Differential centrifugation

[3] Cellular organelles separated by differential centrifugation maintain a relatively high degree of normal functioning, as long as they are not subject to denaturing conditions during isolation.

Centrifugal force separates components not only on the basis of density, but also of particle size and shape.

When a centrifuge is used, Stokes' law must be modified to account for the variation in g-force with distance from the center of rotation.

An ultracentrifuge consists of a refrigerated, low-pressure chamber containing a rotor which is driven by an electrical motor capable of high speed rotation.

Sedimentation depends on mass, shape, and partial specific volume of a macromolecule, as well as solvent density, rotor size and rate of rotation.

Large values of S (faster sedimentation rate) correspond to larger molecular weight.

Elongated proteins have larger frictional coefficients, and sediment more slowly to ensure accuracy.