FREE FATTY ACIDS AS A MAJOR COMPONENT OF THE CHLOROSULFOLIPID MEMBRANE OF OCHROMONAS DANICA.
Item
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Title
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FREE FATTY ACIDS AS A MAJOR COMPONENT OF THE CHLOROSULFOLIPID MEMBRANE OF OCHROMONAS DANICA.
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Identifier
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AAI8515675
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identifier
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8515675
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Creator
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WINICOV, IRENE.
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Date
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1985
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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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The flagellar membrane of the phytoflagellate, Ochromonas danica (primarily dark-grown) had earlier been characterized by lack of phospholipids. The main polar lipids were chloro-substituted alkyl disulfates; the other principle components being free fatty acids (FFAs) and sterols. FFAs are not usually natural membrane components; they are known to uncouple proton gradients. Cell damage or solvent extraction can cause their artifactual production from esterified precursors. This work is an attempt to determine whether or not the free fatty acids are indeed components of the natural membrane of O. danica.;If the FFAs were artifacts, they would most likely have been produced during solvent extraction (solvent-activation of lipolysis is known to occur in plant systems) or during the procedure for flagellar detachment (mechanical wounding can also be associated with lipolysis). Attempts to denature putative solvent-activated lipase(s) through exposure to boiling isopropanol or by crosslinking the flagella with glutaraldehyde prior to extraction failed to eliminate the free fatty acid fraction, nor to significantly alter its composition. Exposure of flagella to albumin resulted in the net transfer of FFAs to the supernatant phase, showing their presence is not caused by solvent activated lipolysis. Finally, levels of labelled free fatty acids failed to rise as a function of time after deflagellation in cells grown in the presence of 10-('14)C -oleic acid. Acid hydrolysis of the total labelled lipid at elevated temperature increased the percentage of counts occurring as unesterified fatty acids (from 2.6% to 64.8%). This, taken together with a corresponding loss of the more polar labelled material (66.8% to 8.2%) indicates that some esterified lipids were present, but probably not broken down during the isolation procedure.;Free fatty acids have also been reported in O. danica's extracellular vesicles. Indeed, liposomes can be formed using sulfolipid, sterol and free fatty acids as membrane components. The surface charge density of the flagellar membrane at low and high pH is consistent with the presence of free fatty acids in an alkyl sulfate membrane. Thus, it seems that unesterified fatty acids are a component of the chlorosulfolipid membrane of Ochromonas danica.
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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.
