Microtubules and vesicles under controlled tension

Abstract

Microtubules trapped inside cell-sized vesicles (∼10-μm diameter) define shapes reminiscent of living cells. In this work, three configurations are studied: an individual microtubule, a linear bundle, and a circular band. Mechanical properties are probed by varying the vesicle membrane tension using micropipet aspiration. Quantitative results include measurements of the persistence length of a single microtubule, 6.3±2.4 mm, and the stretching modulus of the vesicle membrane, ${\mathrm{k}}_{\mathrm{s}}$ ⩾140 erg/${\mathrm{cm}}^2$ . The number of microtubules in a typical bundle is ∼100, and the total length in a typical band is ∼0.5 cm. A tension-induced first-order transition from linear bundle to circular band is observed and modeled. The loss of stability of the bent bundle is associated with a saddle-node bifurcation.