Mammalian Muscle Properties Madden et al. IEEE J. Oceanic Engr. 29: 706, 2004

Skeletal muscle features Muscle surpasses artificial actuators only in the fuel delivery Linear actuation Adapted for intermittent duty and stiffness (compliance) control Versatile force control: recruitment + stiffness modulation (w/o feedback) Madden et al. IEEE J. Oceanic Engr. 29: 706, 2004

Hill model : Force dependence on contraction velocity

MotorSpecific Power Ergs/s-g Force (dynes) Velocity  m/s Actin Polymerization  tubule polymerization Myosin II Kinesin Spasmoneme ,000 Car Striated muscle Bacterial Flagella Limulus aroscome Eukaryote Flagella Mitotic spindle Hz 10 2

McKibben muscle

McK muscles Steel braid wrapped around a rubber tube. Crimped at ends

20N/g

Testing

Antagonistic pairs for smooth torque

Friction in the mesh Filament on filament friction (no sliding relative to the tube)

Properties of McK muscles 1. F static ~ CSA (  r o 2 ) 2. F static ~ P 3. F static is independent of initial length 4. F static max ~ 1/  o 5. F static ~ 1/ 

Molecular Springs & Ratchets Spasmoneme of the Vorticella Acrosome Actin polymerization Mahdevan, L : Science, 288: 95, 2000.

Spasmoneme of the Vorticella

Actin Spring Acrosome needs to penetrate egg jelly. Spring is super-coiled- held twisted by scruin. Ca++  s scruin

Supramolecular ratchets Pawl and ratchet analogy of actin polymerization How controlled? In quiescence, profilin is the shut-off switch. Stimulus such as pH   n presence of actin monomers can start. Listeria  rides  this bus

Overall energy balance

Conducting polymers Large molecular deformations (strains) induced by current Reversible Change in oxidation state

ATP SYNTHASE — A MARVELLOUS ROTARY ENGINE OF THE CELL< previous next >

How does muscle fatigue? Test of a ‘skinned’ muscle fiber from EDL of rat. Can activate by direct stimulation of any step in the cascade. Pederson, TH: Science 305: 1144, 2004

F1 ATPase: A rotary motor Can either make or break ATP, hence is reversible Torque of 40 pN-nM; work in 1/3 rev. is 80 pn-nM (40 * 2  /3) equivalent to free energy from ATP hydrolysis Can see rotation by attaching an actin filament

Rotary Cellular Motors The rotary mechanism of ATP synthase, Stock D, Gibbons C, Arechaga I, Leslie AGW, Walker JE CURRENT OPINION IN STRUCTURAL BIOLOGY,10 (6): DEC ATP synthase - A marvellous rotary engine of the cell, Yoshida M, Muneyuki E, Hisabori T NATURE REVIEWS MOLECULAR CELL BIOLOGY 2 (9): SEP The gamma subunit in chloroplast F-1-ATPase can rotate in a unidirectional and counter-clockwise manner Hisabori T, Kondoh A, Yoshida M FEBS LETTERS 463 (1-2): DEC Constructing nanomechanical devices powered by biomolecular motors.C. Montemagno, G Bachand, Nanotechnology 10: , 1999.

ATP SYNTHASE — A MARVELLOUS ROTARY ENGINE OF THE CELL< previous next >

Nature Reviews Molecular Cell Biology 2; (2001) ATP SYNTHASE — A MARVELLOUS ROTARY ENGINE OF THE CELL < previous next >

ATP SYNTHASE — A MARVELLOUS ROTARY ENGINE OF THE CELL< previous next >

Comparative motors

When L>>  the chain has many bends and is always crumpled in solution – the FJC model applies, with each link approximated as 2  and perfectly flexible joints. To count all possible curved states in a smooth-bending rod in solution- it’s a WLC- supercoiling is possible.

F1 ATPase: A rotary motor Can either make or break ATP, hence is reversible Torque of 40 pN-nM; work in 1/3 rev. is 80 pn-nM (40 * 2  /3) equivalent to free energy from ATP hydrolysis Can see rotation by attaching an actin filament

(