Pep-1 delivers FITC-conjugated A4 peptide into platelets. The bar graph shows fluorescent uptake into platelets when the A4 peptide plus Pep-1 are mixed with PRP (dark bars) or washed platelet suspensions (light bars) for 30 minutes at 37°C. The molar ratio of A4 peptide to Pep-1 is maintained at 1:20 and optimal uptake as measured by flow cytometry occurs with 6.4 μM A4 peptide plus 128 μM Pep-1. The inset shows fluorescent micrographs after washed platelets are incubated with 6.4 μM A4 peptide plus 0 μM Pep-1 (left) or 6.4 μM A4 peptide plus 128 μM Pep-1 (right) and allowed to adhere to glass slides (n = 3; error bars present means + SDs; **P < .01 when compared to 0 A4-FITC by Student t test).