to struggle in this area . However, both force fields produce forking for C2 and C3 at the start of sn-1 chain, which is not in agreement with the experimental data. In general, OPLS3e produces very similar pattern of order parameters at full hydration as CHARMM36: close to experimental values but not within experimental accuracy. However, both force fields have problems with the correct description of g 1 at glycerol backbone, the beginning of the acyl tails, and the double bond of oleoyl chain. Therefore, we can conclude that OPLS3e produces comparable S CH to CHARMM36 at full hydration, suggesting that structural description of POPC is similar and reasonably accurate in these force fields.