Characterization of hapten-human serum albumins and their complexes with specific human antisera.

Human antisera against trimellityl-human serum albumin or diphenylmethane diisocyanate-human serum albumin were fractionated by Sephadex G200. The fractions containing IgG were pooled and reacted with trimellityl 125I-human serum albumin or diphenylmethane diisocyanate-125I-human serum albumin, and these mixtures were again fractionated through Sephadex G200. The resultant chromatographic profiles showed two peaks. The first peak contained hapten-human serum albumin-antibody as demonstrated by the precipitability of radioactivity with anti-human IgG. During these studies it was found that trimellityl-human serum albumin or diphenylmethane diisocyanate-human serum albumin have different elution profiles and electrophoretic mobilities than human serum albumin. Trimellityl-human serum albumin elutes earlier and migrates farther toward the anode than either diphenylmethane diisocyanate-human serum albumin or human serum albumin. Diphenylmethane diisocyanate-human serum albumin elutes earlier and migrates farther toward the anode than human serum albumin. These results may be explained by swelling of the trimellityl-human serum albumin molecule due to the additional negative charges of the trimellityl carboxyl groups and loss of positive charges at basic amino acid binding sites of trimellityl. The lesser changes in diphenylmethane diisocyanate-human serum albumin may result from only the delection of positive charges on basic amino acids of human serum albumin since diphenylmethane diisocyanate contributes no additional charge.