Cardinaud R, Bernengo J C
Biophys J. 1985 Nov;48(5):751-63. doi: 10.1016/S0006-3495(85)83833-9.
Electric birefringence measurements and depolarized light scattering experiments were performed with HMM, LMM, and rod, the three fragments of myosin, under conditions (0.3 M KCl, 0.02 M PO4, pH 7.3) the medium currently used for biochemical assays of myosin in its native state as well as of its subfragments. The comparison of myosin and rod relaxation times (17.2 and 22.8 microseconds, respectively) suggests that the average bend angle in the tail is sharper in intact myosin (90 degrees) whereas rod, when detached from the heads, is a more elongated species with an average bend angle of 120-135 degrees. The LMM relaxation time (6.4 microseconds) is consistent with a rigid linear stick model of length 78 nm. Flexibility in myosin tail is thus confirmed as located in the HMM-LMM hinge. LMM and rod did not exhibit any significant variation of their apparent relaxation times with concentration and the decay curves were best fitted by a single exponential, evidence that the concentration of parallel staggered dimers was negligible in the concentration range studied here (0-7 g/l). This observation lends support to previous results obtained with myosin. Respective HMM, LMM, and rod molecular weights and homogeneity as evaluated by SDS-PAGE analysis were correlated to the Kerr constants of their solutions. Large variations in LMM Kerr constants could be related to the loss of a COOH-terminal peptide on prolonged chymotryptic digestion. Electric birefringence combined with depolarized light scattering is presented as a potential method for net charge distribution studies.
在目前用于肌球蛋白及其亚片段天然状态生化分析的介质条件（0.3M氯化钾、0.02M磷酸根、pH7.3）下，对肌球蛋白的三个片段HMM、LMM和杆状片段进行了电场双折射测量和去偏振光散射实验。肌球蛋白和杆状片段弛豫时间的比较（分别为17.2和22.8微秒）表明，完整肌球蛋白尾部的平均弯曲角度更尖锐（90度），而从头部脱离的杆状片段是一种更细长的物种，平均弯曲角度为120 - 135度。LMM的弛豫时间（6.4微秒）与长度为78nm的刚性线性棒模型一致。因此，证实了肌球蛋白尾部的柔韧性位于HMM - LMM铰链处。LMM和杆状片段的表观弛豫时间随浓度没有任何显著变化，并且衰减曲线最适合用单指数拟合，这表明在此研究的浓度范围（0 - 7g/l）内，平行交错二聚体的浓度可以忽略不计。这一观察结果支持了先前用肌球蛋白获得的结果。通过SDS - PAGE分析评估的各自HMM、LMM和杆状片段的分子量和均一性与其溶液的克尔常数相关。LMM克尔常数的巨大变化可能与长时间胰凝乳蛋白酶消化导致COOH末端肽的丢失有关。电场双折射与去偏振光散射相结合被提出作为一种用于净电荷分布研究的潜在方法。
