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High-pressure Stability (high-pressure + stability)
Selected AbstractsTHERMAL AND HIGH-PRESSURE STABILITY OF PURIFIED PECTIN METHYLESTERASE FROM PLUMS (PRUNUS DOMESTICA)JOURNAL OF FOOD BIOCHEMISTRY, Issue 2 2006CLÁUDIA S. NUNES ABSTRACT Pectin methylesterase (PME) from greengage plums (Prunus domestica) has been extracted and purified using affinity chromatography. Only one band on sodium dodecyl sulfate,polyacrylamide gel electrophoresis was obtained, with an estimated molecular weight of 31 kDa. On isoelectric focusing electrophoresis, two bands with neutral isoelectric points (6.8 and 7.0) were detected. The optimal pH and temperature for plum PME activity were 7.5 and 65C, respectively. A study of purified plum PME thermostability was performed at pH 7.5 and 4.0, indicating a higher thermostability at pH 7.5 than at pH 4.0. A biphasic inactivation behavior was observed for thermal treatments (54,70C), whereas its pressure inactivation could be described by a first-order kinetic model in a pressure range of 650,800 MPa at 25C. Purified plum PME was found to be relatively stable to thermal and pressure (,600 MPa) treatments, compared to PME from other fruits. [source] Multilayer Amorphous-Si-B-C-N/,-Al2O3/,-Al2O3 Membranes for Hydrogen Purification,,ADVANCED ENGINEERING MATERIALS, Issue 6 2010Ravi Mohan Prasad Abstract The hydrogen and carbon monoxide separation is an important step in the hydrogen production process. If H2 can be selectively removed from the product side during hydrogen production in membrane reactors, then it would be possible to achieve complete CO conversion in a single-step under high temperature conditions. In the present work, the multilayer amorphous-Si-B-C-N/,-Al2O3/,-Al2O3 membranes with gradient porosity have been realized and assessed with respect to the thermal stability, geometry of pore space and H2/CO permeance. The ,-Al2O3 support has a bimodal pore-size distribution of about 0.64 and 0.045 µm being macroporous and the intermediate ,-Al2O3 layer,deposited from boehmite colloidal dispersion,has an average pore-size of 8,nm being mesoporous. The results obtained by the N2 -adsorption method indicate a decrease in the volume of micropores,0.35 vs. 0.75,cm3,g,1,and a smaller pore size ,6.8 vs. 7.4 Å,in membranes with the intermediate mesoporous ,-Al2O3 layer if compared to those without. The three times Si-B-C-N coated multilayer membranes show higher H2/CO permselectivities of about 10.5 and the H2 permeance of about 1.05,×,10,8 mol m,2 s,1 Pa,1. If compared to the state of the art of microporous membranes, the multilayer Si-B-C-N/,-Al2O3/,-Al2O3 membranes are appeared to be interesting candidates for hydrogen separation because of their tunable nature and high-temperature and high-pressure stability. [source] In situ Raman scattering studies of high-pressure stability and transformations in the matrix of a nanostructured glass,ceramic compositeJOURNAL OF RAMAN SPECTROSCOPY, Issue 10 2005Kristina E. Lipinska-Kalita Abstract High-pressure Raman scattering studies have been performed on a glass-based composite consisting of nanometer-sized gallium oxide aggregates embedded in a potassium-silicate host glass using the diamond anvil cell technique. The Raman spectra of this heterophase nanocomposite showed a range of pressure-induced structural transformations occurring in the glass matrix. Compression from ambient pressure up to 10.8 GPa indicated a progressive reduction in the width of the intertetrahedral SiOSi angle distribution, which was completely reversible on decompression to ambient pressure. At higher pressures, the Raman spectra demonstrated a breakdown of the intermediate-range order in the glass matrix of the nanocomposite. The enhancement of scattering intensity in the region of the D-defect band at 565 cm,1 together with the blue shift of the main SiOSi symmetric stretching wavenumber are evidence of a permanent reduction in SiO4 ring statistics toward smaller-than-six-ring configurations in the three-dimensional glass network. Starting from 13 GPa, the Raman spectra displayed a remarkable decrease in the scattering intensity of the SiOSi symmetric stretching that has been related to a coordination change of the silicon atom. The Raman spectrum of the composite quenched from 23 GPa to ambient conditions illustrated the pressure-driven, permanent reconstructive modification of the glass matrix in the nanocomposite. The pressure-induced evolution of the Raman peaks assigned to the gallium oxide phase indicated a progressive densification of the nanocrystalline phase, reversible on decompression to ambient pressure. Copyright © 2005 John Wiley & Sons, Ltd. [source] Temperature,pressure stability of green fluorescent protein: A Fourier transform infrared spectroscopy studyBIOPOLYMERS, Issue 4 2002Carsten H. Scheyhing Abstract Green fluorescent protein (GFP) is widely used as a marker in molecular and cell biology. For its use in high-pressure microbiology experiments, its fluorescence under pressure was recently investigated. Changes in fluorescence with pressure were found. To find out whether these are related to structural changes, we investigated the pressure stability of wild-type GFP (wtGFP) and three of its red shift mutants (AFP, GFPmut1, and GFPmut2) using Fourier transform infrared spectroscopy. For the wt GFP, GFPmut1, and GFPmut2 we found that up to 13,14 kbar the secondary structure remains intact, whereas AFP starts unfolding around 10 kbar. The 3-D structure is held responsible for this high-pressure stability. Previously observed changes in fluorescence at low pressure are rationalized in terms of the pressure-induced elastic effect. Above 6 kbar, loss of fluorescence is due to aggregation. Revisiting the temperature stability of GFP, we found that an intermediate state is populated along the unfolding pathway of wtGFP. At higher temperatures, the unfolding resulted in the formation of aggregates of wtGFP and its mutants. © 2002 Wiley Periodicals, Inc. Biopolymers 65: 244,253, 2002 [source] | ||||||||||