Date(s) - 28/01/2015
3:30 pm - 4:30 pm
Title: Protein Long-Range Vibrational Modes
Speaker: Dr. Andrea Markelz
Institute: University of Buffalo
Location: ABB 102
In the dynamical ensemble picture of protein dynamics, it has been suggested that protein structural dynamics access configurations of subsequent functional states. Among the variety of different thermally activated motions within the protein, long range vibrational motions have been found to follow trajectories that reproduce functional conformational change. These vibrations lie in the terahertz frequency range, or picosecond time scale. The possible role of these collective vibrations providing the necessary access to functional configurations has been suggested as a universal mechanism for allosteric control, where by tailoring the long range structural dynamics one can either promote or inhibit function. An important component to pursue this idea is that characterization of long range dynamics. Such characterization would ideally give information concerning specific dynamic networks necessary for functional conformational change. I will introduce the new terahertz spectroscopy techniques can be used to interrogate picosecond motions in proteins, THz TDS, CATM and PV-CATM. Both CATM and PV-CATM were developed in our lab over the last couple of years and provide unprecedented insight into the long range dynamics. Standard transmission measurements find that the THz response scales with protein structural stability. Using anisotropic transmission measurements on aligned molecular systems (specifically crystals) reveal that indeed long-range underdamped intramolecular vibrations exist. Further we find that while calculations show no change in the vibrational density of states with small ligand binding for chicken egg white lysozyme, we see a sizable change in the anisotropic spectrum. We relate this large change upon small ligand binding to the change of the backbone motions accessible in the bound state. This change in the directionality of the motions changes the optical coupling to the vibrations, resulting in a clear signature, in both the calculated and measured spectra. I will discuss the potential of the technique to more fully characterize protein dynamical networks. Such characterization can enable the critical tests of the importance of these motions to function, and whether universal allostery can be achieved by the perturbation of these networks.