Determination of intracellular pH using sensitive, clickable fluorescent probes

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We synthesized and evaluated a series of acidic fluorescent pH probes exhibiting robust pH dependence, high sensitivity and photostability, and excellent cell membrane permeability. Titration analyses indicated that probe 3 could increase its fluorescence intensity 800-fold between pH 8.0 and 4.1. Additionally, its pK a value is optimal for intracellular probing of acidic organelles. Fluorescent imaging of HepG2 and Hela cells further revealed that probe 3 demonstrates outstanding capacity for monitoring of intracellular [H +] levels. The easily accessible terminal alkyne/azido function groups of these probes offer the possibility of rapidly constructing sensor molecule libraries using 'click' chemistry. © 2011 Elsevier Ltd. All rights reserved.

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Bioorganic and Medicinal Chemistry Letters