Complicated answer 8^> : (para)formaldehyde fixation reduces GFP fluorescence
a little, and unless the cells are hazardous or the experiment is a long
one, I
don't see any reason to fix before running them.
I doubt that GFP will leak out of HCHO fixed cells; my understanding is
that there
is a great deal of cross-linking. On the other hand, ethanol fixation causes
immediate loss of GFP. Which brings me to ask: Does anyone have a good
protocol
for doing cell cycle with PI on paraformaldehyde fixed cells? One that
produces
halfway decent CVs?
-- David