Small molecule adsorption on to polyester capillary‐channeled polymer fibers: Frontal analysis of naphthalene and naphthol (naphthalene and naphthol adsorption on capillary‐channeled polymer fibers)

Frontal analysis was carried out employing poly(ethylene‐terephthalate) capillary‐channeled polymer fibers as the stationary phase for the immobilization of low‐molecular‐weight polycyclic aromatic hydrocarbon compounds (naphthol and naphthalene) from 2% methanol/water solutions. The effects of several experimental parameters on the frontal profile, the breakthrough volume, and the equilibrium parameters were determined for each solute. The amount adsorbed at exhaustion of naphthalene and naphthol was also compared. The kinetics and thermodynamics were maintained at relatively fast flow rates/linear velocities (～6–18 mm/s). Comparisons of dynamic capacity revealed that naphthalene was more retained than naphthol, in most situations more than five times that of the naphthol adsorption. This increase in capacity is most likely due to the multilayering of naphthalene on the surface of the fibers through π–π interactions between the solute and the fiber surface and successive layering of solute molecules. The extent of layering is a function of the flow, with faster flow rates (and subsequent shear forces) reducing the extent of adsorbate–adsorbate interactions. Although the overall loading capacity of the capillary‐channeled polymer fibers is far below porous phases, there are a number of attractive attributes that support further development.     

Biosensing applications of clay-modified electrodes: a review

Two-dimensional layered inorganic solids, such as cationic clays and layered double hydroxides (LDHs), also defined as anionic clays, have open structures which are favourable for interactions with enzymes and which intercalate redox mediators. This review aims to show the interest in clays and LDHs as suitable host matrices likely to immobilize enzymes onto electrode surfaces for biosensing applications. It is meant to provide an overview of the various types of electrochemical biosensors that have been developed with these 2D layered materials, along with significant advances over the last several years. The different biosensor configurations and their specific transduction procedures are discussed.      

Micromagnetic simulations of spinel ferrite particles

This paper presents the results of simulations of the magnetization field ac response (at 2-12 GHz) of various submicron ferrite particles (cylindrical dots). The ferrites in the present simulations have the spinel structure, expressed here by M₁−_nZn_nFe₂O₄ (where M stands for a divalent metal), and the parameters chosen were the following: (a) for n=0: M={Fe, Mn, Co, Ni, Mg, Cu }; (b) for n=0.1: M = {Fe, Mg} (mixed ferrites). These runs represent full 3D micromagnetic (one-particle) ferrite simulations. We find evidences of confined spin waves in all simulations, as well as a complex behavior nearby the main resonance peak in the case of the M = {Mg, Cu} ferrites. A comparison of the n=0 and n=0.1 cases for fixed M reveals a significant change in the spectra in M = Mg ferrites, but only a minor change in the M=Fe case. An additional larger scale simulation of a 3 by 3 particle array was performed using similar conditions of the Fe₃O₄ (magnetite; n=0, M = Fe) one-particle simulation. We find that the main resonance peak of the Fe₃O₄ one-particle simulation is disfigured in the corresponding 3 by 3 particle simulation, indicating the extent to which dipolar interactions are able to affect the main resonance peak in that magnetic compound.     

IUPAC critical evaluation of the rotational-vibrational spectra of water vapor. Part II: Energy levels and transition wavenumbers for HDO, HDO, and HDO

This is the second of a series of articles reporting critically evaluated rotational-vibrational line positions, transition intensities, pressure dependences, and energy levels, with associated critically reviewed assignments and uncertainties, for all the main isotopologues of water. This article presents energy levels and line positions of the following singly deuterated isotopologues of water: HD¹⁶O, HD¹⁷O, and HD¹⁸O. The MARVEL (measured active rotational-vibrational energy levels) procedure is used to determine the levels, the lines, and their self-consistent uncertainties for the spectral regions 0-22 708, 0-1674, and 0-12 105 cm⁻¹ for HD¹⁶O, HD¹⁷O, and HD¹⁸O, respectively. For HD¹⁶O, 54 740 transitions were analyzed from 76 sources, the lines come from spectra recorded both at room temperature and from hot samples. These lines correspond to 36 690 distinct assignments and 8818 energy levels. For HD¹⁷O, only 485 transitions could be analyzed from three sources; the lines correspond to 162 MARVEL energy levels. For HD¹⁸O, 8729 transitions were analyzed from 11 sources and these lines correspond to 1864 energy levels. The energy levels are checked against ones determined from accurate variational nuclear motion computations employing exact kinetic energy operators. This comparison shows that the measured transitions account for about 86% of the anticipated absorbance of HD¹⁶O at 296 K and that the transitions predicted by the MARVEL energy levels account for essentially all the remaining absorbance. The extensive list of MARVEL lines and levels obtained are given in the Supplementary Material of this article, as well as in a distributed information system applied to water, W@DIS, where they can easily be retrieved. In addition, the transition and energy level information for H₂¹⁷O and H₂¹⁸O, given in the first paper of this series [Tennyson, et al. J Quant Spectr Rad Transfer 2009;110:573-96], has been updated.     

A novel,simple and sensitive ligand affinity capture method for detecting molecular interactions by MALDI mass spectrometry

A simple and sensitive ligand affinity capture method (LAC) was developed to detect biotinylated biomolecules bound to a biotin–avidin base by matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry (MALDI ToF MS). Glass slides covered with a metal film for MALDI MS applications were treated with amino‐silane and derivatized with biotin followed by binding of avidin. Washing buffers with high ionic strength increased the specificity of the subsequent binding of biotinylated biomolecules to the avidin layer. A combined thin layer‐dried droplet method using α‐cyano‐4‐hydroxycinnamic acid (CHCA) in acetone or ethyl acetate resulted in the most intense ions of biotinylated polymyxin B, whereas the matrix conditions did not influence the detection of angiotensin II. Addition of biotinylated biomolecules in the low femtomole to low picomole range resulted in sufficient ion intensity for detection by the LAC method. The LAC concept was extended by binding of biotinylated lipopolysaccharide to the biotin–avidin base followed by preferential capture and specific detection of the binding antagonist polymyxin B. Copyright © 2008 John Wiley & Sons, Ltd.     

Novel 4-carboxyphenyl-grafted screen-printed electrode for trace Cu(II) determination

This paper reports the interest of 4-carboxyphenyl-grafted screen-printed electrodes (4-CP-SPEs) for trace Cu(II) measurement in water samples. These novel sensors were easily prepared via electrochemically reduction of the corresponding diazonium salt. Detection of Cu(II) was then achieved by immersing the grafted electrode into the sample solution for 10 min, followed by the electrochemical measurement of accumulated metallic ions.The efficiency of the Cu(II) adsorption at the grafted layer was clearly demonstrated. 4-CP-SPEs were able to detect and quantify Cu(II) as low as 5 × 10^?9 and 10^?8 M in a large ionic strength range. Moreover, no major interference of Pb(II) in the determination of Cu(II) is expected in natural water. Electrodes were finally successfully applied for Cu(II) determination in tap water and in estuarine water demonstrating the convenience of such sensors for environmental analysis.     

Efficient Catalytic Promiscuity for Chemically Distinct Reactions

High catalytic proficiencies observed for the native and promiscuous reaction of the Pseudomonas aeruginosa arylsulfatase (PAS; the picture shows transition states of the two substrates with corresponding binding constants K_tx) suggest that the trade‐off between high activity and tight specificity can be substantially relaxed.

     

The metabolic pH response in Lactococcus lactis: an integrative experimental and modelling approach

Lactococcus lactis is characterised by its ability to convert sugar almost exclusively into lactic acid. This organic acid lowers extracellular pH, thus inhibiting growth of competing bacteria. Although L. lactis is able to survive at low pH, glycolysis is strongly affected at pH values below 5, showing reduced rate of glucose consumption. Therefore, in order to deepen our knowledge on central metabolism of L. lactis in natural or industrial environments, an existing full scale kinetic model of glucose metabolism was extended to simulate the impact of lowering extracellular pH in non-growing cells of L. lactis MG1363. Validation of the model was performed using (13)C NMR, (31)P NMR, and nicotinamide adenine dinucleotide hydride auto-fluorescence data of living cells metabolizing glucose at different pH values. The changes in the rate of glycolysis as well as in the dynamics of intracellular metabolites (NADH, nucleotide triphosphates and fructose-1,6-bisphosphate) observed during glucose pulse experiments were reproduced by model simulations. The model allowed investigation of key enzymes at sub-optimum extracellular pH, simulating their response to changing conditions in the complex network, as opposed to in vitro enzyme studies. The model predicts that a major cause of the decrease in the glycolytic rate, upon lowering the extracellular pH, is the lower pool of phosphoenolpyruvate available to fuel glucose uptake via the phosphoenolpyruvate-dependent transport system.     

LC‐MS of streptomycin following desalting of a nonvolatile mobile phase and pH gradient

Streptomycin (SM) is composed of streptidine, streptose and N‐methyl glucosamine sugar moieties. For the determination of SM and its related substances, an ion‐pair LC‐UV detection method using a Supelcosil LC‐ABZ column was developed previously. While analyzing commercial samples, several unknown compounds were detected. Most of these compounds are not yet characterized. In this study, the above LC method was coupled to MS for impurity profiling in a selected commercial sample. However, it could not be directly coupled to MS due to the presence of the nonvolatile salt, buffer and ion‐pair reagent in the mobile phase. So, for structural characterization, each peak eluted from the nonvolatile eluent system was collected and transferred to MS after the desalting process. In total, 16 compounds were studied, 15 compounds including 12 unknowns could be identified.