不对称双酸催化吲哚的Friedel-Crafts烷基化反应:抗衡阴离子调控对映选择性

研究了双酸催化剂对吲哚和β,γ-不饱和α-酮酸酯的不对称Friedel-Crafts烷基化反应.金属铟(III)盐和手性磷酸组成的双酸催化体系可以高效、高选择性地催化吲哚与β,γ-不饱和α-酮酸酯的Friedel-Crafts烷基化反应.简单改变铟(III)盐的抗衡阴离子从F-到Br-,就能使产物的构型发生反转,并同时获得相应的高产率(最高达98%)和高对映选择性(最高大于99%)的1,4-加成产物.     

ChemStable: a web server for rule-embedded naïve Bayesian learning approach to predict compound stability

Predicting compound chemical stability is important because unstable compounds can lead to either false positive or to false negative conclusions in bioassays. Experimental data (COMDECOM) measured from DMSO/H₂O solutions stored at 50 °C for 105 days were used to predicted stability by applying rule-embedded naïve Bayesian learning, based upon atom center fragment (ACF) features. To build the naïve Bayesian classifier, we derived ACF features from 9,746 compounds in the COMDECOM dataset. By recursively applying naïve Bayesian learning from the data set, each ACF is assigned with an expected stable probability (p _s ) and an unstable probability (p _uns ). 13,340 ACFs, together with their p _s and p _uns data, were stored in a knowledge base for use by the Bayesian classifier. For a given compound, its ACFs were derived from its structure connection table with the same protocol used to drive ACFs from the training data. Then, the Bayesian classifier assigned p _s and p _uns values to the compound ACFs by a structural pattern recognition algorithm, which was implemented in-house. Compound instability is calculated, with Bayes’ theorem, based upon the p _s and p _uns values of the compound ACFs. We were able to achieve performance with an AUC value of 84 % and a tenfold cross validation accuracy of 76.5 %. To reduce false negatives, a rule-based approach has been embedded in the classifier. The rule-based module allows the program to improve its predictivity by expanding its compound instability knowledge base, thus further reducing the possibility of false negatives. To our knowledge, this is the first in silico prediction service for the prediction of the stabilities of organic compounds.     

Studies on selective β/β′ bromination of π-extended porphyrins and subsequent coupling reactions

Monobromination of β, β′-π-extended porphyrins was found to selectively occur at the β or β′ position of the porphyrins which is antipodal to the fused aromatic ring. Subsequent Sonogashira or Heck coupling of the resultant bromoporphyrin introduced a carboxylphenylethynyl group or an acrylic acid group to the π-extended porphyrin. The optimal reaction conditions were found for the Sonogashira and Heck coupling reaction. All of the coupling products have shown a broadening and red-shift of the Soret band and Q bands in the UV–Vis absorption spectra compared with the π-extended porphyrin starting materials and the original unmodified porphyrins.     

Alumina nanofibers obtained via electrospinning of pseudo-boehmite sol/PVP solution

Alumina nanofibers were fabricated by calcination of the polyvinylpyrrolidone (PVP)/pseudo-boehmite nanocomposite precursor fibers formed by electrospinning PVP/ethanol solution of dispersed pseudo-boehmite nanoparticles with and without additive of silica. The evolution of the phase, mechanical property and morphological features of the calcined fibers were studied and the effect of adding SiO₂ on the phase transformation of alumina was discussed. Adding SiO₂ can retard the phase transformation of γ-Al₂O₃ to α-Al₂O₃ and therefore inhibit the growth of alumina grains during calcination. Upon calcining the precursor fibers with 4 wt% SiO₂ additive at 1,300 °C, continuous alumina nanofibers with diameter ranging from 300 to 800 nm were obtained. These continuous nanofibers exhibited good flexibility and could be very promising for applications in filtration and catalyst support.     

Fabrication and characterization of NiTiO3 nanofibers by sol–gel assisted electrospinning

Continuous NiTiO₃ nanofibers have been successfully synthesized by a sol–gel assisted electrospinning method followed by calcination at 600 °C in air. These nanofibers were characterized for the morphological, structural and optical properties by scanning electron microscopy (SEM), energy-dispersive X-ray spectrum (EDS), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectra (XPS) and UV–visible (UV–vis) diffuse reflectance spectroscopy (DRS). SEM results reveal that the obtained NiTiO₃ nanofibers are 175 nm in diameter and several micrometers in length after annealing at 600 °C. The XRD analysis shows that the nanofibers possess highly crystalline structure with no impurity phase. In contrast, the NiTiO₃ nanoparticles synthesized at the identical conditions by a sol–gel route have impurities including TiO₂ and NiO. Moreover, the electrospun NiTiO₃ nanofibers are endowed with an obvious optical absorbance in the visible range, demonstrating they have visible light photoresponse.     

液相色谱-串联质谱法同时测定蜂胶中的磺胺及林可胺类药物残留

建立了同时检测蜂胶中16种磺胺及2种林可胺类药物残留的方法,以1.0 mol/L HCl溶液为提取液,经阳离子固相萃取小柱净化富集后,高效液相色谱-串联质谱仪分析。采用Agilent Polaris C18色谱柱(100 mm×2.0 mm,5μm),以甲醇和0.1%甲酸为流动相梯度洗脱,质谱模式为电喷雾正离子监测。该方法前处理简单,分别以13C6-磺胺二甲基嘧啶、13C6-磺胺甲噁唑为磺胺类药物内标、以D3-林可霉素为林可胺类药物内标进行定量,磺胺和林可胺类药物的线性范围均为1.0~50μg/L,相关系数均在0.99以上,方法定量限为10.0μg/kg,在10,20和40μg/kg 3个水平做添加回收,回收率范围为69.5%~114.6%,相对标准偏差小于10%。     

长江下游下蜀黄土的稀土元素物源判别

通过对长江下游镇江、福家湾、新港、芜湖、福路镇等地区下蜀黄土中稀土元素的研究,结合长江古漫滩堆积物及北方黄土沉积物,对下蜀黄土进行了物源判别,得出：下蜀黄土与长江河漫滩之间的各稀土元素的 DF 值绝大部分小于0．2,表现出在各个稀土元素上与河漫滩的接近程度较大,而与北方黄土接近程度较小;由物源指数 PI 计算得出,新港、福路镇、镇江下蜀黄土 PI 值均在0．2附近,表现出下蜀黄土与河漫滩在稀土元素总体上的相似程度极高,物源判别为长江河漫滩;福家湾下蜀黄土物源判别为北方黄土,北方黄土对其有一定影响。总体上,长江下游下蜀黄土受到北方黄土与河漫滩的影响,其中以长江河漫滩影响为主。     

三(4-硝基苯基)甲烷衍生物的结构和振动光谱的理论研究（英文）

用密度泛函理论优化了三苯甲烷(1)和一系列三(4-硝基苯基)甲烷衍生物2,3和4的几何结构,并计算了其红外光谱和拉曼光谱;通过与实验光谱的对比,对实验光谱中的谱峰进行了指认,并从理论上纠正了部分对3和4红外光谱谱峰不合适的实验指认;同时预测了2,3和4的拉曼光谱.结果表明,几种化合物的振动光谱计算结果与相应的实验结果吻合良好;且化合物2,3和4的拉曼光谱具有相似性.     

Fabrication of Pascal-triangle Lattice of Proteins by Inducing Ligand Strategy

A protein Pascal triangle has been constructed as new type of supramolecular architecture by using the inducing ligand strategy that we previously developed for protein assemblies. Although mathematical studies on this famous geometry have a long history, no work on such Pascal triangles fabricated from native proteins has been reported so far due to their structural complexity. In this work, by carefully tuning the specific interactions between the native protein building block WGA and the inducing ligand R-SL , a 2D Pascal-triangle lattice with three types of triangular voids has been assembled. Moreover, a 3D crystal structure was obtained based on the 2D Pascal triangles. The distinctive carbohydrate binding sites of WGA and the intralayer as well as interlayer dimerization of RhB was the key to facilitate nanofabrication in solution. This strategy may be applied to prepare and explore various sophisticated assemblies based on native proteins.     

DNA Nanoribbon-Templated Self-Assembly of Ultrasmall Fluorescent Copper Nanoclusters with Enhanced Luminescence

Fluorescent copper nanoclusters (CuNCs) have been widely used in chemical sensors, biological imaging, and light-emitting devices. However, individual fluorescent CuNCs have limitations in their capabilities arising from poor photostability and weak emission intensities. As one kind of aggregation-induced emission luminogen (AIEgen), the formation of aggregates with high compactness and good order can efficiently improve the emission intensity, stability, and tunability of CuNCs. Here, DNA nanoribbons, containing multiple specific binding sites, serve as a template for in situ synthesis and assembly of ultrasmall CuNCs (0.6 nm). These CuNC self-assemblies exhibit enhanced luminescence and excellent fluorescence stability because of tight and ordered arrangement through DNA nanoribbons templating. Furthermore, the stable and bright CuNC assemblies are demonstrated in the high-sensitivity detection and intracellular fluorescence imaging of biothiols.