Conformational analysis of dipeptides in aqueous solution. II. Molecular structure of glycine and alanine dipeptides by depolarized rayleigh scattering and laser Raman spectroscopy

Abstract
A new approach to the experimental conformational analysis of peptides in aqueous solution is presented and discussed. The basic idea is to combine laser Raman spectroscopy and depolarized Rayleigh scattering in order to interpret scattering properties of the dissolved molecule in terms of both local and global structure. We outline a simple method (anisotropic perturbation treatment) appropriate for solving conformational problems in large molecules by studying together slightly perturbed homologous compounds. This method is applied to the study of the molecular structure of simple glycine and alanine dipeptides. The preferred conformation for such molecules is the seven‐membered chelated ring (C7) additionally stabilized by two intermolecular hydrogen bonds involving one molecule of water.