The MARTINI force field, developed between the groups of Marrink and Tieleman, is a coarse grained force field suited for molecular dynamics simulations of biomolecular systems. The force field has been parametrized in a systematic way, based on the reproduction of partitioning free energies between polar and apolar phases of a large number of chemical compounds.
The model uses a four-to-one mapping where, on average, four heavy atoms are represented by a single interaction center. In order to keep the model simple, only four main types of interaction sites are defined: polar (P), non-polar (N), apolar (C), and charged (Q). Each particle type has a number of subtypes, which allow for an accurate representation of the chemical nature of the underlying atomistic structure.