Preformed clots overlaid with Aβ are resistant to lysis and contain fibrin-bound Aβ. (A) Preformed clots (as described in “Clot turbidity analysis”) containing no Aβ were overlaid with 5μM Aβ₄₂ (dashed line) or control buffer (solid line) for 1 hour, the overlays removed, and the clot surfaces washed. All clots were then overlaid with 10nM tPA to initiate lysis. (B) Half-lysis of clots that had been overlaid with Aβ was significantly delayed compared with control clots (P = .012). (C-H) Confocal microscopy of clots using Alexa Fluor 488–labeled fibrinogen and HiLyte Fluor-555–labeled Aβ prepared as described in “Aβ binding to fibrinogen.” (C-D) Normal clot overlaid with buffer. (E-F) Normal clot overlaid with 555-Aβ₄₂ (3μM) for 1 hour contained fibrin-bound Aβ₄₂ (G-H). Normal clot overlaid with 555-Aβ_1-9 (3μM) for 1 hour did not show specific colocalization between fibrin and Aβ_1-9. Images are representative of ≥ 3 experiments.