Platelet attachment, tether and PMP formation via DAPs. (A) Washed blood-cell suspension (platelet count, 11 000/μL) perfused over dVWFA1 at γ_w of 40 000 s^–1. Sequential frames of a platelet during translocation are shown from right to left: (1) initial membrane-dVWFA1 surface contact with few prominent DAPs (dark circular areas); (2) increase in the contact area and number of DAPs; (3) turn of bottom side up, with platelet seen on its edge (flip-roll motion); (4-6) sliding and rotation of the platelet body from right to left (translocation without rolling). Scale bar = 5 μm. See also Movies S1 and S5. (B) Whole blood containing PPACK perfused over immobilized VWF multimers at γ_w of 6 000 s^–1. After perfusion for 5 seconds, DAPs within the bodies of surface interacting platelets appear as dark areas (see enlarged inset), and tethers (some with pronounced kinks) extend from the body for variable lengths that may exceed 30 μm. Scale bar = 5 μm. (C) The same surface shown in panel B, but after perfusion for 80 seconds; spread platelets are visible. Scale bar = 10 μm. See Movie S1. (D) Washed blood-cell suspension with 20 μg/mL purified VWF perfused over collagen type I fibrils at γ_w of 4000 s^–1. The platelet count was reduced to 11 000/μL to decrease surface coverage, and 10 μM PGE₁ was added to prevent activation. A tethered platelet is seen during initial transient adhesion to collagen-bound VWF. Scale bar = 5 μm. See Movie S4. (E) Washed blood-cell suspension (230 000 platelets/μL) perfused over dVWFA1 at γ_w of 4000 s^–1. Note the attachment to the surface mediated by a DAP within the platelet body. Scale bar = 3 μm. See Movie S5. (F) Washed blood-cell suspension (270 000 platelets/μL) perfused over dVWFA1 at γ_w of 1000 s^–1. Note the attachment to the surface mediated by a DAP at the upstream end of a tether. Scale bar = 3 μm. (See Movie S6).