The informed consent and related protocols were approved by Emory University institutional review boards. Citrated whole blood was obtained from healthy volunteers, from which platelet-rich plasma (PRP) was prepared [30 (link)]. Platelet counts were measured using a Sysmex XP-300 analyzer (Lincolnshire, IL). To measure platelet binding, PRP was incubated with 60 nM noted protein for 10 minutes at room temperature. After washing the samples were mixed with 1 µg/mL FITC-labeled anti-His-tag MAb, fixed and analyzed on a BD FACS Canto-II instrument using FlowJo. The signal was quantitated by the median fluorescence intensity (MFI) for the entire cell population (10,000 cells).