In immobilized systems, a magnetization transfer arises when the transition energies between the states of the 14 N nucleus match those between the states of a I = ½ nucleus (like for instance 1 H) which is dipole-dipole coupled with the 14 N nucleus. This process causes a fast decay of the 1 H magnetization at specific frequencies, and thus the appearance of peaks with a high relaxation rate, called quadrupolar peaks. The contribution to the 1 H relaxation rates due to the coupling with N nuclei can be described by Eq. ( ) 𝑅 1 𝐻𝑁 = 𝐶 𝐻𝑁 [(