Ca2+ binding kinetics of fura-2 and azo-1 from temperature-jump relaxation measurements.
The Ca2+-binding kinetics of fura-2 and azo-1 were studied using temperature-jump relaxation methods. In 140 mM KCl at 20 degrees C, the association and dissociation rate constants for fura-2 were 6.02 x 10(8) M-1s-1 and 96.7 s-1, respectively. The fura-2 kinetics were insensitive to pH over the range 7.4 to 8.4. Azo-1 was studied in 140 mM KCl, at pH 7.4, at 10 degrees and 20 degrees C. At 10 degrees C, azo-1 exhibited association and dissociation rate constants of 1.43 x 10(8) M-1s-1 and 777.9 s-1, respectively; while at 20 degrees C, the corresponding values were 3.99 x 10(8) M-1s-1 and 1,177 s-1. The kinetic results demonstrate that fura-2 and azo-1 are well suited to monitoring rapid changes in intracellular [Ca2+].
Kao
J P
JP
Department of Physiology-Anatomy, University of California, Berkeley 94720.
Tsien
R Y
RY
D001391:Azo Compounds; D001572:Benzofurans; D002118:Calcium; D005456:Fluorescent Dyes; D016257:Fura-2; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D013050:Spectrometry, Fluorescence; D013816:Thermodynamics
D001391:Azo Compounds; D001572:Benzofurans; D005456:Fluorescent Dyes; D002118:Calcium; D016257:Fura-2