Gel filtration of hepatitis B surface antigen: increased size of the native particle

The Stokes radius of umpurified hepatitis B antigen (HBSAg) was determined by chromatography on a carefully calibrated Sepharose 4B column. A value of 14-2 nm was found by this procedure, contrasting with a published value of II nm for purified, pepsin-treated HBSAg. Chromatography at pH 3 appeared to reduce the Strokes radius of HBSAg to II nm. Evidence is presented to show that serum proteins adsorbed to HBSAg can be removed with pepsin or acid.