New mononuclear CuII and ZnII complexes capable of stabilizing phenoxyl radicals as models for the active form of galactose oxidase

Anjos, Ademir dos; Bortoluzzi, Adaı́lton J.; Osório, Renata E. H. M. B.; Peralta, Rosely A.; Friedermann, Geraldo R.; Mangrich, Antônio S.; Neves, Ademir

doi:10.1016/j.inoche.2004.12.022

Cited by 24 publications

(8 citation statements)

References 37 publications

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“…S2. [59]. Interestingly, this process was not observed for complexes 2 and 3, most probably because it is anodic-shifted in relation to complex 3 and therefore out of the investigated potential range (-1.4 to +1.4 V).…”

Section: Electrochemistry Of Fe(iii)ni(ii) Biomimetics Of Ufmentioning

confidence: 87%

Probing the role of the divalent metal ion in uteroferrin using metal ion replacement and a comparison to isostructural biomimetics

et al. 2007

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Purple acid phosphatases (PAPs) are a group of heterovalent binuclear metalloenzymes that catalyze the hydrolysis of phosphomonoesters at acidic to neutral pH. While the metal ions are essential for catalysis, their precise roles are not fully understood. Here, the Fe(III)Ni(II) derivative of pig PAP (uteroferrin) was generated and its properties were compared with those of the native Fe(III)Fe(II) enzyme. The k cat of the Fe(III)Ni(II) derivative (approximately 60 s -1 ) is approximately 20% of that of native uteroferrin, and the Ni(II) uptake is considerably faster than the reconstitution of full enzymatic activity, suggesting a slow conformational change is required to attain optimal reactivity. An analysis of the pH dependence of the catalytic properties of Fe(III)Ni(II) uteroferrin indicates that the l-hydroxide is the likely nucleophile. Thus, the Ni(II) derivative employs a mechanism similar to that proposed for the Ga(III)Zn(II) derivative of uteroferrin, but different from that of the native enzyme, which uses a terminal Fe(III)-bound nucleophile to initiate catalysis. Binuclear Fe(III)Ni(II) biomimetics with coordination environments similar to the coordination environment of uteroferrin were generated to provide both experimental benchmarks (structural and spectroscopic) and further insight into the catalytic mechanism of hydrolysis. The data are consistent with a reaction mechanism employing an Fe(III)-bound terminal hydroxide as a nucleophile, similar to that proposed for native uteroferrin and various related isostructural biomimetics. Thus, only in the uteroferrin-catalyzed reaction are the precise details of the catalytic mechanism sensitive to the metal ion composition, illustrating the significance of the dynamic ligand environment in the protein active site for the optimization of the catalytic efficiency.

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Section: Electrochemistry Of Fe(iii)ni(ii) Biomimetics Of Ufmentioning

confidence: 87%

Probing the role of the divalent metal ion in uteroferrin using metal ion replacement and a comparison to isostructural biomimetics

et al. 2007

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“…A wide number of copper(II) complexes of salen‐type ligands have been described so far, therefore the discussion here will be limited to general considerations and complexes specifically designed to model the GO active site,33–43 in other words those bearing a sterically bulky substituent at the ortho and para positions of each phenol to prevent bis(μ‐phenolate) dimer formation and to stabilize a phenoxyl radical (Figure 3). The copper(II) ion in these complexes is tetracoordinate in a square planar or tetrahedral geometry, as shown by their X‐ray crystal structures and EPR spectroscopy.…”

Section: Galactose Oxidasementioning

confidence: 99%

Ten Years of a Biomimetic Approach to the Copper(II) Radical Site of Galactose Oxidase

2007

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An overview of recent progress in the modeling of the copper(II)‐phenoxyl entity of the metalloenzyme Galactose Oxidase (GO) is presented. GO is an enzyme that is extremely engineered by nature: its active site exhibits several unusual features, such as a coordinated tyrosyl radical, post‐translationally modified amino acids, and π‐stacked residues. Understanding each of these particularities has posed a challenge for chemists, who have consequently developed several biomimetic complexes during the last decade. The properties of representative complexes are described herein, with special emphasis given to copper(II) complexes involving tripodal ligands. All these biomimetic compounds have been developed with the aim of better understanding biologically relevant problems. I show here that the structural attributes, reactivity, electronic properties, self‐processing, and many other properties of GO can be addressed successfully using model complexes.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

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“…The products N,N-[bis-(2-pyridylmethyl)]-N'-[(2-hydroxybenzyl)]-1,3-propanediamine-2-ol (1) 20 and 3,5-di-tert-butyl-2-hydroxybenzyl chloride (2) 21,22 were synthesized according to the methods described in the literature. 1 H NMR (CDCl 3 , d ppm) for product 1 20 : 2.6-2.7 (4H), 3.8-4.0 (7H), 6.7-6.8 (2H), 7.0-7.2 (6H), 7.5 (2H), 8.5 (2H).…”

Section: Synthesis Of the Ligand (H 3 L) And Of The Complex [Cu 2 (Hlmentioning

confidence: 99%

“…[1][2][3][4][5][6][7][8][9] The development of functional models of metalloenzymes for catalyst oxidation reactions is a subject of great interest. [10][11][12][13][14][15][16] Neves et al [17][18][19][20][21][22][23][24][25] have extensively synthesized and characterized model complexes to mimic the active site of the different enzymes (e.g., catechol oxidase, peroxidase, galactose oxidase, catalase, purple acid phosphatase). The majority of O 2 -reactive copper models have been based on the binuclear-Cu catechol oxidase.…”

Section: Introductionmentioning

confidence: 99%

“…6, 2008 (2-hydroxy-3,5-di-tert-butylbenzyl)]-1,3-propanediamine-2-ol (H 3 L) was obtained in good yield using epichlorohydrin, which is widely used as a convenient precursor for the synthesis of unsymmetric ligands containing the central skeleton 1,3-diaminopropan-2-ol. 20,21,24 The H 3 L ligand's structure was confirmed through 1 H NMR spectroscopy and prepared in order to synthesize dinuclear copper(II) complexes in which the molecular spacer alkoxo oxygen atom holds the two metal centers in close proximity and the fifth and sixth coordination positions are available for the coordination of exogenous ligands.The H 3 L ligand reacts in methanolic solution with Cu(CH 3 COO) 2 .H 2 O (stoichiometry 1:2) and addition of NaClO 4 results in the formation of the dinuclear complex [Cu 2 II (HL)(μ-CH 3 COO)](ClO 4 ). This complex was confirmed and characterized through IR, elemental and X-ray crystallographic analysis.…”

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Determination of catechin in green tea using a catechol oxidase biomimetic sensor

Fernandes

Osório

Anjos

et al. 2008

J. Braz. Chem. Soc.

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Um sensor biomimético catecol oxidase, baseado em um novo complexo cobre(II) foi desenvolvido para determinação de catequina em chá verde e os resultados comparados com os obtidos por eletroforese capilar. O complexo dinuclear de cobre(II) [Cu 2 (HL)(µ-CH 3 COO)] (ClO 4 ), contendo o ligante N,N-[bis-(2-piridilmetil)]-N',N'-[(2-hidroxibenzil)(2-hidroxi-3,5-di-tert-butilbenzil)]-1,3-propanodiamino-2-ol (H 3 L), foi sintetizado e caracterizado por IV, 1 H RMN e análise elementar. As melhores condições para otimização do sensor biomimético foram estabelecidas por voltametria de onda quadrada. O melhor desempenho desse sensor foi obtido em 75:15:10% (m/m/m) de pó de grafite:nujol:complexo de cobre(II), tampão fosfato 0,05 mol L -1 (pH 7,5) e freqüência, amplitude de potencial, incremento em 30 Hz, 80 mV, 3,3 mV, respectivamente. A curva analítica foi linear na faixa de concentração 4,95 × 10 -6 a 3,27 × 10 -5 mol L -1 (r=0,9993) com limite de detecção de 2,8 × 10 -7 mol L -1 . Esse sensor biomimético demonstrou longo tempo de estabilidade (9 meses; 800 determinações) e reprodutibilidade com um desvio padrão relativo de 3,5%. A recuperação da catequina em amostras de chá verde variou de 93,8 a 106,9% e a determinação, comparada com a obtida usando eletroforese capilar, mostrou-se aceitável a um nível de confiança de 95%.A catechol oxidase biomimetic sensor, based on a novel copper(II) complex, was developed for the determination of catechin in green tea and the results were compared with those obtained by capillary electrophoresis. The dinuclear copper(II) complex, [Cu 2 (HL)(µ-CH 3 COO)](ClO 4 ), containing the ligand N,N-[bis-(2-pyridylmethyl)]-N',N'-[(2-hydroxybenzyl)(2-hydroxy-3,5-ditert-butylbenzyl)]-1,3-propanediamine-2-ol (H 3 L), was synthesized and characterized by IR, 1 H NMR and elemental analysis. The best conditions for the optimization of the biomimetic sensor were established by square wave voltammetry. The best performance for this sensor was obtained in 75:15:10% (m/m/m) of the graphite powder:nujol:copper(II) complex, 0.05 mol L -1 phosphate buffer solution (pH 7.5) and frequency, pulse amplitude, scan increment at 30 Hz, 80 mV, 3.3 mV, respectively. The analytical curve was linear in the concentration range 4.95 × 10 -6 to 3.27 × 10 -5 mol L -1 (r = 0.9993) with a detection limit of 2.8 × 10 -7 mol L -1 . This biomimetic sensor demonstrated long-term stability (9 months; 800 determinations) and reproducibility with a relative standard deviation of 3.5%. The recovery of catechin from green tea samples ranged from 93.8 to 106.9% and the determination, compared with that obtained using capillary electrophoresis, was found to be acceptable at the 95% confidence level.Keywords: catechin, green tea, biomimetic sensor, square wave voltammetry IntroductionTea is one of the most consumed beverages in the world and was firstly used in China for its medicinal properties 5000 years ago. Recent epidemiological studies have shown that the consumption of tea may help to prevent cancers in humans because the tea l...

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New mononuclear CuII and ZnII complexes capable of stabilizing phenoxyl radicals as models for the active form of galactose oxidase

Cited by 24 publications

References 37 publications

Probing the role of the divalent metal ion in uteroferrin using metal ion replacement and a comparison to isostructural biomimetics

Probing the role of the divalent metal ion in uteroferrin using metal ion replacement and a comparison to isostructural biomimetics

Ten Years of a Biomimetic Approach to the Copper(II) Radical Site of Galactose Oxidase

Determination of catechin in green tea using a catechol oxidase biomimetic sensor

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