ACTIN-FILAMENTS ON MYOSIN BEDS - THE VELOCITY DISTRIBUTION

In vitro studies of actin filaments sliding on a myosin-coated surface are analyzed, filament by filament, at a sampling rate of 30 per seco nd. For each filament, the mean are length coordinate is computed and histograms of instantaneous velocities, along the are length, are esta blished. Two types of motion are observed, depending on the experiment al conditions. The first one is characterized by a homogeneous flow, w ith well defined velocities. In this regime, specific defects are a co nstitutive part of the flow. It is observed at high temperature, at hi gh myosin coverage, and with a particular mode of attachment of myosin to the surface. The second regime shows no clear velocity selection, but a broadband distribution. It is characterized by high friction and is observed at low temperature or low myosin density.