AEI 60 |
| Although similar coordination geometries are encountered at the active sites of several carboxylate-bridged non-heme diiron enzymes, they facilitate different functions. A variable number of water molecules are bound to iron in the active sites as revealed by crystal structure analyses of the enzymes. DFT calculations for sMMOH further indicate that hydrogen bonding to water might be a key factor for the generation of reactive intermediates required to hydroxylate substrates. The role of coordinated water in mediating reactions at carboxylate-bridged diiron(II) centers was examined for synthetic model compounds having the formula [Fe2(µ-O2CArTol)4(4-Rpy)2], where -O2CArTol is 2,6-di-(p-tolyl)benzoate and 4-Rpy is a para-substituted pyridine ligand. A paddlewheel structure (red, see insert) is retained in anhydrous CH2Cl2 solutions, but converts to the windmill aqua form (orange) upon water addition. The kinetics of this process, together with the O2 reactivity of the complex in both anhydrous and aqueous environments, was investigated over a range of temperatures by stopped-flow spectroscopy. Water increases the oxygenation rate by at least 10-fold but has little effect on the activation enthalpies, suggesting that loss of H2O is most likely not a requirement for O2 binding to iron in the transition state. Mechanistic interpretations of the results will be presented. This work was supported by a grant from the National Institute of General Medical Sciences.
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Academic Employment Initiative
8:00 PM-10:00 PM, Monday, 11 September 2006 Moscone Center -- Hall D, Sci-Mix
Academic Employment Initiative |
