Chemical models that mimic the activation of methane by oxygen

Informazioni relative al progetto

ID dell’accordo di sovvenzione: INTAS-93-0315

Progetto chiuso

Data di avvio 1 Agosto 1994

Data di completamento 31 Luglio 1995

Finanziato da

• International Association for the promotion of cooperation with scientists from the independent states of the former Soviet Union (INTAS), 1993-

Costo totale

Nessun dato

Contributo UE

€ 32 000,00

Coordinato da

UNIVERSITY OF WARWICK
United Kingdom

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Risultati sfruttabili

Chemical models that mimic the activation of methane by oxygen

Membrane-bound methane monooxygenase (pMMO) from Methylococcus capsulatus (M) is inactivated by diethyldithiocarbamate. The inactivation of the enzyme correlates with change of ESR signal characteristic for type 2 Cu. Cu2+, but not Fe2+, Mn2+ and Ni2+, completely restores activity and original ESR signal [1]. Purified hydroxylase component of pMMO is constructed from alpha- (45-47 kDa), beta- (27 kDa) and gamma- (25 kDa) peptides. The protein contains Cu and Fe ions. The first and second structures of the peptides are unique and have very high homology resemblance with ammonium monooxygenase only. Kinetic deuterium isotopic effect (KIE) for methane oxidation is equal 25 or more and for ethane oxidation is 2. Remarkable similarity of KIE between pMMO and sMMO is supposed to indicate that the fundamental mechanisms of hydrocarbon oxidation by these two different enzyme systems are identical [2]. In efforts to get sMMO models new dinuclear iron complexes with labile coordination sites were synthesized and characterised. Biomimetic catalytic oxidation by hydrogen peroxide of methane to methanol upon the catalysis of these complexes was demonstrated, albeit with small turnover number, and some evidence of non-radical oxo-transfer in this system was obtained using special substrate probes[3]. The nature of the active oxidant in stoichiometric oxidation of methane to methanol by diiron complexes inside zeolite cages was studied by Moessbauer spectroscopy and its similarity to the active oxidant of MMO was suggested [4]. Finally, a new concept of bridge mechanism for sMMO, involving a high-valent dioxo-diiron intermediate, was proposed [5]. Although the model research has been successful, the results obtained have shown some limitations for simple complexes as metallobiosite models. This has prompted a search for new models which mimic the polypeptide framework in a better way and design and synthesis of new polydentate dinucleating ligands for the preparation of more sophisticated model complexes will be continued.