Autor: Arnold J. Hoff, A.Y. Shkuropatov, R. A. Khatypov, Vladimir A. Shuvalov, Hjalmar P. Permentier, van Gorkom Hj, Marta Germano
Rok vydání: 2000
Předmět:
Zdroj: Photosynthesis Research. 64:189-198
ISSN: 0166-8595
DOI: 10.1023/a:1006407314449
Popis: Pheophytin a (Pheo) in Photosystem II reaction centres was exchanged for 131-deoxo-131-hydroxy-pheophytin a (131-OH-Pheo). The absorption bands of 131-OH-Pheo are blue-shifted and well separated from those of Pheo. Two kinds of modified reaction centre preparations can be obtained by applying the exchange procedure once (RC1×) or twice (RC2×). HPLC analysis and Pheo QX absorption at 543 nm show that in RC1× about 50% of Pheo is replaced and in RC2× about 75%. Otherwise, the pigment and protein composition are not modified. Fluorescence emission and excitation spectra show quantitative excitation transfer from the new pigment to the emitting chlorophylls. Photoaccumulation of Pheo− is unmodified in RC1× and decreased only in RC2×, suggesting that the first exchange replaces the inactive and the second the active Pheo. Comparing the effects of the first and the second replacement on the absorption spectrum at 6 K did not reveal substantial spectral differences between the active and inactive Pheo. In both cases, the absorption changes in the QY region can be interpreted as a combination of a blue shift of a transition at 684 nm, a partial decoupling of chlorophylls absorbing at 680 nm and a disappearance of Pheo absorption in the 676-680 nm region. No absorption decrease is observed at 670 nm for RC1× or RC2×, showing that neither of the two reaction centre pheophytins contributes substantially to the absorption at this wavelength.
Databáze: OpenAIRE
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