National Synchrotron Light Source Symposium

Modest pressures encountered in the biosphere (i.e., below a few kbar) have extraordinary effects on biomembranes and proteins. These include pressure denaturation of proteins, as well as dramatic changes in monomer-multimer association, ligand binding, Membrane ion transport, transcription/translation of proteins, virus infectivity, enzyme kinetics and conformational states. Yet all of the biomaterials involved are highly incompressible. The challenge is to understand the structural coupling between these effects and pressure to elucidate the relevant mechanisms. X-ray diffraction studies of lipids and proteins under pressure will be described. It is seen that the key is not the magnitude of the changes, but rather the differential compressibilities of different parts of the structure, leading to a biasing of conformational substates. Examples will be given of pressure studies on biomembranes and myoglobin. Lessons learned have important implications for the freezing of protein crystals, as is routinely done for protein crystallography.