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CLOCS Aequorin Calcium Calculator
Calcium concentrations are calculated by two different algorithms.
Algorithm #1
n (number of measurements)
Li (light intensity), counts measured at time point i.
Ltot (total counts), [L1 + L2... + Ln]
Lmax (remaining counts), Ltot - [L1 + L2... + Li]
KR (Ca2+ association constant)
KTR (equilibrium between binding states), [T]/[R]
nb (number of binding sites)
ratio = (Li/Lmax)(1/nb)
ratio + (ratio·KTR) - 1
Ca2+[i] = ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
KR - (ratio·KTR)
for normal aequorin:
KR (22°C) = 7.23; KR (37°C)= 7.23 · √
2; nb = 2.99; KTR = 120
for mutated aequorin:
KR (22°C) = 5.57; KR (37°C) = 5.57 · √
2; nb = 1.72; KTR = 4046
Brini et al. (1995) J. Biol. Chem 270, 9896-9903.
Allen et al. (1977) Science 195, 996-998.
Algorithm #2
Ca2+[i] = X · [10(log(Li/Lmax) - Y)](1/Z)
where Z = 2.0;
X = 1; Y = 9 for normal aequorin
X = 1.44; Y = 3.4 for the mutated aequorin.
Rutter et al. (1993) J. Biol. Chem 268, 22385-22390.
Mitchel et al. (2001) J. Cell Biol. 155, 41-51.
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