Synthesis of the methanesulfonates of α-(4-chlorophenyl)-α-[1-(2-chlorophenyl)emenyl]-1H-1,2,4-triazole-1-ethanol and α-[1-(2-chlorophenyl)ethenyl]-α-(2,4-difluorophenyl)-1H-1,2,4-triazole-1-ethanol,alpha styryl carbinol antifungal agents

The methanesulfonates of (α-(4-chlorophenyl)-α-[1-(2-chlorophenyl)ethenyl]-1H-1,2,4-triazole-1-ethanol and α-[1-(2-chlorophenyl)ethenyl]-α-(2,4-difluorophenyl)-1H-1,2,4-triazole-1-ethanol ( 1a, b ) are orally effective α-styryl carbinol derivatives developed for the treatment and prevention of systemic fungal infections. Practical new processes amenable for the large-scale production of these compounds are described. Of note is the selection of dichlorostyrene as a convenient precursor of the styryl portion, modification of a sensitive Grignard addition into a realistic preparative reaction and the use of 1,2,4-triazole simultaneously as a base transfer agent and nucleophile.     

Charge neutralization of ions from benzene

Cross-sections have been measured for the charge neutrilization if ions from benzene in kiloelectron-volt collisions with benezene target molecules. Measured values range from 65 Ų for the symmetric [C₆H₆]⁺? C₆H₆ resonant reactions to 8 Ų for [C₃H₃]⁺? C₆H₆ reactions. Cross-sections computed using a simple resonance charge transfer model compare favourably with experimental data for the symmetric reactions. The cross-sections for asymmetric reactions are smaller that those for they symmetric system and magnitudes of the asymmetric cross-sections are correlated with recombination energies of the respective ions.     

Hydration of CO adsorbed on Pt(100) at cryogenic temperatures in UHV environments

Adsorption of small amounts of D(2)O (ca. 0.01 L exposure) on CO(sat)/Pt(100) surfaces in ultrahigh vacuum at 105 K was found to split the asymmetric peak at 2100 cm(-1) in the infrared reflection absorption spectra attributed to the stretching of CO adsorbed on atop sites into two clearly defined features: an intense component, which shifted toward lower energies due to surface hydration of adsorbed CO (originally at 2100 cm(-1), peak a), and a smaller peak centered at 2094 cm(-1) (peak b), which remained fixed in position even after closing the D(2)O dosing valve. The energies of peaks a and b, as determined by statistical analyses, correlated very well with those reported in the literature for CO adsorbed at high coverages on Pt(100) originally in the (5 x 20) or (hex) reconstruction, and on the unreconstructed Pt(100)-(1 x 1), respectively, at 90 K. On these bases, the asymmetry of the peak observed for CO(sat)/Pt(100) (no D(2)O dosing) is ascribed to the presence of CO linearly adsorbed on these two different sites on the surface, for which the rate of hydration is larger for the (5 x 20) compared to the (1 x 1) phases.     

Improved ultrasonic extraction procedure for the determination of polycyclic aromatic hydrocarbons in sediments

The aim of this work was to optimize an ultrasonic extraction procedure for the determination of polycyclic aromatic hydrocarbons (PAHs) in sediments and to compare it with the reflux procedure using methanolic potassium hydroxide. Sample extracts were purified with a miniaturized silica gel chromatographic column and analyzed by gas chromatography-mass spectrometry (GC-MS). Ultrasonication using n-hexane-acetone (1:1, v/v) solvent mixture on dried homogenized marine sediment gave better precision (smaller relative standard deviation (RSD) values) and comparable quantities of individual PAH's compared to the reflux procedure. Ultrasonication with the n-hexane-acetone (1:1, v/v) mixture, utilizing four 15 min extraction cycles, was found to be sufficient for extracting PAHs from wet sediments. The optimized ultrasonic extraction procedure extracted aliphatic and aromatic hydrocarbons from the National Institute of Standards and Technology SRM 1941a with recoveries greater than 90%. The major advantages of ultrasonication compared to the reflux method are the lower extraction times, simplicity of the apparatus and extraction procedure. The optimized ultrasonication procedure has been used in our laboratory to extract hydrocarbons from naturally wet sediments from rivers, and coastal and marine areas.     

Voltammetry of copper species in estuarine waters: Part III. Use of gelatin to investigate adsorption of natural organic material on the HMDE during DPASV

The comparatively non Cu-complexing surfactant, gelatin, has been substituted on the HMDE for natural organic material during DPASV assay of estuarine waters. It is shown that the effects of adsorption of natural organic material on the electroreduction and electrooxidation of Cu are diverse and act in part through the complexing properties of the organic material.     

Surface dynamics of coadsorbed CO and D2O on Pt(100) in ultrahigh vacuum as studied by time-resolved infrared reflection absorption spectroscopy

Changes in the properties of CO adsorbed at saturation coverages on Pt(100) induced by subsequent coadsorption of fixed amounts of D2O at 105 K in ultrahigh vacuum (UHV) were monitored by time-resolved infrared reflection absorption spectroscopy (tr-IRAS). The linear- and bridge-bonded CO stretching features were found to change in intensity and shift toward lower energies as a function of time at fixed CO and D2O coverages. Also observed was the development of multiple features in both CO spectral regions depending on the amount of D2O on the surface. These findings indicate that, under the conditions of these experiments, the interfacial dynamics are relatively slow, on the order of minutes, involving a gradual rearrangement of adsorbed CO and D2O on the surface to yield surface solvated CO, as has been suggested in the literature (Kizhakevariam et al. J. Chem. Phys. 1994, 100, 6750). This factor should be considered when comparing, quantitatively, shifts induced by water coadsorption with CO on Pt single crystals in UHV with CO adsorption on the same surfaces in electrochemical environments.     

A self-assembled multivalent pseudopolyrotaxane for binding galectin-1

A self-assembled pseudopolyrotaxane consisting of lactoside-displaying cyclodextrin (CD) "beads" threaded onto a linear polyviologen "string" was investigated for its ability to inhibit galectin-1-mediated T-cell agglutination. The CDs of the pseudopolyrotaxane are able to spin around the axis of the polymer chain as well as to move back and forth along its backbone to alter the presentation of its ligand. This supramolecular superstructure incorporates all the advantages of polymeric structures, such as the ability to span large distances, along with a distinctively dynamic presentation of its lactoside ligands to afford a neoglycoconjugate that can adjust to the relative stereochemistries of the lectin's binding sites. The pseudopolyrotaxane exhibited a valency-corrected 10-fold enhancement over native lactose in the agglutination assay, which was greater than the enhancements observed for lactoside-bearing trivalent glycoclusters and a lactoside-bearing chitosan polymer tested using the same assay. The experimental results indicate that supramolecular architectures, such as the pseudopolyrotaxane, provide tools for investigating protein-carbohydrate interactions.     

LONG-RANGE TRIPLET-SINGLET ENERGY TRANSFER FROM ENZYME GENERATED TRIPLET ACETONE TO XANTHENE DYES

Enzyme-generated and protected acetone transfers its energy to xanthene dyes by a nontrivial process. The relative populations of the S₁ state are indicative of the operation of a heavy atom effect, being 1:15:100 for fluorescein, eosine and Rose Bengal. On the other hand Stern-Volmer constants and k _ET⁰ values are similar for the three dyes and are remarkably higher than for collisional processes.
It is tentatively suggested that at least for eosine and Rose Bengal, a triplet-triplet cxciton transfer may occur to populate an upper triplet state of the dye followed by heavy-atom enhanced intersystem crossing to the S₁ state.     

Cooperative two-photon-induced chemical bond formation during a Kr+F2 collision to form KrF

The reactive Kr⁺F₂⁻ potential energy surface is probed by two-photon, laser-induced chemical bond formation during a Kr+F₂ collision. This is compared with the pulsed laser excitation (two-photon) of Kr(2p₉) followed by collision with F₂ leading to the formation of KrF(B, C). In addition to reporting the excitation spectrum for the two-phonon-induced collision process, these techniques were used to determine quenching rate constants of Kr₂F^*. Quenching by Xe gives XeF(B, C) with rate constant (1.5±0.2)×10⁻¹⁰ cm³ s⁻¹; the quenching rate constant for F₂ is (1.5±0.2)×10⁻¹⁰ cm³ s⁻¹, and the radiative lifetime of Kr₂F^* is 240±35 ns. The quenching rate constant for the coupled Kr(2p₈) and Kr(2p₉) levels by F₂ is (13±2)×10⁻¹⁰ cm³ s⁻¹.     

Determination of tea catechins

An overview of analytical methods for the measurement of biologically important tea catechins is presented. Liquid chromatography and capillary electrophoresis are the most cited techniques for catechin separation, identification and quantitation. Liquid chromatography with ultraviolet detection is frequently used; however, mass spectrometry, electrochemical, fluorescence and chemiluminescence detection are also utilized in cases where more sensitive or selective detection is needed. Two modes of capillary electrophoresis, capillary zone electrophoresis and micellar electrokinetic capillary chromatography, have been employed for the determination of catechins. Both modes of capillary electrophoresis are based on ultraviolet detection. Additional analytical techniques, such as gas chromatography, thin-layer chromatography, paper chromatography, spectrophotometry, biosensing, chemiluminescence and nuclear magnetic resonance spectroscopy have also been utilized for the determination of catechins and are reviewed herein.