Representative isothermal titration calorimetry analyses of tetramerization site complexes. All experiments were conducted at 23°C with β16-17 in the reaction cell and the α0-1 peptide in the titration syringe. Top panels show baseline subtracted titration curve raw data; bottom panels show blank corrected integrated areas of the peaks from the top panel (●) and the best data fit using a nonlinear least-squares method (—). The protein concentrations of α0-1 mutants in the syringe were: R34W = 330 μM; K48R = 560 μM; G46V = 680 μM; R28H = 600 μM; V31A = 600 μM; R41W = 650 μM; R45T = 660 μM; R45S = 600 μM. The protein concentrations of the β16-17 wild-type recombinant in the cell were: 18 μM for R34W and 25 to 30 μM in all other cases.