Mass spectrometry and 13C nuclear magnetic resonance spectroscopy of compounds modeling the glycopeptide linkage of glycoproteins |
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Authors: | Karl Blumberg C.Allen Bush |
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Affiliation: | Department of Chemistry, Illinois Institute of Technology, Chicago, Illinois 60616 USA |
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Abstract: | The properties of several compounds useful as models for three-dimensional conformational studies and the investigation of the chemical degradation of glycopeptide linkages both of the N- and O-glycosidic type are described. Using the method of differential chemical shift in H2O and D2O as solvents, the carbon NMR spectrum of N-acetylglucosaminylasparagine, 1-N-acetyl-β-d-glucopyranosylamine, and 1-N-acetyl-2-acetamido-β-d-glucopyranosylamine has been assigned. Electron impact mass spectra of the peracetylated derivatives of the latter two compounds show a peak apparently unique to glycopyranosylamides at , no analog of which is observed in the mass spectra of other peracetylated sugars. As models of the α-O-glycosidic linkage, fully assigned carbon NMR spectra of α-methyl-N-acetylgalactosamine (GalNAc), α-methyl-3-O-methyl GalNAc,and -GlcNAc as well as the disaccharide Glc-β-1 → 3 GalNAc are reported. Because certain anomalies in the chemical shifts and 1JCH observed in the disaccharide and in O-glycosylated glycoproteins are not observed in the simple model compounds, they may result from conformational interactions in the glycopeptides. |
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