Water and protein dynamics in protein - Water mixtures over wide ranges of composition

In this paper, glass transition and water and protein dynamics were studied in water mixtures of two globular proteins, lysozyme and BSA, by DSC, DRS and TSDC measurements. DSC measurements were used for the study of crystallization and melting phenomena of absorbed water. The noncrystallized water has been determined to be about 0.20 and 0.24 for Lysozyme and BSA, respectively, independent on h_w. Dielectric measurements reveal the α relaxation process associated with the glass transition of the hydrated proteins for both systems, in agreement with DSC results. For water fractions where no crystallization of water occurs during cooling our results shown a strong plasticization of T_g. Splitting of the the α relaxation process, observed for h_w >; 0.20, is maybe due to microphase separation occurred on both hydrated proteins at that hydration levels.