Properties of the major component of a peptic digest of rabbit antibody.

The molecular weight of the active, major component isolated from a peptic digest of rabbit antibody was found to be 106,000. After treatment with a disulfide-splitting reagent, the molecular weight was 56,000, and the products migrated as a single peak in the ultracentrifuge. he univalent fragments thus formed can be partially recombined by passage through IR-120 cation-exchange resin at room temperature or by treatment with a difunctional organic mercurial. Some splitting of the pepsin-treated antibody molecule occurs on carboxymethylcellulose at pH 5.4.