The interactions of duroquinol, DBMIB and NQNO with the chloroplast cytochrome bf complex

Fluorescence as a Tool to Understand Changes in Photosynthetic Electron Flow Regulation

“…Some precaution should be taken when using DBMIB, because site of action is concentration dependent, as well as redox sensitive, where DBMIB becomes reduced under light and oxidised in the dark (Bukhov et al 2003). At low concentrations, DBMIB inhibits electron transport on the reducing side of the PQ, but at higher concentrations excess DBMIB will inhibit the Q B site of PSII, located on the oxidising side of the PQ (Moreland 1980;Rich et al 1991). To prevent fluorescence quenching from oxidised DBMIB, it can be used in conjunction with an excess of sodium ascorbate (Kufryk and Vermaas 2006).…”

“…To prevent fluorescence quenching from oxidised DBMIB, it can be used in conjunction with an excess of sodium ascorbate (Kufryk and Vermaas 2006). For every Cytochrome b 6 f complex, one molecule of DBMIB red is needed for complete inhibition of electron transfer through the Cytochrome b 6 f complex (Rich et al 1991). DBMIB can also inhibit mitochondrial electron transport (Durnford et al 1998).…”

Two Menkes-type ATPases Supply Copper for Photosynthesis inSynechocystis PCC 6803

“…Single Turnover Cytochrome Kinetics-Measurements of cytochromes (f plus c 6 ) and of plastocyanin were made by analyses of flash-induced absorbance changes in the visible region using a protocol developed for use with higher plant thylakoid membranes (21,22). Cells were grown in BG-11-C supplemented with specified [copper].…”

“…The cycle of four flashes was repeated 20 times, and the transients at each wavelength were averaged. Changes (⌬A) due to cytochrome b 563 at 563 nm, cytochromes f plus c 6 (which have sufficiently similar spectra that are deconvoluted together) at 554 nm, P700 at 542 nm, and plastocyanin at 575 nm were obtained by matrix deconvolution using the matrix of extinction coefficient values obtained for higher plants (21). This deconvolution can be applied to Synechocystis PCC 6803 without the need to dissipate any generated electric field, because there is no equivalent of the carotenoid bandshift, which would otherwise strongly overlap in this region.…”

Ironies in photosynthetic electron transport: a personal perspective

“…On the one hand, they were well separated in the studies of Kramer and Crofts (1993). On the other hand: (a) our lab found in anaerobic redox titrations of thylakoid membranes that the E m between the two E m values was approximately +50 mV and could not be resolved (Girvin and Cramer 1984;Furbacher et al 1989); (b) Rich et al (1991) were unable by redox titrations of chloroplast membranes and quantitative statistical analyses of the data to assign different midpoint potentials to the two b-563 hemes. It is our opinion that it is best to have a notation that is readily understandable to mitochondriologists as well as photosynthetikers, and is not dependent on a small or debatable experimental difference.…”