Exploring hesperidin-copper complex as an enzyme mimic for monitoring macrophage activity

Journal of Solid State Electrochemistry - The present study evaluates the potential of hesperidin-copper complex for sensing superoxide anions, which is an important marker for the diagnosis of...     

Effect of Chemical Treatment and Fiber Loading on Mechanical Properties of Borassus (Toddy Palm) Fiber/Epoxy Composites

The aim of the present study was to investigate and compare the mechanical properties of untreated and chemically modified Borassus fiber–reinforced epoxy composites. Composites were prepared by the hand lay-up process by reinforcing Borassus fibers with epoxy matrix. To improve the fiber-matrix adhesion properties, alkali (NaOH) and alkali combined with silane (3-aminopropyltriethoxysilane) treatment of the fiber surface was carried out. Examinations through Fourier transform-infrared spectroscopy and scanning electron microscopy (SEM) were conducted to investigate the structural and physical properties of the Borassus fibers. Tensile properties such as modulus and strength of the composites made with chemically modified and untreated Borassus fibers were studied using a universal testing machine. Based on the experimental results, it was found that the tensile properties of the Borassus-reinforced epoxy composites were significantly improved as compared with the neat epoxy. It was also found that the fiber treated with a combination of alkali and silane exhibited superior mechanical properties to alkali-treated and untreated fiber composites. The nature of the fiber/matrix interface was examined through SEM of cryo-fractured samples. Chemical resistance of composites was also found to be improved with chemically modified fiber composites.     

One-pot synthesis of symmetrical and unsymmetrical acridine sulfonamide derivatives catalyzed by p-TSA

Research on Chemical Intermediates - Synthesis of a series of symmetrical and unsymmetrical 1,8-dioxo-octahydroacridine benzenesulfonamide derivatives has been achieved by one-pot, multicomponent...     

Structure and DNA cleavage properties of two copper(II) complexes of the pyridine-pyrazole-containing ligands mbpzbpy and Hmpzbpya

The DNA-cleavage properties of the two copper(II) complexes, [Cu(mbpzbpy)Br(2)](H(2)O)(2.5) (1) and [Cu(mpzbpya)Cl](CH(3)OH) (2), obtained from the ligands 6,6'-bis(3,5-dimethyl-N-pyrazolmethyl)-2,2'-bipyridine) (mbpzbpy) and 6'-(3,5-dimethyl-N-pyrazolmethyl)-2,2'-bipyridine-6-carboxylic acid) (Hmpzbpya), respectively, are reported. Upon coordination to Cu(II) chloride in methanol, one arm of the ligand mbpzbpy is hydrolyzed to form mpzbpya. Under the same experimental conditions, the reaction of mbpzbpy with CuBr(2) does not lead to ligand hydrolysis. The ligand mpzbpya is coordinated to a copper(ii) ion generating a CuN(3)OCl chromophore, resulting in a distorted square-pyramidal environment, whereas with the N(4) mbpzbpy ligand, the Cu(II) ion is four-coordinated in a distorted square planar geometry. Both complexes promote the oxidative DNA cleavage of phiX174 phage DNA in the absence of reductant. The oxidative nature of the DNA cleavage reaction has been confirmed by religation and cell-transformation experiments. Studies using standard radical scavengers suggest the involvement of hydroxyl radicals in the oxidative cleavage of DNA. Although both compounds do convert form I (supercoiled) DNA to form II (nicked, relaxed form), only complex 1 is able to produce small amounts of form III (linearized DNA). This observation may be explained either by the attack of the copper(ii) complexes to only one single strand of DNA, or by a single cleavage event. Statistical analysis of relative DNA quantities present after the treatment with both copper(ii) complexes supports a random mode of DNA cleavage.     

Unique ligand-based oxidative DNA cleavage by zinc(II) complexes of hpyramol and hpyrimol

The zinc(II) complexes reported here have been synthesised from the ligand 4-methyl-2-N-(2-pyridylmethyl)aminophenol (Hpyramol) with chloride or acetate counterions. All the five complexes have been structurally characterised, and the crystal structures reveal that the ligand Hpyramol gradually undergoes an oxidative dehydrogenation to form the ligand 4-methyl-2-N-(2-pyridylmethylene)aminophenol (Hpyrimol), upon coordination to Zn(II). All the five complexes cleave the phiX174 phage DNA oxidatively and the complexes with fully dehydrogenated pyrimol ligands were found to be more efficient than the complexes with non-dehydrogenated Hpyramol ligands. The DNA cleavage is suggested to be ligand-based, whereas the pure ligands alone do not cleave DNA. The DNA cleavage is strongly suggested to be oxidative, possibly due to the involvement of a non-diffusible phenoxyl radical mechanism. The enzymatic religation experiments and DNA cleavage in the presence of different radical scavengers further support the oxidative DNA cleavage by the zinc(II) complexes.     

Investigations on membrane perturbation by chrysin and its copper complex using self-assembled lipid bilayers

The mechanism of membrane interactions of most of the flavonoids in the presence of transition-metal ions is not well-understood. To understand this phenomenon, the present work aims to synthesize a chrysin-copper complex at room temperature and investigate its influence on the electrical characteristics of planar lipid bilayers. The chrysin-copper complex was characterized by various spectroscopic techniques and was found to have a metal/ligand ratio of 1:2 and of cationic nature. Its ability to inhibit 1,1'-diphenyl-2-picrylhydrazyl (DPPH) radicals was not significant at alkaline pH because of the involvement of the 5-hydroxy group in coordination with the copper ion compared to its parent flavonoid, chrysin (p < 0.05). The addition of different concentrations (20-100 μM) of chrysin and the chrysin-copper complex to lipid bilayers decreases the resistance, indicating a strong surface interaction and partial insertion into the bilayer near the lipid-water interface. The dose-dependent reduction in resistance as a result of the chrysin-copper complex is more pronounced in comparison to chrysin, implying that the bulkier and charged chrysin-copper complex displays greater ability to distort the lipid bilayer architecture. These conclusions were further confirmed by curcumin-loaded liposome permeabilization studies, where both chrysin and its Cu(II) complex increased the fluidity in a dose-dependent manner. However, the extent of fluidization by the chrysin-copper complex was nearly twice that of chrysin alone (p < 0.05). The implications of these surface interactions of chrysin and its copper complex on cell membranes were studied using a hypotonic hemolysis assay. Our results demonstrate that, at low concentrations (20 μM), the chrysin-copper complex exhibited twice the protection against hypotonic stress-induced membrane disruption when compared to chrysin. However, this stabilizing effect gradually decreased and became comparable to chrysin at higher concentrations. This biphasic behavior of the chrysin-copper complex could further be explored for therapeutic applications.     

Development and evaluation of a highly sensitive rapid response enzymatic nanointerfaced biosensor for detection of putrescine

Putrescine (1,4-diaminobutane) a biologically active diamine has been found to be a valuable analyte for several clinical and analytical purposes. The present work deals with diamine oxidase immobilized on iron oxide nanoparticles for quantifying the amount of putrescine produced, by the decarboxylation of ornithine, which is converted into hydrogen peroxide by the enzyme diamine oxidase (DAO). This reaction can be quantified using electrochemical techniques, which forms the basis of this work. Iron oxide (Fe(3)O(4)) nanoparticles, synthesized using thermal co-precipitation, were chosen for immobilization of DAO due to its simple preparation procedure, high surface area and cost-effectiveness. The size of the particles was in the range of 25-35 nm and the enzyme was linked covalently by carbodiimide activation and confirmed using FT-IR. For detecting the hydrogen peroxide released in the reaction, a glassy carbon-working electrode coated with enzyme linked iron oxide nanoparticles was poised at +0.4 V versus an Ag/AgCl reference electrode and a platinum wire was used as the counter electrode. A step-wise increase in current was observed and linearity was obtained in the range of 2-8 nM, with 0.65 nM as the minimum detection limit and the response time was found to be 0.3 seconds. Ascorbic acid, a common interfering molecule in biological samples, did not interfere with the measurements indicating the high degree of specificity of the diamine oxidase-based nano-interfaced biosensor.     

On the synergistic catalytic properties of bimetallic mesoporous materials containing aluminum and zirconium: the Prins cyclisation of citronellal

Bimetallic three‐dimensional amorphous mesoporous materials, Al‐Zr‐TUD‐1 materials, were synthesised by using a surfactant‐free, one‐pot procedure employing triethanolamine (TEA) as a complexing reagent. The amount of aluminium and zirconium was varied in order to study the effect of these metals on the Brønsted and Lewis acidity, as well as on the resulting catalytic activity of the material. The materials were characterised by various techniques, including elemental analysis, X‐ray diffraction, high‐resolution TEM, N₂ physisorption, temperature‐programmed desorption (TPD) of NH₃, and ²⁷Al MAS NMR, XPS and FT‐IR spectroscopy using pyridine and CO as probe molecules. Al‐Zr‐TUD‐1 materials are mesoporous with surface areas ranging from 700–900 m² g^?1, an average pore size of around 4 nm and a pore volume of around 0.70 cm³ g^?1. The synthesised Al‐Zr‐TUD‐1 materials were tested as catalyst materials in the Lewis acid catalysed Meerwein–Ponndorf–Verley reduction of 4‐tert‐butylcyclohexanone, the intermolecular Prins synthesis of nopol and in the intramolecular Prins cyclisation of citronellal. Although Al‐Zr‐TUD‐1 catalysts possess a lower amount of acid sites than their monometallic counterparts, according to TPD of NH₃, these materials outperformed those of the monometallic Al‐TUD‐1 as well as Zr‐TUD‐1 in the Prins cyclisation of citronellal. This proves the existence of synergistic properties of Al‐Zr‐TUD‐1. Due to the intramolecular nature of the Prins cyclisation of citronellal, the hydrophilic surface of the catalyst as well as the presence of both Brønsted and Lewis acid sites synergy could be obtained with bimetallic Al‐Zr‐TUD‐1. Besides spectroscopic investigation of the active sites of the catalyst material a thorough testing of the catalyst in different types of reactions is crucial in identifying its specific active sites.     

Characterization of form-stable phase-change material for solar photovoltaic cooling

Solar PV panel cooling is essential to achieve maximum efficiency of PV modules. Phase-change material (PCM) is one of the prominent options to cool the panel and reduce the temperature, since PCMs have low thermal conductivity. Expanded graphite particles are used to enrich the structure and stability as well as to increase the thermal properties. In the present research work, polyethylene glycol (PEG) 1000 is used as a base material and expanded graphite for inclusive particle. A novel form-stable PEG1000/EG composite PCM mixture is prepared, using impregnation and dispersion method. Expanded graphite and PEG1000/EG sample phase compositions are investigated, using X-ray diffraction technique. No new peak is identified in the composite PCM sample. The surface morphology and structure of EG and PEG1000/EG are investigated, using scanning electron microscopy (SEM). Chemical stability analysis is done by Fourier-transform infrared spectroscopy. Thermal properties of the prepared composite PCMs are analysed by differential scanning calorimetry, thermogravimetric analysis (TGA) and KD2 pro analyser. Results show that addition of EG in various propositions (5%, 10% and 15%) enhances the thermal conductivity of PCM samples from 0.3654 to 1.7866 W mK^?1, while melting point and latent heat of fusion of PCM samples are getting reduced. TGA thermographs are used to investigate the thermal stability of the composite PCM samples. TGA curves show that loss of mass happens above the operating temperature, and it is varied with different mass ratios of EG. Characterization of the prepared composite PCM samples is compared and found that PEG1000-85%/EG-15% is the best form-stable PCM, suitable for cooling the solar PV panel as well as to improve the electrical efficiency coupled with a decrease of temperature in the range of 35 °C to 40 °C.