Contribution of the bound water to the dielectric and nuclear magnetic relaxation mechanism of protein solutions

Experimental data indicated that dielectric relaxation of tissues in the UHF and microwave range depend on their water content [1]. The water content was shown to contribute also to the proton nuclear relaxation times; in particular Fatourous et al. [2] obtained a monotonic relationship between the longitudinal relaxation time (T1) of soft tissues and their water content. With the aim of demonstrate the presence of a relationship between dielectric properties and magnetic relaxation mechanisms, we utilized a protein solution as tissue simulator and measured the dielectric permittivity by the open-ended coaxial line method in the frequency range 30 MHz-2.5 GHz. The T1 was measured by a pulsed NMR instrument in the range 4-60 MHz. The analysis of the experimental data shows the presence of a relationship between the two relaxation mechanisms. The results were tentatively discussed in term of the mixture and “FETS” theories which underline the particular role of the water coordinated to the hydration shell of macromolecules.