Quantum Mechanics/Molecular Mechanics Method Combined
with Hybrid All-Atom and Coarse-Grained Model: Theory and Application
on Redox Potential Calculations
We
developed a new multiresolution method that spans three levels
of resolution with quantum mechanical, atomistic molecular mechanical,
and coarse-grained models. The resolution-adapted all-atom and coarse-grained
water model, in which an all-atom structural description of the entire
system is maintained during the simulations, is combined with the
ab initio quantum mechanics and molecular mechanics method. We apply
this model to calculate the redox potentials of the aqueous ruthenium
and iron complexes by using the fractional number of electrons approach
and thermodynamic integration simulations. The redox potentials are
recovered in excellent accordance with the experimental data. The
speed-up of the hybrid all-atom and coarse-grained water model renders
it computationally more attractive. The accuracy depends on the hybrid
all-atom and coarse-grained water model used in the combined quantum
mechanical and molecular mechanical method. We have used another multiresolution
model, in which an atomic-level layer of water molecules around redox
center is solvated in supramolecular coarse-grained waters for the
redox potential calculations. Compared with the experimental data,
this alternative multilayer model leads to less accurate results when
used with the coarse-grained polarizable MARTINI water or big multipole
water model for the coarse-grained layer