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BBA 40036

By Dual-mode Epr, Spectrometry Of, O-pulsed Cytochrome Oxidase, Wilfred R. Hagen A, William R. Dunham A, R Ichard, H. Sands and Robert W. Shaw B


O2-activated bovine heart cytochrome c oxidase has been examined by dual-mode EPR spectrometry. Resonances have been observed at g-- 10 and 4.5 in the parallel mode and at g- 10, 5, 1.8 and 1.7 in the normal mode. The bulk of these signals are interpreted to come from a stoichiometric S-- 2 system with lal = 0.17 cm- I, D = +2.1 cm-1, IEI = 0.026 cm-1, g = 2. Exchange coupling between cytochrome a 3 and Cu B is not indicated. The redox centers in cytochrome c oxidase have been extensively studied by EPR spectrometry for over 25 years [1], which has resulted in a volu-minous data set but not in a unifying interpreta-tion. Of the four potentially EPR exhibiting metal centers, cytochrome a, Cu A, cytochrome a3, CUB, only the first two are currently identified with EPR signals from noninteracting S = 1/2 systems [2,3]. The other two centers have long been consid-ered EPR undetectable in the oxidized enzyme a

Year: 2016
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