Search results for "Pressure"

High-performance liquid chromatography of the mycotoxin sterigmatocystin and its application to the analysis of mouldy rice for sterigmatocystin.

1981

Zur kinetik des einstellvorganges im osmometer. II. Theoretische grundlagen

1961

Es werden Gleichungen fur den zeitlichen Verlauf der Osmometereinstellung fur den Fall abgeleitet, das der geloste Stoff wesentlich langsamer als das Losungsmittel (LM) durch die Membran tritt. Der Verlauf ist abhangig von der Einstellkonstante ζ1 und der Durchtrittskonstante ζ2. Diese einzeln durch Experimente bestimmbaren Konstanten hangen von den Permeationskonstanten Z1 und Z2 der Membran fur das Losungsmittel und die geloste Substanz und von den Osmometerdimensionen ab. Bei der Ableitung wird die Nichtidealitat der Losung, der Balloneffekt und die durch die Verschiebung des Losungsmittels bedingte Konzentrationsanderung berucksichtigt. Wenn in beiden Osmometerkammern die Durchmischung …

Vesicle formation in the membrane of onion cells (Allium cepa) during rapid osmotic dehydration

2009

BACKGROUND AND AIMS Optimization of osmotic dehydration in different plant cells has been investigated through the variation of parameters such as the nature of the sugar used, the concentration of osmotic solutions and the processing time. In micro-organisms such as the yeast, Saccharomyces cerevisiae, the exposure of a cell to a slow increase in osmotic pressure preserves cell viability after rehydration, while sudden dehydration involves a lower rate of cell viability, which could be due to membrane vesiculation. The aim of this work is to study cytoplasmic vesicle formation in onion epidermal cells (Allium cepa) as a function of the kinetics of osmotic pressure variation in the external…

Thermodynamics of yeast cell osmoregulation: Passive mechanisms

1996

International audience; The response of yeast cells to osmotic pressure variations of the medium were studied through the kinetics of cell-volume modifications corresponding to the mass transfer of water and solutes. Osmotic variations were made by modification of the concentration of an external binary solution (polyol/water) without nutritive components. Two phases were distinguished in the thermodynamic response. A transient phase following an osmotic shift, which is characterised by rapid water transfer across the cell membrane and whose kinetics determine cell viability; then, a steady-state phase is reached when the cell volume becomes quasi-constant. The response of the cell during t…

Nature of sterols affects plasma membrane behavior and yeast survival during dehydration.

2011

International audience; The plasma membrane (PM) is a main site of injury during osmotic perturbation. Sterols, major lipids of the PM structure in eukaryotes, are thought to play a role in ensuring the stability of the lipid bilayer during physicochemical perturbations. Here, we investigated the relationship between the nature of PM sterols and resistance of the yeast Saccharomyces cerevisiae to hyperosmotic treatment. We compared the responses to osmotic dehydration (viability, sterol quantification, ultrastructure, cell volume, and membrane permeability) in the wild-type (WT) strain and the ergosterol mutant erg6Δ strain. Our main results suggest that the nature of membrane sterols gover…

Insight into the primary mode of action of TiO2 nanoparticles on Escherichia coli in the dark.

2015

16 pages; International audience; Large-scale production and incorporation of titanium dioxide nanoparticles (NP-TiO2 ) in consumer products leads to their potential release into the environment and raises the question of their toxicity. The bactericidal mechanism of NP-TiO2 under UV light is known to involve oxidative stress due to the generation of reactive oxygen species. In the dark, several studies revealed that NP-TiO2 can exert toxicological effects. However, the mode of action of these nanoparticles is still controversial. In the present study, we used a combination of fluorescent probes to show that NP-TiO2 causes Escherichia coli membrane depolarization and loss of integrity, lead…

Gas jet studies towards an optimization of the IGISOL LIST method

2011

Abstract Gas jets emitted from an ion guide have been studied as a function of nozzle type and gas cell-to-background pressure ratio in order to obtain a low divergent, uniform jet over a distance of several cm. The jet has been probed by imaging the light emitted from excited argon or helium gas atoms. For a simple exit hole or converging-diverging nozzle, the jet diameter was found to be insensitive to the nozzle shape and inlet pressure. Sonic jets with a FWHM below 6 mm were achieved with a background pressure larger than 1 mbar in the expansion chamber. The measurements are supported by the detection of radioactive 219 Rn recoils from an alpha recoil source mounted within the gas cell.…

Prediction of flow patterns during silo discharges using a finite element approach and its preliminary experimental verification

2015

Abstract Obtaining a reliable discharge of particulate solids from a storage silo is a prerequisite to securing operational adequacy in solids handling processes. If a silo is poorly designed, an unreliable interrupted discharge often occurs. In this study, an in-house finite element (FE) program was modified to predict the particulate solids flow patterns during discharges from silos, and the effect of a double-cone insert on such flow patterns. In FE modeling, a Eulerian approach was adopted with an assumption of steady-state flow—a state that greatly facilitated investigations on the effects of double-cone inserts on the flow of particulate solids. Predictions were carried out on whether…

A Newly-Detected Reductase fromRauvolfiaCloses a Gap in the Biosynthesis of the Antiarrhythmic Alkaloid Ajmaline

2002

A new enzyme, 1,2-dihydrovomilenine reductase (E.C. 1.3.1), has been detected in Rauvolfia cell suspension cultures. The enzyme specifically converts 2beta( R)-1,2-dihydrovomilenine through an NADPH-dependent reaction into 17-O-acetylnorajmaline, a close biosynthetic precursor of the antiarrhythmic alkaloid ajmaline from Rauvolfia. A five-step purification procedure using SOURCE 30Q chromatography, hydroxyapatite chromatography, 2',5'-ADP Sepharose 4B affinity chromatography and ion exchange chromatography on DEAE Sepharose and Mono Q delivered an approximately 200-fold enriched enzyme in a yield of approximately 6%. SDS-PAGE showed an M r for the enzyme of approximately 48 kDa. Optimum pH …

Nutraceutical Value of Pantelleria Capers (Capparis spinosa L.)

2019

Abstract: Unopened flower buds of Capparis spinosa L. (capers), generally used in the Mediterranean area as food flavoring, are known to be a good source of bioactive compounds. The aim of this work was to evaluate the nutraceutical value of salt-fermented capers collected from different areas of Pantelleria Island (Italy), testing their methylglyoxal and glyoxal trapping capacity and antioxidant activity by 2,2-diphenyl-1-picryl hydrazyl (DPPH), [2,2-azinobis(3-ethylben- zothiazoline-6-sulfonic acid)] diammonium salt (ABTS), and oxygen radical absorbance capacity (ORAC) assays. Hydrophilic extracts were also characterized by high-performance liquid chromatography–electrospray ionization/ma…