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Biological Chemistry

Sensing Sugars On Proteins

Glycoprotein Analysis: Raman spectroscopy reveals a protein’s glycosylation state

by Laura Cassiday
August 11, 2011

When pharmaceutical companies produce protein-based drugs, they must ensure that the proteins have the proper sugar groups attached. A protein’s so-called glycosylation state can change its stability and function, as well as how the immune system reacts to it. Now, for the first time, researchers demonstrate that Raman spectroscopy can differentiate between the native and glycosylated forms of a protein (Anal. Chem., DOI: 10.1021/ac2012009).

A therapeutic antibody with the wrong sugars may lose its effectiveness or even cause a harmful immune reaction, says Roy Goodacre, a biological chemist at the University of Manchester, in the U.K. Currently, scientists most often characterize glycoproteins using mass spectrometry, he says. But the technique is time consuming and destroys the protein sample.

So Goodacre and his colleagues wanted to see if Raman spectroscopy could detect and quantify protein glycosylation. Chemists previously have used Raman to pinpoint structural features in proteins, such as β-strands. Companies could use the technique to analyze proteins during production without hurting their yields, he says.

To test the principle, the researchers demonstrated that they could distinguish between the Raman spectra of RNase A and RNase B, the sugar-free and glycosylated forms, respectively, of bovine pancreatic ribonuclease, a well-characterized protein. When the scientists removed the sugar group from RNase B with chemical or enzymatic methods, the modified protein’s Raman spectrum resembled that of RNase A. By analyzing mixtures of RNase A and B at different relative concentrations, the researchers showed that they could quantify the fraction of protein that was glycosylated.

Goodacre now plans to test the method on well-characterized antibodies, with the hopes of eventually applying it therapeutic proteins.



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