Evidence for the interaction between the calcium indicator 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid and calcium-binding proteins.

Stopped-flow and static difference spectroscopy experiments have shown that the calcium indicator 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA) interacts with several different calcium-binding proteins (beta-trypsin, parvalbumin, and calmodulin) and with serum albumin under experimental conditions commonly used in biophysical studies. The interaction decreases at high ionic strength. EDTA competes with BAPTA in the interaction with the proteins.