Quantitative analysis of isoflavone aglycones in human serum by solid phase extraction and liquid chromatography-tandem mass spectrometry

This paper describes a liquid chromatography-electrospray-tandem mass spectrometry (LC-ESI-MS/MS) for the qualitative and quantitative analysis of three isoflavone aglycones (glycitein, daidzein and genistein) in human serum. Positive ion mode was used for the detection of these compounds and selective reaction monitoring (SRM) was employed for quantitative measurement. The SRM transitions monitored were as 285.0 → 242.0, 270.0 for glycitein, 255.0 → 137.0, 153.0, 181.0, 199.0 for daidzein and 271.0 → 153.0, 215.0 for genistein. d₃-Daidzein was used as an internal standard for quantitative measurement. The linearity was good from 0.5 to 500 ng/ml. The detection limit based on a signal-to-noise ratio of three was 0.27, 0.38 and 0.29 ng/ml for glycitein, daidzein and genistein, respectively. A newly developed solid phase extraction (SPE) procedure was developed for sample pre-treatment. Good recovery, 92.3-103.2%, for three isoflavone aglycones were obtained. This newly developed method was successfully applied to evaluate isoflavone pharmacokinetic in human serum after oral administration.     

A novel approach to oligonucleotide synthesis using an imidazolium ion tag as a soluble support

The synthesis of oligonucleotides in solution using a soluble, ionic liquid based support is described. Short oligomers of varying base composition were synthesized using this method in high yields and high purity, requiring no chromatography for purification prior to cleavage from the support. The solution-phase-synthesized oligomers were compared to the same sequences prepared using standard gene machine techniques by LCMS. This methodology may provide a cheaper route for the large-scale synthesis of oligonucleotides.     

A new approach for the detection of a nonfluorescent compound by CE-resonance Raman spectroscopy based on the sweeping-MEKC mode

A CE-resonance Raman spectroscopy (CE-RRS) method based on MEKC and sweeping-MEKC modes is described. A nonfluorescent compound, malachite green (MG), and a doubled Nd:YAG laser (532 nm, 300 mW) were selected as model compound and light source, respectively. In order to carry out a quantitative analysis of MG, a monochromator (effective bandwidth, 0.4 nm) was used to collect the specific Raman line at 1616 cm(-1) (N-phi and C-C stretch, corresponding to 582 nm when the wavelength of the exciting source was 532 nm). As a result, the LOD for MG was 10 ppm, based on the MEKC/RRS mode. This could be improved to 5 ppb when the sweeping-MEKC/RRS mode was applied. Furthermore, with the addition of nano-size silver colloids to the CE buffer the detection limits can be further improved, but the data obtained with surface-enhanced resonance Raman spectroscopy (SERRS) are less useful for quantitative purposes.     

Fourier transform ultraviolet-visible spectrometer based on a beam-folding technique

A beam-folding technique in optical interferometry, where the number of beam folds used can be very large, is reported. This technique can be used as a low-cost position-tracking method in a Fourier transform spectrometer (FTS) to cover the broad spectral range from UV to IR. The main advantage gained is the simple position-tracking algorithm used in sampling the interferogram. We have developed a UV-visible FTS, whose wavelength coverage is limited only by the optical elements (350 nm(-1) microm with off-the-shelf components). Preliminary results show that it can achieve a resolution of approximately 4 cm(-1) even with a ball-bearing translation stage.     

Alternating Poly(Pt‐salphen)‐(p‐phenyleneethynylene) as Phosphorescent Conjugated Linear‐Rod and Coilable Sensory Materials

Phosphorescent conjugated polymers consisting of alternating p‐phenylene‐ethynylene and ‘para‐’ or ‘meta‐type’ Pt(II)‐salphen luminophore units have been synthesized. Side‐arms bearing different substituents (n‐alkoxy and acetylated‐sugar) have afforded contrasting emission properties that are attributed to the polymer conformation, extent of π‐stacking interactions and differences in chemical structure. Intriguing selectivity in luminescent sensing of metal ions has been observed.

     

白光LED用铽铕共掺镓酸锌微晶玻璃的制备、结构与发光性能研究

采用溶胶-凝胶法制备了Tb3+/Eu3+共掺ZnGa2O4微晶玻璃,研究了热处理温度对材料显微结构的影响以及不同稀土离子掺杂材料的发光性能.结果表明干凝胶样品在800～900℃温度热处理后可得到透明的含尖晶石结构ZnGaO4微晶玻璃,在1000℃热处理时由于SiO2非晶基体晶化析出三方Zn2SiO4与六方SiO2晶相导致样品失透.在微晶玻璃中具有ZnGa2O4纳米晶到Tb3+与Eu3+的能量传递.在900℃热处理Tb3+/Eu3+∶ZnGa2O4微晶玻璃样品中,Tb3+与Eu3+分别发射绿光和红光,并与ZnGa2O4纳米晶发射的蓝光组合成近白光发射.     

基于宽带多通道的光谱反射率重建方法研究

复制的多光谱数据获取要求图像数据具有设备无关、场景无关特性,能够真实客观表征物体颜色信息。针对获取系统扰动、噪声误差以及光谱重建中训练样本典型代表性与相关性要求,提出了基于正交回归的光谱重建算法,并通过子空间跟踪的训练样本选择算法,选择重建样本与训练样本集中相关性与代表性最好的样本参与光谱重建。实验通过改造后的仙娜宽带多通道成像系统进行验证,数据表明本文提出的方法,所选训练样本能较好的表征样本空间并具有较好的正交性,在宽带多光谱成像方面,重建光谱平均色度误差为3.6,其光谱精度与色度精度较其他方法具有明显提高。     

A simple shear cell for the direct visualization of step-stress deformation in soft materials

We introduce a custom-built stress-controlled shear cell coupled to a confocal microscope for direct visualization of constant-stress shear deformation in soft materials. The torque generator is a cylindrical Taylor–Couette system with a Newtonian fluid between a rotating inner bob and a free-to-move outer cup. A spindle/cone assembly is coaxially coupled to the cup and transfers the torque exerted by the fluid to the sample of interest in a cone-and-plate geometry. We demonstrate the performance of our device in both steady-state and transient experiments with different viscoelastic materials. Our apparatus can conduct unidirectional constant-stress experiments as accurately as most commercial rheometers, with the capability to directly visualize the flow field using tracer particles. Further, our step-stress experiments on viscoelastic materials are devoid of creep ringing, which is an advantageous aspect of our torque generation mechanism. We believe that the device presented here could serve as a powerful and cost-effective tool to investigate the microstructural determinants of nonlinear rheology in complex fluids.     

Onset of Buoyancy-Driven Convection in a Fluid-Saturated Porous Medium Bounded by a Long Cylinder

A theoretical analysis of convective instability driven by buoyancy forces under the transient concentration fields is conducted in an initially quiescent, liquid-saturated, cylindrical porous column. Darcy’s law and Boussinesq approximation are used to explain the characteristics of fluid motion and linear stability theory is employed to predict the onset of buoyancy-driven motion. Under the principle of exchange of stabilities, the stability equations are derived in self-similar boundary-layer coordinate. The present predictions suggest the critical $R_D$ , and the onset time and corresponding wavenumber for a given $R_D$ . The onset time becomes smaller with increasing $R_D$ and follows the asymptotic relation derived in the infinite horizontal porous layer.