Presence Of Complexes Research Articles

Consistent Binding Aptitude of Halides and Oxyanions via Cooperative vs. Non‐Cooperative Binding Modes by Neutral Napthyl Bis‐Urea Receptors

AbstractTwo electron‐rich napthyl ring containing bisurea receptor derived from ortho (L1) and meta (L2)‐phenylenediamine moiety were designed and synthesized for investigating their anion coordination behavior. L1 self‐assembled in presence of organic terephthalate anion into a dimeric pseudo‐capsular host‐assembly sealed by tetrabutylammonium counter cation (Complex 1 c). However, L2 self‐assembled in 2:4 host‐guest fashions (Complex 2 d) with H‐bonded dihydrogenphosphate tetrameric anionic guest in the presence of excess n‐TBA (H2PO4). Further, receptor L1 has been found to self‐assembled into unimolecular cooperative 1:1 complex in presence of spherical Chloride anion (Complex 1 a) and planar Acetate anion (Complex 1 b). Moreover, receptor L2 forms similar kind of non‐capsular host‐guest assembly in presence of spherical halides like Cl−, Br−, and F−. To validate the result obtained in the solid state studies, 1H‐NMR titration experiments have also been performed using n‐TBA salts of anions to inspect the solution state anion binding behavior of isomeric receptors L1 and L2.

The C-terminal tail of the NEIL1 DNA glycosylase interacts with the human mitochondrial single-stranded DNA binding protein

The 16.5 kb mitochondrial genome is subjected to damage from reactive oxygen species (ROS) generated in the cell during normal cellular metabolism and external sources such as ionizing radiation and ultraviolet light. ROS cause harmful damage to DNA bases that could result in mutagenesis and various diseases, if not properly repaired. The base excision repair (BER) pathway is the primary pathway involved in maintaining the integrity of mtDNA. Several enzymes that partake in BER within the nucleus have also been identified in the mitochondria. The nei-like (NEIL) DNA glycosylases initiate BER by excising oxidized pyrimidine bases and others such as the ring-opened formamidopyrimidine and the hydantoin lesions. During BER, the NEIL enzymes interact with proteins that are involved with DNA replication and transcription. In the current manuscript, we detected NEIL1 in purified mitochondrial extracts from human cells and showed that NEIL1 interacts with the human mitochondrial single-stranded DNA binding protein (mtSSB) via its C-terminal tail using protein painting, far-western analysis, and gel-filtration chromatography. Finally, we scrutinized the NEIL1-mtSSB interaction in the presence and absence of a partial-duplex DNA substrate using a combination of multi-angle light scattering (MALS) and small-angle X-ray scattering (SAXS). The data indicate that NEIL1 and homotetrameric mtSSB form a larger ternary complex in presence of DNA, however, the tetrameric form of mtSSB gets disrupted by NEIL1 in the absence of DNA as revealed by the formation of a smaller NEIL1-mtSSBmonomer complex.

UV/solar light induced photocatalytic degradation of phenols and dyes by Fe(PS-BBP)Cl3

A polymer supported complex Fe(PS-BBP)Cl3 [PS = chloromethylated polystyrene divinyl benzene; BBP = 2,6-bis(benzimidazolyl)pyridine] was prepared and characterized by elemental analyses, FT-IR and electronic spectral studies, AAS, magnetic moment measurement, BET surface area measurement and thermal analysis. Its photocatalytic properties were evaluated by studying the degradation of phenolic compounds (phenol, catechol, hydroquinone, p-chlorophenol, p-nitrophenol, o-cresol, p-cresol) and dyes (methyl orange, methyl red, rhodamine B) under UV light illumination to CO2 and H2O in the presence of H2O2. The effects of important parameters such as concentration of Fe(PS-BBP)Cl3 and substrates (phenol or methyl orange), amount of H2O2, and time have been investigated on the rate of degradation of phenol and methyl orange. Complete degradation of phenol and methyl orange occurred at room temperature with Fe(PS-BBP)Cl3 under UV radiation in 30 and 120 min respectively. Experimental results indicated that the reactivity of Fe(PS-BBP)Cl3 is more than its unsupported analogue. The intermediates formed during the process were identified using LCMS. Photoelectrochemical measurements (amperometry) carried out for Fe(PS-BBP)Cl3 revealed the faster migration of photo-induced charge-carriers. The degree of mineralization was also confirmed by chemical oxygen demand (COD) experiments. The results indicated that these could be effectively decolorized and degraded by photocatalytic method, without generation of any hazardous wastes or by-products as evident from the considerable reduction in COD values. The photocatalytic activity of the supported complex in presence of solar light was also investigated.

Regulation of NF-κB by the p105-ABIN2-TPL2 complex and RelAp43 during rabies virus infection.

At the crossroad between the NF-κB and the MAPK pathways, the ternary complex composed of p105, ABIN2 and TPL2 is essential for the host cell response to pathogens. The matrix protein (M) of field isolates of rabies virus was previously shown to disturb the signaling induced by RelAp43, a NF-κB protein close to RelA/p65. Here, we investigated how the M protein disturbs the NF-κB pathway in a RelAp43-dependant manner and the potential involvement of the ternary complex in this mechanism. Using a tandem affinity purification coupled with mass spectrometry approach, we show that RelAp43 interacts with the p105-ABIN2-TPL2 complex and we observe a strong perturbation of this complex in presence of M protein. M protein interaction with RelAp43 is associated with a wide disturbance of NF-κB signaling, involving a modulation of IκBα-, IκBβ-, and IκBε-RelAp43 interaction and a favored interaction of RelAp43 with the non-canonical pathway (RelB and p100/p52). Monitoring the interactions between host and viral proteins using protein-fragment complementation assay and bioluminescent resonance energy transfer, we further show that RelAp43 is associated to the p105-ABIN2-TPL2 complex as RelAp43-p105 interaction stabilizes the formation of a complex with ABIN2 and TPL2. Interestingly, the M protein interacts not only with RelAp43 but also with TPL2 and ABIN2. Upon interaction with this complex, M protein promotes the release of ABIN2, which ultimately favors the production of RelAp43-p50 NF-κB dimers. The use of recombinant rabies viruses further indicates that this mechanism leads to the control of IFNβ, TNF and CXCL2 expression during the infection and a high pathogenicity profile in rabies virus infected mice. All together, our results demonstrate the important role of RelAp43 and M protein in the regulation of NF-κB signaling.

Luminescence of Europium complex enhanced by surface plasmons of gold nanoparticles for possible application in luminescent solar concentrators

The paper consists of two parts, the first part is a short description of continuous brilliant scientific activity of Renata Reisfeld and the second part consists of the new findings of luminescence of Europium complex increased by surface plasmons of gold nanoparticles. The studies were performed in Jerusalem for improvement of efficiency of luminescent solar concentrators. The paper describes synthesis of gold nanoparticles and their incorporation into organically modified silica sol-gel matrix co-doped by Europium complex with ligands of EDTA and polyvinylpyrrolidone. The steady state spectroscopy of samples undoped and co-doped by nanoparticles reveals increase of fluorescence of the complexes in presence of gold nanoparticles. The phenomenon arises from scattered light by the nanoparticles and possibly energy transfer.

A correntropy inspired variable step-size sign algorithm against impulsive noises

The adaptive variable step-size technique is an effective way to improve the convergence rate of an adaptive filtering algorithm. However, for most existing variable step-size sign algorithm against impulsive noise, either the performance is not good enough, or the calculation is complex. In this paper, a correntropy inspired variable step-size method for sign algorithm is proposed. The new variable step-size method is computationally simple and robust to impulsive noises. Theoretical analysis and simulation results demonstrate that the proposed algorithm can achieve desirable performance with low computational complexity in presence of impulsive noises.

Indirect determination of the flavor enhancer maltol in foods and beverages through flame atomic absorption spectrometry after ultrasound assisted-cloud point extraction

A simple ultrasound assisted-cloud point extraction (UA-CPE) method was developed and combined with flame atomic absorption spectrometry (FAAS) for pre-concentration and indirect determination of the flavor enhancer maltol in foods and beverages. The method is based on reduction of Cu(II) to Cu(I) by maltol at pH 6.5, and subsequent selective interaction of Cu(I) with bathocuproine (BCP) to form a ternary complex in presence of sodium dodecyl sulfate (SDS). Under the optimized conditions, pre-concentration of a 35mL sample solution allowed detection of 1.24µgL−1 maltol in a linear range of 4–230µgL−1. The method was validated by intra- and inter-day precision studies ranging from 2.1 to 3.4%, and recoveries ranged from 93.3% to 104.4% using standard addition method. After pretreatment with two different sample preparation steps assisted by ultrasound energy, the proposed method was applied successfully for determination of maltol in selected foods and beverages.

Dimethyl Sulphoxide a Useful Reagent for Organic Synthesis

Dimethyl sulphoxide as a reagent brings about N-methylthiomethylation and N,N/-methyl -thiomethylation in substituted barbituric acids. It converts 4-acetoxy coumarins to corresponding ylides and brings about methylene insertion in 1,6-naphtharidenes at reflux temperature.DMSO activated by trifluoro-aceticanhydride brings about formation of mono, bis and tris-sulphonic substituted derivatives when interacted with cyclo pentadiene and trimethylsilyl cyclopentadiene.This reagent converts 3-Nitro-4-hydroxy coumarins to salicylic acid in dichloromethane at low temperature.DMSO-acetic anhydride reagent converts enols to sulphur ylides, introduces methylthiomethyl group into phenols and oxidizes secondary alcohols to corresponding ketones. It brings about oxidative rearrangement in polyporic acid and converts 4-hydroxy coumarins and its 3-substituted derivatives into a wide range of products under different conditions.DMSO-SO3 pyridine complex in presence of triethyl amine oxidizes cis-diols to corresponding quinones.DMSO-activated by N-bromosuccinimide brings about methylation of alcohols and converts diols to their corresponding methylene-acetals.

Anthraquinone-biimidazole based ruthenium(II) complexes as selective multichannel anion sensors and multi-readout molecular logic gates and memory devices: Combined experimental and DFT/TD-DFT study

In this work we will report anion sensing properties as well as multiple Boolean logic operations of recently reported Ru(II) complexes based on a biimidazole-anthraquinone ligand (Anq-BiimzH2). Covalent linking of electron accepting 9,10-anthraquinone moiety to the biimidazole unit followed by its coordination to Ru(II) center, leads to enhance the acidity of the imidazole NH protons in coordinated Anq-BiimzH2. Two NH protons which adopt a syn conformation in the complexes can be utilized for sensing of selective anions either via hydrogen bonding interaction or by complete proton transfer. The anion sensing studies of the complexes were thoroughly investigated in both organic and pure aqueous media through multiple channels viz. absorption, steady state and time-resolved emission, and 1H NMR spectroscopic techniques as well as by cyclic and square wave voltammetry. The complexes behave as highly sensitive sensors for F−, AcO−, CN−, and to some extent for H2PO4− in acetonitrile without much selectivity. In contrast to acetonitrile, the complexes posses high sensitivity and selectivity towards CN− even in presence of excess of other studied anions in water with detection limit lying in the range between 5.24×10−7 and 6.67×10−7M, making them useful for practical application. By utilizing the optical output signals upon interaction with a particular set of anions (F−, CN−, AcO− and OH−) and H+, the functions of two-inputs INHIBIT and IMPLICATION logic gates as well as three inputs NOR logic gate have been nicely demonstrated. More importantly, the complicated function of memory device was also mimicked by the complexes. Computational investigation with the help of density functional theory (DFT) and time-dependent density functional theory (TD-DFT) were performed to understand and interpret the experimentally observed optical properties of the complexes. Moreover, the experimental trend of the red-shifts of absorption and emission bands upon successive deprotonation of the complexes in presence of selective anions was nicely reproduced by calculations.

Turing patterns induced by cross-diffusion in a predator-prey system in presence of habitat complexity

In this paper, we have investigated the phenomena of Turing pattern formation in a predator-prey model with habitat complexity in presence of cross diffusion. Using the linear stability analysis, the conditions for the existence of stationary pattern and the existence of Hopf bifurcation are obtained. It is shown analytically that the presence of cross diffusion in the system supports the formation of Turing pattern. Two parameter bifurcation analysis are done analytically and corresponding bifurcation diagrams are presented numerically. A series of simulation results are plotted for different biologically meaningful parameter values. Effects of variation of habitat complexity and the predator mortality rate and birth rate of prey on pattern formation are also reported. It is shown that cross-diffusion can lead to a wide variety of spatial and spatiotemporal pattern formation. It is found that the model exhibits spot and stripe pattern, and coexistence of both spot and strip patterns under the zero flux boundary condition. It is observed that cross-diffusion, habitat complexity, birth rate of prey and predator’s mortality rate play a significant role in the pattern formation of a distributed population system of predator-prey type.

Photocatalytic Decolourization of Bromophenol Blue in Aqueous Solution with Cu(II)-Peroxo Complexes in Presence of SDS

In the current work, the photocatalytic decolourization of Bromophenol blue (BrPB) with Cu(II)-peroxo complexes in presence of sodium dodecyl sulfate (SDS) under UV light was investigated. The analytical parameters such as pH, titanium dioxide (TiO2) catalyst dosage, initial concentration of the dye, amounts of H2O2, Cu(II) and SDS affecting the photocatalytic decolourization of BrPB were studied. The obtained optimal values were as follows: pH 6.0, 55 mmol L-1 H2O2, 60 μg L-1 Cu(II), 0.02 mmol L-1 SDS, 5 mg L-1 dye, 1.0 g L-1 TiO The percent removals have been obtained as 81.6% and 76.3% for TiO2 -UV-H2O2-Cu(II) system with and without SDS while they are 74.3% and 66.2% for TiO2-UV system with and without H2O2 under the optimized conditions. Consequently, it has been observed that the maximum removal rate is obtained for TiO2 -UV-H2O2-Cu(II) in presence of SDS at premicellar region with a value of 81.6%. The removal rate of the dye was monitored by measuring the absorbance at 592 nm, using UV-visible spectrophotometer.

A dinuclear ruthenium(II) complex as turn-on luminescent probe for hypochlorous acid and its application for in vivo imaging.

A dinuclear ruthenium(II) complex Ruazo was designed and synthesized, in which oxidative cyclization of the azo and o-amino group was employed for the detection of hypochlorous acid (HClO) in aqueous solution. The non-emissive Ruazo formed highly luminescent triazole-ruthenium(II) complex in presence of HClO and successfully imaged HClO in living cell and living mouse.

Effect of loratadine on the dissolution and bioavailability of gliclazide from its hydroxypropyl-β-cyclodextrin complex

Gliclazide (GZD) is a hypoglycemic agent that has slow dissolution rate and variable bioavailability. Inclusion complex of GZD with hydroxypropyl-β-cyclodextrin (HPβCD) was prepared with the molar ratio 1:2 by solvent evaporation method. The complex was characterized using Fourier transform infra-red spectroscopy and differential scanning calorimetry. Solubility and in vitro dissolution studies were performed at acidic and neutral pH values. Furthermore, the competitive interactions of the antihistamine loratadine (LOR) on the binding of GZD to HPβCD were studied by performing solubility and in vitro dissolution studies of GZD-HPβCD complex in presence and absence of the competing drug at pH values 4.5 and 6.8. GZD-HPβCD complex was found to enhance the dissolution of the drug in all pH values studied. The presence of LOR with GZD-HPβCD complex led to some pH dependent changes in the dissolution of the complex which supported the results obtained from the solubility studies. Using blood glucose level as a pharmacodynamic marker that reflects the bioavailability of GZD, in vivo studies have shown that GZD when given as its HPβCD complex together with LOR exhibits about 25 % lower bioavailability (effect) compared to GZD alone. In an attempt to explain the in vivo and dissolution studies, higher order complexes (aggregates) involving LOR, GZD and HPβCD were proposed. The formation of such larger complexes was supported by stoichiometric and diffusion studies.

Quantum transport behavior of Ni-based dinuclear complexes in presence of zigzag graphene nanoribbon as electrode

Quantum transport properties of some Ni-based dinuclear complexes with different polydentate organic ligands have been studied by applying abinitio density functional theory along with nonequilibrium Green’s function formulations. It is demonstrated that these materials are capable of showing multifunctional spin dependent properties by the influence of edge states of zigzag edged graphene nanoribbons. The current–voltage characteristics of these materials show spin dependent negative differential resistance behavior, spin filtering effect, and also voltage rectifying property. Proper tuning of these materials can alter these effects which may be utilized in various spintronic devices.

Supramolecular effect of curcurbit[7]uril on the binding mode of 2-(4-(dimethylamino) styryl)-1-methylpyridinium iodide with Calf Thymus DNA: From minor groove to intercalative

The effect of curcurbit[7]uril (CB[7]) in the binding mode of 2-(4-(dimethylamino) styryl)-1-methylpyridinium (DASPMI) with Calf Thymus DNA has been discussed in this paper. Red shift, intensity change in absorption and emission spectra and presence of isosbestic point with increasing concentration of CB[7] in groove bound DASPMI–DNA complex indicates a change in binding pattern. Appearance of a third slower component in lifetime decay in presence of CB[7] which gets more slow in high CB[7] concentration is indicative of a new type of binding. Major changes in ct-DNA bands in circular dichroism spectra with addition of CB[7] make a strong case for intercalative binding. Increased computed values of binding constant associated with diminishing quenching constant in presence of potassium iodide make a positive candidate for intercalative binding. Formation of big spherical condensate in DASPMI–DNA complex in presence of CB[7] which grows bigger in higher CB[7] concentration shows a morphological change. Molecular docking nicely portrays the intercalative nature of binding corroborating the experimental evidences.

RNA-Binding Efficacy of N-Phenylbenzohydroxamic Acid: An Invitro and Insilico Approach

RNA has attracted recent attention for its key role in gene expression and hence targeting by small molecules for therapeutic intervention. This study is aimed to elucidate the specificity of RNA binding affinity of parent compound of N-arylhydroxamic acids series, N-phenylbenzohydroxamic acid trivially named as PBHA,C6H5NOH.C6H5C ˭ O. The binding behavior was examined by various biophysical methods such as absorption, fluorescence, and viscosity measurements. Molecular docking was also done. The value of affinity constant and overall binding constant was calculated 5.79 ± 0.03 × 104 M−1 and K’ = 1.09 ± 0.03 × 105 M−1, respectively. The Stern-Volmer constant Ksv obtained was 2.28 ± 0.04 × 104 M−1. The compound (PBHA) shows a concentration-based enhancement of fluorescence intensity with increasing RNA concentration. Fluorescence quenching of PBHA–RNA complex in presence of K4 [Fe(CN)6] was also observed. Viscometric studies complimented the UV results where a continuous increase in relative viscosity of the RNA solution was observed with added optimal PBHA concentration. All the experimental evidences indicate that PBHA can strongly bind to RNA through an intercalative mode.

Synthesis and characterization of ion-imprinted resin for selective removal of UO2 (II) ions from aqueous medium.

In this work, uranyl ion-imprinted resin based on 2-(((4-hydroxyphenyl)amino)methyl)phenol was synthesized by condensation polymerization of its uranyl complex in presence of resorcinol and formaldehyde cross-linkers. Numerous instrumental techniques including elemental analysis, Fourier transform infrared spectroscopy, ultraviolet, (1) H along with (13) C nuclear magnetic resonance spectroscopy have been employed for complete characterization of the synthesized ligand and its uranyl complex. Additionally, the obtained ion-imprinted and non-imprinted resins were investigated using scanning electron microscope and Fourier transform infrared spectroscopy. The effects of various essential parameters such as pH, temperature and contact time on removal of uranyl ions have been examined, and the results indicated that the obtained resin exhibited the optimum activity at pH 5. Furthermore, the adsorption process was spontaneous at all studied temperatures and followed the second-order kinetics model. Also, Langmuir adsorption isotherm exhibited the best fit with the experimental results with maximum adsorption capacity 139.3 mg/g. Moreover, the selectivity studies revealed that the ion-imprinted resin exhibited an obvious affinity toward the uranyl ions in presence of other metal ions compared with the non-imprinted resin.

Methyl- and methoxysalicylatocopper(II) complexes with 2-aminomethylpyridine

Abstract As a part of our systematic study of copper(II) complexes in presence of biologically active ligands, we concluded to realize experiments with methyl- or methoxysalicylatocopper(II) complexes in presence of 2-aminomethylpyridine (ampy) ligand. This has resulted in four new complexes of the formula Cu(XSal)2(ampy) (where XSal are 3-MeSal− = 3-methylsalicylate, 4-MeSal− = 4-methylsalicylate, 5-MeSal− = 5-methylsalicylate, or 4-MeOSal− = 4-methoxylsalicylate anions). The synthesis, elemental analysis and spectral properties (EPR, electronic and infrared) are reported. The Cu(II) atom in all four complexes is probably coordinated by two nitrogen atom of the bidentate chelating ampy as well as monodentate and/or highly asymmetrically chelating salicylate anions. Based on the analyses it was concluded that the structure of these new compounds could be similar to [Cu(HCOO)2(ampy)], or [Cu(CH3COO)2(ampy)] that are reported in the literature.

Synthesis, characterization, antibacterial, DNA binding and cleavage studies of mixed ligand Cu(II), Co(II) complexes.

Mixed-ligand Cu(II), Co(II) complexes of formulae [Co(NSALT)(A.A)(H2O)](1), [Co(OHAPT)(A.A)H2O](2), and [Cu(ESALT)(ABPH)H2O] (3) were obtained by refluxing methanol solutions of copper, cobalt chlorides with the appropriate ligands. The complexes were characterized by the ESI-MASS, vibrational spectroscopy (Fourier transform-IR), (1)H-NMR spectroscopy, UV-vis spectroscopy, TGA, ESR, SEM and powder XRD. The preliminary DNA-binding activity of the complexes was studied by recording electronic absorption spectra of the complexes in presence of CT-DNA. The binding constants of three complexes towards calf thymus DNA (CT-DNA) [1.2 × 10(4)M(-1) for 1, 2.5 × 10(4)M(-1) for 2, and 3.0 × 10(4)M(-1) for 3] indicate strong interaction of 3. Changes in the fluorescence of ethidium bromide in the presence of DNA suggest intercalation into or electrostatic interactions with CT DNA. The quenching constants, KSV towards-DNA calculated through fluorescence spectra are 2.9 × 10(4)M(-1)for 1, 1.8 × 10(4)M(-1) for 2, and 3.2 × 10(4)M(-1) for 3. Docking studies on DNA complexes confirm the binding of 1 and 2 in the major groove of CT-DNA (CTP-1 Endonuclease). Moreover, the antibacterial effect of 1-3 against the five bacterial species was evaluated. The metal complexes have cleavage affinity towards PBR322 plasmid. Furthermore, the antioxidant activities of the complexes were determined by DPPH scavenging activity method.

Fluorescence enhancement and quenching of Eu(TTFA)3 by Ag nanoparticles at different excitations

The luminescence properties of Eu(TTFA)3 complex in presence of silver nanoparticles were investigated at three excitation wavelengths of 350nm, 383nm and 463nm, respectively. Luminescence quenching and enhancement were both observed at three different excitation and emission wavelengths. Luminescence at 612nm, 578nm, 590nm and 650nm were enhanced at excitation wavelength of 350nm, and quenched at excitation wavelength of 383nm. The enhancement factor reached to 1.6 and the quench factor was about 0.65. For 463nm excitation, the luminescence at 612nm was quenched, and the quench factor reached to 0.85. Luminescence at other three emission wavelengths (578nm, 590nm, and 650nm) was enhanced, with the greatest enhancement factor of ~5.