2009) using the crystal structures of PSII core (Guskov et al. 2009) and LHCII (Liu et al. 2004). For the minor antenna complexes, the structure of a monomer of LHCII was used while the pigment composition/occupancy was assigned based on the results of mutation analysis experiments on in vitro reconstituted complexes (Bassi et al. 1999; Remelli et al. 1999; Ballottari et al. 2009; Passarini et al. 2009) The Lhc complexes are densely packed with Chl a and b pigments and the xanthophylls lutein (Lut), violaxanthin (Vx), and neoxanthin

17-AAG mw (Nx) (with the exception of CP24 that does not contain Nx) which are responsible for light absorption and EET. Xanthophyll excitations (xanthophylls are carotenoids which contain oxygen) are rapidly transferred, typically within one ps to the Chls that are in Van der Waals contact with these carotenoids. Chls b transfer excitations to Chls a, which have lower excited-state

Epoxomicin order energy, and on average only a small fraction of the excitations buy BLZ945 (~5 %) is located on Chl b molecules, due to Boltzmann equilibration in the excited state. Via rapid EET between mainly Chls a the excitations end up in the RC (see (Croce and van Amerongen 2011) for a review). Some of the Chl a singlet excitations are transformed into Chl a triplets, which can lead to the formation of destructive singlet oxygen molecules. Fortunately, most of these dangerous Chl triplets (>95 %) are scavenged by the carotenoids that are in Van der Waals contact with Chl a (Barzda et al. 1998; Lampoura et al. 2002; Mozzo et al. 2008a; Carbonera et al. 1992; van der Vos et al. 1991). In this review, we will focus on the study of EET and CS in PSII, starting with the core, followed by outer antenna complexes and supercomplexes. A brief overview will then be given of results on thylakoid membranes, isolated from plants with varying antenna composition as a result of short- and long-term differences in light conditions. At the end, some unsolved problems will be presented together with suggestions for further research.

We would also like to refer Tryptophan synthase to other reviews from recent years for further information (Renger and Schlodder 2010; Vassiliev and Bruce 2008; Renger 2010; Van Amerongen et al. 2003; Minagawa and Takahashi 2004; Barber 2002; Muh et al. 2008; Renger and Renger 2008; Croce and van Amerongen 2011). The PSII core In Fig. 3, the reconstructed picosecond fluorescence kinetics of the PSII core from Thermosynechococcus from two different studies are shown (Miloslavina et al. 2006; van der Weij-de Wit et al. 2011) and the results are nearly identical. Accurate data fitting requires five or more exponentials but two direct observations stand out. Charge separation occurs with an average time constant τ below 100 ps, leading to the relatively fast disappearance of the (fluorescence) signal.