The carboxyl terminus of multimeric VN is masked when VN is incorporated into a fibrin network. The concentration of antibody or biotinylated heparin was determined at which half-maximal binding to plastic-coated multimeric VN was observed. Using this concentration, binding to multimeric VN incorporated into a fibrin network was measured. Relative binding was calculated as percentage binding of antibodies to fibrin/VN divided by binding to VN alone, taking Poab Ra#60 as 100%. This was done for Moabs directed against the amino-terminus (M4, 16A7), the middle portion (19G8, VN7), and the carboxyl terminus (12B5, huMab VN18) of VN and for heparin.