| pubmed-article:2619036 | pubmed:abstractText | Using fundamental concepts of hydrodynamics in porous media, we have rederived the Lumpkin-DèJardin-Zimm (LDZ) model for the gel electrophoresis of reptating, infinitely long, worm-like chains, such as DNA. The force balance provides a constraint for evaluating the correlation among the segment-to-field angles of a given molecular conformation. We have used an approximate analytical expression to account for this correlation in order to apply the present derivation to finite chain lengths. The resulting extended LDZ model predicts a nonlinear variation of electrophoretic mobility (mu) with reciprocal chain length (1/Lc) at low electric field strengths, similar to the one observed. The present derivation is valid only at low electric field strengths, and the predictions of the extended LDZ model fit data for a dimensionless electric field strength, E1*, of less than 1.23. An empirically useful criterion for determining the onset of reptation is also described. The present treatment shows how size-exclusion effects can be included in future theories. Models based on reptation alone are shown to predict a discontinuity in the molecular chain length dependence of mobility at a critical molecular size. Such discontinuities are not observed experimentally. | lld:pubmed |
