Solid‐state 31P NMR investigation on the status of guanine nucleotides in paclitaxel‐stabilized microtubules

Microtubule dynamics is a target for many chemotherapeutic drugs. In order to understand the biochemical effects of paclitaxel on the GTPase activity of tubulin, the status of guanine nucleotides in microtubules was investigated by ³¹P cross‐polarization magic angle spinning (CPMAS) NMR. Microtubules were freshly prepared in vitro in the presence of paclitaxel and then lyophilized in sucrose buffer for solid‐state NMR experiments. A ³¹P CPMAS NMR spectrum with the SNR of 25 was successfully acquired from the lyophilized microtubule sample. The broadness of the ³¹P spectral lines in the spectrum indicates that the molecular environments around the guanine nucleotides inside tubulin may not be as crystalline as reported by many diffraction studies. Deconvolution of the spectrum into four spectral components was carried out in comparison with the ³¹P NMR spectra obtained from five control samples. The spectral analysis suggested that about 13% of the nucleotides were present as GTP and 37% as GDP in the β‐tubulin (E‐site) of the microtubules. It was found that most of the GDPs were present as GDP‐P_i complex in the microtubules, which seems to be one of the effects of paclitaxel binding. Copyright © 2015 John Wiley & Sons, Ltd.     

Quantitative Characterization of Bovine Serum Albumin, α-Lactalbumin and β-Lactoglobulin in Commercial Whey Sample by RP-LC

A simple, sensitive and precise reverse phase liquid chromatographic method has been developed and validated for quantification of bovine serum albumin (BSA), α-lactalbumin (α-La) and β–lactoglobulin (β-Lg) that are removed from whey waste by foam fractionation method. The data is reproducible over a wide concentration range. This optimized method allowed analysis of BSA, α-La, β-Lg in a mixture within 5 min and could be applied to the analysis of a variety of commercial and laboratory whey products within a short time.     

A novel antimicrobial flavonoidic glycoside from the leaves of Alstonia macrophylla Wall ex A. DC (Apocynaceae)

<正>A new flavonoidic glycoside,tricin-4'-O-β-L-arabinoside(1) was isolated from the leaves of Alstonia macrophylla along with two known flavonoids,vitexin and myricetin-3′-rhamnoside-3-O-galactoside.Their structures were established by chemical and spectral evidences.The known compounds were reported for the first time from this plant.Moreover compound 1 was tested for antifungal and antibacterial activities.     

Assessment of thermo-hydraulic performance of MXene-based nanofluid as coolant in a dimpled channel: a numerical approach

Journal of Thermal Analysis and Calorimetry - The present study numerically investigates the optimization of thermal performance in a dimpled channel using a promising genre of nanofluid which is...     

Separation and identification of volatile compounds from liquid cultures of Trichoderma harzianum by GC-MS using three different capillary columns

A simple, fast, repeatable and less laborious sample preparation protocol was developed and applied for the analysis of biocontrol fungus Trichoderma harzianum strain FA1132 by using gas chromatography-mass spectrometry. The match factors for sample spectra with respect to the mass spectra library of fungal volatile compounds were determined and used to study the complex hydrocarbons and other volatile compounds, which were separated by using different capillary columns with nonpolar, medium polar and high polar stationary phases. To date, more than 278 volatile compounds (with spectral match factor at least 90%) such as normal saturated hydrocarbons (C7-C30), cyclohexane, cyclopentane, fatty acids, alcohols, esters, sulfur-containing compounds, simple pyrane and benzene derivatives have been identified. Most of these compounds have not previously been reported. The method described in this paper is a more convenient research tool for the detection of volatile compounds from the cultures of T. harzianum.     

Ultrasensitive Study of Gatifloxacin Based on Its Enhancing Effect on the Cerium (IV)-Sodium Hyposulfite Chemiluminescence Reaction in a Micellar Medium

A sensitive and rapid flow-injection chemiluminescence (CL) method has been developed for the determination of gatifloxacin in pharmaceutical preparations and biological samples. The method is based on the enhancing effect of gatifloxacin on CL emission generated by the interaction of Ce (IV) in sulphuric acid and sodium hyposulphite (Na(2)S(2)O(4)) sensitized by sodium dodecyl benzene sulfonate (SDBS). Strong CL emission was observed when gatifloxacin was injected into the Ce (IV) in sulphuric acid and Na(2)S(2)O(4) solution incorporated with SDBS in a flow-cell. Several experimental parameters affecting the CL reaction were investigated and optimized systematically. Under the optimum conditions, it was found that the CL intensity is proportional to the concentration of gatifloxacin in the range of 1.12 × 10(-11)-4.40 × 10(-9) g mL(-1) with a co-relation coefficient of 0.9994. The limit of detection was found to be 4.87 × 10(-12) g mL(-1) and the relative standard deviation (RSD, n=7) was 1.8% for 4 × 10(-8) g mL(-1) of GFLX. The proposed method offers higher sensitivity, wide linear range and better stability without requiring sophisticated instrumentation. Thus, the proposed method has been successfully applied to the determination of gatifloxacin in pharmaceuticals, serum and human urine.     

Influence of ionic and nonionic hydrotropes on micellar behavior of a cationic gemini surfactant butanediyl-1,4-bis(dimethylcetylammonium bromide)

Micellization of binary systems of a cationic gemini surfactant butanediyl-1,4-bis(dimethylcetylammonium bromide) (16-4-16) and cationic/nonionic hydrotropes (aniline-hydrochloride, 2-methylanilinehydrochloride, 4-methylanilinehydrochloride, hydroxybenzene, 1,3-benzenediol, benzene-1,2,3-triol) have been studied using a conductometric technique. The critical micelle concentrations (cmc) for different mixing mole fractions at different temperatures have been calculated. To explain and compare the results, theoretical models of Clint, Rubingh and Motomura have been used to obtain the ideal cmc, mixed micelle composition, interaction parameters (β(m)), free energies of micellization, and activity coefficients. The mixtures show nonideal behavior and the interactions between the surfactants and the hydrotropes are synergistic in nature which is confirmed by high negative β(m) values and low values of the activity coefficients. Thermodynamic parameters were also obtained from the temperature dependence of the cmc values.     

A multivariate quantification of Box‐Behnken design assisted method development and validation of dextromethorphan hydrobromide and desloratadine simultaneously by reverse‐phase HPLC in in‐house syrup formulation

An innovative high‐performance liquid chromatography assay method was developed and validated for quantification of dextromethorphan hydrobromide and desloratadine simultaneously in monophasic liquid formulation by preparing syrup containing 30 mg/5 mL of dextromethorphan hydrobromide and 1.2 mg/mL of desloratadine. The chromatographic severance was executed by gradient solution A and B. The composition of buffer solution A contained 0.05 M monobasic potassium, then 1 mL triethylamine was added to it and the pH was adjusted to 2.3 with orthophosphoric acid. Methanol was used as solution B. The gradient elution was executed with Kromasil C8 (250 mm × 4.6 mm) column having 1.5 mL/min flow rate and 20 µL injection volume with UV‐estimation at 254 nm for dextromethorphan hydrobromide and DES. The present research was planned according to Box‐Behnken design by utilizing design expert software, using four factors such as column temperature (A), flow rate (B), mobile phase–organic phase (C), and pH (D); correspondingly the selected response variables were resolution between A and B, that is, desloratadine and methyl paraben (Y1), tailing of dextromethorphan hydrobromide (Y2), and tailing of desloratadine (Y3). The parameters such as system suitability, linearity, accuracy, precision, robustness, limit of detection, limit of quantitation, and ruggedness were analyzed to validate the developed method in accordance with current regulatory guidelines.     

Atomistic simulation of the formation of nanoporous silica films via molecular chemical vapor deposition on nonporous substrates

To distinguish thin deposited film characteristics clearly from the influence of substrate morphological properties, the growth mechanism and the macroscale and nanoscale properties of nanoporous SiO(2) films deposited on nonporous silica (SiO(2)) substrates from chemical precursors Si(OH)(4) and TEOS (tetraethoxysilane) via low-pressure chemical vapor deposition are the primary targets of this study. This work employs a kinetic Monte Carlo (KMC) simulation method coupled to the Metropolis Monte Carlo method to relax the strained silica structure. The influence of the deposition temperature (473, 673, and 873 K) on the properties of the SiO(x) layers is addressed via analysis of the film growth rates, density profiles of the deposited thin films, pore size distributions, carbon depth profiles (with respect to TEOS), and voidage analysis for layers of different thicknesses (8-18 nm). A comparison of simulation with experimental results is also carried out.     

Oxidation of butane-1,3-, butane-1,4-, 2-methyl pentane-2,4- and 3-methyl pentane-2,4-diols by cerium(IV) in aqueous acidic medium catalyzed by rhodium(III)

The oxidation kinetics of butane-1,3-diol, butane-1,4-diol, 2-methyl pentane-2,4-diol and 3-methyl pentane-2,4-diol with cerium(IV) catalyzed by rhodium(III) in aqueous sulfuric acid showed a peculiar nature with respect to the variation in oxidant concentration, such that the reaction follows first-order kinetics in [Ce(IV)] at low [Ce(IV)] and then reaches a maximum with increasing [Ce(IV)], beyond which further increase in the oxidant concentration retards the rate. The rate shows direct proportionality with respect to [diol] at low concentrations, becoming independent of [diol] at higher concentrations. The rate is first order in catalyst. Retarding effects are observed when [H⁺] and [Ce(III)] are increased, while [Cl⁻] and hence ionic strength have a positive effect on the rate. Spectroscopic studies confirmed that the primary hydroxyl groups in butane-1,3-diol and butane-1,4-diol resulted in the formation of 3-hydroxy butanal and 4-hydroxy butanal, respectively. In the case of oxidation of the secondary hydroxyl groups in 2-methyl pentane-2,4-diol and 3-methyl pentane-2,4-diol, the products of oxidation were 4-hydroxy-4-methyl pentan-2-one and 4-hydroxy-3-methyl pentan-2-one, respectively.