Transient EPR Spectroscopy and Mechanical Transients in Muscle Fibers

肌肉是生物引擎的原型;其化学燃料ATP的燃烧导致机械力的产生。 这种情况是如何发生的还不是很清楚。 已知相关分子（肌球蛋白和肌动蛋白）形成由肌球蛋白分子的一部分桥接的长的相互交叉的细丝（类似于重叠的梳子）。 根据一个流行的模型，细丝之间的桥燃烧ATP，导致桥的枢转旋转，从而在细丝之间产生应变。 张力可以通过细丝相对于彼此的滑动来减轻，从而缩短肌肉长度。 然而，这种桥梁旋转的证据是缺失的。 Fajer博士建议使用电子顺磁共振（EPR）光谱，一种对分子的取向和动态变化敏感的技术。 由于肌肉没有EPR信号，Fajer博士打算将顺磁探针结合到肌球蛋白的桥部分，这不会干扰肌肉功能，但会特别报告桥的行为。 他将刺激肌肉产生力量，同时记录桥梁的方向和动态变化。 这种方法将直接关联肌肉的结构变化和功能。

The muscle is a prototype of a biological engine; the burning of its chemical fuel, ATP, results in the generation of the mechanical force. How this happens is not very well understood. It is known that molecules involved (myosin and actin) form long inter-digitating filaments (similar to overlapping combs) which are bridged by the portion of the myosin molecule. According to a popular model, the bridge between the filaments burns ATP which causes pivoting rotation of the bridge, thus creating the strain between the filaments. The strain can be relieved by the sliding of the filaments with respect to each other shortening the muscle length. However, the evidence for such a pivoting of the bridge is missing. Dr. Fajer proposes to use electron paramagnetic resonance (EPR) spectroscopy, a technique sensitive to the orientational and dynamic chanees of the molecules. Since the muscle does not have an EPR signal, Dr. Fajer intends to bind a paramagnetic probe to the bridge portion of the myosin which does not perturb muscle function but will report specifically the behavior of the bridge. He will stimulate muscle to produce force and the same time record orientational and dynamic changes of the bridge. Such an approach will directly correlate the structural changes and the function of muscle.