We therefore designed a new mapping scheme (Figure ) that can differentiate between tails that differ by two carbon atoms (e.g. 16C and 18C tails) based on a center-of-geometry mapping of atomistic structures and including hydrogens in the mapping . The 16C tails are differentiated from the 18C tails using a small bead that maps 3 carbon atoms immediately after the glycerol ester bead. In contrast, the 18C tail uses a regular-sized bead that maps 5 carbons at the beginning of the tail. In the new mapping scheme, ester groups are mapped together with their adjacent glycerol carbon to a small SN4a bead (Figure ). Furthermore, the phosphodiester group is now centered on the phosphorus atom with the sn-3 glycerol carbon left out of the mapping (but still implicitly accounted for by the Van der Waals radius of the phosphodiester bead), making comparisons of phosphorus distances between CG, AA, and experimental data consistent.