The effects of intermolecular interactions on the electric field gradients in ice and liquid water

Recent progress in understanding chemical shifts

In the past three or four years computer hardware and software developments have reached the stage where the nuclear magnetic resonance (NMR) spectra of many molecular systems can now be accurately evaluated. Detailed analysis of chemical shifts may soon become a routine part of solid (and liquid) state NMR structure prediction in chemistry and biology, and this Article covers the development of the topic from its earliest beginnings.

Secondary and tertiary structural effects on protein NMR chemical shifts: an ab initio approach

Recent theoretical developments permit the prediction of 1H, 13C, 15N, and 19F nuclear magnetic resonance chemical shifts in proteins and offer new ways of analyzing secondary and tertiary structure as well as for probing protein electrostatics. For 13C, phi, psi torsion angles dominate shielding for C alpha and C beta, but the addition of hydrogen bonding and electrostatics gives even better accord with experiment. For 15NH, side chain (chi 1) torsion angles are also important, as are nearest neighbor sequence effects, whereas for 1HN, hydrogen bonding is particularly significant. For 19F, weak or long-range electrostatic fields dominate 19F shielding nonequivalencies. The ability to predict chemical shifts in proteins from known or test structures opens new avenues to structure refinement or determination, especially for condensed systems.