Vibrational analysis of peptides, polypeptides, and proteins

Abstract

The normal modes have been calculated for three kinds of low energy .gamma.-turn structures resulting from recent conformational energy calculations by Nemethy. Frequencies have been computed for a .gamma.-turn, a mirror-related .gamma.-turn, an inverse .gamma.-turn of CH3-CO-(L-Ala)n-NH-CH3, with n = 3 and n = 5, and for certain 14C and 15N derivatives of the n = 3 molecule. Correlations are evident between amide frequencies and .gamma.-turn structures, and it is found that only amide I modes of peptide groups in the turn are relatively insensitive to the lengths of attached chains.