scholarly journals Proteins in Wonderland: The Magical World of Pressure

Biology ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 6
Author(s):  
Kazuyuki Akasaka ◽  
Akihiro Maeno

Admitting the “Native”, “Unfolded” and “Fibril” states as the three basic generic states of proteins in nature, each of which is characterized with its partial molar volume, here we predict that the interconversion among these generic states N, U, F may be performed simply by making a temporal excursion into the so called “the high-pressure regime”, created artificially by putting the system under sufficiently high hydrostatic pressure, where we convert N to U and F to U, and then back to “the low-pressure regime” (the “Anfinsen regime”), where we convert U back to N (U→N). Provided that the solution conditions (temperature, pH, etc.) remain largely the same, the idea provides a general method for choosing N, U, or F of a protein, to a great extent at will, assisted by the proper use of the external perturbation pressure. A successful experiment is demonstrated for the case of hen lysozyme, for which the amyloid fibril state F prepared at 1 bar is turned almost fully back into its original native state N at 1 bar by going through the “the high-pressure regime”. The outstanding simplicity and effectiveness of pressure in controlling the conformational state of a protein are expected to have a wide variety of applications both in basic and applied bioscience in the future.

1979 ◽  
Vol 50 (9) ◽  
pp. 6032-6032
Author(s):  
S. K. Guharay ◽  
S. N. SenGupta ◽  
M. R. Gupta

Author(s):  
Carl B Agee

Hydrous silicate melts appear to have greater compressibility relative to anhydrous melts of the same composition at low pressures (<2 GPa); however, at higher pressures, this difference is greatly reduced and becomes very small at pressures above 5 GPa. This implies that the pressure effect on the partial molar volume of water in silicate melt is highly dependent on pressure regime. Thus, H 2 O can be thought of as the most compressible ‘liquid oxide’ component in silicate melt at low pressure, but at high pressure its compressibility resembles that of other liquid oxide components. A best-fit curve to the data on from various studies allows calculation of hydrous melt compression curves relevant to high-pressure planetary differentiation. From these compression curves, crystal–liquid density crossovers are predicted for the mantles of the Earth and Mars. For the Earth, trapped dense hydrous melts may reside atop the 410 km discontinuity, and, although not required to be hydrous, atop the core–mantle boundary (CMB), in accord with seismic observations of low-velocity zones in these regions. For Mars, a density crossover at the base of the upper mantle is predicted, which would produce a low-velocity zone at a depth of approximately 1200 km. If perovskite is stable at the base of the Martian mantle, then density crossovers or trapped dense hydrous melts are unlikely to reside there, and long-lived, melt-induced, low-velocity regions atop the CMB are not predicted.


1982 ◽  
Vol 46 (340) ◽  
pp. 329-336 ◽  
Author(s):  
Jørgen Gutzon Larsen

AbstractScattered dunite and lherzolite nodules occur in one of the youngest basanitoid lavas on Ubekendt Ejland. They have protogranular to porphyroclastic textures. The dunites are composed of olivine (Fo93.2−91.9b), enstatite (En93.4−92.8) low in Al2O3 and CaO, and Cr-spinel (61-13% Cr2O3 and 3–55% Al2O3). A solitary lherzolite module has olivine (Fo94.7–94.1), enstatite (En94.7–94.2), Cr-rich spinel, Ti-phlogopite (11% TiO2), and hyalophane. Petrographic evidence suggests that the two latter minerals have not been introduced by magmatic injection from the host in spite of the refractory nature of the coexisting phases, and metasomatic processes prior to the last deformation are therefore indicated. Partial melting of such mantle material would presumably produce small amounts of alkaline liquids even at very high temperatures. Another lherzolite nodule from a lamprophyre dyke has minerals with lower Mg/(Mg + Fe) ratios which, together with its preserved igneous textures, suggest a high-pressure precipitate. The lowest well-esablished equilibrium temperatures of 700–830°C for both dunites and lherzolites indicate a pressure regime of 12-17 kbar, according to the oceanic geotherm, whereas unrealistically high pressure (20–5 kbar) are suggested using the continental shield geotherm.


2017 ◽  
Vol 72 (6) ◽  
pp. 433-439
Author(s):  
Samir F. Matar ◽  
Adel F. Al Alam ◽  
Rainer Pöttgen

AbstractThe nitridoborates Mg3[BN2]N (P63/mmc) and Ca3[BN2]N (P4/mmm) are electron-precise compounds with discrete linear [BN2]3− and isolated N3− anions. Electronic structure calculations reveal pronounced B–N bonding within the [BN2]3− units with more covalent Mg–N vs. Ca–N bonding. Total energy calculation for hexagonal normal-pressure Mg3[BN2]N, orthorhombic high-pressure Mg3[BN2]N and a hypothetical Ca3[BN2]N-type tetragonal Mg3[BN2]N modification revealed that the hexagonal modification is the ground state structure. The band structure for orthorhombic high-pressure Mg3[BN2]N indicates a substantial metallization (delocalization in the high-pressure regime). This peculiar result calls for a reinvestigation of high-pressure Mg3[BN2]N under different high-pressure high-temperature conditions along with physical property studies.


2012 ◽  
Vol 40 (10) ◽  
pp. 2736-2740 ◽  
Author(s):  
Amgad E. Mohamed ◽  
Ali E. Abdou ◽  
Mohamed I. Ismail ◽  
S. Lee ◽  
S. H. Saw

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