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Dong H, Wei G, Cao T, Shao B, Guan X, Strathmann TJ. Insights into the Oxidation of Organic Cocontaminants during Cr(VI) Reduction by Sulfite: The Overlooked Significance of Cr(V). ENVIRONMENTAL SCIENCE & TECHNOLOGY 2020; 54:1157-1166. [PMID: 31858777 DOI: 10.1021/acs.est.9b03356] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Literature works reported that organic cocontaminants could be degraded during Cr(VI), a contaminant, reduction by sulfite (Cr(VI)/sulfite process). However, the role of Cr(V) and Cr(IV) intermediates in the Cr(VI)/sulfite process has been overlooked. In this study, we confirmed the generation of Cr(V) and proposed a new mechanism for the decomposition of coexisting organic contaminants during Cr(VI)/sulfite reactions occurring in oxygenated solutions at pHini 4.0 with the molar ratio of sulfite to Cr(VI) of 10.0. UV-visible and electron paramagnetic resonance (EPR) spectra indicate that Cr(V) was the predominant Cr intermediates in oxygenated solutions, while Cr(IV) accumulated in deoxygenated solutions. The contribution of Cr(V) to the degradation of organic contaminants was verified by the EPR spectra collected at 2 K and using methyl phenyl sulfoxide as a probe compound. Both Cr(V) and SO4•- contributed to the decomposition of organic contaminants in oxygenated solutions, with the relative contributions from each species being strongly dependent on properties of the target organic cocontaminants. The key mechanisms responsible for Cr(V) accumulation were supported by DFT calculations, and the degradation kinetics of organic cocontaminants was simulated with the program Kintecus 6.51. This work advances the fundamental understanding of the oxidative transformation of coexisting organic contaminants in this process.
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Affiliation(s)
- Hongyu Dong
- Shanghai Institute of Pollution Control and Ecological Security , Shanghai 200092 , China
| | | | | | - Binbin Shao
- Shanghai Institute of Pollution Control and Ecological Security , Shanghai 200092 , China
| | - Xiaohong Guan
- Shanghai Institute of Pollution Control and Ecological Security , Shanghai 200092 , China
| | - Timothy J Strathmann
- Department of Civil & Environmental Engineering , Colorado School of Mines , Golden , Colorado 80401 , United States
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Spectroscopic characterization of genotoxic chromium(V) peptide complexes: Oxidation of Chromium(III) triglycine, tetraglycine and pentaglycine complexes. J Inorg Biochem 2016; 162:227-237. [DOI: 10.1016/j.jinorgbio.2016.06.015] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2015] [Revised: 06/07/2016] [Accepted: 06/14/2016] [Indexed: 11/23/2022]
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3
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das Neves RP, Santos TM, Pereira MDL, de Jesus JP. Comparative histological studies on liver of mice exposed to Cr(VI) and Cr(V) compounds. Hum Exp Toxicol 2016; 21:365-9. [PMID: 12269698 DOI: 10.1191/0960327102ht243oa] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Chromium toxicity is strongly dependent on its oxidation state. Cr(VI) is carcinogenic and mutagenic, although its in vivo and in vitro toxic effects are related to its intracellular fate. Inside the cells, Cr(VI) is rapidly reduced to stable Cr(III). As Cr(V) and Cr(IV) species have been reported to be formed in the Cr(VI) reduction pathways, Cr(VI)induced damage is thought, at least in part, to arise from these hypervalent species. The study of Cr(VI) reduction mechanisms and the characterization of the effects of each reactive intermediate constitute important steps towards a better understanding of chromium toxicity. The purpose of this work is to enlarge the scope of Cr(VI)induced alterations in mouse to other chromium species. Our studies have led to the in situ preparation of a new Cr(V) complex, [CrV–BT]2–, a stable compound at neutral pH, which mimics Cr(VI) reduction intermediates. The effect of Cr(V) on the histology of mice liver is assessed and compared with similar Cr(VI) assays. Liver toxicity was examined after single administrations of Cr(VI) or [CrV–BT]2– to mice. Both compounds produced reversible hepatic damage in a time-dependent manner. However, Cr(V) toxic effects have proved to be more rapid than with Cr(VI), permitting the role of Cr(VI) intermediates formed during intracellular chromium reduction to be highlighted.
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Wrobel K, Corrales Escobosa AR, Gonzalez Ibarra AA, Mendez Garcia M, Yanez Barrientos E, Wrobel K. Mechanistic insight into chromium(VI) reduction by oxalic acid in the presence of manganese(II). JOURNAL OF HAZARDOUS MATERIALS 2015; 300:144-152. [PMID: 26177490 DOI: 10.1016/j.jhazmat.2015.06.066] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2015] [Revised: 05/06/2015] [Accepted: 06/30/2015] [Indexed: 06/04/2023]
Abstract
Over the past few decades, reduction of hexavalent chromium (Cr(VI)) has been studied in many physicochemical contexts. In this research, we reveal the mechanism underlying the favorable effect of Mn(II) observed during Cr(VI) reduction by oxalic acid using liquid chromatography with spectrophotometric diode array detector (HPLC-DAD), nitrogen microwave plasma atomic emission spectrometry (HPLC-MP-AES), and high resolution mass spectrometry (ESI-QTOFMS). Both reaction mixtures contained potassium dichromate (0.67 mM Cr(VI)) and oxalic acid (13.3mM), pH 3, one reaction mixture contained manganese sulfate (0.33 mM Mn(II)). In the absence of Mn(II) only trace amounts of reaction intermediates were generated, most likely in the following pathways: (1) Cr(VI)→ Cr(IV) and (2) Cr(VI)+Cr(IV)→ 2Cr(V). In the presence of Mn(II), the active reducing species appeared to be Mn(II) bis-oxalato complex (J); the proposed reaction mechanism involves a one-electron transfer from J to any chromium compound containing CrO bond, which is reduced to CrOH, and the generation of Mn(III) bis-oxalato complex (K). Conversion of K to J was observed, confirming the catalytic role of Mn(II). Since no additional acidification was required, the results obtained in this study may be helpful in designing a new, environmentally friendly strategy for the remediation of environments contaminated with Cr(VI).
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Affiliation(s)
- Katarzyna Wrobel
- Chemistry Department, Division of Natural and Exact Sciences, University of Guanajuato, L. de Retana 5, 36000 Guanajuato, Mexico
| | - Alma Rosa Corrales Escobosa
- Chemistry Department, Division of Natural and Exact Sciences, University of Guanajuato, L. de Retana 5, 36000 Guanajuato, Mexico
| | - Alan Alexander Gonzalez Ibarra
- Chemistry Department, Division of Natural and Exact Sciences, University of Guanajuato, L. de Retana 5, 36000 Guanajuato, Mexico
| | - Manuel Mendez Garcia
- Chemistry Department, Division of Natural and Exact Sciences, University of Guanajuato, L. de Retana 5, 36000 Guanajuato, Mexico
| | - Eunice Yanez Barrientos
- Chemistry Department, Division of Natural and Exact Sciences, University of Guanajuato, L. de Retana 5, 36000 Guanajuato, Mexico
| | - Kazimierz Wrobel
- Chemistry Department, Division of Natural and Exact Sciences, University of Guanajuato, L. de Retana 5, 36000 Guanajuato, Mexico.
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Bartholomäus R, Irwin JA, Shi L, Smith SM, Levina A, Lay PA. Isolation, Characterization, and Nuclease Activity of Biologically Relevant Chromium(V) Complexes with Monosaccharides and Model Diols. Likely Intermediates in Chromium-Induced Cancers. Inorg Chem 2013; 52:4282-92. [DOI: 10.1021/ic3022408] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Ruben Bartholomäus
- Fachbereich Chemie, Philipps-Universität Marburg,
Hans-Meerwein-Strasse, D-35032 Marburg, Germany
- School of Chemistry, The University of Sydney, New South
Wales 2006, Australia
| | - Jennifer A. Irwin
- School of Chemistry, The University of Sydney, New South
Wales 2006, Australia
| | - Liwei Shi
- School of Chemistry, The University of Sydney, New South
Wales 2006, Australia
| | - Siwaporn Meejoo Smith
- School of Chemistry, The University of Sydney, New South
Wales 2006, Australia
- Department of Chemistry, Faculty of Science, Mahidol University, Rama VI Road, Bangkok 10400, Thailand
| | - Aviva Levina
- School of Chemistry, The University of Sydney, New South
Wales 2006, Australia
| | - Peter A. Lay
- School of Chemistry, The University of Sydney, New South
Wales 2006, Australia
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Arakawa H, Weng MW, Chen WC, Tang MS. Chromium (VI) induces both bulky DNA adducts and oxidative DNA damage at adenines and guanines in the p53 gene of human lung cells. Carcinogenesis 2012; 33:1993-2000. [PMID: 22791815 DOI: 10.1093/carcin/bgs237] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Chromium (VI) [Cr(VI)], a ubiquitous environmental carcinogen, is generally believed to induce mainly mutagenic binary and ternary Cr(III)-deoxyguanosine (dG)-DNA adducts in human cells. However, both adenine (A) and guanine (G) mutations are found in the p53 gene in Cr exposure-related lung cancer. Using UvrABC nuclease and formamidopyrimidine glycosylase (Fpg), and ligation-mediated PCR methods, we mapped the distribution of bulky DNA adducts (BDA) and oxidative DNA damage (ODD) in the p53 gene in Cr(VI)-treated human lung cells. We found that both BDA and ODD formed at 2'-deoxyadenosine (dA) and dG bases. To understand the causes for these Cr-induced DNA damages, we mapped the distribution of BDA adducts and ODD in the p53 gene DNA fragments induced by Cr(III), Cr(VI) and Cr(V), the three major cellular Cr forms. We found that (i) dA at -CA- is a major Cr(VI) binding site followed by -GG- and -G-. Cr(VI) does not bind to -GGG-, (ii) Cr(VI)-DNA binding specificity is distinctly different from the Cr(III)-DNA binding in which -GGG- and -GG- are preferential sites, (iii) Cr(V) binding sites include all of Cr(VI) and Cr(III)-DNA binding sites and (iv) Cr(VI) and Cr(V) induce Fpg-sensitive sites at -G-. Together, these results suggest that Cr(VI) induction of BDA and ODD at dA and dG residues is through Cr(V) intermediate. We propose that these Cr(VI)-induced BDA and ODD contribute to mutagenesis of the p53 gene that leads to lung carcinogenesis.
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Affiliation(s)
- Hirohumi Arakawa
- Department of Environmental Medicine, New York University School of Medicine,Tuxedo Park, NY 10987, USA
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Affiliation(s)
- Markus Drees
- Anorganische Chemie, Technische Universität München, Lichtenbergstrasse 4, 85747 Garching, Germany
| | - Thomas Strassner
- Physikalische Organische Chemie, Technische Universität Dresden, 01062 Dresden, Germany
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Sundararajan M, Campbell AJ, Hillier IH. How do enzymes reduce metals? The mechanism of the reduction of Cr(vi) in chromate by cytochromec7proteins proposed from DFT calculations. Faraday Discuss 2011; 148:195-205; discussion 207-28. [DOI: 10.1039/c003830j] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Sala LF, González JC, García SI, Frascaroli MI, Van Doorslaer S. Detection and structural characterization of oxo-chromium(V)-sugar complexes by electron paramagnetic resonance. Adv Carbohydr Chem Biochem 2011; 66:69-120. [PMID: 22123188 DOI: 10.1016/b978-0-12-385518-3.00002-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
This article describes the detection and characterization of oxo-Cr(V)-saccharide coordination compounds, produced during chromic oxidation of carbohydrates by Cr(VI) and Cr(V), using electron paramagnetic resonance (EPR) spectroscopy. After an introduction into the main importance of chromium (bio)chemistry, and more specifically the oxo-chromium(V)-sugar complexes, a general overview is given of the current state-of-the-art EPR techniques. The next step reviews which types of EPR spectroscopy are currently applied to oxo-Cr(V) complexes, and what information about these systems can be gained from such experiments. The advantages and pitfalls of the different approaches are discussed, and it is shown that the potential of high-field and pulsed EPR techniques is as yet still largely unexploited in the field of oxo-Cr(V) complexes. Subsequently, the discussion focuses on the analysis of oxo-Cr(V) complexes of different types of sugars and the implications of the results in terms of understanding chromium (bio)chemistry.
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Affiliation(s)
- Luis F Sala
- Departamento de Químico Física-Área Química General, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Santa Fe, Argentina
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Levina A, Zhang L, Lay PA. Formation and reactivity of chromium(V)-thiolato complexes: a model for the intracellular reactions of carcinogenic chromium(VI) with biological thiols. J Am Chem Soc 2010; 132:8720-31. [PMID: 20527748 DOI: 10.1021/ja101675w] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The nature of the long-lived EPR-active Cr(V) species observed in cells and biological fluids exposed to carcinogenic Cr(VI) has been definitively assigned from detailed kinetic and spectroscopic analyses of a model reaction of Cr(VI) with p-bromobenzenethiol (RSH) in the presence or absence of cyclic 1,2-diols (LH(2)) in aprotic or mixed solvents. The first definitive structures for Cr(V) complexes with a monodentate thiolato ligand, [Cr(V)O(SR)(4)](-) (g(iso) = 1.9960, A(iso) = 14.7 x 10(-4) cm(-1)), [Cr(V)OL(SR)(2)](-) (g(iso) = 1.9854, A(iso) = (15.8-16.2) x 10(-4) cm(-1)) and [Cr(V)(O)(2)(SR)(2)](-) (g(iso) = 1.9828, A(iso) = 6.8 x 10(-4) cm(-1)) were assigned by EPR spectroscopy and electrospray mass spectrometry. The unusually low A(iso) ((53)Cr) value for the latter species is consistent with its rare four-coordinate, bis-oxido structure. The [Cr(V)OL(SR)(2)](-) species are responsible for the transient g(iso) approximately 1.986 EPR signals observed in living cells and animals treated with Cr(VI) (where RSH and LH(2) are biological thiols and 1,2-diols, respectively). For the first time, concentrations of Cr(V) intermediates formed during the reduction of Cr(VI) were determined by quantitative EPR spectroscopy, and a detailed reaction mechanism was proposed on the basis of stochastic simulations of the kinetic curves for Cr(V) species. A key feature of the proposed mechanism is the regeneration of Cr(V) species in the presence of Cr(VI) through the formation of organic free radicals, followed by the rapid reactions of the formed radicals with Cr(VI). The concentration of Cr(V) grows rapidly at the beginning of the reaction, reaches a steady-state level, and then drops sharply once Cr(VI) is spent. Similar mechanisms are likely to operate during the reduction of Cr(VI) in biological environment rich in reactive C-H bonds, including the oxidative DNA damage by Cr(V) intermediates.
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Affiliation(s)
- Aviva Levina
- School of Chemistry, The University of Sydney, Sydney, New South Wales 2006, Australia
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11
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Mangiameli MF, González JC, García S, Bellú S, Santoro M, Caffaratti E, Frascaroli MI, Peregrín JMS, Atria AM, Sala LF. Redox, kinetics, and complexation chemistry of the CrVI/CrV/CrIV -D-glycero-D-gulo-heptono-1,4-lactone System. J PHYS ORG CHEM 2010. [DOI: 10.1002/poc.1745] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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12
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González JC, García S, Bellú S, Peregrín JMS, Atria AM, Sala LF, Signorella S. Redox and complexation chemistry of the CrVI/CrV/CrIV-d-glucuronic acid system. Dalton Trans 2010; 39:2204-17. [DOI: 10.1039/b915652f] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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13
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Levina A, Lay PA. Chemical properties and toxicity of chromium(III) nutritional supplements. Chem Res Toxicol 2008; 21:563-71. [PMID: 18237145 DOI: 10.1021/tx700385t] [Citation(s) in RCA: 160] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The status of Cr(III) as an essential micronutrient for humans is currently under question. No functional Cr(III)-containing biomolecules have been definitively described as yet, and accumulated experience in the use of Cr(III) nutritional supplements (such as [Cr(pic) 3], where pic = 2-pyridinecarboxylato) has shown no measurable benefits for nondiabetic people. Although the use of large doses of Cr(III) supplements may lead to improvements in glucose metabolism for type 2 diabetics, there is a growing concern over the possible genotoxicity of these compounds, particularly of [Cr(pic) 3]. The current perspective discusses chemical transformations of Cr(III) nutritional supplements in biological media, with implications for both beneficial and toxic actions of Cr(III) complexes, which are likely to arise from the same biochemical mechanisms, dependent on concentrations of the reactive species. These species include: (i) partial hydrolysis products of Cr(III) nutritional supplements, which are capable of binding to biological macromolecules and altering their functions; and (ii) highly reactive Cr(VI/V/IV) species and organic radicals, formed in reactions of Cr(III) with biological oxidants. Low concentrations of these species are likely to cause alterations in cell signaling (including enhancement of insulin signaling) through interactions with the active centers of regulatory enzymes in the cell membrane or in the cytoplasm, while higher concentrations are likely to produce genotoxic DNA lesions in the cell nucleus. These data suggest that the potential for genotoxic side-effects of Cr(III) complexes may outweigh their possible benefits as insulin enhancers, and that recommendations for their use as either nutritional supplements or antidiabetic drugs need to be reconsidered in light of these recent findings.
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Remya P, Suresh C, Reddy M. Rapid reduction and complexation of vanadium by 1-phenyl-3-methyl-4-toluoyl-5-pyrazolone: Spectroscopic characterization and structure modelling. Polyhedron 2007. [DOI: 10.1016/j.poly.2007.07.020] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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15
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Ilhan S, Temel H. Synthesis and characterization of a new macrocyclic Schiff base derived from 2,6-diaminopyridine and 1,10-bis(2-formylphenyl)-1,4,7,10-tetraoxadecane and its Cu(II), Ni(II), Pb(II), Co(III) and La(III) complexes. TRANSIT METAL CHEM 2007. [DOI: 10.1007/s11243-007-0276-5] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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16
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Saleh AA. Synthesis and spectroscopic studies of novel mononuclear complexes of cyclic and acyclic Schiff-base derivatives of tridentate and tetradentate coordination with some bivalent transition metal ions. J COORD CHEM 2006. [DOI: 10.1080/00958972512331334199] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Affiliation(s)
- Akila A. Saleh
- a Department of Chemistry , Faculty of Education, Ain Shams University , Roxy, Cairo, Egypt
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17
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Wilkins PC, Johnson MD, Holder AA, Crans DC. Reduction of Vanadium(V) byl-Ascorbic Acid at Low and Neutral pH: Kinetic, Mechanistic, and Spectroscopic Characterization. Inorg Chem 2006; 45:1471-9. [PMID: 16471958 DOI: 10.1021/ic050749g] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
L-Ascorbic acid interacts with vanadium(V) over the pH range of 0.4-7.0 to form three different coordination complexes. Both inner- and outer-sphere electron-transfer pathways are proposed to form vanadium(IV) complexes with L-ascorbate or dehydroascorbate, respectively. Effects of the pH on the coordination of L-ascorbic acid to the vanadium(V) center were observed and are presumably related to the speciation of the vanadium(V) ion. Three vanadium(IV) complexes were observed using ambient-temperature electron paramagnetic resonance spectroscopy. Two of these complexes are proposed to be vanadium(IV) L-ascorbate complexes, and one is consistent with a vanadium(IV) dehydroascorbic acid complex proposed earlier. These reduction reactions will occur under physiological conditions and could be important to the reduction of vanadium(V)-containing coordination complexes used as insulin-enhancing agents for treatment of diabetes.
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Affiliation(s)
- Patricia C Wilkins
- Department of Chemistry and Biochemistry, New Mexico State University, Las Cruces, 88003, USA
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Gez S, Luxenhofer R, Levina A, Codd R, Lay PA. Chromium(V) complexes of hydroxamic acids: formation, structures, and reactivities. Inorg Chem 2005; 44:2934-43. [PMID: 15819581 DOI: 10.1021/ic048317d] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A new family of relatively stable Cr(V) complexes, [Cr(V)O(L)(2)](-) (LH(2) = RC(O)NHOH, R = Me, Ph, 2-HO-Ph, or HONHC(O)(CH(2))(6)), has been obtained by the reactions of hydroxamic acids with Cr(VI) in polar aprotic solvents. Similar reactions in aqueous solutions led to the formation of transient Cr(V) species. All complexes have been characterized by electron paramagnetic resonance spectroscopy and electrospray mass spectrometry. A Cr(V) complex of benzohydroxamic acid (1, R = Ph) was isolated in a pure form (as a K(+) salt) and was characterized by X-ray absorption spectroscopy and analytical techniques. Multiple-scattering analysis of X-ray absorption fine structure spectroscopic data for 1 (solid, 10 K) point to a distorted trigonal-bipyramidal structure with trans-oriented Ph groups and Cr-ligand bond lengths of 1.58 A (Cr-O), 1.88 A (Cr-O(C)), and 1.98 A (Cr-O(N)). Under ambient conditions, 1 is stable for days in aprotic solvents but decomposes within minutes in aqueous solutions (maximal stability at pH approximately 7), which leads predominantly to the formation of Cr(III) complexes. Complex 1 readily undergoes ligand-exchange reactions with biological 1,2-diols, including D-glucose and mucin, in neutral aqueous solutions. It differs from most other types of Cr(V) complexes in its biological activity, since no oxidative cleavage of plasmid DNA in vitro and no significant bacterial mutagenicity (in the TA 102 strain of Salmonella typhimurium) was observed for 1. In natural systems, stabilization of Cr(V) by hydroxamato ligands from bacterial-derived siderophores (followed by ligand-exchange reactions with more abundant carbohydrate ligands) may occur during the biological reduction of Cr(VI) in contaminated soils.
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Affiliation(s)
- Swetlana Gez
- Centre for Heavy Metals Research, School of Chemistry, University of Sydney, NSW, 2006, Australia
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20
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Levina A, Lay PA. Mechanistic studies of relevance to the biological activities of chromium. Coord Chem Rev 2005. [DOI: 10.1016/j.ccr.2004.02.017] [Citation(s) in RCA: 156] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Barnard PJ, Levina A, Lay PA. Chromium(V) Peptide Complexes: Synthesis and Spectroscopic Characterization. Inorg Chem 2005; 44:1044-53. [PMID: 15859285 DOI: 10.1021/ic048322h] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A series of stable Cr(V) model complexes that mimic the binding of Cr(V) to peptide backbones at the C-terminus of proteins have been prepared for N,N-dimethylurea derivatives of the tripeptides Aib3-DMF, AibLAlaAib-DMF, and AibDAlaAib-DMF (Aib = 2-amino-2-methylpropanoic acid, DMF = N,N-dimethylformamide). The Cr(ll) precursor complexes were synthesized by the initial deprotonation of the amide and acid groups of the peptide ligands in DMF with potassium tert-butoxide in the presence of CrCl2. The Cr(II) intermediates thus formed were then immediately oxidized to Cr(V) using tert-butyl hydroperoxide. Spectroscopic and mass-spectrometric analyses of the Cr(V) complexes showed that a new metal-directed organic transformation of the ligand had occurred. This involved a DMF solvent molecule becoming covalently bound to the amine group of the peptide ligand, yielding a urea group, and a third coordinated deprotonated urea nitrogen donor. A metal-directed oxidative coupling has been proposed as a possible mechanism for the organic transformation. The Cr(V/IV) reduction potential was determined for the three Cr(V) complexes using cyclic voltammetry, and in all cases it was quasi-reversible. These are the first isolated and fully characterized Cr(V) complexes with non-sulfur-containing peptide ligands.
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Affiliation(s)
- Peter J Barnard
- Centre for Heavy Metals Research, School of Chemistry, University of Sydney, New South Wales 2006, Australia
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Weeks CL, Levina A, Dillon CT, Turner P, Fenton RR, Lay PA. Synthesis and Characterization of a Chromium(V) cis-Dioxo Bis(1,10-phenanthroline) Complex and Crystal and Molecular Structures of Its Chromium(III) Precursor. Inorg Chem 2004; 43:7844-56. [PMID: 15554650 DOI: 10.1021/ic049008q] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The first structurally characterized Cr(V) dioxo complex, cis-[CrV(O)2(phen)2](BF4) (2, phen=1,10-phenanthroline) has been synthesized by the oxidation of a related Cr(III) complex, cis-[Cr(III)(phen)2(OH2)2](NO3)3.2.5H2O (1, characterized by X-ray crystallography), with NaOCl in aqueous solutions in the presence of excess NaBF4, and its purity has been confirmed by electrospray mass spectrometry (ESMS), EPR spectroscopy, and analytical techniques. Previously reported methods for the generation of Cr(V)-phen complexes, such as the oxidation of 1 with PbO2 or PhIO, have been shown by ESMS to lead to mixtures of Cr(III), Cr(V), Cr(VI), and in some cases Cr(IV) species, 3. Species 3 was assigned as [CrIV(O)(OH)(phen)2]+, based on ESMS and X-ray absorption spectroscopy measurements. A distorted octahedral structure for 2 (CrO, 1.63 A; Cr-N, 2.04 and 2.16 A) was established by multiple-scattering (MS) modeling of XAFS spectra (solid, 10 K). The validity of the model was verified by a good agreement between the results of MS XAFS fitting and X-ray crystallography for 1 (distorted octahedron; Cr-O, 1.95 A; Cr-N, 2.06 A). Unlike for the well-studied Cr(V) 2-hydroxycarboxylato complexes, 2 was equally or more stable in aqueous media (hours at pH=1-13 and 25 degrees C) compared with polar aprotic solvents. A stable Cr(III)-Cr(VI) dimer, [Cr(III)(Cr(VI)O4)(phen)2]+ (detected by ESMS), is formed during the decomposition of 2 in nonaqueous media. Comparative studies of the oxidation of 1 by NaOCl or PbO2 have shown that [Cr(V)(O)2(phen)2]+ was the active species responsible for the previously reported oxidative DNA damage, bacterial mutagenicity, and increased incidence of micronuclei in mammalian cells, caused by the oxidation products of 1 with PbO2. Efficient oxidation of 1 to a genotoxic species, [Cr(V)(O)2(phen)2]+, in neutral aqueous media by a biological oxidant, hypochlorite, supports the hypothesis on a significant role of reoxidation of Cr(III) complexes, formed during the intracellular reduction of Cr(VI), in Cr(VI)-induced carcinogenicity. Similar oxidation reactions may contribute to the reported adverse effects of a popular nutritional supplement, Cr(III) picolinate.
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Affiliation(s)
- Colin L Weeks
- Centre for Heavy Metals Research, School of Chemistry, University of Sydney, NSW 2006, Australia
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Kinetics and mechanism of a macrocyclic chromium(III) complex oxidation to chromium(IV) by hexacyanoferrate(III) in strongly alkaline media. TRANSIT METAL CHEM 2004. [DOI: 10.1007/s11243-004-4991-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Levina A, Lay PA. Solution structures of chromium(VI) complexes with glutathione and model thiols. Inorg Chem 2004; 43:324-35. [PMID: 14704084 DOI: 10.1021/ic034901v] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Chromium(VI) complexes of the most abundant biological reductant, glutathione (gamma-Glu-Cys-Gly, I), are among the likely initial reactive intermediates formed during the cellular metabolism of carcinogenic and genotoxic Cr(VI). Detailed structural characterization of such complexes in solutions has been performed by a combination of X-ray absorption fine structure (XAFS) and X-ray absorption near-edge structure (XANES) spectroscopies, electrospray mass spectrometry (ESMS), UV-vis spectroscopy, and kinetic studies. The Cr(VI) complexes of two model thiols, N-acetyl-2-mercaptoethylamine (II) and 4-bromobenzenethiol (III), were used for comparison. The Cr(VI)-thiolato complexes were generated quantitatively in weakly acidic aqueous solutions (for I and II) or in DMF solutions (for II) or isolated as a pure solid (for III). Contrary to some claims in the literature, no evidence was found for the formation of relatively stable Cr(IV) intermediates during the reactions of Cr(VI) with I in acidic aqueous solutions. The Cr(VI) complexes of I-III exist as tetrahedral [CrO(3)(SR)](-) (IVa) species in the solid state, in solutions of aprotic solvents such as DMF, or in the gas phase (under ESMS conditions). In aqueous or alcohol solutions, reversible addition of a solvent molecule occurs, with the formation of five-coordinate species, [CrO(3)(SR)L](-) (IVb, probably of a trigonal bipyramidal structure, L = H(2)O or MeOH), with a Cr-L bond length of 1.97(1) A (determined by XAFS data modeling). Complex IVb (L = H(2)O) is also formed (in an equilibrium mixture with [CrO(4)](2)(-)) at the first stage of reduction of Cr(VI) by I in neutral aqueous solutions (as shown by global kinetic analysis of time-dependent UV-vis spectra). This is the first observation of a reversible ligand addition reaction in Cr(VI) complexes. The formation of IVb (rather than IVa, as thought before) during the reactions of Cr(VI) with I in aqueous solutions is likely to be important for the reactivity of Cr(VI) in cellular media, including DNA and protein damage and inhibition of protein tyrosine phosphatases.
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Affiliation(s)
- Aviva Levina
- Centre for Heavy Metals Research and Centre for Structural Biology and Structural Chemistry, School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia
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Roldán V, Santoro M, González JC, Salas-Peregrin JM, Signorella S, Sala LF. Kinetics and mechanism of the reduction of CrVI and CrV by d-lactobionic acid. J Inorg Biochem 2004; 98:347-57. [PMID: 14729315 DOI: 10.1016/j.jinorgbio.2003.11.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The oxidation of D-lactobionic acid by Cr(VI) yields the 2-ketoaldobionic acid and Cr(3+) as final products when a 20-times or higher excess of the aldobionic acid over Cr(VI) is used. The redox reaction takes place through a complex multistep mechanism, which involves the formation of intermediate Cr(IV) and Cr(V) species. Cr(IV) reacts with lactobionic acid much faster than Cr(V) and Cr(VI) do, and cannot be directly detected. However, the formation of CrO(2)(2+), observed by the first time for an acid saccharide/Cr(VI) system, provides indirect evidence for the intermediacy of Cr(IV) in the reaction path. Cr(VI) and the intermediate Cr(V) react with lactobionic acid at comparable rates, being the complete rate laws for the Cr(VI) and Cr(V) consumption expressed by: -d[Cr(VI)]/dt=[k(I)+k(II)[H(+)]][lactobionicacid][Cr(VI)], where k(I)=(4.1+/-0.1) x 10(-3) M(-1) s(-1) and k(II)=(2.1+/-0.1) x 10(-2) M(-2) s(-1); and -d[Cr(V)]/dt=[k(III)[H(+)]+(k(IV)+k(V)[H(+)])[lactobionicacid]] [Cr(V)], where k(III)=(1.8+/-0.1) x 10(-3) M(-1) s(-1), k(IV)=(1.1+/-0.1) x 10(-2) M(-1) s(-1) and k(V)=(1.0+/-0.1) x 10(-2) M(-2) s(-1), at 33 degrees C. The Electron Paramagnetic Resonance (EPR) spectra show that five-co-ordinate oxo-Cr(V) bischelates are formed at pH 1-5 with the aldobionic acid bound to Cr(V) through the alpha-hydroxyacid group.
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Affiliation(s)
- Viviana Roldán
- Departamento de Ciencias Básicas, Facultad de Ciencias Veterinarias, UNL, R.P. Kreder 735, Esperanza, Argentina
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Levina A, Codd R, Foran GJ, Hambley TW, Maschmeyer T, Masters AF, Lay PA. X-ray Absorption Spectroscopic Studies of Chromium(V/IV/III)− 2-Ethyl-2-hydroxybutanoato(2−/1−) Complexes. Inorg Chem 2004; 43:1046-55. [PMID: 14753827 DOI: 10.1021/ic030239r] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Structures of the complexes [Cr(V)O(ehba)(2)](-), [Cr(IV)O(ehbaH)(2)](0), and [Cr(III)(ehbaH)(2)(OH(2))(2)](+) (ehbaH(2) = 2-ethyl-2-hydroxybutanoic acid) in frozen aqueous solutions (10 K, [Cr] = 10 mM, 1.0 M ehbaH(2)/ehbaH, pH 3.5) have been determined by single- and multiple-scattering fitting of X-ray absorption fine structure (XAFS) data. An optimal set of fitting parameters has been determined from the XAFS calculations for a compound with known crystal structure, Na[Cr(V)O(ehba)(2)] (solid, 10 K). The structure of the Cr(V) complex [Cr(V)O(ehba)(2)](-) does not change in solution in the presence of excess ligand. Contrary to the earlier suggestions made from the kinetic data (Ghosh, M. C.; Gould, E. S. J. Chem. Soc., Chem. Commun. 1992, 195-196), the structure of the Cr(IV) complex (generated by the Cr(VI) + As(III) + ehbaH(2) reaction) is close to that of the Cr(V) complex (five-coordinate, distorted trigonal bipyramidal) and different from that of the Cr(III) complex (six-coordinate, octahedral). For both Cr(V) and Cr(IV) complexes, some disorder in the position of the oxo group is observed, which is consistent with but not definitive for the presence of geometric isomers. The structure of the Cr(IV) complex differs from that of Cr(V) by protonation of alcoholato groups of the ligands, which leads to significant elongation of the corresponding Cr-O bonds (2.0 vs 1.8 A). This is reflected in the different chemical properties reported previously for the Cr(IV) and Cr(V) complexes, including their reactivities toward DNA and other biomolecules in relation to Cr-induced carcinogenicity.
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Affiliation(s)
- Aviva Levina
- Centre for Structural Biology and Structural Chemistry, School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia
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Micellar effect on the kinetics and mechanism of chromium(VI) oxidation of organic substrates. Coord Chem Rev 2004. [DOI: 10.1016/j.cct.2003.10.012] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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28
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Gonzalez JC, Daier V, Garcia S, Goodman BA, Atria AM, Sala LF, Signorella S. Redox and complexation chemistry of the CrVI/CrV–d-galacturonic acid system. Dalton Trans 2004:2288-96. [PMID: 15278120 DOI: 10.1039/b405777e] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The oxidation of d-galacturonic acid by Cr(VI) yields the aldaric acid and Cr(III) as final products when a 30-times or higher excess of the uronic acid over Cr(VI) is used. The redox reaction involves the formation of intermediate Cr(IV) and Cr(V) species, with Cr(VI) and the two intermediate species reacting with galacturonic acid at comparable rates. The rate of disappearance of Cr(VI), Cr(IV) and Cr(V) depends on pH and [substrate], and the slow reaction step of the Cr(VI) to Cr(III) conversion depends on the reaction conditions. The EPR spectra show that five-coordinate oxo-Cr(V) bischelates are formed at pH < or = 5 with the uronic acid bound to Cr(V) through the carboxylate and the alpha-OH group of the furanose form or the ring oxygen of the pyranose form. Six-coordinated oxo-Cr(V) monochelates are observed as minor species in addition to the major five-coordinated oxo-Cr(V) bischelates only for galacturonic acid : Cr(VI) < or =10 : 1, in 0.25-0.50 M HClO(4). At pH 7.5 the EPR spectra show the formation of a Cr(V) complex where the vic-diol groups of Galur participate in the bonding to Cr(V). At pH 3-5 the Galur-Cr(V) species grow and decay over short periods in a similar way to that observed for [Cr(O)(alpha-hydroxy acid)(2)](-). The lack of chelation at any vic-diolate group of Galur when pH < or = 5 differentiates its ability to stabilise Cr(V) from that of neutral saccharides that form very stable oxo-Cr(V)(diolato)(2) species at pH > 1.
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Affiliation(s)
- Juan C Gonzalez
- Departamento de Quimica, Facultad de Ciencias Bioquimicas y Farmaceuticas, UNR, Suipacha 531, 2000 Rosario, Argentina
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Vasant C, Rajaram R, Ramasami T. Apoptosis of lymphocytes induced by chromium(VI/V) is through ROS-mediated activation of Src-family kinases and caspase-3. Free Radic Biol Med 2003; 35:1082-100. [PMID: 14572611 DOI: 10.1016/s0891-5849(03)00471-4] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Mechanistic insights into Cr(VI)-induced carcinogenicity and possible implication of Cr(V) species formed by the redox reactions of chromium-bearing species have attracted interest. We have previously demonstrated that when human peripheral blood lymphocytes are exposed to the Cr(V) complexes, viz., sodium bis(2-ethyl-2-hydroxybutyrato)oxochromate(V), Na[Cr(V)O(ehba)(2)] and sodium bis(2-hydroxy-2-methylbutyrato)oxochromate(V), Na[Cr(V)O(hmba)(2)], apoptosis and formation of reactive oxygen species (ROS) are observed. The molecular mechanisms involving cellular signaling pathways leading to apoptosis are addressed in the present study. Treatment of lymphocytes with Na[Cr(V)O(ehba)(2)] and K(2)Cr(2)O(7) leads to the activation of the Src-family protein tyrosine kinases namely, p56(lck), p59(fyn), and p56/53(lyn), which then activates caspase-3, both of which are under the partial influence of ROS. Inhibition of the Src-family tyrosine kinases activity by PP2 and of caspase-3 by Z-DEVD-FMK reverses apoptosis, thereby suggesting their importance. Antioxidants only partially reverse the apoptosis induced by Cr(VI/V), suggesting that pathways other than those induced by ROS cannot be ruled out. Although the complex, Na[Cr(V)O(ehba)(2)] is known to be relatively stable in aqueous solutions, previous studies have shown that the Cr(V) complex, Na[Cr(V)O(ehba)(2)] disproportionates to Cr(VI) and Cr(III) forms at pH 7.4 through complex mechanistic processes. Dynamics studies employing EPR data show that the Cr(V) state in Na[Cr(V)O(ehba)(2)] is relatively more stable in RPMI-1640 medium containing plasma. Formation of ROS during the reaction of redox partners with Na[Cr(V)O(ehba)(2)] is an early event and compares favorably in kinetic terms with the reported rate processes for disproportionation. This investigation presents evidence for the direct implication of Cr(V) in Cr(VI)-induced apoptosis of lymphocytes.
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Affiliation(s)
- Chellappa Vasant
- Biochemistry Laboratory, Central Leather Research Institute, Adyar, Chennai, India
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Cawich CM, Ibrahim A, Link KL, Bumgartner A, Patro MD, Mahapatro SN, Lay PA, Levina A, Eaton SS, Eaton GR. Synthesis of a Pyridinium Bis[citrato(2−)]oxochromate(V) Complex and Its Ligand-Exchange Reactions. Inorg Chem 2003; 42:6458-68. [PMID: 14514322 DOI: 10.1021/ic034146l] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The reaction of citric acid (caH(4)) with pyridinium dichromate (PDC) in anhydrous acetone yields pyridinium bis[citrato(2-)]oxochromate(V), pyH[CrO(caH(2))(2)], as a mixed salt with the Cr(III) product. The compound persists in the solid state for months, is highly soluble in water (pH 4.0), and gives a sharp electron paramagnetic resonance (EPR) signal in solution (g(iso) = 1.9781, A(iso)(Cr) = 17.1 x 10(-4) cm(-1)), which is characteristic of d(1) Cr(V). The presence of [Cr(V)O(caH(2))(2)](-) in the solid state was confirmed by electrospray mass spectroscopy, X-ray absorption near-edge structure (XANES), and EPR spectroscopy. Solid-state EPR spectroscopy, XANES, and a spectrophotometric assay showed that the solid is a mixture of [Cr(V)O(caH(2))(2)](-) and a Cr(III)-citrate complex. The structures of the [Cr(V)O(caH(2))(2)](-) and [Cr(III)(caH(2))(2)](-) components of the mixture were established by multiple-scattering MS analysis of the X-ray absorption fine structure data. The structure of [Cr(V)O(caH(2))(2)](-) is similar to that of other 2-hydroxy acid complexes with Cr=O, Cr-O(alcoholato), and Cr-O(carboxylato) bond lengths of 1.59, 1.81, and 1.90 A, respectively. The Cr(III) complex has bond lengths typical for ligands with deprotonated carboxylate and protonated alcohol donors with distances of 1.90 and 1.99 A, respectively, for the Cr-O(carboxylato) and Cr-O(alcohol) bond lengths. In aqueous solution, [CrO(caH(2))(2)](-) is short lived, but it is a convenient starting material for ligand-exchange reactions. It has been used to generate short-lived mixed-ligand Cr(V) complexes with citrate and picolinate, iminodiacetate, 2,2'-bipyridine, or 1,10-phenanthroline, which were characterized by EPR spectroscopy. The g values are between 1.971 and 1.974. For the picolinate, 2,2'-bipyridine, and 1,10-phenanthroline mixed-ligand complexes, there is hyperfine coupling (2.2 x 10(-4) to 2.4 x 10(-4) cm(-1)) to a single proton of the citrate ligand.
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Affiliation(s)
- Carissa M Cawich
- Department of Chemistry, Regis University, Denver, Colorado 80221, USA
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Abstract
Chromium(V) glutathione complexes are among the likely reactive intermediates in Cr(VI)-induced genotoxicity and carcinogenicity. The first definitive structure of one such complex, [Cr(V)O(LH(2))(2)](3)(-) (I; LH(5) = glutathione = GSH), isolated from the reaction of Cr(VI) with excess GSH at pH 7.0 (O'Brien, P.; Pratt, J.; Swanson, F. J.; Thornton, P.; Wang, G. Inorg. Chim. Acta 1990, 169, 265-269), has been determined by a combination of electrospray mass spectrometry (ESMS), X-ray absorption spectroscopy (XAS), EPR spectroscopy, and analytical techniques. In addition, Cr(V) complexes of GSH ethyl ester (gamma-Glu-Cys-GlyOEt) have been isolated and characterized by ESMS, and Cr(III) products of the Cr(VI) + GSH reaction have been isolated and characterized by ESMS and XAS. The thiolato and amido groups of the Cys residue in GSH are responsible for the Cr(V) binding in I. The Cr-ligand bond lengths, determined from multiple-scattering XAFS analysis, are as follows: 1.61 A for the oxo donor; 1.99 A for the amido donors; and 2.31 A for the thiolato donors. A significant electron withdrawal from the thiolato groups to Cr(V) in I was evident from the XANES spectra. Rapid decomposition of I in aqueous solutions (pH = 1-13) occurs predominantly by ligand oxidation with the formation of Cr(III) complexes of GSH and GSSG. Maximal half-lives of the Cr(V) species (40-50 s at [Cr] = 1.0 mM and 25 degrees C) are observed at pH 7.5-8.0. The experimental data are in conflict with a recent communication (Gaggelli, E.; Berti, F.; Gaggelli, N.; Maccotta, A.; Valensin, G. J. Am. Chem. Soc. 2001, 123, 8858-8859) on the formation of a Cr(V) dimer as a major product of the Cr(VI) + GSH reaction, which may have resulted from misinterpretation of the ESMS and NMR spectroscopic data.
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Affiliation(s)
- Aviva Levina
- Centre for Heavy Metal Research, School of Chemistry, University of Sydney, Sydney 2006 NSW, Australia
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Sarkar B, Mukhopadhyay P, Bharadwaj PK. Laterally non-symmetric aza-cryptands: synthesis, catalysis and derivatization to new receptors. Coord Chem Rev 2003. [DOI: 10.1016/s0010-8545(02)00058-9] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Roldán V, Carlos González J, Santoro M, García S, Casado N, Olivera S, Boggio JC, Salas-Peregrin JM, Signorella S, Sala LF. Kinetics and mechanism of the oxidation of disaccharides by CrVI. CAN J CHEM 2002. [DOI: 10.1139/v02-187] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The oxidation of D-lactose, D-maltose, D-melibiose, and D-cellobiose by CrVI yields the corresponding aldobionic acid and Cr3+ as final products when an excess of reducing disaccharide over CrVI is used. The rate law for the CrVI oxidation reaction is expressed by d[CrVI]/dt = kH [disaccharide][CrVI], where the second-order kinetic constant, kH, depends on [H+]. The relative reactivity of the disaccharides with CrVI is expressed as follows: Mel > Lac > Cel > Mal, at 33°C. In acid medium, intermediate CrV forms and reacts with the substrate faster than CrVI. The EPR spectra show that five- and six-coordinate oxo-CrV intermediates are formed, with the disaccharide acting as bidentate ligand. Five-coordinate oxo-CrV species are present at any [H+], whereas six-coordinate ones are observed only at pH < 2, where they rapidly decompose to the redox products. In the pH 37 range, where hexa-coordinate oxo-CrV species are not observed, CrV complexes are stable enough to remain in solution from several days to several months.Key words: chromium, saccharides, kinetics, EPR.
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Rizzotto M, Levina A, Santoro M, García S, Frascaroli MI, Signorella S, Sala LF, Lay PA. Redox and ligand-exchange chemistry of chromium(vi/v)-methyl glycoside systems. ACTA ACUST UNITED AC 2002. [DOI: 10.1039/b204280k] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Strassner T, Muehlhofer M, Grasser S. Isolation of a stable Cr(V) intermediate in the oxidation of aryl-substituted alkenes by chromylchloride. J Organomet Chem 2002. [DOI: 10.1016/s0022-328x(01)01301-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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36
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Levina A, Bailey AM, Champion G, Lay PA. Reactions of Chromium(VI/V/IV) with Bis(O-ethyl-l-cysteinato-N,S)zinc(II): A Model for the Action of Carcinogenic Chromium on Zinc-Finger Proteins1. J Am Chem Soc 2000. [DOI: 10.1021/ja9944047] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Pattison DI, Lay PA, Davies MJ. EPR studies of chromium(V) intermediates generated via reduction of chromium(VI) by DOPA and related catecholamines: potential role for oxidized amino acids in chromium-induced cancers. Inorg Chem 2000; 39:2729-39. [PMID: 11232807 DOI: 10.1021/ic991443a] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The reductions of K2Cr2O7 by catecholamines, DOPA, DOPA-beta,beta-d2, N-acetyl-DOPA, alpha-methyl-DOPA, dopamine, adrenaline, noradrenaline, catechol, 1,2-dihydroxybenzoic acid (DHBA), and 4-tert-butylcatechol (TBC), produce a number of Cr(V) electron paramagnetic resonance (EPR) signals. These species are of interest in relation to the potential role of oxidized proteins and amino acids in Cr-induced cancers. With excess organic ligand, all of the substrates yield Cr species with signals at g(iso) approximately 1.972 (Aiso(53Cr) > 23.9 x 10(-4) cm(-1)). These are similar to signals reported previously but have been reassigned as octahedral Cr(V) species with mixed catechol-derived ligands, [CrV(semiquinone)2(catecholate)]+. Experiments with excess K2Cr2O7 show complex behavior with the catecholamines and TBC. Several weak Cr(V) signals are detected after mixing, and the spectra evolve over time to yield relatively stable substrate-dependent signals at g(iso) approximately 1.980. These signals have been attributed to [Cr(O)L2](L = diolato) species, in which the Cr is coordinated to two cyclized catecholamine ligands and an oxo ligand. Isotopic labeling studies with DOPA (ring or side chain deuteration or enrichment with 15N), and simulation of the signals, show that the superhyperfine couplings originate from the side chain protons, confirming that the catecholamine ligands are cyclized. At pH 3.5, a major short-lived EPR signal is observed for many of the substrates at g(iso) approximately 1.969, but the species responsible for this signal was not identified. Several other minor Cr signals are detected, which are attributed (by comparison with isoelectronic V(IV) species) to Cr(V) complexes coordinated by a single catecholamine ligand (and auxiliary ligands e.g. H2O), or to [Cr(O)L2]- (L = diolato) species with a sixth ligand (e.g. H2O). Addition of catalase or deoxygenation of the solutions did not affect the main EPR signals. When the substrates were in excess (pH > 4.5), primary and secondary (cyclized) semiquinones were also detected. Semiquinone stabilization by Zn(II) complexation yielded stronger EPR signals (g(iso) approximately 2.004).
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Affiliation(s)
- D I Pattison
- School of Chemistry, University of Sydney, NSW, Australia
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