TY - EJOU AU - Herzog, JA. AU - Leonard, TR. AU - Jinha, A. AU - Herzog, W. TI - Titin (Visco-) Elasticity in Skeletal Muscle Myofibrils T2 - Molecular \& Cellular Biomechanics PY - 2014 VL - 11 IS - 1 SN - 1556-5300 AB - Titin is the third most abundant protein in sarcomeres and fulfills a number of mechanical and signaling functions. Specifically, titin is responsible for most of the passive forces in sarcomeres and the passive visco-elastic behaviour of myofibrils and muscles. It has been suggested, based on mechanical testing of isolated titin molecules, that titin is an essentially elastic spring if Ig domain un/refolding is prevented either by working at short titin lengths, prior to any unfolding of Ig domains, or at long sarcomere (and titin) lengths when Ig domain un/refolding is effectively prevented. However, these properties of titin, and by extension of muscles, have not been tested with titin in its natural structural environment within a sarcomere. The purpose of this study was to gain insight into the Ig domain un/refolding kinetics and test the idea that titin could behave essentially elastically at any sarcomere length by preventing Ig domain un/refolding during passive stretch-shortening cycles. Although not completely successful, we demonstrate here that titin’s visco-elastic properties appear to depend on the Ig domain un/refolding kinetics and that indeed, titin (and thus myofibrils) can become virtually elastic when Ig domain un/refolding is prevented. KW - skeletal muscle KW - titin KW - actin KW - myosin KW - stretch-shortening cycles KW - passive properties KW - stiffness KW - elastic KW - visco-elastic KW - energy loss KW - hysteresis KW - muscle properties KW - cross-bridge theory KW - sliding filament theory KW - sarcomere KW - sarcomere mechanics DO - 10.3970/mcb.2014.011.001