DOCSLIB.ORG

Oct 19 Notes to Post

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Oct 19 Notes to Post Measures of Membrane Fluidity: Melting Temperature • Tm (melting temperature) is a phase transition, a change from a more rigid solid-like state to a fluid-like state The fluidity - ease with which lipids move in the plane of the bilayer - of cell membranes has to be precisely regulated because many biological processes (e.g. membrane transport and some enzyme activities) cease when the bilayer fluidity is reduced too much. The fluidity of cell membranes depends on their chemical composition and also on temperature. As the temperature is raised, a synthetic bilayer made of one type of phospholipid undergoes a phase transition from a solid-like state to a more fluid-like state at a characteristic melting point temperature (abbreviated as Tm). At low temperatures the lipids within the bilayer are well- ordered, packed into a crystal-like arrangement in which the lipids are not very mobile and there are many stabilizing interactions. As the temperature is raised, these interactions are weakened, and the lipids are in a less ordered, liquid-like state. Lipids with longer fatty acid chains have more interactions between the hydrophobic fatty acid tails (predominantly van der Waals interactions), stabilizing the crystal-like state and therefore increasing the melting temperature and making the membrane less fluid. 1 Membrane Composition Influences Membrane Fluidity: Fatty Acid Structure unsaturated fatty acid chains saturated fatty acid chains lower Tm higher Tm OH OH O O 17 carbons cis double bond olive oil candle wax oleic acid stearic acid The degree of saturation of the fatty acid chains also affects the melting temperature and membrane fluidity. Fatty acids that are saturated, containing no double bonds, are straight and can pack more tightly than those that have double bonds. The kinks in the unsaturated chains simply make it more difficult to pack them in an orderly manner. As a consequence, the melting temperature of bilayers containing lipids with saturated fatty acids is higher than the melting temperature of bilayers containing lipids with unsaturated fatty acids. Additionally, the fluidity of bilayers containing lipids rich in unsaturated fatty acids is greater than the fluidity of bilayers containing lipids rich in saturated fatty acids. An example of this difference in fluidity and melting temperature is oleic and stearic acid. These two fatty acids have the same number of carbons (17), but they differ dramatically in their fluidity and melting temperature. At room temperature oleic acid is fluid-like (olive oil) and stearic acid is solid-like (candle wax); the melting temperature of oleic acid is lower than that of stearic acid because oleic acid is unsaturated and cannot pack in as orderly a manner as saturated stearic acid. 2 Membrane Composition Influences Membrane Fluidity: Cholesterol Content HO H H H H H Cholesterol is a major component of eukaryotic cells. The ratio of cholesterol to lipid molecules in a membrane can be as high as 1:1. Cholesterol is a member of a class of natural products called steroids, characterized by a 4 ring structure. Although all steroids are based on the same scaffold, they can affect different biological processes, ranging from the development of secondary sex characteristics (testosterone and estrogen) to inflammation (corticosteroids). Like phospholipids, cholesterol is an amphipathic molecule; it has a polar head that contains a hydroxyl group. The rest of cholesterol is hydrophobic, consisting of a rigid 4 ring steroid structure and a hydrocarbon tail. The 4 ring structure makes most of the cholesterol molecule very rigid because bonds between atoms in a ring are not free to rotate as a result of the geometric constraints of being in a ring. 3 Cholesterol Influences Membrane Fluidity Cholesterol interacts with phospholipids by orienting its polar hydroxyl head group close to the polar lipid head group. The rigid rings of cholesterol interact with and partly immobilize the fatty acid chains closest to the polar phospholipid head group. As a consequence, lipid molecules adjacent to cholesterol are less free to adopt different conformations than those in a cholesterol-free membrane region. By decreasing the mobility of a few methylene groups (CH2) in the fatty acids tails, cholesterol makes lipid bilayers less deformable and lessens their permeability to small water-soluble molecules. Therefore, cholesterol makes membranes less fluid. Although cholesterol makes bilayers less fluid, at the high concentrations of cholesterol found in eukaryotic cells, it also prevents fatty acid hydrocarbon chains from coming together and crystallizing. Therefore, cholesterol prevents fatty acid chains from ordering into a crystal- like state. Cholesterol inhibits phase transitions in lipids. At low temperatures it increases membrane fluidity by preventing fatty acid hydrocarbon chains from coming together and crystallizing. Under these conditions cholesterol inhibits the transition from liquid to solid (decreases the membrane freezing point). At high temperatures cholesterol decreases membrane fluidity by immobilizing a few methylene groups in the fatty acid tails of the lipids. Therefore, under these conditions cholesterol increases the melting point. Therefore, cholesterol acts like antifreeze - the temperature of your car engine is modulated by water circulating with antifreeze/coolant which lowers the freezing point of the antifreeze/coolant so it does not freeze in the winter. The antifreeze/coolant also raises the boiling point in the summer so that your engine does not overheat. The influence of cholesterol on membrane properties is critical for the normal functioning of eukaryotic cells. 4 Summary of Main Points • HIV needs host cells to replicate because its genome does not encode all of the proteins required for living systems • HIV recognizes host cells by interacting with specific protein receptors found on the surface of those cell types • Cell membranes are bilayers composed of amphipathic phospholipids containing charged head groups and hydrophobic tails • The hydrophobic effect drives the packing of lipids into structures which minimize exposed hydrophobic groups • Membranes are fluid because phospholipids and proteins can move in the plane of the bilayer; fatty acid structure and cholesterol content influence fluidity 5 October 19, 2006 6 Membrane Proteins and Membrane Transport 1. Membrane proteins a. Association of proteins with membranes b. Transmembrane helices 2. Lipid Rafts 3. Membrane transport a. Membrane permeability b. Transport proteins c. Ion distribution inside and outside cells d. Electrochemical gradient e. Active transport f. Ion channels 4. Membrane potential Lecture Readings Alberts 389-410 7 Membrane Proteins Although the lipid bilayer serves as a permeability barrier and provides the basic structure of all cell membranes, most membrane functions are carried out by membrane proteins, which constitute 50% of the mass of most plasma membranes. Membrane proteins perform many different functions: (1) they can transport ions and metabolites across the membrane (2) anchor the membrane to other proteins that play a roll in cell shape and structure (3) they can function as receptors to detect chemical signals in the environment and relay them to the inside of the cell (4) or they can act as enzymes to catalyze reactions. 8 Proteins Associate with Membranes in Different Ways Proteins can associate with the lipid bilayer in various ways: (a) Transmembrane proteins - These proteins extend through the bilayer and have some mass on both sides. They have hydrophobic sequences in the bilayer, interacting with the hydrophobic tails of lipids, and hydrophilic regions exposed to the aqueous environment on either side of the membrane. (b) Membrane associated - These are proteins located in the cytosol associated with the inner leaflet by an amphipathic alpha-helix (one side of the helix projects hydrophobic residues and the other side projects hydrophilic ones). (c) Lipid-linked - Some proteins lie entirely outside the bilayer, interacting with it using only a covalently attached lipid group. (d) Protein attached - Other proteins are associated only indirectly with the membrane, held there by interactions with one or more membrane proteins. 9 Many Membrane Proteins Cross the Bilayer Using One or More α-Helices Many proteins that have mass on either side of bilayer cross it using alpha-helices. Helical structures are are well-suited for folding in the bilayer. Those that are transmembrane have hydrophobic side chains which can interact with lipid tails. Within membranes, hydrogen bonding in the polypeptide backbone is maximized because water is absent from the bilayer. As a consequence, there is no competition with water for hydrogen bonding. ~20 amino acids are required to traverse the bilayer in an alpha-helical structure. Scientists can take advantage of knowledge of helical propensity of certain amino acids (the preference they have for or against being in an alpha-helical structure) and hydrophobicity to predict transmembrane domains in proteins. 10 Lipid Rafts in the Plasma Membrane protein with fatty protein with longer acid modification transmembrane region lipid bilayer enriched in cholesterol and phospholipids with long fatty acid tails As we saw in the animation, membranes are dynamic and are not uniform. Lipid rafts are a major source of inhomogeneity in the membranes of eukaryotic cells. Lipid rafts are microdomains in the lipid bilayer that are established by attractive
Load more

Recommended publications
  • Membrane Structure Overview Pathology > Cellular Biology & Genetics > Cellular Biology & Genetics
    Membrane Structure Overview Pathology > Cellular Biology & Genetics > Cellular Biology & Genetics PLASMA MEMBRANE • Phospholipid bilayer: bilayer that comprises mostly phospholipids • Fluid mosaic: mosaic of proteins embedded within a fluid phospholipid bilayer • Selectively permeable: some substances move through passively, others use proteins for transport MEMBRANE COMPONENTS • Phospholipids • Proteins • Cholesterol • Carbohydrates PHOSPHOLIPIDS • Amphipathic: hydrophilic head and hydrophobic fatty acid tails • Form liposomes in aqueous environment • Weak hydrophobic interactions = membrane fluidity • Saturated phospholipids: maximize hydrogens in fatty acid tails, no kinks • Unsaturated phospholipids: double bond produces kink, increases fluidity CHOLESTEROL • Temperature buffer • Moderate temperature: decreases fluidity, lessens lateral movement • Low temperature: increases fluidity, prevents solidification PROTEINS • Includes transmembrane proteins that span the bilayer (other types exist) • Proteins provide about half the mass of the membrane CARBOHYDRATES • Glycoproteins: branched carbohydrates covalently bound to proteins • Glycolipids: carbohydrates covalently bound to lipids (extracellular only) 1 / 5 CLINICAL CORRELATION: Blood types • Carbohydrates on surface of red blood cells must be compatible between donor & recipient in blood transfusion FUNCTIONS OF THE CELL MEMBRANE • Cell communication • Import and export of molecules • Cell growth • Cell motility Eukaryotes have internal membranes within the cell, prokaryotes do not.
    [Show full text]
  • Membrane Fluidity and the Perception of Environmental Signals In
    Progress in Lipid Research 42 (2003) 527–543 www.elsevier.com/locate/plipres Review Membrane fluidity and the perception of environmental signals in cyanobacteria and plants Koji Mikami, Norio Murata* Department of Regulation Biology, National Institute for Basic Biology, Okazaki 444-8585, Japan Accepted 22 April 2003 Abstract Photosynthetic organisms, namely, plants and cyanobacteria, are directly exposed to changes in their environment and their survival depends on their ability to acclimate to such changes. Several lines of evi- dence suggest that temperature stress, such as unusually low or high temperatures, and osmotic stress might be perceived by plants and cyanobacteria via changes in the fluidity of their cell membranes. The availability of techniques for gene-targeted mutagenesis and gene transfer, as well as for the analysis of genomes and transcripts, has allowed us to examine and evaluate this hypothesis and its implications. In this review, we summarize recent studies of the regulation of gene expression by changes in the extent of unsaturation of fatty acids and membrane fluidity, and we present a discussion of the induction of gene expression by environmental stress and of sensors of environmental conditions and relationships between their activity and the fluidity of membranes in cyanobacteria and plants. # 2003 Elsevier Ltd. All rights reserved. Contents 1. Introduction ..........................................................................................................................................................
    [Show full text]
  • Biological Membranes
    14 Biological Membranes To understand the structure The fundamental unit of life is the cell. All living things are composed of Goal and composition of biological cells, be it a single cell in the case of many microorganisms or a highly membranes. organized ensemble of myriad cell types in the case of multicellular organisms. A defining feature of the cell is a membrane, the cytoplasmic Objectives membrane, that surrounds the cell and separates the inside of the cell, the After this chapter, you should be able to cytoplasm, from other cells and the extracellular milieu. Membranes also • distinguish between cis and trans surround specialized compartments inside of cells known as organelles. unsaturated fatty acids. Whereas cells are typically several microns (μm) in diameter (although • explain why phospholipids some cells can be much larger), the membrane is only about 10 nanometers spontaneously form lipid bilayers and (nm) thick. Yet, and as we will see in subsequent chapters, the membrane is sealed compartments. not simply an ultra-thin, pliable sheet that encases the cytoplasm. Rather, • describe membrane fluidity and how it membranes are dynamic structures that mediate many functions in the is affected by membrane composition life of the cell. In this chapter we examine the composition of membranes, and temperature. their assembly, the forces that stabilize them, and the chemical and physical • explain the role of cholesterol in properties that influence their function. buffering membrane fluidity. The preceding chapters have focused on two kinds of biological molecules, • explain how the polar backbone namely proteins and nucleic acids, that are important in the workings of a membrane protein can be accommodated in a bilayer.
    [Show full text]
  • Factors Influencing the Membrane Fluidity and the Impact on Production of Lactic Acid Bacteria Starters
    Applied Microbiology and Biotechnology (2019) 103:6867–6883 https://doi.org/10.1007/s00253-019-10002-1 MINI-REVIEW Factors influencing the membrane fluidity and the impact on production of lactic acid bacteria starters Fernanda Fonseca1 & Caroline Pénicaud 1 & E. Elizabeth Tymczyszyn2 & Andrea Gómez-Zavaglia3 & Stéphanie Passot1 Received: 19 April 2019 /Revised: 25 June 2019 /Accepted: 27 June 2019 /Published online: 12 July 2019 # Springer-Verlag GmbH Germany, part of Springer Nature 2019 Abstract Production of lactic acid bacteria starters for manufacturing food, probiotic, and chemical products requires the application of successive steps: fermentation, concentration, stabilization, and storage. Despite process optimization, losses of bacterial viability and functional activities are observed after stabilization and storage steps due to cell exposure to environmental stresses (thermal, osmotic, mechanical, and oxidative). Bacterial membrane is the primary target for injury and its damage is highly dependent on its physical properties and lipid organization. Membrane fluidity is a key property for maintaining cell functionality, and depends on lipid composition and cell environment. Extensive evidence has been reported on changes in membrane fatty acyl chains when modifying fermentation conditions. However, a deep characterization of membrane physical properties and their evolution following production processes is scarcely reported. Therefore, the aims of this mini-review are (i) to define the membrane fluidity and the methods used to assess it and (ii) to summarize the effect of environmental conditions on membrane fluidity and the resulting impact on the resistance of lactic acid bacteria to the stabilization processes. This will make it possible to highlight existing gaps of knowledge and opens up novel approaches for future investigations.
    [Show full text]
  • Phospholipid Bilayer Fibers of Extra- Cellular Matrix (ECM)
    Membrane Functions Cell Membranes 1. boundaries 6. Cell-cell Today’s Topics 2. Localize adhesion • Finish Cell Structure and Movement specific – Cytoskeleton functions – Motor Proteins • Membrane Structure – Fluid Mosaic 5. Cell-cell – How appropriate fluidity is maintained communication • Diffusion and Osmosis http://library.thinkquest.org/C004535/media/cell_membrane.gif 3. Transport Sept 19, 2011 4. Signal detection Figure 7.5 Phospholipid bilayer Fibers of extra- cellular matrix (ECM) Glyco- Carbohydrate protein Glycolipid Fig. 7-2 EXTRACELLULAR SIDE OF MEMBRANE WATER! Hydrophilic head! Cholesterol Microfilaments Peripheral of cytoskeleton proteins Hydrophobic Integral protein tail! CYTOPLASMIC SIDE OF MEMBRANE WATER! Membrane Structure: The Fluid Mosaic Model 1972 Singer & Nicholson • Proteins embedded and floating in a sea hydrophobic of phospholipids A B Phospholipid bilayer hydrophilic Protein and Lipid raft Figure 7.3 1 • Membrane proteins and lipids are Figure 7.6 synthesized in the ER and Golgi The Fluidity of Membranes apparatus 1 Transmembrane glycoproteins ER Secretory protein ~25% of known genes code for membrane Glycolipid Golgi 2 proteins apparatus Vesicle Most drugs target Lateral movement occurs Flip-flopping across the membrane membrane proteins !107 times per second. is rare (! once per month). 3 Plasma membrane: Cytoplasmic face 4 Extracellular face Transmembrane glycoprotein Secreted protein Membrane glycolipid Figure 7.10 Figure 7.7 Evidence for integral membrane proteins: Evidence for membrane fluidity? Freeze-Fracture Electron Microscopy Extracellular layer A cell is frozen and fractured with a knife. The fracture plane often follows the hydrophobic interior of a membrane, splitting the phospholipid bilayer into two separated layers. The membrane proteins go wholly with one of the layers.
    [Show full text]
  • A. Membrane Functions Biological Membranes Are Composed Of… Membrane Lipid Protein
    A. Membrane Functions Biological Membranes are composed of… Membrane Lipid Protein Myelin Sheath 80% 20% Plasma Membrane 50% 50% Mitochondrial 25% 75% Inner Membrane Fig. 5.12: Phospholipids Hydrophilic head 2 Hydrophobic tails Phospholipds are amphipathic molecules (contain both hydrophilic and hydrophobic parts) Phospholipids form Membrane Bilayers Bilayer consisting of two inverted phospholipid layers (leaflets) Hydrophobic ~30 Å ~45 Å Interior (3 nm) (4.5 nm) Hydrophobic interior is an impermeable barrier to passage of hydrophilic molecules, but not to hydrophobic molecules Cholesterol has profound effects on membrane fluidity Fig 7.8: Membrane Fluidity (a) Phospholipid molecules move side-to-side within leaflet easily (lateral diffusion) but do not “flip-flop” across bilayer (transverse diffusion) (b) Phospholipids containing unsaturated acyl chains increase membrane fluidity by reducing packing efficiency (c) Cholesterol reduces membrane fluidity at normal temperatures (reduces phospholipid movement) At low temperatures it keeps membrane fluid (disrupts packing) Membrane Proteins can Move Laterally Within the Lipid Bilayer Membrane proteins labeled with different color fluorescent dyes Supports fluid-mosaic model of a dynamic membrane structure Three Types of Membrane Proteins 1. Integral membrane proteins (transmembrane proteins) Extracellular domain • span the bilayer • transmembrane domain has Transmembrane hydrophobic surface domain • cytosolic and extracellular Cytosolic domains have hydrophilic surfaces domain 2. Lipid-anchored membrane proteins - anchored via a covalently attached lipid 3. Peripheral membrane proteins - interact with hydrophilic lipid head groups or with integral membrane proteins How do proteins cross lipid bilayer membranes? δ- δ+ δ- δ+ Even if the R-groups are hydrophobic, the peptide bond atoms are hydrophilic (polar) and will want to form Hydrogen Bonds; there are no H-bond donors or acceptors in the middle of a lipid bilayer.
    [Show full text]
  • Laurdan Identifies Different Lipid Membranes in Eukaryotic Cells
    UC Irvine UC Irvine Previously Published Works Title Laurdan identifies different lipid membranes in eukaryotic cells Permalink https://escholarship.org/uc/item/9m80z238 ISBN 9781482209891 Authors Gratton, E Digman, MA Publication Date 2014 DOI 10.1201/b17634 License https://creativecommons.org/licenses/by/4.0/ 4.0 Peer reviewed eScholarship.org Powered by the California Digital Library University of California Laurdan Identifies 13 Different Lipid Membranes in Eukaryotic Cells Enrico Gratton and Michelle A. Digman CONTENTS 13.1 Introduction ..................................................................................................283 13.1.1 Spectroscopic Properties of Laurdan................................................283 13.2 The Phasor Approach to Spectral and Lifetime Analysis ............................287 13.3 The Lifetime Phasor Transformation and Its Interpretation .........................289 13.4 Results of the Analysis of the Emission of Laurdan Using Spectral and Lifetime Phasors in GUVs Model Systems .................................................. 291 13.5 The Lifetime Phasor for Laurdan in GUVs ..................................................292 13.6 Live Cell Membrane Fluidity .......................................................................295 13.6.1 Spectral Phasors................................................................................295 13.6.2 Lifetime Phasors in Live 3T3 Cells ..................................................297 13.7 Conclusions and Further Considerations ......................................................299
    [Show full text]
  • Membrane Interactions of Phytochemicals As Their Molecular Mechanism Applicable to the Discovery of Drug Leads from Plants
    Molecules 2015, 20, 18923-18966; doi:10.3390/molecules201018923 OPEN ACCESS molecules ISSN 1420-3049 www.mdpi.com/journal/molecules Review Membrane Interactions of Phytochemicals as Their Molecular Mechanism Applicable to the Discovery of Drug Leads from Plants Hironori Tsuchiya Department of Dental Basic Education, Asahi University School of Dentistry, 1851 Hozumi, Mizuho, Gifu 501-0296, Japan; E-Mail: [email protected]; Tel./Fax: +81-58-329-1266 Academic Editors: Maurizio Battino, Etsuo Niki and José L. Quiles Received: 11 September 2015 / Accepted: 14 October 2015 / Published: 16 October 2015 Abstract: In addition to interacting with functional proteins such as receptors, ion channels, and enzymes, a variety of drugs mechanistically act on membrane lipids to change the physicochemical properties of biomembranes as reported for anesthetic, adrenergic, cholinergic, non-steroidal anti-inflammatory, analgesic, antitumor, antiplatelet, antimicrobial, and antioxidant drugs. As well as these membrane-acting drugs, bioactive plant components, phytochemicals, with amphiphilic or hydrophobic structures, are presumed to interact with biological membranes and biomimetic membranes prepared with phospholipids and cholesterol, resulting in the modification of membrane fluidity, microviscosity, order, elasticity, and permeability with the potencies being consistent with their pharmacological effects. A novel mechanistic point of view of phytochemicals would lead to a better understanding of their bioactivities, an insight into their medicinal benefits, and a strategic implication for discovering drug leads from plants. This article reviews the membrane interactions of different classes of phytochemicals by highlighting their induced changes in membrane property. The phytochemicals to be reviewed include membrane-interactive flavonoids, terpenoids, stilbenoids, capsaicinoids, phloroglucinols, naphthodianthrones, organosulfur compounds, alkaloids, anthraquinonoids, ginsenosides, pentacyclic triterpene acids, and curcuminoids.
    [Show full text]
  • Alterations in the Properties of the Cell Membrane Due to Glycosphingolipid
    www.nature.com/scientificreports OPEN Alterations in the properties of the cell membrane due to glycosphingolipid accumulation in a Received: 3 October 2017 Accepted: 11 December 2017 model of Gaucher disease Published: xx xx xxxx Gyula Batta1,2, Lilla Soltész1, Tamás Kovács1, Tamás Bozó3, Zoltán Mészár4, Miklós Kellermayer 3, János Szöllősi1,5 & Peter Nagy 1 Gaucher disease is a lysosomal storage disease characterized by the malfunction of glucocerebrosidase resulting in the accumulation of glucosylceramide and other sphingolipids in certain cells. Although the disease symptoms are usually attributed to the storage of undigested substrate in lysosomes, here we show that glycosphingolipids accumulating in the plasma membrane cause profound changes in the properties of the membrane. The fuidity of the sphingolipid-enriched membrane decreased accompanied by the enlargement of raft-like ordered membrane domains. The mobility of non-raft proteins and lipids was severely restricted, while raft-resident components were only mildly afected. The rate of endocytosis of transferrin receptor, a non-raft protein, was signifcantly retarded in Gaucher cells, while the endocytosis of the raft-associated GM1 ganglioside was unafected. Interferon- γ-induced STAT1 phosphorylation was also signifcantly inhibited in Gaucher cells. Atomic force microscopy revealed that sphingolipid accumulation was associated with a more compliant membrane capable of producing an increased number of nanotubes. The results imply that glycosphingolipid accumulation in the plasma membrane has signifcant efects on membrane properties, which may be important in the pathogenesis of Gaucher disease. Te plasma membrane constitutes an interface between the cell and its surroundings, and it is the site of numer- ous transmembrane signaling and membrane trafcking events.
    [Show full text]
  • The Cell Membrane
    2 The Cell Membrane The cell’s organelles and its intracellular solutes (some inor­ brane several times (Fig. 2.2B). Others are located more on the ganic and some organic) are contained within the cell by its outside or inside of the membrane. membrane. The membrane has limited and selective perme­ Integral proteins are amphipathic, consisting of two hydro­ ability; it maintains the intracellular concentration of electro­ philic ends separated by an intervening hydrophobic re gion lytes and biologic compounds that is distinctly different from that traverses the hydrophobic core of the bilayer. The hy­ that of the extracellular fluid. Cell membrane function is thus dro philic ends of the integral protein are found outside the an essential one for the health and survival of the cell. membrane, on either its external or internal surface. Integral Membrane Composition A Membranes are complex structures composed of lipids, pro­ teins, and carbohydrates. The cell membrane contains pro­ teins and lipids in a mass ratio of 50:50. An average membrane protein is several times larger than the average lipid molecule, but lipid molecules are ~50 times more numerous than pro­ tein molecules. The ratio is not absolute and varies from mem­ brane to membrane. The exact ratio between the two varies with the function of the cell. For example, the myelin sheath of nerves has ~75% lipids and 25% proteins, whereas membranes involved in energy transduction, such as the inner mitochon­ drial membrane, have 75% proteins and 25% lipids. B The major membrane lipids are phospholipids, glycosphin­ golipids, and cholesterol. Membrane phospholipids are of two types: the phosphoglycerides (Fig.
    [Show full text]
  • Non-Polar Lipids As Regulators of Membrane Properties in Archaeal Lipid Bilayer Mimics
    International Journal of Molecular Sciences Article Non-Polar Lipids as Regulators of Membrane Properties in Archaeal Lipid Bilayer Mimics Marta Salvador-Castell 1 , Nicholas J. Brooks 2 , Roland Winter 3 , Judith Peters 4,5 and Philippe M. Oger 1,* 1 University Lyon, INSA Lyon, CNRS, UMR 5240, CEDEX, F-69621 Villeurbanne, France; [email protected] 2 Department of Chemistry, Imperial College London, London SW7 2AZ, UK; [email protected] 3 Faculty of Chemistry and Chemical Biology, Technische Universität Dortmund, 44227 Dortmund, Germany; [email protected] 4 Université Grenoble Alpes, LiPhy, CEDEX, F-38044 Grenoble, France; [email protected] 5 Institut Laue Langevin, F-38000 Grenoble, France * Correspondence: [email protected]; Tel.: +33-4-72-43-60-01 Abstract: The modification of archaeal lipid bilayer properties by the insertion of apolar molecules in the lipid bilayer midplane has been proposed to support cell membrane adaptation to extreme environmental conditions of temperature and hydrostatic pressure. In this work, we characterize the insertion effects of the apolar polyisoprenoid squalane on the permeability and fluidity of archaeal model membrane bilayers, composed of lipid analogues. We have monitored large molecule and proton permeability and Laurdan generalized polarization from lipid vesicles as a function of temperature and hydrostatic pressure. Even at low concentration, squalane (1 mol%) is able to enhance solute permeation by increasing membrane fluidity, but at the same time, to decrease proton permeability of the lipid bilayer. The squalane physicochemical impact on membrane properties are congruent with a possible role of apolar intercalants on the adaptation of Archaea to extreme Citation: Salvador-Castell, M.; conditions.
    [Show full text]
  • Phospholipids and Membrane Structure © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT for SALE OR DISTRIBUTION NOT for SALE OR DISTRIBUTION
    © Jones & Bartlett Learning, LLC. NOT FOR SALE OR DISTRIBUTION. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC © Jones & Bartlett4 Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Phospholipids and Membrane Structure © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION 4.1 The Big Picture 4.2 Phospholipids Are the Basic Building Blocks of Cellular Membranes © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE4.3 TheOR Fluid–MosaicDISTRIBUTION Model Explains How PhospholipidsNOT FOR SALE OR DISTRIBUTION and Proteins Interact within a Cellular Membrane 4.4 The Smooth Endoplasmic Reticulum and Golgi Apparatus Build Most Eukaryotic Cellular Membrane Components© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC 4.5 Chapter SummaryNOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION 117 3RD PAGES © Jones & Bartlett Learning, LLC. NOT FOR SALE OR DISTRIBUTION. © Jones & Bartlett Learning, LLC4.1 The Big Picture© Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTIONThe purpose of this chapterNOT is to FOR introduce SALE the OR general DISTRIBUTION structure and assembly of mem- branes.
    [Show full text]