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1.
Mauricio Lanznaster Ademir Neves Adailton J. Bortoluzzi Veronika V. E. Aires Bruno Szpoganicz Hernán Terenzi Patricia Cardoso Severino Julie M. Fuller Simon C. Drew Lawrence R. Gahan Graeme R. Hanson Mark J. Riley Gerhard Schenk 《Journal of biological inorganic chemistry》2005,10(4):319-332
A novel heterobinuclear mixed valence complex [FeIIICuII(BPBPMP)(OAc)2]ClO4, 1, with the unsymmetrical N5O2 donor ligand 2-bis[{(2-pyridylmethyl)aminomethyl}-6-{(2-hydroxybenzyl)(2-pyridylmethyl)}aminomethyl]-4-methylphenol (H2BPBPMP) has been synthesized and characterized. A combination of data from mass spectrometry, potentiometric titrations, X-ray absorption and electron paramagnetic resonance spectroscopy, as well as kinetics measurements indicates that in ethanol/water solutions an [FeIII–()OH–CuIIOH2]+ species is generated which is the likely catalyst for 2,4-bis(dinitrophenyl)phosphate and DNA hydrolysis. Insofar as the data are consistent with the presence of an FeIII-bound hydroxide acting as a nucleophile during catalysis, 1 presents a suitable mimic for the hydrolytic enzyme purple acid phosphatase. Notably, 1 is significantly more reactive than its isostructural homologues with different metal composition (FeIIIMII, where MII is ZnII, MnII, NiII, or FeII). Of particular interest is the observation that cleavage of double-stranded plasmid DNA occurs even at very low concentrations of 1 (2.5 M), under physiological conditions (optimum pH of 7.0), with a rate enhancement of 2.7×107 over the uncatalyzed reaction. Thus, 1 is one of the most effective model complexes to date, mimicking the function of nucleases.Electronic Supplementary Material Supplementary material is available for this article at . 相似文献
2.
Two oxime-functionalized diazamesocyclic derivates, namely, N,N′-bis(acetophenoneoxime)-1,4-diazacycloheptane (H2L1) and N,N′-bis(acetophenonoxime)-1,5-diazacyclooctane (H2L2), have been prepared and characterized. Both ligands (obtained in the hydrochloride form) can form stable metal complexes with CuII and NiII salts, the crystal structures of which were determined by X-ray diffraction technique. The reactions of H2L1 with Cu(ClO4)2 and Ni(ClO4)2 afford a penta-coordinated mononuclear complex [Cu(H2L1)Cl] · ClO4 (1) and a four-coordinated monomeric [Ni(HL1)] · ClO4 (2), in which the ligand is monodeprotonated. The ligand H2L2 also forms a quite similar mononuclear [Ni(HL2)] · ClO4 complex with Ni(ClO4)2, according to our previous work. However, reactions of different CuII salts [Cu(ClO4)2, CuCl2 and Cu(NO3)2 for 3, and CuSO4 for 4] with H2L2 in the presence of NaClO4 yield two unusual mono-μ-Cl dinuclear CuII complexes [Cu2(HL2)2Cl] · (ClO4) (3), and [Cu2(H2L2)(HL2)Cl] · (ClO4)2 · (H2O)(4). These results indicate that the resultant CuII complexes (1, 3 and 4) are sensitive to the backbones of diazamesocycles and even auxiliary anions. 相似文献
3.
Xavier FR Peralta RA Bortoluzzi AJ Drago V Castellano EE Haase W Tomkowicz Z Neves A 《Journal of inorganic biochemistry》2011,105(12):1740-1752
In this work we report on the synthesis, crystal structure, and physicochemical characterization of the novel dinuclear [FeIIICdII(L)(μ-OAc)2]ClO4·0.5H2O (1) complex containing the unsymmetrical ligand H2L = 2-bis[{(2-pyridyl-methyl)-aminomethyl}-6-{(2-hydroxy-benzyl)-(2-pyridyl-methyl)}-aminomethyl]-4-methylphenol. Also, with this ligand, the tetranuclear [Fe2IIIHg2II(L)2(OH)2](ClO4)2·2CH3OH (2) and [FeIIIHgII(L)(μ-CO3)FeIIIHgII(L)](ClO4)2·H2O (3) complexes were synthesized and fully characterized. It is demonstrated that the precursor [FeIII2HgII2(L)2(OH)2](ClO4)2·2CH3OH (2) can be converted to (3) by the fixation of atmospheric CO2 since the crystal structure of the tetranuclear organometallic complex [FeIIIHgII(L)(μ-CO3)FeIIIHgII(L)](ClO4)2·H2O (3) with an unprecedented {FeIII(μ-Ophenoxo)2(μ-CO3)FeIII} core was obtained through X-ray crystallography. In the reaction 2 → 3 a nucleophilic attack of a FeIII-bound hydroxo group on the CO2 molecule is proposed. In addition, it is also demonstrated that complex (3) can regenerate complex (2) in aqueous/MeOH/NaOH solution. Magnetochemical studies reveal that the FeIII centers in 3 are antiferromagnetically coupled (J = − 7.2 cm− 1) and that the FeIII-OR-FeIII angle has no noticeable influence in the exchange coupling. Phosphatase-like activity studies in the hydrolysis of the model substrate bis(2,4-dinitrophenyl) phosphate (2,4-bdnpp) by 1 and 2 show Michaelis-Menten behavior with 1 being ~ 2.5 times more active than 2. In combination with kH/kD isotope effects, the kinetic studies suggest a mechanism in which a terminal FeIII-bound hydroxide is the hydrolysis-initiating nucleophilic catalyst for 1 and 2. Based on the crystal structures of 1 and 3, it is assumed that the relatively long FeIII…HgII distance could be responsible for the lower catalytic effectiveness of 2. 相似文献
4.
Kenji Maie Mitsunobu Nakamura Kazushige Yamana 《Nucleosides, nucleotides & nucleic acids》2013,32(4-6):453-462
Bis(ZnII-cyclen)-azobenzene derivative, which has two ZnII-macrocyclic tetraamine complexes connected through azobenzene spacer, has been synthesized as a cross-linking agent for double stranded DNA in aqueous solution. The ZnII-cyclen derivative selectively binds to A-T base pairs producing complexes between the ZnII-cyclen moiety and the imide-deprotonated thymine with breaking A-T base pairs. The azobenzene spacer undergoes cis/trans photoisomerization in the complex between the ZnII-cyclen derivative and the DNA duplex. The conformation of the DNA remarkably changed by photoisomerization of the azobenzene linker, when the ZnII-cyclen derivative binds to the DNA duplex with an interstrand cross-linking manner. 相似文献
5.
Christiane Fernandes Adolfo Horn Jr. Vagner M. de Assis Luciana da S. Mathias Adailton J. Bortoluzzi João Carlos Aquino Almeida 《Journal of inorganic biochemistry》2010,104(11):1214-1223
We synthesized iron(III), cobalt(II), copper(II) and zinc(II) complexes [FeIII(HBPClNOL)Cl2]·H2O (1), [CoII(H2BPClNOL)Cl2] (2), [CuII(H2BPClNOL)Cl]Cl·H2O (3), and [ZnII(HBPClNOL)Cl] (4), where H2BPClNOL is the ligand (N-(2-hydroxybenzyl)-N-(2-pyridylmethyl)[(3-chloro)(2-hydroxy)]propylamine). The complexes obtained were characterized by elemental analysis, IR and UV-visible spectroscopies, electrospray ionization mass spectrometry (ESI-MS), tandem mass spectrometry (MS/MS), and cyclic voltammetry. X-ray diffraction studies were performed for complexes (3) and (4) revealing the presence of mononuclear and dinuclear structures in solid state for (3). However, the zinc complex is mononuclear in solid state. Biological studies of complexes (1)-(4) were carried out in vitro for antimicrobial activity against nine Gram-positive bacteria (Staphylococcus aureus strains RN 6390B, COL, ATCC 25923, Smith Diffuse, Wood 46, enterotoxigenic S. aureus FRI-100 (SEA+), FRI S-6 (SEB+) and SEC FRI-361) and animal strain S. aureus LSA 88 (SEC/SED/TSST-1+). The following sequence of inhibition promoted by the complexes was observed: (4) > (2) > (3) > (1), showing the effect of the metal on the biological activity. To directly observe the morphological changes of the internal structure of bacterial cells after the treatment, transmission electron microscopy (TEM) was employed. For the most active complex [ZnII(HBPClNOL)Cl] (4), granulation deposits around the genetic material and internal material leaking were clearly detected. 相似文献
6.
Liane M. Rossi Adailton J. Bortoluzzi Bruno Szpoganicz Antônio S. Mangrich Eduardo E. Castellano 《Inorganica chimica acta》2005,358(6):1807-1822
The unsymmetric dinucleating ligand N-(2-hydroxybenzyl)-N,N′,N′-tris(2-pyridylmethyl)-1,3-diaminopropan-2-ol (L = H2btppnol) and the corresponding copper(II) complex [Cu2(Hbtppnol)(μ-CH3COO)](ClO4)2 (1) have been recently reported in part in a short communication [Inorg. Chem. Commum. 8 (1999) 334]. In this study, we investigated the ability of complex 1 to promote the hydrolysis of P-O phosphate diester bonds in bis(2,4-dinitrophenyl) phosphate (2,4-BDNPP) and the cleavage of genomic and plasmid DNA molecules. Reaction of 1 with excess of the diester 2,4-BDNPP, at pH 7.0, results in the formation of the monoester phosphate coordinated [Cu2(Hbtppnol)(μ-((NO2)2-C6H3)PO4)]ClO4 (3) complex, which was also characterized by X-ray crystallography. In addition, the stable μ-phosphate complex [Cu2(Hbtppnol)(μ-(NO2-C6H4)PO4)](ClO4) (2) obtained from the reaction of 4-nitrophenyl phosphate with complex 1 was also characterized by X-ray crystallography, indicating that 1 is unable to cleave monoester-phosphate bonds. The kinetics for the promotion of bis(2,4-dinitrophenyl) phosphate (2,4-BDNPP) hydrolysis by complex 1 was investigated as a function of pH, catalyst concentration and substrate concentration. On the basis of kinetic and potentiometric studies, the deuterium isotope effect (kH/kD ∼ 1) and the X-ray structure of the monoester phosphate coordinated [Cu2(Hbtppnol)(μ-((NO2)2-C6H3)PO4)]ClO4 (3) complex as the product of the reaction, we demonstrated that the aquo/hydroxo complex is the active species and the reaction occurs through the formation of a ternary complex in which one CuII binds the substrate and the second copper center has a terminal bound hydroxide to attack the phosphorus atom, at physiological pH. A rate enhancement factor of ∼100 was calculated relative to that measured for the uncatalyzed reaction under identical conditions. Complex 1 effectively promotes the cleavage of double-stranded genomic and plasmid DNA, at physiological pH, probably through a hydrolytic mechanism in agreement with that proposed for the reaction of 1 with 2,4-BDNPP. Finally, cytotoxic activity of 1 in a human small cell lung carcinoma cell line (GLC4) and its cisplatin resistant subline (GLC4/CDDP) was studied and the IC50 values were determined. 相似文献
7.
Jun-Jie Wang 《Inorganica chimica acta》2010,363(7):1377-1385
In our continuing efforts to explore the effects of substituent groups of ligands in the formation of supramolecular coordination structures, seven new CuII complexes formulated as [Cu2(L1)4(DMF)2] (1), {[Cu2(L1)4(Hmta)](H2O)0.75}∞ (2), [Cu2(L2)4(2,2′-bipy)2] (3), [Cu2(L3)4(H2O)2] (4), [Cu2(L3)4(Hmta)]∞ (5), [Cu2(L3)4(Dabco)]∞ (6) and [Cu2(L3)4(Pz)]∞ (7) with three monocarboxylate ligands bearing different substituent groups HL1-HL3 (HL1 = phenanthrene-9-carboxylic acid, HL2 = 2-phenylquinoline-4-carboxylic acid, HL3 = adamantane-1-carboxylic acid, Hmta = hexamethylenetetramine, 2,2′-bipy = 2,2′-bipyridine, Dabco = 1,4-diazabicyclo[2.2.2] octane and Pz = pyrazine), have been prepared and characterized by X-ray diffraction. In 1, 2 and 4-7, each CuII ion is octahedrally coordinated, and carboxylate acid acts as a syn-syn bridging bidentate ligand. While each CuII ion in 3 is penta-coordinated in a distorted square-pyramidal geometry. 1 and 4 both show a dinuclear paddle-wheel block, while 2, 5, 6 and 7 all exhibit an alternated 1D chain structure between dinuclear paddle-wheel units of the tetracarboxylate type Cu2-(RCO2)4 and the bridging auxiliary ligands Hmta, Dabco and Pz. Furthermore, 3 has a carboxylic unidentate and μ1,1-oxo bridging dinuclear structure with the chelating auxiliary ligand 2,2′-bipy. Moreover, complexes 1-6 were characterized by electron paramagnetic resonance (EPR) spectroscopy. 相似文献
8.
To further investigate the solvent effect on the structures of coordination polymers, a series of polymeric CuII complexes have been synthesized and characterized by single-crystal diffraction through combining of 2,3,5,6-tetrachloro-1,4-benzenedicarboxylic acid (H2BDC-Cl4) with CuII perchlorate. The products including {[Cu(BDC-Cl4)(py)3] · H2O}n (py = pyridine) (1), {[Cu(BDC-Cl4)(dioxane)(H2O)2] · dioxane}n (2), and {[Cu2(BDC-Cl4)2(DMF)4] · 2G}n (G = MeOH in 3 and G = EtOH in 4) have been obtained in different mixed solvents systems. With the change of the solvent system from pyridine/H2O (1:1) into dioxane/H2O (1:1), the infinite 1-D CuII-BDC-Cl4 chain motif in 1 is tuned into the 2-D (4,4) layered structure in 2 with the coordination of dioxanes to copper atoms. When the solvent system is changed into DMF/MeOH (1:1), then into DMF/EtOH (1:1), similar 1-D CuII-BDC-Cl4 double chains are afforded in 3 and 4 with different solvents inclusion. Moreover, the judicious choice of binding-guests leads to numerous coordination geometries of CuII centers and final dissimilar supramolecular lattices of 1-4 from 1-D to 3-D via robust hydrogen-bonding interactions. The spectroscopic, thermal, and fluorescent properties of 1-4 have also been investigated. 相似文献
9.
Morré DJ Jiang Z Marjanovic M Orczyk J Morré DM 《Journal of inorganic biochemistry》2008,102(9):1812-1818
A family of cell surface and growth-related proteins, designated ECTO-NOX proteins, carry out both copper-dependent NADH and hydroquinone oxidation and protein disulfide-thiol interchange. The two activities they catalyze alternate to generate a regular period of 24 min in length for the constitutive CNOX. Unexpectedly, CuII salts alone in solution catalyze NADH (or hydroquinone) oxidation with a similar oscillatory pattern. Both patterns consist of five maxima, two of which at physiological temperatures are separated by an interval of 6 min and three of which are separated by intervals of 4.5 min [6 min + 4 (4.5 min)]. EXAFS and infrared spectroscopic measurements on pure water have shown previously that the ratios of ortho and para isomers of the hydrogen atoms of water occur on a similar time scale and produce regular patterns of unequally spaced oscillations similar to those observed with ECTO-NOX proteins and CuIICl2 solutions. Here, we provide results from CuIICl2 solutions that demonstrate that ECTO-NOX-/CuII-catalyzed oscillations in NADH oxidation are phased by exposure to low frequency electromagnetic fields. 相似文献
10.
Aurkie Ray Aliakbar Dehno Khalaji Chahlae Atmani Smail Triki Salvador Cardona-Serra Ray. J. Butcher Duanjun Xu 《Inorganica chimica acta》2010,363(13):3580-1773
By slightly changing the synthetic conditions, we have prepared two closely related linear tetranuclear CuII complexes with the symmetrical ONNO donor tetradentate Schiff-base ligand [H2L = (OH)C6H4(CH3)CN(CH2)3NC(CH3)C6H4(OH)] and with azide ions. These two distinctly coloured crystalline products were characterized by elemental analysis, IR and UV-Vis spectroscopy, CV, EPR spectra and variable temperature magnetic measurements. Single crystal X-ray diffraction studies of the green [Cu4(μ-L)2(μ1,1-N3)2(N3)2] (1) and the red [Cu4(μ-L)2(μ1,1-N3)2(N3)2(H2O)2] (2) crystals show that the coordination environment of the two μ-phenoxo and μ1,1-azido bridged isomorphous tetranuclear CuII complexes are slightly different. Thus, both complexes are formed by very similar building units, although with a significant variation in the bridging Cu-O(phenoxo)-Cu and Cu-N(azido)-Cu bond angles. The consequences of these structural variations on the magnetic properties have been investigated from both the experimental and theoretical points of view by variable temperature magnetic measurements and DFT calculations. 相似文献
11.
12.
New hydrogen-bonding assemblies were synthesized from the reaction of a metalloligand, [Cu(2,4-pydca)2]2− (LCu) (2,4-pydca = 2,4-pyridinedicarboxylate), with a FeII ion or an imidazole in an aqueous medium and crystallographically characterized. The obtained compounds, [Fe(H2O)6][Cu(2,4-pydca)2] (1) and [Cu(2,4-pydca)(imidazole)2] · 2H2O (2), have metalloligand dimer units, [Cu2(2,4-pydca)4]4− and [Cu2(2,4-pydca)2(imidazole)4], respectively, each of which assembles by π-π (1) and hydrogen-bonding (2) interactions to form 1-D metalloligand arrays. The 1-D metalloligand arrays are linked by rich hydrogen-bonding interactions via H2O molecules. 相似文献
13.
Chaitali Biswas Michael G.B. Drew Silvia Gómez-Coca Vassilis Tangoulis 《Inorganica chimica acta》2010,363(5):846-2495
Three new trinuclear copper(II) complexes, [(CuL1)3(μ3-OH)](ClO4)2·3.75H2O (1), [(CuL2)3(μ3-OH)](ClO4)2(2) and [(CuL3)3(μ3-OH)](BF4)2·0.5CH3CN (3) have been synthesized from three tridentate Schiff bases HL1, HL2, and HL3 (HL1 = 2-[(2-amino-ethylimino)-methyl]-phenol, HL2 = 2-[(2-methylamino-ethylimino)-methyl]-phenol and HL3 = 2-[1-(2-dimethylamino-ethylimino)-ethyl]-phenol). The complexes are characterized by single-crystal X-ray diffraction analyses, IR, UV-vis and EPR spectroscopy, and variable-temperature magnetic measurements. All the compounds contain a partial cubane [Cu3O4] core consisting of the trinuclear unit [(CuL)3(μ3-OH)]2+ together with perchlorate or fluoroborate anions. In each of the complexes, the three copper atoms are five-coordinated with a distorted square-pyramidal geometry except in complex 1, in which one of the CuII ions of the trinuclear unit is six-coordinate being in addition weakly coordinated to one of the perchlorate anions. Variable-temperature magnetic measurements and EPR spectra indicate an antiferromagnetic exchange coupling between the CuII ions of complexes 1 and 2, while this turned out to be ferromagnetic for complex 3. Experimental values have been fitted according to an isotropic exchange Hamiltonian. Calculations based on Density Functional Theory have also been performed in order to estimate the exchange coupling constants in these three complexes. Both sets of values indicate similar trends and specially calculated J values establish a magneto-structural correlation between them and the Cu-O-Cu bond angle, in that the coupling is more ferromagnetic for smaller bond angle values. 相似文献
14.
The ATP.Mg-dependent type 1 protein phosphatase is inactive as isolated but can be activated in several different ways. In this report, we show that the phosphatase can also be activated by the Fe2+/ascorbate system. Activation of the phosphatase requires both Fe2+ ion and ascorbate and the level of activation is dependent on the concentrations of Fe2+ ion and ascorbate. In the presence of 20 mM ascorbate, the Fe2+ ion concentrations required for half-maximal and maximal activation are about 0.3 and 3mM, respectively. Several common divalent metal ions, including Co2+, Ni2+, Cu2+, Mg2+, and Ca2+ ions, cannot cooperate with ascorbate to activate the phosphatase, and SH-containing reducing agents such as 2-mercaptoethanol and dithiothreitol cannot cooperate with Fe2+ ion to activate the phosphatase, indicating that activation of the phosphatase by the Fe2+/ascorbate system is a specific process. Moreover, H2O2, a strong oxidizer, could significantly diminish the phosphatase activation by the Fe2+/ascorbate system, suggesting that reduction mechanism other than SH-SS interchange is a prerequisite for the Fe2+/ascorbate-mediated phosphatase activation. Taken together, the present study provides initial evidence for a new mode of type 1 protein phosphatase activation mechanism.Abbreviations MAPK
mitogen-activated protein kinase
- MCO
metal ion-catalyzed oxidation
- kinase FA
the activating factor of ATP.Mg-dependent protein phosphatase
- I2
inhibitor-2
- EDTA
ethylenediaminetetraacetic acid
- MBP
myelin basic protein 相似文献
15.
M. K. Pulatova V. L. Sharygin T. G. Shlyakova A. E. Sipyagina A. M. Wasserman 《Biophysics》2009,54(2):223-231
It has been shown that changes in Fe3+-transferrin and Cu2+-ceruloplasmin pools, which are reliably checked by the EPR technique in whole blood, blood plasma, and serum, as well as changes in the extracellular DNA content in blood plasma are markers of changes in organism radioresistance. This has been proved during the medical examination of the Chernobyl liquidators and civilian population, including children, exposed to low-intensity radiation, as well as during clinical investigation of new radioprotectors. 相似文献
16.
Three new five-coordinate CuII complexes, [Cu(tpy)(phen-dione)](PF6)2, [Cu(phen)(phen-dione)Cl]PF6 and [Cu(bpy)(phen-dione)Cl]PF6 (tpy = 2,2′;6′,2″-terpyridine, phen = 1,10-phenanthroline and phen-dione = 1,10-phenanthroline-5,6-dione) have been prepared and characterized by elemental analysis, IR and UV-Vis spectroscopies and cyclic voltammetry.The complex of [Cu(tpy)(phen-dione)](PF6)2 crystallized with one molecule of acetonitrile. The ortep drawing of [Cu(tpy)(phen-dione)](PF6)2 · CH3CN shows that the coordination geometry around CuII is a distorted trigonal- bipyramid. Due to the steric hindrance of in the unit cell, the tpy ligands in each complex cation cannot interact in a π-π fashion. The effective magnetic moment (μeff) of the complexes was measured by the Evans method. The cyclic voltammograms at Pt disk electrode for these complexes display only one reversible Cu(II)/Cu(I) redox couple. 相似文献
17.
Dinuclear copper(I) complexes with bridging bis(dicyclohexylphosphino)methane (dcpm) or bis(diphenylphosphino)methane (dppm) and 2,2′-bipyridine or 2-[N-(2-pyridyl)methyl]amino-5,7-dimethyl-1,8-naphthyridine (L), [Cu2(bpy)2(dppm)2](BF4)2 (1), [Cu2(bpy)2(dcpm)](BF4)2 (2), [Cu2(L)(dppm)](BF4)2 (3) and [Cu2(L)(dcpm)](BF4)2 (4) were prepared, and their structures were determined by X-ray crystal analysis. Two-, three-, and four-coordinate copper(I) centers are found in these complexes. Compounds 3 and 4 show close CuI?CuI separations of 2.664(3) and 2.674(1) Å, respectively, whereas an intramolecular copper-copper distance of 3.038 Å is found in 2 having only dcpm as an additional bridge. Powdered samples of 1, 3, and 4 display intense and long-lived phosphorescence with λmax at 533, 575, and 585 nm at room temperature, respectively. In the solid state, 2 exhibits only a weak emission at 555 nm. The time-resolved absorption and emission spectra of these complexes were investigated. The difference in the emission properties among complexes 1-4 suggests that both CuI?CuI distances and coordination environment of the copper(I) centers affect the excited-state properties. 相似文献
18.
Thomas Riis-Johannessen John C. Jeffery Craig R. Rice 《Inorganica chimica acta》2005,358(9):2781-2798
Reaction of the potentially tetradentate N-donor ligand 6,6′-bis(4-methylthiazol-2-yl)-2,2′-bipyridine (L1) with the transition metal dications CoII, NiII, CuII, CdII and HgII results in the formation of mononuclear [M(L1)]2+ complexes, in which a planar ligand coordinates to the metals via all four N-donors. In contrast, reaction of L1 with CuI and AgI monocations, affords dinuclear double stranded helicate species [M2(L1)2]2+ (where M = CuI or AgI), in which partitioning of the ligand into two bis-bidentate pyridyl-thiazole chelating units allows each ligand to bridge both metal centres. X-Ray crystallography, electrospray mass spectroscopy and NMR spectroscopy reveal that the complexes [Mn(L1)m]z+ (where n = 1, m = 1 and z = 2, when M = CoII, NiII, CuII, CdII and HgII; n = 2, m = 2 and z = 2, when M = CuI), retain their solid-state structures in solution. Conversely, whilst 1H NMR studies suggest that combination of equimolar amounts of Ag(X)(where ) and L1 (in either nitromethane or acetonitrile) results in the formation of a helicate in solution, in the solid-state, an anion-templating effect gives rise to either mononuclear or dinuclear helicate structures [Agn(L1)n][X]n (where n = 2 when X = OTf−; n = 1 when ). 相似文献
19.
20.
To define the molecular mechanism(s) of carvedilol inhibition of lipid peroxidation we have utilized model systems that allow us to study the different reactions involved in this complex process.Carvedilol inhibits the peroxidation of sonicated phosphatidylcholine liposomes triggered by FeCl2 addition whereas atenolol, pindolol and labetalol are ineffective. The inhibition proved not to be ascribable (a) to an effect on Fe2+ autoxidation and thus on the generation of oxygen derived radical initiators; (b) to the scavenging of the inorganic initiators O·-2 and ·OH; (c) to an effect on the reductive cleavage of organic hydroperoxides by FeCl2; (d) to the scavenging of organic initiators. The observations that (a) carvedilol effectiveness is inversely proportional to the concentration of FeCl2 and lipid hydroperoxides in the assay; (b) the drug prevents the onset of lipid peroxidation stimulated by FeCl3 addition and; (c) it can form a complex with Fe3+, suggest a molecular mechanism for carvedilol action. It may inhibit lipid peroxidation by binding the Fe3+ generated during the oxidation of Fe2+ by lipid hydroperoxides in the substrate. The lag time that carvedilol introduces in the peroxidative process would correspond to the time taken for carvedilol to be titrated by Fe3+; when the drug is consumed the Fe3+ accumulates to reach the critical parameter that stimulates peroxidation. According to this molecular mechanism the antioxidant potency of carvedilol can be ascribed to its ability to bind a species, Fe3+, that is a catalyst of the process and to its lipophilic nature that concentrates it in the membranes where Fe3+ is generated by a site specific mechanism. 相似文献