Cleveland G G, Chang D C, Hazlewood C F, Rorschach H E
Biophys J. 1976 Sep;16(9):1043-53. doi: 10.1016/S0006-3495(76)85754-2.
The anisotropy of the spin-diffusion coefficient Ds of water protons in skeletal muscle has been studied by pulsed NMR methods. The mid-portion of the tibialis anterior muscle of mature male rats was placed in a special sample holder by means of which the muscle fiber orientation theta relative to the diffusion direction could be varied over the range 0 degrees less than or equal to theta less than or equal to 90 degrees. The value of Ds(theta) was determined for theta = 0 degrees, 45 degrees, and 90 degrees. The measured anisotropy Ds(0)/Ds(90) was 1.39, and the value of Ds(0) was 1.39 X 10(-5) cm2/s. These results are interpreted within the framework of a model calculation in which the diffusion equation is solved for a regular hexagonal network similar to the actin-myosin filament network. The large anisotropy, and the large reduction in the value of Ds measured parallel to the filament axes lead to two major conclusions: (a) interpretations in which the reduction in Ds is ascribed to the effect of geometrical obstructions on the diffusion of "free" water are ruled out; and, (b) there is a large fraction of the cellular water associated with the proteins in such a way that its diffusion coefficient is substantially reduced.
利用脉冲核磁共振方法研究了骨骼肌中水质子自旋扩散系数Ds的各向异性。将成年雄性大鼠胫骨前肌的中部置于一个特殊的样品架中，通过该样品架，肌肉纤维相对于扩散方向的取向θ可在0°≤θ≤90°范围内变化。测定了θ = 0°、45°和90°时Ds(θ)的值。测得的各向异性Ds(0)/Ds(90)为1.39，Ds(0)的值为1.39×10(-5) cm2/s。这些结果在一个模型计算的框架内得到解释，在该模型计算中，针对类似于肌动蛋白-肌球蛋白丝网络的规则六边形网络求解扩散方程。大的各向异性以及平行于丝轴测得的Ds值的大幅降低导致两个主要结论：(a) 排除了将Ds降低归因于几何障碍对 “自由” 水扩散影响的解释；(b) 很大一部分细胞内水以其扩散系数大幅降低的方式与蛋白质结合。
