Imidazolate-Stabilized Cu(III): Dioxygen to Oxides at Type 3 Copper Sites.

Imidazole ligation of metals through histidine is extensive among metalloproteins, yet the role of the imidazolate conjugate base is often neglected, despite its potential accessibility when bonded to an oxidized metal center. Using synthetic models of oxygenated tyrosinase enzymes ligated exclusively by monodentate imidazoles, we find that deprotonation of the μ-η:η-peroxidodicopper(II) species triggers redox isomerization to an imidazolate-ligated bis(μ-oxido)dicopper(III) species. Formal two-electron oxidation to Cu(III) remains biologically unprecedented, yet is effected readily by addition of base.

Phenolate-bonded bis(μ-oxido)-bis-copper(III) intermediates: hydroxylation and dehalogenation reactivities.

Exogenous phenolate -hydroxylation by copper oxidants formed from dioxygen is generally thought to occur through one of two limiting mechanisms defined by the structure of the active oxidant: an electrophilic μ-η:η-peroxo-bis-copper(II) species as found in the oxygenated form of the binuclear copper enzyme tyrosinase (oxyTyr), or an isomeric bis(μ-oxido)-bis-copper(III) species (O) with ligated phenolate(s) as evidenced by most synthetic systems. The characterization of the latter is limited due to their limited thermal stability. This study expands the scope of an O species with ligated phenolate(s) using ,'-di--butyl-1,3-propanediamine (DBPD), a flexible secondary diamine ligand.

Selective Oxidation of Exogenous Substrates by a Bis-Cu(III) Bis-Oxide Complex: Mechanism and Scope.

Cu(III)(μ-O) bis-oxides () form spontaneously by direct oxygenation of nitrogen-chelated Cu(I) species and constitute a diverse class of versatile 2e/2H oxidants, but while these species have attracted attention as biomimetic models for dinuclear Cu enzymes, reactivity is typically limited to intramolecular ligand oxidation, and systems exhibiting synthetically useful reactivity with exogenous substrates are limited. (TMPD = , , , -tetramethylpropane-1,3-diamine) presents an exception, readily oxidizing a diverse array of exogenous substrates, including primary alcohols and amines selectively over their secondary counterparts in good yields. Mechanistic and DFT analyses suggest substrate oxidation proceeds through initial axial coordination, followed by rate limiting rotation to position the substrate in the Cu(III) equatorial plane, whereupon rapid deprotonation and oxidation by net hydride transfer occurs.

Exclusive imidazole ligation to CuO and CuCuO cores.

We disclose herein the synthesis and characterization of L2Cu(iii)2O2 and L3Cu(iii)Cu(ii)2O2 complexes with nitrogen ligation exclusively from imidazoles for the first time. Their accessibility by direct oxygenation of a L-Cu(i) precursor and the resulting Cu(iii) formation inform on the kinetic accessibility and thermodynamic superiority of imidazole in stabilizing Cu(iii).

Development of Decreased-Gluten Wheat Enabled by Determination of the Genetic Basis of Barley.

Celiac disease is the most common food-induced enteropathy in humans, with a prevalence of approximately 1% worldwide. It is induced by digestion-resistant, proline- and glutamine-rich seed storage proteins, collectively referred to as gluten, found in wheat (). Related prolamins are present in barley () and rye ().

A realistic in silico model for structure/function studies of molybdenum-copper CO dehydrogenase.

CO dehydrogenase (CODH) is an environmentally crucial bacterial enzyme that oxidizes CO to CO2 at a Mo-Cu active site. Despite the close to atomic resolution structure (1.1 Å), significant uncertainties have remained with regard to the protonation state of the water-derived equatorial ligand coordinated at the Mo-center, as well as the nature of intermediates formed during the catalytic cycle.