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Binary flash‐induced oscillations of [ 14 C]DCMU binding to the photosystem II acceptor complex
Author(s) -
Laasch Henrik,
Urbach Wolfgang,
Schreiber Ulrich
Publication year - 1983
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(83)80463-3
Subject(s) - dcmu , plastoquinone , photosystem ii , chemistry , fluorescence , binding site , biophysics , kinetics , photochemistry , thylakoid , biology , biochemistry , photosynthesis , chloroplast , physics , quantum mechanics , gene
Binding of radioactively‐labelled DCMU to spinach chloroplast membranes is determined following pre‐illumination by single turnover saturating light flashes. When binding is assayed rapidly following inhibitor addition (< 40 s) distinct binary oscillations of [ 14 C]DCMU binding can be observed. By dark‐adapted samples or those, following an even number of flashes, more inhibitor is bound than after one or an odd number of flashes. During longer incubation times (2 min), [ 14 C]DCMU binding becomes independent of flash preillumination. Comparison of the [ 14 C]DCMU binding kinetics following one flash and the kinetics of the DCMU‐induced increase of chlorophyll fluorescence rise reveals a substantial amount of binding which is not accompanied by a corresponding fluorescence rise. These data are discussed within the framework of the ‘inhibitor‐plastoquinone competition model’ [FEBS Lett. (1981) 126, 277–281] and with reference to DCMU binding data derived from fluorescence measurements [Biochim. Biophys. Acta (1982) 682, 245–253].