Interaction rule and mechanism of perfluoroalkyl sulfonates containing different carbon chains with human serum albumin

In this study, the toxic mechanism and effects of perfluorooctane sulfonate (PFOS), perfluorohexane sulfonate (PFHS), and perfluorobutane sulfonate (PFBS) were investigated via spectroscopy, molecular modeling, and calorimetry techniques. Results showed that all three perfluoroalkyl sulfonates (PFASs) bound to human serum albumin (HSA) mainly through electrostatic forces and hydrogen bonds. The backbone and secondary structure of HSA did not significantly change after exposure to PFASs. It may be proposed that the binding changed the local structure around the active site and affected the esterase activity of HSA. Compared with the control group, the inhibited esterase activity of HSA decreased to 28.6%, 43.2%, and 54.4% under the exposure of PFOS, PFHS, and PFBS at 1.3 x 10(-4) mol L-1, respectively. The ITC result reflected that the binding ability increased after lengthening of the carbon chain, which also explained the decreased esterase activity with the increased lengthening of carbon chain. The fluorescence spectra also indicated that the influence on the microenvironment of HSA decreased with the shortening of the carbon chain. This study provided evidence regarding the interaction mechanism and toxicity of PFASs towards HSA in vitro.