Washington, April 1 : Researchers at the University of Michigan have developed a technique to identify and structurally characterize sugars that are suspected to play a significant role in the growth and spread of tumours, setting the stage for new cancer diagnosis and treatment options.

A growing body of evidence points to assemblies of sugars called glycans attached to proteins on cancer cell surfaces as accomplices in the growth and spread of tumours. Researchers have been keen to characterize these glycans, but traditional analytical methods have not been sufficient.

However, analytical chemist Kristina Hakansson’s discovery may now rid them of this problem.

The technique involves mass spectrometry, which can accurately weigh molecules or fragments of molecules, to analyze proteins. In the process, proteins are introduced into the mass spectrometer and fragmented by heating until the weakest bonds break.

Together, the masses of the various fragments provide a sort of fingerprint that reveals the genetic blueprint from which the protein was built, and this information helps researchers confirm the protein’s identity.

The process works well so long as the protein has not been modified after it was produced. But if other chemical groups such as phosphates, sulfates or sugars have been added, the identification method breaks down and the resulting fragments do not give accurate information about either protein’s identity or the exact type and position of sugars present.

“If sugars are attached, for instance, the weakest bonds are not the bonds that hold the protein together; they’re the bonds between the sugars,” Hakansson said.

In order to get around that problem, the researchers used a process called electron capture dissociation (ECD) instead of the usual “shake-it-til-it breaks” method to fragment proteins. But that method required the presence of at least two positive charges, which was not easy to accomplish with acidic molecules, such as proteins with sulfate or phosphate groups attached.

The researchers have been exploring the use of metals such as calcium and iron to carry the necessary positive charges. In the latest research, they extended the technique to sugars, an even more challenging task.

“Sugars are not like other biomolecules. They’re linked rings with lots of branches, like trees. If you cut off a branch, you don’t know which part of the tree it came from,” Hakansson said.

The researchers say that the trick is to make breaks that cut across the ring structures, which they were able to do by using metals as charge carriers, yielding valuable structural information.

The study has been published in the journal Analytical Chemistry. (ANI)