The spin 3/2 state and quantum spin mixtures in haem proteins

Maltempo, Martin M.; Moss, Thomas H.

doi:10.1017/s0033583500002407

Cited by 188 publications

(138 citation statements)

References 62 publications

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“…The presence of thermal spin equilibrium between the two spin states at ambient temperature is common in ferric hemoprotein derivatives {16-18), although optical and/or magnetic susceptibility evidence alone cannot distinguish it from thermal mixing of the two chemically distinct species, one with a high spin and the other with a low spin ground state, each exhibiting no thermal spin equilibrium, or from quantum mechanical admixing of the spin states (19,20). …”

Section: Introductionmentioning

confidence: 99%

Correlation Between the Optical and Magnetic Properties of Ferric N-Acetylated Heme Octapeptide Complexes

Yang¹,

Sauer²

1982

Electron Transport and Oxygen Utilization

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Section: Introductionmentioning

confidence: 99%

Correlation Between the Optical and Magnetic Properties of Ferric N-Acetylated Heme Octapeptide Complexes

Yang¹,

Sauer²

1982

Electron Transport and Oxygen Utilization

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“…Despite the apparent widespread nature of the cytochrome in eubacteria, which includes sulfur-oxidizing [4], photosynthetic [5,61, denitdying [7], and nitrogen-fixing bacteria [S], the specific physiological or biochemical role of any cytochrome c' has remained elusive. Cytochromes c' have the following conserved physiochemical and structural properties.…”

mentioning

confidence: 99%

Cytochrome c′ of Methylococcus Capsulatus Bath

Zahn

Arciero

Hooper

et al. 1996

European Journal of Biochemistry

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Cytochrome c' was isolated from the obligate methylotroph Methylococcus capsulatus Bath. The native and subunit molecular masses of the cytochrome were 34.9 kDa and 16.2 kDa, respectively, with an isoelectric pH of 7.0. The amino acid composition and N-terminal amino acid sequence were consistent with identification of the protein as a cytochrome c'. The electron paramagnetic resonance spectrum of the monoheme cytochrome indicated the presence of a high spin, S = 5/2, heme center that is diagnostic of cytochromes c'. The optical absorption spectra of ferric or ferrous cytochrome c' were also characteristic of cytochromes c'. The ferrocytochrome bound carbon monoxide and nitric oxide, but not isocyanide, cyanide, or azide. Changes in physical properties due to binding of CO or NO to some other c'-type cytochromes have been interpreted as an indication of dimer dissociation. In the case of cytochrome c' from M. capsulatus Bath, analytical ultracentrifugation of the ferricytochrome, the ferrocytochrome, and the ferrocytochrome-CO complex indicate that the changes induced by binding of CO are conformational and are not consistent with dimer dissociation.EPR spectra show that cytochrome c' was reduced in the presence of hydroxylamine only when in a complex with cytochrome P-460. The value of the midpoint potential, Em 7 0 , was -205 mV for cytochrome c' from M. capsulatus Bath, which is well below the range of values reported for other cytochromes c'. The values of midpoint potentials for cytochrome P-460 (Em i.o = -300 mV to -380 mV) and cytochrome cTS5 (E,,, 7.0 = +I75 mV to + I 95 mV-) are less than and greater than, respectively, the value for cytochrome c' and suggest the possibility that the latter may function as an electron shuttle between cytochrome P-460 and cytochrome csSs.

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“…A//? = 1 [29]. Other less well defined, weaker cases of quantum mechanical spin mixing are found in the hemeprotein peroxidases [29].…”

Section: Epr Spectroscopy Of the High-spin Hemementioning

confidence: 96%

“…high-spin siroheme in the dissimilatory sulfite reductase from Desulfosarcina variabilis [30]. According to a model calculation by Maltempo and Moss for tetragonal symmetry [29], the g = 5.8 signal in Hmc defines A/,? = 1.94 and therefore d = 800 cm-' .…”

Section: Epr Spectroscopy Of the High-spin Hemementioning

confidence: 99%

Axial Coordination and Reduction Potentials of the Sixteen Hemes in High‐Molecular‐Mass Cytochrome c from Desulfovibrio Vulgaris (Hildenborough)

Verhagen

Pierik

Wolbert

et al. 1994

European Journal of Biochemistry

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A spectroelectrochemical study is described of the sixteen hemes in the high-molecular-mass, monomeric cytochrome c (Hmc) from the periplasmic space of Desulfovibrio vulgaris, strain Hildenborough. One of the hemes has special properties. In the oxidized state at pH 7 it is predominantly high-spin, S = 512, with a gi value of less than 6 indicative of quantum-mechanical mixing with a low-lying (800 cm-') S = 312 state; the balance is probably a low-spin derivative. The highspin heme has an E,,,7.5 value of +61 mV. The fifteen other hemes are low-spin bis-histidine coordinated with Em,7.5 values of approximately -0.20 V. Two of these hemes exhibit very anisotropic EPR spectra with a g, value of 3.65 characteristic for strained bis-histidine coordination. A previous proposal, namely that methionine is coordinated to one of the hemes Sulfate reducers in general have a high heme content. The heme porphyrin structure is used by these bacteria in two ways. Sirohydrochlorin, the basic component of siroheme, is the prosthetic group of dissimilatory and assimilatory sulfite reductases in the cytoplasm. Protoporphyrin IX is the basic component for b-type and c-type cytochromes in the periplasm, in the cytoplasmic membrane, and also possibly in the cytoplasm. Although some of these proteins have been studied in considerable detail, our knowledge of the number, type, location, biosynthesis, and, especially, the function of these cytochromes is incomplete [l].For example, in the intensively studied Desulfovibrio vulgaris, strain Hildenborough, no cytochromes have yet been identified in the cytoplasm or in the cytoplasmic membrane. Export to the periplasm has been found for three c-type cytochromes, monoheme cSs3 [2], tetraheme c3 [3], and multiheme high-molecular-mass cytochrome c (Hmc) [4] ; the functions of these cytochromes are either debatable or unknown. The existence of a proposed fourth cytochrome, cytochrome c3 (26 kDa) [ 5 ] , has been questioned [4].

show abstract

The spin 3/2 state and quantum spin mixtures in haem proteins

Cited by 188 publications

References 62 publications

Correlation Between the Optical and Magnetic Properties of Ferric N-Acetylated Heme Octapeptide Complexes

Correlation Between the Optical and Magnetic Properties of Ferric N-Acetylated Heme Octapeptide Complexes

Cytochrome c′ of Methylococcus Capsulatus Bath

Axial Coordination and Reduction Potentials of the Sixteen Hemes in High‐Molecular‐Mass Cytochrome c from Desulfovibrio Vulgaris (Hildenborough)

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