One specificity of our CoM model, and of CG models in general, is the absence of an explicit solvent. To access the error introduced on the NMR R 1 when ignoring the spins of the H 2 O molecules, R 1 was re-calculated from the AA PEG-H 2 O mixtures using the same procedure as before [i.e. using Eqs. (2-5)], but while disregarding all the contributions involving the hydrogen atoms of the H 2 O molecules in the double summation in Eq. (2). Our results show that ignoring the H 2 O molecules only matters at low PEG concentration c PEG ≤ 0.1, where it leads to an overestimation of R 1 by a factor up to 2 (Fig. ). Such overestimation of R 1 is likely due to the comparatively slower translational and rotational motions of PEG as compared to H 2 O (Fig. ), since a slower molecular dynamics means faster spin relaxation, i.e. a larger value of R 1 .