Interfacial water at protein surfaces: Wide-line NMR and DSC characterization of hydration in ubiquitin solutions

K. Tompa, P. Bánki, M. Bokor, Pawel Kamasa, György Lasanda, Péter Tompa

Research output: Contribution to journalArticle

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Abstract

Wide-line 1H-NMR and differential scanning calorimetry measurements were done in aqueous solutions and on lyophilized samples of human ubiquitin between -70°C and +45°C. The measured properties (size, thermal evolution, and wide-line NMR spectra) of the protein-water interfacial region are substantially different in the double-distilled and buffered-water solutions of ubiquitin. The characteristic transition in water mobility is identified as the melting of the nonfreezing/hydrate water. The amount of water in the low-temperature mobile fraction is 0.4 g/g protein for the pure water solution. The amount of mobile water is higher and its temperature dependence more pronounced for the buffered solution. The specific heat of the nonfreezing/ hydrate water was evaluated using combined differential scanning calorimetry and NMR data. Considering the interfacial region as an independent phase, the values obtained are 5.0-5.8 J·g-1·K-1, and the magnitudes are higher than that of pure/bulk water (4.2 J·g -1·K-1). This unexpected discrepancy can only be resolved in principle by assuming that hydrate water is in tight H-bond coupling with the protein matrix. The specific heat for the system composed of the protein molecule and its hydration water is 2.3 J·g -1·K-1. It could be concluded that the protein ubiquitin and its hydrate layer behave as a highly interconnected single phase in a thermodynamic sense.

Original languageEnglish
Pages (from-to)2789-2798
Number of pages10
JournalBiophysical Journal
Volume96
Issue number7
DOIs
Publication statusPublished - 2009

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Ubiquitin
Membrane Proteins
Water
Hot Temperature
Differential Scanning Calorimetry
Proteins
Temperature
Thermodynamics
Freezing

ASJC Scopus subject areas

  • Biophysics

Cite this

Interfacial water at protein surfaces : Wide-line NMR and DSC characterization of hydration in ubiquitin solutions. / Tompa, K.; Bánki, P.; Bokor, M.; Kamasa, Pawel; Lasanda, György; Tompa, Péter.

In: Biophysical Journal, Vol. 96, No. 7, 2009, p. 2789-2798.

Research output: Contribution to journalArticle

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