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

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 C=O stretching vibrations and in combination with force field and ab initio calculations it can unambiguously be derived that the peptide contains a stretched, beta-sheet related structure. Thus the peptide serves as an ideal candidate for beta-sheet model systems. By adding one water molecule to the peptide the beta-sheet related structure seems to be preserved with a water molecule being attached to the NHMe group.