Syntheses and structural characterizations of 2-pyridyl(N/O)spirocyclotriphosphazene derivatives

The Cl exchange reaction of hexachlorocyclotriphosphazene, N₃P₃Cl₆ (1), with one equimolar amount of sodium salt of N/O donor type bidentate ligand containing a 2-pyridyl pendant arm (2) afforded, regioselectively, the partly substituted 2-pyridyl(N/O)spirocyclotriphosphazene (3; with a yield of 65%) in THF. The reactions of 3 with excess pyrrolidine, morpholine and 1,4-dioxa-8-azaspiro[4,5]decane (DASD) led to the formation of the tetraamino-2-pyridyl(N/O)spirocyclotriphosphazenes (3a-3c) in high yields. Compound 3 also gave both tetrapiperidino (3d) and gem-bispiperidino (3e) products with excess piperidine. The structures of all the compounds were determined by elemental analyses, ESI-MS, FTIR, HSQC, HMBC and ¹H, ¹³C, and ³¹P NMR techniques. The crystal structure of 3c was identified by single crystal X-ray crystallography. Besides, the compound 3e had one stereogenic P atom, and its chirality was verified by ³¹P NMR spectroscopy in the presence of (S)-(+)-2,2,2-trifluoro-1-(9’-anthryl)-ethanol (CSA).     

Binding of Fluorescein Isothiocyanate to Insulin: A Fluorimetric Labeling Study

The determination of the fluorophore to the protein molar ratio has been studied using fluorescence spectroscopy. The tyrosine fluorescence is measured from insulin (Ins) solutions at wavelengths lambda(ex)/lambda(em) = 276/300 nm and from fluorescein isothiocyanate (FITC) solutions at lambda(em)/lambda(em) = 494/518 nm. Series of solutions prepared from insulin and FITC are tested for conjugation, recording their fluorimetric intensities. Fluorimetric titrations with different formal concentrations are followed either by intrinsic and extrinsic emission intensities at lambda(ex)/lambda(em) = 276 or 494/518 nm and by their typical emission spectra at pH 9.0. All results denoted a binding ratio of 3 moles of FITC/mole of Ins.     

Rapid and Sensitive Determination of Hg(II) Using Polarographic Technique and Application to <Emphasis Type="Italic">Chlorophytum comosum</Emphasis>

A differential pulse polarographic (DPP) method has been used for the indirect determination of Hg(II). With a known amount of cyanuric acid (CA) in polarography cell (B–R buffer, pH 10.5) was added an unknown Hg(II) sample and the Hg(II) concentration is calculated simply from the decrease in the CA peak after reaction with Hg(II). The linear concentration range was between 20 and 120 μM and limit of detection was calculated to be 6.7 μM. The proposed method was successfully applied to the dried leave samples belong to C. comosum plant. The method was extended to the indirect determination of mercury(II) in C. comosum plant and results were in agreement with that obtained by a spectrometric comparison method (ICP-MS). The sufficiently good recoveries and low standard deviations reflect the high accuracy of developed method.     

Ultrasound-assisted adsorption of Pb ions by carbonized/activated date stones from singles/mixed aqueous solutions

This work aims to assess the adsorption efficiency of date stones biowaste subjected to carbonization and activation processes for the removal of Pb ions from single and mixed solutions. Several techniques have been used for characterization of adsorbents such as scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), methylene blue index and point of zero charge (pHpzc). An excellent adsorption capacity of 97.43% is achieved at an initial concentration of 300 ?mg/L, solution volume 75 ?mL of Pb nitrate, adsorbent mass of 0.7 ?g, temperature of 30 ?°C, a stirring speed of 500 ?rpm/min, a contact time of 180 ?min and pH 6. Specifically, a comparison has been conducted between carbonized/activated date stones “CADS” and commercial activated carbon “CAC” besides investigating the influence of the presence of Co ions and the utilization of ultrasound radiation. A higher adsorption rate of 98.16% is reached under ultrasound radiation at Pb(II) initial concentration of 100 ?mg/L for a contact time of 3 ?h. Nevertheless, the temperature has shown a negative effect; the adsorption rate decreases from 98.31% at 18 ?°C to 92.70% at 60 ?°C. The modeling of the experimental adsorption data manifests a type-L isotherm characteristic of Langmuir and Freundlich models. The kinetic study has shown that the experimental data are well described by a pseudo-second-order rate model and controlled by the internal diffusion, a limiting-step that controls the transfer rate of Pb(II) to the adsorbent surface. The calculated thermodynamic parameters (ΔG⁰, ΔH⁰, ΔS⁰) indicate that the adsorption of Pb(II) is spontaneous and exothermic process.     

Automorphisms of the Hatcher-Thurston complex

Let S be a compact, connected, orientable surface of positive genus. Let be the Hatcher-Thurston complex of S. We prove that Aut is isomorphic to the extended mapping class group of S modulo its center. The first author is supported by a Rackham Faculty Fellowship, Horace H. Rackham School of Graduate Studies, University of Michigan. The second author is supported in part by the Turkish Academy of Sciences under the Young Scientists Award Program (MK/TüBA-GEBİP 2003-10).     

The effect of membrane permeability on the response of a catechol biosensor

A mathematical model is developed for the simulation of the amperometric response of a biosensor for catechol using polyphenoloxidase. The model is based on transient diffusion equations containing nonlinear terms of Michaelis-Menten for two space regions: the diffusion layer and the biomembrane containing the immobilized enzyme. The set of partial derivatives of nonlinear equations and the corresponding boundary and initial conditions was solved using the implicit finite difference technique. This numerical solution was then exploited to study the effects of permeability and thickness of the biomembrane on the maximum response of the reduction current and the amplification factor corresponding to the maximum of catalytic activity of the enzyme. This amplification factor increases with the thickness of the biomembrane while permeability is weak. In the case of the low initial concentrations (10^?6 to 5.10^?4 mM), its value is maximal and remains independent of substrate concentration. Also, the amplification factor is more significant when the diffusion resistance is more important, i.e. for high thicknesses or weak permeabilities of the biomembranes.     

Comparing the effect of sub-critical water extraction with conventional extraction methods on the chemical composition of Lavandula stoechas

The volatile extract composition of Lavandula stoechas flowers obtained by hydrodistillation (HD), subcrtical water extraction (SbCWE) and organic solvent extraction under ultrasonic irradiation (USE) were estimated by gas chromatography-mass spectrometry (GC-MS). One hundred and twenty four components were detected in SbCWE extracts while 94 and 65 signals were gained from HD and USE extracts, respectively. Most of the constituents were identified. The major compounds in all three extracts were fenchon, camphor, myrtenyl acetate, myrtenol and 1,8-cineol, but they differ in quantitatively. The total monoterpene hydrocarbons are higher in HD and USE extracts than those of SbCWE extract. However, SbCWE extract had higher concentration of light oxygenated compounds which contributes to the fragrance of the oil in a major extension. Heavy-oxygenated compounds was also in higher abundance in SbCWE extract (9.90%) than those of HD and USE extracts (3.19 and 4.78%, respectively). Effect of temperature on the extraction yield of SbCWE was investigated and while oil yield was increasing with an increase in temperature, a decrease in the extraction ability of sub-critical water toward the more polar compounds such as, 1,8-cineol, camphor and fenchon, was observed. Kinetic studies shown that SbCWE is clearly quicker than conventional alternatives. Most of components of volatile compounds were extracted at 15min.     

Sulphur-enriched thiacalix[4]arenes in the cone conformation: synthesis, crystal structures and cation binding properties

The synthesis and crystal structure of p-tert-butylthia- and p-tert-butylcalix[4]arene derivatives 1–7 substituted at the narrow rim by diethylthiophosphate ester groups, -PS(OEt)₂ are reported. In these compounds the phosphorus atoms are directly attached to the phenolic O atoms of the calix units and the S atoms of the thiophosphate may serve as a two-electron donor to a metal ion. Their crystal structures were solved, which revealed their cone conformation. Their cation-binding properties have been established by liquid-liquid extraction of metal picrates from water into dichloromethane and stability constant determination in acetonitrile using UV-absorption spectrophotometry. Quantitative extraction was achieved for Ag⁺ (%E = 99) with the tetra-substituted thiacalix[4]arene derivative. The complexes were found to be of 1:1 stoichiometry and the location of the metal cations was shown to be nearby the sulphur atoms by ¹H NMR.     

Comparison of newly developed hydroxyl-functionalized monodisperse HILIC columns new HILIC column

In this study, new hydroxyl-functionalized monodisperse polymeric hydrophilic interaction chromatography (HILIC) columns were developed using different derivatization agents. In addition, the influences of derivatization temperature of the best agent and polymer composition on the separation were investigated under HILIC conditions. Monodisperse–porous hydrophilic particles were synthesized by the seeded polymerization method using 3-chloro-2-hydroxypropile methacrylate (HPMA-CL) and ethylene glycol dimethacrylate (EGDMA) monomers. The chloropropyl terminal ends of the poly(HPMA-Cl-co-EGDMA) particles were derivatized with amine group of ethanolamine (EA), diethanolamine, and triethanolamine (TEA) at 80°C through nucleophilic reaction. The performance of synthesized particles was evaluated with the amount of ligand on the particle surfaces, column backpressure, and separation power under HILIC condition. TEA was found to be the best derivatization agent for the separation of toluene, acrylamide, thymine, adenine, and cytosine in respect to resolution factors (>1.5 for all analytes) and theoretical plate numbers (64.562?N/m for acylamide). Upon determination of the best ligand, then the effect of different derivatization temperatures and polymer composition on TEA performance was investigated. Of all the tested polymer compositions, the chromatographic performance of TEA-M-80 (the derivatization of TEA at 80°C together with M polymer composition) was found to be the best.     

Phenolysis of hexachlorocyclotriphosphazatriene

The reactions of hexachlorocyclotriphosphazatriene N₃P₃Cl₆ ( 1 ) with the sodium salts of 2,4,6‐trimethylphenol ( 2a ), 4‐tert‐butyl‐2‐methylphenol ( 2b ), 2‐tert‐butyl‐4‐methylphenol ( 2c ) have been investigated, and monoaryloxy‐substituted phosphazenes N₃P₃Cl₅OAr ( 3–5 ) were obtained. © 2005 Wiley Periodicals, Inc. 16:308–310, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20127