Journal of the American Chemical Society
Journal of the American Chemical Society
5 years ago

Artificial Metalloproteins Containing Co4O4 Cubane Active Sites

Artificial Metalloproteins Containing Co4O4 Cubane Active Sites
Andy I. Nguyen, A. S. Borovik, Lisa Olshansky, Ariel Furst, T. Don Tilley, Jaicy Vallapurackal, Raúl Huerta-Lavorie
Artificial metalloproteins (ArMs) containing Co4O4 cubane active sites were constructed via biotin–streptavidin technology. Stabilized by hydrogen bonds (H-bonds), terminal and cofacial CoIII–OH2 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 Co4O4 active site provided a single H-bond to one of a set of cofacial CoIII–OH2 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 (Co4O4 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.

Publisher URL: http://dx.doi.org/10.1021/jacs.7b13052

DOI: 10.1021/jacs.7b13052

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