Biomolecules under Pressure: Phase Diagrams, Volume Changes, and High Pressure Spectroscopic Techniques

Abstract

Pressure is an equally important thermodynamical parameter as temperature. However, its importance is often overlooked in the biophysical and biochemical investigations of biomolecules and biological systems. This review focuses on the application of high pressure (>100 MPa = 1 kbar) in biology. Studies of high pressure can give insight into the volumetric aspects of various biological systems; this information cannot be obtained otherwise. High-pressure treatment is a potentially useful alternative method to heat-treatment in food science. Elevated pressure (up to 120 MPa) is present in the deep sea, which is a considerable part of the biosphere. From a basic scientific point of view, the application of the gamut of modern spectroscopic techniques provides information about the conformational changes of biomolecules, fluctuations, and flexibility. This paper reviews first the thermodynamic aspects of pressure science, the important parameters affecting the volume of a molecule. The technical aspects of high pressure production are briefly mentioned, and the most common high-pressure-compatible spectroscopic techniques are also discussed. The last part of this paper deals with the main biomolecules, lipids, proteins, and nucleic acids: how they are affected by pressure and what information can be gained about them using pressure. I I also briefly mention a few supramolecular structures such as viruses and bacteria. Finally, a subjective view of the most promising directions of high pressure bioscience is outlined.

Pressure Tuning Studies of Four-Stranded Nucleic Acid Structures

“…Liu et al studied the same c-MYC sequence [ 64 ]. They predicted an elliptic phase boundary for their c-MYC variant, similar to that which was found in the case of several proteins [ 33 , 35 , 72 ]. The elliptic boundary was calculated from the thermodynamic parameters obtained at an atmospheric pressure or within a relatively low (≤160 MPa) pressure range.…”

“…The first has expensive diamond windows, which limit the sample size to a few times ten nanoliter, while the latter usually has sapphire windows, which can only withstand a few hundred MPa. These methods are described in detail in several reviews [ 33 ].…”

“…Although the pressure is an equivalently as important thermodynamic parameter as the temperature, its use is considerably hindered by technical difficulties. For biomolecules, the relevant pressure range is 0–1 GPa, which is 10,000 times higher than the atmospheric pressure and can be reached only by special experimental techniques [ 33 , 34 ]. The reason to perform pressure studies in spite of these difficulties is that the specific molecular information cannot be obtained by other techniques [ 35 , 36 , 37 ].…”

Hysteretic Pressure Dependence of Ca2+ Binding in LH1 Bacterial Membrane Chromoproteins

“…Indicated by empty blue and red rings in Figure B are peak positions of the spectra measured in the course of the pressure release (decompression). The perturbations of proteins induced by hydrostatic compression quite commonly are considered reversible, i.e., the recovery of the protein upon removal of the perturbation involves similar states but in opposite order. ,,, This expectation is here fulfilled only at the low-pressure region below about 3 kbar, where the native sample spectra indeed appear fully recoverable (data not shown). However, after passing the intermediate pressure range, the paths defined by successive B960 band positions along compression (colored balls) and decompression (colored empty rings) of the sample qualitatively deviate from each other below about 4 kbar.…”

“…The volume reduction may be dominated by elimination of the protein packing defects, cavity hydration, the protein structure relaxation, , or combinations of these mechanisms. Although the denaturing effects of pressure on globular proteins are widely recognized (see refs − for reviews), the knowledge about the denaturation of membrane proteins following the high-pressure perturbation is rather limited. ,− The membrane proteins are of course more difficult to handle. However, the most serious obstacle which until very recently restricted profound discussions of denaturation/renaturation processes in membrane proteins was the scarcity of their high-resolution structures.…”