Structure of the tripeptide model Ac–Val–Tyr(Me)–NHMe and its cluster with water investigated by IR/UV double resonance spectroscopy

Abstract

In this paper the structures of the isolated tripeptide model Ac–Val–Tyr(Me)–NHMe (Val = valine, Tyr = tyrosine) and its cluster with water are investigated by mass-, isomer- and state-selective IR/UV double resonance spectroscopy. From the IR spectra both in the region of the NH and CO stretching vibrations and in combination with force field and ab initio calculations it can unambiguously be derived that the peptide contains a stretched, β-sheet related structure. Thus the peptide serves as an ideal candidate for β-sheet model systems. By adding one water molecule to the peptide the β-sheet related structure seems to be preserved with a water molecule being attached to the NHMe group.