Hvidt S, Nestler F H, Greaser M L, Ferry J D
Biochemistry. 1982 Aug 17;21(17):4064-73. doi: 10.1021/bi00260a024.
The frequency dependencies of the storage and loss shear moduli, G' and G", of myosin rod solutions at 1.0 and 7.0 degrees C were measured by use of the Birnboim-Schrag multiple lumped resonator apparatus in solvents with and without glycerol. The infinite dilution moduli were determined and compared with theoretical models for a rigid rod and a freely jointed trinodular rod and with an empirical model for a semiflexible rod. Only the latter could fit the data. A rotational relaxation time of 25 mus and a slowest bending time of 3.1 mus, both reduced to water at 20 degrees C, were determined from the fit. A persistence length of about 130 nm was obtained from either the bending time, the rotational relaxation time, or the intrinsic viscosity. The average thermal excursion of the end of subfragment 2 was estimated to be 26 nm, more than sufficient to span the gap between the thick and thin filaments in muscles at all sarcomere lengths. Thus, a hinge between heavy meromyosin and light meromyosin does not appear necessary for myosin-actin contact. Young's modulus of about 1 x 10(9) N/m2 also makes it unlikely that subfragment 2 can be the elastic element in the Huxley-Simmons model of muscle contraction.
在有甘油和无甘油的溶剂中，使用Birnboim-Schrag多集总谐振器装置测量了肌球蛋白杆溶液在1.0℃和7.0℃下储能剪切模量G'和损耗剪切模量G''的频率依赖性。确定了无限稀释模量，并与刚性杆和自由连接的三节点杆的理论模型以及半柔性杆的经验模型进行了比较。只有后者能拟合数据。根据拟合结果确定了在20℃时均换算为水的25微秒的旋转弛豫时间和3.1微秒的最慢弯曲时间。从弯曲时间、旋转弛豫时间或特性粘度中得到了约130纳米的持久长度。估计亚片段2末端的平均热偏移为26纳米，足以跨越所有肌节长度下肌肉中粗、细肌丝之间的间隙。因此，对于肌球蛋白与肌动蛋白的接触，重酶解肌球蛋白和轻酶解肌球蛋白之间的铰链似乎并非必要。约1×10⁹N/m²的杨氏模量也使得亚片段2不太可能是赫胥黎 - 西蒙斯肌肉收缩模型中的弹性元件。
