BAPTA

Template:Chembox 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.

Complexation

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

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According to X-ray crystallography. the four carboxylates, two amines, and two ether oxygens bind to Ca²⁺.<ref>Template:Cite journal</ref>

There is a range of reported values for the dissociation constant of BAPTA, though 0.2 μM appears consistently.<ref name=pmid9763471>Template:Cite journal</ref> The rate constant for calcium binding is 500 μM⁻¹ s⁻¹.<ref name=pmid9763471/> 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.<ref>Template:Cite journal</ref>

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.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

See also

• EDTA
• EGTA
• Fura-2