The β3 palmitoylated peptide pRKEFAKFEEER but not the nonpalmitoylated version RKEFAKFEEER is platelet permeable. (A) A confocal projection image composed of optical slice images of a single representative normal platelet treated with the FITC-derivatized, nonpalmitoylated peptide RKEFAKFEEE. Images of optical slices of the platelet treated with this peptide revealed no label (not shown). (B) A confocal projection image composed of the optical slice images of single representative normal human platelet treated with the FITC-derivatized, palmitoylated peptide pRKEFAKFEEER. (C) Six representative noncontiguous consecutive optical slice images of this platelet are labeled i-vi. (i) An image of the ventral surface; (ii-v) images of the interior of the platelets; (vi) an image of the dorsal surface of the platelet. The white points in the images represent the FITC fluorescence. These images demonstrate that palmitoylated RKEFAKFEEER, but not nonpalmitoylated RKEFAKFEEER, is platelet permeable and therefore can enter the platelets and reside in their interior.