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Efficiency of interacting molecular motors František Slanina slanina@fzu.cz www.fzu.cz/~slanina. Brownian motion. Maxwell d e mon. Heats hot. Cools cold. Smoluchows ki r atchet. Granular r atchet. Feynman r atchet. On-off ratchet. Thermal ratchet. Pump: rocking ratchet.
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Efficiency of interacting molecular motorsFrantišek Slanina slanina@fzu.cz www.fzu.cz/~slanina
Maxwell demon Heats hot Cools cold
myosin dynein kinesin
Ribosomes ASEP (B.Derrida)
RNA polymerase „traffic jams“ „Christmass tree“
Membrane tubes „traffic jam“
“reversible” ratchet Spatial periodicity Temporal periodicity
Potential Hopping probabilities Measured: expedited absorbed
(full) (empty)
Mean-field approximation Step I: “stroboscopic trick” Time within period which period Position within period Many hops per unit time Time-independent rates Time-independent master equation
Mean-field Step II: effective potential MF1 MF2 or: effective hopping probability Poisson distribution parameter
Mean-field or: effective hopping probability MF3
Recursion: first step For calculation of On condition particle at x On condition two particles at x
Recursion: second step For calculation of On condition particles at x and y Recursion: and so on…
Comparison of MF schemes MF2 MF1 simulation MF3
Phase diagram Non-optimizable phase MF1 MF1 simulation optimizable phase
Work distribution g = 0.12 g = 0
Energy balance current efficiency energy input
Large deviations Fluctuation theorem? l.d.f.
Conclusions • Efficiency increased by not too strong interaction • Current reversals when interaction and/or density increases • Energetic, rather than entropic effect • Complex behavior of response • Large deviations: non-Gaussian Outlook • Realistic model of myosin V • Clarify fluctuation symmetries Thanks: GAČR No. 202/07/0404