Fast-fluorescence dynamics in nonratiometric calcium indicators

The fluorescence decay of high-affinity nonratiometric Ca2+ indicator Oregon Green BAPTA-1 (OGB-1) is analyzed with unprecedented temporal resolution in the two-photon excitation regime. A triple exponential decay is shown to best fit the fluorescence dynamics of OGB-1. We provide a model for accurate measurements of the free Ca2+ concentration and dissociation constants of nonratiometric calcium indicators.