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。 我们的程序关联X射线衍射（甘油化天然纤维）和薄切片EM断层扫描（纤维速冻和冷冻取代）来表征肌球蛋白横桥（肌肉的马达分子）的结构，排列和动态编排在一个水蝽昆虫飞行肌肉（IFM）的无与伦比的结晶规律。X射线结果将通过在相同状态或操作期间快速冷冻的纤维上的平行EM来支持和检查，以直接对结构进行成像。 (IFM给出了任何肌肉的肌球蛋白横桥的最清晰的EM图像。IFM的X射线图案显着不同的其他横纹肌（青蛙骨骼）的XRD研究，反映不同的细丝晶格包装，细丝螺旋几何形状，和全重叠肌节限制在3-5%的长度变化。 肌球蛋白丝、肌动蛋白丝以及两者共同产生的X射线反射（~5 nm）与青蛙肌肉中的一样，我们正在赶上动态（收缩）状态。 得益于APS/BioCAT的光束质量、强度和探测器系统，青蛙肌肉研究的大部分追赶工作可以在另外2年内完成。 我们在这里建议测量来自湿和冷冻IFM的衍射图案，将横桥结合和原肌球蛋白运动的分级X射线信号与[Ca 2 +]依赖的力水平和拉伸激活力的时间依赖性上升相关联，通过X射线干涉来剖析递增的横桥制动和力保持结构响应，时间分辨的横桥角度变化和肌丝弹性（合作者HE Huxley），并将相同或平行的速冻IFM纤维的SAXS冷冻衍射和EM的发现相关联。

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 program correlates X-ray diffraction (glycerinated native fibers) and thin-section EM tomography (fibers quick-frozen & freeze-substituted) to characterize structure, arrangement and dynamic choreography of myosin crossbridges (motor molecules of muscle) in a waterbug insect flight muscle (IFM) of unexcelled crystalline regularity. X-ray results will be supported and checked by parallel EM on fibers quick-frozen during the same state or maneuver, to image structures directly. (IFM gives the clearest EM images of myosin crossbridges of any muscle.) IFM X-ray patterns differ significantly from those of other striated muscles (frog skeletal) studied by XRD, reflecting different filament lattice packing, filament helical geometry, and full-overlap sarcomeres limited to 3-5% length changes. X-ray reflections (to ~5 nm) attributable to myosin filaments, actin filaments, and both jointly, are as well worked out as in frog muscle, and we are catching up regarding dynamic (contraction) states. Thanks to the beam quality, intensity and detector systems at APS/BioCAT, much of the catch-up with frog muscle studies can be done in another 2 years. We propose here to measure diffraction patterns from wet & frozen IFM, relating graded x-ray signals of crossbridge binding and tropomyosin movement to [Ca2+]-dependent force levels & to time-dependent rise of stretch-activated force, dissect incremental crossbridge braking and force-holding structural responses, time-resolve crossbridge angle changes and myofilament elasticity by x-ray interference (collaborator HE Huxley), and to correlate the findings of SAXS cryo-diffraction and EM of the same or parallel quick-frozen IFM fibers.