Test for heparan sulfate functionality? - (Feb/04/2013 )

Hi!
I'm wondering if there is an assay that can test for heparan sulfate binding function. I'm not that familiar with protein interactions studies, I primarily work with virology and cell biology.
I have tested heparan sulfate and it's effect on our virus ability to bind to cells, and we have found that it has no effect. What I now need is a way to show that the heparan sulfate is actually working in binding other proteins so that the lack of effect is due to our virus inability to bind to it.

Is there someone out there that has any advice on how I should do this?

/Maria

All I remember from physiology is that heparin binds to antithrombin. Maybe buy some purified antithrombin, a primary and secondary antibody and use enzyme to show it is actively bound.