The effect of F5 and G2 on fibrin clot lysis in healthy individuals and in a purified system. (A) Fibrinogen-binding Affimers F5 and G2 were tested in turbidimetric assays in plasma from healthy individuals (n = 12) to study interindividual variability, with scaffold control protein included as a control (Co). Data are presented as the mean ± SD of 12 subjects in each group. (B) Effect of Affimer F5 and (C) Affimer G2 compared with scaffold control protein in the 12 individual plasma samples. The statistical significance of the effect of Affimer F5 or G2 was determined using a 2-tailed, paired Student t test. **Difference from scaffold-only control; P < .01. (D) The effect of F5 and G2 on clot lysis and (E) clot maximum absorbance was tested in turbidimetric assays in a purified fibrinogen system to determine whether effects seen in plasma were fibrinogen-specific. Affimer scaffold-only protein was included as a control. Numbers on the x-axis represent Affimer protein:fibrinogen molar ratios. Data are presented as the mean ± SD of 3 independent experiments. Statistical analysis was performed using 1-way ANOVA. Asterisks represent difference from buffer-only control; *P < .05; **P < .01.