Abstract
Creating an artificial functional mimic of the mitochondrial enzyme cytochrome c oxidase (CcO) has been a long-term goal of the scientific community as such a mimic will not only add to our fundamental understanding of how CcO works but may also pave the way for efficient electrocatalysts for oxygen reduction in hydrogen/oxygen fuel cells. Here we develop an electrocatalyst for reducing oxygen to water under ambient conditions. We use site-directed mutants of myoglobin, where both the distal Cu and the redox-active tyrosine residue present in CcO are modelled. In situ Raman spectroscopy shows that this catalyst features very fast electron transfer rates, facile oxygen binding and O–O bond lysis. An electron transfer shunt from the electrode circumvents the slow dissociation of a ferric hydroxide species, which slows down native CcO (bovine 500 s−1), allowing electrocatalytic oxygen reduction rates of 5,000 s−1 for these biosynthetic models.
Highlights
Creating an artificial functional mimic of the mitochondrial enzyme cytochrome c oxidase (CcO) has been a long-term goal of the scientific community as such a mimic will add to our fundamental understanding of how CcO works but may pave the way for efficient electrocatalysts for oxygen reduction in hydrogen/oxygen fuel cells
While none of the synthetic or biochemical models reported so far could match the reactivity exhibited by their natural counterparts, fundamental insights regarding the structure– function correlations of several metalloenzymes have been gained in the process[7,13,14,15]
We report the electrocatalytic properties of the G65YCuBMb immobilized on an Au electrode using the method developed for WT Mb29
Summary
Creating an artificial functional mimic of the mitochondrial enzyme cytochrome c oxidase (CcO) has been a long-term goal of the scientific community as such a mimic will add to our fundamental understanding of how CcO works but may pave the way for efficient electrocatalysts for oxygen reduction in hydrogen/oxygen fuel cells. Stable naturally occurring proteins have been used as scaffolds for creating mimics of several metalloenzymes, such as hydrogenases which are involved in the reversible generation of H2 from water, haem proteins participating in electron transfer and O2-binding, non-haem iron and copper enzymes active in small molecule activation, and even novel enzymes containing non-native cofactors[18,19,20,21,22,23,24] Using this approach, biosynthetic models that structurally and functionally mimic CcO and nitric oxide reductase have been reported[7,25]. We report the electrocatalytic properties of the G65YCuBMb (higher synthetic yields than the tyrosine crosslinked variant) immobilized on an Au electrode using the method developed for WT Mb29
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