Notes: IPG-4 AM is a membrane-permeable fluorescent potassium indicator that has been used to detect intracellular potassium.{62511} It binds to potassium (Kd = 7 mM) and displays excitation/emission maxima of 525/545 nm, respectively. IPG-4 AM is also available in a cell-impermeable form (Item No. 35539).