NMR and molecular dynamics study of the tripeptide L-pyroglutamyl-L-histidylglycine.

The 1H spectrum of L-pyroglutamyl-L-histidylglycine in DMSO-d6 and 1H and 13C NMR spectra in D2O at pH 4.26 to 8.90 have been analysed. 3JHH vicinal coupling constants were used to determine rotamer populations by means of the Karplus equation. Viable molecular geometries were obtained with the aid of molecular dynamics simulations including water as solvent. In DMSO and in aqueous solution at low pH two stable conformations were identified which both have an intramolecular hydrogen bond between the histidine side chain and the C-terminal carboxylate group.