Vesicle formation from temperature jumps in a nonionic surfactant system

When heating a dilute sample of the binary system of tetraethyleneglycol dodecyl ether (C12E4) and water from the micellar phase (L1) into the two-phase region of a lamellar phase (L(alpha)), and excess water (W) vesicles are formed. During heating, one passes a region of phase separation in the micellar phase (L1' + L1') where the initial micelles rapidly fuse into larger aggregates forming the concentrated L1 phase (L1') with a structure of branched cylindrical micelles, a so-called "living network". The static correlation length of the micelles are increasing with increasing concentration, from ca. 10 nm to 80 nm in the concentration range of 0.0001 g/cm3-0.0035 g/cm3. The overlap concentration was determined to 0.0035 g/cm3. When the temperature reaches the L1' + L(alpha) region the network particles transform into bilayer vesicles with a z-average apparent hydrodynamic radius in the order of 200 nm depending on the composition. The size of the final vesicles depends on the extent of aggregation/fusion in the L1' + L1' region and hence on the rate of heating. The aggregation/fusion in the L1' + L1' is slower than diffusion-limited aggregation, and it is shown that 1/100 of the collisions are sticky results in the fusion event.     

Recognition of homo-polynucleotides containing adenine by a phenanthridinium bis-uracil conjugate in aqueous media

Among novel bis-nucleobase-phenanthridinium conjugates bis-uracil analogue stabilized significantly more effective poly-dA-poly-dT and poly-AH(+)-poly-AH(+) than adenine analogue and reference compound . For the alternating poly-dAdT-poly-dAdT however, the binding preference is lost, pointing to the importance of specific interactions of uracils of with homopolynucleotides containing consecutive adenines.     

Laser-tweezer-controlled solid immersion microscopy in microfluidic systems

We describe the creation and implementation of a near-field scanning solid immersion microscope that is specifically tailored for use in microfluidic systems. The microscope comprises a newly fabricated Weierstrass solid immersion lens (SIL), which is detached from its substrate and is free floating in the fluid, and a laser optical tweezer, which serves both as a trapping beam for alignment and positioning of the SIL and as a near-field scanning beam that images the sample through the SIL. A discussion of the SIL's fabrication method is presented along with experimental results that demonstrate the effectiveness of our microscope design.     

Daminin, a bioactive pyrrole alkaloid from the Mediterranean sponge Axinella damicornis

The isolation and characterization of the known pyrrole alkaloid agelongine (6) and of the new natural product daminin (7), the bromine-free analogue of 6, from a specimen of the marine sponge Axinella damicornis is described. Compound 7 showed significant neuroprotective properties. Moreover, for the supply of sufficient material for future medicinal investigations, a short total synthesis of 7 was developed.     

Anodic deposition of lead dioxide at Nafion® covered gold electrode

Anodic electrodeposition of lead dioxide at the bare and Nafion® covered gold electrode was studied by cyclic voltammetry and chronoamperometry. The results showed that Nafion® layer has a favourable effect on the efficiency of the deposition process which was caused by both thermodynamic and kinetic reasons. Electrodeposition process at Nafion® covered gold electrode goes via Pb(III) intermediate species which are stabilized within Nafion® membrane. The final PbO₂ deposit crystallizes in tetragonal β-PbO₂ form.     

Preparation and characterization of PLA composites with modified magnesium hydroxide obtained from seawater

Journal of Thermal Analysis and Calorimetry - Modification of poly(lactic acid) (PLA) was performed with the surface modified magnesium hydroxide (mMH) obtained from seawater. Surface modification...     

Promoting effect of carbon functional groups in methanol oxidation on supported Pt catalyst

The contribution of carbon functional groups (CFG) to methanol oxidation at carbon-supported Pt catalysts is studied in this work. Platinum black, attached in a form of a thin layer to electrochemically treated glassy carbon (GC), is investigated as a model system. Impedance measurements reveal significant changes in capacitive response of GC anodically polarized in H₂SO₄ solution in comparison to unoxidized state. XPS analyses show the increased fraction of oxygen-containing CFGs upon electrochemical treatment of GC. The activity of Pt black attached to oxidized GC for methanol oxidation is more than two times larger in comparison to the catalyst attached to unoxidized GC. Increased activity is most likely due to the promotion of CO_ads removal by increased content of CFGs.