Abstract:
The oxidation potential of the primary electron donor P740 of photosystem I (PS I) of the chlorophyll d dominated cyanobacterium, Acaryochloris marina, has been reinvestigated. We find a midpoint potential of about 450 mV in a photosystem I-enriched membrane fraction as well as in thylakoids, which is significantly higher than that originally reported by Hu et al. (1998). This value, which is, indeed, very similar to that found for P700 in chlorophyll a dominated organisms, is in agreement with results of Bailleul et al. (this Congress). In addition, the extinction difference coefficient for the oxidation of the primary donor has been determined and a value of 45 (plus or minus 4) mM-1 cm-1 at 740 nm was obtained.
