SYNTHETIC TN-GLYCOPEPTIDE RELATED TO HUMAN GLYCOPHORIN-AM - HIGH-FIELD PROTON AND C-13 NUCLEAR MAGNETIC-RESONANCE STUDY

Abstract

Three 2-acetamido-2-deoxy-.alpha.-D-galactopyranoses attached to Ser2, Thr3 and Thr4 of the amino-terminal portion of glycophorin AM are responsible for the so-called TN blood group specificity. The corresponding glycopeptide .**GRAPHIC**. [in which (*) represents the 2-acetamido-2-.alpha.-D-galactopyranosyl residue] obtained by a stepwise peptide coupling strategy was submitted to a detailed high-field NMR analysis. 13C-NMR spectrum confirms the validity of previous assignments made on M sialo and asialoglycopeptides obtained by specific degradation of human glycophorin AM. The 400 MHz 1H-NMR spectrum allowed most of the proton resonances to be assigned. A careful examination of the chemical shifts and coupling constants revealed some interesting features of the conformational properties of the GalNAc-Ser and GalNAc-Thr linkage as well as of the rotational isomerism of Thr and Ser side-chains. Thus, high-field NMR spectroscopy can be successfully used to gain structural and dynamic information on rather sophisticated glycopeptides.