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 研究中心，而研究中心不一定是研究者所在的机构。 我们使用的间接飞行肌肉的巨型水虫Lethocerus（IFM）作为一个高度有序的模型系统研究肌肉的结构和功能。我们已经记录了同步辐射X-射线衍射图案从放松，僵硬和活动（等长收缩=高静态张力[HST]在pCa4.5）状态的甘油化Lethocerus（IFM），探讨其结构动力学如何能够统一与脊椎动物肌肉，包括青蛙骨骼肌（FSM）。使用5米相机，我们能够检测净轴向运动的肌球蛋白头质量朝向或远离肌球蛋白丝中点，通过解决相对强度变化丰富的干扰分裂精细结构的IFM 14.5 nm的反射。当斜拉伸1.5- 2.0%时，松弛状态IFM的高被动刚度使被动张力维持在主动等距F0的30-60%，但14.5nm的间距和粗丝长度仅增加0.02%。因此，99%的松弛肌节延伸必须发生在C-丝/Z-带连接，将被动张力传递到粗丝。用干涉法检测到松弛肌球蛋白头冠架内的包装或形状没有变化。在松弛=等距活化后，IFM 14.5nm的衍射变化不同于FSM报告的那些。间距延长约0.07%（与FSM 1.3%相比），总强度（由于连接和分离头的混合）下降约40%（FSM变化约10%;分离头的贡献不确定）。X射线干涉测量法信号在平均IFM横桥角度或形状上没有净变化（FSM实质上重新排列）。 在19.3 nm的层线上，第一行线斑点的10倍增亮信号为肌动蛋白靶区的交叉桥标记，而新的外部条纹信号为原肌球蛋白移位引起的细丝的空间解阻断。 对HST和僵直的斜坡拉伸实验进行了分析。 这些结果可以与脊椎动物肌肉的结果进行比较和对比，以获得肌肉中基本力产生事件的更统一的图像。

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. We use the indirect flight muscle of the giant water bug Lethocerus (IFM) as a highly ordered model system for studying muscle structure and function. We have recorded synchrotron x-ray diffraction patterns from relaxed, rigor and active (isometric contraction =High Static Tension [HST] at pCa4.5) states of glycerinated Lethocerus (IFM), to explore how its structural dynamics can unify with those of vertebrate muscles including frog skeletal muscle (FSM). Using a 5m camera we were able to detect net axial motions of myosin head mass toward or away from the myosin filament midpoint by resolving relative intensity changes within the rich interference-splitting fine structure of the IFM 14.5nm meridional reflection. When ramp-stretched 1.5-2.0%, the high passive stiffness of Relaxed-State IFM sustains passive tensions to 30-60% of active isometric F0, but the 14.5nm spacing and thick filament length increase together by only 0.02%. Thus 99% of relaxed sarcomere extension must occur in the C-filament/Z-band linkages that transmit passive tension to thick filaments. No change of packing or shape within crown-shelves of relaxed myosin heads is detected interferometrically. Upon Relaxed = Isometric Activation, IFM 14.5nm meridional changes differ from those reported for FSM. Spacing elongates ~0.07% (compared to FSM 1.3%), total intensity (due to mix of attached and detached heads) drops ~40% (FSM changes ¿¿10%; detached head contribution uncertain). X-ray interferometry signals no net change in averaged IFM crossbridge angle or shape (FSM rearranges substantially). On the 19.3 nm layer line, 10-fold brightening of the first row-line spot signals crossbridge labeling of actin Target Zones, while a new outer streak signals steric unblocking of thin filaments by a tropomyosin shift. Ramp-stretch experiments on HST and rigor are being analyzed. These results can be compared and contrasted with those from vertebrate muscle to achieve a more unified picture of the fundamental force generating events in muscle.