Patent ID: 8198040

Claim:
A method of distinguishing dead cells from live cells comprising exposing a mixture of live and dead cells to a phenanthridium derivative of formula (II): wherein R 1 is alkyl having 1 to 6 carbon atoms, perfluoroalkyl having 1 to 6 carbon atoms, or tetra-alkyl ammonium; R 2 is a substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, or substituted or unsubstituted cycloalkyl having 3 to 10 carbon atoms; R 3 is amino, N-alkylamino, N,N-dialkylamino, alkoxy, or carboxyalkyl; and R 4 and R 5 are independently selected from the group consisting of hydrogen, halide, hydroxyl, amino, N-alkylamino, N,N-dialkylamino, alkoxy, carboxyalkyl, alkyl having 1 to 6 carbon atoms, perfluoroalkyl having 1 to 6 carbon atoms, azide, and tetra-alkyl ammonium; or a mono or bis halide salt thereof wherein the phenanthridium derivative has an overall charge of 2 + or higher.