Supporting Information: Atomistic Model for Near-Quantitative. Simulations of Langmuir Monolayers

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1 Supporting Information: Atomistic Model for Near-Quantitative Simulations of Langmuir Monolayers Matti Javanainen,,, Antti Lamberg, Lukasz Cwiklik,, Ilpo Vattulainen,,, and Samuli Ollila,,# Laboratory of Physics, Tampere University of Technology, Tampere, Finland Department of Physics, University of Helsinki, Helsinki, Finland Unaffiliated J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Prague 8, Czech Republic Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Prague 6, Czech Republic MEMPHYS Center for Biomembrane Physics, University of Southern Denmark, Odense, Denmark #Institute of Biotechnology, University of Helsinki, Helsinki, Finland S1

2 Contents S1 Supplementary Methods S2 S1.1 Simulation Parameters S2 S1.2 Simulations of Water with the Slipids Parameter Set S2 S1.3 Simulations of Lipid Bilayers the Slipids Parameter Set S3 S1.4 Simulations of Small Lipid Monolayers S3 S1.5 Lengths of Large Monolayer Simulations S4 S2 Supplementary Results S4 S2.1 OPC4 Water Model With the Slipids Parameter Set S4 S2.2 Lipid Bilayers With the OPC4 Water Model S4 S2.3 Convergence of Large Lipid Monolayer Simulations S6 S2.4 Snapshots of the Large Lipid Monolayer Simulations S9 S2.5 Results for Smaller Monolayers S9 S3 Availability of Simulation Data S13 References S16 S1 Supplementary Methods S1.1 Simulation Parameters The different simulation parameter sets used in the simulations depicted in the main text and in this SI document are given in Table S1. S1.2 Simulations of Water with the Slipids Parameter Set In addition to the demonstration that the bulk properties of OPC4 are reproduced using CHARMM36 parameter set (see the main text), we also simulated the same bulk water S2

3 systems with the Slipids paremeter set (see Table S1). Notably, the isotropic pressure coupling scheme was employed. Additionally, the values of the surface tension of the water air interface (γ (T ) in Eq. 2 in the main paper) were calculated for the OPC4 water model using the Slipids parameter set and the air water interface system described in the main paper. S1.3 Simulations of Lipid Bilayers the Slipids Parameter Set The same bilayers that were simulated with CHARMM36/OPC4 and CHARMM36/TIP(S)3P combinations (see the main paper) were also simulated using the Slipids lipid model 13,14 combined with either the original TIP3P or the OPC4 water model. The Slipids parameter set, given in Table S1, was employed. All simulations were performed using GROMACS 4.6.x. 15 S1.4 Simulations of Small Lipid Monolayers Systems containing two DPPC or POPC lipid monolayers, consisting of a total of 128 lipids and separated by a slab of water, were simulated at 31 K and in a range of areas per lipid. The initial structures of these monolayers were taken as the final structures from Ref. 16. The area per lipid (APL) of the DPPC system was fixed to either 47, 49, 6, 7, 79, 9,1, or 11 Å 2, while the values for POPC were 49, 58, 69, 8, 9, 97, 11, 12, and 13 Å 2. The monolayers were hydrated by a total of 6876 or 69 water molecules (DPPC and POPC systems, respectively), which corresponds to 54 waters per lipid. The box dimension in the normal to the monolayer plane was equal to 28 nm to prevent unscreened interactions taking place through the vacuum. The lipids were modeled with either the Slipids 13,14 or the CHARMM36 17 force fields. For Slipids, the OPC4 model 18 was employed, while results of these monolayers with the TIP3P water model were taken from Ref. 16. For CHARMM36, monolayers were simulated with both OPC4 and the CHARMM-specific TIP(S)3P water models. The simulations were S3

4 run for 1 ns using the CHARMM36 or Slipids parameter sets, respectively. Notably, the monolayers were simulated in the NVT ensemble, and the dispersion correction 4 was applied to energy and pressure also for the CHARMM36 simulations. The values for γ, used in the calculation of surface pressures of the small lipid monolayers, were calculated from small water air interface systems, used also in the evaluation of the effect of LJ cut-off on the surface tension of the OPC water models (see main text). S1.5 Lengths of Large Monolayer Simulations The lengths of each simulated large monolayer system are given in Table S2. S2 Supplementary Results S2.1 OPC4 Water Model With the Slipids Parameter Set In Table S3, the Table 1 in the main text has been modified to contain the results for the bulk water properties of the OPC4 model when simulated with the Slipids parameter set (see Table S1). S2.2 Lipid Bilayers With the OPC4 Water Model In Table S4, the Table 2 in the main text has been extended to contain the results for the bilayer area per lipid of the Slipids/OPC4 combination. Like with CHARMM36, the DPPC bilayer simulated using the Slipids model is also somewhat too compressed, but the mutual agreement between the two water models is excellent. The density profiles for both the Slipids and CHARMM36 together with OPC4 or TIP(S)3P water models are shown in Fig. S1. The behavior of both the CHARMM36 and Slipids models seems to be very similar with both water models. The deuterium order parameters, calculated for the sn-1 tail of both DPPC and POPC S4

5 9 CH 3 CH 2 CO PO 4 N Water OPC4 TIP3P 6 Density (kg/m 3 ) DPPC/Slipids DPPC/CHARMM36 3 POPC/Slipids POPC/CHARMM Distance from bilayer center (nm) Distance from bilayer center (nm) Figure S1: Density profiles of the DPPC and POPC bilayers simulated using CHARMM36 and Slipids models. S5

6 each with both OPC4 and TIP(S)3P water models, is shown in Fig. S2. Upon the change of water model from TIP(S)3P to OPC4, the deuterium order parameters of Slipids bilayer decrease, while those of the CHARMM36 bilayer increase. These changes likely result from the differences of the original water model, as unlike those in TIP3P, the hydrogen atoms in the TIP(S)3P model interact via Lennard-Jones interactions. Fortunately, these changes are very modest..2 Slipids -SCD.1.2 DPPC/OPC4 DPPC/TIP(S)3P CHARMM36.1 POPC/OPC4 POPC/TIP(S)3P Carbon # Figure S2: Deuterium order parameters calculated for the palmitoyl sn-1 tail of DPPC and POPC with OPC4 and TIP3P water models. Experimental values, shown with dots, are taken from refs. 2 and 21 for DPPC and POPC, respectively. Note that the order parameter for the 16th carbon was only measured in experiments for POPC. S2.3 Convergence of Large Lipid Monolayer Simulations The convergence of the larger lipid monolayer simulations is demonstrated using the simulations based on structures extracted from the first expansion simulation (see main text) in Figs. S3, S5, and S4 for the POPC systems at 298 and for the DPPC systems at 298 K and 31 K, respectively. S6

7 Surface tension (mn/m) ns 25 5 ns 5 75 ns 75 1 ns Area per lipid (Å 2 ) Figure S3: Convergence of the surface pressures for the large POPC monolayers at 298 K. Surface tension (mn/m) Surface tension (mn/m) ns 75 1 ns ns 25 5 ns ns ns 5 75 ns ns Area per lipid (Å 2 ) Figure S4: Convergence of the surface pressures for the large DPPC monolayers at 31 K. S7

8 Surface tension (mn/m) Surface tension (mn/m) ns 75 1 ns ns 25 5 ns ns ns 5 75 ns ns Area per lipid (Å 2 ) Figure S5: Convergence of the surface pressures for the large DPPC monolayers at 298 K. S8

9 S2.4 Snapshots of the Large Lipid Monolayer Simulations Selected snapshots from the large POPC monolayers at 298 K and from the large DPPC monolayers at 31 K are shown in Figs. S6 and S7, respectively. Similar snapshots for the large DPPC monolayers at 298 K are shown in Fig. 2 in the main text. Figure S6: Selected napshots of the POPC monolayers at 298 K. Top row, from left to right: 55 Å2, 61 Å2, 67 Å2, and 78 Å2. Bottom row, from left to right: 94 Å2, 11 Å2, and 126 Å2. One monolayer per system is shown from its side as well as from the vacuum side. Water is omitted for clarity. Orange lines highlights a unit simulation cell. S2.5 Results for Smaller Monolayers We also simulated DPPC and POPC monolayers at 31 K and at varying areas per lipid using the Slipids/OPC4, CHARMM36/OPC4, and CHARMM36/TIP(S)3P model combinations S9

10 Figure S7: Selected napshots of the DPPC monolayers at 31 K. Top row, from left to right: 51 Å2, 54 Å2, 57 Å2, and 6 Å2. Bottom row, from left to right: 69 Å2, 78 Å2, and 11 Å2. One monolayer per system is shown from its side as well as from the vacuum side. Water is omitted for clarity. Orange lines highlights a unit simulation cell. S1

11 and compared them to those obtained for the Slipids/TIP3P combination in Ref. 16. Here, the values of γ were set to 49.4±2. mn/m for the TIP3P water model 16 used with the Slipids lipid model. For the TIP(S)3P water model used with the CHARMM36 lipid model, a value of 51.3±.9 mn/m was calculated using the CHARMM36 simulation parameters (see Methods). For OPC4 water, the values of 69.9±.4 mn/m and 67.5±1.3 mn/m were used for the Slipids and CHARMM36 lipid models, respectively, as calculated with the corresponding simulation parameter sets. The pressure area isotherms of the different model combinations, shown together with selected experimental data in Fig. S8 for both DPPC and POPC, suggest that the use of OPC4 water results in a drastic improvement over the TIP3P/TIP(S)3P model. Figure S9 shows also the surface tensions of POPC simulations at 31 K together Surface pressure (mn/m) DPPC POPC Olżyńska 216 von Tscharner 1981 Crane 1999 Mansour Area per lipid (Å 2 ) Slipids/OPC4 Slipids/TIP3P Charmm36/OPC4 Charmm36/TIPS3P Figure S8: Isotherms calculated with different model combinations. Experimental isotherms are taken from Refs. 16 (Olżyńska 216), 22 (von Tscharner 1981), 23 (Crane 1999), and 24 (Mansour 27). with experimental data. 16 As expected, for all areas considered, the tension is larger with the S11

12 OPC4 water model. However, the difference decreases with area per lipid, because water gets less exposed with air when lipid density at the interface increases. Surface tension γ (mn/m) Olzynska 216 Slipids/OPC4 CHARMM36/OPC4 Slipids/TIP3P CHARMM36/TIPS3P Area per lipid (Å 2 ) Figure S9: Surface tensions from simulations and experiment 16 for POPC at 31 K. Most notably, the isotherms obtained with the OPC4 water model agree quite well with experiment at large areas per molecule, where simulations have traditionally struggled. Only slightly negative values for the surface pressure are observed, and the surface pressures seem to converge towards mn/m at large areas, as expected. Here, the CHARMM36/OPC4 combination seems to work somewhat better. Furthermore, no pore formation is observed until APLs of 11 Å 2 and 13 Å 2 for DPPC and POPC, respectively in either the Slipids/OPC4 nor the CHARMM36/OPC4 combination. However, for the TIP(S)3P and CHARMM36, pores arise already at 9 Å 2 for DPPC and POPC, while the corresponding values for the TIP3P/Slipids combination are 9 Å 2 and 1 Å Worth noting is that even the experimental isotherms show mutual deviations. However, this sparks from different compression rates and measurement techniques. Notably, the experiments by Mansour et al. 24 are performed under proper equilibrium conditions. In Fig. S1, the isotherms obtained for POPC using the smaller monolayer systems are compared to those obtained from the larger monolayer systems. For small monolayers, data at 31 K is shown for both CHARMM36 and Slipids force fields combined with the OPC4 water, and for CHARMM36 data at 323 K is also shown. The mutual agreement S12

13 between the isotherms obtained with different models (large and small monolayers), force fields (Slipids and CHARMM36), and temperatures (298 K, 31 K, and 323 K) is good. The weak dependency of the isotherms on temperature is in agreement with experiments. 16, Mansour (Exp.) 298 K Olzynska (Exp.) 298 K Olzynska (Exp.) 31 K CHARMM36 Large 298 K CHARMM36 Small 31 K CHARMM36 Small 323 K Slipids Small 31 K Figure S1: Isotherms for POPC obtained with different force fields, system sizes, and simulation temperatures. Experimental data at two temperatures is shown for comparison. As the APL is increased, the lipids need to cover a larger area of the water air interface. However, this requires the hydrophobic lipid tails eventually come into contact with water, which is unfavorable. In case the surface tension of the pure water air interface is underestimated, the monolayer can negate this energetic penalty through phase separation or the formation of a porous phase. This formation of pores is therefore assumed to be linked to the lipid tail tilt angles not increasing as the area per lipid is increased beneath a certain threshold. Indeed, as shown in Fig. S11, the lipids obtain much larger tilt angles at large ares when simulated with the OPC water model instead of the TIP(S)3P water model. S3 Availability of Simulation Data Simulation data of large monolayers (CHARMM36/OPC4) together with the related files are available online: data for POPC in Refs. 25 and 26, data for DPPC at 298 K in Refs. 27 and 28, and data for DPPC at 31 K at Refs. 29 and 3. Additionally, data for smaller monolayers with the CHARMM36 and Slipids models have S13

14 POPC DPPC Probability Å 2 8 Å 2 11 Å 2 58 Å 2 9 Å 2 12 Å 2 47 Å 2 6 Å 2 9 Å 2 49 Å 2 7 Å 2 1 Å 2 69 Å 2 97 Å 2 13 Å 2 Slipids/OPC4 Slipids/OPC4 49 Å 2 8 Å 2 11 Å 2 58 Å 2 9 Å 2 12 Å 2 79 Å 2 11 Å 2 47 Å 2 6 Å 2 9 Å 2 49 Å 2 7 Å 2 1 Å 2 69 Å 2 97 Å 2 13 Å 2 79 Å 2 11 Å 2 CHARMM36/OPC4 CHARMM36/OPC4 49 Å 2 8 Å 2 58 Å 2 9 Å 2 47 Å 2 7 Å 2 49 Å 2 79 Å 2 69 Å 2 97 Å 2 6 Å 2 9 Å 2 Slipids/TIP3P Slipids/TIP3P 49 Å 2 8 Å 2 58 Å 2 9 Å 2 69 Å 2 97 Å 2 CHARMM36/TIPS3P 47 Å 2 7 Å 2 49 Å 2 79 Å 2 6 Å 2 9 Å 2 CHARMM36/TIPS3P sn-1 tilt angle ( ) Figure S11: The tilt angle distributions of the saturated sn-1 tail. Results for Slipids/TIP3P are taken from Ref. 16. Note that the color coding is only consistent within the lipid type, i.e., within one column. S14

15 been made available. POPC data obtained using CHARMM36 and the TIP(S)3P or OPC4 water models are available at Refs. 31 and 32, respectively. Corresponding DPPC data obtained using CHARMM36 with the TIP(S)3P or OPC4 water models are available at Refs. 33 and 34, respectively. Data for POPC and DPPC obtained using Slipids together with the OPC4 water model are available at Refs. 35 and 36, respectively. The POPC and DPPC data for the Slipids/OPC4 combination was taken from Ref. 16. S15

16 References (1) Páll, S.; Hess, B. A Flexible Algorithm for Calculating Pair Interactions on SIMD Architectures. Comput. Phys. Commun. 213, 184, (2) Darden, T.; York, D.; Pedersen, L. Particle Mesh Ewald: An N log (N) Method for Ewald Sums in Large Systems. J. Chem. Phys. 1993, 98, (3) Essmann, U.; Perera, L.; Berkowitz, M. L.; Darden, T.; Lee, H.; Pedersen, L. G. A Smooth Particle Mesh Ewald Method. J. Chem. Phys. 1995, 13, (4) Shirts, M. R.; Mobley, D. L.; Chodera, J. D.; Pande, V. S. Accurate and Efficient Corrections for Missing Dispersion Interactions in Molecular Simulations. J. Phys. Chem. B 27, 111, (5) Hess, B.; Bekker, H.; Berendsen, H. J.; Fraaije, J. G. LINCS: A Linear Constraint Solver for Molecular Simulations. J. Comput. Chem. 1997, 18, (6) Miyamoto, S.; Kollman, P. A. SETTLE: An Analytical Version of the SHAKE and RATTLE Algorithm for Rigid Water Models. J. Comput. Chem. 1992, 13, (7) in t Veld, P. J.; Ismail, A. E.; Grest, G. S. Application of Ewald Summations to Long-Range Dispersion Forces. J. Chem. Phys. 27, 127, (8) Wennberg, C. L.; Murtola, T.; Hess, B.; Lindahl, E. Lennard-Jones Lattice Summation in Bilayer Simulations Has Critical Effects on Surface Tension and Lipid Properties. J. Chem. Theory Comput. 213, 9, (9) Bussi, G.; Donadio, D.; Parrinello, M. Canonical Sampling Through Velocity Rescaling. J. Chem. Phys. 27, 126, (1) Nosé, S. A Unified Formulation of the Constant Temperature Molecular Dynamics Methods. J. Chem. Phys. 1984, 81, S16

17 (11) Hoover, W. G. Canonical Dynamics: Equilibrium Phase-Space Distributions. Phys. Rev. A 1985, 31, (12) Parrinello, M.; Rahman, A. Polymorphic Transitions in Single Crystals: A New Molecular Dynamics Method. J. Appl. Phys. 1981, 52, (13) Jämbeck, J. P.; Lyubartsev, A. P. Derivation and Systematic Validation of a Refined All-Atom Force Field for Phosphatidylcholine Lipids. J. Phys. Chem. B 212, 116, (14) Jämbeck, J. P.; Lyubartsev, A. P. An Extension and Further Validation of an All- Atomistic Force Field for Biological Membranes. J. Chem. Theory Comput. 212, 8, (15) Pronk, S.; Páll, S.; Schulz, R.; Larsson, P.; Bjelkmar, P.; Apostolov, R.; Shirts, M. R.; Smith, J. C.; Kasson, P. M.; van der Spoel, D. GROMACS 4.5: A High-Throughput and Highly Parallel Open Source Molecular Simulation Toolkit. Bioinformatics 213, btt55. (16) Olżyńska, A.; Zubek, M.; Roeselova, M.; Korchowiec, J.; Cwiklik, L. Mixed DPPC/POPC Monolayers: All-Atom Molecular Dynamics Simulations and Langmuir Monolayer Experiments. BBA-Biomembranes 216, 1858, (17) Klauda, J. B.; Venable, R. M.; Freites, J. A.; O Connor, J. W.; Tobias, D. J.; Mondragon- Ramirez, C.; Vorobyov, I.; MacKerell Jr, A. D.; Pastor, R. W. Update of the CHARMM All-Atom Additive Force Field for Lipids: Validation on Six Lipid Types. J. Phys. Chem. B 21, 114, (18) Izadi, S.; Anandakrishnan, R.; Onufriev, A. V. Building Water Models: A Different Approach. J. Phys. Chem. Lett. 214, 5, S17

18 (19) Kučerka, N.; Nieh, M.-P.; Katsaras, J. Fluid Phase Lipid Areas and Bilayer Thicknesses of Commonly Used Phosphatidylcholines as a Function of Temperature. BBA- Biomembranes 211, 188, (2) Brown, M. F.; Seelig, J.; Häberlen, U. Structural Dynamics in Phospholipid Bilayers From Deuterium Spin Lattice Relaxation Time Measurements. J. Chem. Phys. 1979, 7, (21) Ferreira, T. M.; Coreta-Gomes, F.; Ollila, O. S.; Moreno, M. J.; Vaz, W. L.; Topgaard, D. Cholesterol and POPC Segmental Order Parameters in Lipid Membranes: Solid State 1 H 13 C NMR and MD Simulation Studies. Phys. Chem. Chem. Phys. 213, 15, (22) von Tscharner, V.; McConnell, H. M. An Alternative View of Phospholipid Phase Behavior at the Air-Water Interface. Microscope and Film Balance Studies. Biophys. J. 1981, 36, (23) Crane, J. M.; Putz, G.; Hall, S. B. Persistence of Phase Coexistence in Disaturated Phosphatidylcholine Monolayers at High Surface Pressures. Biophys. J. 1999, 77, (24) Mansour, H. M.; Zografi, G. Relationships Between Equilibrium Spreading Pressure and Phase Equilibria of Phospholipid Bilayers and Monolayers at the Air-Water Interface. Langmuir 27, 23, (25) Javanainen, M. Large POPC Monolayer Simulations With 298 K (Part 1/2). 217; (26) Javanainen, M. Large POPC Monolayer Simulations With 298 K (Part 2/2). 217; S18

19 (27) Javanainen, M. Large DPPC Monolayer Simulations With 298 K (Part 1/2). 217; (28) Javanainen, M. Large DPPC Monolayer Simulations With 298 K (Part 2/2). 217; (29) Javanainen, M. Large DPPC Monolayer Simulations With 31 K (Part 1/2). 217; (3) Javanainen, M. Large DPPC Monolayer Simulations With 31 K (Part 2/2). 217; (31) Javanainen, M.; Cwiklik, L. POPC Monolayer Simulations With 31 K. 217; (32) Javanainen, M.; Cwiklik, L. POPC Monolayer Simulations With 31 K. 217; (33) Javanainen, M.; Cwiklik, L. DPPC Monolayer Simulations With 31 K. 217; (34) Javanainen, M.; Cwiklik, L. DPPC Monolayer Simulations With 31 K. 217; (35) Javanainen, M.; Cwiklik, L. POPC Monolayer Simulations With Slipids+OPC. 217; (36) Javanainen, M.; Cwiklik, L. DPPC Monolayer Simulations With Slipids+OPC. 217; S19

20 Table S1: Simulation parameter sets used in the study given in GROMACS terminology. Either the stochastic dynamics (sd) or the leap-frog (md) integrator is used. t stands for the integration time step. The cut-off scheme is based either on GROMACS-adjusted buffered Verlet lists 1 or neighbour lists (group) with a cut-off of rlist that are updated every nstlist steps. The interactions of atoms within rlist were evaluated every step, while those within rlistlong were evaluated every nstlist and applied at every step. The cut-off Lennard-Jones interactions is given as rvdw, while the forces calculated from the Lennard-Jones potential can be switched (force-switch) between rvdw_switch and rvdw. With long-ranged electrostatic interactions handled with the smooth particle mesh Ewald (PME), 2,3 rcoulomb sets the cut-off for real space part of the calculation. Dispersion correction 4 (dispcorr) can be applied to energy and presure (EnerPres) to account for the missing LJ interactions beyond cutoff. Thermostat is set with t-coupl with a time constant of tau_t, while the same keywords for the barostat are pcoupl and tau_p. The presure coupling geometry is given by pcoupltype. Constraints applied to either bonds involving hydrogen (h-bonds) or to all bonds (all-bonds) with the LINCS 5 algorithm. SETTLE 6 was always used to constrain the structure of water. : GROMACS optimizes the neighbour list update frequency and cut-off length. : GROMACS optimizes the real-space cut-off distance and the PME grid automatically. : Multiple values for rvdw were tested, including LJ-PME. For simulations with LJ-PME, 7,8 the Verlet cut-off scheme was employed. : Dispersion correction was applied to both energy and pressure in monolayer simulations. Also, bulk water simulations using this parameter set were repeated with dispersion correction. : Simulations were run with and without dispersion correction. : No pressure coupling for systems with interfaces (water air interface or monolayer systems). : For bulk water and lipid bilayers, isotropic and semiisotropic pressure coupling schemes were employed. For the air water interface and lipid monolayers, no pressure coupling was employed. OPC CHARMM36 Slipids integrator sd md md t (fs) cut-off scheme group Verlet 1 group nstlist rlist/rlistlong (nm).8/ 1.2 / 1./1.6 coulombtype PME 2,3 PME 2,3 PME 2,3 rcoulomb (nm) vdwtype cut-off cut-off cut-off vdw-modifier force-switch rvdw (nm) rvdw_switch (nm) 1. dispcorr /EnerPres 4 /EnerPres 4 EnerPres 4 tcoupl V-rescale 9 Nose Hoover 1,11 Nose Hoover 1,11 tau_t (ps) pcoupl Parrinello Rahman 12 / Parrinello Rahman 12 / pcoupltype isotropic/ semisotropic/ / semisotropic/ tau_p (ps) 5 1 lipid constraints LINCS: 5 h-bonds LINCS: 5 all-bonds water constraints SETTLE 6 SETTLE 6 SETTLE 6 S2

21 Table S2: Lengths of the larger monolayer simulations. The simulations were continued until their surface pressure showed convergence. Convergence data on frames extracted from the first expansion simulation are shown in Figs. S3, S5, and S4. Isotherm Area per lipid (Å 2 ) Duration (ns) POPC 298 K ns DPPC 298 K DPPC 31 K ns ns ns ns ns ns Table S3: Comparison of selected key properties of bulk water between the original values reported in the OPC4 paper (OPC4) and the results obtained here with with Slipids (OPC4/Slipids) simulation parameters from a box of 2228 waters at 298 K. The experimental values are shown in Expt.. The evaluated properties are density (ρ), self-diffusion coefficient (D), the location of the 1st peak in the oxygen oxygen radial distribution function r OO, and the thermal expansion coefficient α P. Property Orig. OPC4 18 OPC4/Slipids Expt. ρ (kg/ 3 ) 997±1 998±1 997 D (1 5 cm 2 /s) 2.3±.2 2.2± st peak in r OO (Å) α P (1 4 K 1 ) 2.7± Table S4: Areas per lipid calculated for lipid bilayers. Error estimates show standard deviation. Expt. stands for experimental values. Lipid Slipids CHARMM36 TIP3P OPC4 TIP(S)3P OPC4 Expt. 19 DPPC 6.2±1. 6.9±.9 6.5± ± ±1.5 POPC 62.8± ± ± ± ±1.3 S21