L-serine tripeptides: Ac-Ser-Gly, Ala-Ser-Gly and Gly-Ser-Phe

The 1H and 13C n.m.r. spectra of Ac-Ser-Gly, Ala-Ser-Gly and Gly-Ser-Phe tripeptides have been measured and analysed at three different pD values. The n.m.r. parameters of Ser side-chain are nearly pD independent. C alpha H group (13C/1H) of Ser residue of Gly-Ser-Phe shows a consistent pD dependence in acid solutions. Conformational calculations on Ser side-chain show the growing importance of the gauche conformers on the overall conformation of the side-chain all along the three tripeptides.