Effect of Solvent Isotope Composition (H2O and D2O) on Lysozyme Oligomer Formation under Crystallization Conditions

Using the method of small-angle X-ray scattering (SAXS), the temperature dependences (in the range from 4 to 30°C with a step of 1°C) of the lysozyme solution structural organization during the growth of tetragonal crystals were obtained for H2O and D2O solvents. It was found that, regardless of the solvent type, dimers and octamers are formed in the lysozyme crystallization solution. The volume fractions of the oligomers (dimers and octamers) are inversely proportional to a change in temperature, for both H2O and D2O solvents. Under identical temperature conditions, the volume fraction of oligomers in the lysozyme crystallization solution in D2O is approximately 8% higher than in H2O. However, the same oligomer content in the lysozyme crystallization solutions in H2O and D2O is achieved when the temperature of the H2O solution is approximately 10°C lower than that of the D2O solution. This can be explained by the distinct influence of the solvent on protein hydration.