We propose to investigate the role of water and of hydrogen bonding at the water-protein interface in the polymerisation of tubulin ab-hetero-dimers into microtubules, using Quasi-Elastic and Elastic Neutron Scattering with the high-resolution spectrometer IRIS.The experimental results will allow us to quantify the vibrational Mean Square Displacement of protein atoms, and the diffusion coefficient of solvent (water) molecules. These data, in turn, will provide a direct view of the entropy changes across polymerisation, which, in the case of tubulin, is known to be entropy driven. A series of additional measurements has been planned to identify the role of nucleotides (GTP and GDP) bound to tubulin, as well as the effect of taxol, whose remarkable anti-cancer activity is due to its ability to stabilise microtubules with respect to the oligomeric phase.