Pressure effects on weak interactions in biological systems

To understand the principles of pressure effects on biochemical processes, it is helpful to consider the effects of changing volume at molecular levels. Non-covalent interactions constitute the main target for the modulation of biomolecular characteristics through pressure, mainly because they stabilize nearly all the biochemical compounds. On the other hand, the two parameters pressure and temperature must be considered in close relationship since their effects on equilibrium or kinetics-where the role of weak interactions is predominant-are antagonistic in molecular terms. An interpretation of reaction and activation volumes is usually given in terms of intrinsic and solvent contributions. Most covalent bonds participating in the protein primary structure are pressure insensitive, at least up to 1000-1500 MPa. Thus, in the absence of covalent bond formation or breaking, the largest contributions are expected to arise from hydration changes that accompany non-covalent interactions. These structural aspects will be discussed through significant model systems and biochemical examples.