FIGURE 5.

Force-extension curve of Ig 1-8 and Ig 8-15 fragments. Top, location of fragments in spring region of cardiac titin (N2B isoform). An electron micrograph is also shown of a cardiac sarcomere (36) labeled with antibodies that demarcate the N2B-Us, PEVK, and tandem Ig segments; superimposed is a schematic of two titin molecules. A-D, force-extension curves show regularly separated force peaks that were fit with the WLC equation (broken lines). See “Experimental Procedures” for additional details.