Figure 1.

Single-molecule mechanics of ddFLN1–5. (A) Structure of the ddFLN1–5 construct comprising immunoglobulin domains 1–5 including domain 4 (blue). (B) Force–extension curve of ddFLN1–5 unfolding. A total of four immunoglobulin domains are unfolded. Domain 4 unfolding (highlighted in blue) proceeds by means of a stable unfolding intermediate, whereas other immunoglobulin domains are two-state unfolders. (Nuclear magnetic resonance structures are adapted from Fucini et al (1997) and Schwaiger et al (2004).) Orange lines are worm-like chain fits using P=0.5 nm and contour lengths as indicated above the peaks (Bustamante et al, 1994).