Gel pore size

The final step in the process of standardizing our columns was to try and maintain the high quality of columns from batch to batch of gel from the manufacturer. This was done by following the basic procedures outlined earlier for the initial column evaluation with two exceptions. First, we did not continue to use the valley-to-peak ratios or the peak separation parameters. We decided that the D20 values told us enough information. The second modification that we made was to address the issue of discontinuities in the gel pore sizes (18,19). To do this, we selected six different polyethylenes made via five different production processes. These samples are run every time we do an evaluation to look for breaks or discontinuities that might indicate the presence of a gel mismatch. Because the resins were made by several different processes, the presence of a discontinuity in several of these samples would be a strong indication of a problem. Table 21.5 shows the results for several column evaluations that have been performed on different batches of gel over a 10-year period. Table 21.5 shows how the columns made by Polymer Laboratories have improved continuously over this time period. Figure 21.2 shows an example of a discontinuity that was identified in one particular evaluation. These were not accepted and the manufacturer quickly fixed the problem. 

The separation of basic and metal-sensitive compounds is difficult on silica-based stationary phase materials, but these separations can be performed on vinyl alcohol copolymer gels. Examples are the separation of methallothionein from dolphin kidney, a-, j8-, and y-endorphin, and nucleotide and nucleoside mixtures.8 However, an analytical-scale separation may also be performed on surface-modified wide-pore silica gels (pore size 300 A or more), using columns which showed a negative response in the heavy metal test described above. 

Single columns of different pore size were used to determine the effect of gel pore size on degradation. 

In this paper we have immobilized an enzyme within a thermally reversible hydrogel. Immobilized enzymes have been used in a variety of applications, ranging from treatment of diseases to sensors, assays, and industrial processes (15-20). When an enzyme is immobilized within a gel which exhibits reversible shrinking and swelling as the ten rature is raised and lowered through the LCST of the gel matrix polymer, the enzyme may be switched off and on as the substrate diffusion rate is regulated by the gel pore size (5). In adcfition to enzymes, a variety... 

The method of immobilization of the SO, the nature of the matrix (organic polymer, silica gel, pore size distribution) and hence the flexibility and accessibility of coordination positions for SA molecules to the > Cu( II) SO moiety are crucial. 

Because a DNA molecule is a flexible polymer, the assumption in the Ogston model that DNA migrates as an undeformable particle loses validity with increasing size of DNA. The Ogston model predicts that the mobility of DNA with Rg larger than the pore size of the gel will approach 0. However, it actually was observed experimentally that DNA with its Rg larger than the gel pore size keeps migrating. 

We will now combine the mechanisms of size control and a thin starting zone. An electrophoretic matrix can be prepared into which discontinuities in pH and gel pore sizes as well as Kohlrausch conditions are incorporated. 

TABLE 3.9 EiYect of gel pore size on separation of charged biomacromolecules... 

Narayanan J, Xiong J-Y, Liu X-Y (2006) Determination of agarose gel pore size absorbance measurements vis a vis other techniques. J Phys Conf Ser 28 83-86... 

Current treatments of theoretical SEC models, then, express K5 q as a function of the ratio of a parameter of molecular size and gel pore size, or Rg/a, for random-coil polymers, where Rg is the radius of gyration. (See section 2.4 for discussions of Rg and the effective hydrodynamic volume). 

Gels are somewhat difficult to define as they combine the properties of liqnids and nonordeied solids one may characterize them by the fact that they retain their stmctural integrity and do not flow appreciably when removed from their container. However, for the molecnles that are significantly smaller than the gel pore size, the transport of material throngh a gel is similar to mass transport in a fluid (Figure 27). 

Polymerizing gel routes. Precursor metal organic compounds, e.g., alkoxides such as TEOS (tetraethylorthosilicate). Process acid catalyzed hydrolysis and condensation reactions to form gel. Pore sizes 1 to 5 nm. 

In electrophoresis Uterature, gel pore size estimates are oftai obtained from measurements of size dependent mobility of DNA fragments. The pore size estimates... 

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