The concentration ratio of Ole to HSA are 0 (A), 1 (B) and 3 (C). Closed circles are the experimental values for DNSA binding in the presence of ibuprofen (A, B; 20μM, C; 24μM). Solid line represents theoretical curves assuming the independent binding of the two ligands. Broken line represents theoretical curves assuming competitive binding between DNSA and ibuprofen. Dotted line represents theoretical curves assuming anti-cooperative (allosteric) interaction between DNSA and ibuprofen. All theoretical curves were constructed using the association constant for each ligand (A; DNSA 1.2×105 M-1, ibuprofen 37.1×105 M-1, B; DNSA 1.3×105 M-1, ibuprofen 26.7×105 M-1, C; DNSA 1.7×105 M-1, ibuprofen 6.8×105 M-1).