High-throughput separation of DNA and proteins by three-dimensional geometry gel electrophoresis: feasibility studies

We report a novel separation method that is applicable to both DNA and protein samples, based on electrophoresis in a three-dimensional (3-D) geometry. In contrast to conventional electrophoresis, samples are applied in a two-dimensional, planar array to one of the surfaces of a 3-D geometry separation medium. Loading onto a plane results in a very high sample capacity. Sample migration and separation occur along the third spatial dimension, which is perpendicular to the loading plane. The key problem of electrophoresis in a 3-D geometry separation setup is that temperature gradients are caused by Joule's heat, affecting the electrical conductivity and viscosity of the separation medium. A means of achieving straight sample migration under these circumstances is to force heat flow through the separation medium parallel to the axis of sample migration. This can be done by dissipating the heat via the electrode sides of the gel and blocking any other heat transfer. The separation of DNA and proteins by this method has been tested using agarose gel electrophoresis, polyacrylamide gel electrophoresis, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Data were acquired off-line by conventional staining methods as well as on-line by detection of laser-induced fluorescence. We describe how to excise samples from the separation medium for preparative purposes. Possible unique applications of this 3-D geometry electrophoresis separation method are also discussed.     

IR laser ablative decomposition and depolymerisation/repolymerisation of poly(ethylene succinate)

Pulsed IR laser ablation of poly(ethylene succinate) results in the formation of volatile products (mainly carbon oxides, hydrogen, C₁-C₄ hydrocarbons) and affords deposition of polymeric films. Composition, structure and molecular weight distribution of the latter products were examined by EDX-SEM, FTIR, UV and NMR spectroscopy and gel permeation chromatography and revealed to be virtually identical to the initial poly(ethylene succinate). The deposited films and poly(ethylene succinate) decompose in the same way, as proved by TGA analysis. The formation of the volatile products is accounted for by random cleavages of the polymer backbone. The deposition of the polymeric products is judged to be due to molecular ester group interchange and/or a sequence of the C-C bond homolysis and recombination of the produced radicals.     

High resolution applications of laser-induced breakdown spectroscopy for environmental and forensic applications

Laser-induced breakdown spectroscopy (LIBS) has been used in the elemental analysis for a variety of environmental samples and as a proof of concept for a host of forensic applications. In the first application, LIBS was used for the rapid detection of carbon from a number of different soil types. In this application, a major breakthrough was achieved by using a multivariate analytical approach that has brought us closer towards a “universal calibration curve”. In a second application, it has been demonstrated that LIBS in combination with multivariate analysis can be employed to analyze the chemical composition of annual tree growth rings and correlate them to external parameters such as changes in climate, forest fires, and disturbances involving human activity. The objectives of using this technology in fire scar determinations are: 1) To determine the characteristic spectra of wood exposed to forest fires and 2) To examine the viability of this technique for detecting fire occurrences in stems that did not develop fire scars. These examples demonstrate that LIBS-based techniques are inherently well suited for diverse environmental applications. LIBS was also applied to a variety of proof of concept forensic applications such as the analysis of cremains (human cremation remains) and elemental composition analysis of prosthetic implants.     

Laser pyrolysis micro-spectroscopy for modelling fire-induced degradation of ethylene-vinyl acetate systems

A recently developed laser pyrolysis (LP)-Raman/ATR micro-spectroscopic method was applied for analyzing the degradation of polymer systems. The concept behind the method is to combine the micro-scale modelling of fire circumstances with analytical monitoring of the chemical changes in the solid phase of the sample. Samples were irradiated with the infrared beam of a CO₂ laser. The chemical changes were determined by micro-Raman/ATR spectroscopy methods in 200 ms intervals. The applicability of the method is demonstrated here through the pyrolysis of EVA and EVA composites containing metal-modified clays. Rapid depth profiling of few milligrams of sample is feasible with Raman detection, while the ATR sensor is applicable for analysis of fluorescent samples such as Fe coated sepiolite. The acceleration effect of montmorillonite and sepiolite minerals on the degradation of EVA is more pronounced if their surface is coated with Fe atoms. The effects of laser and the cone heater on the ratio of characteristic Raman bands of the polymer are compared and found to be in good correlation.     

Laser Raman and IR spectra and force fields for 2,6-difluorobenzonitrile

Raman spectrum of 2,6-difluorobenzonitrile in the powder form has been recorded in the region 50–4000 cm⁻¹ on a Jasco K-500 spectrophotometer using the 488.0 nm radiation from an argon laser. IR spectra in the region 200–4000 cm⁻¹ have been recorded in KBr pellet and nujol mull on a Nicolet DX spectrometer and in liquid and vapour phases on a Jasco FTIR/7000 spectrometer. Using these observed frequencies force field calculations for the planar and non-planar modes have been carried out assuming a general valence force field.     

Real-time monitoring of Yb vapor density using an extended cavity violet diode laser

Based on laser absorption spectroscopy (LAS), we developed a vapor density monitor for controlling the vaporization rate of Yb using a tunable diode laser. The laser source consisted of an extended cavity violet diode laser which has an emission wavelength of 398.8 nm coincident with the Yb absorption transition line, 6s(2) 1S(0)-6s6p 1P(1). The light emitted from the diode laser was transmitted across an atomic vapor column generated by heating the Yb metal, while the laser frequency was scanned across the atomic transition line. By comparing the amount of incident light to the amount of light transmitted after the light passed through the vapor column, the vapor density was determined using the Beer's law. From the experimental results, we demonstrated that the diode-laser-based LAS operated successfully for the real-time monitoring of the Yb vapor density.     

纳米级无机聚钼酸盐“二级有序聚集体”

介绍了纳米级水溶性无机聚钼酸盐分子的逐步生长合成, 对近年来水溶液中纳米级无机聚钼酸盐分子的奇特自聚集行为进行了简述, 从两亲分子“有序聚集体”概念的角度, 提出了水溶性纳米级无机聚钼酸盐“二级有序聚集体”的概念.     

C70正负离子的激光引发聚合

Ｃ_（７０）正负离子的激光引发聚合刘朝阳，王春儒，黄荣彬，林逢辰，郑兰荪（固体表面物理化学国家重点实验室，厦门大学化学系，厦门，３６１００５）关键词Ｃ_（７０），聚合，激光等离子体Ｃ６０在激光作用下的进一步聚合是近来在Ｃ６０研究中的又一重要发现，Ｙｅｒ...     

激光散射研究单价盐对C8-卵磷脂胶团形成的影响

用激光散射测量确定C_8-卵磷脂临界胶团浓度及其随温度、盐离子的变化。从中导出了胶团分子量, 形成因子, 能量梯级间隔以及标准焓等反映该溶液内分子相互作用的重要参量, 从而导出单价盐调控胶团大小以至形成和解体的规律和方法。