Showing papers on "Solid-state nuclear magnetic resonance published in 1980"
TL;DR: Regularities related to the type, anomeric configuration, site of glycosidic linkage, and sequence of the component sugars glucose, galactose, glucosamine, and galactosamine are suited for elucidation of hitherto unknown structure of more complex glycosphingolipids.
Abstract: The carbohydrate composition of eight glycosphingolipids--glucosylceramide, lactosylceramide, lacto-N-triaosylceramide, neolactotetraosylceramide, IV3Gal alpha neolactotetraosylceramide, globotriaosylceramide, globoside (P-antigen), and Forssman glycolipid (IV3GalNAc alpha GbOse4Cer)--derived from different sources was analyzed by 1H nuclear magnetic resonance at 360 MHz in dimethyl-d6 sulfoxide as solvent. The resonances of all H-1 and H-2 protons as well as those of most of the H-3 and H-4, and of some H-5 protons, of the sugar rings were assigned with the aid of spin decoupling difference spectroscopy. They show regularities related to the type, anomeric configuration, site of glycosidic linkage, and sequence of the component sugars glucose, galactose, glucosamine, and galactosamine. These regularities are thus suited for elucidation of hitherto unknown structure of more complex glycosphingolipids.
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TL;DR: Theoretical considerations indicate that the 31P chemical shift data for the B-form DNA fibers are consistent with the atomic coordinates of the phosphodiester group proposed by Langridge et al. but not with the corresponding coordinates proposed by Arnott and Hukins; the latter result suggests that DNA has significant variations in its backbone conformation along the molecule.
Abstract: 31P nuclear magnetic resonance of highly oriented DNA fibers has been observed for three different conformations, namely, the A, B, and C forms of DNA. At a parallel orientation of the fiber axis with respect to the magnetic field, DNA fibers in both the A and B forms exhibit a single, abnormally broad resonance; in contrast, fibers in the C form show almost the full span of the chemical shift anisotropy (170 ppm). The spectra of the fibers oriented perpendicular indicate that the DNA molecules undergo a considerable rotational motion about the helical axis, with a rate of greater than 2 x 10(3) s-1 for the B-form DNA. Theoretical considerations indicate that the 31P chemical shift data for the B-form DNA fibers are consistent with the atomic coordinates of the phosphodiester group proposed by Langridge et al. [Langridge, R., Wilson, H. R. Hooper, C. W., Wilkins, M. H. F., & Hamilton, L. D. (1960) J. Mol. Biol. 2, 19--37] but not with the corresponding coordinates proposed by Arnott and Hukins [Arnott, S., & Hukins, D. W. L. (1972) Biochem. Biophys. Res. Coomun. 47, 1504--1509], and also lead to the conclusion that the phosphodiester orientation must vary significantly along the DNA molecule. The latter result suggests that DNA has significant variations in its backbone conformation along the molecule.
63 citations
TL;DR: In this article, the longitudinal spin relaxation time T1ρ of protons (1H) in the rotating frame was measured for a spin locking field ranging from 5 to 20 G.
Abstract: Molecular motions and spatial properties of the solid polymer polyethyleneterephthalate have been investigated using high resolution 1H solid state NMR techniques. The longitudinal spin relaxation time T1ρ of protons (1H) in the rotating frame was measured for a spin locking field ranging from 5 to 20 G. The decay of the 1H magnetization indicated the existence of two distinct T1ρ’s and their field dependence shows that they are associated with two mobile phases of the polymer. The 1H magnetization also relaxes under the dipolar narrowed Carr–Purcell (DNCP) multipulse sequence with two dintinct T1y relaxation times. The ratios T1y’s and T1ρ’s deviate significantly from the expected theoretical values. The combined experiment with magic angle spinning and the DNCP sequence followed by homonuclear dipolar decoupling reveals the individual T1y relaxation of the resolved methylene and aromatic protons. These two species of protons were found to relax with the same T1y’s, thus implying that spin diffusion must have taken place under the homonuclear dipolar decoupling multipulse. The qualitative description of spin diffusion under homonuclear decoupling is given. The combined experiment with spin locking and the DNCP sequence yields the correspondence between the two T1ρ’s and the two T1y’s. The long T1ρ corresponds to the short T1y whereas the short T1ρ corresponds to the long T1y. Communication between the two spatial phases via spin diffusion was also observed in this experiment by monitoring the recovery of the 1H magnitization associated with the short T1ρ after it has been eliminated during the spin locking. The total 1H magnetization is allowed to equilibrate in the laboratory frame for a variable time much shorter than T1 after the spin locking field has been turned off. The spatial relationship between the two phases is discussed.
59 citations
TL;DR: It was found that the conformations of the sugar-phosphate backbones of each isomer are similar to each other and areSimilar to the conformation of the parent dinucleoside monophosphates.
Abstract: A series of dideoxyribonucleoside methylphosphonates, d-ApA, d-ApT, d-TpA, and TpT, were synthesized chemically and the diastereoisomers of each dimer were separated [Miller, P. S., Yano, J., Yano, E., Carroll, C., Jayaraman, K., & Ts'o, P. O. P. (1979) Biochemistry 18, 5134]. The 1H NMR spectra of these compounds are similar to those of their parent diester compounds. Specifically, the assignments of the 1H resonances of the two diastereoisomers of d-ApA (designated as 1 and 2) were reaffirmed by comparing with the unmodified, parent d-ApA. The absolute configuration of the phosphonate methyl group of the two isomers (d-ApA)1 and (d-ApA)2 was determined by the NOE technique. The 1H NMR spectra of the diastereoisomers of d-ApA, as well as the corresponding monomer components dAp and CH3pdA, and TpT were analyzed by spectrum simulation techniques. Thus, all the coupling constants and chemical shifts of the proton resonances of the deoxyribofuranose ring and the phosphonate methyl group could be precisely determined. These data provide the information for an analysis of the sugar puckering and backbone conformations of these novel nonionic nucleic acid analogues. It was found that the conformations of the sugar-phosphate backbones of each isomer are similar to each other and are similar to the conformations of the parent dinucleoside monophosphates. The average adenine stacking conformations of (d-ApA)1 and (d-ApA)2 were described in numerical coordinates derived from a computer analysis which included both ring-current magnetic anisotropy and atomic diamagnetic anisotropy effects. The two computer-derived conformational models are similar to those derived from the graphic approximation based only on the ring-current effects. For each pair of dimer analogues, the base stacking mode of isomer 1 is similar to that of its parent diester while the extent of base overlap in isomer 2 is less than that in isomer 1. The results of the conformational analysis based on NMR data are consistent with the results obtained from ultraviolet and circular dichroism measurements on these dimers.
52 citations
51 citations
TL;DR: In this article, the combination of double-quantum NMR with magic angle spinning is demonstrated for deuterium in solids under magic angle spinner angle adjustment and stability.
44 citations
TL;DR: In this paper, the authors investigated the role of dipolar interactions modulated by motion on the line shape of the proton NMR at room temperature in the hydrogen bronze H1.64MoO3.
Abstract: Solid state nuclear magnetic resonance (NMR) has been used to probe the nature of hydrogen in the hydrogen bronze H1.64MoO3. The line shape of the proton NMR at room temperature is found to be associated only with shielding anisotropy. Below 230 K, dipolar interactions become important in broadening the line. The response of the protons under a magic angle spinning experiment indicates that there is predominantly only one type of hydrogen in this sample. The shielding anisotropy indicates that at room temperature this species is not a hydroxyl proton. The longitudinal relaxation time of protons in this material exhibits a minimum between 190–320 K indicating that dipolar interactions modulated by motion are responsible for T1 relaxation. Comparison of longitudinal relaxation times of partially deuterated and nondeuterated samples indicates that there exists a contribution to T1 relaxation not dependent upon interproton distance. There does not appear to be a conduction electron contribution to the proton T1.
38 citations
TL;DR: In this paper, a combination of 113Cd1H cross polarization and magic-angle spinning (≈2.4 kHz) is used to obtain high-resolution solid-state NMR spectra.
TL;DR: Observations provide specific boundary conditions for the construction of molecular models of the conformation(s) of TP5 in aqueous solution by analysis of chemical shift variations with pH, vicinal NH-C alpha H coupling constant data, and amide hydrogen exchange rates.
Abstract: The aqueous solution conformation of Arg-Lys-Asp-Val-Tyr (TP5), corresponding to positions 32-36 of the thymic hormone thymopoietin has been investigated by proton nuclear magnetic resonance (NMR). This pentapeptide fragment retains the biological activity of the parent protein, viz., induction of selective differentiation of T lymphocytes. All the observed NH and CH resonances of TP5 have been assigned, and the solution conformation of this peptide has been investigated by analysis of chemical shift variations with pH, vicinal NH-C alpha H coupling constant data, and amide hydrogen exchange rates. The latter were measured in H2O by using a combination technique consisting of the transfer of solvent saturation and saturation recovery NMR experiments. The data are compatible with the assumption of a highly motile dynamic equilibrium among different conformations for TP5. A comparison of the amide hydrogen exchange rates of the pentapeptide with that of solvated model compounds shows that Val4-NH is significantly shielded from the solvent. In addition, the chemical shift variations with pH suggest that the guanidino-N epsilon H of arginine is associated with one of the carboxylate groups. These observations provide specific boundary conditions for the construction of molecular models of the conformation(s) of TP5 in aqueous solution.
TL;DR: In this paper, the authors measured the line width of the proton resonance as a function of temperature and pressure for four homologues of the alkyl cyanobiphenyl series (5, 6, 7 and 8 CB).
Abstract: 2014 The line width (0394H) of the proton resonance has been measured as a function of temperature and pressure for four homologues of the alkyl cyanobiphenyl series (5, 6, 7 and 8 CB) and also for methoxy-cyanobiphenyl, p-azoxyanisole (PAA) and quinquephenyl. Values of the nematic order parameter (S2 = P2(cos 03B8)>) may be obtained from the results by dividing them by a scaling factor (0394H/S2), which can in some cases be deduced theoretically and in other cases obtained by reference to magnetic susceptibility measurements at atmospheric pressure. Slight changes which we have observed in the shape of the resonance line as opposed to its width suggest that the mean conformation of the molecule is liable to vary with temperature and pressure in cases where it has a flexible end chain, though not otherwise. In principle the scaling factor (0394H/S2) may also vary with temperature and pressure in such cases, but the variation appears to be rather slight in practice. Our results for 5 CB and PAA are in general agreement with those reported by Horn and Faber and McColl respectively, who also used elevated pressures. The magnitude of S2 at the nematic-isotropic transition (S2c) decreases on compression for 5 CB, 7 CB and 8 CB, but for 6 CB and the other substances we have investigated it appears to remain constant. J. Physique 41 (1980) 1165-1172 OCTOBRE 1980,
TL;DR: The nature of hydrogen in H1.7MoO3 has been investigated with solid state nuclear magnetic resonance (NMR) with and without strong proton decoupling and magic angle spinning as discussed by the authors.
Abstract: The nature of hydrogen in H1.7MoO3 has been investigated with solid state nuclear magnetic resonance. Samples prepared utilizing wet chemical reduction of MoO3 in zinc and HCl, and dry hydrogen spillover on platinized MoO3 have been characterized by proton NMR with and without strong proton decoupling and magic angle spinning. The results of these experiments indicate that there are at least two types of protons in these ’’hydrogen molybdenum bronzes’’ with the relative amounts depending upon the method of preparation. The major protonic species in both samples exhibit a shielding anisotropy which negates its identification as a hydroxyl proton in a hydrogen bond or as a proton belonging to H2O undergoing rapid rotation at room temperature. The NMR spectra of protons in samples prepared by different methods are, in addition, distinctly different at 90 K. Photoelectron spectroscopy indicates that the molybdenum species in both types of samples are identical to within the resolution of the experiment.
TL;DR: In this paper, the 13C NMR spectra of friedelan, 21-one, friedelane-21-one and 6-one were recorded and signals assigned using off-resonance decoupling, inversion recovery and lanthanide induced shift techniques.
Abstract: 13C NMR spectra of friedelan, friedelan-21-one, friedelan-6-one, friedelane-321-dione, friedelane-3,6-dione and friedelane-3,6,21-trione have been recorded and signals assigned using off-resonance decoupling, inversion recovery and lanthanide induced shift techniques.
TL;DR: In this article, the properties of XHgCN (X = Cl, Br, I, OAc, CF 3 SO 3, SCN, SPh, SEt and Ph) have been determined and discussed.
TL;DR: In this article, the 13C NMR spectra of methyl 2-pyrone-3, 4-, 5-and 6-carboxylates were studied and the substituent effects on the 2 pyrone ring were compared with those of some model compounds.
Abstract: The 13C NMR spectra of methyl 2-pyrone-3-, 4-, 5- and 6-carboxylates were studied and the substituent effects on the 2-pyrone ring were compared with those of some model compounds. 1H NMR spectra were also recorded and discussed. The long range 13C, 1H coupling constants were obtained, discussed and proved useful in signal assignments.