Hydrodynamics of a DNA molecule in a flow field

The hydrodynamics of a single, fluorescing, DNA molecule held at one end by 'optical tweezers' and subjected to a uniform flow are compared with Monte Carlo simulations that account for the molecule's entropic elasticity, Brownian motion, and hydrodynamic drag. Using self-diffusion data and analytic expressions to obtain the drag in the limits of the undeformed coil and of the fully stretched thread, the predicted chain stretching and mass distribution are in quantitative agreement with measurements. The results explain the success of the nonlinear elastic 'dumbbell' model in predicting the rheological properties of dilute polymer solutions.