The macromolecular properties of blood-group-specific glycoproteins. Characterization of a series of fractions obtained by solvent fractionation.

1. The glycoprotein components of a human ovarian-cyst fluid were isolated by a solvent [95% (w/w) phenol]-extraction procedure; the phenol-insoluble water-soluble glycoprotein was further fractionated by (NH(4))(2)SO(4) and by ethanol to yield eight fractions. 2. The fractions were analysed in terms of amino acids, fucose, galactose, N-acetylglucosamine, N-acetylgalactosamine and sialic acid. Variations occurred, particularly in the proportion of peptide; these were partly correlated with varying extent of serological activity. 3. The fractions were characterized physicochemically in terms of buoyant density and degree of spreading in a density gradient, sedimentation velocity and molecular weight; their partial specific volumes and specific refraction increments were also determined. 4. The fractions showed wide variations in their sedimentation-velocity and density-gradient patterns, and gave evidence of pauci-dispersity in density. The fraction regarded as the most typical blood-group-specific glycoprotein sedimented as a single rapidly spreading peak and was of high molecular weight. 5. Significant correlations were observed between the physical properties of the glycoprotein fractions and the amount of their peptide component. The buoyant densities and sedimentation coefficients varied in a manner that suggested the existence of two families of glycoproteins. 6. It is suggested that variability in the extent of glycosylation, or in the degree of cross-linking, might account for the two families of glycoproteins, and that the extent of cross-linkage might also be a factor determining the solubility of these glycoproteins in hot saturated (NH(4))(2)SO(4).