Ogston sieving mechanism

The retardation of the protein movement has been discussed qualitatively in terms of a sieving mechanism rather than a frictional resistance37). Ogston et al.39) have theoretically described the diffusion as a stochastic process in which the particles move by unit displacements and in which the decrease in the rate of diffusion in a polymer network depends on the probability that a particle finds a hole in the network into which it can move. The relationship derived from this approach is in close agreement with Eq. (35). 

If the sieving mechanism in the matrix is similar to that described by Ogston... 

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. 

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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