1H And 13C NMR chemical shifts of the diastereotopic methyl groups of valyl and leucyl residues in peptides and proteins

Abstract

Stereospecific 1H and 13C NMR assignments for the diastereo-topic methyl groups of the valyl and leucyl residues in a cyclic peptide and in two globular proteins were obtained using biosynthetically direc-ted fractional isotope labeling with 13C. The methyl chemical shifts are analyzed with respect to possible correlations with the stereochemistry of these amino acid side chains.