Does anyone know if there are any drawbacks to staining unfixed vs. fixed cells with propidium iodide? I am planning a high throughput screen for modulators of cell cycle progression in a 96-well format and would like to be able to skip the fixation step in order to speed up my protocol. I stained some cells today without fixing them (I just added a solution containing PI, triton x-100, and RNase to the cells) and it seemed to work very well. Cann anyone advise me on whether or not this strategy would work?
Thanks.

You can use the citrate staining protocol that does not require any fixation. That will reduce your hands-on time (slow addition of cold EtOH can be a pain even for a few samples!), but note that the incubation time for this protocol is longer (overnight+).