We present a computer simulation picture of the dynamical behavior, at room temperature, of water in the region close to a protein surface. We analyzed the probability distribution of water molecules diffusing near the surface, and we found that it deviates from a Gaussian, which is predicted for Brownian particles. Consistently, the mean square displacements of water oxygens show a sublinear trend with time. Moreover, the relaxation of hydration layers around the whole protein is found to follow a stretched exponential decay, typical of complex systems, which could as well be ascribed to the non-Gaussian shape of the propagator. In agreement with such findings, the analysis of water translational and reorientational diffusion showed that not only are the solvent molecule motions hindered in the region close to the protein surface, but also the very nature of the particle diffusive processes, both translational and rotational, is affected. The deviations from the bulk water properties, which put into evidence a deep influence exerted by the protein on the solvent molecule motion, are discussed in connection with the presence of spatial ͑protein surface roughness͒ and temporal ͑distribution of water residence times͒ disorder inherent in the system.

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Measurement of the low temperature neutron excess of scattering of H2O-hydrated plastocyanin relative to D2O-hydrated protein allowed us to reveal the presence of an inelastic peak at about 3.5 meV. This excess of vibrational modes, elsewhere termed "boson peak," is due to the dynamical behavior of the water molecules belonging to the H2O-hydration shell surrounding the protein. The relevance of the boson peak to the dynamical coupling between the solvent and the protein, and hence to the protein functionality is addressed.

Molecular-dynamics ͑MD͒ simulations of a hydrated protein system, performed at different temperatures, allowed us to point out anomalies in the low-frequency spectral features of hydration water. The dynamical structure factor calculated from the water MD trajectories shows, below 180 K, a broad inelastic peak in the low-frequency region (ϳ1.3 meV) reminiscent of the so-called boson peak observed in amorphous disordered materials. Additional evidence of this boson peak is provided by the calculated vibrational density of states. The behavior of the simulated dynamical susceptibility at various temperatures was found to be very similar to that recently obtained by scattering experiments in similar systems. Possible implications of these anomalies in the protein-solvent coupling mechanisms are briefly discussed.

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The intrinsically disordered protein p53 has attracted a strong interest for its important role in genome safeguarding and potential therapeutic applications. However, its disordered character makes difficult a full characterization of p53 structural architecture. A deep knowledge of p53 structural motifs could significantly help the understanding of its functional properties, in connection with its complex binding network. We have applied Raman spectroscopy to investigate the structural composition and the conformational heterogeneity of both full-length p53 and its DNA binding domain (DBD), in different solvent environments. In particular, a careful analysis of the Amide I Raman band, which is highly sensitive to protein secondary structure elements such as α-helices, β-sheets and random coils, has revealed the presence of extended random coils in p53 and predominant β-sheet regions in its DBD. In addition, this analysis has allowed us to explore the ensemble of interchanging conformations in both p53 and its DBD, highlighting a higher conformational heterogeneity in p53 than in its DBD. Furthermore, by applying a principal components analysis, we have identified the principal spectral markers in both p53 and DBD samples. The combination of the two approaches could be insightful for the study of intrinsically disordered proteins, by offering increased versatility and wide application as a label-free, real-time and non-invasive detection method.

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