Department of Mechanical Engineering, Washington University in St. Louis, St. Louis, Missouri, USA.
Biophys J. 2011 Jun 8;100(11):2716-25. doi: 10.1016/j.bpj.2011.05.001.
The distributed propulsive forces exerted on the flagellum of the swimming alga Chlamydomonas reinhardtii by surrounding fluid were estimated from experimental image data. Images of uniflagellate mutant Chlamydomonas cells were obtained at 350 frames/s with 125-nm spatial resolution, and the motion of the cell body and the flagellum were analyzed in the context of low-Reynolds-number fluid mechanics. Wild-type uniflagellate cells, as well as uniflagellate cells lacking inner dynein arms (ida3) or outer dynein arms (oda2) were studied. Ida3 cells exhibit stunted flagellar waveforms, whereas oda2 cells beat with lower frequency. Image registration and sorting algorithms provided high-resolution estimates of the motion of the cell body, as well as detailed kinematics of the flagellum. The swimming cell was modeled as an ellipsoid in Stokes flow, propelled by viscous forces on the flagellum. The normal and tangential components of force on the flagellum (f(N) and f(T)) were related by resistive coefficients (C(N) and C(T)) to the corresponding components of velocity (V(N) and V(T)).The values of these coefficients were estimated by satisfying equilibrium requirements for force and torque on the cell. The estimated values of the resistive coefficients are consistent among all three genotypes and similar to theoretical predictions.
从实验图像数据估计了周围流体对游泳藻类莱茵衣藻鞭毛的分布式推进力。以 125nm 的空间分辨率获得了 350 帧/秒的单鞭毛突变体衣藻细胞的图像，并在低雷诺数流体力学的背景下分析了细胞体和鞭毛的运动。研究了野生型单鞭毛细胞以及缺乏内动力蛋白臂（ida3）或外动力蛋白臂（oda2）的单鞭毛细胞。ida3 细胞表现出短缩的鞭毛波形，而 oda2 细胞的摆动频率较低。图像配准和分类算法提供了细胞体运动的高分辨率估计，以及鞭毛的详细运动学。游泳细胞在斯托克斯流中被建模为一个椭球体，由鞭毛上的粘性力推动。在鞭毛上的力的法向和切向分量（f(N)和 f(T)）通过阻力系数（C(N)和 C(T)）与相应的速度分量（V(N)和 V(T)）相关。通过满足细胞上的力和扭矩的平衡要求来估计这些系数的值。这些阻力系数的估计值在所有三种基因型中都是一致的，与理论预测相似。
