Confocal microscopy of fibrin clots show Aβ binding to fibrin fibrils. Fibrin clots were formed with or without Aβ₄₂ as described in “Aβ binding to fibrin(ogen)” to determine the location of Aβ binding. (Top row) Fibrin visualized with Alexa Fluor 488–labeled fibrinogen (green); (bottom row) Aβ visualized with HiLyte Fluor 555–labeled Aβ (red); (A-B) control clot. (C-D) Clot with only unlabeled Aβ₄₂ shows that fibrin fibers and irregular clusters do not produce signal in the red channel. (E-F) Clot formed with unlabeled Aβ₄₂ and HiLyte Fluor 555–labeled Aβ₄₂ shows colocalization between Aβ and fibrin fibers as well as Aβ and irregular clusters (arrowhead). (G-H) Clot formed without Alexa Fluor 488–labeled fibrinogen but with both unlabeled and labeled Aβ₄₂ shows Aβ signal in the fibrin fiber pattern, confirming that Aβ signal is not Alexa Fluor 488 signal detected in the red channel. (I-J) Clot formed with unlabeled Aβ₄₂ and HiLyte Fluor-555–labeled Aβ_1-9 does not have Aβ signal along fibrin fibers or in aggregates, indicating that the Aβ₄₂ signal represents specific Aβ-fibrin(ogen) binding and not fluorophore entrapment. Images are representative of ≥ 3 experiments.