This system is a membrane protein Aquaporin, a tetrameric ion channel
embedded in a lipid bilayer. 
Aquaporins are proteins found in cells of all types of organisms and
regulate the transport of fluids between cells or organelles, a function
fundamental for all life.
The system was used in microsecond-long simulations with aiming to
carry out mutational studies exploring the structural origins of
aquaporin ammonia selectivity [1].

In such a study a number of mutations are introduced in the protein
creating several variants of the system along the original (included here)
each of which is simulated independently. 
Thanks to the AWH enhanced sampling method, individual simulations
for a specific mutation can themselves be composed of an
ensemble computation made up by multiple simulations, here 32.
This improve sampling beyond what faster simulations through strong
scaling allows.

This simulation use a 2.5 femtosecond time step and h-bond constraints.
The system contains roughly 100,000 atoms and therefore very challenging
for strong scaling.

[1] Lindahl, Viveca & Gourdon, Pontus & Andersson, Magnus & Hess, Berk. (2018).
Permeability and ammonia selectivity in aquaporin TIP2;1: Linking structure to
function. Scientific Reports. 8. 10.1038/s41598-018-21357-2. 
