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Tarrago M, Römelt C, Nehrkorn J, Schnegg A, Neese F, Bill E, Ye S. Experimental and Theoretical Evidence for an Unusual Almost Triply Degenerate Electronic Ground State of Ferrous Tetraphenylporphyrin. Inorg Chem 2021; 60:4966-4985. [PMID: 33739093 DOI: 10.1021/acs.inorgchem.1c00031] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Iron porphyrins exhibit unrivalled catalytic activity for electrochemical CO2-to-CO conversion. Despite intensive experimental and computational studies in the last 4 decades, the exact nature of the prototypical square-planar [FeII(TPP)] complex (1; TPP2- = tetraphenylporphyrinate dianion) remained highly debated. Specifically, its intermediate-spin (S = 1) ground state was contradictorily assigned to either a nondegenerate 3A2g state with a (dxy)2(dz2)2(dxz,yz)2 configuration or a degenerate 3Egθ state with a (dxy)2(dxz,yz)3(dz2)1/(dz2)2(dxy)1(dxz,yz)3 configuration. To address this question, we present herein a comprehensive, spectroscopy-based theoretical and experimental electronic-structure investigation on complex 1. Highly correlated wave-function-based computations predicted that 3A2g and 3Egθ are well-isolated from other triplet states by ca. 4000 cm-1, whereas their splitting ΔA-E is on par with the effective spin-orbit coupling (SOC) constant of iron(II) (≈400 cm-1). Therfore, we invoked an effective Hamiltonian (EH) operating on the nine magnetic sublevels arising from SOC between the 3A2g and 3Egθ states. This approach enabled us to successfully simulate all spectroscopic data of 1 obtained by variable-temperature and variable-field magnetization, applied-field 57Fe Mössbauer, and terahertz electron paramagnetic resonance measurements. Remarkably, the EH contains only three adjustable parameters, namely, the energy gap without SOC, ΔA-E, an angle θ that describes the mixing of (dxy)2(dxz,yz)3(dz2)1 and (dz2)2(dxy)1(dxz,yz)3 configurations, and the ⟨rd-3⟩ expectation value of the iron d orbitals that is necessary to estimate the 57Fe magnetic hyperfine coupling tensor. The EH simulations revealed that the triplet ground state of 1 is genuinely multiconfigurational with substantial parentages of both 3A2g (<88%) and 3Eg (>12%), owing to their accidental near-triple degeneracy with ΔA-E = +950 cm-1. As a consequence of this peculiar electronic structure, 1 exhibits a huge effective magnetic moment (4.2 μB at 300 K), large temperature-independent paramagnetism, a large and positive axial zero-field splitting, strong easy-plane magnetization (g⊥ ≈ 3 and g∥ ≈ 1.7) and a large and positive internal field at the 57Fe nucleus aligned in the xy plane. Further in-depth analyses suggested that g⊥ ≫ g∥ is a general spectroscopic signature of near-triple orbital degeneracy with more than half-filled pseudodegenerate orbital sets. Implications of the unusual electronic structure of 1 for CO2 reduction are discussed.
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Affiliation(s)
- Maxime Tarrago
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470 Mülheim an der Ruhr, Germany
| | - Christina Römelt
- Max-Planck-Institut für Chemische Energiekonversion, Stiftstrasse 34-36, D-45470 Mülheim an der Ruhr, Germany
| | - Joscha Nehrkorn
- Max-Planck-Institut für Chemische Energiekonversion, Stiftstrasse 34-36, D-45470 Mülheim an der Ruhr, Germany
| | - Alexander Schnegg
- Max-Planck-Institut für Chemische Energiekonversion, Stiftstrasse 34-36, D-45470 Mülheim an der Ruhr, Germany
| | - Frank Neese
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470 Mülheim an der Ruhr, Germany
| | - Eckhard Bill
- Max-Planck-Institut für Chemische Energiekonversion, Stiftstrasse 34-36, D-45470 Mülheim an der Ruhr, Germany
| | - Shengfa Ye
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470 Mülheim an der Ruhr, Germany.,State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
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Viciano‐Chumillas M, Blondin G, Clémancey M, Krzystek J, Ozerov M, Armentano D, Schnegg A, Lohmiller T, Telser J, Lloret F, Cano J. Single‐Ion Magnetic Behaviour in an Iron(III) Porphyrin Complex: A Dichotomy Between High Spin and 5/2–3/2 Spin Admixture. Chemistry 2020; 26:14242-14251. [DOI: 10.1002/chem.202003052] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2020] [Indexed: 11/09/2022]
Affiliation(s)
| | - Geneviève Blondin
- CNRS, CEA, IRIG, CBM Université Grenoble Alpes, CEA-Grenoble 38000 Grenoble France
| | - Martin Clémancey
- CNRS, CEA, IRIG, CBM Université Grenoble Alpes, CEA-Grenoble 38000 Grenoble France
| | - Jurek Krzystek
- National High Magnetic Field Laboratory Florida State University Tallahassee FL 32310 USA
| | - Mykhaylo Ozerov
- National High Magnetic Field Laboratory Florida State University Tallahassee FL 32310 USA
| | - Donatella Armentano
- Dipartimento di Chimica e Tecnologie Chimiche (CTC) Università della Calabria 87030 Rende, Cosenza Italy
| | - Alexander Schnegg
- EPR Research Group MPI for Chemical Energy Conversion Stiftstrasse 34–36 45470 Mülheim Ruhr Germany
| | - Thomas Lohmiller
- EPR4Energy Joint Lab Department Spins in Energy Conversion and Quantum Information Science Helmholtz-Zentrum Berlin für Materialien und Energie Kekuléstrasse 5 12489 Berlin Germany
| | - Joshua Telser
- Department of Biological, Physical and Health Sciences Roosevelt University 430 S. Michigan Avenue Chicago IL 60605 USA
| | - Francesc Lloret
- Institut de Ciència Molecular (ICMol) Universitat de València 46980 Paterna Spain
| | - Joan Cano
- Institut de Ciència Molecular (ICMol) Universitat de València 46980 Paterna Spain
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3
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Benini S, Rypniewski WR, Wilson KS, Ciurli S. High resolution crystal structure of Rubrivivax gelatinosus cytochrome c′. J Inorg Biochem 2008; 102:1322-8. [DOI: 10.1016/j.jinorgbio.2008.01.017] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2007] [Revised: 01/06/2008] [Accepted: 01/09/2008] [Indexed: 11/16/2022]
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4
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Bröring M, Köhler S, Link S, Burghaus O, Pietzonka C, Kelm H, Krüger HJ. Iron Chelates of 2,2′-Bidipyrrin: Stable Analogues of the Labile Iron Bilins. Chemistry 2008; 14:4006-16. [DOI: 10.1002/chem.200701919] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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5
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Weiss R, Gold A, Terner J. Cytochromes c‘: Biological Models for the S = 3/2,5/2 Spin-State Admixture? Chem Rev 2006; 106:2550-79. [PMID: 16771459 DOI: 10.1021/cr040416l] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Raymond Weiss
- Laboratoire de Chimie Supramoléculaires, Institut de Science et d'Ingénierie Supramoléculaires, Université Louis Pasteur de Strasbourg, 8 Allée Gaspard Monge, B.P.70028, F-67083 Strasbourg Cedex, France
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6
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Usov OM, Choi PST, Shapleigh JP, Scholes CP. ENDOR Investigation of the Liganding Environment of Mixed-Spin Ferric Cytochrome c‘. J Am Chem Soc 2005; 127:9485-94. [PMID: 15984875 DOI: 10.1021/ja043994s] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The electronic structure of the 5-coordinate quantum-mechanically mixed-spin (sextet-quartet) heme center in cytochrome c' was investigated by electron nuclear double resonance (ENDOR), a technique not previously applied to this mixed-spin system. Cytochrome c' was obtained from overexpressing variants of Rhodobacter sphaeroides 2.4.3. ENDOR for this study was done at the g(//) = 2.00 extremum where single-crystal-like, well-resolved spectra prevail. The heme meso protons of cytochrome c' showed a contact interaction that implied spin delocalization arising from the heme (d(z)(2)) orbital enhanced by iron out-of-planarity. An exchangeable proton ENDOR feature appeared from the proximal His123 Ndelta hydrogen. This Ndelta hydrogen, which crystallographically has no hydrogen-bonding partner and thus belongs to a neutral imidazole, showed a larger hyperfine coupling than the corresponding hydrogen-bonded Ndelta proton from metmyoglobin. The unique residue Phe14 occludes binding of a sixth ligand in cytochrome c', and ENDOR from a proton of the functionally important Phe14 ring, approximately 3.3 A away from the heme iron, was detected. ENDOR of the nitrogen ligand hyperfine structure is a direct probe into the sigma-antibonding (d(z)(2)) and (d(x)(2)-d(y)(2)) orbitals whose energies alter the relative stability and admixture of sextet and quartet states and whose electronic details were thus elucidated. ENDOR frequencies showed for cytochrome c' larger hyperfine couplings to the histidine nitrogen and smaller hyperfine couplings to the heme nitrogens than for high-spin ferric hemes. Both of these findings followed from the mixed-spin ground state, which has less (d(x)(2)-d(y)(2)) character than have fully high-spin ferric heme systems.
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Affiliation(s)
- Oleg M Usov
- Department of Chemistry, Center for Biochemistry and Biophysics, University at Albany, SUNY, Albany, New York 12222, USA
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Sakai T, Ohgo Y, Hoshino A, Ikeue T, Saitoh T, Takahashi M, Nakamura M. Electronic Structures of Five-Coordinate Iron(III) Porphyrin Complexes with Highly Ruffled Porphyrin Ring. Inorg Chem 2004; 43:5034-43. [PMID: 15285680 DOI: 10.1021/ic049825q] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The spin states of the iron(III) complexes with a highly ruffled porphyrin ring, [Fe(TEtPrP)X] where X = F-, Cl-, Br-, I-, and ClO4(-), have been examined by 1H NMR, 13C NMR, EPR, and Mössbauer spectroscopy. While the F-, Cl-, and Br- complexes adopt a high-spin (S = 5/2) state, the I- complex exhibits an admixed intermediate-spin (S = 5/2, 3/2) state in CD2Cl2 solution. The I- complex shows, however, a quite pure high-spin state in toluene solution as well as in the solid. The results contrast those of highly saddled [Fe(OETPP)X] where the I- complex exhibits an essentially pure intermediate-spin state both in solution and in the solid. In contrast to the halide-ligated complexes, the ClO4(-) complex shows a quite pure intermediate-spin state. The 13C NMR spectra of [Fe(TEtPrP)ClO4] are characterized by the downfield and upfield shifts of the meso and pyrrole-alpha carbon signals, respectively: delta(meso) = +342 and delta(alpha-py) = -287 ppm at 298 K. The data indicate that the meso carbon atoms of [Fe(TEtPrP)ClO4] have considerable amounts of positive spin, which in turn indicate that the iron has an unpaired electron in the d(xy) orbital; the unpaired electron in the d(xy) orbital is delocalized to the meso positions due to the iron(d(xy))-porphyrin(a(2u)) interaction. Similar results have been obtained in analogous [Fe(TiPrP)X] though the intermediate-spin character of [Fe(TiPrP)X] is much larger than that of the corresponding [Fe(TEtPrP)X]. On the basis of these results, we have concluded that the highly ruffled intermediate-spin complexes such as [Fe(TEtPrP)ClO4] and [Fe(TiPrP)ClO4] adopt a novel (d(xz), d(yz))3(d(xy))1(d(z)(2)1 electron configuration; the electron configuration of the intermediate-spin complexes reported previously is believed to be (d(xy))2(d(xz)), d(yz))2(d(z)(2))1.
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Affiliation(s)
- Takanori Sakai
- Department of Chemistry, School of Medicine, Toho University, Tokyo 143-8540, Japan
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8
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Ikezaki A, Nakamura M. Models for cytochromes c': spin states of mono(imidazole)-ligated (meso-tetramesitylporphyrinato)iron(III) complexes as studied by UV-Vis, 13C NMR, 1H NMR, and EPR spectroscopy. Inorg Chem 2002; 41:6225-36. [PMID: 12444764 DOI: 10.1021/ic020378t] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
A number of mono(imidazole)-ligated complexes of perchloro(meso-tetramesitylporphyrinato)iron(III), [Fe(TMP)L]ClO(4), have been prepared, and their spin states have been examined by (1)H NMR, (13)C NMR, and EPR spectroscopy as well as solution magnetic moments. All the complexes examined have shown a quantum mechanical spin admixed state of high and intermediate-spin (S = 5/2 and 3/2) states though the contribution of the S = 3/2 state varies depending on the nature of axial ligands. While the complex with extremely bulky 2-tert-butylimidazole (2-(t)()BuIm) has exhibited an essentially pure S = 5/2 state, the complex with electron-deficient 4,5-dichloroimidazole (4,5-Cl(2)Im) adopts an S = 3/2 state with 30% of the S = 5/2 spin admixture. On the basis of the (1)H and (13)C NMR results, we have concluded that the S = 3/2 contribution at ambient temperature increases according to the following order: 2-(t)BuIm < 2-(1-EtPr)Im < 2-MeIm <or= 2-EtIm <or= 2-(i)PrIm < 4,5-Cl(2)Im. The effective magnetic moments determined by the Evans method in CH(2)Cl(2) solution are 5.9 and 5.0 mu(B) at 25 degrees C for [Fe(TMP)(2-(t)BuIm)]ClO(4) and [Fe(TMP)(2-MeIm)]ClO(4), respectively, which further verify the order given above. Comparison of the NMR and EPR data has revealed that the S = 3/2 contribution changes sensitively by the temperature; the S = 3/2 contribution decreases as the temperature is lowered for all the mono(imidazole) complexes examined in this study. The solvent polarity also affects the spin state; polar solvents such as methanol and acetonitrile increase the S = 3/2 contribution while nonpolar solvents such as benzene decrease it. These results are explained in terms of the structurally flexible nature of the mono(imidazole) complexes; structural parameters such as the Fe(III)-N(axial) bond length, displacement of the iron from the N4 core, tilting of the Fe(III)-N(axial) bond to the heme normal, orientation of the coordinated imidazole ligand, etc., could be altered by the nature of the axial ligands as well as by the solvent polarity and temperature. Some mysteries on the spin states of cytochromes c' isolated from various bacterial sources are possibly explained in terms of the flexible nature of the mono(imidazole)-ligated structure.
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Affiliation(s)
- Akira Ikezaki
- Department of Chemistry, School of Medicine, Toho University, Tokyo 143-8540, Japan
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9
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Yoshimura T, Fujii S, Kamada H, Yamaguchi K, Suzuki S, Shidara S, Takakuwa S. Spectroscopic characterization of nitrosylheme in nitric oxide complexes of ferric and ferrous cytochrome c' from photosynthetic bacteria. BIOCHIMICA ET BIOPHYSICA ACTA 1996; 1292:39-46. [PMID: 8547347 DOI: 10.1016/0167-4838(95)00187-5] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Reactions of ferric and ferrous cytochromes c' from four photosynthetic bacteria (Rhodobacter capsulatus ATCC 11166, Rhodopseudomonas palustris ATCC 17001, Rhodospirillum rubrum ATCC 11170, and Chromatium vinosum ATCC 17899) with nitric oxide have been investigated by electronic absorption and electron paramagnetic resonance spectroscopies. The heme iron(III) of these ferric cytochromes c' has been recently reported to be in a quantum mechanically admixed (S = 5/2, 3/2) state [Fujii, S., Yoshimura, T., Kamada, H., Yamaguchi, K., Suzuki, S., Shidara, S. and Takakuwa, S. (1995) Biochim. Biophys. Acta 1251, 161-169]. The affinity of ferric cytochromes c' for NO among these bacterial species (C. vinosum > Rps. palustris approximately Rb. capsulatus >> R. rubrum) was apparently related to the S = 3/2 content in the or der. In the reaction of ferrous cytochrome c' with NO, six- and five-coordinated nitrosylhemes, which represent species with and without a ligand at the axial position trans to nitrosyl group, have been formed. The content of six-coordinated nitrosylheme in NO-ferrous cytochrome c' has been determined to be Rb. capsulatus approximately Rps. palustris > C. vinosum < R rubrum, suggesting that a stability of iron-to-histidine bond decreases with this order. The NO reactions of ferric and ferrous cytochromes c' from photosynthetic bacteria have been compared with those of cytochromes c' from denitrifying bacteria.
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Affiliation(s)
- T Yoshimura
- Institute for Life Support Technology, Yamagata Technopolis Foundation, Japan
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10
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Even MT, Kassner RJ, Dolata M, Meyer TE, Cusanovich MA. Molecular cloning and sequencing of cytochrome c' from the phototrophic purple sulfur bacterium Chromatium vinosum. BIOCHIMICA ET BIOPHYSICA ACTA 1995; 1231:220-2. [PMID: 7578212 DOI: 10.1016/0005-2728(95)00101-n] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The gene for cytochrome c' from Chromatium vinosum was cloned from a HindIII-SalI digest of genomic DNA. A 1.4 kbp fragment containing the gene was sequenced in both directions using the Sanger dideoxy method. The cytochrome c' gene codes for a 154-residue peptide, of which the last 131 amino acids match the previously determined sequence of the protein. The remaining 23 residues represent a signal sequence that is cleaved from the polypeptide upon translocation to the periplasmic space. An additional open reading frame on the other strand of the fragment codes for a peptide that contains four regions that are homologous to corresponding regions of the cytochrome b-type subunit of several Ni-Fe hydrogenases.
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Affiliation(s)
- M T Even
- Department of Chemistry, University of Illinois at Chicago 60607, USA
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Fujii S, Yoshimura T, Kamada H, Yamaguchi K, Suzuki S, Shidara S, Takakuwa S. Electron paramagnetic resonance studies of ferric cytochrome c' from photosynthetic bacteria. BIOCHIMICA ET BIOPHYSICA ACTA 1995; 1251:161-9. [PMID: 7669805 DOI: 10.1016/0167-4838(95)00092-9] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Electronic ground nature of ferric cytochromes c' isolated from five photosynthetic bacteria. Chromatium vinosum ATCC 17899, Rhodobacter capsulatus ATCC 11166, Rhodopseudomonas palustris ATCC 17001, Rhodospirillum molischianum ATCC 14031, and Rhodospirillum rubrum ATCC 11170 has been investigated by electron paramagnetic resonance (EPR) spectroscopy. EPR spectra indicate that the electronic ground state of five ferric cytochromes c' is a quantum mechanical admixed-spin state of a high spin (S = 5/2) and an intermediate spin (S = 3/2) at pH 7.2 and is high-spin state at pH 11.0. At physiological pH, however, the content of an intermediate spin state differs with the bacterial source of the protein: approximately 50%, Chromatium vinosum; approximately 40%, Rhodobacter capsulatus and Rhodopseudomonas palustris; approximately 10%, Rhodospirillum molischianum and Rhodospirillum rubrum. Computer simulation of the spectra supports this diversity of the contribution of an intermediate spin state. Model studies of the ferric porphyrin complexes suggest that the correlation between content of an intermediate spin state and heme iron displacement from the mean heme plane. Therefore, the variation of the content of an intermediate spin state observed in the present study reflects the subtle difference in the degree of heme iron displacement among the proteins.
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Affiliation(s)
- S Fujii
- Institute for Life Support Technology, Yamagata Technopolis Foundation, Japan
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12
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Bominaar EL, Block R. Theoretical model study of the quantum‐mechanically mixed‐spin (S=5/2,3/2) ground state in iron (III) porphyrins. J Chem Phys 1991. [DOI: 10.1063/1.461541] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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13
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Motie M, Kassner RJ, Meyer TE, Cusanovich MA. Cyanide-linked dimer-monomer equilibrium of Chromatium vinosum ferric cytochrome c'. BIOCHIMICA ET BIOPHYSICA ACTA 1991; 1076:97-102. [PMID: 1846081 DOI: 10.1016/0167-4838(91)90225-o] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Cyanide binding to Chromatium vinosum ferricytochrome c' has been studied to further investigate possible allosteric interactions between the subunits of this dimeric protein. Cyanide binding to C. vinosum cytochrome c' appears to be cooperative. However, the cyanide binding reaction is unusual in that the overall affinity of cyanide increases as the concentration of cytochrome c' decreases and that cyanide binding causes the ligated dimer to dissociate to monomers as shown by gel-filtration chromatography. Therefore, the cyanide binding properties of C. vinosum ferricytochrome c' are complicated by a cyanide-linked dimer to monomer dissociation equilibrium of the complexed protein. The dimer to monomer dissociation constant is 20-fold smaller than that for CO linked dissociation constant of ferrocytochrome c'. Furthermore, the pH dependence of both the intrinsic equilibrium binding constant and the dimer to monomer equilibrium dissociation constant was investigated over the pH range of 7.0 to 9.2 to examine the effect of any ionizable groups. The equilibrium constants did not exhibit a significant pH dependence over this pH range.
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Affiliation(s)
- M Motie
- Department of Chemistry, University of Illinois, Chicago 60680
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14
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Trautwein AX, Bill E, Bominaar EL, Winkler H. Iron-containing proteins and related analogs — complementary Mössbauer, EPR and magnetic susceptibility studies. STRUCTURE AND BONDING 1991. [DOI: 10.1007/3-540-54261-2_1] [Citation(s) in RCA: 147] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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15
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La Mar GN, Jackson JT, Dugad LB, Cusanovich MA, Bartsch RG. Proton NMR study of the comparative electronic/magnetic properties and dynamics of the acid in equilibrium with alkaline transition in a series of ferricytochromes c'. J Biol Chem 1990. [DOI: 10.1016/s0021-9258(17)46204-1] [Citation(s) in RCA: 58] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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16
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Motie M, Kassner RJ, Meyer TE, Cusanovich MA. Kinetics of cyanide binding to Chromatium vinosum ferricytochrome c'. Biochemistry 1990; 29:1932-6. [PMID: 2158816 DOI: 10.1021/bi00459a038] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The kinetics of the reversible binding of cyanide by the ferric cytochrome c' from Chromatium vinosum have been studied over the pH range 6.9-9.6. The reaction is extremely slow at neutral pH compared to the reactions of other high-spin ferric heme proteins with cyanide. The observed bimolecular rate constant at pH 7.0 is 2.25 X 10(-3) M-1 s-1, which is approximately 10(7)-fold slower than that for peroxidases, approximately 10(5)-fold slower than those for hemoglobin and myoglobin, and approximately 10(2)-fold to approximately 10(3)-fold slower than that recently reported for the Glycera dibranchiata hemoglobin, which has anomalously slow cyanide rate constants of 4.91 X 10(-1), 3.02 X 10(-1), and 1.82 M-1 s-1 for components II, III, and IV, respectively [Mintorovitch, J., & Satterlee, J. D. (1988) Biochemistry 27, 8045-8050; Mintorovitch, J., Van Pelt, D., & Satterlee, J. D. (1989) Biochemistry 28, 6099-6104]. The unusual ligand binding property of this cytochrome c' is proposed to be associated with a severely hindered heme coordination site. Cyanide binding is also characterized by a nonlinear cyanide concentration dependence of the observed rate constant at higher pH values, which is interpreted as involving a change in the rate-determining step associated with the formation of an intermediate complex between the cytochrome c' and cyanide prior to coordination. The pH dependence of both the binding constant for the formation of the intermediate complex and the association rate constant for the subsequent coordination to the heme can be attributed to the ionization of HCN, where cyanide ion binding is the predominant process.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- M Motie
- Department of Chemistry, University of Illinois, Chicago 60680
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17
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18
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Gupta GP, Lang G, Reed CA, Shelly K, Scheidt WR. Susceptibility and Mössbauer study of an antiferromagnetically coupled admixed‐intermediate spin state in Fe(TPP) (FSbF5)⋅C6H5F. J Chem Phys 1987. [DOI: 10.1063/1.452552] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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19
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Gupta GP, Lang G, Scheidt WR, Geiger DK, Reed CA. Susceptibility and Mössbauer study of coupled admixed‐spin state in [Fe(OEP) (3‐ClPy)]+dimers. J Chem Phys 1986. [DOI: 10.1063/1.451686] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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20
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Andersson KK, Lipscomb JD, Valentine M, Münck E, Hooper AB. Tetraheme cytochrome c-554 from Nitrosomonas europaea. Heme-heme interactions and ligand binding. J Biol Chem 1986. [DOI: 10.1016/s0021-9258(17)36064-7] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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21
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Gupta GP, Lang G, Scheidt WR, Geiger DK, Reed CA. Mössbauer and susceptibility study of inter‐heme spin coupling in [Fe (OEP) (2‐MeHIm)]+dimers. J Chem Phys 1985. [DOI: 10.1063/1.449626] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Kassner RJ, Kykta MG, Cusanovich MA. Binding of cyanide to cytochrome c' from Chromatium vinosum. BIOCHIMICA ET BIOPHYSICA ACTA 1985; 831:155-8. [PMID: 2994739 DOI: 10.1016/0167-4838(85)90163-3] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Spectroscopic evidence is presented which demonstrates the binding of cyanide to the ferric cytochrome c' from Chromatium vinosum. The cytochrome was shown to bind one equivalent of cyanide with an equilibrium constant of 2.1 X 10(4) at pH 7.0 and 25 degrees C. This finding represents the first observation of the binding of an anionic ligand to the heme iron in a ferric cytochrome c'. These results suggest that the binding site of the ferric Chromatium cytochrome c' may be significantly more accessible than previously indicated.
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Abstract
The binding of ethyl isocyanide (EIC) to a representative number of cytochromes c' is demonstrated. Spectroscopic and equilibrium constants have been measured and compared for the binding of EIC to cytochromes c' from the photosynthetic bacteria Chromatium vinosum, Rhodopseudomonas palustris, Rhodospirillum rubrum, and Rhodopseudomonas sphaeroides. While the absorption spectra of the EIC complexes resemble those of EIC complexes of other high-spin hemoproteins, the Soret half band widths and extinction coefficients per heme exhibit more than a 2-fold difference with the values of C. vinosum being most similar to those of Rh. sphaeroides and of Rh. palustris similar to those of Rs. rubrum. The cytochromes exhibit binding equilibria consistent with the ligation of one molecule of EIC per heme in contrast to the reported binding of more than one molecule of CO per heme. The binding constants exhibit more than a 1000-fold difference with the values of C. vinosum being closely similar to those of Rh. sphaeroides and of Rh. palustris similar to those of Rs. rubrum. The lack of correlation between EIC and CO binding properties indicates that electronic factors do not determine the difference in EIC binding properties. The observed correlation between the extinction coefficients, half band widths, and equilibrium constants for EIC complex formation provides the first spectroscopic evidence that the differences in binding properties are associated with sterically hindered ligation to the heme. Although the differences in binding properties provide evidence of steric hindrance, the EIC binding constants for particular cytochromes c' indicate that the distal heme binding site is more accessible than previously indicated.(ABSTRACT TRUNCATED AT 250 WORDS)
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Boso B, Lang G, Reed CA. A Mössbauer spectroscopic study of the six‐coordinate high‐spin ferrous compound (meso‐tetraphenylporphinato) bis(tetrahydrofuran) iron(II). J Chem Phys 1983. [DOI: 10.1063/1.445010] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Jackson JT, La Mar GN, Bartsch RG. Proton nuclear magnetic resonance studies of the ligation states of the monomeric ferricytochrome c' from Rhodopseudomonas palustris. Modulation of axial histidine bonding via variable proton donation. J Biol Chem 1983. [DOI: 10.1016/s0021-9258(18)33058-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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