Molecular Dynamics of Solid-State Lysozyme as Affected by Glycerol and Water: A Neutron Scattering Study

Abstract

Glycerol has been shown to lower the heat denaturation temperature (T(m)) of dehydrated lysozyme while elevating the T(m) of hydrated lysozyme (. J. Pharm. Sci. 84:707-712). Here, we report an in situ elastic neutron scattering study of the effect of glycerol and hydration on the internal dynamics of lysozyme powder. Anharmonic motions associated with structural relaxation processes were not detected for dehydrated lysozyme in the temperature range of 40 to 450K. Dehydrated lysozyme was found to have the highest T(m) by. Upon the addition of glycerol or water, anharmonicity was recovered above a dynamic transition temperature (T(d)), which may contribute to the reduction of T(m) values for dehydrated lysozyme in the presence of glycerol. The greatest degree of anharmonicity, as well as the lowest T(d), was observed for lysozyme solvated with water. Hydrated lysozyme was also found to have the lowest T(m) by. In the regime above T(d), larger amounts of glycerol lead to a higher rate of change in anharmonic motions as a function of temperature, rendering the material more heat labile. Below T(d), where harmonic motions dominate, the addition of glycerol resulted in a lower amplitude of motions, correlating with a stabilizing effect of glycerol on the protein.

Mean-squared atomic displacements in hydrated lysozyme, native and denatured

“…At 220-230 K, the hydration water experiences a dynamical transition [20][21][22][23] that further increases anharmonicity. Finally, the onset of long-range translational motions of hydration water leads to an even faster increase in anharmonicity at temperatures above 240 K [47][48][49]. Thus, several different phenomena could contribute to the experimentally observed increase in the mean-squared displacements.…”

“…However, the exact mechanism of such "enslavement" has been extensively debated. For example, it has been reported that the transition is coupled to the onset of translational motions in hydration water [47][48][49]. In addition, it has been debated whether the transition is a real phenomenon, or merely a manifestation of the fact that the measurable atomic dynamics enter the experimentally accessible resolution window above certain temperatures [17,18,24,25,27].…”

Effect of viscogens on the kinetic response of a photoperturbed allosteric protein

“…To reach that value, a concentration of 40% w/w was needed for sucrose and 54% w/w for glycerol (see glycerol: MW 92), but both have been argued to be highly preferably excluded from the protein surface. [46][47][48] Nevertheless, Fig. 7 shows that glycerol significantly slows the relaxation kinetics in comparison with sucrose.…”

From shell to cell: neutron scattering studies of biological water dynamics and coupling to activity

“…The term 'slaving' has been used to express that water can impose its dynamical fingerprint on a protein 11,12 . Cryo-temperature dependent neutron scattering experiments revealed the solvent dependence of dynamical transitions in soluble proteins [13][14][15][16][17][18][19][20][21] and in RNA 22 and provided insights into the coupling between them. Molecular dynamics simulations suggested the onset of water translational diffusion to be at the origin of the dynamical transition 23,24 .…”