Flow cytometry of DNA content using oxazine 750 or related laser dyes with 633 nm excitation

Abstract
The laser dyes oxazine 750 (OX750), LD700, and rhodamine 800 (R800) can be used in an instrument employing a low-power heliumneon laser source for flow cytometry of DNA content in ethanol-fixed or detergent-permeabilized cells. Cells in near-isotonic medium are stained with 10–30 μM dye, and fluorescence excited at 633 nm. The dyes do not appear to stain RNA, and the intensity of DNA staining is not changed when 2 μMHoechst 33342 is added to cells simultaneously with redexcited dye. The effects on fluorescence of addition of DNA to LD700 or R800 in aqueous solution are strongly influenced by the base composition of the DNA; binding mechanisms remain to be determined.