4N1K synergizes with soluble collagen in platelet aggregation in PRP. Freshly prepared PRP was equilibrated in the aggregometer cuvette at 37°C for 5 minutes and then stimulated with soluble collagen (2.5, 10, or 20 μg/mL). 4N1K (50 μmol/L) or 4NGG, control peptide (50 μmol/L), was added 2 minutes before the soluble collagen. Anti-2 MoAb P1E6 (10 μg/mL) or mIgG (10 μg/mL) was added 2 minutes before agonist addition in the right set of curves. These experiments were repeated 10 times with platelets from different donors.