  Here we report on the translocation of folded polymers through nano-pores
using molecular dynamic simulations. Two cases are studied; one in which a
folded molecule unfolds upon passage and one in which the folding remains
intact as the molecule passes through the nano-pore. The topology of a folded
polymer chain is defined as the arrangement of the intramolecular contacts,
known as circuit topology. In the case where intramolecular contacts remain
intact, we show that the dynamics of passage through a nano-pore varies for
molecules with differing topologies: a phenomenon that can be exploited to
enrich certain topologies in mixtures. We find that the nano-pore allows
reading of topology for short chains. Moreover, when the passage is coupled
with unfolding, the nano-pore enables discrimination between pure states, i.e.,
states for which the majority of contacts are arranged identically. In this
case, as we show here, it is also possible to read the positions of the contact
sites along a chain. Our results demonstrate the applicability of nano-pore
technology to characterize and sort molecules based on their topology.
