PolyP delays fibrinolysis. Fibrin clots were formed with purified fibrinogen (2.4μM) in the absence (gray line) and presence (black line) of polyP₆₅ (325μM). Lysis was induced by including 20pM tissue plasminogen activator (tPA) and 0.24μM plasminogen (A) or 11nM plasmin (B) with fibrinogen before activation with thrombin (0.25 U/mL) and CaCl₂ (5mM). Lysis was monitored by changes in absorbance at 340 nm for 4 hours with time points every 1 minute. Results are normalized to account for polyP-induced changes in turbidity and are expressed as mean ± SEM of the percentage of lysis (n = 6). (C) Lysis was followed as described for tPA and plasminogen but with the addition of various polyP₆₅ concentrations (0-3.25mM). The time to mean time to 50% lysis ± SEM is shown (n = 3). (D) Clots were formed in the presence of monophosphate or polyphosphate of various chain lengths (5-65 phosphate residues) at equivalent monomer concentration (325μM). Lysis by tPA and plasminogen was monitored, and the mean 50% lysis time ± SEM is shown (n = 4). Fifty percent lysis times of statistical significance are denoted with **P < .001 and ***P < .001).