Australia antigen 'ad' and 'ay' subtypes. Purification and partial characterization.

The two commonly-found Australia antigen subtypes have been purified by simple inexpensive, reproducible, physico-chemical methods involving ammonium sulfate precipitation, peptic digestion, calcium phosphate gel fractionation and molecular sieving on Sepharose 4B. The overall recovery of the two subtypes varied between 50 and 60% of the total antigen content on the starting serum. The purified antigens were found homogeneous by discontinuous gel electrophoresis, analytical ultracentrifugation, and isopycnic banding ultracentrifugation. No contaminating serum proteins could be detected by immunoelectrophoresis. The two purified antigen subtypes have similar Stokes radii and buoyant densities. The sedimentation coefficients for the 'ad' and 'ay' subtypes were found to be 33.0 and 40.1 times 10- minus 13 sec, respectively.