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Ultrafast photochemistry of the bc₁ complex

Vos, MH and Reeder, BJ and Daldal, F and Liebl, U (2017) 'Ultrafast photochemistry of the bc₁ complex.' Physical Chemistry Chemical Physics, 19 (9). 6807 - 6813. ISSN 1463-9076

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Abstract

We present a full investigation of ultrafast light-induced events in the membraneous cytochrome bc 1 complex by transient absorption spectroscopy. This energy-transducing complex harbors four redox-active components per monomer: heme c 1 , two 6-coordinate b-hemes and a [2Fe-2S] cluster. Using excitation of these components in different ratios under various excitation conditions, probing in the full visible range and under three well-defined redox conditions, we demonstrate that for all ferrous hemes of the complex photodissociation of axial ligands takes place and that they rebind in 5-7 ps, as in other 6-coordinate heme proteins, including cytoglobin, which is included as a reference in this study. By contrast, the signals are not consistent with photooxidation of the b hemes. This conclusion contrasts with a recent assessment based on a more limited data set. The binding kinetics of internal and external ligands are indicative of a rigid heme environment, consistent with the electron transfer function. We also report, for the first time, photoactivity of the very weakly absorbing iron-sulfur center. This yields the unexpected perspective of studying photochemistry, initiated by excitation of iron-sulfur clusters, in a range of protein complexes.

Item Type: Article
Subjects: Q Science > Q Science (General)
Divisions: Faculty of Science and Health > Biological Sciences, School of
Depositing User: Brandon Reeder
Date Deposited: 04 May 2017 11:54
Last Modified: 01 Mar 2018 02:00
URI: http://repository.essex.ac.uk/id/eprint/19484

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