Analysis of the length increase resulted from loss of stability. (A) Histograms of molecular length increment, l_d, obtained using adsorbed A1A2A3 pulled by GPIbα (blue bars) or anti-His mAb captured A1A2A3 pulled by CR1 (red bars). (B-C) Force-time and displacement-time curves with 2 force drops were converted to force–molecular extension curves: 16 and 10 curves, respectively, obtained by GPIbα (blue) and CR1 (red) pulling with short (l_d ∼ 10-20 nm) length increase (B) as well as 10 and 8 curves (obtained by the 2 pulling methods with the same color codes) with long (l_d ∼ 45-50 nm) length increase (C) are overlaid by aligning the first ascending segment. (D) Possible modes of structural destabilization. A model for the native A1A2A3 structure is shown in the far left panel. Force may disrupt the interdomain interactions to uncouple the quaternary structure of the A1A2A3 tridomain (second panel from left) or disrupt the intradomain interactions to partially (third panel from left) or fully (far right panel) unfold the tertiary structure of the A2 domain.