Inter-peptide hydrogen bonding in monolayers of oligoglycine amphiphiles

N-octadecanoyl oligoglycine (monomer to pentamer) ethyl esters were synthesized. The structures of their monolayers and LB films transferred from pure water were investigated by π-A isotherms and FT-IR reflection absorption spectroscopy (FT-IR, RAS). All the glycine residues were involved in intermolecular hydrogen bonding as indicated by shifts of the NH stretching band and other IR features. The strength of the hydrogen bonds was increased with increasing numbers of the glycine residues in a molecule. The FT-IR characteristics of these monolayers are close to those of polyglycine II, despite the fact that these oligopeptides are not long enough for conformational fixation in bulk water.