Data from: The cross-bridge spring: can cool muscles store elastic energy?

Muscles not only generate force. They may act as springs, providing energy storage to drive locomotion. Although extensible myofilaments are implicated as sites of energy storage, we show that intramuscular temperature gradients may enable molecular motors (cross-bridges) to store elastic strain energy. Using time-resolved small-angle X-ray diffraction paired with in situ measurements of mechanical energy exchange in flight muscle of Manduca sexta we produced high-speed movies of X-ray equatorial reflections indicating cross-bridge association with myofilaments. A temperature gradient within the flight muscle leads to lower cross-bridge cycling in the cooler regions. Those cross-bridges could elastically return energy at the extrema of muscle lengthening and shortening, helping drive cyclic wing motions. These results suggest cross-bridges can perform functions other than contraction, acting as molecular links for elastic energy storage.

肌肉不仅能够产生肌力，还可充当弹簧，通过储存能量来驱动机体运动。尽管此前研究认为可伸展肌丝（extensible myofilaments）是能量储存的位点，但本研究证实，肌内温度梯度可使分子马达（molecular motors）即横桥（cross-bridges）储存弹性应变能。本研究将时间分辨小角X射线衍射（time-resolved small-angle X-ray diffraction）与烟草天蛾（Manduca sexta）飞翔肌的机械能交换原位测量相结合，获得了表征横桥与肌丝结合状态的X射线赤道反射高速影像。飞翔肌内的温度梯度会降低温度较低区域的横桥循环速率，此类横桥可在肌肉伸缩的极值点弹性释放能量，助力翼部周期性运动。上述结果表明，横桥除收缩功能外，还可作为弹性储能的分子连接体发挥作用。