Low-temperature magnetic circular dichroism spectra and magnetisation curves of 4Fe clusters in iron-sulphur proteins from Chromatium and Clostridium pasteurianum

The magnetic circular dichroism (MCD) spectra of the 4Fe clusters in the iron-sulphur proteins high-potential iron protein from Chromatium and the 8Fe ferredoxin from Clostridium pasteurianum have been measured over the wavelength range 300-800 nm at temperatures between approx. 1.5 and 50 K and at ... Ausführliche Beschreibung

1. Person: Johnson, M.K.
Weitere Personen: Thomson, A.J.; Edward Robinson, A.; Rao, K.K.; Hall, D.O.
Quelle: in BBA - Protein Structure Vol. 667, No. 2 (1981), p. 433-451
Weitere Artikel
Format: Online-Artikel
Genre: Ferredoxin, High-potential iron protein, Iron cluster, Magnetic circular dichroism, Magnetization curve, (Chromatium, Cl. pasteurianum)
Sprache: English
Veröffentlicht: 1981
Beschreibung: Online-Ressource
Online Zugang: Online
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Anmerkung: Copyright: Copyright (c) 2002 Elsevier Science B.V.
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520 |a The magnetic circular dichroism (MCD) spectra of the 4Fe clusters in the iron-sulphur proteins high-potential iron protein from Chromatium and the 8Fe ferredoxin from Clostridium pasteurianum have been measured over the wavelength range 300-800 nm at temperatures between approx. 1.5 and 50 K and at magnetic fields up to 5 tesla. In both cases the proteins have been studied in the oxidized and reduced states. The reduced state of high-potential iron protein gives a temperature-independent MCD spectrum up to 20 K, confirming the diamagetism of this state at low temperature. The MCD spectrum of samples of oxidized ferredoxin invariably show the presence of a low concentration of a paramagnetic species, in agreement with the observation that the EPR spectrum always shows a signal at g = 2.01. The paramagnetic MCD spectrum runs across the whole of the wavelength range studied and therefore most probably originates from an iron-sulphur centre. The diamagnetic component of the MCD spectrum of oxidized ferredoxin is very similar to that of reduced high-potential iron protein. The low-temperature MCD spectra of oxidized high-potential iron protein and reduced ferredoxin reveal intense, temperature-dependent bands. The spectra are highly structured with that of high-potential iron protein showing a large number of electronic transitions across the visible region. The MCD spectra of the two different oxidation levels are quite distinctive and should provide a means of establishing the identity of these state of 4Fe clusters in more complex proteins. MCD magnetisation curves have been constructed from detailed studies of the field and temperature dependence of the MCD spectra of the two paramagnetic oxidation states. These plots can be satisfactorily fitted to the theoretically computed curves for an S = 1/2 ground state with the g factors experimentally determined by EPR spectroscopy. The low-temperature MCD spectra of the reduced 2Fe-2S ferredoxin from Spirulina maxima are also presented and MCD magnetisation curves plotted and fitted to the experimentally determined g factors. 
533 |a Online edition  |f Elsevier Journal Backfiles on ScienceDirect 1907 - 2002 ; 041023-8 
655 7 |a Ferredoxin  |2 gnd 
655 7 |a High-potential iron protein  |2 gnd 
655 7 |a Iron cluster  |2 gnd 
655 7 |a Magnetic circular dichroism  |2 gnd 
655 7 |a Magnetization curve  |2 gnd 
655 7 |a (Chromatium, Cl. pasteurianum)  |2 gnd 
689 0 0 |a Ferredoxin 
689 0 1 |a High-potential iron protein 
689 0 2 |a Iron cluster 
689 0 3 |a Magnetic circular dichroism 
689 0 4 |a Magnetization curve 
689 0 5 |a (Chromatium, Cl. pasteurianum) 
689 0 |5 DE-601 
700 1 |a Johnson, M.K. 
700 1 |a Thomson, A.J. 
700 1 |a Edward Robinson, A. 
700 1 |a Rao, K.K. 
700 1 |a Hall, D.O. 
773 0 8 |i in  |t BBA - Protein Structure  |d Amsterdam : Elsevier  |g Vol. 667, No. 2 (1981), p. 433-451  |q 667:2<433-451  |w (DE-601)NLEJ176858709  |x 0005-2795 
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951 |a AR 
952 |d 667  |j 1981  |e 2  |h 433-451 

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