Site-selection spectroscopy of the reaction center complex of photosystem II. 2. Identification of the fluorescing species at 4 K

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

DOI:https://doi.org/10.1021/j100082a049· OSTI ID:6994453

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

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1. Vrije Universiteit, Amsterdam (Netherlands)

Fluorescence emission spectra at 4 K of the D1-D2-Cytb559 reaction center complex of photosystem II, presumably containing six chlorophyll a (Chl a) and two pheophytin a (Pheo a) molecules, were obtained by selective excitation with a tunable, continuous laser ([lambda][sub exc] = 680-691 mm). The bands in the vibrational region (700-800 nm) showed a characteristic structure, which could be used as a [open quotes]fingerprint[close quotes] to identify the emitting pigment at low temperature. By comparison of this [open quotes]fingerprint[close quotes] with those of monomeric Chl a and Pheo a in Triton X-100 detergent, it is unambiguously shown that the steady-state emission arises from a Chl a species for [lambda][sub exc] > 683 nm. The nonselectively excited emission spectrum ([lambda][sub exc] < 679 nm) reveals primarily Chl a emission bands, peaking at 683.7 [+-] 0.3 and 744.0 [+-] 0.5 nm. The shape of this spectrum is significantly different from that of earlier reported emission spectra of D1-D2-Cytb559 complexes with presumably a lower Chl a content (four to five Chl/2 Pheo). These show characteristic bands for Pheo a emission. We conclude that D1-D2-Cytb559 complexes with a higher Chl a content (6 Chl/2 Pheo) contain an additional long-wavelength (680-683 nm) Chl a molecule, which is not related to P-680. The steady-state fluorescence at low temperatures mainly arises from emission of this Chl and not from charge-recombination fluorescence of P-680. 28 refs., 5 figs., 1 tab.

• OSTI ID: 6994453
• 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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ABSORPTION SPECTRA
ADDITIVES
CARBOXYLIC ACIDS
CHLOROPHYLL
COMPLEXES
DETERGENTS
EMISSION SPECTRA
EMULSIFIERS
FLUORESCENCE
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
LASERS
LUMINESCENCE
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHOTOSYNTHETIC REACTION CENTERS
PHYTOCHROMES
PIGMENTS
PORPHYRINS
PROTEINS
SPECTRA
SURFACTANTS
WETTING AGENTS