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Updated: May 7, 2026

Measuring Phagosome pH by Ratiometric Fluorescence Microscopy
Published on: December 7, 2015
Quinoline-based fluorescent probe for ratiometric detection of lysosomal pH
Guoping Li1, Dongjian Zhu, Lin Xue
1Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences , Beijing 100190, P. R. China, and College of Chemistry, Beijing Normal University , Beijing 100875, P. R. China.
Abstract:
A new pH-responsive fluorescent probe has been reported based on protonation-activable resonance charge transfer. In aqueous solution, probe PQ-Lyso exhibits ratiometric detection of pH changes with a large hypsochromic shift of 76 nm and remarkable changes in the fluorescence intensity ratio (R = F(494 nm)/F(570 nm), R/R(0) = 105). Furthermore, PQ-Lyso, which is localized to lysosomes in living cells, can calibrate lysosomal pH using fluorescence ratiometry.
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