Polypeptide and carbohydrate structure of an intact glycoprotein from Raman optical activity.

A vibrational Raman optical activity (ROA) study of bovine alpha1-acid glycoprotein (AGP) is reported. Using the recently introduced ChiralRAMAN instrument from BioTools, Inc., a high-quality ROA spectrum of AGP, measured as a small circularly polarized component in the scattered light, was obtained in the range of 200-1800 cm-1. Comparison with the ROA spectra of beta-lactoglobulin and N,N'-diacetylchitobiose reveals features consistent with previous suggestions that the peptide component of AGP has a structure based on the lipocalin fold, and that the first two glycosidic links after the N-links to asparagine in the pentasaccharide core are of the beta(1-4)-type. A detailed analysis of the band patterns may ultimately provide information on the more conformationally heterogeneous and functionally crucial peripheral oligosaccharide segments. Hence, information about both the polypeptide and carbohydrate components may be obtained from the ROA spectra of intact glycoproteins.