Master equation approach to molecular motors

A master equation approach to molecular motors allows to describe a mechano-chemical cyclic system where chemical and translational degrees of freedom are treated on an equal footing. A generalized detailed balance condition in the out of equilibrium regime has been shown to be compatible with the Fokker-Planck equation in the continuum limit. The Onsager relations hold for stationary states close to equilibrium, provided the generalized detailed balance condition is satisfied. A sensible coarse graining procedure is introduced to deal with the problem of the force dependence of transition rates in chemical kinetics models. Semi-phenomenological considerations in the case of motor proteins lead to a discrete kinetics model, for which interesting observable quantities can be directly calculated and compared with experimental data. The theoretical framework allows for a reduced set of parameters and accounts for the observed force dependence of the observables (velocity, Michaelis constant and randomness).