Thermodynamic properties of bulk and confined water.
The thermodynamic response functions of water display anomalous behaviors. We study these anomalous behaviors in bulk and confined water. We use nuclear magnetic resonance (NMR) to examine the configurational specific heat and the transport parameters in both the thermal stable and the metastable supercooled phases. The data we obtain suggest that there is a behavior common to both phases: that the dynamics of water exhibit two singular temperatures belonging to the supercooled and the stable phase, respectively. One is the dynamic fragile-to-strong crossover temperature (T(L) ≃ 225 K). The second, T* ∼ 315 ± 5 K, is a special locus of the isothermal compressibility K(T)(T, P) and the thermal expansion coefficient α(P)(T, P) in the P-T plane. In the case of water confined inside a protein, we observe that these two temperatures mark, respectively, the onset of protein flexibility from its low temperature glass state (T(L)) and the onset of the unfolding process (T*).
Dipartimento di Fisica e Scienza della Terra Università di Messina and CNISM, I-98168 Messina, Italy.
Francesco
F
Mallamace
Dipartimento di Fisica e Scienza della Terra Università di Messina and CNISM, I-98168 Messina, Italy.
Carmelo
C
Corsaro
Dipartimento di Scienze dell'Ambiente, della Sicurezza, del Territorio, degli Alimenti e della Salute, Università di Messina, I-98166 Messina, Italy.
Domenico
D
Mallamace
IPCF-CNR, I-98166 Messina, Italy.
Sebastiano
S
Vasi
IPCF-CNR, I-98166 Messina, Italy.
Cirino
C
Vasi
Center for Polymer Studies and Department of Physics, Boston University, Boston, Massachusetts 02215, USA.
H Eugene
HE
Stanley