Copper-catalyzed radical cascade reaction of isocyanate and ethers

A novel copper-catalyzed amination of ethers using isocyanates and DTBP is developed. The reaction provides a unique approach to the synthesis of Boc-protected α-aminals through three-component radical cascade reactions. It provides an alternative method for the construction of this type of valuable motifs in high yield. Meanwhile, the method exhibits high tolerance of various functional groups, such as ether, halide, ester and acyl functionalities.     

A cloud point extraction approach using Triton X-100 for the separation and preconcentration of Sudan dyes in chilli powder

A CPE-HPLC (UV) method was developed for the determination of Sudan (I-IV) dyes, non-ionic surfactant Triton X-100 was used to extract and preconcentrate Sudan dyes from chilli powder prior to their determination by HPLC-UV. The separation and determination of Sudan dyes was then carried out in the HPLC-UV system with isocratic elution, and the detector was set at 500 nm. The parameters and variables that affect the extraction were investigated. Under optimum conditions: 3% of Triton X-100 (W/V), 10% of Na₂CO₃ (W/V), heat-assisted at 70 °C for 30 min. Recoveries of the Sudan dyes ranged from 80.70% to 85.45% in chilli powder by CPE method, with all the relative standard deviations of less than 3%. Limit of detection (LOD) and limit of quantification (LOQ) were in the range of 2.0-4.0 and 7.0-12.0 μg kg⁻¹ in chilli powder, respectively.     

(Z,Е)-1[1-(2,4-二氧吡咯烷-3-亚基)乙基]-4-烃基氨基脲类衍生物的合成与除草活性

以取代胺为原料合成6种N4-取代氨基脲,然后与5种3-(1-羟基亚乙基)-吡咯烷-2,4二酮类化合物反应合成了22种新型缩氨基脲类衍生物,即(Z,Е)-1[1-(2,4二氧吡咯烷-3-亚基)乙基]-4-烃基氨基脲,其结构经1H NMR,MS,IR和元素分析确证.初步生物活性测定表明,这类化合物对油菜根和稗草茎的生长具有抑制作用.     

New insights into the ultrasound impact on covalent reactions of myofibrillar protein

In this work, two different covalent reactions, namely, alkaline reaction and free radical oxidation, were selected to compare the difference in the strengthening effects of ultrasound treatment (UDT). The grafting effects were verified by protein electrophoresis and bound gallic acid (GA) assay. Furthermore, non-covalent interactions between myofibrillar protein (MPN) aggregates were destroyed by UDT, as proved by the lower particle sizes and higher ζ-potential. Comparatively, the results from tertiary structure index and circular dichroism revealed UDT-assisted free radical oxidation could lead to better conjugates with greater structural properties. The atomic force microscope (AFME) and protein flexibility showed that MPNs appeared to display as irregular spherical particles after alkaline reaction, however, maintained fibrous structure during the free radical oxidation. Consequently, the combination of UDT and free radical oxidation were more effectively for strengthening the influence of acoustic cavitation on MPNs, of which mechanism was the changes in viscosity properties, microstructure and acoustic cavitation radicals.     

How does the β-ionone effect the spectra of chlorophyll and the excitation energy transfer in solution

This paper presents the excitation spectra and fluorescence spectra of mixed solution containing chlorophyll a(Chla), chlorophyll b(Chlb) and β-ionone of different concentration, investigates the spectral changes of Chla and Chlb caused by β-ionone through optimizing the frontier orbital of Chl-β-ionone compound, and calculates the energy transfer rate between Chla and Chlb by means of the fluorescence Gauss decomposition. The results show that the β-ionone interacts with Chl mainly via the connection between the magnesium atom in Chl molecule and the carbonyl in β-ionone molecule. The formation of Chl-β-ionone compound changes the charge distribution of Chl so greatly that it leads to the red-shift of the excitation spectra and blue-shift of the fluorescence spectra of Chls. Also in the compound the electronic energy located on carbon double bond of β-ionone can be transferred to Chl molecule by the Mg…O bond, which enhances the fluorescence intensity greatly. The calculation of the excitation energy transfer (EET) rate indicates that a small amount of β-ionone can promote the EET between Chla and Chlb.     

A unifying model for matrix-based pairing situations

We present a unifying framework for transferable utility coalitional games that are derived from a non-negative matrix in which every entry represents the value obtained by combining the corresponding row and column. We assume that every row and every column is associated with a player, and that every player is associated with at most one row and at most one column. The instances arising from this framework are called pairing games, and they encompass assignment games and permutation games as two polar cases. We show that the core of a pairing game is always non-empty by proving that the set of pairing games coincides with the set of permutation games. Then we exploit the wide range of situations comprised in our framework to investigate the relationship between pairing games that have different player sets, but are defined by the same underlying matrix. We show that the core and the set of extreme core allocations are immune to the merging of a row player with a column player. Moreover, the core is also immune to the reverse manipulation, i.e., to the splitting of a player into a row player and a column player. Other common solution concepts fail to be either merging-proof or splitting-proof in general.     

Enantioselective synthesis of enol lactones from tandem Michael addition/lactonization catalyzed by a chiral squaramide catalyst

The enantioselective tandem Michael addition reaction of dimedone and related 1,3-dicarbonyl compounds with α,β-unsaturated N-acylated succinimides catalyzed by a chiral squaramide catalyst has been investigated. This reaction provides a new approach for the synthesis of chiral enol lactones in good yields with moderate to high enantioselectivities (up to 88% ee) through the enantioselective Michael addition followed by lactonization and removal of the succinimide auxiliary.     

New flavonoid-<Emphasis Type="Italic">C</Emphasis>-glycosides from <Emphasis Type="Italic">Triticum aestivum</Emphasis>

Two new flavonoid-C-glycosides named triticuside A (1a) and triticuside B (1b) were isolated from bran of Triticum aestivum L. The structures of the two new compounds were elucidated by spectral techniques including ¹H NMR, ¹³C NMR as well as HSQC, HMBC, and COSY. Published in Khimiya Prirodnykh Soedinenii, No. 2, pp. 135–137, March–April, 2008.     

核酸适体识别荧光法检测汞离子

通过对已知的Ni2+适体的改造,发现了对Hg2+有较强结合活性的核酸适体N1,基于N1的二级结构进行改造,获得了具有较高活性的核酸适体N5,并建立了荧光检测方法。以荧光基团FAM标记核酸适体,在94℃变性5 min,室温(25℃)下复性30 min后,适配体与标记有荧光猝灭基团DABCYL的一段互补序列Q2结合(适体与Q2的浓度比为1∶3),加入系列浓度的Hg2+与互补序列竞争结合核酸适体,以荧光信号的变化定量分析Hg2+浓度。结果表明,N1与Hg2+结合呈线性,线性范围为1.25～20 mg/L;检出限为0.62 mg/L;以N1结构为基础改造合成的序列和结构均不同的适体N4,N5,N6,N7对Hg2+的识别结合活性均不同,其中适体N5与Hg2+结合活性最为灵敏,特异性高,线性范围为0.156～2.50 mg/L;检出限为78μg/L。     

泊松冲击下冷贮备可修系统的可靠性分析

本文研究了一类由有限个同质部件和一个修理工组成的冷贮备可修系统在随机冲击下的可靠性问题。假设冲击以泊松过程到达。当冲击到达时,它会独立地对系统中工作的部件产生影响,而不会对冷贮备部件产生影响。每次冲击的量都服从某一确定的分布,受冲击的部件以一定的概率发生故障,其故障概率是冲击量的函数,当工作的部件发生故障时,下一个冷贮备部件立即开始工作,当所有部件故障时,系统故障,故障部件按故障顺序进行修理,修理时间服从指数分布,故障部件能被修理如新。本文显式给出了系统首次故障前平均时间、稳态可用度、稳态故障频度等可靠性指标。