The MARTINI FF was developed in 2004 at the University of Groningen, in the Netherlands by Marrink and his colleagues. It was originally for MD simulations of lipids, but since has been expanded to proteins, carbohydrates, DNA, and most recently, RNA. The MARTINI model has a 4-to-1 heavy atom mapping scheme, where 4 heavy non-hydrogen atoms are grouped together. Therefore, there would be 4 different bead types -polar (P), nonpolar (N), apolar (C), and charged (Q). For bead types N and Q, there are 4 different subtypes for hydrogen bonds -donor (d), acceptor (a), donor and acceptor (da), neither (0). For bead types P and C, a polarity can be assigned, ranging from 1 (low polarity) to 5 (high polarity)