... of the metal ion [45]. The addition of E64, a syn-thetic inhibitor of calpain, did not modify the intensityof the signal observed in the presence of Ca2+alone. The increase in the mAb-binding ... by evaluating the intensityof the light signal generated by the binding of mAb56.3.To perform these investigations, the two preferentialligands of calpain, Ca2+ions and calpastatin, were ... Ca2+ionophore A23187. In resting cells, calpain was poorlystained by the mAb, indicating that it was mainly pre-sent in the low-affinity form (Fig. 6A). Scanning the fluorescence throughout the cell revealed...