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.     

铜催化芳硼酸与亚磷酸酯在空气下的有氧碳-磷氧化偶联反应

在Cu(OAc)2/TMEDA体系催化下,芳硼酸与亚磷酸二乙酯可在室温下以空气为直接氧化剂通过氧化偶联反应生成芳基膦酸酯化合物.该反应使用较为廉价低毒的铜盐为催化剂,不怕水、不怕氧,底物适用范围较广,目标产物选择性高、收率良好.因此,与已知金属催化卤代芳烃的碳-磷偶联反应相比是一种相对温和高效的合成芳基膦酸酯的方法.     

De Novo Design of an Endohedral Heteronuclear Dimetallofullerene (UGd)@C60 with Exceptional Structural and Electronic Properties

Ever since the first synthesis of La@C₈₂ and U@C₂₈, there has been a growing interest in the study of endohedral metallofullerenes (EMFs) because of their great potential in various applications. Here we design a novel heteronuclear EMF (U‐Gd)@C₆₀, by using density functional theory (DFT), which shows an encapsulation energy of about ?5.53 eV, comparable to that of U₂@C_60, La₂@C₈₀, and Lu₂@C₇₆. (U‐Gd)@C₆₀ is found to have a surprising twofold, single‐electron U?Gd bond that results from the strong nanoconfinement of the fullerene, dominated by uranium′s 5f and 6d and gadolinium′s 5d atomic orbitals. The ground state shows an 11‐et high spin state, and the net spins distributed on the U‐pole carbons are relatively scattered, while they are highly concentrated on the Gd‐pole carbons. The exceptional electronic characteristics of this novel EMF, containing both uranium and gadolinium atoms encapsulated, might prove useful for future applications in nuclear energy and biomedicine.     

Determination of the n‐octanol/water partition coefficients of weakly ionizable basic compounds by reversed‐phase high‐performance liquid chromatography with neutral model compounds

A strategy to utilize neutral model compounds for lipophilicity measurement of ionizable basic compounds by reversed‐phase high‐performance liquid chromatography is proposed in this paper. The applicability of the novel protocol was justified by theoretical derivation. Meanwhile, the linear relationships between logarithm of apparent n‐octanol/water partition coefficients (logK_ow′′) and logarithm of retention factors corresponding to the 100% aqueous fraction of mobile phase (logk_w) were established for a basic training set, a neutral training set and a mixed training set of these two. As proved in theory, the good linearity and external validation results indicated that the logK_ow′′–logk_w relationships obtained from a neutral model training set were always reliable regardless of mobile phase pH. Afterwards, the above relationships were adopted to determine the logK_ow of harmaline, a weakly dissociable alkaloid. As far as we know, this is the first report on experimental logK_ow data for harmaline (logK_ow = 2.28 ± 0.08). Introducing neutral compounds into a basic model training set or using neutral model compounds alone is recommended to measure the lipophilicity of weakly ionizable basic compounds especially those with high hydrophobicity for the advantages of more suitable model compound choices and convenient mobile phase pH control.     

Highly Sensitive Fluorometric Assay Method for Acetylcholinesterase Inhibitor Based on Nile Red‐Adsorbed Gold Nanoparticles

A new sensitive fluorometric assay method for acetylcholinesterase (AChE) and its inhibitor was developed using a fluorescent dye, nile red (NR). Due to the fluorescence resonance energy transfer between the NR and the gold nanoparticle (AuNPs), the fluorescence was quenched. AChE can break down acetylthiocholine to produce a thiol‐bearing compound, thiocholine. In the presence of thiocholine, the nile red is replaced from the AuNPs surfaces and simultaneously transformed to a derivative of nile red. The fluorescence intensity of the derivative is much stronger than that of the native nile red with the same concentration and its maximum emission wavelength has a blue shift so that the sensor achieves a good signal‐to‐background ratio. In addition, when organophosphate pesticide (OPs) exists, the activity of AChE can be inhibited, the generation of thiocholine will be prevented and no fluorescence enhancement occurs. The results show that the method is sensitive to AChE and paraoxon with the detection limits of 0.2 mU/mL and 0.05 ng/mL, respectively.