  Persistence length of dsDNA is known to decrease with increase in ionic
concentration of the solution. In contrast to this, here we show that
persistence length of dsDNA increases dramatically as a function of ionic
liquid (IL) concentration. Using all atomic explicit solvent molecular dynamics
simulations and theoretical models we present, for the first time, a systematic
study to determine the mechanical properties of dsDNA in various hydrated ionic
liquids at different concentrations. We find that dsDNA in 50 wt% ILs have
lower persistence length and stretch modulus in comparison to 80 wt% ILs. We
further observe that both persistence length and stretch modulus of dsDNA
increase as we increase the ILs concentration. Present trend of stretch modulus
and persistence length of dsDNA with ILs concentration supports the predictions
of the macroscopic elastic theory, in contrast to the behavior exhibited by
dsDNA in monovalent salt. Our study further suggests the preferable ILs that
can be used for maintaining DNA stability during long-term storage.
