Strategies for O 2 activation by copper enzymes were recently expanded to include mononuclear Cu sites, with the discovery of the copper-dependent polysaccharide monooxygenases, also classified as auxiliary-activity enzymes 9-11 (AA9-11). These enzymes are finding considerable use in industrial biofuel production. Crystal structures of polysaccharide monooxygenases have emerged, but experimental studies are yet to determine the solution structure of the Cu site and how this relates to reactivity. From X-ray absorption near edge structure and extended X-ray absorption fine structure spectroscopies, we observed a change from four-coordinate Cu(II) to three-coordinate Cu(I) of the active site in solution, where three protein-derived nitrogen ligands coordinate the Cu in both redox states, and a labile hydroxide ligand is lost upon reduction. The spectroscopic data allowed for density functional theory calculations of an enzyme active site model, where the optimized Cu(I) and (II) structures were consistent with the experimental data. The O 2 reactivity of the Cu(I) site was probed by EPR and stopped-flow absorption spectroscopies, and a rapid one-electron reduction of O 2 and regeneration of the resting Cu(II) enzyme were observed. This reactivity was evaluated computationally, and by calibration to Cu-superoxide model complexes, formation of an end-on Cu-AA9-superoxide species was found to be thermodynamically favored. We discuss how this thermodynamically difficult one-electron reduction of O 2 is enabled by the unique protein structure where two nitrogen ligands from His1 dictate formation of a T-shaped Cu(I) site, which provides an open coordination position for strong O 2 binding with very little reorganization energy.X-ray absorption spectroscopy | DFT | dioxygen activation | biofuels

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The in-situ polymerization of aniline in the presence of multiwalled carbon nanotubes and (S)-(+)-10-camphorsulfonic acid provides a route to optically active composite materials. Their chiroptical properties suggest that polymers and composite materials adopt similar optical properties indicative of “compact coil” in DMSO and “extended coil” in m-cresol. The optical activity in composite materials is preserved, although somewhat reduced to that of the pure polymer, which is attributed to the polymer phase coating nanotubes. This polymer phase is responsible for the lower electrical resistance observed for composite materials.

A series of zirconium phosphate supported WO x solid acid catalysts with W loadings from 1-25 wt% have been prepared on high surface area zirconium phosphate by a surface grafting method. Catalysts were characterized by N 2 adsorption, FTIR, Raman, UV-Vis, 31 P MAS NMR, pyridine TPD and X-ray methods. Spectroscopic measurements suggest a Keggin-type structure forms on the surface of zirconium phosphate as a (MZrOH 2 + )(ZrPW 11 O 40 52 ) species. All catalysts show high activity in palmitic acid esterification with methanol. These materials can be readily separated from the reaction system for re-use, and are resistant to leaching of the active heteropolyacid, suggesting potential industrial applications in biodiesel synthesis. Experimental Catalyst preparationPorous zirconium phosphate. A simple hydrothermal synthesis procedure was used 24 during which 0.01 mol of zirconium n-propoxide, (70 wt% solution in 1-propanol, Aldrich) was added drop wise to a 60 mL solution of H 3 PO 4 (0.1 mol L 21 ) under stirring. After a further 2 h stirring at room temperature,