BPT allows the calculation of chemical shift gradients and consequently chemical shift driven geometry optimizations. We applied chemical shift driven protein structure refinement to the conformational analysis of a set of Trypanosoma brucei (the causative agent of African sleeping sickness) tryparedoxin peroxidase Px III structures. We found that the interaction of Px III with its reaction partner Tpx seems to be governed by conformational selection rather than by induced fit.

  10. A geometrical parametrization of C1'-C5' RNA ribose chemical shifts calculated by density functional theory

    Science.gov (United States)

    Suardíaz, Reynier; Sahakyan, Aleksandr B.; Vendruscolo, Michele

    2013-07-01

    It has been recently shown that NMR chemical shifts can be used to determine the structures of proteins. In order to begin to extend this type of approach to nucleic acids, we present an equation that relates the structural parameters and the 13C chemical shifts of the ribose group. The parameters in the equation were determined by maximizing the agreement between the DFT-derived chemical shifts and those predicted through the equation for a database of ribose structures. Our results indicate that this type of approach represents a promising way of establishing quantitative and computationally efficient analytical relationships between chemical shifts and structural parameters in nucleic acids.

  11. [Metabolic syndrome and shift work: study of the relationship in workers of a chemical plant].

    Science.gov (United States)

    Taino, Giuseppe; Gazzoldi, Tiziana; Brevi, Marco; Giorgi, Marco; Imbriani, Paola

    2011-01-01

    Metabolic syndrome is defined by several metabolic factors, related to one another, which induce atherosclerotic pathology. These factors are: visceral obesity, atherogenic dyslipidemia, high blood pressure, hyperglycemia, proinflammatory and prothrombotic state. Shift work is known to be related to a series of organic changes, including increased cardiovascular risk independent factors. The aim of our study is to assess if shift work might be a cofactor inducing metabolic syndrome. 119 workers of a chemical industry have been examinated and been divided in two groups: shift workers and daytime workers. We checked if workers were affected by metabolic syndrome, following the ATP III criteria. The results have been statistically compared. The prevalence of metabolic syndrome is significantly higher in night shift workers comparing to other workers. Among night shift workers metabolic syndrome was found in 28 out of 77 (36,36%); in daytime workers the syndrome was observed in 8 workers out of 42 (19,05%) (DR: 2, 43; 95% CI 0,99 - 5,98; p=0,049). This difference is stronger when only over 40 years old subjects were considered. Our results show an association between metabolic syndrome and night shift work. It is therefore necessary, as primary health safety measure, to verify the presence of metabolic syndrome in night shift workers. All aspects of the syndrome should be studied to prevent disease and its clinical complications. The primary prevention activity should be based on specific information and education programs, particulary aimed at learning about a correct lifestyle.

  12. Elucidating the Link between NMR Chemical Shifts and Electronic Structure in d(0) Olefin Metathesis Catalysts.

    Science.gov (United States)

    Halbert, Stéphanie; Copéret, Christophe; Raynaud, Christophe; Eisenstein, Odile

    2016-02-24

    The nucleophilic carbon of d(0) Schrock alkylidene metathesis catalysts, [M] = CHR, display surprisingly low downfield chemical shift (δ(iso)) and large chemical shift anisotropy. State-of-the-art four-component relativistic calculations of the chemical shift tensors combined with a two-component analysis in terms of localized orbitals allow a molecular-level understanding of their orientations, the magnitude of their principal components (δ11 > δ22 > δ33) and associated δ(iso). This analysis reveals the dominating influence of the paramagnetic contribution yielding a highly deshielded alkylidene carbon. The largest paramagnetic contribution, which originates from the coupling of alkylidene σ(MC) and π*(MC) orbitals under the action of the magnetic field, is analogous to that resulting from coupling σ(CC) and π*(CC) in ethylene; thus, δ11 is in the MCH plane and is perpendicular to the MC internuclear direction. The higher value of carbon-13 δ(iso) in alkylidene complexes relative to ethylene is thus due to the smaller energy gap between σ(MC) and π*(MC) vs this between σ(CC) and π*(CC) in ethylene. This effect also explains why the highest value of δ(iso) is observed for Mo and the lowest for Ta, the values for W and Re being in between. In the presence of agostic interaction, the chemical shift tensor principal components orientation (δ22 or δ33 parallel or perpendicular to π(MX)) is influenced by the MCH angle because it determines the orientation of the alkylidene CHR fragment relative to the MC internuclear axis. The orbital analysis shows how the paramagnetic terms, understood with a localized bond model, determine the chemical shift tensor and thereby δ(iso).

  13. Coronary artery atherosclerosis associated with shift work in chemical plant workers by using coronary CT angiography.

    Science.gov (United States)

    Kang, WonYang; Park, Won-Ju; Jang, Keun-Ho; Kim, Soo-Hyeon; Gwon, Do-Hyeong; Lim, Hyeong-Min; Ahn, Ji-Sung; Moon, Jai-Dong

    2016-08-01

    The aim of this study was to investigate whether shift work is related to elevated risk of coronary artery disease (CAD) by determining the coronary artery calcium (CAC) score and the presence of coronary artery stenosis by using coronary artery CT angiography (CCTA). In this study, 110 male workers participated and underwent a CCTA examination for CAC scoring, which represents coronary artery plaque, and were evaluated for luminal stenosis. All of the participants were working in the same chemical plant, of whom 70 worked day shifts and 40 worked rotating shifts. In a multivariate logistic regression analysis, including age, smoking status, alcohol consumption, regular exercise and waist circumference, shift work was associated with a 2.89-fold increase in the odds of developing coronary plaque compared with day work (OR, 2.89; 95% CI 1.07 to 7.82). The association between shift work and coronary plaque was strong after adjustment for age, low-density lipoprotein cholesterol, hypertension and diabetes mellitus (OR, 2.92; 95% CI 1.02 to 8.33). In addition, the number of years of shift work employment was associated with coronary plaque. However, no association was found between shift work and coronary artery stenosis. Shift work could induce CAD onset via the atherosclerotic process, and shift work employment duration was associated with an increased risk of atherosclerosis in male workers. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

  14. 13C solid-state NMR chemical shift anisotropy analysis of the anomeric carbon in carbohydrates.

    Science.gov (United States)

    Chen, Ying-Ying; Luo, Shun-Yuan; Hung, Shang-Cheng; Chan, Sunney I; Tzou, Der-Lii M

    2005-03-21

    (13)C NMR solid-state structural analysis of the anomeric center in carbohydrates was performed on six monosaccharides: glucose (Glc), mannose (Man), galactose (Gal), galactosamine hydrochloride (GalN), glucosamine hydrochloride (GlcN), and N-acetyl-glucosamine (GlcNAc). In the 1D (13)C cross-polarization/magic-angle spinning (CP/MAS) spectrum, the anomeric center C-1 of these carbohydrates revealed two well resolved resonances shifted by 3-5ppm, which were readily assigned to the anomeric alpha and beta forms. From this experiment, we also extracted the (13)C chemical shift anisotropy (CSA) tensor elements of the two forms from their spinning sideband intensities, respectively. It was found out that the chemical shift tensor for the alpha anomer was more axially symmetrical than that of the beta form. A strong linear correlation was obtained when the ratio of the axial asymmetry of the (13)C chemical shift tensors of the two anomeric forms was plotted in a semilogarithmic plot against the relative population of the two anomers. Finally, we applied REDOR spectroscopy to discern whether or not there were any differences in the sugar ring conformation between the anomers. Identical two-bond distances of 2.57A (2.48A) were deduced for both the alpha and beta forms in GlcNAc (GlcN), suggesting that the two anomers have essentially identical sugar ring scaffolds in these sugars. In light of these REDOR distance measurements and the strong correlation observed between the ratio of the axial asymmetry parameters of the (13)C chemical shift tensors and the relative population between the two anomeric forms, we concluded that the anomeric effect arises principally from interaction of the electron charge clouds between the C-1-O-5 and the C-1-O-1 bonds in these monosaccharides.

  15. Influence of alkene substituent in dictating the reaction course to ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences; Volume 129; Issue 12. Influence of alkene substituent in dictating the reaction course to form carbocycles or oxacycles during ring closing metathesis of acyclic trienes. RITABRATA DATTA SUBRATA GHOSH. REGULAR ARTICLE Volume 129 Issue 12 December 2017 pp ...

  16. Accuracy and precision of protein-ligand interaction kinetics determined from chemical shift titrations.

    Science.gov (United States)

    Markin, Craig J; Spyracopoulos, Leo

    2012-12-01

    NMR-monitored chemical shift titrations for the study of weak protein-ligand interactions represent a rich source of information regarding thermodynamic parameters such as dissociation constants (K ( D )) in the micro- to millimolar range, populations for the free and ligand-bound states, and the kinetics of interconversion between states, which are typically within the fast exchange regime on the NMR timescale. We recently developed two chemical shift titration methods wherein co-variation of the total protein and ligand concentrations gives increased precision for the K ( D ) value of a 1:1 protein-ligand interaction (Markin and Spyracopoulos in J Biomol NMR 53: 125-138, 2012). In this study, we demonstrate that classical line shape analysis applied to a single set of (1)H-(15)N 2D HSQC NMR spectra acquired using precise protein-ligand chemical shift titration methods we developed, produces accurate and precise kinetic parameters such as the off-rate (k ( off )). For experimentally determined kinetics in the fast exchange regime on the NMR timescale, k ( off ) ~ 3,000 s(-1) in this work, the accuracy of classical line shape analysis was determined to be better than 5 % by conducting quantum mechanical NMR simulations of the chemical shift titration methods with the magnetic resonance toolkit GAMMA. Using Monte Carlo simulations, the experimental precision for k ( off ) from line shape analysis of NMR spectra was determined to be 13 %, in agreement with the theoretical precision of 12 % from line shape analysis of the GAMMA simulations in the presence of noise and protein concentration errors. In addition, GAMMA simulations were employed to demonstrate that line shape analysis has the potential to provide reasonably accurate and precise k ( off ) values over a wide range, from 100 to 15,000 s(-1). The validity of line shape analysis for k ( off ) values approaching intermediate exchange (~100 s(-1)), may be facilitated by more accurate K ( D ) measurements

  17. Uniform fat suppression in hands and feet through the use of two-point Dixon chemical shift MR imaging

    NARCIS (Netherlands)

    Maas, M.; Dijkstra, P. F.; Akkerman, E. M.

    1999-01-01

    To assess the potential of two-point Dixon chemical shift magnetic resonance imaging to achieve uniform fat suppression in the distal parts of the extremities. Two-point Dixon chemical shift imaging was performed in 31 consecutive patients clinically suspected to have bone marrow disease. In some

  18. PACSY, a relational database management system for protein structure and chemical shift analysis

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Woonghee, E-mail: whlee@nmrfam.wisc.edu [University of Wisconsin-Madison, National Magnetic Resonance Facility at Madison, and Biochemistry Department (United States); Yu, Wookyung [Center for Proteome Biophysics, Pusan National University, Department of Physics (Korea, Republic of); Kim, Suhkmann [Pusan National University, Department of Chemistry and Chemistry Institute for Functional Materials (Korea, Republic of); Chang, Iksoo [Center for Proteome Biophysics, Pusan National University, Department of Physics (Korea, Republic of); Lee, Weontae, E-mail: wlee@spin.yonsei.ac.kr [Yonsei University, Structural Biochemistry and Molecular Biophysics Laboratory, Department of Biochemistry (Korea, Republic of); Markley, John L., E-mail: markley@nmrfam.wisc.edu [University of Wisconsin-Madison, National Magnetic Resonance Facility at Madison, and Biochemistry Department (United States)

    2012-10-15

    PACSY (Protein structure And Chemical Shift NMR spectroscopY) is a relational database management system that integrates information from the Protein Data Bank, the Biological Magnetic Resonance Data Bank, and the Structural Classification of Proteins database. PACSY provides three-dimensional coordinates and chemical shifts of atoms along with derived information such as torsion angles, solvent accessible surface areas, and hydrophobicity scales. PACSY consists of six relational table types linked to one another for coherence by key identification numbers. Database queries are enabled by advanced search functions supported by an RDBMS server such as MySQL or PostgreSQL. PACSY enables users to search for combinations of information from different database sources in support of their research. Two software packages, PACSY Maker for database creation and PACSY Analyzer for database analysis, are available from http://pacsy.nmrfam.wisc.eduhttp://pacsy.nmrfam.wisc.edu.

  19. PACSY, a relational database management system for protein structure and chemical shift analysis

    Science.gov (United States)

    Lee, Woonghee; Yu, Wookyung; Kim, Suhkmann; Chang, Iksoo

    2012-01-01

    PACSY (Protein structure And Chemical Shift NMR spectroscopY) is a relational database management system that integrates information from the Protein Data Bank, the Biological Magnetic Resonance Data Bank, and the Structural Classification of Proteins database. PACSY provides three-dimensional coordinates and chemical shifts of atoms along with derived information such as torsion angles, solvent accessible surface areas, and hydrophobicity scales. PACSY consists of six relational table types linked to one another for coherence by key identification numbers. Database queries are enabled by advanced search functions supported by an RDBMS server such as MySQL or PostgreSQL. PACSY enables users to search for combinations of information from different database sources in support of their research. Two software packages, PACSY Maker for database creation and PACSY Analyzer for database analysis, are available from http://pacsy.nmrfam.wisc.edu. PMID:22903636

  20. Sequence correction of random coil chemical shifts: correlation between neighbor correction factors and changes in the Ramachandran distribution

    DEFF Research Database (Denmark)

    Kjærgaard, Magnus; Poulsen, Flemming Martin

    2011-01-01

    . The contributions from the neighboring residues are typically removed by using neighbor correction factors determined based on each residue's effect on glycine chemical shifts. Due to its unusual conformational freedom, glycine may be particularly unrepresentative for the remaining residue types. In this study, we......Random coil chemical shifts are necessary for secondary chemical shift analysis, which is the main NMR method for identification of secondary structure in proteins. One of the largest challenges in the determination of random coil chemical shifts is accounting for the effect of neighboring residues...... use random coil peptides containing glutamine instead of glycine to determine the random coil chemical shifts and the neighbor correction factors. The resulting correction factors correlate to changes in the populations of the major wells in the Ramachandran plot, which demonstrates that changes...

  1. Semiempirical calculations of ESCA chemical shifts by the SCC-AMEP model

    Science.gov (United States)

    Maksic, Z. B.; Rupnik, K.

    1986-03-01

    ESCA chemical shifts give a direct insight into the charge redistribution accompanying formation of chemical bonds. This remarkable feature follows directly from a finding that inner-shell binding energies are closely related to the potentials exerted on the nuclei in question. We have provided extensive evidence which conclusively shows that electrostatic potentials (EP), evaluated in the atomic monopole (AM) approximation, by using the self-consistent charge (SCC-MO) densities, reproduce observed ESCA data in a surprisingly successful way. This approach, abbreviated heretofore the SCC-AMEP model, has also a considerable predictive power. The results have usually an accuracy which is placed in between the chemical and moderate precision. Hence, the salient features of the basic ESCA lines are well described within the AMEP approximation. Finally, the role of the relaxation energy is briefly discussed.

  2. Quantum mechanical calculations of conformationally relevant 1H and 13C NMR chemical shifts of calixarene systems.

    Science.gov (United States)

    Bifulco, Giuseppe; Gomez-Paloma, Luigi; Riccio, Raffaele; Gaeta, Carmine; Troisi, Francesco; Neri, Placido

    2005-12-22

    [graphs: see text] QM GIAO calculations of 13C and 1H chemical shift values of the ArCH2Ar group have been performed, using the hybrid DFT functional MPW1PW91 and the 6-31G(d,p) basis set, on some representative calixarenes and on a series of simplified calixarene models allowing derivation of chemical shift surfaces versus phi and chi dihedral angles. A good reproduction of experimental data was obtained. The applicability of chemical shift surfaces in the study of calixarene conformational features is illustrated.

  3. Conformationally selective multidimensional chemical shift ranges in proteins from a PACSY database purged using intrinsic quality criteria

    Energy Technology Data Exchange (ETDEWEB)

    Fritzsching, Keith J., E-mail: kfritzsc@brandeis.edu [Brandeis University, Department of Chemistry (United States); Hong, Mei [Massachusetts Institute of Technology, Department of Chemistry (United States); Schmidt-Rohr, Klaus, E-mail: srohr@brandeis.edu [Brandeis University, Department of Chemistry (United States)

    2016-02-15

    We have determined refined multidimensional chemical shift ranges for intra-residue correlations ({sup 13}C–{sup 13}C, {sup 15}N–{sup 13}C, etc.) in proteins, which can be used to gain type-assignment and/or secondary-structure information from experimental NMR spectra. The chemical-shift ranges are the result of a statistical analysis of the PACSY database of >3000 proteins with 3D structures (1,200,207 {sup 13}C chemical shifts and >3 million chemical shifts in total); these data were originally derived from the Biological Magnetic Resonance Data Bank. Using relatively simple non-parametric statistics to find peak maxima in the distributions of helix, sheet, coil and turn chemical shifts, and without the use of limited “hand-picked” data sets, we show that ∼94 % of the {sup 13}C NMR data and almost all {sup 15}N data are quite accurately referenced and assigned, with smaller standard deviations (0.2 and 0.8 ppm, respectively) than recognized previously. On the other hand, approximately 6 % of the {sup 13}C chemical shift data in the PACSY database are shown to be clearly misreferenced, mostly by ca. −2.4 ppm. The removal of the misreferenced data and other outliers by this purging by intrinsic quality criteria (PIQC) allows for reliable identification of secondary maxima in the two-dimensional chemical-shift distributions already pre-separated by secondary structure. We demonstrate that some of these correspond to specific regions in the Ramachandran plot, including left-handed helix dihedral angles, reflect unusual hydrogen bonding, or are due to the influence of a following proline residue. With appropriate smoothing, significantly more tightly defined chemical shift ranges are obtained for each amino acid type in the different secondary structures. These chemical shift ranges, which may be defined at any statistical threshold, can be used for amino-acid type assignment and secondary-structure analysis of chemical shifts from intra

  4. Xenon NMR: Chemical Shifts of a General Anesthetic in Common Solvents, Proteins, and Membranes

    Science.gov (United States)

    Miller, Keith W.; Reo, Nicholas V.; Schoot Uiterkamp, Antonius J. M.; Stengle, Diane P.; Stengle, Thomas R.; Williamson, Kenneth L.

    1981-08-01

    The rare gas xenon contains two NMR-sensitive isotopes in high natural abundance. The nuclide 129Xe has a spin of {textstyle1/2}; 131Xe is quadrupolar with a spin of {textstyle3/2}. The complementary NMR characteristics of these nuclei provide a unique opportunity for probing their environment. The method is widely applicable because xenon interacts with a useful range of condensed phases including pure liquids, protein solutions, and suspensions of lipid and biological membranes. Although xenon is chemically inert, it does interact with living systems; it is an effective general anesthetic. We have found that the range of chemical shifts of 129Xe dissolved in common solvents is ca. 200 ppm, which is 30 times larger than that found for 13C in methane dissolved in various solvents. Resonances were also observed for 131Xe in some systems; they were broader and exhibited much greater relaxation rates than did 129Xe. The use of 129Xe NMR as a probe of biological systems was investigated. Spectra were obtained from solutions of myoglobin, from suspensions of various lipid bilayers, and from suspensions of the membranes of erythrocytes and of the acetylcholine receptor-rich membranes of Torpedo californica. These systems exhibited a smaller range of chemical shifts. In most cases there was evidence of a fast exchange of xenon between the aqueous and organic environments, but the exchange was slow in suspensions of dimyristoyl lecithin vesicles.

  5. Effects of crystallinity and chemical variation on apparent band-gap shift in polycrystalline indium nitride

    Energy Technology Data Exchange (ETDEWEB)

    Chen, P.P.-T., E-mail: patrick.chen@mq.edu.a [Department of Physics and Astronomy, Faculty of Science, Macquarie University, Sydney, NSW 2109 (Australia); Downes, J.E.; Fernandes, A.J.; Butcher, K.S.A.; Wintrebert-Fouquet, M. [Department of Physics and Astronomy, Faculty of Science, Macquarie University, Sydney, NSW 2109 (Australia); Wuhrer, R.; Phillips, M.R. [Microstructural Analysis Unit, Faculty of Science, University of Technology, Sydney, Broadway, NSW 2007 (Australia)

    2011-01-03

    The nature of the apparent band-gap shift in polycrystalline indium nitride thin-films, grown by remote-plasma-enhanced chemical vapour deposition at 535 {+-} 10 {sup o}C, has been investigated separately in relation to growth temperature dependent crystallinity and chemical variation. Substrates of sapphire and gallium nitride on sapphire were used to study the effect of a stress-reduced template on indium nitride crystallite quality and apparent band-gap. To mimic surface growth temperature variations two glass substrates of differing thickness and thermal conductivity were intentionally used for the same growth conditions. The samples were characterised using optical transmission, scanning electron microscope, X-ray diffraction, and high-resolution X-ray photoelectron spectroscopy. The results indicate that the apparent band-gap shift in polycrystalline narrow band-gap indium nitride thin-films is not primarily determined by the quality of indium nitride crystallites but rather it is associated with growth temperature dependent chemical variations in the films.

  6. Aromatic interactions in model peptide β-hairpins: ring current effects on proton chemical shifts.

    Science.gov (United States)

    Rajagopal, Appavu; Aravinda, Subrayashastry; Raghothama, Srinivasarao; Shamala, Narayanaswamy; Balaram, Padmanabhan

    2012-01-01

    Crystal structures of eight peptide β-hairpins in the sequence Boc-Leu-Phe-Val-Xxx-Yyy-Leu-Phe-Val-OMe revealed that the Phe(2) and Phe(7) aromatic rings are in close spacial proximity, with the centroid-centroid distance (R(cen)) of 4.4-5.4 Å between the two phenyl rings. Proton NMR spectra in chloroform and methanol solution reveal a significant upfield shift of the Phe(7) C(δ,δ') H(2) protons (6.65-7.04 ppm). Specific assignments of the aromatic protons have been carried out in the peptide Boc-Leu-Phe-Val-(D)Pro-(L)Pro-Leu-Phe-Val-OMe (6). The anticipated ring current shifts have been estimated from the aromatic ring geometrics observed in crystals for all eight peptides. Only one of the C(δ,δ') H proton lies in the shielding zone with rapid ring flipping, resulting in averaging between the two extreme chemical shifts. An approximate estimate of the population of conformations, which resemble crystal state orientation, may be obtained. Key nuclear Overhauser effects (NOEs) between facing Phe side chains provide support for close similarity between the solid state and solution conformation. Temperature dependence of aromatic ring proton chemical shift and line widths for peptide 6 (Boc-Leu-Phe-Val-(D)Pro-(L)Pro-Leu-Phe-Val-OMe) and the control peptide Boc-Leu-Val-Val-(D)Pro-Gly-Leu-Phe-Val-OMe establish an enhanced barrier to ring flipping when the two Phe rings are in proximity. Modeling studies suggest that small, conformational adjustment about C(α)-C(β) (χ(1) ) and C(β)-C(γ) (χ(2) ) bonds of both the Phe residues may be required in order to permit unhindered, uncorrelated flipping of both the Phe rings. The maintenance of the specific aromatic ring orientation in organic solvents provides evidence for significant stabilizing interaction. Copyright © 2012 Wiley Periodicals, Inc.

  7. An experimental study on relationship between hammett substituent constant and electronic absorption wavelength of some azo dyes

    OpenAIRE

    Sidir, Yadigar Gülseven; Sidir, Isa; Berber, Halil; Tasal, Erol

    2011-01-01

    In this study, absorption spectra of sixteen azo dyes have been recorded in various solvents. These azo dyes have substituents such as OH, SO3H, Cl, I, NO2, C2H5 and OCH3 in different positions of phenyl ring. There is a shift in ?max whose amount is dependent upon the type and position of substituent on the ring. The effects of substituent on the absorption spectra of azo dyes are interpreted by correlation of absorption maximum wavelengths (nm) with the hammett substituent parameters. Charg...

  8. Investigating lipids as a source of chemical exchange-induced MRI frequency shifts.

    Science.gov (United States)

    Shmueli, K; Dodd, S J; van Gelderen, P; Duyn, J H

    2017-04-01

    While magnetic susceptibility is a major contributor to NMR resonance frequency variations in the human brain, a substantial contribution may come from the chemical exchange of protons between water and other molecules. Exchange-induced frequency shifts fe have been measured in tissue and protein solutions, but relatively lipid-rich white matter (WM) has a larger fe than gray matter, suggesting that lipids could contribute. Galactocerebrosides (GC) are a prime candidate as they are abundant in WM and susceptible to exchange. To investigate this, fe was measured in a model of WM lipid membranes in the form of multilamellar vesicles (MLVs), consisting of a 1:2 molar ratio of GC and phospholipids (POPC), and in MLVs with POPC only. Chemical shift imaging with 15% volume fraction of dioxane, an internal reference whose protons are assumed not to undergo chemical exchange, was used to remove susceptibility-induced frequency shifts in an attempt to measure fe in MLVs at several lipid concentrations. Initial analysis of these measurements indicated a necessity to correct for small unexpected variations in dioxane concentration due to its effect on the water frequency shift. To achieve this, the actual dioxane concentration was inferred from spectral analysis and its additional contribution to fe was removed through separate experiments which showed that the water-dioxane frequency shift depended linearly on the dioxane concentration at low concentrations with a proportionality constant of -0.021 ± 0.002 ppb/mM in agreement with published experiments. Contrary to expectations and uncorrected results, for GC + POPC vesicles, the dependence of the corrected fe on GC concentration was insignificant (0.023 ± 0.037 ppb/mM; r(2)  = 0.085, p > 0.57), whereas for the POPC-only vesicles a small but significant linear increase with POPC concentration was found: 0.044 ± 0.008 ppb/mM (r(2)  = 0.877, p lipids to frequency contrast in WM may be

  9. Ab Initio Calculations of Deuterium Isotope Effects on Chemical Shifts of Salt-Bridged Lysines

    DEFF Research Database (Denmark)

    Ullah, Saif; Ishimoto, Takayoshi; Williamson, Mike P.

    2011-01-01

    . This method enables the determination of both the electronic and the protonic (deuteronic) wave functions simultaneously and can directly calculate the geometrical difference induced by H/D isotope effects. The calculations show that the one-bond deuterium isotope effects on 15N nuclear shielding, 1Δ15N......Deuterium isotope effects measure the change in chemical shift on substitution of a proton by deuterium. They have been calculated by direct treatment of the H/D nuclear quantum effect using a multicomponent ab initio molecular orbital method based on a non-Born−Oppenheimer approximation...

  10. Thymic hyperplasia and thymus gland tumors: differentiation with chemical shift MR imaging.

    Science.gov (United States)

    Inaoka, Tsutomu; Takahashi, Koji; Mineta, Masayuki; Yamada, Tomonori; Shuke, Noriyuki; Okizaki, Atsutaka; Nagasawa, Kenichi; Sugimori, Hiroyuki; Aburano, Tamio

    2007-06-01

    To prospectively evaluate chemical shift magnetic resonance (MR) imaging for differentiating thymic hyperplasia from tumors of the thymus gland. The institutional review board approved this study; informed consent was obtained and patient confidentiality was protected. The authors assessed 41 patients (17 male, 24 female; age range, 16-78 years) in whom thymic lesions were seen at chest computed tomography. Patients were assigned to a hyperplasia group (n=23) (18 patients with hyperplastic thymus associated with Graves disease and five with rebound thymic hyperplasia) and a tumor group (n=18) (seven patients with thymomas, four with invasive thymomas, five with thymic cancers, and two with malignant lymphomas). T2-weighted fast spin-echo and T1-weighted in-phase and opposed-phase MR images were obtained in all patients and visually assessed. A chemical shift ratio (CSR), determined by comparing the signal intensity of the thymus gland with that of the paraspinal muscle, was calculated for quantitative analysis. Mean CSRs for the patient groups and subgroups were analyzed by using Welch t and Newman-Keuls tests. Pthymus gland had homogeneous signal intensity in all 23 patients in the hyperplasia group and in 12 of the 18 patients in the tumor group. The mean CSR (+/- standard deviation) was 0.614 +/- 0.130 in the hyperplasia group and 1.026 +/- 0.039 in the tumor group. Mean CSRs in the patients with a hyperplastic thymus and Graves disease, rebound thymic hyperplasia, thymoma, invasive thymoma, thymic cancer, and malignant lymphoma were 0.594 +/- 0.120, 0.688 +/- 0.154, 1.033 +/- 0.043, 1.036 +/- 0.040, 1.020 +/- 0.044, and 0.997 +/- 0.010, respectively. The difference in CSR between the hyperplasia and tumor groups was significant (Pthymus gland signal intensity at chemical shift MR imaging; no tumor group patients had a decrease in thymus gland signal intensity. Chemical shift MR imaging can be used to differentiate thymic hyperplasia from thymic tumors. (c) RSNA

  11. Sclerosing liposarcoma of epididymis: Role of chemical shift magnetic resonance imaging

    Directory of Open Access Journals (Sweden)

    Subramaniyan Ramanathan

    2016-01-01

    Full Text Available Sclerosing liposarcoma of epididymis is a rare extratesticular scrotal tumor with variable prognosis. Ultrasonography is the initial imaging modality of choice for the evaluation of scrotal mass and helps to differentiate testicular and extratesticular masses, thereby narrowing down the differential diagnosis. Magnetic resonance imaging with its excellent soft tissue resolution can help in the further characterization of the nature of the tumor. In this case report, we highlight the role of chemical shift imaging in making a confident preoperative diagnosis of liposarcoma thereby guiding optimal and timely management.

  12. Calculation of NMR chemical shifts. 7. Gauge-invariant INDO method

    Science.gov (United States)

    Fukui, H.; Miura, K.; Hirai, A.

    A gauge-invariant INDO method based on the coupled Hartree-Fuck perturbation theory is presented and applied to the calculation of 1H and 13C chemical shifts of hydrocarbons including ring compounds. Invariance of the diamagnetic and paramagnetic shieldings with respect to displacement of the coordinate origin is discussed. Comparison between calculated and experimental results exhibits fairly good agreement, provided that the INDO parameters of Ellis et al. (J. Am. Chem. Soc.94, 4069 (1972)) are used with the inclusion of all multicenter one-electron integrals.

  13. Optimal voxel size for measuring global gray and white matter proton metabolite concentrations using chemical shift imaging

    DEFF Research Database (Denmark)

    Hanson, Lars Peter Grüner; Adalsteinsson, E; Pfefferbaum, A

    2000-01-01

    Quantification of gray and white matter levels of spectroscopically visible metabolites can provide important insights into brain development and pathological conditions. Chemical shift imaging offers a gain in efficiency for estimation of global gray and white matter metabolite concentrations co...

  14. Four-bond deuterium isotope effects on the chemical shifts of amide nitrogens in proteins.

    Science.gov (United States)

    Tugarinov, Vitali

    2013-11-01

    An approach towards precision NMR measurements of four-bond deuterium isotope effects on the chemical shifts of backbone amide nitrogen nuclei in proteins is described. Three types of four-bond (15) N deuterium isotope effects are distinguished depending on the site of proton-to-deuterium substitution: (4)ΔN(N(i-1)D), (4)ΔN(N(i+1)D) and (4)ΔN(Cβ,(i-1)D). All the three types of isotope shifts are quantified in the (partially) deuterated protein ubiquitin. The (4)ΔN(N(i+1)D) and (4)ΔN(C(β,i-1)D) effects are by far the largest in magnitude and vary between 16 and 75 ppb and -18 and 46 ppb, respectively. A semi-quantitative correlation between experimental (4)ΔN(N(i+1)D) and (4)ΔN(C(β,i-1)D) values and the distances between nitrogen nuclei and the sites of (1)H-to-D substitution is noted. The largest isotope shifts in both cases correspond to the shortest inter-nuclear distances. Copyright © 2013 John Wiley & Sons, Ltd.

  15. Modeling proteins using a super-secondary structure library and NMR chemical shift information.

    Science.gov (United States)

    Menon, Vilas; Vallat, Brinda K; Dybas, Joseph M; Fiser, Andras

    2013-06-04

    A remaining challenge in protein modeling is to predict structures for sequences with no sequence similarity to any experimentally solved structure. Based on earlier observations, the library of protein backbone supersecondary structure motifs (Smotifs) saturated about a decade ago. Therefore, it should be possible to build any structure from a combination of existing Smotifs with the help of limited experimental data that are sufficient to relate the backbone conformations of Smotifs between target proteins and known structures. Here, we present a hybrid modeling algorithm that relies on an exhaustive Smotif library and on nuclear magnetic resonance chemical shift patterns without any input of primary sequence information. In a test of 102 proteins, the algorithm delivered 90 homology-model-quality models, among them 24 high-quality ones, and a topologically correct solution for almost all cases. The current approach opens a venue to address the modeling of larger protein structures for which chemical shifts are available. Copyright © 2013 Elsevier Ltd. All rights reserved.

  16. High spectral specificity of local chemical components characterization with multichannel shift-excitation Raman spectroscopy

    Science.gov (United States)

    Chen, Kun; Wu, Tao; Wei, Haoyun; Wu, Xuejian; Li, Yan

    2015-09-01

    Raman spectroscopy has emerged as a promising tool for its noninvasive and nondestructive characterization of local chemical structures. However, spectrally overlapping components prevent the specific identification of hyperfine molecular information of different substances, because of limitations in the spectral resolving power. The challenge is to find a way of preserving scattered photons and retrieving hidden/buried Raman signatures to take full advantage of its chemical specificity. Here, we demonstrate a multichannel acquisition framework based on shift-excitation and slit-modulation, followed by mathematical post-processing, which enables a significant improvement in the spectral specificity of Raman characterization. The present technique, termed shift-excitation blind super-resolution Raman spectroscopy (SEBSR), uses multiple degraded spectra to beat the dispersion-loss trade-off and facilitate high-resolution applications. It overcomes a fundamental problem that has previously plagued high-resolution Raman spectroscopy: fine spectral resolution requires large dispersion, which is accompanied by extreme optical loss. Applicability is demonstrated by the perfect recovery of fine structure of the C-Cl bending mode as well as the clear discrimination of different polymorphs of mannitol. Due to its enhanced discrimination capability, this method offers a feasible route at encouraging a broader range of applications in analytical chemistry, materials and biomedicine.

  17. WAter Saturation Shift Referencing (WASSR) for chemical exchange saturation transfer experiments

    Science.gov (United States)

    Kim, Mina; Gillen, Joseph; Landman, Bennett. A.; Zhou, Jinyuan; van Zijl, Peter C.M.

    2010-01-01

    Chemical exchange saturation transfer (CEST) is a contrast mechanism exploiting exchange-based magnetization transfer (MT) between solute and water protons. CEST effects compete with direct water saturation and conventional MT processes and generally can only be quantified through an asymmetry analysis of the water saturation spectrum (Z-spectrum) with respect to the water frequency, a process that is exquisitely sensitive to magnetic field inhomogeneities. Here, it is shown that direct water saturation imaging allows measurement of the absolute water frequency in each voxel, allowing proper centering of Z-spectra on a voxel-by-voxel basis independent of spatial B0 field variations. Optimal acquisition parameters for this “water saturation shift referencing” or “WASSR” approach were estimated using Monte Carlo simulations and later confirmed experimentally. The optimal ratio of the WASSR sweep width to the linewidth of the direct saturation curve was found to be 3.3–4.0, requiring a sampling of 16–32 points. The frequency error was smaller than 1 Hz at signal to noise ratios of 40 or higher. The WASSR method was applied to study glycogen, where the chemical shift difference between the hydroxyl (OH) protons and bulk water protons at 3T is so small (0.75–1.25 ppm) that the CEST spectrum is inconclusive without proper referencing. PMID:19358232

  18. Water saturation shift referencing (WASSR) for chemical exchange saturation transfer (CEST) experiments.

    Science.gov (United States)

    Kim, Mina; Gillen, Joseph; Landman, Bennett A; Zhou, Jinyuan; van Zijl, Peter C M

    2009-06-01

    Chemical exchange saturation transfer (CEST) is a contrast mechanism that exploits exchange-based magnetization transfer (MT) between solute and water protons. CEST effects compete with direct water saturation and conventional MT processes, and generally can only be quantified through an asymmetry analysis of the water saturation spectrum (Z-spectrum) with respect to the water frequency, a process that is exquisitely sensitive to magnetic field inhomogeneities. Here it is shown that direct water saturation imaging allows measurement of the absolute water frequency in each voxel, allowing proper centering of Z-spectra on a voxel-by-voxel basis independently of spatial B(0) field variations. Optimal acquisition parameters for this "water saturation shift referencing" (WASSR) approach were estimated using Monte Carlo simulations and later confirmed experimentally. The optimal ratio of the WASSR sweep width to the linewidth of the direct saturation curve was found to be 3.3-4.0, requiring a sampling of 16-32 points. The frequency error was smaller than 1 Hz at signal-to-noise ratios of 40 or higher. The WASSR method was applied to study glycogen, where the chemical shift difference between the hydroxyl (OH) protons and bulk water protons at 3T is so small (0.75-1.25 ppm) that the CEST spectrum is inconclusive without proper referencing.

  19. Reassigning the Structures of Natural Products Using NMR Chemical Shifts Computed with Quantum Mechanics: A Laboratory Exercise

    Science.gov (United States)

    Palazzo, Teresa A.; Truong, Tiana T.; Wong, Shirley M. T.; Mack, Emma T.; Lodewyk, Michael W.; Harrison, Jason G.; Gamage, R. Alan; Siegel, Justin B.; Kurth, Mark J.; Tantillo, Dean J.

    2015-01-01

    An applied computational chemistry laboratory exercise is described in which students use modern quantum chemical calculations of chemical shifts to assign the structure of a recently isolated natural product. A pre/post assessment was used to measure student learning gains and verify that students demonstrated proficiency of key learning…

  20. 129 Xe chemical shift in human blood and pulmonary blood oxygenation measurement in humans using hyperpolarized 129 Xe NMR.

    Science.gov (United States)

    Norquay, Graham; Leung, General; Stewart, Neil J; Wolber, Jan; Wild, Jim M

    2017-04-01

    To evaluate the dependency of the 129 Xe-red blood cell (RBC) chemical shift on blood oxygenation, and to use this relation for noninvasive measurement of pulmonary blood oxygenation in vivo with hyperpolarized 129 Xe NMR. Hyperpolarized 129 Xe was equilibrated with blood samples of varying oxygenation in vitro, and NMR was performed at 1.5 T and 3 T. Dynamic in vivo NMR during breath hold apnea was performed at 3 T on two healthy volunteers following inhalation of hyperpolarized 129 Xe. The 129 Xe chemical shift in RBCs was found to increase nonlinearly with blood oxygenation at 1.5 T and 3 T. During breath hold apnea, the 129 Xe chemical shift in RBCs exhibited a periodic time modulation and showed a net decrease in chemical shift of ∼1 ppm over a 35 s breath hold, corresponding to a decrease of 7-10 % in RBC oxygenation. The 129 Xe-RBC signal amplitude showed a modulation with the same frequency as the 129 Xe-RBC chemical shift. The feasibility of using the 129 Xe-RBC chemical shift to measure pulmonary blood oxygenation in vivo has been demonstrated. Correlation between 129 Xe-RBC signal and 129 Xe-RBC chemical shift modulations in the lung warrants further investigation, with the aim to better quantify temporal blood oxygenation changes in the cardiopulmonary vascular circuit. Magn Reson Med 77:1399-1408, 2017. © 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. © 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine.

  1. 129Xe chemical shift in human blood and pulmonary blood oxygenation measurement in humans using hyperpolarized 129Xe NMR

    Science.gov (United States)

    Norquay, Graham; Leung, General; Stewart, Neil J.; Wolber, Jan

    2016-01-01

    Purpose To evaluate the dependency of the 129Xe‐red blood cell (RBC) chemical shift on blood oxygenation, and to use this relation for noninvasive measurement of pulmonary blood oxygenation in vivo with hyperpolarized 129Xe NMR. Methods Hyperpolarized 129Xe was equilibrated with blood samples of varying oxygenation in vitro, and NMR was performed at 1.5 T and 3 T. Dynamic in vivo NMR during breath hold apnea was performed at 3 T on two healthy volunteers following inhalation of hyperpolarized 129Xe. Results The 129Xe chemical shift in RBCs was found to increase nonlinearly with blood oxygenation at 1.5 T and 3 T. During breath hold apnea, the 129Xe chemical shift in RBCs exhibited a periodic time modulation and showed a net decrease in chemical shift of ∼1 ppm over a 35 s breath hold, corresponding to a decrease of 7–10 % in RBC oxygenation. The 129Xe‐RBC signal amplitude showed a modulation with the same frequency as the 129Xe‐RBC chemical shift. Conclusion The feasibility of using the 129Xe‐RBC chemical shift to measure pulmonary blood oxygenation in vivo has been demonstrated. Correlation between 129Xe‐RBC signal and 129Xe‐RBC chemical shift modulations in the lung warrants further investigation, with the aim to better quantify temporal blood oxygenation changes in the cardiopulmonary vascular circuit. Magn Reson Med 77:1399–1408, 2017. © 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. PMID:27062652

  2. Experimental study of resolution of proton chemical shifts in solids: Combined multiple pulse NMR and magic-angle spinning

    Energy Technology Data Exchange (ETDEWEB)

    Ryan, L.M.; Taylor, R.E.; Paff, A.J.; Gerstein, B.C.

    1980-01-01

    High-resolution nuclear magnetic resonance spectra of protons in rigid, randomly oriented solids have been measured using combined homonuclear dipolar decoupling (via multiple pulse techniques) and attenuation of chemical shift anisotropies (via magic-angle sample spinning). Under those conditions, isotropic proton chemical shifts were recorded for a variety of chemical species, with individual linewidths varying from about 55 to 110 Hz (1--2 ppm). Residual line broadening was due predominately to (i) magnetic-field instability and inhomogeneity, (ii) unresolved proton--proton spin couplings, (iii) chemical shift dispersion, (iv) residual dipolar broadening, and (v) lifetime broadening under the multiple pulse sequences used. The magnitudes of those effects and the current limits of resolution for this experiment in our spectrometer have been investigated. The compounds studied included organic solids (4, 4'-dimethylbenzophenone, 2, 6-dimethylbenzoic acid, and aspirin), polymers (polystyrene and polymethylmethacrylate), and the vitrain portion of a bituminous coal.

  3. Backbone and side chain chemical shift assignments of apolipophorin III from Galleria mellonella.

    Science.gov (United States)

    Crowhurst, Karin A; Horn, James V C; Weers, Paul M M

    2016-04-01

    Apolipophorin III, a 163 residue monomeric protein from the greater wax moth Galleria mellonella (abbreviated as apoLp-IIIGM), has roles in upregulating expression of antimicrobial proteins as well as binding and deforming bacterial membranes. Due to its similarity to vertebrate apolipoproteins there is interest in performing atomic resolution analysis of apoLp-IIIGM as part of an effort to better understand its mechanism of action in innate immunity. In the first step towards structural characterization of apoLp-IIIGM, 99 % of backbone and 88 % of side chain (1)H, (13)C and (15)N chemical shifts were assigned. TALOS+ analysis of the backbone resonances has predicted that the protein is composed of five long helices, which is consistent with the reported structures of apolipophorins from other insect species. The next stage in the characterization of apoLp-III from G. mellonella will be to utilize these resonance assignments in solving the solution structure of this protein.

  4. Improving the chemical shift dispersion of multidimensional NMR spectra of intrinsically disordered proteins

    Energy Technology Data Exchange (ETDEWEB)

    Bermel, Wolfgang [Bruker BioSpin GmbH (Germany); Bruix, Marta [Consejo Superior de Investigaciones Cientificas, Instituto de Quimica Fisica ' ' Rocasolano' ' (Spain); Felli, Isabella C., E-mail: felli@cerm.unifi.it [University of Florence, Department of Chemistry ' Ugo Shiff' (Italy); Kumar, M.V. Vasantha [University of Florence, Magnetic Resonance Center (Italy); Pierattelli, Roberta, E-mail: pierattelli@cerm.unifi.it [University of Florence, Department of Chemistry ' Ugo Shiff' (Italy); Serrano, Soraya [Consejo Superior de Investigaciones Cientificas, Instituto de Quimica Fisica ' ' Rocasolano' ' (Spain)

    2013-03-15

    Intrinsically disordered proteins (IDPs) have recently attracted the attention of the scientific community challenging the well accepted structure-function paradigm. In the characterization of the dynamic features of proteins nuclear magnetic resonance spectroscopy (NMR) is a strategic tool of investigation. However the peculiar properties of IDPs, with the lack of a unique 3D structure and their high flexibility, have a strong impact on NMR observables (low chemical shift dispersion, efficient solvent exchange broadening) and thus on the quality of NMR spectra. Key aspects to be considered in the design of new NMR experiments optimized for the study of IDPs are discussed. A new experiment, based on direct detection of {sup 13}C{sup {alpha}}, is proposed.

  5. Deuterium isotope effect on 13C chemical shifts of tetrabutylammonium salts of Schiff bases amino acids.

    Science.gov (United States)

    Rozwadowski, Z

    2006-09-01

    Deuterium isotope effects on 13C chemical shift of tetrabutylammonium salts of Schiff bases, derivatives of amino acids (glycine, L-alanine, L-phenylalanine, L-valine, L-leucine, L-isoleucine and L-methionine) and various ortho-hydroxyaldehydes in CDCl3 have been measured. The results have shown that the tetrabutylammonium salts of the Schiff bases amino acids, being derivatives of 2-hydroxynaphthaldehyde and 3,5-dibromosalicylaldehyde, exist in the NH-form, while in the derivatives of salicylaldehyde and 5-bromosalicylaldehyde a proton transfer takes place. The interactions between COO- and NH groups stabilize the proton-transferred form through a bifurcated intramolecular hydrogen bond. Copyright (c) 2006 John Wiley & Sons, Ltd.

  6. Amyotrophic lateral sclerosis: diffusion-tensor and chemical shift MR imaging at 3.0 T.

    Science.gov (United States)

    Wang, Sumei; Poptani, Harish; Woo, John H; Desiderio, Lisa M; Elman, Lauren B; McCluskey, Leo F; Krejza, Jaroslaw; Melhem, Elias R

    2006-06-01

    To prospectively determine whether diffusion-tensor magnetic resonance (MR) imaging in conjunction with two-dimensional chemical shift imaging can assist in identifying upper motor neuron involvement and whether disease severity and duration can be predicted based on imaging parameters in patients with amyotrophic lateral sclerosis (ALS). Institutional review board approval and informed consent were obtained for this HIPAA-compliant study. Fifteen patients with ALS (12 men, three women; mean age, 57.3 years) with clinical evidence of upper motor neuron involvement and 10 healthy control subjects (five men and five women; mean age, 49.4 years) were studied. Fractional anisotropy (FA) and apparent diffusion coefficient (ADC) were measured from the corticospinal tracts at the level of the internal capsule. Average N-acetylaspartate (NAA)/creatine-phosphocreatine (Cr) and NAA/choline-containing compounds (Cho) ratios were calculated from the precentral gyrus. Student t test, multiple linear regression analysis, and Spearman correlation coefficients were employed to quantify relationships between imaging and clinical parameters. Patients with ALS exhibited significantly reduced FA values and NAA/Cr and NAA/Cho ratios compared with values in control subjects (Psides of the brain. ADC was elevated significantly in the affected side (Pside were even stronger predictors of disease duration. Moderate but statistically significant correlation was found between the FA values for the affected side and the ALS Functional Rating Scale Revised (ALSFRS-R) score (r=0.51, P<.05). The NAA/Cr ratio also correlated with both the ALSFRS-R and upper motor neuron scores (r=0.50 and 0.54, respectively; P<.05). Diffusion-tensor and two-dimensional chemical shift MR imaging spectroscopy can be used to identify upper motor neuron involvement and predict disease duration in patients with ALS. Copyright (c) RSNA, 2006.

  7. 50 years anniversary of the discovery of the core level chemical shifts. The early years of photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Mårtensson, Nils [Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala (Sweden); Sokolowski, Evelyn [Tvär-Ramsdal 1, 611 99 Tystberga (Sweden); Svensson, Svante, E-mail: Svante.Svensson@fysik.uu.se [Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala (Sweden)

    2014-03-01

    Highlights: • 50 years since the discovery of t the core level chemical shift. • The pioneering years of ESCA. • A critical review of the first core electron chemical shift results. - Abstract: The pioneering years of photoelectron spectroscopy in Uppsala are discussed, especially the work leading to the discovery of the core level chemical shifts. At a very early stage of the project, the pioneering group observed what they described as evidence for chemical shifts in the core level binding energies. However, it can now be seen that the initial observations to a large extent was due to charging of the samples. It is interesting to note that the decisive experiment was realized, not as a result of a systematic study, but was obtained with a large element of serendipity. Only when a chemical binding energy shift was observed between two S2p electron lines in the same molecule, the results were accepted internationally, and the fascinating expansion of modern core level photoelectron spectroscopy could start.

  8. Chemical amplification--cavity attenuated phase shift spectroscopy measurements of atmospheric peroxy radicals.

    Science.gov (United States)

    Wood, Ezra C; Charest, John R

    2014-10-21

    We describe a new instrument for the quantification of atmospheric peroxy radicals (HO2, CH3O2, C2H5O2, etc.) using the chemical amplification method. Peroxy radicals are mixed with high concentrations of NO and CO, causing a chain reaction that produces a measurable increase in NO2 which is quantified by cavity attenuated phase shift (CAPS) spectroscopy, a highly sensitive spectroscopic detection technique. The instrument utilizes two identical reaction chambers, each with a dedicated CAPS NO2 sensor. Similar to all dual-channel chemical amplifiers, one reaction chamber operates in amplification or "ROx" mode and the other in background or "Ox" mode. The peroxy radical mixing ratio is determined by the difference between the two channels' NO2 readings divided by a laboratory-determined chain length. Each reaction chamber alternates between ROx and Ox mode on an anti-synchronized schedule, eliminating the effect of CAPS baseline offsets on the calculated peroxy radical concentrations. The chain length is determined by a new calibration method: peroxyacetyl and methyl peroxy radicals are produced by the photolysis of acetone and quantified as NO2 following reaction with excess NO. We demonstrate the performance of the instrument with results from ambient sampling in Amherst and several diagnostics of its precision. The detection limit while sampling ambient air at a relative humidity (RH) of 40% is 0.6 ppt (1 min average, signal-to-noise ratio =2), with an estimated accuracy of 25% (2σ).

  9. Carbon-13 chemical-shift tensors in indigo: A two-dimensional NMR-ROCSA and DFT Study

    Science.gov (United States)

    Holmes, Sean T.; Dybowski, Cecil

    2016-01-01

    The principal components of the 13C NMR chemical-shift tensors for the eight unique carbon sites of crystalline indigo have been measured using the ROCSA pulse sequence. The chemical shifts have been assigned unambiguously to their respective nuclear sites through comparison of the experimental data to the results of density-functional calculations employing a refined X-ray diffraction structure. These measurements expand the database of measured aromatic 13C chemical-shift tensors to the indole ring. Magnetic shielding calculations for hypoxanthine and adenosine are also reported. Comparisons of calculations that include the effect of the crystalline lattice with calculations that model indigo as an isolated molecule give an estimate of the intermolecular contribution to the magnetic shielding. PMID:26344134

  10. Recoupling of chemical shift anisotropy by R-symmetry sequences in magic angle spinning NMR spectroscopy

    Science.gov (United States)

    Hou, Guangjin; Byeon, In-Ja L.; Ahn, Jinwoo; Gronenborn, Angela M.; Polenova, Tatyana

    2012-10-01

    13C and 15N chemical shift (CS) interaction is a sensitive probe of structure and dynamics in a wide variety of biological and inorganic systems, and in the recent years several magic angle spinning NMR approaches have emerged for residue-specific measurements of chemical shift anisotropy (CSA) tensors in uniformly and sparsely enriched proteins. All of the currently existing methods are applicable to slow and moderate magic angle spinning (MAS) regime, i.e., MAS frequencies below 20 kHz. With the advent of fast and ultrafast MAS probes capable of spinning frequencies of 40-100 kHz, and with the superior resolution and sensitivity attained at such high frequencies, development of CSA recoupling techniques working under such conditions is necessary. In this work, we present a family of R-symmetry based pulse sequences for recoupling of 13C/15N CSA interactions that work well in both natural abundance and isotopically enriched systems. We demonstrate that efficient recoupling of either first-rank (σ1) or second-rank (σ2) spatial components of CSA interaction is attained with appropriately chosen γ-encoded RNnv symmetry sequences. The advantage of these γ-encoded RNnv-symmetry based CSA (RNCSA) recoupling schemes is that they are suitable for CSA recoupling under a wide range of MAS frequencies, including fast MAS regime. Comprehensive analysis of the recoupling properties of these RNnv symmetry sequences reveals that the σ1-CSA recoupling symmetry sequences exhibit large scaling factors; however, the partial homonuclear dipolar Hamiltonian components are symmetry allowed, which makes this family of sequences suitable for CSA measurements in systems with weak homonuclear dipolar interactions. On the other hand, the γ-encoded symmetry sequences for σ2-CSA recoupling have smaller scaling factors but they efficiently suppress the homonuclear dipole-dipole interactions. Therefore, the latter family of sequences is applicable for measurements of CSA parameters in

  11. Chemical shift assignments for F-plasmid TraI (381–569)

    Science.gov (United States)

    Wright, Nathan T.; Majumdar, Ananya

    2011-01-01

    TraI, the F plasmid-encoded nickase, is a 1,756 amino acid protein essential for conjugative transfer of F plasmid DNA from one bacterium to another. While crystal structures of N- and C-terminal domains of F TraI have been determined, central domains of the protein are structurally unexplored. These middle domains (between residues 306 and 1,500) are known to both bind single-stranded DNA (ssDNA) and unwind DNA through a highly processive helicase activity. Of this central region, the more C-terminal portion (~900–1500) appears related to helicase RecD of the E. coli RecBCD complex. The more N-terminal portion (306–900), however, shows limited sequence similarity to other proteins. In an attempt to define the structure of well-folded domains of this middle region and discern their function, we have isolated stable regions of TraI following limited proteolysis. One of these regions, TraI (381–569), was identified and a genetic construct encoding it was engineered. The protein was expressed, purified, and the sequence-specific chemical shifts for it were assigned. PMID:20936510

  12. Chemical shift assignments for F-plasmid TraI (381-569).

    Science.gov (United States)

    Wright, Nathan T; Majumdar, Ananya; Schildbach, Joel F

    2011-04-01

    TraI, the F plasmid-encoded nickase, is a 1,756 amino acid protein essential for conjugative transfer of F plasmid DNA from one bacterium to another. While crystal structures of N- and C-terminal domains of F TraI have been determined, central domains of the protein are structurally unexplored. These middle domains (between residues 306 and 1,500) are known to both bind single-stranded DNA (ssDNA) and unwind DNA through a highly processive helicase activity. Of this central region, the more C-terminal portion (~900-1500) appears related to helicase RecD of the E. coli RecBCD complex. The more N-terminal portion (306-900), however, shows limited sequence similarity to other proteins. In an attempt to define the structure of well-folded domains of this middle region and discern their function, we have isolated stable regions of TraI following limited proteolysis. One of these regions, TraI (381-569), was identified and a genetic construct encoding it was engineered. The protein was expressed, purified, and the sequence-specific chemical shifts for it were assigned.

  13. Analysis of the contributions of ring current and electric field effects to the chemical shifts of RNA bases.

    Science.gov (United States)

    Sahakyan, Aleksandr B; Vendruscolo, Michele

    2013-02-21

    Ring current and electric field effects can considerably influence NMR chemical shifts in biomolecules. Understanding such effects is particularly important for the development of accurate mappings between chemical shifts and the structures of nucleic acids. In this work, we first analyzed the Pople and the Haigh-Mallion models in terms of their ability to describe nitrogen base conjugated ring effects. We then created a database (DiBaseRNA) of three-dimensional arrangements of RNA base pairs from X-ray structures, calculated the corresponding chemical shifts via a hybrid density functional theory approach and used the results to parametrize the ring current and electric field effects in RNA bases. Next, we studied the coupling of the electric field and ring current effects for different inter-ring arrangements found in RNA bases using linear model fitting, with joint electric field and ring current, as well as only electric field and only ring current approximations. Taken together, our results provide a characterization of the interdependence of ring current and electric field geometric factors, which is shown to be especially important for the chemical shifts of non-hydrogen atoms in RNA bases.

  14. Influence of ¹H chemical shift assignments of the interface residues on structure determinations of homodimeric proteins.

    Science.gov (United States)

    Lin, Yi-Jan; Kirchner, Donata K; Güntert, Peter

    2012-09-01

    Homodimeric proteins pose a difficulty for NMR structure determination because the degeneracy of the chemical shifts in the two identical monomers implies an ambiguity in all assignments of distance restraints. For homodimeric proteins, residues involved in the interface between two monomers provide essential intermolecular NOEs. The structure determination of homodimeric proteins hence relies strongly on chemical shift assignments of these interface residues. Our paper discusses the influence of the extent of (1)H chemical shift assignments of interface residues on the structure determinations of homodimeric proteins using the CYANA program. The results reveal that successful structure determinations of homodimeric proteins with automated NOE assignment depend on the percentage of assigned interface residues and that a high completeness of around 80-90% of the (1)H chemical shift assignment in the interface is needed for reliable NMR structure determinations of homodimeric proteins for which no experimental distinction between intra- and intermolecular NOEs, e.g. by filtered NOESY experiments, is available. Our results also show that RMSD and target function values are insufficient to judge the quality of homodimeric structures determined using automated NOE assignment. Structure determinations of homodimeric proteins by NMR using conventional NOESY experiments are thus possible but more challenging than for monomeric proteins. Copyright © 2012 Elsevier Inc. All rights reserved.

  15. Dixon quantitative chemical shift MRI for bone marrow evaluation in the lumbar spine: a reproducibility study in healthy volunteers

    NARCIS (Netherlands)

    Maas, M.; Akkerman, E. M.; Venema, H. W.; Stoker, J.; den Heeten, G. J.

    2001-01-01

    PURPOSE: The purpose of this work was to explore the reproducibility of fat-fraction measurements using Dixon quantitative chemical shift imaging (QCSI) in the lumbar spine (L3, L4, and L5) of healthy volunteers. METHOD: Sixteen healthy volunteers were examined at 1.5 T two times to obtain a

  16. 20(R- and 20(S-Simarolide Epimers Isolated from Simaba cuneata: Chemical Shifts Assignment of Carbon and Hydrogen Atoms

    Directory of Open Access Journals (Sweden)

    Vieira Ivo José Curcino

    1999-01-01

    Full Text Available The C25-quassinoids 20(R- and 20(S-simarolide were isolated from Simaba cuneata, Simaroubaceae. The structures of these two compounds were characterized by spectral data, including 1D and 2D NMR spectra which were also used for the complete assignment of the carbon and hydrogen atom chemical shifts.

  17. A comparison of chemical shift sensitivity of trifluoromethyl tags: optimizing resolution in {sup 19}F NMR studies of proteins

    Energy Technology Data Exchange (ETDEWEB)

    Ye, Libin; Larda, Sacha Thierry; Frank Li, Yi Feng [University of Toronto, UTM, Department of Chemistry (Canada); Manglik, Aashish [Stanford University School of Medicine, Department of Molecular and Cellular Physiology (United States); Prosser, R. Scott, E-mail: scott.prosser@utoronto.ca [University of Toronto, UTM, Department of Chemistry (Canada)

    2015-05-15

    The elucidation of distinct protein conformers or states by fluorine ({sup 19}F) NMR requires fluorinated moieties whose chemical shifts are most sensitive to subtle changes in the local dielectric and magnetic shielding environment. In this study we evaluate the effective chemical shift dispersion of a number of thiol-reactive trifluoromethyl probes [i.e. 2-bromo-N-(4-(trifluoromethyl)phenyl)acetamide (BTFMA), N-(4-bromo-3-(trifluoromethyl)phenyl)acetamide (3-BTFMA), 3-bromo-1,1,1-trifluoropropan-2-ol (BTFP), 1-bromo-3,3,4,4,4-pentafluorobutan-2-one (BPFB), 3-bromo-1,1,1-trifluoropropan-2-one (BTFA), and 2,2,2-trifluoroethyl-1-thiol (TFET)] under conditions of varying polarity. In considering the sensitivity of the {sup 19}F NMR chemical shift to the local environment, a series of methanol/water mixtures were prepared, ranging from relatively non-polar (MeOH:H{sub 2}O = 4) to polar (MeOH:H{sub 2}O = 0.25). {sup 19}F NMR spectra of the tripeptide, glutathione ((2S)-2-amino-4-{[(1R)-1-[(carboxymethyl)carbamoyl] -2-sulfanylethyl]carbamoyl}butanoic acid), conjugated to each of the above trifluoromethyl probes, revealed that the BTFMA tag exhibited a significantly greater range of chemical shift as a function of solvent polarity than did either BTFA or TFET. DFT calculations using the B3LYP hybrid functional and the 6-31G(d,p) basis set, confirmed the observed trend in chemical shift dispersion with solvent polarity.

  18. Two-dimensional concurrent HMQC-COSY as an approach for small molecule chemical shift assignment and compound identification

    Energy Technology Data Exchange (ETDEWEB)

    Hu Kaifeng; Westler, William M.; Markley, John L., E-mail: markley@nmrfam.wisc.edu [University of Wisconsin-Madison, National Magnetic Resonance Facility at Madison (United States)

    2011-04-15

    Chemical shift assignment is the first step toward the structure elucidation of natural products and other chemical compounds. We propose here the use of 2D concurrent HMQC-COSY as an experiment for rapid chemical shift assignment of small molecules. This experiment provides well-dispersed {sup 1}H-{sup 13}C peak patterns that are distinctive for different functional groups plus {sup 1}H-{sup 1}H COSY connectivities that serve to identify adjacent groups. The COSY diagonal peaks, which are phased to be absorptive, resemble {sup 1}H-{sup 13}C HMQC cross peaks. We demonstrate the applicability of this experiment for rapidly and unambiguously establishing correlations between different functional groups through the analysis of the spectrum of a metabolite (jasmonic acid) dissolved in CDCl{sub 3}. In addition, we show that the experiment can be used to assign spectra of compounds in a mixture of metabolites in D{sub 2}O.

  19. Female sea lamprey shift orientation toward a conspecific chemical cue to escape a sensory trap

    Science.gov (United States)

    Brant, Cory O.; Johnson, Nicholas; Li, Ke; Buchinger, Tyler J.; Li, Weiming

    2016-01-01

    The sensory trap model of signal evolution hypothesizes that signalers adapt to exploit a cue used by the receiver in another context. Although exploitation of receiver biases can result in conflict between the sexes, deceptive signaling systems that are mutually beneficial drive the evolution of stable communication systems. However, female responses in the nonsexual and sexual contexts may become uncoupled if costs are associated with exhibiting a similar response to a trait in both contexts. Male sea lamprey (Petromyzon marinus) signal with a mating pheromone, 3-keto petromyzonol sulfate (3kPZS), which may be a match to a juvenile cue used by females during migration. Upstream movement of migratory lampreys is partially guided by 3kPZS, but females only move toward 3kPZS with proximal accuracy during spawning. Here, we use in-stream behavioral assays paired with gonad histology to document the transition of female preference for juvenile- and male-released 3kPZS that coincides with the functional shift of 3kPZS as a migratory cue to a mating pheromone. Females became increasingly biased toward the source of synthesized 3kPZS as their maturation progressed into the reproductive phase, at which point, a preference for juvenile odor (also containing 3kPZS naturally) ceased to exist. Uncoupling of female responses during migration and spawning makes the 3kPZS communication system a reliable means of synchronizing mate search. The present study offers a rare example of a transition in female responses to a chemical cue between nonsexual and sexual contexts, provides insights into the origins of stable communication signaling systems.

  20. Changes of brain metabolite concentrations during maturation in different brain regions measured by chemical shift imaging

    Energy Technology Data Exchange (ETDEWEB)

    Bueltmann, Eva; Lanfermann, Heinrich [Hannover Medical School, Institute of Diagnostic and Interventional Neuroradiology, Hannover (Germany); Naegele, Thomas [University of Tuebingen, Department of Diagnostic and Interventional Neuroradiology, Radiological University Hospital, Tuebingen (Germany); Klose, Uwe [University of Tuebingen, Section of Experimental MR of the CNS, Department of Neuroradiology, Radiological University Hospital, Tuebingen (Germany)

    2017-01-15

    We examined the effect of maturation on the regional distribution of brain metabolite concentrations using multivoxel chemical shift imaging. From our pool of pediatric MRI examinations, we retrospectively selected patients showing a normal cerebral MRI scan or no pathologic signal abnormalities at the level of the two-dimensional 1H MRS-CSI sequence and an age-appropriate global neurological development, except for focal neurological deficits. Seventy-one patients (4.5 months-20 years) were identified. Using LC Model, spectra were evaluated from voxels in the white matter, caudate head, and corpus callosum. The concentration of total N-acetylaspartate increased in all regions during infancy and childhood except in the right caudate head where it remained constant. The concentration of total creatine decreased in the caudate nucleus and splenium and minimally in the frontal white matter and genu. It remained largely constant in the parietal white matter. The concentration of choline-containing compounds had the tendency to decrease in all regions except in the parietal white matter where it remained constant. The concentration of myoinositol decreased slightly in the splenium and right frontal white matter, remained constant on the left side and in the caudate nucleus, and rose slightly in the parietal white matter and genu. CSI determined metabolite concentrations in multiple cerebral regions during routine MRI. The obtained data will be helpful in future pediatric CSI measurements deciding whether the ratios of the main metabolites are within the range of normal values or have to be considered as probably pathologic. (orig.)

  1. Pressure dependence of side chain13C chemical shifts in model peptides Ac-Gly-Gly-Xxx-Ala-NH2.

    Science.gov (United States)

    Beck Erlach, Markus; Koehler, Joerg; Crusca, Edson; Munte, Claudia E; Kainosho, Masatsune; Kremer, Werner; Kalbitzer, Hans Robert

    2017-10-01

    For evaluating the pressure responses of folded as well as intrinsically unfolded proteins detectable by NMR spectroscopy the availability of data from well-defined model systems is indispensable. In this work we report the pressure dependence of 13 C chemical shifts of the side chain atoms in the protected tetrapeptides Ac-Gly-Gly-Xxx-Ala-NH 2 (Xxx, one of the 20 canonical amino acids). Contrary to expectation the chemical shifts of a number of nuclei have a nonlinear dependence on pressure in the range from 0.1 to 200 MPa. The size of the polynomial pressure coefficients B 1 and B 2 is dependent on the type of atom and amino acid studied. For H N , N and C α the first order pressure coefficient B 1 is also correlated to the chemical shift at atmospheric pressure. The first and second order pressure coefficients of a given type of carbon atom show significant linear correlations suggesting that the NMR observable pressure effects in the different amino acids have at least partly the same physical cause. In line with this observation the magnitude of the second order coefficients of nuclei being direct neighbors in the chemical structure also are weakly correlated. The downfield shifts of the methyl resonances suggest that gauche conformers of the side chains are not preferred with pressure. The valine and leucine methyl groups in the model peptides were assigned using stereospecifically 13 C enriched amino acids with the pro-R carbons downfield shifted relative to the pro-S carbons.

  2. Vanadium NMR Chemical Shifts of (Imido)vanadium(V) Dichloride Complexes with Imidazolin-2-iminato and Imidazolidin-2-iminato Ligands: Cooperation with Quantum-Chemical Calculations and Multiple Linear Regression Analyses.

    Science.gov (United States)

    Yi, Jun; Yang, Wenhong; Sun, Wen-Hua; Nomura, Kotohiro; Hada, Masahiko

    2017-11-30

    The NMR chemical shifts of vanadium ( 51 V) in (imido)vanadium(V) dichloride complexes with imidazolin-2-iminato and imidazolidin-2-iminato ligands were calculated by the density functional theory (DFT) method with GIAO. The calculated 51 V NMR chemical shifts were analyzed by the multiple linear regression (MLR) analysis (MLRA) method with a series of calculated molecular properties. Some of calculated NMR chemical shifts were incorrect using the optimized molecular geometries of the X-ray structures. After the global minimum geometries of all of the molecules were determined, the trend of the observed chemical shifts was well reproduced by the present DFT method. The MLRA method was performed to investigate the correlation between the 51 V NMR chemical shift and the natural charge, band energy gap, and Wiberg bond index of the V═N bond. The 51 V NMR chemical shifts obtained with the present MLR model were well reproduced with a correlation coefficient of 0.97.

  3. Evaluation of vertebral bone marrow fat content by chemical-shift MRI in osteoporosis

    Energy Technology Data Exchange (ETDEWEB)

    Gokalp, Gokhan; Mutlu, Fatma Senturk; Yazici, Zeynep; Yildirim, Nalan [Uludag University Medical Faculty, Department of Radiology, Gorukle, Bursa (Turkey)

    2011-05-15

    To quantitatively evaluate vertebral bone marrow fat content and investigate its association with osteoporosis with chemical-shift magnetic resonance imaging (CS-MRI). Fifty-six female patients (age range 50-65 years) with varying bone mineral densities as documented with dual x-ray absorptiometry (DXA) were prospectively included in the study. According to the DXA results, the patients were grouped as normal bone density, osteopenic, or osteoporotic. In order to calculate fat content, the lumbar region was visualized in the sagittal plane by CS-MRI sequence. ''Region of interest'' (ROI)s were placed within L3 vertebral bodies and air (our reference point) at different time points by different radiologists. Fat content was calculated through ''signal intensity (SI) suppression rate'' and ''SI Index''. The quantitative values were compared statistically with those obtained from DXA examinations. Kruskal-Wallis, and Mann-Whitney U tests were used for comparisons between groups. The reliability of the measurements performed by two radiologists was evaluated with the ''intraclass correlation coefficient''. This study was approved by an institutional review board and all participants provided informed consent to participate in the study. Eighteen subjects with normal bone density (mean T score, 0.39 {+-} 1.3 [standard deviation]), 20 subjects with osteopenia (mean T score, -1.79 {+-} 0.38), and 18 subjects with osteoporosis (mean T score, -3 {+-} 0.5) were determined according to DXA results. The median age was 55.9 (age range 50-64 years) in the normal group, 55.5 (age range 50-64 years) in the osteopenic group, and 55.1 (age range 50-65 years) in the osteoporotic group (p = 0.872). In the CS-MRI examination, the values of ''SI suppression ratio'' and ''SI Index'' (median [min:max]) were calculated by the first and second reader, independently. There

  4. Proton Chemical Shift Imaging of the Brain in Pediatric and Adult Developmental Stuttering.

    Science.gov (United States)

    O'Neill, Joseph; Dong, Zhengchao; Bansal, Ravi; Ivanov, Iliyan; Hao, Xuejun; Desai, Jay; Pozzi, Elena; Peterson, Bradley S

    2017-01-01

    Developmental stuttering is a neuropsychiatric condition of incompletely understood brain origin. Our recent functional magnetic resonance imaging study indicates a possible partial basis of stuttering in circuits enacting self-regulation of motor activity, attention, and emotion. To further characterize the neurophysiology of stuttering through in vivo assay of neurometabolites in suspect brain regions. Proton chemical shift imaging of the brain was performed in a case-control study of children and adults with and without stuttering. Recruitment, assessment, and magnetic resonance imaging were performed in an academic research setting. Ratios of N-acetyl-aspartate plus N-acetyl-aspartyl-glutamate (NAA) to creatine (Cr) and choline compounds (Cho) to Cr in widespread cerebral cortical, white matter, and subcortical regions were analyzed using region of interest and data-driven voxel-based approaches. Forty-seven children and adolescents aged 5 to 17 years (22 with stuttering and 25 without) and 47 adults aged 21 to 51 years (20 with stuttering and 27 without) were recruited between June 2008 and March 2013. The mean (SD) ages of those in the stuttering and control groups were 12.2 (4.2) years and 13.4 (3.2) years, respectively, for the pediatric cohort and 31.4 (7.5) years and 30.5 (9.9) years, respectively, for the adult cohort. Region of interest-based findings included lower group mean NAA:Cr ratio in stuttering than nonstuttering participants in the right inferior frontal cortex (-7.3%; P = .02), inferior frontal white matter (-11.4%; P stuttering sample included higher NAA:Cr and Cho:Cr ratios (regression coefficient, 197.4-275; P stuttering severity (r = 0.40-0.52; P = .001-.02). This spectroscopy study of stuttering demonstrates brainwide neurometabolite alterations, including several regions implicated by other neuroimaging modalities. Prior ascription of a role in stuttering to inferior frontal and superior temporal gyri, caudate, and other

  5. Chemical shift of Mn and Cr K-edges in X-ray absorption ...

    Indian Academy of Sciences (India)

    Measurements have been carried out at the energy dispersive EXAFS beamline at INDUS-2 Synchrotron Radiation Source at Raja Ramanna Centre for Advanced Technology, Indore. Energy shifts of ∼8–16 eV were observed for Mn K edge in the Mn-compounds while a shift of 13–20 eV was observed for Cr K edge in ...

  6. Non‐invasive Localization of Thymol Accumulation in Carum copticum (Apiaceae) Fruits by Chemical Shift Selective Magnetic Resonance Imaging

    OpenAIRE

    GERSBACH, P. V.; Reddy, N.

    2002-01-01

    Magnetic resonance imaging was used to localize the site of essential oil accumulation in fruit of Carum copticum L. (Apiaceae). A chemical shift method is described that utilized the spectral properties of the aromatic monoterpene thymol, the major component of the essential oil, to image thymol selectively. The presence of essential oil secretory structures in the fruit and an essential oil containing a high proportion of thymol were confirmed with optical microscopy and gas chromatography‐...

  7. Application of data mining tools for classification of protein structural class from residue based averaged NMR chemical shifts.

    Science.gov (United States)

    Kumar, Arun V; Ali, Rehana F M; Cao, Yu; Krishnan, V V

    2015-10-01

    The number of protein sequences deriving from genome sequencing projects is outpacing our knowledge about the function of these proteins. With the gap between experimentally characterized and uncharacterized proteins continuing to widen, it is necessary to develop new computational methods and tools for protein structural information that is directly related to function. Nuclear magnetic resonance (NMR) provides powerful means to determine three-dimensional structures of proteins in the solution state. However, translation of the NMR spectral parameters to even low-resolution structural information such as protein class requires multiple time consuming steps. In this paper, we present an unorthodox method to predict the protein structural class directly by using the residue's averaged chemical shifts (ACS) based on machine learning algorithms. Experimental chemical shift information from 1491 proteins obtained from Biological Magnetic Resonance Bank (BMRB) and their respective protein structural classes derived from structural classification of proteins (SCOP) were used to construct a data set with 119 attributes and 5 different classes. Twenty four different classification schemes were evaluated using several performance measures. Overall the residue based ACS values can predict the protein structural classes with 80% accuracy measured by Matthew correlation coefficient. Specifically protein classes defined by mixed αβ or small proteins are classified with >90% correlation. Our results indicate that this NMR-based method can be utilized as a low-resolution tool for protein structural class identification without any prior chemical shift assignments. Copyright © 2015 Elsevier B.V. All rights reserved.

  8. Predicting Heats of Explosion of Nitroaromatic Compounds through NBO Charges and 15N NMR Chemical Shifts of Nitro Groups

    Directory of Open Access Journals (Sweden)

    Ricardo Infante-Castillo

    2012-01-01

    Full Text Available This work presents a new quantitative model to predict the heat of explosion of nitroaromatic compounds using the natural bond orbital (NBO charge and 15N NMR chemical shifts of the nitro groups (15NNitro as structural parameters. The values of the heat of explosion predicted for 21 nitroaromatic compounds using the model described here were compared with experimental data. The prediction ability of the model was assessed by the leave-one-out cross-validation method. The cross-validation results show that the model is significant and stable and that the predicted accuracy is within 0.146 MJ kg−1, with an overall root mean squared error of prediction (RMSEP below 0.183 MJ kg−1. Strong correlations were observed between the heat of explosion and the charges (R2 = 0.9533 and 15N NMR chemical shifts (R2 = 0.9531 of the studied compounds. In addition, the dependence of the heat of explosion on the presence of activating or deactivating groups of nitroaromatic explosives was analyzed. All calculations, including optimizations, NBO charges, and 15NNitro NMR chemical shifts analyses, were performed using density functional theory (DFT and a 6-311+G(2d,p basis set. Based on these results, this practical quantitative model can be used as a tool in the design and development of highly energetic materials (HEM based on nitroaromatic compounds.

  9. Protein energetic conformational analysis from NMR chemical shifts (PECAN) and its use in determining secondary structural elements

    Energy Technology Data Exchange (ETDEWEB)

    Eghbalnia, Hamid R.; Wang Liya; Bahrami, Arash [National Magnetic Resonance Facility at Madison, Biochemistry Department (United States); Assadi, Amir [University of Wisconsin-Madison, Mathematics Department (United States); Markley, John L. [National Magnetic Resonance Facility at Madison, Biochemistry Department (United States)], E-mail: eghbalni@nmrfam.wisc.edu

    2005-05-15

    We present an energy model that combines information from the amino acid sequence of a protein and available NMR chemical shifts for the purposes of identifying low energy conformations and determining elements of secondary structure. The model ('PECAN', Protein Energetic Conformational Analysis from NMR chemical shifts) optimizes a combination of sequence information and residue-specific statistical energy function to yield energetic descriptions most favorable to predicting secondary structure. Compared to prior methods for secondary structure determination, PECAN provides increased accuracy and range, particularly in regions of extended structure. Moreover, PECAN uses the energetics to identify residues located at the boundaries between regions of predicted secondary structure that may not fit the stringent secondary structure class definitions. The energy model offers insights into the local energetic patterns that underlie conformational preferences. For example, it shows that the information content for defining secondary structure is localized about a residue and reaches a maximum when two residues on either side are considered. The current release of the PECAN software determines the well-defined regions of secondary structure in novel proteins with assigned chemical shifts with an overall accuracy of 90%, which is close to the practical limit of achievable accuracy in classifying the states.

  10. Toward calculations of the 129Xe chemical shift in Xe@C60 at experimental conditions: relativity, correlation, and dynamics.

    Science.gov (United States)

    Straka, Michal; Lantto, Perttu; Vaara, Juha

    2008-03-27

    We calculate the 129Xe chemical shift in endohedral Xe@C60 with systematic inclusion of the contributing physical effects to model the real experimental conditions. These are relativistic effects, electron correlation, the temperature-dependent dynamics, and solvent effects. The ultimate task is to obtain the right result for the right reason and to develop a physically justified methodological model for calculations and simulations of endohedral Xe fullerenes and other confined Xe systems. We use the smaller Xe...C6H6 model to calibrate density functional theory approaches against accurate correlated wave function methods. Relativistic effects as well as the coupling of relativity and electron correlation are evaluated using the leading-order Breit-Pauli perturbation theory. The dynamic effects are treated in two ways. In the first approximation, quantum dynamics of the Xe atom in a rigid cage takes advantage of the centrosymmetric potential for Xe within the thermally accessible distance range from the center of the cage. This reduces the problem of obtaining the solution of a diatomic rovibrational problem. In the second approach, first-principles classical molecular dynamics on the density functional potential energy hypersurface is used to produce the dynamical trajectory for the whole system, including the dynamic cage. Snapshots from the trajectory are used for calculations of the dynamic contribution to the absorption 129Xe chemical shift. The calculated nonrelativistic Xe shift is found to be highly sensitive to the optimized molecular structure and to the choice of the exchange-correlation functional. Relativistic and dynamic effects are significant and represent each about 10% of the nonrelativistic static shift at the minimum structure. While the role of the Xe dynamics inside of the rigid cage is negligible, the cage dynamics turns out to be responsible for most of the dynamical correction to the 129Xe shift. Solvent effects evaluated with a polarized

  11. Chemical shift of U L3 edges in different uranium compounds ...

    Indian Academy of Sciences (India)

    Administrator

    ion has been investigated by X-ray absorption spectro- scopy (XAS) measurements with synchrotron radiation on few uranium compounds, viz. UF4, U3O8, ammonium diuranate and uranyl nitrate hexahydrate. A relationship between the energy shift and effective charges on U atom in the compounds has been found out. 2.

  12. Chemical shift of Mn and Cr K-edges in X-ray absorption ...

    Indian Academy of Sciences (India)

    ; effective charge. 1. Introduction. It is well known that the X-ray absorption edge of a metal atom changes from its elemental state when it takes part in the formation of a compound. Generally, the absorption edge shifts to higher energy as the ...

  13. Phosphines with N-heterocyclic boranyl substituents.

    Science.gov (United States)

    Kaaz, M; Bender, J; Förster, D; Frey, W; Nieger, M; Gudat, D

    2014-01-14

    A lithio-diazaborole reacted with diamino-chlorophosphines via metathesis to yield previously unavailable phosphinoboranes bearing amino substituents at both the phosphorus and boron atoms, and with Ph2PCl and Mes*PCl2via chloride transfer and reductive PP coupling to give a chloro-diazaborole and the corresponding diphosphine or diphosphene, respectively. Diazaboroles with phenylphosphino- and PH2-substituents were nonetheless accessible via inverse metathesis upon treatment of a bromoborane precursor with phosphides PhnPH2-nM (n = 0-2, M = Li, K). The products were characterised by spectroscopic data and in most cases by single-crystal X-ray diffraction studies which show the molecules to exhibit strongly pyramidal coordination at the phosphorus atom and long BP bonds of 1.93-1.95 Å. The insensitivity of the BP distance towards substituent effects and the tolerance of large sterically induced torsional twists along the BP bond axis suggest the presence of pure single bonds without any contribution from P→B dative π-interactions. This view was confirmed by DFT studies which indicate further that the molecules lack a significant electrophilic character at boron but may act as potential σ-donor/π-acceptor ligands through the phosphorus atom.

  14. Thalassiosira spp. community composition shifts in response to chemical and physical forcing in the northeast Pacific Ocean.

    Directory of Open Access Journals (Sweden)

    Phoebe Dreux Chappell

    2013-09-01

    Full Text Available Diatoms are genetically diverse unicellular photosynthetic eukaryotes that are key primary producers in the ocean. Many of the over 100 extant diatom species in the cosmopolitan genus Thalassiosira are difficult to distinguish in mixed populations using light microscopy. Here we examine shifts in Thalassiosira spp. composition along a coastal to open ocean transect that encountered a three-month-old Haida eddy in the northeast Pacific Ocean. To quantify shifts in Thalassiosira species composition, we developed a targeted automated ribosomal intergenic spacer analysis (ARISA method to identify Thalassiosira spp. in environmental samples. As many specific fragment lengths are indicative of individual Thalassiosira spp., the ARISA method is a useful screening tool to identify changes in the relative abundance and distribution of specific species. The method also enabled us to assess changes in Thalassiosira community composition in response to chemical and physical forcing. Thalassiosira spp. community composition in the core of a three-month-old Haida eddy remained largely (>80% similar over a two-week period, despite moving 24 km southwestward. Shifts in Thalassiosira species correlated with changes in dissolved iron (Fe and temperature throughout the sampling period. Simultaneously tracking community composition and relative abundance of Thalassiosira species within the physical and chemical context they occurred allowed us to identify quantitative linkages between environmental conditions and community response.

  15. Quantum mechanical calculations of conformationally relevant 1H and 13C NMR chemical shifts of N-, O-, and S-substituted calixarene systems.

    Science.gov (United States)

    Bifulco, Giuseppe; Riccio, Raffaele; Gaeta, Carmine; Neri, Placido

    2007-01-01

    QM GIAO calculations of (13)C and (1)H chemical shift values of the ArCH(2)Ar group in N-, O-, and S-substituted calixarene systems were performed with a hybrid DFT functional MPW1PW91 and 6-31G(d,p) basis set. A good reproduction of experimental data was obtained for some representative calixarenes and for a series of simplified calixarene models. This allowed the derivation of chemical shift surfaces versus phi and chi dihedral angles. The applicability of chemical shift surfaces in the study of calixarene conformational features is illustrated.

  16. Pressure dependence of backbone chemical shifts in the model peptides Ac-Gly-Gly-Xxx-Ala-NH2.

    Science.gov (United States)

    Erlach, Markus Beck; Koehler, Joerg; Crusca, Edson; Kremer, Werner; Munte, Claudia E; Kalbitzer, Hans Robert

    2016-06-01

    For a better understanding of nuclear magnetic resonance (NMR) detected pressure responses of folded as well as unstructured proteins the availability of data from well-defined model systems are indispensable. In this work we report the pressure dependence of chemical shifts of the backbone atoms (1)H(α), (13)C(α) and (13)C' in the protected tetrapeptides Ac-Gly-Gly-Xxx-Ala-NH2 (Xxx one of the 20 canonical amino acids). Contrary to expectation the chemical shifts of these nuclei have a nonlinear dependence on pressure in the range from 0.1 to 200 MPa. The polynomial pressure coefficients B 1 and B 2 are dependent on the type of amino acid studied. The coefficients of a given nucleus show significant linear correlations suggesting that the NMR observable pressure effects in the different amino acids have at least partly the same physical cause. In line with this observation the magnitude of the second order coefficients of nuclei being direct neighbors in the chemical structure are also weakly correlated.

  17. 129Xe chemical shift in human blood and pulmonary blood oxygenation measurement in humans using hyperpolarized 129Xe NMR

    OpenAIRE

    Norquay, G.; Leung, G; Stewart, N J; Wolber, J.; Wild, J.M.

    2016-01-01

    Purpose To evaluate the dependency of the 129Xe?red blood cell (RBC) chemical shift on blood oxygenation, and to use this relation for noninvasive measurement of pulmonary blood oxygenation in vivo with hyperpolarized 129Xe NMR. Methods Hyperpolarized 129Xe was equilibrated with blood samples of varying oxygenation in vitro, and NMR was performed at 1.5 T and 3 T. Dynamic in vivo NMR during breath hold apnea was performed at 3 T on two healthy volunteers following inhalation of hyperpolarized...

  18. Beyond DP4: an Improved Probability for the Stereochemical Assignment of Isomeric Compounds using Quantum Chemical Calculations of NMR Shifts.

    Science.gov (United States)

    Grimblat, Nicolás; Zanardi, María M; Sarotti, Ariel M

    2015-12-18

    The DP4 probability is one of the most sophisticated and popular approaches for the stereochemical assignment of organic molecules using GIAO NMR chemical shift calculations when only one set of experimental data is available. In order to improve the performance of the method, we have developed a modified probability (DP4+), whose main differences from the original DP4 are the inclusion of unscaled data and the use of higher levels of theory for the NMR calculation procedure. With these modifications, a significant improvement in the overall performance was achieved, providing accurate and confident results in establishing the stereochemistry of 48 challenging isomeric compounds.

  19. COMPUTATIONAL INVESTIGATION ON THE STRUCTURE AND NMR CHEMICAL SHIFTS OF ENDO-CONE [CS2(p-METHYLCALIX[4]ARENE] COMPLEX

    Directory of Open Access Journals (Sweden)

    Hanggara Sudrajat

    2010-06-01

    Full Text Available The structure and NMR chemical shifts of endo-cone [CS2(p-methylcalix[4]arene] complex have been computationally investigated using BIO+ force fields, semi-empirical (PM3 and ab initio (RHF/6-311G++(d,p calculations. The first comparison of ab initio NMR chemical shift calculations for a calix[4]arene inclusion complex with solid-state 13C NMR chemical shifts based on the 1:1 complex of p-methylcalix[4]arenes with carbon disulfide in endo-cone complexation mode has been reported. The results showed that ab initio (RHF/6-311G++(d,p NMR calculations of the host-guest [CS2(p-methylcalix[4]arene] complex are in good agreement with experimental solid-state NMR data.    Keywords: computational investigation, structure, NMR chemical shifts, [CS2(p-methylcalix[4]arene].

  20. Modeling the chemical shift of lanthanide 4f electron binding energies

    NARCIS (Netherlands)

    Dorenbos, P.

    2012-01-01

    Lanthanides in compounds can adopt the tetravalent [Xe]4fn?1 (like Ce4+, Pr4+, Tb4+), the trivalent [Xe]4fn (all lanthanides), or the divalent [Xe]4f n+1 configuration (like Eu2+, Yb2+, Sm2+, Tm2+). The 4f-electron binding energy depends on the charge Q of the lanthanide ion and its chemical

  1. Effect of N-substituents on redox, optical, and electronic properties of naphthalene bisimides used for field-effect transistors fabrication.

    Science.gov (United States)

    Gawrys, Pawel; Djurado, David; Rimarcík, Ján; Kornet, Aleksandra; Boudinet, Damien; Verilhac, Jean-Marie; Lukes, Vladimír; Wielgus, Ireneusz; Zagorska, Malgorzata; Pron, Adam

    2010-02-11

    Three groups of naphthalene bisimides were synthesized and comparatively studied, namely, alkyl bisimides, alkylaryl ones, and novel bisimides containing the alkylthienyl moiety in the N-substituent. The experimental absorption spectra measured in CHCl(3) exhibit one intensive absorption band that is uniformly detected in the spectral range of 340 to 400 nm for all studied molecules. This band consists of three or four vibronic peaks. The introduction of an alkylthienyl group results in the appearance of an additional band (in the spectral range from 282 to 326 nm, depending on the position of the substituent) that can be ascribed to the pi-pi* transition in the thienyl chromophore. The minimal substituent effect on the lowest electronic transitions was explained using the quantum chemical calculations based on the time-dependent density functional theory. The investigation of the shapes of frontier orbitals have also shown that the oxidation of bisimides containing thiophene moiety is primary connected with the electron abstraction from the thienyl ring. To the contrary, the addition of an electron in the reduction process leads to an increase in the electron density in the central bisimide core. As shown by the electrochemical measurements, the onset of the first reduction potential (so-called "electrochemically determined LUMO level") is sensitive toward the type of the substituent being shifted from about -3.72 eV for bisimides with alkyl substituents to about -3.83 eV for alkylaryl ones and to about -3.94 eV for bisimides with thienyl groups. The presence of the thienyl ring also lowers the energy difference between the HOMO and LUMO orbitals. These experimental data can be well correlated with the DFT calculations in terms of HOMO/LUMO shapes and energies. Taking into account the low position of their LUMO level and their highly ordered supramolecular organization, the new bisimides are good candidates for the use in n-channel field effect transistors

  2. Using chemical shifts to generate structural ensembles for intrinsically disordered proteins with converged distributions of secondary structure.

    Science.gov (United States)

    Ytreberg, F Marty; Borcherds, Wade; Wu, Hongwei; Daughdrill, Gary W

    2015-01-01

    A short segment of the disordered p53 transactivation domain (p53TAD) forms an amphipathic helix when bound to the E3 ubiquitin ligase, MDM2. In the unbound p53TAD, this short segment has transient helical secondary structure. Using a method that combines broad sampling of conformational space with re-weighting, it is shown that it is possible to generate multiple, independent structural ensembles that have highly similar secondary structure distributions for both p53TAD and a P27A mutant. Fractional amounts of transient helical secondary structure were found at the MDM2 binding site that are very similar to estimates based directly on experimental observations. Structures were identified in these ensembles containing segments that are highly similar to short p53 peptides bound to MDM2, even though the ensembles were re-weighted using unbound experimental data. Ensembles were generated using chemical shift data (alpha carbon only, or in combination with other chemical shifts) and cross-validated by predicting residual dipolar couplings. We think this ensemble generator could be used to predict the bound state structure of protein interaction sites in IDPs if there are detectable amounts of matching transient secondary structure in the unbound state.

  3. Calculation of fluorine chemical shift tensors for the interpretation of oriented (19)F-NMR spectra of gramicidin A in membranes.

    Science.gov (United States)

    Sternberg, Ulrich; Klipfel, Marco; Grage, Stephan L; Witter, Raiker; Ulrich, Anne S

    2009-08-28

    A semi-empirical method for the prediction of chemical shifts, based on bond polarization theory, has recently been introduced for (13)C. Here, we extended this approach to calculate the (19)F chemical shift tensors of fluorine bound to aromatic rings and in aliphatic CF(3) groups. For the necessary parametrization, ab initio chemical shift calculations were performed at the MP2 level for a set of fluorinated molecules including tryptophan. The bond polarization parameters obtained were used to calculate the (19)F chemical shift tensors for several crystalline molecules, and to reference the calculated values on a chemical shift scale relative to CFCl(3). As a first biophysical application, we examined the distribution of conformations of a (19)F-labeled tryptophan side chain in the membrane-bound ion channel peptide, gramicidin A. The fluorine chemical shift tensors were calculated from snapshots of a molecular dynamics simulation employing the (19)F-parametrized bond polarization theory. In this MD simulation, published (2)H quadrupolar and (15)N-(1)H dipolar couplings of the indole ring were used as orientational constraints to determine the conformational distribution of the 5F-Trp(13) side chain. These conformations were then used to interpret the spectra of (19)F-labeled gramicidin A in fluid and gel phase lipid bilayers.

  4. Observation of Optical Chemical Shift by Precision Nuclear Spin Optical Rotation Measurements and Calculations.

    Science.gov (United States)

    Shi, Junhui; Ikäläinen, Suvi; Vaara, Juha; Romalis, Michael V

    2013-02-07

    Nuclear spin optical rotation (NSOR) is a recently developed technique for detection of nuclear magnetic resonance via rotation of light polarization, instead of the usual long-range magnetic fields. NSOR signals depend on hyperfine interactions with virtual optical excitations, giving new information about the nuclear chemical environment. We use a multipass optical cell to perform the first precision measurements of NSOR signals for a range of organic liquids and find clear distinction between proton signals for different compounds, in agreement with our earlier theoretical predictions. Detailed first-principles quantum mechanical NSOR calculations are found to be in agreement with the measurements.

  5. Observation of optical chemical shift by precision nuclear spin optical rotation measurements and calculations

    CERN Document Server

    Shi, Junhui; Vaara, Juha; Romalis, Michael V

    2012-01-01

    Nuclear spin optical rotation (NSOR) is a recently developed technique for detection of nuclear magnetic resonance via rotation of light polarization, instead of the usual long-range magnetic fields. NSOR signals depend on hyperfine interactions with virtual optical excitations, giving new information about the nuclear chemical environment. We use a multi-pass optical cell to perform first precision measurements of NSOR signals for a range of organic liquids and find clear distinction between proton signals for different compounds, in agreement with our earlier predictions. Detailed first principles quantum-mechanical NSOR calculations are found to be in good agreement with the measurements.

  6. Liver fat quantification: Comparison of dual-echo and triple-echo chemical shift MRI to MR spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Satkunasingham, Janakan; Besa, Cecilia [Department of Radiology, Body MRI, Icahn School of Medicine at Mount Sinai, One Gustave Levy Place, New York, NY 10029 (United States); Translational and Molecular Imaging Institute, Icahn School of Medicine at Mount Sinai, One Gustave Levy Place, New York, NY 10029 (United States); Bane, Octavia [Translational and Molecular Imaging Institute, Icahn School of Medicine at Mount Sinai, One Gustave Levy Place, New York, NY 10029 (United States); Shah, Ami [Department of Radiology, Body MRI, Icahn School of Medicine at Mount Sinai, One Gustave Levy Place, New York, NY 10029 (United States); Oliveira, André de; Gilson, Wesley D.; Kannengiesser, Stephan [Siemens AG, Healthcare Sector, Erlangen (Germany); Taouli, Bachir, E-mail: bachir.taouli@mountsinai.org [Department of Radiology, Body MRI, Icahn School of Medicine at Mount Sinai, One Gustave Levy Place, New York, NY 10029 (United States); Translational and Molecular Imaging Institute, Icahn School of Medicine at Mount Sinai, One Gustave Levy Place, New York, NY 10029 (United States)

    2015-08-15

    Highlights: • We present a large cohort of patients who underwent dual and triple echo chemical shift imaging against multi-echo T{sub 2} corrected MR spectroscopy (MRS) for liver fat quantification. • Our data suggests that a triple-echo sequence is highly accurate for detection of liver fat, even in the presence of T{sub 2}{sup *} shortening, with minor discrepancies when compared with the advanced fat quantification method. - Abstract: Purpose: To assess the diagnostic value of MRI using dual-echo (2PD) and triple-echo (3PD) chemical shift imaging for liver fat quantification against multi-echo T{sub 2} corrected MR spectroscopy (MRS) used as the reference standard, and examine the effect of T{sub 2}{sup *} imaging on accuracy of MRI for fat quantification. Materials and methods: Patients who underwent 1.5 T liver MRI that incorporated 2PD, 3PD, multi-echo T{sub 2}{sup *} and MRS were included in this IRB approved prospective study. Regions of interest were placed in the liver to measure fat fraction (FF) with 2PD and 3PD and compared with MRS-FF. A random subset of 25 patients with a wide range of MRS-FF was analyzed with an advanced FF calculation method, to prove concordance with the 3PD. The statistical analysis included correlation stratified according to T{sub 2}{sup *}, Bland-Altman analysis, and calculation of diagnostic accuracy for detection of MRS-FF > 6.25%. Results: 220 MRI studies were identified in 217 patients (mean BMI 28.0 ± 5.6). 57/217 (26.2%) patients demonstrated liver steatosis (MRS-FF > 6.25%). Bland-Altman analysis revealed strong agreement between 3PD and MRS (mean ± 1.96 SD: −0.5% ± 4.6%) and weaker agreement between 2PD and MRS (4.7% ± 16.0%). Sensitivity of 3PD for diagnosing FF> 6.25% was higher than that of 2PD. 3PD-FF showed minor discrepancies (coefficient of variation <10%) from FF measured with the advanced method. Conclusion: Our large series study validates the use of 3PD chemical shift sequence for detection of

  7. Structural analysis of flavonoids in solution through DFT 1H NMR chemical shift calculations: Epigallocatechin, Kaempferol and Quercetin

    Science.gov (United States)

    De Souza, Leonardo A.; Tavares, Wagner M. G.; Lopes, Ana Paula M.; Soeiro, Malucia M.; De Almeida, Wagner B.

    2017-05-01

    In this work, we showed that comparison between experimental and theoretical 1H NMR chemical shift patterns, calculated using Density Functional Theory (DFT), can be used for the prediction of molecular structure of flavonoids in solution, what is experimentally accessible for gas phase (electron diffraction methods) and solid samples (X-ray diffraction). The best match between B3LYP/6-31G(d,p)-PCM 1H NMR calculations for B ring rotated structures and experimental spectra can provide information on the conformation adopted by polyphenols in solution (usually DMSO-d6, acetone-d6 as solvents), which may differ from solid state and gas phase observed structures, and also DFT optimized geometry in the vacuum.

  8. Non‐invasive Localization of Thymol Accumulation in Carum copticum (Apiaceae) Fruits by Chemical Shift Selective Magnetic Resonance Imaging

    Science.gov (United States)

    GERSBACH, P. V.; REDDY, N.

    2002-01-01

    Magnetic resonance imaging was used to localize the site of essential oil accumulation in fruit of Carum copticum L. (Apiaceae). A chemical shift method is described that utilized the spectral properties of the aromatic monoterpene thymol, the major component of the essential oil, to image thymol selectively. The presence of essential oil secretory structures in the fruit and an essential oil containing a high proportion of thymol were confirmed with optical microscopy and gas chromatography‐mass spectrometry, respectively. Selective imaging of whole C. copticum fruits showed that thymol accumulation was localized to the secretory structures (canals) situated in the fruit wall. The technique was considered non‐invasive as the seeds used in the imaging experiments remained intact and viable. PMID:12197523

  9. Shifting chemical equilibria in flow--efficient decarbonylation driven by annular flow regimes.

    Science.gov (United States)

    Gutmann, Bernhard; Elsner, Petteri; Glasnov, Toma; Roberge, Dominique M; Kappe, C Oliver

    2014-10-20

    To efficiently drive chemical reactions, it is often necessary to influence an equilibrium by removing one or more components from the reaction space. Such manipulation is straightforward in open systems, for example, by distillation of a volatile product from the reaction mixture. Herein we describe a unique high-temperature/high-pressure gas/liquid continuous-flow process for the rhodium-catalyzed decarbonylation of aldehydes. The carbon monoxide released during the reaction is carried with a stream of an inert gas through the center of the tubing, whereas the liquid feed travels as an annular film along the wall of the channel. As a consequence, carbon monoxide is effectively vaporized from the liquid phase into the gas phase and stripped from the reaction mixture, thus driving the equilibrium to the product and preventing poisoning of the catalyst. This approach enables the catalytic decarbonylation of a variety of aldehydes with unprecedented efficiency with a standard coil-based flow device. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. The predictive accuracy of secondary chemical shifts is more affected by protein secondary structure than solvent environment

    Energy Technology Data Exchange (ETDEWEB)

    Tremblay, Marie-Laurence; Banks, Aaron W.; Rainey, Jan K., E-mail: jan.rainey@dal.c [Dalhousie University, Department of Biochemistry and Molecular Biology (Canada)

    2010-04-15

    Biomolecular NMR spectroscopy frequently employs estimates of protein secondary structure using secondary chemical shift ({Delta}{delta}) values, measured as the difference between experimental and random coil chemical shifts (RCCS). Most published random coil data have been determined in aqueous conditions, reasonable for non-membrane proteins, but potentially less relevant for membrane proteins. Two new RCCS sets are presented here, determined in dimethyl sulfoxide (DMSO) and chloroform:methanol:water (4:4:1 by volume) at 298 K. A web-based program, CS-CHEMeleon, has been implemented to determine the accuracy of secondary structure assessment by calculating and comparing {Delta}{delta} values for various RCCS datasets. Using CS-CHEMeleon, {Delta}{delta} predicted versus experimentally determined secondary structures were compared for large datasets of membrane and non-membrane proteins as a function of RCCS dataset, {Delta}{delta} threshold, nucleus, localized parameter averaging and secondary structure type. Optimized {Delta}{delta} thresholds are presented both for published and for the DMSO and chloroform:methanol:water derived RCCS tables. Despite obvious RCCS variations between datasets, prediction of secondary structure was consistently similar. Strikingly, predictive accuracy seems to be most dependent upon the type of secondary structure, with helices being the most accurately predicted by {Delta}{delta} values using five different RCCS tables. We suggest caution when using {Delta}{delta}-based restraints in structure calculations as the underlying dataset may be biased. Comparative assessment of multiple RCCS datasets should be performed, and resulting {Delta}{delta}-based restraints weighted appropriately relative to other experimental restraints.

  11. Deep-red emissive crescent-shaped fluorescent dyes: substituent effect on live cell imaging.

    Science.gov (United States)

    Liu, Weimin; Zhou, Bingjiang; Niu, Guangle; Ge, Jiechao; Wu, Jiasheng; Zhang, Hongyan; Xu, Haitao; Wang, Pengfei

    2015-04-08

    A series of crescent-shaped fluorescent dyes (CP1-CP6) were synthesized by hybridizing coumarin and pyronin moieties with different amino substituents at both ends. The molecular structures and photophysical properties of these fluorescent dyes were investigated through X-ray diffraction, absorption spectroscopy, and fluorescence spectroscopy. Results show that the fluorescent dyes exhibited crescent-shaped structures, deep-red emissions (approximately 650 nm), and significant Stokes shifts. In live-cell-imaging experiments, CP1 stains mitochondria, whereas CP3 and CP6 stain the lysosomes in a cytoplasm and the RNA in nucleoli. The relationships between different amino substituent groups and the imaging properties of CP dyes were discussed as well. Additionally, findings from the cytotoxicity and photostability experiments on living cells indicated the favorable biocompatibility and high photostability of the CP dyes.

  12. Predictions of the fluorine NMR chemical shifts of perfluorinated carboxylic acids, CnF(2n+1)COOH (n = 6-8).

    Science.gov (United States)

    Liu, Zizhong; Goddard, John D

    2009-12-17

    Perfluorinated carboxylic acids (PFCAs) are a class of persistent environmental pollutants. Commercially available PFCAs are mixtures of linear and branched isomers, possibly with impurities. Different isomers have different physical and chemical properties and toxicities. However, little is known about the properties and the finer details of the structures of the individual branched isomers. Full geometry optimizations for the linear n-alkane (C(6)-C(27)) PFCAs indicated that all have helical structures. The helical angle increases slightly with increasing chain length, from 16.3 degrees in C(6)F(13)COOH to 17.0 degrees in C(27)F(55)COOH. This study predicts (19)F NMR parameters for 69 linear and branched isomers of the perfluoro carboxylic acids C(6)F(13)COOH, C(7)F(15)COOH, and C(8)F(17)COOH. B3LYP-GIAO/6-31++G(d,p)//B3LYP/6-31G(d,p) was used for the NMR calculations with analysis of the chemical shifts by the natural bond orbital method. The predictions of the (19)F chemical shifts revealed the differences among the CF(3), CF(2), and CF groups. In general, the absolute values for the chemical shifts for the CF(3) group are smaller than 90 ppm, for the CF larger than 160 ppm, and for the CF(2) between 110 and 130 ppm. The chemical shifts of the branched isomers are smaller in magnitude than the linear ones. The decrease is correlated with the steric hindrance of the CF(3) groups, the more hindered the CF(3), the greater the decrease in the (19)F chemical shifts. The predicted (19)F chemical shifts are similar to those for analogous perfluoro compounds with other terminal functional groups such as -SO(3)H or -SO(3)NH(2)CH(2)CH(3).

  13. Predictions of the Fluorine NMR Chemical Shifts of Perfluorinated Carboxylic Acids, CnF2n+1COOH (n = 6-8)

    Science.gov (United States)

    Liu, Zizhong; Goddard, John D.

    2009-10-01

    Perfluorinated carboxylic acids (PFCAs) are a class of persistent environmental pollutants. Commercially available PFCAs are mixtures of linear and branched isomers, possibly with impurities. Different isomers have different physical and chemical properties and toxicities. However, little is known about the properties and the finer details of the structures of the individual branched isomers. Full geometry optimizations for the linear n-alkane (C6-C27) PFCAs indicated that all have helical structures. The helical angle increases slightly with increasing chain length, from 16.3° in C6F13COOH to 17.0° in C27F55COOH. This study predicts 19F NMR parameters for 69 linear and branched isomers of the perfluoro carboxylic acids C6F13COOH, C7F15COOH, and C8F17COOH. B3LYP-GIAO/6-31++G(d,p)//B3LYP/6-31G(d,p) was used for the NMR calculations with analysis of the chemical shifts by the natural bond orbital method. The predictions of the 19F chemical shifts revealed the differences among the CF3, CF2, and CF groups. In general, the absolute values for the chemical shifts for the CF3 group are smaller than 90 ppm, for the CF larger than 160 ppm, and for the CF2 between 110 and 130 ppm. The chemical shifts of the branched isomers are smaller in magnitude than the linear ones. The decrease is correlated with the steric hindrance of the CF3 groups, the more hindered the CF3, the greater the decrease in the 19F chemical shifts. The predicted 19F chemical shifts are similar to those for analogous perfluoro compounds with other terminal functional groups such as -SO3H or -SO3NH2CH2CH3.

  14. Substituents' effect in electron attachment to epigenetic modifications of cytosine

    Science.gov (United States)

    Nunes, Fernanda B.; Bettega, Márcio H. F.; Sanchez, Sergio d'Almeida

    2017-06-01

    Epigenetic modifications of cytosine have been found to influence differently in many processes in biological systems. In order to investigate the differences in electron attachment to different epigenetic modifications of cytosine, we reported the A″ component of the integral cross section of electron scattering by cytosine (C) and its epigenetic modifications 5-methylcytosine (5mC), 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC), and 5-carboxylcytosine (5caC). Our results were obtained with the Schwinger multichannel method with pseudopotentials in the static-exchange (SE) and static-exchange plus polarization (SEP) approximations. In addition to the scattering results, we present electron attachment energies obtained through an empirical scaling relation for the five molecules. We observed three π* resonances for C, 5mC, and 5hmC and four for 5fC and 5caC, in both SE and SEP approximations. The cross sections show that the π* resonances of 5mC and 5hmC are located at higher energies than the resonances of C, while the resonances of 5fC and 5caC are located at lower energies. In order to investigate this shift in the resonances' positions, we analyzed the π* lowest-lying orbitals and the electronic density over the molecules. Using the inductive and mesomeric effects, we were able to analyze the influence of each substituent over the molecule and on the resonances' positions.

  15. Inverted cucurbit[n]urils: density functional investigations on the electronic structure, electrostatic potential, and NMR chemical shifts.

    Science.gov (United States)

    Pinjari, Rahul V; Gejji, Shridhar P

    2009-02-19

    Inverted cucurbit[n]uril (i(x)CB[n], x = 1, 2; n = 6-8), the enantiomers of cucurbit[n]uril (CB[n]) comprising one or more inverted glycouril units, show distinct selectivity in recognition toward the guest by the virtue of shape and dimensions of its cavity. The iCB[n] (x = 1 and n = 6, 7) are isolated as intermediates during the synthesis of CB[n]. In this work, density functional theory using the hybrid B3LYP functional has been employed to derive the electronic structure and the NMR chemical shifts in the i(x)CB[n] hosts. The present calculations have shown that the inversion of the glycouril unit of CB[6] and CB[7] engenders a destabilization by 4.2 and 5.7 kJ mol(-1), respectively, and, as opposed to this, the iCB[8] is favored by 18.6 kJ mol(-1) over the corresponding CB[8] host. Likewise, i2CB[7] possessing two inverted glycourils are highly destabilized over CB[7]. A large separation of the inverted glycouril units reduces the repulsion between methine protons inside the cavity, rendering the 1,4-i2CB[n] (n = 7 or 8) to be of lowest energy. Stabilization energies from the self-consistent reaction field (SCRF) theory are calculated with water, ethanol, and tetrahydrofuran (THF) as solvents. Unlike in gas phase and other solvents, the stabilization hierarchy iCB[6] portals. The electron-rich region within the cavity explains the large affinity of CB[n] toward the electron deficient guests. The electronic distribution and shape and size of the cavity thus derived provide insights for the inclusion of guests of different shapes in a variety of i(x)CB[n] hosts. NMR chemical shifts have shown that the methylene protons near the inverted glycouril and the methine protons those are directing toward the cavity yield distinct signals, consistent with those observed in experiments. The protons within the cavity are less affected by solvation.

  16. Intermolecular Interactions in Crystalline Theobromine as Reflected in Electron Deformation Density and (13)C NMR Chemical Shift Tensors.

    Science.gov (United States)

    Bouzková, Kateřina; Babinský, Martin; Novosadová, Lucie; Marek, Radek

    2013-06-11

    An understanding of the role of intermolecular interactions in crystal formation is essential to control the generation of diverse crystalline forms which is an important concern for pharmaceutical industry. Very recently, we reported a new approach to interpret the relationships between intermolecular hydrogen bonding, redistribution of electron density in the system, and NMR chemical shifts (Babinský et al. J. Phys. Chem. A, 2013, 117, 497). Here, we employ this approach to characterize a full set of crystal interactions in a sample of anhydrous theobromine as reflected in (13)C NMR chemical shift tensors (CSTs). The important intermolecular contacts are identified by comparing the DFT-calculated NMR CSTs for an isolated theobromine molecule and for clusters composed of several molecules as selected from the available X-ray diffraction data. Furthermore, electron deformation density (EDD) and shielding deformation density (SDD) in the proximity of the nuclei involved in the proposed interactions are calculated and visualized. In addition to the recently reported observations for hydrogen bonding, we focus here particularly on the stacking interactions. Although the principal relations between the EDD and CST for hydrogen bonding (HB) and stacking interactions are similar, the real-space consequences are rather different. Whereas the C-H···X hydrogen bonding influences predominantly and significantly the in-plane principal component of the (13)C CST perpendicular to the HB path and the C═O···H hydrogen bonding modulates both in-plane components of the carbonyl (13)C CST, the stacking modulates the out-of-plane electron density resulting in weak deshielding (2-8 ppm) of both in-plane principal components of the CST and weak shielding (∼ 5 ppm) of the out-of-plane component. The hydrogen-bonding and stacking interactions may add to or subtract from one another to produce total values observed experimentally. On the example of theobromine, we demonstrate

  17. Rationalizing substituent effects in 1-azathioxanthone photophysics

    Science.gov (United States)

    Junker, Anne Kathrine R.; Just Sørensen, Thomas

    2018-01-01

    The influence of an electron donating substituent on the photophysical properties of 1-azathioxanthone dyes has been investigated using optical spectroscopy and theoretical models. The motivation behind the study is based on the fact that thioxanthones are efficient triplet sensitizers, and thus promising sensitizers for lanthanide centered emission. By adding an aza group to one of the phenyl ring systems, direct coordination to a lanthanide center becomes possible, which makes azathoixanthones great candidates as antenna chromophores in lanthanide(III) based dyes. Here, three 1-azathioxanthone derivatives have been synthesized targeting efficient triplet formation following absorption in the visible range of the spectrum. This is achieved by adding methoxy groups to the 1-azathioxanthone core. The derivatives were characterized using absorption, emission, and time-gated emission spectroscopy, where fluorescent quantum yields, singlet and triplet excited states lifetimes were determined. The experimentally determined photophysical properties of the three 1-azathioxanthone compounds are contrasted to those of the parent thioxanthone and is rationalized using the Strickler–Berg equation, Hückel MO theory, and Dewar’s rules in combination with computational chemistry. We find that the transition energies follow predictions, but that the overall photophysical properties are determined by the relative energies as well as the nature of the involved states in both the singlet and the triplet excited state manifolds.

  18. Linear analysis of carbon-13 chemical shift differences and its application to the detection and correction of errors in referencing and spin system identifications

    Energy Technology Data Exchange (ETDEWEB)

    Wang Liya; Eghbalnia, Hamid R., E-mail: eghbalni@nmrfam.wisc.edu; Bahrami, Arash; Markley, John L. [Biochemistry Department, National Magnetic Resonance Facility at Madison (United States)

    2005-05-15

    Statistical analysis reveals that the set of differences between the secondary shifts of the {alpha}- and {beta}-carbons for residues i of a protein ({delta}{delta}{sup 13}C{sup {alpha}}{sub i}- {delta}{delta}{sup 13}C{sup {beta}}{sub i}) provides the means to detect and correct referencing errors for {sup 1}H and {sup 13}C nuclei within a given dataset. Linear analysis of chemical shifts (LACS) can be used to detect referencing errors and to recalibrate the {sup 1}H and {sup 13}C chemical shift scales if needed. The analysis requires only that the signals be identified with distinct residue types (intra-residue spin systems). LACS allows errors in calibration to be detected and corrected in advance of sequence-specific assignments and secondary structure determinations. Signals that do not fit the linear model (outliers) deserve scrutiny since they could represent errors in identifying signals with a particular residue, or interesting features such as a cis-peptide bond. LACS provides the basis for the automated detection of such features and for testing reassignment hypotheses. Early detection and correction of errors in referencing and spin system identifications can improve the speed and accuracy of chemical shift assignments and secondary structure determinations. We have used LACS to create a database of offset-corrected chemical shifts corresponding to nearly 1800 BMRB entries: 300 with and 1500 without corresponding three-dimensional (3D) structures. This database can serve as a resource for future analysis of the effects of amino acid sequence and protein secondary and tertiary structure on NMR chemical shifts.

  19. Linear analysis of carbon-13 chemical shift differences and its application to the detection and correction of errors in referencing and spin system identifications.

    Science.gov (United States)

    Wang, Liya; Eghbalnia, Hamid R; Bahrami, Arash; Markley, John L

    2005-05-01

    Statistical analysis reveals that the set of differences between the secondary shifts of the alpha- and beta-carbons for residues i of a protein (Deltadelta13C(alpha)i - Deltadelta13C(beta)i) provides the means to detect and correct referencing errors for 1H and 13C nuclei within a given dataset. In a correctly referenced protein dataset, linear regression plots of Deltadelta13C(alpha)i, Deltadelta13C(beta)i, or Deltadelta1H(alpha)i vs. (Deltadelta13C(alpha)i - Deltadelta13C(beta)i) pass through the origin from two directions, the helix-to-coil and strand-to-coil directions. Thus, linear analysis of chemical shifts (LACS) can be used to detect referencing errors and to recalibrate the 1H and 13C chemical shift scales if needed. The analysis requires only that the signals be identified with distinct residue types (intra-residue spin systems). LACS allows errors in calibration to be detected and corrected in advance of sequence-specific assignments and secondary structure determinations. Signals that do not fit the linear model (outliers) deserve scrutiny since they could represent errors in identifying signals with a particular residue, or interesting features such as a cis-peptide bond. LACS provides the basis for the automated detection of such features and for testing reassignment hypotheses. Early detection and correction of errors in referencing and spin system identifications can improve the speed and accuracy of chemical shift assignments and secondary structure determinations. We have used LACS to create a database of offset-corrected chemical shifts corresponding to nearly 1800 BMRB entries: 300 with and 1500 without corresponding three-dimensional (3D) structures. This database can serve as a resource for future analysis of the effects of amino acid sequence and protein secondary and tertiary structure on NMR chemical shifts.

  20. Mapping phosphorylation rate of fluoro-deoxy-glucose in rat brain by 19F chemical shift imaging

    Science.gov (United States)

    Coman, Daniel; Sanganahalli, Basavaraju G.; Cheng, David; McCarthy, Timothy; Rothman, Douglas L.; Hyder, Fahmeed

    2014-01-01

    19F magnetic resonance spectroscopy (MRS) studies of 2-fluoro-2-deoxy-D-glucose (FDG) and 2-fluoro-2-deoxy-D-glucose-6-phosphate (FDG-6P) can be used for directly assessing total glucose metabolism in vivo. To date, 19F MRS measurements of FDG phosphorylation in the brain have either been achieved ex vivo from extracted tissue or in vivo by unusually long acquisition times. Electrophysiological and functional magnetic resonance imaging (fMRI) measurements indicate that FDG doses up to 500mg/kg can be tolerated with minimal side effects on cerebral physiology and evoked fMRI-BOLD responses to forepaw stimulation. In halothane-anesthetized rats, we report localized in vivo detection and separation of FDG and FDG-6P MRS signals with 19F 2D chemical shift imaging (CSI) at 11.7T. A metabolic model based on reversible transport between plasma and brain tissue, which included a non-saturable plasma to tissue component, was used to calculate spatial distribution of FDG and FDG-6P concentrations in rat brain. In addition, spatial distribution of rate constants and metabolic fluxes of FDG to FDG-6P conversion were estimated. Mapping the rate of FDG to FDG-6P conversion by 19F CSI provides an MR methodology that could impact other in vivo applications such as characterization of tumor pathophysiology. PMID:24581725

  1. A multidimensional approach to the analysis of chemical shift titration experiments in the frame of a multiple reaction scheme.

    Science.gov (United States)

    D'Aléo, Anthony; Dumont, Elise; Maury, Olivier; Giraud, Nicolas

    2013-10-01

    We present a method for fitting curves acquired by chemical shift titration experiments, in the frame of a three-step complexation mechanism. To that end, we have implemented a fitting procedure, based on a nonlinear least squares fitting method, that determines the best fitting curve using a "coarse grid search" approach and provides distributions for the different parameters of the complexation model that are compatible with the experimental precision. The resulting analysis protocol is first described and validated on a theoretical data set. We show its ability to converge to the true parameter values of the simulated reaction scheme and to evaluate complexation constants together with multidimensional uncertainties. Then, we apply this protocol to the study of the supramolecular interactions, in aqueous solution, between a lanthanide complex and three different model molecules, using NMR titration experiments. We show that within the uncertainty that can be evaluated from the parameter distributions generated during our analysis, the affinities between the lanthanide derivative and each model molecule can be discriminated, and we propose values for the corresponding thermodynamic constants. Copyright © 2013 John Wiley & Sons, Ltd.

  2. Centerband-only analysis of rotor-unsynchronized spin echo for measurement of lipid (31) P chemical shift anisotropy.

    Science.gov (United States)

    Umegawa, Yuichi; Yamaguchi, Toshiyuki; Murata, Michio; Matsuoka, Shigeru

    2015-07-01

    Structural diversity and molecular flexibility of phospholipids are essential for biological membranes to play key roles in numerous cellular processes. Uncovering the behavior of individual lipids in membrane dynamics is crucial for understanding the molecular mechanisms underlying biological functions of cell membranes. In this paper, we introduce a simple method to investigate dynamics of lipid molecules in multi-component systems by measuring the (31) P chemical shift anisotropy (CSA) under magic angle spinning (MAS) conditions. For achieving both signal separation and CSA determination, we utilized a centerband-only analysis of rotor-unsynchronized spin echo (COARSE). This analysis is based on the curve fitting of periodic modulation of centerband intensity along the interpulse delay time in rotor-unsynchronized spin-echo experiments. The utility of COARSE was examined by using phospholipid vesicles, a three-component lipid raft model system, and archaeal purple membranes. We found that the apparent advantages of this method are high resolution and high sensitivity given by the moderate MAS speed and the one-dimensional acquisition with short spin-echo delays. COARSE provides an alternative method for CSA measurement that is effective in the investigation of lipid polymorphologies. Copyright © 2015 John Wiley & Sons, Ltd.

  3. T1-corrected fat quantification using chemical shift-based water/fat separation: application to skeletal muscle

    Science.gov (United States)

    Karampinos, Dimitrios C.; Yu, Huzanzhou; Shimakawa, Ann; Link, Thomas M.; Majumdar, Sharmila

    2011-01-01

    Chemical shift based water/fat separation, like iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL), has been proposed for quantifying intermuscular adipose tissue (IMAT). An important confounding factor in IDEAL-based IMAT quantification is the large difference in T1 between muscle and fat, which can cause significant overestimation in the fat fraction. This T1 bias effect is usually reduced by employing small flip angles. T1-correction can be performed by employing at least two different flip angles and fitting for T1 of water and fat. In the present work, a novel approach for the water/fat separation problem in a dual flip angle experiment is introduced and a new approach for the selection of the two flip angles, labeled as the unequal small flip angle approach, is developed, aiming to improve the noise efficiency of the T1-correction step relative to existing approaches. It is shown that the use of flip angles, selected such the muscle water signal is assumed to be T1-independent for the first flip angle and the fat signal is assumed to be T1-independent for the second flip angle, has superior noise performance to the use of equal small flip angles (no T1 estimation required) and the use of large flip angles (T1 estimation required). PMID:21452279

  4. A Fast Variant of 1H Spectroscopic U-FLARE Imaging Using Adjusted Chemical Shift Phase Encoding

    Science.gov (United States)

    Ebel, Andreas; Dreher, Wolfgang; Leibfritz, Dieter

    2000-02-01

    So far, fast spectroscopic imaging (SI) using the U-FLARE sequence has provided metabolic maps indirectly via Fourier transformation (FT) along the chemical shift (CS) dimension and subsequent peak integration. However, a large number of CS encoding steps Nω is needed to cover the spectral bandwidth and to achieve sufficient spectral resolution for peak integration even if the number of resonance lines is small compared to Nω and even if only metabolic images are of interest and not the spectra in each voxel. Other reconstruction algorithms require extensive prior knowledge, starting values, and/or model functions. An adjusted CS phase encoding scheme (APE) can be used to overcome these drawbacks. It incorporates prior knowledge only about the resonance frequencies present in the sample. Thus, Nω can be reduced by a factor of 4 for many 1H in vivo studies while no spectra have to be reconstructed, and no additional user interaction, prior knowledge, starting values, or model function are required. Phantom measurements and in vivo experiments on rat brain have been performed at 4.7 T to test the feasibility of the method for proton SI.

  5. Improvement of water saturation shift referencing by sequence and analysis optimization to enhance chemical exchange saturation transfer imaging.

    Science.gov (United States)

    Müller-Lutz, Anja; Matuschke, Felix; Schleich, Christoph; Wickrath, Frithjof; Boos, Johannes; Schmitt, Benjamin; Wittsack, Hans-Jörg

    2016-07-01

    To optimize B0-field inhomogeneity correction for chemical exchange saturation transfer (CEST) imaging by investigating different water saturation shift referencing (WASSR) Z-spectrum shapes and different frequency correction techniques. WASSR Z-spectra were simulated for different B1-fields and pulse durations (PD). Two parameter settings were used for further simulations and experiments (WASSR1: B1=0.1 μT, PD=50ms; WASSR2: B1=0.3 μT, PD=40ms). Four frequency correction techniques were investigated: 1) MinW: Minimum of the spline-interpolated WASSR-spectrum; 2) MSCF: maximum symmetry center frequency algorithm; 3) PMSCF: further development of MSCF algorithm; 4) BFit: fit with Bloch equations. Performance of frequency correction was assessed with Monte-Carlo simulations and in-vivo MR examinations in the brain and intervertebral disks. Different shapes of WASSR-Z-spectra were obtained by changing B1 and PD including spectra with one (1-Peak) or two (2-Peak) minima. WASSR1 resulted in 1-Peak WASSR-spectrum, whereas WASSR2 resulted in 2-Peak WASSR-spectrum. Both Monte-Carlo simulations and in-vivo MR examinations revealed highest accuracy of field-inhomogeneity correction with WASSR1 combined with PMSCF or BFit. Using a WASSR sequence, which results in a Z-spectrum with a single absorption peak, in combination with advanced postprocessing algorithms enables improved B0-field inhomogeneity correction for CEST imaging. Copyright © 2016 Elsevier Inc. All rights reserved.

  6. Theoretical studies on substituent effects of meta-substituted pyridines

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Gab Yong [Catholic University of Taegu-Hyosung, Kyongsan (Korea, Republic of); Song, Young Dae [Yeungnam Univ., Kyongsan (Korea, Republic of)

    2000-06-01

    ab initio molecular orbital calculation is performed to estimate the substituent effects for meta-substituted pyridines. Electrostatic potentials are obtained from ab initio wavefunctions of the optimized structures for the meta-substituted pyridines. Electrostatic potentials are shown to be minimum at nitrogen atom of pyridines. The potential minima are good correlated with the substituent constants, {sigma}{sub m} and with the {delta}pK{sub a}, respectively. It is found that the electrostatic potential minima can be used as a useful measure of substituent effects.

  7. Fully adiabatic 31P 2D-CSI with reduced chemical shift displacement error at 7 T--GOIA-1D-ISIS/2D-CSI.

    Science.gov (United States)

    Chmelík, M; Kukurová, I Just; Gruber, S; Krššák, M; Valkovič, L; Trattnig, S; Bogner, W

    2013-05-01

    A fully adiabatic phosphorus (31P) two-dimensional (2D) chemical shift spectroscopic imaging sequence with reduced chemical shift displacement error for 7 T, based on 1D-image-selected in vivo spectroscopy, combined with 2D-chemical shift spectroscopic imaging selection, was developed. Slice-selective excitation was achieved by a spatially selective broadband GOIA-W(16,4) inversion pulse with an interleaved subtraction scheme before nonselective adiabatic excitation, and followed by 2D phase encoding. The use of GOIA-W(16,4) pulses (bandwidth 4.3-21.6 kHz for 10-50 mm slices) reduced the chemical shift displacement error in the slice direction ∼1.5-7.7 fold, compared to conventional 2D-chemical shift spectroscopic imaging with Sinc3 selective pulses (2.8 kHz). This reduction was experimentally demonstrated with measurements of an MR spectroscopy localization phantom and with experimental evaluation of pulse profiles. In vivo experiments in clinically acceptable measurement times were demonstrated in the calf muscle (nominal voxel volume, 5.65 ml in 6 min 53 s), brain (10 ml, 6 min 32 s), and liver (8.33 ml, 8 min 14 s) of healthy volunteers at 7 T. High reproducibility was found in the calf muscle at 7 T. In combination with adiabatic excitation, this sequence is insensitive to the B1 inhomogeneities associated with surface coils. This sequence, which is termed GOIA-1D-ISIS/2D-CSI (goISICS), has the potential to be applied in both clinical research and in the clinical routine. Copyright © 2012 Wiley Periodicals, Inc.

  8. Using chemical-shift MR imaging to quantify fatty degeneration within supraspinatus muscle due to supraspinatus tendon injuries

    Energy Technology Data Exchange (ETDEWEB)

    Gokalp, Gokhan; Yildirim, Nalan; Yazici, Zeynep [Uludag University Medical Faculty, Department of Radiology, Gorukle, Bursa (Turkey); Ercan, Ilker [Uludag University Medical Faculty, Department of Biostatistics, Gorukle, Bursa (Turkey)

    2010-12-15

    The objective of this study was to prospectively quantify the fatty degeneration of supraspinatus (SSP) muscle due to SSP tendon injuries by using chemical-shift magnetic resonance imaging (CS-MRI). Forty-one patients with suspected rotator cuff tear or impingement examined with MR arthrography were included in the study. The following images were obtained after injection of diluted gadolinium chelate into glenohumeral joint: fat-saturated T1-weighted spin echo in the coronal, axial, and sagittal-oblique plane; fat-saturated T2-weighted and intermediate-weighted fast spin-echo in the coronal-oblique plane; and T1-weighted spin echo in the sagittal-oblique plane. CS-MRI was performed in the coronal plane using a double-echo fast low-angle shot (FLASH) sequence. SSP tendon changes were classified as normal, tendinosis, and partial and complete tear according to MR arthrography findings. Fatty degeneration was quantified after measurement of signal intensity values within the region of interest (ROI) placed over SSP muscle. Signal intensity (SI) suppression ratio and SI index were calculated with the values obtained. Degrees of fatty degeneration depicted in normal subjects and subjects with rotator cuff injuries were compared. Median (min:max) was used as descriptive values. SI suppression ratio was -3.5% (-15.5:3.03) in normal subjects, whereas it was -13.5% (-28.55:-6.60), -30.7% (-41.5:-20.35), and -43.75% (-62:-24.90) in tendinosis, partial and complete tears, respectively. SI index was 0.75% (-6:11.5) in normal subjects. It was 10% (4.50:27), 26.5% (19.15:35.5), and 41% (23.9:57) in tendinosis, partial and complete tears, respectively. The increase in degree of fatty degeneration parallels the seriousness of tendon pathology. CS-MRI is a useful method for grading fat accumulation within SSP muscle. (orig.)

  9. Brain temperature and pH measured by 1H chemical shift imaging of a thulium agent

    Science.gov (United States)

    Coman, Daniel; Trubel, Hubert K.; Rycyna, Robert E.; Hyder, Fahmeed

    2009-01-01

    Temperature and pH are two of the most important physiological parameters and are believed to be tightly regulated because they are intricately related to energy metabolism in living organisms. Temperature and/or pH data in mammalian brain are scarce, however, mainly due to lack of precise and non-invasive methods. At 11.7T, we demonstrate that a thulium-based macrocyclic complex infused through the blood stream can be used to obtain temperature and pH maps of rat brain in vivo by 1H chemical shift imaging (CSI) of the sensor itself in conjunction with a multi-parametric model that depends on several proton resonances of the sensor. Accuracies of temperature and pH determination with the thulium sensor – which has a predominantly extracellular presence – depend on stable signals during the course of the CSI experiment as well as redundancy for temperature and pH sensitivities contained within the observed signals. The thulium-based method compared well with other methods for temperature (1H magnetic resonance spectroscopy (MRS) of N-acetyl aspartate and water; copper-constantan thermocouple wire) and pH (31P MRS of inorganic phosphate and phosphocreatine) assessment, as established by in vitro and in vivo studies. In vitro studies in phantoms with two compartments of differing pH values observed under different ambient temperature conditions generated precise temperature and pH distribution maps. In vivo studies in α-chloralose anesthetized and renal-ligated rats revealed temperature (33–34 °C) and pH (7.3–7.4) distributions in the cerebral cortex which are in agreement with observations by other methods. These results demonstrate that the thulium sensor can be used to measure temperature and pH distributions in rat brain in vivo simultaneously and accurately with 1H CSI. PMID:19130468

  10. Modern MRI tools for the characterization of acute demyelinating lesions: value of chemical shift and diffusion-weighted imaging

    Energy Technology Data Exchange (ETDEWEB)

    Kueker, W.; Mehnert, F.; Mader, I.; Naegele, T. [Department of Neuroradiology, University of Tuebingen Medical School, Hoppe-Seyler-Str. 3, 72076, Tuebingen (Germany); Ruff, J. [Siemens Medical Solutions, Erlangen (Germany); Gaertner, S. [Department of Neurology, University of Tuebingen Medical School, Tuebingen (Germany)

    2004-06-01

    Acute demyelinating lesions occur in various inflammatory disorders of the CNS. Apart from multiple sclerosis, most cases can be attributed to an overshooting immunological response to infectious agents called acute disseminated encephalomyelitis (ADEM). ADEM, which is mostly characterized by a monophasic course, has a multiphasic variant (MDEM). The early application of corticosteroids has been shown to be beneficial for the outcome; thus, an early diagnosis is highly desirable. Furthermore, the differential diagnosis ruling out neoplastic disorders may be difficult using conventional MRI alone. The potential diagnostic value of advanced MR techniques such as chemical shift imaging (CSI) and diffusion-weighted imaging (DWI) was investigated in a patient with MDEM, who had a new lesion in continuity with the initial disease manifestation. CSI was performed at 1.5 T with a long echo time of 135 ms for the evaluation of N-acetyl-aspartate (NAA) and choline (Cho) and with short TE of 30 ms for macromolecules (mm) and myo-Inositol (mI). DWI was performed using a single-shot isotropic EPI sequence. Whereas acute and chronic areas of demyelination were neither distinguishable on T2- nor on contrast-enhanced T1-weigted images, CSI and DWI revealed different metabolite concentrations and diffusion characteristics within the composite lesion, clearly separating acute from chronic areas of demyelination. In conclusion, the addition of CSI and DWI may add to the diagnostic power of MRI in the setting of demyelinating disorders by identifying areas of acute and chronic demyelination, even in the absence of contrast enhancement. (orig.)

  11. Combining ambiguous chemical shift mapping with structure-based backbone and NOE assignment from 15N-NOESY

    KAUST Repository

    Jang, Richard

    2011-01-01

    Chemical shift mapping is an important technique in NMRbased drug screening for identifying the atoms of a target protein that potentially bind to a drug molecule upon the molecule\\'s introduction in increasing concentrations. The goal is to obtain a mapping of peaks with known residue assignment from the reference spectrum of the unbound protein to peaks with unknown assignment in the target spectrum of the bound protein. Although a series of perturbed spectra help to trace a path from reference peaks to target peaks, a one-to-one mapping generally is not possible, especially for large proteins, due to errors, such as noise peaks, missing peaks, missing but then reappearing, overlapped, and new peaks not associated with any peaks in the reference. Due to these difficulties, the mapping is typically done manually or semi-automatically. However, automated methods are necessary for high-throughput drug screening. We present PeakWalker, a novel peak walking algorithm for fast-exchange systems that models the errors explicitly and performs many-to-one mapping. On the proteins: hBclXL, UbcH5B, and histone H1, it achieves an average accuracy of over 95% with less than 1.5 residues predicted per target peak. Given these mappings as input, we present PeakAssigner, a novel combined structure-based backbone resonance and NOE assignment algorithm that uses just 15N-NOESY, while avoiding TOCSY experiments and 13C- labeling, to resolve the ambiguities for a one-toone mapping. On the three proteins, it achieves an average accuracy of 94% or better. Copyright © 2011 ACM.

  12. Using chemical-shift MR imaging to quantify fatty degeneration within supraspinatus muscle due to supraspinatus tendon injuries.

    Science.gov (United States)

    Gokalp, Gokhan; Yildirim, Nalan; Yazici, Zeynep; Ercan, Ilker

    2010-12-01

    The objective of this study was to prospectively quantify the fatty degeneration of supraspinatus (SSP) muscle due to SSP tendon injuries by using chemical-shift magnetic resonance imaging (CS-MRI). Forty-one patients with suspected rotator cuff tear or impingement examined with MR arthrography were included in the study. The following images were obtained after injection of diluted gadolinium chelate into glenohumeral joint: fat-saturated T1-weighted spin echo in the coronal, axial, and sagittal-oblique plane; fat-saturated T2-weighted and intermediate-weighted fast spin-echo in the coronal-oblique plane; and T1-weighted spin echo in the sagittal-oblique plane. CS-MRI was performed in the coronal plane using a double-echo fast low-angle shot (FLASH) sequence. SSP tendon changes were classified as normal, tendinosis, and partial and complete tear according to MR arthrography findings. Fatty degeneration was quantified after measurement of signal intensity values within the region of interest (ROI) placed over SSP muscle. Signal intensity (SI) suppression ratio and SI index were calculated with the values obtained. Degrees of fatty degeneration depicted in normal subjects and subjects with rotator cuff injuries were compared. Median (min:max) was used as descriptive values. SI suppression ratio was -3.5% (-15.5:3.03) in normal subjects, whereas it was -13.5% (-28.55:-6.60), -30.7% (-41.5:-20.35), and -43.75% (-62:-24.90) in tendinosis, partial and complete tears, respectively. SI index was 0.75% (-6:11.5) in normal subjects. It was 10% (4.50:27), 26.5% (19.15:35.5), and 41% (23.9:57) in tendinosis, partial and complete tears, respectively. The increase in degree of fatty degeneration parallels the seriousness of tendon pathology. CS-MRI is a useful method for grading fat accumulation within SSP muscle.

  13. Effect of bulky substituents on thiopyrylium polymethine aggregation in the solid state: A theoretical evaluation of the implications for all-optical switching applications

    KAUST Repository

    Gieseking, Rebecca L.

    2014-11-25

    Polymethine dyes in dilute solutions display many of the optical properties required for all-optical switching applications. However, in thin films, aggregation and polymethine-counterion interactions can substantially modify their properties and limit their utility. Here, we examine the impact of a series of bulky substituents on the solid-state molecular packing of thiopyrylium polymethines by using a theoretical approach combining molecular-dynamics simulations and quantum-chemical calculations. Importantly, it is found that the positions of the substituents near the center and/or ends of the dye determine the extent to which aggregation is reduced; in particular, substituents near the polymethine center primarily modify the type of aggregation that is observed, while substituents near the polymethine ends reduce aggregation and aid in maintaining solution-like properties in the solid state. Our theoretical study elucidates relationships between molecular structure and bulk optical properties and provides design guidelines for all-optical switching materials.

  14. Proton-detected 3D (15)N/(1)H/(1)H isotropic/anisotropic/isotropic chemical shift correlation solid-state NMR at 70kHz MAS.

    Science.gov (United States)

    Pandey, Manoj Kumar; Yarava, Jayasubba Reddy; Zhang, Rongchun; Ramamoorthy, Ayyalusamy; Nishiyama, Yusuke

    2016-01-01

    Chemical shift anisotropy (CSA) tensors offer a wealth of information for structural and dynamics studies of a variety of chemical and biological systems. In particular, CSA of amide protons can provide piercing insights into hydrogen-bonding interactions that vary with the backbone conformation of a protein and dynamics. However, the narrow span of amide proton resonances makes it very difficult to measure (1)H CSAs of proteins even by using the recently proposed 2D (1)H/(1)H anisotropic/isotropic chemical shift (CSA/CS) correlation technique. Such difficulties due to overlapping proton resonances can in general be overcome by utilizing the broad span of isotropic chemical shifts of low-gamma nuclei like (15)N. In this context, we demonstrate a proton-detected 3D (15)N/(1)H/(1)H CS/CSA/CS correlation experiment at fast MAS frequency (70kHz) to measure (1)H CSA values of unresolved amide protons of N-acetyl-(15)N-l-valyl-(15)N-l-leucine (NAVL). Copyright © 2016 Elsevier Inc. All rights reserved.

  15. Measurement of SDS Micelle-Peptide Association Using (1)H NMR Chemical Shift Analysis and Pulsed-Field Gradient NMR Spectroscopy.

    Science.gov (United States)

    Orfi, L; Lin, M; Larive, C K

    1998-04-01

    The binding of two simple tripeptides, glycyl-histidyl-glycine (GHG) and phenylalanyl-histidyl-phenylalanine (FHF) with SDS micelles was examined using (1)H NMR chemical shift analysis and self-diffusion coefficients measured with pulsed-field gradient NMR spectroscopy. The presence of GHG or FHF did not appear to significantly affect the critical micelle concentration (cmc) or the average size of the SDS micelles formed. The chemical shifts of several of the GHG resonances change as a function of SDS concentration, indicating an interaction between the peptide and the micelles. In addition, the concentration-dependent decrease observed for the GHG diffusion coefficients suggests association of the peptide with SDS micelles. The free and micelle-associated GHG are in fast exchange on both the (1)H chemical shift and diffusion time scales. The equilibrium constant for the binding of GHG to SDS micelles was determined from the analysis of the concentration dependence of the histidine C2 and C4 resonances to be 17 ± 5 and 24 ± 6 M(-)(1), respectively. The precision of the equilibrium constants obtained by analysis of the chemical shift data is limited by the small chemical shift changes observed. Analysis of the concentration dependence of the diffusion coefficients produced an equilibrium constant of 17 ± 1 M(-)(1). The more hydrophobic peptide, FHF is strongly associated with the SDS micelles. Because the fraction of free FHF is small in these solutions, it was not possible to determine a formation constant for the interaction of FHF with the SDS micelles by analysis of either the (1)H chemical shift or diffusion coefficient data. The cmc of SDS in 0.10 M Na(2)C(2)O(4) buffer was determined to be 5.4 ± 0.1 mM by analysis of the SDS diffusion coefficients in the absence of the peptides. The SDS cmc could also be extracted from the GHG and FHF diffusion coefficients measured as a function of the SDS concentration. The cmc determined from the GHG diffusion data, 5

  16. Substituent effects on the optical properties of naphthalenediimides: A frontier orbital analysis across the periodic table.

    Science.gov (United States)

    Mulder, Joshua R; Guerra, Célia Fonseca; Slootweg, J Chris; Lammertsma, Koop; Bickelhaupt, F Matthias

    2016-01-15

    A comprehensive theoretical treatment is presented for the electronic excitation spectra of ca. 50 different mono-, di-, and tetrasubstituted naphthalenediimides (NDI) using time-dependent density functional theory (TDDFT) at ZORA-CAM-B3LYP/TZ2P//ZORA-BP86/TZ2P with COSMO for simulating the effect of dichloromethane (DCM) solution. The substituents -XHn are from groups 14-17 and rows 2-5 of the periodic table. The lowest dipole-allowed singlet excitation (S0 -S1 ) of the monosubstituted NDIs can be tuned from 3.39 eV for -F to 2.42 eV for -TeH, while the S0 -S2 transition is less sensitive to substitution with energies ranging between 3.67 eV for -CH3 and 3.44 eV for -SbH2 . In the case of NDIs with group-15 and -16 substituents, the optical transitions strongly depend on the extent to which -XHn is planar or pyramidal as well as on the possible formation of intramolecular hydrogen bonds. The accumulative effect of double and quadruple substitution leads in general to increasing bathochromic shifts, but the increased steric hindrance in tetrasubstituted NDIs can lead to deformations that diminish the effectiveness of the substituents. Detailed analyses of the Kohn-Sham orbital electronic structure in monosubstituted NDIs reveal the mesomeric destabilization of the HOMO as the primary cause of the bathochromic shift of the S0-S1 transition. © 2015 Wiley Periodicals, Inc.

  17. Structure elucidation of the designer drug N-(1-amino-3,3-dimethyl-1-oxobutan-2-yl)-1-(5-fluoropentyl)-3-(4-fluorophenyl)-pyrazole-5-carboxamide and the relevance of predicted (13) C NMR shifts - a case study.

    Science.gov (United States)

    Girreser, Ulrich; Rösner, Peter; Vasilev, Andrej

    2016-07-01

    The detailed structure elucidation process of the new cannabimimetic designer drug, N-(1-amino-3,3-dimethyl-1-oxobutan-2-yl)-1-(5-fluoropentyl)-3-(4-fluorophenyl)-pyrazole-5-carboxamide, with a highly substituted pyrazole skeleton, using nuclear magnetic resonance (NMR) spectroscopic and mass spectrometric (MS) techniques is described. After a first analysis of the NMR spectra and comparison with 48 possible pyrazole and imidazole structures, a subset of six positional isomeric pyrazoles and six imidazoles remained conceivable. Four substituents of the heterocyclic skeleton were identified: a proton bound to a pyrazole ring carbon atom; a 5-fluoropentyl group; a 4-fluorophenyl substituent; and a carbamoyl group, which is N-substituted with a methyl residue carrying a tert.-butyl and a carbamoyl substituent. The 5-fluoropentyl residue is situated at the nitrogen ring atom. Additional NMR experiments like the (1) H,(13) C HMBC were performed, but due to the small number of signals based on long-range couplings, the comparison of predicted and observed (13) C chemical shifts became necessary. The open access Internet shift prediction programs NMRDB, NMRSHIFTDB2, and CSEARCH were employed for the prediction of (13) C shift values which allowed an efficient and unambiguous structure determination. For the identified N-(1-amino-3,3-dimethyl-1-oxobutan-2-yl)-1-(5-fluoropentyl)-3-(4-fluorophenyl)-pyrazole-5-carboxamide, the best agreement between predicted (13) C shifts and the observed chemical shifts and long-range couplings for the pyrazole ring carbon atoms, with a standard error of about 2 ppm, was found with each of the predictions. For the comparison of measured and predicted chemical shifts model compounds with simple substituents proved helpful. The identified compound is a homologue of AZ-037 which is offered by Internet suppliers. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

  18. Durable nitrate-selective chemically modified field effect transistors based on new polysiloxane membranes

    NARCIS (Netherlands)

    Antonisse, M.M.G.; Lugtenberg, R.J.W.; Egberink, Richard J.M.; Engbersen, Johannes F.J.; Reinhoudt, David

    1996-01-01

    Polysiloxane copolymers with different amounts and types of substituents have been synthesized and characterized. Polar substituents determine the polarity and methacrylate groups allow cross-linking and covalent binding of electroactive species. These chemically well-defined homogeneous polymers

  19. Solvent-induced chemical shifts of methoxyl nuclear resonance signals in chalcones by benzene and trifluoroacetic acid

    Science.gov (United States)

    Khurana, Shashi K.; Krishnamoorthy, V.; Parmar, Virinder S.

    The 1H NMR spectra of eight different methoxylated chalcones have separately been recorded, (1) in deuterated chloroform; (2) in a mixture (1:1) of deuterated chloroform and benzene; and (3) in a mixture of deuterated chloroform, benzene and trifluoroacetic acid (2:2:1) and the benzene induced and TFA induced shift values have been assigned to different methoxyl groups. These shift values can serve as a guide in determining the structures of natural or new chalcones. The steric, electronic and conformational factors are discussed to explain the shift values.

  20. The protein amide ¹H(N) chemical shift temperature coefficient reflects thermal expansion of the N-H···O=C hydrogen bond.

    Science.gov (United States)

    Hong, Jingbo; Jing, Qingqing; Yao, Lishan

    2013-01-01

    The protein amide (1)H(N) chemical shift temperature coefficient can be determined with high accuracy by recording spectra at different temperatures, but the physical mechanism responsible for this temperature dependence is not well understood. In this work, we find that this coefficient strongly correlates with the temperature coefficient of the through-hydrogen-bond coupling, (3h)J(NC'), based on NMR measurements of protein GB3. Parallel tempering molecular dynamics simulation suggests that the hydrogen bond distance variation at different temperatures/replicas is largely responsible for the (1)H(N) chemical shift temperature dependence, from which an empirical equation is proposed to predict the hydrogen bond thermal expansion coefficient, revealing responses of individual hydrogen bonds to temperature changes. Different expansion patterns have been observed for various networks formed by β strands.

  1. pH Dependent Spin State Population and 19F NMR Chemical Shift via Remote Ligand Protonation in an Iron(II) Complex (Postprint)

    Science.gov (United States)

    2017-12-11

    rare, and compounds that exhibit such behavior are unsuitable for most biological sensing applications due to pKa values far from biological pH12 or...advantages over the more commonly employed 1H MRS, most notably the absence of endogenous fluorine in living systems.14 Furthermore, the chemical...Indeed, diamagnetic 19F MRS pH probes with pKa values near 7 have been developed for in vivo applications , where a variation in 19F chemical shift of

  2. Design of a hyperpolarized (15)N NMR probe that induces a large chemical-shift change upon binding of calcium ions.

    Science.gov (United States)

    Hata, Ryunosuke; Nonaka, Hiroshi; Takakusagi, Yoichi; Ichikawa, Kazuhiro; Sando, Shinsuke

    2015-08-07

    Ca(2+) is a fundamental metal ion for physiological functioning. Therefore, molecular probes for Ca(2+) analysis are required. Recently, a hyperpolarized NMR probe has emerged as a promising tool. Here, we report a new design of a hyperpolarized NMR probe for Ca(2+), which showed a large chemical shift change upon binding to Ca(2+) and was applied for Ca(2+) sensing in a hyperpolarized state.

  3. Spin-orbit ZORA and four-component Dirac-Coulomb estimation of relativistic corrections to isotropic nuclear shieldings and chemical shifts of noble gas dimers

    DEFF Research Database (Denmark)

    Jankowska, Marzena; Kupka, Teobald; Stobiński, Leszek

    2016-01-01

    Hartree-Fock and density functional theory with the hybrid B3LYP and general gradient KT2 exchange-correlation functionals were used for non-relativistic and relativistic nuclear magnetic shielding calculations of helium, neon, argon, krypton and xenon dimers and free atoms. Relativistic correcti......Hartree-Fock and density functional theory with the hybrid B3LYP and general gradient KT2 exchange-correlation functionals were used for non-relativistic and relativistic nuclear magnetic shielding calculations of helium, neon, argon, krypton and xenon dimers and free atoms. Relativistic...... shieldings and chemical shifts are combined with non-relativistic CCSD(T) calculations using the very large polarization-consistent basis sets aug-pcSseg-4 for He, Ne and Ar, aug-pcSseg-3 for Kr and the AQZP basis set for Xe. For the dimers also zero-point vibrational corrections obtained at the CCSD......(T) level with the same basis sets were added. Best estimates of the dimer chemical shifts are generated from these nuclear magnetic shieldings and the relative importance of electron correlation, zero-point vibrational and relativistic corrections for the shieldings and chemical shifts is analyzed....

  4. NMR and computational studies of the configurational properties of spirodioxyselenuranes. Are dynamic exchange processes or temperature-dependent chemical shifts involved?

    Science.gov (United States)

    Press, David J; McNeil, Nicole M R; Rauk, Arvi; Back, Thomas G

    2012-10-19

    Spirodioxyselenurane 4a and several substituted analogs revealed unexpected (1)H NMR behavior. The diastereotopic methylene hydrogens of 4a appeared as an AB quartet at low temperature that coalesced to a singlet upon warming to 267 K, suggesting a dynamic exchange process with a relatively low activation energy. However, DFT computational investigations indicated high activation energies for exchange via inversion through the selenium center and for various pseudorotation processes. Moreover, the NMR behavior was unaffected by the presence of water or acid catalysts, thereby ruling out reversible Se-O or benzylic C-O cleavage as possible stereomutation pathways. Remarkably, when 4a was heated beyond 342 K, the singlet was transformed into a new AB quartet. Further computations indicated that a temperature dependence of the chemical shifts of the diastereotopic protons results in convergence upon heating, followed by crossover and divergence at still higher temperatures. The NMR behavior is therefore not due to dynamic exchange processes, but rather to temperature dependence of the chemical shifts of the diastereotopic hydrogens, which are coincidentally equivalent at intermediate temperatures. These results suggest the general need for caution in ascribing the coalescence of variable-temperature NMR signals of diastereotopic protons to dynamic exchange processes that could instead be due to temperature-dependent chemical shifts and highlight the importance of corroborating postulated exchange processes through additional computations or experiments wherever possible.

  5. Experimental measurement and theory of substituent effects in π-hydrogen bonding: complexes of substituted phenols with benzene.

    Science.gov (United States)

    Nikolova, Valia; Ilieva, Sonia; Galabov, Boris; Schaefer, Henry F

    2014-08-01

    IR spectroscopic experiments and theoretical DFT computations reveal the effects of aromatic substituents on π-hydrogen bonding between monosubstituted phenol derivatives and benzene. Simultaneous formation of two π-hydrogen bonds (red-shifting O-H···π and blue-shifting ortho-C-H···π) contribute to the stability of these complexes. The interaction of the acidic phenol O-H proton-donating group with the benzene π-system dominates the complex formation. The experimental shifts of O-H stretching frequencies for the different phenol complexes vary in the range 45-74 cm(-1). Strong effects on hydrogen-bonding energies and frequency shifts of electron-withdrawing aromatic substituents and very weak influence of electron-donating groups have been established. Experimental quantities and theoretical parameters are employed in rationalizing the properties of these complexes. The acidities of the proton-donating phenols describe quantitatively the hydrogen-bonding process. The results obtained provide clear evidence that, when the structural variations are in the proton-donating species, the substituent effects on π-hydrogen bonding follow classic mechanisms, comprising both resonance and direct through-space influences. The performance of three alternative DFT functionals (B3LYP, B97-D, and PBE0 combined with the 6-311++G(2df,2p) basis set) in predicting the O-H frequency shifts upon complexation is examined. For comparison, O-H frequency shifts for several complexes were also determined at MP2/6-31++G(d,p).

  6. Structural Diversity and Function of Xyloglucan Sidechain Substituents

    Directory of Open Access Journals (Sweden)

    Alex Schultink

    2014-11-01

    Full Text Available Xyloglucan (XyG is a hemicellulose found in the cell walls of all land plants including early-divergent groups such as liverworts, hornworts and mosses. The basic structure of XyG, a xylosylated glucan, is similar in all of these plants but additional substituents can vary depending on plant family, tissue, and developmental stage. A comprehensive list of known XyG sidechain substituents is assembled including their occurrence within plant families, thereby providing insight into the evolutionary origin of the various sidechains. Recent advances in DNA sequencing have enabled comparative genomics approaches for the identification of XyG biosynthetic enzymes in Arabidopsis thaliana as well as in non-model plant species. Characterization of these biosynthetic genes not only allows the determination of their substrate specificity but also provides insights into the function of the various substituents in plant growth and development.

  7. Antibacterial Activity of New Dibenzoxepinone Oximes with Fluorine and Trifluoromethyl Group Substituents

    Directory of Open Access Journals (Sweden)

    Mariana Carmen Chifiriuc

    2011-09-01

    Full Text Available In this paper we present the antimicrobial activity of some newly synthesized dibenz[b,e]oxepin derivatives bearing the oximino moiety, and fluorine (F and trifluoromethyl (CF3 group substituents. The chemical structure and purity of the new compounds were assessed by using elemental analysis, NMR and FTIR spectroscopy. The new compounds were screened for their antibacterial activity towards Gram-positive and Gram-negative strains, by qualitative and quantitative assays. Our results demonstrated that the CF3 and F disubstituted compounds could be considered for the further development of novel antimicrobial drugs.

  8. Uncovering symmetry-breaking vector and reliability order for assigning secondary structures of proteins from atomic NMR chemical shifts in amino acids.

    Science.gov (United States)

    Yu, Wookyung; Lee, Woonghee; Lee, Weontae; Kim, Suhkmann; Chang, Iksoo

    2011-12-01

    Unravelling the complex correlation between chemical shifts of (13) C (α), (13) C (β), (13) C', (1) H (α), (15) N, (1) H ( N ) atoms in amino acids of proteins from NMR experiment and local structural environments of amino acids facilitates the assignment of secondary structures of proteins. This is an important impetus for both determining the three-dimensional structure and understanding the biological function of proteins. The previous empirical correlation scores which relate chemical shifts of (13) C (α), (13) C (β), (13) C', (1) H (α), (15) N, (1) H ( N ) atoms to secondary structures resulted in progresses toward assigning secondary structures of proteins. However, the physical-mathematical framework for these was elusive partly due to both the limited and orthogonal exploration of higher-dimensional chemical shifts of hetero-nucleus and the lack of physical-mathematical understanding underlying those correlation scores. Here we present a simple multi-dimensional hetero-nuclear chemical shift score function (MDHN-CSSF) which captures systematically the salient feature of such complex correlations without any references to a random coil state of proteins. We uncover the symmetry-breaking vector and its reliability order not only for distinguishing different secondary structures of proteins but also for capturing the delicate sensitivity interplayed among chemical shifts of (13) C (α), (13) C (β), (13) C', (1) H (α), (15) N, (1) H ( N ) atoms simultaneously, which then provides a straightforward framework toward assigning secondary structures of proteins. MDHN-CSSF could correctly assign secondary structures of training (validating) proteins with the favourable (comparable) Q3 scores in comparison with those from the previous correlation scores. MDHN-CSSF provides a simple and robust strategy for the systematic assignment of secondary structures of proteins and would facilitate the de novo determination of three-dimensional structures

  9. [3,3]-Sigmatropic shifts of N-allylhydrazones: quantum chemical comparison of concerted and radical cation pathways.

    Science.gov (United States)

    Siebert, Matthew R; Tantillo, Dean J

    2008-08-07

    N-Allylhydrazones are reported to undergo an elaborate [3,3]-sigmatropic shift/N2 extrusion sequence. Both concerted and radical cation pathways for the [3,3]-sigmatropic shift of several N-allylhydrazones were investigated using B3LYP/6-31+G(d,p) calculations. It was discovered that, assuming facile formation of the N-allylhydrazone radical cation, the rearrangement takes place through a series of low barrier steps energetically preferred to the concerted alternative available to neutral N-allylhydrazones. Subsequent N2 extrusions forming corresponding homoallyl radicals were found to be extremely facile.

  10. Effect of Methyl, Hydroxyl, and Chloro Substituents in Position 3 of 3',4',7-Trihydroxyflavylium: Stability, Kinetics, and Thermodynamics.

    Science.gov (United States)

    Alejo-Armijo, Alfonso; Salido, Sofía; Altarejos, Joaquín; Parola, A Jorge; Gago, Sandra; Basílio, Nuno; Cabrita, Luis; Pina, Fernando

    2016-08-22

    The effect of methyl, hydroxyl, and chloride substituents in position 3 of the 3',4',7-trihydroxyflavylium core structure was studied. The stability, relative energy of each of chemical species (thermodynamics), and their rates of interconversion (kinetics) are very dependent on these substituents. By comparing the mole fraction distribution at equilibrium of the three multistate systems with the parent 3',4',7-trihydroxyflavylium, introduction of a methyl substituent in position 3 increases the mole fraction of hemiketal at the expense of the trans-chalcone and increases the hydration rate very significantly; a hydroxyl substituent in position 3 gives rise to a degradation process, as observed in anthocyanidins. In the case of 3-chloro-3',4',7-trihydroxyflavylium, a dramatic increase of the flavylium cation acidity was observed and a photochromic system can be operated upon irradiation of the respective trans-chalcone in 1 m HCl. According to the photochromic response of 3,3',4',7-tetrahydroxyflavylium and 3',4',7-trihydroxyflavylium, some requirements for a good photochromic performance are discussed. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. The solvent and substituent effects on bond dissociation energies of ...

    Indian Academy of Sciences (India)

    Administrator

    method are the closest to the computed values in acetontrile and the average solvent effect is 0⋅78 kcal/ mol. Subsequently, the substituent ... tion enthalpies and thermochemical properties. (enthalpies of formation, for instance). ..... Program in Science and Technology of Henan Pro- vince (No. 102300410114), Henan ...

  12. Effect of substituent structure on pyrimidine electrophilic substitution

    CSIR Research Space (South Africa)

    Van der Westhuyzen, CW

    2007-01-01

    Full Text Available In an investigation into the electrophilic nitrosation reactions of a series of 4,6-disubstituted pyrimidine derivatives, a subtle interplay between the electronic nature of the C-4 and C-6 substituents and reactivity was found where these were...

  13. Effects of Irritant Chemicals on Aedes aegypti Resting Behavior: Is There a Simple Shift to Untreated “Safe Sites”?

    Science.gov (United States)

    Manda, Hortance; Arce, Luana M.; Foggie, Tarra; Shah, Pankhil; Grieco, John P.; Achee, Nicole L.

    2011-01-01

    Background Previous studies have identified the behavioral responses of Aedes aegypti to irritant and repellent chemicals that can be exploited to reduce man-vector contact. Maximum efficacy of interventions based on irritant chemical actions will, however, require full knowledge of variables that influence vector resting behavior and how untreated “safe sites” contribute to overall impact. Methods Using a laboratory box assay, resting patterns of two population strains of female Ae. aegypti (THAI and PERU) were evaluated against two material types (cotton and polyester) at various dark:light surface area coverage (SAC) ratio and contrast configuration (horizontal and vertical) under chemical-free and treated conditions. Chemicals evaluated were alphacypermethrin and DDT at varying concentrations. Results Under chemical-free conditions, dark material had significantly higher resting counts compared to light material at all SAC, and significantly increased when material was in horizontal configuration. Cotton elicited stronger response than polyester. Within the treatment assays, significantly higher resting counts were observed on chemical-treated dark material compared to untreated light fabric. However, compared to matched controls, significantly less resting observations were made on chemical-treated dark material overall. Most importantly, resting observations on untreated light material (or “safe sites”) in the treatment assay did not significantly increase for many of the tests, even at 25% SAC. Knockdown rates were ≤5% for all assays. Significantly more observations of flying mosquitoes were made in test assays under chemical-treatment conditions as compared to controls. Conclusions/Significance When preferred Ae. aegypti resting sites are treated with chemicals, even at reduced treatment coverage area, mosquitoes do not simply move to safe sites (untreated areas) following contact with the treated material. Instead, they become agitated, using

  14. Effects of irritant chemicals on Aedes aegypti resting behavior: is there a simple shift to untreated "safe sites"?

    Science.gov (United States)

    Manda, Hortance; Arce, Luana M; Foggie, Tarra; Shah, Pankhil; Grieco, John P; Achee, Nicole L

    2011-07-01

    Previous studies have identified the behavioral responses of Aedes aegypti to irritant and repellent chemicals that can be exploited to reduce man-vector contact. Maximum efficacy of interventions based on irritant chemical actions will, however, require full knowledge of variables that influence vector resting behavior and how untreated "safe sites" contribute to overall impact. Using a laboratory box assay, resting patterns of two population strains of female Ae. aegypti (THAI and PERU) were evaluated against two material types (cotton and polyester) at various dark:light surface area coverage (SAC) ratio and contrast configuration (horizontal and vertical) under chemical-free and treated conditions. Chemicals evaluated were alphacypermethrin and DDT at varying concentrations. Under chemical-free conditions, dark material had significantly higher resting counts compared to light material at all SAC, and significantly increased when material was in horizontal configuration. Cotton elicited stronger response than polyester. Within the treatment assays, significantly higher resting counts were observed on chemical-treated dark material compared to untreated light fabric. However, compared to matched controls, significantly less resting observations were made on chemical-treated dark material overall. Most importantly, resting observations on untreated light material (or "safe sites") in the treatment assay did not significantly increase for many of the tests, even at 25% SAC. Knockdown rates were ≤5% for all assays. Significantly more observations of flying mosquitoes were made in test assays under chemical-treatment conditions as compared to controls. When preferred Ae. aegypti resting sites are treated with chemicals, even at reduced treatment coverage area, mosquitoes do not simply move to safe sites (untreated areas) following contact with the treated material. Instead, they become agitated, using increased flight as a proxy indicator. It is this contact

  15. Effects of irritant chemicals on Aedes aegypti resting behavior: is there a simple shift to untreated "safe sites"?

    Directory of Open Access Journals (Sweden)

    Hortance Manda

    2011-07-01

    Full Text Available BACKGROUND: Previous studies have identified the behavioral responses of Aedes aegypti to irritant and repellent chemicals that can be exploited to reduce man-vector contact. Maximum efficacy of interventions based on irritant chemical actions will, however, require full knowledge of variables that influence vector resting behavior and how untreated "safe sites" contribute to overall impact. METHODS: Using a laboratory box assay, resting patterns of two population strains of female Ae. aegypti (THAI and PERU were evaluated against two material types (cotton and polyester at various dark:light surface area coverage (SAC ratio and contrast configuration (horizontal and vertical under chemical-free and treated conditions. Chemicals evaluated were alphacypermethrin and DDT at varying concentrations. RESULTS: Under chemical-free conditions, dark material had significantly higher resting counts compared to light material at all SAC, and significantly increased when material was in horizontal configuration. Cotton elicited stronger response than polyester. Within the treatment assays, significantly higher resting counts were observed on chemical-treated dark material compared to untreated light fabric. However, compared to matched controls, significantly less resting observations were made on chemical-treated dark material overall. Most importantly, resting observations on untreated light material (or "safe sites" in the treatment assay did not significantly increase for many of the tests, even at 25% SAC. Knockdown rates were ≤5% for all assays. Significantly more observations of flying mosquitoes were made in test assays under chemical-treatment conditions as compared to controls. CONCLUSIONS/SIGNIFICANCE: When preferred Ae. aegypti resting sites are treated with chemicals, even at reduced treatment coverage area, mosquitoes do not simply move to safe sites (untreated areas following contact with the treated material. Instead, they become agitated

  16. Hydrogen Atomic Positions of O-H···O Hydrogen Bonds in Solution and in the Solid State: The Synergy of Quantum Chemical Calculations with ¹H-NMR Chemical Shifts and X-ray Diffraction Methods.

    Science.gov (United States)

    Siskos, Michael G; Choudhary, M Iqbal; Gerothanassis, Ioannis P

    2017-03-07

    The exact knowledge of hydrogen atomic positions of O-H···O hydrogen bonds in solution and in the solid state has been a major challenge in structural and physical organic chemistry. The objective of this review article is to summarize recent developments in the refinement of labile hydrogen positions with the use of: (i) density functional theory (DFT) calculations after a structure has been determined by X-ray from single crystals or from powders; (ii) ¹H-NMR chemical shifts as constraints in DFT calculations, and (iii) use of root-mean-square deviation between experimentally determined and DFT calculated ¹H-NMR chemical shifts considering the great sensitivity of ¹H-NMR shielding to hydrogen bonding properties.

  17. Hydrogen Atomic Positions of O–H···O Hydrogen Bonds in Solution and in the Solid State: The Synergy of Quantum Chemical Calculations with 1H-NMR Chemical Shifts and X-ray Diffraction Methods

    Directory of Open Access Journals (Sweden)

    Michael G. Siskos

    2017-03-01

    Full Text Available The exact knowledge of hydrogen atomic positions of O–H···O hydrogen bonds in solution and in the solid state has been a major challenge in structural and physical organic chemistry. The objective of this review article is to summarize recent developments in the refinement of labile hydrogen positions with the use of: (i density functional theory (DFT calculations after a structure has been determined by X-ray from single crystals or from powders; (ii 1H-NMR chemical shifts as constraints in DFT calculations, and (iii use of root-mean-square deviation between experimentally determined and DFT calculated 1H-NMR chemical shifts considering the great sensitivity of 1H-NMR shielding to hydrogen bonding properties.

  18. Strain energies of cubane derivatives with different substituent groups

    Energy Technology Data Exchange (ETDEWEB)

    Fan Xiaowei [Department of Chemistry, Nanjing University of Science and Technology, Nanjing 210094 (China); Ju Xuehai [Department of Chemistry, Nanjing University of Science and Technology, Nanjing 210094 (China)], E-mail: xhju@mail.njust.edu.cn; Xia Qiying [Department of Chemistry, Nanjing University of Science and Technology, Nanjing 210094 (China); Department of Chemistry, Linyi Teachers University, Linyi 276005 (China); Xiao Heming [Department of Chemistry, Nanjing University of Science and Technology, Nanjing 210094 (China)

    2008-02-28

    Homodesmotic reaction and isodesmotic reaction were designed for the computation of strain energies (SE) for a series of cubane derivatives. Total energies of the optimized geometric structures at the DFT-B3LYP/6-31G* level were used to derive the SE. The SE value of cubane is 169.13 kcal/mol for homodesmotic reaction, which is in good agreement with the experimental value. The variation of SE with respect to the number of substituents is similar for the homodesmotic reaction and isodesmotic reaction. The SE values of polynitrocubane and polydifluoroaminocubane increase slightly as up to four substituent groups being added to the cage skeleton. On contrary, the SE dramatically increases when the number of substituent groups m increases from 5 up to 8. For polynitratocubane, the SE decreases slightly at the beginning then increases as the number of group increases. For polyazidocubane, there are very small group effects on the SE. Among four types of substituent groups, the nitro group has greatest effect on the strain energy of caged cubane skeleton. The calculated SE value of octanitrocubane is 257.20 kcal/mol, while that of octaazidocubane is 166.48 kcal/mol via isodesmotic reaction. The azido group releases the strain energy of cubane skeleton when the number of azido groups is less than 7. The interactions among the substituted groups deviated from group additivity. The substituted groups withdraw electrons from the cubane, reducing the repulsion between C-C bonds and resulting the release the strain of the skeleton for isomers with fewer substituents. Group repulsions increase sharply with more and more nitro, nitrato and difluoroamino groups being attached to cubane, resulting large strains of the skeleton. The average negative charges of the substituted groups influence the strain energy of cubane derivatives.

  19. Theoretical study on conformation dynamics of three-station molecular shuttle in different environments and its influence on NMR chemical shifts and binding interactions.

    Science.gov (United States)

    Liu, Pingying; Li, Wei; Liu, Li; Wang, Leyong; Ma, Jing

    2014-10-02

    Microscopic information on conformational flexibility and macrocycle-thread binding interactions is helpful in rational design of novel multistation molecular shuttles with interesting topology and functions. Molecular dynamics (MD) was applied to simulate conformational changes of thread and macrocycle of a three-station molecular shuttle in different chemical environments (vacuum, CD3CN-CDCl3 solution, and crystal). In contrast with the highly distorted thread conformation in the gas phase and nonpolar CDCl3 solution, the solvated thread in CD3CN-CDCl3 (1:1) mix solvents exhibited a relatively rigid structure. Experimental observations of preferential binding at the protonated dibenzylammonium group (station I) were rationalized by quantum chemical calculations of macrocycle-thread binding energies at three different stations. The orthogonality of site-specific binding interactions at three different stations was also revealed by the nearly constant binding energy obtained at each specific recognition center with the replacement of different neighboring groups and terminal stoppers on the thread. Conformational flexibility has little effect on NMR signals of binding sites, but for some protons that are close to the solvent molecules in the first solvent shell, their chemical shifts are sensitive to the local electrostatic environment caused by nearby solvents. In crystal, π stacking induced evident upfield shifts of NMR signals in comparison with the isolated monomer.

  20. Solid state 13C NMR of unlabeled phosphatidylcholine bilayers: spectral assignments and measurement of carbon-phosphorus dipolar couplings and 13C chemical shift anisotropies.

    Science.gov (United States)

    Sanders, C R

    1993-01-01

    The direct measurement of 13C chemical shift anisotropies (CSA) and 31P-13C dipolar splitting in random dispersions of unlabeled L alpha-phase phosphatidylcholine (PC) has traditionally been difficult because of extreme spectral boradening due to anisotropy. In this study, mixtures of dimyristoyl phosphatidylcholine (DMPC) with three different detergents known to promote the magnetic orientation of DMPC were employed to eliminate the powder-pattern nature of signals without totally averaging out spectral anisotropy. The detergents utilized were CHAPSO, Triton X-100, and dihexanoylphosphatidylcholine (DHPC). Using such mixtures, many of the individual 13C resonances from DMPC were resolved and a number of 13C-31P dipolar couplings were evident. In addition, differing line widths were observed for the components of some dipolar doublets, suggestive of dipolar/chemical shift anisotropy (CSA) relaxation interference effects. Oriented sample resonance assignments were made by varying the CHAPSO or DHPC to DMPC ratio to systematically scale overall bilayer order towards the isotropic limit. In this manner, peaks could be identified based upon extrapolation to their isotropic positions, for which assignments have previously been made (Lee, C.W.B., and R.G. Griffin. 1989. Biophys. J. 55:355-358; Forbes, J., J. Bowers, X. Shan, L. Moran, E. Oldfield, and M.A. Moscarello. 1988. J. Chem. Soc., Faraday, Trans. 1 84:3821-3849). It was observed that the plots of CSA or dipolar coupling versus overall bilayer order obtained from DHPC and CHAPSO titrations were linear. Estimates of the intrinsic dipolar couplings and chemical shift anisotropies for pure DMPC bilayers were made by extrapolating shifts and couplings from the detergent titrations to zero detergent. Both detergent titrations led to similar "intrinsic" CSAs and dipolar couplings. Results extracted from an oriented Triton-DMPC mixture also led to similar estimates for the detergent-free DMPC shifts and couplings. The

  1. Prediction of microvascular invasion of hepatocellular carcinomas with gadoxetic acid-enhanced MR imaging: Impact of intra-tumoral fat detected on chemical-shift images

    Energy Technology Data Exchange (ETDEWEB)

    Min, Ji Hye [Department of Radiology and Center for Imaging Science, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul (Korea, Republic of); Kim, Young Kon, E-mail: jmyr@dreamwiz.com [Department of Radiology and Center for Imaging Science, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul (Korea, Republic of); Lim, Sanghyeok [Department of Radiology, Guri Hospital, Hanyang University College of Medicine, Guri (Korea, Republic of); Jeong, Woo Kyoung; Choi, Dongil; Lee, Won Jae [Department of Radiology and Center for Imaging Science, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul (Korea, Republic of)

    2015-06-15

    Highlights: • Intra-tumoral fat detected with MR imaging may suggest lower risk for MVI of HCC. • Alfa-fetoprotein, tumor size, and fat component were associated with MVI of HCC. • Chemical shift MRI should be considered for the evaluation of HCC. - Abstract: Purpose: To investigate the impact of intra-tumoral fat detected by chemical-shift MR imaging in predicting the MVI of HCC. Materials and methods: Gadoxetic acid-enhanced MR imaging of 365 surgically proven HCCs from 365 patients (306 men, 59 women; mean age, 55.6 years) were evaluated. HCCs were classified into two groups, fat-containing and non-fat-containing, based on the presence of fat on chemical-shift images. Fat-containing HCCs were subdivided into diffuse or focal fatty change groups. Logistic regression analyses were used to identify clinical and MR findings associated with MVI. Results: Based on MR imaging, 66 tumors were classified as fat-containing HCCs and 299 as non-fat-containing HCCs. Among the 66 fat-containing HCCs, 38 (57.6%) showed diffuse fatty changes and 28 (42.4%) showed focal fatty changes. MVI was present in 18 (27.3%) fat-containing HCCs and in 117 (39.1%) non-fat-containing HCCs (P = 0.07). Univariate analysis revealed that serum alpha-fetoprotein (AFP) and tumor size were significantly associated with MVI (P < 0.001). A multiple logistic regression analysis showed that log AFP (odds ratio 1.178, P = 0.0016), tumor size (odds ratio 1.809, P < 0.001), and intra-tumoral fat (odds ratio 0.515, P = 0.0387) were independent variables associated with MVI. Conclusion: Intra-tumoral fat detected with MR imaging may suggest lower risk for MVI of HCC and, therefore, a possibly more favorable prognosis, but the clinical value of this finding is uncertain.

  2. CSI 3.0: a web server for identifying secondary and super-secondary structure in proteins using NMR chemical shifts.

    Science.gov (United States)

    Hafsa, Noor E; Arndt, David; Wishart, David S

    2015-07-01

    The Chemical Shift Index or CSI 3.0 (http://csi3.wishartlab.com) is a web server designed to accurately identify the location of secondary and super-secondary structures in protein chains using only nuclear magnetic resonance (NMR) backbone chemical shifts and their corresponding protein sequence data. Unlike earlier versions of CSI, which only identified three types of secondary structure (helix, β-strand and coil), CSI 3.0 now identifies total of 11 types of secondary and super-secondary structures, including helices, β-strands, coil regions, five common β-turns (type I, II, I', II' and VIII), β hairpins as well as interior and edge β-strands. CSI 3.0 accepts experimental NMR chemical shift data in multiple formats (NMR Star 2.1, NMR Star 3.1 and SHIFTY) and generates colorful CSI plots (bar graphs) and secondary/super-secondary structure assignments. The output can be readily used as constraints for structure determination and refinement or the images may be used for presentations and publications. CSI 3.0 uses a pipeline of several well-tested, previously published programs to identify the secondary and super-secondary structures in protein chains. Comparisons with secondary and super-secondary structure assignments made via standard coordinate analysis programs such as DSSP, STRIDE and VADAR on high-resolution protein structures solved by X-ray and NMR show >90% agreement between those made with CSI 3.0. © The Author(s) 2015. Published by Oxford University Press on behalf of Nucleic Acids Research.

  3. sup 13 C NMR study of the C60 cluster in the solid state: Molecular motion and carbon chemical shift anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Yannoni, C.S.; Johnson, R.D.; Meijer, G.; Bethune, D.S.; Salem, J.R. (Almaden Research Center, San Jose, CA (USA))

    1991-01-10

    {sup 13}C NMR spectra of solid buckminsterfullerene, the soccerball-like cluster of 60 carbon atoms, have been obtained at temperatures down to 77 K. The ambient spectrum shows rapid isotropic rotational motion. The motion is sufficiently slow at 77 K that a measurement of the chemical shift tensor of the carbon nucleus can be made. The tensor components (220, 186, 40 ppm) have values that are typical for an aromatic carbon. Spectra at intermediate temperatures suggest the possibility of either growth of a low-temperature phase in which C60 rotation is inhibited or a distribution of rotational correlation times.

  4. Other compounds isolated from Simira glaziovii and the {sup 1}H and {sup 13}C NMR chemical shift assignments of new 1-epi-castanopsol

    Energy Technology Data Exchange (ETDEWEB)

    Araujo, Marcelo F. de; Vieira, Ivo J. Curcino [Universidade Federal Rural do Rio de Janeiro, Seropedica, RJ (Brazil). Dept. de Quimica; Braz-Filho, Raimundo [Universidade Estadual do Norte Fluminense (UENF), Campos dos Goytacases, RJ (Brazil). Centro de Ciencias Tecnologicas. Lab. de Ciencias Quimicas; Carvalho, Mario G. de, E-mail: mgeraldo@ufrrj.br [Universidade Federal do Rio de Janeiro (NPPN/UFRJ), RJ (Brazil). Centro de Ciencias da Saude. Nucleo de Pesquisa em Produtos Naturais

    2012-07-01

    A new triterpene, 1-epi-castanopsol, besides eleven known compounds: sitosterol, stigmasterol, campesterol, lupeol, lupenone, simirane B, syringaresinol, scopoletin, isofraxidin, 6,7,8-trimethoxycoumarin and harman, were isolated from the wood of Simira glaziovii. The structures of the known compounds were defined by 1D, 2D {sup 1}H, {sup 13}C NMR spectra data analyses and comparison with literature data. The detailed spectral data analyses allowed the definition of the structure of the new 1-epi isomer of castanopsol and performance of {sup 1}H and {sup 13}C NMR chemical shift assignments. (author)

  5. Halogen effect on structure and 13C NMR chemical shift of 3,6-disubstituted-N-alkyl carbazoles

    DEFF Research Database (Denmark)

    Radula-Janik, Klaudia; Kupka, Teobald; Ejsmont, Krzysztof

    2013-01-01

    . The relativistic effect of Br and I atoms on nuclear shieldings was modeled using the spin-orbit ZORA method. Significant heavy atom shielding effects for the carbon atom directly bonded with bromine and iodine were observed (~ -10 and ~ -30 ppm while the other carbon shifts were practically unaffected......Structures of selected 3,6-dihalogeno-N-alkyl carbazole derivatives were calculated at the B3LYP/6-311++G(3df,2pd) level of theory and their 13C NMR isotropic nuclear shieldings were predicted using density functional theory (DFT). The model compounds contained 9H-, N-methyl and N-ethyl derivatives...

  6. The Sign of Nuclear Magnetic Resonance Chemical Shift Difference as a Determinant of the Origin of Binding Selectivity: Elucidation of the Position Dependence of Phosphorylation in Ligands Binding to Scribble PDZ1.

    Science.gov (United States)

    Sundell, Gustav N; Vögeli, Beat; Ivarsson, Ylva; Chi, Celestine N

    2018-01-09

    The use of nuclear magnetic resonance chemical shift perturbation to monitor changes taking place around the binding site of a ligand-protein interaction is a routine and widely applied methodology in the field of protein biochemistry. Shifts are often acquired by titrating various concentrations of ligand to a fixed concentration of the receptor and may serve the purpose, among others, of determining affinity constants, locating binding surfaces, or differentiating between binding mechanisms. Shifts are quantified by the so-called combined chemical shift difference. Although the directionality of shift changes is often used for detailed analysis of specific cases, the approach has not been adapted in standard chemical shift monitoring. This is surprising as it would not require additional effort. Here, we demonstrate the importance of the sign of the chemical shift difference induced by ligand-protein interaction. We analyze the sign of the 15N/1H shift changes of the PDZ1 domain of Scribble upon interaction with two pairs of phosphorylated and unphosphorylated peptides. We find that detailed differences in the molecular basis of this PDZ-ligand interaction can be obtained from our analysis to which the classical method of combined chemical shift perturbation analysis is insensitive. In addition, we find a correlation between affinity and millisecond motions. Application of the methodology to Cyclophilin a, a cis-trans isomerase, reveals molecular details of peptide recognition. We consider our directionality vector chemical shift analysis as a method of choice when distinguishing the molecular origin of binding specificities of a class of similar ligands, which is often done in drug discovery.

  7. Time-domain quanification of amplitude, chemical shift, apparent relaxation time T2, and phase by wavelet-transform analysis. Application to biomedical magnetic resonance spectroscopy.

    Science.gov (United States)

    Serrai, H; Senhadji, L; de Certaines, J D; Coatrieux, J L

    1997-01-01

    The wavelet-transform method is used to quantify the magnetic resonance spectroscopy (MRS) parameters: chemical shift, apparent relaxation time T2, resonance amplitude, and phase. Wavelet transformation is a time-frequency representation which separates each component from the FID, then successively quantifies it and subtracts it from the raw signal. Two iterative procedures have been developed. They have been combined with a nonlinear regression analysis method and tested on both simulated and real sets of biomedical MRS data selected with respect to the main problems usually encountered in quantifying biomedical MRS, specifically "chemical noise," resulting from overlapping resonances, and baseline distortion. The results indicate that the wavelet-transform method can provide efficient and accurate quantification of MRS data.

  8. 13C-NMR chemical shift databases as a quick tool to evaluate structural models of humic substances

    DEFF Research Database (Denmark)

    Nyrop Albers, Christian; Hansen, Poul Erik

    2010-01-01

    Models for humic and fulvic acids are discussed based on 13C liquid state NMR spectra combined with results from elemental analysis and titration studies. The analysis of NMR spectra is based on a full reconstruction of the NMR spectrum done with help of 13C-NMR data bases by adding up chemical...

  9. Solid-state NMR chemical-shift perturbations indicate domain reorientation of the DnaG primase in the primosome of Helicobacter pylori

    Energy Technology Data Exchange (ETDEWEB)

    Gardiennet, Carole [Université de Lorraine, CNRS, CRM2, UMR 7036 (France); Wiegand, Thomas [ETH Zurich, Physical Chemistry (Switzerland); Bazin, Alexandre [Université de Lyon 1, Molecular Microbiology and Structural Biochemistry, Labex Ecofect, UMR 5086 CNRS (France); Cadalbert, Riccardo [ETH Zurich, Physical Chemistry (Switzerland); Kunert, Britta; Lacabanne, Denis [Université de Lyon 1, Molecular Microbiology and Structural Biochemistry, Labex Ecofect, UMR 5086 CNRS (France); Gutsche, Irina [Université Grenoble Alpes, Institut de Biologie Structurale (IBS), CNRS, IBS, CEA, IBS (France); Terradot, Laurent, E-mail: l.terradot@ibcp.fr [Université de Lyon 1, Molecular Microbiology and Structural Biochemistry, Labex Ecofect, UMR 5086 CNRS (France); Meier, Beat H., E-mail: beme@ethz.ch [ETH Zurich, Physical Chemistry (Switzerland); Böckmann, Anja, E-mail: a.bockmann@ibcp.fr [Université de Lyon 1, Molecular Microbiology and Structural Biochemistry, Labex Ecofect, UMR 5086 CNRS (France)

    2016-03-15

    We here investigate the interactions between the DnaB helicase and the C-terminal domain of the corresponding DnaG primase of Helicobacter pylori using solid-state NMR. The difficult crystallization of this 387 kDa complex, where the two proteins interact in a six to three ratio, is circumvented by simple co-sedimentation of the two proteins directly into the MAS-NMR rotor. While the amount of information that can be extracted from such a large protein is still limited, we can assign a number of amino-acid residues experiencing significant chemical-shift perturbations upon helicase-primase complex formation. The location of these residues is used as a guide to model the interaction interface between the two proteins in the complex. Chemical-shift perturbations also reveal changes at the interaction interfaces of the hexameric HpDnaB assembly on HpDnaG binding. A structural model of the complex that explains the experimental findings is obtained.

  10. A theoretical study on the electronic structures and photophysical properties of phosphorescent Iridium(iii) complexes with -CH3/H and t-Bu substituents.

    Science.gov (United States)

    Si, Yanling; Qu, Nan; Cui, Liying; Gao, Bo; Wu, Zhijian

    2016-08-02

    The electronic structures and photophysical properties of the recently reported Ir(iii) cyclometallated complexes containing the 2-(1-phenoxy-4-phenyl)-5-methylpyridine ligand (1) were studied via density functional theory and time-dependent density functional theory calculations. To improve the performance and establish the structural-photophysical property relationships, a series of Ir(iii) complexes 2-6 with -CH3/H and t-Bu substituents have been designed according to the experimental complex 1. The calculated results demonstrate that the different substituted ligands not only modify the absorption and emission bands, but also enhance the phosphorescent quantum efficiency. The t-Bu substituent increases the energy levels of the LUMO for complexes 4, 5 and 6 and broadens the HOMO-LUMO energy gaps. When compared with 1, the emission wavelengths for 3 and 6 are red-shifted considerably, while they are slightly blue-shifted for 4 and 5. In particular, the -CH3 and t-Bu substituents in 2, 4 and 5 lead to a relatively high quantum yield. Therefore, the designed complexes 2, 4 and 5 with -CH3/t-Bu substituents are expected to be promising phosphorescence emitters with high quantum efficiency.

  11. Effects of Substituents in Polyvinylcarbazole Structures on Their Optical Properties

    CERN Document Server

    Vertsimakha, Ya; Syromyatnikov, V; Savchenko, I

    2016-01-01

    Absorption, photoluminescence, and photoluminescence excitation spectra of solutions and thin films of N-vinylcarbazole polymers and copolymers with various substituents directly on the carbazole moiety and on the polymer chain were studied comprehensively. Polymers that were used previously to develop polymer composites with polymethine dyes having photosensitivity over a broad spectral range including the visible and near-IR regions were selected for the studies.

  12. An evaluation of substituent effects on aromatic edge-to-face interactions and CF-π versus CH-π interactions using an imino torsion balance model.

    Science.gov (United States)

    Jennings, W Brian; O'Connell, Niamh; Malone, John F; Boyd, Derek R

    2013-08-28

    A selection of imines derived from phenyl t-butyl ketones and substituted 2-phenylethylamines or phenylalanine exhibit slow rotation around the aryl–imino bond at ambient temperature, resulting in a large non-equivalence of the ortho hydrogens in the 1H NMR spectra. This facilitates assessment of aryl substituent effects on the face tilted-T CH–π interaction between a phenyl ring (A) on the imino carbon proximate to the terminal phenyl ring (B). Analysis of the marked temperature dependence of the chemical shift of the interacting ortho hydrogen affords estimates of the opposing enthalpic and entropic factors involved in the rapid equilibrium between the closed edge-to-face conformation and alternative open conformations devoid of a CH–π interaction while in solution. Above ca. 80 °C the entropy term (TΔS) cancels out the enthalpy (ΔH) favouring the closed conformation and open conformations are preferred. Accordingly, commonly reported binding free energies may not be a good measure of the energetic strength of intramolecular aromatic interactions. Investigation of an ortho fluoro substituted compound indicates that a CF–π interaction is at least 1.0 kcal mol−1 weaker in enthalpy than the CH–π interaction. Several X-ray crystal structures depicting an intramolecular edge-to-face interaction are presented.

  13. Chemical potential shift and gap-state formation in SrTiO{sub 3−δ} revealed by photoemission spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Pal, Prabir, E-mail: palp@nplindia.org; Kumar, Pramod; Aswin, V.; Dogra, Anjana; Joshi, Amish G. [CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi 110012 (India)

    2014-08-07

    In this study, we report on investigations of the electronic structure of SrTiO{sub 3} annealed at temperature ranging between 550 and 840 °C in an ultrahigh vacuum. Annealing induced oxygen vacancies (O{sub vac}) impart considerable changes in the electronic structure of SrTiO{sub 3}. Using core-level photoemission spectroscopy, we have studied the chemical potential shift (Δμ) as a function of annealing temperature. The result shows that the chemical potential monotonously increases with electron doping in SrTiO{sub 3−δ}. The monotonous increase of the chemical potential rules out the existence of electronic phase separation in the sample. Using valence band photoemission, we have demonstrated the formation of a low density of states at the near Fermi level electronic spectrum of SrTiO{sub 3−δ}. The gap-states were observed by spectral weight transfer over a large energy scale of the stoichiometric band gap of SrTiO{sub 3} system leading finally to an insulator-metal transition. We have interpreted our results from the point of structural distortions induced by oxygen vacancies.

  14. Correlations of the chemical shift on fasly rotating biological solids by means of NMR spectroscopy; Korrelationen der chemischen Verschiebung an schnell rotierenden biologischen Festkoerpern mittels NMR-Spektroskopie

    Energy Technology Data Exchange (ETDEWEB)

    Herbst, Christian

    2010-04-27

    The basic aim of the thesis was the development and improvement of homo- and heteronuclear feedback sequences for the generation of correlation spectra of the chemical shift. In a first step the possibility of the acquisition of {sup 13}C-{sup 13} correlation spectra of the chemical shift by means of inversion pulses with low RF power factor was studied. Furthermore it was shown that broad-band phase-modulated inversion and universal rotational pulses can be constructed by means of global optimization procedures like the genetic algorithms under regardment of the available RF field strength. By inversion, universal rotational, and 360 pulses as starting values of the optimization efficient homonuclear CN{sub n}{sup {nu}} and RN{sub n}{sup {nu}} mixing sequences as well as heteronuclear RN{sub n}{sup {nu}{sub s},{nu}{sub k}} feedback sequences were generated. The satisfactory power of the numerically optimized sequences was shown by means of the simulation as well by means of correlation experiments of the chemical shift of L-histidine, L-arginine, and the (CUG){sub 97}-RNA. This thesis deals furthermore with the possibility to acquire simultaneously different signals with several receivers. By means of numerically optimized RN{sub n}{sup {nu}{sub s},{nu}{sub k}} pulse sequences both {sup 15}N-{sup 13}C and {sup 13}C-{sup 15}N correlation spectra were simultaneously generated. Furthermore it could be shown that the simultaneous acquisition of 3D-{sup 15}N-{sup 13}C-{sup 13}C and {sup 13}C-{sup 15}N-({sup 1}H)-{sup 1}H correlation spectra is possible. By this in only one measurement process resonance assignments can be met and studies of the global folding performed. A further application of several receivers is the simultaneous acquisition of CHHC, NHHN, NHHC, as well as CHHN spectra. By such experiments it is possible to characterize the hydrogen-bonding pattern and the glycosidic torsion angle {sup {chi}} in RNA. This was demonstrated by means of the (CUG){sub 97

  15. Automated Fragmentation Polarizable Embedding Density Functional Theory (PE-DFT) Calculations of Nuclear Magnetic Resonance (NMR) Shielding Constants of Proteins with Application to Chemical Shift Predictions

    DEFF Research Database (Denmark)

    Steinmann, Casper; Bratholm, Lars Andersen; Olsen, Jógvan Magnus Haugaard

    2017-01-01

    Full-protein nuclear magnetic resonance (NMR) shielding constants based on ab initio calculations are desirable, because they can assist in elucidating protein structures from NMR experiments. In this work, we present NMR shielding constants computed using a new automated fragmentation (J. Phys....... Chem. B 2009, 113, 10380–10388) approach in the framework of polarizable embedding density functional theory. We extend our previous work to give both basis set recommendations and comment on how large the quantum mechanical region should be to successfully compute 13C NMR shielding constants...... that are comparable with experiment. The introduction of a probabilistic linear regression model allows us to substantially reduce the number of snapshots that are needed to make comparisons with experiment. This approach is further improved by augmenting snapshot selection with chemical shift predictions by which we...

  16. Characterization of adrenal lesions using chemical shift MRI: comparison between 1.5 Tesla and two echo time pair selection at 3.0 Tesla MRI.

    Science.gov (United States)

    Nakamura, Shinichi; Namimoto, Tomohiro; Morita, Kosuke; Utsunomiya, Daisuke; Oda, Seitaro; Nakaura, Takeshi; Hirai, Toshinori; Yamashita, Yasuyuki

    2012-01-01

    To compare chemical shift MRI obtained at 1.5 Tesla (T) and two pairs of echo time (TE) in-phase and opposed-phase 3.0T MRI to assess their usefulness for the differentiation between adrenal adenomas and non-adenomas. We evaluated 91 adrenal masses (75 adenomas, 16 non-adenomas) in 85 patients. The MR imaging parameters were: T1-dual-gradient-echo(GRE) [echo times (TEs) = 1.1/2.3 ms (first-echo-pair) or 3.5/4.6 ms (second-echo-pair)] at 3.0T, and T1-dual-GRE (TEs = 2.4/4.8 ms) at 1.5T. Scans were quantitatively assessed for the signal intensity (SI) index, calculated as [(SIin-phase-SIopposed-phase)/(SIin-phase)] × 100(%). To test for differences between adenomas and non-adenomas, we performed quantitative analysis and analysis of variance. For all images, the SI index differed significantly between adenomas and non-adenomas. The sensitivity /specificity of SI index at the first-echo-pair of 3.0T was 100%/ 100%, that of 95.6%/ 100% at the second-echo-pair of 3.0T, and 91.7%/ 88.9% at 1.5T, respectively. At intra-individual comparisons, the SI indices obtained with the second-echo-pair at 3.0T were significantly lower than on the first-echo-pair at 3.0T and 1.5T. Chemical shift MRI at 3.0T provides more accurate differentiation between adenomas and non-adenomas than at 1.5T. The SI index of the first-echo-pair at 3.0T is the most reliable evaluation method for differentiating adrenal adenomas from non-adenomas. Copyright © 2011 Wiley Periodicals, Inc.

  17. Chemical shift MR imaging in the lumbar vertebra: the effect of field strength, scanner vendors and flip angles in repeatability of signal intensity index measurement.

    Science.gov (United States)

    Xiao, Zebin; Li, Jian; Li, Chengqi; Zhang, Yuyang; She, Dejun; Cao, Dairong

    2016-11-25

    To evaluate the reproducibility of signal intensity index (SII) measurements with MRI systems from different vendors and with different field strengths, and to test the effectiveness of flip angle. Thirty-two healthy volunteers (mean age 35.3 ± 9.3 years) were enrolled in this ethics committee-approved study. Chemical shift MR imaging was performed on 1.5- and 3.0-T MR systems from three vendors. Two independent observers measured SII values in five lumbar segments. Inter- and intraobserver agreement was assessed using the interclass correlation coefficients (ICCs). Differences of mean SII values between different field strengths and MR vendors as well as flip angles were compared by using repeated-measures analysis of variance. Differences of mean SII values between different flip angles were also compared by using paired-sample t test. Inter- and intra-observer correlation coefficients showed good agreement (all ICC > 0.75) when measuring SII values at different MR systems (ICCs ranging from 0.896 to 0.983) and flip angles (ICCs ranging from 0.824 to 0.983). There were no significant differences in mean SII values measured by different MR vendors with different field strengths (all p > 0.05 ranging from 0.337 to 0.824). The differences in the mean SII between the four different flip angles were statistically significant (all p measurement using chemical shift MR imaging may be comparable between different MR systems. Also high flip angles showed better stability to quantitate lumbar fat content.

  18. ¹H, ¹⁵N, and ¹³C backbone chemical shift assignment of titin domains A59-A60 and A60 alone.

    Science.gov (United States)

    Czajlik, András; Thompson, Gary S; Khan, Ghulam N; Kalverda, Arnout P; Homans, Steve W; Trinick, John

    2014-10-01

    The giant protein titin is the third most abundant protein of vertebrate striated muscle. The titin molecule is >1 μm long and spans half the sarcomere, from the Z-disk to the M-line, and has important roles in sarcomere assembly, elasticity and intracellular signaling. In the A-band of the sarcomere titin is attached to the thick filaments and mainly consists immunoglobulin-like and fibronectin type III-like domains. These are mostly arranged in long-range patterns or 'super-repeats'. The large super-repeats each contain 11 domains and are repeated 11 times, thus forming nearly half the titin molecule. Through interactions with myosin and C-protein, they are involved in thick filament assembly. The importance of titin in muscle assembly is highlighted by the effect of mutations in the A-band portion, which are the commonest cause of dilated cardiomyopathy, affecting ~1 in 250 (Herman et al. in N Engl J Med 366:619-628, 2012). Here we report backbone (15)N, (13)C and (1)H chemical shift and (13)Cβ assignments for the A59-A60 domain tandem from the titin A59-A69 large super-repeat, completed using triple resonance NMR. Since, some regions of the backbone remained unassigned in A60 domain of the complete A59-A60 tandem, a construct containing a single A60 domain, A60sd, was also studied using the same methods. Considerably improved assignment coverage was achieved using A60sd due to its lower mass and improved molecular tumbling rate; these assignments also allowed the analysis of inter-domain interactions using chemical shift mapping against A59-A60.

  19. Shifts in soil chemical properties and bacterial communities responding to biotransformed dry olive residue used as organic amendment.

    Science.gov (United States)

    Siles, José A; Cajthaml, Tomas; Hernández, Paola; Pérez-Mendoza, Daniel; García-Romera, Inmaculada; Sampedro, Inmaculada

    2015-07-01

    Dry olive residue (DOR) is a waste product derived from olive oil extraction and has been proposed as an organic amendment. However, it has been demonstrated that a pre-treatment, such as its transformation by saprophytic fungi, is required before DOR soil application. A greenhouse experiment was designed where 0 and 50 g kg(-1) of raw DOR (DOR), Coriolopsis floccosa-transformed DOR (CORDOR) and Fusarium oxysporum-transformed DOR (FUSDOR) were added to soil. Analyses of the soil chemical properties as well as the structure and relative abundance of bacterial and actinobacterial communities were conducted after 0, 30 and 60 days following amendment. The different amendments produced a slight decrease in soil pH and significant increases in carbon fractions, C/N ratios, phenols and K, with these increases being more significant after DOR application. Quantitative PCR assays of the 16S rRNA gene and PLFA analyses showed that all amendments favoured bacterial growth at 30 and 60 days, although actinobacterial proliferation was more evident after CORDOR and FUSDOR application at 60 days. Bacterial and actinobacterial DGGE multivariate analyses showed that the amendments produced structural changes in both communities, especially after 60 days of amendment. PLFA data analysis identified changes in soil microbial communities according to the amendment considered, with FUSDOR and CORDOR being less disruptive than DOR. Finally, integrated analysis of all data monitored in the present study enabled us to conclude that the greatest impact on soil properties was caused by DOR at 30 days and that soil showed some degree of resilience after this time.

  20. Substituent Inductive Effects on the Electrochemical Oxidation of Flavonoids Studied by Square Wave Voltammetry and Ab Initio Calculations.

    Science.gov (United States)

    Arroyo-Currás, Netzahualcóyotl; Rosas-García, Víctor M; Videa, Marcelo

    2016-10-27

    Flavonoids are natural products commonly found in the human diet that show antioxidant, anti-inflammatory and anti-hepatotoxic activities. These nutraceutical properties may relate to the electrochemical activity of flavonoids. To increase the understanding of structure-electrochemical activity relations and the inductive effects that OH substituents have on the redox potential of flavonoids, we carried out square-wave voltammetry experiments and ab initio calculations of eight flavonoids selected following a systematic variation in the number of hydroxyl substituents and their location on the flavan backbone: three flavonols, three anthocyanidins, one anthocyanin and the flavonoid backbone flavone. We compared the effect that the number of -OH groups in the ring B of flavan has on the oxidation potential of the flavonoids considered, finding linear correlations for both flavonols and anthocyanidins ( R 2 = 0.98 ). We analyzed the effects that position and number of -OH substituents have on electron density distributions via ab initio quantum chemical calculations. We present direct correlations between structural features and oxidation potentials that provide a deeper insight into the redox chemistry of these molecules.

  1. Anodic oxidation of stilbenes bearing electron-withdrawing ring substituents

    Energy Technology Data Exchange (ETDEWEB)

    Halas, Summer M.; Okyne, Kwame; Fry, Albert J

    2003-06-15

    A number of disubstituted stilbenes bearing either two strong electron-withdrawing groups or one electron-withdrawing and one electron-donating group were synthesized and anodically oxidized in a divided cell in methanol at a carbon anode. A variety of types of products were obtained, most of which have never been observed upon oxidation of alkenes not bearing electron-withdrawing groups. A mechanistic scheme involving 2-methoxy-1,2-diarylethyl cations as key intermediates can account for all of the observed products. The nature of the products from each alkene is strongly correlated with the sum of the Hammett {sigma}{sup +} values of the ring substituents.

  2. Origin of Substituent Effects in Edge-to-Face Aryl-Aryl Interactions.

    Science.gov (United States)

    Wheeler, Steven E; Houk, K N

    2009-01-01

    Substituent effects in the edge-to-face configuration of the benzene dimer have been studied using modern density functional theory. An accurate interaction potential energy curve has been computed for the unsubstituted dimer using ab initio methods with large basis sets. The recommended binding energy for the edge-to-face benzene dimer is 2.31 kcal mol(-1), estimated at the counterpoise-corrected CCSD(T)/aug-cc-pVTZ level of theory. For both edge-ring and face-ring-substituted dimers, interaction energies correlate with sigma(m) for the substituents, indicating that substituent effects can be understood qualitatively in terms of simple electrostatic effects, although in the latter case dispersion results in some scatter in the data. In contrast to prevailing models of substituent effects in benzene dimers, polarization of the pi-system of the substituted ring does not induce substituent effects. For edge-ring-substituted dimers, substituent effects arise from differential electrostatic interactions between the hydrogens on the substituted ring and the pi-cloud of the face ring and direct interactions of the substituents with the unsubstituted ring. For face-ring-substituted dimers, substituent effects arise from direct electrostatic and dispersion interactions of the substituents with the edge ring. Substituents with sigma(m) > 0.12 favor edge ring substitution while for sigma(m) face ring is preferred.

  3. An automated system designed for large scale NMR data deposition and annotation: application to over 600 assigned chemical shift data entries to the BioMagResBank from the Riken Structural Genomics/Proteomics Initiative internal database.

    Science.gov (United States)

    Kobayashi, Naohiro; Harano, Yoko; Tochio, Naoya; Nakatani, Eiichi; Kigawa, Takanori; Yokoyama, Shigeyuki; Mading, Steve; Ulrich, Eldon L; Markley, John L; Akutsu, Hideo; Fujiwara, Toshimichi

    2012-08-01

    Biomolecular NMR chemical shift data are key information for the functional analysis of biomolecules and the development of new techniques for NMR studies utilizing chemical shift statistical information. Structural genomics projects are major contributors to the accumulation of protein chemical shift information. The management of the large quantities of NMR data generated by each project in a local database and the transfer of the data to the public databases are still formidable tasks because of the complicated nature of NMR data. Here we report an automated and efficient system developed for the deposition and annotation of a large number of data sets including (1)H, (13)C and (15)N resonance assignments used for the structure determination of proteins. We have demonstrated the feasibility of our system by applying it to over 600 entries from the internal database generated by the RIKEN Structural Genomics/Proteomics Initiative (RSGI) to the public database, BioMagResBank (BMRB). We have assessed the quality of the deposited chemical shifts by comparing them with those predicted from the PDB coordinate entry for the corresponding protein. The same comparison for other matched BMRB/PDB entries deposited from 2001-2011 has been carried out and the results suggest that the RSGI entries greatly improved the quality of the BMRB database. Since the entries include chemical shifts acquired under strikingly similar experimental conditions, these NMR data can be expected to be a promising resource to improve current technologies as well as to develop new NMR methods for protein studies.

  4. Substituent effect on color tuning of red light emission in photoluminescence and electroluminescence of red fluorophore.

    Science.gov (United States)

    Ryu, Gweon Young; Lee, Sang Gu; Shin, Sung Eui; Park, Jong Jin; Park, Seungho; Shin, Dong Myung

    2010-10-01

    Typical small red light-emitting molecules for organic light emitting diodes (OLEDs) were highly susceptible to fluorescence concentration quenching in solid state. Red fluorophores, (2Z, 2'Z)-3, 3'-[4,4"-bis(dimethylamino)-1,1':4',1"-terphenyl-29',5'-diyl]bis(2-phenylacrylonitrile) (ABCV-P), (2E, 2'E)-3,3'-[4,4"-bis(dimethylamino)-1,1':4',1"-terphenyl-2',5'-diyl]bis[2-(2-thienyl)acrylonitrile] (ABCV-Th) and (2Z, 2'Z)-3,3'-[4,4"-bis(dimethylamino)-1,1':4',1"-terphenyl-2',5'-diyl]bis[2-(2-naphthyl)acrylonitrile] (ABCV-Np), capable of preventing fluorescence concentration quenching were designed and synthesized. These compounds have intramolecular charge transfer (ICT) properties which were estimated by measurement of UV-Visible absorption and photoluminescence (PL) emission spectra with variation of solvent polarity (n-Hexane/Chloroform = 99/1, 1/1; Chloroform; Methylene chloride). The magnitude of ICT for ABCV-Th was measured to be the largest and that for ABCV-Np was slightly larger compared to that for ABCV-P. The magnitude of ICT resulted in a shift of peak wavelength of PL emission. Therefore, this result well supported substituent effect on the color change of PL emission. The peak wavelengths of photoluminescence for ABCV-P, ABCV-Np and ABCV-Th were observed to be 607.5, 611.5 and 617.5 nm, respectively, and those of EL spectra were measured to be 612.5, 619.5, 621.0 nm, respectively. The emission maxima of PL and EL spectra for these red fluorescent compounds were well correlated with substituent effect on ICT for them.

  5. Effect of Basic Site Substituents on Concerted Proton-Electron Transfer in Hydrogen Bonded-Pyridyl Phenols

    Science.gov (United States)

    Markle, Todd F.; Tronic, Tristan A.; DiPasquale, Antonio G.; Kaminsky, Werner

    2012-01-01

    Separated concerted proton-electron transfer (sCPET) reactions of two series of phenols with pendent substituted pyridyl moieties are described. The pyridine is either attached directly to the phenol (HOAr-pyX) or connected through a methylene linker (HOArCH2pyX) (X = 4-NO2, 5-CF3, 4-CH3, 4-NMe2). Electron-donating and -withdrawing substituents also have a substantial effect on the chemical environment of the transferring proton, as indicated by IR and 1H NMR spectra, X-ray structures and computational studies. One-electron oxidation of the phenols occurs concomitantly with proton transfer from the phenolic oxygen to the pyridyl nitrogen. The oxidation potentials vary linearly with the pKa of the free pyridine (pyX), with slopes slightly below the Nerstian value of 59 mV/pKa. For the HOArCH2pyX series, the rate constants ksCPET for oxidation by NAr3•+ or [Fe(diimine)3]3+ vary primarily with the thermodynamic driving force (ΔG°sCPET), whether ΔG° is changed by varying the potential of the oxidant or the substituent on the pyridine, indicating a constant intrinsic barrier λ. In contrast, the substituents in the HOAr-pyX series affect λ as well as ΔG°sCPET, and compounds with electron-withdrawing substituents have significantly lower reactivity. The relationship between the structural and spectroscopic properties of the phenols and their CPET reactivity is discussed. PMID:23176252

  6. Effect of basic site substituents on concerted proton-electron transfer in hydrogen-bonded pyridyl-phenols.

    Science.gov (United States)

    Markle, Todd F; Tronic, Tristan A; DiPasquale, Antonio G; Kaminsky, Werner; Mayer, James M

    2012-12-20

    Separated concerted proton-electron transfer (sCPET) reactions of two series of phenols with pendent substituted pyridyl moieties are described. The pyridine is either attached directly to the phenol (HOAr-pyX) or connected through a methylene linker (HOArCH(2)pyX) (X = 4-NO(2), 5-CF(3), 4-CH(3), and 4-NMe(2)). Electron-donating and -withdrawing substituents have a substantial effect on the chemical environment of the transferring proton, as indicated by IR and (1)H NMR spectra, X-ray structures, and computational studies. One-electron oxidation of the phenols occurs concomitantly with proton transfer from the phenolic oxygen to the pyridyl nitrogen. The oxidation potentials vary linearly with the pK(a) of the free pyridine (pyX), with slopes slightly below the Nerstian value of 59 mV/pK(a). For the HOArCH(2)pyX series, the rate constants k(sCPET) for oxidation by NAr(3)(•+) or [Fe(diimine)(3)](3+) vary primarily with the thermodynamic driving force (ΔG°(sCPET)), whether ΔG° is changed by varying the potential of the oxidant or the substituent on the pyridine, indicating a constant intrinsic barrier λ. In contrast, the substituents in the HOAr-pyX series affect λ as well as ΔG°(sCPET), and compounds with electron-withdrawing substituents have significantly lower reactivity. The relationship between the structural and spectroscopic properties of the phenols and their CPET reactivity is discussed.

  7. QM AND AB INITIO INVESTIGATION ON THE HYDROGEN BONDING, NMR CHEMICAL SHIFTS AND SOLVENT EFFECTS ON THE DPPE

    Directory of Open Access Journals (Sweden)

    M. Monajjemi

    2010-06-01

    Full Text Available The hydrogen bonding effects that were produced from interaction of membrane lipid dipalmitoylphosphatidyl-ethanolamine (DPPE with 1-5 water molecules, has been theoretically  investigated through the quantum mechanical calculations at the Hartree-Fock level of theory and the 3-21G, 6-31G and 6-31G* basis sets with the computational package of Gaussian 98. According to the obtained results of the structural optimization of the isolated DPPE in the gas phase, we can see the evidences of interactions in the head group of this macromolecule (from the molecular point of view we have a proton transfer from the ammonium group to the phosphate oxygen of zwitterionic form. As we know that the hydrogen bonding of DPPE with water molecules which have surrounded its head group plays an important role in the permeability of DPPE. So, in order to understand the microscopic physico-chemical nature of this subject we have analyzed bond and torsion angles of DPPE before and after added water molecules.  In this paper we have theoretically studied the complexes DPPE with water molecules which have surrounded its head group. As mentioned before, this theoretically study has been done through Hartree-Fock level of theory by using simple basis sets. Theoretical data shows that the interaction of head group of DPPE with water molecules causes some changes in the geometry of DPPE which were explained by the contribution of zwitterionic form of DPPE macromolecule, and finally hydrated DPPE becomes stable complex. Comparison between theoretical and experimental geometry data of DPPE macromolecule shows that the calculation at the HF/3-21 level of theory produces results which they are in better agreement with the experimental data. Moreover the hydrogen bonding effects on the NMR shielding tensor of selected atoms in the hydrated complexes of DPPE were reported. The ";Gauge Including Atomic Orbitals"; (GIAO approaches within the SCF-Hartree-Fock approximation have

  8. Electronic structure, molecular electrostatic potential, and NMR chemical shifts in cucurbit[n]urils (n = 5-8), ferrocene, and their complexes.

    Science.gov (United States)

    Pinjari, Rahul V; Gejji, Shridhar P

    2008-12-11

    Electronic structure and molecular electrostatic potential (MESP) in ferrocene (FC), cucurbit[n]urils (CB[n]) with n = 5-8, and their host-guest complexes are obtained within the framework of density functional theory. MESP topography that is employed to gauge the dimensions of the CB[n] cavity estimates that the cavity height increases from 7.25 to 7.70 A along CB[n] homologue series, whereas the diameter of the CB[8] (8.57 A) cavity is larger than twice that of CB[5] (3.91 A). MESP investigations reveal deeper minima near ureido oxygens in CB[5] along with large electron-rich regions at its portal. A lateral interaction of the guest FC with hydrophilic exterior of the CB[n] portal and its encapsulation within hydrophobic cavity of the host are analyzed. The present calculations suggest that CB[5] does not yield stable complexes in either case. FC interacts laterally with CB[6], and inclusion of the guest occurs, both parallel as well as perpendicular to the CB[n] axis, in the cavity of higher homologue. Self-consistent reaction field studies indicate that, in the presence of water as a solvent, encapsulation of FC in parallel fashion is favored within CB[7] and CB[8] cavities. NMR chemical shifts (delta(H)) of CB[n] protons remain practically unchanged with an increase in the cavity size; however, they are influenced significantly by water. The spectra thus obtained in aqueous solution agree with those observed experimentally. The delta(H) values in FC-CB[n] complexes indicate deshielding of FC protons directed toward portals, while those pointing toward nitrogens exhibit up-shifts in the spectra.

  9. Concurrent Increases and Decreases in Local Stability and Conformational Heterogeneity in Cu, Zn Superoxide Dismutase Variants Revealed by Temperature-Dependence of Amide Chemical Shifts.

    Science.gov (United States)

    Doyle, Colleen M; Rumfeldt, Jessica A; Broom, Helen R; Sekhar, Ashok; Kay, Lewis E; Meiering, Elizabeth M

    2016-03-08

    The chemical shifts of backbone amide protons in proteins are sensitive reporters of local structural stability and conformational heterogeneity, which can be determined from their readily measured linear and nonlinear temperature-dependences, respectively. Here we report analyses of amide proton temperature-dependences for native dimeric Cu, Zn superoxide dismutase (holo pWT SOD1) and structurally diverse mutant SOD1s associated with amyotrophic lateral sclerosis (ALS). Holo pWT SOD1 loses structure with temperature first at its periphery and, while having extremely high global stability, nevertheless exhibits extensive conformational heterogeneity, with ∼1 in 5 residues showing evidence for population of low energy alternative states. The holo G93A and E100G ALS mutants have moderately decreased global stability, whereas V148I is slightly stabilized. Comparison of the holo mutants as well as the marginally stable immature monomeric unmetalated and disulfide-reduced (apo(2SH)) pWT with holo pWT shows that changes in the local structural stability of individual amides vary greatly, with average changes corresponding to differences in global protein stability measured by differential scanning calorimetry. Mutants also exhibit altered conformational heterogeneity compared to pWT. Strikingly, substantial increases as well as decreases in local stability and conformational heterogeneity occur, in particular upon maturation and for G93A. Thus, the temperature-dependence of amide shifts for SOD1 variants is a rich source of information on the location and extent of perturbation of structure upon covalent changes and ligand binding. The implications for potential mechanisms of toxic misfolding of SOD1 in disease and for general aspects of protein energetics, including entropy-enthalpy compensation, are discussed.

  10. Determination of the Tautomeric Equilibria of Pyridoyl Benzoyl -Diketones in the Liquid and Solid State through the use of Deuterium Isotope Effects on 1H and 13C NMR Chemical Shifts and Spin Coupling Constants

    DEFF Research Database (Denmark)

    Hansen, Poul Erik; Borisov, Eugeny V.; Lindon, John C.

    2015-01-01

    , in the solution state the 2-bond and 3-bond J(1H–13C) coupling constants have been used to confirm the equilibrium positions. The isotope effects due to deuteriation at the OH position are shown to be superior to chemical shift in determination of equilibrium positions of these almost symmetrical -pyridoyl......-benzoyl methanes. The assignments of the NMR spectra are supported by calculations of the chemical shifts at the DFT level. The equilibrium positions are shown to be different in the liquid and the solid state. In the liquid state the 4-pyridoyl derivative is at the B-form (C-1 is OH), whereas the 2-and 3-pyridoyl...

  11. Chemical constituents of Ottonia corcovadensis Miq. from Amazon forest: {sup 1}H and {sup 13}C chemical shift assignments; Constituintes quimicos de Ottonia corcovadensis Miq. da floresta Amazonica - atribuicao dos deslocamentos quimicos dos atomos de hidrogenio e carbono

    Energy Technology Data Exchange (ETDEWEB)

    Facundo, Valdir A. [Rondonia Univ., Porto Velho, RO (Brazil). Dept. de Quimica; Morais, Selene M. [Ceara Univ., Fortaleza, CE (Brazil). Dept. de Quimica e Fisica; Braz Filho, Raimundo [Universidade Estadual do Norte Fluminense (UENF), Campos dos Goytacases, RJ (Brazil). Setor de Quimica de Produtos Naturais. Lab. de Ciencias Quimicas. Setor de Quimica de Produtos Naturais]. E-mail: braz@uenf.br

    2004-02-01

    In an ethanolic extract of leaves of Ottonia corcovadensis (Piperaceae) were identified sixteen terpenoids of essential oil and the three flavonoids 3',4',5,5',7-penta methoxyflavone (1), 3',4',5,7-tetra methoxyflavone (2) and 5-hydroxy-3',4',5',7-tetra methoxyflavone (3) and cafeic acid (4). Two amides (5 and 6) were isolated from an ethanolic extract of the roots. The structures were established by spectral analysis, meanly NMR (1D and 2D) and mass spectra. Extensive NMR analysis was also used to complete {sup 1}H and {sup 13}C chemical shift assignments of the flavonoids and amides. The components of the essential oil were identified by computer library search, retention indices and visual interpretation of mass spectra. (author)

  12. Ring substituents mediate the morphology of PBDTTPD-PCBM bulk-heterojunction solar cells

    KAUST Repository

    Warnan, Julien

    2014-04-08

    Among π-conjugated polymer donors for efficient bulk-heterojunction (BHJ) solar cell applications, poly(benzo[1,2-b:4,5-b′]dithiophene- thieno[3,4-c]pyrrole-4,6-dione) (PBDTTPD) polymers yield some of the highest open-circuit voltages (VOC, ca. 0.9 V) and fill-factors (FF, ca. 70%) in conventional (single-cell) BHJ devices with PCBM acceptors. In PBDTTPD, side chains of varying size and branching affect polymer self-assembly, nanostructural order, and impact material performance. However, the role of the polymer side-chain pattern in the intimate mixing between polymer donors and PCBM acceptors, and on the development of the BHJ morphology is in general less understood. In this contribution, we show that ring substituents such as furan (F), thiophene (T) and selenophene (S)-incorporated into the side chains of PBDTTPD polymers-can induce significant and, of importance, very different morphological effects in BHJs with PCBM. A combination of experimental and theoretical (via density functional theory) characterizations sheds light on how varying the heteroatom of the ring substituents impacts (i) the preferred side-chain configurations and (ii) the ionization, electronic, and optical properties of the PBDTTPD polymers. In parallel, we find that the PBDT(X)TPD analogs (with X = F, T, or S) span a broad range of power conversion efficiencies (PCEs, 3-6.5%) in optimized devices with improved thin-film morphologies via the use of 1,8-diiodooctane (DIO), and discuss that persistent morphological impediments at the nanoscale can be at the origin of the spread in PCE across optimized PBDT(X)TPD-based devices. With their high VOC ∼1 V, PBDT(X)TPD polymers are promising candidates for use in the high-band gap cell of tandem solar cells. © 2014 American Chemical Society.

  13. Chemical shift effect predicting lymph node status in rectal cancer using high-resolution MR imaging with node-for-node matched histopathological validation

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Hongmei; Zhang, Chongda; Ye, Feng; Liu, Yuan; Zhou, Chunwu [Chinese Academy of Medical Sciences and Peking Union Medical College, Department of Diagnostic Radiology, National Cancer Center/Cancer Hospital, ChaoYang District, Beijing (China); Zheng, Zhaoxu [Chinese Academy of Medical Sciences and Peking Union Medical College, Department of Colorectal Oncology, National Cancer Center/Cancer Hospital, ChaoYang District, Beijing (China); Zou, Shuangmei [Chinese Academy of Medical Sciences and Peking Union Medical College, Department of Pathology, National Cancer Center/Cancer Hospital, ChaoYang District, Beijing (China)

    2017-09-15

    To evaluate the value of the chemical shift effect (CSE) as well as other criteria for the prediction of lymph node status. Twenty-nine patients who underwent radical surgery of rectal cancers were studied with pre- and postoperative specimen MRI. Lymph nodes were harvested from transverse whole-mount specimens and compared with in vivo and ex vivo images to obtain a precise slice-for-section match. Preoperative MR characteristics including CSE, as well as other predictors, were evaluated by two readers independently between benign and metastatic nodes. A total of 255 benign and 35 metastatic nodes were obtained; 71.4% and 69.4% of benign nodes were detected with regular CSE for two readers, whereas 80.0% and 74.3% of metastatic nodes with absence of CSE. The CSE rendered areas under the ROC curve (AUC) of 0.879 and 0.845 for predicting nodal status for two readers. The criteria of nodal location, border, signal intensity and minimum distance to the rectal wall were also useful but with AUCs (0.629-0.743) lower than those of CSE. CSE is a reliable predictor for differentiating benign from metastatic nodes. Additional criteria should be taken into account when it is difficult to determine the nodal status by using only a single predictor. (orig.)

  14. Scan time reduction in {sup 23}Na-Magnetic Resonance Imaging using the chemical shift imaging sequence. Evaluation of an iterative reconstruction method

    Energy Technology Data Exchange (ETDEWEB)

    Weingaertner, Sebastian; Konstandin, Simon; Schad, Lothar R. [Heidelberg Univ., Mannheim (Germany). Computer Assisted Clinical Medicine; Wetterling, Friedrich [Heidelberg Univ., Mannheim (Germany). Computer Assisted Clinical Medicine; Dublin Univ. (Ireland) Trinity Inst. of Neuroscience; Fatar, Marc [Heidelberg Univ., Mannheim (Germany). Dept. of Neurology; Neumaier-Probst, Eva [Heidelberg Univ., Mannheim (Germany). Dept. of Neuroradiology

    2015-07-01

    To evaluate potential scan time reduction in {sup 23}Na-Magnetic Resonance Imaging with the chemical shift imaging sequence (CSI) using undersampled data of high-quality datasets, reconstructed with an iterative constrained reconstruction, compared to reduced resolution or reduced signal-to-noise ratio. CSI {sup 23}Na-images were retrospectively undersampled and reconstructed with a constrained reconstruction scheme. The results were compared to conventional methods of scan time reduction. The constrained reconstruction scheme used a phase constraint and a finite object support, which was extracted from a spatially registered {sup 1}H-image acquired with a double-tuned coil. The methods were evaluated using numerical simulations, phantom images and in-vivo images of a healthy volunteer and a patient who suffered from cerebral ischemic stroke. The constrained reconstruction scheme showed improved image quality compared to a decreased number of averages, images with decreased resolution or circular undersampling with weighted averaging for any undersampling factor. Brain images of a stroke patient, which were reconstructed from three-fold undersampled k-space data, resulted in only minor differences from the original image (normalized root means square error < 12%) and an almost identical delineation of the stroke region (mismatch < 6%). The acquisition of undersampled {sup 23}Na-CSI images enables up to three-fold scan time reduction with improved image quality compared to conventional methods of scan time saving.

  15. Flow-suppressed hyperpolarized 13 C chemical shift imaging using velocity-optimized bipolar gradient in mouse liver tumors at 9.4 T.

    Science.gov (United States)

    Lee, Hansol; Lee, Joonsung; Joe, Eunhae; Yang, Seungwook; Song, Jae Eun; Choi, Young-Suk; Wang, Eunkyung; Joo, Chan Gyu; Song, Ho-Taek; Kim, Dong-Hyun

    2017-11-01

    To optimize and investigate the influence of bipolar gradients for flow suppression in metabolic quantification of hyperpolarized 13 C chemical shift imaging (CSI) of mouse liver at 9.4 T. The trade-off between the amount of flow suppression using bipolar gradients and T2* effect from static spins was simulated. A free induction decay CSI sequence with alternations between the flow-suppressed and non-flow-suppressed acquisitions for each repetition time was developed and was applied to liver tumor-bearing mice via injection of hyperpolarized [1-13 C] pyruvate. The in vivo results from flow suppression using the velocity-optimized bipolar gradient were comparable with the simulation results. The vascular signal was adequately suppressed and signal loss in stationary tissue was minimized. Application of the velocity-optimized bipolar gradient to tumor-bearing mice showed reduction in the vessel-derived pyruvate signal contamination, and the average lactate/pyruvate ratio increased by 0.095 (P flow suppression. Optimization of the bipolar gradient is essential because of the short 13 C T2* and high signal in venous flow in the mouse liver. The proposed velocity-optimized bipolar gradient can suppress the vascular signal, minimizing T2*-related signal loss in stationary tissues at 9.4 T. Magn Reson Med 78:1674-1682, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

  16. ¹³C solid-state NMR analysis of the most common pharmaceutical excipients used in solid drug formulations, Part I: Chemical shifts assignment.

    Science.gov (United States)

    Pisklak, Dariusz Maciej; Zielińska-Pisklak, Monika Agnieszka; Szeleszczuk, Łukasz; Wawer, Iwona

    2016-04-15

    Solid-state NMR is an excellent and useful method for analyzing solid-state forms of drugs. In the (13)C CP/MAS NMR spectra of the solid dosage forms many of the signals originate from the excipients and should be distinguished from those of active pharmaceutical ingredient (API). In this work the most common pharmaceutical excipients used in the solid drug formulations: anhydrous α-lactose, α-lactose monohydrate, mannitol, sucrose, sorbitol, sodium starch glycolate type A and B, starch of different origin, microcrystalline cellulose, hypromellose, ethylcellulose, methylcellulose, hydroxyethylcellulose, sodium alginate, magnesium stearate, sodium laurilsulfate and Kollidon(®) were analyzed. Their (13)C CP/MAS NMR spectra were recorded and the signals were assigned, employing the results (R(2): 0.948-0.998) of GIPAW calculations and theoretical chemical shifts. The (13)C ssNMR spectra for some of the studied excipients have not been published before while for the other signals in the spectra they were not properly assigned or the assignments were not correct. The results summarize and complement the data on the (13)C ssNMR analysis of the most common pharmaceutical excipients and are essential for further NMR studies of API-excipient interactions in the pharmaceutical formulations. Copyright © 2016 Elsevier B.V. All rights reserved.

  17. In vivo application of sub-second spiral chemical shift imaging (CSI) to hyperpolarized 13C metabolic imaging: comparison with phase-encoded CSI.

    Science.gov (United States)

    Mayer, Dirk; Yen, Yi-Fen; Levin, Yakir S; Tropp, James; Pfefferbaum, Adolf; Hurd, Ralph E; Spielman, Daniel M

    2010-06-01

    A fast spiral chemical shift imaging (CSI) has been developed to address the challenge of the limited acquisition window in hyperpolarized (13)C metabolic imaging. The sequence exploits the sparsity of the spectra and prior knowledge of resonance frequencies to reduce the measurement time by undersampling the data in the spectral domain. As a consequence, multiple reconstructions are necessary for any given data set as only frequency components within a selected bandwidth are reconstructed "in-focus" while components outside that band are severely blurred ("spectral tomosynthesis"). A variable-flip-angle scheme was used for optimal use of the longitudinal magnetization. The sequence was applied to sub-second metabolic imaging of the rat in vivo after injection of hyperpolarized [1-(13)C]-pyruvate on a clinical 3T MR scanner. The comparison with conventional CSI based on phase encoding showed similar signal-to-noise ratio (SNR) and spatial resolution in metabolic maps for the substrate and its metabolic products lactate, alanine, and bicarbonate, despite a 50-fold reduction in scan time for the spiral CSI acquisition. The presented results demonstrate that dramatic reductions in scan time are feasible in hyperpolarized (13)C metabolic imaging without a penalty in SNR or spatial resolution. (c) 2010 Elsevier Inc. All rights reserved.

  18. Characterization of mu s-ms dynamics of proteins using a combined analysis of N-15 NMR relaxation and chemical shift: Conformational exchange in plastocyanin induced by histidine protonations

    DEFF Research Database (Denmark)

    Hass, M. A. S.; Thuesen, Marianne Hallberg; Christensen, Hans Erik Mølager

    2004-01-01

    of the exchanging species can be determined independently of the relaxation rates. The applicability of the approach is demonstrated by a detailed analysis of the conformational exchange processes previously observed in the reduced form of the blue copper protein, plastocyanin from the cyanobacteria Anabaena...... shifts were obtained from a series of HSQC spectra recorded in the pH range from 4 to 8. From the R-1 and R-2 relaxation rates, the contribution, R-ex, to the transverse relaxation caused by the exchanges between the different allo-states of the protein were determined. Specifically, it is demonstrated......An approach is presented that allows a detailed, quantitative characterization of conformational exchange processes in proteins on the mus-ms time scale. The approach relies on a combined analysis of NMR relaxation rates and chemical shift changes and requires that the chemical shift...

  19. Substituent distribution within cross-linked and hydroxypropylated sweet potato starch and potato starch

    NARCIS (Netherlands)

    Zhao, J.; Schols, H.A.; Chen Zenghong,; Jin Zhengyu,; Buwalda, P.L.; Gruppen, H.

    2012-01-01

    Revealing the substituents distribution within starch can help to understand the changes of starch properties after modification. The distribution of substituents over cross-linked and hydroxypropylated sweet potato starch was investigated and compared with modified potato starch. The starches were

  20. Accurate ab initio calculations of O-HO and O-H(-)O proton chemical shifts: towards elucidation of the nature of the hydrogen bond and prediction of hydrogen bond distances.

    Science.gov (United States)

    Siskos, Michael G; Tzakos, Andreas G; Gerothanassis, Ioannis P

    2015-09-07

    The inability to determine precisely the location of labile protons in X-ray molecular structures has been a key barrier to progress in many areas of molecular sciences. We report an approach for predicting hydrogen bond distances beyond the limits of X-ray crystallography based on accurate ab initio calculations of O-HO proton chemical shifts, using a combination of DFT and contactor-like polarizable continuum model (PCM). Very good linear correlation between experimental and computed (at the GIAO/B3LYP/6-311++G(2d,p) level of theory) chemical shifts were obtained with a large set of 43 compounds in CHCl3 exhibiting intramolecular O-HO and intermolecular and intramolecular ionic O-H(-)O hydrogen bonds. The calculated OH chemical shifts exhibit a strong linear dependence on the computed (O)HO hydrogen bond length, in the region of 1.24 to 1.85 Å, of -19.8 ppm Å(-1) and -20.49 ppm Å(-1) with optimization of the structures at the M06-2X/6-31+G(d) and B3LYP/6-31+G(d) level of theory, respectively. A Natural Bond Orbitals (NBO) analysis demonstrates a very good linear correlation between the calculated (1)H chemical shifts and (i) the second-order perturbation stabilization energies, corresponding to charge transfer between the oxygen lone pairs and σ antibonding orbital and (ii) Wiberg bond order of the O-HO and O-H(-)O hydrogen bond. Accurate ab initio calculations of O-HO and O-H(-)O (1)H chemical shifts can provide improved structural and electronic description of hydrogen bonding and a highly accurate measure of distances of short and strong hydrogen bonds.

  1. Substituent effects on zinc phthalocyanine derivatives: a theoretical calculation and screening of sensitizer candidates for dye-sensitized solar cells.

    Science.gov (United States)

    Yang, Linlin; Guo, Lianshun; Chen, Qianqian; Sun, Huafei; Yan, Hui; Zeng, Qinghua; Zhang, Xianxi; Pan, Xu; Dai, Songyuan

    2012-09-01

    A series of unsymmetrical phthalocyanine sensitizer candidates with different donor and acceptor substituents, namely ZnPcBPh, ZnPcBOPh, ZnPcBtBu, ZnPcBN(Ph)₂, ZnPcBNHPh, ZnPcBNH₂, ZnPcBNHCH₃ and ZnPcBN(CH₃)₂, were designed and calculated using density functional theory (DFT) and time-dependent DFT calculations. The molecular orbital energy levels, the molecular orbital spatial distributions and the electronic absorption spectra of the ZnPcB series molecules were compared with those of TT7 and TT8 to reveal the substituent effects of different donor and acceptor groups on the phthalocyanine compounds and select good sesitizer candidates. The results show that some of these compounds have considerably smaller orbital energy gaps, red-shifted absorption bands and better charge-separated states, causing them to absorb photons in the lower energy region. Several new absorption bands emerge in the 400-600 nm region, which makes it possible for them to become panchromatic sensitizers. This characteristic is superior to the phthalocyanine sensitizers reported previously, including the current record holder, PcS6. The sensitizer candidates screened in the current work are very promising for providing good performance and might even challenge the photon-to-electricity conversion efficiency record of 4.6% for phthalocyanine sensitizers. Copyright © 2012 Elsevier Inc. All rights reserved.

  2. The use of chemical shift temperature gradients to establish the paramagnetic susceptibility tensor orientation: Implication for structure determination/refinement in paramagnetic metalloproteins

    Energy Technology Data Exchange (ETDEWEB)

    Xia Zhicheng; Nguyen, Bao D.; La Mar, Gerd N. [University of California, Department of Chemistry (United States)

    2000-06-15

    The use of dipolar shifts as important constraints in refining molecular structure of paramagnetic metalloproteins by solution NMR is now well established. A crucial initial step in this procedure is the determination of the orientation of the anisotropic paramagnetic susceptibility tensor in the molecular frame which is generated interactively with the structure refinement. The use of dipolar shifts as constraints demands knowledge of the diamagnetic shift, which, however, is very often not directly and easily accessible. We demonstrate that temperature gradients of dipolar shifts can serve as alternative constraints for determining the orientation of the magnetic axes, thereby eliminating the need to estimate the diamagnetic shifts. This approach is tested on low-spin, ferric sperm whale cyanometmyoglobin by determining the orientation, anisotropies and anisotropy temperature gradients by the alternate routes of using dipolar shifts and dipolar shift gradients as constraints. The alternate routes ultimately lead to very similar orientation of the magnetic axes, magnetic anisotropies and magnetic anisotropy temperature gradients which, by inference, would lead to an equally valid description of the molecular structure. It is expected that the use of the dipolar shift temperature gradients, rather than the dipolar shifts directly, as constraints will provide an accurate shortcut in a solution structure determination of a paramagnetic metalloprotein.

  3. An optimized method for NMR-based plant seed metabolomic analysis with maximized polar metabolite extraction efficiency, signal-to-noise ratio, and chemical shift consistency.

    Science.gov (United States)

    Wu, Xiangyu; Li, Ning; Li, Hongde; Tang, Huiru

    2014-04-07

    Plant metabolomic analysis has become an essential part of functional genomics and systems biology and requires effective extraction of both primary and secondary metabolites from plant cells. To establish an optimized extraction method for the NMR-based analysis, we used the seeds of mungbean (Vigna radiata cv. Elü no. 1) as a model and systematically investigated the dependence of the metabolite composition in plant extracts on various extraction parameters including cell-breaking methods, extraction solvents, number of extraction repeats, tissue-to-solvent ratio, and extract-to-buffer ratio (for final NMR analysis). We also compared two NMR approaches for quantitative metabolomic analysis from completely relaxed spectra directly and from partially relaxed spectra calculated with T1. By maximizing the extraction efficiency and signal-to-noise ratio but minimizing inter-sample chemical-shift variations and metabolite degradations, we established a parameter-optimized protocol for NMR-based plant seed metabolomic analysis. We concluded that aqueous methanol was the best extraction solvent with an optimal tissue-to-solvent ratio of about 1 : 10-1 : 15 (mg per μL). The combination of tissuelyser homogenization with ultrasonication was the choice of cell-breaking method with three repeated extractions being necessary. For NMR analysis, the optimal extract-to-solvent was around 5-8 mg mL(-1) and completely relaxed spectra were ideal for intrinsically quantitative metabolomic analysis although partially relaxed spectra were employable for comparative metabolomics. This optimized method will offer ensured data quality for high-throughput and reliable plant metabolomics studies.

  4. CHEMICALS

    CERN Multimedia

    Medical Service

    2002-01-01

    It is reminded that all persons who use chemicals must inform CERN's Chemistry Service (TIS-GS-GC) and the CERN Medical Service (TIS-ME). Information concerning their toxicity or other hazards as well as the necessary individual and collective protection measures will be provided by these two services. Users must be in possession of a material safety data sheet (MSDS) for each chemical used. These can be obtained by one of several means : the manufacturer of the chemical (legally obliged to supply an MSDS for each chemical delivered) ; CERN's Chemistry Service of the General Safety Group of TIS ; for chemicals and gases available in the CERN Stores the MSDS has been made available via EDH either in pdf format or else via a link to the supplier's web site. Training courses in chemical safety are available for registration via HR-TD. CERN Medical Service : TIS-ME :73186 or service.medical@cern.ch Chemistry Service : TIS-GS-GC : 78546

  5. Studies on a vinyl ruthenium-modified squaraine dye: multiple visible/near-infrared absorbance switching through dye- and substituent-based redox processes.

    Science.gov (United States)

    Chen, Jing; Winter, Rainer F

    2012-08-20

    The bis(vinyl ruthenium)-modified squaraine dye 1 was synthesized by treatment of [RuHCl(CO)(PiPr(3) )(2) ] with bis(ethynyl)-substituted squaraine 8. Spectroscopic and electrochemical measurements on 1 and its organic precursors 6-8 were performed to study the effect of the vinyl ruthenium "substituents," particularly with respect to (poly)electrochromism. Attachment of the vinyl ruthenium moieties endows metal-organic squaraine 1 with two additional oxidation waves and lowers the first two oxidation potentials by approximately 300 mV with respect to its organic precursors. Squaraines 6, 7, 8, and 1 strongly absorb at 648, 663, 656, or 709 nm. Although organic dyes 6, 7, and 8 fluoresce, no room-temperature emission is observed for 1. The radical cations and anions of 6, 7, 8, and 1 as well as the doubly oxidized dications have been studied by IR and UV/Vis/NIR spectroelectrochemistry, and the -/0/+/2+ redox sequences were found to be reversible in each case. Our results indicate that the 1(2-/-/0/+/2+) redox system constitutes a polyelectrochromic switch in which absorption in the visible or the near-infrared range is reversibly turned off or shifted deep into the NIR. They also show that radical cation 1(.+) is an intrinsically delocalized system with only little contribution from the outer vinyl ruthenium tags to the oxidation process. Dication 1(2+) constitutes a class-II mixed-valent system with two electronically different vinyl ruthenium moieties and has an open-shell singlet electronic ground-state structure. ESR and NMR spectra of chemically prepared 1(.+) and 1(2+) corroborate these results. It has also emerged that reduction involves an orbital that is strongly delocalized across the entire squaraine π system and strongly affects the peripheral vinyl ruthenium sites. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Tough Shift

    DEFF Research Database (Denmark)

    Brewer, Robert S.; Verdezoto, Nervo; Holst, Thomas

    2015-01-01

    in a student dormitory and found that players did not shift their electricity use, because they were unwilling to change their schedules and found it easier to focus on reducing electricity use. Based on our findings, we discuss the implications for encouraging shifting, and also the challenges of integrating......Modern electrical grids are increasingly reliant on generation from renewable sources that can vary from hour to hour. This variability has led to the desire to shift the times of the day when electricity is consumed to better match generation. One way to achieve these shifts is by encouraging...... people to change their behavior at home. Leveraging prior research on encouraging reductions in residential energy use through game play, we introduce ShareBuddy: a casual mobile game intended to encourage players not only to reduce, but also to shift their electricity use. We conducted two field studies...

  7. Origin of the chemical shift in X-ray absorption near-edge spectroscopy at the Mn K-Edge in manganese oxide compounds

    NARCIS (Netherlands)

    de Vries, AH; Hozoi, L.; Broer, R.

    2003-01-01

    The absorption edge in Mn K-edge X-ray absorption spectra of manganese oxide compounds shows a shift of several electronvolts in going from MnO through LaMnO3 to CaMnO3. On the other hand, in X-ray photoelectron spectra much smaller shifts are observed. To identify the mechanisms that cause the

  8. Utility of chemical-shift MR imaging in detecting small amounts of fat in extrahepatic abdominal tumors; Utilidad de la tecnica de desplazamiento quimico den RM para la deteccion de pequenas cantidades de grasa en tumores abdominales extrahepaticos

    Energy Technology Data Exchange (ETDEWEB)

    Martin, J.; Falco, J.; Puig, J.; Donoso, L. [Unidad de Diagnostico por Imagen de Alta Tecnologia (UDIAT). Sabadell (Spain)

    1999-07-01

    To determine the utility of the chemical shift technique in magnetic resonance imaging (MRI) to confirm small amounts of fat in extrahepatic intraabdominal tumours. 7 extrahepatic abdominal tumours that are suspected to have fat as seen in the axial computed tomography (TC) are analysed retrospectively. In order to confirm the fat content, the chemical displacement technique with gradient echo sequences (GE) in phase (P) and in opposite phase (OP) was used with MRI 1 T equipment. The tumours corresponded to renal angiomyolipoma (AML) (n=4), intraperitoneal liposarcoma (n=1), retroperitoneal liposarcoma (n=1) and intraabdominal extramedular hematopoiesis (n=1). To confirm the existence of fat in the tumours, we used a quantitative percentage variation parameter of the intensity of the signals (VIS) between the images in P and OP, according to the formula: IS{sub (}p)-IS({sub o}p)x100/IS{sub (}op), where IS is the intensity of the signal. The chemical shift technique showed fat in the seven tumours. Upon visual inspection, all the tumoral areas that were suspected to have fat showed a notable difference in the signal intensity, being hypointense in OP and hyperintense in P. In these areas the average VIS percentage was 170% while in the rest of the tumour the average VIS percentage was 3%. The chemical shift technique with RG sequences can be easily used in MRI equipment and allows us to confirm if a specific abdominal tumour has fat, even if there is only a small quantity. (Author) 13 refs.

  9. Synthesis and evaluation of changes induced by solvent and substituent in electronic absorption spectra of some azo disperse dyes.

    Science.gov (United States)

    Mohammadi, Asadollah; Yazdanbakhsh, Mohammad Reza; Farahnak, Lahya

    2012-04-01

    Five azo disperse dyes were prepared by diazotizing 4'-aminoacetophenone and p-anisidine and coupling with varies N-alkylated aromatic amines. Characterization of the dyes was carried out by using UV-vis, FTIR and 1H NMR spectroscopic techniques. The electronic absorption spectra of dyes are determined at room temperature in fifteen solvents with different polarities. The solvent dependent maximum absorption band shifts, were investigated using dielectric constant (ɛ), refractive index (n) and Kamlet-Taft polarity parameters (hydrogen bond donating ability (α), hydrogen bond accepting ability (β) and dipolarity/polarizability polarity scale (π*)). Acceptable agreement was found between the maximum absorption band of dyes and solvent polarity parameters especially with π*. The effect of substituents of coupler and/or diazo component on the color of dyes was investigated. The effects of acid and base on the visible absorption maxima of the dyes are also reported. Copyright © 2011 Elsevier B.V. All rights reserved.

  10. Theoretical investigation of conformational stabilities and 13C NMR chemical shifts of a seven-membered ring thiosugar, (3R,4R,5R,7S)-7-(hydroxymethyl)thiepane-3,4,5-triol

    Science.gov (United States)

    Tai, Chin-Kuen; Yeh, Pao-Ling; Wu, Yun-Sheng; Shih, Tzenge-Lien; Wang, Bo-Cheng

    2014-06-01

    DFT/B3LYP/6-311++G(d,p) calculations have been performed to obtain optimized structures for fourteen conformers of (3R,4R,5R,7S)-7-(hydroxymethyl)thiepane-3,4,5-triol. These conformers are considered as the twist-chair (TC) and twist-boat (TB) conformations. Among all conformers, the TCS5 and TCS6 conformers appear to be the most energetically stable since they contain an intramolecular hydrogen bond between hydroxyl group at C(8) and S atom. Boltzmann weighting factor analysis provides valuable information on the population of the fourteen conformers, including both the TC and TB conformations. The analysis results demonstrate that the TCS2, TCS5, and TCS6 conformers provide a major population contribution with Boltzamann weighting factors larger than 7% as compared to other conformers. For these conformers of (3R,4R,5R,7S)-7-(hydroxymethyl)thiepane-3,4,5-triol, the GIAO/HF, GIAO/DFT/OPBE, GIAO/DFT/B3LYP and GIAO/DFT/mPW1PW91 calculations with the 6-311++G(d,p), 6-311+G(2d,p), cc-pVDZ and cc-pVTZ basis sets were used to obtain their 13C NMR chemical shifts. The calculated 13C NMR chemical shifts of the TCS2, TCS5, and TCS6 conformers show a close correlation with experimental data, within 2.4-3.0 ppm of MAE values. The experimental 13C NMR chemical shifts represent a combination of contributions from all the conformers. In our investigation, the calculated 13C NMR chemical shifts of the mixture of (3R,4R,5R,7S)-7-(hydroxymethyl)thiepane-3,4,5-triol conformers display a remarkable MAE and RMS improvement comparing to those for each individual conformer. The most appropriate calculation method and basis set to evaluate the theoretical 13C NMR chemical shifts for these conformers are OPBE/6-311+G(2d,p). Calculated results represent that the conformation of (3R,4R,5R,7S)-7-(hydroxymethyl)thiepane-3,4,5-triol can be determined by the intramolecular hydrogen bond which could be simulated by the 13C NMR chemical shift calculation.

  11. Comparison of modified two-point dixon and chemical shift encoded MRI water-fat separation methods for fetal fat quantification.

    Science.gov (United States)

    Giza, Stephanie A; Miller, Michael R; Parthasarathy, Prasiddha; de Vrijer, Barbra; McKenzie, Charles A

    2018-01-10

    Fetal fat is indicative of the energy balance within the fetus, which may be disrupted in pregnancy complications such as fetal growth restriction, macrosomia, and gestational diabetes. Water-fat separated MRI is a technique sensitive to tissue lipid content, measured as fat fraction (FF), and can be used to accurately measure fat volumes. Modified two-point Dixon and chemical shift encoded MRI (CSE-MRI) are water-fat separated MRI techniques that could be applied to imaging of fetal fat. Modified two-point Dixon has biases present that are corrected in CSE-MRI which may contribute to differences in the fat measurements. To compare the measurement of fetal fat volume and FF by modified two-point Dixon and CSE-MRI. Cross-sectional study for comparison of two MRI pulse sequences. Twenty-one pregnant women with singleton pregnancies. 1.5T, modified two-point Dixon and CSE-MRI. Manual segmentation of total fetal fat volume and mean FF from modified 2-point Dixon and CSE-MRI FF images. Reliability was assessed by calculating the intraclass correlation coefficient (ICC). Agreement was assessed using a one-sample t-test on the fat measurements difference values (modified two-point Dixon - CSE-MRI). The difference scores were tested against a value of 0, which would indicate that the measurements were identical. The fat volume and FF measured by modified two-point Dixon and CSE-MRI had excellent reliability, demonstrated by ICCs of 0.93 (P < 0.001) and 0.90 (P < 0.001), respectively. They were not in agreement, with CSE-MRI giving mean fat volumes 180 mL greater and mean FF 3.0% smaller than modified two-point Dixon. The reliability between modified two-point Dixon and CSE-MRI indicates that either technique can be used to compare fetal fat measurements in different participants, but they are not in agreement possibly due to uncorrected biases in modified two-point Dixon. 4 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018. © 2018 International Society for Magnetic

  12. Overall structure and sugar dynamics of a DNA dodecamer from homo- and heteronuclear dipolar couplings and {sup 31}P chemical shift anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Wu Zhengrong; Delaglio, Frank [National Institute of Diabetes and Digestive and Kidney Diseases, Laboratory of Chemical Physics (United States); Tjandra, Nico [National Heart, Lung and Blood Institute, National Cancer Institute, National Institutes of Health, Laboratory of Biophysical Chemistry (United States); Zhurkin, Victor B. [National Cancer Institute, National Institutes of Health, Laboratory of Experimental and Computational Biology (United States); Bax, Ad [National Institute of Diabetes and Digestive and Kidney Diseases, Laboratory of Chemical Physics (United States)

    2003-08-15

    The solution structure of d(CGCGAATTCGCG){sub 2} has been determined on the basis of an exceptionally large set of residual dipolar couplings. In addition to the heteronuclear {sup 13}C-{sup 1}H and {sup 15}N-{sup 1}H and qualitative homonuclear {sup 1}H-{sup 1}H dipolar couplings, previously measured in bicelle medium, more than 300 quantitative {sup 1}H-{sup 1}H and 22 {sup 31}P-{sup 1}H dipolar restraints were obtained in liquid crystalline Pf1 medium, and 22 {sup 31}P chemical shift anisotropy restraints. High quality DNA structures can be obtained solely on the basis of these new restraints, and these structures are in close agreement with those calculated previously on the basis of {sup 13}C-{sup 1}H and {sup 15}N-{sup 1}H dipolar couplings. In the newly calculated structures, {sup 31}P-{sup 1}H dipolar and {sup 3}JsubH3{sup '}Psub couplings and {sup 31}P CSA data restrain the phosphodiester backbone torsion angles. The final structure represents a quite regular B-form helix with a modest bending of {approx}10 deg., which is essentially independent of whether or not electrostatic terms are used in the calculation. Combined, the number of homo- and heteronuclear dipolar couplings significantly exceeds the number of degrees of freedom in the system. Results indicate that the dipolar coupling data cannot be fit by a single structure, but are compatible with the presence of rapid equilibria between C2{sup '}-endo and C3{sup '}-endo deoxyribose puckers (sugar switching). The C2{sup '}-H2{sup '}/H2{sup ''} dipolar couplings in B-form DNA are particularly sensitive to sugar pucker and yield the largest discrepancies when fit to a single structure. To resolve these discrepancies, we suggest a simplified dipolar coupling analysis that yields N/S equilibria for the ribose sugar puckers, which are in good agreement with previous analyses of NMR J{sub HH} couplings, with a population of the minor C3{sup '}-endo form higher for

  13. Distribution of octenylsuccinic substituents in modified A and B polymorph starch granules.

    Science.gov (United States)

    Wang, Chan; He, Xiaowei; Huang, Qiang; Fu, Xiong; Luo, Faxing; Li, Lin

    2013-12-26

    The octenylsuccinic (OS) substituent distribution in octenylsuccinic anhydride (OSA)-modified normal maize and potato starches with different degrees of subsititution (DS) was studied using confocal laser scanning microscopy (CLSM) and surface gelatinization. The remaining non-gelatinized portions of starch granules after removal of surface-gelatinized starch (remaining granules) were studied with light microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy (FTIR), and the level of succinylation. Results showed that greater proportions of the OS groups were present at the periphery than at the core of the granules. However, the granular interior of OS maize starch has higher fluorescent intensity than that of OS potato starch, as shown by CLSM. The DS of OS maize starch degraded less than that of OS potato starch under the same degree of gelatinization. In addition, the characteristic peaks of the remaining OS maize granules in the FTIR were more protruding than that of the OS potato granules after 50% chemical surface gelatinization. The results implied that maize starch displayed much more homogeneous OSA reaction pattern when compared to potato starch. With the special architectures (pinholes and channels) of maize, it is easier to change the location of OS groups than with potato starch by changing reaction conditions or starch pretreatments.

  14. Influence of substituents on the nature of metal⋯π interaction and its cooperativity with halogen bond

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Meng; Cheng, Jianbo, E-mail: li70316@sohu.com, E-mail: liqingzhong1990@sina.com; Yang, Xin; Li, Wenzuo; Xiao, Bo; Li, Qingzhong, E-mail: li70316@sohu.com, E-mail: liqingzhong1990@sina.com [The Laboratory of Theoretical and Computational Chemistry, School of Chemistry and Chemical Engineering, Yantai University, Yantai 264005 (China)

    2015-08-07

    High-level quantum chemical calculations have been performed to investigate the influence of substituents on the metal—π interaction and its cooperative effect with halogen bond in C{sub 2}X{sub 4}⋯MCN⋯ClF (X = H, CN, CH{sub 3}; M = Cu, Ag, Au). The strong electron-withdrawing group CN weakens the metal—π covalent interaction, while the weak electron-withdrawing group CH{sub 3} strengthens it. The metal—π covalent interaction is dominated by electrostatic energy although the AuCN complex has approximately equal electrostatic and polarization contributions. However, the metal—π covalent interaction is governed by polarization energy due to the CN substitution. A cooperative effect is found for the halogen bond and metal—π interactions in C{sub 2}H{sub 4}⋯MCN⋯ClF, while a diminutive effect occurs in the triads by the CN substituent. Orbital interaction analysis indicates that the strong electron-withdrawing group CN causes the C=C group vary from a stronger donor orbital to a stronger acceptor orbital.

  15. Lactones 46. Synthesis, antifeedant and antibacterial activity of γ-lactones with a p-methoxyphenyl substituent.

    Science.gov (United States)

    Mazur, Marcelina; Skrobiszewski, Andrzej; Gładkowski, Witold; Podkowik, Magdalena; Bania, Jacek; Nawrot, Jan; Klejdysz, Tomasz; Wawrzeńczyk, Czesław

    2016-03-01

    Lactones are well known for their biological activity. Grosheimin and repin are potent deterrents against storage pests. The unsaturated lactones have exhibited a wide spectrum of antibacterial activity. In our study we focused on the synthesis and evaluation of the biological activity of anisaldehyde derivatives containing lactone function. Four new lactones were synthesized in one-step reductive dehalogenation or dehydrohalogenation reactions. These compounds, together with halolactones synthesized earlier, were tested for their antifeedant activity towards Sitophilus granaries, Trogoderma granarium and Tribolium confusum. The results of the tests showed that the highest activity, comparable with that of azadirachtin, towards all tested pests (total coefficient of deterrence 143.3-183.9) was observed for lactone with a vinyl substituent. The antibacterial activity of these compounds was also evaluated. The most potent lactone was active towards gram-positive bacteria strains. The results of biological tests showed that halogen atom removal significantly increased the antifeedant properties of γ-lactones with a p-methoxyphenyl substituent. Unsaturated lactones are most promising in the context of their possible industrial application as crop protection agents. Further structural modifications of lactones with aromatic rings are needed to find important structural factors increasing the antibacterial activity. © 2015 Society of Chemical Industry.

  16. Tuning Porphyrin Assembly and Electrochemical Catalytic Activity with Halogen Substituents.

    Science.gov (United States)

    Kawamoto, Teppei; Yoshimoto, Soichiro

    2015-10-27

    The adlayers of three metalloporphyrins, 5,10,15,20-tetrakis(4-methoxyphenyl)porphyrin cobalt(II) (CoTMePP), 5,10,15,20-tetrakis(4-bromophenyl)porphyrin cobalt(II) (CoTBrPP), and 5,10,15,20-tetrakis(4-iodophenyl)porphyrin cobalt(II) (CoTIPP), on Au(111) were investigated at the solid-liquid interface under electrochemical conditions. In situ scanning tunneling microscopy (STM) was employed to investigate the adlayer structures of CoTMePP, CoTBrPP, and CoTIPP in HClO4 solution. Highly ordered adlayers of the three metalloporphyrins were formed on the Au(111) electrode surface by simple immersion into benzene solutions containing each compound. The adlayer structure of the three cobalt porphyrin derivatives was influenced by the functional group on the phenyl moieties. In particular, a characteristic molecular assembly of CoTIPP molecules was found on Au(111) as a result of the I···I interactions between CoTIPP molecules. The adlattice constants increased in the order -OCH3 HClO4, whereas these adlayers were stable in the potential range from 0.90 to 0 V versus the reversible hydrogen electrode. A dependence upon the functional groups among the three CoTPP derivatives was clearly found in the adlattice constants and O2 reduction potentials, revealing that the two-dimensional (2D) molecular assembly and electrochemical activity for dioxygen reduction of the tetraphenylporphyrin derivatives can be tuned by introducing functional groups at the 4 positions of the phenyl moieties, especially iodine substituents.

  17. Influence of imide-substituents on the H-type aggregates of perylene diimides bearing cetyloxy side-chains at bay positions.

    Science.gov (United States)

    Raj, Michael Ruby; Margabandu, Rajamani; Mangalaraja, Ramalinga Viswanathan; Anandan, Sambandam

    2017-12-13

    A series of perylene-3,4:9,10-tetracarboxylic acid diimides (PDIs, namely TYR-PDI, AEP-PDI, CET-PDI, ANP-PDI and KOD-PDI), comprising long linear cetyloxy side-chains functionalized at the 1,7-bay positions and the different substituents (i.e., hydrophobic/hydrophilic segments) symmetrically linked at the two imide-positions of the perylene core were synthesized to investigate the influence of imide-substituent patterns on the aggregation behaviours of PDIs. The photophysical properties of these PDIs were studied by UV-Vis absorption, fluorescence and time-resolved photoluminescence spectroscopy. The differences in the photophysical properties of the PDIs indicate (i) blue-shifted and broadening absorption properties in both solution and thin-films, (ii) red-shifted and broadening fluorescence behavior at their emission maximum in solution, however, blue-shifted fluorescence behavior in thin-films, and (iii) obviously longer fluorescence life-times corresponding to the existence of rotationally displaced H-type aggregates. The formation of short-range ordered rod-like microstructures through face-to-face alignment of columnar rectangular H-type PDI aggregates was rationalized by scanning electron microscopy. The X-ray diffraction study revealed that the formation of well-defined columnar rectangular (Colrp) H-type PDI aggregates indicated a nearly constant intracolumnar stacking distance of ∼3.9 Å for all PDIs. All of these findings were consistent with the formation of hydrophobic/hydrophilic interactions between the imide-substituents in addition to the strong hydrophobic π-π stacking interactions between the conjugated perylene cores, which were enforced in the H-type PDI aggregates that spontaneously self-organized into Colrp structures.

  18. Conformational analysis of a seven-membered ring azasugar, (3R,4R,6S)-trihydroxyazepane: Comparison of GIAO calculation and experimental NMR spectra on 13C chemical shifts

    Science.gov (United States)

    Yeh, Pao-Ling; Tai, Chin-Kuen; Shih, Tzenge-Lien; Hsiao, Hui-Ling; Wang, Bo-Cheng

    2012-06-01

    DFT/B3LYP/6-311++G(d,p) calculation of the relative stable conformations of (3R,4R,6S)-trihydroxyazepane are presented. The GIAO/DFT/OPBE, GIAO/DFT/B3LYP and GIAO/HF single point calculations with 6-311++G(d,p), 6-311+G(2d,p), cc-pVDZ and cc-pVTZ basis sets of (3R,4R,6S)-trihydroxyazepane were conducted to generate their 13C NMR chemical shifts. According to calculation results, 14 (3R,4R,6S)-trihydroxyazepane with optimized structure were generated. There were three conformers which contain the intramolecular hydrogen bonding exhibit a lowest electronic energies and TCN1(eq) was the most stable conformer than others. Boltzmann weighting factor analysis exhibits that TCN1(eq), TCN3(eq) and TCN5(eq) dominate a major contribution among the 14 conformers. The individual calculated NMR results of TCN1(eq), TCN3(eq) and TCN5(eq) represents a quite close correlation with experimental data. Moreover, the experimental 13C NMR chemical shifts gave only the average contribution of all conformers. In our investigation, the calculated 13C NMR chemical shifts of mixture (3R,4R,6S)-trihydroxyazepane exhibit a good agreement with the experimental NMR data. Calculated NMR results of mixture (3R,4R,6S)-trihydroxyazepane conformers display a remarkable MAE and RMS improvement over that of each individual conformer. A good calculation method and basis set choice to evaluate the theoretical chemical shifts for these conformers is HF/cc-pVTZ.

  19. The '2+1' construction of homooxacalix[3]arenes possessing different substituents on their upper rims.

    Science.gov (United States)

    Tsubaki, K; Mukoyoshi, K; Otsubo, T; Fuji, K

    2000-06-01

    Several homooxacalix[3]arenes possessing different substituents on their upper rims were synthesized in yields of 7-20% by a condensation reaction between the p-substituted-phenol dimer and monomer under acidic high-dilution conditions.

  20. The investigation of substituent effects on the fragmentation pathways of pentacoordinated phenoxyspirophosphoranes by ESI-MSn.

    Science.gov (United States)

    Cui, Xiaoyan; Sun, Can; Zhao, Pei; Wang, Yanyan; Guo, Yanchun; Zhao, Yufen; Cao, Shuxia

    2018-01-16

    The fragmentation pathways of pentacoordinated phenoxyspirophosphoranes were investigated in the positive mode by electrospray ionization multistage mass spectrometry (ESI-MSn ). The results demonstrate that the sodium adducts of the title compounds undergo two competitive fragmentation pathways, and the fragmentation patterns are heavily dependent on the various substituent patterns at the phenolic group. An electron-withdrawing substituent at the ortho-position always results in the removal of a corresponding phenol analogue, while cleavage by spiroring opening becomes the predominant fragmentation pathway if an electron-donating substituent is at the phenolic group. The substituent effects on the competitive fragmentation pathways were further elucidated by theoretical calculations, single crystal structure analysis and high-resolution mass spectrometry. The results contribute to the understanding of the gas-phase fragmentation reactions and the structure identification of spirophosphorane analogues by ESI-MSn . This article is protected by copyright. All rights reserved.

  1. Chemically modified field effect transistors with nitrite or fluoride selectivity

    NARCIS (Netherlands)

    Antonisse, M.M.G.; Ruel, Bianca H.M.; Engbersen, Johannes F.J.; Reinhoudt, David

    1998-01-01

    Polysiloxanes with different types of polar substituents are excellent membrane materials for nitrite and fluoride selective chemically modified field effect transistors (CHEMFETs). Nitrite selectivity has been introduced by incorporation of a cobalt porphyrin into the membrane; fluoride selectivity

  2. Reaction pathways and free energy profiles for spontaneous hydrolysis of urea and tetramethylurea: Unexpected substituent effects

    Science.gov (United States)

    Yao, Min; Tu, Wenlong; Chen, Xi; Zhan, Chang-Guo

    2013-01-01

    It has been difficult to directly measure the spontaneous hydrolysis rate of urea and, thus, 1,1,3,3-tetramethylurea (Me4U) was used as a model to determine the “experimental” rate constant for urea hydrolysis. The use of Me4U was based on an assumption that the rate of urea hydrolysis should be 2.8 times that of Me4U hydrolysis because the rate of acetamide hydrolysis is 2.8 times that of N,N-dimethyl-acetamide hydrolysis. The present first-principles electronic-structure calculations on the competing non-enzymatic hydrolysis pathways have demonstrated that the dominant pathway is the neutral hydrolysis via the CN addition for both urea (when pHhydrolysis of amides where alkaline hydrolysis is dominant. Based on the computational data, the substituent shift of free energy barrier calculated for the neutral hydrolysis is remarkably different from that for the alkaline hydrolysis, and the rate constant for the urea hydrolysis should be ~1.3×109-fold lower than that (4.2×10−12 s−1) measured for the Me4U hydrolysis. As a result, the rate enhancement and catalytic proficiency of urease should be 1.2×1025 and 3×1027 M−1, respectively, suggesting that urease surpasses proteases and all other enzymes in its power to enhance the rate of reaction. All of the computational results are consistent with available experimental data for Me4U, suggesting that the computational prediction for urea is reliable. PMID:24097048

  3. {sup 13}C chemical shift anisotropies for carbonate ions in cement minerals and the use of {sup 13}C, {sup 27}Al and {sup 29}Si MAS NMR in studies of Portland cement including limestone additions

    Energy Technology Data Exchange (ETDEWEB)

    Sevelsted, Tine F. [Instrument Centre for Solid-State NMR Spectroscopy, Department of Chemistry and Interdisciplinary Nanoscience Center (iNANO), Aarhus University, DK-8000 Aarhus C (Denmark); Herfort, Duncan [Aalborg Portland A/S,Cementir Holding S.p.A., DK-9100 Aalborg (Denmark); Skibsted, Jørgen, E-mail: jskib@chem.au.dk [Instrument Centre for Solid-State NMR Spectroscopy, Department of Chemistry and Interdisciplinary Nanoscience Center (iNANO), Aarhus University, DK-8000 Aarhus C (Denmark)

    2013-10-15

    {sup 13}C isotropic chemical shifts and chemical shift anisotropy parameters have been determined for a number of inorganic carbonates relevant in cement chemistry from slow-speed {sup 13}C MAS or {sup 13}C({sup 1}H) CP/MAS NMR spectra (9.4 T or 14.1 T) for {sup 13}C in natural abundance. The variation in the {sup 13}C chemical shift parameters is relatively small, raising some doubts that different carbonate species in Portland cement-based materials may not be sufficiently resolved in {sup 13}C MAS NMR spectra. However, it is shown that by combining {sup 13}C MAS and {sup 13}C({sup 1}H) CP/MAS NMR carbonate anions in anhydrous and hydrated phases can be distinguished, thereby providing valuable information about the reactivity of limestone in cement blends. This is illustrated for three cement pastes prepared from an ordinary Portland cement, including 0, 16, and 25 wt.% limestone, and following the hydration for up to one year. For these blends {sup 29}Si MAS NMR reveals that the limestone filler accelerates the hydration for alite and also results in a smaller fraction of tetrahedrally coordinated Al incorporated in the C-S-H phase. The latter result is more clearly observed in {sup 27}Al MAS NMR spectra of the cement–limestone blends and suggests that dissolved aluminate species in the cement–limestone blends readily react with carbonate ions from the limestone filler, forming calcium monocarboaluminate hydrate. -- Highlights: •{sup 13}C chemical shift anisotropies for inorganic carbonates from {sup 13}C MAS NMR. •Narrow {sup 13}C NMR chemical shift range (163–171 ppm) for inorganic carbonates. •Anhydrous and hydrated carbonate species by {sup 13}C MAS and {sup 13}C({sup 1}H) CP/MAS NMR. •Limestone accelerates the hydration for alite in Portland – limestone cements. •Limestone reduces the amount of aluminium incorporated in the C-S-H phase.

  4. Stereochemistry of nucleophilic substitution reactions depending upon substituent: evidence for electrostatic stabilization of pseudoaxial conformers of oxocarbenium ions by heteroatom substituents.

    Science.gov (United States)

    Ayala, Leticia; Lucero, Claudia G; Romero, Jan Antoinette C; Tabacco, Sarah A; Woerpel, K A

    2003-12-17

    Lewis acid-mediated nucleophilic substitution reactions of substituted tetrahydropyran acetates reveal that the conformational preferences of six-membered-ring cations depend significantly upon the electronic nature of the substituent. Nucleophilic substitutions of C-3 and C-4 alkyl-substituted tetrahydropyran acetates proceeded via pseudoequatorially substituted oxocarbenium ions, as would be expected by consideration of steric effects. Substitutions of C-3 and C-4 alkoxy-substituted tetrahydropyran acetates, however, proceeded via pseudoaxially oriented oxocarbenium ions. The unusual selectivities controlled by the alkoxy groups were demonstrated for a range of other heteroatom substituents, including nitrogen, fluorine, chlorine, and bromine. It is believed that the pseudoaxial conformation is preferred in the ground state of the cation because of an electrostatic attraction between the cationic carbon center of the oxocarbenium ion and the heteroatom substituent. This analysis is supported by the observation that selectivity diminishes down the halogen series, which is inconsistent with electron donation as might be expected during anchimeric assistance. The C-2 heteroatom-substituted systems gave moderately high 1,2-cis selectivity, while small alkyl substituents showed no selectivity. Only in the case of the tert-butyl group at C-2 was high 1,2-trans selectivity observed. These studies reinforce the idea that ground-state conformational effects need to be considered along with steric approach considerations.

  5. Resonance Raman Intensities Demonstrate that C5 Substituents Affect the Initial Excited-State Structural Dynamics of Uracil More than C6 Substituents.

    Science.gov (United States)

    Teimoory, Faranak; Loppnow, Glen R

    2016-05-04

    Resonance Raman derived initial excited-state structural dynamics provide insight into the photochemical mechanisms of pyrimidine nucleobases, in which the photochemistry appears to be dictated by the C5 and C6 substituents. The absorption and resonance Raman spectra and excitation profiles of 5,6-dideuterouracil were measured to further test this photochemical dependence on the C5 and C6 substituents. The resulting set of excited-state reorganization energies of the observed internal coordinates were calculated and compared to those of other 5- and 6-substituted uracils. The results show that the initial excited-state dynamics along the C5C6 stretch responds to changes in mass at C5 and C6 in the same manner but that the in-plane bends at C5 and C6 are more sensitive to substituents at the C5 position than at the C6 position. In addition, the presence of two deuterium substituents at C5 and C6 decreases the initial excited-state structural dynamics along these in-plane bends, in contrast to what is observed in the presence of two CH3 groups on C5 and C6. The results are discussed in the context of DNA nucleobase photochemistry. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Shifting Boundaries

    DEFF Research Database (Denmark)

    Blaagaard, Bolette

    2013-01-01

    within journalistic practice of keeping up the idea as well as the practice of journalistic objectivity. Working on from Schudson (2003), Schudson and Anderson (2009) and Tumber and Prentoulis’ (2003) analyses of journalistic professionalism, the article develops the idea of journalistic objectivity...... further on the question of how the students address and react to this paradigmatic shift....

  7. Ultrafast fluorescence study of the effect of carboxylic and carboxylate substituents on the excited state properties of anthracene

    Energy Technology Data Exchange (ETDEWEB)

    Rodríguez-Córdoba, William [Escuela de Física, Universidad Nacional de Colombia Sede Medellín, A.A. 3840, Medellín (Colombia); Noria-Moreno, Raquel; Navarro, Pedro [Universidad Nacional Autónoma de México, Instituto de Química, Ciudad Universitaria, 04510 México, DF (Mexico); Peon, Jorge, E-mail: jpeon@unam.mx [Universidad Nacional Autónoma de México, Instituto de Química, Ciudad Universitaria, 04510 México, DF (Mexico)

    2014-01-15

    With the objective of understanding the interaction between carboxylic substituents and aromatic systems in electronically excited states, we have studied the photophysics of anthracene-9-carboxylic acid and its conjugate base through spectroscopic and computational approaches. We measured the emission spectrum evolution with femtosecond resolution observing that the formation of the relaxed fluorescent state of the acid corresponds to a red shifting of the emission which takes place within the first picosecond after excitation, a time-scale defined by the solvent response (acetone). For the case of the anthracene-9-carboxylate system, the spectral evolution is practically absent, indicating a lack of relaxation of the substituent orientation in the S{sub 1} state. Computational work at the time-dependent density functional theory level, considering the novel state-specific formalism, indicates that for anthracene-9-carboxylic acid, the first electronically excited state evolves from a structure with a nearly 60° dihedral angle between the carboxylic and aromatic systems, to a relaxed structure with a nearly 30° angle. On the other hand, the calculations show that for the salt, the carboxylate group remains decoupled from the aromatic system both in the ground and fluorescent state, remaining in both states at nearly 90°. Our results elucidate that the emission spectra of the acid and conjugate base are defined by the degree of interaction between the carboxylic (or carboxylate) group and the aromatic system. Such interactions are drastically different from the formal charge present in the carboxylate ion. -- Highlights: • Understanding of the interaction between carboxylic substituents and aromatic systems in electronically excited states. • Elucidation of the excited state dynamics of 9-ACA and its conjugated base in acetone solutions. • The spectral evolution time-scale of the aromatic acid and its salt depends on the solvation dynamics. • The

  8. π-face donation from the aromatic N-substituent of N-heterocyclic carbene ligands to metal and its role in catalysis

    KAUST Repository

    Credendino, Raffaele

    2012-05-16

    In this work, we calculate the redox potential in a series of Ir and Ru complexes bearing a N-heterocyclic carbene (NHC) ligand presenting different Y groups in the para position of the aromatic N-substituent. The calculated redox potentials excellently correlate with the experimental ΔE 1/2 potentials, offering a handle to rationalize the experimental findings. Analysis of the HOMO of the complexes before oxidation suggests that electron-donating Y groups destabilize the metal centered HOMO. Energy decomposition of the metal-NHC interaction indicates that electron-donating Y groups reinforce this interaction in the oxidized complexes. Analysis of the electron density in the reduced and oxidized states of representative complexes indicates a clear donation from the C ipso of the N-substituents to an empty d orbital on the metal. In case of the Ru complexes, this mechanism involves the Ru-alkylidene moiety. All of these results suggest that electron-donating Y groups render the aromatic N-substituent able to donate more density to electron-deficient metals through the C ipso atom. This conclusion suggests that electron-donating Y groups could stabilize higher oxidation states during catalysis. To test this hypothesis, we investigated the effect of differently donating Y groups in model reactions of Ru-catalyzed olefin metathesis and Pd-catalyzed C-C cross-coupling. Consistent with the experimental results, calculations indicate an easier reaction pathway if the N-substituent of the NHC ligand presents an electron-donating Y group. © 2012 American Chemical Society.

  9. Superoxide radical-mediated photocatalytic oxidation of phenolic compounds over Ag{sup +}/TiO{sub 2}: Influence of electron donating and withdrawing substituents

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Jiadong [National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology, Beijing Engineering Research Center of Process Pollution Control, Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Xie, Yongbing, E-mail: ybxie@ipe.ac.cn [National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology, Beijing Engineering Research Center of Process Pollution Control, Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190 (China); Han, Qingzhen [State Key Laboratory of Multi-phase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190 (China); Cao, Hongbin [National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology, Beijing Engineering Research Center of Process Pollution Control, Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190 (China); Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300072 (China); Wang, Yujiao [Department of Chemical and Biomedical Engineering, University of Science and Technology Beijing (China); Nawaz, Faheem; Duan, Feng [National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology, Beijing Engineering Research Center of Process Pollution Control, Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190 (China); University of Chinese Academy of Sciences, Beijing 100049 (China)

    2016-03-05

    Highlights: • A weak EWG benefited photocatalytic oxidation of phenols the most. • Phenolic compounds were dominantly oxidized by ·O{sub 2}{sup −}, rather than ·OH, {sup 1}O{sub 2} or h{sup +}. • ·O{sub 2}{sup −} preferred to nucleophilically attack EDG substituted phenols. • ·O{sub 2}{sup −} more likely electrophilically attacked EWG substituted phenols. • ·O{sub 2}{sup −} simultaneously nucleophilically and electrophilically assaulted p-chlorophenol. - Abstract: A comparative study was constructed to correlate the electronic property of the substituents with the degradation rates of phenolic compounds and their oxidation pathways under UV with Ag{sup +}/TiO{sub 2} suspensions. It was verified that a weak electron withdrawing substituent benefited photocatalytic oxidation the most, while an adverse impact appeared when a substituent was present with stronger electron donating or withdrawing ability. The addition of p-benzoquinone dramatically blocked the degradation, confirming superoxide radicals (·O{sub 2}{sup −}) as the dominant photooxidant, rather than hydroxyl radicals, singlet oxygen or positive holes, which was also independent of the substituent. Hammett relationship was established based on pseudo-first-order reaction kinetics, and it revealed two disparate reaction patterns between ·O{sub 2}{sup −} and phenolic compounds, which was further verified by the quantum chemical computation on the frontier molecular orbitals and Mulliken charge distributions of ·O{sub 2}{sup −} and phenolic compounds. It was found that electron donating group (EDG) substituted phenols were more likely nucleophilically attacked by ·O{sub 2}{sup −}, while ·O{sub 2}{sup −} preferred to electrophilically assault electron withdrawing group (EWG) substituted phenols. Exceptionally, electrophilic and nucleophilic attack by ·O{sub 2}{sup −} could simultaneously occur in p-chlorophenol degradation, consequently leading to its highest rate

  10. van der Waals Schottky barriers as interface probes of the correlation between chemical potential shifts and charge density wave formation in 1 T -TiSe2 and 2 H -NbSe2

    Science.gov (United States)

    Li, Ang J.; Zhu, Xiaochen; Rhodes, Daniel; Samouce, Christopher C.; Balicas, Luis; Hebard, Arthur F.

    2017-09-01

    Layered transition-metal dichalcogenide (TMD) materials, i.e., 1 T -TiSe2 and 2 H -NbSe2 , harbor a second-order charge density wave (CDW) transition where phonons play a key role for the periodic modulations of conduction electron densities and associated lattice distortions. We systematically study the transport and capacitance characteristics over a wide temperature range of Schottky barriers formed by intimately contacting freshly exfoliated flakes of 1 T -TiSe2 and 2 H -NbSe2 to n -type GaAs semiconductor substrates. The extracted temperature-dependent parameters (zero-bias barrier height, ideality, and built-in potential) reflect changes at the TMD/GaAs interface induced by CDW formation for both TMD materials. The measured built-in potential reveals chemical-potential shifts relating to CDW formation. With decreasing temperature a peak in the chemical-potential shifts during CDW evolution indicates a competition between electron energy redistributions and a combination of lattice strain energies and Coulomb interactions. These modulations of chemical potential in CDW systems, such as 1 T -TiSe2 and 2 H -NbSe2 harboring second-order phase transitions, reflect a corresponding conversion from short-range to long-range order.

  11. Liquid Crystalline Epoxies with Lateral Substituents Showing a Low Dielectric Constant and High Thermal Conductivity

    Science.gov (United States)

    Guo, Huilong; Lu, Mangeng; Liang, Liyan; Wu, Kun; Ma, Dong; Xue, Wei

    2017-02-01

    In this work, liquid crystalline epoxies with lateral substituents were synthesized and cured with aromatic amines or anhydride. The liquid crystalline phase structure of liquid crystalline epoxies with lateral substituents was determined by polarized optical microscopy. The relationship between thermal conductivity and dielectric properties and liquid crystalline domain structure was discussed in the paper. The samples show high thermal conductivity up to 0.29 W/(m × K), due to the orientation of mesogenic units in epoxies. The sample's low dielectric constant of 2.29 is associated with the oriented mesogenic units and long nonpolar lateral substituents. This indicates a new way to obtain materials with high thermal conductivity and a low dielectric constant by introducing oriented mesogenic units into cross-linked epoxy systems. The water repellency is reflected in the contact angles of 92-98°, which are apparently higher than that of conventional epoxy systems. It was also found that the better toughness of liquid crystalline epoxies with lateral substituents was attributed to the existence of long flexible alkyl lateral substituents.

  12. Effect of carbonitrile and hexyloxy substituents on alternated copolymer of polythiophene-Performances in photovoltaic cells

    Energy Technology Data Exchange (ETDEWEB)

    Berson, Solenn [Institut Nanosciences et Cryogenie, Structures et Proprietes d' Architectures Moleculaires, CEA-INAC/SPrAM/LEMOH UMR 5819 CEA/CNRS/UJF, 17 rue des Martyrs 38054 Grenoble Cedex 09 (France); Institut National de l' Energie Solaire, INES-RDI - Laboratoire des Composants Solaires, CEA-DRT/LITEN/DTS/LCS, 50 avenue du Lac Leman BP 332, 73377 Le Bourget du Lac (France); Cecioni, Samy; Billon, Martial; Kervella, Yann [Institut Nanosciences et Cryogenie, Structures et Proprietes d' Architectures Moleculaires, CEA-INAC/SPrAM/LEMOH UMR 5819 CEA/CNRS/UJF, 17 rue des Martyrs 38054 Grenoble Cedex 09 (France); de Bettignies, Remi; Bailly, Severine; Guillerez, Stephane [Institut National de l' Energie Solaire, INES-RDI - Laboratoire des Composants Solaires, CEA-DRT/LITEN/DTS/LCS, 50 avenue du Lac Leman BP 332, 73377 Le Bourget du Lac (France)

    2010-05-15

    A novel series of regioregular bithiophene disubstituted with a carbonitrile group as electron acceptor and a hexyl or hexyloxy chain as electron donor, have been synthesized. The position and the regioregularity of substituents on bithiophene have been controlled via a head-to-head (HH) or head-to-tail (HT) coupling reaction to give four monomers: the HH and the HT carbonitrilehexylbithiophene monomers and the HH and the HT carbonitrilehexyloxybithiophene monomers. Each of them lead, by chemical polymerization, to four polymers constituted by a polythiophene backbone containing alternating electron-donating and electron-withdrawing units directly connected to the polythiophene. Optical and electrochemical characterizations reveal that all these polymers have a low band gap and absorb at longer wavelengths in comparison with a poly(3-hexylthiophene) (P3HT) film. The planarity of the polythiophene backbone was increased by introduction of sulphur-oxygen (S-O) interactions between hexyloxy chains and thiophene units. In addition, the introduction of carbonitrile groups allows to stabilize the LUMO and the HOMO energy levels of polymers at around -3.10 eV for the LUMO and -5.0/-5.3 eV for the HOMO, which were lower than the ones of P3HT (-2.19 eV for the LUMO and {proportional_to}-4.9 eV for the HOMO). Bulk heterojunction photovoltaic devices were fabricated using blends of these polymers with PCBM ([6,6]-phenyl-C61-butyric acid methyl ester). Power conversion efficiency of 1.07% was obtained under solar illumination AM 1.5 (100 mW cm{sup -2}) from a device containing the polymer synthesized from HT 3-carbonitrile-4'-hexyloxyl-2,2'-bithiophene monomers and PCBM as the active layer. (author)

  13. Fluid Shifts

    Science.gov (United States)

    Stenger, M. B.; Hargens, A. R.; Dulchavsky, S. A.; Arbeille, P.; Danielson, R. W.; Ebert, D. J.; Garcia, K. M.; Johnston, S. L.; Laurie, S. S.; Lee, S. M. C.; hide

    2017-01-01

    Introduction. NASA's Human Research Program is focused on addressing health risks associated with long-duration missions on the International Space Station (ISS) and future exploration-class missions beyond low Earth orbit. Visual acuity changes observed after short-duration missions were largely transient, but now more than 50 percent of ISS astronauts have experienced more profound, chronic changes with objective structural findings such as optic disc edema, globe flattening and choroidal folds. These structural and functional changes are referred to as the visual impairment and intracranial pressure (VIIP) syndrome. Development of VIIP symptoms may be related to elevated intracranial pressure (ICP) secondary to spaceflight-induced cephalad fluid shifts, but this hypothesis has not been tested. The purpose of this study is to characterize fluid distribution and compartmentalization associated with long-duration spaceflight and to determine if a relation exists with vision changes and other elements of the VIIP syndrome. We also seek to determine whether the magnitude of fluid shifts during spaceflight, as well as any VIIP-related effects of those shifts, are predicted by the crewmember's pre-flight status and responses to acute hemodynamic manipulations, specifically posture changes and lower body negative pressure. Methods. We will examine a variety of physiologic variables in 10 long-duration ISS crewmembers using the test conditions and timeline presented in the figure below. Measures include: (1) fluid compartmentalization (total body water by D2O, extracellular fluid by NaBr, intracellular fluid by calculation, plasma volume by CO rebreathe, interstitial fluid by calculation); (2) forehead/eyelids, tibia, and calcaneus tissue thickness (by ultrasound); (3) vascular dimensions by ultrasound (jugular veins, cerebral and carotid arteries, vertebral arteries and veins, portal vein); (4) vascular dynamics by MRI (head/neck blood flow, cerebrospinal fluid

  14. Chemical shift assignments for the apo-form of the catalytic domain, the linker region, and the carbohydrate-binding domain of the cellulose-active lytic polysaccharide monooxygenase ScLPMO10C.

    Science.gov (United States)

    Courtade, Gaston; Forsberg, Zarah; Vaaje-Kolstad, Gustav; Eijsink, Vincent G H; Aachmann, Finn L

    2017-10-01

    The apo-form of the 21.4 kDa catalytic domain and the 10.7 kDa carbohydrate binding domain of the AA10 family lytic polysaccharide monooxygenase ScLPMO10C from Streptomyces coelicolor have been isotopically labeled and recombinantly expressed in Escherichia coli. In this paper, we report the 1H, 13C, and 15N chemical shift assignments of each individual domain as well as an ensemble of the assignment for the full-length protein, including its approximately 30-amino acid long linker.

  15. The anisotropic effect of functional groups in 1H NMR spectra is the molecular response property of spatial nucleus independent chemical shifts (NICS)--conformational equilibria of exo/endo tetrahydrodicyclopentadiene derivatives.

    Science.gov (United States)

    Kleinpeter, Erich; Lämmermann, Anica; Kühn, Heiner

    2011-02-21

    The inversion of the flexible five-membered ring in tetrahydrodicyclopentadiene (TH-DCPD) derivatives remains fast on the NMR timescale even at 103 K. Since the intramolecular exchange process could not be sufficiently slowed for spectroscopic evaluation, the conformational equilibrium is thus inaccessible by dynamic NMR. Fortunately, the spatial magnetic properties of the aryl and carbonyl groups attached to the DCPD skeleton can be employed in order to evaluate the conformational state of the system. In this context, the anisotropic effects of the functional groups in the (1)H NMR spectra prove to be the molecular response property of spatial nucleus independent chemical shifts (NICS).

  16. (1)H, (13)C, and (15)N backbone and side-chain chemical shift assignments for the 36 proline-containing, full length 29 kDa human chimera-type galectin-3.

    Science.gov (United States)

    Ippel, Hans; Miller, Michelle C; Berbís, Manuel Alvaro; Suylen, Dennis; André, Sabine; Hackeng, Tilman M; Cañada, F Javier; Weber, Christian; Gabius, Hans-Joachim; Jiménez-Barbero, Jesús; Mayo, Kevin H

    2015-04-01

    Galectin-3, an adhesion/growth regulatory lectin, has a unique trimodular design consisting of the canonical carbohydrate recognition domain, a collagen-like tandem-repeat section, and an N-terminal peptide with two sites for Ser phosphorylation. Structural characterization of the full length protein with its non-lectin part (115 of 250 residues total) will help understand the multi functionality of this potent cellular effector. Here, we report (1)H, (13)C, and (15)N chemical shift assignments as determined by heteronuclear NMR spectroscopy .

  17. Substituent Effects in CH Hydrogen Bond Interactions: Linear Free Energy Relationships and Influence of Anions.

    Science.gov (United States)

    Tresca, Blakely W; Hansen, Ryan J; Chau, Calvin V; Hay, Benjamin P; Zakharov, Lev N; Haley, Michael M; Johnson, Darren W

    2015-12-02

    Aryl CH hydrogen bonds (HBs) are now commonly recognized as important factors in a number of fields, including molecular biology, stereoselective catalysis, and anion supramolecular chemistry. As the utility of CH HBs has grown, so to has the need to understand the structure-activity relationship for tuning both their strength and selectivity. Although there has been significant computational effort in this area, an experimental study of the substituent effects on CH HBs has not been previously undertaken. Herein we disclose a systematic study of a single CH HB by using traditional urea donors as directing groups in a supramolecular binding cavity. Experimentally determined association constants are examined by a combination of computational (electrostatic potential) and empirical (σm and σp) values for substituent effects. The dominance of electrostatic parameters, as observed in a computational DFT study, is consistent with current CH HB theory; however, a novel anion dependence of the substituent effects is revealed in solution.

  18. Effect of substituents on polarizability and hyperpolarizability values of benzimidazole metal complexes

    Energy Technology Data Exchange (ETDEWEB)

    Praveen, P. A.; Babu, R. Ramesh, E-mail: rampap2k@yahoo.co.in [Crystal Growth and Thin films Laboratory, Department of Physics, Bharathidasan University, Tiruchirappalli - 620 024, Tamilnadu (India)

    2016-05-23

    In this report, the polarizability and first and second order hyperpolarizability values of bis benzimidazole Zn(II)-2R and bis benzimidazole Cd(II)-2R complexes, with different electron donating moieties R (R= Cl, Br, I, Acetate) were calculated using time dependent Hartree-Fock (TDHF) formalism embedded in MOPAC2012 package. Further the role of substituents on polarizability and hyperpolarizability values is investigated for the first time by analyzing the frontier molecular orbitals of the complexes with respect to the electronegativity of the substituents. It is found that the increase in electronegativity of the substituents correspondingly increases the energy gap of the molecules, which in turn reduces the polarizability values of both Zn and Cd benzimidazole complexes. Similarly, increase in electronegativity reduces the electric quadrupole moments of both the metal complexes, which in turn reduces the hyperpolarizability values.

  19. Substituent effects on the spectroscopic properties of Criegee intermediates

    Science.gov (United States)

    Trabelsi, Tarek; Kumar, Manoj; Francisco, Joseph S.

    2017-10-01

    Restricted coupled cluster RCCSD(T) and explicitly correlated coupled cluster RCCSD(T)-F12 methods have been applied to investigate the electronic structures, rotational constants, and harmonic vibrational frequencies of the simplest Criegee intermediate (CH2OO) and its methyl and vinyl substituted analogs. The vinyl substitution of hydrogen in CH2OO slightly increases the C=O bond length but does not affect the OO bond, whereas the methyl substitution of hydrogen increases the OO bond but does not affect the CO bond. Vertical excitation energy for the four low-lying singlet electronic states for each Criegee intermediate has been calculated at the equation-of-motion coupled-cluster method inclusive of single and double excitations and two different basis sets, aug-cc-pVXZ (X = T and Q). The results suggest that the 21A' electronic state of C2H3CHOO is stabilized relative to the 21A' electronic state of CH2OO and CH3CHOO, whereas the 21A' state of syn-CH3CHOO is destabilized relative to the 21A' state of CH2OO. The simulated UV spectra of these species show that there are bathochromic and hyperchromic effects for C2H3CHOO. Finally, the absorption spectra of syn-CH3CHOO, anti-C2H3CHOO, and syn-C2H3CHOO has been red-shifted relative to CH2OO whereas anti-CH3CHOO was blue-shifted.

  20. Toward a physical interpretation of substituent effects: the case of fluorine and trifluoromethyl groups.

    Science.gov (United States)

    Siodła, Tomasz; Ozimiński, Wojciech P; Hoffmann, Marcin; Koroniak, Henryk; Krygowski, Tadeusz M

    2014-08-15

    The application of ab initio and DFT computational methods at six different levels of theory (MP2/cc-pVDZ, MP2/aug-cc-pVTZ, B3LYP/cc-pVDZ, B3LYP/aug-cc-pVTZ, M06/cc-pVDZ, and M06/aug-cc-pVTZ) to meta- and para-substituted fluoro- and trifluoromethylbenzene derivatives and to 1-fluoro- and 1-trifluoromethyl-2-substituted trans-ethenes allowed the study of changes in the electronic and geometric properties of F- and CF3-substituted systems under the impact of other substituents (BeH, BF2, BH2, Br, CFO, CHO, Cl, CN, F, Li, NH2, NMe2, NO, NO2, OH, H, CF3, and CH3). Various parameters of these systems have been investigated, including homodesmotic reactions in terms of the substituent effect stabilization energy (SESE), the π and σ electron donor-acceptor indexes (pEDA and sEDA, respectively), the charge on the substituent active region (cSAR, known earlier as qSAR), and bond lengths, which have been regressed against Hammett constants, resulting mostly in an accurate correspondence except in the case of p-fluorobenzene derivatives. Moreover, changes in the characteristics of the ability of the substituent to attract or donate electrons under the impact of the kind of moiety to which the substituent is attached have been considered as the indirect substituent effect and investigated by means of the cSAR model. Regressions of cSAR(X) versus cSAR(Y) for any systems X and Y allow final results to be obtained on the same scale of magnitude.

  1. Plakilactones G and H from a marine sponge. Stereochemical determination of highly flexible systems by quantitative NMR-derived interproton distances combined with quantum mechanical calculations of 13C chemical shifts

    Directory of Open Access Journals (Sweden)

    Simone Di Micco

    2013-12-01

    Full Text Available In this paper the stereostructural investigation of two new oxygenated polyketides, plakilactones G and H, isolated from the marine sponge Plakinastrella mamillaris collected at Fiji Islands, is reported. The stereostructural studies began on plakilactone H by applying an integrated approach of the NOE-based protocol and quantum mechanical calculations of 13C chemical shifts. In particular, plakilactone H was used as a template to extend the application of NMR-derived interproton distances to a highly flexible molecular system with simultaneous assignment of four non-contiguous stereocenters. Chemical derivatization and quantum mechanical calculations of 13C on plakilactone G along with a plausible biogenetic interconversion between plakilactone G and plakilactone H allowed us to determine the absolute configuration in this two new oxygenated polyketides.

  2. Effect of substituents and structural modification on conformational equilibrium in bis-quinolizidine system

    Science.gov (United States)

    Wysocka, Waleria; Brukwicki, Tadeusz; Włodarczak, Jacek

    2012-06-01

    On the basis of literature interpretation of 13C NMR and 1H NMR spectra of bis-quinolizidine alkaloids, the values of free enthalpy ΔG of conformational equilibria of those compounds were calculated. The results were analysed together with the X-ray and DFT data to discuss the effects of different substituents attached to the sparteine system in various positions as well as the effects of structural modifications on conformational equilibria. The measure of the effect was expressed by ΔΔG value, defined as the difference in ΔG of the compound under consideration and its parent compound without a given substituent.

  3. Using remote substituents to control solution structure and anion binding in lanthanide complexes

    DEFF Research Database (Denmark)

    Tropiano, Manuel; Blackburn, Octavia A.; Tilney, James A.

    2013-01-01

    of the molecule, at a substantial distance from the binding pocket. Herein, we explore these remote substituent effects and explain the observed behaviour through discussion of the way in which remote substituents can influence and control the global structure of a molecule through their demands upon...... conformational space. Peripheral modifications to a binuclear lanthanide motif derived from α,α'-bis(DO3 Ayl)-m-xylene are shown to result in dramatic changes to the binding constant for isophthalate. In this system, the parent compound displays considerable conformational flexibility, yet can be assumed to bind...

  4. Substituent effects on molecular properties of dicarba-closo-dodecarborane derivatives.

    Science.gov (United States)

    Junqueira, Georgia M A; Sato, Fernando

    2014-07-01

    In this paper we study the role played by substituent effects on reactivity and NLO properties of ortho-, meta- and para- dicarba-closo-dodecarborane derivatives at B3LYP/6-31G(d,p) level of theory. In addition correlations with Hammett parameters of the substituents were established. In accordance with obtained results the reactivity properties of derivatives have not been significantly influenced by the isomer type, however the replaced para isomers were the most sensitive to NLO calculations. Moreover, the push-pull para isomers were found to be the most reactive and displayed the largest values of β tot and dipole moment.

  5. The interplay between transient a-helix formation and side chain rotamer distributions in disordered proteins probed by methyl chemical shifts

    DEFF Research Database (Denmark)

    Kjærgaard, Magnus; Iesmantavicius, Vytautas; Poulsen, Flemming M

    2011-01-01

    The peptide backbones of disordered proteins are routinely characterized by NMR with respect to transient structure and dynamics. Little experimental information is, however, available about the side chain conformations and how structure in the backbone affects the side chains. Methyl chemical sh...

  6. Shifting Blame?

    DEFF Research Database (Denmark)

    Garofalo, Orsola; Rott, Christina

    2017-01-01

    by the spokesperson if there is room for shifting blame. The increased punishment results from the messenger’s style of delivery: spokespersons are more likely than decision makers to express emotional regret instead of rational need. Receivers seem to punish the former style of communication because they view......Decision makers frequently have a spokesperson communicate their decisions. In this paper, we address two questions. First, does it matter who communicates an unfair decision? Second, does it matter how the unfair decision is communicated? We conduct a modified dictator game experiment in which...... either the decision maker or a spokesperson communicates the decided allocation to recipients, who then determine whether to punish either of them. We find that receivers punish both the decision maker and the spokesperson more often, and more heavily, for unfair allocations communicated...

  7. 77Se NMR chemical shifts of 9-(arylselanyl)triptycenes: new standard for planar structures of ArSeR and applications to determine the structures in solutions.

    Science.gov (United States)

    Nakamoto, Takashi; Hayashi, Satoko; Nakanishi, Waro

    2008-12-05

    A set of new delta(Se) parameters is proposed as a standard for the planar (pl) orientational effect of p-YC(6)H(4) (Ar) in ArSeR, employing 9-(arylselanyl)triptycenes (1: p-YC(6)H(4)SeTpc). The Se-C(R) bond in ArSeR is placed on the Ar plane in pl and it is perpendicular to the plane in pd. Large upfield shifts are observed for Y = NMe(2), OMe, and Me (-22 to -6 ppm) and large downfield shifts for Y = COOEt, CN, and NO(2) (19-37 ppm), relative to Y = H, with small upfield and moderate downfield shifts by Y of halogens (-1 ppm for Y = F and 4 ppm for Y = Cl and Br). This must be the result of the p(Se)-pi(C(6)H(4))-p(Y) conjugation in 1 (pl). While the character of delta(Se) in 1 (pl) is very similar to that in 9-(arylselanyl)anthracenes (2 (pl)), it is very different from that of 1-(arylselanyl)anthraquinones (3 (pd)). Sets of delta(Se) of 1 and 2 must serve as the standard for pl and that of 3 does for pd in solutions. Structures of various ArSeR in solutions are determined from the viewpoint of the orientational effect based on the standard delta(Se) of 1-3. While the structure of 2-methyl-1-(arylselanyl)naphthalenes is concluded to be all pl in solutions, those of 8-chloro- and 8-bromo-1-(arylselanyl)naphthalenes are all pd, except for Y = COOEt, CN, and NO(2): The equilibrium between pd and pl contributes to those with Y = COOEt, CN, and NO(2). The structure of 1-(arylselanyl)naphthalenes changes depending on Y. The structures of ArSeMe and ArSeCOPh are shown to be pl and pd, respectively, in solutions. Those of ArSePh and ArSeAr seem to change depending on Y. delta(Se) of 1-3 are demonstrated to serve as the standard to determine the structures in solutions. The rules of thumb derived from the characters in delta(Se) for 1-3 are very useful to determine the structures of ArSeR in solutions, in addition to the analysis based on the plots.

  8. Computation provides chemical insight into the diverse hydride NMR chemical shifts of [Ru(NHC)4(L)H]0/+ species (NHC = N-heterocyclic carbene; L = vacant, H2, N2, CO, MeCN, O2, P4, SO2, H-, F- and Cl-) and their [Ru(R2PCH2CH2PR2)2(L)H]+ congeners.

    Science.gov (United States)

    Häller, L Jonas L; Mas-Marzá, Elena; Cybulski, Mateusz K; Sanguramath, Rajashekharayya A; Macgregor, Stuart A; Mahon, Mary F; Raynaud, Christophe; Russell, Christopher A; Whittlesey, Michael K

    2017-02-28

    Relativistic density functional theory calculations, both with and without the effects of spin-orbit coupling, have been employed to model hydride NMR chemical shifts for a series of [Ru(NHC)4(L)H]0/+ species (NHC = N-heterocyclic carbene; L = vacant, H2, N2, CO, MeCN, O2, P4, SO2, H-, F- and Cl-), as well as selected phosphine analogues [Ru(R2PCH2CH2PR2)2(L)H]+ (R = iPr, Cy; L = vacant, O2). Inclusion of spin-orbit coupling provides good agreement with the experimental data. For the NHC systems large variations in hydride chemical shift are shown to arise from the paramagnetic term, with high net shielding (L = vacant, Cl-, F-) being reinforced by the contribution from spin-orbit coupling. Natural chemical shift analysis highlights the major orbital contributions to the paramagnetic term and rationalizes trends via changes in the energies of the occupied Ru dπ orbitals and the unoccupied σ*Ru-H orbital. In [Ru(NHC)4(η2-O2)H]+ a δ-interaction with the O2 ligand results in a low-lying LUMO of dπ character. As a result this orbital can no longer contribute to the paramagnetic shielding, but instead provides additional deshielding via overlap with the remaining (occupied) dπ orbital under the Lz angular momentum operator. These two effects account for the unusual hydride chemical shift of +4.8 ppm observed experimentally for this species. Calculations reproduce hydride chemical shift data observed for [Ru(iPr2PCH2CH2PiPr2)2(η2-O2)H]+ (δ = -6.2 ppm) and [Ru(R2PCH2CH2PR2)2H]+ (ca. -32 ppm, R = iPr, Cy). For the latter, the presence of a weak agostic interaction trans to the hydride ligand is significant, as in its absence (R = Me) calculations predict a chemical shift of -41 ppm, similar to the [Ru(NHC)4H]+ analogues. Depending on the strength of the agostic interaction a variation of up to 18 ppm in hydride chemical shift is possible and this factor (that is not necessarily readily detected experimentally) can aid in the interpretation of hydride chemical shift

  9. The influence of Mg2+ coordination on 13C and 15N chemical shifts in CKI1RD protein domain from experiment and molecular dynamics/density functional theory calculations.

    Science.gov (United States)

    Vícha, Jan; Babinský, Martin; Demo, Gabriel; Otrusinová, Olga; Jansen, Séverine; Pekárová, Blanka; Žídek, Lukáš; Munzarová, Markéta L

    2016-05-01

    Sequence dependence of (13) C and (15) N chemical shifts in the receiver domain of CKI1 protein from Arabidopsis thaliana, CKI1RD , and its complexed form, CKI1RD •Mg(2+), was studied by means of MD/DFT calculations. MD simulations of a 20-ns production run length were performed. Nine explicitly hydrated structures of increasing complexity were explored, up to a 40-amino-acid structure. The size of the model necessary depended on the type of nucleus, the type of amino acid and its sequence neighbors, other spatially close amino acids, and the orientation of amino acid NH groups and their surface/interior position. Using models covering a 10 and a 15 Å environment of Mg(2+), a semi-quantitative agreement has been obtained between experiment and theory for the V67-I73 sequence. The influence of Mg(2+) binding was described better by the 15 Å as compared to the 10 Å model. Thirteen chemical shifts were analyzed in terms of the effect of Mg(2+) insertion and geometry preparation. The effect of geometry was significant and opposite in sign to the effect of Mg(2+) binding. The strongest individual effects were found for (15) N of D70, S74, and V68, where the electrostatics dominated; for (13) Cβ of D69 and (15) N of K76, where the influences were equal, and for (13) Cα of F72 and (13) Cβ of K76, where the geometry adjustment dominated. A partial correlation between dominant geometry influence and torsion angle shifts upon the coordination has been observed. © 2016 Wiley Periodicals, Inc.

  10. Claisen rearrangements of benzyl vinyl ethers: theoretical investigation of mechanism, substituent effects, and regioselectivity.

    Science.gov (United States)

    Krenske, Elizabeth H; Burns, Jed M; McGeary, Ross P

    2017-09-26

    Recently we reported the aromatic Claisen rearrangements of benzyl ketene acetals, which form one of the few examples of aromatic Claisen rearrangements involving benzyl vinyl ethers (as opposed to allyl aryl ethers, which are the usual substrates for aromatic Claisen rearrangements). Theoretical calculations predict that these rearrangements proceed via a concerted [3,3]-sigmatropic transition state, which is similar in geometry to the TS for the Claisen rearrangement of an allyl aryl ether but has a 4 kcal mol-1 higher barrier. The effects of donor (OMe) and acceptor (CN) substituents on the kinetics of the [3,3]-rearrangement mirror those reported for allyl vinyl ethers: the largest substituent effects are seen for 1-OMe, 2-OMe, 2-CN, and 4-CN substituents, which lower the barrier by 5-9 kcal mol-1. Substituents on the aromatic ring have smaller effects on the barrier (≤2 kcal mol-1). The regioselectivities of Claisen rearrangements of meta-substituted benzyl ketene acetals favour 1,2,3-trisubstituted products in preference to the less sterically congested 1,2,4-isomers due to favourable orbital interactions in the 1,2,3 transition state.

  11. Substituent effect on the thermodynamic solubility of structural analogs: relative contribution of crystal packing and hydration.

    Science.gov (United States)

    Ozaki, Shunsuke; Nakagawa, Yoshiaki; Shirai, Osamu; Kano, Kenji

    2014-11-01

    Thermodynamic analysis of the solubility of benzoylphenylurea (BPU) derivatives was conducted to investigate the relative importance of crystal packing and hydration for improving solubility with minor structural modification. The contribution of crystal packing to solubility was evaluated from the change in Gibbs energy on the transition from the crystalline to liquid state. Hydration Gibbs energy was estimated using a linear free-energy relationship between octanol-water partition coefficients and gas-water partition coefficients. The established solubility model satisfactorily explained the relative thermodynamic solubility of the model compounds and revealed that crystal packing and hydration equally controlled solubility of the structural analogs. All hydrophobic substituents were undesirable for solubility in terms of hydration, as expected. On the other hand, some of these hydrophobic substituents destabilized crystal packing and improved the solubility of the BPU derivatives when their impact on crystal packing exceeded their negative influence on hydration. The replacement of a single substituent could cause more than a 10-fold enhancement in thermodynamic solubility; this degree of improvement was comparable to that generally achieved by amorphous formulations. Detailed analysis of thermodynamic solubility will allow us to better understand the true substituent effect and design drug-like candidates efficiently. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association.

  12. Identification of substituent groups and related genes involved in salecan biosynthesis in Agrobacterium sp. ZX09.

    Science.gov (United States)

    Xu, Linxiang; Cheng, Rui; Li, Jing; Wang, Yang; Zhu, Bin; Ma, Shihong; Zhang, Weiming; Dong, Wei; Wang, Shiming; Zhang, Jianfa

    2017-01-01

    Salecan, a soluble β-1,3-D-glucan produced by a salt-tolerant strain Agrobacterium sp. ZX09, has been the subject of considerable interest in recent years because of its multiple bioactivities and unusual rheological properties in solution. In this study, both succinyl and pyruvyl substituent groups on salecan were identified by an enzymatic hydrolysis following nuclear magnetic resonance (NMR), HPLC, and MS analysis. The putative succinyltransferase gene (sleA) and pyruvyltransferase gene (sleV) were determined and cloned. Disruption of the sleA gene resulted in the absence of succinyl substituent groups on salecan. This defect could be complemented by expressing the sleA cloned in a plasmid. Thus, the sleA and sleV genes located in a 19.6-kb gene cluster may be involved in salecan biosynthesis. Despite the lack of succinyl substituents, the molecular mass of salecan generated by the sleA mutant did not substantially differ from that generated by the wild-type strain. Loss of succinyl substituents on salecan changed its rheological characteristics, especially a decrease in intrinsic viscosity.

  13. Discovering Electronic Effects of Substituents in Nitrations of Benzene Derivatives Using GC-MS Analysis

    Science.gov (United States)

    Clennan, Malgorzata M.; Clennan, Edward L.

    2007-01-01

    The nitration of six benzene derivatives having a range of substituents that differ in electronic effects were followed by GC-MS analyses of the crude reaction mixtures and adapted for the second-year organic laboratory. Students pool their results and identify the products by analyzing the mass spectral data of the isomers and by comparing them…

  14. Substituent effif ects on hydrogen bonding in Watson-Crick base pairs. A theoretical study

    NARCIS (Netherlands)

    Fonseca Guerra, C.; van der Wijst, T.; Bickelhaupt, F.M.

    2005-01-01

    We have theoretically analyzed Watson-Crick AT and GC base pairs in which purine C8 and/or pyrimidine C6 positions carry a substituent X = H, F, Cl or Br, using the generalized gradient approximation (GGA) of density functional theory at BP86/TZ2P. The purpose is to study the effects on structure

  15. Synthesis, antimicrobial evaluation and theoretical prediction of NMR chemical shifts of thiazole and selenazole derivatives with high antifungal activity against Candida spp.

    Science.gov (United States)

    Łączkowski, Krzysztof Z.; Motylewska, Katarzyna; Baranowska-Łączkowska, Angelika; Biernasiuk, Anna; Misiura, Konrad; Malm, Anna; Fernández, Berta

    2016-03-01

    Synthesis and investigation of antimicrobial activities of novel thiazoles and selenazoles is presented. Their structures were determined using NMR, FAB(+)-MS, HRMS and elemental analyses. To support the experiment, theoretical calculations of the 1H NMR shifts were carried out for representative systems within the DFT B3LYP/6-311++G** approximation which additionally confirmed the structure of investigated compounds. Among the derivatives, compounds 4b, 4h, 4j and 4l had very strong activity against reference strains of Candida albicans ATCC and Candida parapsilosis ATCC 22019 with MIC = 0.49-7.81 μg/ml. In the case of compounds 4b, 4c, 4h - 4j and 4l, the activity was very strong against of Candida spp. isolated from clinical materials, i.e. C. albicans, Candida krusei, Candida inconspicua, Candida famata, Candida lusitaniae, Candida sake, C. parapsilosis and Candida dubliniensis with MIC = 0.24-15.62 μg/ml. The activity of several of these was similar to the activity of commonly used antifungal agent fluconazole. Additionally, compounds 4m - 4s were found to be active against Gram-positive bacteria, both pathogenic staphylococci Staphylococcus aureus ATCC with MIC = 31.25-125 μg/ml and opportunistic bacteria, such as Staphylococcus epidermidis ATCC 12228 and Micrococcus luteus ATCC 10240 with MIC = 7.81-31.25 μg/ml.

  16. Impact of central metal atoms and F-substituents on the adsorption geometry of phthalocyanine molecules on Cu(111)

    Energy Technology Data Exchange (ETDEWEB)

    Buerker, Christoph; Hosokai, Takuya; Gerlach, Alexander; Schreiber, Frank [Universitaet Tuebingen (Germany); Duhm, Steffen [Chiba University (Japan); Koch, Norbert [HU Berlin (Germany); Yamane, Hiroyuki [Institut for Molecular Science (Germany)

    2010-07-01

    The adsorption geometry of large organic molecules on metal surfaces is essential for understanding and controlling the interface electronic structure, thin film structure and growth mechamism. The X-ray standing wave (XSW) technique is one of the most precise methods to determine the vertical positions of specific atoms relative to the substrate and can therefore establish the adsorption geometry of organic molecules. Metal Phthalocyanines (MPc) as typical organic semiconductors are one of the most suitable systems for XSW experiments due to their chemical stability, high structural symmetry and variability of both the central metal atom and substituents. Using the XSW technique we show how fluorination and a central metal atom affect the adsorption geometry of Pc molecules. We compare the structural differences of metal-free Pc (H{sub 2}Pc), zinc-Pc (ZnPc) and perfluorinated ZnPc (F{sub 16}ZnPc) on Cu(111). The XSW data reveal significant deviations for both the bonding distance and molecular distortion. These results indicate an interaction strength of each atom with the surface depending on its chemical vicinity.

  17. Solid-state (185/187)Re NMR and GIPAW DFT study of perrhenates and Re2(CO)10: chemical shift anisotropy, NMR crystallography, and a metal-metal bond.

    Science.gov (United States)

    Widdifield, Cory M; Perras, Frédéric A; Bryce, David L

    2015-04-21

    Advances in solid-state nuclear magnetic resonance (SSNMR) methods, such as dynamic nuclear polarization (DNP), intricate pulse sequences, and increased applied magnetic fields, allow for the study of systems which even very recently would be impractical. However, SSNMR methods using certain quadrupolar probe nuclei (i.e., I > 1/2), such as (185/187)Re remain far from fully developed due to the exceedingly strong interaction between the quadrupole moment of these nuclei and local electric field gradients (EFGs). We present a detailed high-field (B0 = 21.1 T) experimental SSNMR study on several perrhenates (KReO4, AgReO4, Ca(ReO4)2·2H2O), as well as ReO3 and Re2(CO)10. We propose solid ReO3 as a new rhenium SSNMR chemical shift standard due to its reproducible and sharp (185/187)Re NMR resonances. We show that for KReO4, previously poorly understood high-order quadrupole-induced effects (HOQIE) on the satellite transitions can be used to measure the EFG tensor asymmetry (i.e., ηQ) to nearly an order-of-magnitude greater precision than competing SSNMR and nuclear quadrupole resonance (NQR) approaches. Samples of AgReO4 and Ca(ReO4)2·2H2O enable us to comment on the effects of counter-ions and hydration upon Re(vii) chemical shifts. Calcium-43 and (185/187)Re NMR tensor parameters allow us to conclude that two proposed crystal structures for Ca(ReO4)2·2H2O, which would be considered as distinct, are in fact the same structure. Study of Re2(CO)10 provides insights into the effects of Re-Re bonding on the rhenium NMR tensor parameters and rhenium oxidation state on the Re chemical shift value. As overtone NQR experiments allowed us to precisely measure the (185/187)Re EFG tensor of Re2(CO)10, we were able to measure rhenium chemical shift anisotropy (CSA) for the first time in a powdered sample. Experimental observations are supported by gauge-including projector augmented-wave (GIPAW) density functional theory (DFT) calculations, with NMR tensor calculations also

  18. Iboga alkaloids from Peschiera affinis (Apocynaceae) - unequivocal {sup 1}H and {sup 13}C chemical shift assignments: antioxidant activity; Alcaloides iboga de Peschiera affinis (Apocynaceae) - atribuicao inequivoca dos deslocamentos quimicos dos atomos de hidrogenio e carbono: atividade antioxidante

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Allana Kellen L.; Magalhaes, Ticiane S.; Monte, Francisco Jose Q.; Mattos, Marcos Carlos de; Oliveira, Maria Conceicao F. de; Almeida, Maria Mozarina B.; Lemos, Telma L.G.; Braz-Filho, Raimundo [Universidade Federal do Ceara (UFC), Fortaleza, CE (Brazil). Dept. de Quimica Organica e Inorganica], e-mail: tlemos@dqoi.ufc.br

    2009-07-01

    Six known alkaloids iboga type and the triterpene {alpha}- and {beta}-amyrin acetate were isolated from the roots and stems of Peschiera affinis. Their structures were characterized on the basis of spectral data mainly NMR and mass spectra. 1D and 2D NMR spectra were also used to unequivocal {sup 1}H and {sup 13}C chemical shift assignments of alkaloids. The ethanolic extract of roots, alkaloidic and no-alkaloidic fractions and iso-voacristine hydroxyindolenine and voacangine were evaluated for their antioxidative properties using an autographic assay based on {beta}-carotene bleaching on TLC plates, and also spectrophotometric detection by reduction of the stable DPPH (2,2-diphenyl-1-picrylhydrazyl) free radical. (author)

  19. Exploring the effect of remote substituents and solution structure on the luminescence of three lanthanide complexes

    Energy Technology Data Exchange (ETDEWEB)

    Tropiano, Manuel; Blackburn, Octavia A.; Tilney, James A.; Hill, Leila R. [Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA (United Kingdom); Just Sørensen, Thomas, E-mail: TJS@chem.ku.dk [Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA (United Kingdom); Nano-Science Center and Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 København Ø (Denmark); Faulkner, Stephen, E-mail: stephen.faulkner@chem.ox.ac.uk [Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA (United Kingdom)

    2015-11-15

    Sensitized luminescence from trivalent lanthanide ions relies on an appropriate energy match between the sensitizer’s excited state (triplet or singlet) and the lanthanide excited state manifold, and also an efficient mechanism of energy transfer between the two. Here, the effect of remote substituents on the luminescence properties of a series of related lanthanide complexes has been investigated. The sensitized lanthanide centered emission is not invariably found to occur following excitation of all chromophores in all systems, and it is shown that only the most structurally congested of the systems investigated exhibited pronounced solvatochromism. - Highlights: • Effect of remote substituents and self-assembly on lanthanide luminescence. • Molecular structure rather than chromophore density defines lanthanide sensitization. • Kimura's and Horrocks' approach to determine lanthanide solvation is revisited. • Solvent alters sensitization pathways in multinuclear lanthanide complexes. • Increasing chromophore density may reduce lanthanide luminescence.

  20. Synthesis and properties of acyclic ammonium-based ionic liquids with allyl substituents as electrolytes.

    Science.gov (United States)

    Yim, Taeeun; Choi, Chang Young; Mun, Junyoung; Oh, Seung M; Kim, Young Gyu

    2009-05-15

    Several new acyclic ammonium-TFSI ionic liquids with an allyl substituent(s) were synthesized and their physicochemical and electrochemical properties were characterized. [AAMM]Am-TFSI (3) with two allyl groups showed the widest electrochemical stability window (5.9 V) among the ammonium-based ILs reported to date because of the increment of both the anodic and cathodic limits. The charge-discharge performance of a LiCoO(2)-based half-cell containing [AAMM]Am-TFSI as an electrolyte was better in cycleability (the capacity retention ratio: 99% after 20 cycles) than that of the cell with the corresponding partially saturated analogue, [AMMP]Am-TFSI (2) (the capacity retention ratio: 92% after 20 cycles).

  1. Synthesis and Properties of Acyclic Ammonium-based Ionic Liquids with Allyl Substituents as Electrolytes

    Directory of Open Access Journals (Sweden)

    Young Gyu Kim

    2009-05-01

    Full Text Available Several new acyclic ammonium-TFSI ionic liquids with an allyl substituent(s were synthesized and their physicochemical and electrochemical properties were characterized. [AAMM]Am-TFSI (3 with two allyl groups showed the widest electrochemical stability window (5.9 V among the ammonium-based ILs reported to date because of the increment of both the anodic and cathodic limits. The charge-discharge performance of a LiCoO2-based half-cell containing [AAMM]Am-TFSI as an electrolyte was better in cycleability (the capacity retention ratio: 99% after 20 cycles than that of the cell with the corresponding partially saturated analogue, [AMMP]Am-TFSI (2 (the capacity retention ratio: 92% after 20 cycles.

  2. The influence of terminal substituents of diphenylbutadiene on the parameters of intra- and intermolecular interactions

    Science.gov (United States)

    Kompaneets, V. V.; Vasil'eva, I. A.

    2017-04-01

    We have analyzed the parameters of the Franck-Condon and Herzberg-Teller interactions, which form the fine-structure spectra of diphenylbutadiene substituted derivatives with the general formula X-Ph-(C=C)2-Ph-Y (where X, Y = H, NO2, N(CH3)2, and NH2 are the substituents in different combinations) in solutions of n-paraffins at 4.2 K. The influence of substituents on the vibronic parameters of characteristic bands that describe the states (vibrations, types of deformations upon excitation) of the phenyl rings and diphenylbutadiene polyene bridge has been considered. Data on the influence of the H, NO2, N(CH3)2, or NH2 terminal fragment on the parameters of the intra- and intermolecular interactions of diphenylbutadiene substituted derivatives have been presented.

  3. Substituent effects in double-helical hydrogen-bonded AAA-DDD complexes.

    Science.gov (United States)

    Wang, Hong-Bo; Mudraboyina, Bhanu P; Wisner, James A

    2012-01-27

    Two series of DDD and AAA hydrogen-bond arrays were synthesized that form triply-hydrogen-bonded double-helical complexes when combined in CDCl(3) solution. Derivatization of the DDD arrays with electron-withdrawing groups increases the complex association constants by up to a factor of 30 in those arrays examined. Derivatization of the AAA arrays with electron donating substituents reveals a similar magnitude effect on the complex stabilities. The effect of substitution on both types of arrays are modeled quite satisfactorily (R(2) > 0.96 in all cases) as free energy relationships with respect to the sums of their Hammett substituent constants. In all, the complex stabilities can be manipulated over more than three orders of magnitude (>20 kJ mol(-1)) using this type of modification. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Functionalized ferrocenes: The role of the para substituent on the phenoxy pendant group

    OpenAIRE

    Vera, José L.; Rullán, Jorge; Santos, Natasha; Jiménez, Jesús; Rivera, Joshua; Santana, Alberto; Briggs, Jon; Rheingold, Arnold L.; Matta, Jaime; Meléndez, Enrique

    2014-01-01

    Six ferrocenecarboxylates with phenyl, 4-(1H-pyrrol-1-yl)phenyl, 4-fluorophenyl, 4-chlorophenyl, 4-bromophenyl, 4-iodophenyl as pendant groups were synthesized and fully characterized by spectroscopic, electrochemical and X-ray diffraction methods. The anti-proliferative activity of these complexes were investigated in hormone dependent MCF-7 breast cancer and MCF-10A normal breast cell lines, to determine the role of the para substituent on the phenoxy pendant group. The 4-fluorophenyl ferro...

  5. Ethylene oligomerisation and polymerisation with nickel phosphanylenolates bearing electron-withdrawing substituents: Structure-reactivity relationships.

    Science.gov (United States)

    Kuhn, Pierre; Sémeril, David; Jeunesse, Catherine; Matt, Dominique; Neuburger, Markus; Mota, Antonio

    2006-07-05

    Three SHOP-type catalysts, in which the C=C(O) double bond was substituted by electron-withdrawing substituents, [Ni{Ph2PC(R1)=C(R2)O}Ph(PPh3)] (2: R1,R2 = -C(Me)=NN(Ph)-; 3: R1 = CO2Et, R2 = Ph; 4: R1 = CO2Et, R2 = CF3), were assessed as ethylene-oligomerisation and -polymerisation catalysts and compared to Keim's complex, [Ni{Ph2PCH=C(Ph)O}Ph(PPh3)] (1). A rationale for the influence of the double-bond substituents of the P,O-chelate unit on the catalytic properties is proposed, on the basis of X-ray diffraction studies, spectroscopic data and DFT-B3 LYP calculations. Whatever their relative electron-withdrawing strength, the R1 and R2 substituents induce an increase in activity with respect to catalyst 1. For those systems in which the basicity of the oxygen atom is decreased relative to that of the phosphorus atom, the chain-propagation rate increases with respect to that for catalyst 1. Reduction of the basicity of the P relative to that of the O, however, induces higher chain-termination rates.

  6. ESIPT fluorescent dyes with adjustable optical properties: Substituent and conjugation effects

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Kew-Yu, E-mail: kyuchen@fcu.edu.tw; Tsai, Hsing-Yang; Lin, Wei-Chi; Chu, Hou-Hsein; Weng, Yu-Ching; Chan, Chih-Chieh

    2014-10-15

    Based on the design and synthesis of 10-hydroxybenzo[h]quinoline (3) derivatives, we demonstrate a prototypical system to investigate both substituent and conjugation effects on excited-state intramolecular proton transfer emission through a combination of experimental and theoretical studies. On the one hand, adding an electron-withdrawing substituent at the phenol ring in 3 results in a decrease of HOMO, and hence, an increase in the energy gap of the keto-tautomer emission (o-4 and p-4). An opposite effect is observed when an electron-donating substituent is added (1). On the other hand, the elongation of the p-conjugation length by the installed 2-methylenemalononitrile group (o-2 and p-2) induces further π-electron delocalization, and thus a smaller emission energy gap. Time-dependent density functional theory calculations on these proton transfer dyes are reported in order to rationalize their electronic structure and optical properties. - Highlights: • A novel series of 10-hydroxybenzo[h]quinoline derivatives was synthesized. • These molecules undergo an excited-state intramolecular proton transfer reaction. • The proton-transfer emission can be fine-tuned from 600 nm to 655 nm.

  7. Vibrational dynamics study of the effect of the substituents on the π-conjugation of different bithiophene molecules

    Science.gov (United States)

    Ruiz Delgado, M. C.; Ramírez, F. J.; Hernández, V.; Casado, J.; Enríquez, F.; López Navarrete, J. T.

    2005-06-01

    We report on the FT-Raman spectroscopic study, aided by DFT model chemistry calculations, of three different classes of π-conjugated oligomers: (i) a dicyanomethylene end-capped bithiophene with a quinoidal chemical structure, (ii) a symmetrically dimethyl-substituted system bearing a non-polar aromatic structure in its ground electronic state and (iii) a highly polarized push-pull system with an electron-donor dimethylamino and a electron-acceptor cyano groups attached to its end α,ω-positions. We have optimized the molecular geometries of these three bithienyls at the DFT//B3LYP/6-31G** level, and compared the main skeletal bond lengths of the π-conjugated backbone in terms of the so-called bond-length-alternation (BLA) parameter. The overall summations of the B3LYP/6-31G** atomic charges for the thienyl rings and the various types of end α,ω-substituents have also been compared along the bunch of compounds. Finally we make use of the well-known effective conjugation coordinate (ECC) theory to assess useful information about the π-conjugation, computing the B3LYP/6-31G** value of the force constant associated to the collective ECC vibrational normal mode.

  8. ADMET rules of thumb II: A comparison of the effects of common substituents on a range of ADMET parameters.

    Science.gov (United States)

    Gleeson, Paul; Bravi, Gianpaolo; Modi, Sandeep; Lowe, Daniel

    2009-08-15

    A systematic analysis of data generated in key in vitro assays within GSK has been undertaken to identify what impact a range of common substituents have on a range of ADMET parameters. These include; P450 1A2, 2C9, 2C19, 2D6 and 3A4 inhibition, hERG inhibition, phosphate buffer solubility and artificial membrane permeability. We do this by identifying all matched molecular pairs, differing by the replacement of a hydrogen atom with a list of predefined substituents. For each substituent we calculate the mean difference in the ADMET parameter for all the matched molecular pairs identified, making a statistical assessment of the difference, as well as assessing the diversity for each example to ensure that the results can be generalized. We also relate the change in activity observed for each substituent to differences in their molecular properties in an effort to identify any structural alerts.

  9. Journal of Chemical Sciences | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences. RAMAMOORTHY BOOMISHANKAR. Articles written in Journal of Chemical Sciences. Volume 127 Issue 4 April 2015 pp 619-626 Regular Articles. A tetrakis(amido)phosphonium cation containing 2-pyridyl (Py) substituents,[P(NHPy)4] and its reactivity studies with Ag(I) salts.

  10. Comparison of clinical semi-quantitative assessment of muscle fat infiltration with quantitative assessment using chemical shift-based water/fat separation in MR studies of the calf of post-menopausal women

    Energy Technology Data Exchange (ETDEWEB)

    Alizai, Hamza; Nardo, Lorenzo; Karampinos, Dimitrios C.; Joseph, Gabby B.; Yap, Samuel P.; Baum, Thomas; Krug, Roland; Majumdar, Sharmila; Link, Thomas M. [University of California, San Francisco, Musculoskeletal and Quantitative Imaging Research Group, Department of Radiology and Biomedical Imaging, San Francisco, CA (United States)

    2012-07-15

    The goal of this study was to compare the semi-quantitative Goutallier classification for fat infiltration with quantitative fat-fraction derived from a magnetic resonance imaging (MRI) chemical shift-based water/fat separation technique. Sixty-two women (age 61 {+-} 6 years), 27 of whom had diabetes, underwent MRI of the calf using a T1-weighted fast spin-echo sequence and a six-echo spoiled gradient-echo sequence at 3 T. Water/fat images and fat fraction maps were reconstructed using the IDEAL algorithm with T2* correction and a multi-peak model for the fat spectrum. Two radiologists scored fat infiltration on the T1-weighted images using the Goutallier classification in six muscle compartments. Spearman correlations between the Goutallier grades and the fat fraction were calculated; in addition, intra-observer and inter-observer agreement were calculated. A significant correlation between the clinical grading and the fat fraction values was found for all muscle compartments (P < 0.0001, R values ranging from 0.79 to 0.88). Goutallier grades 0-4 had a fat fraction ranging from 3.5 to 19%. Intra-observer and inter-observer agreement values of 0.83 and 0.81 were calculated for the semi-quantitative grading. Semi-quantitative grading of intramuscular fat and quantitative fat fraction were significantly correlated and both techniques had excellent reproducibility. However, the clinical grading was found to overestimate muscle fat. (orig.)

  11. Primary and metastatic intraaxial brain tumors: prospective comparison of multivoxel 2D chemical-shift imaging (CSI) proton MR spectroscopy, perfusion MRI, and histopathological findings in a group of 159 patients.

    Science.gov (United States)

    Bendini, Matteo; Marton, Elisabetta; Feletti, Alberto; Rossi, Sabrina; Curtolo, Stefano; Inches, Ingrid; Ronzon, Monica; Longatti, Pierluigi; Di Paola, Francesco

    2011-02-01

    This study aims to assess the diagnostic value of multivoxel 2D chemical-shift imaging (CSI) proton magnetic resonance (MR) spectroscopy combined with perfusion magnetic resonance imaging (MRI) in the differential diagnosis and grading of brain tumors by comparing neuroimaging data with histopathological findings obtained after resection or biopsy. A total of 159 patients with a previous brain tumor diagnosis underwent multivoxel 2D CSI proton MR spectroscopy and perfusion MRI. MR spectroscopy multivoxel 2D CSI was performed with an echo time of 30, TR 1,500, FOV 160 mm, acquisition time 7 min 34 s. rCBV maps were evaluated during postprocessing. Statistical analysis was performed on the examination of distributive normality, with logarithmic transformations, Fisher's test, and Bonferroni's test. We used the Pearson's test to compare percentages. In the differential diagnosis between GBM and metastases, MR spectroscopy multivoxel 2D CSI, combined with dynamic contrast enhanced MRI (DCE-MRI) perfusion, reached high sensibility and specificity (p CSI spectroscopy and perfusion imaging has shown a high potential in the differential diagnosis and grading of brain tumors. Further exploration into diagnostic procedures that can significantly distinguish between grade III-IV and grade II tumors is needed.

  12. Neonicotinoid insecticides: reduction and cleavage of imidacloprid nitroimine substituent by liver microsomal and cytosolic enzymes.

    Science.gov (United States)

    Schulz-Jander, Daniel A; Leimkuehler, William M; Casida, John E

    2002-09-01

    The major insecticide imidacloprid (IMI) is known to be metabolized by human cytochrome P450 3A4 with NADPH by imidazolidine hydroxylation and dehydrogenation to give 5-hydroxy-imidacloprid and the olefin, respectively, and by nitroimine reduction and cleavage to yield the nitrosoimine, guanidine, and urea derivatives. More extensive metabolism by human or rabbit liver microsomes with NADPH or rabbit liver cytosol without added cofactor reduces the IMI N-nitro group to an N-amino substituent, i.e., the corresponding hydrazone. A major metabolite on incubation of IMI in the human microsome-NADPH system is tentatively assigned by LC/MS as a 1,2,4-triazol-3-one derived from the hydrazone; the same product is obtained on reaction of the hydrazone with ethyl chloroformate. The hydrazone and proposed triazolone are considered here together (referred to as the hydrazone) for quantitation. Only a portion of the microsomal reduction and cleavage of the nitroimine substituent is attributable to a CYP450 enzyme. The cytosolic enzyme conversion to the hydrazone is inhibited by added cofactors (NAD > NADH > NADP > NADPH) and enhanced by an argon instead of an air atmosphere. The responsible cytosolic enzyme(s) does not appear to be DT-diaphorase (which is inhibited by several neonicotinoids), aldose reductase, aldehyde reductase, or xanthine oxidase. However, the cytosolic metabolism of IMI is inhibited by several aldo-keto-reductase inhibitors (i.e., alrestatin, EBPC, Ponalrestat, phenobarbital, and quercetin). Other neonicotinoids with nitroimine, nitrosoimine, and nitromethylene substituents are probably also metabolized by "neonicotinoid nitro reductase(s)" since they serve as competitive substrates for [(3)H]IMI metabolism.

  13. Relative substituent position on the strength of π-π stacking interactions

    OpenAIRE

    Gung, Benjamin W.; Emenike, Bright U.; Alverez, Celeste N.; Rakovan, John; Kirschbaum, Kristin; Jain, Nirbhay

    2010-01-01

    It was observed that the relative position of the arene substituents have a profound influence on the strength of π-π stacking in the 9-benzyl substituted triptycene system. A new series of model compounds (3a-i) capable of revealing quantitatively π-π stacking interactions was studied. This series of compounds (3a-i) has an ortho substituted methyl group in one of the two interacting arenes and the syn/anti ratios were determined and compared to a series previously studied compounds (4a-i) t...

  14. Origin of Substituent Effects in Edge-to-Face Aryl-Aryl Interactions

    OpenAIRE

    Wheeler, Steven E.; Houk, K. N.

    2009-01-01

    Substituent effects in the edge-to-face configuration of the benzene dimer have been studied using modern density functional theory. An accurate interaction potential energy curve has been computed for the unsubstituted dimer using ab initio methods with large basis sets. The recommended binding energy for the edge-to-face benzene dimer is 2.31 kcal mol-1, estimated at the counterpoise-corrected CCSD(T)/aug-cc-pVTZ level of theory. For both edge-ring and face-ring-substituted dimers, interact...

  15. Two-Step, One-Flask Synthesis of an N-Confused Porphyrin Bearing Pentafluorophenyl Substituents.

    Science.gov (United States)

    Fisher, Julia M; Kensy, Victoria K; Geier, G Richard

    2017-04-21

    A two-step, one-flask reaction of pyrrole and pentafluorobenzaldehyde was investigated as a streamlined synthetic route to an N-confused porphyrin bearing pentafluorophenyl substituents previously prepared by a stepwise route. A survey of acid catalysts, acid catalyst concentration, DDQ quantity, and reaction time was performed with monitoring by HPLC. The targeted N-confused porphyrin was observed from many reaction conditions. The best condition afforded the N-confused porphyrin in an isolated yield of 10-12% (245-281 mg), providing improved access to this interesting porphyrinoid.

  16. Polymerization in Liquid Crystal Medium: Preparation of Polythiophene Derivatives Bearing a Bulky Pyrimidine Substituent

    Directory of Open Access Journals (Sweden)

    Hiromasa Goto

    2010-10-01

    Full Text Available We carried out polycondensation of monomers bearing a bulky pyrimidine substituent in a liquid crystal solvent. The resultant polymers formed nematic liquid crystals. The polymers prepared in liquid crystals had higher coplanarity than the polymers prepared in toluene. This can be due to the fact that the ordered medium of the liquid crystal produces an aggregated structure with well-developed π-stacking between the main chains. The present results demonstrated that polymerization of bulky monomers is possible in liquid crystal solvents.

  17. High resolution NMR theory and chemical applications

    CERN Document Server

    Becker, Edwin D

    1969-01-01

    High Resolution NMR: Theory and Chemical Applications focuses on the applications of nuclear magnetic resonance (NMR), as well as chemical shifts, lattices, and couplings. The book first offers information on the theory of NMR, including nuclear spin and magnetic moment, spin lattice relaxation, line widths, saturation, quantum mechanical description of NMR, and ringing. The text then ponders on instrumentation and techniques and chemical shifts. Discussions focus on the origin of chemical shifts, reference compounds, empirical correlations of chemical shifts, modulation and phase detection,

  18. Experimental and Theoretical Study of O-Substituent Effect on the Fluorescence of 8-Hydroxyquinoline

    Directory of Open Access Journals (Sweden)

    Mohie E. M. Zayed

    2015-02-01

    Full Text Available The synthesis and characterization of different ether and ester derivatives of 8-hydroxyquinoline have been made. UV-visible and fluorescence spectra of these compounds have revealed spectral dependence on both solvent and O-substituent. The fluorescence intensity of ether derivatives revealed higher intensity for 8-octyloxyquinoline compared with 8-methoxyquinoline, whereas those of ester derivatives had less fluorescence than 8-hydroxyquinoline. Theoretical calculations based on Time-dependent density functional theory (TD-DFT were carried out for the quinolin-8-yl benzoate (8-OateQ compound to understand the effect of O-substituent on the electronic absorption of 8-hydroxyquinaline (8-HQ. The calculations revealed comparable results with those obtained from the experimental data. Optimized geometrical structure was calculated with DFT at B3LYP/6-311++G** level of theory. The results indicated that 8-OateQ is not a coplanar structure. The absorption spectra of the compound were computed in gas-phase and solvent using B3LYP and CAM-B3LYP methods with 6-311++G ** basis set. The agreement between calculated and experimental wavelengths was very good at CAM-B3LYP/6-311++G** level of theory.

  19. Effects of a fluoro substituent on the fungal metabolism of 1-fluoronaphthalene

    Energy Technology Data Exchange (ETDEWEB)

    Cerniglia, C.E.; Miller, D.W.; Yang, S.K.; Freeman, J.P.

    1984-08-01

    The metabolism of 1-fluoronaphthalene by Cunninghamella elegans ATCC 36112 was studied. The metabolites were isolated by reverse-phase high-pressure liquid chromatography and characterized by the application of UV absorption, /sup 1/H nuclear magnetic resonance, and mass spectral techniques. C. elegans oxidized 1-fluoronaphthalene predominantly at the 3,4- and 5,6-positions to form trans-3,4-dihydroxy-3,4-dihydro-1-fluoronaphthalene and trans-5,6-dihydroxy-5,6-dihydro-1-fluoronaphthalene. In addition, 1-fluoro-8-hydroxy-5-tetralone, 5-hydroxy-1-fluoronaphthanlene, and 4-hydroxy-1-fluoronaphthalene as well as glucoside, sulfate, and glucuronic acid conjugates of these phenols were formed. Circular dichroism spectra of the trans-3,4- and trans-5,6-dihydrodiols formed from 1-fluoronaphthanlene indicated that the major enantiomers of the dihydrodiols have S,S absolute stereochemistries. In contrast, the trans-5,6-dihydrodiol formed from 1-fluoronaphthalene from 3-methylcholanthrene-treated rats had Cotton effects that are opposite in sign (R,R) to those formed by C. elegans. The results indicate that the fungal monooxygenase-epoxide hydrolase systems are highly stereoselective in the metabolism of 1-fluoronaphthalene and that a fluoro substituent blocks epoxidation at the fluoro-substituted double bond, decreases oxidation at the aromatic double bond that is peri to the fluoro substituent, and enhances metabolism at the 3,4- and 5,6-positions of 1-fluoronaphthalene.

  20. The Influence of Substituent Orientation on the Photovoltaic Performance of Phthalocyanine-Sensitized Solar Cells.

    Science.gov (United States)

    Tejerina, Lara; Martínez-Díaz, M Victoria; Nazeeruddin, Mohammad Khaja; Torres, Tomas

    2016-03-18

    Phthalocyanines (Pcs) are used as sensitizers in dye-sensitized solar cells (DSSCs) because of their stability and intense absorption in the red and near-IR regions. Impressive progress has been made in photovoltaic efficiencies by introduction of bulky peripheral substituents to help suppress macrocycle aggregation. To reach benchmark efficiencies reported for other related dyes, new designs need to be explored. Single carboxy-ZnPc regioisomers substituted at the non-peripheral positions by rigid aryl groups have now been studied, which has shed light on the influence of steric hindrance and/or orientation of the substituent around the anchoring group on the photovoltaic response. The regioisomer bearing the aryl group far away from the anchoring group produces a more effective sensitization of the TiO2 films and higher short-circuit photocurrent density (Jsc). Taking advantage of the good photovoltaic performance in the near-IR region of this ZnPc, it was combined with another appropriate dye for panchromatic sensitization of the mesoporous photoelectrode and an increase of the overall device efficiency. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. A Computational Study of Structure and Reactivity of N-Substitued-4-Piperidones Curcumin Analogues and Their Radical Anions

    Directory of Open Access Journals (Sweden)

    Maximiliano Martínez-Cifuentes

    2016-12-01

    Full Text Available In this work, a computational study of a series of N-substitued-4-piperidones curcumin analogues is presented. The molecular structure of the neutral molecules and their radical anions, as well as their reactivity, are investigated. N-substituents include methyl and benzyl groups, while substituents on the aromatic rings cover electron-donor and electron-acceptor groups. Substitutions at the nitrogen atom do not significantly affect the geometry and frontier molecular orbitals (FMO energies of these molecules. On the other hand, substituents on the aromatic rings modify the distribution of FMO. In addition, they influence the capability of these molecules to attach an additional electron, which was studied through adiabatic (AEA and vertical electron affinities (VEA, as well as vertical detachment energy (VDE. To study electrophilic properties of these structures, local reactivity indices, such as Fukui (f+ and Parr (P+ functions, were calculated, and show the influence of the aromatic rings substituents on the reactivity of α,β-unsaturated ketones towards nucleophilic attack. This study has potential implications for the design of curcumin analogues based on a 4-piperidone core with desired reactivity.

  2. Effect of 2, 5-Substituents on the Stability of Cyclic Nitrone Superoxide Spin Adducts: A Density Functional Theory Approach

    Science.gov (United States)

    Du, Li-Bo; Wang, Lan-Fen; Liu, Yang-Ping; Jia, Hong-Ying; Liu, Yang; Liu, Ke Jian; Tian, Qiu

    2011-01-01

    To design efficient spin traps for superoxide radicals, interest in the elucidation of substituent effects on the stability of superoxide spin adducts has become a necessary priority. In the present study, five cyclic nitrone superoxide spin adducts, i.e. DMPO-OOH, M3PO-OOH, EMPO-OOH, DEPMPO-OOH, and DEPDMPO-OOH, were chosen as model compounds to investigate the effect of 2,5-subsitituents on their stability, through structural analysis and decay thermodynamics using density functional theory (DFT) calculations. Analysis of the optimized geometries reveals that none of the previously proposed stabilizing factors, including intramolecular H-bonds, intramolecular nonbonding interactions, bulky steric protection, nor the C(2)–N(1) bond distance can be used to clearly explain the effect of 2,5-substituents on the stability of the spin adducts. Additionally the effect of the 2,5-substituents on the stability of the superoxide spin adducts cannot be simply clarified by Milliken charges on both atoms (nitroxyl nitrogen and nitroxyl oxygen). Subsequent study found that spin densities on the nitroxyl nitrogen and oxygen are well correlated with the half-life times of the spin adducts, and consequently are the proper parameters to characterize the effect of 2,5-substituents on their stability. Examination of the decomposition thermodynamics further supports the effect of the substituents on the persistence of cyclic nitrone superoxide spin adducts. PMID:20370568

  3. Constituintes químicos de Ottonia corcovadensis Miq. da floresta Amazônica: atribuição dos deslocamentos químicos dos átomos de hidrogênio e carbono Chemical constituents of Ottonia corcovadensis Miq. from Amazon forest: ¹h and 13c chemical shift assignments

    Directory of Open Access Journals (Sweden)

    Valdir A. Facundo

    2004-02-01

    Full Text Available In an ethanolic extract of leaves of Ottonia corcovadensis (Piperaceae were identified sixteen terpenoids of essential oil and the three flavonoids 3',4',5,5',7-pentamethoxyflavone (1, 3',4',5,7-tetramethoxyflavone (2 and 5-hydroxy-3',4',5',7-tetramethoxyflavone (3 and cafeic acid (4. Two amides (5 and 6 were isolated from an ethanolic extract of the roots. The structures were established by spectral analysis, meanly NMR (1D and 2D and mass spectra. Extensive NMR analysis was also used to complete ¹H and 13C chemical shift assignments of the flavonoids and amides. The components of the essential oil were identified by computer library search, retention indices and visual interpretation of mass spectra.

  4. Predicting the Shifts of Absorption Maxima of Azulene Derivatives Using Molecular Modeling and ZINDO CI Calculations of UV-Vis Spectra

    Science.gov (United States)

    Patalinghug, Wyona C.; Chang, Maharlika; Solis, Joanne

    2007-01-01

    The deep blue color of azulene is drastically changed by the addition of substituents such as CH[subscript 3], F, or CHO. Computational semiempirical methods using ZINDO CI are used to model azulene and azulene derivatives and to calculate their UV-vis spectra. The calculated spectra are used to show the trends in absorption band shifts upon…

  5. Substituent effect on the preferred DNA binding mode and affinity of a homologous series of naphthalene diimides.

    Science.gov (United States)

    McKnight, Ruel E; Reisenauer, Eric; Pintado, Manuel V; Polasani, Shivani R; Dixon, Dabney W

    2011-07-15

    A combination of isothermal titration calorimetry (ITC), topoisomerase I DNA unwinding assays, and ethidium bromide displacement studies were employed to investigate the binding of a homologous series of naphthalene diimides (NDI) to DNA. Our results suggest that the nature of the substituent plays a significant role in both the preferred binding mode and relative binding affinity of the compounds of this study. Only intercalative-type binding (K=15±3×10(6)M(-1)) was observed for the NDI with the smallest substituent (trimethyl-ethylamino), while larger members of the series (diethylmethyl-, dipropylmethyl- and dibutylmethyl-ethylamino substituents) adopted an additional binding mode of higher affinity (K(1)=31-78×10(6)M(-1)). Copyright © 2011 Elsevier Ltd. All rights reserved.

  6. Tertiary aminomethylphenols and methylene bisphenols with isobornyl substituents in the reaction with diphenylpicrylhydrazyl and peroxy radicals in ethylbenzene

    Science.gov (United States)

    Mazaletskaya, L. I.; Sheludchenko, N. I.; Shishkina, L. N.; Buravlev, E. V.; Chukicheva, I. Yu.; Kutchin, A. V.

    2013-04-01

    The effect of the structure of aminomethylphenols and methylene bisphenols with isobornyl substituents on their reactivity in interactions with peroxy radicals in ethylbenzene and with 1,1-diphenyl-2-picrylhydrazyl (DPPH) is studied. Isobornylphenols with o-aminomethyl substituents, as opposed to p-aminomethyl derivatives, were found to possess rather low activity in the initiated oxidation of ethylbenzene, due to the formation of intramolecular hydrogen bonds between the hydrogen atom of the OH group and the nitrogen atom of the aminomethyl substituent. An increase in activity of o-aminomethyl-substituted phenols with increasing polarity of the medium is observed in the reaction with DPPH. The reaction rate constants for the interaction between two isomeric 2,2'- and 4,4'-methylene-bisphenols having isobornyl moieties and ethylbenzene peroxy radicals are measured. The ratio between activities of the first and second OH groups in 2,2-methylene-bisphenol is shown to be close to 50.

  7. Nanostructures and Self-Assembly of Organogels via Benzimidazole/Benzothiazole Imide Derivatives with Different Alkyl Substituent Chains

    Directory of Open Access Journals (Sweden)

    Xihai Shen

    2013-01-01

    Full Text Available New benzimidazole/benzothiazole imide derivatives with different alkyl substituent chains were designed and synthesized. Their gelation behaviors in 22 solvents were tested as novel low-molecular-mass organic gelators. The test showed that the alkyl substituent chains and headgroups of benzimidazole/benzothiazole residues in gelators played a crucial role in the gelation behavior of all compounds in various organic solvents. More alkyl chains in molecular skeletons in present gelators are favorable for the gelation of organic solvents. SEM and AFM observations revealed that the gelator molecules self-assemble into different aggregates from wrinkle, lamella and belt to dot with change of solvents. Spectral studies indicated that there existed different H-bond formation between imide groups and hydrophobic force of alkyl substituent chains in molecular skeletons. The present work may give some insights into design and character of new organogelators and soft materials with special molecular structures.

  8. Substituent effects in 1-nitro-4-substituted bicyclo[2.2.2]octane derivatives: inductive or field effects?

    Science.gov (United States)

    Krygowski, Tadeusz M; Oziminski, Wojciech P

    2014-08-01

    Interactions between the NO2 group and 13 different substituents (BF2, BH2, CF3, CH3, CHO, CN, F, NH2, NMe2, NO2, NO, OH, OMe) were investigated computationally for bicyclo[2.2.2]octane (BCO) and benzene substituted at 1,4 and 1,3 positions in the ring. Three methods were employed to estimate the character and strength of the substituent effect: substituent effect stabilization energy (SESE), sigma/pi electron donor acceptor index (sEDA/pEDA) and substituent active region (cSAR) parameter. For the first time the sEDA/pEDA parameters were calculated not for the ring but for the NO2 group. All calculations were performed at the B3LYP/6-31G(d,p) level of theory. For 1,4 derivatives, a direct comparison of slopes of linear regressions between BCO and benzene reveals a much better transmission of the substituent effect in the latter. The ratio of slopes (benzene over BCO) is always larger than 4. It follows that the resonance effects, which are absent in the BCO, dominate in this case. For 1,3 derivatives, because of much lower correlation coefficients, estimated standard deviations (ESD) were used to calculate the ratio instead of the slopes. For these systems the ratio is much closer to the unity, which indicates that only the sigma/through space effects are present and they are of similar magnitude in benzene and BCO. It follows from natural population analysis (NPA) charges that the substituent effect in the studied systems is due mainly to through-space interactions.

  9. The effect of pyridyl substituents on the thermodynamics of porphyrin binding to G-quadruplex DNA.

    Science.gov (United States)

    Rowland, Gerald B; Barnett, Kerry; Dupont, Jesse I; Akurathi, Gopalakrishna; Le, Vu H; Lewis, Edwin A

    2013-12-01

    Most of the G-quadruplex interactive molecules reported to date contain extended aromatic flat ring systems and are believed to bind principally by π-π stacking on the end G-tetrads of the quadruplex structure. One such molecule, TMPyP4, (5,10,15,20-tetra(N-methyl-4-pyridyl)porphyrin), exhibits high affinity and some selectivity for G-quadruplex DNA over duplex DNA. Although not a realistic drug candidate, TMPyP4 is used in many nucleic acid research laboratories as a model ligand for the study of small molecule G-quadruplex interactions. Here we report on the synthesis and G-quadruplex interactions of four new cationic porphyrin ligands having only 1, 2, or 3 (N-methyl-4-pyridyl) substituents. The four new ligands are: P(5) (5-(N-methyl-4-pyridyl)porphyrin), P(5,10) (5,10-di(N-methyl-4-pyridyl)porphyrin), P(5,15) (5,15-di(N-methyl-4-pyridyl)porphyrin), and P(5,10,15) (5,10,15-tri(N-methyl-4-pyridyl)porphyrin). Even though these compounds have been previously synthesized, we report alternative synthetic routes that are more efficient and that result in higher yields. We have used ITC, CD, and ESI-MS to explore the effects of the number of N-methyl-4-pyridyl substituents and the substituent position on the porphyrin on the G-quadruplex binding energetics. The relative affinities for binding these ligands to the WT Bcl-2 promoter sequence G-quadruplex are: K(TMPyP4)≈K(P)(5,15)>KP(5,10,15)>KP(5,10), KP(5). The saturation stoichiometry is 2:1 for both P(5,15) and P(5,10,15), while neither P(5) nor P(5,10) exhibit significant complex formation with the WT Bcl-2 promoter sequence G-quadruplex. Additionally, binding of P(5,15) appears to interact by an 'intercalation mode' while P(5,10,15) appears to interact by an 'end-stacking mode'. Copyright © 2013 Elsevier Ltd. All rights reserved.

  10. OpenShift Workshop

    CERN Multimedia

    CERN. Geneva; Rodriguez Peon, Alberto

    2017-01-01

    Workshop to introduce developers to the OpenShift platform available at CERN. Several use cases will be shown, including deploying an existing application into OpenShift. We expect attendees to realize about OpenShift features and general architecture of the service.

  11. Comparative analysis of the influence of bulky β-alkyl substituents on fluorescent properties of some series of spatially distorted meso-phenyl substituted porphyrins

    Science.gov (United States)

    Sagun, E. I.; Zenkevich, E. I.

    2013-11-01

    We present results of our systematic investigation and comparative analysis of the spectral-kinetic properties of absorption and fluorescence of two series of related planar porphyrins in liquid media at 293 K, in which deviations from the planarity are caused by contact steric interactions of eight peripheral β-pyrrole methyl (-CH3) or ethyl (-C2H5) groups with a successively increasing number (from one to four) and varying position of meso-phenyl (Ph) substituents in the porphyrin macrocycle. It is substantiated that considerable differences between the spectral-kinetic properties of absorption and fluorescence of the octaethyl- and octamethylporphyrin molecules, which have the same number of meso-phenyl substituents, are caused by fundamentally different roles played by β-ethyl and β-methyl groups, which differ in volume and which determine differences in the character of steric interactions and the efficiency of the dynamic relaxation of the tetrapyrrole macrocycle. It is revealed that there is a difference between calculated f theor and experimentally determined f exp values of the fluorescence probability, which is caused by conformational rearrangements of spatially distorted porphyrin macrocycles in the S 1 excited state, which reduce the oscillator strength and lower the energy of the long-wavelength transition S 0 → S 1. It is found that the chemical nature, the size, and the number of bulky -CH3 or -C2H5 β-pyrrole groups affect weakly rate constants of fluorescence quenching by molecular oxygen and do not create noticeable steric hindrances for contact interactions of the oxygen molecule with the π-conjugated system of the tetrapyrrole macrocycle.

  12. Some heterocyclic azo dyes derived from thiazolyl derivatives; synthesis; substituent effects and solvatochromic studies.

    Science.gov (United States)

    Yazdanbakhsh, M R; Mohammadi, A; Abbasnia, M

    2010-12-01

    A series of azo disperse dyes were synthesized by coupling reaction of N,N-diethylaniline, 2-anilinoethanol and N-phenyl-2,2'-iminodiethanol with diazotized aminothiazolyl derivatives as diazo components. These dyes have been prepared in good yields, and were characterized by UV-Vis, FT-IR and 1H NMR spectroscopic techniques. The effects of solvent polarity and various pH on dyes in the visible absorption spectra were evaluated. All dyes exhibit an excellent correlation coefficient (r>0.92) for the linear solvation energy relationship with π* values calculated by Kamlet et al. The influence of the pH on the dyes with electron-donating group implied that these dyes exist in acid-base equilibrium in acidic environment. The effect of substituents of both coupler and diazo component on the color of dyes was investigated as well. Copyright © 2010 Elsevier B.V. All rights reserved.

  13. Influence of substituent heteroatoms on the cytoprotective properties of pyrimidinol antioxidants.

    Science.gov (United States)

    Chevalier, Arnaud; Khdour, Omar M; Schmierer, Margaret; Bandyopadhyay, Indrajit; Hecht, Sidney M

    2017-03-01

    Recently, we described the optimization of novel pyrimidinol-based antioxidants as potential therapeutic molecules for targeting mitochondrial diseases. That study focused on improving the potency and metabolic stability of pyrimidinol antioxidants. This led us to consider the possibility of altering the positions of the exocyclic alkoxy and alkylamino substituents on the pyrimidinol scaffold. Twelve new analogues were prepared and their biological activities were investigated. The metabolic stability of the prepared regioisomers was also assessed in vitro using bovine liver microsomes. Unexpectedly, the 2-alkoxy-4-alkylamino substituted pyrimidinol antioxidants were found to have properties in protecting mitochondrial function superior to the isomeric 4-alkoxy-2-alkylamino substituted pyrimidinols evaluated in all earlier studies. This observation suggests a possible mode of action involving the intermediacy of an ortho-iminoquinone, a species not previously associated with mitochondrial respiratory chain function. Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. Design, synthesis and evaluation of aspirin analogues having an additional carboxylate substituent for antithrombotic activity.

    Science.gov (United States)

    Alagha, Ahmed; Moman, Edelmiro; Adamo, Mauro F A; Nolan, Kevin B; Chubb, Anthony J

    2009-08-01

    Acetylsalicylic acid (aspirin) is an effective long-term prophylaxis of thrombotic events such as heart attacks and strokes. It covalently inhibits prostaglandin-H-synthase by interacting with Arg120 or Tyr385 at the active site allowing delivery of its acetyl group to Ser530. However the structure has not been optimized to fit the active site. We have designed acetylsalicylate analogues with an additional carboxylate substituent which allows simultaneous interaction with Arg120 and Tyr385 whilst positioning the acetyl group in close proximity to Ser530. One of these, an ester derivative which unlike acetylsalicylic acid is non-acidic, may act as useful lead compound for further exploitation of this approach.

  15. Effect of substituent of terpyridines on the DNA-interaction of polypyridyl ruthenium(II) complexes

    Science.gov (United States)

    Patel, Mohan N.; Gandhi, Deepen S.; Parmar, Pradhuman A.

    2011-12-01

    An octahedral complexes of ruthenium with 2,9-dimethyl-1,10-phenanthroline (dmphen) and substituted terpyridine have been synthesized. The Ru II complexes have been characterized by elemental analyses, thermogravimetric analyses, magnetic moment measurements, FT-IR, electronic, 1H NMR and FAB mass spectra. The binding strength and mode of interaction of the complexes with Herring Sperm DNA has been investigated using absorption titration and viscosity measurement studies. Results suggest that the substituent on terpyridine ligand affects the binding mode and binding ability of the complexes. Effect of time and ionic strength on DNA cleavage ability of complex has also been studied by gel electrophoresis. Results suggest that more than 200 mM concentration of NaCl decreases the cleavage ability of complex.

  16. Substituent Dependence of Third-Order Optical Nonlinearity in Chalcone Derivatives

    Science.gov (United States)

    Kiran, Anthony John; Satheesh Rai, Nooji; Chandrasekharan, Keloth; Kalluraya, Balakrishna; Rotermund, Fabian

    2008-08-01

    The third-order nonlinear optical properties of derivatives of dibenzylideneacetone were investigated using the single beam z-scan technique at 532 nm. A strong dependence of third-order optical nonlinearity on electron donor and acceptor type of substituents was observed. An enhancement in χ(3)-value of one order of magnitude was achieved upon the substitution of strong electron donors compared to that of the molecule substituted with an electron acceptor. The magnitude of nonlinear refractive index of these chalcones is as high as of 10-11 esu. Their nonlinear optical coefficients are larger than those of widely used thiophene oligomers and trans-1-[p-(p-dimethylaminobenzyl-azo)-benzyl]-2-(N-methyl-4-pyridinium)-ethene iodide (DABA-PEI) organic compounds.

  17. Exothermic or Endothermic Decomposition of Disubstituted Tetrazoles Tuned by Substitution Fashion and Substituents.

    Science.gov (United States)

    Jia, Yu-Hui; Yang, Kai-Xiang; Chen, Shi-Lu; Huang, Mu-Hua

    2018-01-11

    Nitrogen-rich compounds such as tetrazoles are widely used as candidates in gas-generating agents. However, the details of the differentiation of the two isomers of disubstituted tetrazoles are rarely studied, which is very important information for designing advanced materials based on tetrazoles. In this article, pairs of 2,5- and 1,5-disubstituted tetrazoles were carefully designed and prepared for study on their thermal decomposition behavior. Also, the substitution fashion of 2,5- and 1,5- and the substituents at C-5 position were found to affect the endothermic or exothermic properties. This is for the first time to the best of our knowledge that the thermal decomposition properties of different tetrazoles could be tuned by substitution ways and substitute groups, which could be used as a useful platform to design advanced materials for temperature-dependent rockets. The aza-Claisen rearrangement was proposed to understand the endothermic decomposition behavior.

  18. Role of aromatic substituents on the antiproliferative effects of diphenyl ferrocenyl butene compounds.

    Science.gov (United States)

    Zekri, Ouardia; Hillard, Elizabeth A; Top, Siden; Vessières, Anne; Pigeon, Pascal; Plamont, Marie-Aude; Huché, Michel; Boutamine, Sultana; McGlinchey, Michael J; Müller-Bunz, Helge; Jaouen, Gérard

    2009-06-14

    We have been exploring the cytotoxic effects of conjugated phenylferrocene systems on breast cancer cells. Complexes with p-OH, p-NH(2), and p-NHC(O)CH(3) substitution show particularly high activity, with IC(50) values in the low or sub micromolar range for both the hormone-dependent MCF-7 and hormone-independent MDA-MB-231 breast cancer cell lines. We now present the synthesis, X-ray crystal structures and biochemical studies of analogous halogen or pseudo-halogen para-substituted compounds with R = Cl, (Z)-7a; Br, (Z)-7b; CF(3), (E)-7c; and CN, (E)-7d and (Z)-7d. Lacking hydrogen bonding groups, the compounds have low, but non-zero, relative binding affinity values for the oestrogen receptor alpha (RBA substituent, are more strongly dependent on the presence of a proton in the functional group, supporting our prior proposition that electrophilic quinoid forms of the compounds could be active species in the cell. A correlation of the redox potential of the ferrocenyl moiety with the Hammett-Taft constants of the substituents was observed.

  19. Supramolecular synthons on surfaces : Controlling dimensionality and periodicity of tetraarylporphyrin assemblies by the interplay of cyano and alkoxy substituents

    NARCIS (Netherlands)

    Wintjes, Nikolai; Hornung, Jens; Lobo-Checa, Jorge; Voigt, Tobias; Samuely, Tomáš; Thilgen, Carlo; Stöhr, Meike; Diederich, François; Jung, Thomas A.

    2008-01-01

    The self-assembly of three porphyrin derivatives was studied in detail on a Cu(111) substrate by means of scanning tunneling microscopy (STM). All derivatives have two 4-cyanophenyl substituents in diagonally opposed meso-positions of the porphyrin core. but differ in the nature of the other two

  20. Self-Assembly and Drug Release Capacities of Organogels via Some Amide Compounds with Aromatic Substituent Headgroups

    Directory of Open Access Journals (Sweden)

    Lexin Zhang

    2016-07-01

    Full Text Available In this work, some amide compounds with different aromatic substituent headgroups were synthesized and their gelation self-assembly behaviors in 22 solvents were characterized as new gelators. The obtained results indicated that the size of aromatic substituent headgroups in molecular skeletons in gelators showed crucial effect in the gel formation and self-assembly behavior of all compounds in the solvents used. Larger aromatic headgroups in molecular structures in the synthesized gelator molecules are helpful to form various gel nanostructures. Morphological investigations showed that the gelator molecules can self-assembly and stack into various organized aggregates with solvent change, such as wrinkle, belt, rod, and lamella-like structures. Spectral characterizations suggested that there existed various weak interactions including π-π stacking, hydrogen bonding, and hydrophobic forces due to aromatic substituent headgroups and alkyl substituent chains in molecular structures. In addition, the drug release capacities experiments demonstrated that the drug release rate in present obtained gels can be tuned by adjusting the concentrations of dye. The present work would open up enormous insight to design and investigate new kind of soft materials with designed molecular structures and tunable drug release performance.

  1. Natural bond orbital approach to the transmission of substituent effect through the fulvene and benzene ring systems.

    Science.gov (United States)

    Oziminski, Wojciech P; Krygowski, Tadeusz M

    2011-03-01

    Electronic structure of 22 monosubstituted derivatives of benzene and exocyclically substituted fulvene with substituents: B(OH)(2), BH(2), CCH, CF(3), CH(3), CHCH(2), CHO, Cl, CMe(3), CN, COCH(3), CONH(2), COOH, F, NH(2), NMe(2), NO, NO(2), OCH(3), OH, SiH(3), SiMe(3) were studied theoretically by means of Natural Bond Orbital analysis. It is shown, that sum of π-electron population of carbon atoms of the fulvene and benzene rings, pEDA(F) and pEDA(B), respectively correlate well with Hammett substituent constants [Formula in text] and aromaticity index NICS. The substituent effect acting on pi-electron occupation at carbon atoms of the fulvene ring is significantly stronger than in the case of benzene. Electron occupations of ring carbon atoms (except C1) in fulvene plotted against each other give linear regressions with high correlation coefficients. The same is true for ortho- and para-carbon atoms in benzene. Positive slopes of the regressions indicate similar for fulvene and benzene kind of substituent effect - mostly resonance in nature. Only the regressions of occupation at the carbon atom in meta- position of benzene against ortho- and para-positions gives negative slopes and low correlation coefficients.

  2. Lanthanide ion (III) complexes of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraaminophosphonate (DOTA-4AmP8−) for dual biosensing of pH with CEST (chemical exchange saturation transfer) and BIRDS (biosensor imaging of redundant deviation in shifts)

    Science.gov (United States)

    Huang, Yuegao; Coman, Daniel; Ali, Meser M.; Hyder, Fahmeed

    2014-01-01

    Relaxivity based magnetic resonance of phosphonated ligands chelated with gadolinium (Gd3+) shows promise for pH imaging. However instead of monitoring the paramagnetic effect of lanthanide complexes on the relaxivity of water protons, biosensor (or molecular) imaging with magnetic resonance is also possible by detecting either the non-exchangeable or the exchangeable protons on the lanthanide complexes themselves. The non-exchangeable protons (e.g., –CHx, where 3≥x≥1) are detected using a three-dimensional chemical shift imaging method called Biosensor Imaging of Redundant Deviation in Shifts (BIRDS), whereas the exchangeable protons (e.g., –OH or –NHy, where 2≥y≥1) are measured with Chemical Exchange Saturation Transfer (CEST) contrast. Here we tested the feasibility of BIRDS and CEST for pH imaging of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraaminophosphonate (DOTA-4AmP8−) chelated with thulium (Tm3+) and ytterbium (Yb3+). BIRDS and CEST experiments show that both complexes are responsive to pH and temperature changes. Higher pH and temperature sensitivities are obtained with BIRDS for either complex when using the chemical shift difference between two proton resonances vs. using the chemical shift of a single proton resonance, thereby eliminating the need to use water resonance as reference. While CEST contrast for both agents is linearly dependent on pH within a relatively large range (i.e., 6.3-7.9), much stronger CEST contrast is obtained with YbDOTA-4AmP5− than with TmDOTA-4AmP5−. In addition, we demonstrate the prospect of using BIRDS to calibrate CEST as new platform for quantitative pH imaging. PMID:24801742

  3. Insomnia in shift work.

    Science.gov (United States)

    Vallières, Annie; Azaiez, Aïda; Moreau, Vincent; LeBlanc, Mélanie; Morin, Charles M

    2014-12-01

    Shift work disorder involves insomnia and/or excessive sleepiness associated with the work schedule. The present study examined the impact of insomnia on the perceived physical and psychological health of adults working on night and rotating shift schedules compared to day workers. A total of 418 adults (51% women, mean age 41.4 years), including 51 night workers, 158 rotating shift workers, and 209 day workers were selected from an epidemiological study. An algorithm was used to classify each participant of the two groups (working night or rotating shifts) according to the presence or absence of insomnia symptoms. Each of these individuals was paired with a day worker according to gender, age, and income. Participants completed several questionnaires measuring sleep, health, and psychological variables. Night and rotating shift workers with insomnia presented a sleep profile similar to that of day workers with insomnia. Sleep time was more strongly related to insomnia than to shift work per se. Participants with insomnia in the three groups complained of anxiety, depression, and fatigue, and reported consuming equal amounts of sleep-aid medication. Insomnia also contributed to chronic pain and otorhinolaryngology problems, especially among rotating shift workers. Work productivity and absenteeism were more strongly related to insomnia. The present study highlights insomnia as an important component of the sleep difficulties experienced by shift workers. Insomnia may exacerbate certain physical and mental health problems of shift workers, and impair their quality of life. Copyright © 2014 Elsevier B.V. All rights reserved.

  4. Implementing OpenShift

    CERN Document Server

    Miller, Adam

    2013-01-01

    A standard tutorial-based approach to using OpenShift and deploying custom or pre-built web applications to the OpenShift Online cloud.This book is for software developers and DevOps alike who are interested in learning how to use the OpenShift Platform-as-a-Service for developing and deploying applications, how the environment works on the back end, and how to deploy their very own open source Platform-as-a-Service based on the upstream OpenShift Origin project.

  5. Substituent effects on noncovalent bonds: complexes of ionized benzene derivatives with hydrogen cyanide.

    Science.gov (United States)

    Attah, Isaac K; Hamid, Ahmed M; Meot-Ner Mautner, Michael; El-Shall, M S; Aziz, Saadullah G; Alyoubi, Abdulrahman O

    2013-10-17

    Here, we report the first experimental and computational study of the noncovalent binding energies and structures of ionized benzenes containing electron-withdrawing substituents solvated by one to four HCN molecules. Measured by ion mobility mass spectrometric equilibrium studies, the bond dissociation enthalpies of the first HCN molecule to the fluorobenzene (C6H5F(•+)), 1,4-difluorobenzene (C6H4F2(•+)), and benzonitrile (C6H5CN(•+)) ions (11.2, 11.2, and 9.2 kcal/mol, respectively) are similar to those of HCN with the benzene (C6H6(•+)) and phenyacetylene (C6H5CCH(•+)) radical cations (9.2 and 10.5 kcal/mol, respectively). DFT calculations at the B3LYP/6-311++G(d,p) level show that HCN can form in-plane hydrogen bonds to ring hydrogens, or bind electrostatically to positively charged carbon centers in the ring. The electron-withdrawing substituents increase the bond energy by increasing the partial positive charge on the ring hydrogens that form CH(δ+)---NCH bonds, and by creating a π hole, as evidenced by positive charge centers on the fluorinated ring carbons for electrostatically bonded isomers. In the complexes of benzonitrile(•+), similar to benzene(•+), hydrogen bonded planar isomers have the lowest energy. In the complexes of (fluorinated benzene)(•+), the lowest energy isomers are electrostatically bonded where HCN is perpendicular to the ring and its dipole points to a positively charged ring carbon. However, in all cases the planar hydrogen-bonded and vertical electrostatic isomers have similar binding energies within 1 kcal/mol, although HCN interacts with different sites of the ionized benzenes in these isomers, suggesting that the observed cluster populations are mixtures of the planar and vertical isomers. Further HCN molecules can bind directly to unoccupied ring CH hydrogens or bind to the first-shell HCN molecules to form linear HCN---HCN--- hydrogen bonded chains. The binding energies decrease stepwise to about 6-7 kcal/mol by

  6. Shifting employment revisited

    NARCIS (Netherlands)

    Cremers, Jan; Gramuglia, Alessia

    2014-01-01

    The CLR-network examined in 2006 the phenomenon of undeclared labour, with specific regard to the construction sector. The resulting study, Shifting Employment: undeclared labour in construction (Shifting-study hereafter), gave evidence that this is an area particularly affected by undeclared

  7. Shifted Independent Component Analysis

    DEFF Research Database (Denmark)

    Mørup, Morten; Madsen, Kristoffer Hougaard; Hansen, Lars Kai

    2007-01-01

    Delayed mixing is a problem of theoretical interest and practical importance, e.g., in speech processing, bio-medical signal analysis and financial data modelling. Most previous analyses have been based on models with integer shifts, i.e., shifts by a number of samples, and have often been carried...

  8. OpenShift cookbook

    CERN Document Server

    Gulati, Shekhar

    2014-01-01

    If you are a web application developer who wants to use the OpenShift platform to host your next big idea but are looking for guidance on how to achieve this, then this book is the first step you need to take. This is a very accessible cookbook where no previous knowledge of OpenShift is needed.

  9. DFT study of the effect of substituents on the absorption and emission spectra of Indigo

    Directory of Open Access Journals (Sweden)

    Cervantes-Navarro Francisco

    2012-07-01

    Full Text Available Abstract Background Theoretical analyses of the indigo dye molecule and its derivatives with Chlorine (Cl, Sulfur (S, Selenium (Se and Bromine (Br substituents, as well as an analysis of the Hemi-Indigo molecule, were performed using the Gaussian 03 software package. Results Calculations were performed based on the framework of density functional theory (DFT with the Becke 3- parameter-Lee-Yang-Parr (B3LYP functional, where the 6-31 G(d,p basis set was employed. The configuration interaction singles (CIS method with the same basis set was employed for the analysis of excited states and for the acquisition of the emission spectra. Conclusions The presented absorption and emission spectra were affected by the substitution position. When a hydrogen atom of the molecule was substituted by Cl or Br, practically no change in the absorbed and emitted energies relative to those of the indigo molecule were observed; however, when N was substituted by S or Se, the absorbed and emitted energies increased.

  10. Substituent effects on the pairing and polymerase recognition of simple unnatural base pairs

    Science.gov (United States)

    Hwang, Gil Tae; Romesberg, Floyd E.

    2006-01-01

    As part of an effort to develop stable and replicable unnatural base pairs, we have evaluated a large number of unnatural nucleotides with predominantly hydrophobic nucleobases. Despite its limited aromatic surface area, a nucleobase analog scaffold that has emerged as being especially promising is the simple phenyl ring. Modifications of this scaffold with methyl and fluoro groups have been shown to impact base pair stability and polymerase recognition, suggesting that nucleobase shape, hydrophobicity and electrostatics are important. To further explore the impact of heteroatom substitution within this nucleobase scaffold, we report the synthesis, stability and polymerase recognition of nucleoside analogs bearing single bromo- or cyano-derivatized phenyl rings. Both modifications are found to generally stabilize base pair formation to a greater extent than methyl or fluoro substitution. Moreover, polymerase recognition of the unnatural base pairs is found to be very sensitive to both the position and nature of the heteroatom substituent. The results help identify the determinants of base pair stability and efficient replication and should contribute to the effort to develop stable and replicable unnatural base pairs. PMID:16617144

  11. Effects of para-fluorine substituent of polystyrene on gradient-index fiber-optic properties

    Science.gov (United States)

    Koike, Kotaro; Suzuki, Akifumi; Makino, Kenji; Koike, Yasuhiro

    2015-01-01

    To study the effects of fluorine substituent of polystyrene (PSt) on gradient-index fiber-optic properties, a poly(para-fluorostyrene) (P(p-FSt))-based graded-index plastic optical fiber (GI POF) is fabricated, and its properties are compared with those of a PSt-based GI POF. The para-fluorine substitution positively affects the glass transition temperature (Tg) of the core, wavelength dispersion of the optimum refractive index profile, bandwidth, and attenuation. The core Tg of the P(p-FSt)-based GI POF is 88 °C, which is higher than that of the PSt-based GI POF by 9 °C when both fibers have an identical numerical aperture (NA = 0.2). The optimum refractive index profile coefficient for the P(p-FSt)-based GI POF varies from 2.2 to 2.1 in the 600-800 nm range, whereas that for the PSt-based GI POF varies from 2.6 to 2.3 in the same wavelength region. The bandwidth of the P(p-FSt)-based GI POF is intrinsically higher than that of PSt-based GI POF. Moreover, the fiber attenuation of the P(p-FSt)-based GI POF was significantly smaller than that of the PSt-based GI POF over the source wavelength range. Our study demonstrates that P(p-FSt) has favorable properties as a GI POF base material.

  12. Substituent effects of porphyrins on structures and photophysical properties of amphiphilic porphyrin aggregates.

    Science.gov (United States)

    Hosomizu, Kohei; Oodoi, Masaaki; Umeyama, Tomokazu; Matano, Yoshihiro; Yoshida, Kaname; Isoda, Seiji; Isosomppi, Marja; Tkachenko, Nikolai V; Lemmetyinen, Helge; Imahori, Hiroshi

    2008-12-25

    Substituent effects of porphyrin on the structures and photophysical properties of the J-aggregates of protonated 5-(4-alkoxyphenyl)-10,15,20-tris(4-sulfonatophenyl)porphyrin have been examined for the first time. Selective formation of the porphyrin J-aggregate was attained when suitable length of the alkoxy group was employed for the amphiphilic porphyrin. Namely, a regular leaflike structure was observed for the J-aggregates of protonated 5-(4-octyloxyphenyl)-10,15,20-tris(4-sulfonatophenyl)porphyrin, which was consistent with the results obtained by using the UV-visible absorption and dynamic light-scattering measurements. A bilayer structure in which the hydrophobic alkoxyl groups facing inside the bilayer are interdigitated to each other, whereas the hydrophilic porphyrin moieties are exposed outside, was proposed to explain the unique porphyrin J-aggregate. Fast energy migration and efficient quenching by defect site in the J-aggregates were suggested to rationalize the short lifetimes of the excited J-aggregates.

  13. Aluminum-phosphorus triple bonds: Do substituents make Altbnd6 P synthetically accessible?

    Science.gov (United States)

    Lu, Jia-Syun; Yang, Ming-Chung; Su, Ming-Der

    2017-10-01

    The effect of substitution on the potential energy surfaces of triple-bonded RAltbnd6 PR (R = F, OH, H, CH3, SiH3, SiMe(SitBu3)2, SiiPrDis2, Tbt (C6H2-2,4,6-{CH(SiMe3)2}3), and Ar∗ (C6H3-2,6-(C6H2-2,4,6-i-Pr3)2)) compounds was investigated by using the theoretical methods (i.e., M06-2X/Def2-TZVP, B3PW91/Def2-TZVP, B3LYP/LANL2DZ+dp, and CCSD(T)). The theoretical examinations reveal that all of the triple-bonded RAltbnd6 PR species prefer to adopt a bent form with a roughly perpendicular bond angle (∠ Al-P-R). In addition, the theoretical evidence demonstrates that only the bulkier substituents can efficiently stabilize the central Altbnd6 P triple bond. Moreover, the theoretical analyses (the natural bond orbital, the natural resonance theory, and the charge decomposition analysis) indicate that the bonding characters of the triply bonded RAltbnd6 PR molecules should be described as R‧Al

  14. Substituent effects on the ring-opening mechanism of lithium bromocyclopropylidenoids to allenes.

    Science.gov (United States)

    Azizoglu, Akin; Balci, Metin; Mieusset, Jean-Luc; Brinker, Udo H

    2008-11-07

    The ring-opening reactions of lithium bromocyclopropylidenoids to allenes have been investigated computationally at the B3LYP/6-31G(d) level of theory. Formally, two pathways can be considered: the reaction may either proceed in a concerted fashion or stepwise with the intermediacy of a free cyclopropylidene. In both cases, the loss of the bromide ion determines the kinetic of the reaction. The stability of the reactive intermediate, i.e., the carbene, is dependent on the substituent. Cyclopropylidenes bearing an electron-donating group (+M) are extremely unstable and ring-open readily to the allene. In contrast, bromocyclopropylidenoids with electron-withdrawing groups are particularly stable species. Here, a high energy barrier needs to be overcome in order to split off bromide and to generate the corresponding carbene or allene. Still, for most of the monosubstituted cyclopropylidenes investigated during this study, the activation energy for the cyclopropylidene to allene rearrangement is lower than the energy required for parent compound (X = H) except for X = -SiH3 and -CF3.

  15. Functionalized ferrocenes: The role of the para substituent on the phenoxy pendant group.

    Science.gov (United States)

    Vera, José L; Rullán, Jorge; Santos, Natasha; Jiménez, Jesús; Rivera, Joshua; Santana, Alberto; Briggs, Jon; Rheingold, Arnold L; Matta, Jaime; Meléndez, Enrique

    2014-01-01

    Six ferrocenecarboxylates with phenyl, 4-(1H-pyrrol-1-yl)phenyl, 4-fluorophenyl, 4-chlorophenyl, 4-bromophenyl, 4-iodophenyl as pendant groups were synthesized and fully characterized by spectroscopic, electrochemical and X-ray diffraction methods. The anti-proliferative activity of these complexes were investigated in hormone dependent MCF-7 breast cancer and MCF-10A normal breast cell lines, to determine the role of the para substituent on the phenoxy pendant group. The 4-fluorophenyl ferrocenecarboxylate is inactive in both cell lines while 4-(1H-pyrrol-1-yl)phenyl ferrocenecarboxylate is highly cytotoxic in both cell lines. 4-chlorophenyl and 4-bromophenyl ferrocenecarboxylates have moderate to good anti-proliferative activity in MCF-7 and low anti-proliferative activity on normal breast cell line, MCF-10A whereas the 4-iodophenyl analog is highly toxic on normal breast cell line. The phenyl ferrocenecarboxylate has proliferative effects on MCF-7 and is inactive in MCF-10A. Docking studies between the complexes and the alpha-estrogen receptor (ERα) were performed to search for key interactions which may explain the anti-proliferative activity of 4-bromophenyl ferrocenecarboxylate. Docking studies suggest the anti-proliferative activity of these ferrocenecarboxylates is attributed to the cytotoxic effects of the ferrocene group and not to anti-estrogenic effects.

  16. Molecular binding thermodynamics of spherical guests by β-cyclodextrins bearing aromatic substituents

    Energy Technology Data Exchange (ETDEWEB)

    Li, Nan; Chen, Yong; Zhang, Ying-Ming; Wang, Li-Hua; Mao, Wen-Zhao; Liu, Yu, E-mail: yuliu@nankai.edu.cn

    2014-01-20

    Graphical abstract: - Highlights: • Different conformation of β-CD derivatives. • Enthalpy gain. • High binding ability. - Abstract: The molecular binding behaviors of two β-cyclodextrin (β-CD) derivatives bearing 1,2,3-triazole moieties, i.e. mono-6-deoxy-6-{4-(8-oxymethylquinolino)[1,2,3]triazolyl}-β-CD (1) and mono-6-deoxy-6-{4-(8-oxymethylnaphthol)[1,2,3]triazolyl}-β-CD (3), and their analogs without 1,2,3-triazole moieties, i.e. mono-6-deoxy-6-(8-oxymethylquinolino)-β-CD (2) and mono-6-deoxy-6-(8-oxymethylnaphthol)-β-CD (4) toward spherical guests (±)-borneol and (±)-camphor were investigated to elucidate how substituent moiety of host affects the binding abilities by 2D NMR as well as microcalorimetric titrations in aqueous phosphate buffer solution (pH 7.20) at 298.15 K. The binding modes of host–guest interactions obtained from 2D NMR displayed that host CDs without triazole moieties gave better induce-fit efficiency between hosts and guests, leading to stronger binding abilities. Thermodynamically, the inclusion complexation was driven by enthalpy with the stoichiometry of 1:1. Another factor contributed to the enhanced binding abilities was the enthalpy gain with the smaller entropy loss.

  17. A refined model of the chlorosomal antennae of the green bacterium chlorobium tepidum from proton chemical shift constraints obtained with high-field 2-D and 3-D MAS NMR dipolar correlation spectroscopy

    NARCIS (Netherlands)

    Rossum, van B.E.J.; Steengaard, D.B.; Boender, G.J.; Schaffner, K.; Holzwarth, A.R.; Groot, de H.J.M.

    2001-01-01

    Heteronuclear 2-D and 3-D magic-angle spinning NMR dipolar correlation spectroscopy was applied to determine solid-state 1H shifts for aggregated bacteriochlorophyll c (BChl c) in uniformly 13C-enriched light harvesting chlorosomes of the green photosynthetic bacterium Chlorobium tepidum. A complete

  18. Instantaneous phase shifting deflectometry.

    Science.gov (United States)

    Trumper, Isaac; Choi, Heejoo; Kim, Dae Wook

    2016-11-28

    An instantaneous phase shifting deflectometry measurement method is presented and implemented by measuring a time varying deformable mirror with an iPhone ® 6. The instantaneous method is based on multiplexing phase shifted fringe patterns with color, and decomposing them in x and y using Fourier techniques. Along with experimental data showing the capabilities of the instantaneous deflectometry system, a quantitative comparison with the Fourier transform profilometry method, which is a distinct phase measuring method from the phase shifting approach, is presented. Sources of error, nonlinear color-multiplexing induced error correction, and hardware limitations are discussed.

  19. Regulation of substituent groups on morphologies and self-assembly of organogels based on some azobenzene imide derivatives

    Science.gov (United States)

    Jiao, Tifeng; Wang, Yujin; Zhang, Qingrui; Zhou, Jingxin; Gao, Faming

    2013-04-01

    In this paper, new azobenzene imide derivatives with different substituent groups were designed and synthesized. Their gelation behaviors in 21 solvents were tested as novel low-molecular-mass organic gelators. It was shown that the alkyl substituent chains and headgroups of azobenzene residues in gelators played a crucial role in the gelation behavior of all compounds in various organic solvents. More alkyl chains in molecular skeletons in present gelators are favorable for the gelation of organic solvents. Scanning electron microscopy and atomic force microscopy observations revealed that the gelator molecules self-assemble into different aggregates, from wrinkle, lamella, and belt to fiber with the change of solvents. Spectral studies indicated that there existed different H-bond formations between amide groups and conformations of methyl chains. The present work may give some insight to the design and character of new organogelators and soft materials with special molecular structures.

  20. Shift Verification and Validation

    Energy Technology Data Exchange (ETDEWEB)

    Pandya, Tara M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Evans, Thomas M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Davidson, Gregory G [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Johnson, Seth R. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Godfrey, Andrew T. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2016-09-07

    This documentation outlines the verification and validation of Shift for the Consortium for Advanced Simulation of Light Water Reactors (CASL). Five main types of problems were used for validation: small criticality benchmark problems; full-core reactor benchmarks for light water reactors; fixed-source coupled neutron-photon dosimetry benchmarks; depletion/burnup benchmarks; and full-core reactor performance benchmarks. We compared Shift results to measured data and other simulated Monte Carlo radiation transport code results, and found very good agreement in a variety of comparison measures. These include prediction of critical eigenvalue, radial and axial pin power distributions, rod worth, leakage spectra, and nuclide inventories over a burn cycle. Based on this validation of Shift, we are confident in Shift to provide reference results for CASL benchmarking.

  1. Ab initio CPHF calculations of first hyperpolarizabilities of nitrogen-containing polyenes with donor—acceptor substituents

    Science.gov (United States)

    Tsunekawa, Tetsuya; Yamaguchi, Kizashi

    1992-03-01

    Ab initio CPHF calculations of static hyperpolarizabilities (β) were carried out in order to clarify the effects of nitrogen-atom substitution in π-conjugated chains with donor—acceptor substituents. The β values decrease gradually with the number of nitrogen atoms, and change drastically with the position of nitrogen-atom substitution in the polyenes. The effects of nitrogen-atom substitution are explained by the energy levels and the shapes of the frontier orbitals.

  2. Tuning the physicochemical properties of diverse phenolic ionic liquids for equimolar CO2 capture by the substituent on the anion.

    Science.gov (United States)

    Wang, Congmin; Luo, Huimin; Li, Haoran; Zhu, Xiang; Yu, Bo; Dai, Sheng

    2012-02-13

    Phenolic ionic liquids for the efficient and reversible capture of CO(2) were designed and prepared from phosphonium hydroxide and substituted phenols. The electron-withdrawing or electron-donating ability, position, and number of the substituents on the anion of these ionic liquids were correlated with the physicochemical properties of the ionic liquids. The results show that the stability, viscosity, and CO(2)-capturing ability of these ionic liquids were significantly affected by the substituents. Furthermore, the relationship between the decomposition temperature, the CO(2)-absorption capacity, and the basicity of these ionic liquids was quantitatively correlated and further rationalized by theoretical calculation. Indeed, these ionic liquids showed good stability, high absorption capacity, and low absorption enthalpy for CO(2) capture. This method, which tunes the physicochemical properties by making use of substituent effects in the anion of the ionic liquid, is important for the design of highly efficient and reversible methods for CO(2)-capture. This CO(2) capture process using diverse phenolic ionic liquids is a promising potential method for CO(2) absorption with both high absorption capacity and good reversibility. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Tuning the Physicochemical Properties of Diverse Phenolic Ionic Liquids for Equimolar CO2 Capture by the Substituent on the Anion

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Sheng [ORNL; Luo, Huimin [ORNL; Yu, Bo [ORNL; Li, Haoran [Zhejiang University; Wang, Congmin [ORNL

    2012-01-01

    Phenolic ionic liquids for the efficient and reversible capture of CO{sub 2} were designed and prepared from phosphonium hydroxide and substituted phenols. The electron-withdrawing or electron-donating ability, position, and number of the substituents on the anion of these ionic liquids were correlated with the physicochemical properties of the ionic liquids. The results show that the stability, viscosity, and CO{sub 2}-capturing ability of these ionic liquids were significantly affected by the substituents. Furthermore, the relationship between the decomposition temperature, the CO{sub 2}-absorption capacity, and the basicity of these ionic liquids was quantitatively correlated and further rationalized by theoretical calculation. Indeed, these ionic liquids showed good stability, high absorption capacity, and low absorption enthalpy for CO{sub 2} capture. This method, which tunes the physicochemical properties by making use of substituent effects in the anion of the ionic liquid, is important for the design of highly efficient and reversible methods for CO{sub 2}-capture. This CO{sub 2} capture process using diverse phenolic ionic liquids is a promising potential method for CO{sub 2} absorption with both high absorption capacity and good reversibility.

  4. m-Methoxy Substituents in a Tetraphenylethylene-Based Hole-Transport Material for Efficient Perovskite Solar Cells.

    Science.gov (United States)

    Wu, Fei; Liu, Jianlin; Wang, Gang; Song, Qunliang; Zhu, Linna

    2016-11-07

    Three tetrapheynlethylene derivatives (N,N-di(4-methoxyphenyl)aminophenyl-substituted tetraphenylethylene; TPE-4DPA) with different methoxy positions (pp-, pm-, and po-) have been synthesized and characterized. The methoxy groups can control the oxidation potential of the materials, and the electronic properties of the derivatives were affected by the position of the methoxy substituents. These compounds were synthesized in a facile and cost-effective way, and were applied as hole-transport materials in perovskite solar cells. The corresponding cell performances were compared with respect to their structure modifications, and it was found that the derivative with m-OMe substituents showed the highest power conversion efficiency (PCE) of 15.4 %, with a Jsc value of 20.04 mA cm-2 , a Voc value of 1.07 V, and a fill factor (FF) value of 0.72, which is higher than the p-OMe and o-OMe substituents. Moreover, the PCE of pm-TPE-4DPA is comparable with that of the state-of-the-art 2,2',7,7'-tetrakis(N,N'-di-p-methoxyphenylamine)-9,9'-spirobifluorene under identical conditions. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. The structural analysis and modelling of ring substituent effect for the ortho-derivatives of 1-hydroxynaphthalene-2-carboxanilides and 2-hydroxynaphthalene-1-carboxanilides

    Science.gov (United States)

    Škorňa, Peter; Michalík, Martin; Lukeš, Vladimír; Klein, Erik

    2017-09-01

    The quantum chemical DFT study of 1-hydroxynaphthalene-2-carboxanilide (A-H) and 2-hydroxynaphthalene-1-carboxanilide (B-H) and their selected ortho-derivatives (A-R, B-R) is presented. The structural analysis showed that the energetically preferred conformation is stabilized via the intramolecular hydrogen bonds occurring between the Cdbnd O⋯H-O1 of A-H molecule and Cdbnd O⋯H-O2 groups of B-H molecule. The A-R derivatives are practically planar, while the B-R derivatives are slightly distorted due to the spatial repulsion of hydrogen atoms. The conformation analysis of molecules with deprotonated hydroxyl group supports the concept of existence of two conformer types with respect to the sbnd NHsbnd COsbnd bridge orientation. Stabilization of the naphtholate moiety by a hydrogen bond to the amide sbnd NHsbnd group may allow the compound to cross the membrane to the extracellular space. The ortho substitution effect on the selected calculated properties was analyzed and the theoretical data were correlated with the substituent constants. For the B-R derivatives, the antitubercular activity concentrations were correlated and predicted by the calculated quantities.

  6. Probing substituent effects on the activation of H(2) by phosphorus and boron frustrated Lewis pairs.

    Science.gov (United States)

    Neu, Rebecca C; Ouyang, Eva Y; Geier, Stephen J; Zhao, Xiaoxi; Ramos, Alberto; Stephan, Douglas W

    2010-05-14

    The impact of substituent changes on phosphorus and boron-containing frustrated Lewis pairs (FLPs) has been examined. The phosphites (RO)(3)P R = Me, Ph form classical Lewis acid-base adducts of the formula (RO)(3)PB(C(6)F(5))(3) R = Me ; R = Ph , whereas P(O-2,4-(t)Bu(2)C(6)H(3))(3) and P(O-2,6-Me(2)C(6)H(3))(3) generate FLPs. Nonetheless, these latter combinations do not react with H(2). The more basic phosphinite tBu(2)POR, R = tBu reacts with B(C(6)F(5))(3) to give (tBu(2)(H)PO)B(C(6)F(5))(3). The related species tBu(2)POR, R = Ph ; 2,6-Me(2)C(6)H(3) showed no reaction with B(C(6)F(5))(3) but the FLPs react under H(2) (4 atm) to give [tBu(2)P(OR)H][HB(C(6)F(5))(3)] R = Ph and 2,6-Me(2)C(6)H(3). Similarly, tBu(2)PCl in combination with B(C(6)F(5))(3), generates an FLP that upon addition of H(2), gives [tBu(2)PH(2)][ClB(C(6)F(5))(3)] albeit in low yield. The diborane 1,4-(C(6)F(5))(2)B(C(6)F(4))B(C(6)F(5))(2) in combination with either tBu(3)P or (C(6)H(2)Me(3))(3)P generates FLPs that react with H(2) to give [R(3)PH](2)[1,4-(C(6)F(5))(2)HB(C(6)F(4))BH(C(6)F(5))(2)] (R = tBu , C(6)H(2)Me(3)). Similarly PhB(C(6)F(5))(2) and tBu(3)P react with H(2) giving [tBu(3)PH][HBPh(C(6)F(5))(2)] . The combination of B(OC(6)F(5))(3) and PtBu(3) also generate an FLP which reacts with H(2) to give [HPtBu(3)][B(OC(6)F(5))(4)] , the product of substituent redistribution. The boronic esters, (C(6)H(4)O(2))BC(6)F(5), (C(6)H(3)FO(2))BC(6)F(5) and (C(6)F(4)O(2))BC(6)F(5), and the borate esters B(OC(6)H(3)(CF(3))(2))(3), B(OC(6)H(2)F(3))(3) and B(OC(6)H(4)CF(3))(3) were prepared and shown to generate FLPs with tBu(3)P or (C(6)H(2)Me(3))(3)P. Nonetheless, no reaction with H(2) was observed for . Collectively these data suggest that there is a threshold of combined Lewis acidity and basicity that is required to effect the splitting of H(2).

  7. Major groove substituents and polymerase recognition of a class of predominantly hydrophobic unnatural base pairs.

    Science.gov (United States)

    Lavergne, Thomas; Malyshev, Denis A; Romesberg, Floyd E

    2012-01-23

    Expansion of the genetic alphabet with an unnatural base pair is a long-standing goal of synthetic biology. We have developed a class of unnatural base pairs, formed between d5SICS and analogues of dMMO2 that are efficiently and selectively replicated by the Klenow fragment (Kf) DNA polymerase. In an effort to further characterize and optimize replication, we report the synthesis of five new dMMO2 analogues bearing different substituents designed to be oriented into the developing major groove and an analysis of their insertion opposite d5SICS by Kf and Thermus aquaticus DNA polymerase I (Taq). We also expand the analysis of the previously optimized pair, dNaM-d5SICS, to include replication by Taq. Finally, the efficiency and fidelity of PCR amplification of the base pairs by Taq or Deep Vent polymerases was examined. The resulting structure-activity relationship data suggest that the major determinants of efficient replication are the minimization of desolvation effects and the introduction of favorable hydrophobic packing, and that Taq is more sensitive than Kf to structural changes. In addition, we identify an analogue (dNMO1) that is a better partner for d5SICS than any of the previously identified dMMO2 analogues with the exception of dNaM. We also found that dNaM-d5SICS is replicated by both Kf and Taq with rates approaching those of a natural base pair. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Substituent Effects on the Self-Assembly/Coassembly and Hydrogelation of Phenylalanine Derivatives.

    Science.gov (United States)

    Liyanage, Wathsala; Nilsson, Bradley L

    2016-01-26

    Supramolecular hydrogels derived from the self-assembly of organic molecules have been exploited for applications ranging from drug delivery to tissue engineering. The relationship between the structure of the assembly motif and the emergent properties of the resulting materials is often poorly understood, impeding rational approaches for the creation of next-generation materials. Aromatic π-π interactions play a significant role in the self-assembly of many supramolecular hydrogelators, but the exact nature of these interactions lacks definition. Conventional models that describe π-π interactions rely on quadrupolar electrostatic interactions between neighboring aryl groups in the π-system. However, recent experimental and computational studies reveal the potential importance of local dipolar interactions between elements of neighboring aromatic rings in stabilizing π-π interactions. Herein, we examine the nature of π-π interactions in the self- and coassembly of Fmoc-Phe-derived hydrogelators by systematically varying the electron-donating or electron-withdrawing nature of the side chain benzyl substituents and correlating these effects to the emergent assembly and gelation properties of the systems. These studies indicate a significant role for stabilizing dipolar interactions between neighboring benzyl groups in the assembled materials. Additional evidence for specific dipolar interactions is provided by high-resolution crystal structures obtained from dynamic transition of gel fibrils to crystals for several of the self-assembled/coassembled Fmoc-Phe derivatives. In addition to electronic effects, steric properties also have a significant effect on the interaction between neighboring benzyl groups in these assembled systems. These findings provide significant insight into the structure-function relationship for Fmoc-Phe-derived hydrogelators and give cues for the design of next-generation materials with desired emergent properties.

  9. New aminoporphyrins bearing urea derivative substituents: synthesis, characterization, antibacterial and antifungal activity

    Directory of Open Access Journals (Sweden)

    Gholamreza Karimipour

    2015-06-01

    Full Text Available This work studied the synthesis of 5,10,15-tris(4-aminophenyl-20-(N,N-dialkyl/diaryl-N-phenylurea porphyrins (P1-P4 with alkyl or aryl groups of Ph, iPr, Et and Me, respectively and also the preparation of their manganese (III and cobalt (II complexes (MnP and CoP. The P1-P4 ligands were characterized by different spectroscopic techniques (1H NMR, FTIR, UV-Vis and elemental analysis, and metalated with Mn and Co acetate salts. The antibacterial and antifungal activities of these compounds in vitro were investigated by agar-disc diffusion method against Escherichia coli (-, Pseudomonas aeruginosa (-, Staphylococcus aureus(+, Bacillus subtilis (+ and Aspergillus oryzae and Candida albicans. Results showed that antibacterial and antifungal activity of the test samples increased with increase of their concentrations and the highest activity was obtained when the concentration of porphyrin compounds was 100 µg/mL. The activity for the porphyrin ligands depended on the nature of the urea derivative substituents and increased in the order P1 > P2 > P3 >P4, which was consistent with the order of their liposolubility. MnP and CoP complexes exhibited much higher antibacterial and antifungal activity than P1-P4ligands. Further, the growth inhibitory effects of these compounds was generally in the order CoP complexes > MnP complexes > P1-P4 ligands. Among these porphyrin compounds, CoP1displayed the highest antibacterial and antifungal activity, especially with a concentration of 100 µg/mL, against all the four tested bacteria and two fungi, and therefore it could be potential to be used as drug.

  10. Substituent effects on photosensitized splitting of thymine cyclobutane dimer by an attached indole.

    Science.gov (United States)

    Tang, Wenjian; Zhou, Hongmei; Wang, Jing; Pan, Chunxiao; Shi, Jingbo; Song, Qinhua

    2012-12-21

    In chromophore-containing cyclobutane pyrimidine dimer (CPD) model systems, solvent effects on the splitting efficiency may depend on the length of the linker, the molecular conformation, and the oxidation potential of the donor. To further explore the relationship between chromophore structure and splitting efficiency, we prepared a series of substituted indole-TT model compounds 2 a-2 g and measured their splitting quantum yields in various solvents. Two reverse solvent effects were observed: an increase in splitting efficiency in solvents of lower polarity for models 2 a-2 d with an electron-donating group (EDG), and vice versa for models 2 e-2 g with an electron-withdrawing group (EWG). According to the Hammett equation, the negative value of the slope of the Hammett plot indicates that the indole moiety during the TT-splitting reaction loses negative charge, and the larger negative value implies that the repair reaction is more sensitive to substituent effects in low-polarity solvents. The EDGs of the models 2 a-2 d can delocalize the charge-separated state, and low-polarity solvents make it more stable, which leads to higher splitting efficiency in low-polarity solvents. Conversely, the EWGs of models 2 e-2 g favor destabilization of the charge-separated state, and high-polarity solvents decrease the destabilization and hence lead to more efficient splitting in high-polarity solvents. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. A New Paradigm for Chemical Engineering?

    DEFF Research Database (Denmark)

    Gani, Rafiqul

    businesses has been observed. There is an increasing trend within the chemical industry to focus on products and the sustainable processes that can make them. Do these changes point to a paradigm shift in chemical engineering as a discipline? Historically, two previous paradigm shifts in chemical engineering...... corresponded to major shifts in chemical engineering as a discipline, which affected not only the education of chemical engineers, but also the development of chemical engineering as a discipline. Has the time come for a new paradigm shift that will prepare the current and future chemical engineering graduates...... to tackle the complex problems facing the chemicals based industries and serve the modern society more efficiently? The lecture will review the current status of chemical engineering as a discipline, the proposals for the third paradigm, the need for such a paradigm shift and related educational issues....

  12. The unexpected influence of aryl substituents in N-aryl-3-oxobutanamides on the behavior of their multicomponent reactions with 5-amino-3-methylisoxazole and salicylaldehyde

    Directory of Open Access Journals (Sweden)

    Volodymyr V. Tkachenko

    2014-12-01

    Full Text Available The switchable three-component reactions of 5-amino-3-methylisoxazole, salicylaldehyde and N-aryl-3-oxobutanamides under different conditions were studied and discussed. The unexpected influence of the aryl substituent in N-aryl-3-oxobutanamides on the behavior of the reaction was discovered. The key influence of ultrasonication and Lewis acid catalysts led to an established protocol to selectively obtain two or three types of heterocyclic scaffolds depending on the substituent in the N-aryl moiety.

  13. A STUDY OF THE EFFECT OF SUBSTITUENTS AND OF SOLVENT ON THE REACTIVITY OF THE NORMAL AND ABNORMAL POSITIONS OF UNSYMMETRICAL ORGANIC EPOXIDES

    Science.gov (United States)

    The effects of substituents and solvents on the reaction between styrene oxide and benzylamine were investigated. The rate measurements on the...ethanol, rho is positive for the normal reaction and negative for the abnormal reaction . The effect of substituents in the benzylamine molecule was...determined by a kinetic study of the reactions of m-chloro- and 3,4-dimethylbenzylamine with styrene oxide in ethanol at 3 temperatures . The results

  14. Nurses' shift reports

    DEFF Research Database (Denmark)

    Buus, Niels; Hoeck, Bente; Hamilton, Bridget Elizabeth

    2017-01-01

    practices were described as highly conventionalised and locally situated, but with occasional opportunities for improvisation and negotiation between nurses. Finally, shift reports were described as multifunctional meetings, with individual and social effects for nurses and teams. CONCLUSION: Innovations...... in between-shift communications can benefit from this analysis, by providing for the many functions of handovers that are revealed in field studies. RELEVANCE TO CLINICAL PRACTICE: Leaders and practising nurses may consider what are the best opportunities for nurses to work up clinical knowledge......AIMS AND OBJECTIVES: To identify reporting practices that feature in studies of nurses' shift reports across diverse nursing specialities. The objectives were to perform an exhaustive systematic literature search and to critically review the quality and findings of qualitative field studies...

  15. Rapid Hydrogen Shift Reactions in Acyl Peroxy Radicals

    DEFF Research Database (Denmark)

    Knap, Hasse Christian; Jørgensen, Solvejg

    2017-01-01

    We have used quantum mechanical chemical calculations (CCSD(T)-F12a/cc-pVDZ-F12//M06-2X/aug-cc-pVTZ) to investigate the hydrogen shift (H-shift) reactions in acyl peroxy and hydroperoxy acyl peroxy radicals. We have focused on the H-shift reactions from a hydroperoxy group (OOH) (1,X-OOH H...

  16. Core-substituted naphthalene diimides: influence of\\ud substituent conformation on strong visible absorption

    OpenAIRE

    Quinn, Samuel; Davies, E. Stephen; Pfeiffer, Constance R.; Lewis, William; McMaster, Jonathan; Champness, Neil R.

    2017-01-01

    Substitution of the aromatic core of naphthalene diimide (NDI) chromophores by morpholine leads to molecules with strong absorbance in the visible spectrum. The shift of absorption maxima to lower energy is determined not only by the degree of substitution but also by the relative conformation and orientation of the tertiary amine with respect to the plane of the NDI.

  17. Label-free surface-enhanced infrared spectro-electro-chemical analysis of the Redox potential shift of cytochrome c complexed with a cardiolipin-containing lipid membrane of varied composition

    Science.gov (United States)

    Liu, Li; Wu, Lie; Zeng, Li; Jiang, Xiu-E.

    2015-12-01

    In this study, a lipid membrane was fabricated by fusing cardiolipin-phosphatidylcholine (CL_PC, 1:4) vesicles onto a hydrophobic surface of 1-dodecanethiol (DT) preadsorbed on a nanostructured gold film. By changing the concentration of the DT adsorption solution, we constructed a series of CL_PC-DT bilayers with different hydrophobicity to study the effects of lipid membrane characteristics on the adsorption conformation of cytochrome c (Cyt c). Electrochemical analysis showed that the formal potential is 0.24 V for Cyt c-CL_PC-DT(10), 0.2 V for Cyt c-CL_PC-DT(20), and 0.16 V for Cyt c-CL_PC-DT(40) — a gradual positive shift with the decreasing DT concentration — relative to the potential of native cyt c (0.02 V). Potential-induced surface-enhanced infrared adsorption difference spectroscopy revealed that the gradual positive shift of the formal potential of CL-bound cyt c is determined by the environment with the gradually lowered dielectric constant for the heme cofactor in CL-bound cyt c (Fe3+). Project supported by the National Natural Science Foundation of China (Grant Nos. 91227114, 21322510, and 21105097), the China Postdoctoral Science Foundation (Grant No. 2013M530998), the Natural Science Foundation of Jilin Province, China (Grant No. 201215092), and the President Funds of the Chinese Academy of Sciences.

  18. Shifting employment revisited

    NARCIS (Netherlands)

    Cremers, J.; Gramuglia, A.

    2014-01-01

    The CLR-network examined in 2006 the phenomenon of undeclared labour, with specific regard to the construction sector. The resulting study, Shifting Employment: undeclared labour in construction, gave evidence that this is an area particularly affected by undeclared activities with one of the

  19. Shifting tasks in telecare

    DEFF Research Database (Denmark)

    Nickelsen, Niels Christian Mossfeldt

    2017-01-01

    with focus on shifting tasks was undertaken. Furthermore, the method of ‘Interview to double’ was used the analytical ambition being to explore the becoming of tasks and relations. Analytically the study draws predominantly on Stars notion of ‘infrastructure’. Infrastructure is seen as human and non...

  20. How the Substituent Effect Influences π-Electron Delocalisation in the Ring of Reactants in the Reaction Defining the Hammett Substituent Constants σm and σp

    Directory of Open Access Journals (Sweden)

    Michał K. Cyrański

    2005-01-01

    Full Text Available Abstract: Application of the geometry (HOMA, EN, GEO and magnetism based (NICS, NICS(1 indices of aromaticity to optimised geometry of the ring in 12 meta – and 12 para – substituted benzoic acids and their anions by use of DFT computations at B3LYP/6-311+G(d,p level has shown a very low substituent effect on the π-electron delocalisation. This resembles (qualitatively the resistance of benzene (and typical aromatic systems against reactions leading to the change of π-electron delocalisation.

  1. Understanding and controlling chromaticity shift in LED devices

    Energy Technology Data Exchange (ETDEWEB)

    Davis, Lynn; Mills, Karmann; Lamvik, Michael; Perkins, Curtis; Bobashev, Georgiy; Young, Joseph; Yaga, Robert; Johnson, Cortina

    2017-05-30

    Chromaticity shift in light-emitting diode (LED) devices arises from multiple mechanisms, and at least five different chromaticity shift modes (CSMs) have been identified to date. This paper focuses on the impacts of irreversible phosphor degradation as a cause of chromaticity shifts in LED devices. The nitride phosphors used to produce warm white LEDs are especially vulnerable to degradation due to thermal and chemical effects such as reactions with oxygen and water. As a result, LED devices utilizing these phosphors were found to undergo either a green shift or, less commonly, a red shift depending on the phosphor mix in the LED devices. These types of chromaticity shifts are classified as CSM-2 (green shift) and CSM-5 (red shift). This paper provides an overview of the kinetic processes responsible for green and red chromaticity shifts along with examples from accelerated stress testing of 6” downlights. Both CSMs appear to proceed through analogous mechanisms that are initiated at the surface of the phosphor. A green shift is produced by the surface oxidation of the nitride phosphor that changes the emission profile to lower wavelengths. As the surface oxidation reaction proceeds, reactant limitations slow the rate and bulk oxidation processes become more prevalent. We found that a red chromaticity shift arises from quenching of the green phosphor, also possibly due to surface reactions of oxygen, which shift the emission chromaticity in the red direction. In conclusion, we discuss the implications of these findings on projecting chromaticity.

  2. Effect of intercalator substituent and nucleotide sequence on the stability of DNA- and RNA-naphthalimide complexes.

    Science.gov (United States)

    Johnson, Charles A; Hudson, Graham A; Hardebeck, Laura K E; Jolley, Elizabeth A; Ren, Yi; Lewis, Michael; Znosko, Brent M

    2015-07-01

    DNA intercalators are commonly used as anti-cancer and anti-tumor agents. As a result, it is imperative to understand how changes in intercalator structure affect binding affinity to DNA. Amonafide and mitonafide, two naphthalimide derivatives that are active against HeLa and KB cells in vitro, were previously shown to intercalate into DNA. Here, a systematic study was undertaken to change the 3-substituent on the aromatic intercalator 1,8-naphthalimide to determine how 11 different functional groups with a variety of physical and electronic properties affect binding of the naphthalimide to DNA and RNA duplexes of different sequence compositions and lengths. Wavelength scans, NMR titrations, and circular dichroism were used to investigate the binding mode of 1,8-naphthalimide derivatives to short synthetic DNA. Optical melting experiments were used to measure the change in melting temperature of the DNA and RNA duplexes due to intercalation, which ranged from 0 to 19.4°C. Thermal stabilities were affected by changing the substituent, and several patterns and idiosyncrasies were identified. By systematically varying the 3-substituent, the binding strength of the same derivative to various DNA and RNA duplexes was compared. The binding strength of different derivatives to the same DNA and RNA sequences was also compared. The results of these comparisons shed light on the complexities of site specificity and binding strength in DNA-intercalator complexes. For example, the consequences of adding a 5'-TpG-3' or 5'-GpT-3' step to a duplex is dependent on the sequence composition of the duplex. When added to a poly-AT duplex, naphthalimide binding was enhanced by 5.6-11.5°C, but when added to a poly-GC duplex, naphthalimide binding was diminished by 3.2-6.9°C. Copyright © 2015 Elsevier Ltd. All rights reserved.

  3. Substituent effects on the electron affinities and ionization energies of tria-, penta-, and heptafulvenes: a computational investigation

    DEFF Research Database (Denmark)

    Dahlstrand, Christian; Yamazaki, Kaoru; Kilså, Kristine

    2010-01-01

    The extent of substituent influence on the vertical electron affinities (EAs) and ionization energies (IEs) of 43 substituted tria-, penta-, and heptafulvenes was examined computationally at the OVGF/6-311G(d)//B3LYP/6-311G(d) level of theory and compared with those of tetracyanoquinodimethane...... of the EAs and IEs were rationalized by qualitative arguments based on frontier orbital symmetries for the different fulvene classes with either X or Y being constant. The minimum and maximum values found for the calculated EAs of the tria-, penta-, and heptafulvenes were 0.51-2.05, 0.24-3.63, and 0...

  4. Influence of Halogen Substituents on the Catalytic Oxidation of 2,4,6-Halogenated Phenols by Fe(III-Tetrakis(p-hydroxyphenyl porphyrins and Potassium Monopersulfate

    Directory of Open Access Journals (Sweden)

    Seiya Nagao

    2011-12-01

    Full Text Available The influence of halogen substituents on the catalytic oxidation of 2,4,6-trihalogenated phenols (TrXPs by iron(III-porphyrin/KHSO5 catalytic systems was investigated. Iron(III-5,10,15,20-tetrakis(p-hydroxyphenylporphyrin (FeTHP and its supported variants were employed, where the supported catalysts were synthesized by introducing FeTHP into hydroquinone-derived humic acids via formaldehyde poly-condensation. F (TrFP, Cl (TrCP, Br (TrBP and I (TrIP were examined as halogen substituents for TrXPs. Although the supported catalysts significantly enhanced the degradation and dehalogenation of TrFP and TrCP, the oxidation of TrBP and TrIP was not enhanced, compared to the FeTHP catalytic system. These results indicate that the degree of oxidation of TrXPs is strongly dependent on the types of halogen substituent. The order of dehalogenation levels for halogen substituents in TrXPs was F > Cl > Br > I, consistent with their order of electronegativity. The electronegativity of a halogen substituent affects the nucleophilicity of the carbon to which it is attached. The levels of oxidation products in the reaction mixtures were analyzed by GC/MS after extraction with n-hexane. The most abundant dimer product from TrFP via 2,6-difluoroquinone is consistent with a scenario where TrXP, with a more electronegative halogen substituent, is readily oxidized, while less electronegative halogen substituents are oxidized less readily by iron(III-porphyrin/KHSO5 catalytic systems.

  5. Influence of halogen substituents on the catalytic oxidation of 2,4,6-halogenated phenols by Fe(III)-tetrakis(p-hydroxyphenyl) porphyrins and potassium monopersulfate.

    Science.gov (United States)

    Fukushima, Masami; Mizutani, Yusuke; Maeno, Shouhei; Zhu, Qianqian; Kuramitz, Hideki; Nagao, Seiya

    2011-12-22

    The influence of halogen substituents on the catalytic oxidation of 2,4,6-trihalogenated phenols (TrXPs) by iron(III)-porphyrin/KHSO₅ catalytic systems was investigated. Iron(III)-5,10,15,20-tetrakis(p-hydroxyphenyl)porphyrin (FeTHP) and its supported variants were employed, where the supported catalysts were synthesized by introducing FeTHP into hydroquinone-derived humic acids via formaldehyde poly-condensation. F (TrFP), Cl (TrCP), Br (TrBP) and I (TrIP) were examined as halogen substituents for TrXPs. Although the supported catalysts significantly enhanced the degradation and dehalogenation of TrFP and TrCP, the oxidation of TrBP and TrIP was not enhanced, compared to the FeTHP catalytic system. These results indicate that the degree of oxidation of TrXPs is strongly dependent on the types of halogen substituent. The order of dehalogenation levels for halogen substituents in TrXPs was F > Cl > Br > I, consistent with their order of electronegativity. The electronegativity of a halogen substituent affects the nucleophilicity of the carbon to which it is attached. The levels of oxidation products in the reaction mixtures were analyzed by GC/MS after extraction with n-hexane. The most abundant dimer product from TrFP via 2,6-difluoroquinone is consistent with a scenario where TrXP, with a more electronegative halogen substituent, is readily oxidized, while less electronegative halogen substituents are oxidized less readily by iron(III)-porphyrin/KHSO₅ catalytic systems.

  6. N,N′-Bis(2-cyclohexylethylnaphtho[2,3-b:6,7-b′]dithiophene Diimides: Effects of Substituents

    Directory of Open Access Journals (Sweden)

    Masahiro Nakano

    2016-07-01

    Full Text Available Naphtho[2,3-b:6,7-b′]dithiophene-4,5,9,10-tetracarboxylic diimide (NDTI is a promising electron-deficient building block for n-type organic conductors, and the performance of NDTI-based field-effect transistors (FETs is largely dependent on the substituents that alter the supramolecular organization in the solid state and, in turn, the intermolecular orbital overlap. For this reason, the rational selection of substituent on imide nitrogen atoms and/or thiophene α-positions is the key to developing superior n-type organic semiconductors. We here report new NDTI derivatives having N-(2-cyclohexylethyl groups. Despite their one-dimensional packing structures in the solid state regardless of the presence or absence of chlorine groups at the thiophene α-positions, their FETs show promising performance with electron mobilities higher than 0.1 cm2·V−1·s−1 under ambient conditions. We also discuss how the cyclohexylethyl groups affect the packing structure in comparison with analogous n-octyl derivatives having the same number of carbon atoms.

  7. Role of Solvent and Effect of Substituent on Azobenzene Isomerization by Using Room-Temperature Ionic Liquids as Reaction Media.

    Science.gov (United States)

    Angelini, Guido; Canilho, Nadia; Emo, Mélanie; Kingsley, Molly; Gasbarri, Carla

    2015-08-07

    The effects of a para substituent, as the electron-donating -OCH3 and -OtBu groups and the electron-withdrawing -Br and -F atoms, on azobenzene isomerization have been investigated in a series of imidazolium ionic liquids (BMIM PF6, BMIM BF4, BMIM Tf2N, EMIM Tf2N, BM2IM Tf2N, and HMIM Tf2N). The thermal cis-trans conversion tends to be improved in the presence of the substituent, as pointed out by the first-order rate constants measured at 25 °C. Both the rotation and the inversion mechanisms occur in BMIM Tf2N, EMIM Tf2N, and HMIM Tf2N, as highlighted by typical V-shape Hammett plots, but only rotation takes place in BMIM PF6, BMIM BF4, and BM2IM Tf2N. The possible interactions between the cation and the anion of the solvent and both the isomers of the azobenzene derivatives have been studied by small-wide-angle X-ray scattering (SWAXS). The calculated cis population in the photostationary state and the hardness parameter η of the trans isomer show that azobenzene and F-azobenzene are the less reactive molecules for the trans-cis conversion in all the investigated ionic liquids.

  8. Effects of substituents upon the P···N noncovalent interaction: the limits of its strength.

    Science.gov (United States)

    Scheiner, Steve

    2011-10-20

    Previous work has documented the ability of the P atom to form a direct attractive noncovalent interaction with a N atom, based in large measure on the charge transfer from the N lone pair into the σ* antibonding orbital of the P-H that is turned away from the N atom. As the systems studied to date include only hydrides, the present work considers how substituents affect the interaction and examines whether P···N might compete with other attractive forces such as H-bonds. It is found that the addition of electron-withdrawing substituents greatly strengthens the P···N interaction to the point where it exceeds that of the majority of H-bonds. The highest interaction energy occurs in the FH(2)P···N(CH(3))(3) complex, amounting to 11 kcal/mol. A breakdown of the individual forces involved attributes the stability of the interaction to approximately equal parts electrostatic and induction energy, with a smaller contribution from dispersion.

  9. Synthesis and Optical Properties of Trioxatriangulenium Dyes with One and Two Peripheral Amino Substituents

    DEFF Research Database (Denmark)

    Sørensen, Thomas Just; Laursen, Bo Wegge

    2010-01-01

    Several derivatives of two new dye systems, with one or two dialkylamino donor groups attached to resonant positions at the periphery of a trioxatriangulenium ion, were synthesized. The mono- and bis-dialkylamino trioxatriangulenium salts (A1-TOTA+ and A2-TOTA+) were prepared from methoxy...... were found to be dependent on symmetry and charge localization in the conjugated framework. The trioxatriangulenium dye with two amino groups (A2-TOTA+) was found to be a strong fluorophore with properties as a blue-shifted rhodamine B. The mono-substituted compound (A1-TOTA+) was found to be only...

  10. Interaction of uridine diphosphate glucose analogs with calf liver uridine diphosphate glucose dehydrogenase. Influence of substituents at C-5 of pyrimidine nucleus.

    Science.gov (United States)

    Shibaev, V N; Eliseeva, G I; Kochetkov, N K

    1975-09-22

    The interaction of alpha-D-glucopyranosyl pyrophosphates of 5-X-uridines (X = CH3, NH2, CH3O, I, Br, Cl, OH) with uridine diphosphate glucose (UDPGlc) dehydrogenase (EC 1.1.1.22) from calf liver has been studied. All the derivatives investigated were able to serve as substrates for the enzyme. The apparent Michaelis constants for UDPGlc-analogs were dependent both on electronic and steric factors. Increase of substituent negative inductive effect lead to decrease of pKa for ionization of the NH-group in the uracil nucleus and, consequently, to a diminishing of the proportion of the active analog species under the conditions of assay. After correction for the ionization effect, the Km values were found to depend on the van der Waals radius of the substituent. The value of 1.95 A seems to be critical, as the analogs with bulkier substituents at C-5 showed a decreased affinity to the enzyme. The maximal velocity values of the analogs were also dependent on nature of the substituent. Good linear correlation between log V and substituent hydrophobic phi-constant was observed for a number of the analogs, although V values for the nucleotides with X = H, OH or NH2 were higher than would be expected on the basis of the correlation. The significance of the results for understanding of the topography of UDPGlc dehydrogenase active site is discussed.

  11. Functional dependency of structures of ionic liquids: do substituents govern the selectivity of enzymatic glycerolysis?

    DEFF Research Database (Denmark)

    Guo, Zheng; Chen, Biqiang; Murillo, Rafael López

    2006-01-01

    preference to monoglyceride formation. Interestingly the predicted results from COSMO-RS (a quantum chemical model programme) achieved a good agreement with the experimental data, mapping out the specific solvation from the ILs as well as demonstrating the interaction between ILs, substrates and products...

  12. The shifting beverage landscape.

    Science.gov (United States)

    Storey, Maureen

    2010-04-26

    STOREY, M.L. The shifting beverage landscape. PHYSIOL BEHAV, 2010. - Simultaneous lifestyle changes have occurred in the last few decades, creating an imbalance in energy intake and energy expenditure that has led to overweight and obesity. Trends in the food supply show that total daily calories available per capita increased 28% since 1970. Total energy intake among men and women has also increased dramatically since that time. Some have suggested that intake of beverages has had a disproportional impact on obesity. Data collected by the Beverage Marketing Corporation between 1988-2008 demonstrate that, in reality, fewer calories per ounce are being produced by the beverage industry. Moreover, data from the National Cancer Institute show that soft drink intake represents 5.5% of daily calories. Data from NHANES 1999-2003 vs. 2003-06 may demonstrate a shift in beverage consumption for age/gender groups, ages 6 to>60years. The beverages provided in schools have significantly changed since 2006 when the beverage industry implemented School Beverage Guidelines. This voluntary action has removed full-calorie soft drinks from participating schools across the country. This shift to lower-calorie and smaller-portion beverages in school has led to a significant decrease in total beverage calories in schools. These data support the concept that to prevent and treat obesity, public health efforts should focus on energy balance and that a narrow focus on sweetened beverages is unlikely to have any meaningful impact on this complex problem. Copyright 2010 Elsevier Inc. All rights reserved.

  13. Catastrophic shifts in ecosystems

    Science.gov (United States)

    Scheffer, Marten; Carpenter, Steve; Foley, Jonathan A.; Folke, Carl; Walker, Brian

    2001-10-01

    All ecosystems are exposed to gradual changes in climate, nutrient loading, habitat fragmentation or biotic exploitation. Nature is usually assumed to respond to gradual change in a smooth way. However, studies on lakes, coral reefs, oceans, forests and arid lands have shown that smooth change can be interrupted by sudden drastic switches to a contrasting state. Although diverse events can trigger such shifts, recent studies show that a loss of resilience usually paves the way for a switch to an alternative state. This suggests that strategies for sustainable management of such ecosystems should focus on maintaining resilience.

  14. Repetition and Translation Shifts

    Directory of Open Access Journals (Sweden)

    Simon Zupan

    2006-06-01

    Full Text Available Repetition manifests itself in different ways and at different levels of the text. The first basic type of repetition involves complete recurrences; in which a particular textual feature repeats in its entirety. The second type involves partial recurrences; in which the second repetition of the same textual feature includes certain modifications to the first occurrence. In the article; repetitive patterns in Edgar Allan Poe’s short story “The Fall of the House of Usher” and its Slovene translation; “Konec Usherjeve hiše”; are compared. The author examines different kinds of repetitive patterns. Repetitions are compared at both the micro- and macrostructural levels. As detailed analyses have shown; considerable microstructural translation shifts occur in certain types of repetitive patterns. Since these are not only occasional; sporadic phenomena; but are of a relatively high frequency; they reduce the translated text’s potential for achieving some of the gothic effects. The macrostructural textual property particularly affected by these shifts is the narrator’s experience as described by the narrative; which suffers a reduction in intensity.

  15. Influences of aldehyde type and p-substituent type on structural characteristics of p-alkylphenol aldehyde resins using a molecular simulation

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Sung Seen [Kumho Research and Development Center, Kwangju (Korea, Republic of)

    1999-02-01

    Structural characteristics of isotactic p-alkylphenol acetaldehyde novolak resins with methyl, t-butyl, and t-octyl as the p-substituent and p-t-butylphenol novolak resins with methylene, ethylidene, and propylidene as the linkage were calculated using molecular mechanics and molecular dynamics. The five p-alkylphenol aldehyde resins were found to have common structural characteristics that hydroxyl groups of the p-alkylphenols cluster in the center of the molecule by intramolecular hydrogen bonds of hydroxyl groups of the adjacent p-alkylphenols and the alkyl groups are extended out. Distances between oxygen atoms and between p-carbon atoms of the adjacent p-alkylphenols become longer as the size of the p-substituent increases from methyl to toctyl. Bond angles of the linkage built between the adjacent p-alkylphenols become wider by increasing the p-substituent size and by decreasing the linkage size.

  16. The Diels-Alder Cycloaddition Reaction of Substituted Hemifullerenes with 1,3-Butadiene: Effect of Electron-Donating and Electron-Withdrawing Substituents.

    Science.gov (United States)

    Mojica, Martha; Méndez, Francisco; Alonso, Julio A

    2016-02-12

    The Diels-Alder (DA) reaction provides an attractive route to increase the number of six member rings in substituted Polycyclic Aromatic Hydrocarbons (PAHs). The density functional theory (DFT) B3LYP method has been used in this work to inquire if the substitution of H over the edge of triindenetriphenylene (pristine hemifullerene 1) and pentacyclopentacorannulene (pristine hemifullerene 2), could improve the DA cycloaddition reaction with 1,3-butadiene. The substituents tested include electron-donating (NH₂, OMe, OH, Me, i-Pr) and electron-withdrawing groups (F, COOH, CF₃, CHO, CN, NO₂). The electronic, kinetic and thermodynamic parameters of the DA reactions of the substituted hemifullerenes with 1,3-butadiene have been analyzed. The most promising results were obtained for the NO₂ substituent; the activation energy barriers for reactions using this substituent were lower than the barriers for the pristine hemifullerenes. This leads us to expect that the cycloadditions to a starting fullerene fragment will be possible.

  17. Relative substituent orientation in the structure of cis-3-chloro-1,3-dimethyl-N-(4-nitrophenyl-2-oxocyclopentane-1-carboxamide

    Directory of Open Access Journals (Sweden)

    Matthias Zeller

    2014-09-01

    Full Text Available The structure of the title compound, C14H15ClN2O4, prepared by reaction of a methacryloyl dimer with nitroaniline, was determined to establish the relative substituent orientation on the cyclopentanone ring. In agreement with an earlier proposed reaction mechanism, the amide group and the methyl group adjacent to the chloro substituent adopt equatorial positions and relative cis orientation, whereas the Cl substituent itself and the methyl group adjacent to the amide have axial orientations relative to the mean plane of the five-membered ring. The conformation of the molecule is stabilized by one classical N—H...O (2.18 Å and one non-classical C—H...O (2.23 Å hydrogen bond, each possessing an S(6 graph-set motif. The crystal packing is defined by several non-classical intramolecular hydrogen bonds, as well as by partial stacking of the aromatic rings.

  18. Tandem processes promoted by a hydrogen shift in 6-arylfulvenes bearing acetalic units at ortho position: a combined experimental and computational study

    Directory of Open Access Journals (Sweden)

    Mateo Alajarin

    2016-02-01

    Full Text Available 6-Phenylfulvenes bearing (1,3-dioxolan or dioxan-2-yl substituents at ortho position convert into mixtures of 4- and 9-(hydroxyalkoxy-substituted benz[f]indenes as result of cascade processes initiated by a thermally activated hydrogen shift. Structurally related fulvenes with non-cyclic acetalic units afforded mixtures of 4- and 9-alkoxybenz[f]indenes under similar thermal conditions. Mechanistic paths promoted by an initial [1,4]-, [1,5]-, [1,7]- or [1,9]-H shift are conceivable for explaining these conversions. Deuterium labelling experiments exclude the [1,4]-hydride shift as the first step. A computational study scrutinized the reaction channels of these tandem conversions starting by [1,5]-, [1,7]- and [1,9]-H shifts, revealing that this first step is the rate-determining one and that the [1,9]-H shift is the one with the lowest energy barrier.

  19. Alcaloides iboga de Peschiera affinis (Apocynaceae - Atribuição inequívoca dos deslocamentos químicos dos átomos de hidrogênio e carbono: atividade antioxidante Iboga alkaloids from Peschiera affinis (Apocynaceae - unequivocal 1H and 13C chemical shift assignments: antioxidant activity

    Directory of Open Access Journals (Sweden)

    Allana Kellen L. Santos

    2009-01-01

    Full Text Available Six known alkaloids iboga type and the triterpen α- and β-amyrin acetate were isolated from the roots and stems of Peschiera affinis. Their structures were characterized on the basis of spectral data mainly NMR and mass spectra. 1D and 2D NMR spectra were also used to unequivocal ¹H and 13C chemical shift assignments of alkaloids. The ethanolic extract of roots, alkaloidic and no-alkaloidic fractions and iso-voacristine hydroxyindolenine and voacangine were evaluated for their antioxidative properties using an autographic assay based on β-carotene bleaching on TLC plates, and also spectrophotometric detection by reduction of the stable DPPH (2,2-diphenyl-1-picrylhydrazyl free radical.

  20. Cobalt Tetrabutano- and Tetrabenzotetraarylporphyrin Complexes: Effect of Substituents on the Electrochemical Properties and Catalytic Activity of Oxygen Reduction Reactions.

    Science.gov (United States)

    Ye, Lina; Fang, Yuanyuan; Ou, Zhongping; Xue, Songlin; Kadish, Karl M

    2017-11-06

    Three series of cobalt tetraarylporphyrins were synthesized and characterized by electrochemistry and spectroelectrochemistry. The investigated compounds have the general formula (TpYPP)Co, butano(TpYPP)Co(II), and benzo(TpYPP)Co(II), where TpYPP represents the dianion of the meso-substituted porphyrin, Y is a CH3, H, or Cl substituent on the para position of the four phenyl rings, and butano and benzo are respectively the β- and β'-substituted groups on the four pyrrole rings of the compound. Each porphyrin undergoes one or two reductions depending upon the meso substituent and solvent utilized. Two irreversible reductions are observed for (TpYPP)Co(II) and butano(TpYPP)Co(II) in CH2Cl2 containing 0.1 M tetra-n-butylammonium perchlorate; the first leads to the formation of a highly reactive cobalt(I) porphyrin, which can then rapidly react with a solvent to give a Co(III)CH2Cl as the product. Only one reversible reduction is seen for benzo(TpYPP)Co(II) under the same solution conditions, and the one-electron-reduction product is assigned as a cobalt(II) porphyrin π-anion radical. Three oxidations can be observed for each examined compound in CH2Cl2. The first oxidation is metal-centered for the (TpYPP)Co and benzo(TpYPP)Co(II) derivatives, leading to generation of a cobalt(III) porphyrin with an intact π-ring system, but this redox process is ring-centered in the case of butano(TpYPP)Co(II) and gives a Co(II) π-cation radical product. Each porphyrin was also examined as a catalyst for oxygen reduction reactions (ORRs) when adsorbed on a graphite electrode in 1.0 M HClO4. The number of electrons transferred (n) during ORRs is 2.0 for the butano(TpYPP)Co(II) derivatives, consistent with only H2O2 being produced as a product for the reaction with O2. However, the reduction of O2 using the cobalt benzoporphyrins as catalysts gave n values between 2.6 and 3.1 under the same solution conditions, thus producing a mixture of H2O and H2O2 as the reduction product

  1. Organic/carbon nanotubes hybrid thin films for chemical detection

    Science.gov (United States)

    Banimuslem, Hikmat Adnan

    Metallophthalocyanines (MPcs) are classified as an important class of conjugated materials and they possess several advantages attributed to their unique chemical structure. Carbon nanotubes (CNT), on the other hand, are known to enhance the properties of nano-composites in the conjugated molecules, due to their one dimensional electronic skeleton, high surface area and high aspect ratio. In this thesis, work has been carried out on the investigation of different substituted metal-phthalocyanines with the aim of developing novel hybrid film structures which incorporates these phthalocyanines and single-walled carbon nanotubes (SWCNT) for chemical detection applications. Octa-substituted copper phthalocyanines (CuPcR[8]) have been characterised using UV-visible absorption spectroscopy. Obtained spectra have yielded an evidence of a thermally induced molecular reorganization in the films. Influence of the nature of substituents in the phthalocyanine molecule on the thin films conductivity was also investigated. Octa-substituted lead (II) phthalocyanines (PbPcR[8]) have also been characterized using UV-visible spectroscopy. Sandwich structures of ITO/PbPcR[8]/In were prepared to investigate the electronic conduction in PbPcR[8]. The variation in the J(V) behavior of the films as a result of heat treatment is expected to be caused by changes in the alignment inside the columnar stacking of the molecules of the films. Thin films of non-covalently hybridised SWCNT and tetra-substituted copper phthalocyanine (CuPcR[4]) molecules have been produced. FTIR, DC conductivity, SEM and AFM results have revealed the [mathematical equation]; interaction between SWCNTs and CuPCR[4] molecules and shown that films obtained from the acid-treated SWCNTs/CuPcR[4] hybrids demonstrated more homogenous surface. Thin films of pristine CuPCR[4] and CuPcR[4]/S WCNT were prepared by spin coating onto gold-coated glass slides and applied as active layers for the detection of benzo

  2. The substituent effect from the perspective of local hyper-softness. An example applied on normeloxicam, meloxicam and 4-meloxicam: Non-steroidal anti-inflammatory drugs

    Science.gov (United States)

    Martínez-Araya, Jorge Ignacio; Glossman-Mitnik, Daniel

    2015-01-01

    Normeloxicam, meloxicam and 4-meloxicam were analyzed from the perspective of the conceptual density functional theory perspective to determine the substituent effect exerted by the methyl group that is located at the thiazole ring. This analysis was performed in absence and presence of water. The position of the methyl group suggests that differences that have been experimentally reported in a previous paper can be mainly attributable to electronic effects exerted by the substituent aforementioned group. Finally, the use of total electronic densities is encouraged in future calculations instead of densities of frontier molecular orbitals to obtain more accurate results.

  3. Substituent and structural effects on the kinetics of the reaction of N-(substituted phenylmethylene-m- and -p-aminobenzoic acids with diazodiphenylmethane

    Directory of Open Access Journals (Sweden)

    BRATISLAV Z. JOVANOVIC

    2007-12-01

    Full Text Available The rate constants for the reaction of twenty-two N-(substituted phenyl methylene-m- and -p-aminobenzoic acids with diazodiphenylmethane were determined in absolute ethanol at 30 °C. The effects of substituents on the reactivity of the investigated compounds were interpreted by correlation of the rate constants with LFER equations. The results of quantum mechanical calculations of the mole cular structure together with experimental results gave a better insight into the effects of structure on the transmission of electronic effects of the substituents. New σ constants for substituted benzylideneamino group were calculated.

  4. 1H NMR spectroscopic identification of protonable sites in cryptolepines with C-11 substituents containing two amino functionalities.

    Science.gov (United States)

    Lavrado, João; Paulo, Alexandra; Bichenkova, Elena; Douglas, Kenneth T; Moreira, Rui

    2012-03-01

    Knowledge of protonable sites and acid dissociation constants of cryptolepine derivatives having C-11 substituents containing two amino functionalities is of great importance to the understanding of the mechanism of their antimalarial action, which may contribute to their further development as drug candidates. In this work, we applied (1)H NMR titration to investigate the acid-base characteristics of these polyprotic compounds in the pH range 3-13. We identified three acid-base equilibria with most acid dissociation constants (pK(a)*) being greater than 10.5, which prevented us from using the potentiometric method. Overall, (1)H NMR titration was sensitive and suitable for the determination of pK(a) values for these drug leads. Copyright © 2012 John Wiley & Sons, Ltd.

  5. Influences of Alkyl and Aryl Substituents on Iminopyridine Fe(II- and Co(II-Catalyzed Isoprene Polymerization

    Directory of Open Access Journals (Sweden)

    Lihua Guo

    2016-11-01

    Full Text Available A series of alkyl- and aryl-substituted iminopyridine Fe(II complexes 1a–7a and Co(II complexes 2b, 3b, 5b, and 6b were synthesized. The activator effect, influence of temperature, and, particularly, the alkyl and aryl substituents’ effect on catalytic activity, polymer molecular weight, and regio-/stereoselectivity were investigated when these complexes were applied in isoprene polymerization. All of the Fe(II complexes afforded polyisoprene with high molecular weight and moderate cis-1,4 selectivity. In contrast, the Co(II complexes produced polymers with low molecular weight and relatively high cis-1,4 selectivity. In the iminopyridine Fe(II system, the alkyl and aryl substituents’ effect exhibits significant variation on the isoprene polymerization. In the iminopyridine Co(II system, there is little influence observed on isoprene polymerization by alkyl and aryl substituents.

  6. Photophysical Properties of Benzoylgermane and para-Substituted Derivatives: Substituent Effects on Electronic Transitions.

    Science.gov (United States)

    Feuerstein, Wolfram; Höfener, Sebastian; Klopper, Wim; Lamparth, Iris; Moszner, Norbert; Barner-Kowollik, Christopher; Unterreiner, Andreas-N

    2016-11-04

    In the present study, a selection of basic substitution patterns on benzoyl(trimethyl)germane was investigated using time-dependent density-functional theory (TDDFT) to explore the influence on the stability and on the relative order of the lowest excited electronic states. The theoretical results are in agreement with absorption and fluorescence measurements. We show that electron-withdrawing groups decrease the energetic level of the lowest singlet and triplet state relative to the electron-pushing systems resulting in red-shifted radiative transitions (fluorescence). In the first triplet state electron-withdrawing groups lead to an increased dissociation barrier and a close approach with the singlet ground state before the transition state in the triplet state is reached, favoring radiationless ground-state recovery. The results are also in good agreement with empirical concepts of organic chemistry, therefore providing simple rules for synthetic strategies towards tuning the excited-state properties of benzoylgermanes. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Energy phase shift as mechanism for catalysis

    KAUST Repository

    Beke-Somfai, Tamás

    2012-05-01

    Catalysts are agents that by binding reactant molecules lower the energy barriers to chemical reaction. After reaction the catalyst is regenerated, its unbinding energy recruited from the environment, which is associated with an inevitable loss of energy. We show that combining several catalytic sites to become energetically and temporally phase-shifted relative to each other provides a possibility to sustain the overall reaction by internal \\'energy recycling\\', bypassing the need for thermal activation, and in principle allowing the system to work adiabatically. Using an analytical model for superimposed, phase-shifted potentials of F 1-ATP synthase provides a description integrating main characteristics of this rotary enzyme complex. © 2012 Elsevier B.V. All rights reserved.

  8. Shape-shifting colloids via stimulated dewetting

    Science.gov (United States)

    Youssef, Mena; Hueckel, Theodore; Yi, Gi-Ra; Sacanna, Stefano

    2016-07-01

    The ability to reconfigure elementary building blocks from one structure to another is key to many biological systems. Bringing the intrinsic adaptability of biological systems to traditional synthetic materials is currently one of the biggest scientific challenges in material engineering. Here we introduce a new design concept for the experimental realization of self-assembling systems with built-in shape-shifting elements. We demonstrate that dewetting forces between an oil phase and solid colloidal substrates can be exploited to engineer shape-shifting particles whose geometry can be changed on demand by a chemical or optical signal. We find this approach to be quite general and applicable to a broad spectrum of materials, including polymers, semiconductors and magnetic materials. This synthetic methodology can be further adopted as a new experimental platform for designing and rapidly prototyping functional colloids, such as reconfigurable micro swimmers, colloidal surfactants and switchable building blocks for self-assembly.

  9. Measurements of isotope shifts and hyperfine structure in Ti II

    Energy Technology Data Exchange (ETDEWEB)

    Nouri, Z; Rosner, S D; Holt, R A [Department of Physics and Astronomy, University of Western Ontario, London, ON N6A 3K7 (Canada); Li, R [TRIUMF, 4004 Wesbrook Mall, Vancouver, BC V6 T 2A3 (Canada); Scholl, T J, E-mail: rholt@uwo.c [Department of Medical Biophysics, University of Western Ontario, London, ON N6A 5C1 (Canada)

    2010-06-01

    We have applied fast-ion-beam laser-fluorescence spectroscopy to measure the isotope shifts of 38 transitions in the wavelength range 429-457 nm and the hyperfine structures (hfs) of 22 levels in Ti II. The isotope shift and hfs measurements are the first for these transitions and levels. These atomic data are essential for astrophysical studies of chemical abundances, allowing correction for saturation and the effects of blended lines.

  10. Self-Assembly and Soft Material Preparation of Binary Organogels via Aminobenzimidazole/Benzothiazole and Acids with Different Alkyl Substituent Chains

    Directory of Open Access Journals (Sweden)

    Tifeng Jiao

    2013-01-01

    Full Text Available The gelation behaviors of binary organogels composed of aminobenzimidazole/benzothiazole derivatives and benzoic acid with single-/multialkyl substituent chain in various organic solvents were designed and investigated. Their gelation behaviors in 20 solvents were tested as new binary organic gelators. This showed that the number and length of alkyl substituent chains and benzimidazole/benzothiazole segment have played a crucial role in the gelation behavior of all gelator mixtures in various organic solvents. More alkyl chains in molecular skeletons in present gelators are favorable for the gelation of organic solvents. The length of alkyl substituent chains has also played an important role in changing the gelation behaviors and assembly states. Morphological studies revealed that the gelator molecules self-assemble into different aggregates from wrinkle, lamella, belt, to fiber with change of solvents. Spectral studies indicated that there existed different H-bond formation and hydrophobic force, depending on benzimidazole/benzothiazole segment and alkyl substituent chains in molecular skeletons. The prepared nanostructured materials have wide perspectives and many potential applications in nanoscience and material fields due to their scientific values. The present work may also give new clues for designing new binary organogelators and soft materials.

  11. TOWARDS A RATIONAL DESIGN FOR RESOLVING AGENTS .5. SUBSTITUENT EFFECTS IN THE RESOLUTION OF EPHEDRINE USING A SERIES OF CYCLIC PHOSPHORIC-ACIDS

    NARCIS (Netherlands)

    VANDERHAEST, AD; WYNBERG, H; LEUSEN, FJJ; BRUGGINK, A

    The effects of various aromatic substituents in both ephedrine and a cyclic phosphoric acid on the quality of resolution via diastereomeric salt formation are investigated. The diastereoselective synthesis of a novel series of chloro-substituted ephedrines is described. These chloroephedrines can be

  12. New Soluble Polysiloxane Polymers containing a Pendent Terdentate Aryliamine Ligand substituent Holding a Highly Catalytical Active Organometallic Nickel(II) Centre

    NARCIS (Netherlands)

    Koten, G. van; Kuil, L.A. van de; Grove, D.M.; Zwikker, J.W.; Jenneskens, L.W.; Drenth, W.

    1994-01-01

    A new type of grafted polysiloxane polymer is described in which an aryldiamine substituent, [CsH3(CHzNMe2)2-2,61-, provides a pendant terdentate ligand environment for a catalytically active (0rgano)nickel center. The novel strategy employed involves initial grafting of the aryl bromide

  13. Quantized beam shifts in graphene

    Energy Technology Data Exchange (ETDEWEB)

    de Melo Kort-Kamp, Wilton Junior [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Sinitsyn, Nikolai [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Dalvit, Diego Alejandro Roberto [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-10-08

    We predict the existence of quantized Imbert-Fedorov, Goos-Hanchen, and photonic spin Hall shifts for light beams impinging on a graphene-on-substrate system in an external magnetic field. In the quantum Hall regime the Imbert-Fedorov and photonic spin Hall shifts are quantized in integer multiples of the fine structure constant α, while the Goos-Hanchen ones in multiples of α2. We investigate the influence on these shifts of magnetic field, temperature, and material dispersion and dissipation. An experimental demonstration of quantized beam shifts could be achieved at terahertz frequencies for moderate values of the magnetic field.

  14. Substituent effects on spin state in a series of mononuclear manganese(III) complexes with hexadentate Schiff-Base ligands.

    Science.gov (United States)

    Gildea, Brendan; Harris, Michelle M; Gavin, Laurence C; Murray, Caroline A; Ortin, Yannick; Müller-Bunz, Helge; Harding, Charles J; Lan, Yanhua; Powell, Annie K; Morgan, Grace G

    2014-06-16

    Eleven new mononuclear manganese(III) complexes prepared from two hexadentate ligands, L1 and L2, with different degrees of steric bulk in the substituents are reported. L1 and L2 are Schiff bases resulting from condensation of N,N'-bis(3-aminopropyl)ethylenediamine with 3-methoxy-2-hydroxybenzaldehyde and 3-ethoxy-2-hydroxybenzaldehyde respectively, and are members of a ligand series we have abbreviated as R-Sal2323 to indicate the 323 alkyl connectivity in the starting tetraamine and the substitution (R) on the phenolate ring. L1 hosts a methoxy substituent on both phenolate rings, while L2 bears a larger ethoxy group in the same position. Structural and magnetic properties are reported in comparison with those of a previously reported analogue with L1, namely, [MnL1]NO3, (1e). The BPh4(-) and PF6(-) complexes [MnL1]BPh4, (1a), [MnL2]BPh4, (2a), [MnL1]PF6, (1b'), and [MnL2]PF6, (2b), with both ligands L1 and L2, remain high-spin (HS) over the measured temperature range. However, the monohydrate of (1b') [MnL1]PF6·H2O, (1b), shows gradual spin-crossover (SCO), as do the ClO4(-), BF4(-), and NO3(-) complexes [MnL1]ClO4·H2O, (1c), [MnL2]ClO4, (2c), [MnL1]BF4·H2O, (1d), [MnL2]BF4·0.4H2O, (2d), [MnL1]NO3, (1e), and [MnL2]NO3·EtOH, (2e). The three complexes formed with ethoxy-substituted ligand L2 all show a higher T1/2 than the analogous complexes with methoxy-substituted ligand L1. Analysis of distortion parameters shows that complexes formed with the bulkier ligand L2 exhibit more deformation from perfect octahedral geometry, leading to a higher T1/2 in the SCO examples, where T1/2 is the temperature where the spin state is 50% high spin and 50% low spin. Spin state assignment in the solid state is shown to be solvate-dependent for complexes (1b) and (2e), and room temperature UV-visible and NMR spectra indicate a solution-state spin assignment intermediate between fully HS and fully low spin in 10 complexes, (1a)-(1e) and (2a)-(2e).

  15. Effects of Bulky Substituents of Push-Pull Porphyrins on Photovoltaic Properties of Dye-Sensitized Solar Cells.

    Science.gov (United States)

    Higashino, Tomohiro; Kawamoto, Kyosuke; Sugiura, Kenichi; Fujimori, Yamato; Tsuji, Yukihiro; Kurotobi, Kei; Ito, Seigo; Imahori, Hiroshi

    2016-06-22

    To evaluate the effects of substituent bulkiness around a porphyrin core on the photovoltaic properties of porphyrin-sensitized solar cells, long alkoxy groups were introduced at the meso-phenyl group (ZnPBAT-o-C8) and the anchoring group (ZnPBAT-o-C8Cn, n = 4, 8) of an asymmetrically substituted push-pull porphyrin with double electron-donating diarylamino groups and a single electron-withdrawing carboxyphenylethynyl anchoring group. The spectroscopic and electrochemical properties of ZnPBAT-o-C8 and ZnPBAT-o-C8Cn were found to be superior to those of a push-pull porphyrin reference (YD2-o-C8), demonstrating their excellent light-harvesting and redox properties for dye-sensitized solar cells. A power conversion efficiency (η) of the ZnPBAT-o-C8-sensitized solar cell (η = 9.1%) is higher than that of the YD2-o-C8-sensitized solar cell (η = 8.6%) using iodine-based electrolyte due to the enhanced light-harvesting ability of ZnPBAT-o-C8. In contrast, the solar cells based on ZnPBAT-o-C8Cn, possessing the additional alkoxy chains in the anchoring group, revealed the lower η values of 7.3% (n = 4) and 7.0% (n = 8). Although ZnPBAT-o-C8Cn exhibited higher resistance at the TiO2-dye-electrolyte interface by virtue of the extra alkoxy chains, the reduced amount of the porphyrins on TiO2 by excessive addition of coadsorbent chenodeoxycholic acid (CDCA) for mitigating the aggregation on TiO2 resulted in the low η values. Meanwhile, the ZnPBAT-o-C8-sensitized solar cell showed the lower η value of 8.1% than the YD2-o-C8-sensitized solar cell (η = 9.8%) using cobalt-based electrolyte. The smaller η value of the ZnPBAT-o-C8-sensitized solar cell may be attributed to the insufficient blocking effect of the bulky substituents of ZnPBAT-o-C8 under the cobalt-based electrolyte conditions. Overall, the alkoxy chain length and substitution position around the porphyrin core are important factors to affect the cell performance.

  16. Work shifts in Emergency Medicine

    Directory of Open Access Journals (Sweden)

    Roberto Recupero

    2007-06-01

    Full Text Available Emergency Medicine is known as a high stress specialty. The adverse effect of constantly rotating shifts is the single most important reason given for premature attrition from the field. In this work problems tied with night shift work will be taken into account and some solutions to reduce the impact of night work on the emergency physicians will be proposed.

  17. 15N NMR chemical shifts in papaverine decomposition products

    Science.gov (United States)

    Czyrski, Andrzej; Girreser, Ulrich; Hermann, Tadeusz

    2013-03-01

    Papaverine can be easily oxidized to papaverinol, papaveraldine and 2,3,9,10-tetramethoxy-12-oxo-12H-indolo[2,1-a]isoquinolinium chloride. On addition of alkali solution the latter compound forms 2-(2-carboxy-4,5-dimethoxyphenyl)-6,7-dimethoxyisoquinolinium inner salt. Together with these structures the interesting 13-(3,4-dimethoxyphenyl)-2,3,8,9-tetramethoxy-6a-12a-diazadibenzo[a,g]fluorenylium chloride is discussed, which is formed in the Gadamer-Schulemann reaction of papaverine as a side product. This letter reports the 15N NMR spectra of the above mentioned compounds.

  18. Chemical shift assignments of calmodulin constructs with EF hand mutations.

    Science.gov (United States)

    Piazza, Michael; Guillemette, J Guy; Dieckmann, Thorsten

    2016-04-01

    Calmodulin (CaM) is a ubiquitous cytosolic Ca(2+)-binding protein able to bind and regulate hundreds of different proteins. It consists of two globular domains joined by a flexible central linker region. Each one of these domains contains two EF hand pairs capable of binding to Ca(2+). Upon Ca(2+) binding CaM undergoes a conformational change exposing hydrophobic patches that interact with its intracellular target proteins. CaM is able to bind to target proteins in the Ca(2+)-replete and Ca(2+)-deplete forms. To study the Ca(2+)-dependent/independent properties of binding and activation of target proteins by CaM, CaM constructs with Ca(2+) binding disrupting mutations of Asp to Ala at position one of each EF hand have been used. One target protein of CaM is nitric oxide synthase, which catalyzes the production of nitric oxide. At elevated Ca(2+) concentrations, CaM binds to neuronal NOS and endothelial NOS, making them the Ca(2+)-dependent NOS enzymes. In contrast, inducible NOS is transcriptionally regulated in vivo and binds to CaM at basal levels of Ca(2+). Here we report the NMR backbone and sidechain resonance assignments of C-lobe Ca(2+)-replete and deplete CaM12, N-lobe Ca(2+)-replete and deplete CaM34, CaM1234 in the absence of Ca(2+) and N-lobe Ca(2+)-replete CaM34 with the iNOS CaM-binding domain peptide.

  19. Is there a shift to "active nanostructures"?

    Science.gov (United States)

    Subramanian, Vrishali; Youtie, Jan; Porter, Alan L.; Shapira, Philip

    2010-01-01

    It has been suggested that an important transition in the long-run trajectory of nanotechnology development is a shift from passive to active nanostructures. Such a shift could present different or increased societal impacts and require new approaches for risk assessment. An active nanostructure "changes or evolves its state during its operation," according to the National Science Foundation's (2006) Active Nanostructures and Nanosystems grant solicitation. Active nanostructure examples include nanoelectromechanical systems (NEMS), nanomachines, self-healing materials, targeted drugs and chemicals, energy storage devices, and sensors. This article considers two questions: (a) Is there a "shift" to active nanostructures? (b) How can we characterize the prototypical areas into which active nanostructures may emerge? We build upon the NSF definition of active nanostructures to develop a research publication search strategy, with a particular intent to distinguish between passive and active nanotechnologies. We perform bibliometric analyses and describe the main publication trends from 1995 to 2008. We then describe the prototypes of research that emerge based on reading the abstracts and review papers encountered in our search. Preliminary results suggest that there is a sharp rise in active nanostructures publications in 2006, and this rise is maintained in 2007 and through to early 2008. We present a typology that can be used to describe the kind of active nanostructures that may be commercialized and regulated in the future.

  20. Spectrophotometric studies of complexation of [60]fullerene with series of aromatic hydrocarbon molecules containing flexible phenyl substituents

    Science.gov (United States)

    Ghosh, Kalyan; Chattopadhyay, Subrata; Banerjee, Manas; Bhattacharya, Sumanta

    2006-11-01

    The absorption spectra of the electron donor-acceptor complexes of [60]fullerene with five different aromatic hydrocarbon (AH) molecules containing flexible phenyl substituents have been investigated in toluene medium. An absorption band due to charge transfer (CT) transition is observed in each case in the visible region. The experimental CT transition energies are well correlated with the vertical ionization potentials of the AHs studied (through Mulliken's equation) from which we extract degrees of charge transfer, oscillator and transition dipole strengths of the CT complexes. The degrees of CT in the ground state of the complexes have been found to be very low (0.49-0.55%). The formation constants ( K) for the complexes of [60]fullerene with the aromatic hydrocarbons have been determined by UV-vis spectroscopy. Both K values and PM3 calculations on [60]fullerene/AH complexes reveal that nature of substitution in the donor moiety as well as steric compatibility with the acceptor molecule govern the process of EDA complex formation.

  1. Substituent effect of Fe(β-diketonate)3 on the control of self-assembly FePt-based nanoparticles

    Science.gov (United States)

    Chokprasombat, K.; Harding, P.; Sirisathitkul, C.; Tangwatanakul, W.; Pinitsoontorn, S.; Muneesawang, P.

    2014-06-01

    Three Fe(β-diketonate)3 compounds namely Fe(tmhd)3 (tmhd = 2,2,6,6-tetramethyl-3,5-heptanedionato), Fe(hfac)3 (hfac = hexafluoroacetylaceto), and Fe(dbm)3 (dbm = dibenzoylmethane) were used as substitutes to Fe(acac)3 (acac = acetyleacetonate) in the synthesis of FePt nanoparticles. The obtained superparamagnetic nanoparticles are 4-5 nm in diameter without showing a large size variation with substituent Fe(β-diketonate)3. The synchrotron X-ray absorption spectroscopy confirmed the energy dispersive spectroscopy that as-synthesized nanoparticles were composed of iron oxides and metallic FePt3 alloys. By employing Fe(hfac)3, the Fe fraction was reduced and the magnetization was modest. The use of Fe(dbm)3 as starting materials gave rise to densely packed FePt3/Fe2O3 heterodimers. The replacements of Fe(acac)3 by Fe(tmhd)3 led to the long-range order of nanoparticle assembly with the narrowest size distribution.

  2. Temperature-Dependent Rate Constants and Substituent Effects for the Reactions of Hydroxyl Radicals With Three Partially Fluorinated Ethers

    Science.gov (United States)

    Hsu, K.-J.; DeMore, W. B.

    1995-01-01

    Rate constants and temperature dependencies for the reactions of OH with CF3OCH3 (HFOC-143a), CF2HOCF2H (HFOC-134), and CF3OCF2H (HFOC-125) were studied using a relative rate technique in the temperature range 298-393 K. The following absolute rate constants were derived: HFOC-143a, 1.9E-12 exp(-1555/T); HFOC-134, 1.9E-12 exp(-2006/T); HFOC-125, 4.7E-13 exp(-2095/T). Units are cm(exp 3)molecule(exp -1) s(exp -1). Substituent effects on OH abstraction rate constants are discussed, and it is shown that the CF3O group has an effect on the OH rate constants similar to that of a fluorine atom. The effects are related to changes in the C-H bond energies of the reactants (and thereby the activation energies) rather than changes in the preexponential factors. On the basis of a correlation of rate constants with bond energies, the respective D(C-H) bond strengths in the three ethers are found to be 102, 104, and 106 kcal/mol, with an uncertainty of about 1 kcal/mol.

  3. Red-Shifting versus Blue-Shifting Hydrogen Bonds: Perspective from Ab Initio Valence Bond Theory.

    Science.gov (United States)

    Chang, Xin; Zhang, Yang; Weng, Xinzhen; Su, Peifeng; Wu, Wei; Mo, Yirong

    2016-05-05

    Both proper, red-shifting and improper, blue-shifting hydrogen bonds have been well-recognized with enormous experimental and computational studies. The current consensus is that there is no difference in nature between these two kinds of hydrogen bonds, where the electrostatic interaction dominates. Since most if not all the computational studies are based on molecular orbital theory, it would be interesting to gain insight into the hydrogen bonds with modern valence bond (VB) theory. In this work, we performed ab initio VBSCF computations on a series of hydrogen-bonding systems, where the sole hydrogen bond donor CF3H interacts with ten hydrogen bond acceptors Y (═NH2CH3, NH3, NH2Cl, OH(-), H2O, CH3OH, (CH3)2O, F(-), HF, or CH3F). This series includes four red-shifting and six blue-shifting hydrogen bonds. Consistent with existing findings in literature, VB-based energy decomposition analyses show that electrostatic interaction plays the dominating role and polarization plays the secondary role in all these hydrogen-bonding systems, and the charge transfer interaction, which denotes the hyperconjugation effect, contributes only slightly to the total interaction energy. As VB theory describes any real chemical bond in terms of pure covalent and ionic structures, our fragment interaction analysis reveals that with the approaching of a hydrogen bond acceptor Y, the covalent state of the F3C-H bond tends to blue-shift, due to the strong repulsion between the hydrogen atom and Y. In contrast, the ionic state F3C(-) H(+) leads to the red-shifting of the C-H vibrational frequency, owing to the attraction between the proton and Y. Thus, the relative weights of the covalent and ionic structures essentially determine the direction of frequency change. Indeed, we find the correlation between the structural weights and vibrational frequency changes.

  4. Chemical Emergencies

    Science.gov (United States)

    When a hazardous chemical has been released, it may harm people's health. Chemical releases can be unintentional, as in the case of an ... the case of a terrorist attack with a chemical weapon. Some hazardous chemicals have been developed by ...

  5. Stress shift in rhythmical speech

    Science.gov (United States)

    Quené, Hugo; Port, Robert

    2002-05-01

    In phrases like thirteen men, stress in thirteen is often shifted forward from its canonical final position. Presumably, the occurrence of this optional stress shift may be partly controlled by the rhythm of speech. Work on rhythmic speech production has demonstrated that given a repetition cycle, T, its harmonic fractions like T/2 attract stressed vowel onsets. Comparing phrases like ceMENT thirTEEN and GALaxy thirTEEN, differing in the number of weak syllables between strong ones, it was predicted that, during rhythmic production, the harmonic locations would attract shifted stress. Since shifting stress results in more even distribution of syllables through the cycle, we expected that faster repetition rates would also result in more stress shift. Dependent variables were the relative stress in the second word of each pair, and the location of onset of the nuclear vowel of the stressed syllable. Results confirmed the predictions, first, that with more intermediate unstressed syllables, stress was shifted forward more often (thereby locating the stressed vowel onset closer to T/2) and, second, that stress shifted forward more often at faster speaking rates. [Work supported by Fulbright Visiting Scholar program and by Utrecht University, The Netherlands.

  6. Piezoelectric Ceramics of the (1 − x)Bi0.50Na0.50TiO3–xBa0.90Ca0.10TiO3 Lead-Free Solid Solution: Chemical Shift of the Morphotropic Phase Boundary, a Case Study for x = 0.06

    Science.gov (United States)

    Vivar-Ocampo, Rodrigo; Pardo, Lorena; Ávila, David; Morán, Emilio; González, Amador M.; Bucio, Lauro; Villafuerte-Castrejón, María-Elena

    2017-01-01

    Research and development of lead-free piezoelectric materials are still the hottest topics in the field of piezoelectricity. One of the most promising lead-free family of compounds to replace lead zirconate–titanate for actuators is that of Bi0.50Na0.50TiO3 (BNT) based solid solutions. The pseudo-binary (1 − x)Bi0.50Na0.50TiO3–xBa1 − yCayTiO3 system has been proposed for high temperature capacitors and not yet fully explored as piezoelectric material. In this work, the solid solution with x = 0.06 and y = 0.10 was obtained by two different synthesis routes: solid state and Pechini, aiming at using reduced temperatures, both in synthesis (<800 °C) and sintering (<1150 °C), while maintaining appropriated piezoelectric performance. Crystal structure, ceramic grain size, and morphology depend on the synthesis route and were analyzed by X-ray diffraction, together with scanning and transmission electron microscopy. The effects of processing and ceramic microstructure on the structural, dielectric, ferroelectric, and piezoelectric properties were discussed in terms of a shift of the Morphotropic Phase Boundary, chemically induced by the synthesis route. PMID:28773096

  7. Explaining (Missing) Regulator Paradigm Shifts

    DEFF Research Database (Denmark)

    Wigger, Angela; Buch-Hansen, Hubert

    2014-01-01

    of competition regulation is heaving into sight. It sets out to explain this from the vantage point of a critical political economy perspective, which identifies the circumstances under which a crisis can result in a regulatory paradigm shift. Contrasting the current situation with the shift in EC/EU competition...... capitalism; the social power configuration underpinning the neoliberal order remains unaltered; no clear counter-project has surfaced; the European Commission has been (and remains) in a position to oppose radical changes; and finally, there are no signs of a wider paradigm shift in the EU's regulatory...

  8. Mass Spectrometry in Organic Synthesis: Claisen-Schmidt Base-Catalyzed Condensation and Hammett Correlation of Substituent Effects

    Science.gov (United States)

    Bain, Ryan M.; Pulliam, Christopher J.; Yan, Xin; Moore, Kassandra F.; Mu¨ller, Thomas; Cooks, R. Graham

    2014-01-01

    Undergraduate laboratories generally teach an understanding of chemical reactivity using bulk or semimicroscale experiments with product isolation and subsequent chemical and spectroscopic analysis. In this study students were exposed to mass spectrometry as a means of chemical synthesis as well as analysis. The ionization method used, paper…

  9. A 3D visualization of the substituent effect : A brief analysis of two components of the operational formula of dual descriptor for open-shell systems.

    Science.gov (United States)

    Martínez-Araya, Jorge I; Yepes, Diana; Jaque, Pablo

    2017-12-27

    Six organometallic compounds coming from a basic Mo-based complex were analyzed from the perspective of the dual descriptor in order to detect subtle influences that a substituent group could exert on the reactive core at a long range. Since the aforementioned complexes are open-shell systems, the used operational formula for the dual descriptor is that one defined for those aforementioned systems, which was then compared with spin density. In addition, dual descriptor was decomposed into two terms, each of which was also applied on every molecular system. The obtained results indicated that components of dual descriptor could become more useful than the operational formula of dual descriptor because differences exerted by the substituents at the para position were better detected by components of dual descriptor rather than the dual descriptor by itself.

  10. The effects of substituent position on kinetics of benzene vapour adsorption onto 3-phenylphenoxy substituted metal-free and metallo-phthalocyanines thin films.

    Science.gov (United States)

    Alamin Ali, Haytham Elzien; Can, Nursel; Altun, Selçuk; Odabaş, Zafer

    2016-11-14

    The preparation of metal-free, Zn(ii), In(iii), and Cu(ii)-phthalocyanines containing tetrakis-(3-phenylphenoxy) groups was achieved by employing 3-(3-phenylphenoxy)phthalonitrile (1) and 4-(3-phenylphenoxy)phthalonitrile (2) as starting materials. The phthalonitriles and phthalocyanines were characterized by elemental analysis, infrared, proton nuclear magnetic resonance, ultraviolet-visible, and matrix-assisted laser desorption/ionization time-of-flight mass spectroscopic techniques. The effect of the substituent group on the kinetics of benzene vapour adsorption onto these novel compounds was examined using three kinetics models: the pseudo first-order model, the Elovich equation, and a simple adsorption-desorption model. Results show that the benzene adsorption kinetics strongly depend on the position of the substituent groups.

  11. A Successful Attempt to Obtain the Linear Dependence Between One-Photon and Two-Photon Spectral Properties and Hammett Parameters of Various Aromatic Substituents in New π-Extended Asymmetric Organic Chromophores.

    Science.gov (United States)

    Hu, Nvdan; Gong, Yulong; Wang, Xinchao; Lu, Yao; Peng, Guangyue; Yang, Long; Zhang, Shengtao; Luo, Ziping; Li, Hongru; Gao, Fang

    2015-11-01

    A series of new asymmetric chromophores containing aromatic substituents and possessing the excellent π-extension in space were prepared through multi-steps routes. One-photon and two-photon spectral properties of these new chromophores could be tuned by these substituents finely and simultaneously. The linear correlation of the wave numbers of the one-photon absorption and emission maxima to Hammett parameters of these substituents was presented. Near infrared two-photon absorption emission integrated areas of the target chromophores were correlated linearly to Hammett constants of these substituted groups.

  12. In vitro immunobiological studies of novel 5-(5-nitrofuran-2-yl)-1, 3, 4-thiadiazoles with piperazinyl-linked benzamidine substituents against Leishmania major.

    OpenAIRE

    Farzaneh Rezazadeh Marznaki; Raheleh Shakeri; Sussan Kaboudanian Ardestani; Azar Tahghighi; Alireza Foroumadi

    2013-01-01

    It was recently demonstrated that 5-(5-nitrofuran-2-yl)-1, 3, 4-thiadiazoles with piperazinyl-linked benzamidine substituents are effective in vitro against Leishmania major.Following on this evidence, we used colorimetric assay of acid phosphatase activity in the promastigotes as an indicator for cell viability. Also we studied the effect of these compounds on induction of nitric oxide (NO) in macrophage and production of reactive oxygen species (ROS) in lymphocyte that have important role i...

  13. Bipolar Alq{sub 3}-based complexes: Effect of hole-transporting substituent on the properties of Alq{sub 3}-center

    Energy Technology Data Exchange (ETDEWEB)

    Luo Jianxin [Guangzhou Institute of Chemistry, Chinese Academy of Sciences, Guangzhou 510650 (China); Department of Materials and Chemical Engineering, Hunan Institute of Technology, Hengyang, Hunan 421002 (China); Lu Mangeng, E-mail: mglu@gic.ac.cn [Guangzhou Institute of Chemistry, Chinese Academy of Sciences, Guangzhou 510650 (China); Yang Chaolong [Guangzhou Institute of Chemistry, Chinese Academy of Sciences, Guangzhou 510650 (China); Tong Bihai [Institute of Molecular Engineering and Applied Chemistry, Anhui University of Technology, Maanshan 243002 (China); Liang Liyan [Guangzhou Institute of Chemistry, Chinese Academy of Sciences, Guangzhou 510650 (China)

    2012-09-15

    Two bipolar Alq{sub 3}-based complexes, tris{l_brace}5-[(carbazole-9'-yl)methyl]-8-hydroxyquinoline{r_brace} aluminum (Al(CzHQ){sub 3}) and tris{l_brace}5-[(phenothiazine-9'-yl)methyl]-8-hydroxyquinoline{r_brace} aluminum (Al(PHQ){sub 3}), involving an Alq{sub 3}-center and three hole-transporting substituents (carbazole or phenothiazine), were prepared and characterized. Effects of hole-transporting substituent on the properties of Alq{sub 3}-center were investigated in detail. It is found that the two complexes have improved hole-transporting performance and appropriate thermal stability (the 5%-weight-loss temperatures T{sub 5%}>260 Degree-Sign C). Photoluminescence (PL) spectra indicate that both energy transfer and electron transfer can take place simultaneously in the PL process of these complexes. Both thermodynamics and dynamics of the electron transfer were studied and corresponding parameters were calculated. Energy transfer is favorable for the PL of Alq{sub 3}-center, while electron transfer is unfavorable for the PL of Alq{sub 3}-center. These results will be useful to explore novel OLEDs material with increased efficiency. - Highlights: Black-Right-Pointing-Pointer Effects of substituent on the properties of Alq{sub 3}-center were investigated. Black-Right-Pointing-Pointer Energy transfer and electron transfer can transfer from substituent to Alq{sub 3}-center. Black-Right-Pointing-Pointer The thermodynamics and dynamics of electron transfer were studied. Black-Right-Pointing-Pointer The mechanisms of PL and EL of Al(CzHQ){sub 3} were studied and compared with each other.

  14. New tricyclic and tetracyclic pyranocoumarins with an unprecedented C-4 substituent. Structure elucidation of tamanolide, tamanolide D and tamanolide P from Calophyllum inophyllum of French Polynesia.

    Science.gov (United States)

    Leu, T; Raharivelomanana, P; Soulet, S; Bianchini, J P; Herbette, G; Faure, R

    2009-11-01

    Three new pyranocoumarin derivatives, tamanolide (1), tamanolide D (2) and tamanolide P (3), were isolated from the almond seeds of Calophyllum inophyllum L. (Clusiaceae) grown in French Polynesia. These compounds, having an unprecedented C-4 isobutyl substituent, have been characterized as a new class of pyranocoumarins called tamanolides. Their structures were elucidated on the basis of 1D and 2D NMR techniques (COSY, NOESY, HSQC and HMBC) in association with MS (HR-ESI-MS) data analysis. 2009 John Wiley & Sons, Ltd.

  15. 13C and 1H NMR of 2,6-diaryl-1-hydroxy piperidin-4-one oximes; substituent effects on cis/trans ratio and conformational equilibria.

    Science.gov (United States)

    Díaz, E; Barrios, H; del Río Portilla, F; Guzmán, A; Aguilera, J L; Becerril, R; Jankowski, C K; Reynolds, W F

    2000-10-01

    The reaction of substituted diarylidene acetones with hydroxylamine hydrochloride affords isomeric N-hydroxy diaryl piperidinone oximes as main products. The structures as well as conformational equilibria of these products were established by 1H and 13C NMR spectroscopy and further studied by variable temperature NMR. It was found that the cis/trans ratio of 2,6-substituted piperidine derivatives depended on the position of the substituent on the aromatic ring.

  16. Cationic bis-cyclometallated iridium(III) phenanthroline complexes with pendant fluorenyl substituents: synthesis, redox, photophysical properties and light-emitting cells.

    Science.gov (United States)

    Zeng, Xianshun; Tavasli, Mustafa; Perepichka, Igor F; Batsanov, Andrei S; Bryce, Martin R; Chiang, Chien-Jung; Rothe, Carsten; Monkman, Andrew P

    2008-01-01

    We report the synthesis, characterisation, photophysical and electrochemical properties of a series of cationic cyclometallated Ir(III) complexes of general formula [Ir(ppy)(2)(phen)]PF(6) (ppy=2-phenylpyridine, phen=a substituted phenanthroline). A feature of these complexes is that the phen ligands are substituted with one or two 9,9-dihexylfluorenyl substituents to provide extended pi conjugation, for example, the 3-[2-(9,9-dihexylfluorenyl)]phenanthroline and 3,8-bis[2-(9,9-dihexylfluorenyl)]phenanthroline ligands afford complexes 6 and 9, respectively. A single-crystal X-ray diffraction study of a related complex 18 containing the 3,8-bis(4-iodophenyl)phenanthroline ligand, revealed an octahedral coordination of the Ir atom, in which the metallated C atoms of the ppy ligands occupy cis positions. The complexes 6 and 9 displayed reversible oxidation waves in cyclic voltammetric studies (E(ox)(1/2)=+1.18 and +1.20 V, respectively, versus Ag/Ag(+) in CH(2)Cl(2)) assigned to the metal-centred Ir(III)/Ir(IV) couple. The complexes exhibit strong absorption in the UV region in solution spectra, due to spin-allowed ligand-centred (LC) (1)pi-pi* transitions; moderately intense bands occur at approximately 360-390 nm which are red-shifted with increased ligand length. The photoluminescence spectra of all the complexes were characterised by a broad band at lambda(max) approximately 595 nm assigned to a combination of (3)MLCT and (3)pi-->pi* states. The long emission lifetimes (in the microsecond time-scale) are indicative of phosphorescence: the increased ligand conjugation length in complexes 9 and 17 leads to increased lifetimes for the complexes (tau=2.56 and 2.57 micros in MeCN, respectively) compared to monofluorenyl analogues 6 and 15 (tau=1.43 and 1.39 micros, respectively). DFT calculations of the geometries and electronic structures of complexes 6', 9' (for both singlet ground state (S(0)) and triplet first excited (T(1)) states) and 18 have been performed. In

  17. Influence of different amino substituents in position 1 and 4 on spectroscopic and acid base properties of 9,10-anthraquinone moiety

    Science.gov (United States)

    Wcisło, Anna; Niedziałkowski, Paweł; Wnuk, Elżbieta; Zarzeczańska, Dorota; Ossowski, Tadeusz

    2013-05-01

    A series of novel 1-amino and 1,4-diamino-9,10-anthraquinones, substituted with different alkyl groups, were synthesized as the result of alkylation with amino substituents. All the obtained aminoanthraquinone derivatives were characterized by NMR, IR spectroscopy and mass spectrometry. The spectroscopic properties of these compounds were determined by using UV-Vis spectroscopy in acetonitrile, and in the mixture of acetonitrile and methanol at different pH ranges. The effects of various substituents present in the newly developed anthraquinone derivatives and their ability to form hydrogen bonds between the carbonyl oxygen atom of anthraquinone moiety and nitrogen atom of N-H group in 1-aminoanthraquinone (1-AAQ) and 1,4-diaminoanthraquinone (1,4-DAAQ) were studied. Additionally, the effects of hydrogen bond formation between O-H group in hydroxyethylamino substituent and the carbonyl oxygen atom of anthraquinone were investigated. The spectroscopic behavior of the studied derivatives strongly depended on the solvent-solute interactions and the nature of solvent. The values of pKa for the new anthraquinones were determined by the combined potentiometric and spectrophotometric titration methods.

  18. Antimicrobial and anticancer photodynamic activity of a phthalocyanine photosensitizer with N-methyl morpholiniumethoxy substituents in non-peripheral positions.

    Science.gov (United States)

    Dlugaszewska, Jolanta; Szczolko, Wojciech; Koczorowski, Tomasz; Skupin-Mrugalska, Paulina; Teubert, Anna; Konopka, Krystyna; Kucinska, Malgorzata; Murias, Marek; Düzgüneş, Nejat; Mielcarek, Jadwiga; Goslinski, Tomasz

    2017-07-01

    Photodynamic therapy involves the use of a photosensitizer that is irradiated with visible light in the presence of oxygen, resulting in the formation of reactive oxygen species. A novel phthalocyanine derivative, the quaternary iodide salt of magnesium(II) phthalocyanine with N-methyl morpholiniumethoxy substituents, was synthesized, and characterized. The techniques used included mass spectrometry (MALDI TOF), UV-vis, NMR spectroscopy, and photocytotoxicity against bacteria, fungi and cancer cells. The phthalocyanine derivative possessed typical characteristics of compounds of the phthalocyanine family but the effect of quaternization was observed on the optical properties, especially in terms of absorption efficiency. The results of the photodynamic antimicrobial effect study demonstrated that cationic phthalocyanine possesses excellent photodynamic activity against planktonic cells of both Gram-positive and Gram-negative bacteria. The bactericidal effect was dose-dependent and all bacterial strains tested were killed to a significant degree by irradiated phthalocyanine at a concentration of 1×10(-4)M. There were no significant differences in the susceptibility of Gram-positive and Gram-negative bacteria to the applied photosensitizer. The photosensitivity of bacteria in the biofilm was lower than that in planktonic form. No correlation was found between the degree of biofilm formation and susceptibility to antimicrobial photodynamic inactivation. The anticancer activity of the novel phthalocyanine derivative was tested using A549 adenocarcinomic alveolar basal epithelial cells and the human oral squamous cell carcinoma cells derived from tongue (HSC3) or buccal mucosa (H413). No significant decrease in cell viability was observed under different conditions or with different formulations of the compound. Copyright © 2017 Elsevier Inc. All rights reserved.

  19. Strongly coupled cyclometalated ruthenium-triarylamine hybrids: tuning electrochemical properties, intervalence charge transfer, and spin distribution by substituent effects.

    Science.gov (United States)

    Yao, Chang-Jiang; Nie, Hai-Jing; Yang, Wen-Wen; Shao, Jiang-Yang; Yao, Jiannian; Zhong, Yu-Wu

    2014-12-22

    Nine cyclometalated ruthenium complexes with a redox-active diphenylamine unit in the para position to the RuC bond were prepared. MeO, Me, and Cl substituents on the diphenylamine unit and three types of auxiliary ligands-bis(N-methylbenzimidazolyl)pyridine (Mebip), 2,2':6',2''-terpyridine (tpy), and trimethyl-4,4',4''-tricarboxylate-2,2':6',2''-terpyridine (Me3 tctpy)--were used to vary the electronic properties of these complexes. The derivative with an MeO-substituted amine unit and Me3 tctpy ligand was studied by single-crystal X-ray analysis. All complexes display two well-separated redox waves in the potential region of +0.1 to +1.0 V versus Ag/AgCl, and the potential splitting ranges from 360 to 510 mV. Spectroelectrochemical measurements show that these complexes display electrochromism at low potentials and intense near-infrared (NIR) absorptions. In the one-electron oxidized form, the complex with the Cl-substituted amine unit and Mebip ligand shows a moderate ligand-to-metal charge transfer at 800 nm. The other eight complexes show asymmetric, narrow, and intense intervalence charge-transfer transitions in the NIR region, which are independent of the polarity of the solvent. The Mebip-containing complexes display rhombic or broad isotropic EPR signals, whereas the other seven complexes show relatively narrow isotropic EPR signals. In addition, DFT and time-dependent DFT studies were performed to gain insights into the spin distributions and NIR absorptions. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Cu(II) bis(thiosemicarbazone) radiopharmaceutical binding to serum albumin: further definition of species dependence and associated substituent effects

    Energy Technology Data Exchange (ETDEWEB)

    Basken, Nathan E. [Division of Nuclear Pharmacy, Department of Industrial and Physical Pharmacy, Purdue University, West Lafayette, IN 47907 (United States); Green, Mark A. [Division of Nuclear Pharmacy, Department of Industrial and Physical Pharmacy, Purdue University, West Lafayette, IN 47907 (United States)], E-mail: magreen@purdue.edu

    2009-07-15

    Introduction: The pyruvaldehyde bis(N{sup 4}-methylthiosemicarbazonato)copper(II) (Cu-PTSM) and diacetyl bis(N{sup 4}-methylthiosemicarbazonato)copper(II) (Cu-ATSM) radiopharmaceuticals exhibit strong, species-dependent binding to the IIA site of human serum albumin (HSA), while the related ethylglyoxal bis(thiosemicarbazonato)copper(II) (Cu-ETS) radiopharmaceutical appears to exhibit only nonspecific binding to HSA and animal serum albumins. Methods: To further probe the structural basis for the species dependence of this albumin binding interaction, we examined protein binding of these three radiopharmaceuticals in solutions of albumin and/or serum from a broader array of mammalian species (rat, sheep, donkey, rabbit, cow, pig, dog, baboon, mouse, cat and elephant). We also evaluated the albumin binding of several copper(II) bis(thiosemicarbazone) chelates offering more diverse substitution of the ligand backbone. Results: Cu-PTSM and Cu-ATSM exhibit a strong interaction with HSA that is not apparent with the albumins of other species, while the binding of Cu-ETS to albumin is much less species dependent. The strong interaction of Cu-PTSM with HSA does not appear to simply correlate with variation, relative to the animal albumins, of a single amino acid lining HSA's IIA site. Those agents that selectively interact with HSA share the common feature of only methyl or hydrogen substitution at the carbon atoms of the diimine fragment of the ligand backbone. Conclusions: The interspecies variations in albumin binding of Cu-PTSM and Cu-ATSM are not simply explained by unique amino acid substitutions in the IIA binding pocket of the serum albumins. However, the specific affinity for this region of HSA is disrupted when substituents bulkier than a methyl group appear on the imine carbons of the copper bis(thiosemicarbazone) chelate.

  1. Structures and properties of molecular torsion balances to decipher the nature of substituent effects on the aromatic edge-to-face interaction.

    Science.gov (United States)

    Gardarsson, Haraldur; Schweizer, W Bernd; Trapp, Nils; Diederich, François

    2014-04-14

    Various recent computational studies initiated this systematic re-investigation of substituent effects on aromatic edge-to-face interactions. Five series of Tröger base derived molecular torsion balances (MTBs), initially introduced by Wilcox and co-workers, showing an aromatic edge-to-face interaction in the folded, but not in the unfolded form, were synthesized. A fluorine atom or a trifluoromethyl group was introduced onto the edge ring in ortho-, meta-, and para-positions to the C-H group interacting with the face component. The substituents on the face component were varied from electron-donating to electron-withdrawing. Extensive X-ray crystallographic data allowed for a discussion on the conformational behavior of the torsional balances in the solid state. While most systems adopt the folded conformation, some were found to form supramolecular intercalative dimers, lacking the intramolecular edge-to-face interaction, which is compensated by the gain of aromatic π-stacking interactions between four aryl rings of the two molecular components. This dimerization does not take place in solution. The folding free enthalpy ΔG(fold) of all torsion balances was determined by (1)H NMR measurements by using 10 mM solutions of samples in CDCl3 and C6D6. Only the ΔG(fold) values of balances bearing an edge-ring substituent in ortho-position to the interacting C-H show a steep linear correlation with the Hammett parameter (σ(meta)) of the face-component substituent. Thermodynamic analysis using van't Hoff plots revealed that the interaction is enthalpy-driven. The ΔG(fold) values of the balances, in addition to partial charge calculations, suggest that increasing the polarization of the interacting C-H group makes a favorable contribution to the edge-to-face interaction. The largest contribution, however, seems to originate from local direct interactions between the substituent in ortho-position to the edge-ring C-H and the substituted face ring. © 2014 WILEY

  2. Conjugate Addition/[3,3] Sigmatropic Shift Processes for Formation of Medium-Ring Cyclic Amines - Do They Circumvent the Woodward-Hoffmann Rules?

    Science.gov (United States)

    Painter, Phillip P; Siebert, Matthew R; Tantillo, Dean J

    2015-12-04

    Herein we describe our exploration, using density functional theory calculations, of a conjugate addition-rearrangement sequence that leads to medium-ring cyclic amines. On the basis of the results of our calculations, we conclude that the rearrangement step is rate determining. In addition, we analyze the role of a carbanion lone pair in the rearrangement step, concluding that it functions as a substituent on a [3,3] sigmatropic shift, rather than a nucleophile; thus, the Woodward-Hoffmann rules are not circumvented in this reaction via involvement of orthogonal orbitals on an atom involved in the rearrangement.

  3. shift

    African Journals Online (AJOL)

    during the course of an academic year at the University of Witwatersrand following recent reforms in training and assessment methods Method: All fifth ... Assessment of Psychiatry in medical education at the. University of Witwatersrand ... or two examiners, to assess mainly clinical competence; multiple-choice questions ...

  4. Paradigm Shifts in Ophthalmic Diagnostics.

    Science.gov (United States)

    Sebag, J; Sadun, Alfredo A; Pierce, Eric A

    2016-08-01

    Future advances in ophthalmology will see a paradigm shift in diagnostics from a focus on dysfunction and disease to better measures of psychophysical function and health. Practical methods to define genotypes will be increasingly important and non-invasive nanotechnologies are needed to detect molecular changes that predate histopathology. This is not a review nor meant to be comprehensive. Specific topics have been selected to illustrate the principles of important paradigm shifts that will influence the future of ophthalmic diagnostics. It is our impression that future evaluation of vision will go beyond visual acuity to assess ocular health in terms of psychophysical function. The definition of disease will incorporate genotype into what has historically been a phenotype-centric discipline. Non-invasive nanotechnologies will enable a paradigm shift from disease detection on a cellular level to a sub-cellular molecular level. Vision can be evaluated beyond visual acuity by measuring contrast sensitivity, color vision, and macular function, as these provide better insights into the impact of aging and disease. Distortions can be quantified and the psychophysical basis of vision can be better evaluated than in the past by designing tests that assess particular macular cell function(s). Advances in our understanding of the genetic basis of eye diseases will enable better characterization of ocular health and disease. Non-invasive nanotechnologies can assess molecular changes in the lens, vitreous, and macula that predate visible pathology. Oxygen metabolism and circulatory physiology are measurable indices of ocular health that can detect variations of physiology and early disease. This overview of paradigm shifts in ophthalmology suggests that the future will see significant improvements in ophthalmic diagnostics. The selected topics illustrate the principles of these paradigm shifts and should serve as a guide to further research and development. Indeed

  5. The shifting foundations of nursing.

    Science.gov (United States)

    Law, Kate; Aranda, Kay

    2010-08-01

    In this paper we argue that the concerns generated by the development of Foundation Degrees and the Assistant and Associate Practitioner roles have rekindled some of the unresolved debates regarding the status and identity of nursing and nurses. Through the application of the sociological theories of professionalisation and nostalgia we have identified the shifting and unresolved nature of nursing. We argue that these theories continue to have resonance in the current climate of change and 'upskilling' of the health care workforce and argue, that the shifts illuminated are perhaps so significant as to demonstrate that we have entered a post-nursing era. Copyright 2009 Elsevier Ltd. All rights reserved.

  6. Predator-induced phenotypic plasticity in Daphnia pulex: Uncoupling morphological defenses and life history shifts

    NARCIS (Netherlands)

    Repka, S.; Pihlajamaa, K.

    1996-01-01

    Chemical cues from a predator Chaoborus sp. induce morphological defense (neck spine) and life history shifts (later reproduction, decreased fecundity but larger juvenile size) in the waterflea Daphnia pulex. These shifts have been interpreted either as costs of defense or as separate adaptation. In

  7. Crichton's phase-shift ambiguity

    NARCIS (Netherlands)

    Atkinson, D.; Johnson, P.W.; Mehta, N.; Roo, M. de

    1973-01-01

    A re-examination of the SPD phase-shift ambiguity is made with a view to understanding certain singular features of the elastic unitarity constraint. An explicit solution of Crichton's equations is presented, and certain features of this solution are displayed graphically. In particular, it is shown

  8. Environmental Protection: a shifting focus

    NARCIS (Netherlands)

    Dr. ir. Jan Venselaar

    2004-01-01

    The last two decades have seen a fundamental change in the way chemistry handles environmental issues. A shift in focus has occurred from 'end-of-pipe' to prevention and process integration. Presently an even more fundamental change is brought about by the need for sustainable development. It is

  9. Anthropometric changes and fluid shifts

    Science.gov (United States)

    Thornton, W. E.; Hoffler, G. W.; Rummel, J. A.

    1974-01-01

    Several observations of body size, shape, posture, and configuration were made to document changes resulting from direct effects of weightlessness during the Skylab 4 mission. After the crewmen were placed in orbit, a number of anatomical and anthropometric changes occurred including a straightening of the thoracolumbar spine, a general decrease in truncal girth, and an increase in height. By the time of the earliest in-flight measurement on mission day 3, all crewmen had lost more than two liters of extravascular fluid from the calf and thigh. The puffy facies, the bird legs effect, the engorgement of upper body veins, and the reduced volume of lower body veins were all documented with photographs. Center-of-mass measurements confirmed a fluid shift cephalad. This shift remained throughout the mission until recovery, when a sharp reversal occurred; a major portion of the reversal was completed in a few hours. The anatomical changes are of considerable scientific interest and of import to the human factors design engineer, but the shifts of blood and extravascular fluid are of more consequence. It is hypothesized that the driving force for the fluid shift is the intrinsic and unopposed lower limb elasticity that forces venous blood and then other fluid cephalad.

  10. Does the ARFIMA really shift?

    DEFF Research Database (Denmark)

    Monache, Davide Delle; Grassi, Stefano; Santucci de Magistris, Paolo

    Short memory models contaminated by level shifts have long-memory features similar to those associated to processes generated under fractional integration. In this paper, we propose a robust testing procedure, based on an encompassing parametric specification, that allows to disentangle the level...

  11. The Shift Needed for Sustainability

    Science.gov (United States)

    Smith, Peter A. C.; Sharicz, Carol

    2011-01-01

    Purpose: The purpose of this action research is to begin to assess to what extent organizations have in practice begun to make the shift towards triple bottom line (TBL) sustainability. Design/methodology/approach: A definition of TBL sustainability is provided, and key elements of TBL sustainability considered necessary to success are identified…

  12. Shift Work: Improving Daytime Sleep

    Science.gov (United States)

    ... Good daytime sleep is possible, though, if shift work is a necessary part of your work life. To promote better sleep during the day: ... Take naps. Napping late in the day before work might help you make up your sleep debt. ...

  13. Ruthenium Bis-diimine Complexes with a Chelating Thioether Ligand: Delineating 1,10-Phenanthrolinyl and 2,2'-Bipyridyl Ligand Substituent Effects

    Energy Technology Data Exchange (ETDEWEB)

    Al-Rawashdeh, Nathir A. F.; Chatterjee, Sayandev; Krause, Jeanette A.; Connick, William B.

    2014-01-06

    A new series of ruthenium(II) bis-diimine complexes with a chelating thioether donor ligand has been prepared: Ru(diimine)2(dpte)2+ (diimine=1,10-phenanthroline (phen) (1); 5-CH3-phen (2), 5-Cl-phen (3); 5-Br-phen (4); 5-NO2-phen (5); 3,4,7,8-tetramethyl-phen (6); 4,7-diphenyl-phen (7); 5,5'-dimethyl-2,2'-bipyridine (8); 4,4'-di-tert-butyl-2,2'-bipyridine (9)). Crystal structures of 2, 5, 7 and 9 show that the complexes form 2 of the 12 possible conformational/configurational isomers, adopting compact C2-symmetric structures with short intramolecular transannular interactions between the diimine ligands and dpte phenyl groups; crystals of 2 and 5 contain non-statistical distributions of geometric isomers. In keeping with the π-acidity of the dpte, the Ru(III/II) couple, E°'(Ru3+/2+), occurs at relatively high potentials (1.4-1.7 V vs Ag/AgCl), and the lowest spin-allowed MLCT absorption band occurs near 400 nm. Surprisingly, the complexes also exhibit fluid-solution luminescence originating from a lowest MLCT excited state with lifetimes in the 140-750 ns time range; in acetonitrile, compound 8 undergoes photo-induced solvolysis. Variations in the MLCT energies and redox potentials are quantitatively described using a summative Hammett parameter (σT), as well as using Lever's electrochemical parameters (EL). Recommended parameterizations for 2,2'-bipyridyl and 1,10-phenanthrolinyl ligands were derived from analysis of correlations based on 199 measurements of E°'(Ru3+/2+) for 99 homo- and heteroleptic ruthenium(II) tris-diimine complexes. Variations in E°'(Ru3+/2+) due to substituents at the 4- and 4'-positions of bipyridyl ligands and 4- and 7-positions of phenanthrolinyl ligands are significantly more strongly correlated with σp+ than either σm or σp. Substituents at the 5- and 6-positions of phenanthrolinyl ligands are best described by σm and have effects comparable to those of substituents at the 3

  14. Protein structure refinement using a quantum mechanics-based chemical shielding predictor

    DEFF Research Database (Denmark)

    Bratholm, Lars Andersen; Jensen, Jan Halborg

    2017-01-01

    chemical shielding values (ProCS15) can be used to refine protein structures using Markov Chain Monte Carlo (MCMC) simulations, relating the chemical shielding values to the experimental chemical shifts probabilistically. Two kinds of MCMC structural refinement simulations were performed using force field...... the chemical shift RMSD by 1.0 and 0.7 ppm for CA and N. Conformational averaging has a relatively small effect (0.1–0.2 ppm) on the overall agreement with carbon chemical shifts but lowers the error for nitrogen chemical shifts by 0.4 ppm. If an amino acid specific offset is included the ProCS15 predicted...

  15. Synthesis and Evaluation of Changes Induced by Solvent and Substituent in Electronic Absorption Spectra of New Azo Disperse Dyes Containig Barbiturate Ring

    Directory of Open Access Journals (Sweden)

    Hooshang Hamidian

    2013-01-01

    Full Text Available Six azo disperse dyes were prepared by diazotizing 4-amino hippuric acid and coupled with barbituric acid and 2-thiobarbituric acid. Then, the products were reacted with aromatic aldehyde, sodium acetate, and acetic anhydride, and oxazolone derivatives were formed. Characterization of the dyes was carried out by using UV-Vis, FT-IR, 1H NMR and 13C NMR, and mass spectroscopic techniques. The solvatochromic behavior of azo disperse dyes was evaluated in various solvents. The effects of substituents of aromatic aldehyde, barbiturate, and thiobarbiturate ring on the color of dyes were investigated.

  16. Influence of Halogen Substituents on the Catalytic Oxidation of 2,4,6-Halogenated Phenols by Fe(III)-Tetrakis(p-hydroxyphenyl) porphyrins and Potassium Monopersulfate

    OpenAIRE

    Seiya Nagao; Hideki Kuramitz; Qianqian Zhu; Shouhei Maeno; Masami Fukushima; Yusuke Mizutani

    2011-01-01

    The influence of halogen substituents on the catalytic oxidation of 2,4,6-trihalogenated phenols (TrXPs) by iron(III)-porphyrin/KHSO5 catalytic systems was investigated. Iron(III)-5,10,15,20-tetrakis(p-hydroxyphenyl)porphyrin (FeTHP) and its supported variants were employed, where the supported catalysts were synthesized by introducing FeTHP into hydroquinone-derived humic acids via formaldehyde poly-condensation. F (TrFP), Cl (TrCP), Br (TrBP) and I (TrIP) were examined as halogen substituen...

  17. Influence du cobalt sur le comportement de l'hydroxyde de nickel dans les batteries alcalines du substituant au collecteur de charges

    OpenAIRE

    Gautier, Laurent

    1995-01-01

    Date de soutenance approximative; Ce travail est consacre à la synthèse et à la caractérisation de nouveaux hydroxydes de nickel substitues au cobalt et à l'aluminium. La présence de 25% d'ions trivalents permet d'assurer la cohésion de la structure de type alpha, ainsi que la stabilité chimique de ces matériaux en milieu alcalin concentre. L'étude électrochimique montre que le couple alpha/gamma est parfaitement stabilise lorsque le taux d'aluminium est supérieur a 15%. En revanche, pour des...

  18. Measurement of hyperfine structure and isotope shifts in Gd II

    Science.gov (United States)

    Del Papa, Dylan F.; Rose, Christopher D. M.; Rosner, S. David; Holt, Richard A.

    2017-07-01

    We have applied fast-ion-beam laser-fluorescence spectroscopy to measure the isotope shifts of 73 optical transitions in the wavelength range 421.5-455.8 nm and the hyperfine structures of 35 even parity and 33 odd parity levels in Gd II. Many of the isotope shifts and hyperfine structure measurements are the first for these transitions and levels. These atomic data can be used to correct for saturation and blending in the analysis of stellar spectra to determine chemical abundances. As a result, they have an important impact on studies of the history of nucleosynthesis in the Universe and on the use of photospheric abundance anomalies in Chemically Peculiar stars to infer indirect information about stellar interiors.

  19. VP Anaphors and Object Shift

    DEFF Research Database (Denmark)

    Ørsnes, Bjarne

    2013-01-01

    The article discusses the placement of the VP anaphor det ‘it’ as a complement of verbs selecting VP complements in Danish. With verbs that only allow a VP complement, the VP anaphor must be in SpecCP regardless of its information structure properties. If SpecCP is occupied by an operator......, the anaphor can be in situ, but it cannot shift. With verbs that allow its VP complement to alternate with an NP complement, the VP anaphor can be in SpecCP, shifted or in situ according to the information structural properties of the anaphor. Only if SpecCP is occupied by an operator, must a topical anaphor...

  20. Hadronic shift in pionic hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Hennebach, M.; Gotta, D. [Forschungszentrum Juelich, Institut fuer Kernphysik, Juelich (Germany); Anagnostopoulos, D.F. [University of Ioannina, Department of Materials Science and Engineering, Ioannina (Greece); Dax, A.; Liu, Y.W.; Markushin, V.E.; Simons, L.M. [Paul Scherrer Institut, Laboratory for Particle Physics, Villigen (Switzerland); Fuhrmann, H.; Gruber, A.; Hirtl, A.; Zmeskal, J. [Austrian Academy of Sciences, Stefan Meyer Institute for Subatomic Physics, Vienna (Austria); Indelicato, P. [UPMC Univ. Paris 06, Laboratoire Kastler Brossel, Sorbonne Universites, Paris (France); CNRS, Laboratoire Kastler Brossel, Paris (France); Departement de Physique de l' Ecole Normale Superieure, Laboratoire Kastler Brossel, Paris (France); Manil, B. [UPMC Univ. Paris 06, Laboratoire Kastler Brossel, Sorbonne Universites, Paris (France); Rusi el Hassani, A.J. [Universite Abdelmalek Essaadi, Faculte des Sciences et Techniques, Tanger (Morocco); Trassinelli, M. [Sorbonne Universites, Institut des NanoSciences de Paris, Paris (France); CNRS, Institut des NanoSciences de Paris, Paris (France)

    2014-12-01

    The hadronic shift in pionic hydrogen has been redetermined to be ε {sub 1s} = 7.086 ± 0.007(stat) ± 0.006(sys) eV by X-ray spectroscopy of ground-state transitions applying various energy calibration schemes. The experiment was performed at the high-intensity low-energy pion beam of the Paul Scherrer Institut by using the cyclotron trap and an ultimate-resolution Bragg spectrometer with bent crystals. (orig.)

  1. Into the Era of shifts

    DEFF Research Database (Denmark)

    Dencik, Lars

    2005-01-01

    Globalization and new communication technologies shape new increasingly unpredictable living conditions. Societies as individuals face a world og growing predictive impotence. Traditions loose their power as guides for maneuvering - where traditions was reflection will be. At the same time peoples......, life styles, experiences and sexuality. Even thougts and feelings.In the era of shifts we shall be living with ever more design in an ever less designed world....

  2. Shift Work and Endocrine Disorders

    Directory of Open Access Journals (Sweden)

    M. A. Ulhôa

    2015-01-01

    Full Text Available The objective of this review was to investigate the impact of shift and night work on metabolic processes and the role of alterations in the sleep-wake cycle and feeding times and environmental changes in the occurrence of metabolic disorders. The literature review was performed by searching three electronic databases for relevant studies published in the last 10 years. The methodological quality of each study was assessed, and best-evidence synthesis was applied to draw conclusions. The literature has shown changes in concentrations of melatonin, cortisol, ghrelin, and leptin among shift workers. Melatonin has been implicated for its role in the synthesis and action of insulin. The action of this hormone also regulates the expression of transporter glucose type 4 or triggers phosphorylation of the insulin receptor. Therefore, a reduction in melatonin can be associated with an increase in insulin resistance and a propensity for the development of diabetes. Moreover, shift work can negatively affect sleep and contribute to sedentarism, unhealthy eating habits, and stress. Recent studies on metabolic processes have increasingly revealed their complexity. Physiological changes induced in workers who invert their activity-rest cycle to fulfill work hours include disruptions in metabolic processes.

  3. New bis-, tris- and tetrakis(pyrazolyl)borate ligands with 3-pyridyl and 4-pyridyl substituents: synthesis and coordination chemistry.

    Science.gov (United States)

    Adams, Harry; Batten, Stuart R; Davies, Graham M; Duriska, Martin B; Jeffery, John C; Jensen, Paul; Lu, Jinzhen; Motson, Graham R; Coles, Simon J; Hursthouse, Michael B; Ward, Michael D

    2005-06-07

    The new ligands dihydrobis[3-(4-pyridyl)pyrazol-1-yl]borate [Bp(4py)]-, hydrotris[3-(4-pyridyl)pyrazol-1-yl]borate [Tp(4py)]-, tetrakis[3-(4-pyridyl)pyrazol-1-yl]borate [Tkp(4py)]-, dihydrobis[3-(3-pyridyl)pyrazol-1-yl]borate [Bp(3py)]-, hydrotris[3-(3-pyridyl)pyrazol-1-yl]borate [Tp(3py)]- and tetrakis[3-(3-pyridyl)pyrazol-1-yl]borate [Tkp(4py)]- are derivatives of the well known bis-, tris- and tetrakis-(pyrazolyl)borate cores, bearing 4-pyridyl or 3-pyridyl substituents attached to the pyrazolyl C3 positions. These pyridyl groups cannot chelate to the metal ions in the poly(pyrazolyl) cavity but are externally directed. Structural studies on a range of metal complexes show how, in many cases, coordination of these pendant pyridyl groups to the M(pyrazolyl)n core of an adjacent metal complex fragment results in formation of coordination oligomers or polymeric networks. [Tl(Bp(3py))], [Tl(Bp(4py))] and [Tl(Tp(4py))] form one-dimensional polymeric chains via coordination of one of their pendant pyridyl units to the Tl(I) centre of an adjacent complex fragment; in contrast, in [Tl(Tp(3py))] coordination of all three pendant pyridyl units to separate Tl(I) neighbours results in formation of a two-dimensional polymeric sheet. In [Tl(Tkp(3py))] and [Tl(Tkp(4py))] the Tl(I) is coordinated by two or three of the four pyrazolyl arms, respectively; bridging interactions of pendant 4-pyridyl groups with adjacent Tl(I) centres result in a two-dimensional sheet forming in each case. In Ag(Tkp(4py)) each Ag(I) ion is coordinated by two pyrazolyl rings, and two bridging pyridyl ligands from other complex units, resulting in a one-dimensional chain consisting of pairs of cross-linked zigzag chains. In contrast to these polymeric coordination networks, the structures of [Cu(Tp(4py))] and [(Tp(3py))Cd(CH3CO2)] are dimers, with a pendant pyridyl residue from the first metal centre attaching to a vacant coordination site on the second, and vice versa; these dimers are stabilised by

  4. Redox regime shifts in microbially mediated biogeochemical cycles

    Directory of Open Access Journals (Sweden)

    T. Bush

    2015-06-01

    Full Text Available Understanding how the Earth's biogeochemical cycles respond to environmental change is a prerequisite for the prediction and mitigation of the effects of anthropogenic perturbations. Microbial populations mediate key steps in these cycles, yet they are often crudely represented in biogeochemical models. Here, we show that microbial population dynamics can qualitatively affect the response of biogeochemical cycles to environmental change. Using simple and generic mathematical models, we find that nutrient limitations on microbial population growth can lead to regime shifts, in which the redox state of a biogeochemical cycle changes dramatically as the availability of a redox-controlling species, such as oxygen or acetate, crosses a threshold (a "tipping point". These redox regime shifts occur in parameter ranges that are relevant to the present-day sulfur cycle in the natural environment and the present-day nitrogen cycle in eutrophic terrestrial environments. These shifts may also have relevance to iron cycling in the iron-containing Proterozoic and Archean oceans. We show that redox regime shifts also occur in models with physically realistic modifications, such as additional terms, chemical states, or microbial populations. Our work reveals a possible new mechanism by which regime shifts can occur in nutrient-cycling ecosystems and biogeochemical cycles, and highlights the importance of considering microbial population dynamics in models of biogeochemical cycles.

  5. Chemical use

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This is a summary of research and activities related to chemical use on Neal Smith National Wildlife Refuge between 1992 and 2009. The chemicals used on the Refuge...

  6. N,N'-Bis(2-cyclohexylethyl)naphtho[2,3-b:6,7-b']dithiophene Diimides: Effects of Substituents.

    Science.gov (United States)

    Nakano, Masahiro; Hashizume, Daisuke; Takimiya, Kazuo

    2016-07-28

    Naphtho[2,3-b:6,7-b']dithiophene-4,5,9,10-tetracarboxylic diimide (NDTI) is a promising electron-deficient building block for n-type organic conductors, and the performance of NDTI-based field-effect transistors (FETs) is largely dependent on the substituents that alter the supramolecular organization in the solid state and, in turn, the intermolecular orbital overlap. For this reason, the rational selection of substituent on imide nitrogen atoms and/or thiophene α-positions is the key to developing superior n-type organic semiconductors. We here report new NDTI derivatives having N-(2-cyclohexylethyl) groups. Despite their one-dimensional packing structures in the solid state regardless of the presence or absence of chlorine groups at the thiophene α-positions, their FETs show promising performance with electron mobilities higher than 0.1 cm²·V(-1)·s(-1) under ambient conditions. We also discuss how the cyclohexylethyl groups affect the packing structure in comparison with analogous n-octyl derivatives having the same number of carbon atoms.

  7. Synthesis and catalytic properties of a series of cobalt porphyrins as cytochrome P450 model: the effect of substituents on the catalytic activity.

    Science.gov (United States)

    Hu, Bingcheng; Sun, Chengguo; Deng, Quanzhi; Liu, Zuliang

    2013-08-01

    A series of cobalt porphyrins derived from hemin was prepared as cytochrome P450 models. Effects of substituents at the cobalt deuteroporphyrin-propionate side chains are investigated in oxidation of toluene with air to benzaldehyde and benzyl alcohol without the use of solvent and sacrificial co-reductant. The catalytic activity of cobalt porphyrins depends on the type of substituents. When the electron-withdrawing groups like -Cl, -Br, were introduced into the double propionate side chains, they can increase the catalyst stability and selectivity to benzaldehyde. In comparison with these electron-withdrawing groups, the electron-donor groups, such as -CH 3 , -S-S- and -NH 2 groups, can improve their catalytic activities. Moreover, the electron-donor group containing an unpaired electron (such as -S-S-, -NH 2 ) is benefit for improving its catalytic efficiency and promoting the electron delivery. It can be concluded that the double propionate side chains in the deuteroporphyrin complex may participate in oxidation process and effect electron transfer from the high-valent metalloporphyrin species to the substrate.

  8. Geometric phase shifting digital holography.

    Science.gov (United States)

    Jackin, Boaz Jessie; Narayanamurthy, C S; Yatagai, Toyohiko

    2016-06-01

    A new phase shifting digital holographic technique using a purely geometric phase in Michelson interferometric geometry is proposed. The geometric phase in the system does not depend upon either optical path length or wavelength, unlike dynamic phase. The amount of geometric phase generated is controllable through a rotating wave plate. The new approach has unique features and major advantages in holographic measurement of transparent and reflecting three-dimensional (3D) objects. Experimental results on surface shape measurement and imaging of 3D objects are presented using the proposed method.

  9. Enhancing Thai Students' Learning of Chemical Kinetics

    Science.gov (United States)

    Chairam, Sanoe; Somsook, Ekasith; Coll, Richard K.

    2009-01-01

    Chemical kinetics is an extremely important concept for introductory chemistry courses. The literature suggests that instruction in chemical kinetics is often teacher-dominated at both the secondary school and tertiary levels, and this is the case in Thailand--the educational context for this inquiry. The work reported here seeks to shift students…

  10. Importance of asparagine on the conformational stability and chemical reactivity of selected anti-inflammatory peptides

    Energy Technology Data Exchange (ETDEWEB)

    Soriano-Correa, Catalina, E-mail: csorico@comunidad.unam.mx [Química Computacional, Facultad de Estudios Superiores (FES)-Zaragoza, Universidad Nacional Autónoma de México (UNAM), Iztapalapa, C.P. 09230 México, D.F. (Mexico); Barrientos-Salcedo, Carolina [Laboratorio de Química Médica y Quimiogenómica, Facultad de Bioanálisis Campus Veracruz-Boca del Río, Universidad Veracruzana, C.P. 91700 Veracruz (Mexico); Campos-Fernández, Linda; Alvarado-Salazar, Andres [Química Computacional, Facultad de Estudios Superiores (FES)-Zaragoza, Universidad Nacional Autónoma de México (UNAM), Iztapalapa, C.P. 09230 México, D.F. (Mexico); Esquivel, Rodolfo O. [Departamento de Química, Universidad Autónoma Metropolitana-Iztapalapa (UAM-Iztapalapa), C.P. 09340 México, D.F. (Mexico)

    2015-08-18

    Highlights: • Asparagine plays an important role to anti-inflammatory effect of peptides. • The electron-donor substituent groups favor the formation of the hydrogen bonds, which contribute in the structural stability of peptides. • Chemical reactivity and the physicochemical features are crucial in the biological functions of peptides. - Abstract: Inflammatory response events are initiated by a complex series of molecular reactions that generate chemical intermediaries. The structure and properties of peptides and proteins are determined by the charge distribution of their side chains, which play an essential role in its electronic structure and physicochemical properties, hence on its biological functionality. The aim of this study was to analyze the effect of changing one central amino acid, such as substituting asparagine for aspartic acid, from Cys–Asn–Ser in aqueous solution, by assessing the conformational stability, physicochemical properties, chemical reactivity and their relationship with anti-inflammatory activity; employing quantum-chemical descriptors at the M06-2X/6-311+G(d,p) level. Our results suggest that asparagine plays a more critical role than aspartic acid in the structural stability, physicochemical features, and chemical reactivity of these tripeptides. Substituent groups in the side chain cause significant changes on the conformational stability and chemical reactivity, and consequently on their anti-inflammatory activity.

  11. [3,3]-Sigmatropic shifts and retro-ene rearrangements in cyanates, isocyanates, thiocyanates, and isothiocyanates of the form RX-YCN and RX-NCY.

    Science.gov (United States)

    Koch, Rainer; Finnerty, Justin J; Murali, Sukumaran; Wentrup, Curt

    2012-02-17

    Retro-ene type [2π + 2π + 2σ] and [3,3]-sigmatropic shift reactions involving the substituent groups R in heteroatom-substituted cyanates and thiocyanates RX-YCN and the isomeric isocyanates and isothiocyanates of the type RX-NCY (X = CR(2), NR', O, or S; Y = O or S) have been investigated computationally at the B3LYP/6-311++G(d,p) level. Retro-ene reactions of alkyl derivatives of the title compounds afford alkenes, imines, carbonyl and thiocarbonyl compounds together with HNCO (HNCS) or HOCN (HSCN). [3,3]-Sigmatropic shifts (hetero-Cope rearrangements) of the corresponding allyl, propargyl, benzyl, and aryl derivatives causes allylic rearrangements, propargyl-allenyl rearrangement, conversion of benzyl cyanates to o-isocyanatotoluenes, and conversion of N-cyanatoarylamines to o-isocyanatoanilines, etc. The corresponding rearrangements of allyl thiocyanates, arylamino thiocyanates and isothiocyanates, and arylsulfenyl thiocyanates and isothiocyanates are also described.

  12. Paradigm shifts in corneal transplantation.

    Science.gov (United States)

    Tan, Donald T H; Anshu, Arundhati; Mehta, Jodhbir S

    2009-04-01

    Conventional corneal transplantation, in the form of penetrating keratoplasty (PK), involves full-thickness replacement of the cornea, and is a highly successful procedure. However, the cornea is anatomically a multi-layered structure. Pathology may only affect individual layers of the cornea, hence selective lamellar surgical replacement of only the diseased corneal layers whilst retaining unaffected layers represents a new paradigm shift in the field. Recent advancements in surgical techniques and instrumentation have resulted in several forms of manual, microkeratome and femto-second laser-assisted lamellar transplantation procedures. Anterior lamellar keratoplasty (ALK) aims at replacing only diseased or scarred corneal stroma, whilst retaining the unaffected corneal endothelial layer, thus obviating the risk of endothelial allograft rejection. Posterior lamellar keratoplasty/endothelial keratoplasty (PLK/EK) involves the replacement of the dysfunctional endothelial cell layer only. Whilst significant technical and surgical challenges are involved in performing lamellar micro-dissection of a tissue which is only 0.5 mm thick, the benefits of a more controlled surgical procedure and improved graft survival rates have resulted in a shift away from conventional PK. This review details the current advances in emerging lamellar corneal surgical procedures and highlights the main advantages and disadvantages of these new lamellar corneal procedures.

  13. Cortisol shifts financial risk preferences

    Science.gov (United States)

    Kandasamy, Narayanan; Hardy, Ben; Page, Lionel; Schaffner, Markus; Graggaber, Johann; Powlson, Andrew S.; Fletcher, Paul C.; Gurnell, Mark; Coates, John

    2014-01-01

    Risk taking is central to human activity. Consequently, it lies at the focal point of behavioral sciences such as neuroscience, economics, and finance. Many influential models from these sciences assume that financial risk preferences form a stable trait. Is this assumption justified and, if not, what causes the appetite for risk to fluctuate? We have previously found that traders experience a sustained increase in the stress hormone cortisol when the amount of uncertainty, in the form of market volatility, increases. Here we ask whether these elevated cortisol levels shift risk preferences. Using a double-blind, placebo-controlled, cross-over protocol we raised cortisol levels in volunteers over 8 d to the same extent previously observed in traders. We then tested for the utility and probability weighting functions underlying their risk taking and found that participants became more risk-averse. We also observed that the weighting of probabilities became more distorted among men relative to women. These results suggest that risk preferences are highly dynamic. Specifically, the stress response calibrates risk taking to our circumstances, reducing it in times of prolonged uncertainty, such as a financial crisis. Physiology-induced shifts in risk preferences may thus be an underappreciated cause of market instability. PMID:24550472

  14. Cortisol shifts financial risk preferences.

    Science.gov (United States)

    Kandasamy, Narayanan; Hardy, Ben; Page, Lionel; Schaffner, Markus; Graggaber, Johann; Powlson, Andrew S; Fletcher, Paul C; Gurnell, Mark; Coates, John

    2014-03-04

    Risk taking is central to human activity. Consequently, it lies at the focal point of behavioral sciences such as neuroscience, economics, and finance. Many influential models from these sciences assume that financial risk preferences form a stable trait. Is this assumption justified and, if not, what causes the appetite for risk to fluctuate? We have previously found that traders experience a sustained increase in the stress hormone cortisol when the amount of uncertainty, in the form of market volatility, increases. Here we ask whether these elevated cortisol levels shift risk preferences. Using a double-blind, placebo-controlled, cross-over protocol we raised cortisol levels in volunteers over 8 d to the same extent previously observed in traders. We then tested for the utility and probability weighting functions underlying their risk taking and found that participants became more risk-averse. We also observed that the weighting of probabilities became more distorted among men relative to women. These results suggest that risk preferences are highly dynamic. Specifically, the stress response calibrates risk taking to our circumstances, reducing it in times of prolonged uncertainty, such as a financial crisis. Physiology-induced shifts in risk preferences may thus be an underappreciated cause of market instability.

  15. The spectral shift function and spectral flow

    OpenAIRE

    Azamov, N. A.; Carey, A.L.; Sukochev, F. A.

    2007-01-01

    This paper extends Krein's spectral shift function theory to the setting of semifinite spectral triples. We define the spectral shift function under these hypotheses via Birman-Solomyak spectral averaging formula and show that it computes spectral flow.

  16. Determination of structural, spectral, electronic and biological properties of tosufloxacin boron complexes and investigation of substituent effect

    Science.gov (United States)

    Sayin, Koray; Karakaş, Duran

    2017-10-01

    Quantum chemical calculations are performed over some boron complexes with tosufloxacin. Boron complex with fluorine atoms are optimized at HF/6-31+G(d), B3LYP/6-31+G(d) and M062X/6-31+G(d) level and the best level is determined by comparison of experimental and calculated results. The other complexes are optimized by using the best level. Structural properties, IR and NMR spectrum are examined in detail. Biological activities of mentioned complexes are investigated by some quantum chemical descriptors and molecular docking analyses. As results, it is found that boron complex with fluorine atoms coordinated to boron atom is the best candidate for anticancer drug. Additionally, NLO properties of mentioned complexes are investigated and complex (2) is found as the best candidate for NLO applications.

  17. Individual differences in shift work tolerance

    NARCIS (Netherlands)

    Lammers-van der Holst, H.M.

    2016-01-01

    Shift work is a key feature of our contemporary 24/7 society, employing several successive work teams to sustain around-the-clock operations. However, numerous studies imply that frequently shifting the periods of sleep and wakefulness poses a serious threat to the shift worker’s physical, mental

  18. Primary selection into shift work and change of cardiovascular risk profile.

    Science.gov (United States)

    Yong, Mei; Germann, Christina; Lang, Stefan; Oberlinner, Christoph

    2015-05-01

    A potential "healthy shift worker effect" may bias the studied effect of shift work on health. The observed differences among shift and day workers in health behavior and health outcomes can be caused by: (i) primary selection, (ii) the influence from the shift work-related environment, and (iii) the impact of shift work. We aimed to study these potential sources. A cohort of 4754 male trainees who had finished their professional training and started their career in production in a chemical company between 1995 and 2012 was identified. Among them, 1348 (28%) were involved in rotating shift work and 3406 (72%) in day work. Information on health behavior and risk factors for cardiovascular diseases was retrieved from the medical examinations. This information was then compared (i) at the beginning of training, (ii) at the end of training, and (iii) 3 years after the employment, in relation to the working time. At the beginning of the training, the prevalence of smokers was higher among future shift workers (26% versus 21%), from 1995 to 2012. During the training and the first three years of employment, a marginal decline of systolic blood pressure and an elevation of triglyceride were related with shift work. No difference was found with respect to other risk factors for cardiovascular diseases. Our findings do not support a primary selection in favor of shift workers. An impact of shift work on the risk profile of cardiovascular diseases was not indicated in the observation period.

  19. Ring current shifts in {sup 19}F-NMR of membrane proteins

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Dongsheng, E-mail: liudsh@shanghaitech.edu.cn; Wüthrich, Kurt, E-mail: kwuthrich@shanghaitech.edu.cn [ShanghaiTech University, iHuman Institute (China)

    2016-05-15

    Fluorine-19 NMR markers are attractive reporter groups for use in studies of complex biomacromolecular systems, in particular also for studies of function-related conformational equilibria and rate processes in membrane proteins. Advantages of {sup 19}F-NMR probes include high sensitivity of the {sup 19}F chemical shifts to variations in the non-covalent environment. Nonetheless, in studies of G protein-coupled receptors (GPCR) we encountered situations where {sup 19}F chemical shifts were not responsive to conformational changes that had been implicated by other methods. This prompted us to examine possible effects of aromatic ring current fields on the chemical shifts of {sup 19}F-NMR probes used in GPCRs. Analysis of previously reported {sup 19}F-NMR data on the β{sub 2}-adrenergic receptor and mammalian rhodopsin showed that all {sup 19}F-labeling sites which manifested conformational changes are located near aromatic residues. Although ring current effects are small when compared to other known non-covalent effects on {sup 19}F chemical shifts, there is thus an indication that their contributions are significant when studying activation processes in GPCRs, since the observed activation-related {sup 19}F-NMR chemical shifts are comparable in size to the calculated ring current shifts. Considering the impact of ring current shifts may thus be helpful in identifying promising indigenous or engineered labeling sites for future {sup 19}F-NMR studies of GPCR activation, and novel information may be obtained on the nature of conformational rearrangements near the {sup 19}F-labels. It will then also be interesting to see if the presently indicated role of ring current shifts in membrane protein studies with {sup 19}F-NMR markers can be substantiated by a more extensive data base resulting from future studies.

  20. [Chemical weapons and chemical terrorism].

    Science.gov (United States)

    Nakamura, Katsumi

    2005-10-01

    Chemical Weapons are kind of Weapons of Mass Destruction (WMD). They were used large quantities in WWI. Historically, large quantities usage like WWI was not recorded, but small usage has appeared now and then. Chemical weapons are so called "Nuclear weapon for poor countrys" because it's very easy to produce/possession being possible. They are categorized (1) Nerve Agents, (2) Blister Agents, (3) Cyanide (blood) Agents, (4) Pulmonary Agents, (5) Incapacitating Agents (6) Tear Agents from the viewpoint of human body interaction. In 1997 the Chemical Weapons Convention has taken effect. It prohibits chemical weapons development/production, and Organization for the Prohibition of Chemical Weapons (OPCW) verification regime contributes to the chemical weapons disposal. But possibility of possession/use of weapons of mass destruction by terrorist group represented in one by Matsumoto and Tokyo Subway Sarin Attack, So new chemical terrorism countermeasures are necessary.