Controlling Reactivity and Electron Transfer in De Novo Designed Artificial Cu Proteins by Systematic Primary, Secondary, and Outer Sphere Modulation

Copper-dependent metalloenzymes play essential roles in biology. However, unraveling how the active sites and the surrounding environment influence their functions presents a significant challenge. Inspired by Cu enzymes, we report de novo designed artificial copper proteins (ArCuPs) within trimeric (3SCC) and tetrameric (4SCC) self-assemblies, featuring a trigonal Cu(His) ₃ and a square pyramidal Cu(His) ₄ (OH ₂ ) coordination. 3SCC electrocatalyzes C-H oxidation, but 4SCC does not. Cu ^I -3SCC reacts more rapidly with H ₂ O ₂ compared to O ₂ , while 4SCC is less active. These trends mirror the peroxygenation of lytic polysaccharide monooxygenases (LPMOs) and the unreactive nature of the particulate methane monooxygenase (pMMO) Cu _B site. The differences in reactivity are attributed to inherent reducibility and reoxidation processes, with ET and reorganization energies (l) along with second-sphere and outer-sphere H ₂ O-mediated H-bonding patterns providing further insights. Modulation of second/outer-sphere H-bonding without changing the primary coordination tunes the solvent l, which renders the unreactive 4SCC active for C-H peroxidation.