Size polyacrylamide gels

Polyacrylamide is a well-defined, stable, and rather inert gel with a pore size that can be easily varied. It is mechanically strong, easily handled, and transparent. Due to relatively small pore size, the eddy diffusion is low and hence contributes little to band broadening. However, due to the small pore size, polyacrylamide gels are less suitable for separation of very large molecules such as proteins with molecular mass >300 000 (300 kDa). 

Size Isomers. In solution, hGH is a mixture of monomer, dimer, and higher molecular weight oligomers. Furthermore, there are aggregated forms of hGH found in both the pituitary and in the circulation (16,17). The dimeric forms of hGH have been the most carefully studied and there appear to be at least three distinct types of dimer a disulfide dimer connected through interchain disulfide bonds (8) a covalent or irreversible dimer that is detected on sodium dodecylsulfate- (SDS-)polyacrylamide gels (see Electroseparations, Electrophoresis) and is not a disulfide dimer (19,20) and a noncovalent dimer which is easily dissociated into monomeric hGH by treatment with agents that dismpt hydrophobic interactions in proteins (21). In addition, hGH forms a dimeric complex with ( 2). Scatchard analysis has revealed that two ions associate per hGH dimer in a cooperative... 

N,]S2-diaHyltartardiamide (DATD) [58477-85-3] (37). The cross-linking of polymerized monomer with the comonomer is what controls the pore size of the gel polymer mesh. This level of pore size control makes polyacrylamide gel electrophoresis an effective analytical tool. 

Polyacrylamide gel electrophoresis is one of the most commonly used electrophoretic methods. AnalyMcal uses of this technique center around protein characterization, for example, purity, size, or molecular weight, and composition of a protein. Polyacrylamide gels can be used in both reduced and nonreduced systems as weU as in combination with discontinuous and ief systems (39). 

In the case of polyacrylamide gels, Stellwagen [367] found that buffer type (TAE vs TBE) did not affect the apparent pore size (21 mn for 10.5% T 5% C to 200 mn for 4.6% r/2% C), although more extreme variations in salt content and buffer physical properties may very likely strongly affect pore structure in polyacrylamide gels. 

FIG. 9 Polyacrylamide and agarose size distribution, (a) Agar gels, (b) polyacrylamide gels, and (c) agarose gels. (Reprinted with permission from Ref. 79, Copyright 1995, Academic Press.)... 

Richards, EG Temple, Cl, Some Properties of Polyacrylamide Gels, Nature 230, 92, 1971. Righetti, PG, On the Pore Size and Shape of Hydrophilic Gels for Electrophoretic Analysis In Electrophoresis 81 Walter de Gmyter Berlin, 1981 3. 

Stellwagen, NC, Apparent Pore Size of Polyacrylamide Gels Comparison of Gels Cast and Run in Tris-acetate-EDTA and Tris-borate-EDTA Buffers, Electrophoresis 19, 1542, 1998. Stellwagen, NC Gelfi, C Righetti, PG, The Free Solution Mobility of DNA, Biopolymers 42, 687, 1997. 

---