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P37—Aerobic soil biotransformation of fluorotelomer alcohols
14
Abstracts / Reproductive Toxicology 33 (2012) 1–29
of the parent. Formation of the glutathione conjugate was by far the most significant metabolic pathway in all three species. Another important metabolic pathway resulted in the formation of 6-2 aldehyde (AL) leading sequentially to 6-2 unsaturated aldehyde (UAL), 5-3 UAL, 5-3 unsaturated acid, and 5-3 acid (A). The 6-2 AL also led to production of 6-2 A, 5-3 beta-keto aldehyde, perfluorohexanoic acid, and perfluoropentanoic acid. The metabolic pathways were qualitatively similar between rat, mouse, and human hepatocytes, however, there were differences in metabolic flux leading to differences in the relative amounts of metabolites produced by each species. The observed pathways are similar to those observed following dosing with the structurally similar 8-2 FTOH (C8 F15 CH2 CH2 OH) and preliminary rate calculations indicate that 6-2 FTOH has a similar intrinsic clearance in hepatocytes.
interactions, though without thoughtfully interpreting the results. To improve the fluorescence method, we have developed a novel model for measuring the strength of PFAA binding to human serum albumin (HSA) using changes in the protein’s native fluorescence resulting from conformational changes in the protein. The model has been used to qualitatively and quantitatively characterize the binding of several medium- and long-chain PFAAs to HSA. Results indicate at least 2–3 PFAAs bind to each protein with affinity on the order of 104 M−1 . Binding strengths demonstrate dependence upon perfluorocarbon chain length, ionic head group, and protein concentration. The model is not valid for the binding of short-chain PFAAs to HSA. Results suggest short-chain PFAAs associate with HSA differently than medium- and long-chain PFAAs, such that they fail to promote the same conformational changes in the protein’s tertiary structure.
doi:10.1016/j.reprotox.2011.11.068 doi:10.1016/j.reprotox.2011.11.070 P35—Using on-site bioreactors to determine the fate of N-ethyl perfluorooctane sulfonamidoethanol (N-EtFOSE) at a wastewater treatment plant Kurt R. Rhoads ∗ ,
Katherine H. Rostkowski, Peter K. Kitanidis, Craig
S. Criddle Department of Civil and Environmental Engineering, Stanford University, Stanford, CA, United States On-site rates for aerobic biotransformation of N-ethyl perfluorooctane sulfonamidoethanol (N-EtFOSE), a fluorinated repellent and precursor of perflurooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA), were determined by continuously pumping mixed liquor from an aeration basin into two well-mixed acrylic bioreactors (4 L) operated in parallel. Known masses of N-EtFOSE and bromide were continuously added to the reactors. Reactor effluents were then monitored for bromide, N-EtFOSE, and metabolites of N-EtFOSE. Of the six transformation products reported in batch studies, only N-ethyl perfluorooctane sulfonamido acetate (N-EtFOSAA) was detected in the effluents. Bromide addition to the reactors enabled rate estimates despite variations in flowrate. Pseudo-second order rate coefficients for the N-EtFOSE biotransformation to N-EtFOSAA, predicted using a dynamic model of the reactor system, were k = 2.6 and 2.7 L/g VSS day−1 for the two reactors, in agreement with values measured in batch incubations using undiluted activated sludge from the same source. The relatively slow rates of biotransformation indicate that the majority of NEtFOSE entering a wastewater treatment plant will be volatilized or sorbed to waste solids and not be biotransformed to PFOS. doi:10.1016/j.reprotox.2011.11.069 P36—A novel fluorescence model for studying the binding of medium- to long-chain perfluoroalkyl acids to human serum albumin Paul C. Hebert ∗ , Laura A. MacManus-Spencer Department of Chemistry, Union College, Schenectady, NY, United States Perfluoroalkyl acids (PFAAs) are contaminants of emerging environmental concern recognized as both bioaccumulative and toxic. Binding to proteins is one proposed explanation for the preferential accumulation of PFAAs in the liver, the kidneys, and the blood. Characterization of PFAA binding to serum albumin – the most abundant protein in human blood – has been attempted with many techniques, though results vary widely. Recent studies have demonstrated the use of fluorescence spectroscopy to monitor albumin’s tryptophan emission for analyses of PFC–albumin
P37—Aerobic soil biotransformation of fluorotelomer alcohols N. Wang 1,∗ , J. Liu 2 , R.C. Buck 1 , Patrick W. Folsom 1 , L.M. Sulecki 1 , Barry Wolstenholme 1 , P.K. Panciroli 1 , C.A. Bellin 1 1
E.I. du Pont De Nemours & Co., Inc, Newark, DE, United States Chesapeake Biological Laboratory, University of Maryland Center for Environmental Science, Solomons, MD, United States 2
Fluorotelomer alcohols (FTOHs, F(CF2 )n CH2 CH2 OH,) are a raw material used in the manufacture of fluorotelomer-based products. 8:2 FTOH (C8 F17 CH2 CH2 OH) biotransformation has been extensively studied in activated sludge, soils, sediments and landfills. A shorter chain length homolog, 6:2 FTOH (C6 F13 CH2 CH2 OH) and a longer chain 10:2 FTOH are also raw materials used to manufacture fluorotelomer-based products. The similarities and differences of 6:2 FTOH, 8:2 FTOH and 10:2 FTOH aerobic biodegradation pathways in closed and flow-through test systems will be presented. doi:10.1016/j.reprotox.2011.11.071 P38—Noncovalent interactions of long-chain perfluoroalkyl acids with serum albumin Heather N. Bischel 1,∗ , Laura A. MacManus-Spencer 2 , Richard G. Luthy 1,∗ 1 Department of Civil and Environmental Engineering, Stanford University, Stanford, CA, United States 2 Department of Chemistry, Union College, Schenectady, NY, United States
Preferential distribution of long-chain perfluoroalkyl acids (PFAAs) in the liver, kidney and blood of organisms highlights the importance of PFAA–protein interactions in PFAA tissue distribution patterns. A serum protein association constant may be a useful parameter to characterize the bioaccumulative potential and in vivo bioavailability of PFAAs. In this work, association constants (Ka ) and binding stoichiometries for PFAA–albumin complexes are quantified over a wide range of PFAA:albumin mole ratios. Primary association constants for perfluorooctanoate (PFOA) or perfluorononanoate (PFNA) with the model protein bovine serum albumin (BSA) determined via equilibrium dialysis are on the order of 106 M−1 with one to three primary binding sites. PFNA was greater than 99.9% bound to BSA or human serum albumin (HSA) at a physiological PFAA:albumin mole ratio (<10−3 ), corresponding to a high protein–water distribution coefficient (log KPW > 4). Nanoelectrospray ionization mass spectrometry (nanoESI-MS) data reveal PFAA–BSA complexes with up to eight occupied binding sites at a 4:1 PFAA:albumin mole ratio. Association constants estimated by
Abstracts / Reproductive Toxicology 33 (2012) 1–29
of the parent. Formation of the glutathione conjugate was by far the most significant metabolic pathway in all three species. Another important metabolic pathway resulted in the formation of 6-2 aldehyde (AL) leading sequentially to 6-2 unsaturated aldehyde (UAL), 5-3 UAL, 5-3 unsaturated acid, and 5-3 acid (A). The 6-2 AL also led to production of 6-2 A, 5-3 beta-keto aldehyde, perfluorohexanoic acid, and perfluoropentanoic acid. The metabolic pathways were qualitatively similar between rat, mouse, and human hepatocytes, however, there were differences in metabolic flux leading to differences in the relative amounts of metabolites produced by each species. The observed pathways are similar to those observed following dosing with the structurally similar 8-2 FTOH (C8 F15 CH2 CH2 OH) and preliminary rate calculations indicate that 6-2 FTOH has a similar intrinsic clearance in hepatocytes.
interactions, though without thoughtfully interpreting the results. To improve the fluorescence method, we have developed a novel model for measuring the strength of PFAA binding to human serum albumin (HSA) using changes in the protein’s native fluorescence resulting from conformational changes in the protein. The model has been used to qualitatively and quantitatively characterize the binding of several medium- and long-chain PFAAs to HSA. Results indicate at least 2–3 PFAAs bind to each protein with affinity on the order of 104 M−1 . Binding strengths demonstrate dependence upon perfluorocarbon chain length, ionic head group, and protein concentration. The model is not valid for the binding of short-chain PFAAs to HSA. Results suggest short-chain PFAAs associate with HSA differently than medium- and long-chain PFAAs, such that they fail to promote the same conformational changes in the protein’s tertiary structure.
doi:10.1016/j.reprotox.2011.11.068 doi:10.1016/j.reprotox.2011.11.070 P35—Using on-site bioreactors to determine the fate of N-ethyl perfluorooctane sulfonamidoethanol (N-EtFOSE) at a wastewater treatment plant Kurt R. Rhoads ∗ ,
Katherine H. Rostkowski, Peter K. Kitanidis, Craig
S. Criddle Department of Civil and Environmental Engineering, Stanford University, Stanford, CA, United States On-site rates for aerobic biotransformation of N-ethyl perfluorooctane sulfonamidoethanol (N-EtFOSE), a fluorinated repellent and precursor of perflurooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA), were determined by continuously pumping mixed liquor from an aeration basin into two well-mixed acrylic bioreactors (4 L) operated in parallel. Known masses of N-EtFOSE and bromide were continuously added to the reactors. Reactor effluents were then monitored for bromide, N-EtFOSE, and metabolites of N-EtFOSE. Of the six transformation products reported in batch studies, only N-ethyl perfluorooctane sulfonamido acetate (N-EtFOSAA) was detected in the effluents. Bromide addition to the reactors enabled rate estimates despite variations in flowrate. Pseudo-second order rate coefficients for the N-EtFOSE biotransformation to N-EtFOSAA, predicted using a dynamic model of the reactor system, were k = 2.6 and 2.7 L/g VSS day−1 for the two reactors, in agreement with values measured in batch incubations using undiluted activated sludge from the same source. The relatively slow rates of biotransformation indicate that the majority of NEtFOSE entering a wastewater treatment plant will be volatilized or sorbed to waste solids and not be biotransformed to PFOS. doi:10.1016/j.reprotox.2011.11.069 P36—A novel fluorescence model for studying the binding of medium- to long-chain perfluoroalkyl acids to human serum albumin Paul C. Hebert ∗ , Laura A. MacManus-Spencer Department of Chemistry, Union College, Schenectady, NY, United States Perfluoroalkyl acids (PFAAs) are contaminants of emerging environmental concern recognized as both bioaccumulative and toxic. Binding to proteins is one proposed explanation for the preferential accumulation of PFAAs in the liver, the kidneys, and the blood. Characterization of PFAA binding to serum albumin – the most abundant protein in human blood – has been attempted with many techniques, though results vary widely. Recent studies have demonstrated the use of fluorescence spectroscopy to monitor albumin’s tryptophan emission for analyses of PFC–albumin
P37—Aerobic soil biotransformation of fluorotelomer alcohols N. Wang 1,∗ , J. Liu 2 , R.C. Buck 1 , Patrick W. Folsom 1 , L.M. Sulecki 1 , Barry Wolstenholme 1 , P.K. Panciroli 1 , C.A. Bellin 1 1
E.I. du Pont De Nemours & Co., Inc, Newark, DE, United States Chesapeake Biological Laboratory, University of Maryland Center for Environmental Science, Solomons, MD, United States 2
Fluorotelomer alcohols (FTOHs, F(CF2 )n CH2 CH2 OH,) are a raw material used in the manufacture of fluorotelomer-based products. 8:2 FTOH (C8 F17 CH2 CH2 OH) biotransformation has been extensively studied in activated sludge, soils, sediments and landfills. A shorter chain length homolog, 6:2 FTOH (C6 F13 CH2 CH2 OH) and a longer chain 10:2 FTOH are also raw materials used to manufacture fluorotelomer-based products. The similarities and differences of 6:2 FTOH, 8:2 FTOH and 10:2 FTOH aerobic biodegradation pathways in closed and flow-through test systems will be presented. doi:10.1016/j.reprotox.2011.11.071 P38—Noncovalent interactions of long-chain perfluoroalkyl acids with serum albumin Heather N. Bischel 1,∗ , Laura A. MacManus-Spencer 2 , Richard G. Luthy 1,∗ 1 Department of Civil and Environmental Engineering, Stanford University, Stanford, CA, United States 2 Department of Chemistry, Union College, Schenectady, NY, United States
Preferential distribution of long-chain perfluoroalkyl acids (PFAAs) in the liver, kidney and blood of organisms highlights the importance of PFAA–protein interactions in PFAA tissue distribution patterns. A serum protein association constant may be a useful parameter to characterize the bioaccumulative potential and in vivo bioavailability of PFAAs. In this work, association constants (Ka ) and binding stoichiometries for PFAA–albumin complexes are quantified over a wide range of PFAA:albumin mole ratios. Primary association constants for perfluorooctanoate (PFOA) or perfluorononanoate (PFNA) with the model protein bovine serum albumin (BSA) determined via equilibrium dialysis are on the order of 106 M−1 with one to three primary binding sites. PFNA was greater than 99.9% bound to BSA or human serum albumin (HSA) at a physiological PFAA:albumin mole ratio (<10−3 ), corresponding to a high protein–water distribution coefficient (log KPW > 4). Nanoelectrospray ionization mass spectrometry (nanoESI-MS) data reveal PFAA–BSA complexes with up to eight occupied binding sites at a 4:1 PFAA:albumin mole ratio. Association constants estimated by