Electrophoretic concentration

Electrophoretic concentration techniques are based on the difference in mobility of an analyte in two separate zones, mainly due to differences in electric field strength between the zones.The main advantage of this type of concentration is that no modification of the basic instrument is required. 

Song, S., Singh, A.K., Kirby, B.J., Electrophoretic concentration of proteins at laser-patterned nanoporous membranes in microchips. Anal. Chem. 2004, 76, 4589—4592. 

R. Yamane, H. Motomura, T. Sata and Y. Mizutani, Characteristic properties of ion-exchange membranes prepared by Paste Method and analysis of the results of electrophoretic concentration of sea water, Nippon Kaisui Gakkaishi (Bull. Soc. Sea Water Sci. Jpn.), 1967, 20, 327-337. 

Fig. 14 Effects of tacrine and tamoxifen on mtDNA. The weak bases tacrine and tamoxifen ate protonated in the acidic intermembrane space of mitochondria and electrophoretically concentrated into the mitochondrial matrix. At these high ctmcentrations, they significantly intercalate between DNA bases, thus inhibiting mtDNA replication both directly and by inhibiting topoi-somerases. The decreased synthesis of mtDNA can lead to progressive mtDNA depletion...

As mentioned earlier, the TGF technique is mainly used for electrophoretic concentration and separation of the solutes, and thus the transport of the charged solutes needs to be modeled. For ease of analysis, it is assumed that there is no adsorption of sample solutes onto the capillary wall and no interaction between the sample solutes and the electrolyte components. In additimi, in the vast majority of microfluidic applications, the buffer concentration is many times (100 or more) higher than that of the sample solutes, and hence, the transport equation of the charged solutes can be formulated as... 

Song S et al (2004) Electrophoretic Concentration of Proteins at Laser-Pattened Nanoporous Membranes in Microchips. Anal Chem 76 4589-4592... 

As mentioned earlier, the TGF technique is mainly used for electrophoretic concentration and separation of the solutes, and thus the transport of the charged solutes needs to be modeled. For ease of analysis, it is assumed that there is no adsorption of sample solutes onto the capillary... 

A finite time is required to reestabUsh the ion atmosphere at any new location. Thus the ion atmosphere produces a drag on the ions in motion and restricts their freedom of movement. This is termed a relaxation effect. When a negative ion moves under the influence of an electric field, it travels against the flow of positive ions and solvent moving in the opposite direction. This is termed an electrophoretic effect. The Debye-Huckel theory combines both effects to calculate the behavior of electrolytes. The theory predicts the behavior of dilute (<0.05 molal) solutions but does not portray accurately the behavior of concentrated solutions found in practical batteries. 

The use of agarose as an electrophoretic method is widespread (32—35). An example of its use is in the evaluation and typing of DNA both in forensics (see Forensic chemistry) and to study heritable diseases (36). Agarose electrophoresis is combined with other analytical tools such as Southern blotting, polymerase chain reaction, and fluorescence. The advantages of agarose electrophoresis are that it requires no additives or cross-linkers for polymerization, it is not hazardous, low concentration gels are relatively sturdy, it is inexpensive, and it can be combined with many other analytical methods. 

Blotting techniques may be used in a variety and combination of electrophoretic systems which makes their use widespread and convenient when protein concentrations are minimal and agarose or polyacrylamide is the matrix choice. 

Process Objective UF is used for three principle objectives. First, to fractionate, to pass selectively one component through the membrane with the solvent. Second, to concentrate, to pass the solvent. These two, while different, are related and it is common to purify and concentrate a component siiTuiltaneously. The third objective, quite different, is to produce a solvent stream as a product. An example is the operation of an ultrafilter for producing low-cost permeate. An important apphcation of UF is in the automotive industiy where UF is used to remove water and microsolutes from huge electrophoretic paint tanks for use in rinsing excess paint (dragout) from... 

Fig. 1. Electrophoretic mobility of Hind lll-restrict fragments of X DNA after UV irradiation (A) and DNA electrophoregram trace (B) 1 - control, 2 - after UV irradiation for 3 hours (3.64 J/m2 ), 3, 4 - the same in the presence of Q-AR in concentrations of ICHM and lO M, 5, 6 - the same in the presence of Q-AR at concentrations of lO M and lO M. The arrow shows...

Overbeek and Booth [284] have extended the Henry model to include the effects of double-layer distortion by the relaxation effect. Since the double-layer charge is opposite to the particle charge, the fluid in the layer tends to move in the direction opposite to the particle. This distorts the symmetry of the flow and concentration profiles around the particle. Diffusion and electrical conductance tend to restore this symmetry however, it takes time for this to occur. This is known as the relaxation effect. The relaxation effect is not significant for zeta-potentials of less than 25 mV i.e., the Overbeek and Booth equations reduce to the Henry equation for zeta-potentials less than 25 mV [284]. For an electrophoretic mobility of approximately 10 X 10 " cm A -sec, the corresponding zeta potential is 20 mV at 25°C. Mobilities of up to 20 X 10 " cmW-s, i.e., zeta-potentials of 40 mV, are not uncommon for proteins at temperatures of 20-30°C, and thus relaxation may be important for some proteins. 

Rodbard and Chrambach [77,329] developed a computer program that allows the determination of molecular parameters, i.e., free mobility, molecular radii, molecular weight, and charge or valence, from measured electrophoretic mobilities in gels with different monomer concentrations. For a set of mobility versus gel concentration data they used the Ferguson [18,115,154] equation to obtain the retardation constant from the negative slope and the free mobility from the extrapolated intercept. From the retardation constant they determined the molecular radius using... 

The standard Rodbard-Ogston-Morris-Killander [326,327] model of electrophoresis which assumes that u alua = D nlDa is obtained only for special circumstances. See also Locke and Trinh [219] for further discussion of this relationship. With low electric fields the effective mobility equals the volume fraction. However, the dispersion coefficient reduces to the effective diffusion coefficient, as determined by Ryan et al. [337], which reduces to the volume fraction at low gel concentration but is not, in general, equal to the porosity for high gel concentrations. If no electrophoresis occurs, i.e., and Mp equal zero, the results reduce to the analysis of Nozad [264]. If the electrophoretic mobility is assumed to be much larger than the diffusion coefficients, the results reduce to that given by Locke and Carbonell [218]. 

Waldmann-Meyer, HK, Protein Ion Equilibria, Total Evaluation of Binding Parameters and Net Charge from the Electrophoretic Mobility as a Function of Ligand Concentration. In Recent Developments in Chromatography and Electrophoresis Frigerio, A McCamish, M, eds. Elsevier Scientific Amsterdam, 1980 Vol. 10, p 125. 

Mature human albumin consists of one polypeptide chain of 585 amino acids and contains 17 disulfide bonds. By the use of proteases, albumin can be subdivided into three domains, which have different functions. Albumin has an ellipsoidal shape, which means that it does not increase the viscosity of the plasma as much as an elongated molecule such as fibrinogen does. Because of its relatively low molecular mass (about 69 kDa) and high concentration, albumin is thought to be responsible for 75-80% of the osmotic pressure of human plasma. Electrophoretic smdies have shown that the plasma of certain humans lacks albumin. These subjects are said to exhibit analbuminemia. One cause of this condition is a mutation that affects spUcing. Subjects with analbuminemia show only moderate edema, despite the fact that albumin is the major determinant of plasma osmotic pressure. It is thought that the amounts of the other plasma proteins increase and compensate for the lack of albumin. 

---