Regulation of electroosmotic flow and electrophoretic mobility of proteins for concentration without desalting

Proteins were concentrated and separated in 0.6% poly(ethylene oxide) (PEO) solution using a capillary filled with Tris-borate (TB) buffer prior to analysis and detected by laser-induced native fluorescence using a pulsed Nd:YAG laser. During the concentration and separation, PEO solution entered the capillary by electroosmotic flow. When proteins dissolved in high salts (phosphate-buffered saline) were separated using 0.6% PEO solution prepared in 200 mM TB buffer, pH 9.0, the limits of detection (LODs) at signal-to noise ratios=3 for carbonic anhydrase (CA) and alpha-lactalbumin (alpha-lac) were on the levels of sub microM and microM, respectively. The LOD values compared to those obtained in 38 mM TB buffer were relatively high, which is likely due to salt quenching, Joule heating and poor stacking. To improve sensitivity for analysis of proteins in high-conductivity media, two on-line concentration approaches without desalting were developed. When using a capillary filled with 1.5 M TB buffer, pH 10.0, and PEO solution prepared in 800 mM TB buffer, pH 9.0, the LOD values for CA and alpha-lac were 13.8 nM and 126.0 nM, respectively, which were about 4.7 and 11.2-fold sensitivity enhancements compared to those obtained by a conventional hydrodynamic injection (30 cm height for 10 s), respectively. The sensitivity was further improved by injecting a short plug of low pH buffer after protein injection using a capillary filled with 1.5 M TB buffer, pH 10.0, and PEO solution prepared in 400 mM TB buffer, pH 9.0. A linear relationship between the peak height and the injection volume up to 0.81 microl was obtained and the LOD values for CA and alpha-lac were down to 4.7 and 37.8 nM.     

Electrophoretic mobility of a particle covered with an ion-penetrable membrane

The electrophoretic behavior of a planar particle covered by an ion-penetrable membrane, which simulates a biological entity, is investigated. We show that, in general, a point charge model will overestimate the electrophoretic mobility of a particle and the deviation increases with the increase in the concentration of fixed charge and with the decrease in the thickness of membrane layer. As in the case of a point charge model, the present model also predicts a local maximum in the absolute mobility as the thickness of membrane layer varies. If the sizes of counterions of various valences are the same, then the lower the valence of counterions, the larger the mobility, and the larger the counterions, the greater the mobility. The latter is consistent with the experimental observations in the literature. For the level of the concentration of fixed charge examined, the effect of coions on the mobility is negligible.     

Determination of trace amounts of mercury in water by neutron activation analysis with lubricating base oil as extractant.

This paper deals with a convenient method in the determination of trace amounts of mercury in water. After being irradiated with neutrons, water sample was treated with 7.0M HCIO4 solution and mercury was extracted with lubricating base oil. In such a simple operation, the sensitivity can reach 10(-8)g Hg/4ml H2O.     

Effect of ionic strength, pH and polymer concentration on the separation of DNA fragments in the presence of electroosmotic flow

DNA separations in the presence of electroosmotic flow (EOF) using poly(ethylene oxide) (PEO) solutions have been demonstrated. During the separations, PEO entered capillaries filled with Tris-borate (TB) free buffers by EOF and acted as sieving matrices. We have found that ionic strength and pH of polymer and free solutions affect the bulk EOF and resolution differently from that in capillary zone electrophoresis. The EOF coefficient increases with increasing ionic strength of the free TB buffers as a result of decreases in the adsorption of PEO molecules. In contrast, the bulk EOF decreases with increasing the ionic strength of polymer solutions using capillaries filled with high concentrations of free TB buffers. Although resolution values are high due to larger differential migration times between any two DNA fragments in a small bulk EOF using 10 mM TB buffers, use of a capillary filled with at least 100 mM TB free buffers is suggested for high-speed separations. On the side of PEO solutions, 1.5% PEO solutions prepared in 100 to 200 mM TB buffers are more proper in terms of resolution and speed. The separation of DNA markers V and VI was accomplished less than 29 min in 1.5% PEO solutions prepared in 100 mM TB buffers, pH 7.0 at 500 V/cm using a capillary filled with 10 mM free TB buffers, pH 7.0.     

Role of Microporosity of Activated Carbons on Their Adsorption Abilities for Phenols and Dyes

The amounts of adsorption of two commercial dyes, phenol, and 4-chlorophenol from water on activated carbons were measured at 30°C. The carbons were prepared from cane (bagasse) piths and were activated by steam. The activation temperature and time were in the ranges of 750–840°C and 2 h, respectively. It was shown that the isotherm data of all four solutes could be well fitted by the Langmuir equation under the conditions studied. The adsorption capacities of the solutes were correlated with the microporosity properties of the activated carbons including micropore volume and external surface area. Finally, the adsorption characteristics of the present carbons was compared with those prepared from various agricultural wastes.     

Drag on two nonuniformly structured flocs moving along the axis of a cylindrical tube

The boundary effect on the drag on two identical, nonuniformly structured flocs moving along the axis of a cylindrical tube filled with a Newtonian fluid is investigated at a small to medium larger Reynolds number. A two-layer model is adopted to simulate various possible structures of a floc, and the flow field inside is described by Darcy–Brinkman model. The results of numerical simulation reveal that a convective flow is present in the rear region of a floc when Reynolds number is on the order of 40. The presence of the tube wall and/or the porous structure of a floc has the effect of reducing that convective flow. For a fixed level of the volume-average permeability of a floc, the influence of the tube wall on the drag depends upon floc structure; the influence on a nonuniformly structured floc is more significant than that on a uniformly structured floc. The more nonuniform the floc structure, the more appreciable the deviation of the drag coefficient–Reynolds number curve from a Stokes’-law-like relation becomes. The smaller the volume-average permeability of a floc and/or the smaller the separation distance between the two flocs, the greater is the deviation, but the presence of the tube wall has the effect of reducing that deviation.     

Lithiation of a Silyl Ether: Formation of an ortho‐Fries Hydroxyketone

A hydroxy‐directed alkylation of an N,N‐diethylarylamide using CIPE‐assisted α‐silyl carbanions (CIPE=complex‐induced proximity effect) has been developed using a simple reagent combination of LDA (lithium diisopropylamide) and chlorosilane. A study of the mechanism, and the application of the procedure to an anionic Snieckus–Fries rearrangement for a highly efficient synthesis of the potent phosphatidylinositol 3‐kinase (PI3K) inhibitor LY294002, are reported.     

New correlation equations for predicting filter coefficient ratio of submicron particles at high ionic strength when the diffusiophoretic effect is considered

New correlation equations for the deep-bed filtration, including the term of diffusiophoresis, in addition to the Derjaguin and Landau, Verwey and Overbeek interactions, the Brownian diffusion and the interception, for predicting the initial collection efficiency under the favorable deposition condition and the filter coefficient ratio under the unfavorable deposition condition are derived by using the Brownian dynamics-simulation method. These new correlation equations for predicting the filter coefficient ratio are able to describe previous experimental results especially well for those submicron particles that are at high ionic strength.     

A Simple Approach for Multi‐fidelity Experimentation Applied to Financial Engineering

In practical applications, information about the accuracy or ‘fidelity’ of alternative surrogate systems may be ambiguous and difficult to determine. To address this problem, we propose to treat surrogate system fidelity level as a categorical factor in optimal response surface design. To design the associated experiments, we apply the Expected Integrated Mean Squared Error optimal design criterion, which takes into account both variance and bias errors. The performance of the proposed design was compared using three test cases to four types of alternatives using the Empirical Integrated Squared Error. Because of its ability to foster relatively accurate predictions, the proposed design is recommended in fidelity experimental design, particularly when the experimenters lack sufficient information about the fidelity levels of surrogate systems. The method was applied to the case of intraday trading optimization in which data were collected from the Taiwan Futures Exchange. We also calculated the implied volatility from the Merton's Jump‐diffusion model via the fast Fourier transform algorithm with three different models of varying fidelity levels. Copyright © 2014 John Wiley & Sons, Ltd.