Binding of dapsone and its analogues to human serum albumin.

The binding of dapsone, 4,4'-sulfonylbis(aniline)(1), and its diacetylated derivative, 4,4"'-sulfonylbis(acetanilide)(2), to human serum albumin is reported. To assess the ability of these compounds to displace 4'-[(4-aminophenyl)sulfonyl]acetanilide (3) from albumin, a dialysis rate technique was used. Competition for the bilirubin binding site on albumin was measured with the peroxidase assay. Compounds 1 and 2 strongly displaced both 3 and bilirubin from human serum albumin. The association constants for 1 and 2 with respect to bilirubin binding were 1.29 X 10(3) and 1.15 X 10(4) M-1, respectively. These results suggest that the binding site for 3 and the bilirubin binding site are similar with respect to 1 and 2 and that the binding of dapsone and its derivatives probably does not involve the amino function.