The presence of per and poly-fluoroalkyl substances (PFAS), commonly referred to as forever chemicals, is a global health problem as it triggers serious negative health impacts on humans. Perfluoro(2-methyl-3-oxahexanoic) acid (Gen X) and Perfluorooctanoic acid (PFOA) are two of the most extensively used emerging and legacy PFASs in the industry. The production of PFOA has been banned in the United States since the year 2006. However, both of these compounds are widely available in the enviroment and drinking water systems. In this study, we have monitored the structural alterations to human serum albumin protein (HSA) upon the addition of Gen X using the fluorescence spectroscopy method. The equilibrium association constant for Gen X binding to HSA is 7(±1) × 103 M-1 determined from changes in fluorescence emission data during 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. Additionally, we have performed fluorescence studies to assess the effect of Gen X on the thyroid hormone and fatty acid transport by HSA. The experimental results revealed the association between triiodothyronine (T3) and thyroxine (T4) hormones with HSA increased by ×10 and ×70 respectively in the presence of Gen X. Fluorescence titration data for the HSA in the presence of Palmitic acid and PFOA suggests that fatty acid-binding to the HSA protein decreased up to 1000 µM of PFOA and decreased upon further addition.

Fluorescence study of the binding of toxic PFAS with the HSA protein and the effect on thyroid hormone and fatty acid transport via HSA

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