A Study of the Reaction between Human Serum Albumin and its Homologous Equine Antibody through the Medium of Light Scattering

Abstract

The reaction between bovine serum albumin and homologous equine antibody has been studied by light scattering measurements. Equilibrium is reached more rapidly in the zone of antigen excess than in the zone of antibody excess. The final light scattering values obtained for definite antigen/antibody ratios appear to be the same in the equivalence zone when the final state is approached from either zone of excess, whether one reagent is added to the other all at once, or whether it is added in several successive increments. On the other hand, the reaction on the antigen excess side of the precipitation curve is rapidly and completely reversed by addition of excess antigen, while in the antibody excess zone, additional antibody results in only a very slow reduction in the amount of scattered light at 90° to the incident beam. However reversal is indicated under these conditions also if scattering is measured at angles closer to the incident beam. Large complexes consisting of soluble aggregates of antigen and antibody appear to exist over all possible ratios of antigen to antibody. Specific aggregates are larger in size the closer the reaction takes place to the point of maximum precipitation.