Crystal structures of hydrophobic amino acids:: interaction energies of hydrogen-bonded layers revealed by ab initio calculations

The crystal structures of mixtures Of D- and L-enantiomers of hydrophobic amino acids, either as true racemates or 1: 1 complexes between two different acids, are always divided into hydrophilic and hydrophobic layers. Two different aggregation patterns are observed, each with a unique hydrogen bonding arrangement. In an attempt to find which pattern is inherently the most favourable, ab initio calculations on two-dimensional slabs of the hydrophilic regions in these crystals have been carried out. The results clearly show that one hydrogen bonding pattern has a higher interaction energy. (C) 2003 Elsevier B.V. All rights reserved.