Photosynthetic reaction center electron transfer

C Lautwasser, U Finkele, H Scheer and WZinth (1991) Temperature dependence of the primary electron transfers photosynthetic reaction centers from Rhodobacter sphaeroides. Chem Phys Lett 183 471-477... 

Breton J, Martin J-L, Fleming G R and Lambry J-C 1988 Low-temperature femtosecond spectroscopy of the initial step of electron transfer in reaction centers from photosynthetic purple bacteria Biochemistry 27 8276... 

Likhtenshtein, G.I. (1996a) Role of orbital and dynamic factors in electron transfer in reaction centers of photosynthetic systems. J. Phochem. Photobiol. A Chem. 96, 79-92. 

Zinth, W., and Kaiser, W., 1993, Time-resolved spectroscopy of the primary electron transfer in reaction centers of Rhodobacter sphaeroides and Rhodopseudomonas viridis. In The Photosynthetic Reaction Center, (J. Deisenhofer and J. R. Norris, eds.) Volume 2, 71988, Academic Press, San Diego, USA. 

YD Halsey and WW Parson (1974) Identification of ubiquinone as the secondary electron acceptor in the photosynthetic apparatus of Chromatium vinosum. Biochim Biophys Acta 347 404-416 A Vermeglio (1977) Secondary electron transfer in reaction centers of Rhodopseudomonas sphaeroldes. Out-of-phase periodicity of two for the formation of ubisemiquinone and fully reduced ubiquinone. Biochim Biophys Acta. 459 516-524... 

Fig. 9. (A) Absorption spectrum of Rb. sphaeroides used as a reference to show the Qx and Qy bands of the primary donor (P), BChl [B] and bacteriopheophytin [BO] (B) Femtosecond absorption changes at 920 (a), 785 (b) and 545 nm (c) vs. the delay time of the monitoring pulse measured at room temperature, and (C) absorption changes at 920 (a) and 794 nm (b) measured at 25 K. Figure source (A) see Fig. 7 (B) Holzapfel, Finkele, Kaiser, Oesterheldt, Scheer, Stilz and Zinth (1990) Initial electron transferin the reaction center from Rhodobacter sphaeroides. Proc Nat Acad Sci, USA 87 5170 (C) Zinth and Kaiser (1993) Time-resolved spectroscopy of the primary electron transfer in reaction centers of Rhodobacter sphaeroides and Rhodopseudomonas viridis. I n JR Norris and J Deisenhofer (eds) The Photosynthetic Reaction Center, Voi il, p 82. Acad Press.

Tiede DM, Budil DE, Tang J et al. Symmetry breaking structures involved in the docking of cytochrome c and primary electron transfer in reaction centers of rhodobacter sphaeroides. In Breton J, Vermeglio A, eds. The Photosynthetic Bacterial Reaction Center, Structure and Dynamics. New York Plenum, 1988 13-20. 

J. Jortner and M.E. Michel-Beyerle, Some Asp>ects of Energy Transfer in Antennas and Electron Transfer in Reaction Centers of Photosynthetic Bacteria, in "Antennas and Reaction Centers of Photosynthetic Bacteria", M.E. Michel-Beyerle, ed., Springer-Verlag, Berlin (1985). 

Boxer S G, Goldstein R A, Lockhart D J, Middendorf T R and Takiff L 1989 Excited states, electron-transfer reactions, and intermediates in bacterial photosynthetic reaction centers J. Rhys. Chem. 93 8280-94... 

M Marchi, IN Gehlen, D Chandler, M Newton. Diabatic surfaces and the pathway for primary electron transfer in a photosynthetic reaction center. 1 Am Chem Soc 115 4178-4190, 1993. 

Studies (see, e.g., (101)) indicate that photosynthesis originated after the development of respiratory electron transfer pathways (99, 143). The photosynthetic reaction center, in this scenario, would have been created in order to enhance the efficiency of the already existing electron transport chains, that is, by adding a light-driven cycle around the cytochrome be complex. The Rieske protein as the key subunit in cytochrome be complexes would in this picture have contributed the first iron-sulfur center involved in photosynthetic mechanisms (since on the basis of the present data, it seems likely to us that the first photosynthetic RC resembled RCII, i.e., was devoid of iron—sulfur clusters). 

It is interesting to compare the thermal-treatment effect on the secondary structure of two proteins, namely, bacteriorhodopsin (BR) and photosynthetic reaction centers from Rhodopseudomonas viridis (RC). The investigation was done for three types of samples for each object-solution, LB film, and self-assembled film. Both proteins are membrane ones and are objects of numerous studies, for they play a key role in photosynthesis, providing a light-induced charge transfer through membranes—electrons in the case of RC and protons in the case of BR. 

Studies of ferredoxin [152] and a photosynthetic reaction center [151] have analyzed further the protein s dielectric response to electron transfer, and the protein s role in reducing the reorganization free energy so as to accelerate electron transfer [152], Different force fields were compared, including a polarizable and a non-polarizable force field [151]. One very recent study considered the effect of point mutations on the redox potential of the protein azurin [56]. Structural relaxation along the simulated reaction pathway was analyzed in detail. Similar to the Cyt c study above, several slow relaxation channels were found, which limited the ability to obtain very precise free energy estimates. Only semiquantitative values were... 

Warshel, A. Chu, Z.T. Parson, W.W., Dispersed polaron simulations of electron transfer in photosynthetic reaction centers, Science 1989, 246, 112-116. 

The photosynthetic reaction center (RC) of purple nonsulfur bacteria is the core molecular assembly, located in a membrane of the bacteria, that initiates a series of electron transfer reactions subsequent to energy transfer events. The bacterial photosynthetic RCs have been characterized in more detail, both structurally and functionally, than have other transmembrane protein complexes [1-52]. 

Cytochromes, catalases, and peroxidases all contain iron-heme centers. Nitrite and sulfite reductases, involved in N-O and S-O reductive cleavage reactions to NH3 and HS-, contain iron-heme centers coupled to [Fe ] iron-sulfur clusters. Photosynthetic reaction center complexes contain porphyrins that are implicated in the photoinitiated electron transfers carried out by the complexes. 

Figure 1. Schematic representation of the artificial photosynthetic reaction center by a monolayer assembly by A-S-D triad and antenna molecules for light harvesting (H), lateral energy migration and energy transfer, and charge separation across the membrane via multistep electron transfer (a) Side view of mono-layer assembly, (b) top view of a triad surrounded by H molecules, and (c) energy diagram for photo-electric conversion in a monolayer assembly.

Organized molecular assemblies containing redox chromophores show specific and useful photoresponses which cannot be achieved in randomly dispersed systems. Ideal examples of such highly functional molecular assemblies can be found in nature as photosynthesis and vision. Recently the very precise and elegant molecular arrangements of the reaction center of photosynthetic bacteria was revealed by the X-ray crystallography [1]. The first step, the photoinduced electron transfer from photoreaction center chlorophyll dimer (a special pair) to pheophytin (a chlorophyll monomer without... 

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