Von Willebrand Factor (vWF) is a multimeric glycoprotein that circulates in plasma at a concentration of approximately 10 µg/mL, composed of 260,000 Da subunits held together by disulfide bonds. vWF exists in plasma in various forms, from as small as a dimer with a Mr equal to 520,000 Da to large multimers with Mr equal to 10,000,000 Da.
vWF plays a dual role in normal hemostasis. One role is to facilitate platelet plug formation by forming a bridge between Platelet Glycoprotein 1b and exposed collagen in the sub endothelium. Its second function is to act as a stabilizing cofactor for Factor VIII (FVIII), binding to and delivering functional FVIII. FVIII binds to the amino terminal portion of vWF subunit in a 1:1 molar ratio. Von Willebrand Disease (vWD) is characterized by a decrease in the ability for this bridge to be formed, or as a decrease in biological activity as a result of either a vWF protein deficiency or the presence of abnormal vWF protein.
vWF is purified from citrated human plasma. This preparation is free of FVIII.