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Droge STJ, Hodges G, Bonnell M, Gutsell S, Roberts J, Teixeira A, Barrett EL. Using membrane-water partition coefficients in a critical membrane burden approach to aid the identification of neutral and ionizable chemicals that induce acute toxicity below narcosis levels. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2023; 25:621-647. [PMID: 36779707 DOI: 10.1039/d2em00391k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
The risk assessment of thousands of chemicals used in our society benefits from adequate grouping of chemicals based on the mode and mechanism of toxic action (MoA). We measure the phospholipid membrane-water distribution ratio (DMLW) using a chromatographic assay (IAM-HPLC) for 121 neutral and ionized organic chemicals and screen other methods to derive DMLW. We use IAM-HPLC based DMLW as a chemical property to distinguish between baseline narcosis and specific MoA, for reported acute toxicity endpoints on two separate sets of chemicals. The first set comprised 94 chemicals of US EPA's acute fish toxicity database: 47 categorized as narcosis MoA, 27 with specific MoA, and 20 predominantly ionic chemicals with mostly unknown MoA. The narcosis MoA chemicals clustered around the median narcosis critical membrane burden (CMBnarc) of 140 mmol kg-1 lipid, with a lower limit of 14 mmol kg-1 lipid, including all chemicals labelled Narcosis_I and Narcosis_II. This maximum 'toxic ratio' (TR) between CMBnarc and the lower limit narcosis endpoint is thus 10. For 23/28 specific MoA chemicals a TR >10 was derived, indicative of a specific adverse effect pathway related to acute toxicity. For 10/12 cations categorized as "unsure amines", the TR <10 suggests that these affect fish via narcosis MoA. The second set comprised 29 herbicides, including 17 dissociated acids, and evaluated the TR for acute toxic effect concentrations to likely sensitive aquatic plant species (green algae and macrophytes Lemna and Myriophyllum), and non-target animal species (invertebrates and fish). For 21/29 herbicides, a TR >10 indicated a specific toxic mode of action other than narcosis for at least one of these aquatic primary producers. Fish and invertebrate TRs were mostly <10, particularly for neutral herbicides, but for acidic herbicides a TR >10 indicated specific adverse effects in non-target animals. The established critical membrane approach to derive the TR provides for useful contribution to the weight of evidence to bin a chemical as having a narcosis MoA or less likely to have acute toxicity caused by a more specific adverse effect pathway. After proper calibration, the chromatographic assay provides consistent and efficient experimental input for both neutral and ionizable chemicals to this approach.
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Affiliation(s)
- Steven T J Droge
- Department of Freshwater and Marine Ecology (FAME), Institute for Biodiversity and Ecosystem Dynamics (IBED), Universiteit van Amsterdam (UvA), Science Park 904, 1098XH Amsterdam, The Netherlands.
| | - Geoff Hodges
- Safety and Environmental Assurance Centre, Unilever, Colworth Science Park, Sharnbrook, Bedfordshire, UK
| | - Mark Bonnell
- Environment and Climate Change Canada, Ecological Assessment Division, Science and Risk Assessment Directorate, Gatineau, Quebec, Canada
| | - Steve Gutsell
- Safety and Environmental Assurance Centre, Unilever, Colworth Science Park, Sharnbrook, Bedfordshire, UK
| | - Jayne Roberts
- Safety and Environmental Assurance Centre, Unilever, Colworth Science Park, Sharnbrook, Bedfordshire, UK
| | - Alexandre Teixeira
- Safety and Environmental Assurance Centre, Unilever, Colworth Science Park, Sharnbrook, Bedfordshire, UK
| | - Elin L Barrett
- Safety and Environmental Assurance Centre, Unilever, Colworth Science Park, Sharnbrook, Bedfordshire, UK
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Droge STJ, Scherpenisse P, Arnot JA, Armitage JM, McLachlan MS, Ohe PCVD, Hodges G. Screening the baseline fish bioconcentration factor of various types of surfactants using phospholipid binding data. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2021; 23:1930-1948. [PMID: 34787154 DOI: 10.1039/d1em00327e] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Fish bioconcentration factors (BCFs) are commonly used in chemical hazard and risk assessment. For neutral organic chemicals BCFs are positively correlated with the octanol-water partition ratio (KOW), but KOW is not a reliable parameter for surfactants. Membrane lipid-water distribution ratios (DMLW) can be accurately measured for all kinds of surfactants, using phospholipid-based sorbents. This study first demonstrates that DMLW values for ionic surfactants are more than 100 000 times higher than the partition ratio to fish-oil, representing neutral storage lipid. A non-ionic alcohol ethoxylate surfactant showed almost equal affinity for both lipid types. Accordingly, a baseline screening BCF value for surfactants (BCFbaseline) can be approximated for ionic surfactants by multiplying DMLW by the phospholipid fraction in tissue, and for non-ionic surfactants by multiplying DMLW by the total lipid fraction. We measured DMLW values for surfactant structures, including linear and branched alkylbenzenesulfonates, an alkylsulfoacetate and an alkylethersulfate, bis(2-ethylhexyl)-surfactants (e.g., docusate), zwitterionic alkylbetaines and alkylamine-oxides, and a polyprotic diamine. Together with sixty previously published DMLW values for surfactants, structure-activity relationships were derived to elucidate the influence of surfactant specific molecular features on DMLW. For 23 surfactant types, we established the alkyl chain length at which BCFbaseline would exceed the EU REACH bioaccumulation (B) threshold of 2000 L kg-1, and would therefore require higher tier assessments to further refine the BCF estimate. Finally, the derived BCFbaseline are compared with measured literature in vivo BCF data where available, suggesting that refinements, most notably reliable estimates of biotransformation rates, are needed for most surfactant types.
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Affiliation(s)
- Steven T J Droge
- Institute for Biodiversity and Ecosystem Dynamics, Department Freshwater and Marine Ecology, University of Amsterdam, The Netherlands.
| | - Peter Scherpenisse
- Institute for Risk Assessment Sciences, Utrecht University, The Netherlands
| | - Jon A Arnot
- ARC Arnot Research and Consulting, Toronto, Ontario, Canada
| | | | | | | | - Geoff Hodges
- Safety and Environmental Assurance Centre, Unilever, Colworth Science Park, Sharnbrook, Bedfordshire, UK
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Ross EE, Hoag B, Joslin I, Johnston T. Measurements of Ion Binding to Lipid-Hosted Ionophores by Affinity Chromatography. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:9410-9421. [PMID: 31282163 DOI: 10.1021/acs.langmuir.9b01301] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The binding affinity between antibiotic ionophores and alkali ions within supported lipid bilayers was evaluated using affinity chromatography. We used zonal elution and frontal analysis methods in nanovolume liquid chromatography to characterize the binding selectivity of the carrier and channel ionophores valinomycin and gramicidin A within different phosphatidylcholine bilayers. Distinct binding sensitivity to the lipid phase, both in affinity and selectivity, is observed for valinomycin, whereas gramicidin is less sensitive to changes in a membrane environment, behavior that is consistent with ion binding occurring within the interior of an established channel. There is good agreement between the chromatographic retention and the reported binding selectivity measured by other techniques. Surface potential near the binding site affects ion retention and the apparent association binding constants, but not the binding selectivity or enthalpy measurements. A model accounting for the surface potential contributions of retained ions during frontal analyses yields values close to intrinsic binding constants for gramicidin A (KA for K+ between 70 and 120 M-1) using reasonable estimates of the initial potential that is postulated to arise from the underlying silica.
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Affiliation(s)
- Eric E Ross
- Department of Chemistry & Biochemistry , Gonzaga University , Spokane , Washington 99258 , United States
| | - Bridget Hoag
- Department of Chemistry & Biochemistry , Gonzaga University , Spokane , Washington 99258 , United States
| | - Ian Joslin
- Department of Chemistry & Biochemistry , Gonzaga University , Spokane , Washington 99258 , United States
| | - Taylor Johnston
- Department of Chemistry & Biochemistry , Gonzaga University , Spokane , Washington 99258 , United States
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Droge STJ. Membrane-Water Partition Coefficients to Aid Risk Assessment of Perfluoroalkyl Anions and Alkyl Sulfates. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:760-770. [PMID: 30572703 DOI: 10.1021/acs.est.8b05052] [Citation(s) in RCA: 54] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
This study determined the sorption affinity to artificial phospholipid membranes ( KMW) for series of perfluorinated carboxylates (PFCAs), perfluorinated sulfonates (PFSAs), alkyl sulfates (C xSO4), and 1-alkanesulfonates (C xSO3). A sorbent dilution assay with solid supported lipid membranes (SSLM) showed consistent CF2 unit increments of 0.59, and CH2 unit increments of 0.53, for the log KMW of perfluorinated and hydrogenated anions, respectively. PFSAs sorbed 0.90 log units stronger than analogue PFCAs; C xSO4 sorbed 0.75 log units stronger than analogue C xSO3 anions. The log KMW values for the octyl analogues increase in the order H(CH2)8SO3- (1.74) < H(CH2)8SO4- (2.58) < F(CF2)8CO2- (PFNA, 4.04) < F(CF2)8SO3- (PFOS, 4.88). Intrinsic partition ratios determined on a phospholipid coated HPLC column (IAM-HPLC) closely aligned with SSLM KMW values. COSMO-RS based molecular calculations of KMW aligned with SSLM KMW values for hydrogenated anions with C8-C14 alkyl chains but strongly underestimated CF2 and CH2 unit increments for C4-C8 based anions. Dividing the critical narcotic membrane burden of 100 mmol/kg by the experimental KMW predicts lethal baseline toxicity concentrations (LC50,narc). The LC50,narc coincides with the lowest reported acute LC50 values for several anionic surfactants but were on average about an order of magnitude lower.
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Affiliation(s)
- Steven T J Droge
- Department of Freshwater and Marine Ecology (FAME), Institute for Biodiversity and Ecosystem Dynamics (IBED) , Universiteit van Amsterdam (UvA) , Science Park 904 , 1098XH Amsterdam , Netherlands
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pH-dependent surface electrostatic effects in retention on immobilized artificial membrane chromatography: Determination of the intrinsic phospholipid-water sorption coefficients of diverse analytes. J Chromatogr A 2018; 1570:172-182. [DOI: 10.1016/j.chroma.2018.07.081] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Revised: 07/24/2018] [Accepted: 07/28/2018] [Indexed: 11/18/2022]
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Metzelder F, Schmidt TC. Environmental Conditions Influencing Sorption of Inorganic Anions to Multiwalled Carbon Nanotubes Studied by Column Chromatography. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:4928-4935. [PMID: 28383258 DOI: 10.1021/acs.est.6b06386] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Sorption to carbon-based nanomaterials is typically studied in batch experiments. An alternative method offering advantages to study sorption is column chromatography. Sorbent packed columns are used and sorption data are determined by relating sorbate retention to that of a nonretarded tracer. We have now for the first time applied this technique to study the influence of environmental conditions on sorption of inorganic anions (bromide, nitrite, nitrate, and iodide) to multiwalled carbon nanotubes. Deuterium oxide was used as nonretarded tracer. Sorption isotherms were best described by the Freundlich model. Sorption increased in the order bromide < nitrite < nitrate < iodide. Increasing ionic strength from 1 mM to 100 mM sodium chloride significantly reduced or completely suppressed sorption (bromide, nitrite) due to competition with chloride. pH strongly affected sorption as negatively charged analytes were attracted by the positively charged surface at pH 3. At pH > 4.5 the surface charge was negative, but sorption was still detectable at pH 6 and 9. Consequently, other forces than electrostatic attraction contributed to sorption. These forces may include H-bonding as indicated by sorption enthalpy determined by variation of column temperature. Overall, column chromatography represents a promising alternative in sorption studies to reveal sorbent properties.
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Affiliation(s)
- Florian Metzelder
- Instrumental Analytical Chemistry, University of Duisburg-Essen , Universitätsstrasse 5, 45141 Essen, Germany
| | - Torsten C Schmidt
- Instrumental Analytical Chemistry, University of Duisburg-Essen , Universitätsstrasse 5, 45141 Essen, Germany
- Centre for Water and Environmental Research (ZWU), University of Duisburg-Essen , Universitätsstrasse 2, 45141 Essen, Germany
- IWW Water Centre, Moritzstraße 26, 45476 Mülheim an der Ruhr, Germany
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Droge STJ, Hermens JLM, Gutsell S, Rabone J, Hodges G. Predicting the phospholipophilicity of monoprotic positively charged amines. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2017; 19:307-323. [PMID: 28218330 DOI: 10.1039/c6em00615a] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The sorption affinity of eighty-six charged amine structures to phospholipid monolayers (log KIAM) was determined using immobilized artificial membrane high-performance liquid chromatography (IAM-HPLC). The amine compounds covered the most prevalent types of polar groups, widely ranged in structural complexity, and included forty-seven pharmaceuticals, as well as several narcotics and pesticides. Amine type specific corrective increments were used to align log KIAM data with bilayer membrane sorption coefficients (KMW(IAM)). Using predicted sorption affinities of neutral amines, we evaluated the difference (scaling factor ΔMW) with the measured log KMW(IAM) for cationic amines. The ΔMW values were highly variable, ranging from -2.37 to +2.3 log units. For each amine type, polar amines showed lower ΔMW values than hydrocarbon based amines (CxHyN+). COSMOmic software was used to directly calculate the partitioning coefficient of ionic structures into a phospholipid bilayer (KDMPC-W,cation), including quaternary ammonium compounds. The resulting root mean square error (RMSE) between log KDMPC-W,cation and log KMW(IAM) was 0.83 for all eighty-six polar amines, and 0.47 for sixty-eight CxHyN+ amines. The polar amines were then split into five groups depending on polarity and structural complexity, and corrective increments for each group were defined to improve COSMOmic predictions. Excluding only the group with sixteen complex amine structures (≥4 polar groups, Mw > 400, including several macrolide antibiotics), the resulting RMSE for corrected KDMPC-W,cation values improved to 0.45 log units for the remaining set of 138 polar and CxHyN+ amines.
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Affiliation(s)
- S T J Droge
- Institute for Risk Assessment Sciences, Utrecht University, Yalelaan 104, 3508 TD Utrecht, The Netherlands
| | - J L M Hermens
- Institute for Risk Assessment Sciences, Utrecht University, Yalelaan 104, 3508 TD Utrecht, The Netherlands
| | - S Gutsell
- Safety and Environmental Assurance Centre, Unilever, Sharnbrook, Bedford, UK
| | - J Rabone
- Safety and Environmental Assurance Centre, Unilever, Sharnbrook, Bedford, UK
| | - G Hodges
- Safety and Environmental Assurance Centre, Unilever, Sharnbrook, Bedford, UK
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Timmer N, Droge STJ. Sorption of Cationic Surfactants to Artificial Cell Membranes: Comparing Phospholipid Bilayers with Monolayer Coatings and Molecular Simulations. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:2890-2898. [PMID: 28187261 PMCID: PMC5343551 DOI: 10.1021/acs.est.6b05662] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
This study reports the distribution coefficient between phospholipid bilayer membranes and phosphate buffered saline (PBS) medium (DMW,PBS) for 19 cationic surfactants. The method used a sorbent dilution series with solid supported lipid membranes (SSLMs). The existing SSLM protocol, applying a 96 well plate setup, was adapted to use 1.5 mL glass autosampler vials instead, which facilitated sampling and circumvented several confounding loss processes for some of the cationic surfactants. About 1% of the phospholipids were found to be detached from the SSLM beads, resulting in nonlinear sorption isotherms for compounds with log DMW values above 4. Renewal of the medium resulted in linear sorption isotherms. DMW values determined at pH 5.4 demonstrated that cationic surfactant species account for the observed DMW,PBS. Log DMW,PBS values above 5.5 are only experimentally feasible with lower LC-MS/MS detection limits and/or concentrated extracts of the aqueous samples. Based on the number of carbon atoms, dialkylamines showed a considerably lower sorption affinity than linear alkylamine analogues. These SSLM results closely overlapped with measurements on a chromatographic tool based on immobilized artificial membranes (IAM-HPLC) and with quantum-chemistry based calculations with COSMOmic. The SSLM data suggest that IAM-HPLC underestimates the DMW of ionized primary and secondary alkylamines by 0.8 and 0.5 log units, respectively.
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Droge STJ, Hermens JLM, Rabone J, Gutsell S, Hodges G. Phospholipophilicity of CxHyN(+) amines: chromatographic descriptors and molecular simulations for understanding partitioning into membranes. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2016; 18:1011-23. [PMID: 27118065 DOI: 10.1039/c6em00118a] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Using immobilized artificial membrane high-performance liquid chromatography (IAM-HPLC) the sorption affinity of 70 charged amine structures to phospholipids was determined. The amines contained only 1 charged moiety and no other polar groups, the rest of the molecule being aliphatic and/or aromatic hydrocarbon groups. We systematically evaluated the influence of the amine type (1°, 2°, 3° amines and quaternary ammonium), alkyl chain branching, phenyl ring positioning, charge positioning (terminal vs. central in the molecule) on the phospholipid-water partitioning coefficient (KPLIPW). These experimental results were compared with quantum-chemistry based three-dimensional (3D) molecular simulations of the partitioning of charged amines, including the most likely solute conformers, using a hydrated phospholipid bilayer in the COSMOmic module of COSMOtherm software. Both IAM-HPLC retention data and the simulations suggest that the molecular orientation of charged amines at the location in the bilayer with the lowest calculated Gibbs free energy exerts a strong influence over the partitioning within the membrane. The most favourable position of charged amines coincides with the region where the phosphate anions in the phospholipid bilayer are most abundant. Hydrocarbon units oriented in this layer are located more towards the aqueous phase and contribute less to the overall membrane affinity than hydrocarbon units extending into the more hydrophobic core of the bilayer. COSMOmic simulations explain most of the trends between the structural differences observed in IAM-HPLC based KPLIPW. For this set of cationic structures, the mean absolute difference between COSMOmic simulations and IAM-HPLC data, accounting only for amine type corrective increments, is 0.31 log units.
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Affiliation(s)
- S T J Droge
- Institute for Risk Assessment Sciences, Utrecht University, Yalelaan 104, 3508 TD Utrecht, The Netherlands.
| | - J L M Hermens
- Institute for Risk Assessment Sciences, Utrecht University, Yalelaan 104, 3508 TD Utrecht, The Netherlands.
| | - J Rabone
- Safety and Environmental Assurance Centre, Unilever, Sharnbrook, Bedford, UK
| | - S Gutsell
- Safety and Environmental Assurance Centre, Unilever, Sharnbrook, Bedford, UK
| | - G Hodges
- Safety and Environmental Assurance Centre, Unilever, Sharnbrook, Bedford, UK
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