Determination of the carbon-13 chemical shift and nitrogen-14 electric field gradient tensor orientations with respect to the molecular frame in a polypeptide

Abstract

With the determination of the nulcear spin interaction tensor orientation for the site of interest in a macromolecule it is now possible to achieve very high resolution structural and dynamic information from uniformly aligned samples of a macromolecule. Here the orientation of both the carbonyl 113 C chemical shift and 14 N electric field gradient tensors are determined with respect to the molecular frame for backbone sites in polypeptides from solid state NMR spectroscopy. 15 N and 14 N dipolar coupled 13 C spectra were analysed. In both cases at a 50 MHz 13 C frequency the presence of the dipolar coupling was plainly seen in powder pattern spectra, and for 14 N coupled spectra the effect of the quadrupole interaction was pronounced