A highly sensitive CE-UV method with dynamic coating of silica-fused capillaries for monitoring of nucleotide pyrophosphatase/phosphodiesterase reactions

A new highly sensitive capillary electrophoresis (CE) method applying dynamic coating and on-line stacking for the monitoring of nucleotide pyrophosphatases/phosphodiesterases (NPPs) and the screening of inhibitors was developed. NPP1 and NPP3 are membrane glycoproteins that catalyze the hydrolysis nucleotides, e.g. convert adenosine 5'-triphosphate to adenosine 5'-monophosphate (AMP) and pyrophosphate. Enzymatic reactions were performed and directly subjected to CE analysis. Since the enzymatic activity was low, standard methods were insufficient. The detection of nanomolar AMP and other nucleotides could be achieved by field-enhanced sample injection and the addition of polybrene to the running buffer. The polycationic polymer caused a dynamic coating of the silica-fused capillary, resulting in a reversed electroosmotic flow. The nucleotides migrated in the direction of the electroosmotic flow, whereas the positively charged polybrene molecules moved in the opposite direction, resulting in a narrow sample zone over a long injection time. Using this on-line sensitivity enhancement technique, a more than 70-fold enrichment was achieved for AMP (limit of detection, 46 nM) along with a short migration time (5 min) without compromising separation efficiency and peak shape. The optimized CE conditions were as follows: fused-silica capillary (30 cm effective lengthx75 mum), electrokinetic injection for 60 s, 50 mM phosphate buffer pH 6.5, 0.002% polybrene, constant current of -60 muA, UV detection at 210 nm, uridine 5'-monophosphate as the internal standard. The new method was used to study enzyme kinetics and inhibitors. It opens an easy way to determine the activities of slowly metabolizing enzymes such as NPPs, which are of considerable interest as novel drug targets.     

Water promoted, microwave-assisted oxidative novel deamination of N-aminoquinazolinones

A novel deamination of 2-alkyl/aryl 3-amino-4（3H）-quinazolinones series using aqueous KMnO4 under thermal condition and microwave irradiation is described. Compared to thermal condition, significantly higher yields in much shorter times were observed for reactions under microwave irradiation. A plausible mechanism has been proposed for the oxidative water-promoted deamination.     

Effect of borate buffer on the photolysis of riboflavin in aqueous solution

The photolysis of riboflavin (RF) in the presence of borate buffer (0.1-0.5M) at pH 8.0-10.5 has been studied using a specific multicomponent spectrophotometric method for the determination of RF and photoproducts, formylmethylflavin (FMF), lumichrome (LC) and lumiflavin (LF). The overall first-order rate constants for the photolysis of RF (1.55-4.36 x 10(-2)min(-1)) and the rate constants for the formation of FMF (1.16-3.52 x 10(-2)min(-1)) and LC (0.24-0.84 x 10(-2)min(-1)) have been determined. The values of all these rate constants decrease with an increase in buffer concentration suggesting the inhibition of photolysis reaction by borate species. The kinetic data support the formation of a RF-borate complex involving the ribityl side chain to cause the inhibition of photolysis. The second-order rate constants for the borate inhibited reaction range from 1.17-3.94 x 10(-2)M(-1)min(-1). The log k-pH profiles for the reaction at various buffer concentrations indicate a gradual increase in rate, with pH, up to 10 followed by a decrease in rate at pH 10.5 probably due to ionization of RF and quenching of fluorescence by borate species. A graph of second-order rate constants against pH is a sigmoid curve showing that the rate of photolysis increases with an increase in pH. The results suggest the involvement of excited singlet state, in addition to excited triplet state, in the formation of LC.     

Propagation of the nonlinear damped Korteweg‐de Vries equation in an unmagnetized collisional dusty plasma via analytical mathematical methods

In this article, we consider the problem formulation of dust plasmas with positively charge, cold dust fluid with negatively charge, thermal electrons, ionized electrons, and immovable background neutral particles. We obtain the dust‐ion‐acoustic solitary waves (DIASWs) under nonmagnetized collision dusty plasma. By using the reductive perturbation technique, the nonlinear damped Korteweg‐de Vries (D‐KdV) equation is formulated. We found the solutions for nonlinear D‐KdV equation. The constructed solutions represent as bright solitons, dark solitons, kink wave and antikinks wave solitons, and periodic traveling waves. The physical interpretation of constructed solutions is represented by two‐ and three‐dimensional graphically models to understand the physical aspects of various behavior for DIASWs. These investigation prove that proposed techniques are more helpful, fruitful, powerful, and efficient to study analytically the other nonlinear nonlinear partial differential equations (PDEs) that arise in engineering, plasma physics, mathematical physics, and many other branches of applied sciences.     

Development and validation of a stability-indicating method for determination of free sterols in the Asian medicinal leech Hirudo manillensis

A rapid, simple, sensitive, selective, precise and robust thin-layer chromatography densitometric method for the determination of free sterols in leech was developed and validated on silica gel layer using carbon tetrachloride-methanol-formic acid (9.5:1.5:0.55, v/v/v). Spectrodensitometric scanning was carried using a Camag TLC scanner III at 366 nm after spraying 2% methanolic sulphuric acid, which gave compact spots for cholesterol (R(F) = 0.35 ± 0.02). The regression analysis data for calibration plot implied a good linear relationship (r(2) = 0.99958) between response and concentration over the range 100-600 ng per spot with respect to peak area. The limits of detection and quantification were found to be 13.8 ± 0.51 and 45.01 ± 1.29 ng per spot, respectively. Validation was in accordance to the International Conference on Harmonization guidelines. Cholesterol was subjected to forced stress conditions of oxidation, hydrolysis and heat. Degradation products resulting from the forced stress did not interfere with detection because the degradant peaks were well separated from the cholesterol peak. The densitometric method can be regarded as stability-indicating and can be used for quality control assay of cholesterol in leech extract.     

Electrical fingerprinting, 3D profiling and detection of tumor cells with solid-state micropores

Solid-state micropores can provide direct information of ex vivo or in vitro cell populations. Micropores are used to detect and discriminate cancer cells based on the translocation behavior through micropores. The approach provides rapid detection of cell types based on their size and mechano-physical properties like elasticity, viscosity and stiffness. Use of a single micropore device enables detection of tumor cells from whole blood efficiently, at 70% CTC detection efficiency. The CTCs show characteristic electrical signals which easily distinguish these from other cell types. The approach provides a gentle and inexpensive instrument that can be used for specific blood analysis in a lab-on-a-chip setting. The device does not require any preprocessing of the blood sample, particles/beads attachment, surface functionalization or fluorescent tags and provides quantitative and objective detection of cancer cells.     

Quinoacridine derivatives with one-dimensional aggregation-induced red emission property

A new series of acceptor-donor-acceptor (A-D-A) type quinoacridine derivatives (1-3) with aggregation-induced red emission properties were designed and synthesized. In these compounds, the electron-withdrawing 2-(3,5-bis(trifluoromethyl)phenyl)acetonitrile groups act as electron-accepting units, while the alkyl-substituted conjugated core acts as electron-donating units. The restriction of intramolecular rotation was responsible for the AIE behavior of compounds 1-3. All compounds were employed as building blocks to fabricate one-dimensional (1-D) organic luminescent nano- or microwires based on reprecipitation or slow evaporation approaches. Morphological transition from zero-dimensional (0-D) hollow nanospheres to 1-D nanotubes has been observed by recording SEM and TEM images of aggregated sates of compound 2 in THF/H(2)O mixtures at different aging time. It was demonstrated that the synthesized compounds with different lengths of alkyl chains displayed different wire formation properties. The single-crystal X-ray analysis of compound 2 provided reasonable explanation for the formation of 1-D nano- or microstructures.     

High magnetic exchange coupling constants: a density functional theory based study of substituted schlenk diradicals

The Schlenk diradical has been known since 1915. After a detailed experimental work by Rajca, its magnetic nature has remained more or less unexplored. We have investigated by quantum chemical calculations the nature of magnetic coupling in 11 substituted Schlenk diradicals. Substitution has been considered at the fifth carbon atom of the meta-phenylene moiety. The UB3LYP method has been used to study 12 diradicals including the original one. The 6-311G(d,p) basis set has been employed for optimization of molecular geometry in both singlet and triplet states for each species. The singlet optimization has led to the optimization of the broken-symmetry structure for 10 species including the unsubstituted one. This development makes it possible to carry out further broken symmetry calculations in two ways. The triplet calculation has been done using 6-311++G(d,p) basis set and the optimized triplet geometry in both procedures. The broken symmetry calculations have used the optimized geometries of either the triplet states or the broken symmetry solutions. The first method leads to the prediction of electron paramagnetic resonance (EPR) compatible magnetic exchange coupling constant (J) in the range 517-617 cm(-1). A direct optimization of the broken symmetry geometry gives rise to a lower estimate of J, in the range of 411-525 cm(-1) and compatible with macroscopic Curie studies. The calculated J for the unsubstituted Schlenk diradical is 512 cm(-1) that can be compared with 455 cm(-1) estimated by Rajca. In both cases, introduction of groups with +M and +I effects (Ingold's notation) decreases the J value from that for the unsubstituted Schlenk diradical while -I and -M groups at the same position increases J. These trends have been explained in terms of Hammett constants, atomic spin densities, and dihedral angles.     

Synthesis,characterization, antimicrobial and diuretic study of Mg(II), Mn(II), Fe(II) and VO(II) complexes of chemotherapeutic importance

The synthesis, characterization and diuretic activity of four new biologically active complexes of Mg(II) and VO(II) with bidentate Schiff base ligand acetazolamide–salicylaldimine (L) obtained from the inserted condensation of 5-acetamido-1,3,4-thiadiazole-2-sulphonamide (acetazolamide) with salicylaldehyde in a 1:1 molar ratio have been reported. Using this bidentate ligand complexes of Mg(II), Mn(II), Fe(II) and VO(II) with general formula ML₂ have been synthesized. The synthesized complexes were characterized by several techniques using elemental analysis, FT-IR, electronic spectra, TGA, mass, particle size analysis and molar conductance measurements. The elemental analysis data suggest the stoichiometry to be 1:2 [M:L]. The molar conductance measurements suggest non-electrolytic nature of the complexes. Infrared spectral data agreed with the coordination to the central metal ion through deprotonated phenolic oxygen and azomethine nitrogen atoms. On the basis of spectral studies, octahedral geometry is suggested for Mg(II), Mn(II), Fe(II) and square pyramidal geometry is suggested for VO(II) complexes. The pure drug, synthesized ligand and metal(II) complexes were screened for their antimicrobial activities against Eschericia coli, Bacillus subtilis, Aspergillus niger and Aspergillus flavous. The results show that the metal complexes were more active than the ligand and pure drug against these microbial species as expected. The ligand and its Mg(II) complexes was screened for their diuretic activity also.     

Photocatalytic decolorization of Brilliant Golden Yellow in TiO2 and ZnO suspensions

Photocatalytic decolorization of BGY, an anionic dye, has been investigated in TiO₂ and ZnO aqueous dispersions under UV-light irradiation. Spectrum of the dye has been found unaffected in the pH range 4.21–11.30. Adsorption is a prerequisite for the metal oxide-mediated photodegradation/photodecolorization and the extent of decolorization has been discussed in terms of the Langmuir–Hinshelwood model. Complete decolorization was achieved in case of UV irradiation whereas degradation of BGY was found to be about ca.75%. ZnO-mediated decolorization has appeared to be better and faster. The effects of various parameters, such as catalyst loading, pH and initial concentration of the dye on decolorization have been investigated.