Molecular machines stiffen soft materials

AMOLF researcher Koenderink et al. in a recent issue of the Proceedings of the National Academy of Sciences (PNAS) have discovered that cells use molecular machines to tense and stiffen themselves like a muscle.

Living cells can actively modulate their stiffness in order to squeeze through small orifices in tissues and blood vessels. AMOLF researcher Koenderink et al. in a recent issue of the Proceedings of the National Academy of Sciences (PNAS) have discovered that cells use molecular machines to tense and stiffen themselves like a muscle. This discovery opens the way to design ‘living’ materials which can control their own properties.

Cells rely for their mechanical strength on a skeleton of protein fibers. The researchers constructed an artificial version of this skeleton, composed of protein fibers and molecular motors. The molecular motors actively contracted the fiber network, thereby tensing the fibers like violin strings. The tightened network was up to 1000-fold stiffer than in its relaxed state. This biological design principle may be used to engineer ‘smart’ materials whose properties are controlled by internal, catalytic activity. Such materials would for instance be useful as scaffold materials for tissue repair.

Reference
An active biopolymer network controlled by molecular motors
Gijsje Koenderink, Zvonimir Dogic, Fumi Nakamura, Poul Bendix, Fred MacKintosh, John Hartwig, Tom Stossel, en David Weitz, Proceedings of the National Academy of Sciences (PNAS), 10 augustus 2009 Online Early Edition.

For more information please contact Gijsje Koenderink

Press release on FOM website (in Dutch)

Figure: Molecular motors tighten the cell’s cytoskeleton. The motors (myosin) form bipolar filaments with active motor domains sticking out on both ends. These motors walk along the protein fibers (actin) and contract them towards each other. This tenses the cytoskeleton and makes it up to 1000-fold stiffer.