Chemistry: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.
Complexation
BAPTA, as its conjugate base, binds calcium ions as a decadentate ligand:
- [CH
2OC
6H
4N(CH
2CO
2H)
2]
2 + Ca2+ → Ca[CH
2OC
6H
4N(CH
2CO
2)
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
References
- ↑ Gerig, John T.; Singh, Phirtu; Levy, Louis A.; London, Robert E. (1987). "Calcium complexation with a highly calcium selective chelator: Crystal structure of ca(CaFBAPTA) ·5H2O". Journal of Inorganic Biochemistry 31 (2): 113–121. doi:10.1016/0162-0134(87)80056-9.
- ↑ 2.0 2.1 "The endogenous calcium buffer and the time course of transducer adaptation in auditory hair cells.". The Journal of Neuroscience 18 (20): 8261–77. 15 October 1998. doi:10.1523/JNEUROSCI.18-20-08261.1998. PMID 9763471.
- ↑ Csomós, Attila; Kontra, Bence; Jancsó, Attila; Galbács, Gábor; Deme, Ruth; Kele, Zoltán; Rózsa, Balázs; Kovács, Ervin et al. (Sep 2021). "A Comprehensive Study of the Ca2+ Ion Binding of Fluorescently Labelled BAPTA Analogues" (in en). European Journal of Organic Chemistry 2021 (37): 5248–5261. doi:10.1002/ejoc.202100948. https://chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/ejoc.202100948.
- ↑ "Fluorescent Ca2+ Indicators Excited with Visible Light—Section 19.3". https://www.thermofisher.com/de/de/home/references/molecular-probes-the-handbook/indicators-for-ca2-mg2-zn2-and-other-metal-ions/fluorescent-ca2-indicators-excited-with-visible-light.html.
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