Photosynthetic reaction centre models

Jean-Pierre Sauvage is a CNRS director of research and is located at the Universite Louis Pasteur in Strasbourg, France. His current research interests include the development of models of the photosynthetic reaction centre using transition metals and porphyrins [5], topology (synthetic catenanes and knots) [6], and molecular machines [7]. 

Cowan, J.A., Sanders, J.K.M., Beddard, G.S. and Harrison, R.J. 1987. Modelling the photosynthetic reaction centre photoinduced electron transfer in a pyromellitimide-bridged special pair Porphyrin Dimer, J. Chem. Soc., Chem. Commun., 55-58. 

Deisenhofer, J., Epp, O., Sinning, I., and Michel, H., 1995, Crystallographic refinement at 2.3 resolution and refined model of the photosynthetic reaction centre from Rhodopseudomonas viridis. J. Mol. Biol., 246 4299457. 

Non-Forster fluorescence quenching of trans-etiochlorin by magnesium oc-taethylporphine in phosphatidylcholine vesicles gives evidence for a statistical pair energy trap. Energy transfer also occurs in the excited singlet manifold of chlorophyll. " The photophysics of bis(chlorophyll)-cyclophanes, models of photosynthetic reaction centres, have been explored for use in artificial photosynthesis.Picosecond time-resolved energy transfer in phycobilosomes have also been studied with a tunable laser. The effect of pH on photoreaction cycles of bacteriorhodopsin, " the fluorescence polarization spectra of cells, chromatophores, and chromatophore fractions of Rhodospirillum rubrum, and a brief review of the mechanism and application of artifical photosynthesis are all relevant to the subject of this Chapter. 

Electronic spectra of linear conjugated polyene radical cations are of interest for several reasons. Firstly, such species occur as intermediates in different processes of biological relevance, e.g. the protection of the photosynthetic reaction centre, the charge transfer processes in membranes or in model smdies for photoinduced charge separation. Secondly, they may be involved in the formation of solitons upon doping or photoexcitation of polyacetylene , and finally, they are of theoretical interest because their interpretation requires models which account for non-dynamic correlation. 

Photoinduced charge separation processes in the supramolecular triad systems D -A-A, D -A -A and D -A-A have been investigated using three potential energy surfaces and two reaction coordinates by the stochastic Liouville equation to describe their time evolution. A comparison has l n made between the predictions of this model and results involving charge separation obtained experimentally from bacterial photosynthetic reaction centres. Nitrite anion has been photoreduced to ammonia in aqueous media using [Ni(teta)] " and [Ru(bpy)3] adsorbed on a Nafion membrane. 

Photoconversion entered the story of ET in the 1970s, by which time knowledge of the stracture and function of photosynthetic reaction centres was sufficient to allow the design and synthesis of dyads , D-A ensembles that held the donor and acceptor in well defined locations. The first DA dyads modelled onnatural photosynthetic reaction centres were the porphyrin-qtrinone (P-Q) supermolectrles of Kong and Loach (1978, 1980). 

N Krau, W-D Schubert, O Klukas, P Fromme, HT Witt and W Saenger (1996) Photosystem I at 4 resoiution represents the first structural model of a joint photosynthetic reaction centre and core antenna system. Nature Structural Biology 3 965-973... 

We summarise recent work on computer modelling and simulation of proteins involved in bioenergetic processes and in peptide-membrane interactions. Homology modelling, electrostatic calculations and conformational analysis of a photosynthetic reaction centre protein are described. Bacteriorhodopsin, a light-driven proton pump protein is examined from several aspects, including its hydration and conformational thermodynamics. Finally, we present results on lipid perturbation on interaction with a cyclic decapeptide antibiotic, gramicidin S. 

Ermler U, Fritzsch G, Buchanan SK and Michel H (1994) Structure of the photosynthetic reaction centre from Rhodobacter sphaeroides at 2.65 A resolution Cofactors and protein-cofactor interactions. Structure 2 925-936 Evans SV (1993) SETOR Hardware lighted three-dimensional solid model representations of macro molecules. J Mol Graphics 11 134-138... 

CoUin, J.P, A. Harriman, V. Heitz, F. Odobel, and J.P. Sauvage (1996). Transition metal-assembled multiporphyrinic systems as models of photosynthetic reaction centre. Coord. Chem. Rev. 148, 63-69. 

Water-locked complexes of bis(chlorophyll)s 1 have been proposed to be a model for the special pair of B(Chl)s in the photosynthetic reaction centres [68,69]. These structures (c.f. Fig. 13) were determined by H NMR... 

The fact that the singlet-triplet mixing in radical pairs becomes faster at high fields, due to the increase of the Zeeman interaction, can also permit modelling of the sequential electron-transfer process of both the primary and secondary pairs. The importance of protein dynamics on the electron-transfer rate was noted in a 95 GHz study of bacterial photosynthetic reaction centres with slow electron-transfer rates. ... 

Fig. 3 Schematic model of light-harvesting compartments in photosynthetic organisms and their position with respect to the membrane and the reaction centers. RC1(2) Photosystem I(II) reaction centre. Peripheral membrane antennas Chlorosome/FMO in green sulfur and nonsulfur bacteria, phycobilisome (PBS) in cyanobacteria and rhodophytes and peridinin-chlorophyll proteins (PCP) in dyno-phytes. Integral membrane accessory antennas LH2 in purple bacteria, LHC family in all eukaryotes. Integral membrane core antennas B808-867 complex in green nonsulfur bacteria, LH1 in purple bacteria, CP43/CP47 (not shown) in cyanobacteria and all eukaryotes.

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