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Issue 9, 2013
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Modelling the reduced xanthine oxidase in active sulfo and inactive desulfo forms

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Abstract

Synthesis of two complexes, [NBun4][MoIVO(mnt)(S-Tol)(N–N)] (NN = 2,2′-bipyridine (1a) or 1,10-phenanthroline (1b); mnt = maleonitriledithiolate; S-Tol = toluenethiol) are reported. These on treatment with H2S generate the corresponding [NBun4][MoIVO(mnt)(SH)(N–N)] (2a and 2b) complexes bearing the susceptible hydrosulfide coordination. 2a (and 2b) upon chemical oxidation show EPR spectra with the appearance of a Mo(V) signal at <g> = 1.976 (for 2a and 2b). Such EPR signal changed to another slow Mo(V) signal at <g> = 1.949 at the expense of the initial signal. This conversion is accelerated in the presence of trace amount of moisture in the solvent. These data are similar to the Moco isolated from the xanthine oxidase (XO) as reported by Bray. 2a (and 2b) responds to one electron electrochemical oxidation and the generated pentavalent species responds to proton coupled electron transfer reaction. A predominantly metal centered HOMO is observed in 2a (and 2b) from DFT calculations. In the inhibited Moco of XO bearing a –SH moiety, the HOMO shows considerably less electron density residing on the Mo dxy orbital and maximum electron density is distributed to the phospho-ester group rendering the Mo(IV) center incapable of participating in the electron transfer process manifesting inhibition.

Graphical abstract: Modelling the reduced xanthine oxidase in active sulfo and inactive desulfo forms

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Publication details

The article was received on 17 Aug 2012, accepted on 26 Nov 2012 and first published on 28 Nov 2012


Article type: Paper
DOI: 10.1039/C2DT32309E
Citation: Dalton Trans., 2013,42, 3050-3058
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    Modelling the reduced xanthine oxidase in active sulfo and inactive desulfo forms

    J. Mitra and S. Sarkar, Dalton Trans., 2013, 42, 3050
    DOI: 10.1039/C2DT32309E

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