Redox enzymes catalyze fascinating chemical reactions with excellent regio- and stereo-specificity. Nicotinamide adenine dinucleotide cofactor is essential in numerous redox biocatalytic reactions and needs to be regenerated because it is consumed as an equivalent during the enzymatic turnover. Here we report on unbiased photoelectrochemical tandem assembly of a photoanode (FeOOH/BiVO4) and a perovskite photovoltaic to provide sufficient potential for cofactor-dependent biocatalytic reactions. We obtain a high faradaic efficiency of 96.2% and an initial conversion rate of 2.4 mM h−1 without an external applied bias for the photoelectrochemical enzymatic conversion of α-ketoglutarate to l-glutamate via l-glutamate dehydrogenase. In addition, we achieve a total turnover number and a turnover frequency of the enzyme of 108,800 and 6200 h−1, respectively, demonstrating that the tandem configuration facilitates redox biocatalysis using light as the only energy source.
In green plants, solar-powered electrons are transferred through sophistically arranged photosystems and are subsequently channelled into the Calvin cycle to generate chemical energy. Inspired by the natural photosynthetic scheme, a photoelectrochemical cell (PEC) is constructed configured with protonated graphitic carbon nitride (p-g-C 3 N 4 ) and carbon nanotube hybrid (CNT/p-g-C 3 N 4 ) film cathode, and FeOOH-deposited bismuth vanadate (FeOOH/BiVO 4 ) photoanode for the production of industrially useful chiral alkanes using an old yellow enzyme homologue from Thermus scotoductus (TsOYE). In the biocatalytic PEC platform, photoexcited electrons provided by the FeOOH/BiVO 4 photoanode are transferred to the robust and self-standing CNT/p-g-C 3 N 4 hybrid film that electrocatalytically reduces flavin mononucleotide (FMN) mediator. The p-g-C 3 N 4 promotes a two-electron reduction of FMN coupled with an accelerated electron transfer by the conductive CNT network. The reduced FMN subsequently delivers the electrons to TsOYE for the highly enantioselective conversion of ketoisophorone to (R)-levodione. Under light illumination (>420 nm) and external bias, (R)-levodione is synthesized with the enantiomeric excess value of above 83%, not influenced by the scale of applied bias, simultaneously exhibiting stable and high current efficiency. The results suggest that the biocatalytic PEC made up of economical materials can selectively synthesize high-value organic chemicals using water as an electron donor.
Peptide self-assembly is a facile route to the development of bioorganic hybrid materials that have sophisticated nanostructures toward diverse applications. Here, we report the synthesis of self-assembled peptide (Fmoc-diphenylalanine, Fmoc-FF)/graphitic carbon nitride (g-CN) hydrogels for light harvesting and biomimetic photosynthesis through noncovalent interactions between aromatic rings in Fmoc-FF nanofibers and tris-s-triazine in g-CN nanosheets. According to our analysis, the photocurrent density of the Fmoc-FF/g-CN hydrogel was 1.8× higher (0.82 μA cm) than that of the pristine g-CN. This is attributed to effective exfoliation of g-CN nanosheets in the Fmoc-FF/g-CN network, facilitating photoinduced electron transfers. The Fmoc-FF/g-CN hydrogel reduced NAD to enzymatically active NADH under light illumination at a high rate of 0.130 mol g h and drove light-responsive redox biocatalysis. Moreover, the Fmoc-FF/g-CN scaffold could well-encapsulate key photosynthetic components, such as electron mediators, cofactors, and enzymes, without noticeable leakage, while retaining their functions within the hydrogel. The prominent activity of the Fmoc-FF/g-CN hydrogel for biomimetic photosynthesis resulted from the easy transfer of photoexcited electrons from electron donors to NAD via g-CN and electron mediators as well as the hybridization of key photosynthetic components in a confined space of the nanofiber network.
We present the photoelectrochemical (PEC) regeneration of nicotinamide cofactors (NADH) coupled with the enzymatic synthesis of formate from CO2 towards mimicking natural photosynthesis.
Graphitic carbon nitride (g-C3 N4 ) has a suppressive capability toward Alzheimer's Aβ aggregation under light-illumination. Photoinduced electrons of g-C3 N4 generate reactive oxygen resulting in photooxidation of amyloid peptides that blocks Aβ aggregation. Fe doping of g-C3 N4 frameworks results in enhanced optical properties and even stronger inhibition of Aβ aggregation.
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