Reaction center Rhodobacter sphaeroides

Brederode ME, Jones MR, Van Grondelle R (1997) Primary electron transfer kinetics in membrane-bound Rhodobacter sphaeroides reaction centers a global and target analysis. 

There have been few studies to date of the functionality and stability of AP-trapped photosynthetic reaction centers. Rhodobacter sphaeroides reaction centers were shown to remain intact following trapping with AP A8-75 (a more highly charged analog of A8-35), but neither their functionality nor their stability over time were studied[5]. Synechocystis PCC 6803 PS1 reaction centers trapped with A8-35 and deposited on a gold electrode have been shown to be electrochemically active, but their long-term stability has not been studied[12]. The photochemical activity of A8-35-trapped pea PS2 reaction centers, measured at room temperature by the accumulation of the pheophytin free radical upon illumination, was found to be intermediate between that in chaps and in P-DM solutions [A. Zehetner H. Scheer, personal communication ref. 13],... 

Nagarajan, V., Parson, W. W., Davis D., and Schenck, C. C., 1993, Kinetic and free energy gaps of electron-transfer reactions in Rhodobacter sphaeroides reaction centers. Biochemistry, 32 12324912336. 

Van Stokkum, I. H. M., Beekman, L. M. P., Jones, M. R., Van Brederode, M. E., and Van Grondelle, R., 1997, Primary electron transfer kinetics in membrane-bound Rhodobacter sphaeroides reaction centers A global and target analysis. Biochemistry, 36 11360n 11368. 

While studies of specific acid catalysis of redox cofactors shed light on the intricacies of the electron transfer process [54], the conditions required for preprotonation of the cofactor are highly acidic (pH < 0), and would not generally be found in biological systems. There are, however, systems such as Qb reduction in the Rhodobacter sphaeroides reaction center [55], where kinetic data indicate proton transfer prior to or simultaneous with electron transfer. This would seem to indicate that a general acid process is operative. At first glance, this sort of mechanism would seem to be contrary to the Born-Oppenheimer approximation. This apparent paradox can be avoided, however, if quantum chemical (nonadiabatic) processes are considered. 

Wachtveitl J, Farchaus JW, Das R, Lutz M, Robert B and Mattioli TA (1993) Structure, spectroscopic, and redox properties of Rhodobacter sphaeroides reaction centers bearing point mutations near the primary electron donor. Biochemistry 32 12875-12886... 

Streltsov A M, Aartsma T J, Hoff A J and Shuvalov V A 1997 Oscillations within the B absorption band of Rhodobacter sphaeroides reaction centers upon 30 femtosecond excitation at 865 nm Chem. Phys. Lett. 266 347-52... 

Munge B, Pendon Z, Frank HA et al. Electrochemical reactions of redox cofoctors in Rhodobacter sphaeroides reaction center proteins in lipid films. Bioelectrochem 2001 54 145-150. 

As an illustration, consider some low-temperature absorption spectra we have done on thin-film samples of purified Rhodobacter sphaeroides reaction centers. The three absorption bands of Fig. 3a are plotted as a function of temperature. Note that the band due to the special pair shows a strong temperature-dependent frequency shift (Fig. 3b) of the absorption maximum in addition to a temperature-dependent line width. Figure 3c shows a plot of the line width cr versus temperature, done by fitting three Gaussians (for lack of a theory) to the three peaks observed, and shows that the average value of the phonon field interacting with the chromo-phore has an energy of 150 cm". ... 

Fig. 3. (a) Near-infrared absorption spectrum of Rhodobacter sphaeroides reaction centers as a function of temperature, (b) Absorption maximum of the special pair band at 860 nm plotted versus temperature, (c) Line width of the special pair band at 860 nm versus temperature. (From Austin et al " )... 

Klenina, I.B., I.V. Borvykh, A.Ya. Shkuropatov, P. Gast, and LI. Proskuryakov (2003). Orientation of the Qy optical transition moment of bacteriopheophytin in Rhodobacter sphaeroides reaction centers. Chem. Phys. 294(3), 451-458. 

Site-Directed Mutagenesis of Rhodobacter sphaeroides Reaction Center The Role of Tyrosine L222 169... 

Probing Reaction Center Asymmetiy Using Low Temperature Absorption Spectroscopy of Rhodobacter sphaeroides Reaction Centers Containing Bacteriopheophytin Anions... 

E. Takahashi and C.A. Wraight, Proton and electron transfer in the acceptor quinone complex of Rhodobacter sphaeroides reaction centers characterization of site-directed mutants of the two ionizable residues, Glu and Asp ", in the Qb binding site. Biochemistry 3l 8bb (1992). 

CALCULATIONS OF PROTON UPTAKE IN RHODOBACTER SPHAEROIDES REACTION CENTERS... 

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