CUPANE, Antonio

FOMINA, Margarita

SCHIRO', Giorgio

English

Archivio istituzionale della ricerca - Università di Palermo

“Neutron Scattering Highlights on Water and Biological Systems”, Taormina, 26th-29th May 2012“Neutron Scattering Highlights on Water and Biological Systems”, Taormina, 26th-29th May 2012HYDRATION DEPENDENCE OF MEAN SQUARE DISPLACEMENTS, RELAXATION TIMES AND CALORIMETRIC GLASS TRANSITION IN MYOGLOBIN HYDRATED POWDERSMargarita Fomina, Giorgio Schirò, and Antonio CupaneDipartimento di Fisica, Università di Palermo, Italyfomina.margarita@unipa.itIn this work we investigate the dependence of mean square displacements (MSD), relaxation times (τ) and calorimetric glass transition (Tg) of hydrated Myoglobin powders upon hydration (h) in the ample range 0<h<0.5. MSD were measured with elastic incoherent neutron scattering (EINS) using the spectrometer IN13 at ILL (Grenoble). The effect of increasing hydration on MSD was to increase the amplitude of anharmonic contributions (in agreement with the suggested plasticizing role of hydration water, while the onset temperature of the so-called protein dynamical transition (PDT) was left unaltered, as clearly shown in Fig.1. The relaxation times and the glass transition temperatures of the protein/hydration water system were measured with broadband dielectric spectroscopy (BDS) and differential scanning calorimetry (DSC). At difference with MSD, these quantities were found to depend markedly upon hydration. The relevance of protein/hydration water relaxations (as measured with BDS) and glass transition (as measured with DSC) to the PDT (as measured with EINS) is discussed. Figure 1. Upper panel: MSD vs. T at various hydrations. Middle  panel: ∆MSD, defined as the MSD difference between hydrated and dry samples, as a function of T. Lower panel: normalized ∆MSD as a function of temperature; the normalization temperature is 290K. 2

Hydration dependence of mean square displacements, relaxation times and calorimetric glass transition in myoglobin hydrated powders

https://iris.unipa.it/bitstream/10447/63194/1/Fomina_abstract_bis_Bioneutron2012.doc

Hydration dependence of mean square displacements, relaxation times and calorimetric glass transition in myoglobin hydrated powders

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Archivio istituzionale della ricerca - Università di Palermo