Pressure Dependent Stability Research Articles

Robust Yellow-Violet Pigments Tuned by Site-Selective Manganese Chromophores.

The rational design of multifunctional inorganic pigments relies on the manipulation of ionic valence and local surroundings of a chromophore in structurally and chemically habitable hosts. To date, the development of environmentally benign and intense violet/purple pigments is still a challenge. Here we report a family of A3-xMnxTeO6 and A3-2xMnxLixTeO6 (A = Zn, Mg; x = 0.01-0.15) pigments colored by site-selective Mn2+O4 yellow and Mn3+O5-6 violet chromophores. Zn2.9Mn0.1TeO6 is intense bright yellow, comparable with commercial BiVO4, and has better near-infrared reflectivity (∼89%) in comparison to commercial TiO2. The codoped Li+ "activator" generates holes and charge-balanced Mn3+ (Mn3+O5-6), realizing a color transformation from yellow to the bright violet pigments of A3-2xMnxLixTeO6. The most vivid Mg2.8Mn0.1Li0.1TeO6 is probably the best violet pigment known to date, exhibits excellent chemical and thermodynamic stability, and demonstrates pressure-dependent stability up to 5-7 GPa, before a (reversible) phase transition to pink. Theoretical calculations revealed the correlation between site-preference occupancy and chromophore motifs and predicted a wide color gamut of pigments in Zn3TeO6-hosted 3d transition-metal ions other than manganese.

Pressure-Dependent Stability of Imidazolium-Based Ionic Liquid/DNA Materials Investigated by High-Pressure Infrared Spectroscopy.

1-Butyl-3-methylimidazolium hexafluorophosphate ([C4MIM][PF6])/DNA and 1-methyl-3-propylimidazolium hexafluorophosphate ([C3MIM][PF6])/DNA mixtures were prepared and characterized by high-pressure infrared spectroscopy. Under ambient pressure, the imidazolium C2–H and C4,5–H absorption bands of [C4MIM][PF6]/DNA mixture were red-shifted in comparison with those of pure [C4MIM][PF6]. This indicates that the C2–H and C4,5–H groups may have certain interactions with DNA that assist in the formation of the ionic liquid/DNA association. With the increase of pressure from ambient to 2.5 GPa, the C2–H and C4,5–H absorption bands of pure [C4MIM][PF6] displayed significant blue shifts. On the other hand, the imidazolium C–H absorption bands of [C4MIM][PF6]/DNA showed smaller frequency shift upon compression. This indicates that the associated [C4MIM][PF6]/DNA conformation may be stable under pressures up to 2.5 GPa. Under ambient pressure, the imidazolium C2–H and C4,5–H absorption bands of [C3MIM][PF6]/DNA mixture displayed negligible shifts in frequency compared with those of pure [C3MIM][PF6]. The pressure-dependent spectra of [C3MIM][PF6]/DNA mixture revealed spectral features similar to those of pure [C3MIM][PF6]. Our results indicate that the associated structures of [C4MIM][PF6]/DNA are more stable than those of [C3MIM][PF6]/DNA under high pressures.

First principles investigation of pressure dependent stability, phonon, Debye temperature, physical, mechanical and thermodynamic properties of Rh3Al intermetallic compound

ABSTRACTPressure dependence of stability, phonon, Debye temperature, physical, mechanical and thermodynamic properties of Rh3Al intermetallic compound were investigated by first-principles The calculated cohesive energy (Ec), formation enthalpy (ΔH) show that Rh3Al is a thermodynamically stable compound. Properties related to the phonons of Rh3Al were also obtained. In addition, the transverse sound velocity (νs), longitudinal sound velocity (νl), average sound velocity (νm) and Debye temperature (ΘD) of Rh3Al were calculated by using the VRH method along with pressure range from 0 to 60 GPa. The values of lattice parameters, bulk modulus and its first-order pressure derivative are consistent well with other works. The band structure indicates that Rh3Al compound exhibits a metallic character. Moreover, the total density of states, partial density of states, Mulliken charges and electron density difference have been analysed to explain the physical properties. Based on the stress–strain approach and the Born stability criteria, the mechanical properties were evaluated by elastic constants (Cij), other modulus (B, E, G), (B/G) ratio, Poisson’s ratio (ν), the anisotropic index (A), hardness (H) and compressibility (K) for this intermetallic compound. Finally, the thermodynamic properties, including enthalpy, free energy, entropy and heat capacity are discussed range from 0 to 1000 K.

Exploring the influence of natural cosolvents on the free energy and conformational landscape of filamentous actin and microtubules.

Actin and tubulin, the main components of the cytoskeleton, are responsible for many different cellular functions and can be found in nearly all eukaryotic cells. The formation of filamentous actin (F-actin) as well as microtubules depends strongly on environmental and solution conditions. The self-assembly of both, actin and tubulin, has been found to be among the most pressure sensitive process in vivo. Here, we explored the effects of various types of natural cosolvents, such as urea and the osmolyte trimethylamine-N-oxide (TMAO), on the temperature- and pressure-dependent stability of their polymeric states, F-actin and microtubules. Accumulation of TMAO by deep-sea animals is proposed to protect against destabilizing effects of pressure. The pressure and temperature of unfolding as well as associated enthalpy and volume changes have been determined using Fourier-transform infrared spectroscopy, covering a wide range of pressures and temperatures, ranging from 1 bar to 11 kbar and from 20 to 90 °C, respectively. Complementary thermodynamic measurements have been carried out using differential scanning and pressure perturbation calorimetry. The results obtained helped us explore the effect of the cellular milieu on the limitations of the pressure stability of cytoskeletal assemblies. Conversely to urea, the pressure stability of both polymers increases dramatically in the presence of TMAO, counteracting detrimental effects of both, urea and pressure.

Combined crystal structure prediction and high-pressure crystallization in rational pharmaceutical polymorph screening.

Organic molecules, such as pharmaceuticals, agro-chemicals and pigments, frequently form several crystal polymorphs with different physicochemical properties. Finding polymorphs has long been a purely experimental game of trial-and-error. Here we utilize in silico polymorph screening in combination with rationally planned crystallization experiments to study the polymorphism of the pharmaceutical compound Dalcetrapib, with 10 torsional degrees of freedom one of the most flexible molecules ever studied computationally. The experimental crystal polymorphs are found at the bottom of the calculated lattice energy landscape, and two predicted structures are identified as candidates for a missing, thermodynamically more stable polymorph. Pressure-dependent stability calculations suggested high pressure as a means to bring these polymorphs into existence. Subsequently, one of them could indeed be crystallized in the 0.02 to 0.50 GPa pressure range and was found to be metastable at ambient pressure, effectively derisking the appearance of a more stable polymorph during late-stage development of Dalcetrapib.

Crowding Effects on the Temperature and Pressure Dependent Structure, Stability and Folding Kinetics of STaphylococcal Nuclease

FT-IR spectroscopic, small-angle X-ray scattering (SAXS) and calorimetric measurements have been applied to explore the effect of the macromolecular crowder agent Ficoll on the temperature- and pressure-dependent stability diagram and folding reaction of the monomeric protein Staphylococcal Nuclease (SNase). Additionally, we compare the experimental data with theoretical predictions. Exploring the crowding effect on the pressure-induced unfolding of proteins provides insights in Protein stability and folding under cell-like densely packed conditions. Complementary SAXS measurements were carried out to explore the suitability of the macromolecular crowder agent over a wide range of temperatures and pressures. We found that both temperature- and pressure-induced equilibrium unfolding of SNase is markedly inhibited in 30 wt% Ficoll solutions. The structure of the unfolded state ensemble does not seem to be strongly influenced in the presence of the crowder, however. For comparison, self-crowding effects have been found to become important at SNase concentrations above 10 wt%, only. In contrast to the common notion that macromolecular crowding increases the rate of Protein folding, our kinetic results show that the folding rate of SNase in fact decreases markedly in the presence of Ficoll. These results indicate that besides the commonly encountered excluded volume effect, other factors need to be considered when assessing confinement effects on protein folding kinetics. Among those, crowder-induced viscosity changes seem to be most prominent.

Crowding effects on the temperature and pressure dependent structure, stability and folding kinetics of Staphylococcal Nuclease

FT-IR spectroscopic, small-angle X-ray scattering and calorimetric measurements have been applied to explore the effect of the macromolecular crowder agent Ficoll on the temperature- and pressure-dependent stability diagram and folding reaction of the protein Staphylococcal Nuclease (SNase). Additionally, we compare the experimental data with approximate theoretical predictions. We found that temperature- and pressure-induced equilibrium unfolding of SNase is markedly shifted to higher temperatures and pressures in 30 wt% Ficoll solutions. The structure of the unfolded state ensemble does not seem to be strongly influenced in the presence of the crowder. Self-crowding effects have been found to become important at SNase concentrations above 10 wt% only. Our kinetic results show that the folding rate of SNase decreases markedly in the presence of Ficoll. These results indicate that besides the commonly encountered excluded volume effect, other factors need to be considered when assessing confinement effects on protein folding kinetics. Among those, crowder-induced viscosity changes seem to be prominent.

Pressure dependent stability and structure of carbon dioxide—A density functional study including long-range corrections

First-principles density functional theory (DFT) is used to study the solid-state modifications of carbon dioxide up to pressures of 60 GPa. All known molecular CO2 structures are investigated in this pressure range, as well as three non-molecular modifications. To account for long-range van der Waals interactions, the dispersion corrected DFT method developed by Grimme and co-workers (DFT-D3) is applied. We find that the DFT-D3 method substantially improves the results compared to the uncorrected DFT methods for the molecular carbon dioxide crystals. Enthalpies at 0 K and cohesive energies support only one possibility of the available experimental solutions for the structure of phase IV: the R3c modification, proposed by Datchi and co-workers [Phys. Rev. Lett. 103, 185701 (2009)]. Furthermore, comparing bulk moduli with experimental values, we cannot reproduce the quite large--rather typical for covalent crystal structures--experimental values for the molecular phases II and III.

Pressure-dependent stability of cadmium chloride complexes: Potentiometric measurements at 1–1000 bar and 25°C

Potentiometric measurements were performed in the Cd(NO3)2-KCl-H2O system at 25°C and 1–1000 bar using an isothermal cell with a liquid junction and equipped with a solid contact Cd-selective electrode. At 1 bar, the stepwise equilibrium constant of the fourth cadmium chloride complex CdCl42− has been determined (log K40 = −0.88 ± 0.25). The pressure-dependent stability constants for all cadmium chloride complexes have been experimentally established for the first time. As pressure increases from 1 to 1000 bar, the stability constants for the first, third, and fourth complexes change by less than 0.05 logarithmic units, whereas that for the second complex decreases by 0.33 logarithmic units. On the basis of these data, the partial molar volumes of four cadmium chloride complexes have been determined under standard state conditions: V0(CdCl+) = 2.20 ± 3, V0(CdCl2 (aq)) = 42.21 ± 5, V0(CdCl3−) = 63.47 ± 10, and V0(CdCl42−) = 81.35 ± 15 cm3mol−1. The linear correlation between the nonsolvation contributions of molar volumes and the number of ligands corresponds to the change in coordination from octahedral in Cd2+ and CdCl+ to tetrahedral in CdCl2 (aq), CdCl3−, and CdCl42− complexes. Using theoretical correlations, the HKF parameters allowing calculation of the volumetric properties of cadmium chloride complexes in a wide range of temperature and pressure have been obtained. The pressure effect on cadmium concentration in sphalerite in equilibrium with the H2O-NaCl hydrothermal fluid has been estimated. It is shown that the Cd content in sphalerite increases with pressure.

Pressure-dependent stability of cubic and wurtzite phases within the TiN–AlN and CrN–AlN systems

Ab initio calculations are employed to demonstrate a strong pressure dependence of the maximum AlN mole fraction preserving the cubic phase in Ti1−xAlxN and Cr1−xAlxN hard coatings before transforming to the wurtzite structure. Under a compression of 4 GPa an increase by ∼0.1 AlN mole fraction is obtained for both systems. Consequently, stress-related effects cannot be neglected in the discussion of the wide spread of experimentally obtained stability ranges.

Marasmius scorodonius extracellular dimeric peroxidase — Exploring its temperature and pressure stability

The temperature and pressure dependent stability and function of MsP1, an uncommon peroxidase from the basidiomycetous fungus Marasmius scorodonius were investigated. To this end, a series of biophysical techniques (DSC, fluorescence and FTIR spectroscopy, small-angle X-ray scattering) were combined with enzymatic studies of the enzyme. The dimeric MsP1 turned out to be not only rather thermostable, but also highly resistant to pressure, i.e., up to temperatures of about 65 °C and pressures as high as 8–10 kbar at ambient temperatures. Remarkably, the activity of MsP1 increased by a factor of two until ∼ 500 bar. At about 2 kbar, the enzymatic activity was still as high as under ambient pressure conditions. As revealed by the fluorescence and SAXS data, the increased activity of MsP1 at pressures around 500 bar may result from slight structural changes, which might stabilize the transition state of the enzymatic reaction. Owing to this marked high pressure stability of MsP1, it may represent a valuable tool for industrial high pressure applications.