FIXATION and DNA Staining for Cell Cycle Analysis Protocol. This method of DNA staining utilizes ethanol to fix the cells and permeabilize the membrane, which allows the dye (Propidium Iodide) to enter the cells. Propidium Iodide (PI) is a DNA-binding fluorochrome that intercalates in the double-helix. Ribonuclease-A is used to eliminate the staining of double-stranded RNA.
