Frotas de máquinas microscópicas trabalham em nossas células, realizando tarefas biológicas essenciais e nos mantendo vivos: mero acaso, fortuita necessidade ou design inteligente?

sábado, setembro 14, 2019

Self-straining of actively crosslinked microtubule networks

Sebastian Fürthauer, Bezia Lemma, Peter J. Foster, Stephanie C. Ems-McClung, Che-Hang Yu, Claire E. Walczak, Zvonimir Dogic, Daniel J. Needleman & Michael J. Shelley 

Nature Physics (2019) 

Source/Fonte: Emmanuel Dumont

Cytoskeletal networks are foundational examples of active matter and central to self-organized structures in the cell. In vivo, these networks are active and densely crosslinked. Relating their large-scale dynamics to the properties of their constituents remains an unsolved problem. Here, we study an in vitro active gel made from aligned microtubules and XCTK2 kinesin motors. Using photobleaching, we demonstrate that the gel’s aligned microtubules, driven by motors, continually slide past each other at a speed independent of the local microtubule polarity and motor concentration. This phenomenon is also observed, and remains unexplained, in spindles. We derive a general framework for coarse graining microtubule gels crosslinked by molecular motors from microscopic considerations. Using microtubule–microtubule coupling through a force–velocity relationship for kinesin, this theory naturally explains the experimental results: motors generate an active strain rate in regions of changing polarity, which allows microtubules of opposite polarities to slide past each other without stressing the material.

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