RESUMEN

We report the discovery that the molecule 1-(pyridin-2-ylmethylamino)propan-2-ol (HL) can reduce oxidative stress in neuronal C6 glioma cells exposed to reactive oxygen species (O2-•, H2O2, and •OH) and metal (Cu+) stress conditions. Furthermore, its association with Cu2+ generates [Cu(HL)Cl2] (1) and [Cu(HL)2](ClO4)2 (2) complexes that also exhibit antioxidant properties. Potentiometric titration data show that HL can coordinate to Cu2+ in 1:1 and 1:2 Cu2+:ligand ratios, which was confirmed by monocrystal X-ray studies. The subsequent ultraviolet-visible, electrospray ionization mass spectrometry, and electron paramagnetic resonance experiments show that they can decompose a variety of reactive oxygen species (ROS). Kinetic studies revealed that 1 and 2 mimic the superoxide dismutase and catalase activities. Complex 1 promotes the fastest decomposition of H2O2 (kobs = 2.32 × 107 M-1 s-1), efficiently dismutases the superoxide anion (kcat = 3.08 × 107 M-1 s-1), and scavenges the hydroxyl radical (RSA50 = 25.7 × 10-6 M). Density functional theory calculations support the formation of dinuclear Cu-peroxide and mononuclear Cu-superoxide species in the reactions of [Cu(HL)Cl2] with H2O2 and O2•-, respectively. Furthermore, both 1 and 2 also reduce the oxidative stress of neuronal glioma C6 cells exposed to different ROS, including O2•- and •OH.

Asunto(s)

Antioxidantes , Complejos de Coordinación , Cobre , Estrés Oxidativo , Cobre/química , Cobre/farmacología , Estrés Oxidativo/efectos de los fármacos , Complejos de Coordinación/química , Complejos de Coordinación/farmacología , Complejos de Coordinación/síntesis química , Antioxidantes/farmacología , Antioxidantes/química , Antioxidantes/síntesis química , Teoría Funcional de la Densidad , Especies Reactivas de Oxígeno/metabolismo , Catálisis , Animales , Estructura Molecular , Línea Celular Tumoral , Ratas , Humanos

RESUMEN

A ratiometric electrochemical sensor based on a carbon paste electrode modified with quinazoline-engineered ZnFe Prussian blue analogue (PBA-qnz) was developed for the determination of herbicide butralin. The PBA-qnz was synthesized by mixing an excess aqueous solution of zinc chloride with an aqueous solution of precursor sodium pentacyanido(quinazoline)ferrate. The PBA-qnz was characterized by spectroscopic and electrochemical techniques. The stable signal of PBA-qnz at +0.15 V vs. Ag/AgCl, referring to the reduction of iron ions, was used as an internal reference for the ratiometric sensor, which minimized deviations among multiple assays and improved the precision of the method. Furthermore, the PBA-qnz-based sensor provided higher current responses for butralin compared to the bare carbon paste electrode. The calibration plot for butralin was obtained by square wave voltammetry in the range of 0.5 to 30.0 µmol L-1, with a limit of detection of 0.17 µmol L-1. The ratiometric sensor showed excellent precision and accuracy and was applied to determine butralin in lettuce and potato samples.

RESUMEN

A new cis-dihalo copper(II) complex, [CuII(HLbz)(Cl)2].CH3CN (1), where HLbz = (S)-2-(((2-(2-(pyridin-2-yl)-2H-benzo[e][1,3]oxazin-3(4H)-yl)ethyl)amino)methyl)phenol), was isolated by reacting copper(II) chloride dihydrate and the H2L ligand (H2L = 2,2'-((2-(pyridin-2-yl)imidazolidine-1,3-diyl)bis(methylene))diphenol) in a MeOH/CH3CN (1:3 v/v) mixture. The complex formation occurred via the ligand modification during complexation, producing a unique structure containing 2H-benzo[e][1,3]oxazin, as observed from the single crystal X-ray structure determination. The complex was characterized by elemental analysis, potentiometric titration, spectroscopic techniques (UV-Vis, FT-IR) and conductance measurements. Complex 1 inhibits the growth of myelogenous leukemia cells with an IC50 of 17.3 µmol L-1.

Asunto(s)

Cobre , Fenoles , Cobre/química , Cristalografía por Rayos X , Ligandos , Espectroscopía Infrarroja por Transformada de Fourier

RESUMEN

Herein, we report the synthesis and characterization of the first two AlIII(µ-OH)MII (M = Zn (1) and Cu (2)) complexes with the unsymmetrical ligand H2L{2-[[(2-hydroxybenzyl)(2-pyridylmethyl)]aminomethyl]-6-bis(pyridylmethyl)aminomethyl}-4-methylphenol. The complexes were characterized through elemental analysis, X-ray crystallography, IR spectroscopy, mass spectrometry and potentiometric titration. In addition, complex 2 was characterized by electronic spectroscopy. Kinetics studies on the hydrolysis of the model substrate bis(2,4-dinitrophenyl)phosphate by 1 and 2 show Michaelis-Menten behavior, with 1 being slightly more active (8.31%) than 2 (at pH 7.0). The antimicrobial effect of the compounds was studied using four bacterial strains (Staphylococcus aureus, Pseudomonas aeuruginosa, Shigella sonnei and Shigella dysenteriae) and for both complexes the inhibition of bacterial growth was superior to that caused by sulfapyridine, but inferior to that of tetracycline. The dark cytotoxicity and photocytotoxicity (under UV-A light) of the complexes in a chronic myelogenous leukemia cell line were investigated. Complexes 1 and 2 exhibited significant cytotoxic activity against K562 cells, which undergoes a 2-fold increase on applying 5 min of irradiation with UV-A light. Complex 2 was more effective and a good correlation between cytotoxicity and intracellular concentration was observed, the intracellular copper concentration required to inhibit 50% of cell growth being 3.5 × 10-15 mol cell-1.

Asunto(s)

Aluminio/farmacología , Antineoplásicos/farmacología , Complejos de Coordinación/farmacología , Cobre/farmacología , Monoéster Fosfórico Hidrolasas/metabolismo , Zinc/farmacología , Aluminio/química , Antiinfecciosos/farmacología , Bacterias/efectos de los fármacos , Supervivencia Celular/efectos de los fármacos , Complejos de Coordinación/química , Cobre/química , Cristalografía por Rayos X/métodos , Humanos , Hidrólisis , Células K562 , Cinética , Ligandos , Espectrometría de Masas/métodos , Zinc/química

RESUMEN

In isolated isoniazid (INH)-resistant strains, deletion or mutations in thekatGgene have been identified, which result in loss of catalase-peroxidase activity. This enzyme plays a key role in the activation of this prodrug. As an alternative, the coordination of the INH to metal complexes has been purposed to activate it regardless of enzyme functionality. Although pentacyanido(isoniazid)ferrate(II) complexes have shown to be effective against resistant strains of Mycobacterium tuberculosis, low oral bioavailability was found. In this context, buccal mucosa was selected as an alternative route to the metal complex delivery. Moreover, oral manifestations of tuberculosis(TB) have been observed in some patients, particularly when resistant strains are present, and no therapeutic options are currently available on the market. Pentacyanidoferrate (PCF-INH) and Prussian-blue (PB-INH) complexes were initially prepared and characterized, followed by buccal permeability studies in Franz-type diffusion cells. The electrochemical potential of the complexes demonstrated their ability to self-activate. Job's method suggested the presence of structural defects in PB-INH complexes, which was correlated with permeability results. In fact, PB-INH showed a higher dissociation rate in salt-rich aqueous medium and thus a high transport rate of INH through the buccal mucosa. Its passage through the tissue would not be possible due to the high molecular size. PCF-INH, in turn, presented a lower dissociation rate in the salt-rich aqueous medium, justifying its slower transport rate through the tissue. Taken together, these results suggest that INH-based metal complexes may be efficiently administered through the buccal route, impacting on both oral bioavailability and microbial resistance.

Asunto(s)

Complejos de Coordinación , Mycobacterium tuberculosis , Antituberculosos/farmacología , Proteínas Bacterianas , Catalasa , Farmacorresistencia Bacteriana , Humanos , Isoniazida , Pruebas de Sensibilidad Microbiana , Mutación

RESUMEN

The analysis of oil paints present in historical paintings is commonly carried out for research, authenticity and forensic purposes. This paper proposes potentiometric titration and calculation of the fatty acids concentrations with the aid of the Best7 program as an alternative technique to characterize the oil binders used in works of art. The method involves determining the ratio between the levels of palmitic (P) and stearic (S) acids present in the microhydrolysis products of commercial oil binders and paints. The microhydrolysis products were characterized, using FTIR spectroscopy, by displacement of the carbonyl band and the pKa values for the C16 and C18 in the system studied were determined. The P/S ratios found for the microhydrolysis products of linseed, palm and nut oils were 1.65, 5.91 and 2.42, respectively. For the commercial paints analyzed, values ranging from 1.34 to 1.98 were obtained, characterizing the presence of linseed oil. The values were confirmed by GC-MS and are in agreement with those reported in the literature for the oils investigated in this study.

RESUMEN

As part of efforts to reduce pressure on the Amazon and other biomes, one approach considered by Brazilian authorities and scientists is more intensive use of the soils of the interior of the northeast of the country, which are generally sandy, with low contents of organic matter and low water holding capacity and are frequently affected by severe droughts. In this work, biochars produced from waste biomasses were tested for the improvement of these soils. The highest BET (Brunauer-Emmett-Teller) specific surface areas were observed for all biochars. In the pH range studied, the water hyacinth plants (WH) sample showed the most negative zeta potentials, as well as the highest water holding capacity (WHC) values, while the zeta potentials of two quartzarenic neosol soils were consistent with their WHC values. The results suggested that despite the effect of porosity on water retention, the zeta potential could be associated with the presence of negative charges by which hydrated cationic counterions were absorbed and retained. The surface energy and its polar and dispersive components were associated with water retention, with sugar cane bagasse, orange peel, and water hyacinth biochars presenting higher SE values and larger polar components.

RESUMEN

We describe herein the catecholase-like catalytic activity and dopamine polymerization by using a dinuclear [LCuII(µ-OH)2CuII](ClO4)2 (1) complex where L is the dinucleating triazine-based ligand 6-chloro-N2,N2,N4,N4-tetrakis(pyridin-2-ylmethyl)-1,3,5-triazine-2,4-diamine. The kinetic parameters (kcat = 0.318 s-1, KM = 1.6 × 10-3 mol L-1, and kcat/KM = 198.8 L s-1 mol-1), mechanistic insights into the oxidation of 3,5-di-tert-butyl catechol and early characterization of poly(dopamine) are presented.

Asunto(s)

Materiales Biomiméticos/química , Catecol Oxidasa/química , Complejos de Coordinación/química , Cobre/química , Indoles/química , Polímeros/química , Triazinas/química , Ligandos , Estructura Molecular , Polimerizacion , Propiedades de Superficie

RESUMEN

The synthesis, physico-chemical characterization and cytotoxicity of four new ligands and their respective copper(II) complexes toward two human leukemia cell lines (THP-1 and U937) are reported (i.e. [(HL1)Cu(µ-Cl)2Cu(HL1)]Cl2·H2O (1), [(H2L2)Cu(µ-Cl)2Cu(H2L2)]Cl2·5H2O (2), [(HL3)Cu(µ-Cl)2Cu(HL3)]Cl2·4H2O (3), [(H2L4)Cu(µ-Cl)2Cu(H2L4)]Cl2·6H2O (4)). Ligands HL1 and HL3 contain two pyridines, amine and alcohol moieties with a naphthyl pendant unit yielding a N3O coordination metal environment. Ligands H2L2 and H2L4 have pyridine, phenol, amine and alcohol groups with a naphthyl pendant unit providing a N2O2 coordination metal environment. These compounds are likely to be dinuclear in the solid state but form mononuclear species in solution. The complexes have an antiproliferative effect against both leukemia cell lines; complex (2) exhibits higher activity than cisplatin against U937 (8.20 vs 16.25µmoldm(-3)) and a comparable one against THP-1. These human neoplastic cells are also more susceptible than peripheral blood mononuclear cells (PBMCs) toward the tested compounds. Using C57BL/6 mice an LD50 of 55mgkg(-1) was determined for complex (2), suggesting that this compound is almost four times less toxic than cisplatin (LD50=14.5mgkg(-1)). The mechanism of cell death promoted by ligand H2L2 and by complexes (2) and (4) was investigated by a range of techniques demonstrating that the apoptosis signal triggered at least by complex (2) starts from an extrinsic pathway involving the activation of caspases 4 and 8. This signal is amplified by mitochondria with the concomitant release of cytochrome c and the activation of caspase 9.

Asunto(s)

Antineoplásicos/farmacología , Apoptosis/efectos de los fármacos , Complejos de Coordinación/farmacología , Cobre/química , Naftalenos/farmacología , Receptores de Muerte Celular/metabolismo , Animales , Antineoplásicos/síntesis química , Antineoplásicos/química , Antineoplásicos/toxicidad , Caspasas/metabolismo , Puntos de Control del Ciclo Celular/efectos de los fármacos , Cisplatino/farmacología , Complejos de Coordinación/síntesis química , Complejos de Coordinación/química , Complejos de Coordinación/toxicidad , Citocromos c/análisis , Fragmentación del ADN/efectos de los fármacos , Femenino , Humanos , Ligandos , Masculino , Potencial de la Membrana Mitocondrial/efectos de los fármacos , Ratones , Ratones Endogámicos C57BL , Naftalenos/síntesis química , Naftalenos/química , Naftalenos/toxicidad , Células U937

RESUMEN

We describe herein a novel type of monodisperse water-soluble magnetite nanoparticle coated with pheomelanin using an environmentally-friendly approach in aqueous medium. The results indicate superparamagnetic behaviour at room temperature and show improved negative contrast in T2-weighted MRI with a transverse relaxivity of 218 mM(-1) s(-1).

Asunto(s)

Medios de Contraste/química , Compuestos Férricos/química , Imagen por Resonancia Magnética , Nanopartículas de Magnetita/química , Melaninas/química

RESUMEN

A new carboxylate rich asymmetric tripodal ligand, N-[2-carboxybenzomethyl]-N-[carboxymethyl]-ß-alanine (H3camb), and its di-copper(II), (NH4)2[1]2, and di-zinc(II), ((CH3)4N)2[2]2, complexes have been synthesized as carbohydrate binding models in aqueous solutions. The ligand and complexes have been fully characterized using several techniques, including single crystal X-ray diffraction. The interactions of (NH4)2[1]2 and ((CH3)4N)2[2]2 with D-glucose, D-mannose, D-xylose and xylitol in aqueous alkaline media were investigated using UV-Vis and (13)C-NMR spectroscopic techniques, respectively. The molar conductance, NMR and ESI-MS studies indicate that the complexes dissociate in solution to produce the respective complex anions, 1(-) and 2(-). Complexes 1(-) and 2(-) showed chelating ability towards the naturally abundant and biologically relevant sugars, D-glucose, D-mannose, D-xylose, and xylitol. The complex ions bind to one molar equivalent of the sugars, even in the presence of stoichiometric excess of the substrates, in solution. Experimentally obtained spectroscopic data and computational results suggest that the substrates bind to the metal center in a bidentate fashion. Apparent binding constant values, pK(app), between the complexes and the substrates were determined and a specific mode of substrate binding is proposed. The pK(app) and relativistic density functional theory (DFT) calculated Gibbs free energy values indicate that D-mannose displayed the strongest interaction with the complexes. Syntheses, characterizations, detailed substrate binding studies using spectroscopic techniques, single crystal X-ray diffraction and geometry optimizations of the complex-substrates with DFT calculations are also reported.

Asunto(s)

Ácidos Carboxílicos/química , Complejos de Coordinación/síntesis química , Cobre/química , Monosacáridos/química , Zinc/química , Álcalis/química , Complejos de Coordinación/química , Ligandos

RESUMEN

Described herein is the synthesis, structure, and monoesterase and diesterase activities of a new mononuclear [La(III)(L(1))(NO3)2] (1) complex (H2L(1) = 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.

Asunto(s)

Lantano/química , Fosfatos/química , Dióxido de Silicio/química , Catálisis , Ésteres , Hidrólisis , Difracción de Rayos X

RESUMEN

Here we present the synthesis of the dinuclear complex [Cu(II)2(L)Cl3] (1), where L is the deprotonated form of the 3-[(4,7-diisopropyl-1,4,7-triazacyclononan-1-yl)methyl]-2-hydroxy-5-methylbenzaldehyde ligand. The complex was characterized by single crystal X-ray diffraction, potentiometric titration, mass spectrometry, electrochemical and magnetic measurements, EPR, UV-Vis and IR. Complex 1 is able to increase the hydrolysis rate of the diester bis-(2,4-dinitrophenyl)phosphate (2,4-BDNPP) by a factor of 2700, and also to promote the plasmidial DNA cleavage at pH 6 and to inhibit the formazan chromophore formation in redox processes at pH 7. Using Saccharomyces cerevisiae (BY4741) as a eukaryotic cellular model, we observed that 1 presents reduced cytotoxicity. In addition, treatment of wild-type and mutant cells lacking Cu/Zn-superoxide dismutase (Sod1) and cytoplasmic catalase (Ctt1) with 1 promotes increased survival after H2O2 or menadione (O2˙(-) generator) stress, indicating that 1 might act as a Sod1 and Ctt1 mimetic. Considered together, these results support considerations regarding the dynamic behaviour of an unsymmetrical dinuclear copper(II) complex in solid state and in aqueous pH-dependent solution.

Asunto(s)

Complejos de Coordinación/química , Cobre/química , Compuestos Heterocíclicos/química , Antioxidantes/química , Antioxidantes/metabolismo , Materiales Biomiméticos/síntesis química , Materiales Biomiméticos/metabolismo , Materiales Biomiméticos/farmacología , Catálisis , Complejos de Coordinación/metabolismo , Complejos de Coordinación/farmacología , Cristalografía por Rayos X , ADN/química , ADN/metabolismo , División del ADN , Concentración de Iones de Hidrógeno , Cinética , Ligandos , Magnetismo , Conformación Molecular , Saccharomyces cerevisiae/efectos de los fármacos , Superóxido Dismutasa/metabolismo , Temperatura

RESUMEN

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 [Cu(2)(L1)(µ-OAc)](ClO(4))(2)·(CH(3))(2)CHOH (1) and [Cu(2)(L2)(µ-OAc)](ClO(4))·H(2)O·(CH(3))(2)CHOH (2) were determined by X-ray crystallography. The complex [Cu(2)(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. Acta2005, 358, 1807-1822). Magnetic data show that the Cu(II) 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 Cu(II)-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 Cu(II) 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.

Asunto(s)

Catecol Oxidasa/química , Cobre/química , Hidrolasas/química , Modelos Moleculares , Catálisis , Cristalografía por Rayos X , Espectroscopía de Resonancia por Spin del Electrón , Espectrofotometría Infrarroja

RESUMEN

In this study, chitosan (CTS) was crosslinked with both epichlorohydrin (ECH) and triphosphate (TPP), by covalent and ionic crosslinking, respectively. The resulting new CTS-ECH-TPP adsorbent was characterized by CHN analysis, EDS, FTIR spectroscopy, TGA and DSC, and the adsorption and desorption of Cu(II), Cd(II) and Pb(II) ions in aqueous solution were investigated. Potentiometric studies were also performed and revealed three titratable protons for each pK(a) value of 5.14, 6.76 and 9.08. The results obtained showed that the optimum pH values for adsorption were 6.0 for Cu(II), 7.0 for Cd(II) and 5.0 for Pb(II). The kinetics study demonstrated that the adsorption process proceeded according to the pseudo-second-order model. Three isotherm models (Langmuir, Freundlich and Dubinin-Radushkevich) were employed in the analysis of the adsorption equilibrium data. The Langmuir model resulted in the best fit and the new adsorbent had maximum adsorption capacities for Cu(II), Cd(II) and Pb(II) ions of 130.72, 83.75 and 166.94 mg g(-1), respectively. Desorption studies revealed that HNO(3) and HCl were the best eluents for desorption of Cu(II), Cd(II) and Pb(II) ions from the crosslinked chitosan.

Asunto(s)

Adsorción , Quitosano/química , Metales Pesados/aislamiento & purificación , Cadmio/aislamiento & purificación , Cobre/aislamiento & purificación , Reactivos de Enlaces Cruzados , Epiclorhidrina/química , Cinética , Plomo/aislamiento & purificación , Contaminantes Químicos del Agua/aislamiento & purificación

RESUMEN

The synthesis and structures of two new isostructural mononuclear [Ln(L)(NO(3))(H(2)O)(3)](NO(3))(2) complexes, with Ln = Tb (complex 1) and Eu (complex 2), which display high activity in the hydrolysis of the substrate 2,4-bis(dinitrophenyl)phosphate, are reported. These complexes displayed catalytic behavior similar to the mononuclear gadolinium complex [Gd(L)(NO(3))(H(2)O)(3)](NO(3))(2) previously reported by us (Inorg. Chem. 2008, 47, 2919-2921); one hydrolysis reaction in two stages where the diesterase and monoesterase activities could be monitored separately, with the first stage dependent on and the second independent of the complex concentration. Through potentiometric studies, electrospray ionization mass spectrometry (ESI-MS) analysis, and determination of the kinetic behaviors of 1 and 2 in acetonitrile/water solution, the species present in solution could be identified and suggested a dinuclear species, with one hydroxo group, as the most prominent catalyst under mild conditions. The complexes show high activity (k(1) = 7 and 18 s(-1) for 1 and 2, respectively) and catalytic efficiency. Complexes 1 and 2 were found to be active toward the cleavage of plasmid DNA, and complete kinetic studies were carried out. Studies with a radical scavenger (dimethylsulfoxide) confirmed the hydrolytic action of 1 and 2 in the cleavage of DNA. Studies on the incubation of distamycin with plasmid DNA suggested that 1 and 2 are regio-specific, interacting with the minor groove of DNA. These complexes displayed luminescent properties. Complex 1 showed higher emission intensity than 2 due to a more efficient energy transfer between triplet and emission levels of terbium (T --> (5)D(4)), along with nonradiative deactivation mechanisms of the excited states of europium via multiphonon decays and the ligand-to-metal charge transfer state. Lifetime measurements of the (5)D(4) and (5)D(0) excited levels for 1 and 2, respectively, indicated the numbers of coordinated water molecules for the complexes.

Asunto(s)

Europio/química , Organofosfatos/química , Terbio/química , Catálisis , Cristalografía por Rayos X , ADN/química , Cinética , Luminiscencia , Modelos Moleculares , Plásmidos/química , Potenciometría , Espectrometría de Masa por Ionización de Electrospray , Espectrofotometría Infrarroja

RESUMEN

We report herein the characterization by electrospray ionization (ESI) mass spectrometry (MS), matrix assisted laser desorption ionization (MALDI-MS) and potentiometric titration of three iron(III) compounds: [Fe(III)(HPClNOL)Cl2]·NO3 (1), [Cl(HPClNOL)Fe(III)-(µ-O)-Fe(III)(HPClNOL)Cl]·Cl2·H2O (2) and [(SO4)(HPClNOL)Fe(III)-(µ-O)-Fe(III)(HPClNOL)(SO4)]·6H2O (3), where HPClNOL= 1-(bis-pyridin-2-ylmethyl-amino)-3-chloropropan-2-ol). Despite the fact that the compounds have distinct structures in solid state and non-buffered solution, all compounds present similar ESI and MALDI mass spectra in a buffered medium (pH 7.0). At this pH, the species [(PClNOL)Fe(III)-(µ-O)-Fe(III)(PClNOL)](2+) (m/z 354) was observed for all the compounds under investigation. Potentiometric titration confirms a similar behavior for all compounds, indicating that the dihydroxo form [(OH)(HPClNOL)Fe(III)-(µ-O)-Fe(III)(HPClNOL)(OH)](2+) is the major species at pH 7.0, for all the compounds. The products of the interaction between compounds (1), (2) and (3) and dAMP (2'-deoxyadenosine-5'-monophosphate) in a buffered medium (pH 7.0) were identified by MALDI-MS/MS. The fragmentation data obtained by MS/MS allow one to identify the nature of the interaction between the iron(III) compounds and dAMP, revealing the direct interaction between the iron center and phosphate groups.

Asunto(s)

Nucleótidos de Desoxiadenina/química , Compuestos Férricos/química , Compuestos Férricos/síntesis química , Concentración de Iones de Hidrógeno , Estructura Molecular , Potenciometría , Espectrometría de Masa por Ionización de Electrospray , Espectrometría de Masa por Láser de Matriz Asistida de Ionización Desorción

RESUMEN

The new trinuclear gadolinium complex [Gd(3)L(2)(NO(3))(2)(H(2)O)(4)]NO(3).8H(2)O (1) with the unsymmetrical ligand 2-[N-bis-(2-pyridylmethyl)aminomethyl]-4-methyl-6-[N-bis(2-hydroxy-2-oxoethyl)aminomethyl] phenol (H(3)L) was synthesized and characterized. The new ligand H(3)L was obtained in good yield. Complex 1 crystallizes in an orthorhombic cell, space group Pcab. Kinetic studies show that complex 1 is highly active in the hydrolysis of the substrate 2,4-bis(dinitrophenyl)phosphate (K(m) = 4.09 mM, V(max) = 2.68 x 10(-2) mM s(-1), and k(cat) = V(max)/[1] = 0.67 s(-1)). Through a potentiometric study and determination of the kinetic behavior of 1 in acetonitrile/water solution, the species present in solution could be identified, and a trinuclear monohydroxo species appears to be the most prominent catalyst under mild conditions. Complex 1 displays high efficiency in DNA hydrolytic cleavage, and complete kinetic studies were carried out (K(m) = 4.57 x 10(-4) M, k'(cat) = 3.42 h(-1), and k'(cat)/K(m) = 7.48 x 10(3) M(-1) h(-1)). Studies with a radical scavenger (dimethyl sulfoxide, DMSO) showed that it did not inhibit the activity, indicating the hydrolytic action of 1 in the cleavage of DNA, and studies on the incubation of distamycin with plasmid DNA suggest that 1 is regio-specific, interacting with the minor groove of DNA.

Asunto(s)

Desoxirribonucleasas/química , Gadolinio/química , Modelos Moleculares , Monoéster Fosfórico Hidrolasas/metabolismo , Cinética , Ligandos , Estructura Molecular , Espectrometría de Masa por Ionización de Electrospray , Espectrofotometría Infrarroja

RESUMEN

The design and development of suitable biomimetic catalytic systems capable of mimicking the functional properties of enzymes continues to be a challenge for bioinorganic chemists. In this study, we report on the synthesis, X-ray structures, and physicochemical characterization of the novel isostructural [Fe(III)Co(II)(BPBPMP)(mu-OAc)(2)]ClO(4) (1) and [Ga(III)Co(II)(BPBPMP)(mu-OAc)(2)]ClO(4) (2) complexes with the unsymmetrical dinucleating ligand H(2)BPBPMP (2-bis[{(2-pyridyl-methyl)-aminomethyl}-6-{(2-hydroxy-benzyl)-(2-pyridyl-methyl)}-aminomethyl]-4-methylphenol). The previously reported complex [Fe(III)Zn(II)(BPBPMP)(mu-OAc)(2)]ClO(4) (3) was investigated here by electron paramagnetic resonance for comparison with such studies on 1 and 2. A magneto-structural correlation between the exchange parameter J (cm(-1)) and the average bond lengh d (A) of the [Fe(III)-O-M(II)] structural unit for 1 and for related isostructural Fe(III)M(II) complexes using the correlation J = -10(7) exp(-6.8d) reveals that this parameter is the major factor that determines the degree of antiferromagnetic coupling in the series [(BPBPMP)Fe(III)(mu-OAc)(2)M(II)](+) (M(II) = Mn, Fe, Co, Ni) of complexes. Potentiometric and spectrophotometric titrations along with electronic absorption studies show that, in aqueous solution, complexes 1 and 2 generate the [(HO)M(III)(mu-OH)Co(II)(H(2)O)] complex as the catalytically active species in diester hydrolysis reactions. Kinetic studies on the hydrolysis of the model substrate bis(2,4-dinitrophenyl)phosphate by 1 and 2 show Michaelis-Menten behavior, with 2 being 35% more active than 1. In combination with k(H)/k(D) isotope effects, the kinetic studies suggest a mechanism in which a terminal M(III)-bound hydroxide is the hydrolysis-initiating nucleophilic catalyst. In addition, the complexes show maximum catalytic activity in DNA hydrolysis near physiological pH. The modest reactivity difference between 1 and 2 is consistent with the slightly increased nucleophilic character of the Ga(III)-OH terminal group in comparison to Fe(III)-OH in the dinuclear M(III)Co(II) species.

Asunto(s)

Fosfatasa Ácida/química , Fosfatasa Ácida/metabolismo , Biomimética , Cobalto/química , Compuestos Férricos/química , Galio/química , Glicoproteínas/química , Glicoproteínas/metabolismo , Absorción , Animales , Biocatálisis , Bovinos , Dicroismo Circular , ADN/metabolismo , Electroquímica , Espectroscopía de Resonancia por Spin del Electrón , Compuestos Férricos/metabolismo , Hidrólisis , Cinética , Magnetismo , Potenciometría , Volumetría

RESUMEN

The synthesis, structure, and hydrolase-like catalytic activity of a new mononuclear gadolinium complex [Gd(L)(NO3)(H2O)3](NO3)2 (1) are reported. A clean two-stage kinetic reaction for hydrolysis of the diester 2,4-bis(dinitrophenyl)phosphate by 1 was followed, and the rate constants were determined. A high DNA cleavage activity was also demonstrated. The active species in the hydrolytic process is proposed based on the X-ray structure, electrospray ionization mass spectrometry analysis, and kinetic and potentiometric equilibrium studies of 1.

Asunto(s)

Gadolinio , Hidrolasas/metabolismo , Catálisis , Hidrolasas/química , Hidrólisis , Cinética , Modelos Moleculares , Estructura Molecular