Scientists have used chromophores for decades to detect chemicals, but, until Fido, they weren't sensitive enough to detect trace explosives because each molecule of TNT vapor would switch off just a single chromophore, with the result that faint wisps of evil chemicals caused no visible change in luminosity.

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Their original experiment used a genetic switch to regulate production of a particular receptor molecule for serotonin.

ECONOMIST: Sudden infant death syndrome

Last year Hewlett-Packard, along with a team of scientists from UCLA, proved the ability to make a switch that could be turned off and on, like a transistor, out of a single organic molecule called a catenane.

FORBES: The Science of Small

Last year Hewlett-Packard, along with a team of scientists from UCLA, proved that it is possible to make a switch that can be turned off and on, like a transistor, out of a single organic molecule called a catenane.

FORBES: The science of small