High pressure interferes protein interactions, which can be utilized for regulation of cellular functions. In Escherichia coli, high hydrostatic pressure was observed to fix the flagellar motor rotation to the counter-clockwise direction using high-pressure microscopy. The reversal of the motor rotation is known to be induced by the binding of the chemotaxis signaling protein CheY to the flagellar motor protein FliM. Using parallel cascade selection molecular dynamics (PaCS-MD), we show that high pressure increases the water density in the hydration shell of CheY and considerably induces water penetration into the CheY-FliM interface.

Non-equilibrium molecular dynamics simulations to destroy amyloid fibrils of amyloid-β peptides by ultrasonic wave and infrared laser irradiation are reviewed. The ultrasonic wave was mimicked by time-varying sinusoidal pressure and infrared laser by pulses of oscillating electric field. Atomic-level dynamical behaviors of amyloid-fibril disruption were observed. The similarities and differences in the amyloid fibril disruption by ultrasonic wave and infrared laser are discussed.

The nuclear magnetic resonance (NMR) measurements under high pressure conditions are powerful technique for characterizing protein properties and its conformational changes. Bacterial flagellum is a molecular nano-machine and bacteria move toward favorable condition for survive and growth to rotate flagellar motor, although the molecular mechanism of the motor rotation is still unclear. In this article, we introduce our recently published results that clarified the determination mechanism of the rotational direction by analyzing of FliG, a flagellar rotor protein. Combining the structural analysis of solution NMR and the measurement of high-pressure condition, we revealed that the rearrangement of interaction network in FliG determines the rotational direction.

Shewanella species are widely distributed in aquatic environments including deep-sea conditions. Proteins of deep-sea microorganisms are expected to adapt to the harsh environments, but their underlying mechanisms for the adaptation are still enigmatic because of multifactorial features of the deep-sea environments such as low temperature and high hydrostatic pressure. This review describes a case of the environmental adaptation of Shewanella cytochrome c₅ as a model protein in the aspect of protein stability. Cytochromes c₅ from the deep-sea Shewanella species exhibited higher stability than its homologues from shallow-water areas. Interestingly, the stability of deep-sea cytochromes c₅ is maintained even under the high-pressure conditions. High pressure is known to be a physical factor that affects the stability and functions of protein molecules, and the research using cytochromes c₅ suggests the potential for adaptation against pressure at the molecular levels.

We review our recently published article and related works on pressure denaturation of a protein. The protein structure and its fluctuation are considered at the atomic level and a molecular model is employed for water. The protein intramolecular energy and entropy, hydration free energy (HFE), and a variety of physically insightful constituents of the HFE are calculated using the state-of-the-art methods based on statistical mechanics. By examining the signs and relative magnitudes of the changes in these thermodynamic quantities upon denaturation, we discuss the mechanism of pressure denaturation and structural characteristics of the denatured state.

Effects of ultrasonication to solutions of chemical compounds and polymers have been widely investigated in the field of sonochemistry. Previously, we revealed that ultrasonication to supersaturated protein solutions induces formation of amyloid fibrils, which are protein aggregates causing intractable diseases. We have investigated the mechanism of ultrasonic induction of amyloid fibril formation and attempt to apply this phenomenon to clinical diagnosis by developing ultrasonic instruments. In this article, we review the general effects of ultrasonic cavitation on chemical reactions, summarize the current understanding of the mechanism of ultrasonic induction of amyloid fibril formation, and introduce an example of the clinical application of the originally developed ultrasonic amyloid inducer.

This paper reviews three recently developed multi-anvil techniques. The first technique is the elevation of the pressure limit generated using carbide anvils from 26 GPa to 52 GPa. This increase has been achieved by high-hardness carbide for anvils, tapering of anvil faces around the truncation, high-precision guide blocks, and effective thermal insulation. The second is the expansion of conditions quenching silicate melts to glasses at high pressures, which has been achieved by increasing cooling rate using small furnace volumes, thermally conductive assembly, and external cooling system, which has enabled the synthesis of hydrous ultramafic glasses. The third is a uniform temperature fields with a temperature gradient of less than 10 K/mm, which has been achieved by the zero-temperature gradient furnace consisting of a central cylindrical heater with two heating rods on both ends.

Negative thermal expansion materials were designed by focusing on the phase transition accompanied by volume contraction under high pressure. The coexistence of multiple mechanisms contributes to the improvement of properties, and the domain structure contributes to the phase transition that occurs while changing the phase fraction.

In this article, recent research on novel functional materials using the high-pressure synthesis method is introduced. The target materials are transition metal oxides and natural minerals. This research focuses on the formation of chemical bonds between cations in ilmenite-type vanadates, quantum spin fluctuation in a natural mineral, and colossal negative thermal expansion in perovskite-type vanadates, as well as other properties and functions.