Cross-correlated quadrupolar spin relaxation and carbon-13 lineshapes in the (13)CD(2) spin grouping.

Lineshape calculations are reported for a spin system consisting of a spin-12 nucleus scalar-coupled to two magnetically equivalent spin-1 nuclei, e.g., a CD(2) group. It is found that, because of the differential line broadening, the peak height ratio of the five spin-12 nucleus transitions is expected to deviate from the integrated intensity ratio of 1:2:3:2:1. The deviation is dependent on the extent of cross-correlation between the two quadrupolar interactions. The theoretical predictions for peak height ratios and for bandshapes are tested for the carbon-13 spectrum of perdeuterated ethylene glycol, and iterative fitting is used to obtain an estimate of the extent of the correlation between the quadrupolar interactions for the two deuterons.

Dynamic frequency shifts of complexed ligands: An NMR study of D--1-13C,1-2H-glucose complexed to the Escherichia coli periplasmic glucose/galactose receptor.

The 13C multiplet structure of D--1-13C,1-2H-glucose complexed to the Escherichia coli periplasmic glucose/galactose receptor has been studied as a function of temperature. Asymmetric multiplet patterns observed are shown to arise from dynamic frequency shifts. Multiplet asymmetry contributions resulting from shift anisotropy-dipolar cross correlations were found to be small, with optimal fits of the data corresponding to small, negative values of the correlation factor, chiCD-CSA. Additional broadening at higher temperatures most probably results from ligand exchange between free and complexed states. Effects of internal motion are also considered theoretically, and indicate that the order parameter for the bound glucose is >/=0.9.