Artificial metalloproteins (ArMs) containing Co <sub>4 </sub>O <sub>4 </sub> cubane active sites were constructed via biotin-streptavidin technology. Stabilized by hydrogen bonds (H-bonds), terminal and cofacial Co <sup>III </sup>-OH <sub>2 </sub> mo ...
Artificial metalloproteins (ArMs) containing Co 4 O 4 cubane active sites were constructed via biotin-streptavidin technology. Stabilized by hydrogen bonds (H-bonds), terminal and cofacial Co III -OH 2 moieties are observed crystallographically in a series of immobilized cubane sites. Solution electrochemistry provided correlations of oxidation potential and pH. For variants containing Ser and Phe adjacent to the metallocofactor, 1e - /1H + chemistry predominates until pH 8, above which the oxidation becomes pH-independent. Installation of Tyr proximal to the Co 4 O 4 active site provided a single H-bond to one of a set of cofacial Co III -OH 2 groups. With this variant, multi-e - /multi-H + chemistry is observed, along with a change in mechanism at pH 9.5 that is consistent with Tyr deprotonation. With structural similarities to both the oxygen-evolving complex of photosystem II (H-bonded Tyr) and to thin film water oxidation catalysts (Co 4 O 4 core), these findings bridge synthetic and biological systems for water oxidation, highlighting the importance of secondary sphere interactions in mediating multi-e - /multi-H + reactivity.
Organizational Affiliation:
Department of Chemistry, University of California, Irvine , Irvine, California 92697, United States.,Department of Chemistry, University of California, Berkeley , Berkeley, California 94720, United States.,Chemical Science Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
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