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Séminiare de Giuseppe Bellavia

par Manuel GOUBET - publié le , mis à jour le

The Role of the Environment on Local Transformations of the Water : Application to Bioprotection
Giuseppe BELLAVIA
IUT « A » de Lille, Dép. Mesures Physiques
Lab. UMET - UFR de Physique - BAT P5 CNRS UMR 8207, Université Lille 1, 59655 Villeneuve d’Ascq, France

Water is fundamental in many natural processes [1]. Among these, it plays a significant role
in maintaining protein and cellular structures. Studying the solvent-biomolecule interactions
along with probing the water properties at the interface is then a fundamental task for many
living systems.
Concerning bioprotection, a paradigmatic system is represented by saccharides which
protect proteins against denaturation under extreme environmental conditions as extreme
drought, high or low temperature [2]. Nevertheless, the molecular mechanisms behind this
effect are not yet fully understood. In this regard, our investigations on protein systems such
as amorphous matrices and solutions allowed a better comprehension of the phenomenon.
Recent calorimetric results [3,4] are presented, which allowed explaining bioprotection in
terms of a strong coupling of the biomolecule surface to the embedding water-sugar matrix
via extended hydrogen-bond networks, strongly dependent on water content.
A new method for analyzing protein hydration by Raman spectroscopy is also presented [5],
which provides an insight into protein denaturation in solution. This original approach can be
applied to several systems as well as in presence of co-solvent.
The low-frequency Raman spectroscopy (LFRS) is then introduced as a probe to investigate
the different physical states of the matter (amorphous, crystal, …) and the mechanisms behind
the phase transformations. In this regard, the overlapping low-frequency contributions,
corresponding to fast anharmonic and quasi-harmonic motions, respectively related to the
mean square displacement and the vibrational density of states (VDOS) usually
determined by neutron scattering experiments, can be carefully analyzed. An example is done
as evidence of the coupling between the protein and the solvent dynamics, confirming the
solvent dynamics as a necessary precursor to promote the protein unfolding [6].

References
1. P. Ball, Life’s Matrix : A Biography of Water, ed. University of California Press (2001).
2. J.H.. Crowe, Trehalose As a “Chemical Chaperone”, in Molecular Aspects of the Stress Response :
Chaperones, Membranes and Networks, ed. Springer (2007) 143-158.
3. G. Bellavia, G. Cottone, S. Giuffrida, A. Cupane, L. Cordone, J. Phys. Chem. B, 113, (2009) 11543–11549.
4. G. Bellavia, S. Giuffrida, G. Cottone, A. Cupane, L. Cordone, J. Phys. Chem. B, 115, (2011) 6340–6346.
5. G. Bellavia, A. Hédoux, L. Paccou, S. Achir, Y. Guinet, J. Siepmann, Food Biophysics, 8, (2013) 170-176.
6. G. Bellavia, L. Paccou, Y. Guinet, A. Hédoux, J. Phys. Chem. B, (2014) accepted.