Site-selection spectroscopy of the reaction center complex of photosystem II. I. Triplet-minus-singlet absorption difference. Search for a second exciton band of P-680

Journal Article · Thu Aug 04 04:00:00 EDT 1994 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100082a048· OSTI ID:6939287

Kwa, S L.S.; Eijckelhoff, C; Grondelle, R van; Dekker, J P ^[1]

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1. Vrije Universiteit, Amsterdam (Netherlands)

The D1-D2-Cytb559 reaction center complex of photosystem II was studied at 4 K with triplet-minus-singlet (T-S) absorption difference spectroscopy using selective laser excitation. The T-S spectrum is mainly due to the bleaching of P-680 and significantly differs from the T-S spectrum of monomeric Chl a in detergent. The absorption spectrum ascribed to the primary electron donor, P-680, was interpreted in terms of two distinguishable distributions, around 681 and 684 nm, respectively. These spectral forms could be preferentially selected by relatively blue ([lambda][sub exc] = 661-677 nm) and extremely red excitation ([lambda][sub exc] = 691 nm), respectively. In addition to the bleaching at 681-684 nm, a small band at 667 nm was also observed, which had opposite polarization. We attributed the latter to an exciton band, not associated with a single pigment. Thus upon triplet formation a system consisting of N excitonically coupled pigments (N > 1) is reduced by one due to localization of the triplet state on one of the pigments. The simplest, although not the only, case is given by N = 2, for which P-680 is a dimer with exciton bands at 681-684 and 667 nm. 44 refs., 11 figs.

• OSTI ID: 6939287
• Journal Information: Journal of Physical Chemistry; (United States), Journal Name: Journal of Physical Chemistry; (United States) Vol. 98:31; ISSN JPCHAX; ISSN 0022-3654
• Country of Publication: United States
• Language: English

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BACTERIA
CARBOXYLIC ACIDS
CHLOROPHYLL
COMPLEXES
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
LASERS
MATHEMATICAL MODELS
MICROORGANISMS
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ORGANIC NITROGEN COMPOUNDS
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PHOTOSYNTHETIC REACTION CENTERS
PHYTOCHROMES
PIGMENTS
PORPHYRINS
PROTEINS
QUASI PARTICLES
SPECTROSCOPY
TRIPLETS