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Brainiac

Quantum magic inside the human body

The hydrogen atom in motion.
The hydrogen atom in motion. Fotolia/rost9 - Fotolia

It takes a lot of tricks to make the body tick — from a symphony of microorganisms in the gut to proteins that function like Swiss Army knives. A new study suggests a similarly ingenious mechanism could be behind one of the most important aspects of cellular function.

The study is about the behavior of protons, the subatomic particles that form the nucleus of a hydrogen atom. Like all subatomic particles, protons have a dual (or quantum) nature — sometimes they behave as particles and other times as waves. As particles, they move through the world kind of like you and I do: When they come to a hill or a barrier, they have to go over it, which takes some time. But as waves, they can “tunnel” through the barrier, which can sometimes be a lot faster.

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Protons typically behave as waves only at very low temperatures. But in a paper published in the journal Nature Chemistry in June, Northeastern physicist Paul Champion and his coauthors describe an experiment in which they found that, under common biochemical conditions, protons are able to “tunnel” at room temperature. Among other things, this means that it is possible for protons to act as waves inside the balmy confines of a living organism.

Now switch focus for a moment from protons to mitochondria, the little organelles inside most cells that store and produce energy, acting like batteries. Scientists would like a rock-bottom understanding of how mitochondria are able to trap energy without immediately leaking it back out. Proton tunneling at 98.6 degrees Fahrenheit could provide part of the explanation: Protons tunnel along “wires” composed of water and amino acids across the mitochondrial membrane, but because of the complex dynamics of the tunneling distances, they aren’t able to tunnel back. This leaves protons searching for another route back to equilibrium, which channels them into the machinery by which they’re turned into adenosine triphosphate, the body’s energy currency.

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“Essentially you can make a quantum ratchet, where you get protons that are going in one direction preferentially and they are held out of equilibrium long enough along the tunneling pathway that the ATP synthesis process is able use them like a proton battery,” says Champion.

This suggestion fits with research over the last decade or so that is related to ways that hard-to-observe quantum effects may be hard-wired into basic biological functions. These processes happen so fast, or in concert with a cascade of other biochemical reactions, that they fly under the radar of most experiments. As Champion has begun to put forward both the theory and experimental evidence of proton tunneling at body temperature, there remains skepticism by some in the biological community.

“I’ve given a couple of talks, and I don’t want to say people are rolling their eyes, but people are just not ready yet to think about tunneling in these problems,” he says.


Kevin Hartnett is a writer in South Carolina. He can be reached at kshartnett18@gmail.com.