Friction between biological filaments

Laser tweezers and actin
Laser tweezers and actin

We attach actin filaments to tiny plastic beads and manipulate them with laser tweezers. In presence of the depletant molecules, two actin filaments form a bundle. We move one of the beads with a certain velocity, thus pulling on the bundled filaments. At the same time, we measure the friction force exerted onto the second bead. Read more in this post: Friction on the molecular scale.