通过不对称氢转移/动态动力学拆分合成碳环N^3-嘌呤核苷

N^3-嘌呤核苷由于可能同时被嘌呤和嘧啶代谢酶识别,因而有望作为双靶点药物应用于抗病毒治疗.报道了一种以α-(N^3-嘌呤)取代的环烷酮为原料,通过不对称氢转移反应实现动态动力学拆分,高收率高立体选择性地合成系列碳环N^3-嘌呤核苷化合物.该催化体系也适用于α-嘧啶取代的环烷酮底物,且产物通过进一步衍生,合成了2’-F-,Ac S-,N^3-修饰的碳环嘧啶核苷.     

Numerical and empirical modeling of peak deceleration and stress analysis of polyurethane elastomer under impact loading test

In this work, we present the modeling of the peak deceleration (PD) using data of the experimental drop test. Specimens with different thicknesses and areas tested in the drop test device which has adaptable height and weight. In the empirical modeling of the PD, the thickness, area, drop mass and drop height considered as separable functions. An analytical model and Neural Network (NN) was used as the empirical models. Further, the stress on the material was calculated using differential equations and the Finite Element Method (FEM). The Obtained PD from the experimental test, analytical and NN models was converted to the stress on the material using a derived differential equation. Finally, the best model for analyzing the PD and Stress on the material was presented.     

Network pharmacology-based screening of the active ingredients and potential targets of the genus of Pithecellobium marthae (Britton & Killip) Niezgoda & Nevl for application to Alzheimer’s disease

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder associated with synaptic dysfunction, pathological accumulation of β-amyloid (Aβ), and neuronal loss. Given the prevalence of AD and the lack of effective long-term therapies, there is a pressing need to discover viable leads that can be developed into clinically approved drugs with disease-modifying effects. The analysis of current reported literatures confirms the importance of the plants of Pithecellobium genus as candidate against AD. Hence, it is necessary to identify selective anti-dementia agents from this genus. To explore potential compounds with marked effect on AD in Pithecellobium genus, a compound database based on the methods of network pharmacology prediction was established in this paper by constructing the compound-disease target network. The result showed that the most effective compound in the plants of this genus might be (7′R,8′R)-7′-methoxyl strebluslignanol, and the most potential target might be Macrophage colony-stimulating factor 1 receptor.     

A global potential energy surface and time‐dependent quantum wave packet calculation of Au + H2 reaction

A global potential energy surface (PES) corresponding to the ground state of AuH₂ system has been constructed based on 22 853 ab initio energies calculated by the multireference configuration interaction method with a Davidson correction. The neural network method is used to fit the PES, and the root mean square error is only 1.87 meV. The topographical features of the novel global PES are compared with previous PES which is constructed by Zanchet et al. (Zanchet PES). The global minimum energy reaction paths on the two PESs both have a well and a barrier. Relative to the Au + H₂ reactants, the energy of well is 0.316 eV on the new PES, which is 0.421 eV deeper than Zanchet PES. The calculation of Au(²S) + H₂(X¹Σ_g⁺) → AuH(X¹Σ⁺) + H(²S) dynamical reaction is carried out on new PES, by the time‐dependent quantum wave packet method (TDWP) with second order split operator. The reaction probabilities, integral cross‐sections (ICSs) and differential cross‐sections are obtained from the dynamics calculation. The threshold in the reaction is about 1.46 eV, which is 0.07 eV smaller than Zanchet PES due to the different endothermic energies on the two PESs. At low collision energy (<2.3 eV), the total ICS is larger than the result obtained on Zanchet PES, which can be attributed to the difference of the wells and endothermic energies.     

Swelling behavior and mechanical properties of endlinked poly (dimethylsiloxane) networks and randomly crosslinked polyisoprene networks

Measurements of the equilibrium degree of swelling and of the equilibrium modulus were performed on poly(dimethylsiloxane) networks (PDMS) and on polyisoprene vulcanizates. The results support the concept that topological interactions between network chains, e.g. entanglements or the like, have a large influence on the rubber elastic behavior, at least within a certain range of network densities.PDMS networks having network chains of different lengths and varying functionlities of the crosslinks were prepared in bulk by endlinking fractionated ,-divinyl PDMS via multifunctional hydrogen-siloxanes (f=3 to 22). Natural rubber (NR) and synthetic liquid polyisoprene (IR) were cured in bulk with various amounts of dicumyl peroxide to give randomly crosslinked samples.The experimentally determined moduli and degrees of swelling were compared with theoretical predictions based on the phantom network theory and affine network theory, taking into account only chemical crosslinks. The observed discrepancies can be traced back to a contribution of topological interactions (trapped entanglements) to the total effective network density. The modulus and swelling data are consistent, thus ruling out non-equilibrium effects.     

The Investigation of Interaction Competition Between ATP and DIPP-Ala,Boc-Ala,or Ala by ESI-MS/MS and Theoretical Calculation

The interactions between ATP and N-(O,O-diisopropyl) phosphoryl-L-alanine (DIPP-Ala), N-(tert-butoxycarbonyl)-L-alanine (Boc-Ala), or L-alanine (Ala) were investigated by electrospray ionization tandem mass spectrometry (ESI-MS/MS). The non-covalent complexes between ATP and Boc-Ala or DIPP-Ala were observed, while the complex between ATP and Ala was not found in the mass spectra. The affinity of DIPP-Ala for ATP was confirmed to be stronger than that of Boc-Ala by competition experiment. Through molecular modeling calculations, it was found that the non-covalent complexes were stabilized by intermolecular hydrogen bonds, and the affinity sequence for ATP was DIPP-Ala > Boc-Ala > Ala by comparing their binding energy, ?35.407 kcal/mol, ?15.634 kcal/mol, ?6.555 kcal/mol, respectively. The results implied that a phosphoryl group was a very important functional group to provide an interaction site between amino acids and ATP, and that N-phosphoryl amino acids can be used as a good model of protein in the studies of molecular recognition of ATP.     

Automatic Electronic Tongue for On-Line Detection and Quantification of Organophosphorus and Carbamate Pesticides Using Enzymatic Screen Printed Biosensors

This work presents an automatic system, based on an electronic tongue, for resolution of mixtures of three pesticides. Inhibition detections were performed during the steady state of biosensors response. Three biosensors were built using two enzymes, electric eel (EE), genetically-modified Drosophila melanogaster (B131), and electric eel co-immobilized with drosophila melanogaster (BH). Calibrations curves for paraoxon, dichorlvos, and carbofuran were performed in the ranges 0.4–50.4 µM, 0.01–1.01 µM, 0.01–0.41 µM with LOD of 3.91 × 10^?8, 6.30 × 10^?11, and 5.84 × 10^?10, respectively. An artificial neural network (ANN) was used to model the combined response of three pesticides. A set of 19 mixtures were prepared in order to train the artificial neural network, the modeling was validated with a set of 6 spiked samples of river water. The error and recovery yields were found in consistent with expected values.     

BP网络光度法测定去痛片中的四组分

应用Levenberg-Marquardt优化算法的BP网络,采用紫外分光光度法测定去痛片中四组分的含量。测定低含量组分咖啡因和苯巴比妥时,结合吸光度减法技术。氨基比林、非那西丁、咖啡因和苯巴比妥的平均回收率和RSD分别为99.3%,1.2%：;100.0%,1.1%;100.3%,1.5%;100.1%,1.3%。     

生物质与煤混燃机理:固态沉积特性

为了解在1 200 ℃不同反应时间条件下宜阳煤与水稻秸秆混燃的沉积性质,以18 kW的沉降炉为实验平台,利用扫描电镜及能谱,X射线衍射和电子探针方法对混燃的沉积物进行研究。研究表明,不同的混合比例或者不同反应时间条件下,沉积物中的Si、Al和Ca元素变化不大;表面的钾长石的黏性使沉积物更容易富集,而沉积物内部钾长石使沉积物的结构更加稳定;铝硅酸盐和Fe元素在沉积过程中都起了重要的作用。     

Multiresidue determination of pesticides from aquatic media using polyaniline nanowires network as highly efficient sorbent for microextraction in packed syringe

A simple, rapid and sensitive method based on microextraction in packed syringe (MEPS), in combination with gas chromatography–mass spectrometry (GC–MS) was developed. Polyaniline (PANI) nanowires network was synthesized and used as sorbent of MEPS for the multiresidue determination of selected analytes from triazine, organochlrorine and organophosphorous pesticides in aqueous samples. The PANI nanowires network was prepared using soft template technique and its characterization was studied by scanning electron microscopy (SEM). The presence of micelles in this methodology showed to be an important parameter in shaping the growing polymer. Hexadecyltrimethylammonium bromide (HTAB) was used as structure directing agent in PANI preparation procedure and this was led to the formation of nanowires with diameters ranging from 35 nm to 45 nm. The synthesized PANI nanowires network showed higher extraction capability in comparison with the bulk PANI. Important parameters influencing the extraction and desorption processes including desorption solvent, elution volume, draw–eject cycles of sample, draw–eject mode, pH effect and amount of sorbent were optimized. Limits of detection were in the range of 0.07–0.3 ng mL⁻¹ using time scheduled selected ion monitoring (SIM) mode. The linearity of method was in the range from 0.5–200 ng mL⁻¹ to 0.2–1000 ng mL⁻¹. The method precision (RSD %) with three replicates were in the range of 5.3–18.4% at the concentration level of 5 ng mL⁻¹. The developed method was successfully applied to the Zayandeh-rood river water samples and the matrix factor obtained for the spiked real water samples were in the range of 0.79–0.94.