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National Academy of Sciences, Proceedings of the National Academy of Sciences, 37(102), p. 13087-13092, 2005

DOI: 10.1073/pnas.0503483102

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Initial electron donor and acceptor in isolated Photosystem II reaction centers identified with femtosecond mid-IR spectroscopy

Journal article published in 2005 by Marie Louise Groot ORCID, Natalia P. Pawlowicz, Luuk J. G. W. van Wilderen ORCID, Jacques Breton, Ivo H. M. van Stokkum, Rienk van Grondelle
This paper is made freely available by the publisher.
This paper is made freely available by the publisher.

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Abstract

Despite the apparent similarity between the plant Photosystem II reaction center (RC) and its purple bacterial counterpart, we show in this work that the mechanism of charge separation is very different for the two photosynthetic RCs. By using femtosecond visible-pump–mid-infrared probe spectroscopy in the region of the chlorophyll ester and keto modes, between 1,775 and 1,585 cm –1 , with 150-fs time resolution, we show that the reduction of pheophytin occurs on a 0.6- to 0.8-ps time scale, whereas P + , the precursor state for water oxidation, is formed after ≈6 ps. We conclude therefore that in the Photosystem II RC the primary charge separation occurs between the “accessory chlorophyll” Chl D1 and the pheophytin on the so-called active branch.