Do PI concentrations vary for measuring cell viability and DNA analysis???

From: Rana Nagarkatti (rana_nagarkatti@usa.net)
Date: Tue Jun 19 2001 - 13:19:42 EST


Dear Group,
 I was wondering if the above queston is actually true. The reason being that
I had done some calculations regarding the final conc of PI in various
protocols used for Viability and DNA analysis. and found that ususally for DNA
50ug/ml is the required conc ( for Flow- may be to maintain equilibrium in the
stream etc but any ideas for fluorimetry???)and for viability it is around
1ug/ml. What is the reason? Do higher conc of PI in the staining buffer mean
that more PI will enter the cells or is the cell totally impermeable to the
PI. or that the PI conc used for viability has been standardized based on a
concurrent experiment with say trypan blue or other methods? And how does time
of incubation after adding the dye relate to the conc. After all both the
methods are based on the same prinnciple that PI binds to DNA. Are there any
simple proportionalities involved here eg more the dye less the time or mmore
the dye more enters into the cells etc.
Thanks in advance for all the tips.
Rana Nagarkatti

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