BAPTA is a calcium-selective chelator developed by Dr. Tsien. It has logKCa=6.97 and logKMg=1.77. The basic chelating unit resembles that of EGTA, but the two aliphatic nitrogen atoms are replaced by aromatic nitrogen. Thus, BAPTA is not protonated at physiological pH. BAPTA possesses pKa3=5.47 and pKa4=6.36. This property indicates that the deprotonation step is not included in its calcium complexation step, and it has a higher complexation rate than EGTA because it is not affected by proton interference. BAPTA-AM is an acetoxymethyl ester derivative of BAPTA that can be easily loaded into cells using the AM method. BAPTA-AM is useful for controlling the intracellular calcium concentration.
Hydrolysis of AM ester
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