Highly Enantioselective Phenylacetylene Addition to Benzaldehyde Catalyzed by Chiral Tridentate Ligand

Development of new or improved methods for the asymmetric preparation of chiral propargylic alcohols has gained considerable significance during the past years because they are useful building blocks for the synthesis of many biologically active compounds and natural products.[1] A series of chiral tridentate ligands were conveniently synthesized from amino acids with good yields (Scheme 1).[2] A preliminary study of the enantioselective alkynylation of benzaldehyde catalyzed by this chiral tridentate ligand was carried out and up to 83% ee of chiral propargyl alcohols was obtained (Table 1 ). A further investigation of the tridentate ligand is currently underway.     

GC–MS analysis of phenolic compounds in fuels after conversion to trifluoroacetate esters

The GC–MS characteristics of trifluoroacetate esters of phenolic compounds are discussed. Linear temperature programmed retention indices and total ion current MS response factors of over 120 phenolic esters are reported. The main GC advantages from analysis of trifluoroacetate esters as compared to plain phenols are enhanced volatility and improved resolution. For example, the elution temperature of a given phenol is typically 50 °C greater than that of the corresponding trifluoroacetate ester. Also, while retention of compounds with two trifluoroacetate groups is only moderately greater than mono esters, underivatized dihydroxy compounds are very difficult to elute from any GC column. Complete resolution of isomeric C₀-, C₁- and C₂-alkylphenol esters is readily achieved on conventional fused silica GC columns; resolution of the corresponding underivatized compounds requires specialized GC columns with low temperature limits. In general, mass spectra of trifluoroacetate esters are more characteristic of a given structure than those of the corresponding phenols and may be more rigorously interpreted towards structural elucidation. A table in the report summarizes some of the more important spectral features used in compound identification. Example applications in analysis of coal-, shale- and petroleum-derived materials are presented. Selected ion monitoring is used to determine individual phenolic components in whole distillates; reconstructed ion chromatograms are used to illustrate distributions of selected species as a function of fuel storage and thermal stress.     

Electron Spectroscopy - A Potentially Useful Tool for Environmental Studies

The technique of electron spectroscopy (ESCA) is reviewed. Those aspects are discussed which seem to be of greatest potential interest to workers in environmental studies. Basic theory of the photoelectron ejection process is considered along with the Auger effect. Factors affecting the calculation of electron binding energies are discussed. Instrumentation utilizing both magnetic and electrostatic monochromators is discussed in some detail.

The nature of ESCA data is considered, along with an extensive tabulation of chemical shifts observed for 15 elements. Application of ESCA to surface studies is reviewed, using examples like effect of layers of material on electron intensities, investigations of zeolites and some elementary catalysis studies. A review of the quantitative aspects of ESCA considers the determination of arsenic in soils and the measurement of mixed oxide ratios.     

Advances towards Cell-Specific Gene Transfection: A Small-Molecule Approach Allows Order-of-Magnitude Selectivity

A transfection vector that can home in on tumors is reported. Whereas previous vectors that allow moderately cell selective gene transfection used larger systems, this small-molecule approach paved the way for precise structure-activity relationship optimization. For this, biotin, which mediates cell selectivity, was combined with the potent DNA-binding motif tetralysine-guanidinocarbonypyrrol via a hydrophilic linker, thus enabling SAR-based optimization. The new vector mediated biotin receptor (BR)-selective transfection of cell lines with different BR expression levels. Computer-based analyses of microscopy images revealed a preference of one order of magnitude for the BR-positive cell lines over the BR-negative controls.     

Use of chromatographic pre-concentration for routine uranium bioassay analysis by ICP-MS

Routine monitoring of urine is an effective way to detect occupational intake of radioactive material. Historically, determinations of uranium isotopic ratios have been performed by radiochemical separation followed by alpha spectrometry. With recent advancements in technology, inductively coupled plasma-mass spectrometry (ICP-MS) has become widely available for the determination of trace metals as well as radioactive nuclides with long half-lives, such as ²³⁸U in urine. Furthermore, ICP-MS measurements of ²³⁸U do not require radiochemical separation since the number of atoms in the sample is determined instead of the number of alpha particles emitted. However, this method does not provide good sensitivity for the determination of ²³⁵U due to its shorter half-life. An improved procedure using pre-concentration of uranium and determination by ICP-MS decreases the detection limit by a factor of ten or greater with only slight increase in total analysis time. The method also has the capability of accurately determining the isotopic ratio of the sample, which is very important in cases where enriched or depleted uranium is involved.     

基于纯方位的浅海距离特征量解算分析

目标辐射噪声的LOFAR图中的干涉条纹包含了目标的运动参数和环境信息。当LOFAR图中的干涉条纹模糊或缺失时,其中的目标距离信息将无法提取。对于匀速直线运动的声源目标,仅利用方位信息,通过构造距离特征量和目标方位的关系模型,给出了一种浅海估计距离特征量的补充方法。浅海数值仿真和实验验证表明了该方法的可行性和有效性。     

单矢量水听器估计目标方位的方法与实验

为评估基于单矢量水听器的方位估计能力,在黄海海域对矢量水听器进行实验。矢量水听器吊放于接收船尾部,采用平均声强器和复声强器方位估计方法,并提出以概率密度值最大的方位角作为目标方位估计值的具体处理准则,对恒定方向、匀速行驶的目标船方位进行估计,并求出两种方法的方位估计误差。结果表明,水听器布放深度10 m时,对正横距离为0.42 km的航速10 kn的目标船,平均声强器方法的水平方位角估计误差18°,极角估计误差为5°,可以在离目标船最远1.17 km处估计其方位;复声强法的水平方位角估计误差为13°,极角估计误差为8°,可以在离目标船最远2.35 km处估计其方位。在有接收船的噪声干扰情况下,复声强器比平均声强器方法估计的方位更准确,可以对更远处的噪声源进行方位估计。     

Structural and electronic properties of amorphous bismuth calcium borate from first-principle calculations

Structural Chemistry - We investigatethe electronic and structural properties of two new amorphous materials, Bi6Ca2O28B12 and Bi6Ca2 O28B11:Tm, using density functional theory with a short-range...     

Umbelliferone Decorated Water-soluble Zinc(II) Phthalocyanines – In Vitro Phototoxic Antimicrobial Anti-cancer Agents

In this contribution we report on the synthesis, characterization and application of water-soluble zinc(II) phthalocyanines, which are decorated with four or eight umbelliferone moieties for photodynamic therapy (PDT). These compounds are linked peripherally to zinc(II) phthalocyanine by a triethylene glycol linker attached to pyridines, leading to cationic pyridinium units, able to increase the water solubility of the system. Beside their photophysical properties they were analyzed concerning their cellular distribution in human hepatocyte carcinoma (HepG2) cells as well as their phototoxicity towards HepG2 cells, Gram-positive (S. aureus strain 3150/12 and B. subtilis strain DB104) and Gram-negative bacteria (E. coli strain UTI89 and E. coli strain Nissle 1917). At low light doses and concentrations, they exhibit superb antimicrobial activity against Gram-positive bacteria as well as anti-tumor activity against HepG2. They are even capable to inactivate Gram-negative bacteria, whereas the dark toxicity remains low. These unique water-soluble compounds can be regarded as all-in-one type photosensitizers with broad applications ranges in the future.     

Lactose as a “Trojan Horse” for Quantum Dot Cell Transport

A series of glycan‐coated quantum dots were prepared to probe the effect of glycan presentation in intracellular localization in HeLa and SV40 epithelial cells. We show that glycan density mostly impacts on cell toxicity, whereas glycan type affects the cell uptake and intracellular localization. Moreover, we show that lactose can act as a “Trojan horse” on bi‐functionalized QDs to help intracellular delivery of other non‐internalizable glycan moieties and largely avoid the endosomal/lysosomal degradative pathway.