Chemists in the US have created fluorescent probes that can detect enzymes affecting our emotions.

The team, led by Christopher Chang at the University of California, Berkeley, is the first to develop chemical tools that measure directly monoamine oxidase (MAO) activity in living cells.

MAOs catalyse amine oxidation and the enzymes are responsible for breaking down amine-containing neurotransmitters such as serotonin and dopamine. Altered MAO activity levels have been linked with diseases such as depression and MAO inhibitors are often used to treat both depression and anxiety. Our MAO levels, determined by our genes, may also affect aspects of our personality, said Chang.

Chang's MAO probes are amine derivatives of the red-fluorescent dye, resorufin. The probes are oxidised by MAOs to give intermediates which break down to generate the dye. As MAO activity increases, more resorufin is produced, causing an increase in red fluorescence which is measured.

Monoamine oxidase enzymes catalyse molecular probes (left) to breakdown, eventually giving the dye resorufin

The new probes can move through cell membranes, making them capable of detecting MAOs within cells. Also, unlike earlier methods, these probes detect MAO activity directly without the need for external secondary activating enzymes or reagents.

In the future, said Chang, these tools could be used in drug discovery in screens for new inhibitors, or for diagnosis of diseases where altered levels of MAO activity are typical.

Sarah Corcoran