Heidlauf Thomas, Klotz Thomas, Rode Christian, Siebert Tobias, Röhrle Oliver
Institute of Applied Mechanics (CE), University of Stuttgart, Stuttgart, Germany.
Stuttgart Research Centre for Simulation Technology (SRC SimTech), University of Stuttgart, Stuttgart, Germany.
PLoS Comput Biol. 2017 Oct 2;13(10):e1005773. doi: 10.1371/journal.pcbi.1005773. eCollection 2017 Oct.
Contractions on the descending limb of the total (active + passive) muscle force-length relationship (i. e. when muscle stiffness is negative) are expected to lead to vast half-sarcomere-length inhomogeneities. This is however not observed in experiments-vast half-sarcomere-length inhomogeneities can be absent in myofibrils contracting in this range, and initial inhomogeneities can even decrease. Here we show that the absence of half-sarcomere-length inhomogeneities can be predicted when considering interactions of the semi-active protein titin with the actin filaments. Including a model of actin-titin interactions within a multi-scale continuum-mechanical model, we demonstrate that stability, accurate forces and nearly homogeneous half-sarcomere lengths can be obtained on the descending limb of the static total force-length relation. This could be a key to durable functioning of the muscle because large local stretches, that might harm, for example, the transverse-tubule system, are avoided.
在总（主动+被动）肌肉力-长度关系的下降支上的收缩（即当肌肉刚度为负时）预计会导致大量半肌节长度不均匀性。然而，在实验中并未观察到这一点——在这个范围内收缩的肌原纤维中可能不存在大量半肌节长度不均匀性，而且初始不均匀性甚至可能会降低。在这里，我们表明，当考虑半活性蛋白肌联蛋白与肌动蛋白丝的相互作用时，可以预测半肌节长度不均匀性的不存在。在多尺度连续介质力学模型中纳入肌动蛋白-肌联蛋白相互作用模型，我们证明在静态总力-长度关系的下降支上可以获得稳定性、精确的力和几乎均匀的半肌节长度。这可能是肌肉持久功能的关键，因为避免了可能会损害例如横管系统的大的局部拉伸。
