Purification and biophysical characterization of hepatitis B antigen.

Hepatitis B antigen (HB Ag) has been purified from serum by pepsin digestion and equilibrium sedimentation. The sedimentation coefficient, density, particle size, and electrophoretic mobility have been determined before and after purification and found to be unaltered. In addition, the diffusion constant and molecular weight of purified HB Ag have been documented. Because the biophysical characteristics found are not consistant with those of any known virus, it is believed that native HB Ag is made up almost entirely of incomplete virus.