In vitro photocurrents from spinach thylakoids following Mn depletion and Mn-cluster reconstitution

Biohybrid devices that generate an electrical signal under the influence of light due to photochemical reactions in photosynthetic pigment-protein complexes have many prospects. On the one hand, the oxygen-evolving complex of photosystem II allows the use of ubiquitous water as a source of electrons for photoinduced electron transfer in such devices; on the other hand, it is the most vulnerable part of the photosynthetic apparatus. From the perspective of sustainable operation of bio-based hybrid devices, it is helpful to analyze how removing or modifying the Mn cluster will affect the performance of the bio-hybrid device. This work analyzed photocurrent generation in a liquid three-electrode solar cell based on manganese-depleted and reactivated thylakoid membranes. Membranes lacking Mn could not produce any significant photocurrent until manganese chloride was added. After adding MnCl₂, the cell could produce current when exposed to light. This current was about a few percent from cells with intact thylakoid membranes. However, the photoactivation procedure made it possible to restore up to 75 % of the photocurrent of cells based on intact thylakoid membranes. The main objective of this work is to answer the question about the possibility of photocurrent generation in a biohybrid system based on thylakoid membranes using artificial analogs of the native oxygen-evolving complex. Photoactivation with manganese chloride is the simplest way to obtain preparations devoid of the native Mn cluster, but capable of oxidizing water.