Solution conformation of asparagine-linked oligosaccharides: .alpha.(1-6)-linked moiety

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Abstract
The solution conformation is presented for representatives of each of the major classes of asparaginyl oligosaccharides. In this report the conformation of the .alpha.(1-6)-linked moiety is described. The conformational properties of these glycopeptides were determined by high-resolution 1H NMR in conjunction with potential energy calculations. The NMR parameters that were used in this analysis were chemical shifts and nuclear Overhauser enhancements. Potential energy calculations were used to evaluate the preferred conformers available for the different linkages in glycopeptides and to draw conclusions about the behavior in solution of these molecules. For all classes, identical conformations were found for the 6-arm except for the torsional angle, .omega., about the C5.sbd.C6 bond of the .alpha.1-6 linkage. For high mannose and hybrid structures .omega. was -60.degree., for bisected biantennary complex structures .omega. was 180.degree., and for complex biantennary structures averaging between -60.degree. and 180.degree. occurs.