Glycyl Methylene Chemical Shift Non‐Equivalence in Small Peptides. Diasteriomers of Leu‐Gly‐Phe

Abstract

Abstract Main possibilities for the origin of glycyl methylene chemical shift non‐equivalence in Gly‐containing small peptides are reviewed together with new data obtained at 300 and 360 MHz 1 H‐nmr spectroscopy. An unexpected behaviour, both in glycyl methylene chemical shift non‐equivalence as in the similarity of mean shift values of these protons in the diasteriomeric tripeptides Leu‐Gly‐Phe rules out the electric field gradient contributions being of major importance. Changes in conformational features, both of the back‐bone as of the side chain rotation in function of pH are revealed, as follows from a study of coupling constants.