Multiscale modeling of complex molecular systems, such
as macromolecules,
encompasses methods that combine information from fine and coarse
representations of molecules to capture material properties over a
wide range of spatiotemporal scales. Being able to exchange information
between different levels of resolution is essential for the effective
transfer of this information. The inverse problem of reintroducing
atomistic degrees of freedom in coarse-grained (CG) molecular configurations
is particularly challenging as, from a mathematical point of view,
it is an ill-posed problem; the forward mapping from the atomistic
to the CG description is typically defined via a deterministic operator
(“one-to-one” problem), whereas the reversed mapping
from the CG to the atomistic model refers to creating one representative
configuration out of many possible ones (“one-to-many”
problem). Most of the backmapping methods proposed so far balance
accuracy, efficiency, and general applicability. This is particularly
important for macromolecular systems with different types of isomers,
i.e., molecules that have the same molecular formula and sequence
of bonded atoms (constitution) but differ in the three-dimensional
configurations
of their atoms in space. Here, we introduce a versatile deep learning
approach for backmapping multicomponent CG macromolecules with chiral
centers, trained to learn structural correlations between polymer
configurations at the atomistic level and their corresponding CG descriptions.
This method is intended to be simple and flexible while presenting
a generic solution for resolution transformation. In addition, the
method is aimed to respect the structural features of the molecule,
such as local packing, capturing therefore the physical properties
of the material. As an illustrative example, we apply the model on
linear poly(lactic acid) (PLA) in melt, which is one of the most popular
biodegradable polymers. The framework is tested on a number of model
systems starting from homopolymer stereoisomers of PLA to copolymers
with randomly placed chiral centers. The results demonstrate the efficiency
and efficacy of the new approach.