13C-n.m.r.-spectral study of the mode of interaction of Gd 3+ and Mn 2+ with two vicinally di- O- d-galactosylated tripeptides

Abstract

Natural-abundance, 13C-n.m.r. spectroscopy was used to study the binding of Gd 3+ and Mn 2+ to two vicinally di- O-α- and -β- d-galactosylated tripeptides composed of Gly and l-Thr. Gd 3+ and Mn 2+ appear to interact with the α- d-Gal groups of the di- O-α- d-galactosylated tripeptide at two sites: near O-6′, and in the vicinity of O-2′ and Thr O-3. The metal-ion-binding to the β- d-Gal groups of the di- O-β- d-galactosylated tripeptide indicates that a strong binding-site exists near O-6′ and, possibly, several weak ones near O-3′ and Thr O-3. In the case of the di- O-α- d-galactosylated tripeptides, vicinal glycosylation appears to have little effect on the metal-ion-binding of the α- d-Gal groups.