Caesium chloride gradients

CsCl gradients can be used either instead of sucrose gradients, or as an additional purification step after sucrose gradients. CsCl gradients are formed automatically during centrifugation, from a single-density solution (isopycnic, or self-forming, gradients). This is a property of the heavy salt.

1. Resuspend the virus in its buffer (Table 4).  
2. Make the solution 1.37 g/ml CsCl; final concentration.  
This is the density where most picorna-like viruses will band.  
3. Centrifuge 28,000 rpm for 16-24 hours at 15oC-20oC.

Higher centrifugation speeds will create steeper gradients.