For discrimination of viable from non-viable mammalian cells in multicolor flow cytometric applications. BD Horizon™ Fixable Viability Stain 575V reacts with and covalently binds to cell-surface and intracellular amines. Permeable plasma cell membranes allow for the intracellular diffusion of the dye and covalent binding to higher overall concentrations of amines than in nonpermeable live cells.