Are you doing this assessment visually, or by flow cytometry?  In either case, propidium iodide wouldn't be my first choice for assessing viability.  It is quite cytotoxic, and unless you keep the concentration very low it will kill the cells.  It also requires use of a fluorescence microscope. One of the classic methods like trypan blue staining would be my preference for visual assessment.  It has low toxicity and can be viewed with a standard light microscope. If you do want to do the assessment visually by fluorescence, fluorescein diacetate would be my first choice. It's very fast acting and is not cytotoxic. For flow cytometric assessment PI can be used successfully if you keep the concentration very low. This is not a problem in flow cytometry because the cytometer is much more sensitive to low level fluorescence emission than the human eye is. But again, I find fluorescein diacetate a more reliable method for assessing viability by flow cytometry, for the same reasons mentioned above. 

> ----------
> From: 	histonet-bounces@lists.utsouthwestern.edu on behalf of William Ares
> Sent: 	Monday, April 16, 2007 3:14 PM
> To: 	histonet@lists.utsouthwestern.edu
> Subject: 	[Histonet] propidium iodide protocol
> 
> Does anyone have a protocol that they can share for use of propidium iodide to assess cell death in culture (medulloblastoma culture, if that makes a difference)?  I'm using both 96 well plates and 35ml flasks and Sigma Aldrich's Propidium Iodide Solution.  Thanks.
> 
> 
> William Ares
> Research Technician
> Laboratory of Molecular and Developmental Neuroscience
> Weill Medical College of Cornell University
> Tel: (212) 746 5056
> Email: wia2005@med.cornell.edu
> 
> 
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