Fluorescence study on site-specific binding of perfluoroalkyl acids to human serum albumin

Binding of five perfluoroalkyl acids with human serum albumin (HSA) was investigated by site-specific fluorescence. Intrinsic fluorescence of tryptophan-214 in HSA was monitored upon addition of the chemicals. Although perfluorobutyl acid (PFBA) and perfluorobutane sulfonate (PFBS) did not cause fluorescence change, perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS), and perfluorododecanoic acid (PFDoA) induced fluorescence quenching, from which binding constant of 2.7 x 10(5) M(-1) for PFOA and 2.2 x 10(4) M(-1) for PFOS was calculated. Two fluorescent probes, dansylamide (DA) and dansyl-L: -proline (DP), were employed in fluorescence displacement measurements to study the interaction at two Sudlow's binding sites. At Site I, both PFBA and PFBS displaced DA with binding constants of 1.0 x 10(6) M(-1) and 2.2 x 10(6) M(-1). At Site II, PFBS and PFDoA displaced DP with binding constants of 6.5 x 10(6) M(-1) and 1.2 x 10(6) M(-1), whereas PFBA did not bind. The data were compared with fatty acids to evaluate the potential toxicological effect of these environmental chemicals.