CONFORMATION OF GLYCOPEPTIDES AND GLYCOPROTEINS

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The purpose of this research is to advance knowledge concerning the principles which govern the three dimensional conformations of glycoproteins and to relate molecular shape to biological function by methods similar to those which have been used for polypeptides, proteins and polynucleotides. The conformations of glycoproteins will be determined with special emphasis on their oligosaccharide moieties and their glycopeptide linkage. As conformational models for mucin glycoproteins, the research will use the antifreeze glycoprotein of polar fish as well as blood group A, B, H and Lewis active structures isolated from ovarian cyst mucins. The latter materials include oligosaccharide alditols, glycopeptides and a high molecular weight polysaccharide with blood group A active side chains attached to a polylactosamine backbone. Proton NMR spectra, including proton nuclear Overhauser enhancements (n.O.e.) for the model compounds will be interpreted with the help of conformational energy calculations with empirical potential functions. NMR coupling constants and n.O.e. will be calculated from the coordinates of the low energy molecular conformations for comparison with experimental data. Evidence for internal motion and molecular flexibility will be sought for oligosaccharides with 1-6 linkages by experiments on the temperature dependence of the conformation and by NMR relaxation methods. Conformational calculations for flexible molecules having no single low energy conformation will use statistical Monte Carlo methods. The contributions on non-bonded, electrostatic and solvophobic interactions to the molecular forces responsible for the observed conformations will be determined by experimental measurements of the conformation in nonaqueous solvents and by computational methods.