Lucia Comeza, Silvia Corezzib, Marco Paolantonic, Paola Sassic, Assunta Morresic, Daniele Fiorettob
aCNR-IOM, c/o Dipartimento di Fisica e Geologia, Via Pascoli, I-06123 Perugia, Italy
bDipartimento di Fisica e Geologia, Università di Perugia, Via Pascoli, I-06123 Perugia, Italy
cDipartimento di Chimica, Biologia e Biotecnologie Università di Perugia, Via Elce di Sotto, 8, I-06123 Perugia, Italy
The Extended frequency range Depolarized Light Scattering (EDLS), has been demonstrated to be a powerful tool to access the fast dynamics of water in a diversity of binary systems, including sugars and proteins’ aqueous solutions. EDLS enables one to disentangle solute from solvent dynamics and, into the latter, bulk from hydration water contributions [1-8]. Here, it is used for the first time in a ternary system by studying a lysozyme-trehalose aqueous solution over a broad time scale, from hundreds to fractions of ps. We provide experimental evidence that the sugar, present in the ternary solution in sufficient quantity for biopreservation, strongly modifies the solvation properties of the protein. By comparing aqueous solutions of lysozyme with and without trehalose, we show that the combined action of sugar and protein produces an exceptional slowdown of the restructuring of a fraction of water molecules around the protein, namely more than twice the corresponding value in the absence of trehalose. We also demonstrate that the dynamics of these hydrating water molecules get slower and slower upon cooling. On the basis of these findings and the general agreement with molecular dynamics results on the same system [9,10], we hypothesize that such a hyperslow water close to lysozyme is preserved from crystallization by the presence of trehalose in the mixture, and thus it plays a key role in protecting the biomolecule.
References
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