Catalogo Articoli (Spogli Riviste)

OPAC HELP

Titolo:
Models for the active site in galactose oxidase: Structure, spectra and redox of copper(II) complexes of certain phenolate ligands
Autore:
Vaidyanathan, M; Palaniandavar, M;
Indirizzi:
Bharathidasan Univ, Dept Chem, Tiruchchirappalli 620024, India Bharathidasan Univ Tiruchchirappalli India 620024 rappalli 620024, India
Titolo Testata:
PROCEEDINGS OF THE INDIAN ACADEMY OF SCIENCES-CHEMICAL SCIENCES
fascicolo: 3, volume: 112, anno: 2000,
pagine: 223 - 238
SICI:
0253-4134(200006)112:3<223:MFTASI>2.0.ZU;2-7
Fonte:
ISI
Lingua:
ENG
Soggetto:
HETEROLEPTIC TRIPODAL COMPLEXES; SPIN-RESONANCE SPECTRA; CRYSTAL-STRUCTURE; ELECTRONIC-PROPERTIES; O,N LIGANDS; COORDINATION; CHEMISTRY; PERCHLORATE; MONONUCLEAR; REACTIVITY;
Keywords:
Cu(II) phenolate complexes; X-ray structures; electronic spectra; electron paramagnetic resonance spectra; redox behaviour; galactose oxidase;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
52
Recensione:
Indirizzi per estratti:
Indirizzo: Palaniandavar, M Bharathidasan Univ, Dept Chem, Tiruchchirappalli 620024, India Bharathidasan Univ Tiruchchirappalli India 620024 India
Citazione:
M. Vaidyanathan e M. Palaniandavar, "Models for the active site in galactose oxidase: Structure, spectra and redox of copper(II) complexes of certain phenolate ligands", P I A S-CH, 112(3), 2000, pp. 223-238

Abstract

Galactose oxidase (GOase) is a fungal enzyme which is unusual among metalloenzymes in appearing to catalyse the two electron oxidation of primary alcohols to aldehydes and H2O2. The crystal structure of the enzyme reveals that the coordination geometry of mononuclear copper(II) ion is square pyramidal, with two histidine imidazoles. a tyrosinate, and either H2O (pH 7.0) or acetate (from buffer, pH 4.5) in the equatorial sites and a tyrosinate ligand weakly bound in the axial position. This paper summarizes the results of our studies on the structure, spectral and redox properties of certain novel models for the active site of the inactive form of GOase. The monophenolato Cu(II) complexes of the type [Cu(L1)X][H(L1) = 2-(bis(pyrid-2-ylmethyl)aminomethyl)-4-nitrophenol and X- = Cl- 1, NCS- 2, CH3COO- 3, ClO4- 4] reveal a distorted square pyramidal geometry around Cu(II) with an unusual axial coordination of phenolate moiety. The coordination geometry of 3 is reminiscent of the active site of GOase with an axial phenolate and equatorialCH3COO- ligands. All the present complexes exhibit several electronic and EPR spectral features which are also similar to the enzyme. Further, to establish the structural and spectroscopic consequences of the coordination oftwo tyrosinates in GOase enzyme, we studied the monomeric copper(II) complexes containing two phenolates and imidazole/pyridine donors as closer structural models for GOase. N,N-wdimethylethylenediamine and N,N'-dimethylethylenediamine have been used as starting materials to obtain a variety of 2,4-disubstituted phenolate ligands. The X-ray crystal structures of the complexes [Cu(L5)(py)], (8) [H-2(L5) = N,N-dimethyl-N',N'-bis(2-hydroxy-4-nitrobenzyl) ethylenediamine, py = pyridine] and [Cu(L8)(H2O)] (11), [H-2(L8) = N,N'-dimethyl-N,N'-bis(2-hydroxy-4-nitrobenzyl)ethylenediamine] reveal distorted square pyramidal geometries around Cu(II) with the axial tertiary amine nitrogen and water coordination respectively. Interestingly, for the latter complex there are two different molecules present in the same unit cell containing the methyl groups of the ethylenediamine fragment cia to each other in one molecule and trans to each other in the other. The ligand field and EPR spectra of the model complexes reveal square-based geometries even in solution. The electrochemical and chemical means of generating novel radical species of the model complexes, analogous to the active form of the enzyme is presently under investigation.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 24/11/20 alle ore 08:12:18