BAPTA

BAPTA (1,2-bis(o-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid) is a calcium-specific aminopolycarboxylic acid. The presence of four carboxylic acid functional groups makes possible the binding of two calcium ions. The extensive flexibility of the carboxylate ligands is critical to the coordination of calcium and other metal ions.

There is a range of reported values for the dissociation constant of BAPTA, though 0.2 µM appears consistently. The rate constant for calcium binding is 500 µM⁻¹ s⁻¹.