Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Difference spectra, photosynthetic reaction centers

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. [Pg.1125]

In similar studies of photosynthetic reaction centers, the width of the zero-phonon hole for the reactive bacteriochlorophyll dimer was related to the time constant for electron transfer to a neighboring molecule [56, 67, 68]. Figure 4.23 shows a typical hole spectrum (the difference between absorption spectra measured with the excitation laser on and off) for a sample of reaction centers that was excited at 10,912 cm at 5 K. The holes in this experiment resulted from the... [Pg.189]

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]... 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]...
Fig. 4. Difference absorption spectrum of photoreduced bacleriopheophytin (B Fig. 4. Difference absorption spectrum of photoreduced bacleriopheophytin (B<D) [AA(BO -Bd))] obtained by photochemicai accumulation. See text for experimental details. Figure source (A) Shuvalov, Klimov, Krakhmaleva, Moskalenko and Krasnovsky (1976) Photoconversion of bacteriopheophytin in reaction centers of Rhodospirillum rubrum and Chromatium minutissimum. DokI Akad Nauk SSSR 227 986 (B) Tiede, Prince and Dutton (1976) EPR and optical spectroscopic properties of the electron carrier intermediate between the reaction center bacteriochlorophylls and the primary acceptor in Chromatium vinosum. Biochim Biophys Acta 449 452 (C) van Grondelle, Romijn and Holmes (1976) Photoreduction of the long-wavelength bacteriopheophytin in reaction centers and chromatophores of the photosynthetic bacterium Chromatium vinosum. FEBS Lett 72 188.
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. 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. 4. 23 The spectrum of a photochemical hole burned in the long-waveloigth absorption band of a sample of photosynthetic bacterial reaction centers at 5 K [68]. The gray curve is the difference between absorption spectra measured with the excitation laser on and off. The excitation frequency was 10,912 cm. Note the sharp zero-phonon hole PH, upward arrow) at 10,980 cm . The downward arrows indicate the centers of two discrete vibrational (phonon) bands that are linked to the zero-phonon transition. The solid curve is a theoretical hole spectrum calculated as described in the text... Fig. 4. 23 The spectrum of a photochemical hole burned in the long-waveloigth absorption band of a sample of photosynthetic bacterial reaction centers at 5 K [68]. The gray curve is the difference between absorption spectra measured with the excitation laser on and off. The excitation frequency was 10,912 cm. Note the sharp zero-phonon hole PH, upward arrow) at 10,980 cm . The downward arrows indicate the centers of two discrete vibrational (phonon) bands that are linked to the zero-phonon transition. The solid curve is a theoretical hole spectrum calculated as described in the text...

See other pages where Difference spectra, photosynthetic reaction centers is mentioned: [Pg.79]    [Pg.448]    [Pg.523]    [Pg.314]    [Pg.851]    [Pg.387]    [Pg.187]    [Pg.200]    [Pg.376]    [Pg.223]    [Pg.260]    [Pg.111]    [Pg.75]    [Pg.578]    [Pg.255]    [Pg.281]    [Pg.367]    [Pg.123]   


SEARCH



Difference spectra, photosynthetic

Photosynthetic reaction center

Photosynthetic reactions

Reaction center

Spectrum reaction

© 2024 chempedia.info