Some aspects of NMR techniques for the conformational analysis of peptides

Abstract

An outline is given of some new NMR spectroscopic approachcs to the spatial structure of peptidcs in solution which have been recently suggested and tcsted in the Shemyakin Institute for Chemistry of Natural Products. The previously derivcd angular dcpendence of the peptidc vicinal 3 JNHCH coupling constant has been refined on the basis of the latest experimental data. It has hecn found that ion-dipole intcraction of thc type C=O M + (wherc M + is an alkali metal ion) Ieads to a low ficld shift of thc 13 C signal of the carbonyl group. This effcct permits determination of the number and location of the Iigand groups which form thc intcrnal cavity of pcptidc and depsipeptide complcxones. The effect of 'shift reagents' on the NMR spectra shcds certain light on the spatial structure of peptides in solution, and, in particular, gives considerable information on the configuration of the amide bond and on the rotational states of the Ccr--C 11 bond. The INDOR and signals on combination frequency have been used for detection of 'hidden' signals (their multiplicity, chemical shift and splitting) and on thc assignment of the NH signals in the proton NMR spectra of peptides.