Resonance Raman spectroscopy of cytochrome bc1 complexes from Rhodospirillum rubrum: Initial characterization and reductive titrations

Photo-induced dynamics of the heme centers in cytochrome bc1

“…The ultrafast behaviors, and more specifically, the relaxation of photo-excited hemes, has indeed been the object of intense study since the late 1980s. 11,12 For example, the hemes in cyt c and cyt b 5 , which are structurally comparable to the c 1 -and b-hemes of the bc 1 complex, respectively, 13,14 are known to dissociate from their axial ligand within femtoseconds as a response to light absorption. [14][15][16] While the early steps of the heme photo-cycle still raises questions, it is generally accepted that photoexcitation of the heme is followed by an electron transfer (ET) to the iron d-orbitals, 16 which in turn is believed to trigger the ligand dissociation in ferrous complexes.…”

Spectro-Electrochemical Investigation of the bc1 Complex from the Yeast Saccharomyces cerevisiae using Surface Enhanced B-Band Resonance Raman Spectroscopy

“…Midpoint potentials from +265 mV to +300 mV and from +190 mV to +290 mV were reported for heme c 1 and the Rieske center, respectively, whereas -30 mV to +100 mV, and -90 mV to -30 mV were found for heme b H and b L , respectively. (Hobbs, Kriauciunas et al 1990;Le Moigne, Schoepp et al 1999) So obviously, the b-type hemes do not exchange electrons directly with the electrode. In order to find out about ubiquinone Q 10 , we added this coenzyme to the lipid/DDM buffer solution used for dialysis.…”

“…The spectra were sub-divided into different ranges for better interpretation. Tentative band assignments were performed according to SERR spectra obtained from two different sources both using the bacterial bc 1 complex (Hobbs, Kriauciunas et al 1990;Le Moigne, Schoepp et al 1999) from Rhodospirillum rubrum under conditions mentioned above (Table 2). In general, frequency modes observed upon B-band excitations over the entire frequency range showed band profiles with higher intensities at the negative potential than at the positive potential (Fig.…”

“…Spectra are analyzed on the basis of previous investigations of the bc 1 complex in different oxidation states obtained by adding reducing compounds in solution. (Hobbs, Kriauciunas et al 1990;Le Moigne, Schoepp et al 1999) These data are used to find out whether or not electrochemical reduction/oxidation of the bc 1 complex can be accomplished under the experimental conditions described above.…”

“…(Kitagawa, Kyogoku et al 1975;Spiro 1975;Kitagawa, Ozaki et al 1978;Spiro 1978) RR spectra were obtained mostly from B-band (Soret) excitations, (Spiro 1988) whereas Q-band excited spectra are less intensive and informative at low protein concentrations. (Le Moigne, Schoepp et al 1999) Soret excitation and Q-band resonance was applied for investigations of the bacterial (Hobbs, Kriauciunas et al 1990;Le Moigne, Schoepp et al 1999) and mitochondrial bc 1 complex (Gao, Qin et al 1998), respectively. In these cases the redox state of the hemes was altered by adding soluble redox compounds such as ascorbate and sodium hydrosulphite to the protein, which was present in the detergent-solubilized form.…”