Electrophoretic mobility concentration effect

Thus, under constant applied electric field, the mobility is determined primarily by the pore size of the gel matrix. In this case the so-called Ferguson plot gives the relationship between the gel concentration and the electrophoretic mobility (sieving effect). In this method, the logarithm of the electrophoretic mobility is plotted as a function of gel concentration. The intercept of this plot may be interpreted as being related to the charge on the solute and the intercept as related to its size or shape. Conversely, the separation and analysis of nucleic... 

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. 

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]. 

Electrokinetic (also called electromigration) injection is performed by placing the inlet of the capillary and an electrode in the sample vial. Following this a voltage is applied during a defined period of time. The sample constituents are actively carried into the capillary, and when present, the EOF also passively carries them into the capillary. For this reason, neutral compounds are also injected. The active migration is due to the effective electrophoretic mobilities of the constituents. The amount (B), in units of concentration injected into the capillary is expressed by [2,38]... 

Compounds 40—43 interacted with bovine brain-calmodulin as detected in a SDS-PAGE electrophoresis. Calmodulin treated with the lactones had lower electrophoretic mobility than untreated calmodulin. The effect was comparable to that of chlorpromazine, a well known calmodulin inhibitor. In addition, different concentrations of compounds 40 and 41 inhibited calmodulin-depen dent PDEl. The inhibitory activity of herbaru-mins 1 (IC50 = 14.2 xM) and II (IC50 = 6.6 xM) was higher than that of chlorpromazine (IC50 = 9.8... 

To evaluate + for each metal ion, values of p8 are required at each concentration. While this can often be evaluated from electrophoretic mobility data, the high ionic strengths—Le., pH < 2—preclude meaningful measurement of mobilities. However, it can be seen that when ij/s and cf)+ are equal and opposite then adsorption is reduced to zero. The adsorption of Na+ is reduced to zero at the z.p.c. since, in this case, + is negligibly small. With Ni2+ and Cu2+ the pH must be reduced—i.e., made more positive—by 1.3 pH units to effect zero adsorption. Since near the z.p.c. ips and i//0, the total double layer potential, are approximately equal and given by the Nernst Equation, then... 

The Effect of NaCl on the Electrophoretic Mobility of PS Latex Particle. The em of the Dow 357 nm latex in the H-form and Na-form, along with two other Dow monodisperse latexes in the H-form with diameters of 795 and 1100 nm, was measured as a function of NaCl concentration. The results in Figure 1 show that the em for all three latexes increased with increasing concentration of NaCl to a maximum at about 1 x 10 "2 M NaCl followed by a rapid decrease. Converting the electrophoretic mobility to zeta potential, using tables derived by Ottewill and Shaw (6) from the results of Wiersma et al. in order to account for relaxation and retardation effects, led to the same dependency as shown in Figure 2. 

The importance of PS in membranes for the distribution process can be derived from a study by Smejtek et al. [80] on aminopyridines. Aminopyridines are known to facilitate synaptic transmission at low calcium concentrations, an effect associated with the block of K+ channels. For a series of aminopyridines, the zeta-potential (Q of PS vesicles in the presence of such aminopyridines was determined. The zeta-poten-tial was determined from the electrophoretic mobility, x ... 

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