Novel Capsular Aggregates from Flexible Tripodal Triureas with Cs Symmetry

Tris(2‐ and 3‐ureidobenzyl)amines with C_s symmetry self‐assemble in solution forming mixtures of regioisomeric capsular aggregates, one of which is chiral and the other centrosymmetric. Under certain conditions, a predominance of the centrosymmetric regioisomer is found before equilibrium, that is, a mixture close to the statistical ratio of the two species is reached. In the solid state, there is a preference for the centrosymmetric capsules. Molecular models of both regioisomeric aggregates have been built and analyzed for comparison. Guests inside capsules formed by self‐assembly of desymmetrized tris(3‐ureidobenzyl)amines feel different magnetic environments, depending on whether they are inside a chiral or an achiral regioisomeric container. Of special significance are the experiments with a more flexible triurea endowed with an ureidopropylic arm, which self‐assembles with the same efficiency as the more rigid tris(ureidobenzyl)amines.     

Cytotoxic and NF-κB inhibitory sesquiterpene lactones from Piptocoma rufescens

Six new (1-6) and eight known germacranolide-type sesquiterpene lactones, along with several known phenylpropanol coumarates and methylated flavonoids, were isolated from the leaves of Piptocoma rufescens, collected in the Dominican Republic. The new compounds were identified by analysis of their spectroscopic data, with the molecular structure of 3 being established by single-crystal X-ray diffraction. The absolute configurations of the sesquiterpene lactones isolated were determined from their CD and NOESY NMR spectra, together with the analysis of Mosher ester reactions. Bioassay screening results showed the majority of the sesquiterpene lactones isolated (1-13) to be highly cytotoxic toward the HT-29 human colon cancer cell line, with the most potent compound being 15-deoxygoyazensolide (10, IC(50), 0.26 μM). In addition, several of the sesquiterpene lactones exhibited NF-κB (p65) inhibitory activity.     

Mixed electrolytes in hydrophobic interaction chromatography†

An essential part of the modulation of protein‐binding capacity in hydrophobic interaction chromatography is the buffer‐salt system. Besides using “single” electrolytes, multicomponent electrolyte mixtures may be used as an additional tool. Both the protein solubility and the binding capacity depend on the position of a salt in the so‐called Hofmeister series. Specific interactions are observed for an individual protein‐salt combination. For salt mixtures, selectivity, recovery, and binding capacity do not behave like for the single salts that are positioned in between the two mixed components in the Hofmeister series, as the continuous correlation would suggest. Thus, finding strategies for mixed salts could potentially lead to improved capacities in hydrophobic interaction chromatography. Mixtures of ammonium sulfate, sodium citrate, sodium sulfate, sodium chloride, sodium acetate, and glycine were used to investigate the binding capacities for lysozyme and a monoclonal antibody on various hydrophobic resins. Resin capacity for two investigated proteins increases when mixtures consisting of a chaotropic and a kosmotropic salt are applied. It seems to be related to the rather basic isoelectric points of the proteins.     

经Opuntia dilenii haw植物提取液绿色合成制备的纳米铝酸锌的催化性质(英文)

Various nanosized zinc aluminate(ZnAl2O4) samples were prepared by a conventional and a mi- crowave method both with and without using Opuntia dilenii haw plant extract,and were charac- terized by X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR),high resolution scanning electron microscopy(HRSEM),energy dispersion scanning(EDX),temperature dependent conductance measurements, thermoelectric power measurements, ultraviolet-visible (UV-Vis) diffuse reflectance spectroscopy,and photoluminescence spectroscopy.The formation of a pure ZnAl2O4 phase was confirmed by XRD and FT-IR.A change in morphology from nanosized plates to nanosized sheets with,respectively,the conventional and microwave heating methods was clearly shown by HRSEM.UV-Vis diffusion reflectance spectroscopy measured the band gaps of ZnAl2O4 nanosized plates and nanosized sheets as 3.5 and 3.9 eV,respectively.The synthesized ZnAl2O4 was single crystalline and has three photoluminescence emissions at 482,528,and 540 nm.ZnAl2O4 nanosized sheets prepared by the microwave method showed higher catalytic activity for the oxida- tion of benzyl alcohol(85% conversion) than ZnAl2O4 nanosized plates prepared by the convention- al method(60% conversion).     

The influence of the liquid crystalline core geometry on the mesogenicity of novel chiral 2-(4-substituted-phenoxy)propanonitriles

Abstract

The synthesis and characterization of seven novel (R)-2-(4-substituted-phenoxy)propanonitriles are described. The propanonitriles were prepared to evaluate their potential use as thermochromics and ferroelectric dopants, as well as to determine their twist sense properties. The materials exhibit smectic and chiral nematic phases of high thermal stability; the mesogenic behaviour of the nitriles is directly related to the type of two-ring core unit employed. The effects of the different molecular geometries and polarizabilities of the liquid crystalline cores on mesophase stability are discussed, particularly in relation to other members of this series. The chiral nematic phase of the propanonitriles is assigned as having a left-handed twist sense from contact preparation studies, and this is in agreement with rules relating absolute configuration and molecular structure to helical twist sense.