Activation energy of single-stranded DNA moving through cross-linked polyacrylamide gels at 300 V/cm effect of temperature on sequencing rate in high-electric-field capillary gel electrophoresis

In DNA sequencing, single-stranded DNA fragments are separated by gel electrophoresis. This separation is based on a sieving mechanism where DNA fragments are retarded as they pass through pores in the gel. In this paper, we present the mobility of DNA sequencing fragments as a function of temperature; mobility is determined in 4% T LongRanger gels at an electric field of 300 V/cm. The temperature dependence is compared with the predictions of the biased reptation model. The model predicts that the fragment length for the onset of biased reptation with stretching increases with the square of temperature; the data show that the onset of biased reptation with stretching decreases with temperature. Biased reptation fails to model accurately the temperature dependence of mobility. We analyzed the data and extracted the activation energy for passage of sequencing fragments through the gel. For fragments containing less than ca. 200 bases, the activation energy increases linearly with the number of bases at a rate of 25 J/mol per base; for longer fragments, the activation energy increases at a rate of 6.5 J/mol per base. This transition in the activation energy presumably reflects a change in conformation of the DNA fragments; small fragments exist in a random coil configuration and larger fragments migrate in an elongated configuration.     

Preliminary characterization of anhydrous ethanol used in Brazil as automotive fuel

This work reports preliminary studies on the characterisation of anhydrous ethanol (AEA) used as an automotive fuel mixed with gasoline in Porto Alegre (South Brazil). Pre-concentration of the impurities contained in 1000 ml of AEA was carried on through solid-phase extraction using XAD4 resin. The main compounds in the extract were identified by means of spectral data from the library of the equipment. The concentrate was then fractionated using a preparative liquid chromatographic column filled with activated silica gel and the elution procedure was carried out with, n-hexane, n-hexane-benzene (1:1, v/v) and dichloromethane. Prior to analysis by GC-MS, each fraction was reduced to 1 ml with a gentle stream of nitrogen. Saturated linear hydrocarbons and aromatic hydrocarbons eluted in the first fraction and oxygenated compounds such as aldehydes. ketones and alcohols, eluted in the second one. were the main compounds detected in the sample.     

Determination of moxifloxacin in tablets and human urine by square-wave adsorptive voltammetry

This work presents an electroanalytical methodology developed for square-wave voltammetry based in the electrochemical reduction in hanging mercury drop electrode (HMDE), which is simple, fast, reliable and sensitive for determination of moxifloxacin (MOXI) in tablets and spiked urine human samples. The support electrolyte that provided a more defined and intense peak current for MOXI determination was the phosphate buffer 0.04 mol l^{− 1} pH 8.0. In the best-optimized conditions the drug presented an only peak of reduction at − 1.38 V vs. Ag/AgCl, using an E_acc. of − 0.30 V. An LOD of 0.44 and 3.20 ng ml^{− 1} and an LOQ of 1.46 and 10.60 ng ml^{− 1} were found for the pure standard of moxifloxacin and in the presence of matrix, respectively. A good recovery was obtained for assay spiked urine samples and a good quantification of MOXI was achieved in a commercial formulation. The methodology proposed was more sensitive than the spectrofluorimetric and spectrophotometric method with precision and accuracy equivalent.     

溶胶-凝胶技术制备高效液相色谱氧化锆填料

 以氧氯化锆水解得到溶胶,然后以Span－80和Tween－85混合非离子表面活性剂为乳化剂、环己烷为有机相制成W／O型乳状液,用其控制粒度,可得到2～10μm的ZrO2凝胶微球。通过比表面积、孔容、孔径测试及对6种不同性质的物质的吸附试验表明,该微球产物可作为高效液相色谱填料。     

Cloud point extraction of vanadium in parenteral solutions using a nonionic surfactant (PONPE 5.0) and determination by flow injection-inductively coupled plasma optical emission spectrometry

A preconcentration and determination methodology for vanadium at trace levels in parenteral solutions was developed. Cloud point extraction was successfully employed for the preconcentration of vanadium prior to inductively coupled plasma atomic optical emission spectrometry (ICP-OES) coupled to a flow injection (FI) system. The vanadium was extracted as vanadium-2-(5-bromo-2-pyridylazo)-5-diethylaminophenol [V-(5-Br-PADAP)] complex, at pH 3.7 mediated by micelles of the nonionic surfactant polyoxyethylene (5.0) nonylphenol (PONPE 5.0). The extracted surfactant-rich phase (100 mul) was mixed with 100 mul of ethanol and this final volume injected into ICP-OES for the vanadium determination. Under these conditions, the 50 ml sample solution preconcentration allowed raising an enrichment factor of 250-fold; however, it was possible to obtain a theoretical enrichment factor of 500-fold. The lower limit of detection (LOD) obtained under the optimal conditions was 16 ng l(-1). The precision for 10 replicate determinations at the 2.0 mug l(-1) V level was 2.3% relative standard deviation (RSD), calculated with the peak heights. The calibration graph using the preconcentration system for vanadium was linear with a correlation coefficient of 0.9996 at levels near the detection limits up to at least 50 mug l(-1). The method was successfully applied to the determination of vanadium in parenteral solution samples.     

A dominance-based rough set approach applied to evaluate the credit risk of sovereign bonds

4OR - Even though sovereign bonds represent low-risk alternatives that give investors a healthy income, the risk assessment process for these bonds is still considered subjective because of the...     

The inclusion of rhodium(II)α-methyl-cinnamate in β-cyclodextrin

The preparation and characterization of the 1:1 inclusion compound of rhodium(II) -methyl cinnamate in -cyclodextrin is reported. Evidence of inclusion was obtained from X-ray powder diffraction results, Raman, IR and UV-Vis spectroscopic studies and thermal analysis. Given the potential antitumor activity of the rhodium(II) carboxylate and its virtual insolubility in water, its inclusion in -cyclodextrin opens the possibility for its transference to the aqueous phase.