13C-N.M.R.-SPECTRAL STUDY OF THE MODE OF BINDING OF Gd(3+) TO VARIOUS GLUCOPEPTIDES

Article abstract of DOI:10.1016/0008-6215(83)88387-6

Natural-abundance, 13C-n.m.r. spectroscopy was used to study the mode of binding of Gd(3+) to mono-O-glycosylated L-serine and tripeptides variously composed of Gly and L-Thr.When the amino and carboxyl groups of the amino acid are not blocked, strong interaction of Gd(3+) with them is observed; this is also readily apparent with some related, nonglycosylated peptides.When the amino and carboxyl and carboxyl groups of the amino acid are blocked, noticeble interaction of Gd(3+) with the glycosidic oxygen atom (O-3) and O-2' for the glycopeptide containing α-D-Galp, and with O-3 and N-2' for the glycopeptide containing α-D-GalpNAc, is observed.Weak interactions are also possible with O-4' and O-6' of the glycosyl groups.Although the amino acids were protected, these metal ion-carbohydrate interactions may still be mediated, to some extent, by the acetyl protecting the amino group and by the ester group on the amino acid.