K²⁷⁰-Q²⁹² from D3 of HK blocks TM-60 binding to platelets. Biotinylated TM-60 (58 nmol/L) binding to gel-filtered platelets was measured fluorometrically with binding in the absence of peptide set equal to 100%. The peptide concentration was from 2 to 10 μmol/L. Concentrations from 10 to 100 μmol/L of peptide did not result in further blocking greater than 50% and therefore are not shown. Note that the ordinate begins at 50% binding, reflecting the maximal inhibition encountered for the peptide effect on thrombin.