Humans are only able to use five senses to perceive the world around us. In the animal world, many are also able to sense the magnetic field of the earth. Researchers have reported new findings on magnetic sensing in birds and recently presented their research. Scientists at the University of Oldenburg in Germany and Oxford in the UK have been gathering evidence that suggests the magnetic sensing of migratory birds like European robins is based on a specific light-sensitive protein in the eye.
In their research, the team demonstrated a protein called cryptochrome 4 found in the bird’s retina is sensitive to magnetic fields and could be the magnetic sensor that scientists have been searching for. Researchers on the project extracted the genetic code for cryptochrome 4 found in night-migratory European robins and was able for the first time to produce the photoactive molecule in large quantities using bacterial cell cultures.
Another team of researchers used a range of magnetic resonance and optical spectroscopy techniques to study the protein and demonstrate its sensitivity to magnetic fields. Researchers on the project can also discern the mechanism that gives rise to the sensitivity, which is said to be another important advance. Electrons able to move within the molecule after blue-light activation play a critical role.
Proteins, like cryptochrome, have chains of amino acids and robin cryptochrome 4 has 527 of them. Researchers in the project found that four of those 527 amino acids known as tryptophans are essential for the magnetic properties of the molecule. Calculations showed that electrons jump from one tryptophan to the next, generating something called radical pairs that are magnetically sensitive. Experiments showed that the generated radical pairs are essential to explain the observed magnetic field effects.
The team believes the results they found are important because they show for the first time molecule from the visual apparatus of a migratory bird is sensitive to magnetic fields. However, the team is clear that they have not found definitive proof that cryptochrome 4 is the magnetic sensor the team is looking for.