ACTA

Primary Electron Transfer Reactions in Membrane-Bound Open and Closed Reaction Centers from Purple Bacterium Rhodobacter sphaeroides

K. Gibasiewicz^a, M. Pajzderska^a, J. Karolczak^a, G. Burdziński^a, A. Dobek^a and M.R. Jones^b
^aDepartment of Physics, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań, Poland
^bSchool of Biochemistry, Medical Sciences Building, University of Bristol, University Walk, Bristol, BS8 1TD, United Kingdom

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Most ultrafast transient absorption studies of primary electron transfer in reaction centers from purple bacteria have been performed in complexes isolated from their natural lipid membrane environment using detergent. In this contribution we present near-UV-vis transient absorption studies of reaction centers embedded in their natural membrane environment. The evolution of absorption spectra recorded with subpicosecond resolution and reflecting primarily electron transfer reactions has been compared to data obtained previously for isolated reaction centers. We conclude that the overall spectral evolution in both types of samples is similar, and the environment of the reaction center protein has only a minor effect on the primary electron transfer reactions. The differences between the two samples are explained in terms of different energetic levels (and their different temporal evolution) of the two initial charge separated states P⁺B_A^- and P⁺H_A^-, with P being the primary electron donor and B_A and H_A the two consecutive electron acceptors. Additionally, in the electric field generated by P⁺H_A^-, B_A in membrane-bound reaction centers undergoes a stronger electrochromic shift than in isolated reaction centers.

DOI: 10.12693/APhysPolA.122.263
PACS numbers: 82.50.-m, 87.64.K-, 87.15.M-