(537a) Receptor-Ligand Interactions of Thrombin with Glycosaminoglycans On Self-Assembled Monolayer Platforms

Heparan sulfate and heparin are sulfated polysaccharides that interact with a number of proteins and mediate a host of biological responses. Heparin is known to regulate several steps of the coagulation cascade. Its interaction with thrombin, factor Xa and factor XIa, key coagulation enzymes, is the primary reason for its use as an anticoagulant for the past 7 decades. Yet, the fundamental molecular bases for these interactions remain unclear. Understanding the specificity of these interactions may result in better anticoagulants. Atomic force microscopy (AFM) is a valuable tool for uncovering bio-recognition at a molecular level. Here we present a novel platform that allows us to elucidate covalently immobilized glycosaminoglycans (GAGs) to a mixed self-assembled monolayer (SAM) platform of N-hydroxysuccinimide (NHS) and oligoethylene glycol (OEG)-terminated thiols on ultraflat gold surfaces. Directional immobilization of chemical modified heparin as 2,6-diaminopyridinyl heparin via the reducing end allowed us to probe the interactions of thrombin in real time and under varying conditions (interactions in the presence of NaCl, pH and varying chain lengths). The interaction profiles and rupture forces for these binding under physiological conditions can be used to quantitatively understand the role of GAGs in blood coagulation. This experimental platform provides an attractive strategy to study protein interactions at interfaces as well as to screen for novel anticoagulants.