Porosity gradient gels

After electrophoresis is over and the proper experimental data are gathered, they can be handled by two-step or one-step methods. Among the former, the most promising approach appears to be that of Lambin and Fine [76], who observed that there is a linear relationship between the migration distance of proteins and the square root of electrophoresis time, provided that time is kept between 1 and 8 h. The slopes of the regression lines of each protein are an indication of molecular size. When the slopes of the various regression lines thus obtained are plotted against the respective 

2) ExPASy Server (2D liver, plasma, etc. SWISS-(PROT, 2DPAGE, 3D1MAGE), BIOSCI, Melanie software) 

3) CSH QUEST Protein Database Center (2D REF52 rat, mouse embryo, yeast. Quest software) 

4) NCI/FCRDC LMMB Image Processing Section (GELLAB software) 

coli Gene-Protein Database Project-EC02DBASE (in NCBl repository) 

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Porosity gradient gels are prepared by continuously changing the acrylamide concentration... 

Equations for the pressure and drying stress distributions are given in a free gel body dried from both sides by Brinker and Scherer [1] for a number of different conditions. In most of the calculations a uniform porosity and permeability in the gel is assumed. This seems inconsistent with the above-mentioned differential strain (rate). According to Brinker and Scherer density gradients in dried gels are experimentally not observed and so must be small enough to be ignored in a first approximation. 

In order to avoid the development of the capillary gradient stresses responsible for the collapse of the porosity (and subsequently the surface area) of the dry solid, one must operate a process where the surface tension of the liquid phase is zeroed. Such a situation is easily realized by drying the wet gels above the critical temperature T , and pressure P, of the liquid phase (i.e., at supercritical temperature and pressure) because when one liquid reaches (or exceeds) its critical temperature, its surface tension vanishes. The critical parameters are functions of the chemical nature of the liquid for instance. Table 3.2 gives some values for common liquids. 

Here, 5 is the solid network stress and i)) the porosity, and a negative hquid pressure is considered as compressive equivalent equations hold for the y- and z-directions. For a small cube of gel or very low evaporation rates m, liquid can easily flow to keep pressure gradients negligible, and uniform can be assumed. Then, the liquid pressure is entirely balanced by the solid network stress a = lyPw (negative stress indicates compression), and the wet gel shrinks with no total stress, 0 = 0. If the gel has a purely elastic solid network, then volumetric strain, that is, relative volume change, is given by... 

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