胆碱类低共熔溶剂的物性及应用

作为一种新型的离子液体,胆碱类低共熔溶剂具有相比于其他离子液体更为突出的特点,如低毒、生物可降解、价格低廉等,这些特点使得此类离子液体在绿色化学和工程化学中受到越来越多的关注。本文分析了胆碱类低共熔溶剂的凝固点、熔点、溶解度、黏度、表面张力、电导率等物性随温度、组成、水分等因素的变化及理论预测模型,并介绍了胆碱类低共熔溶剂在润滑、功能材料制备、电化学、有机合成及生物质催化转化等方面的潜在应用。最后就胆碱类低共熔溶剂研究及应用中存在的问题及难点对其前景做出展望。     

Amperometric nonenzymatic determination of glucose based on a glassy carbon electrode modified with nickel(II) oxides and graphene

We have developed a stable and sensitive nonenzymatic glucose sensor by modifying a glassy carbon electrode (GCE) with a composite incorporating nickel(II) oxides and reduced graphene. The oxides were generated by directly electrodepositing nickel on the GCE with a graphene modifier using a multi-potential pulse process, and then oxidizing nickel to nickel(II) oxides by potential cycling. In comparison to the conventional nickel(II) oxides-modified GCE, this new nickel(II) oxides-graphene modified GCE (NiO-GR/GCE) has an about 1.5 times larger current response toward the nonenzymatic oxidation of glucose in alkaline media. The response to glucose is linear in the 20 μM to 4.5 mM concentration range. The limit of detection is 5 μM (at a S/N of 3), and the response time is very short (<3 s). Other beneficial features include selectivity, reproducibility and stability. A comparison was performed on the determination of glucose in commercial red wines by high-performance liquid chromatography (HPLC) and revealed the promising aspects of this sensor with respect to the determination of glucose in real samples.

Supramolecular organogelators based on Janus type AT nucleosides

J-AT nucleoside-based organogelators 1a and 1b were designed and synthesized. They were endowed with unparalleled superiority to natural nucleobase analogues 2–6 to gelate aromatic solvents due to their excellent self-assembly properties. The J-AT nucleoside-based organogelators showed a specific self-complementary base pair recognition characteristic. The gel stabilities of 1a and 1b were drastically influenced by adenine analogue 2, hardly affected by thymine analogue 3, uracil analogue 4, cytosine analogue 5, and mildly interrupted by guanine analogue 6.     

Message passing interface and multithreading hybrid for parallel molecular docking of large databases on petascale high performance computing machines

A mixed parallel scheme that combines message passing interface (MPI) and multithreading was implemented in the AutoDock Vina molecular docking program. The resulting program, named VinaLC, was tested on the petascale high performance computing (HPC) machines at Lawrence Livermore National Laboratory. To exploit the typical cluster‐type supercomputers, thousands of docking calculations were dispatched by the master process to run simultaneously on thousands of slave processes, where each docking calculation takes one slave process on one node, and within the node each docking calculation runs via multithreading on multiple CPU cores and shared memory. Input and output of the program and the data handling within the program were carefully designed to deal with large databases and ultimately achieve HPC on a large number of CPU cores. Parallel performance analysis of the VinaLC program shows that the code scales up to more than 15K CPUs with a very low overhead cost of 3.94%. One million flexible compound docking calculations took only 1.4 h to finish on about 15K CPUs. The docking accuracy of VinaLC has been validated against the DUD data set by the re‐docking of X‐ray ligands and an enrichment study, 64.4% of the top scoring poses have RMSD values under 2.0 Å. The program has been demonstrated to have good enrichment performance on 70% of the targets in the DUD data set. An analysis of the enrichment factors calculated at various percentages of the screening database indicates VinaLC has very good early recovery of actives. © 2013 Wiley Periodicals, Inc.     

Plutonium-239 sorption and transport on/in unsaturated sediments: comparison of batch and column experiments for determining sorption coefficients

Sorption (distribution) coefficients of plutonium were most often derived by static batch experiments. However, it is not clear how unsaturated flow conditions including moisture content and pore water velocity change the sorption coefficients. Transport experiments of plutonium through the unsaturated sediments packed into the columns were then performed in order to determine the sorption coefficients (column-K _ds). Static batch experiments were also conducted to obtain batch-K _ds and then compare the differences between batch-K _ds and column-K _ds. The results show that unsaturated flow conditions had no significant effect on column-K _ds, and the average column-K _d value was 1.74 ± 0.02 m³/kg. By comparison, batch-K _d values spanned several orders of magnitude, regardless of the specified liquid–solid conditions. Moreover, the batch-K _d (22.7 m³/kg) at the standard L/S (4 mL/g) recommended by ASTM D 4319 was over an order of magnitude larger than the average column-K _d.     

Highly Stereoselective Conjugate Addition and α‐Alkynylation Reaction with Electron‐Deficient Alkynes Catalyzed by Chiral Scandium(III) Complexes

The highly Z‐selective asymmetric conjugate addition of 3‐substituted oxindoles to alkynyl carbonyl compounds has been developed by using scandium complexes of chiral N,N′‐dioxides under mild conditions. The thermodynamically unstable Z‐olefin derivatives were obtained in excellent yields and high enantiomeric and geometric control. The catalyst was also found to be effective in the asymmetric acetylenic substitution reaction of 3‐substituted oxindoles, giving excellent enantioselectivities.     

Substituent Effects on Oxidation‐Induced Formation of Quinone Methides from Arylboronic Ester Precursors

A series of arylboronic esters containing different aromatic substituents and various benzylic leaving groups (Br or N⁺Me₃Br^?) have been synthesized. The substituent effects on their reactivity with H₂O₂ and formation of quinone methide (QM) have been investigated. NMR spectroscopy and ethyl vinyl ether (EVE) trapping experiments were used to determine the reaction mechanism and QM formation, respectively. QMs were not generated during oxidative cleavage of the boronic esters but by subsequent transformation of the phenol products under physiological conditions. The oxidative deboronation is facilitated by electron‐withdrawing substituents, such as aromatic F, NO₂, or benzylic N⁺Me₃Br^?, whereas electron‐donating substituents or a better leaving group favor QM generation. Compounds containing an aromatic CH₃ or OMe group, or a good leaving group (Br), efficiently generate QMs under physiological conditions. Finally, a quantitative relationship between the structure and activity has been established for the arylboronic esters by using a Hammett plot. The reactivity of the arylboronic acids/esters and the inhibition or facilitation of QM formation can now be predictably adjusted. This adjustment is important as some applications may benefit and others may be limited by QM generation.     

广义sine-Gordon方程高精度隐式紧致差分方法

本文研究一类二维非线性的广义sine-Gordon(简称SG)方程的有限差分格式.首先构造三层时间的紧致交替方向隐式差分格式,并用能量分析法证明格式具有二阶时间精度和四阶空间精度.然后应用改进的Richardson外推算法将时间精度提高到四阶.最后,数值算例证实改进后的算法在空间和时间上均达到四阶精度.     

An integrated plastic microchip for enhancing electrophoretic separation using tunable pressure-driven backflows

Microfluidic CE (MCE) is an effective solution for rapid and sensitive determination of multiple analytes. Herein, a dynamic coated cyclic olefin copolymer microchip was developed having an on-chip micropump for fluid velocity adjusting in electrophoretic separations. This micropump was fabricated by constructing a polyacrylamide gel membrane at one channel terminal. Once applying electric field across the membrane, a pressure-driven flow generated automatically to balance the electroosmotic flow (EOF) mismatch at the channel-membrane interface. The influence of gel precursor concentration and operating voltages on the fluid velocity was carefully evaluated. Moreover, the highly integration of injection, separation, and pumping units of the MCE system minimized the dead volume and provides satisfied column efficiency. Experiments showed that by adjusting of pumping voltage reduced the fluid velocity by a factor of 6, resulting six- and threefold resolving power enhancements of rhodamine dye mixture and amino acid mixture, respectively. Furthermore, the developed MCE method was applied for rhodamines and amino acids quantitation in food and cosmetics, with standard addition recoveries of 87.3–106.9% and 89.9–117.4%, respectively. These results were also confirmed by standard HPLC method, revealing the application potential in fast and onsite analysis of complex samples.     

石榴状凝胶微球固定化漆酶的制备、 表征及降解双酚A

采用铜/锌复合金属磷酸盐晶体和海藻酸钙凝胶双重包覆技术对漆酶进行固定化, 制得石榴状Alg@Cu₃/Zn₃(PO₄)₂@Lac的凝胶微球. SEM, EDX和FTIR表征结果表明, 在凝胶微球内部, 漆酶被成功固定于由海藻酸钙凝胶包覆的铜/锌复合金属磷酸盐晶体内, 铜/锌复合金属磷酸盐晶体镶嵌于海藻酸钙凝胶网格的孔隙中而呈石榴状. 以2,2′-联氮双(3-乙基苯并噻唑啉-6-磺酸)(ABTS)为底物, 经酶学性质研究表明, 在无机盐晶体和海藻酸钙凝胶的双重保护下, Alg@Cu₃/Zn₃(PO₄)₂@Lac的耐热性、 耐酸性以及储存稳定性比游离漆酶均有不同程度增强. 将Alg@Cu₃/Zn₃(PO₄)₂@Lac应用于双酚A(BPA)的降解, 采用孔径约1 mm滤网实现快速回收, 经6次循环利用, 对BPA的降解率下降约14%, 显示出比较稳定的重复利用性和便捷的可操作性, 这主要得益于海藻酸钙和铜/锌无机盐晶体对漆酶蛋白分子的双重保护.