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1. •Collective motion of molecular motors, pumps, self propelled systems
   

Biological cells are typically micron-sized factories being run by nano-sized molecular motors which work in presence of strong fluctuations. Molecular motors like kinesins, dyneins (microtubule associated) or myosins (F-actin associated) use chemical energy derived from ATP hydrolysis, and exploits asymmetry of the polymeric tracks (microtubule or F-actin) to move in an overall unidirectional manner even in presence of strong thermal and chemical noise. Often these motors carry cargo in a cooperative manner. Even after decades of active research, the mechanism of how motor proteins work is not yet fully understood.

  

We recently built up a discrete model for stochastic particle pump interacting via hard core repulsion in presence of external periodic force that cancel over a whole period. Still at specific phase relations we obtain time-averaged directed motion of particles. This time-averaged directed current is a function of driving frequencies and phases. We find a particle-hole symmetry that led to a current reversal at half-filling of the system. We used stochastic simulations complemented by a perturbative calculation. Some of the results are published in Europhys. Lett. 94 (2011) 30006.We are currently extending this work to continuum Langevin dynamics of particle pumps and stochastic ratchet model of molecular motors to probe cooperative transport.