Fluorescence study of the structure and dynamics of model phospholipid bilayers using coronene and 4-coronenyl butyric-phosphatidylcholine.
Item
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Title
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Fluorescence study of the structure and dynamics of model phospholipid bilayers using coronene and 4-coronenyl butyric-phosphatidylcholine.
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Identifier
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AAI9908361
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identifier
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9908361
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Creator
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Shen, Bo.
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Contributor
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Adviser: Lesley Davenport
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Date
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1998
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Language
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English
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Publisher
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City University of New York.
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Subject
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Chemistry, Physical | Chemistry, Biochemistry | Biophysics, General
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Abstract
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The effects of melittin on submicrosecond lipid dynamics have been investigated using the long-lived fluorescence probes, coronene and 4-coronenyl butyric-phosphatidylcholine (Cor-PC). Both coronene ({dollar}\tau\sb{lcub}\rm av{rcub} = 200{dollar}ns) and Cor-PC ({dollar}\tau\sb{lcub}\rm av{rcub} = 120{dollar}ns) exhibit long mean fluorescence lifetimes and strong rotational sensitivity to lipid bilayer disordering events occuring on the submicrosecond timescale. Cor-PC, which resides at a fixed location within the lipid bilayers, has the advantage that it can provide both structural and dynamic information arising from specific sites within the bilayer. In the presence of melittin in 'gel' phase lipid, an increase in emission anisotropy values was detected for both coronene and Cor-PC labeled SUVs, suggesting an ordering of the lipid packing. Cor-PC is particularly sensitive to the presence of melittin in the gel phase, suggesting that this fluorophore is reporting more directly on lipid-peptide interactions. In contrast, the short-lived ({dollar}\langle\tau\rangle\sim 10{dollar}ns) fluorescence probe, 1,6-diphenyl-1,3,5-hexatriene (DPH), reports little change in {dollar}\langle\rm r\rangle{dollar}, and appears not sensitive to submicrosecond lipid dynamics.;Time-resolved emission anisotropy decays for Cor-PC and coronene labeled DMPC SUVs were fitted using two rotational correlation times. The fast rotational correlation time ({dollar}\Phi\sb1{dollar}) is invariant in the presence of melittin. The slower rotational correlation time ({dollar}\Phi\sb2{dollar}) increased dramatically in the presence of peptide, suggesting that melittin has a significant effect on lipid dynamics within the submicrosecond 'time window', resulting in a decrease in rotational motions for the long-lived fluorophore. {dollar}\Phi\sb2{dollar} of coronene showed less sensitivity due to the non-fixed location of coronene within the lipid bilayers. While less sensitive to the effect of peptide on the gel-phase lipid dynamics, a decreased freedom of wobble for DPH was observed in the presence of melittin, suggesting increased average bilayer ordering.;Fluorescence quenching experiments suggests that coronene is located deeper within the apolar region of the lipid bilayers compared with Cor-PC. In the presence of melittin, quenching of Cor-PC labeled DMPC SUVs proved more difficult due to the more ordered lipid bilayers in the presence of peptide. The ordering of the bilayers is further supported from excimer studies using pyrene labeled DMPC vesicles. Excimer formation is hindered due to the decreased bilayer microviscosity in the presence of melittin.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
