Controlling the protein dynamical transition with sugar-based bioprotectant matrices. A neutron scattering study - Bulking Agents

Controlling the protein dynamical transition with sugar-based bioprotectant matrices. A neutron scattering study
20 March 2006
elena cornicchi, matteo marconi, Giuseppe Onori and Alessandro Paciaroni
Biophysical Journal
Abstract
Through elastic neutron scattering we measured the mean square displacements of the hydrogen atoms of lysozyme embedded in a glucose-water glassy matrix as a function of the temperature and at various water contents. The elastic intensity of all the samples has been interpreted in terms of the double-well model in the whole temperature range. The dry sample shows an onset of anharmonicity at around 100K, which can be attributed to the activation of methyl group reorientations. Such a protein intrinsic dynamics is decoupled from the external environment on the whole investigated temperature range. In the hydrated samples an additional and larger anharmonic contribution is provided by the protein dynamical transition, which appears at a higher temperature Td. As hydration increases the coupling between the protein internal dynamics and the surrounding matrix relaxations becomes more effective. The behaviour of Td that, as a function of the water content, diminishes by around 60K, supports the picture of the protein dynamics as driven by solvent relaxations. A possible connection between the protein dynamical response vs T and the thermal stability in glucose-water bioprotectant matrices is proposed.
Key Words: bioprotectant matrices, glucose-water mixtures, neutron scattering, picosecond dynamics, protein dynamical transition, thermal stability
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