More recently, several studies have also demonstrated that ADAMTS-13 in solution may exhibit various conformations [31,32], and at least, some are sensitive to the changes in environmental pH [32], metal ions (Ca2+ and Zn2+) [33,34], and the interaction with VWF substrate [32,35] or antibodies in patients with TTP [32,36]. Here, VWF is linked to thrombotic thrombocytopenic purpura.