Temperature-pressure configurational landscape of lipid bilayers and proteins.

High hydrostatic pressure has been used as a physical parameter for studying the stability and energetics of biomolecular systems, such as lipid bilayers and proteins, but also because high pressure is an important feature of certain natural membrane environments. By using a variety of spectroscopic and scattering techniques, the temperature and pressure dependent structure and phase behaviour of various lipid systems and proteins have been studied and are discussed. A thermodynamic approach is presented for studying the stability of proteins as a function of both temperature and pressure. Moreover, the effect of various chaotropic and kosmotropic cosolvents on the temperature- and pressure-dependent structure and stability of proteins is discussed. The results demonstrate that combined temperature-pressure-cosolvent dependent studies can help delineate the free energy landscape of proteins and hence help elucidate which features and thermodynamic parameters are essential in determining the stability of the native conformational state of proteins. We also introduce pressure as a kinetic variable. Applying the pressure-jump relaxation technique in combination with time-resolved synchrotron X-ray diffraction and spectroscopic techniques, the kinetics of un/refolding of lipid mesophases and proteins has been studied. Finally, recent advances in using pressure for studying misfolding and aggregation of proteins will be elucidated.