Enzymatic resolution of bicyclic 1-heteroarylamines using Candida antarctica lipase B

Candida antarctica lipase B has been used to kinetically resolve a structurally diverse series of bicyclic 1-heteroaryl primary amines by enantioselective acetylation. High yields of either enantiomer could be obtained with excellent enantioselectivity (90-99% ee), while the undesired enantiomer could, in some cases, be recycled by thermal racemization. The absolute stereochemistry of the products was confirmed by an X-ray crystal structure.     

Thermal transformations of selected transition metals oxyhydroxides

We investigated the features of the glass transition relaxation of two room temperature ionic liquids using DSC. An important observation was that the heat capacity jump, that is the signature of the glass transition relaxation, shows a particularly strong value in this type of new and promising materials, candidates for a range of applications. This suggests a high degree of molecular mobility in the supercooled liquid state. The study of the influence of the heating rate on the temperature location of the glass transition signal, allowed the determination of the activation energy at the glass transition temperature, and the calculation of the fragility index of these two ionic glass-formers. It was concluded that this kind of materials belong to the class of relatively strong glass-forming systems. This revised version was published online in July 2006 with corrections to the Cover Date.     

Photodynamic Therapy Efficacy Enhanced by Dynamics: The Role of Charge Transfer and Photostability in the Selection of Photosensitizers

Progress in the photodynamic therapy (PDT) of cancer should benefit from a rationale to predict the most efficient of a series of photosensitizers that strongly absorb light in the phototherapeutic window (650–800 nm) and efficiently generate reactive oxygen species (ROS=singlet oxygen and oxygen‐centered radicals). We show that the ratios between the triplet photosensitizer–O₂ interaction rate constant (k_D) and the photosensitizer decomposition rate constant (k_d), k_D/k_d, determine the relative photodynamic activities of photosensitizers against various cancer cells. The same efficacy trend is observed in vivo with DBA/2 mice bearing S91 melanoma tumors. The PDT efficacy intimately depends on the dynamics of photosensitizer–oxygen interactions: charge transfer to molecular oxygen with generation of both singlet oxygen and superoxide ion (high k_D) must be tempered by photostability (low k_d). These properties depend on the oxidation potential of the photosensitizer and are suitably combined in a new fluorinated sulfonamide bacteriochlorin, motivated by the rationale.     

Silicone‐urethane membranes for lithium batteries. Part 1. Moisture‐cured poly(siloxane‐urethane‐urea) elastomers containing polyethylene oxide (PEO) segments – synthesis and characterization as potential membrane materials

Poly(siloxane‐urethane‐urea) elastomers containing both polysiloxane and polyethylene oxide (PEO) segments in the polymer chain were obtained by moisture‐curing of NCO‐terminated poly(siloxane‐urethane) prepolymers synthesized from isophorone diisocyanate and mixtures of polyoxyethylene diols and polysiloxane diols with various molecular weights. Mechanical properties of the moisture‐cured films and their swelling ability in solvent mixtures commonly used in lithium batteries were investigated, and it was found that they were greatly influenced by PEO content in the polymer. PEO content in the polymer was also found to affect very much the electric conductivity of the films after immersion in lithium salt solution in ethylene carbonate–dimethyl carbonate solvent mixture. At high contents of PEO in the polymer chain specific conductivities of the films in a range of 10^?3, Scm^?1 could be achieved at room temperature. Based on the results of Scanning Electron Microscopy with X‐ray Analysis (SEM/EDS) investigations and wide‐angle X‐ray scattering and small‐angle X‐ray scattering studies, it could be anticipated that the reason for good conductivity of the films might be their specific supramolecular structure that potentially facilitated lithium ion mobility. Copyright © 2015 John Wiley & Sons, Ltd.     

Development and Application of new C30-Modified TLC Plates

JPC – Journal of Planar Chromatography – Modern TLC - This paper reports the efficiency of the C30 phase for HPLC and TLC separation of a mixture of tocopherol homologs and...     

Comparison of Different Sorbents for Solid-Phase Extraction of Phenoxyalkanoic Acid Herbicides

An HPLC procedure for determination of phenoxyalkanoic acid herbicides in water samples is proposed. The analytical column Phenomenex C18(2) Luna 5 µm and UV detection at 225 nm were applied. Baseline resolution was achieved in isocratic mode with a mobile phase consisting of acetonitrile/acetic acid (40/60, v/v), adjusted to pH 2.5. SPE sorbents – C₁₈ BondElut, phenyl-silica, LiChrolut SAX and polymeric sorbents – were compared for isolation and preconcentration of 6 phenoxyalkanoic acid herbicides. Higher (above 95%) and more reproducible recoveries were obtained with polymeric and phenyl-silica sorbents using pure methanol for elution. The method was tested for river water samples with the limit of detection in the range of 2–3 µg L⁻¹ (for 50 mL sample) and a reproducibility of 5% RSD.     

Mechanical and thermal properties of green polylactide composites with natural fillers

Green composites of PLA with micropowders derived from agricultural by-products such as oat husks, cocoa shells, and apple solids that remain after pressing have been prepared by melt mixing. The thermal and mechanical properties of the composites, including the effect of matrix crystallization and plasticization with poly(propylene glycol), have been studied. All fillers nucleated PLA crystallization and decreased the cold-crystallization temperature. They also affected the mechanical properties of the compositions, increasing the modulus of elasticity but decreasing the elongation at break and tensile impact strength although with few exceptions. Plasticization of the PLA matrix improved the ductility of the composites.     

Surface analysis of a cold leg section of an SS316-lithium loop

Compatibility studies of austenitic stainless steel AISI 316 with liquid lithium for fusion application have shown that a porous ferritic layer is formed on the surface of the steel in the hot leg of a loop experiment due to depletion of alloying elements. The concentration profiles of the removed elements across the cross section of the tube reveal a pronounced step between the austenite matrix and the porous ferrite which is not expected in a normal diffusion process. The removed elements are partly deposited on the surface of the cold leg.In this study we looked at the boundary between the nickel rich deposit and the original matrix of a section of the cold (435 °C) leg. On the surface of the austenite, the expected grain boundary attack of lithium was observed. Additionally, to a depth of about one grain size, chromium and molybdenum were depleted and lithium seemed to also have attacked the bulk material, resulting in a splitting up into smaller grains with decomposed concentrations of the alloying elements, i.e. iron with large amounts of nickel and iron with chromium and small nickel amounts.In this paper a suggestion is put forward describing a reaction mechanism leading to the porous layer in the hot leg as a result of the instability of AISI 316 and its decomposition into two phases under the influence of liquid lithium.Dedicated to Professor Günther Tölg on the occasion of his 60th birthday