Ca2+ indicator component

2',7'-Difluorofluorescein (Oregon green 488) is a fluorescein derivative and a pH-sensitive fluorescent probe (pK_a ~4.7). Upon excitation at 488 nm, 2',7'-Difluorofluorescein exhibits pH-sensitive fluorescence intensity through the formation of dianions, while its pH sensitivity decreases under excitation at 450 nm, allowing its use in ratiometric pH analysis. 2',7'-Difluorofluorescein can be used for the quantitative analysis of pH values in the range of 2-7 in submicron aerosol particles. 2',7'-Difluorofluorescein undergoes buffer-mediated and buffer-free excited-state proton transfer between different protonated forms, and its cationic form undergoes rapid excited-state deprotonation. 2',7'-Difluorofluorescein is resistant to photodegradation, maintains stable absorption and fluorescence properties within the physiological pH range, and serves as a fluorescent protein label, a component of Ca ²⁺ indicators, a fluorescent imaging agent, and an anisotropy probe .