Researchers discover that DNA naturally fluoresces

August 15, 2016, Northwestern University
A depiction of the double helical structure of DNA. Its four coding units (A, T, C, G) are color-coded in pink, orange, purple and yellow. Credit: NHGRI

A Northwestern University team recently caught DNA doing something that has never been seen before: it blinked.

For decades, textbooks have stated that macromolecules within living cells, such as DNA, RNA, and proteins, do not fluoresce on their own. Technology instead relies on special fluorescence dyes to enhance contrast when macromolecules are imaged.

But now Professors Vadim Backman, Hao Zhang, and Cheng Sun have discovered that macromolecule structures in living cells do, in fact, naturally fluoresce. This finding could open the next frontier of biological discovery by paving a new way for label-free, super-resolution nanoscopic imaging and expanding the understanding of biological processes.

"Everybody has overlooked this effect because nobody asked the right question," said Backman, Walter Dill Scott Professor of Biomedical Engineering in Northwestern's McCormick School of Engineering. "It sounds cliché, but you get the answer to the question you ask. When we actually asked the right question, we got a very different answer than expected."

This research is described in the August 15 issue of the Proceedings of the National Academy of Sciences. Backman and Zhang served as the study's co-senior authors. Biqin Dong, a postdoctoral fellow in Zhang's laboratory, and Luay Almassalha, a graduate student in Backman's laboratory, are co-first authors of the paper.

"There are textbooks that say biological molecules don't absorb and don't fluoresce," said Zhang, associate professor of biological engineering. "It's what everyone learns; it's a part of training, so nobody questions it."

The reason why no one spotted the fluorescence before? The molecules were in the "," a condition in which they do not absorb or emit light. But just because they spend so much time in the dark state does not mean they never emit light. Backman likens the situation to athletic interval training.

"Sprinters alternate running very, very fast and resting," Backman explained. "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."

Backman, Zhang, and Sun discovered that when illuminated with visible light, the molecules get excited and light up well enough to be imaged without fluorescent stains. When excited with the right wavelength, they even light up better than they would with the best, most powerful fluorescent labels.

"This is ideal because staining is toxic," Zhang said, "and it makes imaging less precise."

This toxicity makes it tricky to get an accurate image of the active processes in living cells because they die immediately after the application of fluorescent stains. There are special dyes used to image , but those just cause the cells to die slower.

"The cell might die in two hours, so you can still do imaging in the first half hour," Backman said. "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, Zhang, and Sun, the world soon might know.

Explore further: Enhancing molecular imaging with light

More information: Superresolution intrinsic fluorescence imaging of chromatin utilizing native, unmodified nucleic acids for contrast, www.pnas.org/cgi/doi/10.1073/pnas.1602202113

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17 comments

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Pooua
3 / 5 (1) Aug 15, 2016
So, all of our cytological treatments are based on dead and dying cells? This could explain why I feel this way!
tinitus
Aug 15, 2016
This comment has been removed by a moderator.
askhari139
5 / 5 (1) Aug 15, 2016
The link to the PNAS paper is not working. Can you please check again and update it?
Steelwolf
1 / 5 (6) Aug 16, 2016
I remember reading a part of a study where they showed that DNA not only lets loose light, it absorbs it also, and when it absorbs light it tightens the curl, releasing light loosens the curl of the DNA, so light from the day/night cycle directly affects the proteins that the cells are making due to the different corresponding shapes in the DNA between loose and tight curls. This was known back in the '80s, at least, most likely earlier than that.
Eikka
5 / 5 (1) Aug 16, 2016
The people are known to emanate visible light too and the fast growing parts of your body (like the nails) are glowing the most


But the nails are dead keratinous mass just like hair is. The nails themselves don't grow. The nail root is where the action is.

Sounds like made-up bullshit to me. Known by who?
tinitus
Aug 16, 2016
This comment has been removed by a moderator.
tkkanno
5 / 5 (1) Aug 16, 2016
wtf is this article. They reference the august 15th edition of PNAS (which doesn't exist, the current issue is the 16th August), give a dead link to a non-existent paper after a google search, and purport something that seems to already be known.
The only thing I could find is that the Zhang lab work on fluorescent probes for STORM super-resolution microscopy.
dschinner
not rated yet Aug 17, 2016
I remember reading a part of a study where they showed that DNA not only lets loose light, it absorbs it also, and when it absorbs light it tightens the curl, releasing light loosens the curl of the DNA, so light from the day/night cycle directly affects the proteins that the cells are making due to the different corresponding shapes in the DNA between loose and tight curls. This was known back in the '80s, at least, most likely earlier than that.


This sounds very interesting.Do you remember the author?Thank you.
Eikka
not rated yet Aug 17, 2016
Nothing prohibits you in googling it and verifying it before raising doubts, right?


Well, the wikipedia article links the glowing effect to oxidative stress, and it propably doesn't have anything to do with cell multiplication, cell communication, healing etc. but rare oxidation events that release energy by radiation.

The events are so rare that you get only a handful of photons out every now and then.
Steelwolf
not rated yet Aug 18, 2016
@ dschinner, No, sorry i do not have the author there, although I have looked since ye posted asking. I remember it from a magazine article back when I was in the Navy 35 years ago, so remembering the author's name from an article written similar to these, It may have been in Nature Magazine or similar. But it was one of those little facts that stuck in my mind back in the days before Internet, when ya actually had to go Looking for information and read actual, physical papers and books.
tinitus
Aug 18, 2016
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tinitus
Aug 18, 2016
This comment has been removed by a moderator.
tinitus
Aug 18, 2016
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tinitus
Aug 18, 2016
This comment has been removed by a moderator.
tinitus
Aug 18, 2016
This comment has been removed by a moderator.
tinitus
Aug 18, 2016
This comment has been removed by a moderator.
baudrunner
1 / 5 (1) Aug 20, 2016
It has long been known that neurons give off sparks when they fire. That's why they call them "firing "neurons". It is just a chemical reaction. Chemical reactions occur in cells, and DNA is always very actively transcribing genes. This giving off of light as a result of a chemical reaction is called Chemiluminescence. Why is this phenomenon, which has been observed for a very long time, article-worthy today?

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