Washington, Dec 30: Scientists at the University of North Carolina School of Medicine have pinpointed the link between light signal and circadian rhythms.

Aziz Sancar, and his colleagues have identified the genes that direct circadian rhythms in people, mice, fruit flies, fungi and several other organisms.

The research is important as it could help scientists understand sleep disorders, jet lag, cancer, bipolar disorder, depression and other diseases.

Sancar discovered a human protein called cryptochrome 15 years ago; it ''resets'' the circadian clock but he didn't know how.

In the current study, the team used fruit flies (Drosophilia melanogaster) to purify cryptochrome and developed a biochemical test that shows when and how the protein transmits signals.

"We can now detect the protein at work. When we expose cryptochrome to blue light in fruit flies, a millisecond of light exposure has a half-life during which we can examine the mechanism in the laboratory," said Sancar.

"We can follow the molecular signals after light exposure and have a reliable model to test various hypotheses about how light interacts with the circadian systems we know are so important to biological processes."

The paper is published this week in the Proceedings of the National Academy of Sciences. (ANI)