1.    It is often necessary to try more than one technique before finding the one that will work best with your cells.

2.    Some cell types tend to clump during the propidium iodide staining procedure.  If cell clumps are present, there is a good possibility that the cells cannot be analyzed since they will clog the sample intake line of the flow cytometer.

3.    You should always examine at least one of your sample tubes prior to bringing them to the FACS lab to see if clumping is present.  The easiest way to do this is with a hemacytometer and low power (10x or 20x) objective of a microscope.

4.    Please have your samples in Falcon #2063 tubes when you bring them to the lab.  THESE ARE THE ONLY TUBES THAT WILL WORK ON THE FACS.

5.    If the cells you are working with are adherent cells and you are using trypsin to detach them from culture dishes, you should not let these cells stay in the presence of trypsin for any length of time longer than necessary.