2013). Recently, it was also found that in Arabidopsis plants, the amount of M trimers is decreasing when the grow-light intensity is increased from 100 to 800 μmol photons m−2 s−1, whereas the amount of “extra” trimers remains the same. Decreasing on the other hand the

intensity to 20 μmol photons m−2 s−1, leads to an increase in the amount of “extra” trimers, whereas the amount of M trimers now remains unaltered (Kouril et al. 2012). For nearly all time-resolved studies in the literature, detailed information about the antenna composition is lacking. In the past, various studies have been performed on BBY preparations Selleckchem Adriamycin (Berthold et al. 1981). The kinetics of these membranes were for instance described by a single lifetime of 210 ps

(Schilstra et al. 1999) or with a major lifetime of 140 ps and a minor lifetime of 330 ps (Van Mieghem et al. 1992). More recently, two studies were done that showed average lifetimes in the order of 150–160 ps (Broess et al. 2006, 2008) and the results were interpreted with a coarse-grained model that uses the C2S2M2 structure as a basis. Like in the ERPE model, it was assumed that primary charge separation (with rate k CS or inverse rate/transfer time τ CS) is reversible (first charge-separated state is ΔG lower in energy than the state in which the RC is excited in the Q y state). Secondary charge separation (with rate k RP or inverse rate/transfer find more time τ RP) was supposed to be irreversible. EET was modeled by assuming hopping to occur between neighboring (monomeric) complexes with a rate called k h (or inverse rate/hopping time τ h ) that was assumed to be the same for all hopping steps, whereas each rate was scaled with the number of pigments per complex. The basic difference with the earlier ERPE model is the fact that the supercomplex is used as a structural model to include EET steps and the fact that the hopping rate

is not assumed to be infinitely fast. Using this model it was shown that different combinations of τ CS and τ H can describe the data nearly equally well (Broess et al. 2006), reminiscent Carteolol HCl of the data fitting results for core samples. Although it was not possible to extract more details about the charge transfer kinetics in the RC, it was possible to conclude that the BBY data could not be explained with published parameters for charge separation as obtained from time-resolved studies on cores by for instance Vasilliev et al. (Vassiliev et al. 2002) and Miloslavina et al. (Miloslavina et al. 2006) and other studies. Good resemblance could only be obtained when both the rate of charge separation and the drop in free energy upon charge separation were increased. It was also argued that previously published results on isolated PSII RC (Andrizhiyevskaya et al. 2004; Groot et al. 2005) were not in accordance with the BBY results.