Institution: | Department of Chemistry, Clemson University, Clemson, SC 29631, USA Laboratoire de Chimie Bioorganique, Faculté des Sciences, 33 rue Louis Pasteur, 84000, Avignon, France |
Abstract: | 13C nuclear magnetic resonance spectroscopy (13C n.m.r.) was used to determine the pH titration parameters for the N-terminal N ,N-13C]dimethylamino and N ,N-13C]monomethylamino groups of glycophorins AM and AN, and some 28 related glycoproteins, glycopeptides and peptides. The results show that glycosylation of the Ser and Thr residues at positions 2, 3 and 4 of the glycophorins have a pronounced effect on the titration parameters. Substitution of amino acids 4 and 5 in the glycophorin sequence appears to minimally affect our titration parameters. Internal hydrogen-bonding involving the N-terminal Ser residue may explain some of the unusual pH titration results observed for glycophorin AM. |