A Langmuir trough enables the measurement of lipid monolayer surface tension as a function of its area, thereby providing insighs into the behavior of PS and TFLL. Moreover, monitoring the changes in the resulting surface pressure-area isotherms upon the addition of biomolecules-such as proteins and drugs-into the aqueous subphase can be used to understand their binding to membranes. Above the main transition temperature (T m ) of the phospholipid, the monolayer remains in the fluid-like liquid expanded (L e ) phase over a large range of areas. Below the T m value, L e phase transforms upon compression to a gel-like liquid condensed (L c ) phase through a coexistence plateau. At very large areas, the pores form in the monolayer and a gas-L e coexistence appears at very low surface pressures close to 0 mN/m. Due to their physiological importance, monolayers modeling PS or TFLL have been sub-ject to numerous computational studies which have utilized both coarse-grained and atomistic molecular dynamics (MD) simulation approaches. MD simulations are also used to complement spectroscopic monolayer experiments, for example to understand ion binding to membranes. 9 However, MD simulations have struggled to correctly capture the interactions at interfaces between polar and non-polar environments that provide PS and TFLL their functionality, yet these interactions need to be properly balanced to reproduce experimental pressure-area isotherms. This discrepancy has been suggested to arise from underestimated water-air surface tension of common water models and the truncation of long-range van der Waals interactions which compromises the description of acyl chainvacuum interface. We have recently demonstrated that the CHARMM36 ("C36" from now on) lipid model combined with the 4-point OPC water model ("OPC4" from now on) provides nearly quantitative agreement with experimental surface pressure-area isotherms of both singlecomponent and multi-component 19 lipid monolayers. This is because OPC4 water model reproduces the surface tension of water with a Lennard-Jones (LJ) cuto↵ of 1.2-1.4 nm that is consistent with common lipid models such as the C36 and Slipids 20 ones. Thus, the OPC4 water model enables more realistic simulations of lipid monolayers without the need to re-parameterize the entire lipid model. However, this approach still su↵ers from the issues related the missing attractive long-range van der Waals forces due to the truncation of the LJ potential. On the other hand, these long-range van der Waals interactions are included in the recent version of C36 lipid model, coined C36/LJ-PME, through a PME-like algorithm. In this model, the glycerol and ester regions of lipids are modified to avoid over-condensation resulting from the increased attraction. Our earlier studies suggest that a water model with correct surface tension is necessary to reproduce experimental surface pressure-area isotherms and phase behaviour of lipid monolayers. Inclusion of long-range LJ interactions increase the surface tension of the used CHARMM-specific TIP3P (TIPS3P) water model, albeit not enough for it to match experiment. The C36/LJ-PME was demonstrated to reproduce the experimental surface tensions at three di↵erent areas for a DPPC monolayer, yet its ability to reproduce experimental surface pressure-area isotherms or lipid monolayer phase behaviour has not been evaluated.