Ternary complex formation of the nickel(II), 2,2’-bipyridine, 1,10’-Phenanthroline and some aminoacids
TL;DR: In this article, the results of a speciation study on the ternary complexes present in Ni(II)- 1,10 phenanthroline (Phen)-amino acids and Ni (II)- 2,2-bipyridine (Bipy) amino acids were reported.
Abstract: In this work we report the results of a speciation study on the ternary complexes present in the ternary Ni(II)- 1,10 phenanthroline (Phen)-amino acids and Ni(II)- 2,2-bipyridine (Bipy)-amino acids...
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01 Sep 1996
TL;DR: Copper(II) complexes with 2,9-dimethyl derivative phenanthrolines were observed to be more active against Staphylococcus aureus and Escherichia coli.
Abstract: The antimicrobial activities of some copper(II) binary complexes with unsubstituted and different substituted phenanthroline ligands were investigated. A considerable increase in the biocidal activity of the ligands on being coordinated with the copper(II) ions was observed in terms of their minimum inhibitory concentration (MIC) values.
EPR measurements were performed at room and low temperature with the aim of gaining an insight into the structure/activity relationship of these complexes. Subtle differences in the chemical arrangement result in appreciable differences in the antimicrobial activity. Copper complexes with 2,9-dimethyl derivative phenanthrolines were observed to be more active against Staphylococcus aureus and Escherichia coli .
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TL;DR: In this paper , the chemistry of four new mononuclear mixed ligand Fe(III), Co(II), Cu(II) and Cd(II)-cliques constructed from furfural type imine ligand (L), and the co ligand 2,2'-bipyridine in addition to assessing their antimicrobial activity against some bacterial, and fungi strains.
Abstract: The present investigation goal was to investigate the chemistry of four new mononuclear mixed ligand Fe(III), Co(II), Cu(II), and Cd(II) complexes constructed from furfural-type imine ligand (L), and the co ligand 2,2'-bipyridine in addition to assessing their antimicrobial activity against some bacterial, and fungi strains. The structure of the complexes was interpreted by different spectroscopic techniques such as MS, IR, 1H NMR, UV-Vis, elemental analysis, TG-DTG, conductivity, and magnetic susceptibility measurements. The correlation of all results revealed that ligand (L) acts as a neutral ONNO tetradentate whereas the co ligand acts as a neutral NN bidentate. The coordination of the ligands with the metal ions in a molar ratio of 1:1:1 leads to formation of an octahedral geometry around the metal ions. The octahedral geometry has been validated and optimized by DFT analysis. Conductivity data showed the electrolytic nature of all complexes. The thermal stability of all complexes was deduced in addition to evaluating some thermodynamic, and kinetic parameters using Coats-Redfern method. Furthermore, all complexes in comparison to their parent ligands were tested for their biological potency against some pathogenic bacterial, and fungi strains using the paper disk diffusion method. [CdL(bpy)](NO3)2 complex revealed the highest antimicrobial activity.
TL;DR: In this article , Ni(II) complexes formed with 1,10-phenanthroline (Phen) and the amino acids glycine (Gly, HL), α-alanine (Ala, HL, β-alanines (βAla), proline (Pro, HL) were studied in aqueous solution using 1.0 M NaCl at 25 °C as an ionic medium.
Abstract: Ternary Ni(II) complexes formed with 1,10-phenanthroline (Phen) and the amino acids glycine (Gly, HL), α-alanine (Ala, HL), β-alanine (βAla, HL), proline (Pro, HL), phenylalanine (Phe, HL), methionine (Met, HL), serine (Ser, HL) and threonine (Thr, HL) were studied in aqueous solution using 1.0 M NaCl at 25 °C as an ionic medium. The systems were studied by potentiometric measurements. Analysis of the potentiometric data was done with the least-squares-based program LETAGROP, supporting the formation of species Ni(Phen)(HL)2+, Ni(Phen)(L)+, Ni(Phen)(L)(OH), Ni(Phen)2(L)+ and Ni(Phen)(L)2. Species distribution diagrams were generated and the relative stabilities were analyzed using Δ log10 K, log10 X and % RS values.
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TL;DR: Hyperquad simulation and speciation (HySS) as mentioned in this paper is a computer program written for the Windows operating system on personal computers which provides simulating titration curves and a system for providing speciation diagrams.
1,400 citations
"Ternary complex formation of the ni..." refers methods in this paper
...The species distribution diagrams were generated with the HySS computer program [46], resulting in the βpqr and the βpqrs values summarised in (Tables 1–3)....
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1,328 citations
TL;DR: A surprisingly high structural similarity between the urease catalytic domain and that of the zinc-dependent adenosine deaminase reveals a remarkable example of active site divergence.
Abstract: The crystal structure of urease from Klebsiella aerogenes has been determined at 2.2 A resolution and refined to an R factor of 18.2 percent. The enzyme contains four structural domains: three with novel folds playing structural roles, and an (alpha beta)8 barrel domain, which contains the bi-nickel center. The two active site nickels are 3.5 A apart. One nickel ion is coordinated by three ligands (with low occupancy of a fourth ligand) and the second is coordinated by five ligands. A carbamylated lysine provides an oxygen ligand to each nickel, explaining why carbon dioxide is required for the activation of urease apoenzyme. The structure is compatible with a catalytic mechanism whereby urea ligates Ni-1 to complete its tetrahedral coordination and a hydroxide ligand of Ni-2 attacks the carbonyl carbon. A surprisingly high structural similarity between the urease catalytic domain and that of the zinc-dependent adenosine deaminase reveals a remarkable example of active site divergence.
722 citations
"Ternary complex formation of the ni..." refers background in this paper
...Nickel (II) is an essential element that plays an active role in metalloenzyme hydrogenase [37,38], and it also has a key role in the function of methyl-coenzyme M reductase (MCR) [37–40]....
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TL;DR: Platinum complexes have been shown by X-ray diffraction methods to be valuable electron-dense probes of the intercalative process and generally of nucleic acid structure and the photophysical properties of bound intercalators have provided useful information concerning nucleic acids structure.
Abstract: Binding of the chiral metal complexes [Ru(bpy),]CI, (I), [ R ~ ( p h e n ) ~ ] C l ~ (11), and [Ru(DIP),]CI2 (111) to calf thymus DNA is examined by following changes in the photophysical properties of these probes with use of steady-state as well as time-resolved methods. Increasing luminescence is seen for the ruthenium complexes I1 and I11 with DNA addition whereas no enhanced luminescence is detectable for I. A biexponential decay in luminescence is found for I1 and I11 with emission lifetimes of the complexes bound to DNA appearing 3-5 times longer than those of the free complexes. Quenching of the luminescence by the ferrocyanide anion further amplifies the ability to distinguish bound forms. I* is quenched by ferrocyanide in the presence of DNA as efficiently as in its absence, indicating little or no binding. In contrast, biphasic Stern-Volmer plots are found for I1 and 111, indicating extensive protection of 11* and III* in the presence of DNA from ferrocyanide. Here emission quenching was found to be completely static as a result of counterion condensation at the DNA polyanion. Emission polarization measurements revealed that the binding of I1 and 111 to DNA is accompanied by significant increases in the steady-state polarization. The results are interpreted in terms of two binding modes: electrostatic, which is easily quenched by ferrocyanide and contributes no polarization in emission, and intercalative, which is protected from ferrocyanide quenching and, since rigidly bound, retains emission polarization. The distinction becomes more apparent for I11 where significant enantiomeric selectivity is observed on binding to DNA. Thus A-Ru(DIP),*+ binds to DNA both electrostatically and by intercalation; extensive curvature is seen in Stern-Volmer plots, and increases in polarization are observed. The b isomer, which gives strictly linear Stern-Volmer plots, binds only electrostatically. This chiral discrimination for intercalative binding is explained in terms of the helical asymmetry of a right-handed DNA structure which is matched by the asymmetry of the A isomer but precludes binding by the A isomer. The nature and dynamics of binding small molecules to biopolymers represents an area of active investigation. Studies directed toward the design of siteand conformation-specific reagents provide routes toward rational drug design as well as a means to develop sensitive chemical probes of polymer structure. A simple example is given by the intercalation of small heterocyclic dyes into DNA.'-4 This noncovalent binding mode where the dye stacks between adjacent base pairs of the D N A duplex is particularly favored by positively charged species possessing a planar aromatic moiety. Intercalators tend to be strongly mutagenic and some have shown promising chemotherapeutic a ~ t i v i t y . ~ Their carcinogenecity and antitumor activity furthermore correlate well with DNA binding affinity. Moreover, the photophysical properties of bound intercalators have provided useful information concerning nucleic acid structure. Ethidium is a common fluorescence probe for D N A and has recently been employed in examinations of the torsional rigidity of the double helix.6 Cationic metal complexes possessing planar aromatic ligands also may bind to D N A by intercalation.' Platinum complexes have been shown by X-ray diffraction methods to be valuable electron-dense probes of the intercalative process and generally of nucleic acid structure.s-10 Metallointercalators which cleave DNA,\" owing to the redox activity of the metal center, have furthermore been successfully employed in footprinting studies of drug binding and in the examination of higher-order chromatin s t r ~ c t u r e . ' ~ J ~ Chiral octahedral metal complexes containing aromatic ligands have been found recently to display enantiomeric selectivity in binding to double helical DNA.I4 Equilibrium dialysis of DNA with the racemic mixture of chiral metal complexes showed the optical enrichment of the less favored isomer in the dialysate. Absolute configuration assignments for tris(phenanthro1ine)ruthenium(I1) complexes revealed that it is the A isomer that binds preferentially to right-handed B-DNA.lS Ruthenium(I1) complexes have been particularly useful in monitoring stereoselective binding to DNA not only because of the stability of enantiomers but also because of the sensitivity of their photophysical properties to DNA binding.15 Luminescence enhancements and absorption hypochromism in the intense metal to ligand charge transfer band *To whom reprint requests should be sent. 0002-7863/85/ 1507-55 18$01.50/0 (MLCT) accompany DNA binding. Furthermore, enantiomers of tris(diphenylphenanthroline)ruthenium(II) have been shown to be useful chemical probes for helix handedness, since absorption decreases accompany binding of the A isomer but not of the A isomer to a right-handed helix, whereas spectrophotometric titrations indicate that both isomers bind equally to Z-form poly dGC.I6 In this report a detailed study of the photophysical properties of ruthenium(I1) complexes in the presence of DNA has been carried out. We were interested in determining how spectroscopic characteristics of the ruthenium(I1) complexes vary as a function of DNA binding, whether different modes of DNA binding might be distinguished by using these photophysical properties, and how best to detect chiral discrimination so as to optimize the sensitivity and utility of our spectroscopic probes for DNA handedness. The relatively long lifetimes of these complexes, their excellent, readily (1) Berman, M. H.; Young, P. R. Annu. Rev. Biophys. Bioeng. 1981, I O , 87. (2) Gale, E. F.; Cundliffe, E.; Reynolds, P. E.; Richmond, M. H.; Waring, M. \"The Molecular Basis of Antibiotic Action\"; Wiley: London, 1972; p 173. (3) Waring, M . J . Mol. Biol. 1970, 54, 247. (4) Lerman, L. S. J. Mol. Biol. 1961, 3, 18. (5 ) Neidle, S. Prog. Med. Chem. 1979, 16, 151. (6) (a) Le Pecq, J. B.; Paoletti, C. J . Mol. Biol. 1967, 27, 87. (b) Le Pecq, (7) Lippard, S. J. Acc. Chem. Res. 1978, 1 I , 21 1 . (8) Lippard, S. J.; Bond, P. J.; Wu, K. C.; Bauer, W. R. Science 1976, 194, J. B.; Paoletti, C. Ibid. 1967, 27, 2080. 7 36 . (9) Wang, A. H.; Nathans, J.; van der Marcel, G.; van Boom, J. H.; Rich, (IO) Wang, Y . S.; Lippard, S. J. J . Chem. Soc., Chem. Commun. 1977, A. Nature (London) 1978, 276, 471. .. 824. (11) Barton, J. K. Comments Inorg. Chem. 1985, 3, 321. (12) (a) Hertzberg, R. P.; Dervan, P. B. J. Am. Chem. SOC. 1982, 104, 313. (b) Van Dyke, M. W.; Hertzberg, R. P.; Dervan, P. B. Proc. Natl. Acad. Sci. U.S.A. 1982, 79, 5470. (c) Van Dyke, M. W.; Dervan, P. B. Biochemistry 1983, 22, 2373. (13) (a) Reich, K. A.; Marshall, L. E.; Graham, D. R.; Sigman, D. S. J. A m . Chem. SOC. 1981,103, 3582. (b) Pope, L. E.; Sigman, D. S. Proc. Natl. Acad. Sci. U.S.A. 1984, 81, 3. (c) Cartwright, I. L.; Elgin, S. C. R. \"9. Acids. Res. 1982, 10, 5835. (14) (a) Barton, J. K.; Dannenberg, J. J.; Raphael, A. L. J . Am. Chem. SOC. 1982, 104, 4967. (b) Barton, J. K. J . Biomol. Struct. Dyn. 1983, 1 , 621. ' (15) Barton, J. K.; Danishefsky, A. T.; Goldberg, J. M . J . Am. Chem. SOC. 1984, 106, 2172. (16) Barton, J. K.; Bade , L. A.; Danishefsky, A. T.; Alexandrescu, A. Proc. Natl. Acad. Sci. U.S.A. 1984, 81, 1961.
584 citations
TL;DR: The chiral ruthenium complexes, with luminescence characteristics indicative of binding modes, and stereo- selectivities that may be tuned to the helix topology, may be useful molecular probes in solution for nucleic acid secondary structure.
Abstract: Binding of tris(phenanthroline)ruthenium(II), R~(phen),~+, enantiomers to nucleic acids of different base compositions and structure was examined by equilibrium dialysis and photophysical methods. Measurement of enantioselectivity combined with photophysical experiments permits the structural characterization of two noncovalent binding modes of the ruthenium(I1) complexes to the DNA helix, one intercalatively bound mode showing a strong chiral preference for A-R~(phen)~'+ and the other, a surface-bound mode along the DNA major groove, showing a weak preference for A-R~(phen),~+. Luminescence decay of R~(phen),~+ isomers in the presence of DNA shows components of two different lifetimes. Quenching of the emission with ferrocyanide results in nonlinear Stern-Volmer plots. Finite polarization in the emission of both A- and A-R~(phen)~~+ in the presence of DNA is indicative of intercalation; greater polarization is found consistently for A-R~(phen)~~+ with DNA. The total binding affinity of R~(phen),~+ to DNA is ionic strength dependent in a manner consistent with the release of 2.2 counterions per bund ruthenium. Although binding to DNA of Ru(phen)p shows no clear dependence on the guanine-cytosine (GC) content of the DNA, variations in enantiomeric preferences both as a function of GC content and as a function of ionic strength are observed. Chiral discrimination for A-Ru(phen),2+ increases both with the percent GC and with increasing Na+ concentration. Based upon the stereoselectivities found by steady-state emission polarization, the variations are attributed to changes in chiral preferences for intercalation. This variation may indicate local changes in DNA groove size, e.g. a compression along the helix axis direction with increasing ionic strength or increasing percent GC. Weak surface binding, having a preference for A-R~(phen),~+, is observed with double-stranded RNA. For both R~(phen)~~+ and RU(DIP),~+ (DIP = 4,7-diphenyl- phenanthroline), binding to T4 DNA glycosylated in the major groove is markedly diminished compared to binding to calf thymus DNA. The chiral ruthenium complexes, with luminescence characteristics indicative of binding modes, and stereo- selectivities that may be tuned to the helix topology, may be useful molecular probes in solution for nucleic acid secondary structure
508 citations