Probing the electronic structure of transition metal ion centres in proteins by coherent Raman-detected electron paramagnetic resonance spectroscopy

Bingham, S. J.; Börger, Birgit; Gutschank, Jörg; Suter, Dieter; Thomson, Andrew J.

doi:10.1007/s007750050004

Cited by 15 publications

(14 citation statements)

References 17 publications

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“…To calculate actual spectra, one needs to take into account also the effect of g-value anisotropy on the efficiency of the microwave excitation and on the evolution of the magnetization. A detailed calculation 15,16 shows that for an axially symmetric system the microwave modulated MCD ∆ x along the direction of laser beam propagation is where T(θ) ) tanh(g(θ)µ B B 0 /2kT) is the Boltzmann factor, f(θ,σ) is a line shape function with line width σ, and C ⊥ ) (C x + C y )/2. Figure 1c shows the corresponding ODEPR powder spectrum for an axially symmetric g-"tensor" and C ⊥ ) 0.…”

Section: Optical Anisotropy From Epr Line Shapementioning

confidence: 99%

Deconvolution and Assignment of Different Optical Transitions of the Blue Copper Protein Azurin from Optically Detected Electron Paramagnetic Resonance Spectroscopy

et al. 2001

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Abstract:Magnetic circular dichroism is a powerful spectroscopic tool for the assignment of optical resonance lines. An extension of this technique, microwave-modulated circular dichroism, provides additional details, in particular information about the orientation of optical transition moments. It arises from magnetization precessing around the static magnetic field, excited by a microwave field, in close analogy to electron paramagnetic resonance (EPR). In this paper we investigate the visible and near-infrared spectrum of the blue copper protein Pseudomonas aeruginosa azurin. Using a nonoriented sample (frozen solution), we apply this technique to measure the variation of the optical anisotropy with the wavelength. A comparison with the optical anisotropies of the possible ligand-field and charge-transfer transitions allows us to identify individual resonance lines in the strongly overlapping spectrum and assign them to specific electronic transitions. The technique is readily applicable to other proteins with transition metal centers.

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Section: Optical Anisotropy From Epr Line Shapementioning

confidence: 99%

Deconvolution and Assignment of Different Optical Transitions of the Blue Copper Protein Azurin from Optically Detected Electron Paramagnetic Resonance Spectroscopy

et al. 2001

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“…15,16,8 For an ͑effective͒ spin Sϭ1/2 ground state with three distinct g-values and a powderlike sample, the microwave modulated, transverse MCD ⌬⑀ x along the direction of laser beam propagation is…”

Section: A Fundamentalsmentioning

confidence: 99%

Magnetic and optical anisotropy of Clostridium pasteurianum rubredoxin from optically detected electron paramagnetic resonance

Börger

Suter

2001

The Journal of Chemical Physics

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The high-spin Fe͑III͒-center of oxidized rubredoxin from Clostridium pasteurianum shows a complicated, temperature-dependent EPR spectrum. We combine conventional EPR spectroscopy with optically detected EPR ͑ODEPR͒ to elucidate the electronic structure of this protein metal center. The ODEPR experiment, which can be considered as coherent Raman scattering or modulated magnetic circular dichroism ͑MCD͒, yields spectra that depend on the relative orientation of optical and magnetic dipole moments. A detailed analysis of the spectra shows that they correspond to a zero-field splitting of Dϭϩ46.3 GHz and a strong rhombic distortion with E/D ϭ0.25. In the frozen solution, conformational strain gives rise to variation of the rhombicity, which can be measured quantitatively from the EPR line shape. Analysis of the ODEPR line shapes yields the orientation of the optical anisotropy with respect to the magnetic g-tensor. We compare the results from this study to published results on EPR, optical spectroscopy, and MCD.

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“…A description of the experiment using the well-known theories of EPR and magneto-optical spectroscopy enables a satisfactory analysis of the experimental spectra and can thus give additional information about the correlations between magnetic and optical properties of the protein's active site. 27 …”

Section: Discussionmentioning

confidence: 99%

Optically detected electron paramagnetic resonance by microwave modulated magnetic circular dichroism

Börger

Bingham

Gutschank

et al. 1999

The Journal of Chemical Physics

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Electron paramagnetic resonance ͑EPR͒ can be detected optically, with a laser beam propagating perpendicular to the static magnetic field. As in conventional EPR, excitation uses a resonant microwave field. The detection process can be interpreted as coherent Raman scattering or as a modulation of the laser beam by the circular dichroism of the sample oscillating at the microwave frequency. The latter model suggests that the signal should show the same dependence on the optical wavelength as the MCD signal. We check this for two different samples ͓cytochrome c-551, a metalloprotein, and ruby (Cr 3ϩ :Al 2 O 3 )͔. In both cases, the observed wavelength dependence is almost identical to that of the MCD signal. A quantitative estimate of the amplitude of the optically detected EPR signal from the MCD also shows good agreement with the experimental results.

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Probing the electronic structure of transition metal ion centres in proteins by coherent Raman-detected electron paramagnetic resonance spectroscopy

Cited by 15 publications

References 17 publications

Deconvolution and Assignment of Different Optical Transitions of the Blue Copper Protein Azurin from Optically Detected Electron Paramagnetic Resonance Spectroscopy

Deconvolution and Assignment of Different Optical Transitions of the Blue Copper Protein Azurin from Optically Detected Electron Paramagnetic Resonance Spectroscopy

Magnetic and optical anisotropy of Clostridium pasteurianum rubredoxin from optically detected electron paramagnetic resonance

Optically detected electron paramagnetic resonance by microwave modulated magnetic circular dichroism

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