In the last decade, the coherent collective dynamics of hydration water in biomolecules became experimentally accessible thanks to the development of new instrumentation for neutron Brillouin spectroscopy.
With an appropriate use of isotope substitution and contrast methods, THz modes propagating in hydration water could be singled out and studied for biological systems of increasing complexity, spanning from the model protein Ribonuclease A, to the more complex DNA, up to entire living cells of Escherichia coli. The experimental results revealed both similarities and differences with respect to the previously known behavior of bulk water. The observed differences have been further confirmed by new data measured in similar experimental conditions for bulk water.
The picture emerging from a comparison of collective modes in bulk and hydration water provides complementary information about the longstanding problem of the dynamical effects of water confinement, and hydrogen-bo