Structure of an Iron(II) Dioxygen Complex; A Model for Oxygen Carrying Hemeproteins

Collman, James P.; Gagné, Robert R.; Reed, Christopher A.; Robinson, Ward T.; Rodley, G. A.

doi:10.1073/pnas.71.4.1326

Cited by 236 publications

(106 citation statements)

References 17 publications

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“…We calculate that 0.10 electron is transferred to the 02 [in agreement with our earlier calculations (19) (27) and 1200 for model CoO2 systems (28). Indeed, our overall wavefunction and geometry are quite consistent with the early model of Pauling (21).…”

supporting

confidence: 79%

Molecular description of dioxygen bonding in hemoglobin.

Olafson¹,

Goddard²

1977

Proc. Natl. Acad. Sci. U.S.A.

132

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From ab initio quality calculations on model systems, we conclude that in unliganded Fe-porphyrin the Fe lies in the plane for both the high-spin (q) and intermediate-spin (t) We will discuss the bonding of oxygen to hemoglobin (Hb) or myoglobin (Mb) using the results of theoretical calculations of the electronic structure of model systems representing Feporphyrin, Fe-porphyrin plus an additional nitrogenous axial ligand (deoxy Mb), and 02 bound to the latter five-coordinate complex (MbO2). In all cases the Fe is found to be high-or intermediate-spin (S = 2 or 1) with six electrons in the d orbitals. In no case (not even with the six-coordinate complexes) do we find a low-lying state in which the Fe is in a low-spin state (t2g6, S = 0). We find that the properties of these model complexes are consistent with the observed properties of the active sites of Mb and Hb and that these calculations give additional insight into the protein-modified behavior of the active site of Hb. In this paper we outline the qualitative description that emerges; detailed results will appear elsewhere. Model calculations

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supporting

confidence: 79%

Molecular description of dioxygen bonding in hemoglobin.

Olafson¹,

Goddard²

1977

Proc. Natl. Acad. Sci. U.S.A.

132

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“…Our Mossbauer measurements of the oxygenated model indicate a close similarity to oxyhemoglobin with respect to isomer shift, quadrupole splitting, and lineshape over a range of temperature. X-ray studies of the N-Me-imid oxygenated complex show a statistical disorder in oxygen position at room temperature [4]. We believe this is a dynamic thermal distribution and have accounted for and analyzed the observed Mossbauer spectra in terms of it [5]: In the present paper we discuss the relevance of such.an analysis to the oxygen binding sites ia hemoglobin and myoglobin.…”

mentioning

confidence: 99%

“…Discussion. -The zero-field spectra from the N-Me imid model compound have been successfully analyzed and accounted for in terms of a dynamic relaxation model 151 based on the published crystal structure [4] of this compound. Briefly, this model is as follows.…”

mentioning

confidence: 99%

Conformational Changes in Heme Proteins and Model Compounds

Spartalian

Lang

1976

J. Phys. Colloques

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Résumé. -On a mesuré des spectres Môssbauer de hémoglobine, myoglobine et quelques composés modèles de type hème à différentes températures. Chaque échantillon a donné un doublet quadrupolaire dont la largeur des raies et l'éclatement quadrupolaire dépend de la température. On a comparé les spectres des protéines naturelles avec les spectres d'un des composés modèles étudié en détail avec la spectroscopie Môssbauer et on conclut qu'on peut attribuer la variation en fonction de la température à la relaxation de l'oxygène parmi des conformations différentes.Abstract. -Zero-field Mossbauer spectra of oxygenated hemoglobin, myoglobin and some of their model compounds were recorded at various temperatures. Each sample gave rise to quadrupole doublet with temperature-dependent linewidth and quadrupole splitting. We have compared the native protein spectra with the spectra from one of the model compounds extensively studied by Mossbauer spectroscopy, and we conclude that oxygen relaxation between conformational states is responsible for the temperature dependence in both cases.

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“…4 A structural basis for discrimination against CO was suggested based on the crystal structures of MbCO which seemed to indicate that the protein forces CO to bind in a bent Fe-C-O geometry. 5 It was found that CO binds to model hemes with a linear Fe-C-O geometry 6 but binds to Mb in a bent geometry, 5 and that O 2 binds to model hemes [7][8][9] and Mb with a similar bent Fe-O-O geometry. 10 Considering that the O 2 prefers to bind to the heme in a bent geometry, which is unaffected by the Mb, it was presumed that the protein forces CO to bind in a bent geometry, thereby reducing the affinity of the heme in Mb for CO relative to O 2 .…”

Section: Introductionmentioning

confidence: 99%

The Orientation of CO in Heme Proteins Determined by Time-Resolved Mid-IR Spectroscopy: Anisotropy Correction for Finite Photolysis of an Optically Thick Sample

2002

Bulletin of the Korean Chemical Society

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A systematic way of determining the equilibrium orientation of carbon monoxide (CO) in heme proteins using time-resolved polarized mid-IR spectroscopy is presented. The polarization anisotropy at pump-probe delay time of zero in the limit of zero photolysis and the angular distribution function of CO are required to obtain the equilibrium orientation of CO. An approach is developed for determining the polarization anisotropy in the zero-photolysis limit from the anisotropy measured under finite photolysis conditions in an optically thick sample where the fraction of molecules photolyzed decreases as the pump pulse passes through and is absorbed by the sample. This approach is verified by measuring the polarization anisotropy of CO of carbonmonoxy myoglobin at various levels of photolysis. This method can be readily applied to other photoselection experiments determining precise angle between transition dipoles.

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Structure of an Iron(II) Dioxygen Complex; A Model for Oxygen Carrying Hemeproteins

Abstract: The preliminary structural characterization of a reversible ferrous dioxygen complex is reported. Mono(N-methyl imidazole) (dioxygen) meso-tetra (aa,a,ao-pivalamidephenyl) porphinatoiron(II), [Fe(02)

Cited by 236 publications

References 17 publications

Molecular description of dioxygen bonding in hemoglobin.

Molecular description of dioxygen bonding in hemoglobin.

Conformational Changes in Heme Proteins and Model Compounds

The Orientation of CO in Heme Proteins Determined by Time-Resolved Mid-IR Spectroscopy: Anisotropy Correction for Finite Photolysis of an Optically Thick Sample

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