Selection of fibrinogen-binding Affimers after phage panning. After phage panning, fibrinogen-binding Affimers were tested in turbidimetric assays in a plasma system to determine effects of the Affimers on clot formation and lysis. (A) The effect of scaffold-only control protein and (B) 15 Affimer proteins with distinct sequences on fibrin clot lysis (B). The red dotted line shows threefold increase in prolongation of clot lysis. (C) The effect of F5 and G2 on fibrin clot lysis and (D) clot maximum absorbance in human plasma turbidimetric assays. (E) The effect of linear peptides of the 2 variable regions of Affimer proteins F5 (P1F5 and P2F5) and G2 (P1G2 and P2G2) on fibrin clot lysis and (F) clot maximum absorbance. Numbers on the x-axis (A,C-F) 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, comparisons made against buffer-only control (A,C-F) or scaffold (B). **P< .01.