Figure 2

Calcium-association and -dissociation kinetics for the YTnC indicator investigated using stopped-flow fluorimetry. (a–c) Calcium-association kinetics curves for YTnC, GCaMP6f and NTnC, respectively. (d) Observed Ca²⁺-association rate constants determined from association curves for YTnC and control GCaMP6f and NTnC GECIs. For the YTnC indicator, fast (green) and slow (grey) exponents are shown. The solid lines represent the fitting curves to the equation k_obs = k_on × [Ca²⁺]ⁿ + k_off. (e) Relative contribution of monoexponents A₁/(A₁ + A₂) and A₂/(A₁ + A₂) for the YTnC indicator, where A₁ and A₂ are the pre-exponential factors in the association curve equation ΔFlu(t) = A₁ × exp(−k^on_obs1 × t)−A₂ × exp(−k^on_obs2 × t). The dots correspond to the A₁ and A₂ values, which were approximated by a linear equation (R² = 5.083). (f) Calcium-dissociation kinetics for YTnC, GCaMP6f and NTnC GECIs. Starting concentration of free Ca²⁺ was 1000 nM. Three replicates were averaged for analysis. Whiskers correspond to SD error.