Acridine orange hydrochloride is a cell and organelle membrane permeable fluorescent dye that targets nucleic acids. Acridine orange can either be incorporated into double helical nucleic acids (detected by green fluorescence at 530 nm), or bind electrostatically to phosphate groups of single-stranded molecules (detected by red fluorescence at 640 nm), which renders it the ability to differently stain DNA and RNA or single-stranded DNA in situ. For unfixed cells, acridine orange staining can still be used as a simple, fast approach of obtaining information on cell cycle status and cell ploidy levels from DNA staining (green fluorescence), as well as cell transcriptional activity from RNA measurements (red fluorescence), in a flow cytofluorometric system. Thus, acridine orange may serve as a useful cytochemical stain for cell-cycle and apoptosis studies.?

References:

1.?McMaster GK, Carmichael GG. Analysis of single- and double-stranded nucleic acids on polyacrylamide and agarose gels by using glyoxal and acridine orange. Proceedings of the National Academy of Sciences of the United States of America, 1977, 74(11): 4835-4838.

2.?Traganos F, Darzynkiewicz Z, Sharpless T, et al. Simultaneous staining of ribonucleic and deoxyribonucleic acids in unfixed cells using acridine orange in a flow cytofluorometric system. Journal of Histochemistry and Cytochemistry, 1977, 25(1): 46-56.