Studies on the structure of brain ganglioside

Abstract

A preparation of brain ganglioside, homogeneous by electro-phoretic and ultracentrifugal studies, was examined by a quantitative step-wise hydrolytic procedure. Diffusible products were quantitatively separated from those which are non-diffusible at each hydrolytic step by exhaustive dialysis. The diffusible and non-diffusible fractions thus obtained were analyzed in terms of dry weight, N, neuraminic acid, hexosamine, hexose and reducing sugar, partitioned by paper-chromato-graphic and ion-exchange procedures, and the subtractions further hydrolyzed and analyzed. The mode of linkage of the neuraminic acid components was demonstrated. Oligosaccharide fragments were isolated, the hexoses shown to be exclusively galactose and glucose, and the hexosamine, galactosamine. The galactosamine content was 10%, and a reaction of galactosamine on heating with concentrated acid was observed. A glucocerebroside was cloven from the intact ganglioside, characterized and named gangliocerebroside. A hexo-dicerebroside was also isolated. The constant order of release of constituents, together with the evidence regarding the structure of isolated fragments, was used to formulate the structure of the repeating unit of the molecule. Observations were made relevant to the overall structure and orientation of the macromolecular glycolipid.