Glycine and alanine: a theoretical study of solvent effects upon energetics and molecular response properties

In the present work, we show that polarisable continuum model is able to re produce the stability of zwitterionic forms of amino acids alanine and glyc ine in water solution at B3-LYP/6-31G (d) level of theory. The model is the n extended to the calculation of vibrational frequencies, Vibrational circu lar dichroism spectra and nuclear magnetic resonance chemical shifts. The a greement with experimental data is good, except in the case of vibrations w here specific hydrogen bond interactions are involved. In the latter case, a supermolecular approach may help in the predictions of some vibrational f requencies of the groups which form hydrogen bonds. (C) 2000 Elsevier Scien ce B.V. All rights reserved.