Capillary electrochromatography of proteins on an anion-exchanger column

Capillary electrochromatography (CEC) of proteins was carried out using 50-microm-i.d. fused-silica capillaries packed with 5-microm silica beads having strong anion-exchanger functions attached to hydrophilic spacers at the chromatographic surface. The siliceous microspheres and the capillary innerwall were treated first with a heterobifunctional silanizing agent and reacted subsequently with a vinyl monomer containing quaternary ammonium groups to form a "tentacular" anion exchanger. A mixture of bovine carbonic anhydrase, alpha-lactalbumin, soybean trypsin inhibitor, and ovalbumin was separated using CEC by isocratic elution in the codirectional mode with aqueous phosphate buffer, pH 7.0, containing sodium chloride. The retention mechanism of isocratic CEC for proteins on the anion-exchanger column was illustrated by the results of a study on the effect of salt concentration on the separation. The potential of CEC for protein separation with high resolution was also demonstrated by electrochromatograms of conalbumin and hemoglobin variants. The results shed light on the mechanism of protein separation by isocratic CEC, which is believed to be a combination of chromatographic retention by electrostatic interactions and electrophoretic migration. Assuming that the contributions of the two mechanisms to the overall migration velocity are additive, an electrochromatographic resolution equation was derived and compared to the resolution equation in HPLC to reveal the constituents responsible for the enhancement of resolution by CEC with respect to that in HPLC. The advantage of CEC was also examined by comparing peak capacities in CEC on an, isocratic platform with peak capacities obtained with isocratic and gradient elution HPLC.     

固定化酵母菌填充柱对锶的吸附特性研究

锶为具有很强毒性的裂变产物.结合生物吸附和固定化技术的优点,用海藻酸钠-氯化钙包埋法制作固定酵母菌颗粒并填充成吸附柱,研究了固定化酵母菌颗拉的特性和在静态、动态吸附下的吸附率、吸附容量和柱层析参数.结果表明,酵母菌固定化颗粒具有较高的比表面积和较好的机械承受能力.静态吸附结果表明,填充柱具有较高的吸附容量,吸附平衡时平...     

A prototype electrochemical chromatographic column for use with proteins

We developed electrochemical hardware and media targeted for protein chromatography. Two types of stationary phases were investigated. The first comprised gold-plated stainless 316L beads coated with a self-assembled monolayer of 6-mercaptohexan-1-ol and was expected to behave like an ion-exchange resin in the presence of an electric field. The secondary stationary phase comprised the first stationary phase with further functionalization with immobilized heme moieties and was expected to behave like immobilized metal affinity resin. We tested apparatus with both stationary phases using ribonuclease A as a model protein and applied potentials from -0.3 to +0.3 V versus the saturated calomel electrode. Despite low binding capacities, we demonstrated that protein retention on both stationary phases could be controlled with an applied potential. The greatest extent of electromodulation was achieved with the mercaptohexanol-based ion-exchange media.     

Dynamic buckling of an elastoplastic column

Dynamic buckling of columns under axial step loading which produces plastic behaviour is investigated. An experimental study is described and an elastoplastic model is developed in order to analyse the buckling process. Good agreement is obtained between the theoretical predictions and experimental results which justifies the main assumptions underlying the model.     

Study on the concentration of an enzyme immobilized by Langmuir-Blodgett films

Urease is an enzyme which decomposes urea into NH₃ and CO₂. We can produce a urea sensor by immobilizing urease on the pH sensor, and the Langmuir-Blodgett (LB) method has been expected to be useful as one of the immobilizing methods. We have measured for the first time the amount of urease adsorbed onto the LB film and shown that the relationship between the amount of adsorbed urease and the concentration in the solution can be expressed by an equation similar to the Langmuir adsorption isotherm.     

Modeling of chromium (VI) biosorption by immobilized Spirulina platensis in packed column

This study describes biosorption of chromium (VI) by immobilized Spirulina platensis, in calcium alginate beads. Three aspects viz. optimization of bead parameters, equilibrium conditions and packed column operation were studied and subsequently modeled. Under optimized bead diameter (2.6 mm), calcium alginate concentration (2%, w/v) and biomass loading (2.6%, w/v) maximum biosorption was achieved. 140 g l⁻¹ loading of optimized beads resulted in 99% adsorption of chromium (VI) ions from an aqueous solution containing 100 mg l⁻¹ of chromium (VI). The quantitative chromium (VI) uptake was effectively described by Freundlich adsorption isotherm. The immobilized S. platensis beads were further used in a packed bed column wherein the effects of bed height, feed flow rate, inlet chromium (VI) ion concentration were studied by assessing breakthrough time. The performance data were tested for various models fitting in order to predict scale up-design parameters such as breakthrough time and column height. Results were encouraging.     

Frictional properties of an immobilized fluorinated polymer nanosheet

The frictional properties of an immobilized fluorinated polymer nanosheet were investigated to develop an ultrathin solid lubrication film with an excellent wear-resistant. N-(1H,1H-Pentadecafluorooctylmethacrylamide) copolymers containing carboxyl group as a reactive moiety form a stable monolayer on the water surface and a highly ordered reactive fluorinated polymer nanosheet can be fabricated by the Langmuir-Blodgett technique. The reactive fluorinated polymer nanosheet was immobilized onto solid substrates through chemical binding with an aminosilane coupling agent, and the film showed smooth surface even after the reaction. The immobilized fluorinated polymer nanosheet had a low friction coefficient and strong wear-resistant.     

Dynamic bifurcation buckling of an impacted column

In this paper, the dynamic counterpart of the celebrated Euler buckling problem is formulated and solved by considering the case of a slender column that is impacted by a falling mass. We introduce a new notion, that of the time to buckle, “t^∗”, which is the corresponding critical quantity analogous to the critical load in static Euler buckling. A set of experimental results previously presented by Gladden et al. [J.R. Gladden, N.Z. Handzy, A. Belmonte, E. Villermaux, Dynamic buckling and fragmentation in brittle rods, Physical Review Letters 94 (3) (2005) 035503], are used to illustrate the notions we introduce and as a means for comparison against the predictions of our work.     

Parametric resonance in an oscillating water column

A common type of device for wave-energy extraction is an oscillating water column (OWC) with a compression chamber. Peak performance of most OWC systems occurs at resonance with the driving waves. At resonance, oscillations increase linearly in time until damping inhibits further growth. Parametric resonance is introduced as a means of exciting the oscillations of the water column. In parametric resonance, oscillations increase exponentially in time. The use of this kind of resonance may increase the performance of OWC systems. This type of resonance occurs when one of the parameters in an oscillator varies periodically. Asymptotic methods are used to study the nonlinear dynamics of an OWC with parametric resonance. These results are compared with those of a numerical model of a real experimental laboratory setup.     

Response of an annual cylindrical liquid column in zero-gravity

An annular liquid layer is subjected in a zero-gravity environment to harmonic axial- and pitching excitation. The liquid is treated as frictionless and is held together by free surface tension, which acts as the restoring force. The response of the system has been determined for the free surface elevation and the velocity distribution. It was found, that the first resonance response is sharply tuned and could easily be missed in a sweeping experiment. Damping was introduced in the resonance terms.     

一起上塔液悬故障的处理

简介了6000m^3／h空分设备上塔液悬故障的现象及原因，从减少上升蒸汽和回流液体两方面详细分析了消除液悬的措施。     

一起上塔液悬故障的处理

简介了6000m~3/h空分设备上塔液悬故障的现象及原因,从减少上升蒸汽和回流液体两方面详细分析了消除液悬的措施。     

Electrochemical assay of thrombin immobilized on carbon electrodes using an electrogenic and chromogenic substrate

The enzymatic and electrochemical features of an immobilized thrombin chemically modified electrode, operating as a voltammetric biosensor, are compared with the availability of a substrate permitting both an electrochemical and spectrophotometric assay of thrombin. Such a device enables the detection of products issued from the enzymatic hydrolysis inside the diffusion layer of the stationary electrode.     

Removal of lead (II) ions from synthetic and real effluents using immobilized Pinus sylvestris sawdust: adsorption on a fixed-bed column

The purpose of this work was to evaluate the potential of Pinus sylvestris sawdust, in a continuous flow removal of lead (II) ions from synthetic and industrial aqueous effluents. The kinetic parameters obtained in a batch process were used to scale-up the process on a mini-column and to choose the breakthrough model. The column experimental data concerning the volumes treated were correlated using the bed depth service time model. These experimental data closely fitted the bed depth service time model at 10% of the breakthrough curve. The results from the bed depth service time model on the mini-column were then used to design a pilot plant adsorption unit. The performance of the pilot plant column accurately agreed with that obtained from the mini-column. The experiments carried out in a dynamic reactor allowed to bring out the influence of various parameters on the efficiency of the P. sylvestris sawdust. In addition, the process was checked for the treatment of industrial aqueous effluents on a pilot plant scale and the results were in accordance with those obtained from synthetic effluents.     

On the buckling of a column in an elastic medium

One deals with the buckling of a cantilever column in an elastic medium by the aid of the differential eqns (2), (2′) with bilocal conditions (3), (3′). Introducing the conventional load (4), one considers the three cases P_cr < P₀, P_cr = P₀ and P_cr > P₀ and one determines the corresponding characteristics eqns (8″), (12), (15″). The reduced critical load P_cr/P₎ and the reduced critical length l_cr/l are listed in a table and plotted into diagrams for various values of an adimensional magnitude bl. One obtains also the asymptotic formulae (16), (16′).     

Capillary isoelectric focusing of proteins with liquid core waveguide laser-induced fluorescence whole column imaging detection

A capillary isoelectric focusing (CIEF) system with liquid core waveguide (LCW) laser-induced fluorescence whole column imaging detection was developed in this study. A Teflon AF 2400 capillary was used as both the separation channel and the axially illuminated LCW. The excitation light was introduced at one end of the capillary, and propagated forward within the capillary. As the Teflon AF 2400 capillary has a refractive index (n = 1.29-1.31) lower than that of water (n = 1.33), total internal reflection was very apparent The employment of the Teflon AF 2400 capillary avoided the use of high refractive index additives such as glycerol, accommodating the system to wider applications. Due to its inert chemical properties, the capillary exhibited limited protein adsorption and electroosmotic flow; thus, the need for capillary preconditioning with polymeric solution and the addition of polymeric additives into the sample mixture can be avoided. Three types of proteins, naturally fluorescent proteins, covalently labeled proteins, and noncovalently labeled proteins, were examined using this method. CIEF under denaturing conditions was also explored, and several advantages over the native mode were found. When compared to a commercially available instrument with UV detection, the separation efficiency and peak capacity were similar while the detection sensitivity was enhanced by 3-5 orders of magnitude.