Novel fabrication of silver-coated glass capillaries for ready SERS-based detection of dissolved chemical species

A novel method to deposit a highly surface-enhanced Raman scattering (SERS) active silver film onto the inside surface of a glass capillary is developed. Firstly, Ag sol was synthesized by the reaction of AgNO₃ with poly-(ethylenimine) (PEI), and then toluene and benzenethiol (BT) were added into the sol. The mixture was flowed through the glass capillary to obtain the SERS-active Ag film-coated glass capillary. The SERS activity of the Ag-coated capillary was dependent on the amount of PEI and BT used. In addition, BT could be easily desorbed from the Ag surface by treating it with a borohydride solution, maintaining the initial SERS activity. The SERS enhancement factor at 632.8-nm excitation was estimated to be on the order of 10⁶. The detection limits of adenine and dipicolinic acid were then as low as 1.0 × 10⁻⁸ and 1.0 × 10⁻⁷ M, respectively, based on an S/N ratio of 3. This clearly suggests that the Ag-coated capillary is an invaluable device for the analysis of effluent chemicals by SERS.     

Development of the electrochemical biosensor for organophosphate chemicals using CNT/ionic liquid bucky gel electrode

Organophosphorus hydrolase (OPH) immobilized on CNT/ionic liquid (IL) electrodes were prepared by using three different intrinsic kinds of ILs, as binders. CNTs/ILs lead to dramatic electrochemical enhancements with respect to response time, stability, and sensitivity of composite electrodes. In addition, the electrochemical and biocatalytic properties of three-composite electrodes were strongly influenced by different types of ILs used, as verified by cyclic voltammetry and chronoamperometry. These results were attributed to the conformational changes of the microenvironment between the OPH and the composite electrodes within three different types of ILs. In particular, the biocatalytic signals of three OPH/CNT/ILs-modified electrodes increased linearly to the concentration of paraoxon in a wide range of 2–20 μM. These findings provide a deep understanding of the role of each IL on the modified electrodes, enabling to enhance electrochemical properties for biosensors.     

Characterizing the origins of bottled water on the South Korean market using chemical and isotopic compositions

We analyzed the major elements and stable isotopes of oxygen, hydrogen, and carbon (dissolved inorganic carbon: DIC) in various types of bottled water (domestic and foreign) commercially available in South Korea to classify the water types and to identify their origins. Only marine waters and some sparkling waters could be discriminated by their physicochemical compositions. Oxygen and hydrogen isotopes made marine waters more distinguishable from other water types. The determination of the carbon isotope composition of DIC was clearly useful for distinguishing between naturally and artificially sparkling waters. In addition, statistical analysis also appeared to aid in the discrimination of bottled water types. Our results indicate that a method that combines chemical and stable isotope composition analysis with statistical analysis is the most useful for discriminating water types and characterizing the origins of bottled water.     

Metal ion sensing novel calix[4]crown fluoroionophore with a two-photon absorption property

1,3-Alternate calix[4]arene-based fluorescent chemosensors bearing two-photon absorbing chromophores have been synthesized, and their sensing behaviors toward metal ions were investigated via absorption band shifts as well as one- and two-photon fluorescence changes. Free ligands absorb the light at 461 nm and weakly emit their fluorescence at 600 nm when excited by UV-vis radiation at 461 nm, but no two-photon excited fluorescence is emitted by excitation at 780 nm. Addition of an Al(3+) or Pb(2+) ion to a solution of the ligand causes a blue-shifted absorption and enhanced fluorescence due to a declined resonance energy transfer (RET) upon excitation by one- and two-photon processes. Addition of a Pb(2+) ion to a solution of 1.K(+) results in a higher fluorescence intensity than the original 1.Pb(2+) complex regardless of one- or two-photon excitation, due to the allosteric effect induced by the complexation of K(+) with a crown loop.     

Membrane activation: selective vesicle fusion via small molecule recognition

We report herein the induction of selective vesicle fusion with biological recognition motifs not natively associated with lipid bilayer fusion, thus broadening the scope of recognition-guided membrane activation. Our system employs vancomycin glycopeptide, coupled to the antimicrobial peptide magainin, and D-Ala-D-Ala-OH dipeptide coupled to a phospholipid derivative, as surface-bound fusogens. Fusion was characterized by dynamic light scattering and FRET experiments with lipid bound fluorophores. We have demonstrated here that appropriately designed membrane anchored molecular recognition motifs have the biomimetic ability to activate specific membrane mergers; this principle has resonance with goals in targeted chemical delivery and nanoscale compartmentalized chemistry.     

Indium-mediated one-pot three-component reaction of aromatic amines, enol ethers, and allylic bromides

[reaction: see text] A new and efficient indium-mediated one-pot three-component reaction for the synthesis of N-aryl-substituted homoallylamines from aromatic amines, enol ethers, and allylic bromides in THF at room temperature is described.     

Dynamics of probes in model glassy matrices

The dynamics of diatomic probe molecules in matrices composed of hard spheres are studied using molecular dynamics simulations. The matrix particles are connected to fixed attachment points by strings of length, l, which is varied from l-->infinity (fluid) to 0 ("glass"). The probe diffusion coefficient, D interpolates smoothly between these limits when l is changed. As l is decreased, D displays a transition from a power-law l dependence, which is well fit by the mode-coupling theory expression, to an Arrhenius l dependence. Single particle analysis shows that the hopping motion sets in for l much larger than a critical length, l(c), and Arrhenius behavior occurs when hopping becomes the dominant mode of transport. The system displays dynamic heterogeneity even though there is no growing dynamic correlation length of any kind.     

Generation of Patterned Neuronal Networks on Cell‐Repellant Poly(oligo(ethylene glycol) Methacrylate) Films

The utilization of non‐biofouling poly(oligo(ethylene glycol) methacrylate) (pOEGMA) films as a background material for the generation of neuronal patterns is reported here. Our previously reported method, which was surface‐initiated, atom transfer radical polymerization of OEGMA, and subsequent activation of terminal hydroxyl groups of pOEGMA with disuccinimidyl carbonate, was employed for the generation of activated pOEGMA films on glass. Poly‐L ‐lysine was then microcontact‐printed onto the activated polymer films, followed by backfilling with poly(ethylene glycol) moieties. E18 hippocampal neurons were cultured on the chemically patterned substrate, and the resulting neuronal networks were analyzed by phase‐contrast microscopy and whole‐cell patch clamp method. The results indicated that the pOEGMA films played an important role in the generation of good‐quality neuronal patterns for up to two weeks without any negative effects to neurons.     

Total synthesis of (+)-roxaticin via C-C bond forming transfer hydrogenation: a departure from stoichiometric chiral reagents, auxiliaries, and premetalated nucleophiles in polyketide construction

A total synthesis of the oxo-polyene macrolide (+)-roxaticin is achieved in 20 steps from 1,3-propanediol. In this approach, 9 of 10 C-C bonds formed in the longest linear sequence are made via metal catalysis, including 7 C-C bonds formed by iridium catalyzed alcohol C-C coupling. Notably, the present synthesis, which represents the most concise preparation of any oxo-polyene macrolide reported to date, is achieved in the absence of chiral reagents and chiral auxiliaries with minimal use of premetalated C-nucleophiles.     

Determination of zearalenone by liquid chromatography/tandem mass spectrometry and application to a pharmacokinetic study

Zearalenone, a mycotoxin biosynthesized by various Fusarium fungi, is widely found as a contaminant in grains and animal feeds. This study describes a rapid and sensitive LC/MS/MS assay method for the quantification of zearalenone in rat serum. The assay was validated to demonstrate the specificity, linearity, recovery, lower limit of quantification (LLOQ), accuracy and precision. The multiple reaction monitoring was based on the transition of m/z 317.0 → 130.9 for zearalenone and 319.0 → 204.8 for zearalanone (internal standard). The assay utilized a single liquid–liquid extraction with t‐butyl methyl ether and isocratic elution, and the LLOQ was 0.5 ng/mL using 0.1 mL rat serum. The assay was linear over a concentration range from 0.5 to 200 ng/mL, with correlation coefficients >0.9996. The mean intra‐ and inter‐day assay accuracy was 101.2–112.9 and 96.3–108.0%, respectively. The mean intra‐ and inter‐day precision was between 1.3–7.6 and 3.6–10.6%, respectively. The developed assay was applied to a pharmacokinetic study after a bolus intravenous injection of zearalenone in rats. Copyright © 2009 John Wiley & Sons, Ltd.