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Useful numbers

Hydrogen bond 20 kJ/mol = 8 kT
kT 2.5 kJ/mol
Maximum speed of myosin past actin 4 microns per sec
Maximum Myosin cycling frequency 40 Hz
Length of one myosin/actin filament 2 micron
Stress sustained by muscle 30 tons per m^2 = 43 psi
Muscle concentrations [ATP] =8.1 mM
[ADP] = 0.93 mM
[Pi] = 8.1 mM
Diffusion coefficient: ATP in cytoplasm 1.5 x 10-12 m2/sec 0.15 x 10-5 cm2/sec
D: PO4 in water ~10 x 10-12 m2/sec ~1 x 10-5 cm2/sec
D: O2 in water: 20 x 10-12 m2/sec 2 x 10-5 cm2/sec
D: CO2 in water: 16 x 10-12 m2/sec 1.6 x 10-5 cm2/sec
the diffusion coefficient for a sphere is: D = kT/(6 pi eta r )
For a sphere of one micron diameter in water at room temperature D = 4.4e-9 cm^2/sec = 4.4e-13 m^2/sec
Drag coefficient (in f = phi v) is phi = 6 pi eta r = 9.5e-6 g/sec = 9.5e-9 Kg/sec
Drag coefficient for a 5 nm sphere is phi = 6 pi eta r = 5e-8 g/sec = 5e-12 Kg/sec
Dissipation produced by one 5nm sphere moving at 4 microns per sec = phi v^2 = 5e-12 Kg/sec * 4e-6 m/sec * 4e-6 m/sec = 8e-23 J/sec
Dissipation per mole = 48J/sec = 1J per (Myosin cycle) (c.f. 40kJ or so free energy liberated)
Lengthscale of cell 20 micron

Site last modified Tue Jul 5 12:32:01 BST 2005