Li Wenting, Hu Yuhong, Bischel Heather N
Department of Civil and Environmental Engineering, University of California Davis, Davis, CA 95616, USA.
Toxics. 2021 Mar 17;9(3):63. doi: 10.3390/toxics9030063.
Drinking water contaminated by fluorosurfactant-based aqueous film-forming foams (AFFF) is a source of human exposure to poly- and perfluoroalkyl substances (PFAS). However, assessment of bioaccumulation potentials of diverse PFAS in commercial products such as AFFF have been insufficient and challenging, especially due to a lack of analytical standards. Here we explore the value of suspect screening, equilibrium dialysis, and molecular-docking simulations to identify potentially bioaccumulative PFAS. We exposed human serum albumin (HSA) protein to dilutions of a legacy AFFF produced by 3M in 1999 using equilibrium dialysis and screened in-vitro protein-binding affinities using high-resolution mass spectrometry (HRMS). Through suspect screening, we identified 32 PFAS and 18 hydrocarbon surfactants in the AFFF that bound to HSA. Quantification of noncovalent association constants for 26 PFAS standards confirmed that many PFAS, including the short-chain perfluoropropane sulfonic acid (log K= 4.1 ± 0.2 M), exhibit strong binding affinities with HSA. At least five PFAS in AFFF (including three PFAS with less than five perfluorocarbons) remained bound to the precipitated HSA pellet after extensive solvent washing-an indication of high PFAS binding potential. Three PFAS (PFBS, PFOS, and PFOA) were confirmed in the protein pellet with analytical standards and quantified after acid digestion-this sample fraction accounted for 5 to 20% of each compound mass in the sample. We calculated pseudo-bioconcentration factors (BCF) for PFAS that suspect screening flagged as noncovalently bound or potentially covalently bound. Most PFAS exhibiting high BCF, especially those with seven perfluorocarbons, contained a carboxylic acid or a sulfonic acid. Finally, we used molecular docking to simulate HSA binding affinities for 62 ligands (26 PFAS targets, 18 PFAS qualified in AFFF, and 18 hydrocarbon surfactants qualified in AFFF). We found that molecular docking can effectively separate HSA-binding and -nonbinding compounds in AFFF. In-vitro and in-silico approaches described in this study provide replicable, high-throughput workflows for assessing bioaccumulation potentials of diverse PFAS in commercial products.
饮用受含氟表面活性剂水成膜泡沫（AFFF）污染的水是人类接触多氟和全氟烷基物质（PFAS）的一个来源。然而，评估AFFF等商业产品中多种PFAS的生物累积潜力一直不够充分且具有挑战性，尤其是由于缺乏分析标准。在此，我们探索可疑物筛查、平衡透析和分子对接模拟在识别潜在生物累积性PFAS方面的价值。我们使用平衡透析将人血清白蛋白（HSA）蛋白暴露于3M公司1999年生产的一种传统AFFF的稀释液中，并使用高分辨率质谱（HRMS）筛选体外蛋白结合亲和力。通过可疑物筛查，我们在与HSA结合的AFFF中鉴定出32种PFAS和18种烃类表面活性剂。对26种PFAS标准品的非共价缔合常数进行定量分析证实，许多PFAS，包括短链全氟丙烷磺酸（log K = 4.1 ± 0.2 M），与HSA表现出很强的结合亲和力。经过大量溶剂洗涤后，AFFF中至少有五种PFAS（包括三种全氟碳数少于五个的PFAS）仍与沉淀的HSA沉淀结合，这表明PFAS具有很高的结合潜力。通过分析标准品在蛋白沉淀中确认了三种PFAS（PFBS、PFOS和PFOA），并在酸消化后进行了定量分析，该样品部分占样品中每种化合物质量的5%至20%。我们计算了可疑物筛查标记为非共价结合或潜在共价结合的PFAS的伪生物浓缩因子（BCF）。大多数表现出高BCF的PFAS，尤其是那些含有七个全氟碳的PFAS，含有羧酸或磺酸。最后，我们使用分子对接模拟了62种配体（26种PFAS靶标、18种在AFFF中鉴定出的PFAS和18种在AFFF中鉴定出的烃类表面活性剂）与HSA的结合亲和力。我们发现分子对接可以有效地分离AFFF中与HSA结合和不结合的化合物。本研究中描述的体外和计算机模拟方法为评估商业产品中多种PFAS的生物累积潜力提供了可重复的高通量工作流程。
