The influence of the presence of oligosaccharide branches was examined with respect to the behavior of glycopolypeptides in empirical molecular weight estimation methods in the presence of sodium dodecyl sulfate (NaDodSO4). This examination was conducted by comparing the gel chromatographic and gel electrophoretic behaviors in the presence of NaDodSO4 of 13 glycopolypeptides of known chemical and physical properties to those of regular polypeptides. Errors in the gel chromatographic molecular weight for glycopolypeptides in NaDodSO4 varied from -22% to +10% and indicated that the hydrodynamic behavior of the glycopolypeptide--NaDodSO4 complex could not be correlated with the amount of carbohydrate in the glycopolypeptide. NaDodSO4 binding measurements on a number of the glycopolypeptides suggest that the polypeptide moiety binds the nominal weight ratio of NaDodSO4, while the carbohydrate portion exhibits little or no NaDodSO4 binding. As has been reported by others, the polyacrylamide gel electrophoretic behavior of glycopolypeptide--NaDodSO4 complexes yielded abnormally high molecular weight estimates. In general, the error of these estimates diminished with decreasing porosity of the gel; however, each glycopolypeptide behaved in a unique fashion. Treatment of the electrophoretic data by any of several empirical means provided no reliable way to correct for the glycopolypeptides' aberrant behavior.

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The effects of oligosaccharide branch chains on the hydrodynamic behavior of reduced glycopolypeptides was examined by gel chromatography in random coil producing solvents. This entailed a comparison of the gel chromatographic behavior in the presence of concentrated guanidinium chloride of 16 glycopolypeptides of known physical and chemical properties to that of regular polypeptides. For most of the glycopolypeptides employed, the presence of oligosaccharide branches sufficiently perturbed the dimensions of the unfolded glycopolypeptide such that its effective hydrodynamic radius was the same as that of a linear polypeptide of the same total mass. For this reason, gel chromatography in random coil producing solvents appears to be the most reliable empirical method to obtain a first approximation of the molecular weight of a glycopolypeptide. Glycopolypeptides rich in N-acetylneuraminic acid, and thus possessing low isoionic points, exhibited more pronounced deviations in their electrophoretic behavior in the presence of 8 M urea than those glycopolypeptides whose ionic properties were similar to those of the polypeptide standards employed.

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