VWF and von Willebrand disease (hereditary or acquired): An alternative binding-site for collagen in the VWF protein is located in the A1 domain, as has been demonstrated by various research groups.83,90–93 However, opposite findings have been reported concerning the contribution of the A1-domain in facilitating VWF-platelet interactions under conditions of flow.79,94 Nevertheless, it appears that some mutations in the A1 domain found in VWD patients may affect collagen binding, providing a rationale for the bleeding tendency in these patients.95–98