The partition and transport behavior of cytotoxic ionic liquids (ILs) through the DPPC bilayer: Insights from molecular dynamics simulation

Figures & data

Figure 1. Molecular structures of Choline (a), BEH (b), DEP (c) and TMP (d) with partial atom charges along with the structure of DPPC lipid (e).

Figure 2. Mass density of different components for DPPC lipid bilayer system (a), different anionic species of ILs (b), and water (c).

Table 1. Coordination numbers of water to DPPC atoms in the simulated systems.

System	Coordination number around (O) atom	Coordination number around (N) atom
DPPC reference	1.24	4.07
CTMP in DPPC	1.26	4.16
CBEH in DPPC	1.26	4.14
CDEP in DPPC	1.25	4.22

Figure 3. Free energy profiles for anionic species of ILs along the bilayer z-axis.

Figure 4. Snapshots of the final configuration of the DPPC lipids and water molecules and ILs, BEH (Green) (a), DEP (Orange) (b), TPM (Blue) (c). In all systems choline is as yellow.

Figure 5. Electrostatic potential of the simulated systems.

Table 2. The values of area per lipid (APL), thickness of bilayer (D_B), lipid lateral diffusion coefficient (D_L), anion species lateral diffusion coefficient (D_A), electrostatic potential in the middle of membrane (ω_Mid), maximum electrostatic potential (ω_Max) and DPPC head group P–N tilt angle (α_P–N) of the simulated bilayer systems.

Properties	DPPC in presence of CDEP	DPPC in presence of CBEH	DPPC in presence of CTMP	DPPC reference (Without ILs)
APL (Å^2)	61.78 (±0.21)	62.28 (±0.15)	62.28 (±0.15)	61.04 (±0.13)
DB (nm)	3.77 (±0.21)	3.81 (±0.40)	3.75 (±0.10)	3.87 (±0.15)
	5.80	10.70	3.86	5.20
	778.40 (±204.30)	9.30 (±3.90)	17.20 (±1.10)	–
ωMid (V)	0.57	0.61	0.53	0.61
ωMax (V)	0.77	0.78	0.74	0.83
αP-N(degree)	89.84 (±4.39)	89.68 (±4.66)	90.08 (±4.59)	90.56 (±3.84)

Figure 6. The deuterium order parameters for different carbon atoms in the SN-1 and SN-2 chains in presence three kinds of ILs.

Table 3. Average number of different hydrogen bonds in the simulated systems.

Simulation systems	Number of ILs	H-bonds between anion species and choline	H-bonds between anion species and water	H-bonds between DPPC and choline	H-bonds between DPPC and water
DPPC + Water (Reference)	0	–	–	–	779.469 (±3.6)
DPPC + Water + CTMP	2	0.006 (±0.0)	3.549 (±0.2)	0.376 (±0.0)	790.009 (±3.9)
DPPC + Water + CBEH	2	0.019 (±0.0)	6.977 (±0.2)	0.395 (±0.0)	784.162 (±3.8)
DPPC + Water + CDEP	2	0.0010 (±0.0)	1.438 (±0.1)	0.346 (±0.0)	783.740 (±4.1)

Figure 7. The mean square displacement of the anion species of ILs in the simulated systems, BEH and TMP (a), and DEP (b).