Question

Why is SOS (sucrose octasulfate) used instead of heparin in many studies?

Answer 1

SOS or Sucrose octasulfate is often used instead of heparin because it is an effective heparin mimic in its interaction with thrombin. It was found that SOS binds thrombin with a K(d) of ~1.4M, comparable to that of the much larger polymeric heparin measured under the same conditions. Hydrogen bonding interactions make a larger contribution to thrombin binding of SOS than to heparin. SOS binding to exosite II inhibits thrombin's catalytic activity with high potency and X-ray crystal structured showed that 2 molecules of SOS are bound nonequivalently to expose II portions of a thrombin dimer, in contrast to 1:2 stoichiometry of the heparin-thrombin complex.