Yeh Y, Corcoran M E, Baskin R J, Lieber R L
Biophys J. 1983 Dec;44(3):343-51. doi: 10.1016/S0006-3495(83)84308-2.
Light diffraction spectra from single or small bundles of skinned striated muscle fibers show large changes in polarization properties when muscles are placed into rigor. The technique of combining optical diffraction and ellipsometry measurements has previously been shown by Yeh and Pinsky to be a sensitive probe of periodic anisotropic regions of the fiber. In the present work, using this method, the observed spectrum shows marked decrease in the measured phase angle, delta, as the fiber approaches the rigor state. The degree of phase angle change is a function of sarcomere length: Maximum overlap of approximately 2.3 microns gives the most change in delta a delta delta R-R approximately 35 degrees decrease for a bundle of three fibers. At a sarcomere length of 2.9 microns this delta delta R-R value is only 10 degrees. At a nonoverlapping length of approximately 3.8 microns, delta does not vary at all upon the removal of ATP. The rigor state was confirmed by stiffness measurements made after small-amplitude (0.75%), quick length changes. Upon re-relaxation, the stiffness of the skinned fiber decreased to the value of the resting state (4 mM ATP) and the phase angle delta returned to its original value. A model based on either anisotropic subunit-2 (S-2) movements or other cross-bridge-related structural anisotropy (form birefringence) changes during the relaxed-rigor transition is suggested.
当肌肉进入僵直状态时，来自单个或一小束去皮横纹肌纤维的光衍射光谱显示出偏振特性的巨大变化。Yeh和Pinsky先前已证明，将光学衍射和椭圆偏振测量相结合的技术是纤维周期性各向异性区域的灵敏探针。在本研究中，使用该方法，观察到的光谱显示，随着纤维接近僵直状态，测量的相角δ显著减小。相角变化的程度是肌节长度的函数：在约2.3微米的最大重叠时，三根纤维束的δ变化最大，δR-R约减小35度。在2.9微米的肌节长度下，该δR-R值仅为10度。在约3.8微米的非重叠长度下，去除ATP后δ根本不变。通过在小幅度（0.75%）快速长度变化后进行的刚度测量证实了僵直状态。重新松弛后，去皮纤维的刚度降至静息状态（4 mM ATP）的值，相角δ恢复到其原始值。提出了一个基于各向异性亚基-2（S-2）运动或在松弛-僵直转变过程中其他与横桥相关的结构各向异性（形态双折射）变化的模型。
