  Recent work has shown that the resistive force arising from viscous effects
within the pore region could explain [Ghosal, S. Phys. Rev. E. vol. 71, 051904
(2006) and Phys. Rev. Lett. vol. 98, 238104 (2007)] observed translocation
times in certain experiments involving voltage driven translocations of DNA
through nanopores. The electrokinetic flow inside the pore and the accompanying
viscous effects also play a crucial role in the interpretation of experiments
where the DNA is immobilized inside a nanopore[U. Keyser, et al., Nature
Physics vol. 2, 473 (2006)]. In this paper the viscous force is explicitly
calculated for a nanopore of cylindrical geometry. It is found that the
reduction of the tether force due to viscous drag and due to charge reduction
by Manning condensation are of similar size. The result is of importance in the
interpretation of experimental data on tethered DNA.
