Dielectric study on membrane adsorption and release: Relaxation mechanism and diffusion dynamics

Dielectric monitoring of the adsorption or release process of salicylic acid (SA) by chitosan membrane shows that the dielectric spectra of the chitosan membrane/ SA solution systems change regularly in the adsorption or release process. By analyzing the regularity, a new mechanism for the relaxations is proposed. The concentration polarization layer (CPL) caused by SA adsorption or release is confirmed to be essential for the dielectric relaxations. The changes of the spectra with time are explained by account of the relationship between CPL properties and dielectric strength. Based on this relaxation mechanism, a theoretical method can be established to calculate dynamical parameters of inner structure of the adsorption or release systems from their dielectric spectra. Therefore, dielectric spec- troscopy is demonstrated to be a promising method for estimating interfacial distribution of ionic sub- stances and their binding to membrane in a non-invasive way.     

Syntheses of (-)-oleocanthal, a natural NSAID found in extra virgin olive oil, the (-)-deacetoxy-oleuropein aglycone, and related analogues

Phenolic compounds extracted from extra virgin olive oil have attracted considerable recent attention. One of the components, (-)-oleocanthal (1), an inhibitor of the COX-1 and COX-2 enzymes, possesses similar potency as the NSAID ibuprofen. In this, a full account, we disclose the first- and now second-generation syntheses of both enantiomers of the oleocanthals, as well as the first synthesis of the closely related (-)-deacetoxy-oleuropein aglycone and a series of related analogues for structure activity studies. To demonstrate the utility of the second-generation synthesis, multigram quantities of (-)-oleocanthal were prepared in 10 steps (14% overall yield) from commercially available D-lyxose.     

Palladium nanocrystals bound by {110} or {100} facets: from one pot synthesis to electrochemistry

A facile one-pot tactic is developed for the selective synthesis of either rhombic dodecahedral or cubic Pd nanocrystals with high yields. By applying a mild cleaning process, we establish for the first time reasonable and distinct electrochemical features corresponding to {110} or {100} facet predominated Pd nanocrystals.     

硫酸化氧化锆固体超强酸

硫酸化氧化锆(SZ)是一种固体超强酸催化剂,它能高效催化异构化、烷化、酰化、环化、裂解、酯化和酯交换等多种类型的催化反应。1979年,日本科学家Hino和Arata发现SZ能在室温催化丁烷异构化反应,首次提出了SZ是一种酸性比100%浓硫酸还强一万倍的固体超强酸,从而引起了科学家们对SZ研究的浓厚兴趣。经过了三十多年发展,研究者们在SZ的合成、改性、表征和应用等方面取得了许多新的研究成果。本文综述了SZ几十年来的研究进展,内容主要包括SZ的合成方法,表面结构和酸性机理,研究者们对SZ性质的不同看法,SZ的改性及应用。     

Enantioselective concomitant creation of vicinal quaternary stereogenic centers via cyclization of alkynols triggered addition of azlactones

An asymmetric cyclization of alkynols triggered addition of azlactones catalyzed by a combined catalyst system consisting of a chiral gold phosphate and a phosphoric acid produces conformationally restricted amino acid precursors bearing vicinal quaternary stereogenic centers in high levels of stereoselectivity.     

ICP-MS法测定欧盟玩具新指令限制的17种可迁移元素

根据欧盟玩具安全新指令( 2009/48/EC)的要求,应用电感耦合等离子体质谱(ICP-MS)法测定玩具材料中硼、铝、铬、锰、钴、镍、铜、锌、砷、硒、锶、镉、锡、锑、钡、汞、铅17种可迁移元素含量,使用碰撞反应池技术消除某些多原子离子干扰.方法检出限为0.5～75μg/kg,加标回收率在85.4％～109％之间,相对...     

Comprehensive characterization of the N-glycosylation status of CD44s by use of multiple mass spectrometry-based techniques

The CD44 family are type-1 transmembrane glycoproteins which are important in mediating the response of cells to their microenvironment, including regulation of growth, survival, differentiation, and motility. All these important functions have been reported to be regulated by N-glycosylation; however, little is known about this process. In the CD44 family, the most prolific isoform is CD44 standard type (CD44s). In this work, an integrated strategy combining stable isotope labeling, chemical derivatization, hydrophilic-interaction liquid chromatographic (HILIC) separation, and mass spectrometric (MS) identification was used to perform a comprehensive qualitative and quantitative survey of the N-glycosylation of recombinant CD44s. Specifically, the occupation ratios of the N-glycosites were first determined by MS with (18)O labeling; the results revealed five glycosites with different occupation ratios. Next, N-glycans were profiled by chemical derivatization and exoglycosidase digestion, followed by MALDI-TOF-MS and HILIC-ESI-MS-MS analysis. Interestingly, the quantitative analysis showed that non-sialylated, fucosylated complex-type glycans dominated the N-glycans of CD44s. Furthermore, the site-specific N-glycan distributions profiled by LC-ESI-MS(E) indicated that most glycosites bore complex-type glycans, except for glycosite N100, which was occupied by high-mannose-type N-glycans. This is the first comprehensive report of the N-glycosylation of CD44s. Figure Strategies for characterization of the N-glycosylation status of CD44s.     

Synthesis and characterization of high molecular weight poly(1,2-propylene carbonate-<Emphasis Type="Italic">co</Emphasis>-1,2-cyclohexylene carbonate) using zinc complex catalyst

Using supported multi-component zinc dicarboxylate catalyst,poly（1,2-propylene carbonate-co-1,2-cyclohexylene carbonate）（PPCHC） was successfully synthesized from carbon dioxide（CO₂） with propylene oxide（PO） and cyclohexene oxide（CHO）.The conversion of epoxides dramatically increased up to 89.7%（yield:384.2 g of polymer per g of Zn） with increasing reaction temperature from 60℃to 80℃.The optimized reaction temperature is 80℃.The chemical structure,the molecular weight,as well as thermal and mechanical properties of the resulting terpolymers were investigated extensively. When CHO feed content（mol%） is lower than 10%,the PPCHC terpolymers have number average molecular weight（M_n） ranging from 102×10³ to 202×10³ and molecular weight distribution（MWD） values ranging from 2.8 to 3.5.In contrast to poly（propylene carbonate）（PPC）,the introduction of small amount of CHO leads to increase in the glass transition temperature from 38.0℃to 42.6℃.Similarly,the mechanical strength of the synthesized terpolymer is greatly enhanced due to the incorporation of CHO.These improvements in mechanical and thermal properties are of importance for the practical application of PPC.     

NASICON-based H2 Sensor Using CoCrMnO4 Insensitive Reference Electrode and Buried Au Sensing Electrode

This work focuses on the H2 sensing performance of the sensor with buried Au sensing electrode and spi- nel-type oxide CoCrMnO4 insensitive reference electrode within sodium super ionic conductor（NASICON） film. The sensor showed the highest response to H2 gas on the insensitive material sintering at 800 ~C. Compared with those of the traditional structure device, the sensitivity and selectivity of the sensor using buried sensing electrode were greatly improved, giving a response of-177 mV in 9x10 5 g/L H2, which was about 3.5 times higher than that of sensors with traditional structure. Moreover, the AV value of the sensing device exhibited linear relationship to the logarithm of H2 concentration and the sensitivity（slope） was -135 mV/decade. A sensing mechanism related to the mixed potential was proposed for the present sensor.