CM⁃Phos配体在钯催化交叉偶联反应中的应用

本文综合评述了近年来2-[2-(二环己膦基)苯基]-1-甲基-1H-吲哚(CM-Phos)膦配体及其衍生物在钯催化的交叉偶联反应中的应用, 主要根据不同种类的交叉偶联反应进行系统性分述, 并对该领域的发展前景进行了展望.     

一种蓝光发射星型有机分子的合成及光电性质

采用分子设计的思想,通过多步反应合成了一种新型的以N原子为中心的蓝光发射星型有机小分子。用1H NMR,MS和元素分析进行了表征,研究了化合物的热稳定性和真空镀膜膜层的光致发光性质,用循环伏安法测定了其电化学性能。结果表明,这种合成的有机化合物光致发光性能优良(量子效率达到87%),热稳定性好,可作为制作有机电致发光器件的候选材料。     

“绿色”液体激光介质的非线性光学特性研究

 利用氧化钕和盐酸为原料制得Nd(phen)2Cl3(三氯二邻菲罗啉合钕),测得其光谱特性并以稀土氧化钕、苯甲酸和邻菲罗啉为原料制得绿色液体激光介质钕离子的配合物——NdB3phen（三苯甲酸—邻菲罗啉合钕）.利用飞秒激光器,采用单光束Z-扫描法研究了NdB3phen的三阶非线性光学特性.结果表明:当入射飞秒激光脉冲波长为400 nm,峰值功率密度为2.94×1014 W/m2,脉宽为117 fs时,测得样品NdB3phen的非线性折射率为－2.84×10－18 cm2/W|NdB3phen在开孔条件下呈现反饱和吸收现象,测出双光子吸收系数的值为9.11×10－12 m/W.实验结果表明,NdB3phen的双光子吸收系数和非线性折射率随着光强的增强而增大.     

Generalised twists, , and the p-energy over a space of measure preserving maps

Let be a bounded Lipschitz domain and consider the energy functional

with p]1,∞[ over the space of measure preserving maps

In this paper we introduce a class of maps referred to as generalised twists and examine them in connection with the Euler–Lagrange equations associated with over . The main result is a surprising discrepancy between even and odd dimensions. Here we show that in even dimensions the latter system of equations admit infinitely many smooth solutions, modulo isometries, amongst such maps. In odd dimensions this number reduces to one. The result relies on a careful analysis of the full versus the restricted Euler–Lagrange equations where a key ingredient is a necessary and sufficient condition for an associated vector field to be a gradient.     

Using FTIR spectroscopy to detect sericin on historic silk

Silks represent some of the most precious ancient and historic textile artefacts in collections worldwide.Their optimum preservation demands an appreciation of their characteristics.One important concern,especially with regard to ancient Chinese silks,is whether the fabrics have been degummed.Silks with remnant sericin gum coating the fibroin fibres would require different conservation protocol.In previous research on aged silks,the presence of sericin has been inferred from amino acid analysis of hydrolysa...     

The invariants of the non-degenerate representations of the group of the pseudo-orthogonal matrices SO (p, 1)

The invariants of the non-degenerate representations of the group of pseudo-orthogonal matrices SO(p, 1) are constructed.     

一种新型高速电影经纬仪

112高速电影经纬仪是一种新型的高速光电跟踪测量设备,可用于快速飞行目标的轨迹测量和姿态记录,单台完成定位,并有实时输出的功能。该设备与传统的电影经纬仪相比,具有明显的特点,它采用双反射镜跟踪的结构方式,减少了运动部分的惯量,并提高同步数据采集处理速率到200次/秒和高速同步摄影频率到200f/s,有利于高速跟踪测量。该设备采用电视跟踪、计算机程序控制、单杆操纵等多种跟踪方式,可根据不同的目标特性方便地选用或组合使用,可靠地完成对目标的自动捕获和跟踪测量,最大跟踪速度为90°/秒,最大跟踪加速度为90°/秒²。本文还介绍了该设备在靶场使用情况。     

Comparison of multiple gene assembly methods for metabolic engineering

A universal, rapid DNA assembly method for efficient multigene plasmid construction is important for biological research and for optimizing gene expression in industrial microbes. Three different approaches to achieve this goal were evaluated. These included creating long complementary extensions using a uracil-DNA glycosylase technique, overlap extension polymerase chain reaction, and a SfiI-based ligation method. SfiI ligation was the only successful approach for assembling large DNA fragments that contained repeated homologous regions. In addition, the SfiI method has been improved over a similar, previous published technique so that it is more flexible and does not require polymerase chain reaction to incorporate adaptors. In the present study, Saccharomyces cerevisiae genes TAL1, TKL1, and PYK1 under control of the 6-phosphogluconate dehydrogenase promoter were successfully ligated together using multiple unique SfiI restriction sites. The desired construct was obtained 65% of the time during vector construction using four-piece ligations. The SfiI method consists of three steps: first a SfiI linker vector is constructed, whose multiple cloning site is flanked by two three-base linkers matching the neighboring SfiI linkers on SfiI digestion; second, the linkers are attached to the desired genes by cloning them into SfiI linker vectors; third, the genes flanked by the three-base linkers, are released by SfiI digestion. In the final step, genes of interest are joined together in a simple one-step ligation.     

The diverse roles of flavin coenzymes--nature's most versatile thespians

Flavin coenzymes play a variety of roles in biological systems. This Perspective highlights the chemical versatility of flavins by reviewing research on five flavoenzymes that have been studied in our laboratory. Each of the enzymes discussed in this review [the acyl-CoA dehydrogenases (ACDs), CDP-6-deoxy-l-threo-d-glycero-4-hexulose-3-dehydrase reductase (E3), CDP-4-aceto-3,6-dideoxygalactose synthase (YerE), UDP-galactopyranose mutase (UGM), and type II isopentenyl diphosphate:dimethylallyl diphosphate isomerase (IDI-2)] utilizes flavin in a distinct role. In particular, the catalytic mechanisms of two of these enzymes, UGM and IDI-2, may involve novel flavin chemistry.     

Analysis of UDP-d-Apiose/UDP-d-Xylose Synthase-Catalyzed Conversion of UDP-d-Apiose Phosphonate to UDP-d-Xylose Phosphonate: Implications for a Retroaldol-Aldol Mechanism

UDP-d-apiose/UDP-d-xylose synthase (AXS) catalyzes the conversion of UDP-d-glucuronic acid to UDP-d-apiose and UDP-d-xylose. An acetyl-protected phosphonate analogue of UDP-d-apiose was synthesized and used in an in situ HPLC assay to demonstrate for the first time the ability of AXS to interconvert the two reaction products. Density functional theory calculations provided insight into the energetics of this process and the apparent inability of AXS to catalyze the conversion of UDP-d-xylose to UDP-d-apiose. The data suggest that this observation is unlikely to be due to an unfavorable equilibrium but rather results from substrate inhibition by the most stable chair conformation of UDP-d-xylose. The detection of xylose cyclic phosphonate as the turnover product reveals significant new details about the AXS-catalyzed reaction and supports the proposed retroaldol-aldol mechanism of catalysis.