Track membrane with immobilized colloid silver particles

A method for modification of track membranes by immobilization of polymer complexes of colloid silver nanoparticles on the surface of microfiltration membranes was developed. The antimicrobial properties of track membranes modified with silver nanoparticles were tested on E. coli, Ps. aeruginosa, St. aureus, and B. cereus.     

Instrumental neutron activation analysis of tree rings for dendrochemical studies

Instrumental neutron activation analysis (INAA) was employed to determine zinc, cadmium and potassium concentrations in the growth rings of ponderosa pine (Pinus ponderosa Dougl.) trees growing along the shores of Lake Roosevelt in Washington State, U.S.A. where mineral processing activities have resulted in high burdens of zinc and cadmium in the lake sediments. The tree growing along the contaminated waterway display elevated concentrations of zinc in its growth rings relative to a tree growing along an uncontaminated tributary of Lake Roosevelt. Cadmium concentrations in the growth rings from both sites are similar from 1988 to 1993. Water quality data indicate an increased concentration of cadmium in the lake from 1984 to 1988. The increased concentrations of cadmium in the lake water were reflected in apparent increases in concentrations of cadmium in individual rings of the tree sampled at the contaminated site. This suggests that translocation of cadmium in the sapwood of heartwood-forming species does not occur in the short term, and thus may not be a limiting factor in using trees as environmental monitors for cadmium. In addition, five-year tree ring segments were analyzed and subsequently reanalyzed as individual single-year ring segments. The analytical data obtained for the pooled individual rings are essentially the same as for the five-year segments, demonstrating the utility of NAA for dendrochemical studies.     

Acoustically levitated droplets — a new tool for micro and trace analysis

First experiences with the technique of acoustical levitation of droplets in the field of analytical and atmospheric chemistry are reported. Acoustical levitation enables the contactless handling of solid and liquid microsamples. This avoids adsorption of analyte at and desorption of contaminants from container walls especially for liquid samples. Common experiments of sample preparation procedures were conducted in levitated drops like liquid/liquid extractions, solvent exchange, and analyte enrichment by evaporation of the solvent. A first approach was made to use acoustical levitation for the simulation of atmospheric chemistry situations. Received: 10 October 1996 / Revised: 25 October 1996 / Accepted: 25 October 1996     

Calculation of hydrophobic interactions from molecular dynamics,surface areas,and experimental hydrocarbon solubilities

Using experimental solubilities and partial pressures for hydrocarbon solution in water and molecular dynamics calculations of hydrocarbon water interaction energies, hydrocarbon–water cavity potentials are obtained and then plotted vs. accessible surface area. The data used is mainly for aliphatic hydrocarbons, but benzene is included. Molecular dynamics calculations of pairs of hydrocarbon molecules together with the cavity potential curve are then used to obtain hydrophobic interaction free energies between the hydrocarbon pairs. While the cavity potential change is related to a change in surface area for hydrocarbon systems, the hydrocarbon–water interaction energy is not, so that the hydrophobic binding energy is not. The results are in agreement with previous results by a different method (R.B. Hermann, In Seventh Jerusalem Symposium on Quantum Pharmacology, E. Bergman and B. Pullman, Eds., D. Reidel, Dordrecht, 1974, p. 441) in that there is little or no solvent-induced binding free energy between small hydrocarbon molecules in a dilute aqueous solution. It is proposed that the cavity potential vs. accessible surface area curve obtained here can be used together with OPLS parameters to calculate both hydrocarbon–water solvation free energies and hydrophobic interactions. © 1993 John Wiley & Sons, Inc.     

Use of the quartz crystal microbalance for kinetic studies of thermal decomposition of solids

A quartz crystal microbalance has been proposed for studies on the temperature dependence of the linear rate of a reaction interface advance in topochemical reactions of the thermal decomposition of solids. A quartz crystal microbalance has been used in investigations of the CuSO₄ · 5H₂O dehydration. The data agree fairly well with those available in the literature. Advantages and disadvantages of the method proposed are discussed.     

Comparative studies of reactions of commercial polymers with molecular oxygen,singlet oxygen,atomic oxygen and ozone—II. Reactions with 1,2-polybutadiene

The oxidations of 1,2-polybutadiene by molecular oxygen, singlet oxygen, atomic oxygen and ozone have been studied using u.v. and i.r. spectroscopic methods. Some possible implications of the results of oxidation in the presence of singlet oxygen (parallel free radical oxidation) and atomic oxygen (formation of NO₂ and its reaction with polymer) are discussed. Crosslinking was observed during all types of oxidation. A new mechanism involving formation of free radicals has been considered in detail. During ozonization of 1,2-polybutadiene, formation of formaldehyde and formic acid were detected. An ozonization mechanism has been proposed.     

Raney nickel reductions—VIII A synthesis of 1:2-benzanthracene and its 3′-methyl and 4-methyl derivatives

1:2-Benzanthracene and the 3′-methyl derivative have been prepared by Raney nickel reduction of the sulphuric esters of the leuco derivatives of 1:2-benzanthraquinone and 4′-chloro-3′-methyl-1:2-benzanthraquinone, followed by dehydrogenation. 3-Hydroxy-1:2-benzanthraquinone was methylated in the 4-position by formaldehyde, sodium hydrosulphite and sodium hydroxide solution (the Marschalk reaction). Simultaneous reduction of the nuclear hydroxyl and quinone groups was effected by Raney nickel reduction of the trisulphuric ester of 3:9:10-trihydroxy-4-methyl-1:2-benzanthracene, and the resultant hexahydro-4-methyl-1:2-benzanthracene was dehydrogenated to 4-methyl-1:2-benzanthracene. The preparation of 3:4:9:10-dibenzopyrene from Mayvat brilliant red AF by Raney nickel reduction of the sulphuric ester of the leuco derivative and subsequent dehydrogenation is described.     

LC–MS Determination and Pharmacokinetic Study of a Novel Sulfonylurea: Potential Hypoglycemic Agent in Rat Plasma

To support preclinical pharmacokinetic investigation of 1-[4-[2-(4-bromobenzene-sulfonaminoethyl)phenylsufonyl]-3-(trans-4-methylcyclohexyl)urea (G004), a rapid, sensitive and specific high-performance liquid chromatography–electrospray ionization mass spectrometry (LC–ESI-MS) method was developed and validated. Glibenclamide was employed as internal standard. After liquid–liquid extraction the analyte was analyzed on a Kromasil C₁₈ column (150 × 2.0 mm i.d.) with a mobile phase consisted of acetonitrile–water (0.05% acetic acid), 30:70 (v/v). The flow rate was 0.2 mL min⁻¹. Detection was performed on a quadrupole mass spectrometer using an electrospray ionization interface and the selected-ion monitoring (SIM) mode. The retention time was about 3.5 and 4.2 min for Glibenclamide and G004, respectively. The assay was linear over the concentration range of 2.0–500.0 ng mL⁻¹. Extraction Recovery of G004 in rat plasma was more than 87%. The intra- and inter-assay precision was lower than 11.5% (CV). This validated method was successfully applied to the pharmacokinetics of G004 in rats.     

Charge transfer complexes of methylnaphthalene derivatives with TCNE in CCl4.

The spectrophotometric and thermodynamic properties of different substituted methylnaphthalenes charge transfer (CT) complexes with tetracyanoethylene have been studied in carbon tetrachloride. The spectral characteristics of the CT bands have also been discussed in relation to the positions of methyl groups. The formation constants and the spectral properties of the complexes are markedly affected with the substitution position of the methyl groups. The ionization potentials of the donors are determined.     

Carbohydrate analysis prepares to enter the "Omics" era

In this issue, Houseman and Mrksich describe a carbohydrate array preparation method that can be used to analyze protein-carbohydrate interactions and to characterize the substrate specificity of a carbohydrate-modifying enzyme. Carbohydrate chips were prepared by a novel procedure that allows the covalent attachment of carbohydrate-diene conjugates to a specially engineered monolayer surface. The surface presents a precisely controllable ratio of reactive benzoquinone and inert ethylene glycol groups. Nonspecific adsorption of proteins to the surface is extremely low, and the surface is compatible with popular detection techniques. The immobilization technique was demonstrated to be compatible with recently developed automated solid phase carbohydrate synthesis methods, paving the way for the development of highly complex carbohydrate arrays.