Researchers explain how birds navigate

London, May 1 : Scientists have long known that migrating birds use a navigation system that involves the Earth's magnetic field when they fly to specific places in specific seasons. Now, they have uncovered the underlying mechanism behind this inherent global positioning system (GPS) that helps our feathered friends do so.

One of the hypotheses to explain this phenomenon states that birds make use of magnetically-sensitive chemical reactions initiated by light (called chemical magnetoreception) to orient themselves.

And now, researchers from Arizona State University and the University of Oxford, have created a sophisticated molecule, which, when illuminated is sensitive to the magnitude as well as the direction of magnetic fields as tiny as the Earth's.

"Although the chemical magnetoreception mechanism for avian magnetic navigation has been discussed by many investigators, our research provides the first proof that this mechanism can actually function with magnetic fields as small as those of the Earth," Nature quoted ASU's Devens Gust, professor of chemistry and biochemistry in the College of Liberal Arts and Sciences, as saying.

He added: "The design, synthesis and a few initial magnetic field effect studies were done at ASU in the context of artificial photosynthetic solar energy conversion. The Oxford group, led by Peter Hore, professor of chemistry, realized that these effects might be relevant to chemical magnetoreception, constructed the extremely sensitive apparatus needed to observe the phenomena, and carried out the appropriate experiments."

A decade back, a research team at Arizona State led by Gust, created a molecular "triad," which, when exposed to light, resulted in a short-lived, high-energy charge-separated molecules whose lifetime was influenced by magnetic fields. These molecules, however, had nothing to do with bird navigation.

Recently, a similar triad molecule was synthesized by Paul Liddell, assistant research professional working with Gust and to investigate its molecular properties, the researchers used lasers that sent out pulses of light lasting only one-thousand millionth's of a second. The experiments had to be completely shielded from the Earth's magnetic field.

This unique molecule is made up of three units (a carotene-porphyrin-fullerene triad). After it is excited by light, it forms a charge-separated state with the negative charge on the soccer-ball-like fullerene (or buckyball) portion and the positive charge on the rod-like carotene portion.

The charge-separated species' lifetime is sensitive to the magnitude and direction of a weak magnetic field, similar to that of the Earth, before it returns to the normal state. In its charge separated state, this triad molecule can be considered as having little bar magnets at either end - so far apart that only a weak interaction is possible between them.

"These results provide a clear proof of principle that the magnetic compass sense of migratory birds is based on a magnetically-sensitive chemical reaction whose product yields and/or rate depend on the orientations of the molecules involved with respect to the geomagnetic field," added a researcher.

According to Gust, the knowledge of animal navigation systems has a big ecological importance as weak, man-made magnetic fields are produced by many widely-used technologies, like power lines and communications equipment. And, this may also enable a diagnostic test of the magnetoreceptor mechanism.

"Of course, this research does not prove that birds actually use this mechanism, only that they could. But, there is a large body of research on birds that is consistent with the magnetoreception idea," added Gust.

This work provides some insight into the structure and dynamic design features needed for a molecular interpretation of how the birds go about keeping their appointments in strange places across the world.

The study has appeared in the latest advanced online publication of the journal Nature.

ANI