  Biomolecular folding and function are often coupled. During molecular
recognition events, one of the binding partners may transiently or partially
unfold, allowing more rapid access to a binding site. We describe a simple
model for this flycasting mechanism based on the capillarity approximation and
polymer chain statistics. The model shows that flycasting is most effective
when the protein unfolding barrier is small and the part of the chain which
extends towards the target is relatively rigid. These features are often seen
in known examples of flycasting in protein-DNA binding. Simulations of
protein-DNA binding based on well-funneled native-topology models with
electrostatic forces confirm the trends of the analytical theory.
