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. Due to its properties, it is used in research to chelate Ca²⁺, similarly to EGTA and EDTA.

BAPTA

Names
Preferred IUPAC name 2,2′,2′′,2′′′-[Ethane-1,2-diylbis(oxy-2,1-phenylenenitrilo)]tetraacetic acid
Identifiers
CAS Number	85233-19-8 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:60888 Y
ChemSpider	94562 Y
ECHA InfoCard	100.157.377
PubChem CID	104751
UNII	K22DDW77C0 Y
CompTox Dashboard (EPA)	DTXSID30234432
InChI InChI=1S/C22H24N2O10/c25-19(26)11-23(12-20(27)28)15-5-1-3-7-17(15)33-9-10-34-18-8-4-2-6-16(18)24(13-21(29)30)14-22(31)32/h1-8H,9-14H2,(H,25,26)(H,27,28)(H,29,30)(H,31,32) Y Key: FTEDXVNDVHYDQW-UHFFFAOYSA-N Y InChI=1/C22H24N2O10/c25-19(26)11-23(12-20(27)28)15-5-1-3-7-17(15)33-9-10-34-18-8-4-2-6-16(18)24(13-21(29)30)14-22(31)32/h1-8H,9-14H2,(H,25,26)(H,27,28)(H,29,30)(H,31,32) Key: FTEDXVNDVHYDQW-UHFFFAOYAD
SMILES O=C(O)CN(c2ccccc2OCCOc1ccccc1N(CC(=O)O)CC(=O)O)CC(=O)O
Properties
Chemical formula	C22H24N2O10
Molar mass	476.433
Density	1.494 g/cm3
Melting point	177 to 179 °C (351 to 354 °F; 450 to 452 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

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

BAPTA is a component of some fluorescent calcium ion indicators such as Calcium Green and Oregon Green 488 BAPTA-1 and -2 (OGB-1, OGB2). These indicators change their fluorescence intensity and fluorescence lifetime depending on the calcium ion concentration.^[2]