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

Area of Science:

• Biophysical Chemistry
• Enzyme Catalysis
• Photochemistry

Background:

• Multi-copper oxidases, like laccase, are crucial enzymes in biological redox processes.
• Ruthenium-polypyridyl complexes are well-established photosensitizers for light-driven reactions.
• Understanding electron transfer pathways in enzymes is key to designing artificial photosynthetic systems.

Purpose of the Study:

• To investigate photoinduced electron transfer (PIET) in multi-copper oxidases by covalently grafting ruthenium photosensitizers.
• To explore the influence of photosensitizer positioning on PIET pathways within the enzyme.
• To assess the efficiency and robustness of these novel enzyme-photosensitizer hybrid systems.

Main Methods:

• Covalent grafting of ruthenium-polypyridyl photosensitizers onto laccase.
• Characterization of four distinct Ru-laccase hybrids with varying photosensitizer positions relative to copper centers (T1 and TNC).
• Photophysical studies including continuous irradiation and laser flash photolysis to monitor electron transfer dynamics.

Main Results:

• Demonstrated successful grafting and formation of functional Ru-laccase hybrids.
• Observed direct photoreduction of the trinuclear copper center (TNC) without prior reduction of the Type 1 copper center (T1).
• Highlighted the significant impact of distance and the intervening protein matrix on PIET efficiency and pathways.

Conclusions:

• The strategic placement of photosensitizers is critical for controlling electron transfer in enzyme-photosensitizer hybrids.
• The developed hybrid systems exhibit efficient and robust photoactivity, suggesting potential for sustainable photocatalysis.
• This work provides mechanistic insights into enzyme-mediated electron transfer and opens avenues for bio-inspired artificial photosynthesis.