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Non-coupled binuclear (NCBN) copper monooxygenases are metalloenzymes centrally involved in the biosynthesis of neurotransmitters and signaling peptides. The most famous is dopamine β-monooxygenase, which oxidizes dopamine into norepinephrine through C–H activation. This enzyme family is widely thought to operate through a unique methionine-ligated cupric superoxide intermediate. The copper–sulfur interaction has proven critical for turnover, raising still-unresolved questions on why Nature employs an oxidizable methionine residue within an oxygenation active site. In this seminar, I will describe our recent work on the first cupric superoxide model complex with a demonstrable Cu–S interaction. Resonance Raman, EXAFS (extended X-ray absorption fine structure), and magnetic circular dichroism (MCD) studies will provide insight into the geometric and electronic structures, especially in comparison with an all-nitrogen ligand analog. Hydrogen atom abstraction reactivity will be described, showing this complex to be both a structural and a functional model for the active site of NCBN enzymes.
