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Center for Nonlinear Studies |
Proteins are complex systems that connect biology, biophysics, biochemistry, chemistry, and physics. (Mathematicians have complained why are we left out.). Proteins share similarities with supercooled liquids and glasses, such as the existence of an energy landscape and α and β fluctuations, but they are far more complex. They can be studied in much more detail. Protein research therefore has not only impact in the life sciences, but also in materials science. Protein functions require motions, but less is known about the motions than about structures and functions. The beautiful pictures of proteins that grace the pages of Nature and Science often create the impression that proteins are rigid and function independently of their environment. Proteins are, however, surrounded by hydration water and they are embedded in a bulk solvent. Here we introduce a model that relates the motions in the hydration shell and the bulk solvent to the motions in the protein. The model is based on an energy landscape and motivated by experiments with myoglobin that separately monitor the external and internal fluctuations over a broad temperature range. The data show that the α fluctuations of the bulk solvent drive the large-scale protein motions and that the β fluctuations of the hydration water drive the internal protein motions. The model assigns clear functional roles to the bulk solvent and the hydration water and it has predictive power; the fluctuations in the hydration water forecast the internal protein fluctuations. These results hint that the protein surface is functionally as important as the interior. The data and the model suggest new experiments and prove that there is no “dynamic transition” near 200 K in proteins.
Host: Bob Ecke, T-CNLS