May 27, 1980

New calcium indicators and buffers with high selectivity against magnesium and protons: design, synthesis, and properties of prototype structures

R Y Tsien


A new family of high-affinity buffers and optical indicators for Ca2+ is rationally designed and synthesized. The parent compound is 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA), a relative of the well-known chelator EGTA [ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid] in which methylene links between oxygen and nitrogen are replaced by benzene rings. BAPTA and its derivatives share the high (greater than 10(5)) selectivity for Ca2+ over Mg2+ of EGTA but are very much less affected by pH changes and are faster at taking up and releasing Ca2+. The affinity of the parent compound for Ca2+ (dissociation constant 1.1 x 10(-7) M in 0.1 M KCl) may be strengthened or weakened by electron-releasing or -withdrawing substituents on the aromatic rings. The Ca2+ and Mg2+ affinities may further be altered by replacing the ether oxygens by heterocyclic nitrogen atoms. The compounds described are fluorescent Ca2+ indicators absorbing in the ultraviolet region; the very large spectral shifts observed on binding Ca2+ fit the prediction that complexation should hinder the conjugation of the nitrogen lone-pair electrons with the aromatic rings. Derivatives with quinoline nuclei are notable for their hig...Continue Reading

  • References
  • Citations960


  • We're still populating references for this paper, please check back later.

Mentioned in this Paper

Calcium [EPC]
Tissue Membrane
Magnesium Measurement
Ethylene Glycol Measurement
Structure-Activity Relationship

About this Paper

Related Feeds

BRAIN Initiative Cell Census Network (BICCN)

The BRAIN Initiative Cell Census Network aims to identify and provide experimental access to the different brain cell types to determine their roles in health and disease. Discover the latest research from researchers in the BRAIN Initiative Cell Census Network here.