Quantitation of pulling VWF-A1 from biotinylated GPIb-IX. (A) Plot of lifetimes of the GPIb-IX/VWF-A1 bond vs force (mean ± SEM, n >3). Shown in the insert is a representative histogram of unbinding force (collected under a pulling speed of 100 nm/s) used to obtain bond lifetimes.³⁹  (B) Fit of unfolding force vs extension data to the WLC model (dashed line), which yielded a contour length of 25.1 ± 0.3 nm. Extension distances were sorted by unfolding force into 4-pN bins. A histogram of extension (insert) was used to find peak extension. Unfolding forces were averaged for each bin (n = 23-51 per bin). Error bars are 1 SD for force and half-bin width for extension.