Separation and identification of enzymatically prepared dephosphorylated products of myo‐inositolhexakisphosphate using LC‐MS

LC‐MS technique described here is a new way for the separation and direct determination of UV–Vis insensitive inositol phosphates (InsP₂‐InsP₆). This circumvents the need of radioisotopic labeling and post‐column derivatization techniques. The method involves separation of various enzymatically dephosphorylated derivatives of InsP₆ on C₁₈‐column using MeOH/H₂O (30:70 v/v) and their identification using electron spray ionization MS in positive ion mode (+pESI‐MS). The LC‐MS studies revealed that the purified phytase from Aspergillus niger van Teighem hydrolyzes InsP₆ in a sequential manner leading to InsP₂ (InsP₂·2Na, t_R 4.4–4.54 min, base peak m/z 382.9) as the end product.     

Stress Degradation Behavior of Desipramine Hydrochloride and Development of Suitable Stability-Indicating LC Method

A simple reverse phase liquid chromatographic method was developed for the quantitative determination of desipramine hydrochloride and its related impurities in bulk drugs which is also stability-indicating. During the forced degradation at hydrolysis, oxidative, photolytic and thermal stressed conditions, the degradation results were only observed in the oxidative stress condition. The blend of the degradation product and potential impurities were used to optimize the method by an YMC Pack Pro C₁₈ stationary phase. The LC method employs a linear gradient elution with the water–acetonitrile–trifluoroacetic acid as mobile phase. The flow rate was 1.0 mL min^?1 and the detection wavelength 215 nm. The stressed samples were quantified against a qualified reference standard and the mass balance was found close to 99.0% (w/w) when the response of the degradant was considered to be equal to the analyte (i.e. desipramine). The developed RP-LC method was validated in agreement with ICH requirements.     

Growth of highly oriented crystalline polyaniline films by self-organization

Silicon substrates with (100) orientation were modified with amino-silane self-assembled monolayer (SAM) to provide amino (NH(2)) moieties at the substrate surface. Self-organization of polyaniline during chemical polymerization, on this modified surface, leads to the growth of highly oriented films at the substrate-polymer interface. The morphology studied using scanning electron microscopy and atomic force microscopy revealed the formation of polymer film with well faceted pyramidal crystallites. XPS and FTIR spectroscopy were used to analyze the chemical structure of the film. X-ray diffraction measurements show the crystalline nature of the polyaniline, whose lattice parameters are in agreement with the reported values. This study underlines the importance of a SAM in deciding the structure and morphology of the deposited polymer.     

Use of chlorinated carbon and silicon precursors for epitaxial growth of 4H‐SiC at very high growth rates

A possibility to apply the advantages of chlorinated carbon precursors, which had been previously used in low‐temperature epitaxial growth of 4H‐SiC, to achieve very high growth rates at higher growth temperatures was investigated. Silicon tetrachloride was used as the silicon precursor to suppress gas‐phase homogeneous nucleation. The temperature increase from 1300 °C (which is the temperature of the previously reported low‐temperature halo‐carbon epitaxial growth) to 1600 °C enabled an increase of the precursor flow rates and consequently of the growth rate from 5 to more than 100 μm/h without morphology degradation. High quality of the epilayers was confirmed by low‐temperature photoluminescence spectroscopy and time‐resolved luminescence. No evidences of homogeneous nucleation were detected, however, liquid Si droplet formation on the epilayer surface seems to remain a bottleneck at very high growth rate. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Comparison of Spectroscopic and Lasing Properties of Different Types of Sol-Gel Glass Matrices Containing Rh-6G

Rhodamine-6G (Rh-6G) is embedded in sol-gel glass samples which have been prepared by three different methods namely: 1) using HCl as catalyst and glycerol as Drying Control Chemical Additive (DCCA), 2) using HCl as catalyst at 60 °C and drying at room temperature and 3) using HCl as catalyst at 60 °C and heated at 600 °C for 3 h. Comparative studies of spectroscopic and lasing properties of the three types of Rh-6G containing samples were carried out with the lapse of time upto 8 months. Photostability of Rh-6G containing sol-gel samples is measured in terms of half life under Nitrogen laser pumping as number of pulses of N₂ laser necessary to reduce the dye laser intensity to 50% of the original value and value is 7500 pulses at 1.67 Hz rate. The best performance of Rh-6G, as far as its spectroscopic and lasing properties are concerned was found in third type of host matrices using HCl as catalyst at 60 °C and heated at 600 °C for 3 h.     

Nuclear symmetry energy effects in finite nuclei and neutron star

Within a relativistic mean-field model with nonlinear isoscalar–isovector coupling, we explore the possibility of constraining the density dependence of nuclear symmetry energy from a systematic study of the neutron skin thickness of finite nuclei and neutron star properties. We find the present skin data supports a rather stiff symmetry energy at subsaturation densities that corresponds to a soft symmetry energy at supranormal densities. Correlation between the skin of ²⁰⁸Pb and the neutron star masses and radii with kaon condensation has been studied. We find that ²⁰⁸Pb skin estimate suggest star radii that reveals considerable model dependence. Thus precise measurements of neutron star radii in conjunction with skin thickness of heavy nuclei could provide significant constraint on the density dependence of symmetry energy.     

Optimized synthesis of [3-N]-labeled uridine phosphoramidites

A short and high-yielding synthetic route to [3-¹⁵N]-labeled uridine phosphoramidite 1 (26% overall yield from uridine) has been developed. This will enable automated synthesis of isotopically labeled RNA strands and facilitate their use in structural studies.     

湍流流动中鲨鱼皮表面流体减阻研究进展

快速游动的鲨鱼, 其皮肤表面沿流动方向有序地排列着沟槽状结构, 人们认为这种结构能在湍流流动 中减小表面摩擦阻力. 人们仿真这种生物结构来进行实验研究和应用, 通过复制和改善鲨鱼皮肤表面沟槽状 结构, 使得摩擦阻力最大减小了近10%. 在实验和模拟仿真中, 人们不断讨论和研究湍流流动阻力的形成机制 和沟槽减阻的理论特性. 本文综述了沟槽减阻理论特性的一些研究方法, 并且归纳定义了沟槽减阻最优几何 形状及其尺寸; 详细考虑流体流动的特点, 给出了一种用来选择最优沟槽形状及其尺寸的方法; 综述了目前的 沟槽加工制造技术. 由于鲨鱼皮肤表面存在少量黏液, 从仿生学的角度, 文章最后综述并展望了通过局部应用 疏水性材料来改变沟槽附近流场属性, 从而达到更大程度上减小阻力的目标.      

Triangular CdS nanostructure: effect of Mn doping on photoluminescence,electron spin resonance,and magneto-optical properties

In this paper, we report synthesis and study of magneto-optic Faraday effect for dilute magnetic semiconductor nanostructure. The colloidal CdS nanocrystals were prepared via hot injection method and successfully doped with Mn²⁺ cations. The synthesized nanoparticles were characterized by using UV–Vis spectroscopy, X-ray diffraction, photoluminescence spectroscopy, transmission electron microscopy, and electron spin resonance spectroscopy. Systematic studies on effect of Mn²⁺ doping on photoluminescence, electron spin resonance, and magneto-optical properties are carried out. UV–Vis spectral analysis confirms blue shift in bandgap of CdS nanoparticles due to quantum confinement effect. The X-ray diffraction study confirms hexagonal wurtzite phase formation of CdS nanoparticles without any impurity phases. TEM analysis confirms uniform particle size, having particle size distribution around 5 nm. As-synthesized undoped CdS shows triangular-shaped nanocrystals with hexagonal structure; however, triangular shape of CdS nanoparticles is not conserved after Mn²⁺ doping. The photoluminescence characteristic spectra of Mn²⁺-doped CdS nanocrystals showed emission band at 660 nm and its intensity was found to increase with increasing Mn²⁺ concentration. Electron spin resonance signal, with six-line hyperfine structure splitting, confirmed doping of Mn²⁺ ions in CdS lattice. Magneto-optic measurements showed linear variation of Faraday rotation with respect to applied magnetic field, indicating paramagnetic behavior of Mn-doped CdS. The highest Verdet constant 24.81 deg/T cm was observed for 2% Mn-doped CdS nanocrystals, which further decreases with increasing Mn²⁺ concentration.

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Graphical abstract Illustration of Magneto-optic Faraday effect using dilute magnetic semiconductors (TEM image of triangular CdS nanoparticles)