The good agreement on the values of R 1 obtained between experimental results or AA simulations and G-CG model with reconstructed hydrogens, G-CG-H, attests that only the low-frequency motions of the system matter for the calculation of NMR relaxation rates. Higher frequency motions, such as bond vibrations, are not present in the G-CG-H trajectories, with no apparent consequences on the calculation of R 1 . Therefore, as long as the CG model reproduces the rotational and translational dynamics of the molecules, and as long as the average distance between the re-introduced hydrogen atoms is correct, NMR relaxation rates can be extracted from a CG simulation. As alternatives to the numerical procedure used here to perform RCG, several other RCG methods have proven successful, including the use of virtual sites , or the backmapping of atoms using machine learning approaches . In the present contribution, only the longitudinal relaxation rate R 1 induced by dipole-dipole interaction was considered because it is the relevant relaxation mechanism for the PEG-water system. A priori, the reconstruction of atomic details employed here for the calculation of R 1 could be used as well to calculate the transversal dipolar relaxation rate R 2 from a G-CG model since a similar level of atomic details is required. However, in the case of nuclei with spin quantum number I ≥ 1, the NMR relaxation tends to be dominated by quadrupolar interaction . Its calculation requires the accurate estimate of the autocorrelation function of the electric field gradient at the nucleus, a quantity that depends on the intra-atomic electronic charge distribution and is typically computed using ab initio molecular dynamics methods or classical MD with a polarizable model . Therefore, the determination of quadrupolar interaction from a G-CG model would require the reconstruction of a higher level of details than the one required for dipolar interaction, such as Hartee-Fock or QM/MM level. The possibility of using a G-CG model to measure such quadrupolar interaction should be subject of future investigation.