Examples of selectivity for open/closed reducing sugar binding?

gravenewworld

Reducing sugars really exist in open+closed forms that occur in equilibrium in solution correct? Are there any known examples of where say a pathogen interacts with the glycocalyx (like influenza for instance) only when reducing sugars are open (or only when closed)? Or are most carbohydrates on the surface capped with sialic acid (which doesn't have open/closed forms?)?