Net motion of a charged macromolecule in a ratchet-slit†
Abstract
Hydrodynamic effects in a ratchet channel may produce counterintuitive phenomena. We report herein a net motion investigation of a charged macromolecule in a ratchet-slit under an AC electric field using explicit solvent molecular dynamics. A negative net motion was discovered and complex responses to the slit structure, external electric field and charge distribution were explored. It has been demonstrated that the complex responses originate from the competition among three ratchet forces in the diffusion of macromolecules, i.e. the entropy force, solvent dissipative force and conformation inversion resistance (the first force produces positive net motion, while the other two contribute to the negative net motion together). This new transport mechanism can be applied to developing novel effective techniques for the separation of bio-macromolecules with different charge sequences.