Figure 1.
Water models used in the MARTINI force field.
a) Standard model; b) polarizable model. Shaded orange spheres correspond to the van der Waals radii of the central particles W.
Figure 2.
Particle density and dielectric constant of polarizable water at T = 300 K as a function of charge q and angle force constant Kθ.
In a) and b), k was kept fixed at 4.2 kJ mol−1 rad−2, whereas q was fixed to a value of 0.46 in c) and d). Dashed lines indicate the experimental dielectric constant (ε = 78.4 at 298 K) and the density of real water (ρ = 996 kg m−3 at 300 K [31]), respectively.
Table 1.
Final parameter set and selected properties of the polarizable water model.
Table 2.
Hydration free energies ΔGhydr for selected bead types, in kJ mol−1.
Table 3.
Overview of interaction levels for charged particle typesa.
Figure 3.
Properties of water-hexadecane interface.
a) Potential of mean force for CG butane, and b) particle density profiles for the standard and the polarizable water models (black and red curves, respectively).
Figure 4.
Distributions of the dipole moment in polarizable MARTINI water (black curve) and SPC/E water (red curve).
Figure 5.
Temperature dependence of polarizable water model.
Particle density (a) and dielectric constant (b) are compared to experimental values (taken from [27], [31]).
Figure 6.
Radial distribution functions (RDFs) of ions and water in a 0.4 M NaCl salt solution.
Insets show the molecules used to compute the RDFs.
Figure 7.
Distributions of the particle density for different CG groups of DPPC bilayer, with respect to the bilayer center (Z = 0).
Figure 8.
Polarization effects across a DPPC bilayer (bilayer center at Z = 0).
a) Electrostatic potentials across the bilayer for both standard and polarizable water models. b) Distribution of the dipole moment across the bilayer in the case of polarizable water. Only the Z-component of the dipole moment is shown.
Figure 9.
PMFs of translocation of Na+ and Cl− ions through a DPPC bilayer, with respect to the distance from the membrane center.
The standard water model is compared to the polarizable water model with and without long-range electrostatics (PME).
Table 4.
Heights of the energy barriers (in kJ mol−1) for Na+ and Cl− translocation across a DPPC membrane.
Figure 10.
Electroporation of an octane slab by an electric field.
Water is shown as balls and sticks. The octane slab is depicted as white transparent spheres. The direction and magnitude of the external field is indicated by the arrow.
Figure 11.
Electroporation of a DPPC membrane by an ionic imbalance.
The polarizable water is shown as transparent yellow spheres, the lipid head groups as blue (choline) and golden (phosphate) spheres, the lipid tails as green sticks, and the sodium ions as large green balls. Formation of the pore is indicated by the yellow arrow. The direction and magnitude of the effective field is indicated by the black arrow.
Figure 12.
Ion leakage across a DPPC bilayer.
Lipids are shown in green (heads as spheres, tails as bonds), sodium ions in cyan, and the polarizable water as purple, transparent beads with the positive WP particle in pink and the negative WM particle in orange.