The simulation lengths of different membrane systems are listed in Table . The v-rescale thermostat is used for temperature coupling with a coupling constant of 1 ps. Pressure is controlled semiisotropically at 1 bar. Parrinello-Rahman barostat is used for pressure coupling with a coupling constant of 12 ps and compressibility of 3×10 -4 bar -1 . Position restraint is applied on the phosphate beads of each lipid along the z-direction in order to avoid unnecessary undulation of the larger membranes. It is observed in the earlier studies that memrane undulations can cause phase seperation in the bilayer membarne . The real cell membrane consists of transmembrane proteins which significantly reduce this sort of undulations . However, in the present work, we have considered only the lipid membrane of an E. coli bacteria (without protien) and it is composed of 14 different type of lipids. Hence the membrane undulation can stimulate an unrealistic phase seperation which will impede the correct determination of the structural properties as well. Therfore, in the current work we have kept the membrane flat with weak position restraining. We have done the restraining with a harmonic force constant of 2 kJ mol -1 nm -2 applied on the phosphate beads of all of the lipids on the lower leaflet along the z-direction . Thus, both the local and global undulations of the membrane leaflets are inhibited. We have used the Verlet cutoff scheme with a Verlet-buffertolerance of 0.005 kJ/mol/ps. The van der Waals cutoff is set to 1.1nm using the potential-shift-Verlet method and coulomb cutoff is fixed to 1.1 nm. We have removed the centre-of-mass movement at every 100 steps.