FC relaxometry can also shed light on the dynamics of biological samples in the solid state, as for instance dry (lyophilized) proteins and frozen protein solutions, or in sedimented systems or low-level rehydrated lyophilized protein systems. In these cases, the relaxation profiles can be described by a power law in proton Larmor frequency (𝑅 1 = 𝐴𝜔 -𝐵 with B = 0.76-0.78), resulting from rotationally immobilized protein protons with mobility restricted to geometries having lower dimensionality than the usual three dimensional diffusion, and considering an efficient magnetization transfer between protein and water protons. The low field relaxation rates can be as large as hundreds or thousands of s -1 , and then the rates progressively decrease with increasing frequencies. These profiles have also been fitted using the model free approach (Eq. 2), with correlation times usually ranging between 10 -6 and 10 -9 s.