Molecular dynamics simulations of duplex stretching reveal the importance of entropy in determining the biomechanical properties of DNA.

Advances in nanomanipulation techniques have made it possible to measure the response of an individual biomolecule to a force applied in the laboratory. Experiments that stretch a single molecule of duplex DNA have been difficult to interpret theoretically, particularly as the major changes in molecular structure caused by the force cannot be measured. In principle, computer simulation can calculate these conformational changes in atomic level detail, but to date such studies have failed to reproduce the experimental data due to the computational expense of the calculations. Here we show that a combination of molecular modeling and statistical physics can be used successfully to understand the stretching behavior of DNA. Our simulations provide new information about the dynamics of DNA denaturation under force in atomic level detail and also show the importance of entropy in determining biomechanical properties in general.