Interactions of N-alkyl-2-pyrrolidinone surfactants with DMPC bilayers.
Item
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Title
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Interactions of N-alkyl-2-pyrrolidinone surfactants with DMPC bilayers.
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Identifier
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AAI3231940
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identifier
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3231940
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Creator
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Kopkalli, Yasemin.
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Contributor
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Adviser: Lesley Davenport
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Date
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2006
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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 | Biophysics, General
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Abstract
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There is great interest in identifying and characterizing new surfactants with predictable solubilization and reconstitution characteristics for use in membrane research. Among them, Triton X-100 and octyl glucoside (OG) are the best-studied surfactants. However, no physical data is available characterizing the interactions of two non-ionic pyrrolidinone surfactants, N-(2-ethylhexyl)-2-pyrrolidinone (C2,6P) and N-octyl-2pyrrolidinone (C8P), with lipid bilayers. In the present study, their physical effects on dimyristoylphosphatidylcholine small unilamellar vesicles (DMPC SUVs) above the lipid phase transition temperature are described using surface tension, fluorescence spectroscopy, and isothermal titration calorimetry (ITC) methodologies.;Surface tension methods show significant deviations from ideal behavior (attractive interactions) for these surfactant/lipid mixtures. In addition, fluorescence intensity studies of DPH and TMA-DPH labeled SUVs suggest that C8P interacts more favorably with both the acyl chain and head group regions of the bilayer over the corresponding branched chain C2,6P analogue. This is further supported by fluoresecence emission anisotropy measurements (EA). Both surfactants affect the membrane lipid order within the acyl chain region, and the corresponding phospholipid 'melt' transition temperature (Tm ) values, which decrease linearly with increasing surfactant concentrations. Using the van't Hoff model, the lipid bilayer-water partition coefficients for these surfactants have been estimated from the depression of the lipid phase transition temperature. Values for the lipid partition coefficient for C8P [(1.22+/-0.08)x104] versus C2,6P [(4.09+/-0.78)x10 3] further supports a more favorable bilayer association for C8P.;ITC data reveals an endothermic association for both C8P and C2,6P together with a somewhat higher binding affinity [(6.78+/-0.92)x10 -4M] for C8P compared with C2,6P [(8.46+/-0.83)x10 -4 M], as predicted from fluorescence studies.;We propose that C8P interacts and affects the lipid packing of bilayer membranes to a greater extent than C2,6P. Interactions of C2,6P appears to be more localized within the head group region of the bilayer. We conclude that C8P has great potential for biological applications, particularly membrane solubilization and membrane formation from micellar mixtures. In contrast, C2,6P may have potential for solubilization of extrinsic surface associated membrane proteins.
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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.
