Notes: ICR-1 is a cell-impermeable fluorescent calcium indicator. It binds to calcium (Kd = 480 nM) and displays excitation/emission maxima of 580/660 nm, respectively. ICR-1 can be used in lipid membrane-free systems or liposomes or can be introduced into cells by electroporation, microinjection, or other methods. ICR-1 is also available in a cell-permeable form (Item No. 34985).