US chemists have measured an isolated carbohydrate-pi interaction for the first time. The interaction is implicated in carbohydrate-protein recognition, which mediates cell-cell recognition and plays a role in bacterial and viral infection. 

Understanding the energy requirements of the carbohydrate-pi interaction could lead to new approaches to disrupting it. 'Quantifying non-covalent interactions is an important step towards designing inhibitors,' said Marcey Waters, a bioorganic chemist at the University of North Carolina, in Chapel Hill.

The carbohydrate-pi interaction is a significant component of protein-carbohydrate binding. It is formed when a sugar group interacts with the face of an aromatic ring; however, its magnitude has remained unknown. Now, Waters and her co-workers have quantified this important stabilising interaction. 

To measure the interaction, the US group used a model peptide system containing a tryptophan amino acid and a carbohydrate group. A carbohydrate-pi interaction is formed as the peptide folds into a hairpin structure. The effects of other non-covalent interactions were measured by amino acid substitutions, allowing the researchers to isolate and quantify the stabilising effect of the carbohydrate-pi interaction.      

Waters commented that the work could have far-reaching interest. 'Carbohydrate recognition is not only an important biological problem,' she explained, 'it is also one of the most significant challenges in the field of molecular recognition.' 

Russell Johnson

This article has been updated (3 October 2007) to more accurately reflect the role of carbohydrate-protein interactions in viral infection.