Binding properties of 14E11. (A) Coomassie blue–stained 10% polyacrylamide gel of human (H) and mouse (M) recombinant fXI. (B-C) Western blots of nonreducing 10% polyacrylamide gels of mouse (B) and human (C) normal (N) and fXI-deficient (XI^−/−) plasmas, using biotinylated-14E11 for detection. rXI in panel B indicates recombinant mouse fXI control. (D) Binding of biotinylated-14E11 to immobilized mouse fXI (○), human fXI (●), or human fXIa (□), as described in “Methods.” (E) Western blot of nonreducing 10% polyacrylamide gel of human fXI (hXI), human prekallikrein (PK), and human fXI in which the A1, A2, A3, or A4 domain has been replaced with the corresponding domain from PK. Position for fXI dimer is indicated to the right by “D,” and for monomeric PK by “M.” Note fXI with the PK A4 domain is a monomer because A4 mediates fXI dimer formation. (F) Western blot (left panel) of a nonreducing 10% polyacrylamide gel of human fXI (hXI) and individual human fXI apple domains linked to tPA. The right panel is a stained gel showing the recombinant apple domain-tPA chimeras. Note the A4 chimera forms a dimer. For panels A-C and E, positions of molecular mass standards in kDa are at the left of the figures, and for panel F at the right.