Preferential hydration of lysozyme in water/glycerol mixtures: A small-angle neutron scattering study

Abstract

In solution small-angle neutron scattering has been used to study the solvation properties of lysozyme dissolved in water/glycerol mixtures. To detect the characteristics of the protein-solvent interface, 35 different experimental conditions (i.e., protein concentration, water/glycerol fraction in the solvent, content of deuterated compounds) have been considered and a suitable software has been developed to fit simultaneously the whole set of scattering data. The average composition of the solvent in the close vicinity of the protein surface at each experimental condition has been derived. In all the investigated conditions, glycerol resulted especially excluded from the protein surface, confirming that lysozyme is preferentially hydrated. By considering a thermodynamic hydration model based on an equilibrium exchange between water and glycerol from the solvation layer to the bulk, the preferential binding coefficient and the excess solvation number have been estimated. Results were compared with data previously derived for ribonuclease A in the same mixed solvent: even if the investigated solvent compositions were very different, the agreement between data is noticeable, suggesting that a unique mechanism presides over the preferential hydration process. Moreover, the curve describing the excess solvation number as a function of the solvent composition shows the occurrence of a region of maximal hydration, which probably accounts for the changes in protein stability detected in the presence of cosolvents.

Effect of glycerol and dimethyl sulfoxide on the phase behavior of lysozyme: Theory and experiments

“…Its increase with increasing temperature and glycerol content is consistent with previous findings. 12,20,22 As mentioned above, glycerol affects b 2 (T) less than DMSO, i.e., the addition of 10 vol.% glycerol has about the same effect as 5 vol.% DMSO (Figs. 6(b) and 6(c)), although the optical properties of the two solvents suggest a similar effect on A ν > 0 and thus A (Fig.…”

“…23,39 However, measurements with protein powders often indicate larger values, for example 1 ≤ ε p ≤ 10 for wet lysozyme powder, 40 20 ≤ ε p ≤ 37 for hydrated lysozyme crystals 41 and, based on MD simulations, ε p = 25.7 for lysozyme in aqueous solution. 42 The larger values are attributed to water or moisture leading to hydration and some water penetration.…”

“…This is supported by observations of Priev et al 19 Their experiments indicate an increase of the hydration shell upon addition of glycerol and, at the same time, a decrease of the core volume of BPTI. Similarly, using small-angle neutron scattering, Sinibaldi et al 20 observed, upon increasing the glycerol content, a significant increase of the hydration shell of lysozyme from 0.3 nm to 0.6 nm, and a small decrease of the core volume of lysozyme of about 6%, such that the total effective protein volume increases by at least about 13%. 20,21 In the presence of glycerol, Esposito et al 22 furthermore observed an increase of the hydrodynamic radius with increasing temperature.…”

“…Similarly, using small-angle neutron scattering, Sinibaldi et al 20 observed, upon increasing the glycerol content, a significant increase of the hydration shell of lysozyme from 0.3 nm to 0.6 nm, and a small decrease of the core volume of lysozyme of about 6%, such that the total effective protein volume increases by at least about 13%. 20,21 In the presence of glycerol, Esposito et al 22 furthermore observed an increase of the hydrodynamic radius with increasing temperature. Using computer simulations, Vagenende et al 12 found that glycerol preferentially interacts with the hydrophobic patches on the lysozyme surface.…”

Combining structure and dynamics: non-denaturing high-pressure effect on lysozyme in solution

“…The attractive Yukawian potential is related to short-range attraction and depends on the energy at the protein-protein contact J and on the characteristic decay length d. This potential can be influenced by pressure through modifications of the lateral chain mobility as well as by changes in protein hydration properties or in protein surface architecture. Therefore, equation (3.1) was used to analyse in a unique fitting calculation (called global fit approach (Ortore et al 2005Sinibaldi et al 2007)) all the scattering curves as a function of pressure. Among the parameters of the model, some are known, whereas others are found by the fitting procedure.…”