A fungal nonribosomal peptide synthetase module that can synthesize thiopyrazines

A nonribosomal peptide synthetase-like enzyme (NRPS325) from Aspergillus terreus was reconstituted in vitro and was shown to synthesize thiopyrazines using an unprecedented mechanism. Substrate promiscuity of NRPS325 toward different amino acids and free thiols was explored to produce >60 different thiopyrazine compounds.     

连续氢化物发生端视ICP-AES法测定水中痕量硒和汞

报道了用自制的在线氢化物连续发生装置,应用端视ICP-AES法测定水中痕量硒和汞。不需要专用氢化物发生装置,分析成本低。在完成非氢化法测定或氢化法测定时不需拆卸或安装。方法简便、快速。测定水中硒和汞的测定,其检出限分别为2×10-4和1×10-4mg·L-1。     

Preparation of Mn3O4 nanocrystallites by low-temperature solvothermal treatment of γ-MnOOH nanowires

The preparation of trimanganese tetroxide (Mn₃O₄) nanocrystallites from γ-MnOOH nanowires under mild conditions has been achieved by two steps: first, γ-MnOOH nanowires with a mean diameter of about 12 nm and lengths of up to several micrometers were directly prepared via hydrothermal reaction between KMnO₄ and toluene in water at 180°C for 24 h; then, pure Mn₃O₄ nanocrystallites could be obtained by solvothermal treatment of the γ-MnOOH nanowires in ethylenediamine (EDA) and ethylene glycol (EG) at 150°C for 24 h. It was found that the Mn₃O₄ product obtained in EDA comprised well-defined nanocrystallites with the size in the range of 15-35 nm, while the one obtained in EG consisted of aggregated nanoparticles with the size of less than 18 nm.The possible formation mechanism of nanocrystalline Mn₃O₄ in EDA and EG and reasons for the different effects of various solvents on the products were also proposed.     

多孔纳米氧化铝薄膜上荧光分子光谱特性研究

通过两步电化学阳极氧化技术制备了孔径为40nm的多孔纳米阳极氧化铝材料(AAO),在AAO薄膜上分别填充了几种有机荧光分子使其形成高度有序的有机-无机复合体发光阵列,测定了此复合体的发射光谱．结果表明,AAO薄膜对有机分子具有较强的结合能力,其结合能力来源于物理和化学的协同作用．在AAO纳米薄膜上的有机荧光分子的最大发射波长均产生了明显的蓝移现象,初步探讨了此现象的机理．有机分子填充进入高度有序的AAO纳米孔阵列之中时,有机分子的聚集形式会发生改变并且也是高度有序的,同时由于极化作用使有机分子沿着纳米孔的轴向具有相对优势的分子取向,使有机分子在AAO纳米薄膜上形成了接近单分子层的高度有序的排列方式,增强了发光效率．     

The growth of perylene on Ru(0001)

The structure of perylene adsorbed on Ru(0001) surface has been studied by ultraviolet photoemission spectroscopy (UPS) and low-energy electron diffraction. An ordered p(4x4) structure is observed from a monolayer (about 4 A thickness) of the perylene on Ru(0001) surface. UPS measurements show the molecular features, from the perylene multiplayer, between 2 and 10 eV below the Fermi level. Angle-resolved ultraviolet photoemission spectroscopy measurements suggest that the perylene molecular plane is parallel to the substrate. Temperature dependent UPS measurements show that the perylene multilayer is stable on Ru(0001) surface up to 125 degrees C. The desorption of the multilayer and the decomposition of the monolayer are observed above 125 degrees C.     

System-oriented dispersion models of general-shaped electrophoresis microchannels

This paper presents a system-oriented model for analyzing the dispersion of electrophoretic transport of charged analyte molecules in a general-shaped microchannel, which is represented as a system of serially connected elemental channels of simple geometry. Parameterized analytical models that hold for analyte bands of virtually arbitrary initial shape are derived to describe analyte dispersion, including both the skew and broadening of the band, in elemental channels. These models are then integrated to describe dispersion in the general-shaped channel using appropriate parameters to represent interfaces of adjacent elements. This lumped-parameter system model offers orders-of-magnitude improvement in computational efficiency over full numerical simulations, and is verified by results from experiments and numerical simulations. The model is used to perform a systematic parametric study of serpentine channels consisting of a pair of complementary turn microchannels, and the results indicate that dispersion in a particular turn can contribute to either an increase or decrease of the overall band broadening. The efficiency and accuracy of the system model is further demonstrated by its application to general-shaped channels that occur in practice, including a serpentine channel with multiple complementary turns and a multi-turn spiral-shaped channel. The results indicate that our model is an accurate and efficient simulation tool useful for designing optimal electrophoretic separation microchips.     

O2 dissociative adsorption on the Cu‐, Ag‐, and W‐doped Al(111) surfaces from DFT computation

The O₂ adsorption and dissociation on M‐doped (M = Cu, Ag, W) Al(111) surface were studied by density functional theory. The adsorption energy of adsorbate, the average binding energy and surface energy of Al surface, and the doping energy of doping atom were calculated. All the doped atoms can be stably combined with Al atoms, while being slightly embedded in the surface to a certain depth. The TOP‐type surfaces are the most stable doped surfaces for O₂ adsorption, which is related to the orbital hybridization between the adsorbate and the surface atoms, the electronegativity, and the orbital energy level of the doping atoms. Moreover, the O atoms and doping atoms contribute significantly to the density of states (DOS), especially the O‐p orbital electrons and the d orbital electrons of doping atoms. The degree of O₂ dissociation is related to the doping atoms on Al surfaces, and the doping atoms actually resist the dissociation of O₂. W atoms have the best resistance effect on the O₂ dissociation as compared with Cu and Ag atoms, especially W‐1NN surface, which has both large barrier energy and reaction energy.     

Mixed charged zwitterionic self-assembled monolayers as a facile way to stabilize large gold nanoparticles

Here we report a facile way of stabilizing large gold nanoparticles (AuNPs) by mixed charged zwitterionic self-assembled monolayers (SAMs). The citrate-capped AuNPs with diameters ranging from 16 nm to even ～100 nm are well stabilized via a simple place exchange reaction with a 1:1 molar ratio mixture of negatively charged sodium 10-mercaptodecanesulfonic acid (HS-C10-S) and positively charged (10-mercaptodecyl)-trimethyl-ammonium bromide (HS-C10-N4). The 16 nm AuNPs protected by mixed charged zwitterionic SAMs not only show much better stability than the single negatively or positively charged AuNPs, but also exhibit exciting stability as well as those modified by monohydroxy (1-mercaptoundec-11-yl) tetraethylene glycol (HS-C11-EG4). Importantly, 16 nm AuNPs protected by mixed SAMs exhibit good stability in cell culture medium with 10% FBS and strong protein resistance, especially with excellent resistance against plasma adsorption. Moreover, the mixed charged zwitterionic SAMs are also able to well-stabilize larger AuNPs with a diameter of 50 nm, and to help remarkably improve their stability in saline solution compared with HS-C11-EG4 protected ones. When it comes to AuNPs with a diameter of 100 nm, the mixed charged zwitterionic SAM protected nanoparticles retain a smaller hydrodynamic diameter and even better long-term stability than those modified by mercaptopolyethylene glycol (M(w) = 2000, HS-PEG2000). The above results demonstrated that the mixed charged zwitterionic SAMs are able to have a similar effect on stabilizing the large gold nanoparticles just like the single-component zwitterionic SAMs. Concerning its ease of preparation, versatility, and excellent properties, the strategy based on the mixed charged zwitterionic SAM protection might provide a promising method to surface tailoring of nanoparticles for biomedical application.     

不同氧化程度氧化石墨烯的制备及湿敏性能研究

基于氧化石墨烯具有多种含氧官能团和极大的比表面积,研究了不同氧化程度氧化石墨烯的湿敏性能。采用改进的Hummers法制备不同氧化程度的氧化石墨,经过超声分散制备氧化石墨烯水相分散液后,制成氧化石墨烯薄膜湿敏元件。采用X射线衍射、原子力显微镜、红外光谱、拉曼光谱和X射线光电子能谱对实验样品的结构和谱学特性进行表征。结果表明:石墨经氧化后,底面间距增大为0.9 nm左右;随氧化剂用量的增加,氧化石墨中石墨的衍射峰逐渐消失,石墨相微晶尺寸逐渐减小,O/C原子比逐渐增大,氧化程度逐渐升高;氧化石墨烯在水相分散液中可达单层分散,单层氧化石墨烯厚度约为1.3 nm;氧化石墨烯表面接有-OH、C-O-C、C=O和COOH官能团,且官能团含量随氧化程度的升高而增大;氧化石墨烯薄膜元件在室温下对湿度的响应时间约3 s,灵敏度达99%;在11.3%-93.6%相对湿度范围内,元件的电阻随湿度升高显著减小,较高氧化程度的氧化石墨烯薄膜的电阻对数与相对湿度呈线性变化;氧化程度越高,元件灵敏度越高,响应时间越短。     

Highly ordered mesoporous Cr2O3 materials with enhanced performance for gas sensors and lithium ion batteries

Highly ordered mesoporous Cr(2)O(3) materials with high specific surface area and narrow pore size distribution were successfully prepared by a vacuum assisted impregnation method. Both 2-dimensional hexagonal and 3-dimensional cubic Cr(2)O(3) mesoporous replicas from SBA-15 and KIT-6 templates exhibit enhanced performance for gas sensors and lithium ion batteries, compared to the bulk Cr(2)O(3) counterpart.