Endorepellin supports platelet adhesion. (A) Human platelets with or without anti-α2β1 antibody (10 μg/mL) were added to wells coated with collagen (100 μg/mL), endorepellin (ER, 20 μg/mL) or 1% BSA for 90 minutes at 37°C followed by fixation with 4% paraformaldehyde and crystal violet colorimetric analysis. Mean OD₅₆₀ ± SE from 4 separate experiments shown (A-D). (B) Experiment similar to that shown in panel A with the addition of liquid phase ER (20 μg/mL) with or without PP1 (10 μM) to collagen-coated (100 μg/mL) wells. (C) Experiment similar to that shown in panel A (coating with collagen, 100 μg/mL, or ER, 20 μg/mL, repeated with OD₅₆₀ analyzed at different incubation time points. (D) Experiment similar to that shown in panel A with different coating concentrations (1-150 μg/mL) of collagen with or without liquid-phase ER (20 μg/mL) or different coating concentrations of ER (1-150 μg/mL). (E) Effects of different concentrations of the α2β1-integrin–specific triple-helical collagen peptide GFOGER on platelet adhesion to collagen or ER. (F) Effects of different platelet receptor function blocking antibodies or nonfunction-blocking anti-α2β1 antibody 12F1 (each tested at 10 μg/mL) or magnesium-free conditions on platelet adhesion to endorepellin.