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Chemical Gradients Trigger and Guide Movement of Giant Lipid Vesicles
376a
Tuesday, February 14, 2017
values of donor and acceptor probes. Since FRET depends on the distance between donors and acceptors, and this distance depends upon the domain size, this study makes possible the measurement of nanodomain size. We found domain sizes of 10.0 5 2.5 nm of radius for nanodomains in DSPC/POPC/ Chol and bSM/POPC/Chol. 1853-Pos Board B173 Chemical Gradients Trigger and Guide Movement of Giant Lipid Vesicles Baharan Ali Doosti, Tatsiana Lobovkina. Chalmers, Gothenburg, Sweden. Directed cell movement is one of the central biological processes, and is vital for early embryonic development, wound healing, and spreading of cancer. Migration of cells is often directed by chemical signals and involves various cell components. The cytoskeleton and proteins in the membrane are featured as the key players. However, little is known about the response of lipids to chemical cues. To address this question, we used giant lipid vesicles as the cell membrane model system, that were deposited on a glass substrate. We show that chemical gradients trigger and guide the movement of entire lipid vesicles, mimicking the cell body translocation. Our results are important for understanding the membrane response during migratory cell behavior. 1854-Pos Board B174 Modeling Tissue Specific Plasma Membranes in Silico Helgi I. Ingolfsson, Timothy S. Carpenter, Felice C. Lightstone. Lawrence Livermore National Laboratory, Livermore, CA, USA. The detailed lipid organization of cellular membranes remains rather elusive. A typical plasma membrane contains hundreds of different lipid species that are actively regulated by the cell. This is far greater diversity than is needed to maintain bilayer barrier properties and to solvate membrane proteins. Marked differences are found in the lipids composition of different cells and tissue types. How do these tissue specific differences affect the overall lipid organization or the average bilayer properties? We start to address these questions by modeling biologically realistic plasma membranes (PM) from different tissues using coarse-grained Martini molecular dynamics simulations. Lipidomics literature for both whole cell and PM fractions was explored and characteristic differences between different tissues identified. Biologically realistic idealized PMs for a few tissue types were constructed based on their identified differences and previous simulation work on an idealized mammalian membrane (Ingo´lfsson, et al. Lipid organization of the plasma membrane. JACS, 136:14554-14559, 2014). Multiple large-scale simulations (multi microsecond long and ~0.1 square micron large) were preformed; providing a high-resolution view of the lipid organization of these different bilayers. We analyzed a variety of membrane physicochemical properties, including: lipid-lipid interactions, bilayer bulk material properties, domain formation and coupling between the bilayer leaflets, and evaluate the main differences between the different tissue types. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC5207NA27344. Release number: LLNL-ABS-703500. 1855-Pos Board B175 Phospholipid Head Groups Provide Differentially Stable Membrane Environments for Vitamin E Andres T. Cavazos, Michaela E. Bell, Zachary L. Leach, Jacob J. Kinnun, Stephen R. Wassall. Department of Physics, IUPUI, Indianapolis, IN, USA. Vitamin E (a-tocopherol) is a lipid-soluble antioxidant that has a primary role of protecting phospholipids from oxidation in membranes. Whether there is preferential interaction between a-tocopherol and specific phospholipids to optimize this function has been a longstanding question. Here we compare the effect of a-tocopherol on the molecular organization of two oleic acid-containing phospholipids, 1-palmitoyl-2-oleoyl-sn-glycerophosphatidylethanolamine (16:0-18:1PE, POPE) and 1-palmitoyl-2-oleoyl-sn-glycerophosphatidylcholine (16:0-18:1PC, POPC) in mixtures with 5, 10 and 20 mol % a-tocopherol. By solid-state 2H NMR spectroscopy, we directly observed POPC-d31 and POPE-d31 (analogs of POPC and POPE with a perdeuterated sn-1 chain) in the mixed membranes. The spectra observed with POPE-d31 in the presence of a-tocopherol consist of a superposition of two spectral components that we ascribe to a-tocopherol promoting a transition from lamellar (La) to inverted hexagonal (HII) phase. This transition is not observed in mixtures of POPC-d31 with a-tocopherol where only a single spectral component due to the La phase was recorded. The molecular origin of the differential in bilayer stability between POPE and POPC will be discussed in terms of head group spacing and the ability to accommodate a-tocopherol.
1856-Pos Board B176 Physical Chemical Properties of Silver Nanoparticles Stabilized with Polyether-Block-Amide Interacting with Cellular Membrane Models at the Air-Water Interface Luciano Caseli, Gustavo B. Soriano, Roselaine S. Oliveira, Fernanda F. Camilo. Ciencias Exatas e da Terra, Universidade Federal de Sao Paulo, Diadema-SP, Brazil. It is known that silver nanoparticles can be applied as antimicrobial agent, used in hygiene and surgical products. However, the molecular mechanism by which they act in the plasma membrane and in the cell wall is not completely understood in detail. For this reason, it is relevant to find models by which studying such interactions is possible. One of these models is the formation of lipid Langmuir monolayers at the air-water interface, in which half a membrane can be mimicked with good control of the chemical composition, surface density and viscoelasticity parameters. In this present work, we investigated the interaction between silver nanoparticles stabilized with polyether-block-amide (PEBA) dispersed in 1-butyl alcohol with Langmuir monolayers of dipalmitoyl phosphatidyl choline (DPPC). The interaction was investigated with surface pressure-area isotherms, polarization modulation infrared reflection-absorption spectroscopy (PM-IRRAS), and Brewster angle microscopy (BAM). The nanoparticles expanded the DPPC monolayers, and changed the hydrophobic bands of the lipid observed in the vibrational spectra. Data of BAM show the formation of aggregates due to insertion of the nanoparticles. These behaviors found for the mixed monolayer are probably attributed to the high surface activity of the nanoparticles. However, in the absence of the lipid, there is no formation of real Langmuir film of the nanoparticles, being its surface activity governed by a dynamic process of adsorption and desorption during the compression and the rearrangement of the molecular system of the metallic nanoparticle and the stabilizing agent (PEBA), leading the formation of aggregates. We believe these results can provide an interesting clue to understand the role of the nanoparticle and stabilizing agent on its possible action against microbial cellular membranes. 1857-Pos Board B177 Membrane Permeation of Gasotransmitters Christopher N. Rowley. Department of Chemistry, Memorial University of Newfoundland, St. John’s, NL, Canada. NO, CO, and H2S are endogenous gasotransmitters. Using the solubility-diffusion model [1], we calculated the membrane permeability of these molecules across model bilayers using molecular dynamics simulations. Replica exchange MD [2] and Generalized Langevin methods [3] were used to calculate the potential of mean force and diffusion coefficient profile of permeation, respectively. The membrane permeability of these compounds were all predicted to be very high (> 1 cm/s) [4], indicating these molecules can cross membranes freely. Hydrophobicity and high diffusivity are consistent features of the gasotransmitters, which allows them to reach their intracellular targets quickly. [1] Awoonor-Williams, Rowley BBA - Biomembranes, 2016, doi: 10.1016/ j.bbamem.2015.12.014 [2] Lee, C., et al. J. Chem. Inf. Model. 2016 doi: 10.1021/acs.jcim.6b00022 [3] Gaalswyk, K., Awoonor-Williams, E., Rowley, C. N., J. Chem. Theory Comput. 2016, doi: 10.1021/acs.jctc.6b00747 [4] Riahi, S., Rowley C.N. J. Am. Chem. Soc. 2014, doi: 10.1021/ja508063s 1858-Pos Board B178 Effects of Ester and Ether Linkage in Phospholipids on Ld D Lo Domain Size Transition for a Four-Component Lipid Bilayer Mixture Wen-Chyan Tsai, Gerald W. Feigenson. Molecular Biology and Genetics, Cornell University, Ithaca, NY, USA. A coexisting liquid disordered (Ld) and liquid ordered (Lo) region in the fourcomponent bilayer mixture, distearoyl-phosphatidylcholine/dioleoyl-phosphatidylcholine/stearoyl-oleoyl-phosphatidylcholine/cholesterol (DSPC/DOPC/ SOPC/CHOL), displays a transition from nanoscopic to macroscopic lipid domains. Giant unilamellar vesicles (GUVs) were generated using the electroformation technique and visualized with an inverted fluorescent microscope. C12:0-DiI (0.02 mol%), partitioning into the Ld phase, was used for visualization of lipid domain patterns. At mole fraction 0.45/0.31/0.24 = DSPC/ (DOPCþSOPC)/CHOL, a transition was observed by tuning the compositional ratio of DOPC to SOPC from 0.25 to 0.6. The influence of phospholipid ether linkages on the domain size transition is elucidated using ether-linked DSPC and DOPC in the four-lipid mixture. Our goal is to evaluate the influence due to varying dipole-dipole repulsion in the phospholipid membrane containing ester vs ether-linked phospholipids. The results presented in the study
Tuesday, February 14, 2017
values of donor and acceptor probes. Since FRET depends on the distance between donors and acceptors, and this distance depends upon the domain size, this study makes possible the measurement of nanodomain size. We found domain sizes of 10.0 5 2.5 nm of radius for nanodomains in DSPC/POPC/ Chol and bSM/POPC/Chol. 1853-Pos Board B173 Chemical Gradients Trigger and Guide Movement of Giant Lipid Vesicles Baharan Ali Doosti, Tatsiana Lobovkina. Chalmers, Gothenburg, Sweden. Directed cell movement is one of the central biological processes, and is vital for early embryonic development, wound healing, and spreading of cancer. Migration of cells is often directed by chemical signals and involves various cell components. The cytoskeleton and proteins in the membrane are featured as the key players. However, little is known about the response of lipids to chemical cues. To address this question, we used giant lipid vesicles as the cell membrane model system, that were deposited on a glass substrate. We show that chemical gradients trigger and guide the movement of entire lipid vesicles, mimicking the cell body translocation. Our results are important for understanding the membrane response during migratory cell behavior. 1854-Pos Board B174 Modeling Tissue Specific Plasma Membranes in Silico Helgi I. Ingolfsson, Timothy S. Carpenter, Felice C. Lightstone. Lawrence Livermore National Laboratory, Livermore, CA, USA. The detailed lipid organization of cellular membranes remains rather elusive. A typical plasma membrane contains hundreds of different lipid species that are actively regulated by the cell. This is far greater diversity than is needed to maintain bilayer barrier properties and to solvate membrane proteins. Marked differences are found in the lipids composition of different cells and tissue types. How do these tissue specific differences affect the overall lipid organization or the average bilayer properties? We start to address these questions by modeling biologically realistic plasma membranes (PM) from different tissues using coarse-grained Martini molecular dynamics simulations. Lipidomics literature for both whole cell and PM fractions was explored and characteristic differences between different tissues identified. Biologically realistic idealized PMs for a few tissue types were constructed based on their identified differences and previous simulation work on an idealized mammalian membrane (Ingo´lfsson, et al. Lipid organization of the plasma membrane. JACS, 136:14554-14559, 2014). Multiple large-scale simulations (multi microsecond long and ~0.1 square micron large) were preformed; providing a high-resolution view of the lipid organization of these different bilayers. We analyzed a variety of membrane physicochemical properties, including: lipid-lipid interactions, bilayer bulk material properties, domain formation and coupling between the bilayer leaflets, and evaluate the main differences between the different tissue types. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC5207NA27344. Release number: LLNL-ABS-703500. 1855-Pos Board B175 Phospholipid Head Groups Provide Differentially Stable Membrane Environments for Vitamin E Andres T. Cavazos, Michaela E. Bell, Zachary L. Leach, Jacob J. Kinnun, Stephen R. Wassall. Department of Physics, IUPUI, Indianapolis, IN, USA. Vitamin E (a-tocopherol) is a lipid-soluble antioxidant that has a primary role of protecting phospholipids from oxidation in membranes. Whether there is preferential interaction between a-tocopherol and specific phospholipids to optimize this function has been a longstanding question. Here we compare the effect of a-tocopherol on the molecular organization of two oleic acid-containing phospholipids, 1-palmitoyl-2-oleoyl-sn-glycerophosphatidylethanolamine (16:0-18:1PE, POPE) and 1-palmitoyl-2-oleoyl-sn-glycerophosphatidylcholine (16:0-18:1PC, POPC) in mixtures with 5, 10 and 20 mol % a-tocopherol. By solid-state 2H NMR spectroscopy, we directly observed POPC-d31 and POPE-d31 (analogs of POPC and POPE with a perdeuterated sn-1 chain) in the mixed membranes. The spectra observed with POPE-d31 in the presence of a-tocopherol consist of a superposition of two spectral components that we ascribe to a-tocopherol promoting a transition from lamellar (La) to inverted hexagonal (HII) phase. This transition is not observed in mixtures of POPC-d31 with a-tocopherol where only a single spectral component due to the La phase was recorded. The molecular origin of the differential in bilayer stability between POPE and POPC will be discussed in terms of head group spacing and the ability to accommodate a-tocopherol.
1856-Pos Board B176 Physical Chemical Properties of Silver Nanoparticles Stabilized with Polyether-Block-Amide Interacting with Cellular Membrane Models at the Air-Water Interface Luciano Caseli, Gustavo B. Soriano, Roselaine S. Oliveira, Fernanda F. Camilo. Ciencias Exatas e da Terra, Universidade Federal de Sao Paulo, Diadema-SP, Brazil. It is known that silver nanoparticles can be applied as antimicrobial agent, used in hygiene and surgical products. However, the molecular mechanism by which they act in the plasma membrane and in the cell wall is not completely understood in detail. For this reason, it is relevant to find models by which studying such interactions is possible. One of these models is the formation of lipid Langmuir monolayers at the air-water interface, in which half a membrane can be mimicked with good control of the chemical composition, surface density and viscoelasticity parameters. In this present work, we investigated the interaction between silver nanoparticles stabilized with polyether-block-amide (PEBA) dispersed in 1-butyl alcohol with Langmuir monolayers of dipalmitoyl phosphatidyl choline (DPPC). The interaction was investigated with surface pressure-area isotherms, polarization modulation infrared reflection-absorption spectroscopy (PM-IRRAS), and Brewster angle microscopy (BAM). The nanoparticles expanded the DPPC monolayers, and changed the hydrophobic bands of the lipid observed in the vibrational spectra. Data of BAM show the formation of aggregates due to insertion of the nanoparticles. These behaviors found for the mixed monolayer are probably attributed to the high surface activity of the nanoparticles. However, in the absence of the lipid, there is no formation of real Langmuir film of the nanoparticles, being its surface activity governed by a dynamic process of adsorption and desorption during the compression and the rearrangement of the molecular system of the metallic nanoparticle and the stabilizing agent (PEBA), leading the formation of aggregates. We believe these results can provide an interesting clue to understand the role of the nanoparticle and stabilizing agent on its possible action against microbial cellular membranes. 1857-Pos Board B177 Membrane Permeation of Gasotransmitters Christopher N. Rowley. Department of Chemistry, Memorial University of Newfoundland, St. John’s, NL, Canada. NO, CO, and H2S are endogenous gasotransmitters. Using the solubility-diffusion model [1], we calculated the membrane permeability of these molecules across model bilayers using molecular dynamics simulations. Replica exchange MD [2] and Generalized Langevin methods [3] were used to calculate the potential of mean force and diffusion coefficient profile of permeation, respectively. The membrane permeability of these compounds were all predicted to be very high (> 1 cm/s) [4], indicating these molecules can cross membranes freely. Hydrophobicity and high diffusivity are consistent features of the gasotransmitters, which allows them to reach their intracellular targets quickly. [1] Awoonor-Williams, Rowley BBA - Biomembranes, 2016, doi: 10.1016/ j.bbamem.2015.12.014 [2] Lee, C., et al. J. Chem. Inf. Model. 2016 doi: 10.1021/acs.jcim.6b00022 [3] Gaalswyk, K., Awoonor-Williams, E., Rowley, C. N., J. Chem. Theory Comput. 2016, doi: 10.1021/acs.jctc.6b00747 [4] Riahi, S., Rowley C.N. J. Am. Chem. Soc. 2014, doi: 10.1021/ja508063s 1858-Pos Board B178 Effects of Ester and Ether Linkage in Phospholipids on Ld D Lo Domain Size Transition for a Four-Component Lipid Bilayer Mixture Wen-Chyan Tsai, Gerald W. Feigenson. Molecular Biology and Genetics, Cornell University, Ithaca, NY, USA. A coexisting liquid disordered (Ld) and liquid ordered (Lo) region in the fourcomponent bilayer mixture, distearoyl-phosphatidylcholine/dioleoyl-phosphatidylcholine/stearoyl-oleoyl-phosphatidylcholine/cholesterol (DSPC/DOPC/ SOPC/CHOL), displays a transition from nanoscopic to macroscopic lipid domains. Giant unilamellar vesicles (GUVs) were generated using the electroformation technique and visualized with an inverted fluorescent microscope. C12:0-DiI (0.02 mol%), partitioning into the Ld phase, was used for visualization of lipid domain patterns. At mole fraction 0.45/0.31/0.24 = DSPC/ (DOPCþSOPC)/CHOL, a transition was observed by tuning the compositional ratio of DOPC to SOPC from 0.25 to 0.6. The influence of phospholipid ether linkages on the domain size transition is elucidated using ether-linked DSPC and DOPC in the four-lipid mixture. Our goal is to evaluate the influence due to varying dipole-dipole repulsion in the phospholipid membrane containing ester vs ether-linked phospholipids. The results presented in the study