Understanding the molecular basis of biological processes forms an important foundation for biomedical research into disease and drug development. Mass spectrometry has long played an important role in determining the primary sequence of proteins and carbohydrates. More recently, hybrid ion mobility time of flight instruments have enabled the investigation of the higher order structure of biomolecules. Research in the Amster lab has applied these methods to study the interaction of Roundabout 1 (Robo1), a glycoprotein, and heparan sulfate (HS). Ion mobility-mass spectrometry analysis allowed the determination of protein-carbohydrate stoichiometry (Fig. 1)and revealed two distinct conformations of Robo1 (Fig. 2). Figure 1 - Native mass spectrum of Robo1 and Arixtra showing the formation of both 1:1 and 2:1 protein:carbohydrate complexes. Figure 2 - (Left) Working models for two conformations of Robo1. (Right) Ion mobility arrival time distributions show a change in relative populations of the two conformations upon binding heparan sulfate (HS).
