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Digitale Medien

Investigation of the plastoquinone pool size and fluorescence quenching in thylakoid membranes and Photosystem II (PS II) membrane fragments (2000)

Kurreck, Jens ; Schödel, René ; Renger, Gernot

Springer

Photosynthesis research 63 (2000), S. 171-182

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ISSN: 1573-5079

Schlagwort(e): Chlorophyll fluorescence ; non-photochemical quenching ; Photosystem II ; thylakoid membranes

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie

Notizen: Abstract The efficiency of oxidized endogenous plastoquinone-9 (PQ-9) as a non-photochemical quencher of chlorophyll fluorescence has been analyzed in spinach thylakoids and PS II membrane fragments isolated by Triton X-100 fractionation of grana stacks. The following results were obtained: (a) After subjection of PS II membrane fragments to ultrasonic treatment in the presence of PQ-9, the area over the induction curve of chlorophyll fluorescence owing to actinic cw light increases linearly with the PQ-9/PS II ratio in the reconstitution assay medium; (b) the difference of the maximum fluorescence levels, Fmax, of the induction curves, measured in the absence and presence of DCMU, is much more pronounced in PS II membrane fragments than in thylakoids; (c) the ratio Fmax(-DCMU)/Fmax(+DCMU) increases linearly with the content of oxidized PQ-9 that is varied in the thylakoids by reoxidation of the pool after preillumination and in PS II membrane fragments by the PQ-9/PS II ratio in the reconstitution assay; (d) the reconstitution procedure leads to tight binding of PQ-9 to PS II membrane fragments, and PQ-9 cannot be replaced by other quinones; (e) the fluorescence quenching by oxidized PQ-9 persists at low temperatures, and (f) oxidized PQ-9 preferentially affects the F695 of the fluorescence emission spectrum at 77 K. Based on the results of this study the oxidized PQ-9 is inferred to act as a non-photochemical quencher via a static mechanism. Possible implications for the nature of the quenching complex are discussed.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1023/A:1006303510458

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Digitale Medien

Primärprozesse der Photosynthese und ihre Modellierung (1999)

Kurreck, Jens ; Niethammer, Dominique ; Kurreck, Harry

Weinheim : Wiley-Blackwell

Chemie in unserer Zeit 33 (1999), S. 72-83

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ISSN: 0009-2851

Schlagwort(e): Chemistry ; Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Photosynthesis is one of the most fascinating fields of current interdisciplinary research. It seems miraculous that Nature, in the process of evolution, has managed to bring about a 100% quantum yield in charge separation occurring in the primary processes within the photosynthetic reaction centers. In fact, wasteful deactivation of the photoexcited electronic states into the ground state should be favoured and thus prevent charge separation. Biomimetic model compounds have been synthesized, essentially from porphyrins and quinones, resembling the redoxactive cofactors, Nature has developed. The underlying philosophy of this approach is to design and prepare suitable organic molecules allowing the specific properties of the complex electron transfer reactions to be tuned appropriately. Special emphasis is given the through comparison of structures and functions of native and artificial systems. The prominent electron transfer characteristics are discussed in particular by using time-resolved picosecond fluorescence and time-resolved EPR techniques.

Zusätzliches Material: 9 Ill.