A Molecular Orbital Study on the Side Chain Structures of Tyrosine and Phenylalanine

Abstract

The structure of the side chains of tyrosine and phenylalanine was analyzed by ab initio LCAO-MO calculations. The conformation of the tyrosine side chain of glycyltyrosine, the conformations of the side chains of many tyrosine and phenylalanine residues in proteins, and the conformation of tyrosine could be explained on the basis of calculations for ethylbenzene. It is shown that the dihedral angle (C_α-C_β-C_γ-C_δ1) of these molecules is determined by the exchange repulsion between the aromatic ring and the C_α-C_β bond.