Biology

Scientists observe live cells responding to magnetic fields for first time

Scientists observe live cells ...
Scientists may have discovered new evidence explaining the cellular mechanism for how birds and other animals can navigate using the Earth's magnetic field
Scientists may have discovered new evidence explaining the cellular mechanism for how birds and other animals can navigate using the Earth's magnetic field
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Scientists may have discovered new evidence explaining the cellular mechanism for how birds and other animals can navigate using the Earth's magnetic field
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Scientists may have discovered new evidence explaining the cellular mechanism for how birds and other animals can navigate using the Earth's magnetic field
Microscope images of cells showing where they were irradiated with blue light (left), causing them to fluoresce (center) – the right image overlays the two prior images
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Microscope images of cells showing where they were irradiated with blue light (left), causing them to fluoresce (center) – the right image overlays the two prior images
An animation showing the cells' fluorescence dimming in response to a magnetic field
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An animation showing the cells' fluorescence dimming in response to a magnetic field
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One of the most remarkable “sixth” senses in the animal kingdom is magnetoreception – the ability to detect magnetic fields – but exactly how it works remains a mystery. Now, researchers in Japan may have found a crucial piece of the puzzle, making the first observations of live, unaltered cells responding to magnetic fields.

Many animals are known to navigate by sensing the Earth’s magnetic field, including birds, bats, eels, whales and, according to some studies, perhaps even humans. However, the exact mechanism at play in vertebrates isn’t well understood. One hypothesis suggests it’s the result of a symbiotic relationship between the animals and magnetic field-sensing bacteria.

But the leading hypothesis involves chemical reactions induced in cells through what’s called the radical pair mechanism. Essentially, if certain molecules are excited by light, electrons can jump between them to their neighbors. That can create pairs of molecules with a single electron each, known as a radical pair. If the electrons in those molecules have matching spin states, they will undergo chemical reactions slowly, and if they’re opposites the reactions occur faster. Since magnetic fields can influence electron spin states, they could induce chemical reactions that change an animals’ behavior.

In the living cells of animals with magnetoreception, proteins called cryptochromes are thought to be the molecules that undergo this radical pair mechanism. And now, researchers at the University of Tokyo have observed cryptochromes responding to magnetic fields for the first time.

The team worked with HeLa cells, a lab-grown line of human cervical cancer cells that are often used for these types of experiments. They focused on the cells’ flavin molecules, a subunit of cryptochromes which fluoresce under blue light.

An animation showing the cells' fluorescence dimming in response to a magnetic field
An animation showing the cells' fluorescence dimming in response to a magnetic field

The researchers irradiated the cells with blue light so that they fluoresced, then swept a magnetic field over them every four seconds. And each time it swept over them, the fluorescence of the cells dropped by about 3.5 percent.

The team says that this dimming is evidence of the radical pair mechanism at work. Basically, when flavin molecules are excited by light they either produce radical pairs or fluoresce. The magnetic field influences more of the radical pairs to have the same electron spin states, slowing down their chemical reactions and dimming the overall fluorescence.

“We’ve not modified or added anything to these cells,” says Jonathan Woodward, co-lead author of the study. “We think we have extremely strong evidence that we’ve observed a purely quantum mechanical process affecting chemical activity at the cellular level.”

The team says that the magnetic field used in the experiments was about the same as a regular fridge magnet, which is much stronger than the Earth’s natural field. But interestingly, weaker magnetic fields can actually make it easier for the electron spin states in radical pairs to switch.

That could mean that the radical pair mechanism is at play in animals with magnetoreception, but further work will be needed to know for sure.

The research was published in the journal Proceedings of the National Academy of Sciences.

Source: University of Tokyo

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10 comments
10 comments
Nobody
So, how does this relate to direction? How do they know that many animals aren't just keying off of other things like the sun, shadows, smells or even the green algae on the north side of trees and even buildings. My wife marvels at my always knowing north just driving through a strange area. Just look for the green algae side and that is north. If the sun is high in the sky, all the shadows point northward. Even the majority of roads and buildings are oriented north and south or east and west. It is more about good observation than magnetic fields which I am sure many animals use as well.
rpark
...would the fluorescence have dimmed 3.5% every 4 seconds just due to the earth's ambient magnetic field, without introducing an additional field ?
1stClassOPP
Isn’t that marvellous? The more observations made, the more things we learn and marvel at.
Bruce H. Anderson
Years ago I read an article about electromagnetic fields around power lines. The article stated that there is an increase in cellular activity when in a magnetic field. It didn't say what kind of activity, or if it was detrimental or beneficial. This looks like this experiment was using a static magnetic field, and maybe the jury is still out on what effects the observed activity has on the cells. Still a lot to learn about the human body.
Intellcity
When I was in grade school to Junior high I always "knew" which way North was. Day, night, indoors, outdoors, totally overcast, didn't matter. Then I moved to Australia. I totally lost my sense of direction. I had to learn to use the sun or a compass. I couldn't walk a straight line in the woods.
christopher
FWIW - I recall that (at least in birds, maybe all animals) the receptors are in their eyes and only work in the day time.
Glenn Rosendahl
Nobody - thanks for the north direction hints. Only problem for me is they will not work in the southern hemisphere...
Nobody
@Glenn Rosendahl, In the southern hemisphere the same clues should point South. I should have also mentioned the North star at night but you will have to substitute the Southern Cross for that one.
Irl
I am quite surprised that nobody has noted that bacteria, and some higher animals, have the ability to segregate nanocrystals of (I believe) magnetite. These are so small that each is a single domain and thus strongly magnetic. The bacteria build up a half dozen of these and they automatically link up north-to-south. The resulting magnet is strong enough that it reorients the bacteria along the Earth's field. This is useful because (except on the equator) the field has a vertical component, aiding the bacteria to reach the muddy bottom where they like to live.
Krista Baker
Are HeLa cells live and unaltered?