Bird Migration Influenced by Toxic Molecule

As scientists and biologists continue to struggle to discover exactly what causes birds to migrate with such accuracy, it seems new breakthroughs continue to be made. A recent discovery reported in the June Biophysical Journal sheds exciting new light on a still relatively misunderstood process of nature.

The discovery was made by Klaus Schulten (Swanlund Chair in Physics at Illinois) and his collaborator Ilia Solov’yov (Frankfurt Institute for Advanced Studies). It seems that Solov’yov did not know that the molecule known as superoxide was toxic and was using it in studies of the biomechanical process of the cryptochrome protein found in the eye of a bird. Superoxide is a toxic molecule that is known to damage cells and cause disease. Now it seems it also plays a constructive role in the process that enables birds to ‘visualise’ the Earth’s magnetic field.

It turns out that superoxide is an ideal reaction partner when paired with the cryptochrome protein. In 2000 it was discovered that this protein plays a key role in the development of a bird’s geomagnetic sense, since chemical reactions can take place in the protein in response to magnetic fields. However magnetic fields interact so weakly with molecules that up until now it was virtually impossible to understand how these reactions could take place. It was thought that changes in the electromagnetic field, such as would occur when the bird changed direction while flying, would have an effect on freely tumbling spins of electrons in the birds eye which would essentially serve as a compass that pointed north or south. Researchers then supposed that the cryptochrome recruited a reaction partner with ‘zero-spin’ and it was proposed that oxygen was that partner.

Now it seems researchers had it backwards. It may not be oxygen, but rather its close cousin superoxide, that serves as the reaction partner in this process. Initially the toxicity of the molecule caused Klaus Schulten to dismiss the idea presented by Solov’yov. But then he realized that the toxicity of the molecule was actually crucial to the role it played in the process. Most living organisms, such as birds, have mechanisms for reducing the concentrations of superoxide in the body to prevent it from damaging the organism. The molecule needs to be present – but only in low concentrations. In birds, it is the presence of this molecule that makes the biomechanical compass work effectively.