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. 1988 Apr;53(4):635-9.
doi: 10.1016/S0006-3495(88)83142-4.

Ca2+ binding kinetics of fura-2 and azo-1 from temperature-jump relaxation measurements

J P Kao  1 , R Y Tsien
Affiliations

Ca2+ binding kinetics of fura-2 and azo-1 from temperature-jump relaxation measurements

J P Kao et al. Biophys J. 1988 Apr.

Abstract

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+].

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