Electrokinetic DNA transport in 20 nm-high nanoslits: Evidence for movement through a wall-adsorbed (original) (raw)
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Electrophoresis, 2004
We study the effect of matrix chain molecular weight Mw and concentration c on the electrophoretic mobility μ of large linear and star-like, branched DNA in polymer solutions. Polyethylene oxide (PEO) with narrow molecular weight distributions form the main focus of this study. For PEO concentrations ranging from one half the overlap concentration, c*, to 3c*, the effective drag coefficient, ζ , satisfies the following approximate scaling relationship, ζ . Here, μ0 is the electrophoretic mobility in free solution. While the concentration dependence is consistent with predictions from the transient entanglement coupling (TEC) model, the molecular weight dependence is significantly weaker. Although a similar dependence of mobility on Mw can be predicted when nonentangling collisions are the dominant source of drag, a model based on these collisions alone cannot reproduce the experimental observations. We also find that the architecture of large DNA does not affect either the concentration dependence or molecular weight dependence of the electrophoretic mobility.
Electrophoretic mobility of linear and star-branched DNA in semidilute polymer solutions
Electrophoresis, 2006
Electrophoresis of large linear T2 (162 kbp) and 3-arm star-branched (NArm = 48.5 kbp) DNA in linear polyacrylamide (LPA) solutions above the overlap concentration c* has been investigated using a fluorescence visualization technique that allows both the conformation and mobility μ of the DNA to be determined. LPA solutions of moderate polydispersity index (PI ∼ 1.7–2.1) and variable polymer molecular weight Mw (0.59–2.05 MDa) are used as the sieving media. In unentangled semidilute solutions (c*<c<ce), we find that the conformational dynamics of linear and star-branched DNA in electric fields are strikingly different; the former migrating in predominantly U- or I-shaped conformations, depending on electric field strength E, and the latter migrating in a squid-like profile with the star-arms outstretched in the direction opposite to E and dragging the branch point through the sieving medium. Despite these visual differences, μ for linear and star-branched DNA of comparable size are found to be nearly identical in semidilute, unentangled LPA solutions. For LPA concentrations above the entanglement threshold (c>ce), the conformation of migrating linear and star-shaped DNA manifest only subtle changes from their unentangled solution features, but μ for the stars decreases strongly with increasing LPA concentration and molecular weight, while μ for linear DNA becomes nearly independent of c and Mw. These findings are discussed in the context of current theories for electrophoresis of large polyelectrolytes.