Acridine Orange

Acridine Orange

After entry into an acidic granule, Acridine Orange (AO) becomes protonated and thus trapped within the granule membrane. The resulting high concentrations in the granules results in a red-shift and self-quenching. Upon granular alkalization, as occurs in exocytosis, AO is neutralized and thus can again cross the granular membrane.

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Acridine Orange After entry into an acidic granule, Acridine Orange (AO) becomes protonated and thus trapped within the granule membrane. The resulting high concentrations in the granules results in a red-shift and self-quenching. Upon granular alkalization, as occurs in exocytosis, AO is neutralized and thus can again cross the granular membrane.


Two-color imaging allows quantification of granule alkalization events upon cell stimulation.