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Wu H, Hemmingsen L, Sauer SPA. On the geometry dependence of the nuclear magnetic resonance chemical shift of mercury in thiolate complexes: A relativistic density functional theory study. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2024; 62:648-669. [PMID: 38773942 DOI: 10.1002/mrc.5452] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2024] [Revised: 04/19/2024] [Accepted: 04/22/2024] [Indexed: 05/24/2024]
Abstract
Thiolate containing mercury(II) complexes of the general formula [Hg(SR)n ]2 - n have been of great interest since the toxicity of mercury was recognized. 199Hg nuclear magnetic resonance spectroscopy (NMR) is a powerful tool for characterization of mercury complexes. In this work, the Hg shielding constants in a series of [Hg(SR)n ]2 - n complexes are therefore investigated computationally with particular emphasis on their geometry dependence. Geometry optimizations and NMR chemical shift calculations are performed at the density functional theory (DFT) level with both the zeroth-order regular approximation (ZORA) and four-component relativistic methods. The four exchange-correlation (XC) functionals PBE0, PBE, B3LYP, and BLYP are used in combination with either Dyall's Gaussian-type (GTO) or Slater-type orbitals (STOs) basis sets. Comparing ZORA and four-component calculations, one observes that the calculated shielding constants for a given molecular geometry have a constant difference of ∼ 1070 ppm. This confirms that ZORA is an acceptable relativistic method to compute NMR chemical shifts. The combinations of four-component/PBE0/v3z and ZORA/PBE0/QZ4P are applied to explore the geometry dependence of the isotropic shielding. For a given coordination number, the distance between mercury and sulfur is the key factor affecting the shielding constant, while changes in bond and dihedral angles and even different side groups have relatively little impact.
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Affiliation(s)
- Haide Wu
- Department of Chemistry, University of Copenhagen, Copenhagen, Denmark
| | - Lars Hemmingsen
- Department of Chemistry, University of Copenhagen, Copenhagen, Denmark
| | - Stephan P A Sauer
- Department of Chemistry, University of Copenhagen, Copenhagen, Denmark
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2
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Barrios-Rodriguez CA, Bezerra MF, Ristau N, Mendonça DM, Pires TT, de Souza Paulino LR, Lacerda LDD. Biological and ecological traits rather than geography control mercury (Hg) in scutes of marine turtles from the Southwest Atlantic. MARINE POLLUTION BULLETIN 2024; 200:116085. [PMID: 38325203 DOI: 10.1016/j.marpolbul.2024.116085] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Revised: 01/23/2024] [Accepted: 01/27/2024] [Indexed: 02/09/2024]
Abstract
The use of sentinel species in monitoring programs for toxic metals such as mercury (Hg) is essential to understand these pollutants' impact on the environment. For this purpose, it is essential to use organisms that have a lifespan compatible with the residence time of Hg in the oceans, and preferably with a wide geographical distribution, such as sea turtles. Here, we assess the regional variability of Hg concentrations using carapace scutes of four sea turtle species along the foraging and spawning area in the northeast coastline of Brazil. Mercury concentrations in samples showed no relationship with the environmental Hg levels (obtained from literature). Rather, Hg concentrations varied according to species-specific biological, and ecological traits. Characteristics such as the ontogenetic shift in the diet of Chelonia mydas, capital breeding in females, depth of foraging in oceanic waters, and selectivity of food items, such as in Eretmochelys imbricata, significantly influenced Hg concentrations.
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Affiliation(s)
- César Augusto Barrios-Rodriguez
- Laboratório de Biogeoquímica Costeira, Instituto de Ciências do Mar, Universidade Federal do Ceará, Fortaleza, Ceará, Brazil.
| | - Moises Fernandes Bezerra
- Laboratório de Biogeoquímica Costeira, Instituto de Ciências do Mar, Universidade Federal do Ceará, Fortaleza, Ceará, Brazil
| | | | | | | | | | - Luiz Drude de Lacerda
- Laboratório de Biogeoquímica Costeira, Instituto de Ciências do Mar, Universidade Federal do Ceará, Fortaleza, Ceará, Brazil
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Barrios-Rodríguez CA, de Lacerda LD, Fernandes-Bezerra M. A Pilot Study of Mercury Distribution in the Carapace of Four Species of Sea Turtles from Northeastern Brazil. BULLETIN OF ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY 2023; 110:99. [PMID: 37243788 DOI: 10.1007/s00128-023-03745-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Accepted: 05/19/2023] [Indexed: 05/29/2023]
Abstract
Scutes present very complex morphologies with different growth rates at different areas of the carapace that can change the accumulation process of essential and non-essential metals. To infer the effects of morphology and growth on Hg concentrations in scutes, we mapped them in the carapace of one individual of four species of sea turtles sampled along the Brazilian coast. The results showed that Hg concentrations were higher in the vertebral scutes of Chelonia mydas and Eretmochelys imbricata suggesting variation in growth rates of different carapace areas since the vertebral area is the first to develop prior to costal areas. Caretta caretta and Lepidochelys olivacea did not show differences between carapace areas. The preliminary data from this pilot study indicate that vertebral scutes may be suitable for monitoring Hg in C. mydas and E. imbricata, since they reflect longer exposure period. A species-to-species comparison of Hg concentrations is not possible due to the small number of sampled individuals, nevertheless, E. imbricata showed remarkably lower Hg concentrations compared to the other three species. Further studies are required for all four species, with a larger number of individuals, preferentially of varying life stages, due to the unknown effects of different diets, Hg exposure, and migration histories.
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Affiliation(s)
- César Augusto Barrios-Rodríguez
- Laboratório de Biogeoquímica Costeira, Instituto de Ciências do Mar, Universidade Federal do Ceará, Av. Abolição, 3207, Fortaleza, Ceará, 60165-081, Brasil.
| | - Luiz Drude de Lacerda
- Laboratório de Biogeoquímica Costeira, Instituto de Ciências do Mar, Universidade Federal do Ceará, Av. Abolição, 3207, Fortaleza, Ceará, 60165-081, Brasil
| | - Moises Fernandes-Bezerra
- Laboratório de Biogeoquímica Costeira, Instituto de Ciências do Mar, Universidade Federal do Ceará, Av. Abolição, 3207, Fortaleza, Ceará, 60165-081, Brasil
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Abstract
While 199Hg NMR is a well-established tool for elucidating details of coordination chemistry in biochemical and inorganic complexes, historically the technique has been associated with the use of an extremely toxic chemical, dimethylmercury [Me2Hg or (CH3)2Hg], as a reference standard. In the 25 years since an accidental exposure to Me2Hg led to the tragic death of Dr. Karen Wetterhahn, the community has learned a great deal about the insidious neurotoxicity of this compound as well as more appropriate ways to avoid exposure. Here, we track the general shift toward the use of alternative mercury reference standards and away from Me2Hg.
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Affiliation(s)
- David Z. Zee
- The Chemistry of Life Processes Institute, Northwestern University, Evanston, Illinois 60208, United States
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Christopher P. Singer
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Thomas V. O’Halloran
- The Chemistry of Life Processes Institute, Northwestern University, Evanston, Illinois 60208, United States
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
- Department of Chemistry, Molecular Biosciences, Northwestern University, Evanston, Illinois 60208, United States
- The Elemental Health Institute, Michigan State University, East Lansing, Michigan 48824, United States
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan 48824, United States
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
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Eckert P, Johs A, Semrau JD, DiSpirito AA, Richardson J, Sarangi R, Herndon E, Gu B, Pierce EM. Spectroscopic and computational investigations of organometallic complexation of group 12 transition metals by methanobactins from Methylocystis sp. SB2. J Inorg Biochem 2021; 223:111496. [PMID: 34271330 PMCID: PMC10569158 DOI: 10.1016/j.jinorgbio.2021.111496] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Revised: 05/17/2021] [Accepted: 05/26/2021] [Indexed: 12/30/2022]
Abstract
Methanotrophic bacteria catalyze the aerobic oxidation of methane to methanol using Cu-containing enzymes, thereby exerting a modulating influence on the global methane cycle. To facilitate the acquisition of Cu ions, some methanotrophic bacteria secrete small modified peptides known as "methanobactins," which strongly bind Cu and function as an extracellular Cu recruitment relay, analogous to siderophores and Fe. In addition to Cu, methanobactins form complexes with other late transition metals, including the Group 12 transition metals Zn, Cd, and Hg, although the interplay among solution-phase configurations, metal interactions, and the spectroscopic signatures of methanobactin-metal complexes remains ambiguous. In this study, the complexation of Zn, Cd, and Hg by methanobactin from Methylocystis sp. strain SB2 was studied using a combination of absorbance, fluorescence, extended x-ray absorption fine structure (EXAFS) spectroscopy, and time-dependent density functional theory (TD-DFT) calculations. We report changes in sample absorbance and fluorescence spectral dynamics, which occur on a wide range of experimental timescales and characterize a clear stoichiometric complexation dependence. Mercury L3-edge EXAFS and TD-DFT calculations suggest a linear model for HgS coordination, and TD-DFT suggests a tetrahedral model for Zn2+ and Cd2+. We observed an enhancement in the fluorescence of methanobactin upon interaction with transition metals and propose a mechanism of complexation-hindered isomerization drawing inspiration from the wild-type Green Fluorescent Protein active site. Collectively, our results represent the first combined computational and experimental spectroscopy study of methanobactins and shed new light on molecular interactions and dynamics that characterize complexes of methanobactins with Group 12 transition metals.
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Affiliation(s)
- Peter Eckert
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA.
| | - Alexander Johs
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA
| | - Jeremy D Semrau
- Civil & Environmental Engineering, The University of Michigan, Ann Arbor, MI 48109, USA
| | - Alan A DiSpirito
- Roy J. Carver Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, IA 50011, USA
| | - Jocelyn Richardson
- Structural Molecular Biology Division, SLAC National Accelerator Laboratory, Menlo Park, CA 94306, USA
| | - Ritimukta Sarangi
- Structural Molecular Biology Division, SLAC National Accelerator Laboratory, Menlo Park, CA 94306, USA
| | - Elizabeth Herndon
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA
| | - Baohua Gu
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA
| | - Eric M Pierce
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA.
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Manceau A, Gaillot AC, Glatzel P, Cherel Y, Bustamante P. In Vivo Formation of HgSe Nanoparticles and Hg-Tetraselenolate Complex from Methylmercury in Seabirds-Implications for the Hg-Se Antagonism. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2021; 55:1515-1526. [PMID: 33476140 DOI: 10.1021/acs.est.0c06269] [Citation(s) in RCA: 67] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
In vivo and in vitro evidence for detoxification of methylmercury (MeHg) as insoluble mercury selenide (HgSe) underlies the central paradigm that mercury exposure is not or little hazardous when tissue Se is in molar excess (Se:Hg > 1). However, this hypothesis overlooks the binding of Hg to selenoproteins, which lowers the amount of bioavailable Se that acts as a detoxification reservoir for MeHg, thereby underestimating the toxicity of mercury. This question was addressed by determining the chemical forms of Hg in various tissues of giant petrels Macronectes spp. using a combination of high energy-resolution X-ray absorption near edge structure and extended X-ray absorption fine structure spectroscopy, and transmission electron microscopy coupled to elemental mapping. Three main Hg species were identified, a MeHg-cysteinate complex, a four-coordinate selenocysteinate complex (Hg(Sec)4), and a HgSe precipitate, together with a minor dicysteinate complex Hg(Cys)2. The amount of HgSe decreases in the order liver > kidneys > brain = muscle, and the amount of Hg(Sec)4 in the order muscle > kidneys > brain > liver. On the basis of biochemical considerations and structural modeling, we hypothesize that Hg(Sec)4 is bound to the carboxy-terminus domain of selenoprotein P (SelP) which contains 12 Sec residues. Structural flexibility allows SelP to form multinuclear Hgx(Se,Sec)y complexes, which can be biomineralized to HgSe by protein self-assembly. Because Hg(Sec)4 has a Se:Hg molar ratio of 4:1, this species severely depletes the stock of bioavailable Se for selenoprotein synthesis and activity to one μg Se/g dry wet in the muscle of several birds. This concentration is still relatively high because selenium is naturally abundant in seawater, therefore it probably does not fall below the metabolic need for essential selenium. However, this study shows that this may not be the case for terrestrial animals, and that muscle may be the first tissue potentially injured by Hg toxicity.
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Affiliation(s)
- Alain Manceau
- Université Grenoble Alpes, CNRS, ISTerre, 38000 Grenoble, France
| | - Anne-Claire Gaillot
- Université Nantes, CNRS, Institut des Matériaux Jean Rouxel, IMN, 44000 Nantes, France
| | - Pieter Glatzel
- European Synchrotron Radiation Facility (ESRF), 71 Rue des Martyrs, 38000 Grenoble, France
| | - Yves Cherel
- Centre d'Etudes Biologiques de Chizé (CEBC), CNRS-La Rochelle Université, 79360 Villiers-en-Bois, France
| | - Paco Bustamante
- La Rochelle Université, CNRS, Littoral Environnement et Sociétés (LIENSs), 17000, La Rochelle, France
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Bourdineaud JP, Gonzalez-Rey M, Rovezzi M, Glatzel P, Nagy KL, Manceau A. Divalent Mercury in Dissolved Organic Matter Is Bioavailable to Fish and Accumulates as Dithiolate and Tetrathiolate Complexes. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:4880-4891. [PMID: 30719924 DOI: 10.1021/acs.est.8b06579] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
The freshwater cyprinid Tanichthys albonubes was used to assess the bioavailability of divalent mercury (Hg(II)) complexed in dissolved organic matter (DOM) to fish. The fish acquired 0.3 to 2.2 μg Hg/g dry weight after 8 weeks in aquaria containing DOM from a Carex peat with complexed mercury at initial concentrations of 14 nM to 724 nM. Changes in the relative proportions of dithiolate Hg(SR)2 and nanoparticulate β-HgS in the DOM, as quantified by high energy-resolution XANES (HR-XANES) spectroscopy, indicate that Hg(SR)2 complexes either produced by microbially induced dissolution of nanoparticulate β-HgS in the DOM or present in the original DOM were the forms of mercury that entered the fish. In the fish with 2.2 μg Hg/g, 84 ± 8% of Hg(II) was bonded to two axial thiolate ligands and one or two equatorial N/O electron donors (Hg[(SR)2+(N/O)1-2] coordination), and 16% had a Hg(SR)4 coordination, as determined by HR-XANES. For comparison, fish exposed to Hg2+ from 40 nM HgCl2 contained 10.4 μg Hg/g in the forms of dithiolate (20 ± 10%) and tetrathiolate (23 ± 10%) complexes, and also Hg xS y clusters (57 ± 15%) having a β-HgS-type local structure and a dimension that exceeded the size of metallothionein clusters. There was no evidence of methylmercury in the fish or DOM within the 10% uncertainty of the HR-XANES. Together, the results indicate that inorganic Hg(II) bound to DOM is a source of mercury to biota with dithiolate Hg(SR)2 complexes as the immediate species bioavailable to fish, and that these complexes transform in response to cellular processes.
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Affiliation(s)
- Jean-Paul Bourdineaud
- Institut Européen de Chimie et Biologie, Université de Bordeaux, CNRS , 2 rue Escarpit , 33607 Pessac , France
| | - Maria Gonzalez-Rey
- Laboratoire EPOC , Université de Bordeaux, CNRS , 33120 Arcachon , France
| | - Mauro Rovezzi
- European Synchrotron Radiation Facility (ESRF) , 71 Rue des Martyrs , 38000 Grenoble , France
| | - Pieter Glatzel
- European Synchrotron Radiation Facility (ESRF) , 71 Rue des Martyrs , 38000 Grenoble , France
| | - Kathryn L Nagy
- Department of Earth and Environmental Sciences , University of Illinois at Chicago , MC-186, 845 West Taylor Street , Chicago , Illinois 60607 , United States
| | - Alain Manceau
- ISTerre, Université Grenoble Alpes, CNRS , 38000 Grenoble , France
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Karri R, Chalana A, Das R, Rai RK, Roy G. Cytoprotective effects of imidazole-based [S 1] and [S 2]-donor ligands against mercury toxicity: a bioinorganic approach. Metallomics 2019; 11:213-225. [PMID: 30488926 DOI: 10.1039/c8mt00237a] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Here we report the coordination behaviour of an imidazole-based [S1]-donor ligand, 1,3-dimethyl-imidazole-2(3H)-thione (L1), and [S2]-donor ligand, 3,3'-methylenebis(1-methyl-imidazole-2(3H)-thione) (L2) or 4,4'-(3,3'-methylenebis-(2-thioxo-2,3-dihydro-imidazole-3,1-diyl))dibutanoic acid (L3), with HgX2 (X = Cl, Br or I) in solution and the solid state. NMR, UV-Vis spectroscopic, and single crystal X-ray studies demonstrated that L1 or L2 coordinated rapidly and reversibly to the mercury center of HgX2 through the thione moiety. Treatment of L2 with HgCl2 or HgBr2 afforded 16-membered metallacycle k1-(L2)2Hg2Cl4 or k1-(L2)2Hg2Br4 where two Cl or Br atoms are located inside the ring. In contrast, treatment of L2 with HgI2 afforded a chain-like structure of k1-[L2Hgl2]n, possibly due to the large size of the iodine atom. Interestingly, [S1] and [S2]-donor ligands (L1, L2, and L3) showed an excellent efficacy to protect liver cells against HgCl2 induced toxicity and the strength of their efficacy is in the order of L3 > L2 > L1. 30% decrease of ROS production was observed when liver cells were co-treated with HgCl2 and L1 in comparison to those cells treated with HgCl2 only. In contrast, 45% and 60% decrease of ROS production was observed in the case of cells co-treated with HgCl2 and thiones L2 and L3, respectively, indicating that [S2]-donor ligands L2 and L3 have better cytoprotective effects against oxidative stress induced by HgCl2 than [S1]-donor ligand L1. Water-soluble ligand L3 with N-(CH2)3CO2H substituents showed a better cytoprotective effect against HgCl2 toxicity than L2 in liver cells.
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Affiliation(s)
- Ramesh Karri
- Department of Chemistry, School of Natural Sciences, Shiv Nadar University, NH91, Dadri, Gautam Buddha Nagar, UP 201314, India.
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Avellan A, Stegemeier JP, Gai K, Dale J, Hsu-Kim H, Levard C, O'Rear D, Hoelen TP, Lowry GV. Speciation of Mercury in Selected Areas of the Petroleum Value Chain. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2018; 52:1655-1664. [PMID: 29224346 DOI: 10.1021/acs.est.7b05066] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Petroleum, natural gas, and natural gas condensate can contain low levels of mercury (Hg). The speciation of Hg can affect its behavior during processing, transport, and storage so efficient and safe management of Hg requires an understanding of its chemical form in oil, gas and byproducts. Here, X-ray absorption spectroscopy was used to determine the Hg speciation in samples of solid residues collected throughout the petroleum value chain including stabilized crude oil residues, sediments from separation tanks and condensate glycol dehydrators, distillation column pipe scale, and biosludge from wastewater treatment. In all samples except glycol dehydrators, metacinnabar (β-HgS) was the primary form of Hg. Electron microscopy on particles from a crude sediment showed nanosized (<100 nm) particles forming larger aggregates, and confirmed the colocalization of Hg and sulfur. In sediments from glycol dehydrators, organic Hg(SR)2 accounted for ∼60% of the Hg, with ∼20% present as β-HgS and/or Hg(SR)4 species. β-HgS was the predominant Hg species in refinery biosludge and pipe scale samples. However, the balance of Hg species present in these samples depended on the nature of the crude oil being processed, i.e. sweet (low sulfur crudes) vs sour (higher sulfur crudes). This information on Hg speciation in the petroleum value chain will inform development of better engineering controls and management practices for Hg.
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Affiliation(s)
- Astrid Avellan
- Carnegie Mellon University , Pittsburgh, Pennsylvania 15213, United States
- Center for Environmental Implications of Nanotechnology , Pittsburgh, Pennsylvania 15213, United States
| | - John P Stegemeier
- Carnegie Mellon University , Pittsburgh, Pennsylvania 15213, United States
- Center for Environmental Implications of Nanotechnology , Pittsburgh, Pennsylvania 15213, United States
| | - Ke Gai
- Carnegie Mellon University , Pittsburgh, Pennsylvania 15213, United States
- Center for Environmental Implications of Nanotechnology , Pittsburgh, Pennsylvania 15213, United States
| | - James Dale
- Center for Environmental Implications of Nanotechnology , Pittsburgh, Pennsylvania 15213, United States
- Geological and Environmental Science, Virginia Tech , Blacksburg, Virginia 24061, United States
| | - Heileen Hsu-Kim
- Center for Environmental Implications of Nanotechnology , Pittsburgh, Pennsylvania 15213, United States
- Civil & Environmental Engineering, Duke University , Durham, North Carolina 27708-0287, United States
| | - Clément Levard
- Center for Environmental Implications of Nanotechnology , Pittsburgh, Pennsylvania 15213, United States
- Aix Marseille Univ., CNRS, IRD, Coll. France, CEREGE , Aix en Provence, France
| | - Dennis O'Rear
- Chevron Energy Technology Company , Richmond, California 94802, United States
| | - Thomas P Hoelen
- Chevron Energy Technology Company , Richmond, California 94802, United States
| | - Gregory V Lowry
- Carnegie Mellon University , Pittsburgh, Pennsylvania 15213, United States
- Center for Environmental Implications of Nanotechnology , Pittsburgh, Pennsylvania 15213, United States
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Application of Heteronuclear NMR Spectroscopy to Bioinorganic and Medicinal Chemistry ☆. REFERENCE MODULE IN CHEMISTRY, MOLECULAR SCIENCES AND CHEMICAL ENGINEERING 2018. [PMCID: PMC7157447 DOI: 10.1016/b978-0-12-409547-2.10947-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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11
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Thomas SA, Gaillard JF. Cysteine Addition Promotes Sulfide Production and 4-Fold Hg(II)-S Coordination in Actively Metabolizing Escherichia coli. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:4642-4651. [PMID: 28353340 DOI: 10.1021/acs.est.6b06400] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The bacterial uptake of mercury(II), Hg(II), is believed to be energy-dependent and is enhanced by cysteine in diverse species of bacteria under aerobic and anaerobic conditions. To gain insight into this Hg(II) biouptake pathway, we have employed X-ray absorption spectroscopy (XAS) to investigate the relationship between exogenous cysteine, cellular metabolism, cellular localization, and Hg(II) coordination in aerobically respiring Escherichia coli (E. coli). We show that cells harvested in exponential growth phase consistently display mixtures of 2-fold and 4-fold Hg(II) coordination to sulfur (Hg-S2 and Hg-S4), with added cysteine enhancing Hg-S4 formation. In contrast, cells in stationary growth phase or cells treated with a protonophore causing a decrease in cellular ATP predominantly contain Hg-S2, regardless of cysteine addition. Our XAS results favor metacinnabar (β-HgS) as the Hg-S4 species, which we show is associated with both the cell envelope and cytoplasm. Additionally, we observe that added cysteine abiotically oxidizes to cystine and exponentially growing E. coli degrade high cysteine concentrations (100-1000 μM) into sulfide. Thermodynamic calculations confirm that cysteine-induced sulfide biosynthesis can promote the formation of dissolved and particulate Hg(II)-sulfide species. This report reveals new complexities arising in Hg(II) bioassays with cysteine and emphasizes the need for considering changes in chemical speciation as well as growth stage.
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Affiliation(s)
- Sara A Thomas
- Department of Civil and Environmental Engineering, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Jean-François Gaillard
- Department of Civil and Environmental Engineering, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208, United States
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