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Issue 4, 2017
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Ultrafast dynamics of the photo-excited hemes b and cn in the cytochrome b6f complex

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Abstract

The dynamics of hemes b and cn within the cytochrome b6f complex are investigated by means of ultrafast broad-band transient absorption spectroscopy. On the one hand, the data reveal that, subsequent to visible light excitation, part of the b hemes undergoes pulse-limited photo-oxidation, with the liberated electron supposedly being transferred to one of the adjacent aromatic amino acids. Photo-oxidation is followed by charge recombination in about 8.2 ps. Subsequent to charge recombination, heme b is promoted to a vibrationally excited ground state that relaxes in about 4.6 ps. On the other hand, heme cn undergoes ultrafast ground state recovery in about 140 fs. Interestingly, the data also show that, in contrast to previous beliefs, Chl a is involved in the photochemistry of hemes. Indeed, subsequent to heme excitation, Chl a bleaches and recovers to its ground state in 90 fs and 650 fs, respectively. Chl a bleaching allegedly corresponds to the formation of a short lived Chl a anion. Beyond the previously suggested structural role, this study provides unique evidence that Chl a is directly involved in the photochemistry of the hemes.

Graphical abstract: Ultrafast dynamics of the photo-excited hemes b and cn in the cytochrome b6f complex

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Supplementary files

Article information


Submitted
25 Nov 2016
Accepted
28 Dec 2016
First published
04 Jan 2017

Phys. Chem. Chem. Phys., 2017,19, 3287-3296
Article type
Paper

Ultrafast dynamics of the photo-excited hemes b and cn in the cytochrome b6f complex

R. Agarwal and A. A. P. Chauvet, Phys. Chem. Chem. Phys., 2017, 19, 3287
DOI: 10.1039/C6CP08077D

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