Seeing Previously Invisible Molecules for the First Time

Researchers have developed a new microscopic technique for seeing, in color, molecules with undetectable fluorescence. The room-temperature technique allows researchers to identify previously unseen molecules in living organisms and offers broad applications in biomedical imaging and research.

Fluorescence is a phenomenon in which an electron in a molecule absorbs energy from light and moves to a higher energy level or excited state. The energy of the light is contained in a unit called a photon.

After a very brief stay at the excited state, the electron returns to its previous energy level, or ground state, by emitting a new photon. The energy of the released photon is discharged in wavelengths of detectable visible light lasting only a few billionths of a second.

"Since these molecules do not fluoresce, they have literally been overlooked by modern optical microscopes," says X. Sunney Xie, a chemist at Harvard University.

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Image credit: X. Sunney Xie, Department of Chemistry and Chemical Biology, Harvard University