At 11:22 15/3/2001, Juan Oliver M.D. wrote: >I have an embryonic pluripotent cell line that has a subpopulation of >cells with a spontaneous strong signal with a FACScalibur in FL3 (7AAD); >the remarkable finding is that this population of cells increases its >signal one log in FL3 after PI addition (FL2); >10 micoliters of 0.1 mg/ml into ~ 1ml. >Nobody in our facility can explain it; any suggestions would be appreciated. >Thanks, Juan Oliver My simple mind wants a simple explanation, here is my attempt: In most actively growing cultures I have seen, there are lots of dead cells. Assuming you're analysing the cells live from culture, the 7AAD will label dead cells. PI will also label dead cells, and it's emission will be bright in both FL2 and FL3; therefore the cells appearing in FL3 will be dead cells labelled additively with both 7AAD and PI. If the cells are fixed or otherwise permeablised, both 7AAD and PI should label any cell that has DNA. Hope that makes sense.... Joseph. -- Joseph Webster, Flow Cytometry Facility Centenary Institute, Sydney AUSTRALIA.
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