# compute inner pressure and elastic membrane force

Dear all,

I am trying to model the tissue morphogenesis based on cell-cell interactions. In this tissue, the shape of cell is ellipsoid but right now I am assuming them as a sphere. The cell membrane is made up of a triangulated mesh of harmonic springs.

I want to include growth in the cell which is equivalent to expanding the size of the cell. The literature suggests internal pressure in the cell (coming from osmotic pressure) is equivalent to membrane elastic force at equilibrium. If the internal pressure (or turgor pressure) greater than a fixed threshold then the cell growth rate is proportional to excess pressure.

When I am running the simulation with below commands, cell shape gets crumpled. Please guide me how to calculate the internal pressure and elastic force for each cell individually. So that the cell shape maintained and also able to incorporate the growth in the cell. I read the manual but did not get which command will work here. This tissue can have 1000-10000 cells and each cell can have 100-200 atoms on its surface depends on the mesh bin-size.

bond_style harmonic
bond_coeff 1 1000 2.3867
angle_style harmonic
angle_coeff 1 300.0 60.0
mass * 1.0
neighbor 0.5 bin
neigh_modify delay 0
pair_style lj/cut 3.6
pair_coeff * * 1 2.3867
variable T equal 0.23
variable LD equal 1.0
variable P equal 0.05
fix 11 all nve
fix 1 all npt temp {T} {T} {LD} iso {P} {P} {LD}

If you have any suggestion to improve my above steps or alternative idea then please let me know. I don’t have anyone who is ready to discuses on these issues with me. If anyone interested in collaboration to understand the mechanics of tissue morphogenesis then I am happy to do. And more can be discussed on personal email, Skype, etc.

Thank you.

Regards,
Ankit Agrawal

Postdoc fellow in Computational Biology

Weizmann Institute of Science,

Israel

I think you should look in the literature for people
who have used LAMMPS to model squishy cells. I’ve
heard of a few such groups. Their papers would
likely explain how they setup and parameterized
their models to give the kind of effects you are
looking for.

Steve