John Gayda

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We present a new examination of the EPR redox titration data for the tetraheme cytochrome c3 from Desulfovibrio vulgaris Miyazaki. Our analysis includes the contribution of the interaction potentials between the four redox sites and is based on the model previously developed for the study of cytochrome c3 from Desulfovibrio desulfuricans Norway. We(More)
A single crystal of cytochrome c3 from Desulfovibrio desulfuricans Norway is studied by electron paramagnetic resonance at low temperature. The orientation of the principal axis corresponding to the largest g value is determined for the 12 heme groups in the crystal unit cell. The comparison of these directions to the normals to the heme planes, determined(More)
Electron paramagnetic resonance spectra were recorded of three forms of Desulphovibrio gigas ferredoxin, FdI, FdI' and FdII. The g = 1.94 signal seen in dithionite-reduced samples is strong in FdI, weaker in FdI' and very small in FdII. The g = 2.02 signal in the oxidized proteins is weak in FdI and strongest in FdII. It is concluded that most of the 4Fe-4S(More)
In cytochromes c3 which contain four hemes per molecule, the redox properties of each heme may depend upon the redox state of the others. This effect can be described in terms of interaction redox potentials between the hemes and must be taken into account in the characterization of the redox properties of the molecule. We present here a method of(More)
The ferredoxins are characterized by a strong temperature dependence of the electronic spin-lattice relaxation time T1. The measurement of this dependence above the liquid nitrogen temperature has been presented in earlier work [1] for the 2-iron-2-sulfur ferredoxin of the blue green alga Spirulina maxima. The different relaxation mechanisms which could be(More)
The soluble hydrogenase from Desulfovibrio africanus has been isolated and characterized. The enzyme consists of two subunits of 65 kDa and 27 kDa. Its absorption spectrum is typical of an iron-sulfur protein. The protein contains 12 iron atoms, 10 labile sulfur atoms and 0.9 nickel atom per molecule. D. africanus hydrogenase is rapidly activated under(More)
A two-iron-two-sulphur non-haem iron protein, the ferredoxin from Spirulina maxima, has been studied by means of electron paramagnetic resonance (EPR) in the range where the spectrum loses resolution with increasing temperature. The spin-lattice relaxation times were deduced from linewidths measured by spectral simulation and their variation as a function(More)
A model is proposed to explain the variation of some physical parameters within the reduced [2Fe-2S] ferredoxin group. According to this model, the main effects result from a variable mixing of some d orbitals of the Fe2+ ion owing to rhombic distortion of the active site having the same geometrical character, but different in intensity, for each protein.(More)
Two classes of [2Fe-2S] proteins have been defined according to the mean value gav of their g tensor components (Bertrand, P., Guigliarelli, B., Gayda, J.P., Beardwood, P. and Gibson, J.F. (1985) Biochim. Biophys. Acta 831, 261-266). To characterize their magnetic properties better, we have compared the spin-lattice relaxation behavior of typical proteins(More)