BAPTA

BAPTA (1,2-bis(o-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid) is an aminopolycarboxylic acid with a high affinity for calcium. It is a white solid. It is used in research to chelate Ca²⁺, as it behaves 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

Complexation

BAPTA, as its conjugate base, binds calcium ions as a decadentate ligand:

[CH₂OC₆H₄N(CH₂CO₂H)₂]₂ + Ca²⁺ → Ca[CH₂OC₆H₄N(CH₂CO₂)₂]2−2 + 4 H⁺

According to X-ray crystallography. the four carboxylates, two amines, and two ether oxygens bind to Ca²⁺.^[1]

There is a range of reported values for the dissociation constant of BAPTA, though 0.2 μM appears consistently.^[2] The rate constant for calcium binding is 500 μM⁻¹ s⁻¹.^[2] The complexation process of calcium ion to BAPTA can be deconvoluted into three main processes: conformational changes of the glicol linker, nitrogen conjugation and electronic effects changes of the benzene rings.^[3]

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.^[4]

See also

• EDTA
• EGTA
• Fura-2