  The Martini 3 force field is a full re-parametrization of the Martini
coarse-grained model for biomolecular simulations. Due to the improved
interaction balance it allows for more accurate description of condensed phase
systems. In the present work we develop a consistent strategy to parametrize
carbohydrate molecules accurately within the framework of Martini 3. In
particular, we develop a canonical mapping scheme that decomposes arbitrarily
large carbohydrates into a limited number of fragments. Bead types for these
fragments have been assigned by matching physicochemical properties of mono-
and disaccharides. In addition, guidelines for assigning bonds, angles, and
dihedrals are developed. These guidelines enable a more accurate description of
carbohydrate conformations than in the Martini 2 force field. We show that
models obtained with this approach are able to accurately reproduce osmotic
pressures of carbohydrate water solutions. Furthermore, we provide evidence
that the model differentiates correctly the solubility of the poly-glucoses
dextran (water soluble) and cellulose (water insoluble, but soluble in
ionic-liquids). Finally, we demonstrate that the new building blocks can be
applied to glycolipids, being able to reproduce membrane properties and to
induce binding of peripheral membrane proteins. These test cases demonstrate
the validity and transferability of our approach.
