INSECT FLIGHT MUSCLE HOT, COLD, PULLED AND PULLING

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。本文以巨型水虫的间接飞行肌（IFM）为模型系统，研究其结构和功能。我们记录了甘油化Lethocerus （IFM）在松弛、严格和活跃（等距收缩=高静态张力[HST]在pCa4.5）状态下的同步加速器x射线衍射图，以探索其结构动力学如何与脊椎动物肌肉（包括青蛙骨骼肌（FSM））的结构动力学相统一。利用5m摄像机，通过解析IFM 14.5nm经向反射的丰富干涉分裂精细结构内的相对强度变化，我们能够检测肌凝蛋白头团向或远离肌凝蛋白丝中点的净轴向运动。当坡道拉伸1.5-2.0%时，松弛态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间距和粗丝长度仅增加0.02%。因此，99%的松弛肌节伸展必须发生在将被动张力传递到粗纤维的c -丝/ z -带连接中。在松弛的肌球蛋白头的冠状架内未检测到包装或形状的变化。在松弛=等长激活时，IFM的14.5nm经向变化与FSM的不同。间隔延长~0.07%（与FSM相比为1.3%），总强度（由于连接和分离头的混合）下降~40% （FSM变化¿¿10%；分离头贡献不确定）。x射线干涉测量显示IFM交叉桥的平均角度或形状没有净变化（FSM基本上重新排列）。在19.3 nm的层线上，第一行斑点的10倍亮化标志着肌动蛋白靶区的交叉桥标记，而新的外条纹标志着原肌球蛋白位移对细丝的立体解封。分析了斜面拉伸实验在高温下的性能和严密性。这些结果可以与脊椎动物肌肉的结果进行比较和对比，以获得肌肉中产生基本力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.