  Water diffusion through membrane proteins is a key aspect of cellular
function. Essential processes of cellular metabolism are driven by osmotic
pressure, which depends on water channels. Membrane proteins such as aquaporins
(AQPs) are responsible for enabling water transport through the cell membrane.
AQPs are highly selective, allowing only water and relatively small polar
molecules to cross the membrane. Experimentally, estimation of water flux
through membrane proteins is still a challenge, and hence accurate simulations
of water transport are of particular importance. We present a numerical study
of water diffusion through AQP1 comparing three water models: TIP3P, OPC and
TIP4P/2005. Bulk diffusion, diffusion permeability and osmotic permeability are
computed and compared among all models. The results show that there are
significant differences between TIP3P (a particularly widespread model for
simulations of biological systems), and the more recently developed TIP4P/2005
and OPC models. We demonstrate that OPC and TIP4P/2005 reproduce protein-water
interactions and dynamics in excellent agreement with experimental data. From
this study, we find that the choice of the water model has a significant effect
on the computed water dynamics as well as its molecular behaviour within a
biological nanopore.
