ANEPPS dyes are fast responding membrane potential dyes. Biotium offers both Di-4-ANEPPS and Di-8-ANEPPS. Di-4-ANEPPS has the problem of being internalized in cells over long-term, so it is mainly used for short-term experiments. However, because Di-8-ANEPPS is more lipophilic, the dye is better retained in the outer leaflet of cell plasma membranes and thus more suitable for long-term membrane potential studies. Di-8-ANEPPS is also more photostable and less phototoxic than Di-4-ANEPPS.
