Photoinduced Electron Transfer in Ruthenium-Polypyridyl-Modified Laccases: Probing Pathways From the Surface to the Metal Centers

This study explores the grafting of a ruthenium-polypyridyl photosensitizer onto the surface of a multi-copper oxidase to investigate photoinduced electron transfer (PIET) processes within the enzyme. Four Ru-laccase covalent hybrids unique in the position of the ruthenium complex relative to the Type 1 copper (T1) and trinuclear copper (TNC) centers of the enzyme are compared. The strategic positioning of the photosensitizer highlights the roles of distance and intervening medium on PIET pathways. Our results reveal photoreduction scenarios where the TNC center is reduced directly without first passing through the T1 center. We further illustrate the efficiency and robustness of these hybrid systems through continuous irradiation experiments and laser flash photolysis, shedding light on mechanistic pathways and potential applications in sustainable photocatalysis.