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2.
Dalton Trans ; (33): 6468-71, 2009 Sep 07.
Artigo em Inglês | MEDLINE | ID: mdl-19672489

RESUMO

This paper shows for the first time that the spectral features of the ternary complex of tyrosinase/O2/phenol, trapped at low temperature using the very slow substrate 3,5-difluorophenol, are those of a mu-eta2:eta2-peroxidodicopper(II) species, and that this remains the only enzyme species under turnover and substrate saturation conditions.


Assuntos
Monofenol Mono-Oxigenase/metabolismo , Fenóis/química , Catálise , Cobre/química , Monofenol Mono-Oxigenase/química , Espectrofotometria Ultravioleta , Streptomyces antibioticus/enzimologia , Temperatura
4.
Dalton Trans ; (28): 3035-42, 2007 Jul 28.
Artigo em Inglês | MEDLINE | ID: mdl-17622421

RESUMO

A general method for the preparation of multidentate ligands comprised of a multi-imine platform derived from 1,1,1-tris(aminomethyl)ethane or tris(aminoethyl)amine connected to bi- and tridentate N-donor chelates has been developed. The feasibility of the method has been demonstrated through the synthesis and characterization of a large set of these ligand types. Complexation to Cu(I) was accomplished for several cases, yielding tri- and tetracopper(I) complexes that have been characterized in solution by NMR spectroscopy and conductivity, and in the solid state by elemental analysis, mass spectrometry, and/or X-ray crystallography. These complexes are potentially useful for modeling multicopper protein active sites.


Assuntos
Cobre/química , Nitrogênio/química , Cristalografia por Raios X , Condutividade Elétrica , Ligantes , Modelos Moleculares , Estrutura Molecular
5.
J Am Chem Soc ; 127(51): 18031-6, 2005 Dec 28.
Artigo em Inglês | MEDLINE | ID: mdl-16366554

RESUMO

The dicopper(I) complex [Cu2(MeL66)]2+ (where MeL66 is the hexadentate ligand 3,5-bis-{bis-[2-(1-methyl-1H-benzimidazol-2-yl)-ethyl]-amino}-meth ylbenzene) reacts reversibly with dioxygen at low temperature to form a mu-peroxo adduct. Kinetic studies of O2 binding carried out in acetone in the temperature range from -80 to -55 degrees C yielded the activation parameters DeltaH1(not equal) = 40.4 +/- 2.2 kJ mol(-1), DeltaS1)(not equal) = -41.4 +/- 10.8 J K(-1) mol(-1) and DeltaH(-1)(not equal) = 72.5 +/- 2.4 kJ mol(-1), DeltaS(-1)(not equal) = 46.7 +/- 11.1 J K(-1) mol(-1) for the forward and reverse reaction, respectively, and the binding parameters of O2 DeltaH degrees = -32.2 +/- 2.2 kJ mol(-1) and DeltaS degrees = -88.1 +/- 10.7 J K(-1) mol(-1). The hydroxylation of a series of p-substituted phenolate salts by [Cu2(MeL66)O2]2+ studied in acetone at -55 degrees C indicates that the reaction occurs with an electrophilic aromatic substitution mechanism, with a Hammett constant rho = -1.84. The temperature dependence of the phenol hydroxylation was studied between -84 and -70 degrees C for a range of sodium p-cyanophenolate concentrations. The rate plots were hyperbolic and enabled to derive the activation parameters for the monophenolase reaction DeltaH(not equal)ox = 29.1 +/- 3.0 kJ mol(-1), DeltaS(not equal)ox = -115 +/- 15 J K(-1) mol(-1), and the binding parameters of the phenolate to the mu-peroxo species DeltaH degrees(b) = -8.1 +/- 1.2 kJ mol(-1) and DeltaS degrees(b) = -8.9 +/- 6.2 J K(-1) mol(-1). Thus, the complete set of kinetic and thermodynamic parameters for the two separate steps of O2 binding and phenol hydroxylation have been obtained for [Cu2(MeL66)]2+.


Assuntos
Cobre/química , Monofenol Mono-Oxigenase/química , Monofenol Mono-Oxigenase/metabolismo , Peróxidos/química , Fenóis/química , Materiais Biomiméticos/química , Cátions Bivalentes , Hidroxilação , Cinética , Compostos Organometálicos/química , Fenóis/metabolismo , Termodinâmica
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