We’ve told you before, but we’re glad to tell you again: Just about anything will glow if you give it the opportunity. The latest entry in the ency-glow-pedia? DNA. In a recently published paper in the Proceedings of the National Academy of Sciences, researchers described seeing DNA molecules blinking like Christmas lights. 

Along with carbohydrates, fats, and proteins, deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are part of the group known as macromolecules. These big molecules make up the bulk of your cells and are therefore pretty darn important. Many scientists have spent many years studying macromolecules under microscopes, but they often come up against a frustrating obstacle: stains. (No, not that Stains.)

One of the most essential tools in biology today is the fluorescent microscope, which uses fluorescent and phosphorescent light to study biological matter like tissues and cells.

Protein filaments in a cancer cell. Image credit: Howard Vindin via Wikimedia Commons // CC BY-SA 4.0

The problem is that macromolecules don’t produce light—or at least that’s what the textbooks say. And because they don’t make their own light, they have to be treated with fluorescent stains to get them to show up. But it’s a devil’s bargain. The stains are toxic to living organisms, which means that scientists end up looking at dying cells. 

The stains confuse matters as much as they help, says co-senior author and Northwestern University engineer Vadim Backman. “The cell might die in two hours, so you can still do imaging in the first half hour,” he said in a press statement. “But what exactly are you measuring? What are you actually seeing? Are you looking at real processes of the cell? Or are you looking at processes in a cell that is about to die? Nobody knows.”

Thanks to Backman and his colleagues, all that confusion could become a thing of the past. The team had been looking at nucleotides (the building blocks of DNA) under a microscope when they saw a strange flash. They realized that under normal, visible light, DNA could in fact emit a fluorescent glow. It just wasn’t doing it all of the time. 

They realized that most studies had looked at the DNA in between flashes—kind of like watching a runner after a race.

“Sprinters alternate running very, very fast and resting,” Backman says. “You might catch them when they are resting and assume they aren’t doing anything. That’s what DNA and proteins do. They fluoresce for a very short time and then rest for a very long time.”

Further experiments revealed that hitting the macromolecules with just the right wavelength of light could make them glow just as brightly as any stained tissue. 

Backman and his colleagues are hopeful that these findings will lead to less complicated microscopy in the future. He credits their success to good old-fashioned scientific curiosity. 

“It sounds cliché, but you get the answer to the question you ask,” he said. “When we actually asked the right question, we got a very different answer than expected.”

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