Rostock 2019 – scientific programme

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MO: Fachverband Molekülphysik

MO 21: Coupled Systems

MO 21.4: Talk

Thursday, March 14, 2019, 15:00–15:15, S HS 001 Biologie

Spectroscopic observation of protein influence on charge transfer dynamics in individual YM210W reaction centers of purple bacteria — •Pavel Malý^1,2,4, Michael R. Jones³, Tomáš Mančal¹, and Rienk van Grondelle² — ¹Charles University, Prague, Czech Republic — ²Vrije Universiteit Amsterdam, The Netherlands — ³University of Bristol, United Kingdom — ⁴present address: University of Würzburg, Germany

In photosynthetic reaction centers (RCs) the energy from sunlight is used to drive charge separation, providing the driving potential for subsequent chemical reactions. Due to the presence of charge transfer (CT) and charge separated (CS) states, the pigments in the RC interact strongly with their protein environment. This sensitivity causes a large dynamic disorder in the RCs due to the protein fluctuations. In this work we report on a first single-molecule spectroscopy study on individual YM210W RC mutants from purple bacterium Rb. Sphaeroides. In the single RCs we observe fluorescence (FL) intensity blinking, spectral diffusion and lifetime fluctuations. We obtain both static distributions and dynamic traces, the observed behavior fully agrees with the anticipated dynamic disorder. We find that with increasing FL peak wavelength the spectrum width linearly increases, while the lifetime exponentially decreases. We quantitatively describe the experiments by an excitonic model including charge separation. This model, explaining both bulk and single-RC measurements, shows that the charge separation rate is determined by the fluctuations of the P⁺B⁻ CT state energy, caused by the protein fluctuations.