We show in this paper that the change of the internal structure of a sarcomere in a rabbit glycerinated psoas muscle fiber can be examined by analyzing the intensity change of the first- and the second-order optical diffraction lines. A unit-cell (sarcomere)-structure model has been applied to the estimation of the length of thick filaments in a muscle fiber while they undergo dissociation. The optical factors, except for the unit-cell-structure factor, hardly changed during the dissociation of the filaments. Our results show that thick filaments dissociate from both ends on increasing the KCl concentration in the presence of 10 mM pyrophosphate and 5 mM MgCl2. Micromolar concentrations of Ca2+ suppressed to some extent the dissociation of thick filaments. The disassembly of thick filaments occurred at higher KCl concentrations in the absence of pyrophosphate. There was a correlation between the stability of the thick filament structure and cross-bridge formation, which was induced either by the addition of micromolar concentrations of Ca2+ in the presence of Mg-pyrophosphate or by removal of Mg-pyrophosphate.
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机译：我们在本文中表明，通过分析一阶和二阶光学衍射线的强度变化，可以检查兔甘油化腰大肌纤维中肌节的内部结构的变化。单位细胞（肌节）结构模型已应用于估计肌肉纤维中的细丝在解离时的长度。除单胞结构因子外，光学因子在细丝解离期间几乎不变。我们的结果表明，在存在10 mM焦磷酸盐和5 mM MgCl2的情况下，随着KCl浓度的增加，粗丝会从两端解离。 Ca2 +的微摩尔浓度在一定程度上抑制了长丝的解离。在没有焦磷酸盐的情况下，较高的KCl浓度会发生粗丝的分解。粗丝结构的稳定性和跨桥形成之间存在相关性，这是通过在焦磷酸镁存在下添加微摩尔浓度的Ca2 +或通过去除焦磷酸镁来诱导的。
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