Yagi N, Horiuti K, Takemori S
Department of Pharmacology, Tohoku University School of Medicine, Japan.
J Muscle Res Cell Motil. 1998 Jan;19(1):75-86.
X-ray diffraction experiments were performed on rat soleus and psoas muscles using synchrotron radiation from a multipole wiggler. The X-ray diffraction patterns were recorded at a time resolution of 16.7 ms with an X-ray image intensifier and a CCD video camera. A bundle of 10-15 muscle fibres was activated by photorelease of 2.2 mM ATP from 7 mM caged-ATP at 15 degrees C. In soleus muscle fibres in the presence of 40 microns Ca2+, the tension developed with a half-time of 0.13 s. The intensities of the (1,1) equatorial reflection and the actin layer-lines at 1/36 nm-1 and 1/5.9 nm-1 decreased from their rigor values in the first 16.7 ms frame to a level higher than in the resting state, and then remained unchanged during the tension development. The intensity of the 14.5 nm meridional reflection increased as the tension developed. These results show that after the ATP release some myosin heads are stereospecifically attached to actin well before tension development, and suggest that their number does not change markedly on contraction.
使用来自多极摆动器的同步辐射对大鼠比目鱼肌和腰大肌进行了X射线衍射实验。用X射线图像增强器和电荷耦合器件（CCD）摄像机以16.7毫秒的时间分辨率记录X射线衍射图案。在15℃下，通过从7毫摩尔笼化ATP中光释放2.2毫摩尔ATP来激活一束10 - 15根肌纤维。在存在40微米钙离子的比目鱼肌纤维中，张力以0.13秒的半衰期发展。（1,1）赤道反射以及1/36纳米⁻¹和1/5.9纳米⁻¹处肌动蛋白层线的强度在第一个16.7毫秒帧中从其强直值下降到高于静息状态的水平，然后在张力发展过程中保持不变。14.5纳米子午线反射的强度随着张力的发展而增加。这些结果表明，在ATP释放后，一些肌球蛋白头部在张力发展之前就立体特异性地附着于肌动蛋白，并且表明它们的数量在收缩时不会明显变化。
