Fatty Acid Micelles Research Articles

Oxidation of ferrous iron during peroxidation of lipid substrates

Oxidation of Fe 2+ in solution was dependent upon medium composition and the presence of lipid. The complete oxidation of Fe 2+ in 0.9% saline was markedly accelerated in the presence of phosphate or EDTA and the ferrous oxidation product formed was readily recoverable as Fe 2+ by ascorbate reduction. In contrast, in the presence of either brain synaptosomal membranes, phospholipid liposomes, fatty acid micelles or H 2O 2, less than 50% of the Fe 2+ oxidized during an incubation could be recovered as Fe 2+ via reduction with ascorbate. In the presence of unsaturated lipid, oxidation of Fe 2+ was associated with peroxidation of lipid, as assessed by the uptake of O 2 and formation of thiobarbituric acid-reactive products during incubations. Although relatively little Fe 2+ oxidation or lipid peroxidation occurred in saline with synaptosomes or linoleic acid micelles during an incubation with Fe 2+ alone, significant Fe 2+ oxidation and lipid peroxidation occurred in incubations containing a 1:1 ratio of Fe 2+ and Fe 2+. Extensive Fe 2+ oxidation and lipid peroxidation also occurred with Fe 2+ alone in saline incubations with either linolenic or arachidonic acid acid micelles or liposomes prepared from dilinoleoylphosphatidylcholine. While a 1:1 ratio of Fe 2+ and Fe 3+ enhanced thiobarbituric acid-reactive product formation in incubations containing linolenic or arachidonic micelles, it reduced the rate of O 2 consumption as compared with Fe 2+ alone. The results demonstrate that oxidation of Fe 2+ in incubations containing lipid substrates is linked to and accelerated by peroxidation of those substrates. Furthermore, the results suggest that oxidation of Fe 2+ in the presence of lipid or H 2O 2 creates forms of iron which differ from those formed during simple Fe 2+ autoxidation.

Protein kinase C activation by cis-fatty acid in the absence of Ca2+ and phospholipids.

Protein kinase C has been shown to be a phospholipid/Ca2+-dependent enzyme activated by diacylglycerol (Nishizuka, Y. (1984) Nature 308, 693-697; Nishizuka, Y. (1984) Science 225, 1365-1370). We have reported that unsaturated fatty acids (oleic acid and arachidonic acid) can activate protein kinase C independently of Ca2+ and phospholipid (Murakami, K., and Routtenberg, A. (1985) FEBS Lett. 192, 189-193). This study shows that other cis-fatty acids such as linoleic acid also fully activate protein kinase C in the same manner. None of the saturated fatty acids (C:4 to C:18) nor the detergents (sodium dodecyl sulfate and Triton X-100) tested here were as effective as oleic acid. Unlike oleic acid, these detergents strongly inhibited protein kinase C activity induced by Ca2+/phosphatidylserine (PS) and diacylglycerol. Lowering the critical micelle concentration of oleic acid by increasing ionic strength also strongly inhibited oleic acid activation of protein kinase C activity. Dioleoylphosphatidylserine activated protein kinase C effectively (Ka = 7.2 microM). On the other hand, dimyristoylphosphatidylserine, which contains saturated fatty acids at both acyl positions, failed to activate protein kinase C even in the presence of Ca2+. These observations suggest that: protein kinase C activation by free fatty acid is specific to the cis-form and is not due to their detergent-like action, cis-fatty acid activation is due to the direct interaction of protein kinase C with the monomeric form of cis-fatty acids and not with the micelles of fatty acids, and cis-fatty acids at acyl positions in PS are also important for Ca2+/PS activation of protein kinase C.

Inactivation of soluble 17β-hydroxysteroid dehydrogenase of human placenta by fatty acids

The sensitivity of soluble, 17β-hydroxysteroid dehydrogenase (17β-HSD) of human placenta to inactivation by fatty acids was examined. Exposure to the unsaturated fatty acids oleic, arachidonic, linoleic and linolenic acid resulted in the loss of activity. Methyl and ethyl esters of oleic acid, the saturated fatty acid, stearic acid and prostaglandins E 2 and F 2α were without effect. Inactivation by oleic acid required the fatty acid at levels above its critical micelle concentration, 50 μM, as estimated by light-scattering. Steroid substrates and inhibitors did not protect against inactivation. NAD +, NADH, NADP + and NADPH did protect. The concentrations of NADP +, 50 μM, and NAD, 1.5 mM, necessary for complete protection were significantly greater than their respective Michaelis constants, 0.16 β M and 15.2 μM. The data suggest that soluble 17β-HSD can bind to fatty acid micelles and that the binding site(s) on the enzyme are at or near pyridine nucleotide binding sites.

Effect of micellar lipids on rabbit intestinal brush-border membrane phospholipid bilayer integrity studied by 31P NMR.

The effect of biliary salts and fatty acids on the bilayer structure of rabbit intestinal brush-border membranes was studied using the nonperturbing probe 31P NMR. The broad, asymmetric lineshape of the 31P NMR spectrum of isolated brush-border vesicles demonstrates that their component phospholipids are organized in extended bilayers. These membranes are not significantly perturbed by incubation with physiological concentrations of biliary salts (3, 9, 18 mM), demonstrating that the vesicles are highly stable, corresponding to their biological function. However, the emergence of a narrow peak superimposed on the broad lineshape indicates that a small proportion of the membrane phospholipids has reached isotropic motion, which may correspond to external or internal micellar structures. Incubation with mixed micelles of fatty acids and taurochlorate show that long-chain fatty acids enhance the membrane-perturbing effect of taurocholate while short-chain, water-soluble fatty acids do not, suggesting a difference in the absorption mechanisms.

A comparison of substrate-dependent fatty acyl-CoA synthetase activities and ATP hydrolysis in membrane pellets from normal and trembler mouse sciatic nerves

Acyl-CoA synthetase activity was investigated in membrane fractions from normal and Trembler mouse sciatic nerves. Stearoyl-CoA synthesis in the Trembler assays was always about twice that observed in the control experiments under various conditions of CoA and ATP concentrations. In experiments using varying concentrations of fatty acid, the activation of stearate was very low in both systems (normal and Trembler), up to a substrate concentration of 20 mM, suggesting that fatty acid micelles are required for full activity. ATP, at concentrations of up to 1 mM, was totally (Trembler) or partially (control) hydrolyzed within 15 min, resulting in an apparently lower ligase activity in the mutant than in the control when an ATP-regenerating system was not added. The activation of saturated fatty acids decreased with increasing chain length. However, lignoceroyl-CoA formation was detected in the mutant but not in the control.

A reaction between the superoxide free radical and lipid hydroperoxide in sodium linoleate micelles

The oxidation of unsaturated fatty acid micelles by the superoxide free radical ( O ⨪ 2 ), during γ irradiation in the presence of formate, is kinetically distinct from oxidation by hydroxyl free radicals (HO.). The evidence suggests that a direct reaction between ( O ⨪ 2 ) and lipid hydroperoxide initiates a chain oxidation process in the micelles. While tetranitromethane, which reacts rapidly with ( O ⨪ 2 ), protects the micelles from oxidation, active superoxide dismutase is no more effective than its apoprotein, due to lack of penetration of the micellar environment. We discuss these findings in the light of recent literature, and with reference to their possible significance for biological systems.

A Study of the Peroxidation of Fatty Acid Micelles Promoted by Ionizing Radiation, Hydrogen Peroxide and Ascorbate

A Study of the Peroxidation of Fatty Acid Micelles Promoted by Ionizing Radiation, Hydrogen Peroxide and Ascorbate

A Study of the Peroxidation of Fatty Acid Micelles Promoted by Ionizing Radiation, Hydrogen Peroxide and Ascorbate

the kinetics of peroxidation of fatty acid micelles promoted by ionizing radiation, hydrogen peroxide and ascorbate were compared. At the dose-rate range of ionizing radiation studied, the higher the dose-rate, the greater the total dose required to produce the same effect. With ascorbate, the rate of lipid peroxidation was dependent on the concentration of the promoter only up to 1 X 10(-4) M, beyond which a decreasing rate of peroxidation induction was observed. Higher concentration of ascorbate also suppressed the promoting effect of ionizing radiation. Formate, a hydroxyl radical scavenger, inhibited the peroxidation process promoted by these three agents. Caesium was found to be slightly inhibitory. EDTA and deoxycholate were also inhibitory, which may be attributed to iron-chelating and micelle-disrupting capacity, respectively. Addition of iron (Fe2+ or Fe3+) to EDTA-chelated fatty acid micelles re-initiated the peroxidation process. The ease of fatty acid oxidation at pH 7.5 was arochidonic (20:4) greater than linolenic (18:3) greater than linoleic (18:2). This order was reversed at pH 11.5. Similarities in the kinetics of peroxidation obtained suggest that certain biological sequelae encountered in cells treated with these seemingly dissimilar agents might arise through some common mechanism(s).

Mechanisms of interference of nonesterified fatty acids in radioimmunoassays of steroids

Addition of nonesterified fatty acids caused an apparent increase in unbound steroid present in supematants in radioimmunoassays for steroids utilizing dextran-coated charcoal. Nonesterified fatty acid interference occurred at the initial binding interaction between steroid and its antiserum, and also at the step separating bound from unbound steroid. It was determined that nonesterified fatty acids, which had been added to radioimmunoassays, formed micelles and trapped steroids. The extent of the entrapment was inversely related to the number of polar groups in the steroid molecule, that is, hydrophobic steroids more easily interacted with the non-esterified fatty acid micelles. However, if the charcoal concentration were increased, the nonesterified fatty acid effect was eliminated for assays of polar steroids and greatly reduced for non-polar steroid assays.

Characterization of anisotropic motion in fatty acid micelles by analysis of transverse relaxation in an AX2 nuclear spin system

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCharacterization of anisotropic motion in fatty acid micelles by analysis of transverse relaxation in an AX2 nuclear spin systemJames H. Prestegard and David M. GrantCite this: J. Am. Chem. Soc. 1978, 100, 15, 4664–4668Publication Date (Print):July 1, 1978Publication History Published online1 May 2002Published inissue 1 July 1978https://doi.org/10.1021/ja00483a005RIGHTS & PERMISSIONSArticle Views123Altmetric-Citations27LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (587 KB) Get e-Alerts Get e-Alerts

Promotion of Radiation Peroxidation in Models of Lipid Membranes by Caesium and Rubidium Counter-ions: Micellar Linoleic and Linolenic Acids

Caesium and rubidium counter-ions increase peroxidation in irradiated micelles of linoleic (18 : 2) and linolenic (18 : 3) acids. The effect is specific to Cs+ and Rb+ in the alkali metal series. The effect is independent of the salts used (Cl-, NO3-, ClO4-) and, therefore, independent of the chaotropic nature, and reactivity with hydroxyl radicals of Cl-, NO3- and ClO4-. The promotion of peroxidation by Cs+ and Rb+ is interpreted in terms of their effect on fatty acid micelle structure. The dependence of radiation peroxidation on lipid structure in the micelles may be significant for studies of peroxidation in highly structured cell membranes.

Activation of Hagemen Factor by saturated fatty acids.

SUMMARYThe effect of suspensions of saturated fatty acids or oleic acid on the coagulation of plasma and on the release of plasma kinin was determined by quantitative methods. The activity of the saturated series (C8‐C22) increases enormously with the length of the carbon chain. Oleic acid is practically inactive. Evidence is presented that the reaction is mediated by adsorption and activation of Hageman factor by the fatty acid micelles. The differences between the activity of the fatty acids are related to the physical conditions at the surface of the particles.