Influence of membrane lipid composition on the activity of functionally reconstituted LmrA under high hydrostatic pressure

In cellular membranes, proteins and lipids are in sensitive macromolecular interaction influencing each other. To evaluate this interaction, the multi-drug transporter LmrA from Lactococcus lactis was functionally reconstituted in vesicles consisting of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), DMPC+10 mol% cholesterol and the model raft mixture DOPC/1,2-dipalmitoyl-sn-glycero-3-phosphocholine/cholesterol (1:2:1) and in natural membrane lipids at 30 °C. The lateral structure and organization of these proteoliposomes were modulated using high hydrostatic pressure. A sharp pressure-induced fluid-to-gel phase transition is observed without an extended two-phase region. The possibility for lipid sorting, such as for DMPC/cholesterol bilayers, has an inhibitory effect on the LmrA activity. A fluid-like membrane phase over the whole pressure range with suitable hydrophobic matching, such as for DOPC, prevents the membrane protein from high-pressure inactivation up to 200 MPa. Under high-pressure conditions, highest LmrA activities, exceeding those at ambient pressure, are achieved for heterogeneous lipid matrices with a small hydrophobic mismatch and the ability of lipid sorting.     

Effect of hydrostatic pressure on the phase transition of ferroelectric PbTiO3

The effect of hydrostatic pressure on the dielectric constant of the Nb-doped lead titanate ceramics was measured up to 60 kbar at room temperature. From the previously observed pressure dependence of lattice parameters and the present results, it is concluded that the tetragonality decreases linearly with a slope of ?7.6×10^?4/kbar and that the pressure dependence of the tetragonal-cubic transition temperature is ?8.4K/kbar.     

Phase transformations in equiatomic alloy TiZr at pressure up to 70 kbar

The effect of pressure on the α ? β and ω ? β transformations in the equiatomic alloy TiZr is studied by the differential thermal analysis (DTA) and calorimetric technique. The α-β equilibrium at atmospheric pressure occurs at a temperature of 579°C, and the heat of transition ΔH is 40.9±2.0 J/g. As the pressure increases up to 28 kbar, the temperature of the α-β equilibrium linearly decreases, dT/dP=?2.2±0.3 K/kbar. In the pressure range 28–48 kbar, the β-phase undergoes a transition to the two-phase (α + ω) state upon cooling to room temperature. At pressures above the triple point with the coordinates P=49±3 kbar and T=460±30°C, the cooling of the β-phase gives rise to only the hexagonal ω-phase with the unit cell parameters a=4.843 Å, c=2.988 Å, and c/a=0.617 under normal conditions. The slope of the ω-β equilibrium boundary is positive at pressures up to 70 kbar, dT/dP≈0.46 K/kbar. The ω → α transformation at atmospheric pressure proceeds in the temperature range T=425–470°C with the enthalpy of transition ΔH=2.8 J/g.     

Effect of high hydrostatic pressure processing and squeezing pressure on some quality properties of pomegranate juice against thermal treatment

The aim of this study was to investigate the effect of high hydrostatic pressure (HHP) treatment (200, 300, 400?MPa; 5°C, 15°C and 25°C; 5 and 10 min) on some quality properties of pomegranate juice. Juice samples are obtained under industrial conditions at two different squeezing pressure levels (100 and 150?psi – 0.689 and 1.033?MPa, respectively). Results are compared against conventional thermal treatment (85°C/10 min) and raw sample. For all three processing temperature, HHP combinations at 400?MPa for 10 min were sufficient to decrease the microbial load around 4.0 log cycles for both squeeze levels. All HHP treatments showed no significant decrease at antioxidant activity, total phenolic content and monomeric anthocyanin pigment concentrations, while there was a significant decrease (p?≤?.05) in thermal-treated samples. Being the highest sugar alcohol in pomegranate juice, mannitol content must be considered for determining the authenticity, and mannitol content increased with squeezing pressure and thermal treatment.     

Structural transition of the human lymphocyte plasma membrane: an ESR approach

Summary The electron spin resonance spectroscopy and the spin label technique have been used to study the thermotropic structural transition of the plasma membrane ofin toto human peripheral blood lymphocytes in the temperature range (25÷41)°C. A discontinuity in the plot probe order parametervs. temperature, at a temperature of about 31°C, is observed. This discontinuity is upward shifted to a temperature of 35°C in the presence of staphylococcal enterotoxinB and is no longer observed when using isolated plasma membrane. These results are interpreted as being due to a change in the structural properties of the lipid phase of plasma membrane during the activation of the lymphocyte cells.     

流体静压力下快离子导体Rb4Cu16I7Cl13离子电导的研究

在流体静压力为0.5—11.6kbar,温度-80—80℃范围内,测量了Rb₄Cu₁₆I₇Cl₁₃多晶粉末“松散”样品和“致密”样品的离子电导。“松散”样品电导与压力的关系表明,在4.0—5.0kbar附近,电导存在极大值;“致密”样品电导随压力单调下降。在一定压力下,“致密”样品电导率随温度变化的趋势与常压结果相同,压力对Rb₄Cu₁₆I₇Cl_关键词：     

Investigation of the alterations induced in erythrocyte membrane physical characteristics of non-insulin-dependent type II diabetic Patients: an ESR study

The physical and dynamic properties of intact erythrocyte membranes of two groups, diabetic patients treated by diet alone (27 women and 41 men, 40–75 years old) and healthy subjects (controls) (25 women and 35 men, 35–75 years old) were investigated by electron spin resonance (ESR) spectroscopy. 5-doxyl stearic acid (5-DSA) and 4-maleimido-2,2,6,6-tetramethyl-piperidine-1-oxyl (MAL-6) are employed as spin labels throughout the experiments. While 5-DSA monitors the membrane surface region and gives information about the order of lipids in this region through the order parametersS′, MAL-6 binds thiol groups S-H to the membrane protein and gives information about possible protein conformational changes. Order parameters were calculated from room temperature spectra recorded for intact erythrocytes labeled with 5-DSA and the values of 0.682±0.004 and 0.666±0.004 were obtained for diabetic patients and controls, respectively. Variations of theh ₍₋₁₎,h ₍₀₎,h ₍₊₁₎ and 2A ₁₁ parameters in the temperature range of 10–50 °C were also studied and fairly different behaviors were observed for both groups, especially for theh ₍₋₁₎ parameter. Line intensitiesW andS characterizing the concentrations of weakly and strongly immobilized MAL-6 species bound to S-H groups of intact erythrocyte membrane proteins were used to calculate theW/S ratios. They were found to be 34.1±1.9 and 30.5±2.4 for diabetic patients and controls, respectively. While line intensitiesT, those of theM ₁=−1 high-field resonance line associated with the weakly immobilized S-H sites, of both groups exhibit a very similar microwave saturation behavior in the range of 0.5–20 mW, line intensitiesW of both groups saturated differently. Variations of line intensitiesS, W andT with temperature were also investigated in the temperature range of 10–50 °C and characteristic differences were observed to exist between two groups implying a less fluid erythrocyte membrane for diabetic patients. Increases in the order parameterS′ and in theW/S ratio are considered as major factors attributable to the alteration in the physical and dynamic properties of erythrocyte membrane in the diabetic state.     

High pressure effect on the electrical properties of NiS2

A semiconductor-metal transition in the electrical resistance of NiS₂, which has been suggested to be a Mott transition, is observed with decreasing temperature under pressure up to 44 kbar. The transition temperature increases with pressure with a slope of $\text{dT}\text{dP}\text{= 6 ± 1 K/kbar}$. The activation energy in a semiconducting region is found to decrease with increasing pressure and to vanish at about 46 kbar. The critical pressure and temperature are predicted to be 46 ± 2 kbar and 350 ± 20 K.     

几种含羟基化合物对红细胞膜流动性的影响

利用氮氧自由基自旋标记物 CAT-16 和 5-DSA 较为详尽地探讨了两类含羟基化合物 - 羟胺衍生物与苯酚取代物对红细胞膜流动性变化的影响. 实验结果表明：当非双亲性的小分子苯酚取代物插入红细胞膜内,膜的整体有序性降低和流动性增加;羟胺衍生物可作为促氧化剂诱导产生过氧化自由基,促使膜内磷脂间发生化学偶联,从而降低生物膜的内部流动性. 在红细胞膜的表面,标记物分子运动基本不受偶联影响,综合效应来自小分子插入导致的膜流动性增加.     

Equation of state of sodium chloride up to 32 kbar and 500°C2

The length change of a 25mm long single crystal of NaCl has been determined as a function of hydrostatic pressure up to 32 kbar and temperatures up to 500°C using an electrical contact piezometer with tungsten carbide as a standard. The measurements were carried out in an end loaded piston cylinder apparatus. The length change of the tungsten carbide standard is small compared to that of NaCl and therefore reliable data are obtained. Compression data by Bridgman[1] and thermal expansion data by Kennametal Inc. were used for the equation of state of tungsten carbide. We estimated an absolute uncertainty in the length change measurement of NaCl of ±0.7%. The temperature was accurate within 0.3°C. The uncertainty in pressure is ±0.4%. The results are compared with Decker's [2] equation of state which is frequently used when NaCl is taken as a standard in high pressure work. At room temperature we find a smaller compression of NaCl than Decker and find excellent agreement with Bridgman's[3] data. At higher temperatures we find very good agreement between our data and Decker's equation of state.     

Conversion of ortho-para H2O isomers in water and a jump in erythrocyte fluidity through a microcapillary at a temperature of 36.6±0.3°C

A mechanism is proposed for the previously observed [1] jump in erythrocyte fluidity through a microcapillary 1.3 μm in diameter at a temperature of 36.6±0.3°C. Our interpretation is based on the experimental evidence both for existence of ortho and para H₂O isomers in water and on spin-selective interaction of proteins with para H₂O isomers as hydration shells of biomolecules are being formed [2]. It is important that the formation of hydration shells of proteins and DNA in aqueous solutions is accompanied by an increase in the Brillouin shift to 0.4 cm⁻1 (≃0.25 cm⁻¹ in water), which points to the formation of icelike structures. We believe that the coincidence of the translational energy kT of the Brownian motion and the energy of the rotational quanta for the 3₁₃–2₀₂ transition of para H₂O isomers at the temperature 36.6°C increases the probability for excitation of para H₂O isomers in collisions. Collisions mix quantum states of closely spaced levels in para H₂O (3₁₃, 285.2 cm⁻¹) and ortho H₂O (3₃₀, 285.4 cm⁻¹) and induce conversion of para isomers to ortho H₂O. It is assumed that this conversion in the icelike hydration shell of hemoglobin (Hb) is accelerated under the catalyzing effect of oxygen and iron present in Hb and triggers a chain reaction: release of ortho H₂O isomers through the erythrocyte membrane→compaction of Hb molecules and increase in concentration of catalysts→acceleration of conversion→structural gel-sol transition. It is the sequence of these processes that provides a jump in fluidity of erythrocytes through a microcapillary and the anomalous increase in fluidity of the aqueous solution of hemoglobin by almost an order of magnitude at temperatures close to 36.6°C and an increase in the solution concentration by a factor of 1.7.     

Pressure dependence of the superconducting transition temperature of a (Mo0.6Ru0.4)86B14 metallic glass

We have studied the pressure dependence of the superconducting transition temperature of amorphous (Mo_0.6Ru_0.4)₈₆B₁₄ for hydrostatic pressures up to P ～ 9 kbar. The transition temperature T_c decreases with pressure at a rate dT_c/dP=-(9±1) mK kbar^-1. We estimate the Grüneisen parameter and the volume dependence of the electron-phonon coupling constant.     

Interactive effect of pressure and temperature on the preservation of rat primary-cultured astrocytes and human glioblastoma cell line A172

Environmental factors such as temperature and pressure are important determinants of cell survival. Although the effect of temperature on cell preservation has been previously reported, the effects of pressure, an equally important thermodynamic parameter, have not been sufficiently investigated. In this study, we investigated the effect of temperature and pressure on cellular viability, morphology, adhesiveness, cell death, cell cycle and glucose metabolism in rat primary-cultured astrocytes and A172 human glioblastoma cell line subjected to 4-day preservation. It was revealed that under favorable preservation conditions (temperature: 15°C–20°C, pressure: 0.1–30?MPa) (1) cell morphology and adhesiveness of preserved cells were maintained similar to freshly isolated cells; (2) cell cycle was arrested; (3) glucose uptake and intra/extra-cellular pH decrease were suppressed. These results suggest that lowering temperature to 15°C–20°C or increasing pressure up to 30?MPa at temperatures of 20°C–25°C can reduce cellular metabolism and maintain cell-membrane fluidity, thus resulting in higher viability.     

Regenerated gratings in air-hole microstructured fibers for high-temperature pressure sensing

We present thermally regenerated fiber Bragg gratings in air-hole microstructured fibers for high-temperature, hydrostatic pressure measurements. High-temperature stable gratings were regenerated during an 800 °C annealing process from hydrogen-loaded Type I seed gratings. The wavelength shifts and separation of grating peaks were studied as functions of external hydrostatic pressure from 15 to 2400 psi, and temperature from 24 °C to 800 °C. This Letter demonstrates a multiplexible pressure and temperature sensor technology for high-temperature environments using a single optical fiber feedthrough.     

Effects of hydrostatic pressure and temperature on catalytic activity of Horse Liver Alcohol Dehydrogenase (HLADH)

Abstract

We have studied the effects of hydrostatic pressure and/or temperature on the catalytic activity of Horse Liver Alcohol Dehydrogenase (HLADH). The Vmax, Km and thermo-dynamical activation volume were determined versus pressure in the range of 0.1 to 225 MPa at ambient temperature (29°C) and at the optimal temperature of HLADH (53°C).     

等静压下0.75Pb（Mg1/3Nb2/3）O3-0.25PbTiO3陶瓷的介电性能研究

研究了等静压对0.75Pb（Mg_1/3Nb_2/3）O₃-0.25PbTiO₃（PMN-25PT）陶瓷介电温谱的影响,PMN-25PT剩余极化随等静压变化和等静压压致相变.结果表明,随着压力增加,PMN-25PT的介电峰值温度T_m降低,/+{dT_m}/-{dP}≈-4℃/kbar,极化弛豫增强;剩余极化随压力增加连续减小;介电常数对压力的依赖关系与对温度场的依赖相似,压力诱导PMN-25PT发生弛豫铁电—顺电相变,相变为宽化的渐变过程,频率色散和极化弛豫更加强烈和普遍. 关键词： 铌镁酸铅-钛酸铅 等静压 介电弛豫 压致相变     

Pressure dependence of dielectric properties of the LiNaGe4O9 ferroelectric

Dielectric properties of lithium–sodium–tetragermanate (LNG) LiNaGe₄O₉ crystal were investigated under hydrostatic pressure. The phase diagram and phase transition temperature as a function of pressure was constructed. Up to 200 MPa the dependence of T_C on pressure is linear with negative slope of 8.5 K/GPa. The influence of pressure on the Curie–Weiss law was observed. It was also shown that with increasing pressure the maximum value of the electric permittivity and Curie–Weiss constant are decreasing. The obtained results revealed complex mechanism of phase transition in the ferroelectric LNG.     

Dielectric Properties of Fine-Grained BaTiO3 Ceramics under High Pressure

We investigate the temperature dependence of the dielectric constant of BaTiO3 ceramic with coarse to nanograin size under different hydrostatic high pressures up to 5000 bar in the range between room temperature and 200℃. The ferroelectric-to-paraelectric phase transition temperatures Tc are determined from the peak of dielectric constant versus temperature. The values of average grain-size are estimated from the SEM images. It is found that the magnitude of dTc/dp varies considerably from sample to sample depending on grain size. The Curie point Tc of the sample with small grain size decreases more sharply than that of samples with larger one.     

Differential thermal analysis at high pressures—VII: Phase behaviour of solid methanol up to 3kbar

The phase behaviour of solid methanol was investigated from -196°C to the melting temperature and up to 3 kbar, using a low-temperature high-pressure dta apparatus. The melting temperature rises from -98°C at 1 atm to -64°C at 2775 bar. Solid methanol exhibits a transition at atmospheric pressure at approximately -115°C; the transition has a strong tendency to superheat and to occur at -110°C. The transition temperature rises from approximately -115°C at 1 atm to -81°C at 2725 bar. Small impurities of water induce a “second transition” at -117.3°C that must be attributed to the water-methanol eutectic. Volume changes accompanying the phase transition have been calculated using the Clausius Clapeyron equation.     

Moderate hydrostatic pressure–temperature combinations for inactivation of Bacillus subtilis spores

We report the effect of using moderate hydrostatic pressure, 40–140?MPa, at moderate temperature (38–58°C) to inactivate Bacillus subtilis spores in McIlvaine's citric phosphate buffer at pH 6. We have investigated several parameters: pressure applied, holding time, pressure cycling, and temperature. The kinetics of spore inactivation is reported. The results show that spore inactivation is exponentially proportional to the time the sample is exposed to pressure. Spore germination and inactivation occur at the hydrostatic pressures/temperature combinations we explored. Cycling the pressure while keeping the total time at high pressure constant does not significantly increase spore inactivation. We show that temperature increases spore inactivation at two different rates; a slow rate below 33°C, and at a more rapid rate at higher temperatures. Increasing pressure leads to an increase in spore inactivation below 95?MPa; however, further increases in pressure give a similar rate kill. The time dependence of the effect of pressure is consistent with the first-order model (R²?>?0.9). The thermal resistance values (Z_T) of B. subtilis spores are 30°C, 37°C, and 40°C at 60, 80, 100?MPa. The increase in Z_T value at higher pressures indicates lower temperature sensitivity. The pressure resistance values (Z_P) are 125, 125 and 143?MPa at 38°C, 48°C, and 58°C. These Z_P values are lower than those reported for B. subtilis spores in the literature, which indicates higher sensitivity at pressures less than about 140?MPa. We show that at temperatures <60°C, B. subtilis spores are inactivated at pressures below 100?MPa. This finding could have implications for the design of the sterilization equipment.