To evaluate the validity of deducing R 1 from CG models, we performed NMR R 1 measurements from the CoM of the PEG monomers as extracted from the AA models, assuming that an effective number of spins n eff was located at each CoM position. This a-posteriori coarsegraining procedure allows us to separate the known intrinsic discrepancies between AA and G-CG models from the potential error on the values of R 1 introduced by the coarse-graining itself.