Aligned arrays of nanotubes and segmented nanotubes on substrates fabricated by electrodeposition onto nanorods

We describe an electrochemical-based approach to create vertically aligned nanotube arrays on substrates. Initially, nanoporous anodic alumina films are used as templates to electrodeposit nanorods, and then the alumina templates are removed and nanotube arrays are electrodeposited using the nanorod arrays as templates. We have used this approach to fabricate gold nanotube arrays using nickel nanorods as templates. By anodizing the ends of the nickel nanorods before gold electrodeposition, no deposition occurs at the ends of the rods, resulting in open-ended nanotubes. In addition, we have used layered nickel-gold nanorods as templates to create gold nanostructure arrays with alternating segments of filled and empty nanotubes. This approach is versatile and may be used to electrodeposit a wide range of nanotube materials with good control over the nanotube dimensions.     

Ferrocene-containing cationic lipids: influence of redox state on cell transfection

A ferrocene-containing, redox-active cationic lipid that can be transformed using electrochemical methods yields large differences in cell transfection depending on the oxidation state of the lipid. Expression of enhanced green fluorescent protein and firefly luciferase occurs at very high levels when DNA lipoplexes are formulated using the lipid in the reduced state. In contrast, transfection is negligible when oxidized lipid is used. These observations suggest the basis of a general method that could be used to transform inactive lipoplex formulations to an active form through the application of externally applied electrical potentials. The ability to activate lipoplexes toward transfection electrochemically and "on demand" could create new opportunities to deliver DNA in vitro and in vivo with both spatial and temporal control.     

FTIR analysis and monitoring of synthetic aviation engine oils

Synthetic turbine oils from military aircraft engines were analysed for antioxidant content and total acid number using infrared (IR) spectroscopy. Two-dimensional IR correlation analysis was employed to investigate and interpret observed trends in the spectra, as acid was formed and antioxidant species were depleted in the oils, as a function of aging and engine wear. Principal components and partial least squares algorithms were used and compared for the development of calibration and prediction models. Transmission IR spectrometry is demonstrated to be effective for the analysis and monitoring of synthetic aviation turbine engine oils and shown to provide rapid and accurate information as compared with traditional analytical techniques and methods.     

Simplifying oligosaccharide synthesis: efficient synthesis of lactosamine and siaylated lactosamine oligosaccharide donors

A practical sequence is described for converting d-glucosamine into peracetylated Gal(beta-1,4)GlcNTroc(beta1-S)Ph and Neu5Ac(alpha-2,3)Gal(beta-1,4)GlcNTroc(beta1-S)Ph building blocks using a synthetic strategy based on chemoenzymatic oligosaccharide synthesis. The known trichloroethoxycarbonyl, N-Troc, protecting group was selected as a suitable protecting group for both enzymatic and chemical reaction conditions. These oligosaccharide building blocks proved effective donors for the beta-selective glycosylation of the unreactive OH-3 of a polymeric PEG-bound acceptor and for the axial OH-2 of a mannose acceptor in good yields. The resulting complex oligosaccharides are useful for vaccine and pharmaceutical applications.     

Rapid assessment of beta-asarone content of Acorus calamus by micellar electrokinetic capillary chromatography

This report outlines a rapid, reproducible method for the determination of beta-asarone, a known carcinogen, using micellar electrokinetic capillary chromatography (MEKC)-UV-vis absorbance and a simple alcohol extraction. The MEKC method is based on a running buffer comprised of 100 mM sodium dodecyl sulfate (SDS), pH 10. The method is reproducible and provides baseline separation of alpha-asarone and beta-asarone. This protocol was used to determine the beta-asarone content of Acorus calamus rhizome of a diploid variety harvested from the wetlands of the United States and the triploid variety from India obtained commercially. The results indicate raw product that originated from India contained 4.4% w/w beta-asarone, while that from the United States contained 0.2% w/w beta-asarone. Neither sample contained detectable concentrations of alpha-asarone. This is the first report of the use of MEKC to determine asarone in a natural source.     

The molecular structure of the tris(2-mercapto-1-tolylimidazolyl)hydroborato zinc(2-mercapto-1-tolylimidazole) complex, [[Tm(p-Tol)]Zn(mim(p-Tol))][ClO4]: intermolecular N-H...OClO3versus intramolecular N-H...S hydrogen bonding interactions of the mercaptoimidazole ligand

The molecular structure of the tris(2-mercapto-1-tolylimidazolyl)hydroborato complex [[Tm(p-Tol)]Zn(mim(p-Tol))][ClO(4)].3MeCN has been determined by X-ray diffraction, thereby demonstrating that the mim(p-Tol) ligand exhibits a N-H...O hydrogen bond with the [ClO(4)](-) counterion, [[Tm(p-Tol)]Zn(mim(p-Tol))...(OClO(3))], rather than hydrogen bond with a sulfur of the [Tm(p-Tol)] ligand. DFT calculations on a series of related complexes, namely [[Tm(Me)]Zn(mim(Me))](+), [[Tm(Me)]Zn(mim(Me))]...(OClO(3))], [[Tm(Me)]Zn(mim(Me))]...[O(H)Me]](+), and [[Tm(Me)]Zn(mim(Me))]...(NCMe)](+) demonstrate that an intramolecular N-H...S hydrogen bond within [[Tm(Me)]Zn(mim(Me))](+) is also less favored than the corresponding hydrogen bonding interactions with MeCN, MeOH, and [ClO(4)](-). The inability of the sulfur atoms of [Tm(R)] ligand to act as an effective hydrogen bond acceptor is in marked contrast to the ability of sulfur atoms in thiolate ligands to participate in the formation of N-H...S hydrogen bonds, an observation that reflects the "thione"versus"thiolate" nature of the [Tm(R)] ligand.     

SPIN TRAPPING OF FREE RADICALS PRODUCED FROM NITROSOAMINE CARCINOGENS

Abstract— Using the spin trap 5,5-dimethylpyrroline-1-oxide we have demonstrated that the nitrosoamine carcinogen, 1-nitrosopiperidine, upon incubation with rat liver microsomes and nuclei produces two trapped free radical species. One trapped species is the hydroxyl free radical whereas the other is a free radical of unknown structure of the carcinogen itself. Three other nitrosoamine carcinogens tested, including diethylnitrosoamine, dimethylnitrosoamine and 1-nitrosopyrroline yielded similar results with the exception that the trapped carcinogen radical differs dependent upon the compound used. Oxygen was required to produce the hydroxyl free radical but its presence decreased the yield of the carcinogen radical. Both cyanide and α-tocopherol acetate caused a decrease in the yield of the carcinogen free radical. Some heat-labile inhibitor(s) of radical production was/were present in the cytosol. The amount of radical produced was not proportional to the P₄₅₀ content.     

Effects of Congo red on the drag reduction properties of poly(ethylene oxide) in aqueous solution based on drop impact images

The presence of very small amounts (ppm) of high-MW polymers in solution produces high levels of drag reduction in a turbulent flow. This phenomenon, often termed as the Toms effect, is highly dependent not only on MW, but also on the flexibility of the macromolecular chain. The Toms effect can be studied through the images of the structures produced after the drop impact against shallow solution surfaces. The splash structures composed of crown, cavity, and Rayleigh jet are highly dependent on the elongational properties of the solution. This work presents the effects of Congo red on the drag reduction properties of poly(ethylene oxide) in aqueous solutions through the analysis of splash structures. Results obtained in this analysis indicate that Congo red molecules act as physical cross-linking agents, decreasing the polymer elasticity and its drag reduction capacity. It was observed that the maximum height of the Rayleigh jet can be used as a sensitive parameter to the complexation between the dye and the polymer molecules.     

Comparison of dodecoxycarbonylvaline microemulsion, solvent-modified micellar and micellar pseudostationary phases for the chiral analysis of pharmaceutical compounds

A direct comparison of dodecoxycarbonylvaline (DDCV) microemulsion, micellar and butanol-modified micellar aggregate systems was performed employing both 2 and 4% DDCV. With respect to either DDCV concentration, use of the micellar system provided the largest elution range, followed by the butanol-modified micellar system and ultimately the microemulsion. Using 2% DDCV, all three aggregate analyses yielded similar values for enantioselectivity, resolution and retention factors that were slightly better using the micellar phase, but efficiencies were consistently better using either the microemulsion or butanol-modified micellar phases. Largely, the microemulsion and butanol-modified micellar phases behaved fairly similar, although use of the butanol-modified micelle provided resolution and efficiency that were slightly better for all but two of the compounds. While reasonable separations were achieved using 2% DDCV, the results using 4% DDCV for the microemulsion system were far superior. Analyses using analogous micellar and butanol-modified micellar aggregates were unstable, making them unsuitable for use at that surfactant concentration.