Question

Cell organelle gradient after sucrose density gradient centrifugation

Answer 1

Density gradient centrifugation can be performed either as rate zonal or as isopyknic centrifugation. In rate zonal centrifugation, the particles sediment as a narrow zone through a preformed gradient. This technique is used analytically for sedimentation rate measurements, and preparatively for separation of particles with different sedimentation coefficients. In isopyknic centrifugation, particles are separated purely on the basis of their density. Isopyknic centrifugation can be carried out both in preformed and in self-forming gradients. In self-forming gradients, the sample is mixed with the gradient medium, centrifuged, and as the solute molecules sediment to form the gradient, the sample molecules band at their isopyknic points. When preformed gradients are used, the size of the particles will affect the rate at which they reach their isopyknic positions.