Search results for "fluidit"

The lipid composition, fluidity, and Mg2+-ATPase activity of rice (Oryza sativa L. cv. Bahia) shoot plasma membranes: effects of ABA and GA3

1992

Six-day-old rice plants (Oryza sativa L., cv Bahia) were grown for 5 days more in nutrient solution culture containing 10−5 M abscisic acid (ABA) or gibberellic acid (GA3) (treated plants). Plasma membrane (PM) vesicles were isolated from the shoots of treated or control plants, and ATPase hydrolytic and proton-pumping activity, fluidity, and free sterol and phospholipid composition were determined. Both treatments resulted in modified plant growth and increases in PM fluidity. The ATPase hydrolytic activity was decreased by 25% of control values with ABA treatment and by 35% with GA3. Both treatments reduced proton-pumping by 23%. GA3 treatment reduced the relative amount (%) of stigmaster…

Inactivation of a small heat shock protein affects cell morphology and membrane fluidity in Lactobacillus plantarum WCFS1.

2011

A small heat shock gene of Lactobacillus plantarum strain WCFS1 was deleted using a Cre-lox based system. Compared to the wild type, the ∆hsp 18.55 mutant strain displayed a similar growth rate when cultivated either under optimal temperature or under different stress conditions such as heat, low pH and salt stress. However, a longer lag phase was observed when the ∆hsp 18.55 mutant strain was cultivated under short intense heat stress (50 °C). This suggests that the hsp 18.55 gene of L. plantarum may be involved in recovery of L. plantarum stressed cells in the early stage of high temperature stress. In addition, morphology of the mutant cells, investigated by scanning electron microscopy,…

Lipid content of Saccharomyces cerevisiae strains with different degrees of ethanol tolerance

1992

We analysed the fatty acid and sterol compositions of various Saccharomyces cerevisiae strains with ethanol tolerance varying from 4% to 12% (v/v) ethanol and at different concentrations of ethanol. The results we obtained agree with the existence of a relationship between membrane fluidity and ethanol tolerance but they do not support a direct role of unsaturated fatty acids in this tolerance. On the other hand, they support the importance of ergosterol in this phenomenon.

Alteration in membrane fluidity and lipid composition, and modulation of H(+)-ATPase activity in Saccharomyces cerevisiae caused by decanoic acid.

1996

Decanoic acid, a lipophilic agent, inhibited in vitro the plasma membrane H+-ATPase of Saccharomyces cerevisiae grown in YPD medium. Conversely, when decanoic acid (35 μM) was present in the growth medium, the measured H+-ATPase activity was four times higher than that of control cells. K m, and pH and orthovanadate sensitivity were the same for the two growth conditions, which indicated that H+-ATPase activation was not due to conformational changes in the enzyme. The activation process was not entirely reversible which showed that plasma membrane H+-ATPase activation is due to several mechanisms. 1,6-diphenyl-1,3,5-hexatriene anisotropy performed on protoplasts from cells grown in YPD rev…

Bimodal Effect of Amphiphilic Biocide Concentrations on Fluidity of Lipid Membranes

1996

Abstract Using the spin label method (ESR) it has been shown that biologically active, amphiphilic compounds (quaternary ammonium salts -AS) containing polar heads with single and double positive charge caused, at low concentrations, decrease fluidity of liposome membranes formed with egg yolk lecithin (EYL). At higher concentrations an increase in fluidity was observed. With compounds having a single positive charge minimum fluidity of membrane structure occurs in the range of 1 to 3%, with compounds containing double positive charge -in the range of 4 -6 % . That effect does not depend on polar head size and length of alkyl chains of the AS used. Analysis of the electrostatic interaction …

Fluidity of liposome membranes doped with organic tin compounds: ESR study.

2008

The kinetics of change in the fluidity of liposome membranes, obtained in the process of sonication of Egg Yolk Lecithin (EYL), with the admixture of organic tin compounds, was investigated. Five compounds were selected for the research: three differed in the length of hydrocarbon chains, (CH(3))(4)Sn, (C(2)H(5))(4)Sn, and (C(3)H(7))(3)SnCl, whereas two differed in the number of aromatic rings, (C(6)H(5))(2)SnCl(2) and (C(6)H(5))(3)SnCl. The concentration of the compounds in proportion to EYL was 2 mol-%. Electron Spin (paramagnetic) Resonance (ESR) was applied using two spin probes TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) and 16-DOXYL-stearic acid methyl ester (2-ethyl-2-(15-methoxy-15…

Self-Assembling of Peptide/Membrane Complexes by Atomistic Molecular Dynamics Simulations

2007

Abstract Model biological membranes consisting of peptide/lipid-bilayer complexes can nowadays be studied by classical molecular dynamics (MD) simulations at atomic detail. In most cases, the simulation starts with an assumed state of a peptide in a preformed bilayer, from which equilibrium configurations are difficult to obtain due to a relatively slow molecular diffusion. As an alternative, we propose an extension of reported work on the self-organization of unordered lipids into bilayers, consisting of including a peptide molecule in the initial random configuration to obtain a membrane-bound peptide simultaneous to the formation of the lipid bilayer. This strategy takes advantage of the…

Incorporation of Membrane Proteins in Solid-Supported Lipid Layers

1995

Distinct amino acids of  the Oenococcus oeni small heat shock protein Lo18 are essential for damaged protein protection and membrane stabilization

2010

The small heat shock protein (smHsp) Lo18 from lactic acid bacteria Oenococcus oeni reduces in vitro thermal aggregation of proteins and modulates the membrane fluidity of native liposomes. An absence of information relating to the way in which the smHsp demonstrates a stabilizing effect for both proteins and membranes prompted this study. We expressed three Lo18 proteins with amino acid substitutions in Escherichia coli to investigate their ability to prevent E. coli protein aggregation and their capacity to stabilize E. coli whole-cell membranes. Our results showed that the alanine 123 to serine substitution induces a decrease in chaperone activity in denaturated proteins, and that the ty…

Solid State NMR Structure Analysis of the Antimicrobial Peptide Gramicidin S in Lipid Membranes: Concentration-Dependent Re-alignment and Self-Assemb…

2008

Antimicrobial peptides can kill bacteria by permeabilizing their cell membrane, as these amphiphilicmolecules interact favourably with lipid bilayers. This mechanism of action is attributed eitherto the formation of a peptide “carpet” on the membrane surface, or to a transmembranepore. However, the structure of such a pore has not yet been resolved under relevant conditions.Gramicidin S is a symmetrical cyclic β-sheet decapeptide, which has been previouslyshown by solid state NMR to lie flat on the membrane surface at low peptide:lipid ratios (≤ 1:80).Using highly sensitive 19F-NMR, supported by 15N-labelling,we found that gramicidin S can flip into an upright transmembrane alignment at hig…