The earth has a magnetic field, and some animals such as monarch butterflies and turtles can use it to navigate during their long migrations. Researchers have now discovered that at high levels, a molecule called flavin adenine dinucleotide (FAD), can stimulate an organism to be sensitive to magnetism. This molecule can be found in many different cell types in various kinds of animals, and it suggests that the ability to sense a magnetic field, or magnetoreception, might be more common than we knew. The findings, which used a fruit fly model, have been reported in Nature.
Magnetosensitivity is thought to involve an electron-transfer reaction that includes FAD and a chain of tryptophan residues within the photoreceptor protein cryptochrome. Cryptochrome is light-sensitive, and can be found in animal and plant cells.
"The absorption of light by the cryptochrome results in movement of an electron within the protein which, due to quantum physics, can generate an active form of cryptochrome that occupies one of two states. The presence of a magnetic field impacts the relative populations of the two states, which in turn influences the active lifetime of this protein," explained study co-author Dr. Alex Jones, a quantum chemist from the National Physical Laboratory.
In this study, the researchers genetically altered the cryptochrome protein in the fruit fly so that it lacked the portion that binds to FAD. However, these altered flies were still able to sense magnetic fields.
This study suggested that cells are able to sense magnetic fields even if only a small part of cryptochrome is present, a "striking" finding, noted first study author Dr. Adam Bradlaugh of The University of Manchester. "That shows cells can, at least in a laboratory, sense magnetic fields through other ways."
One of those other ways is through FAD, and while this light sensor typically attaches to cryptochrome to boost magnetosensitivity, it can also impart magnetic sensitivity itself at high levels, said Bradlaugh.
Magnetoreception, sometimes called the sixth sense, is far more challenging to study than other senses such as vision and hearing, because magnetic fields have much less energy compared to other stimuli such as photons or sound waves, Bradlaugh added.
This study has provided new insights into how environmental factors, such as those that generate electromagnetic noise, might be affecting processes that help cells sense magnetic fields, or animals that use those fields to survive.
"This study may ultimately allow us to better appreciate the effects that magnetic field exposure might potentially have on humans," added co-corresponding study author Professor Ezio Rosato of The University of Leicester. "Moreover, because FAD and other components of these molecular machines are found in many cells, this new understanding may open new avenues of research into using magnetic fields to manipulate the activation of target genes; that is considered a holy grail as an experimental tool and possibly eventually for clinical use."
Sources: University of Manchester, Nature