Efficiency of interacting molecular motors
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Efficiency of interacting molecular motors František Slanina [email protected] fzu.cz/~slanina PowerPoint PPT Presentation


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Efficiency of interacting molecular motors František Slanina [email protected] 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 motors František Slanina [email protected] fzu.cz/~slanina

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Efficiency of interacting molecular motorsFrantišek Slanina

[email protected]

www.fzu.cz/~slanina


Brownian motion


Maxwell demon

Heats

hot

Cools

cold


Smoluchowski ratchet


Granular ratchet


Feynman ratchet


On-off ratchet


Thermal ratchet


Pump: rocking ratchet


Quantum ratchet


Muscles


cytoskeleton


cytoskeletal traffic


Cell division


myosin

dynein

kinesin


Hand-over-hand mechanism


Neurons


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


Without interaction


(full)

(empty)


With interaction


Gained efficiency


At strong interaction


Response


Response


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…


Mean-field MF1


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


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