Effects of electron correlation and the environment on the conformational preferences of the β-alanine dipeptide

The conformational preferences of the beta-alanine dipeptide have been determined in the gas-phase using HF/6-31G(d) and MP2/6-31G(d) geometry optimizations. The conformational energy of the six resulting minima was estimated by single point calculations at both the HF/6-311G(d,p) and MP2/6-311G(d,p) levels. Self-consistent reaction field calculations using the polarizable continuum method were performed in order to evaluate the effect of the solvent on the relative stability of the different minima. Furthermore, the theoretical results obtained for the dipeptide have been compared with the conformational preferences found for the beta-alanine residue in small peptides by examination of the Cambridge Structural Data Base. The influence of both electron correlation and the environment on the conformational energies is discussed. (C) 2000 Elsevier Science B.V. All rights reserved.