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