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1.
Artificial cytochromes c have been prepared with Fe(III) and Co(III) tetrasulfonated phthalocyanines in place of heme. Their structure and properties have been investigated by difference spectroscopy, CD, epr, electrophoresis, molecular weight estimation, and potentiometric measurements. The visible absorption spectra show the main peak at 650 nm for the iron compound 685 nm for the cobalt one. It is shown by CD experiments that incorporation of Fe(III)L or Co(III)L into apocytochrome c markedly increases helical content of the protein. Its conformation is, however, significantly altered as compared with the native cytochrome c. The epr and spectroscopic data show that the iron and cobalt phthalocyanine models represent the low spin species with the metal ions in trivalent state. Electrophoresis and molecular weight estimation indicate these complexes to be monomers. Both phthalocyanine complexes have not affinity for additional ligands characteristic for hemoglobin. They react, however, with CO, NO, and CN- when they are reduced with dithionite. Moreover, Co(II)L-apocyt c is able to combine with oxygen suggesting a structural feature in common with the oxygen-carrying heme proteins. Iron(II) complex in the same conditions is oxidized directly to the ferric state. The half-reduction potentials of Fe(III)L-apocyt c and Co(III)L-apocyt c are +374 mV and +320 mV, respectively. These complexes are reduced by cytochrome c and cytochrome c reductase (cytochrome bc1).  相似文献   

2.
A new series of pendant-type polymer-cobalt(III) complexes, [Co(LL)2(BPEI)Cl]2+, (where BPEI?=?branched polyethyleneimine, LL?=?dipyrido[3,2-a:2′,3′-c](6,7,8,9-tetrahydro)phenazine (dpqc), dipyrido[3,2-d:2′,3′-f]quinoxaline (dpq) and imidazo[4,5-f]1,10-phenanthroline (ip)) each with three different degrees of coordination have been synthesized and characterized. Studies to know the mode and strength of interaction between these polymer–metal complexes and calf thymus DNA have been performed by UV–Visible absorption and emission techniques. Among these series, each polymer metal complex having higher binding strength with DNA has been selected to test against human cancer/normal cell lines. On the basis of these spectral studies, it is proposed that our polymer–metal complexes bind with DNA mainly through intercalation along with some electrostatic binding. The order of binding strength for the complexes with ligand, dpqc?>?dpq?>?ip. The analysis of the results suggests that polymer–cobalt(III) complexes with higher degree of coordination effectively binds with DNA due to the presence of large number of positively charged cobalt(III) chelates in the polymer chain which cooperatively act to increase the overall binding strength. These polymer–cobalt(III) complexes with hydrophobic ligands around the cobalt(III) metal centre favour the base stacking interactions via intercalation. All the complexes show very good anticancer activities and increasing of binding strength results in higher inhibition value. The polymer–cobalt(III) complex with dpqc ligand possess two fold increased anticancer activity when compared to complexes with other ligands against MCF-7 cells. Besides, the complexes were insensitive towards the growth of normal cells (HEK-293) at the IC50 concentration.  相似文献   

3.
The polymer–cobalt(III) complexes, [Co(bpy)(dien)BPEI]Cl3 · 4H2O (bpy = 2,2′‐bipyridine, dien = diethylentriamine, BPEI = branched polyethyleneimine) were synthesized and characterized. The interaction of these complexes with human serum albumin (HSA) and bovine serum albumin (BSA) was investigated under physiological conditions using various physico‐chemical techniques. The results reveal that the fluorescence quenching of serum albumins by polymer–cobalt(III) complexes took place through static quenching. The binding of these complexes changed the molecular conformation of the protein considerably. The polymer–cobalt(III) complex with x = 0.365 shows antimicrobial activity against several human pathogens. This complex also induces cytotoxicity against MCF‐7 through apoptotic induction. However, further studies are needed to decipher the molecular mode of action of polymer–cobalt(III) complex and for its possible utilization in anticancer therapy. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

4.
Raman and IR studies are carried out on carnosine (beta-alanyl-L-histidine, Carnos) and its complexes with cobalt(II) at different metal/ligand ratios and basic pH. Binuclear complexes that bind molecular oxygen are formed and information regarding the O-O bridge is obtained from the Raman spectra. When the Co(II)/Carnos ratio is 相似文献   

5.
Square-pyramidal (Ph3X)bis(4,5-dichloro-1,2-benzosemiquinonediiminato)cobalt(III) complexes (X = As, Sb or P) have been synthesized. The kinetics of axial substitution for the triphenylantimony complex have been studied for 10 entering ligands (L*). The reaction is of reversible second-order in both directions for all complexes. Labile behavior is indicated by the rate constants in the range from 6.33 × 103 (for L* = Ph3P in MeOH) to 5.4 (L* = py in CH2Cl2) M−1 s−1. The kinetics is consistent with an Ia mechanism. The log of the second-order rate constant for axial substitution is a linear function of nucleophilic reactivity nPt°, which is due to the trans-labilizing effect of the entering ligand in the six-coordinate transition state.  相似文献   

6.
Two novel cobalt(III) mixed-polypyridyl complexes [Co(phen)(2)(dpta)](3+) and [Co(phen)(2)(amtp)](3+) (phen=1,10-phenanthroline, dpta=dipyrido-[3,2-a;2',3'-c]- thien-[3,4-c]azine, amtp=3-amino-1,2,4-triazino[5,6-f]1,10-phenanthroline) have been synthesized and characterized. The interaction of these complexes with calf thymus DNA was investigated by spectroscopic, cyclic voltammetry, and viscosity measurements. Results suggest that the two complexes bind to DNA via an intercalative mode. Moreover, these Co(III) complexes have been found to promote the photocleavage of plasmid DNA pBR322 under irradiation at 365nm. The mechanism studies reveal that hydroxyl radical (OH()) is likely to be the reactive species responsible for the cleavage of plasmid DNA by [Co(phen)(2)(dpta)](3+) and superoxide anion radical (O(2)(-)) acts as the key role in the cleavage reaction of plasmid DNA by [Co(phen)(2)(amtp)](3+).  相似文献   

7.
The synthesis of tetradentate cobalt(II) salicylaldiminato complexes and their catalytic evaluation in the oxidation of phenol is reported. Tetradentate cobalt complexes [Co(Ln)2] were obtained by reacting the N-(aryl)salicylaldimine ligands (HL1–HL6) with cobalt acetate in a 2:1 mole ratio. All complexes were characterized using FT-IR and elemental analysis. X-ray crystal structures of complexes 1, 2 and 5 have also been obtained. All complexes were found to be active for the oxidation process.  相似文献   

8.
The synthesis of four guanidine-pyridine hybridligands and their spectroscopic features in MeCN are described. In order to demonstrate their coordinating properties, the corresponding cobalt(II)chloride complexes have been prepared and completely characterised by means of X-ray structure analysis, UV/Vis spectroscopy and mass spectrometry. The neutral complexes {1,1,3,3-tetramethyl-2-(quinolin-8-yl)guanidine}cobalt(II)-dichloride [Co(TMGqu)Cl2] and {N-(1,3-dimethylimidazolidin-2-yliden)pyridin-8-amine}cobalt(II)-dichloride [Co(DMEGpy)Cl2] exhibit a tetrahedral coordination of the cobalt atom, whereas in bis[chlorobis{N-(1,3-dimethylimidazolidin-2-yliden)quinolin-8-amine}cobalt(II)]tetrachlorocobaltate [Co(DMEGqu)2Cl]2[CoCl4] and chlorobis{1,1,3,3-tetramethyl-2-((pyridin-2-yl)methyl)guanidine}cobalt(II)chloride [Co(TMGpy)2Cl]Cl, the cobalt atom is coordinated in a trigonal pyramidal environment. These trigonal pyramidal complex cations represent the first bis(chelated) guanidine cobalt complexes in which the pyridine donor resides on the apical position and the guanidine donor forms with the chlorine atom the base of the pyramid. Besides the structural characterisation, the quenching effect of the cobalt(II) ion (d7) on the ligand fluorescence has been studied.  相似文献   

9.
The synthesis, characterization and catalytic activity of a series of tetra-halogeno-dimethyl salen cobalt (II) complexes are reported in this paper. The investigated complexes of cobalt (II) with Schiff bases are: αα′-di-methyl Salen cobalt (II) [Co(dMeSalen)], 3,3′,5,5′-tetra chloro α,α′-di-methyl Salen cobalt (II), [Co(tCldMeSalen)], 3,3′-di-bromo 5,5′-di-chloro α,α′-di-methyl Salen cobalt (II), [Co(tBrdMeSalen)], 3,3′,5,5′-tetra bromo α,α′-di-methyl Salen cobalt (II), [Co(tBrdMeSalen)] and 3,3′,5,5′-tetra iodo α,α′-di-methyl Salen cobalt (II), [Co(tIdMeSalen)] (where Salen is bis(salicylaldehyde)ethylenediamine). The characterization of the complexes was performed by elemental analysis, cyclic voltammetry, UV-Vis, IR and EPR spectroscopies. The study was made in DMF, and pyridine was used for coordination as axial base. The redox potential is influenced by the substituent grafted on aromatic ring and in the azomethynic position and also by the molecules coordinating in axial position (solvent, DMF, or pyridine). The catalytic oxygenation of 2,6-di-tert-butylphenol by these complexes leads to the obtention of benzoquinone and diphenoquinone products. The cobalt (II) complexes form reversible adducts with molecular oxygen.  相似文献   

10.
Trace elements such as copper and cobalt have been associated with virus-host interactions. However, studies to show the effect of conjugation of copper(II) or cobalt(III) metal centers to thiosemicarbazone ligand(s) derived from either food additives or mosquito repellent such as 2-acetylethiazole or citral, respectively, on Zika virus (ZIKV) or dengue virus (serotype 2; DENV2) infections have not been explored. In this study, we show that four compounds comprising of thiosemicarbazone ligand derived from 2-acetylethiazole viz., (E)-N-ethyl-2-[1-(thiazol-2-yl)ethylidene]hydrazinecarbothioamide (acetylethTSC) (compound 1), a copper(II) complex with acetylethTSC as a ligand (compound 2), a thiosemicarbazone ligand-derived from citral (compound 3) and a cobalt(III) complex with a citral-thiosemicarbazone ligand (compound 4) increased DENV2 and ZIKV replication in both mosquito C6/36 cells and human keratinocytes (HaCaT cells). Treatment of both cell lines with compounds 2 or 4 showed increased dengue viral titers at all three tested doses. Enhanced dengue viral plaque formation was also noted at the tested dose of 100 μM, suggesting higher production of infectious viral particles. Treatment with the compounds 2 or 4 enhanced ZIKV and DENV2 RNA levels in HeLa cell line and primary cultures of mouse bone marrow derived dendritic cells. Also, pre- or post treatments with conjugated compounds 2 or 4 showed higher loads of ZIKV or DENV2 envelope (E) protein in HaCaT cells. No changes in loads of E-protein were found in ZIKV-infected C6/36 cells, when compounds were treated after infection. In addition, we tested bis(1,10-phenanthroline)copper(II) chloride ([Cu(phen)2]Cl2, (compound 5) and tris(1,10-phenanthroline)cobalt(III) chloride ([Co(phen)3]Cl3, (compound 6) that also showed enhanced DENV2 loads. Also, we found that copper(II) chloride dehydrate (CuCl2·2H2O) or cobalt(II) chloride hexahydrate (CoCl2·6H2O) alone had no effects as “free” cations. Taken together, these findings suggest that use of Cu(II) or Co(III) conjugation to organic compounds, in insect repellents and/or food additives could enhance DENV2/ZIKV loads in human cells and perhaps induce pathogenesis in infected individuals or individuals pre-exposed to such conjugated complexes.

Importance

Mosquito-borne diseases are of great concern to the mankind. Use of chemicals/repellents against mosquito bites and transmission of microbes has been the topic of interest for many years. Here, we show that thiosemicarbazone ligand(s) derived from 2-acetylethiazole or citral or 1,10-phenanthroline upon conjugation with copper(II) or cobalt(III) metal centers enhances dengue virus (serotype 2; DENV2) and/or Zika virus (ZIKV) infections in mosquito, mouse and human cells. Enhanced ZIKV/DENV2 capsid mRNA or envelope protein loads were evident in mosquito cells and human keratinocytes, when treated with compounds before/after infections. Also, treatment with copper(II) or cobalt(III) conjugated compounds increased viral titers and number of plaque formations. These studies suggest that conjugation of compounds in repellents/essential oils/natural products/food additives with copper(II) or cobalt(III) metal centers may not be safe, especially in tropical and subtropical places, where several dengue infection cases and deaths are reported annually or in places with increased ZIKV caused microcephaly.  相似文献   

11.
Structural data for complexes of hyaluronic acid and 3d metals(II) of the fourth group of the periodic table are lacking. A combined QM/MM method was used to solve the structure of the first coordination sphere around the cobalt(II) ion. Some available experimental data were compared with the results obtained via computation and were found to be in good agreement. Our results open the way for using molecular modeling to solve the structure of other metal(II) hyaluronates.  相似文献   

12.
Four cobalt(III) polypyridyl complexes, [Co(phen)3−n(dpq)n]3+ (phen = 1,10-phenanthroline, dpq = dipyrido[3,2-f:2′,3′-h]-quinoxaline) (n = 0, 1, 2, and 3) were synthesized and the influences of the dpq ligand on the photophysical properties, electrochemical properties, DNA binding affinities, as well as photonuclease activities of the complexes, were examined in detail. The presence of dpq ligand increases the DNA binding affinities of the corresponding complexes remarkably with respect to [Co(phen)3]3+. With the sequential substitution of phen ligand by dpq ligand, the 1O2 quantum yields of the corresponding complexes are enhanced greatly. As a result, the photonuclease activities follow the order of [Co(dpq)3]3+ > [Co(phen)(dpq)2]3+ > [Co(phen)2(dpq)]3+ ? [Co(phen)3]3+. It was found all the examined complexes can generate OH upon UV irradiation, and OH is also involved in DNA photocleavage as reactive oxygen species.  相似文献   

13.
The second-order rate constants for interaction of a number of cobalt(II) complexes (including the aquated ion) with bovine apocarbonic anhydrase have been measured at pH equal to 7.5, 25 degrees C and I equal 0.1 M. The ease of entry of cobalt decreases, in general, as the number of its coordinated watersdecreases. The highest complexes (bis or tris) do not react. The Mono cobalt(II) -8-quinolinol-5-sulfonate and, particularly, 8-quinolinol complexes react very much more rapidly with apoenzyme than does Co(H20)6-2+ ion. The results are discussed.  相似文献   

14.
Cobalt(II) complexes with the non-steroidal anti-inflammatory drug naproxen in the presence or absence of nitrogen-donor heterocyclic ligands (pyridine, 2,2′-bipyridine or 1,10-phenanthroline) have been synthesized and characterized with physicochemical and spectroscopic techniques. The deprotonated naproxen acts as monodentate ligand coordinated to Co(II) ion through a carboxylato oxygen. The crystal structure of [bis(aqua)bis(naproxenato)bis(pyridine)cobalt(II)], 2 has been determined by X-ray crystallography. The EPR spectrum of complex 2 in frozen solution reveals that it retains its structure. UV study of the interaction of the complexes with calf-thymus DNA (CT DNA) has shown that the complexes can bind to CT DNA and [(2,2′-bipyridine)bis(methanol)bis(naproxenato)cobalt(II)] exhibits the highest binding constant to CT DNA. The cyclic voltammograms of the complexes recorded in DMSO solution and in the presence of CT DNA in 1/2 DMSO/buffer (containing 150 mM NaCl and 15 mM trisodium citrate at pH 7.0) solution have shown that they can bind to CT DNA by the intercalative binding mode which has also been verified by DNA solution viscosity measurements. Competitive study with ethidium bromide (EB) has shown that the complexes can displace the DNA-bound EB indicating that they bind to DNA in strong competition with EB. Naproxen and its cobalt(II) complexes exhibit good binding propensity to human or bovine serum albumin proteins having relatively high binding constant values. The antioxidant activity of the compounds has been evaluated indicating their high scavenging activity against hydroxyl free radicals and superoxide radicals.  相似文献   

15.
Cobalt(III) complexes of diacetyl monooxime benzoyl hydrazone (dmoBH2) and diacetyl monooxime isonicotinoyl hydrazone (dmoInH2) have been synthesized and characterized by elemental analyses and spectroscopic methods. The X-ray crystal structures of the two hydrazone ligands, as well as that of the cobalt(III) complex [CoIII(dmoInH)2]Cl·2H2O, are also reported. It is found that in the cobalt(III) complexes the Co(III) ion is hexa-coordinated, the hydrazone ligands behaving as mono-anionic tridentate O,N,N donors. In the [CoIII(dmoInH)2]Cl·2H2O complex, the amide and the oxime hydrogens are deprotonated for both the ligands, while the isonicotine nitrogens are protonated. In the [CoIII(dmoBH)2]Cl complex, only the amide nitrogens are deprotonated. It is shown that the additional hydrogen bonding capability of the isonicotine nitrogen results in different conformation and supramolecular structure for dmoInH2, compared to dmoBH2, in the solid state. Comparing the structure of the [CoIII(dmoInH)2]Cl·2H2O with that of the Zn(II) complex of the same ligand, reported earlier, it is seen that the metal ion has a profound influence on the supramolecular structure, due to change in geometrical dispositions of the chelate rings.  相似文献   

16.
Cobalt(II) ion and L-carnosine produce two different complexes when mixed in aqueous solution at pH 7.2. One complex has coordination of N-3 of the imidazole ring to the cobalt(II) and is produced when the concentration of peptide exceeds that of cobalt(II). The second complex has chelation of three nitrogen atoms of a single carnosine. This second complex produces a reversible oxygen carrier by making stable mixed chelates with additional carnosine, histidine or cysteine. These results indicate that cobalt complexes with mixed ligands should be of more importance invivo than those with carnosine as the only ligand. They provide an explanation for the high activity and substrate specificity of carnosinase in kidney.  相似文献   

17.
The interaction of surfactant–cobalt(III) complexes [Co(bpy)(dien)TA](ClO4)3 · 3H2O (1) and [Co(dien)(phen)TA](ClO4)3 · 4H2O (2), where bpy = 2,2′‐bipyridine, dien = diethylenetriamine, phen = 1,10‐phenanthroline and TA = tetradecylamine with human serum albumin (HSA) under physiological conditions was analyzed using steady state, synchronous, 3D fluorescence, UV/visabsorption and circular dichroism spectroscopic techniques. The results show that these complexes cause the fluorescence quenching of HSA through a static mechanism. The binding constant (Kb) and number of binding‐sites (n) were obtained at different temperatures. The corresponding thermodynamic parameters (?G°, ?H° and ?S°) and Ea were also obtained. According to Förster's non‐radiation energy transfer theory, the binding distance (r) between the complexes and HSA were calculated. The results of synchronous and 3D fluorescence spectroscopy indicate that the binding process has changed considerably the polarity around the fluorophores, along with changes in the conformation of the protein. The antimicrobial and anticancer activities of the complexes were tested and the results show that the complexes have good activities against pathogenic microorganisms and cancer cells. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

18.
In order to obtain information on a way of prosthetic group binding by apocytochrome c in phthalocyanine-substituted cytochrome c, modification of these complexes by carboxymethylation at methionines, as well as cleavage with cyanogen bromide, has been performed. Properties of the reaction products have been investigated by spectroscopic methods, gel electrophoresis, column chromatogrdphy, peptide mapping, and amino acid analysis. Spectrophotometric data indicate that carboxymethylation results in a complete loss of the S-Fe sensitive 695 nm absorption band that appears in absorption spectra of the phthalocyanine-substituted cytochromes c. Unlike unmodified complexes, carboxymethylated derivatives are capable of ligating with typical iron ligands, in both oxidation states. Studies of iron and cobalt tetrasulfonated phthalocyanine interactions with fragments of cytochrome c demonstrate complex formation solely with the heme fragment apopeptides. These complexes do not exhibit a 695 nm absorption band. The results of the chemical examination suggest that the metal phthalocyanine of the model complexes is coordinated axially with histidine-18 and methionine-80 of apocytochrome c, in spite of the weakening of its heme crevice. Identification of these ligands by nuclear magnetic resonance method is difficult due to low solubility of the model complexes.  相似文献   

19.
The spectroscopy, electrochemistry and electrogenerated chemiluminescence (ECL) of eight bisalicylideneethylenediamino (salen) metal complexes are reported. Two of the complexes contain an unsubstituted salen ligand and either cobalt(II) or nickel(II). The others have 1,2-cyclohexanediamonio-N,N′-bis(3,5-di-t-butylsalicylidene) as the ligand, and chromium(III), aluminum(III), cobalt(II), cobalt(III) or manganese(II) as the metal center. The complexes have lowest energy absorption maxima between 350 and 430 nm. When excited at these wavelengths, the complexes emit between 417 and 594 nm in acetonitrile. Photoluminescence efficiencies (?em) were between 0.0310 and 23.8 compared to Ru(bpy)32+ (bpy = 2,2′-bipyridine; ?em = 1), with the aluminum complexes displaying the most intense photoluminescence. Both reversible and irreversible oxidative electrochemistry is displayed by the metal–salen complexes with oxidation potentials ranging between +0.152 and +1.661 V versus Ag/AgCl. The ECL intensity peaks at a potential corresponding to oxidation of both TPrA and the salen systems, indicating that both are involved in the ECL reaction sequence. ECL efficiencies (?ecl) were between 0.0018 and 0.0086 when compared to Ru(bpy)32+ (?ecl = 1) in acetonitrile (0.05 M tri-n-propylamine (TPrA) as an oxidative–reductive ECL coreactant). Also, qualitative studies using transmission filters suggest that the complexes emit ECL in approximately the same region as their photoluminescence, indicating that the same excited state is formed in both experiments.  相似文献   

20.
Abstract

For efficient designing of metallodrugs, it is imperative to analyse the binding affinity of those drugs with drug-carrying serum albumins to comprehend their structure–activity correlation for biomedical applications. Here, cobalt(II) and cobalt(III) complexes comprising three phendione ligands, [Co(phendione)3]Cl2 (1) and [Co(phendione)3]Cl3 (2), where, phendione = 1,10-phenanthroline-5,6-dione, has been chosen to contrast the impact of their hydrophobicity and ionicity on binding with bovine serum albumin (BSA) through spectrophotometric titrations. The attained hydrophobicity values using octanol/water partition coefficient method manifested that complex 1 is more hydrophobic than complex 2, which could be attributed to lesser charge on its coordination sphere. The interaction of complexes 1 and 2 with BSA using steady state fluorescence studies revealed that these complexes quench the intrinsic fluorescence of BSA through static mechanism, and the extent of quenching and binding parameters are higher for complex 2. Further thermodynamics of BSA-binding studies revealed that complexes 1 and 2 interact with BSA through hydrophobic and hydrogen bonding/van der Waals interactions, respectively. Further, UV–visible absorption, circular dichroism and synchronous fluorescence studies confirmed the occurrence of conformational and microenvironmental changes in BSA upon binding with complexes 1 and 2. Molecular docking studies have also shown that complex 2 has a higher binding affinity towards BSA as compared to complex 1. This sort of modification of ionicity and hydrophobicity of metal complexes for getting desirable binding mode/strength with drug transporting serum albumins will be a promising pathway for designing active and new kind of metallodrugs for various biomedical applications.

Communicated by Ramaswamy H. Sarma  相似文献   

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