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The reaction of oxyhemoglobin with nitric oxide: EPR evidence for an iron(III)-nitrate intermediate. Inorganica Chim Acta 2015. [DOI: 10.1016/j.ica.2015.07.037] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Surducan M, Makarov SV, Silaghi-Dumitrescu R. O-S Bond Activation in Structures Isoelectronic with Ferric Peroxide Species Known in O-O-Activating Enzymes: Relevance for Sulfide Activation and Sulfite Reductases. Eur J Inorg Chem 2014. [DOI: 10.1002/ejic.201402657] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Zucca P, Rescigno A, Rinaldi AC, Sanjust E. Biomimetic metalloporphines and metalloporphyrins as potential tools for delignification: Molecular mechanisms and application perspectives. ACTA ACUST UNITED AC 2014. [DOI: 10.1016/j.molcata.2013.09.010] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Aggarwal A, Singh S, Samson J, Drain CM. Adaptive organic nanoparticles of a teflon-coated iron (III) porphyrin catalytically activate dioxygen for cyclohexene oxidation. Macromol Rapid Commun 2012; 33:1220-6. [PMID: 22517679 DOI: 10.1002/marc.201200107] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2012] [Indexed: 11/08/2022]
Abstract
Self-organized organic nanoparticles (ONP) are adaptive to the environmental reaction conditions. ONP of fluorous alkyl iron(III) porphyrin catalytically oxidize cyclohexene to the allylic oxidation products. In contrast, the solvated metalloporphyrin yields both allylic oxidation and epoxidation products. The ONP system facilitates a greener reaction because about 89% reaction medium is water, molecular oxygen is used in place of synthetic oxidants, and the ambient reaction conditions used require less energy. The enhanced catalytic activity of these ONP is unexpected because the metalloporphyrins in the nanoaggregates are in the close proximity and the TON should diminish by self-oxidative degradation. The fluorous alkyl chain stabilizes the ONP toward self-oxidative degradation.
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Affiliation(s)
- Amit Aggarwal
- Department of Chemistry and Biochemistry, Hunter College, New York, NY 10065, USA
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Aggarwal A, Singh S, Drain CM. Nanoaggregates of Mn(III)tetraperfluorophenylporphyrin: a greener approach for allylic oxidation of olefins. J PORPHYR PHTHALOCYA 2012. [DOI: 10.1142/s1088424611004130] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Organic nanoparticles of metalloporphyrins can be a versatile catalyst for the selective oxidation of alkenes and other hydrocarbons. The catalytic activity of the metalloporphyrin depends on the nature of the central metal atom, peripheral groups, and the architecture of the porphyrin macrocycle. Herein, we report the catalytic activity of organic nanoparticles of 5,10,15,20-tetrakis-(2,3,4,5,6-pentafluorophenyl)porphyrinato manganese(III), Mn (III)TPPF20, for the oxidation of cyclohexene using molecular oxygen as an oxidant in aqueous solvent under ambient conditions. While the solvated metalloporphyrins catalytically oxidize alkenes to the corresponding epoxide with a modest turn-over numbers, ca. 30 nm organic nanoparticles of Mn (III)TPPF20 have enhanced catalytic activity with up to a two-fold greater turn-over number and yields only allylic oxidation products. The activity of organic nanoparticles is slow compared to the solvated metalloporphyrins. These organic nanoparticles catalytic systems facilitate a greener reaction since ca. 89% of the reaction medium is water, molecular oxygen is used in place of man-made oxidants, and the ambient reaction conditions require less energy. This organic nanoparticle catalytic system also avoids using halogenated solvents commonly used in solution phase reactions. The enhanced catalytic activity of these organic nanoparticles is unexpected because the metalloporphyrins in the nanoaggregates are in the close proximity and the turn-over number should diminish by self-oxidative degradation.
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Affiliation(s)
- Amit Aggarwal
- Department of Chemistry and Biochemistry, Hunter College and Graduate Centre of the City University of New York, NY 10065, USA
| | - Sunaina Singh
- Department of Chemistry and Biochemistry, Hunter College and Graduate Centre of the City University of New York, NY 10065, USA
| | - Charles M. Drain
- Department of Chemistry and Biochemistry, Hunter College and Graduate Centre of the City University of New York, NY 10065, USA
- The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
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Silaghi-Dumitrescu R. A density functional investigation of hydrogen peroxide activation by high-valent heme centers: implications for the catalase catalytic cycle. J PORPHYR PHTHALOCYA 2012. [DOI: 10.1142/s1088424610002161] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Catalases employ a tyrosinate-ligated ferric heme in order to catalyze the dismutation of hydrogen peroxide to O2 and water. In the first half of the catalytic cycle, H2O2 oxidizes Fe(III) to the formally Fe(V) state commonly referred to as Compound I. The second half of the cycle entails oxidation of a second hydrogen peroxide molecule by Compound I to dioxygen. The present study employs density functional (DFT) calculations to examine the nature of this second step of the catalatic reaction. In order to account for the unusual choice of tyrosinate as an axial ligand in catalases, oxidation of hydrogen peroxide by an imidazole-ligated Compound I is also examined, bearing in mind that imidazole-ligated hemoproteins such as myoglobin or horseradish peroxidase tend to display little, if any, catalatic activity. Furthermore, in order to gauge the importance of the cation radical of Compound I in peroxide activation, the performance of Compound II (the one-electron reduced version of Compound I, formally Fe(IV) ), is also examined. It is found that hydrogen peroxide oxidation occurs in a quasi-concerted manner, with two hydrogen-atom transfer reactions, and that the tyrosinate ligand is in no way required at this stage. We propose that the role of the tyrosinate is purely thermodynamic, in avoiding accumulation of the much less peroxide-reactive ferrous form in vivo – all in line with the predominantly thermodynamic role of the cysteinate ligands in enzymes such as cytochromes P450.
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Alfonso-Prieto M, Oberhofer H, Klein ML, Rovira C, Blumberger J. Proton Transfer Drives Protein Radical Formation in Helicobacter pylori Catalase but Not in Penicillium vitale Catalase. J Am Chem Soc 2011; 133:4285-98. [DOI: 10.1021/ja1110706] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- M. Alfonso-Prieto
- Computer Simulation & Modeling Laboratory, Parc Científic de Barcelona, Baldiri Reixac 4, 08028 Barcelona, Spain
- Institute for Computational Molecular Science, Temple University, 1900 North 12th Street, Philadelphia, Pennsylvania 19122, United States
| | - H. Oberhofer
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom
| | - M. L. Klein
- Institute for Computational Molecular Science, Temple University, 1900 North 12th Street, Philadelphia, Pennsylvania 19122, United States
| | - C. Rovira
- Computer Simulation & Modeling Laboratory, Parc Científic de Barcelona, Baldiri Reixac 4, 08028 Barcelona, Spain
- Institut de Química Teòrica i Computacional (IQTCUB), Universitat de Barcelona, 08028 Barcelona, Spain
- Institució Catalana de Recerca i Estudis Avançats (ICREA), 08010 Barcelona, Spain
| | - J. Blumberger
- Department of Physics and Astronomy, University College London, London WC1E 6BT, United Kingdom
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Silaghi-Dumitrescu R, Makarov SV, Uta MM, Dereven'kov IA, Stuzhin PA. Redox non-innocence of a nitrido bridge in a methane-activating dimer of iron phthalocyanine. NEW J CHEM 2011. [DOI: 10.1039/c0nj00827c] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Silaghi‐Dumitrescu R, Makarov SV. Hydrocarbon Oxygenation by Metal Nitrite Adducts: Theoretical Comparison with Ferryl‐Based Oxygenation Agents. Eur J Inorg Chem 2010. [DOI: 10.1002/ejic.200901044] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
| | - Sergei V. Makarov
- State University of Chemistry and Technology, Engels str. 7, 153000 Ivanovo, Russia
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Smeureanu G, Aggarwal A, Soll CE, Arijeloye J, Malave E, Drain CM. Enhanced catalytic activity and unexpected products from the oxidation of cyclohexene by organic nanoparticles of 5,10,15,20-tetrakis-(2,3,4,5,6-pentafluorophenyl)porphyrinatoiron(III) in water by using O2. Chemistry 2010; 15:12133-40. [PMID: 19777510 DOI: 10.1002/chem.200901086] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The catalytic oxidation of alkenes by most iron porphyrins using a variety of oxygen sources, but generally not dioxygen, yields the epoxide with minor quantities of other products. The turnover numbers for these catalysts are modest, ranging from a few hundred to a few thousand depending on the porphyrin structure, axial ligands, and other reaction conditions. Halogenation of substituents increases the activity of the metalloporphyrin catalyst and/or makes it more robust to oxidative degradation. Oxidation of cyclohexene by 5,10,15,20-tetrakis-(2,3,4,5,6-pentafluorophenyl)porphyrinato iron(III), ([Fe(III)(tppf(20))]) and H(2)O(2) is typical of the latter: the epoxide is 99 % of the product and turnover numbers are about 350.1-4 Herein, we report that dynamic organic nanoparticles (ONPs) of [Fe(III)(tppf(20))] with a diameter of 10 nm, formed by host-guest solvent methods, catalytically oxidize cyclohexene with O(2) to yield only 2-cyclohexene-1-one and 2-cyclohexene-1-ol with approximately 10-fold greater turnover numbers compared to the non-aggregated metalloporphyrin in acetonitrile/methanol. These ONPs facilitate a greener reaction because the reaction solvent is 89 % water and O(2) is the oxidant in place of synthetic oxygen sources. This reactivity is unexpected because the metalloporphyrins are in close proximity and oxidative degradation of the catalyst should be enhanced, thus causing a significant decrease in catalytic turnovers. The allylic products suggest a different oxidative mechanism compared to that of the solvated metalloporphyrins. These results illustrate the unique properties of some ONPs relative to the component molecules or those attached to supports.
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Affiliation(s)
- Gabriela Smeureanu
- Department of Chemistry and Biochemistry, Hunter College of the City University of New York, 695 Park Avenue, New York, NY 10065, USA
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Kis Z, Makarov SV, Silaghi-Dumitrescu R. Computational investigations on the electronic structure and reactivity of thiourea dioxide: sulfoxylate formation, tautomerism and dioxygen liberation. J Sulphur Chem 2010. [DOI: 10.1080/17415990903505902] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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Silaghi-Dumitrescu R. High-valent metalloporphyrins in hydrocarbon activation: metal(v)-oxo or metal(v)-hydroxo? NEW J CHEM 2010. [DOI: 10.1039/c0nj00297f] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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15
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Superoxide interaction with nickel and iron superoxide dismutases. J Mol Graph Model 2009; 28:156-61. [DOI: 10.1016/j.jmgm.2009.06.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2008] [Revised: 06/09/2009] [Accepted: 06/10/2009] [Indexed: 11/22/2022]
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Abstract
The self-assembly and self-organization of porphyrins and related macrocycles enables the bottom-up fabrication of photonic materials for fundamental studies of the photophysics of these materials and for diverse applications. This rapidly developing field encompasses a broad range of disciplines including molecular design and synthesis, materials formation and characterization, and the design and evaluation of devices. Since the self-assembly of porphyrins by electrostatic interactions in the late 1980s to the present, there has been an ever increasing degree of sophistication in the design of porphyrins that self-assemble into discrete arrays or self-organize into polymeric systems. These strategies exploit ionic interactions, hydrogen bonding, coordination chemistry, and dispersion forces to form supramolecular systems with varying degrees of hierarchical order. This review concentrates on the methods to form supramolecular porphyrinic systems by intermolecular interactions other than coordination chemistry, the characterization and properties of these photonic materials, and the prospects for using these in devices. The review is heuristically organized by the predominant intermolecular interactions used and emphasizes how the organization affects properties and potential performance in devices.
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Affiliation(s)
- Charles Michael Drain
- Department of Chemistry and Biochemistry, Hunter College and Graduate Center of the City University of New York, 695 Park Avenue, New York, New York 10065, USA.
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Menyhárd DK. Comparative computational analysis of active and inactive cofactors of nitric oxide synthase. J Phys Chem B 2009; 113:3151-9. [PMID: 19708267 DOI: 10.1021/jp8083056] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Nitric oxide synthases (NOSs) are heme proteins that catalyze the formation of nitric oxide from L-Arg in the presence of oxygen. Of the two electrons required for the first step of the reaction, the second is primarily donated by the tetrahydrobiopterin (H4B) cofactor bound adjacent to the heme, which is eventually reduced back to resting state by the ultimate electron source of the reaction, the flavins of the NOS reductase domain. Density functional theory calculations were carried out to identify those protonation states of different cofactor molecules that best support radicalization of the cofactor and the coupled increase in the electron density of the heme-bound oxygen molecule. Three cofactor molecules were studied, native H4B, an active analogue, 5-methyl-H4B, and the inactive 4-amino-H4B. Findings support the emerging model where H4B and 5-methyl-H4B are coupled proton/electron sources of NOS catalysis, while 4-amino-H4B is an inhibitor due to its inability to donate the catalytically required proton.
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Affiliation(s)
- Dóra K Menyhárd
- Department of Inorganic and Analytical Chemistry, Budapest University of Technology and Economy, Budapest, Szent Gellért tér 4., H-1111, Hungary.
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Hersleth HP, Hsiao YW, Ryde U, Görbitz CH, Andersson KK. The influence of X-rays on the structural studies of peroxide-derived myoglobin intermediates. Chem Biodivers 2008; 5:2067-2089. [PMID: 18972498 DOI: 10.1002/cbdv.200890189] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
In recent years, the awareness of potential radiation damage of metal centers in protein crystals during crystallographic data collection has received increasing attention. The radiation damage can lead to radiation-induced changes and reduction of the metal sites. One of the research fields where these concerns have been comprehensively addressed is the study of the reaction intermediates of the heme peroxidase and oxygenase reaction cycles. For both the resting states and the high-valent intermediates, the X-rays used in the structure determination have given undesired side effects through radiation-induced changes to the trapped intermediates. However, X-rays have been used to generate and trap the peroxy/hydroperoxy state in crystals. In this review, the structural work and the influence of X-rays on these intermediates in myoglobin are summarized and viewed in light of analogous studies on similar intermediates in peroxidases and oxygenases.
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Affiliation(s)
- Hans-Petter Hersleth
- University of Oslo, Department of Molecular Biosciences, P. O. Box 1041 Blindern, N-0316 Oslo
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Silaghi-Dumitrescu R. Halide Activation by Heme Peroxidases: Theoretical Predictions on Putative Adducts of Halides with Compound I. Eur J Inorg Chem 2008. [DOI: 10.1002/ejic.200800732] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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20
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Balcells D, Raynaud C, Crabtree RH, Eisenstein O. A rational basis for the axial ligand effect in C-H oxidation by [MnO(porphyrin)(X)]+ (X = H2O, OH-, O2-) from a DFT study. Inorg Chem 2008; 47:10090-9. [PMID: 18788735 DOI: 10.1021/ic8013706] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Oxyl radical character in the MnO group of the title system is shown from a density functional theory study to be essential for efficient C-H cleavage, which is a key step in C-H oxidation. Since oxyl species have elongated Mn-O bonds relative to the more usual oxo species of type MnO, the normal expectation would be that high trans-influence ligands X should facilitate oxyl character by elongating the Mn-O bond and thus enhance both oxyl character and reactivity. Contrary to this expectation, but in line with the experimental data (Jin, N.; Ibrahim, M.; Spiro, T. G.; Groves, J. T. J. Am. Chem. Soc. 2007, 129, 12416), we find that reactivity increases along the series X = O(2-) < OH(-) < H2O for the following reasons. The ground-state singlet (S) is unreactive for all X, and only the higher-energy triplet (T) and quintet (Q) states have the oxyl character needed for reactivity, but the higher trans-influence X ligands are also shown to increase the S/T and S/Q gaps, thus making attainment of the needed T and Q states harder. The latter effect is dominant, and high trans-influence X ligands thus disfavor reaction. The higher reactivity in the presence of acid noted by Groves and co-workers is thus rationalized by the preference for having X = H2O over OH(-) or O(2-).
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Affiliation(s)
- David Balcells
- Institut Charles Gerhardt Montpellier, UMR 5253 CNRS-UM2-ENSCM-UM1, Universite Montpellier 2, cc-1501 Place Eugene Bataillon, 34095, Montpellier, France
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Chiavarino B, Cipollini R, Crestoni ME, Fornarini S, Lanucara F, Lapi A. Probing the Compound I-like reactivity of a bare high-valent oxo iron porphyrin complex: the oxidation of tertiary amines. J Am Chem Soc 2008; 130:3208-17. [PMID: 18278912 DOI: 10.1021/ja077286t] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The mechanisms of oxidative N-dealkylation of amines by heme enzymes including peroxidases and cytochromes P450 and by functional models for the active Compound I species have long been studied. A debated issue has concerned in particular the character of the primary step initiating the oxidation sequence, either a hydrogen atom transfer (HAT) or an electron transfer (ET) event, facing problems such as the possible contribution of multiple oxidants and complex environmental effects. In the present study, an oxo iron(IV) porphyrin radical cation intermediate 1, [(TPFPP)*+ Fe(IV)=O]+ (TPFPP = meso-tetrakis (pentafluorophenyl)porphinato dianion), functional model of Compound I, has been produced as a bare species. The gas-phase reaction with amines (A) studied by ESI-FT-ICR mass spectrometry has revealed for the first time the elementary steps and the ionic intermediates involved in the oxidative activation. Ionic products are formed involving ET (A*+, the amine radical cation), formal hydride transfer (HT) from the amine ([A(-H)]+, an iminium ion), and oxygen atom transfer (OAT) to the amine (A(O), likely a carbinolamine product), whereas an ionic product involving a net initial HAT event is never observed. The reaction appears to be initiated by an ET event for the majority of the tested amines which included tertiary aliphatic and aromatic amines as well as a cyclic and a secondary amine. For a series of N,N-dimethylanilines the reaction efficiency for the ET activated pathways was found to correlate with the ionization energy of the amine. A stepwise pathway accounts for the C-H bond activation resulting in the formal HT product, namely a primary ET process forming A*+, which is deprotonated at the alpha-C-H bond forming an N-methyl-N-arylaminomethyl radical, A(-H)*, readily oxidized to the iminium ion, [A(-H)]+. The kinetic isotope effect (KIE) for proton transfer (PT) increases as the acidity of the amine radical cation increases and the PT reaction to the base, the ferryl group of (TPFPP)Fe(IV)=O, approaches thermoneutrality. The ET reaction displayed by 1 with gaseous N,N-dimethylaniline finds a counterpart in the ET reactivity of FeO+, reportedly a potent oxidant in the gas phase, and with the barrierless ET process for a model (P)*+ Fe(IV)=O species (where P is the porphine dianion) as found by theoretical calculations. Finally, the remarkable OAT reactivity of 1 with C6F5N(CH3)2 may hint to a mechanism along a route of diverse spin multiplicity.
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Affiliation(s)
- Barbara Chiavarino
- Dipartimento di Chimica e Tecnologia delle Sostanze Biologicamente Attive, Università di Roma La Sapienza P.le A. Moro 5, I-00185, Roma, Italy
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Vidossich P, Alfonso-Prieto M, Carpena X, Loewen PC, Fita I, Rovira C. Versatility of the Electronic Structure of Compound I in Catalase-Peroxidases. J Am Chem Soc 2007; 129:13436-46. [DOI: 10.1021/ja072245i] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Affiliation(s)
- Pietro Vidossich
- Contribution from the Centre de Recerca en Química Teòrica, Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain, Institut de Biologia Molecular (IBMB-CSIC), Institut de Recerca Biomèdica (IRB), Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain, Department of Microbiology, University of Manitoba, Winnipeg MB R3T 2N2, Canada, Institució Catalana de Recerca i Estudis Avançats (ICREA), Passeig Lluís Companys, 23, 08018 Barcelona, Spain
| | - Mercedes Alfonso-Prieto
- Contribution from the Centre de Recerca en Química Teòrica, Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain, Institut de Biologia Molecular (IBMB-CSIC), Institut de Recerca Biomèdica (IRB), Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain, Department of Microbiology, University of Manitoba, Winnipeg MB R3T 2N2, Canada, Institució Catalana de Recerca i Estudis Avançats (ICREA), Passeig Lluís Companys, 23, 08018 Barcelona, Spain
| | - Xavi Carpena
- Contribution from the Centre de Recerca en Química Teòrica, Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain, Institut de Biologia Molecular (IBMB-CSIC), Institut de Recerca Biomèdica (IRB), Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain, Department of Microbiology, University of Manitoba, Winnipeg MB R3T 2N2, Canada, Institució Catalana de Recerca i Estudis Avançats (ICREA), Passeig Lluís Companys, 23, 08018 Barcelona, Spain
| | - Peter C. Loewen
- Contribution from the Centre de Recerca en Química Teòrica, Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain, Institut de Biologia Molecular (IBMB-CSIC), Institut de Recerca Biomèdica (IRB), Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain, Department of Microbiology, University of Manitoba, Winnipeg MB R3T 2N2, Canada, Institució Catalana de Recerca i Estudis Avançats (ICREA), Passeig Lluís Companys, 23, 08018 Barcelona, Spain
| | - Ignacio Fita
- Contribution from the Centre de Recerca en Química Teòrica, Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain, Institut de Biologia Molecular (IBMB-CSIC), Institut de Recerca Biomèdica (IRB), Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain, Department of Microbiology, University of Manitoba, Winnipeg MB R3T 2N2, Canada, Institució Catalana de Recerca i Estudis Avançats (ICREA), Passeig Lluís Companys, 23, 08018 Barcelona, Spain
| | - Carme Rovira
- Contribution from the Centre de Recerca en Química Teòrica, Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain, Institut de Biologia Molecular (IBMB-CSIC), Institut de Recerca Biomèdica (IRB), Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain, Department of Microbiology, University of Manitoba, Winnipeg MB R3T 2N2, Canada, Institució Catalana de Recerca i Estudis Avançats (ICREA), Passeig Lluís Companys, 23, 08018 Barcelona, Spain
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Stephenson NA, Bell AT. Mechanistic insights into iron porphyrin-catalyzed olefin epoxidation by hydrogen peroxide: Factors controlling activity and selectivity. ACTA ACUST UNITED AC 2007. [DOI: 10.1016/j.molcata.2007.05.005] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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24
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Hersleth HP, Uchida T, Røhr AK, Teschner T, Schünemann V, Kitagawa T, Trautwein AX, Görbitz CH, Andersson KK. Crystallographic and Spectroscopic Studies of Peroxide-derived Myoglobin Compound II and Occurrence of Protonated FeIV–O. J Biol Chem 2007; 282:23372-86. [PMID: 17565988 DOI: 10.1074/jbc.m701948200] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
High resolution crystal structures of myoglobin in the pH range 5.2-8.7 have been used as models for the peroxide-derived compound II intermediates in heme peroxidases and oxygenases. The observed Fe-O bond length (1.86-1.90 A) is consistent with that of a single bond. The compound II state of myoglobin in crystals was controlled by single-crystal microspectrophotometry before and after synchrotron data collection. We observe some radiation-induced changes in both compound II (resulting in intermediate H) and in the resting ferric state of myoglobin. These radiation-induced states are quite unstable, and compound II and ferric myoglobin are immediately regenerated through a short heating above the glass transition temperature (<1 s) of the crystals. It is unclear how this influences our compound II structures compared with the unaffected compound II, but some crystallographic data suggest that the influence on the Fe-O bond distance is minimal. Based on our crystallographic and spectroscopic data we suggest that for myoglobin the compound II intermediate consists of an Fe(IV)-O species with a single bond. The presence of Fe(IV) is indicated by a small isomer shift of delta = 0.07 mm/s from Mössbauer spectroscopy. Earlier quantum refinements (crystallographic refinement where the molecular-mechanics potential is replaced by a quantum chemical calculation) and density functional theory calculations suggest that this intermediate H species is protonated.
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Affiliation(s)
- Hans-Petter Hersleth
- Department of Chemistry, University of Oslo, PO Box 1033, Blindern, Oslo N-0315, Norway
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25
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Liu X, Wang Y, Han K. Systematic study on the mechanism of aldehyde oxidation to carboxylic acid by cytochrome P450. J Biol Inorg Chem 2007; 12:1073-81. [PMID: 17661096 DOI: 10.1007/s00775-007-0277-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2007] [Revised: 05/22/2007] [Accepted: 07/05/2007] [Indexed: 11/26/2022]
Abstract
The mechanism of aldehyde to carboxylic acid conversion catalyzed by P450 enzymes via a series of reactions was studied systematically for the first time with density functional theory calculations. A two-state reactivity mechanism has been proposed, which can be adopted for many aldehyde oxidation reactions catalyzed by P450 enzymes. The mechanism involves initial hydrogen abstraction as the rate-limiting step and this is followed by steps of oxygen rebound without barriers owing to the quick recombination of the resultant radical species. Meanwhile, in an attempt to explore whether there exist some rules for the hydroxylation of aldehyde substrates by P450, the transition state barriers of the rate-limiting step for a series of aldehyde hydroxylation reactions have been compared. A predictive pattern of extended barrier/bond energy correlation for different hydroxylations of aldehyde substrates by P450 has been established, which was further confirmed to be a reliable reactivity scale by experimental results.
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Affiliation(s)
- Xiaojing Liu
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, People's Republic of China
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26
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Silaghi-Dumitrescu R, Reeder B, Nicholls P, Cooper C, Wilson M. Ferryl haem protonation gates peroxidatic reactivity in globins. Biochem J 2007; 403:391-5. [PMID: 17214588 PMCID: PMC1876371 DOI: 10.1042/bj20061421] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2006] [Revised: 01/02/2007] [Accepted: 01/10/2007] [Indexed: 02/04/2023]
Abstract
Ferryl (Fe(IV)=O) species are involved in key enzymatic processes with direct biomedical relevance; among others, the uncontrolled reactivities of ferryl Mb (myoglobin) and Hb (haemoglobin) have been reported to be central to the pathology of rhabdomyolysis and subarachnoid haemorrhage. Rapid-scan stopped-flow methods have been used to monitor the spectra of the ferryl species in Mb and Hb as a function of pH. The ferryl forms of both proteins display an optical transition with pK approximately 4.7, and this is assigned to protonation of the ferryl species itself. We also demonstrate for the first time a direct correlation between Hb/Mb ferryl reactivity and ferryl protonation status, simultaneously informing on chemical mechanism and toxicity and with broader biochemical implications.
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Affiliation(s)
- Radu Silaghi-Dumitrescu
- *Department of Biological Sciences, University of Essex, Colchester CO4 3SQ, U.K
- †Domeniul Chimie, Universitatea Babeş-Bolyai, Str. Arany János 11, RO-3400 Cluj-Napoca, Romania
| | - Brandon J. Reeder
- *Department of Biological Sciences, University of Essex, Colchester CO4 3SQ, U.K
| | - Peter Nicholls
- *Department of Biological Sciences, University of Essex, Colchester CO4 3SQ, U.K
| | - Chris E. Cooper
- *Department of Biological Sciences, University of Essex, Colchester CO4 3SQ, U.K
| | - Michael T. Wilson
- *Department of Biological Sciences, University of Essex, Colchester CO4 3SQ, U.K
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27
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Horner O, Mouesca JM, Solari PL, Orio M, Oddou JL, Bonville P, Jouve HM. Spectroscopic description of an unusual protonated ferryl species in the catalase from Proteus mirabilis and density functional theory calculations on related models. Consequences for the ferryl protonation state in catalase, peroxidase and chloroperoxidase. J Biol Inorg Chem 2007; 12:509-25. [PMID: 17237942 DOI: 10.1007/s00775-006-0203-9] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2006] [Accepted: 12/21/2006] [Indexed: 11/24/2022]
Abstract
The catalase from Proteus mirabilis peroxide-resistant bacteria is one of the most efficient heme-containing catalases. It forms a relatively stable compound II. We were able to prepare samples of compound II from P. mirabilis catalase enriched in (57)Fe and to study them by spectroscopic methods. Two different forms of compound II, namely, low-pH compound II (LpH II) and high-pH compound II (HpH II), have been characterized by Mössbauer, extended X-ray absorption fine structure (EXAFS) and UV-vis absorption spectroscopies. The proportions of the two forms are pH-dependent and the pH conversion between HpH II and LpH II is irreversible. Considering (1) the Mössbauer parameters evaluated for four related models by density functional theory methods, (2) the existence of two different Fe-O(ferryl) bond lengths (1.80 and 1.66 A) compatible with our EXAFS data and (3) the pH dependence of the alpha band to beta band intensity ratio in the absorption spectra, we attribute the LpH II compound to a protonated ferryl Fe(IV)-OH complex (Fe-O approximately 1.80 A), whereas the HpH II compound corresponds to the classic ferryl Fe(IV)=O complex (Fe=O approximately 1.66 A). The large quadrupole splitting value of LpH II (measured 2.29 mm s(-1) vs. computed 2.15 mm s(-1)) compared with that of HpH II (measured 1.47 mm s(-1) vs. computed 1.46 mm s(-1)) reflects the protonation of the ferryl group. The relevancy and involvement of such (Fe(IV)=O/Fe(IV)-OH) species in the reactivity of catalase, peroxidase and chloroperoxidase are discussed.
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Affiliation(s)
- O Horner
- Laboratoire de Physicochimie des Métaux en Biologie, UMR CEA/CNRS/Université Joseph Fourier 5155, CEA/Grenoble, 38054, Grenoble Cedex 9, France
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28
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Bassan A, Blomberg MRA, Borowski T, Siegbahn PEM. Theoretical studies of enzyme mechanisms involving high-valent iron intermediates. J Inorg Biochem 2006; 100:727-43. [PMID: 16513176 DOI: 10.1016/j.jinorgbio.2006.01.015] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2005] [Revised: 01/12/2006] [Accepted: 01/16/2006] [Indexed: 01/21/2023]
Abstract
Recent theoretical contributions to the elucidation of mechanisms for iron containing enzymes are reviewed. The method used in most of these studies is hybrid density functional theory with the B3LYP functional. Three classes of enzymes are considered, the mononuclear non-heme enzymes, enzymes containing iron dimers, and heme-containing enzymes. Mechanisms for both dioxygen and substrate activations are discussed. The reactions usually go through two half-cycles, where a high-valent intermediate Fe(IV)O species is created in the first half-cycle, and the substrate reactions involving this intermediate occur in the second half-cycle. Similarities between the three classes of enzymes dominate, but significant differences also exist.
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Affiliation(s)
- Arianna Bassan
- Department of Physics, Stockholm University, AlbaNova University Center, Stockholm Center for Physics, Astronomy and Biotechnology, SE-106 91, Stockholm, Sweden
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29
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Horner O, Oddou JL, Mouesca JM, Jouve HM. Mössbauer identification of a protonated ferryl species in catalase from Proteus mirabilis: Density functional calculations on related models. J Inorg Biochem 2006; 100:477-9. [PMID: 16442627 DOI: 10.1016/j.jinorgbio.2005.12.010] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2005] [Accepted: 12/13/2005] [Indexed: 11/30/2022]
Abstract
The Proteus mirabilis catalase is one of the most efficient heme-containing catalase and forms a relatively stable compound II. Samples of compound II were prepared from PMC enriched in (57)Fe. For the first time, two different forms of compound II, namely low pH compound II (LpH II) (43%) and high pH compound II (HpH II) (25%), have been characterized by Mössbauer spectroscopy at pH 8.3. The ratio LpH II/HpH II increases irreversibly with decreasing pH. The large quadrupole splitting value of LpH II (DeltaE(Q)=2.29 (2) mm/s, with delta(/Fe)=0.03 (2) mm/s), compared to that of HpH II (DeltaE(Q)=1.47 (2) mm/s, with delta(/Fe)=0.07 (2) mm/s), reflects the protonation of the ferryl group. Quadrupole splitting values of 1.46 and 2.15mm/s have been computed by DFT for optimized models of the ferryl compound II (model 1) and the protonated ferryl compound II (model 2), respectively, starting from the Fe(IV)O model initially published by Rovira and Fita [C. Rovira, I. Fita, J. Phys. Chem. B 107 (2003) 5300-5305]. Therefore, we attribute the LpH II compound to a protonated ferryl Fe(IV)-OH complex, whereas the HpH II compound corresponds to the classical ferryl Fe(IV)O complex.
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Affiliation(s)
- O Horner
- Laboratoire de Physicochimie des Métaux en Biologie, UMR 5155, CEA/Grenoble, 38054 Grenoble cedex 9, France
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30
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Udit AK, Hill MG, Gray HB. Electrochemical generation of a high-valent state of cytochrome P450. J Inorg Biochem 2006; 100:519-23. [PMID: 16504300 DOI: 10.1016/j.jinorgbio.2006.01.011] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2006] [Accepted: 01/16/2006] [Indexed: 11/18/2022]
Abstract
Cyclic voltammetry performed at rapid scan rates on cytochrome P450 from Pseudomonas putida (P450CAM) in didodecyldimethylammonium bromide (DDAB) films on graphite electrodes revealed a couple (E) at 830mV (vs Ag/AgCl). E was not significantly observed at scan rates less than 30V/s at room temperature, suggesting that the oxidized species is unstable. The lifetime of E could be prolonged at 4 degrees C, which allowed reversible access to E at scan rates as low as 1V/s. E was found to be sensitive to imidazole in solution and to variations in pH, suggesting that the redox reaction is occurring at the metal center (i.e., Fe(IV/III)). Electrolysis reactions with different P450 substrates revealed that the electrochemically generated high-valent species is able to convert thioanisole to methyl phenyl sulfoxide.
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Affiliation(s)
- Andrew K Udit
- Department of Chemistry, Occidental College, 1600 Campus Road, Los Angeles, CA 91030, USA.
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31
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Hersleth HP, Ryde U, Rydberg P, Görbitz CH, Andersson KK. Structures of the high-valent metal-ion haem–oxygen intermediates in peroxidases, oxygenases and catalases. J Inorg Biochem 2006; 100:460-76. [PMID: 16510192 DOI: 10.1016/j.jinorgbio.2006.01.018] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2005] [Revised: 01/09/2006] [Accepted: 01/09/2006] [Indexed: 11/22/2022]
Abstract
Peroxidases, oxygenases and catalases have similar high-valent metal-ion intermediates in their respective reaction cycles. In this review, haem-based examples will be discussed. The intermediates of the haem-containing enzymes have been extensively studied for many years by different spectroscopic methods like UV-Vis, EPR (electron paramagnetic resonance), resonance Raman, Mössbauer and MCD (magnetic circular dichroism). The first crystal structure of one of these high-valent intermediates was on cytochrome c peroxidase in 1987. Since then, structures have appeared for catalases in 1996, 2002, 2003, putatively for cytochrome P450 in 2000, for myoglobin in 2002, for horseradish peroxidase in 2002 and for cytochrome c peroxidase again in 1994 and 2003. This review will focus on the most recent structural investigations for the different intermediates of these proteins. The structures of these intermediates will also be viewed in light of quantum mechanical (QM) calculations on haem models. In particular quantum refinement, which is a combination of QM calculations and crystallography, will be discussed. Only small structural changes accompany the generation of these intermediates. The crystal structures show that the compound I state, with a so called pi-cation radical on the haem group, has a relatively short iron-oxygen bond (1.67-1.76A) in agreement with a double-bond character, while the compound II state or the compound I state with a radical on an amino acid residue have a relatively long iron-oxygen bond (1.86-1.92A) in agreement with a single-bond character where the oxygen-atom is protonated.
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Affiliation(s)
- Hans-Petter Hersleth
- Department of Chemistry, University of Oslo, P.O. Box 1033 Blindern, N-0315 Oslo, Norway
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Terner J, Palaniappan V, Gold A, Weiss R, Fitzgerald MM, Sullivan AM, Hosten CM. Resonance Raman spectroscopy of oxoiron(IV) porphyrin π-cation radical and oxoiron(IV) hemes in peroxidase intermediates. J Inorg Biochem 2006; 100:480-501. [PMID: 16513173 DOI: 10.1016/j.jinorgbio.2006.01.008] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2005] [Accepted: 01/04/2006] [Indexed: 11/15/2022]
Abstract
The catalytic cycle intermediates of heme peroxidases, known as compounds I and II, have been of long standing interest as models for intermediates of heme proteins, such as the terminal oxidases and cytochrome P450 enzymes, and for non-heme iron enzymes as well. Reports of resonance Raman signals for compound I intermediates of the oxo-iron(IV) porphyrin pi-cation radical type have been sometimes contradictory due to complications arising from photolability, causing compound I signals to appear similar to those of compound II or other forms. However, studies of synthetic systems indicated that protein based compound I intermediates of the oxoiron(IV) porphyrin pi-cation radical type should exhibit vibrational signatures that are different from the non-radical forms. The compound I intermediates of horseradish peroxidase (HRP), and chloroperoxidase (CPO) from Caldariomyces fumago do in fact exhibit unique and characteristic vibrational spectra. The nature of the putative oxoiron(IV) bond in peroxidase intermediates has been under discussion in the recent literature, with suggestions that the Fe(IV)O unit might be better described as Fe(IV)-OH. The generally low Fe(IV)O stretching frequencies observed for proteins have been difficult to mimic in synthetic ferryl porphyrins via electron donation from trans axial ligands alone. Resonance Raman studies of iron-oxygen vibrations within protein species that are sensitive to pH, deuteration, and solvent oxygen exchange, indicate that hydrogen bonding to the oxoiron(IV) group within the protein environment contributes to substantial lowering of Fe(IV)O frequencies relative to those of synthetic model compounds.
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Affiliation(s)
- James Terner
- Department of Chemistry, Virginia Commonwealth University, Richmond, VA 23284-2006, USA.
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Kozlowski PM, Kuta J, Ohta T, Kitagawa T. Resonance Raman enhancement of FeIVO stretch in high-valent iron porphyrins: An insight from TD-DFT calculations. J Inorg Biochem 2006; 100:744-50. [PMID: 16529819 DOI: 10.1016/j.jinorgbio.2006.01.021] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2005] [Revised: 01/10/2006] [Accepted: 01/10/2006] [Indexed: 11/23/2022]
Abstract
Density functional theory (DFT) has been applied to explain the origin of resonance Raman enhancement associated with the Fe(IV)=O stretch observed in iron(IV)oxo porphyrins. To accomplish this electronic excitations of the Im-(Por)Fe(IV)=O model were computed in the 1.5-4.0 eV spectral range using time-dependent DFT (TD-DFT). All electronic transitions having dominant pi-->pi* character were analyzed and assigned in terms of one-electron excitations. It was found that the most intense Soret band has a multi-component character, but the pi (a(2u))-->pi*(d(xz),d(yz)) and pi (a(1u))-->pi*(d(xz),d(yz)) electronic excitations are primarily responsible for observed resonance enhancement of the Fe(IV)=O stretch.
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Affiliation(s)
- Pawel M Kozlowski
- Department of Chemistry, University of Louisville, 2330 South Brook Street, Louisville, KY 40292, USA.
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34
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Stephenson NA, Bell AT. Influence of Solvent Composition on the Kinetics of Cyclooctene Epoxidation by Hydrogen Peroxide Catalyzed by Iron(III) [tetrakis(pentafluorophenyl)] Porphyrin Chloride [(F20TPP)FeCl]. Inorg Chem 2006; 45:2758-66. [PMID: 16529501 DOI: 10.1021/ic0521776] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The epoxidation of cyclooctene catalyzed by iron(III) [tetrakis(pentafluorophenyl)] porphyrin chloride [(F20TPP)FeCl] was investigated in alcohol/acetonitrile solutions in order to determine the effects of the alcohol composition on the reaction kinetics. It was observed that alcohol composition affects both the observed rate of hydrogen peroxide consumption (the limiting reagent) and the selectivity of hydrogen peroxide utilization to form cyclooctene epoxide. The catalytically active species are formed only in alcohol-containing solvents as a consequence of (F(20)TPP)FeCl dissociation into [(F20TPP)Fe(ROH)]+ cations and Cl- anions. The observed reaction kinetics are analyzed in terms of a proposed mechanism for the epoxidation of the olefin and the decomposition of H2O2. The first step in this scheme is the reversible coordination of H2O2 to [(F20TPP)Fe(ROH)]+. The O-O bond of the coordinated H2O2 then undergoes either homolytic or heterolytic cleavage. The rate of homolytic cleavage is found to be independent of alcohol composition, whereas the rate of heterolytic cleavage increases with alcohol acidity. Heterolytic cleavage is envisioned to form iron(IV) pi-radical cations, whereas homolytic cleavage forms iron(IV) hydroxo cations. The iron(IV) radical cations are active for olefin epoxidation, whereas the iron(IV) cations catalyze the decomposition of H2O2. Reaction of iron(IV) pi-radical cations with H2O2 to form iron(IV) hydroxo cations is also included in the mechanism, a process that is favored by alcohols with a high charge density on the O atoms. The proposed mechanism describes successfully the effects of H2O2, cyclooctene, and porphyrin concentrations, as well as the effects of alcohol concentration.
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Affiliation(s)
- Ned A Stephenson
- Chemical Sciences Division, Lawrence Berkeley Laboratory and Department of Chemical Engineering, University of California, Berkeley, California 94720-1462, USA
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35
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Abstract
Heme-thiolate proteins (HTPs) play critical biological roles by catalyzing challenging chemical reactions. The ability of HTPs to selectively oxidize inert substrates under mild conditions has led to much research aimed at the development of useful in vitro oxidation technology. Very complex electron transfer machinery is required to support HTP chemistry, and electrochemical methods provide many of the needed components. The challenge is to find a system that has good electrode-enzyme electronic coupling that, in turn, would drive catalytic turnover at relatively high rates. Several systems reviewed herein have shown promise in experimental work on components that could be part of a molecular machine for the selective oxidation of organic substrates.
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Affiliation(s)
- Andrew K Udit
- Department of Chemistry, Occidental College, Los Angeles, CA 90041, USA
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36
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Silaghi-Dumitrescu R, Cooper CE. Transient species involved in catalytic dioxygen/peroxide activation by hemoproteins: possible involvement of protonated Compound I species. Dalton Trans 2005:3477-82. [PMID: 16234928 DOI: 10.1039/b505440k] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Interaction of hemoproteins with peroxide leads in several cases to transient formation of ferric peroxo, ferric hydroperoxo, and "high-valent", formally Fev, oxo or hydroxo Compound species. Here, density functional calculations on ferric peroxo, ferric hydroperoxo, Compound and protonated Compound heme active site models are reported. The theoretical results, including calculated isotropic Fermi contact couplings and anisotropic spin dipole couplings, are found to generally correlate well with experimental EPR/ENDOR data. Hydrogen bonding and solvation affect the ferric-peroxo/ferrous-superoxo electromerism. The transition between the two electromers appears smooth, but neither hydrogen bonding to up to two water molecules, nor solvation appear able to dramatically alter the redox state of the superoxo ligand or of the iron. The presence of almost one full unpaired electron on the iron and of one full unpaired electron on the dioxygenic ligand in the "ferric-peroxo" state suggests a possible description of non-protonated "ferric-peroxo" as {ferric-superoxo+porphyrin radical}. Emerging from the DFT data is the possibility that a protonated Compound has already been detected in ENDOR experiments on cytochrome P450. The general feasibility of a protonated Compound in P450 monooxygenases is probed in light of these findings. To encompass the multiple mechanisms available in P450 for substrate oxidation, we define "mechanistic promiscuity" as the feature allowing an enzyme to perform the same reaction, with the same product, using more than one mechanism.
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Poulos TL. Intermediates in P450 catalysis. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2005; 363:793-806; discussion 1035-40. [PMID: 15901536 DOI: 10.1098/rsta.2004.1537] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Cytochromes P450 catalyse the insertion of one O2-derived oxygen atom in unactivated C-H bonds, and as such, are potent oxidants. A significant amount is known about the P450 catalytic cycle owing partly to the single heme group at the active site that provides spectroscopic handles in tracking various intermediates. A sophisticated array of electron paramagnetic, electron double nuclear resonance, and more traditional absorption spectroscopies have been able to identify key intermediates, while crystallography has defined the structure of the substrate-free, -bound, and oxy-complexes. What has remained elusive is the Fe(IV)=O intermediate, thought to be the active hydroxylating agent. Here, theory and especially density functional calculations have provided valuable insights.
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Affiliation(s)
- Thomas L Poulos
- Department of Molecular Biology and Biochemistry and the Program in Chemical and Structural Biology, University of California, Irvine, CA 92697-3900, USA.
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39
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Aboelella NW, Kryatov SV, Gherman BF, Brennessel WW, Young VG, Sarangi R, Rybak-Akimova EV, Hodgson KO, Hedman B, Solomon EI, Cramer CJ, Tolman WB. Dioxygen Activation at a Single Copper Site: Structure, Bonding, and Mechanism of Formation of 1:1 Cu−O2 Adducts. J Am Chem Soc 2004; 126:16896-911. [PMID: 15612729 DOI: 10.1021/ja045678j] [Citation(s) in RCA: 166] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
To evaluate the fundamental process of O(2) activation at a single copper site that occurs in biological and catalytic systems, a detailed study of O(2) binding to Cu(I) complexes of beta-diketiminate ligands L (L(1) = backbone Me; L(2) = backbone tBu) by X-ray crystallography, X-ray absorption spectroscopy (XAS), cryogenic stopped-flow kinetics, and theoretical calculations was performed. Using synchrotron radiation, an X-ray diffraction data set for L(2)CuO(2) was acquired, which led to structural parameters in close agreement to theoretical predictions. Significant Cu(III)-peroxo character for the complex was corroborated by XAS. On the basis of stopped-flow kinetics data and theoretical calculations for the oxygenation of L(1)Cu(RCN) (R = alkyl, aryl) in THF and THF/RCN mixtures between 193 and 233 K, a dual pathway mechanism is proposed involving (a) rate-determining solvolysis of RCN by THF followed by rapid oxygenation of L(1)Cu(THF) and (b) direct, bimolecular oxygenation of L(1)Cu(RCN) via an associative process.
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Affiliation(s)
- Nermeen W Aboelella
- Department of Chemistry, Center for Metals in Biocatalysis, and Supercomputer Institute, University of Minnesota, 207 Pleasant Street SE, Minneapolis, MN 55455, USA
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