Characterization of catechol 1,2-dioxygenase from cell extracts of <Emphasis Type="Italic">Sphingomonas xenophaga</Emphasis> QYY

Sphingomonas xenophaga QYY, capable of growing significantly on more than ten kinds of aromatic compounds as sole carbon source, was used to study characterization of catechol 1,2-dioxygenase (C12O) in cell extracts. Characterization of the crude C12O showed that the maximum activity was obtained at 40–70°C and pH 7.8–8.8. Metal ions had different influences on the activity of crude C12O. It was suggested that strain QYY possessed an inducible and ferric-dependent C12O. Kinetic studies showed that the value of V _max and K _m was 0.25 μmol catechol/L/mg protein/min and 52.85 μmol/L, respectively. In addition, the partial purification of C12O was achieved by a HiTrap Q Sepharose column chromatography. Supported by the National Natural Science Foundation of China (Grant No. 50608011) and the 39th Postdoctoral Funds of China (Grant No. 20060390983)     

直射太阳光差分吸收光谱反演NO2整层垂直柱浓度

在直射太阳光差分吸收光谱技术(DS-DOAS)中,通常采用测量期间较干净大气条件下太阳天顶角最小时的测量谱作为参考谱反演整层垂直柱浓度(VCD)。由于参考谱中依然含有未知的NO2吸收结构,因此得到的是VCD的相对值。该文将大气外层高精度太阳夫琅禾费标准光谱与仪器函数卷积后作为参考谱,避免了参考谱中含有NO2的吸收结构引入的误差。通过研究3月7日用此新方法获得的斜柱浓度(SCD)与通常方法获得的差分斜柱浓度(dSCD)的比较,新方法反演SCD的误差小于1.6×1016 molecules.cm-2;通常方法反演SCD的误差在4.25×1016 molecules.cm-2附近,采用新方法误差减少了62%以上。最后将DS-DOAS测量的NO2整层VCD与多轴差分吸收光谱技术(MAX-DOAS)测得的NO2对流层VCD进行了对比,结果表明新方法可以有效的改进通常方法计算VCD的误差。     

Self-powered solar-blind photodiodes based on EFG-grown(100)-dominant β-Ga2O3 substrate

We report the edge-defined-film-fed(EFG)-grown β-Ga₂O₃-based Schottky photodiodes.The device has a reverse leakage current of ~nA and a rectified ratio of ~10⁴ at ±5 V.In addition,the photodiode detector shows a dark current of 0.3 pA,a photo-responsivity(R) of 2.875 mA/W,a special detectivity(D*) of 10¹⁰ Jones,and an external quantum efficiency(EQE) of 1.4% at zero bias,illustrating a self-powered operation.This work may advance the development of the Ga₂O₃-based Schottky diode solar-blind photodetectors.     

Continuous-Wave Raman Lasing from Metal-Linked Organic Dimer Microcrystals

Stimulated Raman scattering offers an alternative strategy to explore continuous-wave (c.w.) organic lasers, which, however, still suffers from the limitation of inadequate Raman gain in organic material systems. Here we propose a metal-linking approach to enhance the Raman gain of organic molecules. Self-assembled microcrystals of the metal linked organic dimers exhibit large Raman gain, therefore allowing for c.w. Raman lasing. Furthermore, broadband tunable Raman lasing is achieved in the organic dimer microcrystals by adjusting excitation wavelengths. This work advances the understanding of Raman gain in organic molecules, paving a way for the design of c.w. organic lasers.     

Evaluation of an electrochemical sensor based on gold nanoparticles supported on carbon nanofibers for detection of tartrazine dye

Journal of Solid State Electrochemistry - An electrochemical sensor for the detection of tartrazine (Tz), a synthetic azo dye customarily found in commercial soft drinks, is herein reported. This...     

Characterization of Electrospun Polysuccinimide-Dopamine Conjugates and Effect on Cell Viability and Uptake

Biocompatible nanofibrous systems made by electrospinning have been studied widely for pharmaceutical applications since they have a high specific surface and the capability to make the entrapped drug molecule amorphous, which increases bioavailability. By covalently conjugating drugs onto polymers, the degradation of the drug as well as the fast clearance from the circulation can be avoided. Although covalent polymer–drug conjugates have a lot of advantages, there is a lack of research focusing on their nano-formulation by electrospinning. In this study, polysuccinimide (PSI) based electrospun fibrous meshes conjugated with dopamine (DA) are prepared. Fiber diameter, mechanical properties, dissolution kinetics and membrane permeability are thoroughly investigated, as these are crucial for drug delivery and implantation. Dopamine release kinetics prove the prolonged release that influenced the viability and morphology of periodontal ligament stem cells (PDLSCs) and SH-SY5Y cells. The presence of dopamine receptors on both cell types is also demonstrated and the uptake of the conjugates is measured. According to flow cytometry analysis, the conjugates are internalized by both cell types, which is influenced by the chemical structure and physical properties. In conclusion, electrospinning of PSI-DA conjugates alters release kinetics, meanwhile, conjugated dopamine can play a key role in cellular uptake.     

Supersaturation and crystal size distribution changes during the precipitation of Nickel ammonium sulphate hexahydrate

The desupersaturation of nickel ammonium sulphate aqueous solutions, during the precipitation of the hydrated salt, has been followed by refractive index measurements. The addition of seed crystals has a considerable effect on the desupersaturation process: the induction and latent periods and the crystal size distribution are all greatly reduced. The precipitated crystal size follows V . WEIMARN'S rules, viz, the median size (a) passes through a maximum with increasing supersaturation for a given crystallization time, and (b) decreases with increasing supersaturation, for precipitations which have virtually ceased. The crystal yield increases with both supersaturation and time, but the size distribution remains fairly constant with time for supersaturations, S > 2.     

An Anomalous Electron Configuration Among 3d Transition Metal Atoms

Physical properties of materials are mainly determined by valence electron configurations, where different valence shells would induce divergent phenomena. In compounds containing Sc²⁺, 3d electron occupancy is expected, the same as other transition metal atoms like Ti³⁺. But this situation still awaits experimental verification in inorganic materials. Here, we selected ScS to measure the valence electron density and orbital population of Sc²⁺ through delicate quantitative convergent-beam electron diffraction. With the absence of 3d orbital features around Sc-atom sites and the nearly bare population of t_2g orbital, the unintuitive occupation of 4s orbital in Sc²⁺ is concluded. It should be the first time to report such a special electron configuration in a transition metal compound, in which 4s rather than 3d orbital is preferred. Our findings reveal the distinct behavior of Sc and probable ways to modulate material properties by controlling electron orbitals.