Formation and Characterization of Hybrid Bilayers and Diffusion of Cations Across Liposomal Membranes: Studies Based on Polymerizable Lipids

Persistent Link:
http://hdl.handle.net/10150/194428
Title:
Formation and Characterization of Hybrid Bilayers and Diffusion of Cations Across Liposomal Membranes: Studies Based on Polymerizable Lipids
Author:
Ratnayaka, Saliya Nalin
Issue Date:
2007
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Cellular energy transduction processes are often driven by transmembrane ion gradients, and a number of artificial membrane systems have been developed that allow for chemically or light-induced transport of ions across lipid bilayers. These liposomal architectures, however, are not readily interfaced to a solid-state transducer. A significant step toward this goal is described here by assessing the possibility of coupling a lipid bilayer directly to a transducer to form a stable uniform film using hybrid bilayer membranes (HBMs).Although the surface attachment of self-assembled monolayer increases the robustness of the lipid assembly, HBMs cannot maintain film uniformity under harsher conditions due to the absence of strong lipid-lipid interactions. Therefore, HBMs were prepared and characterized using a cross-linking polymerizable lipid, bis-SorbPC. Several parameters relating to lipid deposition and film stabilization through polymerization were examined. Film characterization strongly suggests that polymerization of bis-SorbPC stabilizes the HBM such that its structure is largely preserved even after the dehydration process. This work suggests that network formation in the upper monolayer is not enough to prevent oligomer desorption, intermonolayer covalent linking is also a prerequisite in making uniform, defect-free planar supported lipid assemblies.Some of the challenges associated with the application of lipids involve the creation of supported bilayers that are stable to chemical and physical disruptions, yet retain their ion barrier properties, and allow transmembrane ion transport by lipid-soluble shuttles. Polymerized lipid films provide the stability required for these structures, but permeability properties of cations across poly(lipid) membranes are not known. Therefore, convenient liposome-based proton and calcium permeability assays were developed. These assays were applied to various poly(lipid) compositions.In addition, three novel sorbyl-substituted head group polymerizable lipids, which have been synthesized based on a strategy that head group polymerization would minimally perturb the characteristic ion impermeability of the membrane, were evaluated for their lipid characteristics and ability to form polymers. None of these compounds forms vesicles by itself. Therefore, attempts were made to form mixed vesicles with other fluid lipids. The miscibility of the mixed monolayers was assessed using Langmuir isotherms.
Type:
text; Electronic Dissertation
Keywords:
polymerizable lipids; sorbyl lipids; hybrid bilayers; proton permeability; calcium permeability; bola lipids
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Chemistry; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Saavedra, Steven S.
Committee Chair:
Saavedra, Steven S.

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleFormation and Characterization of Hybrid Bilayers and Diffusion of Cations Across Liposomal Membranes: Studies Based on Polymerizable Lipidsen_US
dc.creatorRatnayaka, Saliya Nalinen_US
dc.contributor.authorRatnayaka, Saliya Nalinen_US
dc.date.issued2007en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractCellular energy transduction processes are often driven by transmembrane ion gradients, and a number of artificial membrane systems have been developed that allow for chemically or light-induced transport of ions across lipid bilayers. These liposomal architectures, however, are not readily interfaced to a solid-state transducer. A significant step toward this goal is described here by assessing the possibility of coupling a lipid bilayer directly to a transducer to form a stable uniform film using hybrid bilayer membranes (HBMs).Although the surface attachment of self-assembled monolayer increases the robustness of the lipid assembly, HBMs cannot maintain film uniformity under harsher conditions due to the absence of strong lipid-lipid interactions. Therefore, HBMs were prepared and characterized using a cross-linking polymerizable lipid, bis-SorbPC. Several parameters relating to lipid deposition and film stabilization through polymerization were examined. Film characterization strongly suggests that polymerization of bis-SorbPC stabilizes the HBM such that its structure is largely preserved even after the dehydration process. This work suggests that network formation in the upper monolayer is not enough to prevent oligomer desorption, intermonolayer covalent linking is also a prerequisite in making uniform, defect-free planar supported lipid assemblies.Some of the challenges associated with the application of lipids involve the creation of supported bilayers that are stable to chemical and physical disruptions, yet retain their ion barrier properties, and allow transmembrane ion transport by lipid-soluble shuttles. Polymerized lipid films provide the stability required for these structures, but permeability properties of cations across poly(lipid) membranes are not known. Therefore, convenient liposome-based proton and calcium permeability assays were developed. These assays were applied to various poly(lipid) compositions.In addition, three novel sorbyl-substituted head group polymerizable lipids, which have been synthesized based on a strategy that head group polymerization would minimally perturb the characteristic ion impermeability of the membrane, were evaluated for their lipid characteristics and ability to form polymers. None of these compounds forms vesicles by itself. Therefore, attempts were made to form mixed vesicles with other fluid lipids. The miscibility of the mixed monolayers was assessed using Langmuir isotherms.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectpolymerizable lipidsen_US
dc.subjectsorbyl lipidsen_US
dc.subjecthybrid bilayersen_US
dc.subjectproton permeabilityen_US
dc.subjectcalcium permeabilityen_US
dc.subjectbola lipidsen_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineChemistryen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorSaavedra, Steven S.en_US
dc.contributor.chairSaavedra, Steven S.en_US
dc.contributor.committeememberArmstrong, Neal R.en_US
dc.contributor.committeememberWysocki, Vicki H.en_US
dc.contributor.committeememberHall, Jr., Henry K.en_US
dc.contributor.committeememberZheng, Zhipingen_US
dc.identifier.proquest2158en_US
dc.identifier.oclc659747264en_US
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