How molecular knots can pass through each other
  We propose a mechanism in which two molecular knots pass through each other and swap positions along a polymer strand. Associated free energy barriers in our simulations only amount to a few $k_{B}T$, which may enable the interchange of knots on a single DNA strand. 
Benjamin Trefz, Jonathan Siebert and Peter Virnau
physics.bio-ph cond-mat.soft q-bio.BM