Regular Paper LIGHT-INDUCED ABSORPTION SPECTRA OF THE D1-D2-CYTOCHROME b559 COMPLEX OF PHOTOSYSTEM II: EFFECT OF METHYL VIOLOGEN CONCENTRATION

Content Provider	Semantic Scholar
Author	Yruela, Inmaculada Torrado, Elena De Gregorio Roncel, Mercedes Picorel, Rafael
Copyright Year	2008
Abstract	The light-induced difference absorption spectra associated to the photoaccumulation of reduced pheophytin a were studied in the isolated D1-D2-Cyt b559 complex in the presence of variable methyl viologen concentrations and different illumination conditions under anaerobiosis. Depending on the methyl viologen/reaction centre ratio, the relative intensities of the spectral bands at 681.5±0.5, 667.0±0.5 and 542.5±0.5 nm were modified. The reduced pheophytin a located at the D1-branch of the complex absorbs at 681.7±0.5 nm, and at least two additional pigment species contribute to the Qy band of the difference absorption spectra with maxima at 667.0±0.5 and 680.5±0.5 nm. We propose the additional species correspond to a peripheral chlorophyll a and the pheophytin a located at the D2-branch of the complex, respectively. The blue absorbing chlorophyll at 667 nm is susceptible to chemical redox changes with a midpoint reduction potential of +470 mV. The Qx absorption bands of both pheophytins localised at the D2and D1branch of the D1-D2-Cyt b559 complex were at 540.7±0.5 and 542.9±0.5, respectively. The results indicated that the two pheophytin molecules can be photoreduced in the D1-D2-Cyt b559 complex in certain experimental conditions.
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Alternate Webpage(s)	https://digital.csic.es/bitstream/10261/3956/1/Yruela_Photosynth%20ResOct2000.pdf
Language	English
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Content Type	Text
Resource Type	Article