Interference of Solvatochromic Twist in Amyloid Nanostructure for Light-Driven Biocatalysis

Amyloid self-assembly is a powerful bottom-up approach for the synthesis of sophisticated organic nanostructures that possess fascinating structural flexibility. This study adds a dimension to the research on amyloid self-assembly by expanding its scope to the field of photobiocatalysis. We demonstrate visible-light-driven regeneration of nicotinamide adenine dinucleotide (NAD+) using solvatochromic Congo red (CR) hybridized with an amyloid-derived peptide (Fmoc-FF) nanostructure. In the course of an in situ self-assembly process of Fmoc-FF peptides, CR molecules were hybridized into a Fmoc-FF nanofiber network through π–π interactions between the nonpolar fluorenyl group of Fmoc-FF and the aromatic moieties of CR. This hybridization made CR dyes capable of photoredox catalysis because the planarization of CR induced by the Fmoc-FF degenerated the twisted intramolecular charge-transfer state of the dye; the incorporation of CR into the Fmoc-FF nanostructure increased CR’s fluorescence intensity 9 times and generated a photocurrent by 400 nA cm–2. The photocatalytic Fmoc-FF/CR hydrogel facilitated O2 reduction-coupled NAD+ regeneration under visible light. The NAD+ regeneration yield of the Fmoc-FF/CR hybrid was 5 times higher than that of free CR. Furthermore, the in situ regenerated NAD+ activated NAD+-dependent redox enzymes for alcohol oxidation; the Fmoc-FF/CR hybrid achieved a substantially high total turnover number of enzymes of 42 953, which was 5.8 times larger than that with free CR.