Electrophoresis Ogston model

Morris [250] extended the Ogston model to gel electrophoresis. He found empirically that the product of parameters (/v) for gel filtration was proportional to the total monomer con-... 

Tietz, D, Evaluation of Mobihty Data Obtained from Gel Electrophoresis Shategies in the Computation of Particle and Gel Properties on the Basis of the Extended Ogston Model, Advances in Electrophoresis 2, 109, 1988. 

Figure 9.2 Native gel electrophoresis of the Tetrahymena P4—P6 RNA. (A) The folded and extended forms equilibrate rapidly, producing a single band whose mobility reflects the average structure of the RNA. U1, U2, BP5/5a refer to mutations in a hinge region. RNAs were run on native 6% (19 1 monorbis) polyacrylamide gel in TBE + 10 mM MgCl2 at 25 C. (B) Ferguson plot shows that the relative mobility (M) depends linearly on gel concentration, as predicted by the Ogston model. Reprinted from Szewczak and Cech (1997).

Tietz D (1988) In Chrambach A, Dunn MJ, Radola BJ (eds) Evaluation of mobility data obtained from gel electrophoresis strategies on the computation of particle and gel properties on the basis of the extended Ogston model, Advances in Electrophoresis, vol 2. VCH, Weinheim... 

Slater GW, Guo HE (1996) An exactly solvable Ogston model of gel electrophoresis I. The role of symmetry and randtunuess of the gel structure. Electrophoresis 17 977-988... 

The experimental literature on electrophoresis in polymer solutions invokes theoretical models, including the Langevin-Rondelez treatment(8), the Ogston model(9), and reptation-type models(4). The Langevin and Rondelez form treated in the last chapter is modified for electrophoresis by replacing 5 with /x and omitting the 7o/ 7 term, leading to... 

As seen in other chapters, the Ogston sieving model also does not describe sedimentation or diffusion through polymer solutions (cross-linked gels are a separate question not considered here), so its invocation in electrophoresis seems problematic. Conclusions about transport mechanics, drawn from relationships between measurements and a hypothesized Ogston model, are therefore subject to reservations. 

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]. 

Locke, BR Trinh, SH, When Can the Ogston-Morris-Rodbard-Chrambach Model be Applied to Gel Electrophoresis, Electrophoresis 20, 00, 1999. 

Figure 9.1 Models for macromolecular electrophoresis. (A) Reptation of long DNA fragments through a polyacrylamide gel. Redrawn from Bloomfield et al. (2000). (B) Ogston sieve model, which applies when Rg of the macromolecule is smaller than the diameter of the pore. (C) Scanning electron micrograph of the interior of a 7.5% (w/v) polyacrylamide gel. Reprinted from Yuan et al. (2006) with permission.

Locke, B. R., and Trinh, S. H. (1999). When can the Ogston-Morris-Rodbard-Chrambach model be applied to gel electrophoresis Electrophoresis 20, 3331—3334. 

FIGURE 12. Different mechanisms of the migration of DNA under an electric field through a sieving matrix (hydroxyethyl cellulose) in capillary electrophoresis. The mechanisms of DNA migration are (i) Ogston mechanism of sizing (ii) reptation model and (iii) reptation with orientation. 

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