Design and structure of UHRA compounds and efficacy in blocking thrombin binding to polyP. (A) Representative structure of a typical UHRA scaffold (in this case, for UHRA-10) containing a dendritic polyglycerol core bearing the randomly distributed polyP-binding groups (R) and an outer shell of short-chain polyethylene glycols. The molecular weight and number of R groups was varied to generate the other UHRAs. (B) Fifty percent inhibitory concentration (IC₅₀) values for the ability of 16 UHRA compounds to inhibit thrombin binding to immobilized polyP. Arrows indicate the 4 compounds selected for further study: UHRA-8 (R = 24; 23 kDa), UHRA-9 (R = 16; 16 kDa), UHRA-10 (R = 11; 10 kDa), and UHRA-14 (R = 7; 10 kDa).