  The continuum-rod model has emerged as an efficient tool to describe the
long-length-scale structural-deformations of DNA which are critical to
understanding the nature of many biological processes such as gene expression.
However, a significant challenge in continuum-mechanics-based modeling of DNA
is to estimate its constitutive law, which follows from its interatomic
bond-stiffness. Experiments and all-atom molecular dynamics (MD) simulations
have suggested that the constitutive law is nonlinear and non-homogeneous
(sequence-dependent) along the length of DNA. In this paper, we present an
estimation method and a validation study using discrete-structure simulations.
We consider a simple cantilever-rod with an artificially constructed, discrete
lattice-structure which gives rise to a constitutive law. Large deformations
are then simulated. An effective constitutive-law is estimated from these
deformations using inverse methods. Finally, we test the estimated law by
employing it in the continuum rod-model and comparing the simulation results
with those of discrete-structure simulations under a different cantilever
loading-conditions.
