Researchers said that they have discovered how a human egg captures a human sperm for fertilization.  The discovery may be the breakthrough that infertile couples have been searching for.   

In the study, a team of researchers found that sugar chain sialyl-lewis-x sequence (SLeX) enables the outer coat of the egg to become sticky, which binds the egg and sperm. 

Scientists and doctors have long known that a sperm identifies and egg when proteins on the sperm match and bind to sugars in the egg's outer coating.  A successful match enables integration.  The final step is delivery of the sperm's DNA into the egg.

The researchers used ultra-sensitive imaging technology to identify the molecules that hijack the binding process and found that SLeX binds sperm and eggs.

The study included collaborators from the Department of Life Sciences at Imperial College London, the University of Missouri, the University of Hong Kong, the Academia Sinica in Taiwan, and the Imperial College of London, who identified this molecule as the molecule that makes the egg's outer coat sticky.

According to the World Health Organisation (WHO), various degrees of infertility are present in about 15 percent of reproductive-aged couples globally.   The causes of infertility are still unknown.