Baskin R J, Yeh Y, Burton K, Chen J S, Jones M
Biophys J. 1986 Jul;50(1):63-74. doi: 10.1016/S0006-3495(86)83439-7.
Optical ellipsometry studies of single, skinned muscle fibers conducted on the diffraction orders have yielded spectra that are sensitive to the state of the fiber. The linearly polarized light field vector becomes elliptically polarized as it passes through the fiber and may be collected at the diffraction orders. Fibers that have been subjected to extraction of myosin (0.6 M KCl) retain a weak diffraction pattern and exhibit a substantially decreased depolarization of incident linearly polarized light. A significant decrease in polarization is seen in skinned fibers that are subject to an increase in pH from 7.0 to 8.0. This increase in pH results in a decrease of approximately 30% in the depolarization angle of single fibers. The major decrease in depolarization angle that we observe at pH 8.0 is consistent with the notion that as cross-bridges move out from the shaft of the thick filament, their ability to cause depolarization of the incident linearly polarized light decreases. This interpretation is also consistent with the work of Ueno and Harrington where the decrease in the ability to cross-link S-1 and S-2 to the thick filament at pH 8.2 suggests cross-bridge movement away from the thick filament. A large decrease in birefringence, seen after treatment of skinned fibers with alpha-chymotrypsin, appears to be related to the breakdown of myosin into rod, S-1, heavy meromyosin, and light meromyosin.
对单根去表皮肌纤维的衍射级次进行椭圆偏振光研究，得到了对纤维状态敏感的光谱。线偏振光场矢量在穿过纤维时会变成椭圆偏振光，并可在衍射级次处收集。用肌球蛋白提取液（0.6 M KCl）处理过的纤维保留了微弱的衍射图样，并表现出入射线偏振光的去极化程度大幅降低。在pH从7.0增加到8.0的去表皮纤维中，观察到偏振度显著降低。pH值的这种增加导致单根纤维的去极化角度降低约30%。我们在pH 8.0时观察到的去极化角度的主要降低与这样一种观点一致，即随着横桥从粗肌丝轴向外移动，它们引起入射线偏振光去极化的能力降低。这种解释也与上野和哈林顿的研究结果一致，他们发现在pH 8.2时，S-1和S-2与粗肌丝交联的能力下降，这表明横桥从粗肌丝上移开。在用α-胰凝乳蛋白酶处理去表皮纤维后观察到的双折射大幅降低，似乎与肌球蛋白分解为杆状、S-1、重酶解肌球蛋白和轻酶解肌球蛋白有关。
