Energy/entropy partition of force at DNA stretching

We compute by molecular simulation the energy/entropic partition of the force in a stretched double-stranded (ds)DNA molecule that is not yet available from the single-molecule measurements. Simulation using the coarse-grained wormlike chain (WLC) model predicts a gradual decrease in the internal (bending) energy of DNA at stretching. The ensuing negative energy contribution to force f(U) is outweighed by the positive entropy contribution f(S). The ratio f(U)/f, used to assess the polymer elasticity, is about -1 at the moderate extension of DNA. At the high extension, the extra energy expenses due to the contour length elongation make the ratio f(U)/f less negative. The simulation findings of the hybrid energy/entropy nature of DNA elasticity at weak and moderate forces are supported by computations using the thermoelastic method mimicking the polymer experiments in bulk. It is contended that the observation of the negative energy elasticity in DNA can be generalized to other semiflexible polymers described by the WLC model.

Automated summary

This study uses molecular simulation to compute the energy/entropic partition of force in stretched DNA, showing a decrease in internal energy and an increase in positive entropy contribution during moderate extension. It suggests that the negative energy elasticity in DNA can be generalized to other semiflexible polymers described by the WLC model.