New York, Sep 27 (IANS): The ultra-stable properties of the proteins that allow whales to remain active while holding their breath for up to two hours could hold the key to creating synthetic blood, scientists believe.

In the study, the researchers from Rice University compared the muscle protein myoglobin from humans, whales and other deep-diving mammals.

Myoglobin holds oxygen inside muscle cells, and the study found that marine mammals have ultra-stable versions of myoglobin that tend not to unfold.

The researchers found that stability was the key for cells to make large amounts of myoglobin, which explains why deep-diving mammals can load their muscle cells with far more myoglobin than humans.

"Whales and other deep-diving marine mammals can pack 10-20 times more myoglobin into their cells than humans can, and that allows them to 'download' oxygen directly into their skeletal muscles and stay active even when they are holding their breath," said lead researcher professor John Olson.

"The reason whale meat is so dark is that it's filled with myoglobin that is capable of holding oxygen. But when the myoglobin is newly made, it does not contain heme. The stability of heme-free myoglobin is the key factor that allows cells to produce high amounts of myoglobin," Olson said.

Olson has spent two decades studying haemoglobin -- a larger, more complex oxygen-carrying protein in blood. His goal is to create synthetic blood for use in transfusions.

Hospitals and trauma specialists currently rely on donated blood, which is often in short supply and has a limited storage life.

"Our results confirm that protein stability is the key. This work is very important for our projects on synthetic blood substitutes and determining the toxicity of acellular haemoglobin," Olson said.

The paper was published in the Journal of Biological Chemistry.