Figure 3.

Mechanical anisotropy of the streptavidin tetramer. a) A schematic illustrates the AFM experimental geometry of the [(SNase-I27)₃- SM]₄ construct. b) Examples of force-extension curves show 6 unfolding force peaks of SNase modules without (top panel) or with unfolding force peaks of I27 domains (bottom panel). Thin gray lines are WLC model fits to both sets of curves with ΔLc = 48 nm (SNase, top), 45 nm (SNase, bottom) and 30 nm (I27, bottom), and p = 0.7 nm (SNase) and 0.4 nm (I27). c) The comparison of pdfs which were obtained based on the last force peaks from (b) and similar recordings (black circles in (b); black solid line, n = 56) and detachment forces of I27-(SNase-I27)₃ constructs (gray circle in Figure S7; gray dashed line in Figure 3c, n = 160).