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.     

铜氧团簇负离子的产生

自Smalley等利用激光蒸发／超声分子束载带（ix／un）法产生c。。问起，这种方法逐渐成为形成高质量气相团簇的常用实验手段，其中分子束载带的主要作用是缓冲气体通过提供三体碰撞稳定动力学激发的团簇并促进高质量团簇的形成．但0’Keef6门和Cre。Sy同的实验发现无需利用缓冲     

Determination of minor elements in steelmaking flue dusts using laser ablation inductively coupled plasma mass spectrometry

Element determination in solid waste products from the steel industry usually involves the time-consuming step of preparing a solution of the solid. Laser ablation (LA) inductively coupled plasma mass spectrometry (ICP-MS) has been applied to the analysis of Cr, Ni, Cu, As, Cd and Sn, elements of importance from the point of view of their impact on the environment, in electric arc furnace flue dust (EAFD). A simple method of sample preparation as pressed pellets using a mixture of cellulose and paraffin as binder material was applied. Calibration standards were prepared spiking multielement solution standards to a 1:1 ZnO + Fe₂O₃ synthetic matrix. The wet powder was dried and mechanically homogenised. Quantitative analysis were based on external calibration using a set of matrix matched calibration standards with Rh as a internal standard. Results obtained using only one-point for calibration without matrix matched, needing less time for standardization and data processing, are also presented. Data are calculated for flue dust reference materials: CRM 876-1 (EAFD), AG-6203 (EAFD), AG-6201 (cupola dust) and AG-SX3705 (coke ashes), and for two representative electrical arc furnace flue dusts samples from Spanish steelmaking companies: MS-1 and MS-2. For the reference materials, an acceptable agreement with certificate values was achieved, and the results for the MS samples matched with those obtained from conventional nebulization solutions (CN). The analytical precision was found to be better than 7% R.S.D. both within a single pellet and between several pellets of the same sample for all the elements.     

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.     

Features in the vibrational relaxation of laser excited Freon-22 molecules

The vibration-translation (V-T) of laser excited Freon-22 (CF₂HC1) molecules has been studied. An interferometric technique allows simultaneous measurement of the initial energy 〈E〉 stored in the molecules, and of the V-T relaxation time. Consequently, the V-T relaxation time and the energy released per collision can be determined as a function of the energy absorbed from the laser field. Three distinct regions have been observed for these dependences. This behaviour observed and reported by us for Freon-22 confirms the role played in the relaxation process by the initial distribution of the vibrational energy, and agrees qualitatively with the experimental results for other polyatomic molecules.     

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.