Photobleaching of the resonance Raman lines of cytochromes in living yeast cells

Redox State of Cytochromes in Frozen Yeast Cells Probed by Resonance Raman Spectroscopy

“…The Raman spectrum of yeast cells measured with a 532 nm laser excitation contains a contribution from the resonance Raman lines of cytochromes. The contribution of the cytochrome lines decreases with the laser exposition (26). Representative Raman spectra of the yeast cells at room temperature and in the frozen state (-100 C) measured at the beginning and end of irradiation exposure are shown in Fig.…”

“…3 C; note that a logarithmic scale is used for t À1 ). Since the photobleaching rate has a peculiar irradiation power dependence (26), the temperature dependence of t À1 was studied in detail for three irradiation powers ( Fig. 3 C).…”

“…Next, we used the photobleaching process to investigate cytochrome redox activity in the ETC of freezing cells. In the framework of the model we proposed previously (26), the photobleaching response comes from photoinduced and native redox reactions. The rate of the photoinduced process has a quadratic dependence on the irradiation intensity.…”

“…Recently, an approach that measures redox reaction rates based on the photobleaching effect of cytochrome resonance Raman lines was proposed (26). In this approach, laser radiation excites the resonance Raman scattering and therefore allows one to quantify the amount of the reduced cytochromes.…”

“…This photoinduced oxidation decreases the amount of reduced cytochromes and results in photobleaching of the resonance Raman lines. The photobleaching rate of the resonance Raman lines versus the irradiation power can be described by a square function plus a constant, where the square part is responsible for the photoinduced processes and the constant is responsible for the native cytochrome redox reactions (26). Therefore, resonance Raman spectroscopy can be used to characterize the native cytochrome reaction rates of the ETC.…”