@article{starnes_green_reif_belcher_2024, title={An in vitro and machine learning framework for quantifying serum albumin binding of per- and polyfluoroalkyl substances}, volume={10}, ISSN={["1096-0929"]}, url={https://doi.org/10.1093/toxsci/kfae124}, DOI={10.1093/toxsci/kfae124}, abstractNote={Abstract Per- and polyfluoroalkyl substances (PFAS) are a diverse class of anthropogenic chemicals; many are persistent, bioaccumulative, and mobile in the environment. Worldwide, PFAS bioaccumulation causes serious adverse health impacts, yet the physiochemical determinants of bioaccumulation and toxicity for most PFAS are not well understood, largely due to experimental data deficiencies. As most PFAS are proteinophilic, protein binding is a critical parameter for predicting PFAS bioaccumulation and toxicity. Among these proteins, human serum albumin (HSA) is the predominant blood transport protein for many PFAS. We previously demonstrated the utility of an in vitro differential scanning fluorimetry assay for determining relative HSA binding affinities for 24 PFAS. Here, we report HSA affinities for 65 structurally diverse PFAS from 20 chemical classes. We leverage these experimental data, and chemical/molecular descriptors of PFAS, to build 7 machine learning classifier algorithms and 9 regression algorithms, and evaluate their performance to identify the best predictive binding models. Evaluation of model accuracy revealed that the top performing classifier model, logistic regression, had an AUROC statistic of 0.936. The top performing regression model, support vector regression, had an R2 of 0.854. These top performing models were then used to predict HSA-PFAS binding for chemicals in the EPAPFASINV list of 430 PFAS. These developed in vitro and in silico methodologies represent a high-throughput framework for predicting protein-PFAS binding based on empirical data, and generate directly comparable binding data of potential use in predictive modeling of PFAS bioaccumulation and other toxicokinetic endpoints.}, journal={TOXICOLOGICAL SCIENCES}, author={Starnes, Hannah M. and Green, Adrian J. and Reif, David M. and Belcher, Scott M.}, year={2024}, month={Oct} }
 @article{starnes_belcher_2024, title={Protocol for evaluating protein-polyfluoroalkyl substances in vitro using differential scanning fluorimetry}, volume={5}, ISSN={["2666-1667"]}, url={https://doi.org/10.1016/j.xpro.2024.103386}, DOI={10.1016/j.xpro.2024.103386}, abstractNote={Per- and polyfluoroalkyl substances (PFAS) are ubiquitous synthetic chemicals that threaten public health, and serum albumin binding of PFAS represents one major variable influencing PFAS toxicokinetics. In this protocol, we describe a differential scanning fluorimetry (DSF) assay suitable for the rapid determination of the relative binding affinities of serum albumin proteins to different PFAS. Herein, we address common experimental challenges related to PFAS solubility constraints, the high background fluorescence of DSF with serum albumins, and the limitations of using DSF-derived dissociation constants (K}, number={4}, journal={STAR PROTOCOLS}, author={Starnes, Hannah M. and Belcher, Scott M.}, year={2024}, month={Dec} }
 @article{starnes_jackson_rock_belcher_2024, title={Quantitative cross-species comparison of serum albumin binding of per- and polyfluoroalkyl substances from five structural classes}, volume={3}, ISSN={["1096-0929"]}, url={https://doi.org/10.1093/toxsci/kfae028}, DOI={10.1093/toxsci/kfae028}, abstractNote={Abstract
               Per- and polyfluoroalkyl substances (PFAS) are a class of over 8000 chemicals, many of which are persistent, bioaccumulative, and toxic to humans, livestock, and wildlife. Serum protein binding affinity is instrumental in understanding PFAS toxicity, yet experimental binding data is limited to only a few PFAS congeners. Previously, we demonstrated the usefulness of a high-throughput, in vitro differential scanning fluorimetry assay for determination of relative binding affinities of human serum albumin for 24 PFAS congeners from 6 chemical classes. In the current study, we used this assay to comparatively examine differences in human, bovine, porcine, and rat serum albumin binding of 8 structurally informative PFAS congeners from 5 chemical classes. With the exception of the fluorotelomer alcohol 1H, 1H, 2H, 2H-perfluorooctanol (6:2 FTOH), each PFAS congener bound by human serum albumin was also bound by bovine, porcine, and rat serum albumin. The critical role of the charged functional headgroup in albumin binding was supported by the inability of albumin of each species tested to bind 6:2 FTOH. Significant interspecies differences in serum albumin binding affinities were identified for each of the bound PFAS congeners. Relative to human albumin, perfluoroalkyl carboxylic and sulfonic acids were bound with greater affinity by porcine and rat serum albumin, and the perfluoroalkyl ether acid congener bound with lower affinity to porcine and bovine serum albumin. These comparative affinity data for PFAS binding by serum albumin from human, experimental model, and livestock species reduce critical interspecies uncertainty and improve accuracy of predictive bioaccumulation and toxicity assessments for PFAS.}, journal={TOXICOLOGICAL SCIENCES}, author={Starnes, Hannah M. and Jackson, Thomas W. and Rock, Kylie D. and Belcher, Scott M.}, year={2024}, month={Mar} }
 @article{rock_polera_guillette_starnes_dean_watters_stevens-stewart_belcher_2023, title={Domestic Dogs and Horses as Sentinels of Per- and Polyfluoroalkyl Substance Exposure and Associated Health Biomarkers in Gray's Creek North Carolina}, volume={57}, ISSN={["1520-5851"]}, url={https://doi.org/10.1021/acs.est.3c01146}, DOI={10.1021/acs.est.3c01146}, abstractNote={Central North Carolina (NC) is highly contaminated with per- and polyfluoroalkyl substances (PFAS), in part due to local fluorochemical production. Little is known about the exposure profiles and long-term health impacts for humans and animals that live in nearby communities. In this study, serum PFAS concentrations were determined using liquid chromatography high-resolution mass spectrometry and diagnostic clinical chemistry endpoints were assessed for 31 dogs and 32 horses that reside in Gray's Creek NC at households with documented PFAS contamination in their drinking water. PFAS were detected in every sample, with 12 of the 20 PFAS detected in ≥50% of samples from each species. The average total PFAS concentrations in horses were lower compared to dogs who had higher concentrations of PFOS (dogs 2.9 ng/mL; horses 1.8 ng/mL), PFHxS (dogs 1.43 ng/mL, horses < LOD), and PFOA (dogs 0.37 ng/mL; horses 0.10 ng/mL). Regression analysis highlighted alkaline phosphatase, glucose, and globulin proteins in dogs and gamma glutamyl transferase in horses as potential biomarkers associated with PFAS exposure. Overall, the results of this study support the utility of companion animal and livestock species as sentinels of PFAS exposure differences inside and outside of the home. As in humans, renal and hepatic health in domestic animals may be sensitive to long-term PFAS exposures.}, number={26}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, author={Rock, Kylie D. and Polera, Madison E. and Guillette, Theresa C. and Starnes, Hannah M. and Dean, Kentley and Watters, Mike and Stevens-Stewart, Debra and Belcher, Scott M.}, year={2023}, month={Jun}, pages={9567–9579} }