Synthesis and Characterization of Two Improved NMR Indicators for Cytosolic Ca2+: 3FBAPTA and 35FBAPTA

✍ Scribed by Louis A. Levy; Scott A. Gabel; Robert E. London

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 610 KB
• Volume: 34
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/(sici)1097-458x(199606)34:6<440::aid-omr901>3.0.co;2-m

✦ Synopsis

Fluorinated derivatives of the calcium-selective chelator BAPTA [ 1,2-bis(2-aminophenoxy)ethane-N,N,N,Ntetraacetic acid] are popular NMR probes for cytosolic calcium ion concentration. Two such derivatives were synthesized and evaluated, 3FBAPTA [ 1,2-bis(2-amino-3-fluorophenoxy)ethane-N,N,N,N-tetraacetic acid J and 35FBAPTA [ 1,2-bis(2-amino-3,5-difluorophenoxy)ethane-N,N,N,W-tetraacetic acid]. The dissociation constant ratios obtained at 37 "C were PDF/PDF = 0.60 and K","{PDF = 0.88; similar values were obtained at 25 'C. Hence 3FBAPTA binds calcium ions more tightly than SFBAPTA [ 1,2-bis(2-amino-5-fluorophenoxy)ethane-N,N,N,Ntetraacetic acid, the currently most frequently utilized indicator], while the doubly substituted derivative exhibits intermediate affinity. The dissociation rate constants for the calcium complexes measured at 37 "C exhibit a similar trend, with k? I > k3_5, > k? Both of the additional derivatives exhibit slow exchange kinetics, and should be superior fluorine NMR probes owing to the decreased TI values and, in the case of 35FBAPTA, the presence of two calcium-sensitive fluorine nuclei which are measured simultaneously.