STRUCTURAL STUDIES OF MUSCLE TRANSIENTS

肌肉收缩的中心谜团是酶是如何 Mysoin Head(十字桥)将储存的能量转化为机械能量 工作。X射线衍射是为数不多的生物物理技术之一。 它允许收集关于 生理上相关的毫秒时标和这类实验 实际上是同步辐射最早的用途之一。其中之一 这些实验的目标一直是检测结构的变化 由于肌肉交叉桥的动作由快速同步 机械瞬变。到目前为止，这样的实验仅限于 非常强的反射，例如基于肌球蛋白的14.3 nm反射 和赤道。我们最近获得了2毫秒的时间分辨数据 首次显示肌动蛋白为基础的强度变化 反射(主要在5，9和5.1 nm层线上) 肌肉交叉桥的同步动作..通过测量以下方面的变化 2.72 nm子午线反射的位置作为 残留力在给定的快速释放后，我们也能够 测量肌肉细丝的瞬时弹性，数量 希望建立肌肉模型的肌肉生理学家对此非常感兴趣。 我们能够在BioCAT光束线上获得高质量的数据 并且正在尝试使用 肌动蛋白、肌球蛋白和原肌球蛋白的已知晶体结构。

The central mystery of muscle contraction is how the enzymatic mysoin heads (crossbridges) convert the energy stored into mechanical work. X-ray diffraction is one of the few biophysical techniques which allows collection of structural information on the physiologically relevant ms time scale and these kinds of experiments were in fact one of the first uses of synchrotron radiation. One of the goals of these experiments has been to detect structural changes due to the action of muscle crossbridges synchronized by rapid mechanical transients. Such experiments so far have been limited to very strong reflections such as the myosin-based 14.3 nm reflection and the equator. We recently obtained 2 ms time resolved data that showed, for the first time, intensity changes in actin -based reflections (mainly on the 5,9 and 5.1 nm layer lines) due to synchronized action of muscle crossbridges.. By measuring changes in the position of the 2.72 nm meridional reflection as a function of the residual force after a given quick release, we were also able to measure the instantaneous elasticity of muscle filaments, quantities of intense interest to muscle physiologists who wish to model muscle. We were able to obtain excellent quality data on the BioCAT beamline and are in the process of attempting to model this data using the known crystal structures of actin, myosin and tropomysosin.