The influence of aptamers on PF4 binding to platelets is shown. (For details of aptamer structure, please compare with Figure 1A.) The following 4 aptamers (▪) were tested in increasing doses for promoting PF4 binding to platelets in comparison with heparin (gray line) as the positive control: (A) 57mer–RNA tetracycline aptamer, (B) 77mer–RNA FMN aptamer, (C) 44mer–DNA protein C aptamer, and (D) 15mer–DNA thrombin aptamer. All data represent mean ± SD of 3 independent experiments. The figures indicate that PF4 binding to platelets correlates with the length and the size of double-stranded domains of the aptamers.