Individuality of Amino Acid Residues in Protected Peptides. Conformational and β-Sheet Structure-Disrupted Behaviors of Resin-Bound Peptides

Abstract

Abstract The conformational behavior of cross-linked polystyrene resin-bound peptides swollen in CH2Cl2 was analyzed using IR absorption spectroscopy. All of the resin-bound peptides easily aggregated with each other through intermolecular hydrogen bonding to form a β-sheet structure. The disruption of the β-sheet structure was further investigated by a solvent titration method in order to clarify the individuality of amino acid residues. At a pentapeptide level, the β-sheet structure was easily disrupted by the addition of a small amount of HFIP. On the other hand, at a larger peptide level, the disrupted behavior of the β-sheet structure was different from each other according to the amino acid composition. Based on the view that the secondary structure of globular proteins reflects the individuality of the 20 kinds of amino acid residues in proteins, we attempted to evaluate how easily the β-sheet structure of peptides is disrupted by HFIP using the average conformation values: 〈Pα〉, 〈Pβ〉, and 〈Pc〉. As a result, the β-sheet structure-disruption of peptides having a low potential for a β-sheet→helix transformation as well as for the randomness was difficult by adding increasing amounts of HFIP. On the other hand, that of the peptides having a 〈Pc〉 value larger than 0.85 and/or a high potential for the β-sheet→helix transformation proceeded smoothly upon adding increasing amounts of HFIP.