Joint Research for Heparin-Platelet Interaction

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The key disaachride sequence (abbreviated as NS6S-I2S) in heparin for the binding to platelets was confirmed by the synthetic approach. That is the synthetic model disaccharide containing NS6S-I2S demonstrated a higher platelet affinity than the heparinase I-digested disaccharide although they both contain the same number of sulfates per molecule.Further evaluation for the determination of essential sequence in heparin for the binding to platelets and evaluation of the clustering or polymer effect are now under examination using heparinase I digested and synthetic oligosaccharides, as well as NMR spectroscopy combined with molecular modeling.The similar binding competitive approach was applied to determine the binding domain structure in heparin for von Willebrand factor. Interestingly, the same key disaccharide (NS6S-I2S) was found to be crucial for the binding phenomena.To detect and isolate the heparin-binding protein (s) on the intact platelet surface, we have developed a new heterobifunctional photo-crosslinking reagent (AA-D). The cross-linker was succeeded to label pharmaceutical heparins as well as the [^3H] -heparin without losing heparin's anticoagulant anti-Xa activity. The AA-D labelled [^3H] -heparin possessed highly specific cross-linking potency to antithrombin III compared with ovalbumin, which was analyzed by the newest imaging technology ([^3H] -BAS system). This procedure were then applied to the detection and isolation of heparin-binding proteins on the surface of intact platelets. By only a three-days exposure using a imaging plate in the [^3H] -BAS system, 2 bands at about 100 and 115 kDa were observed, suggesting real heparin binding proteins on the intact platelet cell surfaces. These proteins are now being purified and analyzed for their amino acid sequence.