Per- and polyfluoroalkyl substances (PFAS) are synthetic fluorinated chemicals with hydrophobic and lipophobic properties that are used in the production of manufactured goods including nonstick pans, fire retardant, cosmetics, and much more. Perfluorooctanoic acid (PFOA) was one of the main PFAS used in US manufacturing facilities until the early 2000s, when a phase out of PFOA began due to concerns about its persistence, bioaccumulation and toxicity (PBT). One so-called replacement PFAS that emerged is hexafluoropropylene oxide-dimer acid (HFPO-DA), also known as GenX. Now there is a need for information about the potential PBT nature of HFPO-DA. PFAS are unique organic chemicals in that they tend to accumulate in high protein-dense areas in organisms, such as the bloodstream and the liver. Human serum albumin (HSA) is the most highly abundant protein in blood plasma, and it acts as a transport system for endogenous chemicals such as fatty acids. The goal of this research is to evaluate the binding competition between HFPO-DA and various fatty acids to HSA. Three model fatty acids were selected for the studies. Arachidonic and linoleic acids are both polyunsaturated fatty acids; arachidonic acid is associated with modulating neuronal cortical excitability and sodium channels, while linoleic acid plays an important role in the synthesis of arachidonic acid in the body. Stearic acid is a saturated fatty acid, being the third most abundant fatty acid in human hepatocytes, which account for about 80% of cells in the human liver. In this research, the binding competition is examined through an equilibrium dialysis method coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS) to measure concentrations of bound versus free HFPO-DA. Preliminary results suggest no significant change in HFPO-DA binding to HSA in the presence of the selected fatty acids. Average log KPW values are: 2.95 ± 0.08 (HFPO-DA/HSA control), 3.01 ± 0.01 (with arachidonic acid), and 2.92 ± 0.05 (with linoleic acid). Initial data (one experiment) with stearic acid reveals a log KPW of 2.88. Ongoing work is focused on investigating (1) the effects of pre-equilibration of the fatty acids to HSA prior to HFPO-DA binding and (2) the conformational changes that HFPO-DA and fatty acids (both independent of one another and concurrently) may induce in the structure of HSA.
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