8.592 - HST.452J (Spring 2026)

Statistical Physics in Biology

Lecture 14

Molecular Motors

1. Molecular motors:
   • Kinesin and Dynein move in opposite directions along microtubules consuming ATP
   • Myosin moves on actin filaments (offline animation) [youtube]
   • Ron Vale's iBiology lecture on kinesin discovery (offline animation)
2. General scheme of motor transport:
• Asymmetry for directionality
• Rectification of fluctuations by consumption of energy
3. Motion in a noisy environment

• Feynman's ratchet and pawl:  (youtube)                
•       (R. Di Leonardo, et al PNAS 2010)
• Simulation of a (flashing ratchet) Brownian motor      (BrownianMotor.html)
• (flashing ratchet video)   (Brownian Ratchet)

• Asymmetric hopping models:

• "The force exerted by a molecular motor," M.E. Fisher & A.B. Kolomeisky, PNAS 96, 6597 (1999).
• Multiple internal states
• Solution with two internal state
• Einstein force, stalling force
• Efficiency at maximum power; T. Schmiedl & U. Seifert EPL

(Lecture notes)

Some related links

• Kinesin Home Page
• Kinesin Motors - the Movies
• The inner life of a cell
• Capturing and viewing single molecules:
  • Optical tweezers
  • Fluorescent light microscopy
• "Ratchets, power strokes, and molecular motors," H. Wang & G. Oster, Appl. Phys. A 75, 315 (2002).
• "The physics of molecular motors," C. Bustamante, D. Keller, & G. Oster, Acc. Chem. Res. 34, 412, (2001),