Electron spin resonance studies of manganese(II) and copper(II) salts of poly(ethylene-co-methacrylic acid)s

The ionic interaction of poly(ethylene-co-methacrylic acid) ionomer neutralized with Mn²⁺ or Cu²⁺ was studied by ESR spectroscopy to explore the local structure in the ionic aggregate. ESR spectra of the ethylene ionomer were obtained as functions of degree of neutralization and temperature. The existence of both isolated and aggregated cations in the ionomer was confirmed by ESR. In addition, the formation of a Cu²⁺?Cu²⁺ dimer structure similar to the crystal structure of copper acetate monohydrate was found in ethylene ionomer containing the Cu²⁺. Cation-cation interactions changed markedly around 70°C with increasing temperature, representing the onset of the motion of cations in the aggregated ionic structure.     

Design and construction of glutamine binding proteins with a self-adhering capability to unmodified hydrophobic surfaces as reagentless fluorescence sensing devices

The chemically and genetically remodeling of proteins with ligand binding specificities can be utilized to synthesize various protein-based microsensors for detecting single biomolecules. Here, we describe the construction and characterization of fluorophore-labeled glutamine binding proteins (QBP) and derivatives coupled to the independently designed hydrophobic polypeptide (E12) that can adhere onto solid surfaces via hydrophobic interactions. The single cysteine mutant (N160C QBP) modified with the three environmentally sensitive fluorescent dyes (IAANS, acrylodan, and IANBD ester) showed increased changes in fluorescence intensity induced by glutamine binding. The use of these conjugates as reagentless fluorescence sensors enables us to determine the glutamine concentrations (0.1-50 microM) in homogeneous solution. The fusion of N160C QBP with E12, (Gly4-Ser)n spacers (GSn), and IANBD resulted in the novel fluorescence sensing elements having an adhering capability to hydrophobic surfaces of unmodified microplates. In ELISA and fluorescence experiments for the microplates treated with a series of the conjugates, IANBD-labeled N160C QBP-GS1-E12 displayed the best reproducibility in adhesion onto the hydrophobic surfaces and the precise correlation between fluorescence changes and glutamine concentrations. The performance of the biosensor-attached microplate for glutamine titrations demonstrated that the hydrophobic interaction of E12 with solid surfaces is useful for effective immobilization of proteins that need specific conformational movements in recognizing particular biomolecules. Therefore, the technique using E12 as a surface-linking domain for protein adhesion onto unmodified substrates could be applied effectively to prepare microplates/arrays for a wide variety of high-throughput assays on chemical and biological samples.     

Total Synthesis of (±)-Nanaomycin A and (±)-Frenolicin

Efficient synthesis of (±)-nanaomycin A and (±)-frenolicin from a versatile intermediate is described.     

Accurate size determination of PS latex nanoparticles in aqueous solution using pulsed field gradient nuclear magnetic resonance spectroscopy

The accurate size determination of nanoparticles in solution is an important subject in nano/bio-technologies. However, interactions between particles induce a significant misinterpretation of the size determination by PFG-NMR method. In the sodium dodecyl sulfate (SDS) aqueous solution, we observed the significant change of the apparent size of PS-latex that depended on the concentration of SDS. In this Letter, accurate size determination of PS latex was carried out by extrapolation methods varying both the concentrations of the PS latex and the SDS in aqueous solution. The proposed method makes it possible to compare the determined sizes of nanoparticles in the liquid-phase by PFG-NMR to those by differential mobility analyzer (DMA) in the gas-phase.     

Radical deoxygenation of 3-azatricyclo[2.2.1.0]heptan-5-ols to 2-azabicyclo[2.2.1]hept-5-enes and 1,2-dihydropyridines

Additions of alkyl or aryl Grignard reagents, or pyridin-3-yl-lithiums or lithium alkoxides, to exo-5,6-epoxy-7-(tert-butoxycarbonyl)-2-tosyl-7-azabicyclo[2.2.1]hept-2-ene lead to 7-substituted-1-tosyl-3-azatricyclo[2.2.1.0^2,6]heptan-5-ols. Radical deoxygenations of 7-alkyl-1-tosyl-3-azatricyclo[2.2.1.0^2,6]heptan-5-ols give 7-alkyl-4-tosyl-2-azabicyclo[2.2.1]hept-5-enes, whereas 7-aryl-1-tosyl-3-azatricyclo[2.2.1.0^2,6]heptan-5-ols give 2-(arylmethyl)-5-tosyl-1,2-dihydropyridines.     

QCM study of microbiological activity during long-term exposure to atmosphere—aluminium colonisation by <Emphasis Type="Italic">Aspergillus Niger</Emphasis>

The study demonstrated a possibility to sense the activity of microorganisms on metals in situ under atmosphere conditions using a quartz crystal microbalance (QCM) as a sensitive mass change detector. Other innovative aspects of the QCM application include long-term monitoring (over month), taking count of the influence of atmospheric pressure and application of Al-glued foil electrodes. The research subject was aluminium colonisation by Aspergillus niger Tiegh., a filamentous ascomycete fungus. The difference between the QCM data for abiotic and biotic samples reflected microbiological activity, which resulted in exponential mass gain during exposure. The increase in mass was due to various phenomena, i.e. development of biomass, secretion of metabolites, water uptake by the colony and microbially induced corrosion. The glued foil method demonstrated a possibility to expand the scope of the QCM studies from evaporated, sputtered or electroplated materials to those, from which thin foils may be produced. Dedicated to Professor Dr. Algirdas Vaškelis on the occasion of his 70th birthday.     

Enhancing the effect of the nanofiber network structure on thermoresponsive wettability switching

This letter reports the enhancing effects of a nanofiber network structure on stimuli-responsive wettability switching. Thermoresponsive coatings composed of nanofibers were prepared by electrospinning from thermoresponsive polymer poly(N-isopropylacrylamide) (PNIPAAm). The nanofiber coatings showed a large amplitude of thermoresponsive change in the wettability from hydrophilic to hydrophobic states compared to a smooth cast film. In particular, the combination of the surface chemistry and unique topology of the electrospun nanofiber coatings enables a transition from the Wenzel state to the metastable Cassie-Baxter state with an increase in temperature and consequently an enhanced amplitude of change in the water contact angles: the apparent contact angle differences between 25 and 50 °C are Δθ*(25-50?°C?)= 108 and 10° for the nanofiber coatings with a diameter of 830 nm and a smooth cast film, respectively. The fabrication of the 3D nanofiber network structure by electrospinning from stimuli-responsive materials is a promising option for highly responsive surfaces in wettability.