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Heteronuclear Single Quantum Coherence (heteronuclear + single_quantum_coherence)
Selected AbstractsTemperature-induced reversible conformational change in the first 100 residues of ,-synucleinPROTEIN SCIENCE, Issue 3 2006Brian C. McNulty Abstract Natively disordered proteins are a growing class of anomalies to the structure,function paradigm. The natively disordered protein ,-synuclein is the primary component of Lewy bodies, the cellular hallmark of Parkinson's disease. We noticed a dramatic difference in dilute solution 1H- 15N Heteronuclear Single Quantum Coherence (HSQC) spectra of wild-type ,-synuclein and two disease-related mutants (A30P and A53T), with spectra collected at 35°C showing fewer cross-peaks than spectra acquired at 10°C. Here, we show the change to be the result of a reversible conformational exchange linked to an increase in hydrodynamic radius and secondary structure as the temperature is raised. Combined with analytical ultracentrifugation data showing ,-synuclein to be monomeric at both temperatures, we conclude that the poor quality of the 1H- 15N HSQC spectra obtained at 35°C is due to conformational fluctuations that occur on the proton chemical shift time scale. Using a truncated variant of ,-synuclein, we show the conformational exchange occurs in the first 100 amino acids of the protein. Our data illustrate a key difference between globular and natively disordered proteins. The properties of globular proteins change little with solution conditions until they denature cooperatively, but the properties of natively disordered proteins can vary dramatically with solution conditions. [source] HSQC pulse sequences for 19FMAGNETIC RESONANCE IN CHEMISTRY, Issue 4 2008Bruce Adams Abstract Heteronuclear single quantum coherence (HSQC) sequences using adiabatic (or composite) 180° pulses, suitable for applications requiring wide spectral widths in F2, are described. The sequences can be used with or without multiplicity editing. One variant will work even in the presence of homonuclear couplings that are equal to the heteronuclear 1-bond coupling. Copyright © 2008 John Wiley & Sons, Ltd. [source] Microstructure of glycidylmethacrylate/vinyl acetate copolymers by two-dimensional nuclear magnetic resonance spectroscopyJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 23 2001A. S. Brar Abstract Glycidylmethacrylate/vinyl acetate copolymers were prepared by solution polymerization with benzene as a solvent and benzoyl peroxide as an initiator. Copolymer compositions were determined from 1H NMR spectra, and comonomer reactivity ratios were determined by the Kelen,Tudos (KT) method and the nonlinear least-squares error-in-variable method (EVM). The reactivity ratios obtained from KT and EVM were rG = 37.4 ± 12.0 and rV = 0.036 ± 0.019 and rG = 35.2 and rV = 0.03, respectively. Complete spectral assignments of 13C and 1H NMR spectra were done with the help of distortionless enhancement by polarization transfer and two-dimensional 13C,1H heteronuclear single quantum coherence and total correlation spectroscopy. The methyl, methine, and methylene carbon resonance showed both stereochemical and compositional sensitivity. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 4051,4060, 2001 [source] Identification of oleuropein oligomers in olive pulp and pomaceJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 10 2006Susana M Cardoso Abstract Analysis of a purified fraction from acetone extracts of olive pulp and pomace by electrospray ionisation tandem mass spectrometry (ESI-MSn) showed the presence of oleuropein oligomers, whose occurrence has not been reported previously in the literature. The main ionic species (m/z 1613) in the ESI-MS spectrum was an oleuropein trimer containing three linkages through the hydroxytyrosol backbone. In both samples, oleuropein dimers (m/z 1075), trimers comprising two hydroxytyrosol linkages (m/z 1615), tetramers (m/z 2153) and pentamers (m/z 2691) were also detected by MS. The occurrence of oleuropein oligomers was also observed by nuclear magnetic resonance (NMR). 13C, 13C distortionless enhancement by polarisation transfer DEPT 90, 13C DEPT 135, gHSQC (heteronuclear single quantum coherence) and gHMBC (heteronuclear multiple bond coherence) spectra showed all carbon and proton resonances of oleuropein with the exception of the low-mobility and asymmetric signals of the aromatic rings. Since mature olives were used in this study, it is possible that the disappearance of oleuropein that has been described to occur with the olive fruit maturation, could be associated with the formation of phenolic oligomers together with lower-molecular-weight compounds resulting from its degradation. Copyright © 2006 Society of Chemical Industry [source] Synthesis of rhodium(III) complexes with tris/tetrakis-benzimidazoles and benzothiazoles,quick identification of cyclometallation by nuclear magnetic resonance spectroscopyMAGNETIC RESONANCE IN CHEMISTRY, Issue 8 2009N. Chandrashekhar Abstract Reactions of rhodium(III) halides with multidentate N,S -heterocycles, (LH3) 1,3,5-tris(benzimidazolyl)benzene (L1H3; 1), 1,3,5-tris(N -methylbenzimidazolyl) benzene (L2H3; 2) and 1,3,5-tris(benzothiazolyl)benzene (L3H3; 3), in the molar ratio 1:1 in methanol,chloroform produced mononuclear cyclometallated products of the composition [RhX2(LH2)(H2O)] (X = Cl, Br, I; LH2 = L1H2, L2H2, L3H2). When the metal to ligand (1,3 or 1,2,4,5-tetrakis(benzothiazolyl)benzene [L4H2; 4]) molar ratio was 2:1, the reactions yielded binuclear complexes of the compositions [Rh2Cl5(LH2)(H2O)3] (LH2 = L1H2, L2H2, L3H2) and [Rh2X4(L4)(H2O)2] (X = Cl, Br, I). Elemental analysis, IR and 1H nuclear magnetic resonance (NMR) chemical shifts supported the binuclear nature of the complexes. Cyclometallation was detected by conventional 13C NMR spectra that showed a doublet around ,190 ppm. Cyclometallation was also detected by gradient-enhanced heteronuclear multiple bond correlation (g-HMBC) experiment that showed cross-peaks between the cyclometallated carbon and the central benzene ring protons of 1,3. Cyclometallation was substantiated by two-dimensional 1H1H correlated experiments (gradiant-correlation spectroscopy and rotating frame Overhauser effect spectroscopy) and 1H13C single bond correlated two-dimensional NMR experiments (gradient-enhanced heteronuclear single quantum coherence). The 1H15N g-HMBC experiment suggested the coordination of the heterocycles to the metal ion via tertiary nitrogen. Copyright © 2009 John Wiley & Sons, Ltd. [source] Complete assignments of 1H and 13C NMR spectral data for three new triterpenoid saponins from Ilex hainanensis Merr.MAGNETIC RESONANCE IN CHEMISTRY, Issue 2 2009Xiao-Qing Chen Abstract Three new oleanane-type triterpenoid saponins, ilexhainanoside C, D and E, all with 24, 28-dioic acid groups, were isolated from the leaves of Ilex hainanensis. They were 3,-hydroxyolean-12-ene-24, 28-dioic acid-28- O -,- D -glucopyranoside(1), 3,, 19,-dihydroxyolean-12-ene-24, 28-dioic acid-28- O -,- D -glucopyranoside(2) and 3,, 29-dihydroxyolean-12-ene-24, 28-dioic acid-28- O -,- D -glucopyranoside(3). The structures of these three new compounds were elucidated and complete assignments of the 1H and 13C NMR spectroscopic data were achieved by 1D and 2D NMR experiments [heteronuclear single quantum coherence (HSQC), HMBC and rotational nuclear Overhauser effect spectroscopy (ROESY)]. Copyright © 2008 John Wiley & Sons, Ltd. [source] Characterization of nonderivatized plant cell walls using high-resolution solution-state NMR spectroscopy,MAGNETIC RESONANCE IN CHEMISTRY, Issue 6 2008Daniel J. Yelle Abstract A recently described plant cell wall dissolution system has been modified to use perdeuterated solvents to allow direct in-NMR-tube dissolution and high-resolution solution-state NMR of the whole cell wall without derivatization. Finely ground cell wall material dissolves in a solvent system containing dimethylsulfoxide- d6 and 1-methylimidazole- d6 in a ratio of 4:1 (v/v), keeping wood component structures mainly intact in their near-native state. Two-dimensional NMR experiments, using gradient-HSQC (heteronuclear single quantum coherence) 1-bond 13C1H correlation spectroscopy, on nonderivatized cell wall material from a representative gymnosperm pinus taeda (loblolly pine), an angiosperm Populus tremuloides (quaking aspen), and a herbaceous plant Hibiscus cannabinus (kenaf) demonstrate the efficacy of the system. We describe a method to synthesize 1-methylimidazole- d6 with a high degree of perdeuteration, thus allowing cell wall dissolution and NMR characterization of nonderivatized plant cell wall structures. Copyright © 2008 John Wiley & Sons, Ltd. [source] Assignments of 1H and 13C NMR spectral data for ondansetron and its two novel metabolites, 1-hydroxy-ondansetron diastereoisomersMAGNETIC RESONANCE IN CHEMISTRY, Issue 10 2006Mingyu Duan Abstract Assignments of 1H and 13C NMR chemical shifts were made by means of heteronuclear single quantum coherence (HSQC) and heteronuclear multiple bond correlation (HMBC) experiments for ondansetron, and by means of 1H- 1H correlation spectroscopy (1H- 1H COSY) and two-dimensional nuclear Overhauser effect spectroscopy (NOESY) experiments for two novel metabolites (M1 and M2) of ondansetron. These two metabolites were isolated for the first time from Mucor circinelloides. Copyright © 2006 John Wiley & Sons, Ltd. [source] All three Ca2+ -binding loops of photoproteins bind calcium ions: The crystal structures of calcium-loaded apo-aequorin and apo-obelinPROTEIN SCIENCE, Issue 3 2005Lu Deng HLH, helix,loop,helix; HSQC, heteronuclear single quantum coherence; RMSD, root mean square deviation; SAD, single wavelength anomalous dispersion Abstract The crystal structures of calcium-loaded apoaequorin and apo-obelin have been determined at resolutions 1.7 Å and 2.2 Å, respectively. A calcium ion is observed in each of the three EF-hand loops that have the canonical calcium-binding sequence, and each is coordinated in the characteristic pentagonal bipyramidal configuration. The calcium-loaded apo-proteins retain the same compact scaffold and overall fold as the unreacted photoproteins containing the bound substrate, 2-hydroperoxycoelenterazine, and also the same as the Ca2+ -discharged obelin bound with the product, coelenteramide. Nevertheless, there are easily discerned shifts in both helix and loop regions, and the shifts are not the same between the two proteins. It is suggested that these subtle shifts are the basis of the ability of these photoproteins to sense Ca2+ concentration transients and to produce their bioluminescence response on the millisecond timescale. A mechanism of intrastructural transmission of the calcium signal is proposed. [source] | ||||||||||