2007) in order to maintain the excitation balance between the two photosystems (Wientjes et al. 2013). The LHCII trimer is associated with the core on the opposite side of the Lhca’s via the

PsaH subunit (Lunde et al. 2000; Kouril et al. 2005). This complex is very sensitive to detergent, but it is stable in digitonian (Kouril et al. 2005; Pesaresi et al. 2009), and recently, it was purified to homogeneity (Galka et al. 2012). It was shown that the Tucidinostat Energy transfer from the LHCII trimer to the PSI core is extremely fast. Indeed, the presence of the trimer increases the antenna size of PSI by almost 25 %, while the increase in overall trapping time is only 6 ps (Wientjes et al. 2013), which indicates that there is a very good connection between the outer antenna and the core. In summary, in most conditions, the PSI supercomplexes Selonsertib in vivo also bind one LHCII trimer in addition to the four Lhca’s. EET from LHCII to PSI core

is extremely fast, making LHCII a perfect light harvester for the system. The PSI-LHCI complex of green algae In recent years, the study of the PSI-LHCI supercomplex has been extended to organisms other than higher plants, revealing differences in the number and organization of the antenna complexes. An overview of the PSI antennae in the different organisms can be found in Busch and Hippler (2011). It seems that in mosses, green and red algae PSI-LHCI complexes with different antenna sizes are present. In the green alga TEW-7197 price Chlamydomonas reinhardtii there are nine Lhca genes (Elrad and Grossman 2004), and the largest purified supercomplex contains nine Lhca subunits per core (Drop et al. 2011) although smaller complexes have also been purified (Stauber et al. 2009). The additional (when compared to plants) 5 Lhca’s form a second outer half ring around the core that is connected to the core via the 4 Lhca’s forming the inner ring HAS1 (Drop et al. 2011). The larger size of PSI of C. reinhardtii increases its light-absorption

capacity but also slows down the excitation trapping. However, the fluorescence emission at low temperature peaks around 715 nm, which is 20 nm blue-shifted as compared to that of plant PSI (Bassi et al. 1992; Germano et al. 2002). Therefore, C. reinhardtii PSI contains red forms that on average are at higher energies than the ones in plants (Gibasiewicz et al. 2005b), and this speeds up the trapping process. In vitro reconstitution of the 9 Lhca’s of C. reinhardtii has indicated that Lhca2, 4, and 9 are the antenna complexes that contain red pigments (Mozzo et al. 2010), but the exact number of red pigments in PSI of this alga is not known. Energy transfer and trapping in C. reinhardtii PSI-LHCI were investigated by two groups (Melkozernov et al. 2004; Ihalainen et al. 2005c). The results differ substantially, especially concerning the long decay component.