Photosynthetic bacterial

Figure Bl.15.16. Two-pulse ESE signal intensity of the chemically reduced ubiqumone-10 cofactor in photosynthetic bacterial reaction centres at 115 K. MW frequency is 95.1 GHz. One dimension is the magnetic field value Bq, the other dimension is the pulse separation x. The echo decay fiinction is anisotropic with respect to the spectral position.

Jean J M, Chan C-K and Fleming G R 1988 Electronic energy transfer in photosynthetic bacterial reaction centers Isr. J. Chem. 28 169-75... 

The spectroscopy and dynamics of photosynthetic bacterial reaction centers have attracted considerable experimental attention [1-52]. In particular, application of spectroscopic techniques to RCs has revealed the optical features of the molecular systems. For example, the absorption spectra of Rb. Sphaeroides R26 RCs at 77 K and room temperature are shown in Fig. 2 [42]. One can see from Fig. 2 that the absorption spectra present three broad bands in the region of 714—952 nm. These bands have conventionally been assigned to the Qy electronic transitions of the P (870 nm), B (800 nm), and H (870 nm) components of RCs. By considering that the special pair P can be regarded as a dimer of two... 

In the study of the ultrafast dynamics of photosynthetic bacterial reaction centers, we are concerned with the photoinduced electron transfer [72]... 

Casadio, R., Venturoli, G. and Melandri, B. A. (1988). Evaluation of the electrical capacitance in biological membranes at different phospholipid to protein ratios -a study in photosynthetic bacterial chromatophores based on electrochromic effects, Eur. Biophys. J., 16, 243-253. 

J. Breton and A. Vermeglio (eds.), The Photosynthetic Bacterial Reaction Center -Structure and Dynamics , Plenum Press, New York and London, 1988. 

Kirmaier, C. Holten, D. In The Photosynthetic Bacterial Reaction Center-Structure and Dynamics, Breton, J., Vermeglio, A., Eds. Plenum New York, 1988 p 219. 

Fig. 1.6. Photosynthetic bacterial reaction center for Rsp. viridis. The chromophores are indicated but not the protein part of the structure, helices, etc., holding the whole unit...

Due to the carbon substrate requirement, photosynthetic bacterial systems are most suitable for integration into the second of a two-stage process, following a dark fermentation reaction. In this case the effluent from the first stage fermentation be comes the feedstock for the second stage photosynthetic process, as described above. 

Chains of redox cofactors for long range electron transfer are clearly the way electrons are transferred over the tens of angstroms dimensions of membranes and their proteins. Once again, purple photosynthetic bacterial reaction centers provide an archetype for understanding electron transfer chain design and behavior. The heme chain in Rps. viridis... 

Parson, W. W., Chu, Z. T., and Warshel, A., 1998, Reorganization energy of the initial electron-transfer step in photosynthetic bacterial reaction centers Biophysical Journal 74 182nl91. 

Beroza, P., Fredkin, D. R., Okamura, M. Y., and Feher, G., 1992, Proton transfer pathways in the reaction center of Rhodobacter sphaeroides a computational study. In The Photosynthetic Bacterial Reaction Center II (J. Breton and A. VermEglio, eds.) pp. 3639374. Plenum Press, New York. 

Parson, W. W., 1996, Photosynthetic bacterial reaction centers. In Protein Electron Transfer (D. S. Bendall, ed.) pp. 1259160, BIOS Scientific Publishers Ltd. Oxford, U.K. 

Figure 19.10. Electron Chain in the Photosynthetic Bacterial Reaction Center. The absorption of light by the special pair (P960) results in the rapid transfer of an electron from this site to a bacteriopheophytin (BPh), creating a photoinduced charge separation (steps 1 and 2). (The asterisk on P960 stands for excited state.) The possible return of the electron from the pheophytin to the oxidized special pair is suppressed by the "hole" in the special pair being refilled with an electron from the cytochrome subunit and the electron from the pheophytin being transferred to a quinone (Q ) that is farther away from the special pair (steps 3 and 4). The reduction of a quinone (Qg) on the periplasmic side of the membrane results in the uptake of two protons from the periplasmic space (steps 5 and 6). The reduced quinone can move into the quinone pool in the membrane (step 7).

In the Jimmy Member, in a strata-bound setting at the boundary above the clastic Manjeri sediment and before the eruption of the volcanic rocks of the Reliance Fm, the isotopic and textural evidence and C abundance implies that a non-photosynthetic bacterial mat grew, supported by a complex sulphur cycle, and by fermentation of organic debris, methanogenesis and methanotrophy. It should, however, be stressed that the evidence for depth below the... 

The bacterial strains constituting BC1 were isolated by spreading the culture onto LB agar plates (8). A photosynthetic bacterial strain was identified by sequence analysis of its 16S rRNA gene. The numerical profiles of the other isolated bacteria were tested using API 20E strips (Bio Merieux S. A, France). 

Hirata, Y, Nukanobu, K, Hara, M. (1992). Preparation of stable Langmuir-Blodgett film of photosynthetic bacterial reaction center from Rhodopseudomonas viridis using poly-L-lysine. Chem. Lett., 227-230. 

Fig. 11. Photosynthetic bacterial reaction center represented by a simplified model consisting of the reaction center and lightharvesting complexes (A), a three-dimensional model consisting of the L-, M-, H- and C-subunits (B, left) and the corresponding simplified model consisting of cofactors only (B, right). (C) illustration of the electron-transfer reactions with their associated reaction times.

The near-infrared absorption spectra of purple photosynthetic bacterial cells as well as their chromato-phore membranes show absorption bands near 800, 820, 850 and 870-890 nm, as illustrated in Fig. 2 (B) by the spectram of Chromatium-vinosum chromatophores, where most of the absorption bands originate from the BChl molecules present in the membrane. The BChl-a molecules are present in three lightharvesting BChl-protein complexes B875 with an absorption peak between 870 and 880 nm, B800-850 with peaks at 800 and 850 nm, and B 800-820 with peaks at 800 and 820 nm. Here the letter B refers to bulk pigment, and the numbers refers to the wavelengths of absorption peak of the complex in the near infrared. 

In photosynthetic bacterial reaction centers, an iron atom is located between the two quinones and interacts magnetically with the reduced semiquinone to yield a broad EPR signal with a pronounced peak at g=1.8, as discussed in the previous chapter. This EPR signal upon flash excitation displays an oscillatory pattern with a periodicity of 2, similar to that in Pig. 3 (B). We modify the equation shown in the previous section by incorporating the iron atom into the representation of the reaction center and indicate the observed magnetic interaction of iron with the semiquinone by placing these two species inside a pair of braces, , as shown in Fig. 4, top. 

CA Wraight (1977) Electron acceptors of photosynthetic bacterial reaction centers. Direct observation ofoscil-latory behaviour suggesting two closely equivalent ubiquinones. Biochim Biophys Acta. 459 525-531 RK Clayton (1980) Photosynthesis Physical Mechanisms and Chemical Patterns, pp 215-216. Cambridge University Press... 

P Beroza, DR Fredkin, MY Okamura and G Feher (1992) Proton transferpathways in the reaction center of Rhodobacter sphaeroldes A computational study. In J Breton and A Vermeglio (eds) The Photosynthetic Bacterial Reaction Center II Structure, Function and Dynamics, pp 363-374. Plenum U Ermler, G Fritzsch, SK Buchanan and H Michel (1994) Structure of the photosynthetic reaction centre from Rhodobacter sphaeroldes at 2.65 resolution cofactors and protein-cofactor Interactions. Structure 2 925-936... 

Based on the nature of the cytochromes, there are two kinds of photosynthetic bacterial reaction centers. The first kind, represented by that of Rhodobacter sphaeroides, has no tightly bound cytochromes. For these reaction centers, as shown schematically in Fig. 2, left, the soluble cytochrome C2 serves as the secondary electron donor to the reaction center the RC also accepts electrons from the cytochrome bc complex by way ofCytc2- The rate of electron transfer from cytochrome to the reaction center is sensitive to the ionic strength of the medium. Functionally, cytochrome C2 is positioned in a cyclic electron-transport loop. In Rb. sphaeroides, Rs. rubrum and Rp. capsulata cells, the two molecules of cytochromes C2 per RC are located in the periplasmic space between the cell wall and the cell membrane. When chromatophores are isolated from the cell the otherwise soluble cytochrome C2 become trapped and held by electrostatic forces to the membrane surface at the interface with the inner aqueous phase. These cytochromes electrostatically bound to the membrane can donate electrons to the photooxidized P870 in tens of microseconds at ambient temperatures, but are unable to transfer electrons to P870 at low temperatures. 

Fig. 2. Two kinds of photosynthetic bacterial reaction centers based on the nature of binding of the cytochromes to the membrane. P is the primary electron donor T is the intermediate electron acceptor No." refers to Cyt per RC. See text for discussion. Figure adapted from PL Dutton and RC Prince (1978) Reaction center-driven cytochrome interactions in electron and proton translocation and energy coupling. In RK Clayton and WR Sistrom (eds) Photosynthetic Bacteria, p 525. Plenum Press.

Fig. 3. Top row formulation of the reaction sequence involved In the photochemical charge separation of the photosynthetic bacterial reaction center. (D is the excitation and charge separation. the electron transfer to the (secondary) acceptors, and the electron donation by a secondary donor, the cytochrome, to the photooxidized primary donor P. Figure adapted from RK Clayton (1980) Photosynthesis. Physical Mechanism and Chemical Patterns, p 91. Cambridge Univ Press.

HA Frank and CA Violette (1989) Monomeric bacteriochlorophyll is required for the triplet energy transfer between the primary donor and the carotenoid in photosynthetic bacterial reaction centers. Biochim Biophys Acta 976 222-232... 

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