Preliminary studies have already revealed the importance of water in the proper biological functioning of proteins. IBS researchers, in collaboration with the Institut Laue-Langevin, recently observed the movement of water molecules on the surface of proteins and correlated them with protein dynamics, which are essential to the biological activity of proteins. The researchers found that the water molecules have a rotational movement on themselves at a temperature less than -30°C; below this temperature, proteins are not active. When the temperature is higher than -30°C, corresponding to the beginning of activity for proteins, water molecules still rotate on themselves, but begin to exert a translational diffusion. Therefore, it is the ability of water to "dance" on protein surfaces that makes the proteins dynamic enough to be functional.
To successfully carry out this study, the researchers used neutron scattering technology combined with simulations of molecular dynamics. In order to mask the signal of the proteins while only keeping the signal of the water molecules at their surface, the researchers resorted to producing deuterated proteins, in which the hydrogen atoms are replaced by atoms of its isotope, deuterium.
These results provide a better understanding of the conditions necessary for the biological activity of proteins. Applications can be envisioned, for example, to control the stability of therapeutic proteins in a solid state, such as insulin, which is used as a treatment for diabetes.