Glass transition and dynamics in BSA-water mixtures over wide ranges of composition studied by thermal and dielectric techniques

Panagopoulou, A; Kyritsis, A; Sabater I Serra, R; Gomez Ribelles, JL; Shinyashiki, N; Pissis, P

dc.contributor.author	Panagopoulou, A	en
dc.contributor.author	Kyritsis, A	en
dc.contributor.author	Sabater I Serra, R	en
dc.contributor.author	Gomez Ribelles, JL	en
dc.contributor.author	Shinyashiki, N	en
dc.contributor.author	Pissis, P	en
dc.date.accessioned	2014-03-01T02:02:15Z
dc.date.available	2014-03-01T02:02:15Z
dc.date.issued	2011	en
dc.identifier.issn	15709639	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/29298
dc.subject	Dielectric relaxation	en
dc.subject	Glass transition	en
dc.subject	Hydrated protein	en
dc.subject	Molecular mobility	en
dc.subject	Plasticization	en
dc.subject	Uncrystallized water	en
dc.subject.other	bovine serum albumin	en
dc.subject.other	water	en
dc.subject.other	article	en
dc.subject.other	crystallization	en
dc.subject.other	differential scanning calorimetry	en
dc.subject.other	electrochemical impedance spectroscopy	en
dc.subject.other	glass transition temperature	en
dc.subject.other	priority journal	en
dc.subject.other	thermally stimulated luminescence	en
dc.subject.other	water content	en
dc.subject.other	Bovinae	en
dc.title	Glass transition and dynamics in BSA-water mixtures over wide ranges of composition studied by thermal and dielectric techniques	en
heal.type	journalArticle	en
heal.identifier.primary	10.1016/j.bbapap.2011.07.014	en
heal.identifier.secondary	http://dx.doi.org/10.1016/j.bbapap.2011.07.014	en
heal.publicationDate	2011	en
heal.abstract	Protein-water dynamics in mixtures of water and a globular protein, bovine serum albumin (BSA), was studied over wide ranges of composition, in the form of solutions or hydrated solid pellets, by differential scanning calorimetry (DSC), thermally stimulated depolarization current technique (TSDC) and dielectric relaxation spectroscopy (DRS). Additionally, water equilibrium sorption isotherm (ESI) measurements were performed at room temperature. The crystallization and melting events were studied by DSC and the amount of uncrystallized water was calculated by the enthalpy of melting during heating. The glass transition of the system was detected by DSC for water contents higher than the critical water content corresponding to the formation of the first sorption layer of water molecules directly bound to primary hydration sites, namely 0.073 (grams of water per grams of dry protein), estimated by ESI. A strong plasticization of the Tg was observed by DSC for hydration levels lower than those necessary for crystallization of water during cooling, i.e. lower than about 0.3 (grams of water per grams of hydrated protein) followed by a stabilization of Tg at about - 80 °C for higher water contents. The α relaxation associated with the glass transition was also observed in dielectric measurements. In TSDC a microphase separation could be detected resulting in double Tg for some hydration levels. A dielectric relaxation of small polar groups of the protein plasticized by water, overlapped by relaxations of uncrystallized water molecules, and a separate relaxation of water in the crystallized water phase (bulk ice crystals) were also recorded. © 2011 Elsevier B.V. All Rights Reserved.	en
heal.journalName	Biochimica et Biophysica Acta - Proteins and Proteomics	en
dc.identifier.doi	10.1016/j.bbapap.2011.07.014	en
dc.identifier.volume	1814	en
dc.identifier.issue	12	en
dc.identifier.spage	1984	en
dc.identifier.epage	1996	en