Speaker
Timo Ikonen
Description
We study the dynamics of flexible, semiflexible and
self-avoiding polymer chains under the Kramers metastable
potential. Due to thermal noise the polymers, initially in
the metastable well, can cross the potential barrier, but
these events are rare at low temperatures.
To speed up the slow rate processes in computer simulations
we employ the hyperdynamics method using the path-integral
representation of the relevant Langevin dynamics [1]. In
this study, we extend the method for many-particle systems
with internal degrees of freedom, such as the polymer chain.
We study the regime where the well size is comparable to
chain length. We find that the flexible, semi-flexible and
self-avoiding chains exhibit qualitatively different
behavior. For the flexible chain, the crossing rate
decreases monotonically with the polymer length (L), while
for the semi-flexbile chain the rate saturates at a level
that depends on the chain stiffness. For the self-avoiding
chain, on the other hand, the rate varies non-monotonically
with L. For L less than Lm, the rate decreases as L
increases, while for L > Lm, the rate increases
approximately linearly with L. We attribute this behavior to
the coil-to-stretch transition of the chain, which lowers
the effective free energy barrier and enhances the crossing
rate. This effect can be instrumental in efficient
separation of biopolymers.
[1] L. Y. Chen and N. J. M Horing, J. Chem. Phys. 126,
224103 (2007).
