VWF labeling efficiency and specificity by immunogold method.

(A) Individual VWF molecules are almost completely covered by gold spheres. VWF bound to collagen was visualized by polyclonal anti-VWF antibody treatment, followed by protein-A–conjugated gold (15-nm diameter beads). (B) Magnified detail of the area delimited by a white square. (C) Nonspecific binding of immunogold on collagen. PBS-perfused collagen surface was treated like the previous sample. Although several markers are present on the surface (white arrow), these nonspecifically bound particles do not form clusters and are, therefore, readily distinguishable from specifically bound gold. Collagen layer covers the surface uniformly and forms small filaments (black arrow). Pictures taken in tapping mode AFM have lateral dimensions of 5 × 5 μm (for A and C) or 1 × 1 μm (B), height scale ranges from 0 to 20 nm (bright to dark). Ultralever “D” tip, F = 158 kHz, setpoint is approximately 90% of the free vibration amplitude.