Tuning Protein Dynamics by Modulating Solvent Motions through Glassy Matrices, Sol-Gels and Reverse Micelles

Many proteins can be viewed as nanodevices whose functions are controlled by a complex array of molecular motions. Functionally important protein dynamics pose a difficult challenge for study in that they span orders of magnitude with respect to amplitudes and time scales. One approach to organizing and systematically studying protein dynamics is based on the degree to which the different protein motions are slaved to different categories of solvent motion. This approach is the basis for the solvent slaving model of Frauenfelder and coworkers and our protein dynamic state model. In the present work, we describe how sol-gels, trehalose-derived glasses and reverse micelles can be used as matrices to systematically tune these different categories of protein dynamics through modulation of solvent dynamics and confinement volume. Through this approach we can dissect out the factors that control the activation energies and onset of activation for dynamics in hemeproteins such as hemoglobin and myoglobin that control substrate/ligand diffusion within the protein as well as escape from or entry into the protein from the solvent.