Brangwynne Clifford P, Koenderink Gijsje H, Barry Ed, Dogic Zvonimir, MacKintosh Frederick C, Weitz David A
Harvard School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA.
Biophys J. 2007 Jul 1;93(1):346-59. doi: 10.1529/biophysj.106.096966. Epub 2007 Apr 6.
Microscope images of fluctuating biopolymers contain a wealth of information about their underlying mechanics and dynamics. However, successful extraction of this information requires precise localization of filament position and shape from thousands of noisy images. Here, we present careful measurements of the bending dynamics of filamentous (F-)actin and microtubules at thermal equilibrium with high spatial and temporal resolution using a new, simple but robust, automated image analysis algorithm with subpixel accuracy. We find that slender actin filaments have a persistence length of approximately 17 microm, and display a q(-4)-dependent relaxation spectrum, as expected from viscous drag. Microtubules have a persistence length of several millimeters; interestingly, there is a small correlation between total microtubule length and rigidity, with shorter filaments appearing softer. However, we show that this correlation can arise, in principle, from intrinsic measurement noise that must be carefully considered. The dynamic behavior of the bending of microtubules also appears more complex than that of F-actin, reflecting their higher-order structure. These results emphasize both the power and limitations of light microscopy techniques for studying the mechanics and dynamics of biopolymers.
波动生物聚合物的显微镜图像包含了大量有关其潜在力学和动力学的信息。然而，要成功提取这些信息，需要从数千张噪声图像中精确确定细丝的位置和形状。在此，我们使用一种新的、简单但稳健的、具有亚像素精度的自动图像分析算法，以高空间和时间分辨率对丝状（F-）肌动蛋白和微管在热平衡状态下的弯曲动力学进行了精确测量。我们发现，细长的肌动蛋白丝的持久长度约为17微米，并呈现出与粘性阻力预期相符的q(-4)依赖的弛豫谱。微管的持久长度为几毫米；有趣的是，微管的总长度与刚性之间存在小的相关性，较短的细丝显得更柔软。然而，我们表明，这种相关性原则上可能源于必须仔细考虑的固有测量噪声。微管弯曲的动态行为也比F-肌动蛋白的更复杂，这反映了它们的高阶结构。这些结果强调了光学显微镜技术在研究生物聚合物力学和动力学方面的优势和局限性。
