Quantum theory of the structure and bonding in proteins: Part 9. The proline dipeptide

Abstract

The conformational energy map of the dipeptide containing the proline residue is reported. It is shown that the C 7, hydrogen bond, the polyproline helix and the 3 10 helix all occur in regions of low energy of the map. The problem of the conformation of the pyrrolidine ring is solved in an approximate manner. All possible C 10 hydrogen bonds are examined and the agreement between experiment and theory is generally good. The repulsions between non-bonded hydrogen atoms are examined. The population changes which accompany hydrogen bond formation are the same as those found in the earlier work.