scholarly journals Intrinsic lipid curvatures of mammalian plasma membrane outer leaflet lipids and ceramides

2021 ◽  
Author(s):  
Michael Kaltenegger ◽  
Johannes Kremser ◽  
Moritz P. K. Frewein ◽  
Douwe J. Bonthuis ◽  
Primoz Ziherl ◽  
...  
Keyword(s):  
Saturated Hydrocarbon ◽  
Acyl Chain ◽  
Molecular Shape ◽  
Intrinsic Curvature ◽  
Membrane Function ◽  
Outer Leaflet ◽  
Hydrocarbon Chains ◽  
Unsaturated Acyl ◽  
Dynamics Simulations ◽  
Chain Lengths

We developed a global X-ray data analysis method to determine the intrinsic curvatures of lipids hosted in inverted hexagonal phases. In particular, we combined compositional modelling with molecular shape-based arguments to account for non-linear mixing effects of guest-in-host lipids on intrinsic curvature. The technique was verified by all-atom molecular dynamics simulations and applied to sphingomyelin and a series of phosphatidylcholines and ceramides with differing composition of the hydrocarbon chains. We report positive lipid curvatures for sphingomyelin and all phosphatidylcholines with disaturated and monounsaturated hydrocarbons. Substitution of the second saturated hydrocarbon with an unsaturated acyl chain in turn shifted the intrinsic lipid curvatures to negative values. All ceramides, with chain lengths varying between C2:0 and C24:0, displayed significant negative lipid curvature values. Moreover, we report non-additive mixing for C2:0 ceramide and sphingomyelin. Our findings manifest the high and manifold potential of lipids to modulate physiological membrane function.

scholarly journals The Optimal Lipid Chain Length of a Membrane-Permeabilizing Lipopeptide Results From the Balance of Membrane Partitioning and Local Damage

2021 ◽  
Vol 12 ◽  
Author(s):  
Jessica Steigenberger ◽  
Yentl Verleysen ◽  
Niels Geudens ◽  
José C. Martins ◽  
Heiko Heerklotz
Keyword(s):  
Chain Length ◽  
Acyl Chain ◽  
Local Perturbation ◽  
Spontaneous Curvature ◽  
Modes Of Action ◽  
Outer Leaflet ◽  
Membrane Partitioning ◽  
Lipid Chain ◽  
Calcein Release ◽  
Chain Lengths

Pseudodesmin A (PSD) is a cyclic lipodepsipeptide produced by Pseudomonas that kills certain bacteria at MIC1/2 in the single micromolar range, probably by permeabilizing their cellular membranes. Synthetic PSD variants, where the native decanoic (C10) acyl chain is varied in length from C4 to C8 and C12 to C14 carbons, were described to be not or less active against a panel of gram-positive strains, as compared to native PSD-C10. Here, we test the membrane-permeabilizing activity of PSD-C4 through PSD-C14 in terms of calcein release from liposomes, which is characterized in detail by the fluorescence-lifetime based leakage assay. Antagonistic concentrations and their chain length dependence agree well for liposome leakage and antimicrobial activity. The optimal chain length is governed by a balance between membrane partitioning (favoring longer chains) and the local perturbation or “damage” inflicted by a membrane-bound molecule (weakening for longer chains). Local perturbation, in turn, may involve at least two modes of action. Asymmetry stress between outer and inner leaflet builds up as the lipopeptides enter the outer leaflet and when it reaches a system-specific stability threshold, it causes a transient membrane failure that allows for the flip of some molecules from the outer to the inner leaflet. This cracking-in may be accompanied by transient, incomplete leakage from the aqueous cores of the liposomes observed, typically, for some seconds or less. The mismatch of the lipopeptide with the lipid leaflet geometry, expressed for example in terms of a spontaneous curvature, has two effects. First, it affects the threshold for transient leakage as described. Second, it controls the rate of equilibrium leakage proceeding as the lipopeptide has reached sufficient local concentrations in both leaflets to form quasi-toroidal defects or pores. Both modes of action, transient and equilibrium leakage, synergize for intermediate chain lengths such as the native, i.e., for PSD-C10. These mechanisms may also account for the reported chain-length dependent specificities of antibiotic action against the target bacteria.

Molecular Dynamics Simulation Study of Lecithin Inhibiting Hydrate-Dissociation

2017 ◽  
Vol 890 ◽  
pp. 252-259
Author(s):  
Le Wang ◽  
Guan Cheng Jiang ◽  
Xin Lin ◽  
Xian Min Zhang ◽  
Qi Hui Jiang
Keyword(s):  
Molecular Dynamics ◽  
Water Movement ◽  
Simulation Analysis ◽  
Mass Density ◽  
Dynamics Simulation ◽  
Dissociation Process ◽  
Hydrate Dissociation ◽  
Hydrocarbon Chains ◽  
Dynamics Simulations ◽  
Mass Density Profile

Molecular dynamics simulations are used to study the dissociation inhibiting mechanism of lecithin for structure I hydrates. Adsorption characteristics of lecithin and PVP (poly (N-vinylpyrrolidine)) on the hydrate surfaces were performed in the NVT ensemble at temperatures of 277K and the hydrate dissociation process were simulated in the NPT ensemble at same temperature. The results show that hydrate surfaces with lecithin is more stable than the ones with PVP for the lower potential energy. The conformation of lecithin changes constantly after the balanced state is reached while the PVP molecular dose not. Lecithin molecule has interaction with lecithin nearby and hydrocarbon-chains of lecithin molecules will form a network to prevent the diffusion of water and methane molecules, which will narrow the available space for hydrate methane and water movement. Compared with PVP-hydrate simulation, analysis results (snapshots and mass density profile) of the dissociation simulations show that lecithin-hydrate dissociates more slowly.

A fluorescence enhancement assay of cell fusion

1977 ◽  
Vol 28 (1) ◽  
pp. 167-177
Author(s):  
P.M. Keller ◽  
S. Person ◽  
W. Snipes
Keyword(s):  
Absorption Spectrum ◽  
Energy Transfer ◽  
Emission Spectrum ◽  
Cell Fusion ◽  
Saturated Hydrocarbon ◽  
Photon Emission ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Hydrocarbon Chains ◽  
Fluorescent Molecules

Two probes were synthesized which consist of fluorescent molecules conjugated to saturated hydrocarbon chains, 18 carbons long, to ensure their localization into cellular membranes. There is an overlap between the emission spectrum of one probe (donor) and the absorption spectrum of the other probe (acceptor). By the use of appropriate wavelengths it is possible to specifically excite the donor probe and record the fluorescence of the acceptor probe. Two cell populations, each labelled with one of the probes, were infected with a virus that causes cell fusion, mixed in equal proportions, and the fluorescence of the acceptor probe measured as a function of time after infection. An increase in fluorescence was observed beginning at the time of onset of cell fusion indicating a mixing of the fluorescent membrane molecules. An investigation of the distance dependence indicated that the increase in fluorescence was mainly due to resonance energy transfer and not to photon emission and reabsorption. Resonance energy transfer requires that the 2 probes be close together and that there be an overlap of the emission spectrum of the donor probe and the absorption spectrum of the acceptor probe. The possible application of this assay to other types of membrane fusion is noted.

Acylation du (cyclopropylméthyl)triméthylsilane. Une nouvelle voie d'accès aux énones non conjuguées

1981 ◽  
Vol 59 (5) ◽  
pp. 802-806 ◽  
Author(s):  
M. Grignon-Dubois ◽  
J. Dunoguès ◽  
R. Calas
Keyword(s):  
Saturated Hydrocarbon ◽  
Chloroacetyl Chloride ◽  
Competitive Reaction ◽  
Acyl Chlorides ◽  
Unsaturated Ketones ◽  
Unsaturated Acyl ◽  
Catalytic Role ◽  
Convenient Route ◽  
Allylic Cleavage

Acylation of (cyclopropylmethyl)trimethylsilane using RCOCl/AlCl3 (R: saturated hydrocarbon group) constitutes a mild, convenient route to β,γ-unsaturated ketones free from the conjugated isomers. With α,β-unsaturated acyl chlorides a competitive reaction between the C—H and C—Si allylic cleavage is observed whereas chloroacetyl chloride affords the γ,δ-ethylenic corresponding ketone. A mechanism involving the catalytic role of HCl in the formation of β,γ-unsaturated and chloroketones is proposed.

scholarly journals Visualization of domain formation in the inner and outer leaflets of a phospholipid bilayer.

1988 ◽  
Vol 106 (6) ◽  
pp. 1885-1892 ◽  
Author(s):  
D M Haverstick ◽  
M Glaser
Keyword(s):  
Phosphatidic Acid ◽  
Digital Image ◽  
Acyl Chain ◽  
Fluorescence Microscope ◽  
Phospholipid Bilayer ◽  
Domain Formation ◽  
Charge Coupled Device ◽  
Image Processor ◽  
Outer Leaflet ◽  
Naturally Occurring

Large vesicles (5-10-micron in diameter) were formed in the presence of phospholipids fluorescently labeled on the acyl chain and visualized using a fluorescence microscope, charge-coupled-device camera and digital image processor. When such vesicles contained a fluorescent phosphatidic acid (PA) and were exposed to 2 mM CaCl2 or 0.5 mM PrCl3, it was possible to visualize PA-enriched domains within the vesicles. Calcium-induced domain formation was reversible in the presence of 4 mM EGTA. Vesicles were formed containing fluorescent PA on either the inner or outer leaflet of the bilayer and the patching and dissolution of patching were studied under conditions where calcium was present on the outside of the vesicle and where calcium was distributed across the bilayer. In addition, vesicles were formed with two different fluorescent PA's, one on the inner leaflet and a different one on the outer leaflet of the bilayer. The results of the experiments show that in vesicles formed primarily with naturally occurring phospholipids such as egg phosphatidylcholine or brain phosphatidylethanolamine, there was no coordinate action of the two leaflets of the bilayer. An exception to this was found, however, if the vesicles were formed in the presence of primarily dioleoyl phospholipids (greater than 95 mol %). In these vesicles there was a coordinate or coupled response to calcium by the two leaflets of the bilayer. In most cases, however, the two leaflets of the bilayer showed independent or uncoupled domain formation.

Water and solute permeability of rat lung caveolae: high permeabilities explained by acyl chain unsaturation

2005 ◽  
Vol 289 (1) ◽  
pp. C33-C41 ◽  
Author(s):  
Warren G. Hill ◽  
Eyad Almasri ◽  
W. Giovanni Ruiz ◽  
Gerard Apodaca ◽  
Mark L. Zeidel
Keyword(s):  
Water Permeability ◽  
Acyl Chain ◽  
Water Flux ◽  
High Water ◽  
Fatty Acyl ◽  
Rat Lung ◽  
Membrane Structures ◽  
Solute Permeability ◽  
Outer Leaflet ◽  
Osmotic Water

Caveolae are invaginated membrane structures with high levels of cholesterol, sphingomyelin, and caveolin protein that are predicted to exist as liquid-ordered domains with low water permeability. We isolated a caveolae-enriched membrane fraction without detergents from rat lung and characterized its permeability properties to nonelectrolytes and protons. Membrane permeability to water was 2.85 ± 0.41 × 10−3 cm/s, a value 5–10 times higher than expected based on comparisons with other cholesterol and sphingolipid-enriched membranes. Permeabilities to urea, ammonia, and protons were measured and found to be moderately high for urea and ammonia at 8.85 ± 2.40 × 10−7and 6.84 ± 1.03 × 10−2 respectively and high for protons at 8.84 ± 3.06 × 10−2 cm/s. To examine whether caveolin or other integral membrane proteins were responsible for high permeabilities, liposomes designed to mimic the lipids of the inner and outer leaflets of the caveolar membrane were made. Osmotic water permeability to both liposome compositions were determined and a combined inner/outer leaflet water permeability was calculated and found to be close to that of native caveolae at 1.58 ± 1.1 × 10−3 cm/s. In caveolae, activation energy for water flux was high (19.4 kcal/mol) and water permeability was not inhibited by HgCl2; however, aquaporin 1 was detectable by immunoblotting. Immunostaining of rat lung with AQP1 and caveolin antisera revealed very low levels of colocalization. We conclude that aquaporin water channels do not contribute significantly to the observed water flux and that caveolae have relatively high water and solute permeabilities due to the high degree of unsaturation in their fatty acyl chains.

scholarly journals The substrate-binding cap of the UDP-diacylglucosamine pyrophosphatase LpxH is highly flexible, enabling facile substrate binding and product release

2018 ◽  
Vol 293 (21) ◽  
pp. 7969-7981 ◽  
Author(s):  
Thomas E. Bohl ◽  
Pek Ieong ◽  
John K. Lee ◽  
Thomas Lee ◽  
Jayakanth Kankanala ◽  
...  
Keyword(s):  
Rational Design ◽  
Substrate Binding ◽  
Flexible Substrate ◽  
Binding Mode ◽  
Antibiotic Development ◽  
Product Release ◽  
Outer Leaflet ◽  
Hydrogen Deuterium ◽  
Dynamics Simulations ◽  
Secondary Membrane

Gram-negative bacteria are surrounded by a secondary membrane of which the outer leaflet is composed of the glycolipid lipopolysaccharide (LPS), which guards against hydrophobic toxins, including many antibiotics. Therefore, LPS synthesis in bacteria is an attractive target for antibiotic development. LpxH is a pyrophosphatase involved in LPS synthesis, and previous structures revealed that LpxH has a helical cap that binds its lipid substrates. Here, crystallography and hydrogen–deuterium exchange MS provided evidence for a highly flexible substrate-binding cap in LpxH. Furthermore, molecular dynamics simulations disclosed how the helices of the cap may open to allow substrate entry. The predicted opening mechanism was supported by activity assays of LpxH variants. Finally, we confirmed biochemically that LpxH is inhibited by a previously identified antibacterial compound, determined the potency of this inhibitor, and modeled its binding mode in the LpxH active site. In summary, our work provides evidence that the substrate-binding cap of LpxH is highly dynamic, thus allowing for facile substrate binding and product release between the capping helices. Our results also pave the way for the rational design of more potent LpxH inhibitors.

Pressure effect on the bilayer phase transition of asymmetric lipids with an unsaturated acyl chain

2010 ◽  
Vol 1189 (1) ◽  
pp. 77-85 ◽  
Author(s):  
Kaori Tada ◽  
Masaki Goto ◽  
Nobutake Tamai ◽  
Hitoshi Matsuki ◽  
Shoji Kaneshina
Keyword(s):  
Phase Transition ◽  
Pressure Effect ◽  
Acyl Chain ◽  
Unsaturated Acyl

scholarly journals The contributions of biosynthesis and acyl chain remodelling to the molecular species profile of phosphatidylcholine in yeast

2005 ◽  
Vol 33 (5) ◽  
pp. 1146-1149 ◽  
Author(s):  
H.A. Boumann ◽  
A.I.P.M. de Kroon
Keyword(s):  
Stable Isotope ◽  
Species Composition ◽  
Molecular Species ◽  
Acyl Chain ◽  
Membrane Lipid ◽  
Molecular Species Composition ◽  
Stable Isotope Labelling ◽  
Membrane Function ◽  
Isotope Labelling ◽  
Acyl Chains

Phosphatidylcholine (PC) is a very abundant membrane lipid in most eukaryotes, including yeast. The molecular species profile of PC, i.e. the ensemble of PC molecules with acyl chains differing in number of carbon atoms and double bonds, is important for membrane function. Pathways of PC synthesis and turnover maintain PC homoeostasis and determine the molecular species profile of PC. Studies addressing the processes involved in establishing the molecular species composition of PC in yeast using stable isotope labelling combined with detection by MS are reviewed.

Abstract 16607: Age-induced Endoplasmic Reticulum Stress in the Heart: Role of Increased Very Long-chain Ceramides

Circulation ◽  
2020 ◽  
Vol 142 (Suppl_3) ◽  
Author(s):  
Qun Chen ◽  
Anna Kovilakath ◽  
Jeremy Allegood ◽  
Lauren A Cowart ◽  
Edward J Lesnefsky
Keyword(s):  
Er Stress ◽  
Mitochondrial Dysfunction ◽  
Acyl Chain ◽  
Membrane Domains ◽  
Ceramide Synthase ◽  
Age Related ◽  
Chain Lengths ◽  
Endoplasm Reticulum ◽  
Long Chain

Introduction: Mitochondrial function is impaired in aged hearts. Increased endoplasm reticulum (ER) stress contributes to the mitochondrial dysfunction observed during aging. Ceramides (CRMD) are sphingolipid metabolites that contribute key roles in cell signaling. Increased CRMD can lead to ER stress. Ceramide synthase enzymes (CerS) generate chain length specific CRMD with the CerS isoform 2 (Cers2) forming very long chain CRMD of ≥ 20 carbon acyl chain lengths. Hypothesis: An increase in CRMD content during aging contributes to age-related ER stress. Methods: Male mice (3, 18, 24 mo.) from the NIA colony were studied. Cardiac mitochondria (MITO), mitochondrial associated membranes (MAM), and ER were isolated from mouse hearts. CRMD content was measured using LC-MS. The contents of CerS enzymes were measured by immunoblotting in myocardial homogenates. Results: ER stress increased progressively during aging with increased contents of cleaved ATF6 and CHOP, indicators of increased ER stress, evident at 18 and 24 mo. (Panel A) (all data mean±SEM; *p<0.05 vs. 3 mo., † p<0.05 vs. 18 mo.). Aging increased very long-chain CRMD (≥C20) in ER (Panel B) at 18 and 24 mo. Similar CRMD trends were observed MAM (Panel C), shared membrane domains where ER and MITO interact. The content of CerS2 was increased at 24 mo. compared to 3 mo. (Panel D, n=4 each age). In contrast, the contents of CerS isoforms 4 and 5, that generate shorter chain CRMD (<C20) were unchanged (not shown). CRMD contents in MITO were unaltered with age (not shown). Thus, increased generation of very long chain CRMD in the ER is the likely mechanism of increased ER stress in the aged heart. Conclusion: Aging increased ER CRMD content by enhancing the formation of very long chain CRMD in ER by an increase in CerS2 content, concomitant with the onset of ER stress. The increase in age-induced ER stress, in turn, leads to mitochondrial dysfunction in the aged heart.

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