Shear-flow-induced unfolding of polymeric globules

Abstract

The behavior of a single collapsed polymer under shear flow is examined using hydrodynamic simulations and scaling arguments. Below a threshold shear rate γ̇*, the chain remains collapsed and only deforms slightly, while above γ̇* the globule exhibits unfolding/refolding cycles. Hydrodynamics are crucial: In the free draining case, γ̇* scales with the globule radius R as γ̇*∼R-1, while in the presence of hydrodynamic interactions γ̇*∼R. Experiments on the globular von Willebrand protein confirm the presence of an unfolding transition at a well-defined critical shear rate. © 2006 The American Physical Society.