Washed platelets were preincubated with or without abciximab (10 μg/mL) for 30 minutes before being incubated with two concentrations of TRAP-14 mer under aggregating conditions. Samples were taken at the peak of the aggregation (2 minutes) and platelet proteins were separated by SDS-polyacrylamide gel electrophoresis before the detection of tyrosine-phosphate groups by Western blotting using the monoclonal antibody PY99.