Modeling interphase chromosomes: Microrheology

The nucleus of eukaryotic cells is one of the most investigated organelle but its complete understanding is far from being reached. Recently considerable efforts have been devoted to experimentally analyze its viscoelastic properties, in particular through microrheology techniques.

We employ molecular dynamics computer simulations comparing experimental data with theoretical models.
Mimicking experiments, we consider a polymeric model representing the crowding of interphase chromosomes [1] containing hundreds of brownian free particles as in [2]. We consider several sizes for particles from the tiny chromatin fiber to the mesh size of the chromatin solution. Tracking the motion of these fictitious nanoprobes we compute dynamical proprieties.

Then we investigate a simple variation of this polymeric model including a set of spring which modifies dramatically the viscoelastic properties. Interestingly, we observed the cage-and-escape dynamics peculiar for short times dynamics of nanoprobes seen in experiments.
We generalize also the model to the situation where active regulatory mechanics are present [3].

[1] A. Rosa, R. Everaers, PLoS Comput Biol., 4(8): e1000153 (2008)
[2] M. Valet, A. Rosa, J Chem Phys., 141, 245101 (2014)
[3] J. Smrek, K. Kremer, Phys. Rev. Lett., 118, 098002 (2017)