Generation of Electric Potential Difference by Chromatophores from Photosynthetic Bacteria in the Presence of Trehalose under Continuous Illumination

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Liya A. Vitukhnovskaya^1,2, Andrei A. Zaspa¹, and Mahir D. Mamedov^1,a*

¹Belozersky Institute of Physical-Chemical Biology, Moscow State University, 119992 Moscow, Russia

²Semenov Federal Research Center for Chemical Physics, Russian Academy of Sciences, 119991 Moscow, Russia

^* To whom correspondence should be addressed.

Received June 27, 2023; Revised July 20, 2023; Accepted August 26, 2023

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Measurement of electrical potential difference (Δψ) in membrane vesicles (chromatophores) from the purple bacterium Rhodobacter sphaeroides associated with the surface of a nitrocellulose membrane filter (MF) impregnated with a phospholipid solution in decane or immersed into it in the presence of exogenous mediators and disaccharide trehalose demonstrated an increase in the amplitude and stabilization of the signal under continuous illumination. The mediators were the ascorbate/N,N,N′N′-tetramethyl-p-phenylenediamine pair and ubiquinone-0 (electron donor and acceptor, respectively). Although stabilization of photoelectric responses upon long-term continuous illumination was observed for both variants of chromatophore immobilization, only the samples immersed into the MF retained the functional activity of reaction centers (RCs) for a month when stored in the dark at room temperature, which might be due to the preservation of integrity of chromatophore proteins inside the MF pores. The stabilizing effect of the bioprotector trehalose could be related to its effect on both the RC proteins and the phospholipid bilayer membrane. The results obtained will expand current ideas on the use of semi-synthetic structures based on various intact photosynthetic systems capable of converting solar energy into its electrochemical form.

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KEY WORDS: chromatophores, reaction center, cytochrome bc₁ complex, membrane filter, semiconductor, continuous illumination, electrical potential

DOI: 10.1134/S0006297923100024

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