Question

Separation of cell organelles by differential centrifugation

Answer 1

Differential centrifugation (also differential velocity centrifugation) is a common procedure in biochemistry and cell biologyused to separate organelles and other sub-cellular particles on the basis ofsedimentation rate. Although often applied in biological analysis, differential centrifugation is a general technique also suitable for crude purification of non-living suspended particles (e.g. nanoparticles, colloidal particles,viruses). In a typical case where differential centrifugation is used to analyze cell-biological phenomena (e.g. organelle distribution), a tissue sample is first lysed to break the cell membranes and release the organelles and cytosol. The lysate is then subjected to repeated centrifugations, where particles that sediment sufficiently quickly at a given centrifugation force for a given time form a compact "pellet" at the bottom of the centrifugation tube. After each centrifugation, the supernatant (non-pelleted solution) is removed from the tube and re-centrifuged at an increased centrifugal force and/or time. Differential centrifugation is suitable for crude separations on the basis of sedimintation rate, but more fine grained purifications may be done on the basis of density throughequilibrium density-gradient centrifugation