Fig. 1.

(a) Mean normalized Tyr (○) and Phe (●) fluorescence changes as a function of total [Ca²⁺] using Eq. 4. (b) Mean normalized Phe fluorescence change as a function of total [Pb²⁺] for the N-terminal domain with calculated K_d of 1.40 ± 0.30 µM. (c) Relative Tyr fluorescence as a function of Pb²⁺:CaM complex formation. The observed biphasic fluorescent response is divided into (d) Phase 1 with a calculated K_d of 0.73 ± 0.10 µM and (e) Phase 2 with a calculated K_d of 1.93 ± 0.32 µM. The calculated K_d for Phase 2 of the Tyr fluorescence falls within the standard deviation calculated for Phe fluorescence in the N-terminal domain.