Figure 1.

(A) pH-dependency of normalized amplitudes of 514 nm absorbance (■, ●) and 528 nm emission (□, ○; excitation was at 510 nm) of EYFP (○, ●) and EYFP-V68L/Q69K (■, □). EYFP-V68L/Q69K is synonymous with “10C Q69K” (15). During the titrations, no shift in absorbance or emission maximum was observed. (B) pH-dependency of YC2 (●, ○ ) and YC2.1 (■, □). The emission ratios (528/476 nm) were measured in the presence of 100 μM CaCl₂ (■, ●) or 100 μM EGTA (□, ○) at various pHs. (Inset) Schematic structures of YC2.1 and YC2.