AN EXAMINATION OF INTERMOLECULAR AND INTRAMOLECULAR HYDROGEN-BONDING IN BIOMOLECULES BY AM1 AND MNDO/M SEMIEMPIRICAL MOLECULAR-ORBITAL STUDIES

The recent NMDO/M modification and parameterization of the MNDO molecular orbital method has been used to analyze intermolecular hydrogen bonding between amino acids and water, and intramolecular hydrogen bonding in monosaccharides. The results have been compared to AM1 calculations on the same systems. The MNDO/M calculations gave values which were similar to ab initio calculations with respect to the intermolecular interactions, but yielded significantly poorer results for the intramolecular interactions. The AM1 procedure performed better on the intramolecular interactions than the MNDO/M procedure, but frequently provided unfavorable three-centered hydrogen bonding geometries for the intermolecular interactions.