Chapter nine - Acridine Orange as a Probe for Cell and Molecular Biology

Abstract

In the specialized field of fluorescent probes, the basic fluorescent dye acridine orange (AO) emerges as the most popular one. This chapter discusses the use of AO as a probe for cell and molecular biology. AO was synthesized in 1889, but its first biological applications were reported only in 1940. AO, 3,6-dimethylaminoacridine, is a weak base, which is readily soluble in water. It is usually prepared and sold as a zinc complex of a hydrochloride salt. The chapter covers different fields of AO application and pays more attention to some uses other than flow cytometry. Particular attention is paid to the most important works published in Russian and, therefore, largely inaccessible to Western readers. When used under appropriate conditions, AO acts as an excellent cytochemical probe for nucleic acids. It gives bright green fluorescence to DNA (nucleus) and deep red fluorescence to RNA (cytoplasm and nucleoli). An important condition for obtaining such a picture is proper fixation.