In Eq. 2, the parameter b depends on the squared energy of the dipole-dipole interactions and on the number of long-living (i.e. for a time > 𝜏 𝑐(𝑛) ) water molecules and exchanging macromolecular protons, and the parameter a on the contribution to the relaxation rate from interactions modulated with correlation times shorter than 𝜏 𝑐(𝑛) (e.g. from very labile water molecules, with very short lifetime) and from non-dispersive terms.