Recent studies examining small RNAs appear to show that some of the observed effects (especially destabilizing effects) might be due to the release of solvent-excluded cavities. However, the degree of stabilization is quite low, mostly because their structure depends more on hydrogen bonds (which are little affected by pressure) than on changes in ionization states and solvent interactions. Unlike proteins, the helical forms of DNA and RNA are stabilized by hydrostatic pressure. (45-47) Most of these studies have addressed the impact of pressure on the stability of double helical nucleic acids. Figure 2Īs compared to proteins, there are fewer studies on the effects of pressure on nucleic acids. (34) In the case of macromolecular assemblages, cavities have been particularly shown to be related to metastability, (35-37) and therefore high pressure has proved to be a key tool for exploring their packing. Electrostriction is particularly important in hetero protein–protein interactions, as has been demonstrated for the interaction of cytochrome b5 with cytochrome c (33) and of myosin light chain calmodulin-binding domain with calcium-saturated calmodulin.
(30-32) The volume change is the net result of the disappearance of protein cavities, the electrostriction of the broken electrostatic interactions, and the reduced volume upon additional hydration. Because of the great number of atoms present in a protein molecule, packing defects cannot be prevented, which leads to the formation of cavities. (30) The packing among the various domains of proteins plays a major role in their stabilization. The predominant contribution of cavities for the volume change was clearly demonstrated in Royer’s experiments using an SNase mutant (Figure 2B–D).
The fundamental chemico-biological principles upon which a plethora of applications in biomedicine and biotechnology rest will be discussed in this Review.Īlmost a century after Bridgman’s publication, the consensus is that pressure affects proteins due to many factors, where in many cases water-excluded cavities can dominate. High pressure has also been used to study viruses and other infectious agents for the purpose of sterilization (e.g., in food processing) and in the development of vaccines as well as being widely utilized for the nonthermal processing of food. The use of high pressure as a research tool promises to further contribute to our ability to identify the mechanisms underlying these defects and develop therapies for these diseases, as in earlier studies on prion proteins, the p53 tumor suppressor protein, and transthyretin. The wide range of diseases that result from protein misfolding has made this an important research focus for pharmaceutical and biotechnology companies. Because partially folded intermediates, leading in some cases to misfolding and the occurrence of protein aggregates, are stabilized by pressure, the application of high pressure permits the characterization of these aggregation reactions. Applying high pressure is also an excellent approach for studying situations in which protein folding occurs incorrectly, such as in the so-called protein folding disorders, which include Alzheimer’s, Parkinson’s, tumoral, and prion diseases.
In vitro studies performed under equilibrium or kinetic conditions involving hydrostatic pressure have provided useful information about protein conformational changes and interactions, including those that depend on the presence of other partners, such as nucleic acids, cofactors, and ions. (7) Equilibrium and kinetic analyses of molecules under high hydrostatic pressure have resulted in great advances, allowing the appraisal of protein folding and misfolding landscapes. In the case of proteins, high-pressure approaches can reveal transient conformations that occur during the unfolding process but are not easily assessed using other methods.