Fig. 3. SDS—PAGE analysis of titin isoform expression in quadriceps (vastus) muscles of cow, dog, rabbit and mouse. Cow vastus appears to express three titin bands, while dog, rabbit and mouse each express two. Looking at the most abundant isoform within each muscle type, there is a noticeable shift in expression from the largest, and hence most compliant, isoform (in the cow) to the smallest, stiffest isoform (in the mouse). The lowest mobility band present in each lane is nebulin (780 kDa).