title: Study of the phase transition in lysozyme crystals by Raman spectroscopy.
abstract: BACKGROUND
  Recently, it has been revealed that tetragonal lysozyme crystals show a phase transition at 307 K upon heating. The underlying mechanisms of the phase transition are still not fully understood. Here we focus on the study of high-frequency vibrational modes arising from the protein and their temperature evolution in the vicinity of Tph as well as on the detailed study of crystalline water dynamics near Tph.
  
  
  METHODS
  Raman experiments have been performed at temperatures 295–323 K including Tph. The low-frequency modes and the modes of fingerprint region, CH- and OH-stretching regions have been analyzed.
  
  
  CONCLUSIONS
  In spite of the absence of noticeable rearrangements in protein structure, the high-frequency vibrational modes of lysozyme located in the fingerprint region have been found to exhibit the features of critical dynamics near Tph. Pronounced changes in the dynamics of α-helixes and Tyr residues exposed on the protein surface point to the important role of H-bond rearrangements at the phase transition. Additionally the study of temperature evolution of OH-stretching modes has shown an increase in distortions of tertahedral H-bond network of crystalline water above Tph. These changes in water dynamics could play a crucial role in the mechanisms of the phase transition.
  
  
  CONCLUSIONS
  The present results shed light on the mechanisms of the phase transition in lysozyme crystals.
authors.affiliation: Jülich Center for Neutron Science (JCNS), Forschungszentrum Jülich GmbH, Outstation at MLZ, Lichtenbergstraße 1, 85747 Garching, Germany; A.F. Ioffe Physical Technical Institute, Politekhnicheskaya ul. 26, 194021 St. Petersburg, Russian Federation. Electronic address: a.frontzek@fz-juelich.de.
authors.forename: Anna V
authors.initials: AV
authors.lastname: Frontzek
authors.affiliation: Université Lille Nord de France, F-59000 Lille, France, USTL UMET UMR CNRS 8207, F-59655 Villeneuve d'Ascq Cedex, France.
authors.forename: Laurent
authors.initials: L
authors.lastname: Paccou
authors.affiliation: Université Lille Nord de France, F-59000 Lille, France, USTL UMET UMR CNRS 8207, F-59655 Villeneuve d'Ascq Cedex, France.
authors.forename: Yannick
authors.initials: Y
authors.lastname: Guinet
authors.affiliation: Université Lille Nord de France, F-59000 Lille, France, USTL UMET UMR CNRS 8207, F-59655 Villeneuve d'Ascq Cedex, France.
authors.forename: Alain
authors.initials: A
authors.lastname: Hédoux
mesh_terms: D003460:Crystallization; D009113:Muramidase / Q000737:chemistry*; D044367:Phase Transition; D017433:Protein Structure, Secondary; D013059:Spectrum Analysis, Raman / Q000379:methods*; D014732:Vibration
chemical_list: D009113:Muramidase
keywords: Phase transition; Raman spectroscopy; Tetragonal lysozyme crystal