ExoSensor 517: a dual-analyte fluorescent chemosensor for visualizing neurotransmitter exocytosis.

A dual-analyte fluorescent chemosensor (ExoSensor 517) for the direct visualization of neurotransmitters released upon exocytosis is presented. The sensor exploits the high concentration of neurotransmitters (e.g., glutamate, norepinephrine, and dopamine) and the pH gradient between the vesicle and synaptic cleft. The cooperative recognition elements require both binding and a change in environmental pH to afford a fluorescence response which makes ExoSensor 517 one of the first integrated molecular logic gates to be used for biological applications.