Spectrofluorimetric study of the binding of 1-anilinonaphthalene-8-sulfonate to bovine serum albumin.

We studied the binding of the fluorescent probe 1-anilinonaphthalene-8- sulfonate to bovine serum albumin by spectrofluorimetric techniques. The binding of this probe to bovine serum albumin was via two types of sites: one with a high affinity constant but relatively fewer in number and the other with a lower affinity constant but greater in number. The number of binding sites of each type of site and their respective association constants varied with the features of the moiety and the temperature. The results indicate that the simplistic interpretation involving a single type of interaction of hydrophobic nature can no longer be supported and that additional involvement of other, nonhydrophobic types of binding should be considered. This thermodynamic study allowed calculation of changes in enthalpy, Gibbs free energy, and entropy values that are consistent with this hypothesis.