Density Rate zonal centrifugation

In rate-zonal centrifugation (or velocity sedimentation) the sample is loaded as a thin layer on the top of a density gradient medium. During centrifugation, the sample separates into bands, and the particles are separated on the basis of their different sedimentation coefficients (s). For biological particles, the coefficient s is mainly related to the size of the particles. This process is illustrated in Figure 13.7(a). 

Figure 18.4 Rate zonal centrifugation in a preformed liquid density gradient.

Figure 10.10 Rate-zonal centrifugation. (A) Sample layered over a continuous density gradient. (B) Position of zones due to different size of particles at the termination of centrifugation. Note that separation is due to differences in size and shape.

Density-gradient centrifugation, although not readily scalable, is a popular technique for final purification of viruses [Poison, 1993], Either rate-zonal centrifugation, where the separation is based on differences in sedimentation rate, or isopycnic equihbrium centrifugation, where the separation is based solely on density differences, is used. Further details on these techniques can be found in Dobrota and... 

Fig. 11. (a) Differential centrifugation (pelleting), where time 1 < time 2 < time 3 < time, (b) Rate zonal separation in a swinging-bucket rotor, where tube 1 represents the density gradient solution, tube 2 the sample plus the gradient, and tube 3 the separation of sample particles under a centrifugal force, where... 

Figure 3 Rate-zonal separations in a swinging-bucket rotor. (A) Centrifuge tube fiiied with density gradient soiution, (B) sample applied to top of gradient, and (C) under centrifugal force, particles move at different rates depending upon their mass. Courtesy of Beckman Coulter, Inc.)...

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