Showing papers on "Solid-state nuclear magnetic resonance published in 1970"

Bulk susceptibility corrections in nuclear magnetic resonance experiments using superconducting solenoids

Abstract: WHEN A NUCLEAR magnetic resonance (NMR) spectrum is referenced with an external standard contained either in a capillary inserted coaxially in a cylindrical sample or in the annular region of a coaxial sample, the observed chemical shift must be corrected for the difference in the bulk susceptibilities of the sample and the reference compound ( I ) . This problem has been treated at length for the conventional magnet/sample configuration, such as that of the Varian A-60 or HA-100 spectrometer, where the applied polarizing magnetic field is transverse to the long axis of the cylindrical sample (2). For this magnet/sample geometry, the bulk susceptibility correction to the observed chemical shift has been shown to be

Magnetic relaxation in ordered systems.

Abstract: NUCLEAR magnetic resonance (NMR) spectroscopy is one of the most promising techniques to be recently applied to the study of lipid, protein and water interactions in biological and other ordered and semi-ordered systems. NMR studies of the water in many hydrated biological systems have been interpreted in terms of the existence of “structured”, “ice-like” or “bound” water1–6. Likewise, line broadening in ordered liquid crystalline and biological systems has often been taken as an indication of restriction of molecular motion7–13. We should like to point out some possible pitfalls in interpreting the results of limited relaxation or line width data in terms of changes in molecular mobility arising from specific interactions, in systems which are not isotropic liquids and are not always homogeneous. We have carried out a spin-echo NMR study of the dimethyldodecylamine oxide–deuterium oxide system—a system in which anisotropic ordered structures exist and one for which considerable X-ray and continuous wave NMR data are available9,14. This system is an ideal one for the study of the effects of molecular ordering and anisotropy on the measured NMR parameters because the structure can be changed from isotropic to anisotropic simply by a slight change in composition or temperature.

13-C nuclear magnetic resonance spectrum of gramicidin S-A, a decapeptide antibiotic.

Abstract: ALTHOUGH proton magnetic resonance spectroscopy has improved our knowledge of the structure and function of biopolymers, especially complex peptides and proteins1, it has not yet solved such problems as determining the conformation of a protein in solution. The nearest approach has been the analysis of the spectrum of gramicidin S-A2, a peptide of molecular weight 1,120 (Fig. 1). The technique used there is theoretically applicable to biopolymers of higher molecular weight, but the experimental difficulties are almost insurmountable.

Nuclear Magnetic Resonance Spectroscopy of Bicyclobutane

Abstract: The proton and carbon‐13 nuclear magnetic resonance spectra of bicyclobutane have been analyzed in detail. The use of information from NMR spectra of bicyclobutane in a nematic solvent permits an unambiguous assignment of all chemical shifts and spin–spin interactions to specific nuclei. Some of the assignments differ from previously published ones. A long‐range indirect spin–spin coupling of 5.9 Hz is found between the two exo protons, and an indirect coupling of 16.0 Hz is observed between the exo proton and the carbon‐13 to which the other exo proton is bonded.