title: Water induced effects on the thermal response of a protein.
abstract: A model protein and surrounding water have been investigated at different temperatures. We have detected an anomalous compression of the protein near the freezing point of water-a compression not obviously related to the negative thermal expansion of the solvent. Moreover, the physiological protein working temperature (T=300 K) appears to be related to the activation of exchange of vicinal water with the bulk and the concomitant absorption of heat by hydrophilic amino acids. The inferred activation was interpreted on the basis of degenerate tetrahedral order between the hydration shell and the bulk. The results support the notion that the dynamics of vicinal water makes a substantial contribution to the activity optimum of proteins.
authors.affiliation: Dipartimento di Fisica and INFM, Università La Sapienza, Piazzale Aldo Moro 5, 00185 Rome, Italy.
authors.forename: Simone
authors.initials: S
authors.lastname: Melchionna
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Briganti
authors.forename: Paola
authors.initials: P
authors.lastname: Londei
authors.forename: Piero
authors.initials: P
authors.lastname: Cammarano
mesh_terms: D004926:Escherichia coli / Q000201:enzymology; D006860:Hydrogen Bonding; D010444:Peptide Elongation Factor Tu / Q000737:chemistry*; D017434:Protein Structure, Tertiary; D013696:Temperature; D013816:Thermodynamics; D014867:Water / Q000737:chemistry*
chemical_list: D014867:Water; D010444:Peptide Elongation Factor Tu