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Diffusible crosslinkers cause superexponential friction forces
##manager.scheduler.building##: Edificio San Jose
##manager.scheduler.room##: Auditorio 1
Date: 2019-07-12 11:45 AM – 12:00 PM
Last modified: 2019-06-10
Abstract
Cells require precise control over the spatial organization of their components before cell division,
since elements such as the chromosome copies need to be distributed exactly over both daughter cells.
This spatial organization is provided by the mitotic spindle,
which mainly consists of stiff polymers called microtubules.
The mitotic spindle needs to define the cell midzone while the microtubules continuously grow, shrink, and slide past one another.
Therefore, specialized proteins crosslink microtubules and stabilize the structure by providing friction forces between sliding filaments.
However, it remains unknown how cells control these friction forces, and how the drag coefficient depends on the number of crosslinkers
and on the overlap length between sliding filaments.
We have performed a theoretical study of the friction forces caused by crosslinking proteins,
using a model that was previously successful in explaining entropic force generation between overlapping microtubules.
Crosslinkers thermally diffuse within the overlap region, allowing for the relative movement of the microtubules.
We find using computer simulations that this movement is limited by free-energy barrier crossings caused by the hopping of crosslinkers,
and we analytically calculate the exact expression of the free-energy profile.
Using Arrhenius equation and the Einstein relation,
the analytical solution leads us to predict that the friction coefficient increases superexponentially with the density of the crosslinking proteins.
We hypothesize that this provides cells with a mechanism for the precise control of the mitotic spindle.
since elements such as the chromosome copies need to be distributed exactly over both daughter cells.
This spatial organization is provided by the mitotic spindle,
which mainly consists of stiff polymers called microtubules.
The mitotic spindle needs to define the cell midzone while the microtubules continuously grow, shrink, and slide past one another.
Therefore, specialized proteins crosslink microtubules and stabilize the structure by providing friction forces between sliding filaments.
However, it remains unknown how cells control these friction forces, and how the drag coefficient depends on the number of crosslinkers
and on the overlap length between sliding filaments.
We have performed a theoretical study of the friction forces caused by crosslinking proteins,
using a model that was previously successful in explaining entropic force generation between overlapping microtubules.
Crosslinkers thermally diffuse within the overlap region, allowing for the relative movement of the microtubules.
We find using computer simulations that this movement is limited by free-energy barrier crossings caused by the hopping of crosslinkers,
and we analytically calculate the exact expression of the free-energy profile.
Using Arrhenius equation and the Einstein relation,
the analytical solution leads us to predict that the friction coefficient increases superexponentially with the density of the crosslinking proteins.
We hypothesize that this provides cells with a mechanism for the precise control of the mitotic spindle.