BAPTA
Chemical compound
BAPTA (1,2-bis(o-amino phenoxy)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.
01Complexation
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+.
There is a range of reported values for the dissociation constant of BAPTA, though 0.2 μM appears consistently. The rate constant for calcium binding is 500 μM−1 s−1. 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.
BAPTA is a component of some fluorescent calcium ion indicators such as Fluo-4, 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.
Sources and credits
This article is adapted from the Wikipedia article “BAPTA”, written by its contributors and licensed under CC BY-SA 4.0. Fathomly has changed the layout, removed citation markers, navigation and maintenance notices, and adjusted punctuation. This adapted version is shared under the same license. For references, see the original article.
Images, from Wikimedia Commons:
- BAPTA.svg by NEUROtiker (talk), Public domain
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