Development of electrophoretically mediated microanalysis method for the kinetics study of flavin-containing monooxygenase in a partially filled capillary

An electrophoretically mediated microanalysis method with a partial filling technique was developed for flavin-containing monooxygenase, form 3 (FMO3). The in-line enzymatic reaction was performed in 100 mM phosphate reaction buffer (pH 7.4) whereas 150 mM phosphate buffer (pH 3.3) was used as a background electrolyte. A long plug of cofactor NADPH dissolved in reaction buffer was hydrodynamically injected into a fused-silica capillary, followed by enzyme and substrate solution. The reaction was initiated at 37 degrees C in the thermostated part of the cartridge by the application of 9 kV for 0.9 min. The voltage was turned off to increase the product amount (zero-potential amplification) and again turned on at a constant voltage of 10 kV to elute all the components. Direct detection was performed at 191 nm. The developed electrophoretically mediated microanalysis method was applied for the kinetics study of FMO3 using clozapine as a substrate probe. A Michaelis-Menten constant (K(m)) of 410.3 microM was estimated from the corrected peak area of the product, clozapine N-oxide. The calculated value of the maximum reaction velocity (V(max)) was found to be 1.86 nmol/nmol enzyme/min. The acquired FMO3 kinetic parameters are in accordance with the published literature data.     

Multi-compound electrophoretic assays for tyramine oxidase with a UV area detector imaging multiple windows on a looped capillary

Active pixel sensor UV area imaging and capacitively coupled contactless conductivity detection have been applied in an electrophoretically mediated microanalysis (EMMA) assay for substrate specificity of tyramine oxidase (Arthrobacter sp.). Use of the UV area imaging detector to monitor four windows in a capillary with three loops provided intrinsic self-referencing for all species and identified tyramine and 2-phenethylamine as the only reactive components in a multi-compound mixture. Continuous engagement EMMA experiments showed significant benefits by comparison with plug-plug EMMA, improving sensitivity by extending enzyme-substrate interaction times and allowing measurement of time-dependent reaction in the substrate zones passing the four windows.     

Sporulenes, heptaprenyl metabolites from Bacillus subtilis spores

Sporulene, a C 35-terpenoid hydrocarbon with an unusual pentacyclic structure, is produced by Bacillus subtilis during sporulation.     

A tungsten complex containing a highly delocalized metal–ligand system

Nucleophilic attack of (triphenylphosphonio)cyclopentadienide on the dichlorodiazomethane–tungsten complex trans‐[BrW(dppe)₂(N₂CCl₂)]PF₆ [dppe is 1,2‐bis(diphenylphosphino)ethane] results in C—C bond formation and affords the title compound, trans‐[W(C₂₄H₁₈ClN₂P)Br(C₂₆H₂₄P₂)₂]PF₆·0.6CH₂Cl₂. This complex, bis[1,2‐bis(diphenylphosphino)ethane]bromido{chloro[3‐(triphenylphosphonio)cyclopentadienylidene]diazomethanediido}tungsten hexafluorophosphate dichloromethane 0.6‐solvate, contains the previously unknown ligand chloro[3‐(triphenylphosphonio)cyclopentadienylidene]diazomethane. Evidence from bond lengths and torsion angles indicates significant through‐ligand delocalization of electron density from tungsten to the nominally cationic phosphorus(V) centre. This structural analysis clearly demonstrates that the tungsten–dinitrogen unit is a powerful π‐electron donor with the ability to transfer electron density from the metal to a distant acceptor centre through an extended conjugated ligand system. As a consequence, complexes of this type could have potential applications as nonlinear optical materials and molecular semiconductors.     

δ‐Sulfanilamide

The δ polymorph of sulfanilamide (or 4‐aminobenzenesulfonamide), C₆H₈N₂O₂S, displays an overall three‐dimensional hydrogen‐bonded network that is dominated by a two‐dimensional substructure with R²₂(8) rings; these result from dimeric N—H...O interactions between adjacent sulfonamide groups. This study shows how the polymorphism of sulfanilamide is linked to its versatile hydrogen‐bonding capabilities.     

Protecting, patterning, and scaffolding supported lipid membranes using carbohydrate glasses

Disaccharides are known to protect sensitive biomolecules against stresses caused by dehydration, both in vivo and in vitro. Here we demonstrate how interfacial accumulation of trehalose can be used to (1) produce rugged supported lipid bilayers capable of near total dehydration; (2) enable spatial patterning of membrane micro-arrays; and (3) form stable bilayers on otherwise lipophobic substrates (e.g., metal transducers) thus affording protecting, patterning, and scaffolding of lipid bilayers.     

Expression of maternal isotopes in offspring: implications for interpreting ontogenetic shifts in isotopic composition of consumer tissues

When evaluating ontogenetic shifts in isotopic composition of consumer tissues within the context of a dietary analysis, the isotopic starting point of consumers in the population should not be ignored. Neonate isotopic composition may be different from that of juveniles and adults; in general, neonate tissues are built from maternal resources rather than food resources. Thus, the range of isotope values observed within a population of consumers may be significantly impacted by consumer isotope ratios at birth. Long-term goals of my research involve the use of stable isotopes to assess the role diet plays in driving population level differences in life history and demography observed among three pigmy rattlesnake (Sistrurus miliarius; family Viperidae) populations. For meaningful interpretation of field-collected data, it was important to determine starting (i.e., at birth) isotopic compositions of rattlesnakes from the study populations. We quantified isotopic composition of pregnant pigmy rattlesnake scale tissue, isotopic composition of neonate scale tissue and the degree that neonate scale tissue isotopic composition reflected the isotopic composition of maternal scale tissue. Collectively, neonate isotopic composition was highly variable among-litters; average litter delta(13)C values spanned 7 per thousand and average litter delta(15)N values spanned 2.8 per thousand. Over 95 % of the variation in offspring isotopic composition was expressed among litters. Thus, high levels of among-litter isotopic variation were largely due to the retention of a maternal signal. Results of the enclosure study suggest that highly variable isotopic signatures in young animals within field populations could easily reflect the retention of a maternal signal rather than differences in resource utilisation among younger snakes.     

Electrochemical Detection of β-Lactoglobulin Allergen Using Titanium Dioxide/Carbon Nanochips/Gold Nanocomposite-based Biosensor

A label-free electrochemical immunosensor was developed for the ultra-sensitive detection of β-lactoglobulin (β-LG). The novel nanocomplex of carbon nanochips, colloidal gold nanoparticles and titanium dioxide nanoparticles TiO₂/CNC/AuC were constructed on conducting polymer, chitosan, and were characterised using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). This nanocomplex interface was studied using cyclic voltammetry (CV) and showed great improvement at the gold electrode surface with enhanced electrochemical performance, sensitivity and selectivity for β-lactoglobulin. Under optimal parameters, the square wave voltammetry (SWV) response curve was determined from 0.01 pg/mL to 500 pg/mL using [Fe(CN)₆]^3−/4−] redox probe. The calibration plot illustrates a linear relationship between log β-LG concentration and SWV current, with the limit of detection determined to be 0.01 pg/mL. This immunosensor displayed high sensitivity, selectivity, reproducibility and stability, and can be utilised for the detection of β-LG in real food samples.     

A porous silicon–carbon anode with high overall capacity on carbon fiber current collector

A porous silicon–carbon anode on a lightweight carbon fiber current collector is reported here for lithium-ion batteries. This Si–C anode was synthesized through a one-step carbonization of a Si-poly(acrylonitrile-co-methyl acrylate) precursor, which was directly deposited on a carbon fiber mat. The carbon fiber curent collector allows higher loading of active materials, resulting in high energy to mass and area ratios. The obtained Si–C electrode demonstrated superior overall capacity, cyclability, and rate capacity.     

Macroinitiator halide effects in galactoglucomannan‐mediated single electron transfer‐living radical polymerization

Chloro (Cl)‐ and bromo (Br)‐functionalized macroinitiators were successfully prepared from the softwood hemicellulose O‐acetylated galactoglucomannan (AcGGM) and then explored and evaluated with respect to their ability and efficiency of initiating single electron transfer‐living radical polymerization (SET‐LRP). Both halogenated species effectively initiate SET‐LRP of an acrylate and a methacrylate monomer, respectively, yielding brushlike AcGGM graft copolymers, where the molecular weights are accurately controlled via the monomer:macroinitiator ratio and polymerization time over a broad range: from oligomeric to ultrahigh. The nature of the halogen does not influence the kinetics of polymerization strongly, however, for acrylate graft polymerization, AcGGM‐Cl gives a somewhat higher rate constant of propagation, while methacrylate grafting proceeds slightly faster when the initiating species is AcGGM‐Br. For both monomers, the macroinitiator efficiency is superior in the case of AcGGM‐Br. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011