AB-INITIO MODELING OF PEPTIDE BIOSYNTHESIS

Ab initio calculations (HF/3-21G) have been used to study the mechanis m of peptide biosynthesis ((RCOOR2)-C-1 + (RNH2)-N-3 --> (RCONHR3)-C-1 + (ROH)-O-2). Two or four water molecules are included to represent t he primary solvent shell. The studies show that the reaction proceeds via a gauche or trans transition state if it starts from the reactant' s gauche or trans complex. The energy barrier of the reaction with two water molecules is calculated to be 27.96 (gauche) or 26.85 kcal mol( -1) (trans), while that of the reaction with four water molecules is o nly 14.82 (gauche) or 13.21 kcal mol(-1) (trans). (C) 1998 Elsevier Sc ience B.V.