To better represent the underlying atomistic cholesterol reference structure, two tiny beads were added to the layout on the cholesterol rough side (Figure ). These two beads (R5 and R6) directly account for the two methyl groups that protrude axially relative to the sterol core. The remaining beads of the sterol core (ROH, R1, R2, R3, and R4) were then placed to match the underlying atomistic solvent accessible surface area (SASA) (Figure ) and avoid very short intramolecular bead-bead distances, as recommended in the Martini 3 parameterization guidelines . Small beads were used to construct the cholesterol core (R1, R2, R3, and R4) except for the terminal hydroxyl core (ROH). The latter as well as the aliphatic chain (C1, and C2) were described as regular beads. The Martini 2 cholesterol topology accounted for the off-ring methyl groups by controlling the protrusion of the corresponding CG beads . However, this approach cannot fully recover the atomistic cholesterol shape without compromising the planarity of the sterol core and creating pockets on the cholesterol surface opposite the methyl groups (smooth side). As will be seen in the following sections, the new updated bead layout ensures a more accurate packing of cholesterol within the lipid acyl chain structure compared to the Martini 2 model.