RELATION BETWEEN MAGNETICALLY-APPLIED FORCE AND VELOCITY IN BEADS COATED WITH RABBIT MYOSIN, SLIDING ON ACTIN CABLES IN NITELLOPSIS CELLS

We have succeeded in controlling the sliding movement of myosin-coated magnetizable beads on actin cables in Nitellopsis cells by the inhomo geneous magnetic field adjacent to a small, strong permanent magnet. T he relation between magnetic force acting on the bead and the bead vel ocity was, in many respects, similar to that obtained from the same sy stem by the use of centrifugal force (Oiwa et al., 1990). In particula r, force favouring the motion (negative load) had little effect on the velocity until it was sufficient to pull the bead off the actin, wher eas a relatively small positive load caused a reduction in velocity to a plateau value. Although the present method does not allow a good co ntrol of force direction, it demonstrates the promise of magnetic forc e in studying in vitro motility.