Binuclear metallohydrolases are a structurally diverse group of enzymes that use binuclear metal ion centers to catalyze the hydrolysis of amides and esters of carboxylic and phosphoric acids. A ...current understanding of metallohydrolase-catalyzed reactions is presented.
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Herein, we report the synthesis and characterization, through elemental analysis, electronic spectroscopy, electrochemistry, potentiometric titration, electron paramagnetic resonance, and ...magnetochemistry, of two dinuclear copper(II) complexes, using the unsymmetrical ligands N′,N′,N-tris(2-pyridylmethyl)-N-(2-hydroxy-3,5-di-tert-butylbenzyl)-1,3-propanediamin-2-ol (L1) and N′,N′-bis(2-pyridylmethyl)-N,N-(2-hydroxybenzyl)(2-hydroxy-3,5-di-tert-butylbenzyl)-1,3-propanediamin-2-ol (L2). The structures of the complexes Cu2(L1)(μ-OAc)(ClO4)2·(CH3)2CHOH (1) and Cu2(L2)(μ-OAc)(ClO4)·H2O·(CH3)2CHOH (2) were determined by X-ray crystallography. The complex Cu2(L3)(μ-OAc)2+ 3; L3 = N-(2-hydroxybenzyl)-N′,N′,N-tris(2-pyridylmethyl)-1,3-propanediamin-2-ol was included in this study for comparison purposes only (Neves et al. Inorg. Chim. Acta 2005, 358, 1807–1822). Magnetic data show that the CuII centers in 1 and 2 are antiferromagnetically coupled and that the difference in the exchange coupling J found for these complexes (J = −4.3 cm–1 for 1 and J = −40.0 cm–1 for 2) is a function of the Cu–O–Cu bridging angle. In addition, 1 and 2 were tested as catalysts in the oxidation of the model substrate 3,5-di-tert-butylcatechol and can be considered as functional models for catechol oxidase. Because these complexes possess labile sites in their structures and in solution they have a potential nucleophile constituted by a terminal CuII-bound hydroxo group, their activity toward hydrolysis of the model substrate 2,4-bis(dinitrophenyl)phosphate and DNA was also investigated. Double electrophilic activation of the phosphodiester by monodentate coordination to the CuII center that contains the phenol group with tert-butyl substituents and hydrogen bonding of the protonated phenol with the phosphate O atom are proposed to increase the hydrolase activity (K ass. and k cat.) of 1 and 2 in comparison with that found for complex 3. In fact, complexes 1 and 2 show both oxidoreductase and hydrolase/nuclease activities and can thus be regarded as man-made models for studying catalytic promiscuity.
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Herein, we report the synthesis and characterization of the new di-iron(III) complex (bbpmp)(H2O)(Cl)FeIII(μ-Ophenoxo)FeIII(H2O)Cl)Cl (1), with the symmetrical ligand ...2,6-bis{(2-hydroxybenzyl)(pyridin-2-yl)methylaminomethyl}-4-methylphenol (H3bbpmp). Complexes 2 with the unsymmetrical ligand H2bpbpmp — {2-(2-hydroxybenzyl)(2-pyridylmethyl)aminomethyl-6-bis(pyridylmethyl) aminomethyl}-4-methylphenol and 3 with the ligand L1=4,11-dimethyl-1,8-bis{2-N-(di-2-pyridylmethyl)aminoethyl}cyclam were included for comparison purposes. Complex 1 was characterized through elemental analysis, X-ray crystallography, magnetochemistry, electronic spectroscopy, electrochemistry, mass spectrometry and potentiometric titration. The magnetic data show a very weak antiferromagnetic coupling between the two iron centers of the dinuclear complex 1 (J=−0.29cm−1). Due to the presence of labile coordination sites in both iron centers the hydrolysis of both the diester model substrate 2,4-BDNPP and DNA was studied in detail. Complex 1 was also able to catalyze the oxidation of the substrate 3,5-di-tert-butylcatechol (3,5-DTBC) to give the corresponding quinone, and thus it can be considered as a catalytically promiscuous system.
The synthesis, X-ray structure and catalytic promiscuity (diesterase and catecholase activity) of a new dinuclear FeIII complex are here reported. Display omitted
•Dinuclear Iron(III) complex using a symmetric ligand•Synthesis, X-ray structure, magnetic properties and solution studies of the dinuclear catalyst•Ability of the complex to catalyze different reactions (catalytic promiscuity)
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
In this report, we demonstrate how UV-light exposure can enhance DNA cleavage promoted by two copper(II) complexes of tetracyclines and 1,10-phenanthroline about 40 times in comparison to ...nonirradiated conditions. In addition, new aspects regarding their DNA binding properties, as well as the mechanism of the cleavage reaction, were also investigated.
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A gold electrode surface was modified using a dinuclear copper complex Cu
II
2 (Ldtb)(μ-OCH
3)(BPh
4) and then coated with a chitosan film. This biomimetic polymer film-coated electrode was employed ...to eliminate the interference from ascorbic acid and uric acid in the sensitive and selective determination of dopamine. The optimized conditions obtained for the biomimetic electrode were 0.1
M phosphate buffer solution (pH 8.0), complex concentration of 2.0
×
10
−4
M, 0.1% of chitosan and 0.25% of glyoxal. Under the optimum conditions, the calibration curve was linear in the concentration range of 4.99
×
10
−7 to 1.92
×
10
−5
M, and detection and quantification limits were 3.57
×
10
−7
M and 1.07
×
10
−6
M, respectively. The recovery study gave values of 95.2–102.6%. The lifetime of this biomimetic sensor showed apparent loss of activity after 70 determinations. The results obtained with the modified electrode for dopamine quantification in the injection solution matrix were in good agreement with those of the pharmacopoeia method.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Described herein is the synthesis, structure, and monoesterase and diesterase activities of a new mononuclear LaIII(L1)(NO3)2 (1) complex (H2L1 = ...2-bis{(2-pyridylmethyl)-aminomethyl}-6-N-(2-pyridylmethyl) aminomethyl))-4-methyl-6-formylphenol) in the hydrolysis of 2,4-bis(dinitrophenyl)phosphate (2,4-BDNPP). When covalently linked to 3-aminopropyl-functionalized silica, 1 undergoes disproportionation to form a dinuclear species (APS-1), whose catalytic efficiency is increased when compared to the homogeneous reaction due to second coordination sphere effects which increase the substrate to complex association constant. The anchored catalyst APS-1 can be recovered and reused for subsequent hydrolysis reactions (five times) with only a slight loss in activity. In the presence of DNA, we suggest that 1 is also converted into the dinuclear active species as observed with APS-1, and both were shown to be efficient in DNA cleavage.
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Purple acid phosphatases (PAPs) are a group of metallohydrolases that contain a dinuclear FeIIIMII center (MII = Fe, Mn, Zn) in the active site and are able to catalyze the hydrolysis of a variety of ...phosphoric acid esters. The dinuclear complex (H2O)FeIII(μ-OH)ZnII(L-H)(ClO4)2 (2) with the ligand 2-N-bis(2-pyridylmethyl)aminomethyl-4-methyl-6-N′-(2-pyridylmethyl)(2-hydroxybenzyl) aminomethylphenol (H2 L-H) has recently been prepared and is found to closely mimic the coordination environment of the FeIIIZnII active site found in red kidney bean PAP (Neves et al. J. Am. Chem. Soc. 2007, 129, 7486). The biomimetic shows significant catalytic activity in hydrolytic reactions. By using a variety of structural, spectroscopic, and computational techniques the electronic structure of the FeIII center of this biomimetic complex was determined. In the solid state the electronic ground state reflects the rhombically distorted FeIIIN2O4 octahedron with a dominant tetragonal compression aligned along the μ-OH−Fe−Ophenolate direction. To probe the role of the Fe−Ophenolate bond, the phenolate moiety was modified to contain electron-donating or -withdrawing groups (−CH3, −H, −Br, −NO2) in the 5-position. The effects of the substituents on the electronic properties of the biomimetic complexes were studied with a range of experimental and computational techniques. This study establishes benchmarks against accurate crystallographic structural information using spectroscopic techniques that are not restricted to single crystals. Kinetic studies on the hydrolysis reaction revealed that the phosphodiesterase activity increases in the order −NO2 ←Br ←H ←CH3 when 2,4-bis(dinitrophenyl)phosphate (2,4-bdnpp) was used as substrate, and a linear free energy relationship is found when log(k cat/k 0) is plotted against the Hammett parameter σ. However, nuclease activity measurements in the cleavage of double stranded DNA showed that the complexes containing the electron-withdrawing −NO2 and electron-donating −CH3 groups are the most active while the cytotoxic activity of the biomimetics on leukemia and lung tumoral cells is highest for complexes with electron-donating groups.
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Three new α,α′-diimine ligands were synthesized based on condensation of 1,10-phenanthroline-5,6-dione with 1,2-phenylenediamine derivatives using different approaches. All compounds were fully ...characterized by IR,
1H and
13C NMR, UV–visible, and MS spectroscopies. We report the first example of a dipyrido3,2-
f:2′,3′-
hquinoxalino2,3-
bquinoxaline, which exhibits a strong absorption at 430
nm and an interesting electrochemical behavior. These new molecules may have biological potential and are of synthetic and technological importance.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
A new tetranuclear copper(II) complex which mimics the active site of catechol oxidase was synthesized and characterized by IR, CHN, electronic spectroscopic and
1H NMR methods. The title complex Cu
...2(μ-OH)(bpbpmp-NO
2)
2ClO
4
2 was employed in the construction of a novel biomimetic sensor and used in the determination of chlorogenic acid by square wave voltammetry. The performance and optimization of the resulting biomimetic sensor were studied in detail. The best response of this sensor was obtained for 75:15:10% (w/w/w) ratio of the graphite powder:nujol:Cu(II) complex, 0.1
mol
L
−1 phosphate buffer solution (pH 7.0), with frequency, pulse amplitude, and scan increment at 30
Hz, 100
mV, and 3.0
mV, respectively. The chlorogenic acid concentration was linear in the range of 5.0
×
10
−6 to 1.45
×
10
−4
mol
L
−1 (
r
=
0.9985) with a detection limit of 8.0
×
10
−7
mol
L
−1. This biomimetic sensor demonstrated long-term stability (250 days; 640 determinations) and reproducibility, with a relative standard deviation of 10.0%. The recovery study of chlorogenic acid in coffee samples gave values from 93.2% to 106.1% and the concentrations determined showed good agreement when compared with those obtained using capillary electrophoresis at the 95% confidence level.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Three new iron(III) complexes with the ligand N,N‘-bis(2-hydroxybenzyl)-N,N‘-bis(pyridin-2-ylmethyl)ethylenediamine, H2bbpen, containing electron-donating and -withdrawing groups (Me, Br, NO2) in the ...5-position of the phenol rings were synthesized and fully characterized by IR spectroscopy, ESI mass spectrometry, and CHN elemental analyses. X-ray structures of the iron(III) complexes containing NO2 and Me groups were determined. The effects of the substituents on the electronic properties of the complexes were detected by UV−visible spectroscopy, cyclic voltammetry, and X-ray crystallography. Linear correlations between the Hammett parameter for the substituents (σp) and the FeIII/FeII redox potentials or ligand−metal charge-transfer (LMCT) processes of the complexes were obtained. A theoretical study using DFT is presented and shows good agreement between the experimental and calculated data.
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