Difference spectra, photosynthetic

Fig. 10. Absorption spectrum of purified tubular membrane of Rb. sphaeroides at 77 K. The inset shows the dithionite-minus-ferricyanide difference spectrum of the same sample in the cytochrome a-band region. The right side shows results of gel-electrophoresis measurements. See text for discussion. Figure and data source Jungas, Ranck, Rigaud, Joliot and Vermdglio (1999) Supramoiecular organization of the photosynthetic apparatus of Rhodobacter sphaeroides. EMBO J 18 536.

Fig. 9. (A) and (B) Absorbance difference spectrum of Cf. aurantiacus reaction centers measured 10 ms after a 13-/rs saturating xenon flash was applied sample absorbance at 865 nm was 9x10. (C) and (D) are the absorbance difference spectra measured the same way as in (A) and (B), except that the reaction-center sample contained Asc and PMS as an exogenous reductant. The dashed spectrum in (C) is the in vitro difference spectrum of vitamin K-1 in methanol obtained by EJ Land by pulse radiolysis. Figure source Vasmel and Amesz (1983) Photoreduction of menaquinone in the reaction centers of the green photosynthetic bacterium Chloroflexus aurantiacus. Biochim Biophys Acta 724 119-121.

Fig. 5. (A) Structure of the chlorophyll-a epimer (B) The in vitro oxidized-minus-reduced difference spectrum of dimeric Chi a compared with that of P700 (of spinach). Figure source Watanabe, Kobayashi, Hongu, Nakazato, Hiyama and Murata (1985) Evidence that a chlorophyll a dimer constitutes the photochemical reaction centre (P700) in photosynthetic apparatus. FEBS Lett 191 2255. The light-induced difference spectrum for P700 was originally in Hiyama and Ke (1972) Difference spectra and extinction coefficient of P700. Biochim Biophys Acta 267 163.

Fig. 6.7 FTIR difference spectrum (light-minus-dark) of the absorbance changes associated with electron transfer from the special pair of bacteriochlorophylls (P) to a quinone (Qa) in photosynthetic reaction centers of Rhodobacter sphaeroides. The negative absorption changes result mainly from loss of absorption bands of P the positive changes, from the absorption bands of the oxidized dimer (P ). These measurements were made with a thin film of reaction centers at 100 K. The amplitudes are scaled arbitrarily. Adapted from [101]...

In IQQS.Bartsch 15) isolated from the photosynthetic bacterium, Chro-matium, a brown protein which contained non-heme iron, but was not a ferredoxin. It differed from ferredoxin by absorption spectrum, redox potential, and EPR signal at g = 1.94 Bearden et al. 17)). 

Fig. 4. Difference absorption spectrum of photoreduced bacleriopheophytin (B

Fig. 4. (A and B) Absorbance-difference spectra accompanying the S-state transitions So- S, S,- S2 and S2-> S3 in oxygen-evolving spinach chloroplast particles (the BBY preparation). In (B), a calcium-depleted preparation was used for measuring the spectrum for the 82 83 transition. Figure source (A) Lavergne (1991) Improved UV-visible spectra of the S-transitions in the photosynthetic oxygen-evolving system. Biochim Biophys Acta 1060 185 (B) van Leeuwen. Heimann and van Gorkom (1993) Absorbance difference spectra of the S-state transitions in photosystem II. Photosynthesis Res 38 328.

There are totally 11 chromophores in the bacterial photosynthetic reaction center (PSRC) of Rhodopseudomonas (Rps.) virids. Since the excitation process of the reaction center is the primary event of the photo-induced electron transfer in the reaction center, the detailed analysis of the absorption spectrum is one of the key steps for the understanding of photochemistry of the system. The chromophores included in the PSRC are bacteriochlorophyll b dimer (special pair, P), bacteriochlorophyll in L- and M-branches (Bl and B ), bacteriopheophytin in L- and M-branches (Hl and Hm), menaquinone (MQ), ubiquinone (UQ) and four different hemes, c-552, c-554, c-556, and c-559 in c-type cytochrome subunit. 

For more detailed discussions of the biochemical aspects of the PS II, such as the role of the various polypeptides or differences between the PS IIs, the reader is directed to one of several reviews and compilations. The OEC and PS II have been extensively reviewed over the past several years. The review by Debus in 1992 sums up much of the knowledge obtained on PS II to that point (42). The Photosynthetic Congress, held every few years, has produced several volumes of material from a broad spectrum of researchers covering the whole of photosynthesis with current results to the time of that Congress (51). A 1996 book edited by Ort and Yocum (48) contains several chapters covering various aspects of photosynthesis, from PS II to PS I. Manganese modeling chemistry has also been extensively covered by reviews (24, 26-31, 34, 37, 45, 50). 

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