Insight in the electron transfer from a redox polymer to a photoactive protein

Rafał Białek*, Kalyani Thakur, Adrian Ruff, Michael R Jones , Wolfgang Schuhmann, Charusheela Ramanan, Krzysztof Gibasiewicz*

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

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Abstract

Biohybrid photoelectrochemical systems in photovoltaic or biosensor applications have gained considerable attention in recent years. While the photoactive proteins engaged in such systems usually maintain an internal charge separation quantum yield of nearly 100%, the subsequent steps of electron and hole transfer beyond the protein often limit the overall system efficiency and their kinetics remain largely uncharacterized. To reveal the dynamics of one of such charge-transfer reactions, we report on the reduction of Rhodobacter sphaeroides reaction centers (RCs) by Os-complex-modified redox polymers (P-Os) characterized using transient absorption spectroscopy. RCs and P-Os were mixed in buffered solution in different molar ratios in the presence of a water-soluble quinone as an electron acceptor. Electron transfer from P-Os to the photoexcited RCs could be described by a three-exponential function, the fastest lifetime of which was on the order of a few microseconds, which is a few orders of magnitude faster than the internal charge recombination of RCs with fully separated charge. This was similar to the lifetime for the reduction of RCs by their natural electron donor, cytochrome c2. The rate of electron donation increased with increasing ratio of polymer to protein concentrations. It is proposed that P-Os and RCs engage in electrostatic interactions to form complexes, the sizes of which depend on the polymer-to-protein ratio. Our findings throw light on the processes within hydrogel-based biophotovoltaic devices and will inform the future design of materials optimally suited for this application.
Original languageEnglish
Number of pages10
JournalJournal of Physical Chemistry B
Early online date25 Nov 2020
DOIs
Publication statusE-pub ahead of print - 25 Nov 2020

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