The RC absorption spectrum is wide (600–900 nm), yet only one absorption wavelength is monitored in this study in order to simplify the analysis. The 802 nm absorption band is the primary absorption band, and a more elaborate analysis over a wider spectral range may change our main results only slightly. To the authors’ knowledge, a detailed

account of photoexcitation dynamics of RCs at room temperatures has not been previously BYL719 solubility dmso reported on. We can refer to the recent work by Olenchuk et al. (2007), which PD-0332991 solubility dmso describes the RCs equilibration dynamics at room temperatures; however, that work emphasizes the case of samples with rather strongly absorbing RC concentrations (or very low light photoexcitation levels) Quisinostat mouse where the classical BLB formalism breaks down. Conclusion Detailed examination of the RCs

equilibration kinetics under a sudden increase of the CW actinic light intensity from the dark to a particular steady-state level, I exp, provides a tool for the correct and independent estimation of the light intensity parameter α, the scaling factor to measure the molecule photoexcitation frequency. This parameter is very important for the correct theoretical modeling of the RCs dynamics, especially in determining the details of charge separation induced structural transitions in RCs. The models used here to describe the photobleaching kinetics and to determine the parameter α fits the experimental results very well and shows a reasonable agreement with the results of previous studies of electron transfer kinetics in isolated and membrane bound RCs. In other studies, the case of strong absorption that may

cause saturation absorption was discussed theoretically and analyzed empirically for isolated RCs (Olenchuk et al. 2007). Our work more fully illustrates the methodology for the classical BLB formalism and emphasizes the analysis of experimental results when light scattering occurs, which allows Adenosine for applying the BLB formalism to estimate the α factor. Acknowledgments The authors would like to thank Dr. M.R. Jones for samples of the antenna-free membranes of Rb. sphaeroides photosynthetic bacteria (strain RCO1), Dr. N. Woodbury for Triton X-100 isolated RCs, and Drs. G. Feher and M. Okamura for the LDAO isolated RCs that they each generously provided for these studies. Open Access This article is distributed under the terms of the Creative Commons Attribution Noncommercial License which permits any noncommercial use, distribution, and reproduction in any medium, provided the original author(s) and source are credited.