The fluorescent probe prodan characterizes the warfarin binding site on human serum albumin

The fluorescent probe Prodan (6-propionyl-2-dimethylaminonaphthalene) binds with high affinity to human serum albumin (HSA), The spectral characterist ics of the Prodan bound to the protein are very different from the free Pro dan in solution, These differences allowed the spectra to be deconvoluted i nto log-normal bands in order to quantify the bound and unbound ligand and to calculate the binding constant at different temperatures. From such temp erature dependence, we found the binding to be exothermic with a van't Hoff enthalpy of -22.8 kJ mol(-1). Thermodynamic analysis suggests that the int eraction may be mainly caused by hydrophobic forces and electrostatic inter actions. The above analysis of the spectra and the measures of the fluoresc ence polarization during the successive presence of six specific drugs sugg est that the Prodan binding site corresponds with the warfarin binding site on HSA, whereas under the present experimental conditions the other charac teristic binding sites of HSA were not affected, Thus, this fluorescent pro be provides a rapid and simple means for the characterization of a specific binding site on HSA and also for detecting potential or nonspecific drug-p rotein interactions.