2003/10/22 by Yacov Kantor, Mehran Kardar · 12 citations
Biochemistry, Genetics and Molecular Biology · Chemistry · Engineering · Physics and Astronomy · #Electrostatics and Colloid Interactions #Fuel Cells and Related Materials #Nanopore and Nanochannel Transport Studies #cond-mat.soft #cond-mat.stat-mech #q-bio.BM
paper · pdf · doi:10.1103/physreve.69.021806
published as Physical Review E 69, 021806 (2004) · 13 pages, RevTeX4, 16 eps figures
arxiv created 2003/10/22 · openalex publication_date 2004/02/26 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We consider the passage of long polymers of length N through a hole in a membrane. If the process is slow, it is in principle possible to focus on the dynamics of the number of monomers s on one side of the membrane, assuming that the two segments are in equilibrium. The dynamics of s(t) in such a limit would be diffusive, with a mean translocation time scaling as N2 in the absence of a force, and proportional to N when a force is applied. We demonstrate that the assumption of equilibrium must break down for sufficiently long polymers (more easily when forced), and provide lower bounds for the translocation time by comparison to unimpeded motion of the polymer. These lower bounds exceed the time scales calculated on the basis of equilibrium, and point to anomalous (subdiffusive) character of translocation dynamics. This is explicitly verified by numerical simulations of the unforced translocation of a self-avoiding polymer. Forced translocation times are shown to strongly depend on the method by which the force is applied. In particular, pulling the polymer by the end leads to much longer times than when a chemical potential difference is applied across the membrane. The bounds in these cases grow as N2 and N1+nu, respectively, where nu is the exponent that relates the scaling of the radius of gyration to N. Our simulations demonstrate that the actual translocation times scale in the same manner as the bounds, although influenced by strong finite size effects which persist even for the longest polymers that we considered (N=512).