Centrifugation

Describe Major factors in selection of a tube (plastic) material

Clarity Chemical resistance Sealing mechanism (if needed)

Describe the Criteria for successful isopycnic separation

Density of the sample particle must fall within the limits of the gradient densities. Any gradient length is acceptable. The run time must be sufficient for the particles to band at their isopycnic point. Excessive run times have no adverse effect.

Describe the Criteria for successful rate-zonal centrifugation

Density of the sample solution must be less than that of the lowest density portion of the gradient. Density of the sample particle must be greater than that of the highest density portion of the gradient. The pathlength of the gradient must be sufficient for the separation to occur. Time is important. If you perform too long runs, particles may all pellet at the bottom of the tube.

How do you select the appropriate centrifuge tube

Prevents sample leakage or loss Ensures chemical compatibility Allows easy sample recovery

Describe the Properties of particle sedimenting through a liquid in a centrifugal field

Rate is dependent on diameter of particle Only sediments into stable pellet if gravitational field can overcome random thermal motion of particle Viscosity of liquid retards rate of sedimentation Density

What is the Purity of fraction determined by

measuring enzyme content