INSECT FLIGHT MUSCLE HOT, COLD, PULLED AND PULLING

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得主要资金， 因此可以在其他CRISP条目中表示。所列机构为 中心，不一定是研究者的机构。 我们的整体计划将X射线衍射（XRD，甘油化天然纤维）和 薄切片EM断层扫描（纤维速冻和冷冻替代），以表征 肌球蛋白桥的结构、排列和动态编排（肌肉运动 分子）在一个水蝽昆虫飞行肌肉（IFM）的无与伦比的晶体规则性。X-的 射线图案与在相同时间内速冻的纤维的平行EM相关。 平衡状态，扰动或过渡，直接成像的形状和模式， 十字桥，在这肌肉比任何其他更清晰。最近的进展（附后）使我们 提出了IFM著名的拉伸激活（SA）过程的未知结构触发因素， 这也可能揭示哺乳动物心肌中类似的过程。已发布的 来自3个主要IFM州（RLX，ACT和RIG）的XRD图谱图库（PNAS，2008）显示了相同的结果。 ACT结构通过2种不同的RLX <$ACT途径，Ca 2+激活（pCa 4.5）和 SA（pCa 5.7）。 SA循环工作回路形式的引人注目的新XRD“电影”（生物物理学 Abst，2009），由正弦2%/2 Hz长度变化驱动，显示了 多次反射，信号著名的主要行动，由crossbridge和原肌球蛋白。一个 现在，由拉伸并保持长度步触发的SA的另一种单发形式， 支持工作循环电影提出的模型，表明原肌球蛋白进入 在横桥开始连接和产生力之前的ON位置。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Our overall program correlates X-ray diffraction (XRD, of glycerinated native fibers) and thin-section EM tomography (fibers quick-frozen & freeze-substituted) to characterize structure, arrangement and dynamic choreography of myosin crossbridges (muscle¿s motor molecules) in a waterbug insect flight muscle (IFM) of unexcelled crystalline regularity. X- ray patterns are correlated with parallel EM of fibers quick-frozen during the same equilibrium state, perturbation or transition, to image directly the shapes and patterns of crossbridges, clearer in this muscle than any other. Recent progress (attached) has poised us to suggest the unknown structural trigger for IFM¿s famous stretch-activation (SA) process, which may also throw light on the similar process in mammalian heart muscle. A published gallery (PNAS, 2008) of XRD patterns from 3 major IFM states, RLX, ACT & RIG, shows the same ACT structure reached by 2 distinct RLX¿ACT pathways, Ca2+ -activation (at pCa 4.5) and SA (at pCa 5.7). Striking new XRD "movies" of the cycling work-loop form of SA (Biophysics Abst, 2009), driven by sinusoidal 2%/2Hz length changes, show cycling intensity changes in multiple reflections that signal well-known major actions by crossbridges and tropomyosin. An alternate single-shot form of SA, triggered by a stretch-and-hold length-step, is now supporting the model suggested by the work-loop movies, indicating that tropomyosin moves into ON position before crossbridges begin to attach and generate force.