In experiment, a single microtubule is constrained to move in only two dimensions, so that the entire filament is in focus and also it is simple to analyze its shape.
Using this technique, the flexural rigidity of microtubules was calculated to be,≈2.19±0.14×10-23 Nm2. If the inner and outer diameters of the microtubule are 18 and 30 nm respectively, then its area moment of inertia is: 6.155 ×10-32 m4. Then making the assumption that the filament is isotropic, its Young’s modulus can be calculated as, 0.356 ×109 N/m2 or 0.356 GPa. The persistence length of microtubule is obtained as 5200±200 μm.
These numbers for actin filaments: Flexural rigidity: 7.29 ± 0.44×10-26 Nm2. Young’s modulus: 2.6 GPa and the persistence length is obtained as 17.7 ± 1.1 μm
What its means is that the compliance of the cell is primarily due to the bending and sliding and filaments rather that due to stretching.
Young’s modulus for several other proteinaceous filaments:
Silk (Bombyx mori): 5-10 GPa
Keratin in wool: 4 GPa
Collagen: 0-2.5 GPa±
Rubber like proteins: elastin, resilin and abductin: 0.6 MPa |
