title: Analysis of the mechanism of lysozyme pressure denaturation from Raman spectroscopy investigations, and comparison with thermal denaturation.
abstract: Pressure denaturation of lysozyme dissolved in H(2)O and D(2)O was analyzed using Raman investigations in a wide frequency range. The simultaneous analysis of regions corresponding to the molecular fingerprint of the protein (500-1800 cm(-1)), and the low- (50-450 cm(-1)) and high- (2600-3800 cm(-1)) frequency spectra, allow us to probe protein denaturation and the organization of water molecules. The pressure- and heat-induced transformations are compared. Both pressure- and heat-denatured states are obtained through an intermediate state characterized by intact secondary structure and enhanced water penetration in the tertiary structure. As a consequence of a weaker penetration upon pressurizing, it was found that the pressure-denatured state was partially unfolded compared with the heat-denatured state. The mechanism of pressure denaturation was related to the disruption of the hydrogen-bond network of water onto a set of clusters characterized by strengthened O - H interactions, inducing a hardening of protein dynamics. The mechanism is opposite to that observed upon heating, i.e., the softening of the hydrogen bond network of water inducing a softer protein dynamics. The analysis of the intramolecular O-H stretching reveals that pressurizing lysozyme aqueous solution favors the development of low-density water from the protein surface to the bulk, contrasting to the compression of pure water leading to crystallization of high-density ice-VI.
authors.affiliation: Université Lille Nord de France, Lille, France. alain.hedoux@univ-lille1.fr
authors.forename: Alain
authors.initials: A
authors.lastname: Hédoux
authors.forename: Yannick
authors.initials: Y
authors.lastname: Guinet
authors.forename: Laurent
authors.initials: L
authors.lastname: Paccou
mesh_terms: D009113:Muramidase / Q000737:chemistry*; D011312:Pressure; D011489:Protein Denaturation; D013059:Spectrum Analysis, Raman; D013696:Temperature
chemical_list: D009113:Muramidase