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Unprecedently large 37Cl/ 35Cl equilibrium isotopic fractionation on nano-confinement of chloride anion. Sci Rep 2022; 12:1768. [PMID: 35110604 PMCID: PMC8811032 DOI: 10.1038/s41598-022-05629-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Accepted: 01/14/2022] [Indexed: 11/09/2022] Open
Abstract
Confinement can result in unusual properties leading to new, exciting discoveries in the nano-realm. One such consequence of confinement at the nanoscale is extremally large isotopic fractionation, especially at sub-van der Waals distances. Herein, on the example of chlorine isotope effects, we show that at conditions of nanoencapsulation these effects may reach values by far larger than observed for the bulk environment, which in the case of nanotubes can lead to practical applications (e.g., in isotopic enrichment) and needs to be considered in analytical procedures that employ nanomaterials.
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2
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Paneth A, Paneth P. Isotopic Consequences of Host-Guest Interactions; Noncovalent Chlorine Isotope Effects. J Phys Chem B 2021; 125:1874-1880. [PMID: 33570409 PMCID: PMC8023698 DOI: 10.1021/acs.jpcb.0c10691] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2020] [Revised: 01/24/2021] [Indexed: 12/03/2022]
Abstract
Although weak intermolecular interactions are the essence of most processes of key importance in medicine, industry, environment, and life cycles, their characterization is still not sufficient. Enzymatic dehalogenations that involve chloride anion interaction within a host-guest framework is one of the many examples. Recently published experimental results on host-guest systems provided us with models suitable to assess isotopic consequences of these noncovalent interactions. Herein, we report the influence of environmental and structural variations on chlorine isotope effects. We show that these effects, although small, may obscure mechanistic interpretations, as well as analytical protocols of dehalogenation processes.
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Affiliation(s)
- Agata Paneth
- Department of Organic Chemistry, Faculty of Pharmacy, Medical University of Lublin, Chodźki 4a, 20-093 Lublin, Poland
| | - Piotr Paneth
- Institute of Applied Radiation Chemistry, Faculty of Chemistry, Lodz University of Technology, Żeromskiego 116, 90-924 Lodz, Poland
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3
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Tang C, Tan J, Fan Y, Zheng K, Yu Z, Peng X. Theoretical evaluation of inter-ion and intra-ion isotope effects in fragmentation: insights into chlorine and bromine isotope effects of halogenated organic compounds occurring in electron ionization mass spectrometry. RSC Adv 2020; 10:13749-13758. [PMID: 35492996 PMCID: PMC9051552 DOI: 10.1039/c9ra09155f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Accepted: 03/17/2020] [Indexed: 11/21/2022] Open
Abstract
A theoretical basis is proposed for elucidating the details and implications of chlorine and bromine isotope effects in dehalogenation reactions.
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Affiliation(s)
- Caiming Tang
- State Key Laboratory of Organic Geochemistry
- Guangzhou Institute of Geochemistry
- Chinese Academy of Sciences
- Guangzhou 510640
- China
| | - Jianhua Tan
- Guangzhou Quality Supervision and Testing Institute
- Guangzhou 510110
- China
| | - Yujuan Fan
- State Key Laboratory of Organic Geochemistry
- Guangzhou Institute of Geochemistry
- Chinese Academy of Sciences
- Guangzhou 510640
- China
| | - Ke Zheng
- State Key Laboratory of Organic Geochemistry
- Guangzhou Institute of Geochemistry
- Chinese Academy of Sciences
- Guangzhou 510640
- China
| | - Zhiqiang Yu
- State Key Laboratory of Organic Geochemistry
- Guangzhou Institute of Geochemistry
- Chinese Academy of Sciences
- Guangzhou 510640
- China
| | - Xianzhi Peng
- State Key Laboratory of Organic Geochemistry
- Guangzhou Institute of Geochemistry
- Chinese Academy of Sciences
- Guangzhou 510640
- China
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4
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Abstract
Approaches to determine chlorine kinetic isotope effects (Cl-KIEs) on enzymatic dehalogenations are discussed and illustrated by representative examples. Three aspects are considered. First methodology for experimental measurement of Cl-KIEs, with stress being on FAB-IRMS technique developed in our laboratory, is described. Subsequently, we concentrate our discussion on the consequences of reaction complexity in the interpretation of experimental values, a problem especially important in cases of polychlorinated reactants. The most fruitful studies of enzymatic dehalogenations by Cl-KIEs require their theoretical evaluation, hence the computational focus of the second part of this chapter.
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5
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Miska ME, Shouakar-Stash O, Holmstrand H. Stable chlorine isotope analysis of chlorinated acetic acids using gas chromatography/quadrupole mass spectrometry. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2015; 29:2341-2348. [PMID: 26563705 DOI: 10.1002/rcm.7407] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2015] [Revised: 09/23/2015] [Accepted: 09/23/2015] [Indexed: 06/05/2023]
Abstract
RATIONALE The environmental occurrence of chlorinated acetic acids (CAAs) has been extensively studied, but the sources and transport are still not yet fully understood. A promising approach for source apportionment and process studies is the isotopic characterization of target compounds. We present the first on-line stable chlorine isotope analysis of CAAs by use of gas chromatography/quadrupole mass spectrometry (GC/qMS). METHODS Following approved procedures for concentration analysis, CAAs extracted into MTBE were methylated to GC-amenable methyl esters (mCAAs). These mCAAs were then analyzed by GC/qMS for their stable chlorine isotope composition using a sample/standard-bracketing approach (CAA standards in the range δ(37) Cl -6.3 to -0.2 ‰, Standard Mean Ocean Chloride). RESULTS Cross-calibration of the herein presented method with off-line reference methods (thermal ionization and continuous-flow GC isotope ratio mass spectrometry; TI-MS and CF-GC/IRMS, respectively) shows good agreement between the methods (regression slope for GC/qMS vs reference method data sets: 0.92 ± 0.29). Sample amounts as small as 10 pmol Cl can herewith be analyzed with a precision of 0.1 to 0.4 ‰. CONCLUSIONS This method should be useful for environmental studies of CAAs at ambient concentrations in precipitations (<0.06 to 100 nmol L(-1) ), surface waters (<0.2 to 5 nmol L(-1) ) and soil (<0.6 to 2000 nmol kg(-1) dry soil) where conventional off-line methods cannot be applied.
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Affiliation(s)
- Milena E Miska
- Department of Environmental Science and Analytical Chemistry, Stockholm University, Stockholm, Sweden
| | - Orfan Shouakar-Stash
- Department of Earth and Environmental Sciences, University of Waterloo, Waterloo, Ontario, Canada
- Isotope Tracer Technologies Inc, Waterloo, Ontario, Canada
| | - Henry Holmstrand
- Department of Environmental Science and Analytical Chemistry, Stockholm University, Stockholm, Sweden
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6
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Gui J, Chen Z, Zhang Y, Zhang L, Liu F. Novel Approach to Stable Chlorine Isotope Analysis using Gas Chromatography-Negative Chemical Ionization Mass Spectrometry. ANAL LETT 2014. [DOI: 10.1080/00032719.2014.954122] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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7
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Grzybkowska A, Kaminski R, Dybala-Defratyka A. Theoretical predictions of isotope effects versus their experimental values for an example of uncatalyzed hydrolysis of atrazine. Phys Chem Chem Phys 2014; 16:15164-72. [DOI: 10.1039/c4cp00914b] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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8
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Bae SY, Winemiller MD. Mechanistic Insights into the Hydrolysis of 2-Chloroethyl Ethyl Sulfide: The Expanded Roles of Sulfonium Salts. J Org Chem 2013; 78:6457-70. [DOI: 10.1021/jo400392b] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- Su Y. Bae
- Research and Technology
Directorate, U.S. Army, Edgewood Chemical Biological Center (ECBC), Aberdeen
Proving Ground, Maryland 21010-5424, United States
| | - Mark D. Winemiller
- Research and Technology
Directorate, U.S. Army, Edgewood Chemical Biological Center (ECBC), Aberdeen
Proving Ground, Maryland 21010-5424, United States
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9
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Affiliation(s)
- Katarzyna Świderek
- Departamento de Quimica Fisica, Universitat de Valencia, 46100 Burjasot (Valencia),
Spain
| | - Piotr Paneth
- Institute of Applied
Radiation
Chemistry, Faculty of Chemistry, Lodz University of Technology, Zeromskiego 116, 90-924 Lodz, Poland
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10
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Hofstetter TB, Berg M. Assessing transformation processes of organic contaminants by compound-specific stable isotope analysis. Trends Analyt Chem 2011. [DOI: 10.1016/j.trac.2010.10.012] [Citation(s) in RCA: 111] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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11
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Oxidative dechlorination of halogenated phenols catalyzed by two distinct enzymes: Horseradish peroxidase and dehaloperoxidase. Arch Biochem Biophys 2011; 505:22-32. [DOI: 10.1016/j.abb.2010.09.018] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2010] [Revised: 09/15/2010] [Accepted: 09/19/2010] [Indexed: 11/21/2022]
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12
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Aeppli C, Holmstrand H, Andersson P, Gustafsson Ö. Direct Compound-Specific Stable Chlorine Isotope Analysis of Organic Compounds with Quadrupole GC/MS Using Standard Isotope Bracketing. Anal Chem 2009; 82:420-6. [DOI: 10.1021/ac902445f] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Christoph Aeppli
- Department of Applied Environmental Science (ITM), Stockholm University, Stockholm, Sweden, and Laboratory for Isotope Geology, Swedish Museum of Natural History, Stockholm, Sweden
| | - Henry Holmstrand
- Department of Applied Environmental Science (ITM), Stockholm University, Stockholm, Sweden, and Laboratory for Isotope Geology, Swedish Museum of Natural History, Stockholm, Sweden
| | - Per Andersson
- Department of Applied Environmental Science (ITM), Stockholm University, Stockholm, Sweden, and Laboratory for Isotope Geology, Swedish Museum of Natural History, Stockholm, Sweden
| | - Örjan Gustafsson
- Department of Applied Environmental Science (ITM), Stockholm University, Stockholm, Sweden, and Laboratory for Isotope Geology, Swedish Museum of Natural History, Stockholm, Sweden
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13
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Dybala-Defratyka A, Szatkowski L, Kaminski R, Wujec M, Siwek A, Paneth P. Kinetic isotope effects on dehalogenations at an aromatic carbon. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2008; 42:7744-7750. [PMID: 19031855 DOI: 10.1021/es800276y] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
In order to interpret the observed isotopic fractionation it is necessaryto understand its relationship with the isotope effect(s) on steps that occur during the conversion of the initial reactant to the final product. We examine this relationship from the biochemical point of view and elaborate on the consequences of the assumptions that it is based on. We illustrate the discrepancies between theoretical and experimental interpretation of kinetic isotope effects on examples of dehalogenation reactions that occur at an aromatic carbon atom. The examples include 4-chlorobenzoyl-CoA dehalogenase-catalyzed conversion of 4-chlorobenzoyl-CoA to 4-hydroxybenzoyl-CoA, dehaloperoxidase-catalyzed conversion of 2,4,6-trichlorophenol to 2,6-dichloroquinone, and spontaneous hydrolysis of atrazine at pH 12. For this latter reaction we have measured the chlorine kinetic isotope effect and estimated its value theoretically at the DFT level of theory. Results of chlorine kinetic isotope effects suggest that the studied dechlorination reactions proceed in a single step with significant weakening of the carbon-chlorine bond in the transition state.
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Affiliation(s)
- Agnieszka Dybala-Defratyka
- Institute of Applied Radiation Chemistry, Technical University of Lodz, Zeromskiego 116, 90-924 Lodz, Poland
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Elsner M, Hunkeler D. Evaluating Chlorine Isotope Effects from Isotope Ratios and Mass Spectra of Polychlorinated Molecules. Anal Chem 2008; 80:4731-40. [DOI: 10.1021/ac702543y] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Martin Elsner
- Institute of Groundwater Ecology, Helmholtz Zentrum München—National Research Center for Environmental Health, Ingolstädter Landstrasse 1, D-85764 Neuherberg, Germany, and University of Neuchâtel, Centre for Hydrogeology, Rue Emile Argand 11, CH-2009 Neuchâtel, Switzerland
| | - Daniel Hunkeler
- Institute of Groundwater Ecology, Helmholtz Zentrum München—National Research Center for Environmental Health, Ingolstädter Landstrasse 1, D-85764 Neuherberg, Germany, and University of Neuchâtel, Centre for Hydrogeology, Rue Emile Argand 11, CH-2009 Neuchâtel, Switzerland
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15
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Dybała-Defratyka A, Rostkowski M, Matsson O, Westaway KC, Paneth P. A new interpretation of chlorine leaving group kinetic isotope effects; a theoretical approach. J Org Chem 2004; 69:4900-5. [PMID: 15255714 DOI: 10.1021/jo049327z] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The chlorine leaving group kinetic isotope effects (KIEs) for the S(N)2 reactions between methyl chloride and a wide range of anionic, neutral, and radical anion nucleophiles were calculated in the gas phase and, in several cases, using a continuum solvent model. In contrast to the expected linear dependence of the chlorine KIEs on the C(alpha)-Cl bond order in the transition state, the KIEs fell in a very small range (1.0056-1.0091), even though the C(alpha)-Cl transition state bond orders varied widely from approximately 0.32 to 0.78, a range from reactant-like to very product-like. This renders chlorine KIEs, and possibly other leaving-group KIEs, less useful for studies of reaction mechanisms than commonly assumed. A partial explanation for this unexpected relationship between the C(alpha)-Cl transition state bond order and the magnitude of the chlorine KIE is presented.
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Affiliation(s)
- Agnieszka Dybała-Defratyka
- Institute of Applied Radiation Chemistry, Technical University of Lodz, Zeromskiego 116, 90-924 Lodz, Poland
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16
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Fang YR, Gao Y, Ryberg P, Eriksson J, Kołodziejska-Huben M, Dybała-Defratyka A, Madhavan S, Danielsson R, Paneth P, Matsson O, Westaway KC. Experimental and theoretical multiple kinetic isotope effects for an SN2 reaction. An attempt to determine transition-state structure and the ability of theoretical methods to predict experimental kinetic isotope effects. Chemistry 2003; 9:2696-709. [PMID: 12772284 DOI: 10.1002/chem.200204119] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The secondary alpha-deuterium, the secondary beta-deuterium, the chlorine leaving-group, the nucleophile secondary nitrogen, the nucleophile (12)C/(13)C carbon, and the (11)C/(14)C alpha-carbon kinetic isotope effects (KIEs) and activation parameters have been measured for the S(N)2 reaction between tetrabutylammonium cyanide and ethyl chloride in DMSO at 30 degrees C. Then, thirty-nine readily available different theoretical methods, both including and excluding solvent, were used to calculate the structure of the transition state, the activation energy, and the kinetic isotope effects for the reaction. A comparison of the experimental and theoretical results by using semiempirical, ab initio, and density functional theory methods has shown that the density functional methods are most successful in calculating the experimental isotope effects. With two exceptions, including solvent in the calculation does not improve the fit with the experimental KIEs. Finally, none of the transition states and force constants obtained from the theoretical methods was able to predict all six of the KIEs found by experiment. Moreover, none of the calculated transition structures, which are all early and loose, agree with the late (product-like) transition-state structure suggested by interpreting the experimental KIEs.
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Affiliation(s)
- Yao-Ren Fang
- Department of Chemistry and Biochemistry, Laurentian University Sudbury, Ontario P3E 2C6, Canada
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17
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Westaway KC, Gao Y, Fang YR. The effect of inert salts on the structure of the transition state in the SN2 reaction between thiophenoxide ion and butyl chloride. J Org Chem 2003; 68:3084-9. [PMID: 12688776 DOI: 10.1021/jo026879d] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The effect of inert salts on the structure of the transition state has been determined by measuring the secondary alpha deuterium and the chlorine leaving group kinetic isotope effects for the S(N)2 reaction between n-butyl chloride and thiophenoxide ion in both methanol and DMSO. The smaller secondary alpha deuterium isotope effects and very slightly larger chlorine isotope effects found in both solvents when the inert salt is present suggests that the S(N)2 transition state is tighter and more product-like, with a shorter S-C(alpha) and very a slightly longer C(alpha)-Cl bond when the added salt is present. The salt effect on the reaction in methanol where the reacting nucleophile is the solvent-separated ion-pair complex is much greater than the salt effect on the reaction in DMSO where the reacting nucleophile is the free ion. This greater change in transition-state structure found when the inert salt is present in methanol is consistent with the solvation rule for S(N)2 reactions. The greater change in the S-C(alpha) bond is predicted by the bond strength hypothesis. A rationale for the changes found in transition-state structure when the inert salt is present is suggested for both the free-ion and the ion-pair reactions.
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Affiliation(s)
- Kenneth Charles Westaway
- Department of Chemistry and Biochemistry, Laurentian University, Sudbury, Ontario P3E 2C6, Canada.
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18
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Abstract
Enzymatic dehalogenation reactions are important for the bioremediation of the environment because of the increasing anthropogenic pollution with halogen-containing organic compounds. Chlorine kinetic isotope effects have been measured for four hydrolytic dehalogenases. On the basis of these isotope effects, several details of the mechanisms of the enzymatic dehalogenation reactions have been revealed.
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Affiliation(s)
- Piotr Paneth
- Institute of Applied Radiation Chemistry, Department of Chemistry, Technical University of Lodz, Zeromskiego 116, 90-924 Lodz, Poland
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19
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Lewandowicz A, Rudzinski J, Luo L, Dunaway-Mariano D, Paneth P. Determination of the chlorine kinetic isotope effect on the 4-chlorobenzoyl-CoA dehalogenase-catalyzed nucleophilic aromatic substitution. Arch Biochem Biophys 2002; 398:249-52. [PMID: 11831856 DOI: 10.1006/abbi.2001.2722] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The chlorine kinetic isotope effect (KIE) on the dehalogenation of 4-chlorobenzoyl-CoA catalyzed by 4-chlorobenzoyl-CoA dehalogenase has been measured at room temperature and optimal pH. The measured value of (37)k = 1.0090 +/- 0.0006 is larger than the KIEs recently measured for haloalkane and fluoroacetate dehalogenase. This indicates that the transition state for dissociation of chloride ion from the Meisenheimer intermediate is sensitive to the chlorine isotopic substitution. Simple modeling suggests that this sensitivity originates in the high isotopic sensitivity of the C-Cl bond bending modes.
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Affiliation(s)
- Andrzej Lewandowicz
- Institute of Applied Radiation Chemistry, Technical University of Lodz, Zeromskiego 116, Lodz, 90-924, Poland
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20
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Jia ZS, Rudziński J, Paneth P, Thibblin A. Borderline between E1cB and E2 mechanisms. Chlorine isotope effects in base-promoted elimination Reactions. J Org Chem 2002; 67:177-81. [PMID: 11777456 DOI: 10.1021/jo0159340] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The chlorine leaving group isotope effect has been measured for the base-promoted elimination reaction of 1-(2-chloro-2-propyl)indene (1-Cl) in methanol at 30 degrees C: k(35)/k(37) = 1.0086 +/- 0.0007 with methoxide as the base and k(35)/k(37) = 1.0101 +/- 0.0001 with triethylamine (TEA) as the base. These very large chlorine isotope effects combined with large kinetic deuterium isotope effects of 7.1 and 8.4, respectively, are consistent not with the irreversible E1cB mechanism proposed previously (J. Am. Chem. Soc. 1977, 99, 7926) but with the E2 mechanism with transition states having large amounts of hydron transfer and very extensive cleavage of the bond to chlorine.
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Affiliation(s)
- Zhi Sheng Jia
- Institute of Chemistry, University of Uppsala, P.O. Box 531, SE-751 21 Uppsala, Sweden
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21
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Lewandowicz A, Sicinska D, Rudzinski J, Ichiyama S, Kurihara T, Esaki N, Paneth P. Chlorine kinetic isotope effect on the fluoroacetate dehalogenase reaction. J Am Chem Soc 2001; 123:9192-3. [PMID: 11552840 DOI: 10.1021/ja0160400] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- A Lewandowicz
- Institute of Applied Radiation Chemistry, Technical University of Lodz, Zeromskiego 116, 90-924 Lodz, Poland
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Lewandowicz A, Rudziński J, Tronstad L, Widersten M, Ryberg P, Matsson O, Paneth P. Chlorine kinetic isotope effects on the haloalkane dehalogenase reaction. J Am Chem Soc 2001; 123:4550-5. [PMID: 11457241 DOI: 10.1021/ja003503d] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We have found chlorine kinetic isotope effects on the dehalogenation catalyzed by haloalkane dehalogenase from Xanthobacter autotrophicus GJ10 to be 1.0045 +/- 0.0004 for 1,2-dichloroethane and 1.0066 +/- 0.0004 for 1-chlorobutane. The latter isotope effect approaches the intrinsic chlorine kinetic isotope effect for the dehalogenation step. The intrinsic isotope effect has been modeled using semiempirical and DFT theory levels using the ONIOM QM/QM scheme. Our results indicate that the dehalogenation step is reversible; the overall irreversibility of the enzyme-catalyzed reaction is brought about by a step following the dehalogenation.
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Affiliation(s)
- A Lewandowicz
- Department of Chemistry, Technical University of Lodz, Zeromskiego 116, 90-924 Lodz, Poland
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Koerner T, Westaway KC, Poirier RA, Wang Y. An unusually large secondary α-deuterium kinetic isotope effect in hydride ion SN2 reactions. CAN J CHEM 2000. [DOI: 10.1139/v00-100] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Theoretical calculations at the HF/6-31+G* level suggest the secondary α-deuterium kinetic isotope effects for hydride ion SN2 reactions are much larger than expected for the structure of the transition state. The secondary α-deuterium kinetic isotope effects for the SN2 reactions between sodium borohydride (hydride ion) and para-methyl- and para-chlorobenzyl chlorides are much larger than expected as the theoretical calculations suggest. It appears the secondary α-deuterium isotope effects are larger than expected for the structure of the SN2 transition state because the hydride ion is too small to affect the CαH(D) out-of-plane bending vibrations in the transition state.Key words: secondary α-deuterium kinetic isotope effects, SN2, nucleophilic substitution, transition state, substituent effects.
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Koerner T, Fang YR, Westaway KC. Using Incoming Nucleophile Primary Hydrogen−Deuterium Kinetic Isotope Effects To Model the SN2 Transition State. J Am Chem Soc 2000. [DOI: 10.1021/ja000441i] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Terry Koerner
- Contribution from the Department of Chemistry and Biochemistry, Laurentian University, Sudbury, Ontario, Canada P3E 2C6
| | - Yao-ren Fang
- Contribution from the Department of Chemistry and Biochemistry, Laurentian University, Sudbury, Ontario, Canada P3E 2C6
| | - Kenneth Charles Westaway
- Contribution from the Department of Chemistry and Biochemistry, Laurentian University, Sudbury, Ontario, Canada P3E 2C6
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