Brenner B, Yu L C, Podolsky R J
Biophys J. 1984 Sep;46(3):299-306. doi: 10.1016/S0006-3495(84)84026-6.
Equatorial x-ray diffraction patterns from single skinned rabbit psoas fibers were studied at various ionic strengths to obtain structural information regarding cross-bridge formation in relaxed muscle fibers. At ionic strengths between 20 and 50 mM, the intensity of the 11 reflection, I11, of the relaxed state was close to that of the rigor state, whereas the intensity of the 10 reflection, I10, was approximately twice that of rigor reflection. Calculations by two-dimensional Fourier synthesis indicated that substantial extra mass was associated with the thin filaments under these conditions. With increasing ionic strength between 20 and 100 mM, I10 increased and I11 decreased in an approximately linear way, indicating net transfer of mass away from the thin filaments towards the thick filaments. These results provided evidence that cross-bridges were formed in a relaxed fiber at low ionic strengths, and that the number of cross-bridges decreased as ionic strength was raised. Above mu = 100 mM, I10 and I11 both decreased, indicating the onset of increasing disorder within the filament lattice.
在不同离子强度下研究了来自单根去皮兔腰大肌纤维的赤道X射线衍射图谱，以获取有关松弛肌纤维中横桥形成的结构信息。在离子强度为20至50 mM之间时，松弛状态下11反射（I11）的强度接近僵直状态，而10反射（I10）的强度约为僵直反射的两倍。二维傅里叶合成计算表明，在这些条件下，大量额外质量与细肌丝相关。随着离子强度在20至100 mM之间增加，I10增加而I11以近似线性的方式下降，表明质量从细肌丝向粗肌丝净转移。这些结果提供了证据，表明在低离子强度下松弛纤维中形成了横桥，并且随着离子强度升高，横桥数量减少。在μ = 100 mM以上，I10和I11均下降，表明丝晶格内无序度增加的开始。
