STUDIES ON THE SURFACE PH AND PROTONATION STATE OF MONOALKYL ANIONIC MEMBRANES AND LIPOSOMES.
Item
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Title
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STUDIES ON THE SURFACE PH AND PROTONATION STATE OF MONOALKYL ANIONIC MEMBRANES AND LIPOSOMES.
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Identifier
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AAI8302562
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identifier
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8302562
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Creator
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HELLER, MICHAEL.
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Contributor
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Thomas H. Haines
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Date
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1982
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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, Biochemistry
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Abstract
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It has been shown that the flagellar membrane of the phytoflagellate, Ochromonas danica, lacks phospholipids. This novel membrane contains as its polar lipids 1, 14-docosanedisulfate (together with 1, 15-tetracosanedisulfate) with from 0 to 6 chloro groups replacing hydrogens on the chain (Chen, Pousada and Haines, J. Biol. Chem. 251, 1835-1842 (1976)). The single-chain amphiphiles represent 70% of the total lipids, with sterols ((TURN)12%) and free fatty acids ((TURN)17%) constituting the remainder. When this work was done it was not clear whether or not the free fatty acids were a structural component of the membrane or an artifact produced during isolation. It should be noted that O. danica is a unicellular alga that lacks an outer protective wall or membrane visible in the electron microscope. It extrudes vesicles of its plasma membrane in the log phase of growth and these "extracellular vesicles" have likewise been shown to consist of the above lipids in the same proportions.;As a model system with which to explore this unique natural membrane, liposomes were prepared from a combination of single-chain amphiphiles such as oleic acid or oleyl sulfate (SOS) either in combination with cholesterol or chain alcohols. Experiments were designed to seek explanations for the remarkable concentration of anions in the bilayer-most notably the secondary sulfate which appears to be in the low dielectric where it is presumably neutralized (uncharged). Examination of the protonation state of the anions (uncharged on protonation) was performed by ('13)C-NMR. In the same vesicle and/or membrane system the pH at the surface (as opposed to that in the bulk aqueous phase) was measured directly by alkylated pH indicators hydrophobically bound to the membrane surface. The surface pH was expected to be 1 to 3 pH units below that of the bulk phase according to the Gouy-Chapman theory. This was found to be the case for both model vesicles and the natural membrane.
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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.
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Program
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Biochemistry
