LENGTH DEPENDENCE OF DISPLACEMENT FLUCTUATIONS AND VELOCITY IN MICROTUBULE SLIDING MOVEMENT DRIVEN BY SEA-URCHIN SPERM OUTER ARM BETA-DYNEIN IN-VITRO

We have studied the dependence on microtubule length of sliding veloci ty and positional fluctuation from recorded trajectories of microtubul es sliding over sea urchin sperm outer arm beta dynein in a motility a ssay in vitro. The positional fluctuation was quantified by calculatin g the mean-square displacement deviation from the average, the calcula tion of which yields an effective diffusion coefficient. We have found that (1) the sliding velocity depends hyperbolically on the microtubu le length, and (2) the effective diffusion coefficients do not depend on the length for sufficiently long microtubules. The length dependenc e of the sliding velocity indicates that the duty ratio, defined as th e force producing period over the total cycle time of beta dynein inte raction with microtubule, is very small. The length independence of th e effective diffusion coefficient indicates that there is a correlatio n in the sliding movement fluctuation of microtubules. (C) 1997 Elsevi er Science B.V.