Dynamics of a tethered polymer in shear flow

The dynamics of a single polymer tethered to a solid surface in a shear flo w was observed using fluorescently labeled DNA chains. Dramatic shear enhan ced temporal fluctuations in the chain extension were observed. The rate of these fluctuations initially decreased for increasing shear rate (gamma)ov erdot and increased above a critical (gamma)overdot. Simulations revealed t hat these anomalous dynamics arise from a continual recirculating motion of the chain or cyclic dynamics. These dynamics arise from a coupling of the chain velocity in the flow direction to thermally driven fluctuations of th e chain in the shear gradient direction.