ULTRACENTRIFUGE STUDIES OF EFFECTS OF THIOCYANATE ION ON ANTIGEN-ANTIBODY SYSTEMS

The use of chaotropic ions has recently been suggested as a means of dissociating antigen-antibody complexes [1]. The present paper reports on sedimentation velocity measurements on antigen-antibody systems which have been exposed to high concentrations of thiocyanate (SCN), the most effective of these ions. The systems include bovine and human serum albumins and ovalbumin, and their complexes with their respective antibodies. Several effects of SCN are shown. Antibody immunospecifically purified by 3 M SCN at neutral pH retained its ability to combine with antigen to form soluble and insoluble complexes. In 3 M SCN, the concentration used for antibody purification, no significant amount of irreversible gross structural changes was discerned in any of the proteins. at 4·5 M and above, SCN caused changes in the sedimentation behavior of γ-globulin, antigens, and complexes. These changes were reversible by dialysis, except gelation, which was particularly pronounced for ovalbumin at 6 M SCN. 1·5 M SCN readily dissolved specific precipitates in AG excess; 3 M SCN was required to dissolve and dissociate specific precipitates formed in the equivalence zone. © 1969.