indo 1 (potassium salt)

Indo-1 (potassium salt) is a ratiometric fluorescent calcium indicator. It is ideal for analyses using flow cytometry, as it uses a single excitation source, typically 349-364 nm light from an argon-ion laser. The emission maximum shifts from 475-485 nm without calcium to 400-410 nm when Indo-1 (potassium salt) binds calcium. Indo-1 (potassium salt) is prone to photobleaching, which limits its usefulness in methods involving microscopy.

Rhod-2 (potassium salt) is a water-soluble, red fluorescent calcium indicator. It exhibits a significant shift in fluorescence intensity upon calcium binding (ex max = 549 nm; calcium-free v. ex em max = 552 581 nm; calcium-bound). Unlike the UV-excitable indicators fura-2 and indo-1 , there is no accompanying spectral shift.