Rate Zonal Centrifugation (density gradient) - (Jan/31/2010 )

This method states that you layer your sample atop a density gradient (i.e. sucrose) and centrifuge for a specific amount of time, this will separate the elements based on size and shape. But this method is also states that if you centrifuge for too long, then you'll pellet EVERYTHING in your sample. This part makes no sense. A density gradienty typically goes up to 1.8g/mL. Anything < 1.79g/ml within your sample will never get pelleted right?

the sample's unit density will be greater than the dense solution through which you are pushing it. it will, given enough time and centrifugal force, pellet.

mdfenko on Feb 1 2010, 10:32 AM said:

TI don't understand how this is different than equilibrium-gradient centrifugation (aka isopycnography) , which is based on the same premise of using a gradient. Only when you centrifuge, everything separates based on density.

Ahrenhase on Feb 2 2010, 04:45 PM said:

yes. but if you let it continue the "bands" will continue to migrate towards the bottom of the tube, albeit slowly.