Phase behavior of an extended surfactant in water and a detailed characterization of the concentrated phases

The formation of microemulsions with triglycerides at ambient conditions can be improved by increasing the surfactant-water and surfactant-oil interactions. Therefore, extended surfactants were developed, which contain hydrophilic/lipophilic linkers. They have the ability to stretch further into the oil and water phase and enhance the solubility of oil in water. In this work, the phase behavior of a chosen extended surfactant (C(12-14)-PO(16)-EO(2)-SO(4)Na, X-AES) in H(2)O/D(2)O at high surfactant concentrations (30-100 wt %) and at temperatures between 0 and 90 °C is studied for the first time. The lyotropic liquid crystals formed were determined by optical microscopy, small-angle X-ray scattering (SAXS), and (2)H and (23)Na NMR, and a detailed phase diagram of the concentrated area is given. The obtained mesophases are a hexagonal phase (H(1)), at low temperatures and small concentrations, a lamellar phase (L(α)) at high temperatures or concentrations, a bicontinuous cubic phase (V(2)) as well as a reverse hexagonal phase (H(2)). To our knowledge, this is the first surfactant that forms both H(1) and H(2) phases without the addition of a third compound. From the (2)H NMR quadrupole splittings of D(2)O, we have examined water binding in the L(α) and the H(2) phases. There is no marked difference in the bound water between the two phases. Where sufficient water is present, the number of bound water molecules per X-AES is estimated to be ca. 18 with only small changes at different temperatures. Similar results were obtained from the (23)Na NMR data, which again showed little difference in the ion binding between the L(α) and the H(2) phases. The X-ray diffraction data show that X-AES has a much smaller average length in the L(α) phase compared to the all-trans length than in the case for conventional surfactants. At very high surfactant concentrations an inverse isotropic solution (L(2)), containing a small fraction of solid particles, is formed. This isotropic solution is clearly identified and the size of the reversed micelles was determined using (1)H NMR measurements. Furthermore, the solid particles within the L(2) phase and the neat surfactant were analyzed. The observed results were compared to common conventional surfactants (e.g., sodium dodecyl sulfate, sodium lauryl ether sulfate, and sodium dodecyl-p-benzene sulfonate), and the influence of the hydrophilic/lipophilic linkers on the phase behavior was discussed.     

Cyclic lipoundecapeptide tensin from Pseudomonas fluorescens strain 96.578

The crystal structure of the non‐ribosomal lipoundecapeptide tensin from Pseudomonas fluorescens has been solved as an ethyl acetate/bis‐water solvate (tensin ethyl acetate dihydrate, C₆₇H₁₁₅N₁₂O₂₀·C₄H₈O₂·2H₂O) to a resolution of 0.8 Å. The primary structure of tensin is β‐hydroxydecanoyl‐d ‐Leu‐d ‐Asp‐d ‐allo‐Thr‐d ‐Leu‐d ‐Leu‐d ‐Ser‐l ‐Leu‐d ‐Gln‐l ‐Leu‐l ‐Ile‐l ‐Glu. The peptide is a lactone linking the Thr3 O_γ atom to the C‐terminal C atom. The stereochemistry of the β‐hydroxy acid has been shown to be S. The peptide shows structural resemblance to the non‐ribosomal cyclic lipopeptide fengycin from Bacillus subtilis. The structure of tensin is essentially helical (3₁₀‐helix), with the cyclic peptide wrapping around a hydrogen‐bonded water molecule. The lipopeptide is amphipathic in good agreement with its function as a biosurfactant.     

An Efficient Protocol for the Epoxidation of Acid-and Acid/Base-Sensitive Alkenes With m-Chloroperoxybenzoic Acid

An efficient protocol for the epoxidation of acid-and acid/base-sensitive alkenes with m-chloroperoxybenzoic acid and using 2,6-di-tert-butylpyridine as a buffer is described.     

Isotopenpreis der Dr.-Karleugen-Habfast-Stiftung

Es wird über die Entwicklung energie- und richtungsunabhängiger Ionisationskammern sowie über die Konzeption und Wirkungsweise des Dosimeters VA-J-18 berichtet, das als Dosis- und Dosisleistungsmeβgerät vorwiegend für den klinischen Einsatz in der Strahlentherapie vorgesehen ist. Auf Grund des hohen MeβSumfangs ist es atich für die meβtechnische Überwachung strahlenmedizinischer oder -biologischer Experimente sowie für Strahlenschutzmessungen und Aktivitätsbestimmungen geeignet.     

Surface modified polypropylene pipette tips packed with a monolithic plug of adsorbent for high-throughput sample preparation

UV-initiated poly(butyl methacrylate-ethylene glycol dimethacrylate) porous polymer monoliths were prepared in situ in polypropylene-based pipette tips for high-throughput sample preparation. Prior to the in situ polymerization, the surface of the PP tips was modified. In this work, two different surface modification approaches were tested for this purpose. First the photoinitiator benzophenone was used to generate radicals at the surface of PP by hydrogen abstraction. In the second modification approach, a thin layer of a polymer was directly grafted to the surface. The effect of surface modification was measured by contact angle measurements of a drop of water at the surface. As a result of the surface modification, scan electron microscopy images indicate a covalent attachment of the monolith to the wall of the pipette tip. Pipette tips modified with 5% BP in methanol and packed with a plug of monolith were further evaluated for high-throughput sample preparation. Using a liquid handling system, the extraction performance of packed pipette tips was tested for the analysis of ropivacaine in plasma samples. The recovery and reproducibility results were in accordance with internationally accepted criteria for qualitative and quantitative analysis of the test substance, ropivacaine.     

Determination of volatilization (dissipation) and secondary deposition of pesticides in a field study using passive dosimeters

The volatilization and secondary deposition of the herbicides prosulfocarb and pendimethalin were measured using passive dosimeters with Chinese cabbage and soil as collective material. Passive dosimeters were placed in the field before spraying and at three distances downwind after spraying. The volatilization of prosulfocarb and pendimethalin determined as dissipation was 80 and 60% of the applied amount from the cabbage surface, while no significant loss was measured from soil surfaces after 48?h. The secondary deposition of prosulfocarb and pendimethalin 25?m from the spray zone was 2 and 4% on the leaf surface as well as on the soil surface. At 5?m distance, 6 and 10% of the field dose of prosulfocarb and pendimethalin could be determined on dosimeters with leaves, and 4 and 8% of the field dose could be determined on soil surfaces.