Tracer Studies on F-Actin Fluctuations

We present a study on the fluctuations of semiflexible actin filaments using fluorescence videomicroscopy, focusing on the end-to-end fluctuations of single filaments. In order to specifically measure the position of the polymer’s ends, we developed a novel noninvasive method that consists of annealing short end tags to the filaments. This allows us to probe polymer fluctuations to a very high accuracy. We compared the distribution of the end-to-end distance with recent theoretical results, and found excellent agreement. We also studied the dynamics of the mean-square end-to-end distance $\delta R^2(t)$ and orientation of the ends, $\delta {\Theta }^2(t)$, finding power laws $t^{3/4}$ and $t^{1/4}$, respectively. Scaling behavior for $\delta R^2(t)$ is observed over several decades in relaxation time in agreement with theoretical results.