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P Somasundaran - One of the best experts on this subject based on the ideXlab platform.
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nmr study of micellar microstructures of cationic single chain and gemini surfactants and their mixtures with nonionic surfactant n dodecyl β d maltoside
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2008Co-Authors: Qiuqing Yang, Qiong Zhou, P SomasundaranAbstract:Abstract Microstructures of the micelles of cationic surfactants, dodecyltrimethyl ammonium chloride (DTAC), alkane-bis(dodecyl dimethyl ammonium chloride) (12-4-12 and 12-8-12 geminis) in aqueous solutions, as well as the mixed micelles of their mixtures respectively with nonionic sugar-based surfactant n-dodecyl-β- d -maltoside (DM) were studied using NMR by 1H chemical shift, self-diffusion coefficient, spin–spin and spin–lattice relaxation time, and two-dimensional nuclear Overhauser enhancement (2D NOESY). In individual aqueous solution, 12-8-12 gemini molecules seem to be tighter packed in the micelles than 12-4-12 gemini, and DTAC molecules are looser packed than both gemini surfactants in the micelles. Calculated hydration dynamics radii indicate that DTAC is the largest in size, while 12-8-12 gemini is the smallest. It is suggested that in the mixed micelles of DM and cationic surfactant, all three cationic surfactants studied give similar relative molecular arrangement to DM, with the methylene group next to the ammonium head in the near vicinity of penultimate sugar ring. The short intermolecular distance between the two headgroups of surfactants in their mixed micelles, evidenced by the existence of intermolecular cross-peaks in 2D NOESY Spectrum, implies attractive interactions between DM and these cationic surfactants. The interactions between DM and 12-4-12, and 12-8-12 geminis are stronger than that of DM and DTAC, and increase in spacer length of cationic gemini from 12-4-12 to 12-8-12 results in increased interactions with DM in their mixed micelles.
Patricia Verheyden - One of the best experts on this subject based on the ideXlab platform.
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h nmr study of the solution structure of ac amp2 a sugar binding antimicrobial protein isolated from amaranthus caudatus
Journal of Molecular Biology, 1996Co-Authors: Jose C Martins, Dominique Maes, Remy Loris, H Pepermans, Lode Wyns, Rudolph Willem, Patricia VerheydenAbstract:Abstract The conformation in water of antimicrobial protein 2 from Amaranthus caudatus (Ac-AMP2) was determined using 1 H NMR, DIANA and restrained molecular modeling. Ac-AMP2 is a 30 amino acid residue, lectin-like protein that specifically binds to chitin, a polymer of β-1,4- N -acetyl- D -glucosamine. After sequence specific resonance assignments, a total of 198 distance restraints were collected from 2D NOESY buildup spectra at 500 MHz at pH 2, supplemented by a 2D NOESY Spectrum at 600 MHz. The location of the three previously unassigned disulfide bridges was determined from preliminary DIANA structures, using a statistical analysis of intercystinyl distances. The solution structure of Ac-AMP2 is presented as a set of 26 DIANA structures, further refined by restrained molecular dynamics using a simulated annealing protocol in the AMBER force field, with a backbone r.m.s.d. for the well defined Glu3-Cys28 segment of 0.69(±0.12) A. The main structural element is an antiparallel β-sheet from Met13 to Lys23 including a β I -turn over Gln17-Phe18 with a β bulge at Gly19. In addition, a β′ I turn over Arg6-Gly7, a β′ III turn over Ser11-Gly12 and a helical turn from Gly24 to Cys28 are identified. This structure is very similar to the equivalent regions of the X-ray structure of wheat germ agglutinin and the NMR structure of hevein.
Qiuqing Yang - One of the best experts on this subject based on the ideXlab platform.
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nmr study of micellar microstructures of cationic single chain and gemini surfactants and their mixtures with nonionic surfactant n dodecyl β d maltoside
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2008Co-Authors: Qiuqing Yang, Qiong Zhou, P SomasundaranAbstract:Abstract Microstructures of the micelles of cationic surfactants, dodecyltrimethyl ammonium chloride (DTAC), alkane-bis(dodecyl dimethyl ammonium chloride) (12-4-12 and 12-8-12 geminis) in aqueous solutions, as well as the mixed micelles of their mixtures respectively with nonionic sugar-based surfactant n-dodecyl-β- d -maltoside (DM) were studied using NMR by 1H chemical shift, self-diffusion coefficient, spin–spin and spin–lattice relaxation time, and two-dimensional nuclear Overhauser enhancement (2D NOESY). In individual aqueous solution, 12-8-12 gemini molecules seem to be tighter packed in the micelles than 12-4-12 gemini, and DTAC molecules are looser packed than both gemini surfactants in the micelles. Calculated hydration dynamics radii indicate that DTAC is the largest in size, while 12-8-12 gemini is the smallest. It is suggested that in the mixed micelles of DM and cationic surfactant, all three cationic surfactants studied give similar relative molecular arrangement to DM, with the methylene group next to the ammonium head in the near vicinity of penultimate sugar ring. The short intermolecular distance between the two headgroups of surfactants in their mixed micelles, evidenced by the existence of intermolecular cross-peaks in 2D NOESY Spectrum, implies attractive interactions between DM and these cationic surfactants. The interactions between DM and 12-4-12, and 12-8-12 geminis are stronger than that of DM and DTAC, and increase in spacer length of cationic gemini from 12-4-12 to 12-8-12 results in increased interactions with DM in their mixed micelles.
Ad Bax - One of the best experts on this subject based on the ideXlab platform.
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2D and 3D NMR Study of Phenylalanine Residues in Proteins by Reverse Isotopic Labeling
Journal of the American Chemical Society, 1994Co-Authors: Geerten W. Vuister, Soon-jong Kim, Ad BaxAbstract:A protein isotopic labeling strategy is presented which offers improved NMR sensitivity and resolution relative to the commonly used uniform l3C labeling approach. Incorporation of specific residues at natural abundance into an otherwise fully W-enriched protein yields lH line widths for the unlabeled residues which are not adversely affected by 13C and makes it possible to selectively focus on interactions between the unlabeled residues and the remainder of the protein. Modifications of l3C editing and 12C filtering procedures are described which optimize their sensitivity and resolution. The experiments are used to obtain complete assignments for all 10 phenylalanine aromatic spin systems in the DNA-binding domain of Drosophila heat shock factor and to obtain a large number of structurally important long-range NOE constraints. A novel J correlation experiment is also described which makes it possible to measure HLHB J couplings in larger proteins and yields quantitative values for all 10 phenylalanines in the DNAbinding domain of Drosophila heat shock factor. In recent years, 3D and 4D NMR combined with uniform 13C and 1SN enrichment has become an established procedure for determining the solution structures of proteins with spectra too complex for conventional homonuclear 1H studies.'-3 The resonance assignment part of this approach relies largely on determination of intraresidue J connectivities via the large and well-resolved one-bond 1H-l3C, 1H-lsN, 13C-13C, and l3C-15N Jcouplings.1-5 The 1H-lH NOE interactions, which are critical for structure determination, are typically severely overlapped in the conventional 2D NOESY Spectrum but are dispersed in a 4D Spectrum according to the frequencies of the 13C or 15N attached to each of the protons. Although the approach outlined above has been applied successfully to a large range of proteins, there are inherent problems associated with the use of l3C isotopic enrichment. Most importantly, the strong one-bond 1H-13C dipolar interaction is even larger than the dipolar interaction between geminal protons, causing a dramatic decrease in the 1H Tz. Despite these short 7'2 values, the high intrinsic sensitivity of many of the 3D J correlation experiments allows their application to proteins larger than 30 kDa. However, the rapid transverse relaxation severely affects measurement of the inherently much weaker NOE interactions, particularly for Cfi methylene and other non-methylgroup side-chain protons in the rigid parts of the protein. Measurement of the structurally important Ha-H@ J couplings is also adversely affected by the increase in lH line width caused by W, and very few accurate values have been reported for larger proteins. Although the assignment problem has largely been solved by the uniform 13C labeling approach, identification of the aromatic resonances of phenylalanine residues remains notoriously difficult. 1 National Institute of Diabetes and Digestive and Kidney Diseases. t National Cancer Institute. t Present address: Bijvoet Center for Biomolecular Research, Padualaan Abstract published in Advance ACS Abstracts, September 1, 1994. (1) Clore, G. M.; Gronenborn, A. M. NMR of Proteins; MacMillan:published in Advance ACS Abstracts, September 1, 1994. (1) Clore, G. M.; Gronenborn, A. M. NMR of Proteins; MacMillan: (2) Wagner, G. J. Biomol. NMR 1993, 3, 315-385. (3) Bax, A.; Grzesiek, S. Acc. Chem. Res. 1993, 26, 131-138. (4) Palmer, A. G.; Fairbrother, W. J.; Cavanagh, J.; Wright, P. E.; Rance, (5) Olejniczak, E. T.; Xu, R. X.; Fesik, S. W. J . Biomol. NMR 1992, 2, 8, 3584CH Utrecht, The Netherlands.
Rong Zhang - One of the best experts on this subject based on the ideXlab platform.
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conformations of oxidized glutathione in aqueous urea solution by all atom molecular dynamic simulations and 2D NOESY Spectrum
Journal of Solution Chemistry, 2013Co-Authors: Rong Zhang, Guodong Huang, Wei ZengAbstract:All-atom molecular simulations and two-dimensional nuclear overhauser effect spectra have been used to study the conformations and interactions of oxidized glutathione (GSSG) in aqueous urea solution. The simulations were characterized by intramolecular distance, radius of gyration, solvent-accessible surface area, and root-mean-square deviation. Interestingly, the two chains connected by the GSSG disulfide linkage exhibited different flexibilities in the aqueous urea solution. GSSG can convert from “extended” to “folded” states in the simulations. Its preferred conformation in aqueous urea solutions is “extended”, which was confirmed by the 2D nuclear magnetic resonance (NMR) experiment. The two different types of amide hydrogen atoms in cysteine and glycine also showed different capacities to form N–H⋯O hydrogen bonds. The results were confirmed by temperature-dependent NMR experiment.
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molecular dynamics simulations and 2D NOESY Spectrum study on the different behaviors of glutathione disulfide in different solutions
Principles and Practice of Constraint Programming, 2012Co-Authors: Rong Zhang, Wei Zeng, Xin Meng, Jingman HuangAbstract:Abstract All-atom molecular dynamics simulations and 2D nuclear Overhauser effect spectroscopy (NOESY) were used to study the interactions and conformations of glutathione disulfide (GSSG) in aqueous and DMSO solutions. GSSG showed variations in conformation in the two solutions, shifting between extended and folded states. Showing preference for extension in aqueous solution and folding for a long time in DMSO are observed by the simulations. The interesting phenomena have been proved by the 2D NMR experiment. The NMR experimental results show agreement with the molecular dynamics simulations.