Fixing Cells with Paraformaldehyde ( PFA )
Prepare PFA from powder Dilute with PBS .
Store the undiluted stock at - 20°C until needed .
Add and equal volume of the 4 % stock to samples to end up with a final concentration of at most 2 % PFA .
Fix cells on ice for 15 - 30 minutes on ice , Wash 2x with PBS
