  Nonlinear elastic responses of short and stiff polyelectrolytes are
investigated by dynamic simulations on a single molecule level. When a
polyelectrolyte condensate undergoes a mechanical unfolding, two types of
force-extension curves, i.e., a force plateau and a stick-release pattern, are
observed depending on the strength of the electrostatic interaction. We provide
a physical interpretation of such force-extension behavior in terms of
intramolecular structures of the condensates. We also describe a charge
distribution of condensed counterions onto a highly stretched polyelectrolyte,
which clarifies a formation of one-dimensional strongly correlated liquid at
large Coulomb coupling regime where a stick-release pattern is observed. These
findings may provide significant insights into the relationship between a
molecular elasticity and a molecular mechanism of like-charge attractions
observed in a wide range of charged biopolymer systems.
