ISSN:
0173-0835
Keywords:
Chemistry
;
Biochemistry and Biotechnology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Isoelectric focusing (IEF) runs, e.g. on ultrathin gels, are characterized by an extensive change of gel electric parameters, caused by the rearrangement of carrier ampholyte components from a uniform distribution to a highly ordered pH gradient. A particularly important parameter is the specific resistance ϱ [Ohm*cm] which has been determined in polymerization mixtures (with and without carrier ampholytes) and in 125× 0.15 mm ultrathin gels, pH 3-10 with 5 %T, 3 %C, 5 % Servalyt carrier ampholytes, pH 3-10. The starting specific resistance ϱ of ultrathin IEF gels, calculated from the geometric gel dimensions and electric current values (V, mA), is in agreement with the data determined directly in 30 mL samples of polymerization mixtures by using a conductivity meter. Electric specific conductivity/Volthour (Vh) plots proved to be a valuable tool for the evaluation of gel systems with and without protein samples during IEP runs. These plots are usually S-shaped, indicating that the key part of pH gradient formation takes places in a relatively short time. A “good” ultrahin gel, after a short lag phase, shows a rapid increase in specific resistance due to a rapid pH gradient formation and a slope of about 18 Ohm*cm/Vh. IEF is finished in about 3000 Vh. After prolonged gel storage, and especially in partially dried gels, the electrical parameters approach equilibrium only slowly, as indicated by the relatively shallow slope (8.9 Ohm*cm/Vh). Accordingly, separations need more than 4000 Vh. In gels with salt containing samples, after normal IEF for about 1750 Vh, cracks appear, often followed by sparking at about 2700 Vh, accompanied by a sharp (often intermittent) drop in specific resistance.
Additional Material:
3 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/elps.11501301138
