Development of a Fluorescence Model for the Binding of Medium- to Long-Chain Perfluoroalkyl Acids to Human Serum Albumin Through a Mechanistic Evaluation of Spectroscopic Evidence

Abstract

A novel model for measuring the strength of perfluoroalkyl acid (PFAA) binding to human serum albumin (HSA) by use of the protein's native fluorescence is described. The model is derived from published properties of HSA and its interactions with other surfactants; it is consistent with these properties and experimental observations. The model's validity has been tested with both medium- to long-chain PFAAs (perfluoroheptanoate, perfluorooctanoate, perfluorononanoate, perfluorodecanoate, perfluoroundecanoate, perfluorohexanesulfonate, and perfluorooctanesulfonate) and short-chain PFAAs (perfluorohexanoate and perfluorobutanesulfonate). These experiments confirm the model as a valid description for the binding of medium- to long-chain PFAAs to HSA. Results indicate at least 2-3 PFAAs bind to each protein with affinity on the order of 10(4) M(-1). These binding strengths exhibit a dependence on protein concentration. Measured PFAA binding constants are approximately 10% of those values reported for fatty acids of similar chain length; correcting for protein concentration suggests the binding strengths may be as low as 2-3% of the corresponding fatty acids' affinities. Like fatty acids, the carboxylate PFAAs exhibit a trend of generally increasing binding strength with increased chain length. The model does not appear valid for the binding of short-chain PFAAs to HSA. Hill binding coefficients, fluorescence intensity measurements, and wavelengths of maximum emission suggest short-chain PFAAs associate with HSA differently and fail to promote the same conformational changes in the protein's tertiary structure as the medium- to long-chain PFAAs.

Tissue Distribution and Whole Body Burden of the Chlorinated Polyfluoroalkyl Ether Sulfonic Acid F-53B in Crucian Carp (Carassius carassius): Evidence for a Highly Bioaccumulative Contaminant of Emerging Concern

“…29 In the present study we utilized the high mass accuracy and spectral resolving power of Orbitrap HRMS to investigate interferences and confidently identify F-53B. 3 ] − , observed in HRMS MS 2 full scan mode for tissue sample, were identical to those in the F-53B standard solution, with similar relative abundance and isotopic ratios of 35 Cl to 37 Cl (about 3:1) (shown in Figure 1a and b). The observation of the molecular ion (m/z = 530.89754; Δm = −0.593 ppm) and characterized ion (m/z = 350.94479; Δm = 1.917 ppm) in tissue samples at identical retention times with those of standard solutions further confirmed the presence of F-53B (Figure 1c).…”

Characterization of Alizarin Red S binding sites and structural changes on human serum albumin: A biophysical study

“…Site II is known as indole-benzodiazepine site and corresponds to the pocket of subdomain IIIA, the interior pocket comprises hydrophobic amino acid residues and the exterior presents two important amino acid residues (Arg 410 and Tyr 411 ) [7]. As the major soluble protein components of the circulating system, HSA is responsible for distributing and metabolizing many endogenous and exogenous ligands such as fatty acids, bilirubin, metal ions, steroids, pharmaceuticals and several dyes [8][9][10][11]. The exceptional ability of HSA to interact with these ligands is attributed to the presence of multiple binding sites.…”

Strong associations of short‐chain perfluoroalkyl acids with serum albumin and investigation of binding mechanisms

“…A wide range of association constants (10 2 -10 6 /M) for C 8 and C 9 PFAAs with rat [12], human [12,16,17,[19][20][21][22], and bovine [18,22,23] albumins are reported. Primary association constants for PFOA and perfluorononanoate (PFNA) with BSA suggest binding through specific high-affinity interactions.…”