Molecular motors: velocity speed-up, bidirectional motion and confinement-induced rectification
Paolo Malgaretti (University of Barcelona)
The energy-consuming motion of molecular motors is responsible form many cellular tasks, ranging from cargo transport, cellular signalling and cellular division. The performances of single motors are strongly affected by the environment in which they work. Variation in ATP concentration, viscosity of the cytoplasm due to molecular crowding and motor-motor interactions can strongly affect the overall performances of molecular motors. Here I will focus on how the cytoplasm molecular motors move in affects single as well collective molecular motors dynamics. On one hand I will show that, due to their reduced sizes and velocities, molecular motors move in the low Reynolds regime where the large range of the hydrodynamic interaction lead to collective behaviour not captured by the rigid-coupling picture. Such interaction lead to large velocity speed-up that can be up to two order of magnitude as compared to the single motor case. On the other hand hydrodynamic coupling can lead to spontaneous symmetry breaking when motors pulling on opposite direction act on the same cargo.
On the other hand the high concentration of suspended molecules and proteins in the cytoplasm as well as local geometrical confinement imposed by organelles or large vesicles in suspension can affect molecular motors dynamics.
I will show that the effective space motors can explore while moving along a filament lead to a local bias that, coupling to the motor intrinsic stepping mechanism, provides an alternative route to control molecular motors velocity.
 P. Malgaretti, I. Pagonabarraga, D. Frenkel « Running faster together: Huge Speed up of Thermal Ratchets due to Hydrodynamic Coupling, Phys. Rev. Lett. 109, 168101 (2012)
 P.Malgaretti, I. Pagonabarraga, J-F. Joanny, in preparation
 P.Malgaretti, I. Pagonabarraga, J. M. Rubi, Confined Brownian ratchets, J. Chem. Phys. 138, 194906 (2013)