DRAQ5 Labeling of Nuclear DNA in Live and Fixed Cells

Abstract This unit describes the use of a novel DNA‐detecting far‐red‐fluorescing dye, DRAQ5, a modified anthraquinone, which has a unique combination of properties exploitable by cytometry. These include a high capacity to permeate the cell membrane, a high DNA binding affinity and selectivity, a fluorescence emission spectrum beyond that of fluorescein, phycoerythrin, Texas Red, Cy3, and EGFP, and excitation characteristics separate from those of propidium iodide. In this unit, methods are presented for preparation and analysis of both live and fixed cells stained with DRAQ5. While the focus is on flow cytometric assays, typical imaging applications are also indicated because the staining protocols share the same essential features.