Resolution of alkenylacylglycerol moieties of natural glycerophospholipids by gas-liquid chromatography on polar capillary columns

Chemical constituents of the soft corals Sinularia vanderlandi and Sinularia gravis from the coast of Madagascar

The crude extracts of the Madagascan soft corals Sinularia vanderlandi and Sinularia gravis (Alcyoniidae) showed activity against Plasmodium falciparum which led us to study their chemical constituents. The new cadinane-type sesquiterpenoid vanderlandin (1) has been obtained from S. vanderlandi along with 24-methylenecholesterol (2). Four new compounds, the spatane-type diterpenoid gravilin (3), the monoalkylmonoacylglycerol 4, the dihomoditerpenoid ketone 5, and isodecaryiol (9), along with the three known compounds (+)-(S)-geranyllinalool (6), (-)-(R)-nephthenol (7), and 11,12-epoxysarcophytol A (8) have been isolated from the methanol extract of S. gravis. The structures were elucidated based on extensive spectroscopic methods, in particular various 2D NMR techniques. The structure of isodecaryiol (9) including its absolute configuration could be confirmed by X-ray diffraction.

Dietary Docosahexaenoic Acid Suppresses T Cell Protein Kinase Cθ Lipid Raft Recruitment and IL-2 Production

To date, the proximal molecular targets through which dietary n-3 polyunsaturated fatty acids (PUFA) suppress the inflammatory process have not been elucidated. Because cholesterol and sphingolipid-enriched rafts have been proposed as platforms for compartmentalizing dynamically regulated signaling assemblies at the plasma membrane, we determined the in vivo effects of fish oil and highly purified docosahexaenoic acid (DHA; 22:6n-3) on T cell microdomain lipid composition and the membrane subdomain distribution of signal-transducing molecules (protein kinase C (PKC)theta;, linker for activation of T cells, and Fas/CD95), before and after stimulation. Mice were fed diets containing 5 g/100 g corn oil (control), 4 g/100 g fish oil (contains a mixture of n-3 PUFA) plus 1 g/100 g corn oil, or 4 g/100 g corn oil plus 1 g/100 g DHA ethyl ester for 14 days. Dietary n-3 PUFA were incorporated into splenic T cell lipid raft and soluble membrane phospholipids, resulting in a 30% reduction in raft sphingomyelin content. In addition, polyclonal activation-induced colocalization of PKCtheta; with lipid rafts was reduced by n-3 PUFA feeding. With respect to PKCtheta; effector pathway signaling, both AP-1 and NF-kappaB activation, IL-2 secretion, and lymphoproliferation were inhibited by fish oil feeding. Similar results were obtained when purified DHA was fed. These data demonstrate for the first time that dietary DHA alters T cell membrane microdomain composition and suppresses the PKCtheta; signaling axis.

High-performance liquid chromatographic resolution of reverse isomers of 1,2-diacyl-rac-glycerols as 3,5-dinitrophenylurethanes

The resolution of reverse isomers remains a major unsolved problem in glycerolipid chromatography. We have investigated the separation of the reverse isomers of 1,2-diacyl-rac-glycerols under a variety of high-performance liquid chromatography (HPLC) conditions. The reverse isomers of diacylglycerols having various pairs of acyl groups including short and highly unsaturated chains, which were prepared by partial Grignard degradation of the corresponding triacylglycerols, were chromatographed as 3,5-dinitrophenylurethanes. Excellent resolution was achieved for the reverse isomers of very different pairs of acyl groups, such as acetate-palmitate and docosahexaenoate-palmitate, by chiral-phase HPLC on columns containing (R)- and (S)-1-(1-naphthyl)ethylamine polymeric phases, reversed-phase HPLC on a highly efficient C18 column (4 microm particle size) and silver ion HPLC on a silver loaded cation-exchange column. The chiral-phase HPLC also permitted complete enantiomer resolution for all the reverse isomers examined. No satisfactory resolution by any of the HPLC methods, however, was obtained for the reverse isomers possessing minor differences in chain lengths and degree of unsaturation, such as laurate-palmitate and oleate-linoleate. The limitations of resolution and characteristics of elution are described.

Determination of rat liver triglycerides by gas-liquid chromatography and reversed-phase high-performance liquid chromatography

Rats fed with a fat-free or an olive oil-rich diet were employed to compare the response of two chromatographic techniques in the determination of rat liver triglyceride (TG) molecular species composition. Gas-liquid chromatography (GLC) on polarizable liquid phase and reversed-phase high-performance liquid chromatography (RP-HPLC) have been commonly employed for TG analysis, obtaining a similar number of chromatographic peaks when used for animal tissue TG determination. In the present study similar results were achieved with regard to most relevant chromatographic peaks, however, important differences were found in the content of minor TGs. Indeed, RP-HPLC permitted separation of long chain polyunsaturated fatty acids, which were not detected by GLC, while the latter technique reported a higher number of myristoyl-containing TG species. RP-HPLC analysis reported a greater number of TGs, with more similarity to a random composition, made up from the liver fatty acid composition. Therefore, it was concluded that utilization of both techniques would be helpful for liver TG analysis as the use of only one of them does not provide a complete profile of liver TGs. Nevertheless RP-HPLC seems to be more useful for this purpose since revealed a more extensive profile.

Lipid structure of rat adipocyte plasma membranes following dietary lard and fish oil

We have determined the changes in the lipid structure of the adipocyte plasma membranes of rats receiving lard or fish oil in their diet. For this purpose, mature Wistar rats were fed 20% (w/w) lard or fish oil diets for 22 days, when the plasma membranes of the epididymal and perirenal adipocytes were prepared. Detailed analysis of the membrane lipids by chromatographic methods showed that dietary fat exerted a major effect on the lipid class and molecular species composition of the phospholipids. As a result of fish oil feeding, significant increases in the 20:5(n-3), 22:5(n-3) and 22:6(n-3) were detected in all glycerophospholipid classes, while the 18:1(n-9) and 18:2(n-6) and to a lesser extent 20:4(n-6) decreased. Incorporation of n-3 fatty acids increased the phosphatidylcholine/sphingomyelin ratio without changing the total phospholipid or free cholesterol content of the membrane. Fish oil feeding also caused a marked increase in the proportion of 24:1 in sphingomyelins, which occurred mainly at the expense of 18:0 and 24:0. New n-3 fatty acid-containing species appeared in the choline and ethanolamine glycerophospholipids, when compared to membrane lipids from lard-fed rats. Membranes from fish oil fed rats also had moderately higher levels of ether lipids. Few differences were seen between the membranes of the epididymal and perirenal adipocytes. It is concluded that dietary fish oils modify the lipid structure of rat adipocyte plasma membranes by increasing the ratio of phosphatidylcholine to sphingomyelin and by increasing the proportion of molecular species with polyunsaturated fatty acids, which would be anticipated to increase the fluidity of the lipid bilayer of adipocyte plasma membranes.

Reorientational properties of fluorescent analogues of the protein kinase C cofactors diacylglycerol and phorbol ester

The reorientational properties of the fluorescently labelled protein kinase C (PKC) cofactors diacylglycerol (DG) and phorbol ester (PMA) in vesicles and mixed micelles have been investigated using time-resolved polarised fluorescence. The sn-2 acyl chain of DG was replaced by diphenylhexatriene- (DPH) propionic acid, while a dansyl labelled analogue of phorbol ester was used. The extent of ordering of DPH-DG in vesicles turned out to be slightly different from that of the control choline lipid DPH-PC. Addition of PKC to vesicles containing 30 mole% brain PS considerably slowed down the DPH-DG anisotropy decay. This was not observed when DPH-DG was replaced by DPH-PC. Analysis of the fluorescence anisotropy decays of these DPH-lipids in micelles polyoxyethylene-9-laurylether mixed with 10 mole% of the essential phosphatidylserine allowed estimation of their lateral diffusion, orientation distribution and reorientational dynamics within the micelles. Addition of PKC resulted in a significantly slower decay of the fluorescence anisotropy of both DPH-DG and DPH-PC even in the absence of calcium, indicating a calcium independent complexation of PKC with the PS containing micelles. Addition of calcium resulted in a further reduction of the decay of anisotropy of DPH-DG but not of DPH-PC indicating that the Ca2+ dependent immobilisation is cofactor-specific. Similar specific interactions with PKC resulted in a slower decay of dansylated PMA when calcium and PS were present.

Methods for the analysis of triacylglycerols

This article discusses the methods most commonly employed in the analysis of the triacylglycerols (TAGs) in natural fats and considers the main advantages and disadvantages of each and the techniques for optimising analytical conditions. Complete analysis of the composition of a natural fat calls for a method of extracting and purifying the triglyceride fraction, normally by preparatory thin-layer and column chromatography. Determination of the individual components of triglyceride mixtures still entails certain difficulties, namely, the separation and identification of the TAGs in natural fats. High-performance liquid chromatography (HPLC) offers significant advantages over gas and thin-layer chromatography. Many workers have developed non-aqueous, reversed-phase HPLC systems capable of successfully resolving complex mixtures of TAGs, and combining reversed-phase (RP) HPLC and argentation chromatography may improve the results. Identification of the TAGs separated by HPLC becomes an extremely complex task if many different fatty acids are involved and if the sn-stereoscopic positions on the glycerol are to be determined. Enzymatic analysis and chiral-phase chromatography are capable of localising fatty acids on the TAG molecule. In closing, some of the most interesting biomedical applications of TAG analysis are summarised.

The interaction between protein kinase C and lipid cofactors studied by simultaneous observation of lipid and protein fluorescence

The interaction of protein kinase C (PKC) with lipids was probed by a dual approach. Pyrene-labeled lipid analogues of diacylglycerol, phosphatidylserine (PS), phosphatidylinositol (PI), phosphatidylinositol 4-phosphate (PIP), and phosphatidylcholine (PC) were used both as acceptors of tryptophan excitation energy of PKC and as membrane probes for intra- and intermolecular lipid chain collisions by measuring the ratio of excimer-to-monomer fluorescence intensity (EM). Both in micelles of polyoxyethylene 9-lauryl ether and in dioleoyl-PC vesicles, interaction of PKC with monopyrenyl PS (pyr-PS) in the absence of calcium resulted in a relatively slow decrease of the EM value. This effect on the lipid dynamics was accompanied by quenching of the tryptophan fluorescence of PKC. Addition of calcium resulted in a rapid further decrease of the EM ratio of pyr-PS and in additional quenching of the tryptophan fluorescence. When 4 mol % of pyr-PS was replaced by 0.5 mol % of dipyrenyl-labeled diacylglycerol a decrease of the intramolecular excimer formation rate and tryptophan fluorescence could only be detected in the presence of calcium and PS. Strong binding was also observed with dipyrenyl-labeled PIP (dipyr-PIP), but not with the other dipyrenyl-labeled lipids: PI, PS, or PC. In addition, the EM ratios of dipyr-PIP were not affected by phorbol 12-myristate 13-acetate, indicating that phorbol 12-myristate 13-acetate and dipyr-PIP can bind simultaneously to PKC.

An extended method for separating and quantitating molecular species of phospholipids

An improved and extended method for separating and quantitating molecular species of four phospholipid classes is presented. Crude lipid extract is first separated into phospholipid classes on a silica column. Each phospholipid class is then separated into molecular species without derivatization using high-performance liquid chromatography on columns packed with octadecyl silica. Quantitation of individual species is achieved by measuring absorbance at 205 nm. Factors for converting absorbancies to mol fractions have been determined. Quantitation by absorbance at 205 nm agrees well with quantitation by gas chromatography which is preferred to quantitation by phosphate analysis. One hundred phospholipid species have been identified. A table of relative retention times of molecular species is provided. Examples of quantitative analyses of species composition are presented.

Improved determination of individual molecular species of phosphatidylcholine in biological samples by high-performance liquid chromatography with internal standards

Phosphatidylcholine isolated from samples of bile, liver and plasma was converted into 1,2-diradylglycerobenzoate molecular species by hydrolysis with phospholipase C and reaction with benzoic anhydride. Up to seventeen molecular species were separated and determined by reversed-phase high-performance liquid chromatography with detection at 230 nm. The major improvement introduced here was the use of distearoylphosphatidylcholine as the internal standard, which corrected the results for incomplete hydrolysis and benzoylation. Other improvements concerned the clean-up of benzoyl derivatives and the chromatographic separation. The analytical results obtained were validated by comparison with the results of either lipid phosphorus or gas chromatographic determinations.

Plasma lipid profiling by liquid chromatography with chloride-attachment mass spectrometry

A sensitive high-performance liquid chromatographic assay was developed using chloride attachment negative chemical ionization mass spectrometry for detection of glyceryl esters and ceramides, and positive chemical ionization mass spectrometry for detection of free cholesterol and cholesteryl esters in minimal quantities of plasma. The novel technique was validated by high temperature gas-liquid chromatography with flame ionization detection. Sample preparation was achieved by phospholipase C digestion of whole plasma, total lipid extraction and derivatization of any free carboxyl and hydroxyl groups by trimethyl- or tert-butyldimethyl-chlorosilane. The lipids were separated by reverse phase HPLC with 20-90% propionitrile in acetonitrile containing 1% dichloromethane, which served as the reagent and the source of chloride. Negative chemical ionization with chloride attachment is estimated to provide about 100 times higher response for the triacylglycerols and the trimethylsilyl or tert-butyldimethylsilyl ethers of diacylglycerols, and about 500 times higher response for the trimethylsilyl or tert-butyldimethylsilyl ethers of ceramides than positive chemical ionization mass spectrometry. Determination of the full negative chemical ionization mass spectra showed that each glycerolipid and ceramide species yielded a single ionic species corresponding to the chloride-attachment product of the parent ion. The cholesteryl esters and ethers failed to attach chloride and remained undetected by negative chemical ionization. However, the cholesteryl esters and ethers gave a high response for the steroid nucleus in positive chemical ionization mass spectrometry. Chloride attachment negative chemical ionization mass spectrometry is suitable for the unequivocal identification of plasma glycerolipids and ceramides in high-performance liquid chromatography and for the quantitation of molecular species in any unresolved peaks following appropriate calibration of the instrument response.

Effects of dietary n-3 and n-6 polyunsaturated fatty acids on macrophage phospholipid classes and subclasses

This study examined the effects of n-3 and n-6 polyunsaturated fatty acid alimentation on murine peritoneal macrophage phospholipids. Mice were fed complete diets supplemented with either corn oil predominantly containing 18:2n-6, borage oil containing 18:2n-6 and 18:3n-6, fish/corn oil mixture containing 18:2n-6, 20:5n-3 and 22:6n-3, or fish/borage oil mixture containing 18:2n-6, 18:3n-6, 20:5n-3 and 22:6n-3. After two weeks, the fatty acid levels of glycerophosphoserines (GPS), glycerophosphoinositols (GPI), sphingomyelin (SPH), and of the glycerophosphocholine (GPC) and glycerophosphoethanolamine (GPE) phospholipid subclasses were determined. We found that mouse peritoneal macrophage GPC contain primarily 1-O-alkyl-2-acyl (range for the dietary groups, 24.6-30.5 mol %) and 1,2-diacyl (63.2-67.2 mol %), and that GPE contains 1-O-alk-1'-enyl-2-acyl (40.9-47.4 mol %) and 1,2-diacyl (44.2-51.2 mol %) subclasses. In general, fish oil feeding increased macrophage 20:5n-3, 22:5n-3 and 22:6n-3 levels while simultaneously reducing 20:4n-6 in GPS, GPI, GPE and GPC subclasses except for 1-O-alk-1'-enyl-2-acyl GPC. Administration of 18:3n-6 rich diets (borage and fish/borage mixture) resulted in the accumulation of 20:3n-6 (2-carbon elongation product of 18:3n-6) in most phospholipids. In general, the novel combination of dietary 18:3n-6 and n-3 PUFA produced the highest 20:3n-6/20:4n-6 phospholipid fatty acid ratios. This study demonstrates that marked differences in the responses of macrophage phospholipid classes and subclasses exist following dietary manipulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Composition of mouse peritoneal macrophage phospholipid molecular species

The individual molecular species composition of diacyl, alkylacyl and alkenylacyl glycerophospholipids was determined in mouse peritoneal macrophages. A marked heterogeneity in the relative composition (mol%) of macrophage ether and ester phospholipid individual species was noted. High concentrations of 16:0-20:4 were found in ether phospholipids such as alkenylacyl glycerophosphoethanolamine (GPE; 27.5 mol%) and alkylacyl glycerophosphocholine (GPC; 16.6%) as compared to mol% levels of 16:0-20:4 in diacyl GPE (5.7%) and diacyl GPC (8.1%), respectively. Interestingly, alkenylacyl GPE was highly enriched in 1-ether (16:0) relative to alkylacyl GPC. The predominant diacyl molecular species in glycerophosphoinositol (GPI) and glycerophosphoserine (GPS) were 18:0-20:4 (59.1%) and 16:0-18:1 (41.1%), respectively. It is noteworthy that the level of 18:0-20:4 was several times higher in diacyl GPI (59.1%) than in diacyl GPS (11.1%), diacyl GPE (25.7%), and diacyl GPC (3.7%). The most abundant molecular species in diacyl GPC and diacyl GPE were 16:0-18:1 (29.9%) and 18:0-20:4 (25.7%), respectively. The abundance of 20:4 in ether phospholipids, specifically 16:0-20:4 and 18:0-20:4, in alkylacyl GPC is significant in view of the role these antecedents play in the biosynthesis of platelet-activating factor (PAF) and 20:4-derived eicosanoids in stimulated macrophages. The unique molecular species composition of the peritoneal macrophage distinguishes this cell type from others.

Interactions of thiophosphatidic acid with enzymes which metabolize phosphatidic acid. Inhibition of phosphatidic acid phosphatase and utilization by CDP-diacylglycerol synthase

Thiophosphatidic acid (1,2-diacyl-sn-glycero-3-phosphorothioate; thioPA) was chemically synthesized from egg phosphatidylcholine-derived 1,2-diacylglycerol and PSCl3 and tested for its effects on enzymes which utilize phosphatidic acid (PA) in phospholipid biosynthesis. The compound was not a substrate for rat liver cytosolic PA phosphatase and strongly inhibited this enzyme activity. ThioPA was also a potent inhibitor of purified membrane-associated PA phosphatase from Saccharomyces cerevisiae in a competitive manner and exhibited an apparent Ki = 60 microM. In contrast, purified CDPdiacylglycerol synthase (PA:CTP cytidylyltransferase) from this organism was able to convert thioPA to CDP-diacylglycerol. The apparent Vmax for thioPA was 7-fold lower than that for PA, whereas the apparent Km for thioPA (70 microM) was 4-fold lower than that for PA. Calculation of the specificity constant (Vmax/Km) demonstrated that PA was the preferred substrate. These properties of thioPA indicate that this substance may prove useful in studies of phospholipid metabolism and function.

Relative gas-liquid chromatographic retention factors of trimethylsilyl ethers of diradylglycerols on polar capillary columns

Gas-liquid chromatography (GLC) on polar capillary columns provides a highly reproducible resolution and quantitation of molecular species of diradylglycerols when analyzed as the trimethylsilyl (TMS) ethers. In the absence of peak collection and determination of fatty acids or mass spectrometry, peak identification is obtained on the basis of relative retention times of reference standards or of relative retention times calculated from the additive contributions of component fatty chains. Unlike simple esters, complex mixtures of diradylglycerols present special problems in GLC peak identification, which must be attended to by auxiliary separations prior to GLC analysis. In the present study the positional sn-1,2(2,3)- and X-1,3-isomers were resolved by borate thin-layer chromatography (TLC) while the alkenylacyl-, alkylacyl- and diacylglycerols were separated as their TMS ethers by normal-phase high-performance liquid chromatography. The diradylglycerol nature of the sample was further verified by GLC determination of the carbon number distribution, which must be consistent with the composition of the fatty chains of the sample. Under these conditions the identification and quantitation of the molecular species on the polar capillary columns was always consistent with the total fatty acid composition of the sample, as well as with the fatty acid composition of any argentation TLC fractions isolated from some of the samples prior to the polar capillary GLC. Due to the great complexity of the natural diradylglycerol mixtures some peak overlaps occurred, which were reflected in their relative retention times. Nevertheless, a determination of diradylglycerol peak identity from relative retention times proved very satisfactory provided the above described procedures were employed.

Molecular species of glycerophospholipids and sphingomyelins of human erythrocytes: improved method of analysis

This study reports the application of modern methods of molecular species analysis in determination of the structure of both major and minor glycerophospholipids and sphingomyelins of human erythrocytes. Individual phospholipid classes were resolved from total lipid extracts by thin-layer chromatography. Diradylglycerols were released by phospholipase C and converted into trimethylsilyl ethers, which were resolved into the alkenylacyl, alkylacyl and diacylglycerol subclasses by normal phase high performance liquid chromatography. Molecular species of diradylglycerols and ceramides were quantitated according to carbon and double bond number by gas liquid chromatography using a fused silica capillary column wall-coated with bonded RTx-2330. The molecular species of ceramides were determined by GC/MS. The diradyl glycerophosphocholines contained 93.0% diacyl, 4.6% alkylacyl and 2.5% alkenylacyl, while the diradyl glycerophosphoethanolamines were made up of 48.8% diacyl, 47.8% alkenylacyl and 3.4% alkylacyl subclasses. Analysis of the molecular species showed that the long chain polyunsaturated acids were mainly combined with C16 in all diradyl GPC subclasses and in diacyl GPE, while in the alkylacyl and alkenylacyl GPE and in diacyl glycerophosphoinositol and diacyl glycerophosphoserine they were combined mainly with C18 saturated fatty chains. In addition to the C16 and C18 alkyl and alkenyl, the ether fractions also contained significant proportions of C20, C22 and C24 chains. The molecular species of the ceramide moieties of the SPH were made up largely of mono- and diunsaturated species. Over 200 molecular species were identified and quantitated in a representative sample of human red blood cells.

A simplified approach to the analysis of subclasses of phospholipids: application to human platelets

A procedure for the determination of the proportions of diacyl, alkenylacyl and alkylacyl subclasses of glycerophospholipids was developed. The procedure involves: (1) acid methanolysis of the phospholipid followed by Bligh/Dyer extraction of fatty acid methyl esters (FAME) derived from acyl chain types, dimethylacetals (DMA) derived from alkenyl ether chain types, and lysoalkyl phosphatidic acids (lysoalkyl-PA) derived from alkyl ether chain types; and (2) subsequent acetolysis to convert the lysoalkyl-PA to monoalkyl glycerol diacetates (MAGD). GLC analysis and quantitation (using internal standard, 21:0 FAME) of FAME, DMA and MAGD allowed calculation of the proportions of the three molecular subclasses. The methanolysis/acetolysis procedure gave an overall mean phospholipid recovery of 95 +/- 3%. Analysis of the major phospholipids in four separate preparations of fresh resting human platelets by this procedure showed the following range of molecular subclasses: phosphatidylcholine (PC), 86-92 mol % diacyl, 6-10 mol % alkylacyl and 2-3 mol % alkenylacyl; and phosphatidylethanoline (PE), 39-60 mol % diacyl, 5-8 mol % alkylacyl and 34-55 mol % alkenylacyl. The results of these subclass analyses were in general agreement with those reported in the literature.

Molecular species of glycerolipids of Ehrlich ascites cells and of their fat granules

Ehrlich ascites cells were grown in mice and were isolated by centrifugation of the ascites fluid. The cells were lysed with distilled water, and the floating fat particles were collected by centrifugation. The particles contained about 90% neutral and 10% polar lipid. The neutral lipid was made up of about 50% triacylglycerol, 30% alkyldiacylglycerol, 3% cholesteryl esters, 3% free cholesterol and 4% free diacylglycerols. The phospholipid fraction was comprised of about 50% phosphatidylcholine, 35% phosphatidylethanolamine, 10% sphingomyelin and small amounts (less than 5% total) of serine and/or inositol phosphatides. The triacylglycerol and alkyldiacylglycerol fractions possessed total carbon number and fatty acid compositions closely similar to those reported in the literature for whole ascites cells and for a cell membrane preparation. Likewise, the fatty acid composition of phospholipids from the granules in general was similar to that reported for Ehrlich ascites cells. On the basis of the polar and neutral lipid ratio, the lipid granules of the ascites cells were calculated to possess lipid core diameters of 30-50 nm, which were 40-70 times smaller than those (up to 2 mu) measured for the lipid granules of the intact cells by electron microscopy. The characterization of the lipid composition of the Ehrlich ascites lipid granules was completed by determining the molecular species composition of the diacyl, alkylacyl and alkenylacyl phosphatidylethanolamines and of the diacyl and alkylacyl phosphatidylcholines of the ascites cells. It is concluded that the alkyldiacylglycerols of the Ehrlich ascites cells occur largely in the cytoplasmic lipid granules, which appear to consist of many particles of the size and structure of very low density lipoproteins enclosed in membranous sacs.

Alkylacylglycerol molecular species in the glycosylinositol phospholipid membrane anchor of bovine erythrocyte acetylcholinesterase

Bovine erythrocyte acetylcholinesterase, a glycosylinositol phospholipid anchored membrane enzyme, was digested with phosphatidylinositol-specific phospholipase C and the released glycerol-containing moieties were identified and quantitated. About 96% of the total was alkylacylglycerol, of which sn-1-stearyl-2-stearoylglycerol, sn-1-stearyl-2-oleoylglycerol and sn-1-oleyl-2-stearoylglycerol accounted for 69%, 13% and 10%, respectively. These alkylacylglycerols are in marked contrast to the exclusively diacylglycerol species present in phosphatidylinositol from bovine erythrocyte membranes. This difference suggests that assembly of the membrane anchor of Ebo AChE involves a selected cellular pool of diradylglycerols.

Composition and fatty acid content of rat ventral prostate phospholipids

The major phospholipids of rat ventral prostate have been separated and examined using thin-layer chromatography, gas chromatography and mass spectrometry. The main phospholipid classes were choline and ethanolamine glycerophospholipids, accounting for 77.9% of total lipid phosphorus. The prostate also contained small amounts of serine glycerophospholipids and sphingomyelin. The relative proportions of fatty acids in the different phospholipid classes were also determined. Arachidonic acid in prostatic phospholipids is contributed primarily by ethanolamine glycerophospholipids. This fraction contained 65-69 mol% plasmalogens, whereas choline and serine glycerophospholipid fractions contained less than 5 mol% plasmalogens. Ethanolamine, choline and serine plasmalogens contained mainly vinyl ethers of palmitic and stearic aldehydes. Ethanolamine plasmalogens also contained the vinyl ether of oleic aldehyde.

Lipids and their constituents

Many tissues, cells and body fluids possess characteristic lipid composition that can be readily recognized without full resolution and quantitation of individual molecular species. Various chromatographic methods have been adopted for this purpose and are extensively employed in biomedical research. Although lipid profiles are known to change with disease and lipid profiling holds considerable potential for clinical diagnosis, few routines have been established for this purpose. This is partly due to the laborious nature of the simpler methods and the high cost of automated systems. A combination of thin-layer or liquid chromatography with universal detection systems promises to provide more attractive analytical routines for clinical application in the future. At present thin-layer chromatography is the simplest and most rapid qualitative assay for both neutral and polar lipids. Low-temperature gas chromatography is still the method of choice for fatty acid analyses, while high-temperature gas chromatography is eminently suited for quantitative analysis of intact neutral lipids. The availability of the flame ionization and mass detectors now makes high-performance liquid chromatography more useful for profiling both neutral and polar lipids. Combinations of gas or liquid chromatography with mass spectrometry must remain of specialized interest only because of the prohibitive costs of operation.

Quantitative analysis of fatty acid methyl esters and dimethyl acetals on a polar (free fatty acid phase) capillary column

Separation of fatty acid methyl esters and dimethyl acetals from complex biological samples has been achieved by gas-liquid chromatography on a capillary column coated with free fatty acid phase. Response-correcting factors were determined, showing rather large variations with fatty acid length. Polyunsaturated fatty acid methyl esters were shown to have lower responses than saturated species, whereas dimethyl acetals and equivalent methyl esters were found to give similar responses. Total fatty acid and aldehyde compositions of human and simian erythrocytes were determined and compared, showing a somewhat higher level of linoleate and arachidonate, and a lower level of plasmalogens in simian erythrocytes.

Comparative study of the molecular species of chloropropanediol diesters and triacylglycerols in milk fat

In an effort to establish the origin of the fatty acid esters of 3-chloropropanediol, which recently have been isolated in small amounts from goat milk, we compared the molecular species composition of the chlorohydrin diesters and of goat milk triacylglycerols. The chloropropanediol diesters were found to be composed of molecular species containing C10-C18 fatty acids and corresponded closely in carbon number to those calculated for the long chain sn-1,2-diacylglycerol moieties of goat milk triacylglycerols. The molecular species of goat milk total triacylglycerols contained C4-C18 fatty acids. It is suggested that triacylglycerols and chloropropanediol diesters are derived from the same pool of long chain fatty acids. A molecular distillate of bovine milk fat did not contain chloropropanediol diesters, while the available samples of human milk fat were shown to contain alkyldiacylglycerols as the major components of a neutral lipid fraction corresponding in polarity to the chloropropanediol diesters.

Acylation of lysophosphatidylcholine and glycerolphosphate and fatty acid pattern in phosphatidylcholine and -ethanolamine in microsomes of normal and dystrophic human muscle

Phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were isolated from microsomes obtained from normal and dystrophic human muscle and the fatty acid (FA) pattern estimated by GLC. In PC a decrease of the fatty acids of 16:0 and 18:2 and an increase of 18:0 and 18:1 was observed. In PE the decrease measured 18:2 and the increase 18:0 and 18:1. The acylation of lysophosphatidylcholine (LPC) and glycerol-3-phosphate (G3P) was measured in a microsomal system containing exogenously added LPC or G3P and labelled palmitic and oleic acid CoA esters. The incorporation of both labelled fatty acids in LPC-forming PC is reduced in dystrophic microsomes. On the other hand the acylation of glycerolphosphate and the formation of phosphatidic acid (PA) is greater in dystrophic microsomes when compared with normal controls. Possible correlations between the shifted FA pattern and the acylation rate by dystrophic microsomes measured in vitro in the two systems are discussed.

Determination of plasma total lipid profiles by capillary gas-liquid chromatography

We have obtained improved qualitative and quantitative information about plasma lipid composition by adopting capillary gas-liquid chromatography to the determination of plasma total lipid profiles. The new procedure takes advantage of the good recoveries of high molecular weight solutes provided by short capillary columns as well as of the absence of sample fractionation during on-column injection. The major improvements in the gas-liquid chromatographic determination of plasma lipid profiles are the greatly increased carbon number resolution of the solutes and the minimal sample size requirements on the capillary columns. In many instances there is a partial resolution of the saturated and unsaturated molecules within a carbon number, which provides clues to the fatty acid composition of the molecular species. In other respects the new plasma total lipid profiles are similar to those obtained on packed columns. The plasma lipids are dephosphorylated by phospholipase C and trimethylsilylated before analysis.

Molecular species of plant phosphatidylinositol with selective cytotoxicity towards tumor cells

The molecular species of highly purified phosphatidylinositol from soybeans were determined as an aid in the investigation of the mechanism of their reported selective cytotoxicity towards tumor cells. Unlike the animal phosphatidylinositol, which contains predominantly stearic acid in the sn-1 and arachidonic in the sn-2 position (18:0 20:4), the soybean phosphatidylinositol was found to contain mainly linoleic acid in the sn-2 position and palmitic (16:0 18:2), stearic (18:0 18:2) and linoleic (18:2 18:2) acids in the sn-1 position of its molecular species.