The role of water in protein's behavior: The two dynamical crossovers studied by NMR and FTIR techniques.
The role the solvent plays in determining the biological activity of proteins is of primary importance. Water is the solvent of life and proteins need at least a water monolayer covering their surface in order to become biologically active. We study how the properties of water and the effect of its coupling with the hydrophilic moieties of proteins govern the regime of protein activity. In particular we follow, by means of Fourier Transform Infrared spectroscopy, the thermal evolution of the amide vibrational modes of hydrated lysozyme in the temperature interval 180 K < T < 350 K. In such a way we are able to observe the thermal limit of biological activity characterizing hydrated lysozyme. Finally we focus on the region of lysozyme thermal denaturation by following the evolution of the proton Nuclear Magnetic Resonance (NMR) spectra for 298 K < T < 366 K with the High-Resolution Magic Angle Spinning probe. Our data suggest that the hydrogen bond coupling between hydration water and protein hydrophilic groups is crucial in triggering the main mechanisms that define the enzymatic activity of proteins.
Dipartimento di Fisica e Scienze della Terra, Università di Messina, Viale F. Stagno D'Alcontres 31, 98166 Messina, Italy ; CNR-IPCF, Istituto per i Processi Chimico-Fisici, Viale F. Stagno D'Alcontres 37, 98158 Messina, Italy.
Francesco
F
Mallamace
Dipartimento di Fisica e Scienze della Terra, Università di Messina, Viale F. Stagno D'Alcontres 31, 98166 Messina, Italy.
Carmelo
C
Corsaro
Dipartimento di Scienze dell'Ambiente, della Sicurezza, del Territorio, degli Alimenti edella Salute, Università di Messina, Viale F. Stagno d'Alcontres 31, 98166 Messina, Italy.
Domenico
D
Mallamace
Dipartimento di Fisica e Scienze della Terra, Università di Messina, Viale F. Stagno D'Alcontres 31, 98166 Messina, Italy.
Sebastiano
S
Vasi
CNR-IPCF, Istituto per i Processi Chimico-Fisici, Viale F. Stagno D'Alcontres 37, 98158 Messina, Italy.
Cirino
C
Vasi
Dipartimento di Scienze dell'Ambiente, della Sicurezza, del Territorio, degli Alimenti edella Salute, Università di Messina, Viale F. Stagno d'Alcontres 31, 98166 Messina, Italy.
Giacomo
G
Dugo
Amide bending mode; HR-MAS; Hydration water; Lysozyme unfolding; Protein dynamic transition