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A standard method for separating substances or objects on the basis of differences in density or size by applying a centrifugal force. In the simplest method particulate material is sedimented at the bottom of a tube, leaving a soluble supernatant. More complex methods involve the use of a density gradient and separating on the basis of size (which affects the rate of movement through a viscous solution), and density (which affects the equilibriuim position in the gradient). At very high g values (ultracentrifugation) it is possible to separate macromolecules (often on a caesium chloride density gradient), although this is now rarely done. In continuous centrifugation the supernatant is removed continuously as it is formed. See Svedberg units.

Subjects: Medicine and Health.

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