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Hagen WR. Low-frequency EPR of ferrimyoglobin fluoride and ferrimyoglobin cyanide: a case study on the applicability of broadband analysis to high-spin hemoproteins and to HALS hemoproteins. J Biol Inorg Chem 2022; 27:497-507. [PMID: 35802192 PMCID: PMC9399021 DOI: 10.1007/s00775-022-01948-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Accepted: 06/04/2022] [Indexed: 11/29/2022]
Abstract
An EPR spectrometer has been developed that can be tuned to many frequencies in the range of ca 0.1–15 GHz. Applicability has been tested on ferrimyoglobin fluoride (MbF) and ferrimyoglobin cyanide (MbCN). MbF has a high-spin (S = 5/2) spectrum with 19F superhyperfine splitting that is only resolved in X-band along the heme normal. Low-frequency EPR also resolves the splitting in the heme plane. Measurement of linewidth as a function of frequency provides the basis for an analysis of inhomogeneous broadening in terms of g-strain, zero-field distribution, unresolved superhyperfine splittings and dipolar interaction. Rhombicity in the g tensor is found to be absent. MbCN (S = 1/2) has a highly anisotropic low spin (HALS) spectrum for which gx cannot be determined unequivocally in X-band. Low-frequency EPR allows for measurement of the complete spectrum and determination of the g-tensor.
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Affiliation(s)
- Wilfred R Hagen
- Department of Biotechnology, Delft University of Technology, Delft, The Netherlands.
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2
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Synthesis of pure iron(II) mesotetraphenylchlorin complexes via a versatile general method of iron insertion into chlorins. Inorganica Chim Acta 2013. [DOI: 10.1016/j.ica.2013.01.012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Ikezaki A, Nakamura M, Juillard S, Simonneaux G. 13C NMR Studies of the Electronic Structure of Low-Spin Iron(III) Tetraphenylchlorin Complexes. Inorg Chem 2006; 45:6728-39. [PMID: 16903729 DOI: 10.1021/ic060508o] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A series of low-spin six-coordinate (tetraphenylchlorinato)iron(III) complexes [Fe(TPC)(L)2]+/- (L = 1-MeIm, CN-, 4-CNPy, and (t)BuNC) have been prepared, and their (13)C NMR spectra have been examined to reveal the electronic structure. These complexes exist as the mixture of the two isomers with the (d(xy))2(d(xz), d(yz))3 and (d(xz), d(yz))4(d(xy))1 ground states. Contribution of the (d(xz), d(yz))4(d(xy))1 isomer has increased as the axial ligand changes from 1-MeIm, to CN(-) (in CD2Cl2 solution), CN- (in CD(3)OD solution), and 4-CNPy, and then to tBuNC as revealed by the meso and pyrroline carbon chemical shifts; the meso carbon signals at 146 and -19 ppm in [Fe(TPC)(1-MeIm)2]+ shifted to 763 and 700 ppm in [Fe(TPC)(tBuNC)2]+. In the case of the CN- complex, the population of the (d(xz), d(yz))4(d(xy))1 isomer has increased to a great extent when the solvent is changed from CD2Cl2 to CD3OD. The result is ascribed to the stabilization of the d(xz) and d(yz) orbitals of iron(III) caused by the hydrogen bonding between methanol and the coordinated cyanide ligand. Comparison of the 13C NMR data of the TPC complexes with those of the TPP, OEP, and OEC complexes has revealed that the populations of the (d(xz), d(yz))4(d(xy))1 isomer in TPC complexes are much larger than those in the corresponding TPP, OEC, and OEP complexes carrying the same axial ligands.
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Affiliation(s)
- Akira Ikezaki
- Department of Chemistry, School of Medicine, Toho University, Ota-ku, Tokyo 143-8540, Japan
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Benda R, Schünemann V, Trautwein AX, Cai S, Reddy Polam J, Watson CT, Shokhireva TK, Walker FA. Models of the bis-histidine-coordinated ferricytochromes: Mössbauer and EPR spectroscopic studies of low-spin iron(III) tetrapyrroles of various electronic ground states and axial ligand orientations. J Biol Inorg Chem 2003; 8:787-801. [PMID: 12898323 DOI: 10.1007/s00775-003-0472-5] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2002] [Accepted: 05/19/2003] [Indexed: 10/26/2022]
Abstract
The EPR and magnetic Mössbauer spectra of a series of axial ligand complexes of tetrakis(2,6-dimethoxyphenyl)porphyrinatoiron(III), [(2,6-(OMe)(2))(4)TPPFeL(2)](+), where L= N-methylimidazole, 2-methylimidazole, or 4-(dimethylamino)pyridine, of one axial ligand complex of tetraphenylporphyrin, the bis(4-cyanopyridine) complex [TPPFe(4-CNPy)(2)](+), and of one axial ligand complex of tetraphenylchlorin, [TPCFe(ImH)(2)](+), where ImH=imidazole, have been investigated and compared to those of low-spin Fe(III) porphyrinates and ferriheme proteins reported in the literature. On the basis of this and previous complementary spectroscopic investigations, three types of complexes have been identified: those having (d(xy))(2)(d(xz),d(yz))(3) electronic ground states with axial ligands aligned in perpendicular planes (Type I), those having (d(xy))(2)(d(xz),d(yz))(3) electronic ground states with axial ligands aligned in parallel planes (Type II), and those having the novel (d(xz),d(yz))(4)(d(xy))(1) electronic ground state (Type III). A subset of the latter type, with planar axial ligands aligned parallel to each other or strong macrocycle asymmetry that yield rhombic EPR spectra, cannot be created using the porphyrinate ligand. Type I centers are characterized by "large g(max)" EPR spectra with g>3.2 and well-resolved, widely spread magnetic Mössbauer spectra having A(zz)/ g(N)mu(N)>680 kG, with A(xx) negative in sign but much smaller in magnitude than A(zz), while Type II centers have well-resolved rhombic EPR spectra with g(zz)=2.4-3.1 and also less-resolved magnetic Mössbauer spectra, and usually have A(zz)/ g(Nmu(N) in the range of 440-660 kG (but in certain cases as small as 180 kG) and A(xx) again negative in sign but only somewhat smaller (but occasionally larger in magnitude) than A(zz), and Type III centers have axial EPR spectra with g( upper left and right quadrants ) approximately 2.6 or smaller and g( vertical line )<1.0-1.95, but often not resolved, and less-resolved magnetic Mössbauer spectra having A(zz)/ g(N)mu(N) in the range of 270-400 kG, and A(xx) again negative in sign but much smaller in magnitude than A(zz). An exception to this rule is [TPPFe(4-CNPy)(2)](+), which has A(xx)/ g(N)mu(N)=-565 kG, A(yy)/ g(N)mu(N)=629 kG, and A(zz)/ g(N)mu(N)=4 kG. A subset of Type II complexes (Type II') have rhombicities ( V/Delta) much greater than 0.67 and A(zz)/ g(N)mu(N) ranging from 320 to 170 kG, with A(xx) also negative but with the magnitude of A(xx) significantly larger than that of A(zz). These classifications are also observed for a variety of ferriheme proteins, and they lead to linear correlations between A(zz) and either A(xx), g(zz), or V/Delta for Types I and II (but not for A(zz) versus V/Delta for Type II'). Not enough data are yet available on Type III complexes to determine what, if any, correlations may be observed.
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Affiliation(s)
- Rüdiger Benda
- Institut für Physik, Universität Lübeck, Ratzeburger Allee 160, 23538, Lübeck, Germany
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Simonneaux G, Kobeissi M, Toupet L. Electronic structure of iron chlorins: characterization of bis(l-valine methyl ester)(meso-tetraphenylchlorin)iron(III)triflate and bis(l-valine methyl ester)(meso-tetraphenylchlorin)iron(II). Inorg Chem 2003; 42:1644-51. [PMID: 12611534 DOI: 10.1021/ic026039h] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The synthesis and characterization of the two iron chlorin complexes [Fe(III)(TPC)(NH(2)CH(CO(2)CH(3))(CH(CH(3))(2)))(2)]CF(3)SO(3) (1) and Fe(II)(TPC)[(NH(2)CH(CO(2)CH(3))(CH(CH(3))(2))](2) (2) are reported. The crystal structure of complex 1 has been determined. The X-ray structure shows that the porphyrinate rings are weakly distorted. The metal-nitrogen distances to the reduced pyrrole N(4), 2.034(4) A, and to the pyrrole trans to it N(2), 2.012(4) A, are longer than the distances to the two remaining nitrogens [N(1), 1.996(4) A, and N(3), 1.984(4) A], leading to a core-hole expansion of the macrocycle due to the reduced pyrrole. The (1)H NMR isotropic shifts at 20 degrees C of the different pyrrole protons of 1 varied from -0.8 to -48.3 ppm according to bis-ligated complexes of low-spin ferric chlorins. The EPR spectrum of [Fe(TPC)(NH(2)CH(CO(2)CH(3))(CH(CH(3))(2)))(2)]CF(3)SO(3) (1) in solution is rhombic and gives the principal g values g(1) = 2.70, g(2) = 2.33, and g(3) = 1.61 (Sigmag(2) = 15.3). These spectroscopic observations are indicative of a metal-based electron in the d(pi) orbital for the [Fe(TPC)(NH(2)CH(CO(2)CH(3))(CH(CH(3))(2)))(2)]CF(3)SO(3) (1) complex with a (d(xy))(2)(d(xz)d(yz))(3) ground state at any temperature. The X-ray structure of the ferrous complex 2 also shows that the porphyrinate rings are weakly distorted. The metal-nitrogen distances to the reduced pyrrole N(4), 1.991(5) A, and to the pyrrole trans to it N(2), 2.005(6) A, are slightly different from the distances to the two remaining nitrogens [N(1), 1.988(5) A, and N(3), 2.015(5) A], leading to a core-hole expansion of the macrocycle due to the reduced pyrrole.
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Affiliation(s)
- Gérard Simonneaux
- Laboratoire de Chimie Organométallique et Biologique, UMR CNRS 6509, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France.
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Kobeissi M, Toupet L, Simonneaux G. Electronic structure of low-spin ferric chlorins: characterization of bis(dimethylphenylphosphine)(meso-tetraphenylchlorinato)iron(III) triflate. Inorg Chem 2001; 40:4494-9. [PMID: 11487363 DOI: 10.1021/ic0013328] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- M Kobeissi
- Laboratoire de Chimie Organométallique et Biologique, URA CNRS 415, Université de Rennes 1, 35042 Rennes Cedex, France
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Walker F. Magnetic spectroscopic (EPR, ESEEM, Mössbauer, MCD and NMR) studies of low-spin ferriheme centers and their corresponding heme proteins. Coord Chem Rev 1999. [DOI: 10.1016/s0010-8545(99)00029-6] [Citation(s) in RCA: 234] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Pilard MA, Guillemot M, Toupet L, Jordanov J, Simonneaux G. Effect of Phosphorus Axial π-Acceptors in Iron(III) Porphyrinates: Characterization of Low-Spin Complexes [(PPh(OMe)2)2Fe(T(p-Me)PP)]CF3SO3 and [(PPh(OEt)2)2Fe(T(p-Me)PP)]CF3SO3. Inorg Chem 1997. [DOI: 10.1021/ic9704849] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Marie-Agnès Pilard
- Laboratoire de Chimie Organométallique et Biologique, URA CNRS 415, Université de Rennes 1, 35042 Rennes Cedex, France, Groupe de Physique Cristalline, UA CNRS 040804, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France, and Service de Chimie Inorganique et Biologique, CENG, 38054 Grenoble Cedex, France
| | - Maud Guillemot
- Laboratoire de Chimie Organométallique et Biologique, URA CNRS 415, Université de Rennes 1, 35042 Rennes Cedex, France, Groupe de Physique Cristalline, UA CNRS 040804, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France, and Service de Chimie Inorganique et Biologique, CENG, 38054 Grenoble Cedex, France
| | - Loïc Toupet
- Laboratoire de Chimie Organométallique et Biologique, URA CNRS 415, Université de Rennes 1, 35042 Rennes Cedex, France, Groupe de Physique Cristalline, UA CNRS 040804, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France, and Service de Chimie Inorganique et Biologique, CENG, 38054 Grenoble Cedex, France
| | - J. Jordanov
- Laboratoire de Chimie Organométallique et Biologique, URA CNRS 415, Université de Rennes 1, 35042 Rennes Cedex, France, Groupe de Physique Cristalline, UA CNRS 040804, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France, and Service de Chimie Inorganique et Biologique, CENG, 38054 Grenoble Cedex, France
| | - Gérard Simonneaux
- Laboratoire de Chimie Organométallique et Biologique, URA CNRS 415, Université de Rennes 1, 35042 Rennes Cedex, France, Groupe de Physique Cristalline, UA CNRS 040804, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France, and Service de Chimie Inorganique et Biologique, CENG, 38054 Grenoble Cedex, France
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Walker FA, Nasri H, Turowska-Tyrk I, Mohanrao K, Watson CT, Shokhirev NV, Debrunner PG, Scheidt WR. π-Acid Ligands in Iron(III) Porphyrinates. Characterization of Low-Spin Bis(tert-butylisocyanide)(porphyrinato)iron(III) Complexes Having (dxz,dyz)4(dxy)1 Ground States. J Am Chem Soc 1996. [DOI: 10.1021/ja961971a] [Citation(s) in RCA: 127] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- F. Ann Walker
- Contribution from the Department of Chemistry, University of Arizona, Tucson, Arizona 85721, Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, and Department of Physics, University of Illinois, Urbana-Champaign, Illinois 61801
| | - Habib Nasri
- Contribution from the Department of Chemistry, University of Arizona, Tucson, Arizona 85721, Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, and Department of Physics, University of Illinois, Urbana-Champaign, Illinois 61801
| | - Ilona Turowska-Tyrk
- Contribution from the Department of Chemistry, University of Arizona, Tucson, Arizona 85721, Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, and Department of Physics, University of Illinois, Urbana-Champaign, Illinois 61801
| | - K. Mohanrao
- Contribution from the Department of Chemistry, University of Arizona, Tucson, Arizona 85721, Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, and Department of Physics, University of Illinois, Urbana-Champaign, Illinois 61801
| | - C. Todd Watson
- Contribution from the Department of Chemistry, University of Arizona, Tucson, Arizona 85721, Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, and Department of Physics, University of Illinois, Urbana-Champaign, Illinois 61801
| | - Nikolai V. Shokhirev
- Contribution from the Department of Chemistry, University of Arizona, Tucson, Arizona 85721, Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, and Department of Physics, University of Illinois, Urbana-Champaign, Illinois 61801
| | - Peter G. Debrunner
- Contribution from the Department of Chemistry, University of Arizona, Tucson, Arizona 85721, Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, and Department of Physics, University of Illinois, Urbana-Champaign, Illinois 61801
| | - W. Robert Scheidt
- Contribution from the Department of Chemistry, University of Arizona, Tucson, Arizona 85721, Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, and Department of Physics, University of Illinois, Urbana-Champaign, Illinois 61801
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Cheesman MR, Walker FA. Low-Temperature MCD Studies of Low-Spin Ferric Complexes of Tetramesitylporphyrinate: Evidence for the Novel (dxz,dyz)4(dxy)1 Ground State Which Models the Spectroscopic Properties of Heme d. J Am Chem Soc 1996. [DOI: 10.1021/ja960344i] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Myles R. Cheesman
- Contribution from the Centre for Metalloprotein Spectroscopy and Biology, School of Chemical Sciences, University of East Anglia, Norwich NR4 7TJ, Great Britain, and Department of Chemistry, University of Arizona, Tucson, Arizona 85721
| | - F. Ann Walker
- Contribution from the Centre for Metalloprotein Spectroscopy and Biology, School of Chemical Sciences, University of East Anglia, Norwich NR4 7TJ, Great Britain, and Department of Chemistry, University of Arizona, Tucson, Arizona 85721
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Owens JW, Robins M, O'Connor CJ. A comparison of the magnetic and crystal field properties of protoporphyrin-IX, hemeoctapeptide and heme proteins. Inorganica Chim Acta 1995. [DOI: 10.1016/0020-1693(95)04698-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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12
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Magliozzo RS, Peisach J. Electron spin echo envelope modulation spectroscopic study of iron-nitrogen interactions in myoglobin hydroxide and Fe(III) tetraphenylporphyrin models. Biochemistry 1992; 31:189-99. [PMID: 1310029 DOI: 10.1021/bi00116a028] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The electron-nuclear coupling in low-spin iron complexes including myoglobin hydroxide (MbOH) and two related model compounds, Fe(III) tetraphenylporphyrin(pyridine)(OR-) (R = H or CH3) and Fe(III) tetraphenylporphyrin(butylamine)(OR-) was investigated using electron spin echo envelope modulation (ESEEM) spectroscopy. The assignment of frequency components in ESEEM spectra was accomplished through the use of nitrogen isotopic substitution wherever necessary. For example, the proximal imidazole coupling in MbOH was investigated without interference from the contributions of porphyrin 14N nuclei after substitution of the heme in native Mb with 15N-labeled heme. Computer simulation of spectra using angle selected techniques enabled the assignment of parameters describing the hyperfine and quadrupole interactions for axially bound nitrogen of imidazole in MbOH, of axial pyridine and butylamine in the models, and for the porphyrin nitrogens of the heme in native MbOH. The isotropic component of axial nitrogen hyperfine interactions exhibits a trend from 5 to 4 MHz, with imidazole (MbOH) greater than pyridine greater than amine. The nuclear quadrupole interaction coupling constant e2Qq was near 2 MHz for all nitrogens in these complexes. The Qzz axis of the nuclear quadrupole interaction tensor for the proximal imidazole nitrogen in MbOH was found to be aligned near gz (gmax) in MbOH, suggesting that gz is near the heme normal. A crystal field analysis, that allows a calculation of rhombic and axial splittings for the d orbitals of the t2g set in a low-spin heme complex, based on the g tensor assignment gz greater than gy greater than gx, yielded results that are consistent with the poor pi-acceptor properties expected for the closed shell oxygen atom of the hydroxide ligand in MbOH. A discussion is presented of the unusual results reported in a linear electric field effect in EPR (LEFE) study of MbOH published previously [Mims, W. B., & Peisach, J. (1976) J. Chem. Phys. 64, 1074-1091].
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Affiliation(s)
- R S Magliozzo
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Yeshiva University, Bronx, New York 10461
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Steup MB, Muhoberac BB. Preparation and spectral characterization of the heme d1.apomyoglobin complex: an unusual protein environment for the substrate-binding heme of Pseudomonas cytochrome oxidase. J Inorg Biochem 1989; 37:233-57. [PMID: 2557389 DOI: 10.1016/0162-0134(89)80045-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The heme d1 prosthetic group isolated from Pseudomonas cytochrome oxidase combines with apomyoglobin to form a stable, optically well-defined complex. Addition of ferric heme d1 quenches apomyoglobin tryptophan fluorescence suggesting association in a 1:1 molar ratio. Optical absorption maxima for heme d1.apomyoglobin are at 629 and 429 nm before, and 632 and 458 nm after dithionite reduction; they are distinct from those of heme d1 in aqueous solution but more similar to those unobscured by heme c in Pseudomonas cytochrome oxidase. Cyanide, carbon monoxide and imidazole alter the spectrum of heme d1.apomyoglobin demonstrating axial coordination to heme d1 by exogeneous ligands. The cyanide-induced optical difference spectra exhibit isosbestic points, and a Scatchard-like analysis yields a linear plot with an apparent dissociation constant of 4.2 X 10(-5) M. However, carbon monoxide induces two absorption spectra with Soret maxima at 454 or 467 nm, and this duplicity, along with a shoulder that correlates with the latter before binding, suggests multiple carbon monoxide and possibly heme d1 orientations within the globin. The 50-fold reduction in cyanide affinity over myoglobin is more consistent with altered heme pocket interactions than the intrinsic electronic differences between the two hemes. However, stability of the heme d1.apomyoglobin complex is verified further by the inability to separate heme d1 from globin during dialysis and column chromatography in excess cyanide or imidazole. This stability, together with a comparison between spectra of ligand-free and -bound derivatives of heme d1-apomyoglobin and heme d1 in solution, implies that the prosthetic group is coordinated in the heme pocket through a protein-donated, strong-field ligand. Furthermore, the visible spectrum of heme d1.apomyoglobin varies minimally with ligand exchange, in contrast to the Soret, which suggests that much spectral information concerning heme d1 coordination in the oxidase is lost by interference from heme c absorption bands. A comparison of the absorption spectra of heme d1.apomyoglobin and Pseudomonas cytochrome oxidase, together with a critical examination of the previous axial ligand assignments from magnetic resonance techniques in the latter, implies that it is premature to accept the assignment of bishistidine heme d1 coordination in oxidized, ligand-free oxidase and other iron-isobacteriochlorin-containing enzymes.
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Affiliation(s)
- M B Steup
- Department of Chemistry, Purdue University School of Science, Indiana University-Purdue University, Indianapolis
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Characterization of some low spin complexes of ferric hemeoctapeptide from cytochrome-c. Inorganica Chim Acta 1988. [DOI: 10.1016/s0020-1693(00)91890-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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