Electrophoresis cell

Phdnicin, Phdnizin, n. phenicin, phoenicin. Phoresezelle, /. electrophoresis cell. 

Fig. 11-4. UV trace of piperoxan enantiomers eluting from mini-prep electrophoresis cell.

Electrophoresis involves the movement of a charged particle through a liquid under the influence of an applied potential difference. A sample is placed in an electrophoresis cell, usually a horizontal tube of circular cross section, fitted with two electrodes. When a known potential is applied across the electrodes, the particles migrate to the oppositely charged electrode. The direct current voltage applied needs to be adjusted to obtain a particle velocity that is neither too fast nor too slow to allow for errors in measurement and Brownian motion, respectively. It is also important that the measurement is taken reasonably quickly in order to avoid sedimentation in the cell. Prior to each measurement, the apparatus should be calibrated with particles of known zeta potential, such as rabbit erythrocytes. 

Figure 8.1 Exploded view of an electrophoresis cell. The components of the Bio-Rad Mini-PROTEAN 3 are shown. The inner chamber can hold one or two gels. It contains an electrode assembly and a clamping frame. The interior of the inner assembly constitutes the upper buffer compartment (usually the cathode compartment). The chamber is placed in the tank to which buffer is added. This constitutes the lower (anode) buffer compartment. Electrical contact is made through the lid.

The electrical current in an electrophoresis cell is carried largely by the ions supplied by buffer compounds. Proteins constitute only a small proportion of the current-carrying ions in an electrophoresis cell. Buffer systems for electrophoresis are classified as either continuous or discontinuous, depending on whether one or more buffers are used. They are further classified as native or denaturing, depending on whether their compositions maintain or destroy protein structure and activity. 

Figure 8.5 Effect of pH on protein mobility. Hemoglobin A (pi 7.1) and Hemoglobin C (pi 7.4) were electrophoresed in eight of the McLellan native, continuous buffer systems (Table 8.1). The diagram is drawn to scale. Migration is from top to bottom as shown by the vertical arrows. Bands marked A or C indicate the positions of the two hemoglobin variants in each gel representation. The polarities of the voltages applied to the electrophoresis cell are indicated by + and - signs above and below the vertical arrows. Run times are shown below the arrows. Note the polarity change between the gel at pH 7.4 and the one at pH 8.2. This reflects the pis of the two proteins (and was accomplished by reversing the leads of the electrophoresis cell at the power supply).

FIG. 12.10 Velocity profiles in electrophoresis cells (a) velocity (as time-1) of Klebsiella aerogenes particles as a function of their location in a rectangular electrophoresis cell (redrawn with permission from A. M. James, in Surface and Colloid Science, Vol. 11 (R. J. Good, and R. R. Stromberg, Eds.), Plenum, New York, 1979) (b) location of the surface of zero liquid velocity in a cylindrical capillary. 

Electrophoretic mobilities of the alumina particles were determined for the same conditions as were used to obtain the adsorption isotherms. For this purpose, a sample of the alumina suspension was transferred to the electrophoresis cell for measurement of the electrophoretic mobilities. A Zeta-Meter was used for this part of the program. 

To test this idea, a Bio-Rad Protean II electrophoresis cell and Bio-Rad Model 3000xi computer-controlled power supply were used to carry out the electrophoretic separation and recovery of pre-stained and unstained protein calibration standards (lysozyme, soybean trypsin inhibitor, carbonic anhydrase, ovalbumin, bovine serum albumin and phosphorylase B) obtained from Bio-Rad Laboratories. Standard SDS-gel electrophoresis techniques were used [167]. 

Schwartz, D. C., and C. R. Cantor, Separation of yeast chromosome-sized DNAs by pulsed field gradient gel electrophoresis. Cell 37 67-75, 1984. 

The electrophoresis cell usually consists of a horizontal glass tube, of either rectangular or circular cross-section, with an electrode at each end and sometimes with inlet and outlet taps for cleaning and filling (Figures 7.5 and 7.6). Platinum black electrodes are adequate... 

Good descriptions of practical experimental techniques in conventional electrophoresis can be found in Refs. [81,253,259]. For the most part, these techniques are applied to suspensions and emulsions, rather than foams. Even for foams, an indirect way to obtain information about the potential at foam lamella interfaces is by bubble electrophoresis. In bubble microelectrophoresis the dispersed bubbles are viewed under a microscope and their electrophoretic velocity is measured taking the horizontal component of motion, since bubbles rapidly float upwards in the electrophoresis cells [260,261]. A variation on this technique is the spinning cylinder method, in which a bubble is held in a cylindrical cell that is spinning about its long axis (see [262] and p.163 in Ref. [44]). Other electrokinetic techniques, such as the measurement of sedimentation potential [263] have also been used. 

Electrophoresis can also be conducted on-line, as an element of industrial process monitoring and/or control. In this case a slip-stream sample is usually withdrawn from a process vessel, diluted in a mixing tank to reduce the sample turbidity, and then pumped through an electrophoresis cell that is fitted with stop-flow solenoid valves. The flow is stopped for long enough to make an electrophoresis measurement and then resumed. The sampling can be either intermittent or continuous. An example is described in reference [265]). 

Catsimpoolas N, Griffith AL, Skrabut EM, et al. 1976. Differential Cr uptake of human peripheral lymphocytes separated by density gradient electrophoresis. Cell Immunol 25 317-321. 

Fig. 79 Sketch of a continuous, carrier—free electrophoresis cell...

In [139] a new design of an electrophoresis cell with a flat rectangular chamber is presented in which the smallest cell dimension is arranged parallel and not perpendicular to the electric field. It is claimed that this arrangement allows a simple scale-up. 

Make the acrylamide/urea solution up to 99 ml with H20, add 0.8 ml 10% ammonium persulphate and 50 p TEMED (NNN N -Tetramethylethylene-diamine). Mix briefly by swirling and pour into the electrophoresis cell (Section 3.1.2.) making sure that no bubbles are trapped in the gel mixture. Insert the slot former (12—20 slots) made from a piece of Plasticard (Fig. 3.3.), place the gel raised slightly from the horizontal and put a weight over the top of the gel to ensure a tight fit of the slot former. 

Different pH in the two dimensions (De Wachter and Fiers 1972) In this method, separations are carried out at pH 3.5 and pH 8. The electrophoresis cell is that designed by Akroyd (1968) with altered dimensions. The two glass plates are for this purpose separated by 2 mm thick Perspex side walls (Fig. 8.6). The dimensions of the gels are 40 x 20 cm for the separation in the first dimension and 30 x 25 cm for the second dimension. 

After the run, a gel slice containing the RNA region is cut out with a scalpel or razor blade. The gel slice is put into the electrophoresis cell perpendicularly to the long axis, and set into the cell in a manner similar to that described above. The new acrylamide solution (20%) is poured into the cell and allowed to polymerise around and below the 10% strip. Because the 20% gel adheres tenaciously to the Perspex apparatus, it was found necessary to coat with fluorocarbon both the slot former and a region of about 2 cm around the two sides and bottom of the coolant plates that are in direct contact with the gel. Unless the cell is treated in this way, it is very difficult to remove the slot former after polymerisation or to dismantle the apparatus after the run. While the 20% gel polymerises, coolant is circulated to prevent the accumulation of air bubbles between the gel and the plates. Electrophoresis in the second dimension is carried out as in the first, but over a period of 17 hr at the same voltage. 

Zeta potential measurements are also performed on the NanoZS. All samples are diluted 1 10 (v v) with water. A folded electrophoresis cell is used (Malvern instruments GmbH, Germany) for Laser Doppler Anemometry (LDS) measurements. 

The cuvette or electrophoresis cell is placed in the NanoZS and allowed to equilibrate to the pre-set temperature (25°C). 

On the other hand, the intervening media used in electrophoresis have much lower conductivity, and an equivalent circuit for an electrophoresis cell includes a resistor between the capacitors at the electrode-solution interfaces. Across the support medium, potential is now (usually) a linear function of distance, and the electric field thus generated is responsible for driving the electrophoretic separation. Electrophoresis occurs at the electrodes used in electrophoresis, to maintain the... 

A few illustrations of home-made electrophoresis cells can be found in the older literature [225,250,251]. 

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