Journal
NANO LETTERS
Volume 18, Issue 6, Pages 4015-4022Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.nanolett.8b01522
Keywords
Prussian Blue; Fe3O4; iron oxide; catalysis; enzyme model; surface modification
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Funding
- Minerva Center for Biohybrid Complex Systems
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Catalyzed oxygen insertion into C-H bonds represents a continuous challenge in chemistry. Particularly, driving this process at ambient temperature and aqueous media represents a holy grail in catalysis. We report on the catalyzed cascade transformations of L-tyrosine or L-phenylalanine to dopachrome in the presence of L-ascorbic acid/H2O2 as oxidizing mixture and CuFe-Prussian Blue-like nanoparticles, Fe3O4 nanoparticles or Au nanoparticles as catalysts. The process involves the primary transformation of L-tyrosine to L-DOPA that is further oxidized to dopachrome. The transformation of L-phenylalanine to dopachrome in the presence of CuFe-Prussian Blue-like nanoparticles and L-ascorbic acid/H2O2 involves in the first step the formation of L-tyrosine and, subsequently, the operation of the catalytic oxidation cascade of L-tyrosine to L-DOPA and dopachrome. Electron spin resonance experiments demonstrate that ascorbate radicals and hydroxyl radicals play cooperative functions in driving the different oxygen-insertion processes. In addition, the aerobic elecrocatalyzed oxidation of L-tyrosine to dopachrome in the presence of naphthoquinone-modified Fe3O4 nanoparticles and L-ascorbic acid is demonstrated. In this system, magnetic-field attraction of the naphthoquinone-modified Fe(3)O(4 )nanoparticles onto the electrode allows the quinone-mediated electrocatalyzed reduction of O-2 to H2O2 (bias potential -0.5 V vs SCE). The electrogenerated H2O2 is then utilized to promote the transformation of L-tyrosine to dopachrome in the presence of L-ascorbic acid and Fe3O4 catalyst.
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