Life is dynamic and this dynamism is intimately related to the dynamism of protein molecules themselves. The dynamism depends on weak chemical bonding or interatomic potentials, which fluctuate under physiological conditions. By using high pressure NMR spectroscopy, one can explore these fluctuations in atomic details under closely physiological conditions. This paper discusses the manner how high pressure NMR experiments can detect such fluctuations, while conventional NMR spectroscopy fails. The unique nature of the pressure perturbation, as opposed to temperature, is emphasized, which enables exploration, with least perturbation, the subtle nature of such fluctuations, which produce the low-populated, high-energy sub-states of proteins essential for function.
The structure, stability, and function of dihydrofolate reductase from a deep-sea bacterium, Moritella profunda, are compared with those from Escherichia coli to briefly demonstrate the thermodynamic principles of hydrostatic pressure, which affects the structural stability and function of proteins in solution. The results clearly indicate the importance of hydration on the molecular adaptation of proteins to extreme environments such as high or low temperatures, acidic or alkaline solutions, high salinity, and high hydrostatic pressure.
In this article, we reviewed recent high pressure studies on the helix-coil transition of various types of model peptides. All results showed the pressure-induced stabilization or refolding, which are apparently opposite to the case of pressure denaturation of proteins. We proposed a thermodynamic model explaining these apparent opposing results. In the end, we noted that unfolding/folding of secondary structure of model peptides are suitable model systems for exploring molecular mechanism of the pressure denaturation which cannot be explained by cavity model.
Bilayer-membrane properties of the most frequently used lipid in membrane studies, dipalmitoylphosphatidylcholine (DPPC), are described. And then, barotropic bilayer phase behavior of various kinds of phospholipids with a different molecular structure from DPPC is explained in comparison with that of the DPPC bilayer. A slight difference in the molecular structure has a marked influence on the membrane state of the bilayer. Systematic pressure study using the DPPC bilayer enables us to understand the role and meaning of various phospholipids existing in biological membranes.
Starch gelatinizes when sufficiently heated in the presence of sufficient amount of water. Upon gelatinization, starch crystallinity is lost with the granules swollen. Depending on the botanical origin of starch, requirements for heat gelatinization may differ. Starch gelatinization can also be induced by high hydrostatic pressure. Requirements for pressure gelatinization may also differ depending on botanical origin of starch, pressure, water, and temperature. Characteristics of pressure gelatinization will be briefly reviewed as compared with heat gelatinization.
High hydrostatic pressure and low temperature characterize the majority of oceanic environments in terms of the volume occupied. Deep-sea organisms have adapted to survive under such extreme conditions. High pressure and low temperature exert profound physiological impacts on biological membranes, primarily resulting in tighter packing and restricting the rotational motion of acyl chains. The maintenance of appropriate membrane fluidity is crucial for life under low-temperature and high-pressure conditions. Of the spectroscopic techniques available to study membrane properties, fluorescence anisotropy measurement is a common useful method providing information on dynamic membrane properties. Recently we developed a new system that enabled fluorescence anisotropy measurement under high pressure. Using this system, we elucidated the dynamic properties of the membrane in a deep-sea bacterium o23Shewanella violaceao20 under high pressure.
This article reviews the progress of research on the dying mechanism of yeast cells by hydrostatic pressure. The reason that yeast dies under lethal condition is related to many complex features such as destruction of the cellular structures and degeneration of the damaged functions. In order to understand the dying mechanisms under high pressure, we have to focus on not only the damages by pressure but also the repairing mechanisms. The later must be more important than the former.
Yeast strains isolated from different Kimchi products were indicated to belong to Kazachstania (Saccharomyces) servazzii by their rRNA gene sequences. One isolate, the strain MK1 was used to obtain the hydrostatic-pressure sensitive mutant, MK1-HPS, by repeating three cycles of 100-MPa hydrostatic-pressure treatment for 10 min and selection of colonies appeared in a delayed fashion after treatment. MK1-HPS was significantly sensitive to hydrostatic-pressure treatment, and it formed no colonies and did not produce gas in an airtight-sealed culture after 200-MPa hydrostatic-pressure treatment for 60 min. MK1-HPS exhibited the similar fermentation activity as MK1. Production of Kimuchi using MK1-HPS is expected to suppress gas formation during storage after high-pressure treatment.