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Type: Journal article
Title: Electronic Structure Description of the cis-MoOS Unit in Models for Molybdenum Hydroxylases
Author: Doonan, C.
Rubie, N.
Peariso, K.
Harris, H.
Knottenbelt, S.
George, G.
Young, C.
Kirk, M.
Citation: Journal of the American Chemical Society, 2008; 130(1):55-65
Publisher: Amer Chemical Soc
Issue Date: 2008
ISSN: 0002-7863
Statement of
Christian J. Doonan, Nick D. Rubie, Katrina Peariso, Hugh H. Harris, Sushilla Z. Knottenbelt, Graham N. George, Charles G. Young, and Martin L. Kirk
Abstract: The molybdenum hydroxylases catalyze the oxidation of numerous aromatic heterocycles and simple organics and, unlike other hydroxylases, utilize water as the source of oxygen incorporated into the product. The electronic structures of the cis-MoOS units in CoCp2[TpiPrMoVOS(OPh)] and TpiPrMoVIOS(OPh) (TpiPr = hydrotris(3-isopropylpyrazol-1-yl)borate), new models for molybdenum hydroxylases, have been studied in detail using S K-edge X-ray absorption spectroscopy, vibrational spectroscopy, and detailed bonding calculations. The results show a highly delocalized Mo=S pi* LUMO redox orbital that is formally Mo(dxy) with approximately 35% sulfido ligand character. Vibrational spectroscopy has been used to quantitate Mo-Ssulfido bond order changes in the cis-MoOS units as a function of redox state. Results support a redox active molecular orbital that has a profound influence on MoOS bonding through changes to the relative electro/nucleophilicity of the terminal sulfido ligand accompanying oxidation state changes. The bonding description for these model cis-MoOS systems supports enzyme mechanisms that are under orbital control and dominantly influenced by the unique electronic structure of the cis-MoOS site. The electronic structure of the oxidized enzyme site is postulated to play a role in polarizing a substrate carbon center for nucleophilic attack by metal activated water and acting as an electron sink in the two-electron oxidation of substrates.
Keywords: Molybdenum; Mixed Function Oxygenases; Metalloproteins; Spectrum Analysis; Binding Sites; Molecular Conformation; Electrons; Models, Molecular
Description: Copyright © 2008 American Chemical Society
RMID: 0020095689
DOI: 10.1021/ja068512m
Appears in Collections:Chemistry publications
Environment Institute publications

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