http://www.cnr.it/ontology/cnr/individuo/prodotto/ID33175
New Mediators for the Enzyme Laccase: Mechanistic Features and Selectivity in the Oxidation of non-phenolic Substrates (Articolo in rivista)
- Type
- Label
- New Mediators for the Enzyme Laccase: Mechanistic Features and Selectivity in the Oxidation of non-phenolic Substrates (Articolo in rivista) (literal)
- Anno
- 2005-01-01T00:00:00+01:00 (literal)
- Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#doi
- 10.1039/b507657a (literal)
- Alternative label
Astolfi P., Brandi P., Galli C., Gentili P., Gerini M. F., Greci L., Lanzalunga O. (2005)
New Mediators for the Enzyme Laccase: Mechanistic Features and Selectivity in the Oxidation of non-phenolic Substrates
in New journal of chemistry (1987)
(literal)
- Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori
- Astolfi P., Brandi P., Galli C., Gentili P., Gerini M. F., Greci L., Lanzalunga O. (literal)
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- Pagina fine
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- Rivista
- Note
- ISI Web of Science (WOS) (literal)
- Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#affiliazioni
- Dipartimento di Chimica, Universita` 'La Sapienza', and IMC-CNR Sezione Meccanismi di
Reazione
Dipartimento di Scienze dei Materiali e della Terra, Universita` di Ancona (literal)
- Titolo
- New Mediators for the Enzyme Laccase: Mechanistic Features and Selectivity in the Oxidation of non-phenolic Substrates (literal)
- Abstract
- New mediators of laccase have been comparatively evaluated and ranked towards the benchmark aerobic
oxidation of p-MeO-benzyl alcohol. The mechanism of oxidation of this non-phenolic substrate by each
mediator, which is initially oxidised by laccase to the Medox form, has been assessed among three
alternatives. The latter make the phenoloxidise laccase competent for the indirect oxidation of non-phenolic
(and thus 'unnatural') substrates. Experimental characterisation of the mediators, by means of
spectrophotometric, electrochemical and thermochemical survey, is reported. Clear-cut evidence for the
formation of a benzyl radical intermediate in the oxidation of a particular benzyl alcohol with laccase and a
{N-OH mediator is attained by means of a trapping experiment. The selectivity of the laccase-catalysed
oxidation of two competing lignin and polysaccharide model compounds has been assessed by using the
highly proficient 4-MeO-HPI mediator, and found very high in favour of the former model. This evidence is
in keeping with the operation of a radical hydrogen-abstraction process that efficiently cleaves the benzylic
rather than the aliphatic C-H bond of the two models. Significant is the finding that catechol, i.e., a model
of recurring phenolic structures in lignin, once oxidised to aryloxyl radical by laccase is capable to mediate a
radical oxidation of non-phenolic compounds. This supports a fully-fledged role of laccase as a delignifying
enzyme in nature by way of no other mediators than the very phenolic groups of lignin. Finally, an
evaluation of the dissociation energy of the NO-H bond of HBT, which is not accessible experimentally, is
provided by the use of a thermochemical cycle and theoretical calculations. (literal)
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- Autore CNR
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