9305711 Schulte Variations in pressure and temperature are combined with time- resolved Raman spectroscopy to study reaction parameters and motions relevant for protein function. The principal focus is on two prototype processes: ligand binding to myoglobin and light energy transduction in the proton-pump bacteriorhodopsin. The protein is brought to a particular state of the Gibbs free energy surface by changing pressure and temperature. A sudden external perturbation, for instance a pressure jump or a laser flash, initiates a reaction or a relaxation. Kinetic studies of vibrational modes that change in position and intensity explore the highly degenerate energy surface and relaxation phenomena. In addition to monitoring Raman bands in the visible we use excitation in the near-infrared to obtain Raman spectra in the absence of undesired photochemistry and resonance enhancement. These investigations provide new information on the arrangement of the conformational energy surface in myoglobin and bacteriorhodopsin, pressure effects on protein dynamics and on the molecular structure of bacteriorhodopsin activation. %%% The dynamics structures which proteins maintain to perform biological functions are distinguished by changes in energy and volume from the unfolded polypeptide chain. Site-selective spectroscopic studies at variable temperature and pressure provide insight into the relative energy scales of molecular interactions in the stabilization of the biologically active molecule. Vibrational marker bands are used to monitor structural changes and motions in myoglobin and bacteriorhodopsin and correlate them with protein function. Since proteins share similarities in the thermodynamic, structural and dynamic properties with many disordered systems such as glasses, new insights from this research will have an impact on models for disorder and complexity in other fields of science. ***
