Abstract
Semiquinone oscillations induced by light pulses in the presence of exogenous electron donors are a valuable source of information on the kinetics and thermodynamics of ubiquinone chemistry relevant to the QB site of the photosynthetic reaction center (RC). In previous attempts to achieve the quantitative interpretation of data, the ubiquinone concentration was considered constant during the experiment since it was much bigger than that of RC. In this work, we extended existing models to low ubiquinone concentrations revealing several hidden processes taking place during the ubiquinone photoreduction and enabling the evaluation of the ubiquinone binding constant K Q at the QB site. The proposed approach provides for the first time the evaluation of K Q without any preliminary treatment of ubiquinone extraction from the binding site, thereby better preserving its native structure.
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Acknowledgments
The work was supported by a grant from the Italian Ministry of Education Prin MIUR 2010 (2010C4R8M8). Donato Frascati and Annalisa Bottalico's help with some experimental measurements is acknowledged. We thank the members of the European Cooperation in Science and Technology network, PHOTOTECH COST TD1102, for helpful discussions.
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Ciriaco, F., Tangorra, R.R., Antonucci, A. et al. Semiquinone oscillations as a tool for investigating the ubiquinone binding to photosynthetic reaction centers. Eur Biophys J 44, 183–192 (2015). https://doi.org/10.1007/s00249-015-1013-1
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DOI: https://doi.org/10.1007/s00249-015-1013-1