Reacts with and covalently binds to cell-surface and intracellular amines Permeable plasma cell membranes, such as those present in necrotic cells, allow intracellular diffusion of dye and covalent binding to higher overall concentrations of amines than in non-permeable live cells Necrotic cells present in a typical in vitro assay label with higher levels of dye increases their fluorescence intensity 10-20 fold over viable cells Labeled cells can be fixed with formaldehyde for downstream decontamination, freezing and/or permeabilization and subsequent intracellular staining while maintaining stable viability stain fluorescence Excited by Red laser (with an excitation maximum of 649nm) and has fluorescence emission maximum of 660nm Flow cytometry, Intracellular staining