New imaging technique catches DNA ‘blinking’ on

Method avoids need for fluorescent dyes to see cellular molecules

fluorescing dna

LIGHTING UP  When stimulated with light, DNA “blinks” on, making cellular structures (chromosome shown) visible without the need for fluorescent dyes.

B. Dong et al/PNAS 2016

BOSTON — A new imaging technique takes advantage of DNA’s natural ability to “blink” in response to stimulating light.  The new approach will allow unprecedented views of genetic material and other cellular players. It’s the first method to resolve features smaller than 10 nanometers in unmodified, live cells, biomedical engineer Vadim Backman said February 17 at the annual meeting of the American Association for the Advancement of Science.

DNA and proteins don’t naturally give off light, conventional wisdom holds, so scientists have developed fluorescent dyes to attach to such molecules to make them visible in the darkness of a cell (SN: 6/5/13, p. 20). But Backman and Hao Zhang, both of Northwestern University in Evanston, Ill., discovered that when DNA is tickled with particular wavelengths of light, it “blinks” on, momentarily shining brighter than it would with the most powerful fluorescent tags. Backman and Zhang designed a setup that excites cells with light and then collects the spectra of the emitted light, allowing them to discern different kinds of biomolecules.

The scientists are calling their setup SICLON, for spectroscopic intrinsic-contrast photon-localization optical nanoscopy. They have already used it to peer at the inner walls of microtubules, structures that help separate chromosomes during cell division. The approach has allowed the researchers to collect images of structures a mere 6.2 nanometers across (a DNA molecule is roughly 3 nanometers across). The researchers hope to explore physical changes that occur when cells become cancerous, Backman said.

Editor’s note: This story was updated March 1, 2017, to clarify the description of the imaging technique. 

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