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Predicting Critical Micelle Concentrations with Molecular Dynamics Simulations and COSMOmic. CHEM-ING-TECH 2017. [DOI: 10.1002/cite.201700061] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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52
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Bittermann K, Goss KU. Assessing the toxicity of ionic liquids - Application of the critical membrane concentration approach. CHEMOSPHERE 2017; 183:410-418. [PMID: 28554025 DOI: 10.1016/j.chemosphere.2017.05.097] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Revised: 05/13/2017] [Accepted: 05/15/2017] [Indexed: 06/07/2023]
Abstract
Charged organic chemicals are a prevailing challenge for toxicity modelling. In this contribution we strive to recapitulate the lessons learned from the well-known modelling of narcosis (or baseline toxicity) of neutral chemicals and apply the concept to charged chemicals. First we reevaluate the organism- and chemical independent critical membrane concentration causing 50% mortality,.cmemtox, based on a critical revision of a previously published toxicity dataset for neutral chemicals. In accordance to values reported in the literature we find a mean value for cmemtox of roughly 100 mmol/kg (membrane lipid) for a broad variety of 42 aquatic organisms (333 different chemicals), albeit with a considerable scatter. Then we apply this concept to permanently charged ionic liquids (ILs). Using COSMOmic, a quantum mechanically based mechanistic model that makes use of the COSMO-RS theory, we predict membrane-water partition coefficients (Kmem/w) of the anionic and cationic IL components. Doing so, cmemtox(total) for permanently charged ILs can be estimated assuming independent, concentration additive contributions of the cationic and its respective anionic species. The resulting values for some of the toxicity data for ionic liquids are consistent with the expected range for baseline toxicity for neutral chemicals while other values are consistently greater or smaller. Based on the calculation of toxic ratios we identify ILs that exert a specific mode of toxic action. Limitations of the modelling approach especially but not exclusively due to the use of nominal concentrations instead of freely-dissolved concentrations in the published literature are critically discussed.
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Affiliation(s)
- Kai Bittermann
- UFZ - Helmholtz Centre for Environmental Research, Permoserstr. 15, D-04318 Leipzig, Germany.
| | - Kai-Uwe Goss
- UFZ - Helmholtz Centre for Environmental Research, Permoserstr. 15, D-04318 Leipzig, Germany; University of Halle-Wittenberg, Institute of Chemistry, Kurt Mothes Str. 2, D-06120 Halle, Germany.
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53
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Dołżonek J, Cho CW, Stepnowski P, Markiewicz M, Thöming J, Stolte S. Membrane partitioning of ionic liquid cations, anions and ion pairs - Estimating the bioconcentration potential of organic ions. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2017; 228:378-389. [PMID: 28554027 DOI: 10.1016/j.envpol.2017.04.079] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Revised: 04/25/2017] [Accepted: 04/26/2017] [Indexed: 05/26/2023]
Abstract
Recent efforts have been directed towards better understanding the persistency and toxicity of ionic liquids (ILs) in the context of the "benign-by-design" approach, but the assessment of their bioaccumulation potential remains neglected. This paper reports the experimental membrane partitioning of IL cations (imidazolium, pyridinium, pyrrolidinium, phosphonium), anions ([C(CN)3]-, [B(CN)4]-, [FSO2)2N]-, [(C2F5)3PF3]-, [(CF3SO2)2N]-) and their combinations as a measure for estimating the bioconcentration factor (BCF). Both cations and anions can have a strong affinity for phosphatidylcholine bilayers, which is mainly driven by the hydrophobicity of the ions. This affinity is often reflected in the ecotoxicological impact. Our data revealed that the bioconcentration potential of IL cations and anions is much higher than expected from octanol-water-partitioning based estimations that have recently been presented. For some ILs, the membrane-water partition coefficient reached levels corresponding to BCFs that might become relevant in terms of the "B" (bioaccumulation potential) classification under REACH. However, this preliminary estimation need to be confirmed by in vivo bioconcentration studies.
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Affiliation(s)
- Joanna Dołżonek
- Department of Environmental Analysis, Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland; Center for Environmental Research and Sustainable Technology (UFT), Faculty 4, University of Bremen, Leobener Strasse, 28359 Bremen, Germany.
| | - Chul-Woong Cho
- School of Chemical Engineering, Chonbuk National University, Chonbuk, Jeonju 561-756, Republic of Korea
| | - Piotr Stepnowski
- Department of Environmental Analysis, Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland
| | - Marta Markiewicz
- Center for Environmental Research and Sustainable Technology (UFT), Faculty 4, University of Bremen, Leobener Strasse, 28359 Bremen, Germany
| | - Jorg Thöming
- Center for Environmental Research and Sustainable Technology (UFT), Faculty 4, University of Bremen, Leobener Strasse, 28359 Bremen, Germany
| | - Stefan Stolte
- Department of Environmental Analysis, Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland; Center for Environmental Research and Sustainable Technology (UFT), Faculty 4, University of Bremen, Leobener Strasse, 28359 Bremen, Germany.
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54
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Baumer A, Bittermann K, Klüver N, Escher BI. Baseline toxicity and ion-trapping models to describe the pH-dependence of bacterial toxicity of pharmaceuticals. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2017; 19:901-916. [PMID: 28574566 DOI: 10.1039/c7em00099e] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
In numerous studies on the toxicity of ionisable organic chemicals, it has been shown that the toxicity was typically higher, when larger fractions of the neutral species were present. This observation was explained in some cases by slower uptake of charged species. In other cases it was suggested that the neutral species has intrinsically higher toxicity than the charged species or is alone responsible for the toxicity. However, even permanently charged and organic chemicals with multiple acid and base functional groups and zwitterions are toxic. We set out to reconcile the divergent views and to compare the various existing models for describing the pH-dependence of toxicity with the goal to derive one model that is valid independent of the type and number of charges on the molecule. To achieve this goal we measured the cytotoxicity of 18 acidic, 15 basic and 9 multiprotic/zwitterionic pharmaceuticals at pH 5.5 to pH 9 with the bioluminescence inhibition test using Aliivibrio fischeri (Microtox assay). This assay is useful for an evaluation of various models to describe pH-dependent toxicity because the majority of chemicals act as baseline toxicants in this 30 min cytotoxicity assay. Therefore baseline toxicity with constant membrane concentrations of the sum of all chemical species of approximately 200 mmol kglip-1 served for the validation of the suitability of the various tested models. We confirmed that most tested pharmaceuticals acted as baseline toxicants in this assay at all examined pH values, when toxicity was modeled with a mixture model of concentration addition between the neutral species and all charged species. An ion trapping model, that assumes that the membrane permeability of charged species is kinetically limited, improved model predictions for some pharmaceuticals and pH values. However, neither unhindered uptake nor no uptake of the charged species were ideal models; the reality lies presumably between the two limiting cases with a slower uptake of the charged species than the neutral species. For practical applications a previously developed QSAR model with the ionisation-corrected liposome-water distribution ratio as the sole physicochemical descriptor proved to be generally applicable for all ionisable organic chemicals including those with multiple charges and zwitterions.
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Affiliation(s)
- Andreas Baumer
- Helmholtz Centre for Environmental Research - UFZ, Permoserstr. 15, DE-04318 Leipzig, Germany.
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55
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Knauer K, Homazava N, Junghans M, Werner I. The influence of particles on bioavailability and toxicity of pesticides in surface water. INTEGRATED ENVIRONMENTAL ASSESSMENT AND MANAGEMENT 2017; 13:585-600. [PMID: 27862913 DOI: 10.1002/ieam.1867] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2015] [Revised: 08/27/2016] [Accepted: 11/10/2016] [Indexed: 06/06/2023]
Abstract
Environmental risk assessment is an essential part of the approval process for pesticides. Exposure concentrations are compared with ecotoxicological data obtained from standardized laboratory studies and, if available, from field studies to determine the risk of a substance or formulation for aquatic communities. Predicted concentrations in surface waters are derived using, for example, the European FOrum for the Co-ordination of pesticide fate models and their USe (FOCUS) or the German Exposit models, which distinguish between exposure to dissolved and particle-associated pesticide concentrations, because the dissolved concentration is thought to be the best predictor of bioavailability and toxicity. Water and particle-associated concentrations are estimated based on the organic carbon-water partitioning coefficient (KOC ). This review summarizes published information on the influence of natural suspended solids on bioavailability and toxicity of pesticides to aquatic organisms (algae, invertebrates and fish), and the value of log KOC and log KOW (octanol-water coefficient) as sole predictors of the bioavailable fraction is discussed. The information showed that: 1) the quality and origin of suspended solids played an important role in influencing pesticide bioavailability and toxicity; 2) a decrease in toxicity due to the presence of suspended solids was shown only for pyrethroid insecticides with log KOW greater than 5, but the extent of this reduction depended on particle concentration and size, and potentially also on the ecotoxicological endpoint; 3) for pesticides with a log KOW less than 3 (e.g., triazines, carbamates, and organophosphates), the impact of particles on bioavailability and toxicity is small and species dependent; and 4) pesticide bioavailability is greatly influenced by the test species and their physiology (e.g., feeding behavior or digestion). We conclude that exposure of aquatic organisms to pesticides and environmental risk of many pesticides might be underestimated in prospective risk assessment, when predicted environmental concentration is estimated based on the KOC of a compound. Integr Environ Assess Manag 2017;13:585-600. © 2016 SETAC.
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Affiliation(s)
- Katja Knauer
- Federal Office for Agriculture, Bern, Switzerland
| | - Nadzeya Homazava
- Swiss Centre for Applied Ecotoxicology Eawag-EPFL, Dübendorf, Switzerland
| | - Marion Junghans
- Swiss Centre for Applied Ecotoxicology Eawag-EPFL, Dübendorf, Switzerland
| | - Inge Werner
- Swiss Centre for Applied Ecotoxicology Eawag-EPFL, Dübendorf, Switzerland
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56
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Yordanova D, Ritter E, Gerlach T, Jensen JH, Smirnova I, Jakobtorweihen S. Solute Partitioning in Micelles: Combining Molecular Dynamics Simulations, COSMOmic, and Experiments. J Phys Chem B 2017; 121:5794-5809. [DOI: 10.1021/acs.jpcb.7b03147] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- D. Yordanova
- Institute of Thermal Separation
Processes, Hamburg University of Technology, Eissendorfer Strasse 38, 21073 Hamburg, Germany
| | - E. Ritter
- Institute of Thermal Separation
Processes, Hamburg University of Technology, Eissendorfer Strasse 38, 21073 Hamburg, Germany
| | - T. Gerlach
- Institute of Thermal Separation
Processes, Hamburg University of Technology, Eissendorfer Strasse 38, 21073 Hamburg, Germany
| | - J. H. Jensen
- Institute of Thermal Separation
Processes, Hamburg University of Technology, Eissendorfer Strasse 38, 21073 Hamburg, Germany
| | - I. Smirnova
- Institute of Thermal Separation
Processes, Hamburg University of Technology, Eissendorfer Strasse 38, 21073 Hamburg, Germany
| | - S. Jakobtorweihen
- Institute of Thermal Separation
Processes, Hamburg University of Technology, Eissendorfer Strasse 38, 21073 Hamburg, Germany
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57
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Fischer FC, Henneberger L, König M, Bittermann K, Linden L, Goss KU, Escher BI. Modeling Exposure in the Tox21 in Vitro Bioassays. Chem Res Toxicol 2017; 30:1197-1208. [DOI: 10.1021/acs.chemrestox.7b00023] [Citation(s) in RCA: 84] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Fabian C. Fischer
- Department
Cell Toxicology, Helmholtz Centre for Environmental Research - UFZ, Permoserstraße 15, 04318 Leipzig, Germany
| | - Luise Henneberger
- Department
Cell Toxicology, Helmholtz Centre for Environmental Research - UFZ, Permoserstraße 15, 04318 Leipzig, Germany
| | - Maria König
- Department
Cell Toxicology, Helmholtz Centre for Environmental Research - UFZ, Permoserstraße 15, 04318 Leipzig, Germany
| | - Kai Bittermann
- Department
Analytical Environmental Chemistry, Helmholtz Centre for Environmental Research - UFZ, Permoserstraße 15, 04318 Leipzig, Germany
| | - Lukas Linden
- Department
Analytical Environmental Chemistry, Helmholtz Centre for Environmental Research - UFZ, Permoserstraße 15, 04318 Leipzig, Germany
| | - Kai-Uwe Goss
- Department
Analytical Environmental Chemistry, Helmholtz Centre for Environmental Research - UFZ, Permoserstraße 15, 04318 Leipzig, Germany
| | - Beate I. Escher
- Department
Cell Toxicology, Helmholtz Centre for Environmental Research - UFZ, Permoserstraße 15, 04318 Leipzig, Germany
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58
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Molina-Fernandez N, Perez-Conde C, Rainieri S, Sanz-Landaluze J. Method for quantifying NSAIDs and clofibric acid in aqueous samples, lumpfish (Cyclopterus lumpus) roe, and zebrafish (Danio rerio) eleutheroembryos and evaluation of their bioconcentration in zebrafish eleutheroembryos. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2017; 24:10907-10918. [PMID: 27164891 DOI: 10.1007/s11356-016-6671-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Accepted: 04/10/2016] [Indexed: 06/05/2023]
Abstract
Pharmaceuticals such as nonsteroidal anti-inflammatory drugs (NSAIDs) and lipid regulators are being repeatedly detected at low concentrations (pg · mL-1-ng · mL-1) in the environment. A large fraction of these compounds are ionizable. Ionized compounds show different physico-chemical properties and environmental behavior in comparison to their neutral analogs; as a consequence, the quantification methods currently available, based on the neutral molecules, might not be suitable to detect the corresponding ionized compounds. To overcome this problem, we developed a specific analytical method to quantify NSAIDs and lipid regulators (i.e., ibuprofen, diclofenac, naproxen, and clofibric acid) and their ionized compounds. This method is based on three steps: (1) the extraction of the organic compounds with an organic solvent assisted with an ultrasonic probe, (2) the cleaning of the extracts with a dispersive SPE with C18, and (3) the determination of the chemical compounds by GC-MS (prior derivatization of the analytes). We demonstrated that the proposed method can successfully quantify the pharmaceuticals and their ionized compounds in aqueous samples, lumpfish eggs, and zebrafish eleutheroembryos. Additionally, it allows the extraction and the cleanup of extracts from small samples (0.010 g of wet weight in pools of 20 larvae) and complex matrixes (due to high lipid content) and can be used as a basis for bioaccumulation assays performed with zebrafish eleutheroembryos in alternative to OECD test 305.
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Affiliation(s)
- N Molina-Fernandez
- Department of Analytical Chemistry, Faculty of Chemical Science, Complutense University of Madrid, Avenida Complutense s/n, 28040, Madrid, Spain
| | - C Perez-Conde
- Department of Analytical Chemistry, Faculty of Chemical Science, Complutense University of Madrid, Avenida Complutense s/n, 28040, Madrid, Spain
| | - S Rainieri
- Food Research Division, AZTI, Parque Tecnológico de Bizkaia, Astondo Bidea 609, 48160, Derio, Spain
| | - J Sanz-Landaluze
- Department of Analytical Chemistry, Faculty of Chemical Science, Complutense University of Madrid, Avenida Complutense s/n, 28040, Madrid, Spain.
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59
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ARMITAGE JAMESM, ERICKSON RUSSELLJ, LUCKENBACH TILL, NG CARLAA, PROSSER RYANS, ARNOT JONA, SCHIRMER KRISTIN, NICHOLS JOHNW. Assessing the bioaccumulation potential of ionizable organic compounds: Current knowledge and research priorities. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 2017; 36:882-897. [PMID: 27992066 PMCID: PMC6172661 DOI: 10.1002/etc.3680] [Citation(s) in RCA: 94] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Revised: 07/20/2016] [Accepted: 11/04/2016] [Indexed: 05/19/2023]
Abstract
The objective of the present study was to review the current knowledge regarding the bioaccumulation potential of ionizable organic compounds (IOCs), with a focus on the availability of empirical data for fish. Aspects of the bioaccumulation potential of IOCs in fish that can be characterized relatively well include the pH dependence of gill uptake and elimination, uptake in the gut, and sorption to phospholipids (membrane-water partitioning). Key challenges include the lack of empirical data for biotransformation and binding in plasma. Fish possess a diverse array of proteins that may transport IOCs across cell membranes. Except in a few cases, however, the significance of this transport for uptake and accumulation of environmental contaminants is unknown. Two case studies are presented. The first describes modeled effects of pH and biotransformation on the bioconcentration of organic acids and bases, while the second employs an updated model to investigate factors responsible for accumulation of perfluorinated alkyl acids. The perfluorinated alkyl acid case study is notable insofar as it illustrates the likely importance of membrane transporters in the kidney and highlights the potential value of read-across approaches. Recognizing the current need to perform bioaccumulation hazard assessments and ecological and exposure risk assessment for IOCs, the authors provide a tiered strategy that progresses (as needed) from conservative assumptions (models and associated data) to more sophisticated models requiring chemical-specific information. Environ Toxicol Chem 2017;36:882-897. © 2016 SETAC.
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Affiliation(s)
- JAMES M. ARMITAGE
- University of Toronto Scarborough, Toronto, Ontario, Canada
- Address correspondence to
| | - RUSSELL J. ERICKSON
- Office of Research and Development, National Health and Environmental Effects Research Laboratory, Mid-Continent Ecology Division, US Environmental Protection Agency, Duluth, Minnesota, USA
| | - TILL LUCKENBACH
- Department Bioanalytical Ecotoxicology, UFZ — Helmholtz Centre for Environmental Research, Leipzig, Germany
| | - CARLA A. NG
- Department of Civil and Environmental Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - RYAN S. PROSSER
- School of Environmental Sciences, University of Guelph, Guelph, Ontario, Canada
| | - JON A. ARNOT
- University of Toronto Scarborough, Toronto, Ontario, Canada
- ARC Arnot Research and Consulting, Toronto, Ontario, Canada
| | - KRISTIN SCHIRMER
- Eawag, Department of Environmental Toxicology, Swiss Federal Institute of Aquatic Science and Technology, Duebendorf, Switzerland
- EPFL, School of Architecture, Civil and Environmental Engineering, Lausanne, Switzerland
- Institute of Biogeochemistry and Pollutant Dynamics, ETHZ, Zurich, Switzerland
| | - JOHN W. NICHOLS
- Office of Research and Development, National Health and Environmental Effects Research Laboratory, Mid-Continent Ecology Division, US Environmental Protection Agency, Duluth, Minnesota, USA
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Escher BI, Baumer A, Bittermann K, Henneberger L, König M, Kühnert C, Klüver N. General baseline toxicity QSAR for nonpolar, polar and ionisable chemicals and their mixtures in the bioluminescence inhibition assay with Aliivibrio fischeri. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2017; 19:414-428. [PMID: 28197603 DOI: 10.1039/c6em00692b] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
The Microtox assay, a bioluminescence inhibition assay with the marine bacterium Aliivibrio fischeri, is one of the most popular bioassays for assessing the cytotoxicity of organic chemicals, mixtures and environmental samples. Most environmental chemicals act as baseline toxicants in this short-term screening assay, which is typically run with only 30 min of exposure duration. Numerous Quantitative Structure-Activity Relationships (QSARs) exist for the Microtox assay for nonpolar and polar narcosis. However, typical water pollutants, which have highly diverse structures covering a wide range of hydrophobicity and speciation from neutral to anionic and cationic, are often outside the applicability domain of these QSARs. To include all types of environmentally relevant organic pollutants we developed a general baseline toxicity QSAR using liposome-water distribution ratios as descriptors. Previous limitations in availability of experimental liposome-water partition constants were overcome by reliable prediction models based on polyparameter linear free energy relationships for neutral chemicals and the COSMOmic model for charged chemicals. With this QSAR and targeted mixture experiments we could demonstrate that ionisable chemicals fall in the applicability domain. Most investigated water pollutants acted as baseline toxicants in this bioassay, with the few outliers identified as uncouplers or reactive toxicants. The main limitation of the Microtox assay is that chemicals with a high melting point and/or high hydrophobicity were outside of the applicability domain because of their low water solubility. We quantitatively derived a solubility cut-off but also demonstrated with mixture experiments that chemicals inactive on their own can contribute to mixture toxicity, which is highly relevant for complex environmental mixtures, where these chemicals may be present at concentrations below the solubility cut-off.
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Affiliation(s)
- Beate I Escher
- Helmholtz Centre for Environmental Research - UFZ, Permoserstr. 15, DE-04318 Leipzig, Germany. and Eberhard Karls University Tübingen, Environmental Toxicology, Center for Applied Geosciences, 72074 Tübingen, Germany
| | - Andreas Baumer
- Helmholtz Centre for Environmental Research - UFZ, Permoserstr. 15, DE-04318 Leipzig, Germany. and Department of Clinical Pharmacy, Leipzig University, Eilenburger Str. 15a, 04317 Leipzig, Germany
| | - Kai Bittermann
- Helmholtz Centre for Environmental Research - UFZ, Permoserstr. 15, DE-04318 Leipzig, Germany.
| | - Luise Henneberger
- Helmholtz Centre for Environmental Research - UFZ, Permoserstr. 15, DE-04318 Leipzig, Germany.
| | - Maria König
- Helmholtz Centre for Environmental Research - UFZ, Permoserstr. 15, DE-04318 Leipzig, Germany.
| | - Christin Kühnert
- Helmholtz Centre for Environmental Research - UFZ, Permoserstr. 15, DE-04318 Leipzig, Germany.
| | - Nils Klüver
- Helmholtz Centre for Environmental Research - UFZ, Permoserstr. 15, DE-04318 Leipzig, Germany.
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61
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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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62
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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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63
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Lopes D, Jakobtorweihen S, Nunes C, Sarmento B, Reis S. Shedding light on the puzzle of drug-membrane interactions: Experimental techniques and molecular dynamics simulations. Prog Lipid Res 2017; 65:24-44. [DOI: 10.1016/j.plipres.2016.12.001] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Revised: 11/30/2016] [Accepted: 12/03/2016] [Indexed: 12/20/2022]
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64
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Klüver N, Vogs C, Altenburger R, Escher BI, Scholz S. Development of a general baseline toxicity QSAR model for the fish embryo acute toxicity test. CHEMOSPHERE 2016; 164:164-173. [PMID: 27588575 DOI: 10.1016/j.chemosphere.2016.08.079] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Revised: 08/15/2016] [Accepted: 08/17/2016] [Indexed: 06/06/2023]
Abstract
Fish embryos have become a popular model in ecotoxicology and toxicology. The fish embryo acute toxicity test (FET) with the zebrafish embryo was recently adopted by the OECD as technical guideline TG 236 and a large database of concentrations causing 50% lethality (LC50) is available in the literature. Quantitative Structure-Activity Relationships (QSARs) of baseline toxicity (also called narcosis) are helpful to estimate the minimum toxicity of chemicals to be tested and to identify excess toxicity in existing data sets. Here, we analyzed an existing fish embryo toxicity database and established a QSAR for fish embryo LC50 using chemicals that were independently classified to act according to the non-specific mode of action of baseline toxicity. The octanol-water partition coefficient Kow is commonly applied to discriminate between non-polar and polar narcotics. Replacing the Kow by the liposome-water partition coefficient Klipw yielded a common QSAR for polar and non-polar baseline toxicants. This developed baseline toxicity QSAR was applied to compare the final mode of action (MOA) assignment of 132 chemicals. Further, we included the analysis of internal lethal concentration (ILC50) and chemical activity (La50) as complementary approaches to evaluate the robustness of the FET baseline toxicity. The analysis of the FET dataset revealed that specifically acting and reactive chemicals converged towards the baseline toxicity QSAR with increasing hydrophobicity. The developed FET baseline toxicity QSAR can be used to identify specifically acting or reactive compounds by determination of the toxic ratio and in combination with appropriate endpoints to infer the MOA for chemicals.
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Affiliation(s)
- Nils Klüver
- UFZ - Helmholtz Centre for Environmental Research, Department of Cell Toxicology, Permoserstr. 15, 04318, Leipzig, Germany; UFZ - Helmholtz Centre for Environmental Research, Department of Bioanalytical Ecotoxicology, Permoserstr. 15, 04318, Leipzig, Germany.
| | - Carolina Vogs
- UFZ - Helmholtz Centre for Environmental Research, Department of Bioanalytical Ecotoxicology, Permoserstr. 15, 04318, Leipzig, Germany
| | - Rolf Altenburger
- UFZ - Helmholtz Centre for Environmental Research, Department of Bioanalytical Ecotoxicology, Permoserstr. 15, 04318, Leipzig, Germany; RWTH Aachen University, Institute for Environmental Research, Biologie V, Worringerweg 1, 52074, Aachen, Germany
| | - Beate I Escher
- UFZ - Helmholtz Centre for Environmental Research, Department of Cell Toxicology, Permoserstr. 15, 04318, Leipzig, Germany; Eberhard Karls University Tübingen, Center for Applied Geosciences, Environmental Toxicology, Hölderlinstr. 12, 72074, Tübingen, Germany
| | - Stefan Scholz
- UFZ - Helmholtz Centre for Environmental Research, Department of Bioanalytical Ecotoxicology, Permoserstr. 15, 04318, Leipzig, Germany
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Pearlstein RA, Dickson CJ, Hornak V. Contributions of the membrane dipole potential to the function of voltage-gated cation channels and modulation by small molecule potentiators. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1859:177-194. [PMID: 27836643 DOI: 10.1016/j.bbamem.2016.11.005] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2016] [Revised: 10/28/2016] [Accepted: 11/06/2016] [Indexed: 01/27/2023]
Abstract
The membrane dipole potential (Ψd) constitutes one of three electrical potentials generated by cell membranes. Ψd arises from the unfavorable parallel alignment of phospholipid and water dipoles, and varies in magnitude both longitudinally and laterally across the bilayer according to membrane composition and phospholipid packing density. In this work, we propose that dynamic counter-balancing between Ψd and the transmembrane potential (ΔΨm) governs the conformational state transitions of voltage-gated ion channels. Ψd consists of 1) static outer, and dynamic inner leaflet components (Ψd(extra) and Ψd(intra), respectively); and 2) a transmembrane component (ΔΨd(inner-outer)), ariing from differences in intra- and extracellular leaflet composition. Ψd(intra), which transitions between high and low energy states (Ψd(intra, high) and Ψd(intra, low)) as a function of channel conformation, is transduced by the pore domain. ΔΨd(inner-outer) is transduced by the voltage-sensing (VS) domain in summation with ΔΨm. Potentiation of voltage-gated ion channels is of interest for the treatment of cardiac, neuronal, and other disorders arising from inherited/acquired ion channel dysfunction. Potentiators are widely believed to alter the rates and voltage-dependencies of channel gating transitions by binding to pockets in the membrane-facing and other regions of ion channel targets. Here, we propose that potentiators alter Ψd(intra) and/or Ψd(extra), thereby increasing or decreasing the energy barriers governing channel gating transitions. We used quantum mechanical and molecular dynamics (MD) simulations to predict the overall Ψd-modulating effects of a series of published positive hERG potentiators partitioned into model DOPC bilayers. Our findings suggest a strong correlation between the magnitude of Ψd-lowering and positive hERG potentiation across the series.
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Affiliation(s)
- Robert A Pearlstein
- Global Discovery Chemistry, Computer-Aided Drug Discovery, Novartis Institutes for BioMedical Research, 181 Mass Ave., Cambridge, MA 02139, USA.
| | - Callum J Dickson
- Global Discovery Chemistry, Computer-Aided Drug Discovery, Novartis Institutes for BioMedical Research, 181 Mass Ave., Cambridge, MA 02139, USA
| | - Viktor Hornak
- Global Discovery Chemistry, Computer-Aided Drug Discovery, Novartis Institutes for BioMedical Research, 181 Mass Ave., Cambridge, MA 02139, USA
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Murakami K, Hori K, Maeda K, Fukuyama M, Yoshida Y. Distribution and Adsorption of Ionic Species into a Liposome Membrane and Their Dependence upon the Species and Concentration of a Coexisting Counterion. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:10678-10684. [PMID: 27687781 DOI: 10.1021/acs.langmuir.6b03162] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The distribution of ions into a bilayer lipid membrane (BLM) and their adsorption on the BLM are investigated by extracting a hydrophobic cation, rhodamine 6G (R6G+), into a liposome through the dialysis membrane method. R6G+ distribution mainly depends upon the concentration of the coexisting anion and its species (Cl-, Br-, BF4-, ClO4-, and picrate). On the other hand, R6G+ adsorption on the BLM surface follows the Langmuir adsorption model and is independent of the coexisting anion in the aqueous phase. We propose an extraction model of ionic species into the BLM, to explain the dependence of extraction of ionic species upon the coexisting anion. In this model, an ion is distributed with a coexisting counterion into the BLM and then forms an ion pair in the BLM. Here, the ion adsorption equilibrium on the BLM surface is independent of the species and concentration of the coexisting counterion under the same ionic strength. On the basis of this model, we estimate the distribution constant of R6G+ and anion (KD), the ion-pair formation constant in the BLM (Kip), and the R6G+ adsorption constant on the BLM surface (Kad). Even for an ultrathin membrane system, such as a BLM, R6G+ is distributed with a coexisting counterion and the distribution equilibrium of the ionic species at the water-BLM interface is analyzable similar to that at the water-organic solvent interface.
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Affiliation(s)
- Koji Murakami
- Department of Chemistry and Materials Technology and ‡Faculty of Molecular Chemistry and Engineering, Kyoto Institute of Technology , Matsugasaki, Sakyo, Kyoto 606-8585, Japan
| | - Kisho Hori
- Department of Chemistry and Materials Technology and ‡Faculty of Molecular Chemistry and Engineering, Kyoto Institute of Technology , Matsugasaki, Sakyo, Kyoto 606-8585, Japan
| | - Kohji Maeda
- Department of Chemistry and Materials Technology and ‡Faculty of Molecular Chemistry and Engineering, Kyoto Institute of Technology , Matsugasaki, Sakyo, Kyoto 606-8585, Japan
| | - Mao Fukuyama
- Department of Chemistry and Materials Technology and ‡Faculty of Molecular Chemistry and Engineering, Kyoto Institute of Technology , Matsugasaki, Sakyo, Kyoto 606-8585, Japan
| | - Yumi Yoshida
- Department of Chemistry and Materials Technology and ‡Faculty of Molecular Chemistry and Engineering, Kyoto Institute of Technology , Matsugasaki, Sakyo, Kyoto 606-8585, Japan
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67
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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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68
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Henneberger L, Goss KU, Endo S. Equilibrium Sorption of Structurally Diverse Organic Ions to Bovine Serum Albumin. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2016; 50:5119-5126. [PMID: 27098963 DOI: 10.1021/acs.est.5b06176] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Reliable partitioning data are essential for assessing the bioaccumulation potential and the toxicity of chemicals. In contrast to neutral organic chemicals, the partitioning behavior of ionogenic organic chemicals (IOCs) is still a black box for environmental scientists. Partitioning to serum albumin, the major protein in blood plasma, strongly influences the freely dissolved concentration of many chemicals (including IOCs), which affects their transport and distribution in the body. Because consistent data sets for partitioning of IOCs are rarely available, bovine serum albumin-water partition coefficients (KBSA/w) were measured in this study for 45 anionic and 4 cationic organic chemicals, including various substituted benzoic and naphthoic acids, sulfonates and several pesticides and pharmaceuticals. The results of this study suggest that binding to BSA is substantially influenced by the three-dimensional structure of the chemicals and the position of substitutions on the sorbing molecules. For example, we found a difference of >1.5 log units between isomeric chemicals such as 3,4-dichlorobenzoic acid and 2,6-dichlorobenzoic acid, and 1-naphthoic acid and 2-naphthoic acid. Conventional modeling approaches (e.g., based on octanol-water partition coefficients) poorly predict log KBSA/w of organic ions (R(2) ≤ 0.5), partially because they do not capture the observed steric effects. Hence, alternative modeling strategies will be required for accurate prediction of serum albumin-water partition coefficients of organic ions.
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Affiliation(s)
- Luise Henneberger
- Helmholtz Centre for Environmental Research UFZ, Permoserstrasse 15, D-04318 Leipzig, Germany
| | - Kai-Uwe Goss
- Helmholtz Centre for Environmental Research UFZ, Permoserstrasse 15, D-04318 Leipzig, Germany
- University of Halle-Wittenberg , Institute of Chemistry, Kurt-Mothes-Strasse 2, D-06120 Halle, Germany
| | - Satoshi Endo
- Helmholtz Centre for Environmental Research UFZ, Permoserstrasse 15, D-04318 Leipzig, Germany
- Osaka City University , Urban Research Plaza & Graduate School of Engineering, Sugimoto 3-3-138, Sumiyoshi-ku, 558-8585 Osaka, Japan
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69
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Equations for the Partition of Neutral Molecules, Ions and Ionic Species from Water to Water–Methanol Mixtures. J SOLUTION CHEM 2016. [DOI: 10.1007/s10953-016-0479-5] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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70
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Goss KU, Endo S. Comment on "Application of the Activity Framework for Assessing Aquatic Ecotoxicology Data for Organic Chemicals". ENVIRONMENTAL SCIENCE & TECHNOLOGY 2016; 50:4139-4140. [PMID: 26954491 DOI: 10.1021/acs.est.5b05534] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Affiliation(s)
- Kai-Uwe Goss
- Helmholtz Centre for Environmental Research- UFZ , Permoserstr. 15, 04318 Leipzig, Germany
| | - Satoshi Endo
- Osaka City University , Urban Research Plaza & Graduate School of Engineering, Sugimoto 3-3-138, Sumiyoshi-ku, 558-8585 Osaka, Japan
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71
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Golius A, Gorb L, Michalkova Scott A, Hill FC, Shukla M, Goins AB, Johnson DR, Leszczynski J. Experimental and computational study of membrane affinity for selected energetic compounds. CHEMOSPHERE 2016; 148:322-327. [PMID: 26820779 DOI: 10.1016/j.chemosphere.2016.01.010] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2015] [Revised: 12/14/2015] [Accepted: 01/04/2016] [Indexed: 06/05/2023]
Abstract
The affinity of various energetic compounds for a biological membrane was investigated using experimental and computational techniques. We measured octanol-water (log(Kow)) and liposome-water (log(Klipw)) partition coefficients for the following chemicals: trinitrotoluene (TNT), 2,4-dinitrotoluene (2,4-DNT), 2,6-dinitrotoluene (2,6-DNT), 2,4-dinitroanisole (DNAN), 2methoxy-5-nitrophenol (2M5NP), 2,4,6-trinitrobenzene (TNB), and 2,4-dinitrophenol (2,4-DNP). In order to determine log(Klipw) experimentally, we used artificial solid supported lipid liposomes produced under trade mark TRANSIL. Log(Kow) value were predicted with several program packages including the COSMOthermX software. Log(Klipw) were estimated with COSMOmic as implemented in the COSMOthermX program package. In order to verify accuracy of our experimentally obtained results, we performed basic statistical analysis of data taken from the literature. We concluded that compounds considered in this study possess a moderate ability to penetrate into membranes. Comparison of both coefficients has shown that in general, the log(Kow) values are slightly smaller than log(Klipw).
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Affiliation(s)
- Anastasiia Golius
- Department of Chemistry and Biochemistry, Jackson State University, Jackson, MS, USA
| | | | | | - Frances C Hill
- U.S. Army Engineer Research and Development Center, Vicksburg, MS, USA
| | - Manoj Shukla
- U.S. Army Engineer Research and Development Center, Vicksburg, MS, USA
| | | | | | - Jerzy Leszczynski
- Department of Chemistry and Biochemistry, Jackson State University, Jackson, MS, USA.
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72
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Abraham MH, Acree WE. Descriptors for ions and ion-pairs for use in linear free energy relationships. J Chromatogr A 2016; 1430:2-14. [DOI: 10.1016/j.chroma.2015.07.023] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2015] [Revised: 07/02/2015] [Accepted: 07/03/2015] [Indexed: 11/28/2022]
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73
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Droge STJ. Dealing with Confounding pH-Dependent Surface Charges in Immobilized Artificial Membrane HPLC Columns. Anal Chem 2015; 88:960-7. [DOI: 10.1021/acs.analchem.5b03708] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- Steven T. J. Droge
- Institute for Risk Assessment
Sciences, Utrecht University, Yalelaan 104, 3508 TD Utrecht, The Netherlands
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74
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Ng CA, Hungerbuehler K. Exploring the Use of Molecular Docking to Identify Bioaccumulative Perfluorinated Alkyl Acids (PFAAs). ENVIRONMENTAL SCIENCE & TECHNOLOGY 2015; 49:12306-14. [PMID: 26393377 DOI: 10.1021/acs.est.5b03000] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Methods to predict the bioaccumulation potential of per- and polyfluorinated alkyl substances (PFAS) are sorely needed, given the proliferation of these substances and lack of data on their properties and behavior. Here, we test whether molecular docking, a technique where interactions between proteins and ligands are simulated to predict both bound conformation and interaction affinity, can be used to predict PFAS binding strength and biological half-life. We show that an easy-to-implement docking program, Autodock Vina, can successfully redock perfluorooctanesulfonate (PFOS) to human serum albumin with deviations smaller than 2 Å. Furthermore, predicted binding strengths largely fall within one standard deviation of measured values for perfluorinated alkyl acids (PFAAs). Correlations with half-lives suggest both membrane partitioning and protein interactions are important, and that serum albumin is only one of a number of proteins controlling the fate of these chemicals in organisms. However, few data are available for validation of our approach as a broad screening tool, and available data are highly variable. We therefore call for collection of new data, particularly including proteins other than serum albumin and substances beyond perfluorooctanoic acid (PFOA) and PFOS. The methods we discuss in this work can serve as a framework for guiding such data collection.
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Affiliation(s)
- Carla A Ng
- Institute for Chemical and Bioengineering, ETH Zurich , CH-8093 Zurich, Switzerland
| | - Konrad Hungerbuehler
- Institute for Chemical and Bioengineering, ETH Zurich , CH-8093 Zurich, Switzerland
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75
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Geisler A, Oemisch L, Endo S, Goss KU. Predicting storage-lipid water partitioning of organic solutes from molecular structure. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2015; 49:5538-45. [PMID: 25834931 DOI: 10.1021/es506336m] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Partitioning to storage fat is the major process for bioaccumulation of many neutral organic chemicals. In this work, we evaluated the performance of four predictive models, ABSOLV, COSMOtherm, KOWWIN, and SPARC to calculate storage lipid-water partition coefficients. In a first step of the validation, we used over 300 literature data for chemicals with relatively simple molecular structures. For these compounds the overall performance was similar for all models with a root-mean-square error (rmse) between 0.45 and 0.61 log units. Clear differences became visible in the second validation step where a subset with only H-bond-donor compounds was used. Here, COSMOtherm and SPARC performed clearly better with an rmse of 0.35 and 0.42 log units, respectively, compared to ABSOLV and KOWWIN with an rmse of 0.91 and 0.85 log units, respectively. The last step in our validation was a comparison with experimental values for 22 complex, multifunctional chemicals (including pesticides, hormones, mycotoxins) that we measured specifically for this validation purpose. For these chemicals, predictions by all models were less accurate than those for simpler chemicals. COSMOtherm performed the best (rmse 0.71 log units) while the other methods showed considerably poorer results (rmse 1.29 (ABSOLV), 1.25 (SPARC), and 1.62 (KOWWIN) log units).
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Affiliation(s)
- Anett Geisler
- †UFZ - Helmholtz Centre for Environmental Research, Permoserstraße 15, D-04318 Leipzig, Germany
| | - Luise Oemisch
- †UFZ - Helmholtz Centre for Environmental Research, Permoserstraße 15, D-04318 Leipzig, Germany
| | - Satoshi Endo
- †UFZ - Helmholtz Centre for Environmental Research, Permoserstraße 15, D-04318 Leipzig, Germany
| | - Kai-Uwe Goss
- †UFZ - Helmholtz Centre for Environmental Research, Permoserstraße 15, D-04318 Leipzig, Germany
- ‡University of Halle-Wittenberg, Institute of Chemistry, Kurt Mothes Straße 2, D-06120 Halle, Germany
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76
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Treu G, Drost W, Jöhncke U, Rauert C, Schlechtriem C. The Dessau workshop on bioaccumulation: state of the art, challenges and regulatory implications. ENVIRONMENTAL SCIENCES EUROPE 2015; 27:34. [PMID: 27752435 PMCID: PMC5044950 DOI: 10.1186/s12302-015-0067-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2015] [Accepted: 12/07/2015] [Indexed: 05/10/2023]
Abstract
Bioaccumulation plays a vital role in understanding the fate of a substance in the environment and is key to the regulation of chemicals in several jurisdictions. The current assessment approaches commonly use the octanol-water partition coefficient (log KOW) as an indicator for bioaccumulation and the bioconcentration factor (BCF) as a standard criterion to identify bioaccumulative substances show limitations. The log KOW does not take into account active transport phenomena or special structural properties (e.g., amphiphilic substances or dissociating substances) and therefore additional screening criteria are required. Regulatory BCF studies are so far restricted to fish and uptake through the gills. Studies on (terrestrial) air-breathing organisms are missing. Though there are alternative tests such as the dietary exposure bioaccumulation fish test described in the recently revised OECD test guideline 305, it still remains unclear how to deal with results of alternative tests in regulatory decision-making processes. A substantial number of bioaccumulation fish tests are required in regulation. The development of improved test systems following the 3R principles, namely to replace, reduce and refine animal testing, is thus required. All these aspects stress the importance to further develop the assessment of bioaccumulation. The Dessau Workshop on Bioaccumulation which was held from June 26th to 27th 2014, in Dessau, Germany, provided a comprehensive overview of the state of the art of bioaccumulation assessment, provided insights into the problems and challenges addressed by the regulatory authorities and described new research concepts and their regulatory implications. The event was organised by UBA (Dessau, Germany) and Fraunhofer IME (Schmallenberg, Germany). About 50 participants from industry, regulatory bodies and academia listened to 14 lectures on selected topics and joined the plenary discussions.
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Affiliation(s)
- Gabriele Treu
- Umweltbundesamt (UBA), PO Box 1406, 06844 Dessau-Rosslau, Germany
| | - Wiebke Drost
- Umweltbundesamt (UBA), PO Box 1406, 06844 Dessau-Rosslau, Germany
| | - Ulrich Jöhncke
- Umweltbundesamt (UBA), PO Box 1406, 06844 Dessau-Rosslau, Germany
| | - Caren Rauert
- Umweltbundesamt (UBA), PO Box 1406, 06844 Dessau-Rosslau, Germany
| | - Christian Schlechtriem
- Fraunhofer Institute for Molecular Biology and Applied Ecology (IME), PO Box 12 60, 57377 Schmallenberg, Germany
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