Relative potencies of polyP inhibitors. (A) Inhibitor concentrations resulting in 50% reduction of thrombin binding to immobilized polyP (IC₅₀) are plotted for the 21 most potent substances tested, expressed in terms of mass (left) and molarity (right). Inhibitors that were also used in panels B and C are numbered in parentheses. Data are mean ± SE (n = 3). (B) Plot of IC₅₀ values of the 11 numbered substances from panel A for inhibition of heparin-mediated inactivation of factor Xa by antithrombin (y-axis) versus inhibition of thrombin binding to immobilized polyP (x-axis). Dotted line represents equivalent potency. Data are mean ± bidirectional SE (although error bars are within the symbols; n = 3). (C) Effectiveness of polyP inhibitors in prolonging clotting. Clotting of human plasma was initiated by long-chain polyP (P), polyguanylic acid (RNA), kaolin (K), diatomaceous earth (Dia), or tissue factor (TF). Data are mean inhibitor concentrations that doubled the clotting time relative to no inhibitor (EC_double) ± SE (n = 4). Horizontal dotted lines indicate that the clotting time with that initiator was either unaffected by the inhibitor or was not prolonged sufficiently to reach a doubling point, even at 100 μg/mL inhibitor.