The quest for energy traps in the CP43 antenna of photosystem II

摘要: Abstract To identify energy traps in CP43, a subcomplex of the photosystem II antenna system, site energies and excitonic couplings QY transitions chlorophyll (Chl) pigments bound to CP43 are computed using electrostatic models pigment–protein pigment–pigment interactions. The computations based on recent crystal structures core complex with resolutions 1.9 2.1 A compared earlier results obtained at 2.9 A resolution. Linear optical spectra (i.e., absorption, linear dichroism, circular fluorescence) simulated couplings, refinement fit for energies, dynamical theory lineshapes. A comparison root mean square deviation about 100 cm−1 between directly calculated refined maximum range 350 cm−1 shows that combined quantum chemical/electrostatic approach provides semi-quantitative agreement experiment. Possible reasons deviations discussed, including limits lineshape as well structural alterations upon detachment from complex. Based simulations, an assignment two low-energy exciton states B where observed hole burning studies, is suggested. State assigned localized state Chl 37 lumenal layer pigments. delocalized over several cytoplasmic layer. delocalization explains smaller inhomogeneous width spectra, which proposed be due exchange narrowing. largely confirms our suggestion was calculations resolution structure. Interestingly, latter structure, closer value than This explained by variation influence lipids might different isolated CP43. remove remaining uncertainties B, target sites mutagenesis experiments computations. In particular, it suggested mutate Trp C63 close probe identity Arg C41 47 B.