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Cebecauer M, Amaro M, Jurkiewicz P, Sarmento MJ, Šachl R, Cwiklik L, Hof M. Membrane Lipid Nanodomains. Chem Rev 2018; 118:11259-11297. [PMID: 30362705 DOI: 10.1021/acs.chemrev.8b00322] [Citation(s) in RCA: 128] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Lipid membranes can spontaneously organize their components into domains of different sizes and properties. The organization of membrane lipids into nanodomains might potentially play a role in vital functions of cells and organisms. Model membranes represent attractive systems to study lipid nanodomains, which cannot be directly addressed in living cells with the currently available methods. This review summarizes the knowledge on lipid nanodomains in model membranes and exposes how their specific character contrasts with large-scale phase separation. The overview on lipid nanodomains in membranes composed of diverse lipids (e.g., zwitterionic and anionic glycerophospholipids, ceramides, glycosphingolipids) and cholesterol aims to evidence the impact of chemical, electrostatic, and geometric properties of lipids on nanodomain formation. Furthermore, the effects of curvature, asymmetry, and ions on membrane nanodomains are shown to be highly relevant aspects that may also modulate lipid nanodomains in cellular membranes. Potential mechanisms responsible for the formation and dynamics of nanodomains are discussed with support from available theories and computational studies. A brief description of current fluorescence techniques and analytical tools that enabled progress in lipid nanodomain studies is also included. Further directions are proposed to successfully extend this research to cells.
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Affiliation(s)
- Marek Cebecauer
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences , Dolejškova 3 , 18223 Prague 8 , Czech Republic
| | - Mariana Amaro
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences , Dolejškova 3 , 18223 Prague 8 , Czech Republic
| | - Piotr Jurkiewicz
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences , Dolejškova 3 , 18223 Prague 8 , Czech Republic
| | - Maria João Sarmento
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences , Dolejškova 3 , 18223 Prague 8 , Czech Republic
| | - Radek Šachl
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences , Dolejškova 3 , 18223 Prague 8 , Czech Republic
| | - Lukasz Cwiklik
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences , Dolejškova 3 , 18223 Prague 8 , Czech Republic
| | - Martin Hof
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences , Dolejškova 3 , 18223 Prague 8 , Czech Republic
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Tanphaichitr N, Kongmanas K, Faull KF, Whitelegge J, Compostella F, Goto-Inoue N, Linton JJ, Doyle B, Oko R, Xu H, Panza L, Saewu A. Properties, metabolism and roles of sulfogalactosylglycerolipid in male reproduction. Prog Lipid Res 2018; 72:18-41. [PMID: 30149090 PMCID: PMC6239905 DOI: 10.1016/j.plipres.2018.08.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Revised: 08/20/2018] [Accepted: 08/21/2018] [Indexed: 12/16/2022]
Abstract
Sulfogalactosylglycerolipid (SGG, aka seminolipid) is selectively synthesized in high amounts in mammalian testicular germ cells (TGCs). SGG is an ordered lipid and directly involved in cell adhesion. SGG is indispensable for spermatogenesis, a process that greatly depends on interaction between Sertoli cells and TGCs. Spermatogenesis is disrupted in mice null for Cgt and Cst, encoding two enzymes essential for SGG biosynthesis. Sperm surface SGG also plays roles in fertilization. All of these results indicate the significance of SGG in male reproduction. SGG homeostasis is also important in male fertility. Approximately 50% of TGCs become apoptotic and phagocytosed by Sertoli cells. SGG in apoptotic remnants needs to be degraded by Sertoli lysosomal enzymes to the lipid backbone. Failure in this event leads to a lysosomal storage disorder and sub-functionality of Sertoli cells, including their support for TGC development, and consequently subfertility. Significantly, both biosynthesis and degradation pathways of the galactosylsulfate head group of SGG are the same as those of sulfogalactosylceramide (SGC), a structurally related sulfoglycolipid important for brain functions. If subfertility in males with gene mutations in SGG/SGC metabolism pathways manifests prior to neurological disorder, sperm SGG levels might be used as a reporting/predicting index of the neurological status.
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Affiliation(s)
- Nongnuj Tanphaichitr
- Chronic Disease Program, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada; Department of Obstetrics/Gynecology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada; Department of Biochemistry, Microbiology, Immunology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada.
| | - Kessiri Kongmanas
- Chronic Disease Program, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada; Department of Biochemistry, Microbiology, Immunology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada; Division of Dengue Hemorrhagic Fever Research, Department of Research and Development, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand
| | - Kym F Faull
- Pasarow Mass Spectrometry Laboratory, University of California, Los Angeles, California, USA
| | - Julian Whitelegge
- Pasarow Mass Spectrometry Laboratory, University of California, Los Angeles, California, USA
| | - Federica Compostella
- Dipartimento di Biotecnologie Mediche e Medicina Traslazionale, Università degli Studi di Milano, Via Saldini 50, 20133 Milano, Italy
| | - Naoko Goto-Inoue
- Department of Marine Science and Resources, College of Bioresource Sciences, Nihon University, Kanagawa 252-0880, Japan
| | - James-Jules Linton
- Chronic Disease Program, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada
| | - Brendon Doyle
- Chronic Disease Program, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada; Department of Biochemistry, Microbiology, Immunology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada
| | - Richard Oko
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada
| | - Hongbin Xu
- Chronic Disease Program, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada; Department of Biochemistry, Microbiology, Immunology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada
| | - Luigi Panza
- Department of Pharmaceutical Sciences, Università del Piemonte Orientale, Largo Donegani 2, 28100 Novara, Italy
| | - Arpornrad Saewu
- Chronic Disease Program, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada
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Rodi PM, Maggio B, Bagatolli LA. Direct visualization of the lateral structure of giant vesicles composed of pseudo-binary mixtures of sulfatide, asialo-GM1 and GM1 with POPC. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1860:544-555. [PMID: 29106974 DOI: 10.1016/j.bbamem.2017.10.022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Revised: 10/23/2017] [Accepted: 10/24/2017] [Indexed: 11/16/2022]
Abstract
We compared the lateral structure of giant unilamellar vesicles (GUVs) composed of three pseudo binary mixtures of different glycosphingolipid (GSL), i.e. sulfatide, asialo-GM1 or GM1, with POPC. These sphingolipids possess similar hydrophobic residues but differ in the size and charge of their polar head group. Fluorescence microscopy experiments using LAURDAN and DiIC18 show coexistence of micron sized domains in a molar fraction range that depends on the nature of the GSLs. In all cases, experiments with LAURDAN show that the membrane lateral structure resembles the coexistence of solid ordered and liquid disordered phases. Notably, the overall extent of hydration measured by LAURDAN between the solid ordered and liquid disordered membrane regions show marked similarities and are independent of the size of the GSL polar head group. In addition, the maximum amount of GSL incorporated in the POPC bilayer exhibits a strong dependence on the size of the GSL polar head group following the order sulfatide>asialo-GM1>GM1. This observation is in full harmony with previous experiments and theoretical predictions for mixtures of these GSL with glycerophospholipids. Finally, compared with previous results reported in GUVs composed of mixtures of POPC with the sphingolipids cerebroside and ceramide, we observed distinctive curvature effects at particular molar fraction regimes in the different mixtures. This suggests a pronounced effect of these GSL on the spontaneous curvature of the bilayer. This observation may be relevant in a biological context, particularly in connection with the highly curved structures found in neural cells.
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Affiliation(s)
- Pablo M Rodi
- MEMPHYS - Center for Biomembrane Physics, Denmark; Departamento de Física, Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Argentina
| | - Bruno Maggio
- Departamento de Química Biológica-CIQUIBIC, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Argentina
| | - Luis A Bagatolli
- MEMPHYS - Center for Biomembrane Physics, Denmark; Yachay EP/Yachay Tech University, San Miguel de Urcuqui, Ecuador.
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Honke K. Biological functions of sulfoglycolipids and the EMARS method for identification of co-clustered molecules in the membrane microdomains. J Biochem 2017; 163:253-263. [DOI: 10.1093/jb/mvx078] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2017] [Accepted: 09/03/2017] [Indexed: 01/24/2023] Open
Affiliation(s)
- Koichi Honke
- Department of Biochemistry, Kochi University Medical School, Kohasu, Oko-cho, Nankoku, Kochi 783–8505, Japan
- Center for Innovative and Translational Medicine, Kochi University Medical School, Kohasu, Oko-cho, Nankoku, Kochi 783–8505, Japan
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Hasan IY, Mechler A. Analytical approaches to study domain formation in biomimetic membranes. Analyst 2017; 142:3062-3078. [PMID: 28758651 DOI: 10.1039/c7an01038a] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Novel characterization methods open new horizons in the study of membrane mixtures.
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Affiliation(s)
- Imad Younus Hasan
- La Trobe Institute for Molecular Science
- La Trobe University
- Melbourne
- Australia
| | - Adam Mechler
- La Trobe Institute for Molecular Science
- La Trobe University
- Melbourne
- Australia
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Grassi S, Prioni S, Cabitta L, Aureli M, Sonnino S, Prinetti A. The Role of 3-O-Sulfogalactosylceramide, Sulfatide, in the Lateral Organization of Myelin Membrane. Neurochem Res 2015; 41:130-43. [DOI: 10.1007/s11064-015-1747-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2015] [Revised: 10/22/2015] [Accepted: 10/24/2015] [Indexed: 12/12/2022]
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7
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Peter Slotte J. Molecular properties of various structurally defined sphingomyelins -- correlation of structure with function. Prog Lipid Res 2013; 52:206-19. [PMID: 23295259 DOI: 10.1016/j.plipres.2012.12.001] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2012] [Revised: 12/20/2012] [Accepted: 12/21/2012] [Indexed: 01/10/2023]
Abstract
Sphingomyelins are important phospholipids in plasma membranes of most cells. Because of their dominantly saturated nature, they affect the lateral structure of membranes, and contribute to the regulation of cholesterol distribution within membranes, and in cells. However, the abundance of molecular species present in cells also implies that sphingomyelins have other, more specific functions. Many of these functions are currently unknown, but are under extensive study. Mostly model membrane studies have shown that sphingomyelins (and other sphingolipids), in contrast to glycerophospholipids, have important hydrogen bonding properties which in several important ways confer specific functional properties to this abundant class of membrane phospholipids. The often very asymmetric nature of sphingomyelins, arising from mismatch in length between the long chain base and N-acyl chains, also impose specific properties (e.g., interdigitation) to sphingomyelins not seen with glycerophospholipids. In this review, the latest sphingomyelin literature will be scrutinized, and an effort will be made to correlate the molecular structure of sphingomyelin with functional properties. In particular, the effects of head group properties, interfacial hydrogen bonding, long chain base hydroxylation, N-acyl chain hydroxylation, and N-acyl chain methyl-branching will be discussed.
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Affiliation(s)
- J Peter Slotte
- Biochemistry, Department of Biosciences, Åbo Akademi University, Tykistökatu 6A, 20520 Turku, Finland.
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9
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Peters GH, Hansen FY, Møller MS, Westh P. Effects of Fatty Acid Inclusion in a DMPC Bilayer Membrane. J Phys Chem B 2008; 113:92-102. [DOI: 10.1021/jp806205m] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Günther H. Peters
- Department of Chemistry, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark; Department of Life Sciences and Chemistry, Roskilde University, 4000 Roskilde, Denmark; and MEMPHYS-Center for Biomembrane Physics
| | - Flemming Y. Hansen
- Department of Chemistry, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark; Department of Life Sciences and Chemistry, Roskilde University, 4000 Roskilde, Denmark; and MEMPHYS-Center for Biomembrane Physics
| | - Martin S. Møller
- Department of Chemistry, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark; Department of Life Sciences and Chemistry, Roskilde University, 4000 Roskilde, Denmark; and MEMPHYS-Center for Biomembrane Physics
| | - Peter Westh
- Department of Chemistry, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark; Department of Life Sciences and Chemistry, Roskilde University, 4000 Roskilde, Denmark; and MEMPHYS-Center for Biomembrane Physics
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Carrer DC, Schreier S, Patrito M, Maggio B. Effects of a short-chain ceramide on bilayer domain formation, thickness, and chain mobililty: DMPC and asymmetric ceramide mixtures. Biophys J 2006; 90:2394-403. [PMID: 16428286 PMCID: PMC1403173 DOI: 10.1529/biophysj.105.074252] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
An important part of natural ceramides contain asymmetric hydrocarbon chains. We have used calorimetry, atomic force microscopy, and electron paramagnetic resonance to study the effect of ceramide chain asymmetry in mixtures of C8Cer with DMPC as a model system of hydrocarbon chain disparity. A phase diagram is provided along with information on the thickness of the membrane and the mobility of the chains at different temperatures both below and above the phase transition temperature of the mixtures. The results indicate a partial interdigitation of C8Cer chains in the gel phase, producing a correlation between the organization of both hemilayers. Our data suggest that the effects of ceramides on biomembranes may be bimodal and similar to those of cholesterol.
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Affiliation(s)
- Dolores C Carrer
- Departamento de Química Biológica-CIQUIBIC, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina.
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Abstract
There is a growing awareness of the utility of lipid phase behavior data in studies of membrane-related phenomena. Such miscibility information is commonly reported in the form of temperature-composition (T-C) phase diagrams. The current index is a conduit to the relevant literature. It lists lipid phase diagrams, their components and conditions of measurement, and complete bibliographic information. The main focus of the index is on lipids of membrane origin where water is the dispersing medium. However, it also includes records on acylglycerols, fatty acids, cationic lipids, and detergent-containing systems. The miscibility of synthetic and natural lipids with other lipids, with water, and with biomolecules (proteins, nucleic acids, carbohydrates, etc.) and non-biological materials (drugs, anesthetics, organic solvents, etc.) is within the purview of the index. There are 2188 phase diagram records in the index, the bulk (81%) of which refers to binary (two-component) T-C phase diagrams. The remainder is made up of more complex (ternary, quaternary) systems, pressure-T phase diagrams, and other more exotic miscibility studies. The index covers the period from 1965 through to July, 2001.
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Affiliation(s)
- Rumiana Koynova
- Biochemistry, Biophysics, Chemistry, The Ohio State University, 100 West 18th Avenue, Columbus, OH 43210, USA
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12
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Attar M, Kates M, Bou Khalil M, Carrier D, Wong PT, Tanphaichitr N. A Fourier-transform infrared study of the interaction between germ-cell specific sulfogalactosylglycerolipid and dimyristoylglycerophosphocholine. Chem Phys Lipids 2000; 106:101-14. [PMID: 10930563 DOI: 10.1016/s0009-3084(00)00147-x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In this study, we investigated structural and dynamic changes of sulfogalactosylglycerolipid (SGG) and dimyristoylglycerophosphocholine (DMPC) in a liposomal system (SGG+DMPC, molar ratio 2:3) by Fourier-transform infrared (FTIR) spectroscopy. Cooling of the preheated SGG liposomes (5-65 degrees C) revealed that the liquid crystalline-to-gel phase transition was centered at 45 degrees C. SGG+DMPC liposomes showed a single phase transition at 28 degrees C. Spectral changes of the ester C&z. dbnd6;O groups of SGG and DMPC in the mixed liposomes indicated a decrease in their interfacial hydrogen bonding intermolecularly and with water. Analysis of SGG's symmetric and antisymmetric CH(2) stretching bands revealed that the insertion of DMPC into SGG bilayers increased the number of gauche conformers in SGG's hydrocarbon chains. Overall, the SGG+DMPC liposomes were homogeneous, with reduced interfacial hydrogen bonding and increased orientational and conformational disorder of SGG's hydrocarbon chains.
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Affiliation(s)
- M Attar
- Hormones/Growth/Development Research Group, Loeb Health Research Institute, 725 Parkdale Avenue, K1Y 4E9, Ottawa, Ont., Canada
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Verstraeten SV, Keen CL, Golub MS, Oteiza PI. Membrane composition can influence the rate of Al3+-mediated lipid oxidation: effect of galactolipids. Biochem J 1998; 333 ( Pt 3):833-8. [PMID: 9677347 PMCID: PMC1219651 DOI: 10.1042/bj3330833] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
In the first part of the present study we investigated the effects of pre-natal and early postnatal exposure of mice to high levels of dietary Al3+ on myelin lipid composition and lipid oxidation. We found: (1) a significantly higher (104%; P<0.01) content of brain myelin galactolipids in the high-Al3+ group than in controls, and, (2) a significant correlation (r2=0.70; P<0.01) between the concentration of myelin galactolipids and TBARS (2-thiobarbituric acid-reactive substances) content, a parameter of lipid oxidation. Based on these results, we evaluated in an in vitro model (liposomes) whether galactolipids could affect the capacity of Al3+ to stimulate Fe2+-initiated lipid oxidation, and whether this effect could be due to the promotion of changes in membrane physical properties (membrane phase separation and rigidification). The presence of galactolipids (10-40 mol%) in the liposomes caused a concentration-dependent increase in the stimulatory effect of Al3+ on Fe2+-induced TBARS production, and on the ability of Al3+ to induce phase separation and membrane rigidification. The capacity of Al3+ (10-100 microM) to induce lateral phase separation in liposomes composed of phosphatidylcholine/phosphatidylserine/galactolipid (36:24:40, molar ratio) was correlated significantly (r2=0.99; P<0. 001) with the stimulatory action of Al3+ on Fe2+-induced TBARS production. We propose that the high content of galactolipids found in myelin from Al3+-intoxicated mice could favour Al3+-induced changes in membrane physical properties, with the subsequent acceleration of lipid oxidation rates.
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Affiliation(s)
- S V Verstraeten
- Department of Biological Chemistry-IQUIFIB (UBA-CONICET), School of Pharmacy and Biochemistry, University of Buenos Aires, Junín 956, 1113 Buenos Aires, Argentina
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Attar M, Wong PT, Kates M, Carrier D, Jaklis P, Tanphaichitr N. Interaction between sulfogalactosylceramide and dimyristoylphosphatidylcholine increases the orientational fluctuation of their lipid hydrocarbon chains. Chem Phys Lipids 1998; 94:227-38. [PMID: 9779587 DOI: 10.1016/s0009-3084(98)00057-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The objective of this study was to investigate the interaction between sulfogalactosylceramide (SGC) and dimyristoylphosphatidylcholine (DMPC) in a mixed model liposomal system (molar ratio SGC:DMPC, 2:3). Structural and dynamic changes of the liposome components were monitored by Fourier-transform infrared spectroscopy (FTIR). Thermotropic FTIR analysis of the mixed liposomes showed a single gel/liquid crystalline phase transition, centered at approximately 42 degrees C. Spectral changes of the amide and ester C = O bands arising from functional groups at the interfacial region indicated a reduced hydrogen bonding of these groups in the mixed liposomes. Pressure-tuning FTIR of mixed liposomes showed that the methylene chains of SGC and DMPC were more orientationally disordered than those of the individual lipid SGC liposomes or DMPC liposomes. These results suggest that the mixed liposomes (molar ratio SGC:DMPC, 2:3) consisted of a homogeneous mixture of SGC and DMPC molecules in which mutual shielding reduced hydrogen bonding in the interfacial region, with a concurrent increase in the orientational disorder of the hydrocarbon chains of both SGC and DMPC.
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Affiliation(s)
- M Attar
- Hormone Growth and Development Research Group, Loeb Medical Research Institute, Ottawa, Ont., Canada
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Boggs JM, Koshy KM. Do the long fatty acid chains of sphingolipids interdigitate across the center of a bilayer of shorter chain symmetric phospholipids? BIOCHIMICA ET BIOPHYSICA ACTA 1994; 1189:233-41. [PMID: 8292629 DOI: 10.1016/0005-2736(94)90070-1] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Novel cerebroside sulfate (CBS) spin labels containing long chain C24 or C26 fatty acids with a nitroxide spin label on the 22nd carbon were synthesized and used to investigate the ability of the long fatty acid chains of glycosphingolipids to interdigitate across the center of a non-interdigitated bilayer of phospholipids formed of symmetric saturated or unsaturated shorter fatty acid chain species, in the presence or absence of cholesterol. The motion of these long chain spin labels incorporated at 1 mole% in dimyristoylphosphatidylcholine (diC14-PC), dipalmitoylphosphatidylcholine (diC16-PC), distearoylphosphatidylcholine (diC18-PC), dibehenoylphosphatidylcholine (diC22-PC), spingomyelin (SM), 1-stearoyl-2-oleoylphosphatidylcholine (18:0.18:1-PC), and dimyristoylphosphatidylethanolamine (diC14-PE) was compared to that of CBS spin labels containing stearic acid spin labeled at the 5th carbon and at the 16th carbon. The results indicated that the C26 chain is interdigitated in the gel phase of diC14-PC, diC16-PC, SM, and possibly diC18-PC, but not diC14-PE, and the C24 chain may interdigitate in diC14-PC but not in the other phospholipids. Thus in order to interdigitate across the center of gel phase bilayers, the long acyl chain of the sphingolipid probably must be long enough to nearly span the phospholipid bilayer. The inability to interdigitate in diC14-PE is likely due to the close packing of this lipid in the gel phase. The C26 chain may also be interdigitated in these lipids in the presence of cholesterol at low temperatures. However, at physiological temperatures in the presence of cholesterol and in the liquid-crystalline phase of all the lipids, the results indicate that the long acyl chain of the glycosphingolipid is not interdigitated, but rather must terminate at the bilayer center. This may force the carbohydrate headgroup of the glycosphingolipid farther above the bilayer surface, allowing it to be recognized better by various carbohydrate binding ligands and proteins.
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Affiliation(s)
- J M Boggs
- Department of Biochemistry, Hospital for Sick Children, Toronto, Ontario, Canada
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