The presence of per and poly-fluoroalkyl substances (PFAS), commonly referred to as forever chemicals, in aquatic systems is a serious global health problem. We report herein structural alterations to human serum albumin (HSA) upon addition of perfluoro(2-methyl-3-oxahexanoic) acid (Gen X) monitored by changes to the fluorescence spectra. Gen X, a widely used emerging PFAS, used as a replacement for the banned perfluorooctanoic acid (PFOA). The equilibrium association constant for Gen X binding to HSA is 7(±1) × 103 M-1 determined from changes in fluorescence emission data during the titration with Gen X. Site-specific HSA binding fluorophores, 8-anilinonaphthalene-1-sulfonic acid (1,8-ANS), warfarin and dansyl-L-Proline were used to investigate the specific binding sites of Gen X on the HSA. A competitive displacement study provides the association constants for Gen X with HSA at the 1,8-ANS, warfarin and dansyl-L-Proline binding sites to be 6.25 × 104 M-1 , 1.1 × 106 M-1, and 8.4 × 106 M-1, respectively. These results illustrate the strong and specific binding sites of Gen X on HSA. Additionally, we have performed fluorescence studies to assess the effect of Gen X on the thyroid hormone transport by HSA. The experimental results showed that the association between triiodothyronine (T3) and HSA protein does not change significantly. However, the association between thyroxine (T4) hormone and HSA increased significantly.

Fluorescence study on the binding of toxic PFAS, Gen X with the HSA protein and the effect on thyroid hormone transport via HSA

ACS Spring 2022

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