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1
Johnson, Benjamin Robert Grant. "Biomimetic scaffolds for phospholipid bilayers." Thesis, University of Leeds, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.417752.
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Ries, Ryan Scott. "Molecular thin films phospholipid bilayers and biosensors /." Diss., Restricted to subscribing institutions, 2004. http://proquest.umi.com/pqdweb?did=795970741&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Goodchild, James Andrew. "Interleaflet and substrate coupling in phospholipid bilayers." Thesis, University of Leeds, 2018. http://etheses.whiterose.ac.uk/22739/.
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Since the existence of lateral organisation in the cell membrane was first proposed by Erwin London in 1997, much has been discovered about the complex behaviour of lipid bilayers. Whilst some membrane proteins involved in signalling are almost as mobile as lipid molecules, such as the photoreceptor protein rhodopsin, others such as the peripheral glycoprotein fibronectin are virtually static. This has been linked to the existence of phase separated micro-domains, sometimes known as lipid rafts, in model systems. However, there are still many open questions, including the effect of asymmetry and curvature on bilayers. Domains in the two leaflets of a model bilayer always align, or register. Conversely, the plasma membrane is asymmetric in composition, which implies that different phases can exist across the bilayer midplane, known as anti-registration. Hydrophobic mismatch at phase boundaries should favour a fully anti-registered bilayer in model systems, implying an interleaflet coupling force drives registration. In this thesis, hydrophobic mismatch between phases is controlled, with anti-registered domains forming at a mismatch of 8 carbons per leaflet. A coupling free energy of 0.021 kBT/nm2 was determined, in close agreement with the only other experimental study using a different methodology, and refining the values found via simulation. Methods are explored to induce anti-registration with lower mismatch, and to characterise the orientation of the anti-registered states. Arising from this work is a greater understanding of how substrate choice for supported bilayers greatly affects phase behaviour. Glass, used in fluorescence microscopy experiments, and PDMS (Polydimethylsiloxane), used to create flexible and curved bilayer substrates, result in nanoscale domain formation compared to micro-scale domains on atomically flat mica. This difference is investigated and it is found that the hydrodynamic motion of domains is hindered by rougher substrates, having great implications for the study and understanding of supported lipid bilayers.
4
Graham, Ian Stanley. "Experimental and theoretical investigations of charged phospholipid bilayers." Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=75664.
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Lipid systems containing charged species are examined by both experiment and theory. Experimental studies of the mixing of phosphatidylcholine or phosphatidylethanolamine with phosphatidic acid show that calcium induces fast ($ leq$1s) phase separation of these otherwise miscible systems, and that this can occur in an isolated bilayer. Ionogenic behaviour is theoretically investigated using a new electrolyte model which explicitly includes both the solvent and particle sizes, and a binding model which uses Guggenheim combinatorics to treat non 1-1 binding stoichiometries. This work predicts a reduced dielectric constant near charged surfaces and strong repulsive forces between closely spaced ($<$15A) surfaces. A reanalysis of data from charged monolayers experiments indicates (1) that the new electrolyte model describes double layer behaviour at high surface charge densities better than the traditional Derjaguin - Landau - Verwey - Overbeek (DLVO) theory, (2) that calcium and magnesium bind to phosphatidylserine monolayers with a 1-1 stoichiometry.
5
Ross, Eric E. "Stabilized supported lipid bilayers from polymerizable phospholipid monomers." Diss., The University of Arizona, 2003. http://hdl.handle.net/10150/280498.
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Lipid films are often described as potential surface coatings for the 'biofunctionalization' of solid interfaces because of the ability to support tethered and integrated receptor protein activity and their ability to suppress the non-specific adsorption of soluble proteins. One significant shortcoming of lipid assemblies is the inherent lack of stability required for many technological applications because the non-covalent forces between the constituent lipids are relatively weak. In this work, polymerized, supported lipid bilayers ((poly)PSLBs) composed of diene functionalized lipids have been prepared and characterized. Several parameters relating (poly)PSLB structure and stability to observations made in studies of polymerized bilayer vesicles will be described, including a comparison of UV photopolymerization and redox-initiated radical polymerization, the number and location of the polymerizable moieties in the lipid monomer, and a comparison to PSLBs produced with diacetylene lipids. Redox-initiated polymerization of films composed of bis-substituted diene lipids with at least one polymerizable moiety located near the acyl terminus produces dried PSLBs that are highly uniform and stable. All other conditions yielded PSLBs that contained a high density of defects after drying, including those formed from diacetylene lipids. The nonspecific adsorption of bovine serum albumin (BSA) is used to further characterize the polymer films to fluid PC bilayers, which have been established as protein adsorption "inert" surfaces. The results show that the protein resistance of a cross-linked (poly)PSLB composed of bis-sorbyl phosphatidylcholine (bis-SorbPC) is equivalent to that of a fluid PSLB composed of 1-palmitoyl-2-oleoylphosphatidylcholine (POPC), even after the former has been dried and rehydrated. Furthermore, the (poly)PSLB films can be formed in patterns or patterned with immobilized proteins by microprinting techniques which may facilitate their use in microarray detection schemes.
6
Barfoot, Richard Jonathan. "Minimal F-actin cytoskeletal systems for phospholipid bilayers." Thesis, University of Leeds, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.496553.
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Roscoe, Patricia Anne. "The binding of C2 domains to phospholipid bilayers." Thesis, University of Southampton, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.416909.
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Ng, Sarah S. "Rate dependent rupture of solid-supported phospholipid bilayers." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/35058.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2006.<br>Includes bibliographical references (leaves 29-31).<br>An experimental study on solid-supported phospholipid bilayers was performed in order to investigate rate-dependent behavior of force and probability of bilayer rupture. 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) solid-supported lipid bilayers were created on mica using vesicle fusion technique and then ruptured normal to the surface using a silicon nitride cantilever tip (radius#80nm). High resolution force spectroscopy was performed using the Molecular Force Probe (1D) to obtain force versus distance curves between the tip and substrate, varying the rate of penetration between a range of 250 nm/sec to 8.0 pm/sec. Statistical analysis was used to find distributions for average yield distance and yield force at different rates to find correlations in our data. Lastly, experimental data was compared to proposed theoretical models that describe rupture probability as a function of activation energy. A two yield force profile on approach was achieved with consistency at all rates. The yield forces occurred at statistical significant distances of around 4 nm and 9 nm, which are consistent with bond calculations of the phospholipid. However, no relationship was found between force and tip velocity within the range of experimentation.<br>(cont.) Because rupture occurred even at the lowest penetration rates, activation energy for bilayer rupture appears to be quite low. Moreover, this also suggests that standard atomic force microscopy imaging stimulates perturbation of the surface, leading to imprecise characterization. Further investigation into a larger range of tip velocities, as well as the role of tip radius on rupture probability are recommended for a greater quantitative understanding of solid-supported bilayers.<br>S.B.
9
Altawallbeh, Ghaith. "Endothelial Nitric Oxide Synthase on Nanoscale Phospholipid Bilayers." Cleveland State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=csu1480640206186696.
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Burley, Andrew. "Effects of composition on the properties of phospholipid bilayers." Thesis, University of Birmingham, 2013. http://etheses.bham.ac.uk//id/eprint/4055/.
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The composition of biological phospholipid membranes has a significant effect on many processes which is as yet poorly understood. Dimyristoyl-phosphatidyl-serine (DMPS) and dimystristoyl-phosphatidyl-ethanolamine (DMPE) are commonly found in cell membranes. The properties of supported bilayers composed of mixtures of these two phospholipids were investigated using electrochemical techniques, infrared spectroscopy and neutron reflectometry. Polarisation-modulated infrared reflectance spectroscopy investigations suggest that the lipid tail groups adopt one conform at 20% DMPS and a different conformation at 30% DMPS concentration in DMPE. Differential capacity measurements show that bilayers composed of 20% DMPS or less behave similarly to pure DMPE while at 40% DMPS concentrations or higher the bilayer behaves similarly to pure DMPS. Electrochemical impedance spectroscopy indicates that bilayers containing DMPS are more effective barriers to the passage of anions than DMPE bilayers: the opposite is true for cations. It is hypothesized that the negative charge residing on the DMPS head group plays a major role in these changes. Neutron reflectometry data indicate that a 10% DMPS bilayer gains water and finally detaches from the substrate when it is subjected to an increasing negative potential. These observations help explain the shape of the capacity curve with potential.
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Jaschonek, Stefan [Verfasser]. "Molecular simulations of reversible mechanical unfolding and of phospholipid bilayers / Stefan Jaschonek." Mainz : Universitätsbibliothek Mainz, 2017. http://d-nb.info/1137884843/34.
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Sharp, Jeffrey Michael. "Direct measurement of colloidal forces between biological particles and Langmuir phospholipid bilayers." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0011394.
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Madrid, Elena. "Electrochemical and spectroscopic studies of phospholipid bilayers supported on Au(111) electrodes." Thesis, University of Birmingham, 2012. http://etheses.bham.ac.uk//id/eprint/3651/.
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Electrochemistry and polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) measurements were used to characterize the structure and organization of a mimetic biological membrane supported at a Au(111) electrode surface to determine the influence of molecule structure on ensemble properties. Creation and deposition of mimetic membranes was carried out by combining Langmuir-Blodgett / Langmuir-Schaefer (LBLS) techniques. The LB-LS methodology allows the building of symmetric bilayers and more realistic systems based on a mixture of phospholipids that can be asymmetrically distributed across the bilayer. The phospholipids that have been studied in this work are DMPC, DMPE and DMPS. They differ from each other in the headgroup. However, they are all symmetric lipids with two saturated acyl chains of 14 carbon atoms. The electrochemical techniques have characterized the permeability of the film and have detected phase transitions of the lipids at the electrode. PM-IRRAS has provided information regarding the phase state, orientation of phospholipid acyl chains and degree of hydrogen bonding of the headgroup and glycerol region as the applied field was varied. Results have shown that DMPE bilayers contain less solvent content than DMPC and DMPS bilayers. DMPE molecules packed more tightly due to the hydrogen bonding network between the phosphate and the ammonium group of the neighbouring DMPE molecules which hinder the bilayer from hydration. The hydrocarbon chain orientation was less tilted from the surface normal than that of DMPC but very similar to DMPS at adsorption potentials. During desorption, DMPS has increased hydration of the carbonyl groups and the acyl chains tilted, increasing the compactness between them. The headgroups of DMPS remain hydrated, which increases the capacity of the bilayer.
14
Ringstad, Lovisa. "Interaction Between Antimicrobial Peptides and Phospholipid Membranes Effects of Peptide Length and Composition /." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-101989.
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Davis, Joseph E. "Refinement, validation, and application of a charge equilibration force field for simulations of phospholipid bilayers." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 67 p, 2009. http://proquest.umi.com/pqdweb?did=1885474371&sid=2&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Cardon, Thomas B. "X-band EPR Spectroscopy of Spin-labeled Membrane Biomolecules Incorporated into Magnetically Aligned Phospholipid Bilayers." Miami University / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=miami1154747640.
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Rashid, Ashi. "Studies of inorganic and organic interactions with supported and free standing phospholipid monolayers and bilayers." Thesis, University of Leeds, 2015. http://etheses.whiterose.ac.uk/10681/.
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The application of self-assembled monolayers on Hg in biosensor technology dictates the need to develop a thorough understanding of the system by using it to develop the structure-activity relations of biologically active compounds and upgrading the system to stable bilayer configurations on Hg. In this thesis four aspects of the properties of phospholipid layers on Hg in electric fields have been investigated as follows: (1) Effects of electrolyte ions on the potential-induced phase transitions exhibited by 1,2-dioleoyl phosphatidylcholine (DOPC) monolayer on hanging mercury drop electrode (HMDE) and mercury film electrode (MFE) are examined using alternating current voltammetry (ACV) and chronoamperometry. Results show that the underlying mechanism of phase transitions is affected by the concentration and sizes of electrolyte ions affecting the structure of electrical double layer at the lipid electrolyte and Hg electrolyte interface. (2) Fluorescence spectroscopic and electrochemical impedance techniques have been applied to study the interaction of substituted biphenyls with DOPC vesicles and Hg supported monolayers. The extent and type of interaction of substituted biphenyls with membrane models depends on the position and electron withdrawing/donating properties of substituents. (3) Electrochemical impedance used to study the interactions of small di- and tri-peptides of prebiotic relevance with DOPC monolayers on Hg shows that dispersion and electrostatic forces are responsible for interactions between DOPC monolayer and relatively apolar, and polar charged peptides respectively. In addition, an increase in their chain length causes an increase in DOPC/peptide interactions. (4) DOPC bilayers can be supported on HMDE and their lipid density varied by controlling the electrode area using RCV. The bilayer configurations are found less permeable than monolayers to aqueous Zn2+ at potentials positive to -1.2 V using chronoamperometry. Impedance studies have highlighted the ion movements into the DOPC bilayer as dielectric relaxation. Furthermore, silica nanoparticles have also been found to interact with bilayer configurations using RCV.
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Pinheiro, Teresa J. T. "The interaction of cytochrome c with anionic phospholipid bilayers : a nuclear and electron magnetic resonance study." Thesis, University of Oxford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333368.
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Adem, Seid Muhie. "DEVELOPMENT AND CHARACTERIZATION OF STABILIZED PHOSPHOLIPID COATINGS FOR OPEN TUBULAR AND PACKED CAPILLARY SEPARATIONS." Diss., The University of Arizona, 2010. http://hdl.handle.net/10150/204067.
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Phosphorylcholine (PC) based phospholipid bilayers have been explored as coating materials for various substrates due to their inherent resistance to non-specific protein adsorption. Phospholipids have been used for coatings in capillary electrophoresis (CE) to suppress electroosmotic flow (EOF) and to obtain better separation of proteins. Here, a series of investigations geared towards developing highly stable phospholipid based biomimetic stationary phases for chromatographic separations was performed.Fluid phospholipid bilayers lack the desired chemical and physical stability to serve as long-term coatings. In this work, highly stable phospholipid coatings generated via crosslinking polymerization of bis-SorbPC monomers were investigated. Reproducible EOF and migration times for model proteins were obtained for coated capillaries that were kept at room temperature for up to two months. Furthermore, the effects of surfactants, pH and capillary inner diameter (i.d.) on the stability of the lipid coating were investigated.In an alternate approach, stabilized phospholipid coatings for capillary electrophoresis were investigated via formation of hybrid monolayers. The capillary surface was chemically modified with a cyano group followed by deposition of phospholipid monomers. In this approach, marked enhancements in coating stability were attained with commercially available reagents. The hybrid coating was utilized for protein separations and gave efficiencies comparable to non-stabilized lipid coated capillaries.Fused silica capillaries were modified with phospholipid bilayers that were chemically tuned to introduce specific affinity binding agents, while minimizing nonspecific protein adsorption to the capillary wall. The wall of fused silica was functionalized with DOGS-NTA-Ni2+ lipid to present binding sites inside the capillary for 6xHis-tagged proteins. Fluorescence microscopy and changes in electrophoretic mobility were used to follow the interaction of the model proteins with the functionalized silica surface.The structural similarity of lipid vesicles to cell membranes made them attractive in developing stationary phases for both liquid chromatography and capillary electrophoresis to study interactions between analytes and phospholipid membranes. Stabilized PLB coated silica microspheres were prepared via polymerization of lipid monomers and displayed enhanced stability to extended storage and organic solvent. These highly stable microspheres, while minimizing nonspecific protein adsorption, were also functionalized with DOGS-NTA-Ni2+ and effectively bind 6xHis-EGFP proteins.
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Albertorio, Fernando. "Supported phospholipid membranes as biometric labs-on-a-chip: analytical devices that mimic cell membrane architectures and provide insight into the mechanism of biopreservation." Texas A&M University, 2003. http://hdl.handle.net/1969.1/5923.
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This dissertation focuses on the applications of solid supported phospholipid
membranes as mimics of the cellular membrane using lab-on-a-chip devices in order to
study biochemical events such as ligand-receptor binding and the chemical mechanism
for the preservation of the biomembrane. Supported lipid bilayers (SLBs) mimic the
native membrane by presenting the important property of two-dimensional lateral
fluidity of the individual lipid molecules within the membrane. This is the same
property that allows for the reorganization of native membrane components and
facilitates multivalent ligand-receptor interactions akin to immune response, cell
signaling, pathogen attack and other biochemical processes.
The study is divided into two main facets. The first deals with developing a
novel lipopolymer supported membrane biochip consisting of Poly(ethylene glycol)
(PEG)-lipopolymer incorporated membranes. The formation and characterization of the
lipopolymer membranes was investigated in terms of the polymer size, concentration
and molecular conformation. The lateral diffusion of the PEG-bilayers was similar to
the control bilayers. The air-stability conferred to SLBs was determined to be more effective when the PEG polymer was at, or above, the onset of the mushroom-to-brush
transition. The system is able to function even after dehydration for 24 hours. Ligandreceptor
binding was analyzed as a function of PEG density. The PEG-lipopolymer acts
as a size exclusion barrier for protein analytes in which the binding of streptavidin was
unaffected whereas the binding of the much larger IgG and IgM were either partially or
completely inhibited in the presence of PEG.
The second area of this study presents a molecular mechanism for in vivo
biopreservation by employing solid supported membranes as a model system. The
molecular mechanism of how a variety of organisms are preserved during stresses such
as anhydrobiosis or cryogenic conditions was investigated. We investigated the
interaction of two disaccharides, trehalose and maltose with the SLBs. Trehalose was
found to be the most effective in preserving the membrane, whereas maltose exhibited
limited protection. Trehalose lowers the lipid phase transition temperature and
spectroscopic evidence shows the intercalation of trehalose within the membrane
provides the chemical and morphological stability under a stress environment.
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Xie, Qiongdan. "Nanoscale Confinement Effects on Poly(ε-Caprolactone) Crystallization at the Air/Water Interface & Surfactant Interactions with Phospholipid Bilayers". Diss., Virginia Tech, 2010. http://hdl.handle.net/10919/37477.
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Two-dimensional (2D) nanoscale confinement effects on poly(ε-caprolactone) (PCL) crystallization were probed through crystallization studies of PCL-b-poly(tert-butyl acrylate) (PCL-b-PtBA) copolymers, PCL with bulky tri-tert-butyl ester endgroups (PCL triesters), PCL with triacid end groups (PCL triacids), and magnetic nanoparticles stabilized by PCL triacid (PCL MNPs) at the air/water (A/W) interface. Thermodynamic analyses of surface pressure-area per monomer (Π−A)) isotherms for the Langmuir films at the A/W interface showed that PCL-b-PtBA copolymers, PCL triheads and PCL MNPs all formed homogenous monolayers below the dynamic collapse pressure of PCL, Π<sub>C</sub> ~11 mN•m⁻¹. For compression past the collapse point, the PCL monolayers underwent a phase transition to three-dimensional (3D) crystals and the nanoscale confinements impacted the PCL crystalline morphologies. Studies of PCL-b-PtBA copolymers revealed that the morphologies of the LB-films became smaller and transitioned to dendrites with defects, stripes and finally nano-scale cylindrical features as the block length of PtBA increased.
For the case of PCL triester, irregularly shaped crystals formed at the A/W interface and this was attributed to the accumulation of bulky tert-butyl ester groups around the crystal growth fronts. In contrast, regular, nearly round-shaped lamellar crystals were obtained for PCL triacids. These morphological differences between PCL triacids and PCL triesters were molar mass dependent and attributed to differences in dipole density and the submersion of carboxylic acid groups in the subphase. Nonetheless, enhanced uniformity for PCL triacid crystals was not retained once the polymers were tethered to the spherical surface of a PCL MNP. Instead, the PCL MNPs exhibited small irregularly shaped crystals. This nano-scale confinement effect on the surface morphology at the A/W interface was also molar mass dependent. For the small molar mass PCL MNPs, two layers of collapsed nanoparticles were observed.
In a later chapter, studies of polyethylene glycol (PEG) surfactant adsorption onto phospholipid bilayers through quartz crystal microbalance with dissipation monitoring (QCM-D) measurements revealed a strong dependence of the adsorption and desorption kinetics on hydrophobic tail group structure. PEG surfactants with a single linear alkyl tail inserted and saturated the bilayer surface quickly and the surfactants had relatively fast desorption rates. In contrast, PEG lipids, including dioleoyl PEG lipids and cholesterol PEGs, demonstrated slower adsorption and desorption kinetics. The interactions of Pluronics and Nonoxynol surfactants with phospholipid bilayers were also studied. Pluronics showed no apparent affinity for the phospholipid bilayer, while the Nonoxynol surfactants damaged the lipid bilayers as PEG chain length decreased.
â<br>Ph. D.
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Guo, Yachong. "Association of polymers and small solute molecules with phospholipid membranes." Doctoral thesis, Universitat Rovira i Virgili, 2016. http://hdl.handle.net/10803/385852.
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El present treball està dedicat a les aplicacions pràctiques de diversos mètodes teòrics i de simulació incloent la dinàmica molecular, Montecarlo i la mitjana dels càlculs del camp per entendre les propietats físiques del sistema bicapa lipídica, així com la interacció dels objectes a escala nanomètrica en contacte amb lípids desenvolupament i bicapes. En particular, el treball es tracten els següents temes: 1. Optimització i equilibri de propietats bicapes lipídiques utilitzant única cadena de la teoria de camp mig. 2. El desenvolupament del model i estudiar les propietats d'equilibri de bicapes de lípids oxidats amb camp mitjà i els mètodes de dinàmica molecular 3. Estudi de les propietats d'equilibri de doble capa amb nanopartícules utilitzant camp mitjà i els mètodes de Montecarlo. Optimització de polímer translocacional través de la tècnica 5. Mètodes estadístics GPU membrana utilitzats per a les propietats superficials de micro fulles d'alteració bicapes lipídiques.<br>El presente trabajo está dedicado a las aplicaciones prácticas de varios métodos teóricos y de simulación incluyendo la dinámica molecular, Monte Carlo y la media de los cálculos del campo para entender las propiedades físicas del sistema bicapa lipídica, así como la interacción de los objetos a escala nanométrica en contacto con lípidos desarrollo y bicapas. En particular, el trabajo se tratan los siguientes temas: 1. Optimización y equilibrio de propiedades bicapas lipídicas utilizando única cadena de la teoría de campo medio. 2. El desarrollo del modelo y estudiar las propiedades de equilibrio de bicapas de lípidos oxidados con campo medio y los métodos de dinámica molecular 3. Estudio de las propiedades de equilibrio de bicapa con nanopartículas utilizando campo medio y los métodos de Monte Carlo. Optimización de polímero translocacional través de la técnica 5. Métodos estadísticos GPU membrana utilizados para las propiedades superficiales de micro cuchillas de alteración bicapas lipídicas.<br>Present work is devoted to the development and practical applications of several theoretical and simulation methods including Molecular dynamics, Monte Carlo and Mean field calculations to understand the physical properties of the lipid bilayer system as well as the interaction of nano-scale object in contact with lipid bilayers. In partcular, the work covers the following topics: 1. Optimization and equilibrium properties of lipid bilayers using Single Chain Mean Field theory. 2. Developing the model and study the equilibrium properties of bilayers with oxidized lipids with mean field and molecular dynamics methods 3. Study the equilibrium properties of bilayer with nanoparticles using mean field and Monte Carlo methods4. Optimization of translocational polymer through membrane GPU technique 5. Statistical methods used to the surface properties of micro blades disrupting lipid bilayers.
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Hatta, Ichiro, Susumu Okazaki, Kimiko Oono, and Yoshimichi Andoh. "A molecular dynamics study of the lateral free energy profile of a pair of cholesterol molecules as a function of their distance in phospholipid bilayers." AIP Publishing, 2012. http://hdl.handle.net/2237/20839.
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Lindahl, Erik. "Computational Modeling of Biological Membrane and Interface Dynamics." Doctoral thesis, Stockholm : Tekniska högsk, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3141.
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Pham, Quoc Dat. "Effects of Oxidized Phospholipids and Heavy Water on the Structure of Phospholipid Bilayer Membranes." Thesis, Umeå universitet, Kemiska institutionen, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-57935.
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Flippin, Stefanie Lee. "Synthesis of phospholipid analogs /." Electronic version (PDF), 2003. http://dl.uncw.edu/etd/2003/flippins/stefanieflippin.pdf.
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Wohl, Christopher John Jr. "Photochemical Applications to the Study of Complexity Phospholipid Bilayer Environments." VCU Scholars Compass, 2006. http://scholarscompass.vcu.edu/etd/1269.
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The physical and biophysical properties of a biological membrane model, phosphatidylcholine bilayers, were investigated using novel spiropyran/merocyanine molecular probes. The femtosecond to second dynamics of this system's photochemistry enabled bilayer viscosity and free volume to be studied over a broad time scale. Spiropyrans/merocyanines with different polarity were synthesized by changing the substitution of the indole moiety enabling determination of the trans-membrane properties of the bilayer. In addition, transient grating spectroscopy was used to study thermal energy transfer in phospholipid bilayers on a picosecond time scale.Femtosecond transient absorption spectroscopy was used to study the photo-induced spiropyran ring-opening and isomerization reactions that produce the highly polar merocyanine species. The hindered rotation of the merocyanine bridge results in several metastable merocyanine isomers. The merocyanine ground state was determined to be populated predominantly by two isomers (TTC and TTT). Selective photoexcitation of these isomers results in excited state isomerization producing a third isomer (τ = 60 ps). Merocyanine thermal ring-closing was observed on a seconds time scale. Reaction kinetics, and solvatochromic and photochromic properties of merocyanines and spiropyrans were used to determine the bilayer physical properties. Bilayer viscosity was determined from merocyanine isomerization kinetics. Phospholipid bilayer free volume (the unoccupied volume enclosed in the bilayer) was determined from a modified Kramers' analysis. The greatest free volume was found in the extreme interior of the bilayer, while the head-group region exhibited the least free volume in qualitative agreement with molecular dynamics simulations of these bilayer systems. Free volumes determined via ps experiments were lower than those determined on a seconds time scale due to reduced acyl chain dynamics on the ps time scale.Femtosecond transient grating spectroscopy was used to study the rate of thermal energy transfer from photo-excited porphyrin molecules to the surrounding solvent. Thermal energy transfer was observed as photo-acoustic waves propelled through the system upon relaxation of photo-excited porphyrin molecules in aqueous solution and embedded in bilayers. For liposome solutions, a bimodal energy transfer model was developed. The determined rate constants suggest that energy transfer occurs predominantly via thermal diffusion and vibrational energy transfer, while lipid dynamics (isomerizations) are not involved.
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Harb, Frédéric. "Etude d' un système biomimétique simple : diffusion brownienne et mobilité électrophorétique d' une protéine membranaire modèle insérée dans une bicouche lipidique supportée." Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM4073/document.
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Après le génome, le nouveau défi est celui du protéome. Nous avons progressé vers la mise au point de la séparation électrophorétique des protéines membranaires dans un milieu qui leur conviendrait, type bicouche lipidique supportée. La grandeur principale, mesurée par FRAPP, a été le coefficient de diffusion de lipides ainsi que des protéines. L'étude du comportement de la bicouche supportée a permis de mettre en évidence, pour certains supports et dans certaines conditions de température, la formation d'une phase ondulée (ou ripple) malgré la proximité du support. La diminution de la portée des interactions coulombiennes par adjonction de sel se traduit par une augmentation de plusieurs ordres de grandeur du coefficient de diffusion, approchant au final le comportement d'une bicouche libre, tout en conservant les étapes caractéristiques de la transition gel/fluide. L'ordre de grandeur de ces énergies d'interactions a été estimé à partir des courbes D= f(T) et validé par une étude préliminaire originale de DSC sur des bicouches lipidiques supportées. L'α-Hémolysine s'insère spontanément sous forme d'un pore heptamérique dans nos bicouches supportées et diffuse librement. En l'incubant en phase mixte (zones gel+ zones fluide), nous observons la formation de complexes de protéines. La dépendance du coefficient de diffusion avec la taille de l'objet est en 1/R2, R étant le rayon équivalent de la partie insérée de l'objet. L'application d'un champ électrique montre un transport électrophorétique dont la direction et l'importance sont modulées par la charge de l'objet. La mobilité électrophorétique varie également en 1/R2<br>After the genome, the new challenge is the proteome. We have progressed toward electrophoretic separation of membrane proteins in a medium that they love, a supported lipid bilayer. The main parameter, measured by FRAPP, was the diffusion coefficient of different objects (lipids, proteins). Studying bilayer behaviour has showed that, on particular supports and in a given temperature range, ripple phase can exist, despite the proximity of the support. Adding salt decreases coulombic interactions which turns to increase the diffusion coefficient over several orders of magnitude, reaching the value for a free-standing bilayer in the fluid phase, meanwhile the main characteristic steps of the global gel/fluid transition are still observed. Estimation of the value of the interaction energy has been made and compared to results of a preliminary DSC study. α-Hémolysin self-inserts spontaneously as an heptameric pore in supported bilayers and diffuses freely. Incubating in a gel/fluid mixture leads to protein complex formation. Diffusion varies with size as 1/R2, R being the equivalent radius of the inserted part of the object. Applying an electric field results in an electrophoretic motion where direction and magnitude are modulated by the charge of the object. Electrophoretic mobility varies also as 1/R2. Size dependence, magnitude of mobilities and a simple building protocol allow to hope carrying out soon a real electrophoretic separation of a protein mixture
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Monem, A. S. M. A. "Angular light scattering from phospholipid vesicles and the effect of magnetic fields." Thesis, University of Southampton, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373565.
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Hammond, K. "Investigations into the physical properties of some selected synthetic phospholipid bilayer systems." Thesis, University of Manchester, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376588.
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Domènech, Cabrera Òscar. "Structure and Physicochemical Properties of Phospholipidic Monolayers and Bilayers. LB and AFM Studies." Doctoral thesis, Universitat de Barcelona, 2007. http://hdl.handle.net/10803/2758.
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The main objective of this Ph. D. Thesis work was to study the physicochemical properties of the inner membrane of mitochondria and the interaction of "cyt c" with model membranes. Suitable techniques were used to accomplish this objective: Langmuir and Langmuir Blodgett films, fluorescence spectroscopy, Brewster Angle Microscopy and Atomic Force Microscopy.<br/><br/>The general conclusion of this Thesis is: "Calcium induces HII phases in POPE:CL (0.8:0.2, mol:mol) samples in solution. This composition is the most stable mixed monolayer of both phospholipids and corresponds to the native molar fraction in the inner membrane of the mitochondrion. The extension of these inverted micelles forms planar bilayers on solid supports displaying lateral lipid segregation of CL enriched domains where cyt "c can" bind specifically. In this configuration POPC can remain as a spacer in POPE enriched domains forming the matrix of the membrane". The inverse process would be a possible vindication to the release of "cyt c" from the inner membrane of mitochondrion during apoptosis.
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Lu, Junxia. "Solid-state NMR studies of phospholipid model membranes and membrane-associated macromolecules." Miami University / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=miami1184090235.
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Chien, Chih-Ta. "Development of a saposin A based native-like phospholipid bilayer system for NMR studies." Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/289703.
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Membrane proteins are important targets that represent more than 50% of current drug targets. However, characterisation of membrane proteins falls behind compared to their soluble counterparts. The most challenging part of membrane protein research is finding a suitable membrane mimetic that stabilises them in solution and maintains their native structure and function. The recently developed saposin-A (SapA) based lipid nanoparticle system seems to be advantageous over existing membrane mimetic system. It provides a native-like lipid bilayer, high incorporation yield and more importantly size adaptability. SapA lipid nanoparticles have been applied to structural studies and two high-resolution structures of membrane proteins were previously obtained using cryo-electron microscopy. This thesis aimed to study small-to-medium sized membrane proteins in SapA lipid nanoparticles using NMR spectroscopy. We first explore the mechanism of SapA lipid nanoparticle formation for the purpose of establishing an incorporation protocol that can be applied to most membrane proteins. The effect of pH and the presence of detergents on the opening of SapA was investigated in Chapter 2. A proposed energy diagram describing the mechanism of SapA opening is reported with which we were able to develop a protocol that can generate different sizes of SapA-1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) nanoparticles. In addition, we also showed that SapA can form lipid nanoparticles with various lipid compositions, showing the versatility of the system. In Chapter 3, we validated the ability of SapA lipid nanoparticles to be used as a membrane mimetic. A -barrel model protein, bacterial outer membrane protein X (OmpX), was incorporated into SapA-DMPC nanoparticles and a 2D 15N-1H correlation NMR spectrum was recorded. Our result was compared to the NMR parameters of the same protein in MSP nanodiscs from the literature, and it was concluded that SapA lipid nanoparticles indeed provide a lipid bilayer environment similar to MSP nanodiscs. Because of high incorporation yield, we were able to incorporate OmpX into different lipid compositions to investigate the effect of lipid head groups and aliphatic chains on the membrane protein's chemical environment. Next, the applicability of SapA lipid nanoparticles was expanded to -helical transmembrane proteins in Chapter 4. Two microbial rhodopsins, Anabaena sensory rhodopsin (ASR) and Natronomonas pharaonis sensory rhodopsin II (pSRII), were tested. The parameters for expression and purification of ASR were first screened for the optimal yield. Although incorporation of ASR resulted in inhomogeneous particles due to imperfect experimental procedure, pSRII in SapA-DMPC nanoparticles showed high sample quality. The 2D NMR spectrum of pSRII in SapA-DMPC nanoparticles shows distinct differences to pSRII in detergent micelles, suggesting substantial effects from the membrane mimetic on the conformation of the membrane protein. Despite the good NMR spectral quality considering the large particle size, perdeuteration of pSRII and the lipids will be necessary for further investigation. With the SapA lipid nanoparticles established, we aimed to use it for the study of a biologically important G protein-coupled receptor, 1-adrenergic receptor (1AR), discussed in Chapter 5. The possibility of expressing 1AR using a cell-free expression system was explored first. Although a good amount of the protein was obtained, only a fraction of it was functional. Therefore, a conventional baculovirus-insect cell expression system was used to produce selective isotope labelled 1AR for NMR studies. NMR spectra of 1AR in SapA-DMPC nanoparticles with activating ligands and an intracellular binding partner were recorded and compared to the spectra of the same protein in detergents. This revealed a more active-like conformation of ligand-bound 1AR in the lipid bilayer, suggesting that certain parts of the protein are sensitive to the membrane mimetic used. This emphasises the importance of using a native-like membrane mimetic to capture the full properties of membrane proteins. In conclusion, I demonstrate in this thesis that SapA lipid nanoparticles are a versatile membrane mimetic system that can accommodate membrane proteins with different sizes and folds. This system is also compatible with solution NMR spectroscopy enabling structure and dynamics studies of biologically important membrane proteins. We believe SapA lipid nanoparticles will have a significant impact on membrane protein research in the future.
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Gardam, Michael A. "Mixing of sphingolipids with phospholipids in lipid bilayer membranes : calorimetric and fluorescence studies." Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=55671.
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Winschel, Christine A. "Accurate Methodology for Monitoring Biomembrane Events." VCU Scholars Compass, 2012. http://scholarscompass.vcu.edu/etd/2860.
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Abstract ACCURATE METHODOLOGY FOR MONITORING BIOMEMBRANE EVENTS By Christine A. Winschel, Ph.D. A Dissertation submitted in partial fulfillment of the requirements for the degree of Doctorate of Philosophy in Chemistry at Virginia Commonwealth University. Virginia Commonwealth University, 2012 Major Director: Dr. Vladimir A. Sidorov ASSOCIATE PROFESSOR, DEPARTMENT OF CHEMISTRY This study describes the synthesis and characterization of a new receptor (cyclen 1) capable of strong selective binding of pyrene-based anionic dyes under near-physiological conditions. This receptor comprises four naphthylthiourea groups tethered to a cyclen core via an ester linkage. The most important finding was the ability of cyclen 1 to bind efficiently to a pH-sensitive pyranine dye, a dye that is commonly used in various biomembrane assays. The high affinity of cyclen 1 to pyranine, its impermeability to the lipid bilayer membrane, fast kinetics of binding, and ability to quench pyranine’s fluorescence were used as a basis for a new membrane leakage assay. This membrane leakage assay is fully compatible with the commonly applied pH-stat transport assay, and therefore it allows for differentiation of ion transport and nonselective leakage mechanisms within a single set of experiments. In the second part of this study a new methodology for the detection of lipid flip was developed. This methodology relies on the quenching of the fluorescence of a newly synthesized cascade-blue-labeled lipid through complex formation with cyclen 1. This receptor-dye complexation also has high affinity for binding at micromolar concentrations and can be reversed by either competitive displacement of the lipid probe or by enzymatic degradation of the receptor leading to the label release and fluorescence dequenching. This new methodology is suitable for the study of lipid flip in both model spherical bilayer membranes and in-vitro experiments, and is less invasive to the model and cell membranes than the commonly utilized 7-nitro-1,2,3-benzoxadiazol-4-yl (NBD)-dithionite methodology. Lastly, new pH-sensitive lipids were synthesized and utilized in the formulation of liposomes suitable for controlled drug release. These liposomes contain various amounts of internal NaCl and undergo internal acidification upon the exogenous addition of an HCl co-transporter in a physiologically relevant NaCl solution. Therefore, acidification ultimately leads to the hydrolysis of the pH-sensitive lipids and subsequent contents release. These liposomes were found to be insensitive to physiological concentrations of human serum albumin and to be non-toxic to cells at concentrations exceeding pharmacological relevance. These results render this new drug release model potentially suitable for in vivo applications.
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JUNG, JANGWOOK PHILIP. "Computer Simulation of Transport of Small Molecules Through a Gas Channel Embedded in a Phospholipid Bilayer." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1131054184.
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LADHA, PARAG. "POLYMERIC MEMBRANE SUPPORTED BILAYER LIPID MEMBRANES RECONSTITUTED WITH BIOLOGICAL TRANSPORT PROTEINS." University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1145901880.
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Giordani, Cristiano. "Structural and dynamic NMR studies on distribution and aggregation of cholesterol in solution and in phospholipid bilayer." 京都大学 (Kyoto University), 2007. http://hdl.handle.net/2433/136836.
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Korfhagen, Scott. "Stabilization of Scaffold-Supported, Photopolymerized Bilayer Lipid Membranes with Gramicidin-D for Novel Fuel Cells." University of Cincinnati / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1212085821.
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Strömstedt, Adam A. "Antimicrobial Peptide Interactions with Phospholipid Membranes : Effects of Peptide and Lipid Composition on Membrane Adsorption and Disruption." Doctoral thesis, Uppsala universitet, Institutionen för farmaci, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-100966.
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The interactions between antimicrobial peptides and phospholipid membranes were investigated, in terms of lipid headgroup variations and the role of cholesterol, as well as peptide composition and structure. Also strategies for increasing proteolytic stability were evaluated. The interactions were studied on model membranes in the form of liposomes and supported bilayers, through a combination of ellipsometry, fluorescence spectroscopy, circular dichroism, dynamic light scattering, electrophoresis, electron cryomicroscopy, and bacterial/cell culture experiments. The findings showed that membrane tolerance against the lytic activity of melittin, was increased on anionic membranes by electrostatic arrest in the headgroup region, and was reduced by hydration repulsion. The presence of cholesterol caused a reduction in melittin adsorption, while at the same time reducing membrane tolerance per adsorbed peptide. Differences in membrane leakage mechanisms were also attributed to cholesterol, where large scale structural effects contributed to the leakage, while other membranes followed the pore formation model. Substituting specific amino acids for tryptophan on an LL-37 derivative, was shown to increase stability against bacterial proteases, while at the same time significantly increasing antibacterial properties. These substitutions, as well as terminal modifications, increased adsorption and membrane lytic properties in a way that was less dependent on electrostatics. Furthermore, by comparing short cationic peptides with oligotryptophan end-tagged versions, the lytic mechanism of end-tagged peptides, and the different contributions of arginine and lysine to membrane adsorption and disruption were demonstrated. This thesis is a contribution to the development of antimicrobial peptides as therapeutic alternatives to conventional antibiotics.
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Scholtysek, Peggy [Verfasser], Alfred [Akademischer Betreuer] Blume, Jörg [Akademischer Betreuer] Kreßler, and Thomas [Akademischer Betreuer] Wolff. "Chirale und achirale Polymere in Wechselwirkung mit Phospholipid-Monolayern und -Bilayern / Peggy Scholtysek. Betreuer: Alfred Blume ; Jörg Kreßler ; Thomas Wolff." Halle, Saale : Universitäts- und Landesbibliothek Sachsen-Anhalt, 2014. http://d-nb.info/106071745X/34.
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Engvall, Caroline. "Drug Partitioning into Natural and Artificial Membranes : Data Applicable in Predictions of Drug Absorption." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-5752.
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Prates, Erica Teixeira 1985. "Dinamica molecular de articaina em membranas POPC." [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/248872.
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Orientadores: Munir Salomão Skaf, Monica Andrea Pickholz<br>Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica<br>Made available in DSpace on 2018-08-14T17:06:24Z (GMT). No. of bitstreams: 1
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Previous issue date: 2009<br>Resumo: Neste trabalho foi feito o estudo das interações da articaína, um anestésico local de ampla aplicação médico-odontológica, com membranas modelo de POPC (palmitoil-oleil-fosfatidilcolina) em condições próximas às biologicamente relevan- tes empregando-se simulações computacionais de dinâmica molecular. Em uma primeira etapa, empregamos métodos quânticos para modelar a articaína com base no campo de força CHARMM. Das simulações de equilíbrio da articaína em POPC, foi possível obter informações como o seu comportamento conformacional e sua posi- ção transversal na bicamada, assim como suas interações especícas com os lipídios. Os estudos foram realizados para os estados neutro e protonado da articaína, consi- derando também seus isômeros ópticos. Estas análises, em conjunto com resultados experimentais de H-RMN realizados pela Prof. Eneida de Paula (IB-UNICAMP) e pelo Prof. Leonardo F. Fraceto (Dpto. de Eng. Ambiental - UNESP, Sorocaba - SP), demonstram que a articaína, em sua forma neutra, posiciona-se preferencial- mente na interface membrana/água, onde interage frequentemente com os lipídios através de ligações de hidrogênio. Através de ferramentas como perfil de densidade eletrônica do sistema, da parte teórica, e perfil do tempo de relaxação longitudinal para diferentes regiões dos lipídios, da parte experimental, foi discutida a lipossolubilidade da articaína em relação a outros anestésicos. Também foram realizadas simulações de não equilíbrio, utilizando a técnica de Dinâmica Molecular de Caminho Induzido, em que uma molécula de articaína foi removida do interior da membrana para o meio aquoso, através de uma força aplicada em seu centro de massa. Com a aplicação da igualdade de Jarzynski a estas simulações, foi possível estimar a energia livre de partição da ATC neutra (forma mais potente) entre os estados em que encontra-se no seio aquoso e no interior da membrana POPC.<br>Abstract: We studied the interactions of articaine - a local anesthetic widely used for me- dical and odontological applications - with model membranes of POPC (palmitoyl-oleyl-phosphatidylcholine) at biological relevant conditions. We have employed molecular dynamics technique, which allowed us to investigate the system at molecular level. Firstly, we applied quantum mechanical methods to parametrize articaine molecule based on CHARMM force field. We have done extensive molceular dynamics simulations, taking into account the different ionization states of the drug (neutral and protonated) as well as its optical isomers. From the equilibirum simulations of articaine in POPC membranes, we investigated the conformational behaviour of the drug, its tranversal position and its specific interactions with the lipids and water molecules. Our results show a preferential orientation of the articaine molecule within the membrane. Neutral articaine was mainly found at the lipid head/water interface, in very good agreement with H-RMN experimental results from Prof. Eneida de Paula (IB-UNICAMP) and Prof. Leonardo F. Fraceto (Dpto. de Eng. Ambiental - UNESP, Sorocaba - SP) and from literature (C. Song et al, 2008). By studying properties like electronic density prole and longitudi- nal time relaxation for different regions of the lipid molecules, we discussed the lipossolubility of articaine in comparison to other local anesthetics. We have also performed non-equilibrium simulations, using steered molecular dynamics (SMD) technique. A single articaine molecule was extracted from the membrane to the wa- ter phase, by applying an external force in its mass centre. Coupling the Jarzynski identity to the SMD simulations, we estimated the partition free energy of the neutral drug (the most potent specie) in POPC membranes.<br>Mestrado<br>Físico-Química<br>Mestre em Química
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Sugiura, Miwa. "Effects of eicosapentaenoic acid-containing phospholipids on the formation of membrane proteins from Shewanella livingstonensis Ac10." Kyoto University, 2018. http://hdl.handle.net/2433/235099.
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Kyoto University (京都大学)<br>0048<br>新制・課程博士<br>博士(農学)<br>甲第21379号<br>農博第2303号<br>新制||農||1071(附属図書館)<br>学位論文||H30||N5152(農学部図書室)<br>京都大学大学院農学研究科応用生命科学専攻<br>(主査)教授 栗原 達夫, 教授 植田 充美, 教授 小川 順<br>学位規則第4条第1項該当
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Boija, Elisabet. "Partitioning of Drugs and Lignin Precursor Models into Artificial Membranes." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7098.
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Crowley, John J. "Cholesterol and Phospholipid Modulation of BK[subscript Ca] Channel Activity and Ethanol Sensitivity: a dissertation." eScholarship@UMMS, 2003. https://escholarship.umassmed.edu/gsbs_diss/107.
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The large conductance Ca++-activated K+ channel (BKCa) regulates neuronal excitability through the efflux of K+, in response to membrane depolarization and increases in intracellular Ca++. The activity of the BKCa channel is increased by acute exposure to ethanol (EtOH), which is thought to underlie, in part, the influence of the drug on peptide hormone release from neurohypophysial nerve terminals (Dopico et al., 1996, 1998). Moreover, chronic EtOH exposure attenuates acute drug action on hormone release, and reduces the sensitivity of BKCa channels to acute EtOH exposure (Knott et al., 2002). The factors regulating EtOH action on BKCa channels are not well understood. Several lines of evidence suggest, however, that the lipid composition of the plasma membrane may influence channel sensitivity to the drug. The plasma membrane is highly complex in its organization (Welti and Glaser, 1994; Brown and London, 1998). There is a growing body of literature indicating that the local lipid composition of the membrane can influence the function of ion channels, including BKCa (Chang et al., 1995a, b; Moczydlowski et al., 1985; Park et al., 2003; Turnheim et al., 1999). Interestingly, chronic exposure to EtOH in animal models results in alterations in the composition of synaptic plasma membranes, including changes in the amount and distribution of membrane cholesterol (CHS) (Chin et al., 1978; Chin et al., 1979; Wood et al., 1989). The significance of these alterations is unclear. Here, we set out to determine the ability of membrane lipids to modulate BKCa channel activity and EtOH sensitivity. To address this, we implement the planar lipid bilayer technique, allowing control of both the protein and lipid components of the membrane. Native BKCa channels retain EtOH sensitivity in this reductionist preparation (Chu et al., 1998), and we extend the study here to examine cloned human brain (hslo) BKCachannels.
We show here that hslo channels maintain their characteristic large conductance, voltage and Ca++-dependent gating, and sensitivity to 50 mM EtOH in bilayers cast from a 3:1 mixture of 1-pamiltoyl-2-oleoyl-phosphatidylethanolamine (POPE) and 1-pamiltoyl-2-oleoyl-phosphatidylserine (POPS). The addition of CHS to the bilayer decreases both the basal activity and EtOH sensitivity of the channels, in a concentration-dependent manner. This lends support to the notion that alterations in plasma membrane CHS levels following chronic EtOH exposure may reflect adaptations to the acute actions of the drug on ion channels. Furthermore, the EtOH sensitivity and CHS modulation of these reconstituted hslo channels are greatly reduced in the absence of negatively charged POPS in the bilayer (pure POPE). Based on these findings, we look to gain mechanistic insight into the lipid headgroup and acyl chain properties that may regulate BKCa channel modulation by EtOH and CHS. When POPS is replaced with the uncharged lipid 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC), the hslo response to EtOH and CHS is restored, suggesting that the loss of negative surface charge or PS headgroup structure itself cannot explain the lack of channel modulation by these agents in POPE bilayers. Moreover, increases in the proportion of unsaturated acyl chains in the bilayer cannot significantly influence the hslo response to EtOH. The loss of EtOH sensitivity in pure POPE and CHS-containing bilayers may, therefore, reflect the propensity of POPE and CHS to form nonlamellar (nonbilayer) structures. Regarding the basal activity of the channel, we demonstrate that decreases in negative surface charge, increases in the proportion of unsaturated acyl chains, and increases in the complexity of head group interactions can all influence the steady-state activity of reconstituted hslochannels, relative to control POPE/POPS (3:1) bilayers. Overall, these data further suggest the ability of the local lipid environment to regulate the basal function and EtOH sensitivity of an ion channel protein.
Parts of this dissertation have appeared in separate publications:
Treistman, S.N., O'Connell, R.J., and Crowley, J.J. (2002). Artificial Bilayer Techniques in Ion Channel Study. In Methods in Alcohol-Related Neuroscience Research, D. Lovinger and Y. Liu, eds. (Boca Raton, Florida: CRC Press)
Crowley, J.J., Treistman, S.N., and Dopico, A.M. (2003). Cholesterol antagonizes ethanol potentiation of human BKCA channels in binary phospholipid bilayers. Mol. Pharma. 64(2):364-372.
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Garrison, Kevin Lee. "Design, Fabrication, and Validation of Membrane-Based Sensors." Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/33542.
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Hair cell structures are one of the most common forms of sensing elements found in nature. In humans, approximately 16,000 auditory hair cells can be found in the cochlea of the ear. Each hair cell contains a stereocilia, which is the primary structure for sound transduction. This study looks to develop and characterize a bilayer lipid membrane (BLM) operated artificial hair cell sensor that resembles the stereocilia of the human ear. To develop this sensor, a flexible substrate with internal compartments for hosting the biomolecules and mating cap are constructed and experimentally characterized. The regulated attachment method (RAM) is used to form bilayers within the sealed device. Capacitance measurements of the encapsulated bilayer show that the sealing cap slightly compresses the bottom insert and reduces the size of the enclosed bilayer. Single channel measurements of alamethicin peptides further verify that the encapsulated device can be used to detect the gating activity of transmembrane proteins in the membrane.
The flexible substrate was incorporated into a low-noise, portable test fixture. The response of the sensor and tip velocity of the hair were measured with respect to an impulse input on the test fixture and several frequency response functions (FRFs) were created. The FRF between the sensor and the tip velocity was used to show that the hair vibration was transmitted to the bilayer for certain hair lengths. The transfer function between the sensor and the input was used to show the effect of membrane potential on sensor response.<br>Master of Science
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Charitat, Thierry. "Contributions théorique et expérimentale à l'étude des propriétés élastiques de systèmes physiques "inspirés" de la biologie." Université Joseph Fourier (Grenoble ; 1971-2015), 1997. http://www.theses.fr/1997GRE10179.
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La premiere partie de cette these est consacree a l'etude theorique des proprietes elastiques de reseaux de passages connectant des bicouches phospholipidiques. Elle a ete motivee par des observations experimentales faites par michalet et al. Le calcul que nous proposons prend en compte la conservation du volume du systeme. Il nous a permis de montrer que ces reseaux sont destabilises par les deformations de cisaillement, qui sont energetiquement plus favorables que les deformations de compression. La contrainte de volume permet aussi de determiner la densite de passages dans ces systemes. Enfin, la generalisation aux systemes multilamellaires de la notion de courbure constante introduite par michalet et al, met en evidence un comportement collectif remarquable des passages. La seconde partie concerne l'etude des interactions entre un peptide (la penetratine) et les phospholipides de la membrane cellulaire. Celle-ci est modelisee par une bicouche deposee sur un substrat solide par la methode de langmuir-blodgett. L'essentiel du travail expose dans cette these a consiste a developper un protocole experimental permettant de caracteriser ces bicouches par reflectivite de neutrons. Il a ainsi ete possible d'observer pour la premiere fois des quadricouches controlees de dspc. Enfin, les premiers resultats que nous avons obtenus sur l'etude de l'influence de la penetratine, montrent une influence importante du peptide sur la bicouche. La derniere partie de ce travail s'interesse aux proprietes elastiques d'un fil ferme spontanement courbe. Elle s'inscrit dans le cadre de la theorie classique de l'elasticite, et fait intervenir un couplage local entre la courbure et la torsion qui permet d'expliquer l'existence d'un etat metastable observable sur une rondelle de caoutchouc. Une application a l'adn est envisagee.
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Cvetkov, Teresa L. "Cytochrome c Oxidase from Rhodobacter sphaeroides: Oligomeric Structure in the Phospholipid Bilayer and the Structural and Functional Effects of a C-Terminal Truncation in Subunit III." Wright State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=wright1279028849.
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Harnois, Isabelle. "Determination du mode d'action d'un lipopeptide antifongique : l'iturine a, proprietes amphiphiles et interactions avec les membranes." Orléans, 1988. http://www.theses.fr/1988ORLE2006.
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