The various effects of PolyP on blood clotting are strikingly dependent on polymer length. Specific activities of polyP are plotted versus polyP polymer lengths, normalized in each case to 100% maximal activity. The data are replotted from Smith et al²⁷  (but on linear axes) for: (A) triggering of plasma clotting via the contact pathway, (B) modulating fibrin clot turbidity, (C) accelerating factor V activation, and (D) abrogating TFPI anticoagulant function; and from Choi et al²⁹  for (E) promoting factor XI back-activation by thrombin. (E) polyP longer than 350 mers was not tested. In each panel, the pink bar represents the approximate size of polyP secreted from activated human platelets (∼ 60 to ∼ 100 mers),^8,25,27  and yellow rectangle, the approximate size of microbial polyphosphate (ranging from < 100 mers to > 1500 mers).²⁷