VWF activity assays and multimer analysis
Binding of the recombinant VWF (rWF) to platelet GPIb (VWF:GPIb) was assessed using a particle enhanced assay (Siemens Healthcare, Marburg, Germany) on a BCS XP coagulation analyzer. Furthermore, binding of the rVWF to collagen type I (VWF:CB) was determined by the ELISA method (Technoclone, Vienna, Austria) according to the manufacturer’s instructions. The VWF activities were expressed as ratios to secreted VWF. rVWF multimers of concentrated secreted rVWF were analyzed by 1.6% SDS-agarose gel electrophoresis as described before .