Six new monoterpenoid indole alkaloids from the aerial part of Gelsemium elegans

Six new monoterpenoid indole alkaloids along with four known analogues were isolated from the aerial part of Gelsemium elegans. Their structures with absolute configurations were elucidated by NMR, HRESIMS, X-ray diffraction, CD spectra, and molecular modeling calculation. Among them, gelselenidine (1) is a new gelsedine-type alkaloid with a 2,3-epoxybutane unit. Gelseziridine (2) is the first example of monoterpenoid indole alkaloids with an oxaziridine residue. Compounds 6 and 7 are a pair of N₄ epimers of humantenine N₄-oxide. A plausible biogenetic pathway for compounds 1-4 was also proposed.     

Constructing a blue light photodetector on inorganic/organic p-n heterojunction nanowire arrays

We described a new structure photodetector, which is constructed by p-n heterojunction nanowire arrays of PANI (polyaniline)/CdS. The nanowire arrays exhibit excellent rectifying features and a diode nature and show a sensitive spectral response to blue light under 420 nm. The rectification ratio plots of different illumination intensities show straight line behavior, implying that the quantitative detection of illumination intensity can be achieved. The p-n heterojunction nanowire array is a great candidate for applications in high-sensitivity and high-speed blue light photodetectors.     

A Novel Glutamate Transport System in Poly(γ-Glutamic Acid)-Producing Strain <Emphasis Type="Italic">Bacillus subtilis</Emphasis> CGMCC 0833

Bacillus subtilis CGMCC 0833 is a poly(γ-glutamic acid) (γ-PGA)-producing strain. It has the capacity to tolerate high concentration of extracellular glutamate and to utilize glutamate actively. Such a high uptake capacity was owing to an active transport system for glutamate. Therefore, a specific transport system for l-glutamate has been observed in this strain. It was a novel transport process in which glutamate was symported with at least two protons, and an inward-directed sodium gradient had no stimulatory effect on it. K _m and V _m for glutamate transport were estimated to be 67 μM and 152 nmol⁻¹ min⁻¹ mg⁻¹ of protein, respectively. The transport system showed structural specificity and stereospecificity and was strongly dependent on extracellular pH. Moreover, it could be stimulated by Mg²⁺, NH₄⁺, and Ca²⁺. In addition, the glutamate transporter in this strain was studied at the molecular level. As there was no important mutation of the transporter protein, it appeared that the differences of glutamate transporter properties between this strain and other B. subtilis strains were not due to the differences of the amino acid sequence and the structure of transporter protein. This is the first extensive report on the properties of glutamate transport system in γ-PGA-producing strain.     

EXISTENCE AND UNIQUENESS OF SOLUTIONS TO A NONLINEAR FRACTIONAL DIFFERENTIAL EQUATION

The initial value problem of a nonlinear fractional differential equation is discussed in this paper. Using the nonlinear alternative of Leray-Schauder type and the contraction mapping principle,we obtain the existence and uniqueness of solutions to the fractional differential equation,which extend some results of the previous papers.     

Evidence of negative-index refraction in nonlinear chemical waves

The negative index of refraction of nonlinear chemical waves has become a recent focus in nonlinear dynamics researches. Theoretical analysis and computer simulations have predicted that the negative index of refraction can occur on the interface between antiwaves and normal waves in a reaction-diffusion (RD) system. However, no experimental evidence has been found so far. In this Letter, we report our experimental design in searching for such a phenomenon in a chlorite-iodide-malonic acid (CIMA) reaction. Our experimental results demonstrate that competition between waves and antiwaves at their interface determines the fate of the wave interaction. The negative index of refraction was only observed when the oscillation frequency of a normal wave is significantly smaller than that of the antiwave. All experimental results were supported by simulations using the Lengyel-Epstein RD model which describes the CIMA reaction-diffusion system.     

空心阴极放电条纹特性的光谱诊断

利用发射光谱法,研究了圆柱型空心阴极放电条纹的特性.测量了条纹区的发射光谱,在此基础E计算得到r电子激发温度、相对电子密度和电子平均能量的空间分布特性.结果表明条纹区的光强、电子激发温度和电子密度均呈非等幅的周期性变化.与暗纹中心处相比,明纹中心具有较高的电子激发温度和较低的电子密度.由阴极向阳极,明纹中心处的电子激发温度幅值逐渐减小.此外,条纹区的电子激发温度随着电流的增加而增加.     

A strategy for liquid chromatography/tandem mass spectrometry based quantitation of pegylated protein drugs in plasma using plasma protein precipitation with water-miscible organic solvents and subsequent trypsin digestion to generate surrogate peptides for detection

Recently, we have developed liquid chromatography/tandem mass spectrometry (LC/MS/MS)-based methods for the quantitation of pegylated therapeutic proteins in plasma. The methods are based on the LC/MS/MS detection of a surrogate peptide generated from trypsin digestion of the therapeutic protein. Various parameters related to the bioanalytical methods were evaluated and optimized, including the preparation of calibration standards and quality control samples, sample extraction, internal standard selection and its stage of addition, trypsin digestion, and non-specific binding. In this paper, we report the development of a method for a specific pegylated therapeutic protein and detail the various optimization steps undertaken. Simple extraction of the pegylated therapeutic protein from plasma was achieved via the precipitation of the endogenous proteins in plasma using acidic isopropanol and the resulting supernatant extract was subjected to trypsin digestion. A unique tryptic peptide arising from the pegylated therapeutic protein was used for LC/MS/MS-based detection and quantitation. A protein and a peptide were used as internal standards, with the former added before the sample extraction and the latter after the sample extraction. The method developed is simple, sensitive, specific and rugged, and has been implemented in a high throughput 96-well format to analyze plasma samples from in vivo studies. A required lower limit of quantitation (LLOQ) of 10 ng/mL, expressed in terms of the concentration of the protein drug, was easily achieved.     

离子辐照对磷烯热导率的影响及其机制分析

通过离子辐照产生缺陷,可以非常有效地调控磷烯诸多物理性质.本文应用分子动力学方法模拟离子辐照磷烯的过程,给出了缺陷的形成概率与入射离子能量、离子种类以及离子入射角度之间的关系,并且应用非平衡态分子动力学计算辐照后磷烯热导率的变化.以缺陷形成概率为切入点,系统地研究了辐照离子的能量、辐照剂量、离子的种类以及离子的入射角度对磷烯热导率的影响.应用晶格动力学方法研究了空位缺陷对磷烯声子参与率的影响,并计算了声子局域模式的空间分布.基于量子微扰和键弛豫理论,指出空位缺陷明显降低磷烯热导率的最重要物理机制是空位缺陷附近的低配位原子对声子强烈散射.本文研究可为缺陷工程调控磷烯的热输运性质提供理论参考.