New Biosensor Does Molecular Flash Dance

Scientists have developed a molecular flashbulb that's timed to go off when two molecules embrace. The finding, reported in today's issue of Science, could someday lead to ultrasensitive methods for screening potential drugs or fragments of pathogens in the blood and other bodily fluids.

To try to develop a more sensitive probe for isolating individual peptides--short strands of amino acids--from a pool of similar molecules, a team led by chemist Clark Still of Columbia University 4 years ago synthesized small organic compounds that selectively fish out peptides dissolved in chloroform. In their latest work, Still's team strung these molecules, called chemosensors, with a molecule called a fluorophore that glows when the sensor alters its shape after binding to a peptide. According to Still, the flash of just a single bound pair is bright enough to be seen by the naked eye--making it at least 300% more sensitive than previous chemosensors.

But the sensor has a major shortcoming that prevents it from being used to detect biologically important peptides--such as neurotransmitters or fragments of viral coat proteins--in biological samples: It doesn't work in water, the milieu of life. Still says he hopes to overcome this hurdle soon. Nevertheless, the new sensor is "quite an achievement," says Roger Tsien, a neurobiologist at the University of California, San Diego. "It's a conceptual breakthrough," adds chemist Paul Bartlett of the University of California, Berkeley, that "will turn on a lot of light bulbs."