Conformation of model, alanine and proline containing tetrapeptides in water

Abstract
CD [circular dichroism] spectra of model alanine and prolyl-alanine tetrapeptides were measured at different pH values. An analysis of the spectra shows that proline in position 2 or 4 of a tetrapeptide favors folding of the peptide chain, and unfolding when it is in position 3. Changes in CD spectra evidence growing amounts of the .beta.-turn conformation upon increasing pH, independent of proline position in the peptide chain.