Dose-related effects of early-life intake of sn-2 palmitate, a specific positionally distributed human milk fatty acid, on the composition and metabolism of the intestinal microbiota

sn2 Palmitate in human milk plays an important role in the physiological health of infants by reducing mineral loss, improving stool hardness, and relieving constipation. Also, sn-2 palmitate modulates intestinal microbiota. However, it remains unclear whether the effects of sn-2 palmitate on infant gut microbiota are dose-dependent. In this study, we investigated the effects of low, medium, and high doses (600, 1,800, and 5,400 mg/kg body weight, respectively) of sn-2 palmitate on the structure, composition, and metabolic function of intestinal microbes in mice. Our results showed that high doses of sn-2 palmitate significantly modulated α- and β-diversity of the intestinal microbiota. The relative abundance of Lachnospiraceae_NK4A136_group decreased with increasing doses of sn-2 palmitate. In contrast, the abundances of Bacteroidetes phylum, Bacteroides, uncultured_Lachnospiraceae, and uncultured_Muribaculaceae were positively correlated with sn-2 palmitate doses. The number of genes predicted encoding autophagy-yeast, phospholipase D signaling pathway, and pentose and glucuronate interconversion metabolic functions of intestinal microbiota increased with increasing doses of sn-2 palmitate. In addition, low and medium doses of sn-2 palmitate significantly upregulated the arginine and proline metabolic pathways, and high doses of sn-2 palmitate significantly increased purine metabolism. Our results revealed that the effects of sn-2 palmitate intake early in life on the composition and metabolism of the intestinal microbiota of mice showed dose-related differences. The study is expected to provide a scientific basis for the development of infant formulas.

Phytotoxic and antioxidant effects of dichloromethane fraction of Smilax Brasiliensis Sprengel

Dichloromethane (DCM) fraction and sub-fractions obtained from Smilax brasiliensis leaves were examined in order to determine their phytotoxic and antioxidant effects. The dichloromethane fraction was submitted to a preparative layer chromatography leading to seven sub-fractions (DCM1-DCM7). Gas chromatography-mass spectrometry (GC-MS) was performed on the dichloromethane sub-fractions. The DCM sub-fractions presented phytotoxic potential; at a concentration of 125 µg per plate, DCM6 and DCM4 showed the strongest results on Lactuca sativa and Allium cepa, respectively. The DCM fraction and DCM4 sub-fraction were more effective than 2,6-di-tert-butyl-4-methylphenol (BHT) at scavenging the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical. Analysis by GC-MS showed the presence of methyl palmitate (33.05%) in DCM4 and methyl palmitate (17.29%) and methyl oleate (50.96%) in DCM6, suggesting that the activities exhibited by the sub-fractions may be attributed, at least partially, to these major compounds. These results indicate that the DCM sub-fractions of S. brasiliensis could be used as natural herbicides and antioxidants.

Expression of the Arabidopsis WRINKLED 1 transcription factor leads to higher accumulation of palmitate in soybean seed

Soybean (Glycine max [L.] Merr.) is a commodity crop highly valued for its protein and oil content. The high percentage of polyunsaturated fatty acids in soybean oil results in low oxidative stability, which is a key parameter for usage in baking, high temperature frying applications, and affects shelf life of packaged products containing soybean oil. Introduction of a seed-specific expression cassette carrying the Arabidopsis transcription factor WRINKLED1 (AtWRI1) into soybean, led to seed oil with levels of palmitate up to approximately 20%. Stacking of the AtWRI1 transgenic allele with a transgenic locus harbouring the mangosteen steroyl-ACP thioesterase (GmFatA) resulted in oil with total saturates up to 30%. The creation of a triple stack in soybean, wherein the AtWRI1 and GmFatA alleles were combined with a FAD2-1 silencing allele led to the synthesis of an oil with 28% saturates and approximately 60% oleate. Constructs were then assembled that carry a dual FAD2-1 silencing element/GmFatA expression cassette, alone or combined with an AtWRI1 cassette. These plasmids are designated pPTN1289 and pPTN1301, respectively. Transgenic events carrying the T-DNA of pPTN1289 displayed an oil with stearate levels between 18% and 25%, and oleate in the upper 60%, with reduced palmitate (<5%). While soybean events harboring transgenic alleles of pPTN1301 had similar levels of stearic and oleate levels as that of the pPTRN1289 events, but with levels of palmitate closer to wild type. The modified fatty acid composition results in an oil with higher oxidative stability, and functionality attributes for end use in baking applications.

Enzymatic lipophilization of epicatechin with free fatty acids and its effect on antioxidative capacity in crude camellia seed oil

BACKGROUND

Crude camellia seed oil is rich in free fatty acids, which must be removed to produce an oil of acceptable quality. In the present study, we reduced the free fatty acid content of crude camellia seed oil by lipophilization of epicatechin with these free fatty acids in the presence of Candida antarctica lipase B (Novozym 435), and this may enhance the oxidative stability of the oil at the same time.

RESULTS

The acid value of crude camellia seed oil reduced from 3.7 to 2.5 mgKOH g^-1 after lipophilization. Gas chomatography-mass spectrometry analysis revealed that epicatechin oleate and epicatechin palmitate were synthesized in the lipophilized oil. The peroxide, p-anisidine, and total oxidation values during heating of the lipophilized oil were much lower than that of the crude oil and commercially available camellia seed oil, suggesting that lipophilized epicatechin derivatives could help enhance the oxidative stability of edible oil.

CONCLUSION

The enzymatic process to lipophilize epicatechin with the free fatty acids in crude camellia seed oil described in the present study could decrease the acid value to meet the quality standards for commercial camellia seed oil and, at the same time, obtain a new edible camellia seed oil product with good oxidative stability. © 2016 Society of Chemical Industry.

Curation of the Mammalian Palmitoylome Indicates a Pivotal Role for Palmitoylation in Diseases and Disorders of the Nervous System and Cancers

Palmitoylation involves the reversible posttranslational addition of palmitate to cysteines and promotes membrane binding and subcellular localization. Recent advancements in the detection and identification of palmitoylated proteins have led to multiple palmitoylation proteomics studies but these datasets are contained within large supplemental tables, making downstream analysis and data mining time-consuming and difficult. Consequently, we curated the data from 15 palmitoylation proteomics studies into one compendium containing 1,838 genes encoding palmitoylated proteins; representing approximately 10% of the genome. Enrichment analysis revealed highly significant enrichments for Gene Ontology biological processes, pathway maps, and process networks related to the nervous system. Strikingly, 41% of synaptic genes encode a palmitoylated protein in the compendium. The top disease associations included cancers and diseases and disorders of the nervous system, with Schizophrenia, HD, and pancreatic ductal carcinoma among the top five, suggesting that aberrant palmitoylation may play a pivotal role in the balance of cell death and survival. This compendium provides a much-needed resource for cell biologists and the palmitoylation field, providing new perspectives for cancer and neurodegeneration.

Protein localization is essential for mediating protein function within the cellular context. Mislocalization of proteins can offset cellular balance, influencing whether a cell lives or dies. Many proteins are directed to cellular membranes through the addition of fats, or lipidation. In particular, palmitoylation involves the reversible addition of the fatty acid palmitate to cysteines. Its reversibility makes it a unique form of lipidation allowing its dynamic regulation. Recent advancements in fast, sensitive, non-radioactive methods to detect palmitoylation have led to an explosion in the identification of palmitoylated proteins through proteomics studies. However, the data is hidden in large supplemental tables in various formats. Thus, we curated a list of palmitoylated proteins revealing that approximately 10 percent of the human genome encodes for a proteoform that is palmitoylated. Computational analysis confirmed that palmitoylation is involved in protein localization and indicated a new role in metabolism. Importantly, we found that palmitoylation was enriched at neuronal synapses and in disorders of the nervous system, including Schizophrenia and Huntington disease. Interestingly, palmitoylation was equally enriched in cancers. Consequently, we suggest that palmitoylation plays a critical role in cell fate and our compendium provides a plethora of targets for neurodegeneration and cancer.

Efficient Separation and Analysis of Triacylglycerols: Quantitation of β-Palmitate (OPO) in Oils and Infant Formulas

A high-efficiency, convenient, and reliable method for the separation of structurally similar triacylglycerols is detailed and applied in the quantitative analysis of 1,3-dioleoyl-2-palmitoylglycerol (OPO) in infant formulas and OPO oils. OPO is an important lipid component in "humanized" infant formula. A fast preparative isolation of an OPO-containing fraction from the crude complex mixture, by nonaqueous reversed phase HPLC, followed by Ag(+)-HPLC with detection at 205 nm allowed fine separation and detection of the desired fraction. OPO was quantitated independently of its regioisomer 1,2-dioleoyl-3-palmitoylglycerol (OOP) and isomers of stearoyl-linoleoyl-palmitoyl glycerol that might be present in infant formulas. For samples with low OPO content, an evaporative light-scattering detector (ELSD) was more preferable than UV detection, with a calculated LOD of 0.1 μg of OPO injected and LOQ of 0.3 μg. The method, which showed high reproducibility (RSD < 5%), was suitable for both high OPO content oils and low OPO products such as unenriched infant formula. A number of possible interference issues were considered and dealt with.

Construction of transplastomic lettuce (Lactuca sativa) dominantly producing astaxanthin fatty acid esters and detailed chemical analysis of generated carotenoids

The plastid genome of lettuce (Lactuca sativa L.) cv. Berkeley was site-specifically modified with the addition of three transgenes, which encoded β,β-carotenoid 3,3'-hydroxylase (CrtZ) and β,β-carotenoid 4,4'-ketolase (4,4'-oxygenase; CrtW) from a marine bacterium Brevundimonas sp. strain SD212, and isopentenyl diphosphate isomerase from a marine bacterium Paracoccus sp. strain N81106. Constructed transplastomic lettuce plants were able to grow on soil at a growth rate similar to that of non-transformed lettuce cv. Berkeley and generate flowers and seeds. The germination ratio of the lettuce transformants (T0) (98.8%) was higher than that of non-transformed lettuce (93.1 %). The transplastomic lettuce (T1) leaves produced the astaxanthin fatty acid (myristate or palmitate) diester (49.2% of total carotenoids), astaxanthin monoester (18.2%), and the free forms of astaxanthin (10.0%) and the other ketocarotenoids (17.5%), which indicated that artificial ketocarotenoids corresponded to 94.9% of total carotenoids (230 μg/g fresh weight). Native carotenoids were there lactucaxanthin (3.8%) and lutein (1.3 %) only. This is the first report to structurally identify the astaxanthin esters biosynthesized in transgenic or transplastomic plants producing astaxanthin. The singlet oxygen-quenching activity of the total carotenoids extracted from the transplastomic leaves was similar to that of astaxanthin (mostly esterified) from the green algae Haematococcus pluvialis.

Effects of ethanol and long-chain ethyl ester concentrations on volatile partitioning in a whisky model system

Ethanolic atmospheric pressure chemical ionization mass spectrometry (APCI-MS) was used to analyze the headspace concentrations of a test set of 14 whisky volatile compounds above a series of aqueous ethanolic solutions differing in alcohol content (5-40% ABV) and with regard to concentration of ethyl hexadecanoate (0-500 mg/L). The latter was selected to represent the long-chain ethyl esters found at various concentrations in new-make spirit. Headspace ion intensities were modeled against ethanol and ethyl hexadecanoate concentrations as factors. A separate model was prepared for each compound. Not surprisingly, ethanol content in the range of 5-40% ABV had a significant effect (P < 0.0001) on headspace volatile concentrations of all volatile compounds, whereas the ethyl hexadecanoate concentration had a selective effect of reducing headspace concentrations of the more hydrophobic compounds (log P > 2.5). This finding is discussed in terms of the "structuring" effects of ethyl hexadecanoate when present above critical micelle concentration, leading to the selective incorporation of hydrophobic volatile compounds into the interior of micelle-like structures. Data presented illustrate that dilution of whiskies to 23% ABV for "nosing" in the presence of long-chain ethyl esters is likely to change the balance of volatile compounds in the headspace and thus the perceived aroma character.

Simultaneous measurement of phosphatidylglycerol and disaturated-phosphatidylcholine palmitate kinetics from alveolar surfactant. Study in infants with stable isotope tracer, coupled with isotope ratio mass spectrometry

Disaturated-phosphatidylcholine (DSPC) and phosphatidylglycerol (PG) are respectively the first and the third most abundant phospholipid in human alveolar surfactant. Their concentration decreases in airway surfactant of adults and infants with respiratory distress syndrome and cystic fibrosis. In this study, we used mass spectrometry (IRMS) to investigate the turnover of DSPC and PG in tracheal aspirates (TA) obtained from infants with normal or diseased lungs. We studied eight infants requiring mechanical ventilation: two with no lung disease, four with diaphragmatic hernia, one with ATP-binding cassette sub-family A member 3 heterozygote mutation and one with sepsis. Patients received deuterated water for 48 h as metabolic precursors of palmitate-DSPC and palmitate-PG. Serial TAs were obtained every 6 h for five days or until extubation. DSPC and PG were isolated from TA by column and high-performance thin layer chromatography. Deuterium enrichments of palmitate-DSPC and PG residues were measured by IRMS coupled with a gas chromatographer. Median secretion time (ST), peak time (PT) and fractional synthesis rate (FSR) were 3.7 [0.9- 13.4] h, 71.0 [52.2 - 85.2] h and 6.6 [6.3 - 11.1] %/day for DSPC and 19.3 [6.4 - 22.8] h, 49.0 [33.0 - 52.5] h and 5.8 [4.8 - 10.9] %/day for PG. This study shows that it is feasible to use deuterium derived from body water to trace simultaneously airway surfactant DSPC and PG in humans. When compared within the same patient, DSPC and PG had similar fractional synthesis rates, but PG had a shorter PT, suggesting differences in the life cycle of these essential surfactant components.

GC-based analysis of plant stanyl fatty acid esters in enriched foods

Approaches for the capillary gas chromatographic (GC) based analysis of intact plant stanyl esters in enriched foods were developed. Reference compounds were synthesized by enzyme-catalyzed transesterifications. Their identities were confirmed by means of mass spectrometry. Using a medium polar trifluoropropylmethyl polysiloxane stationary phase, long-chain plant stanyl esters could be separated according to their stanol moieties and their fatty acid chains. Thermal degradation during GC analysis was compensated by determining response factors; calibrations were performed for ten individual plant stanyl esters. For the analysis of low-fat products (skimmed milk drinking yogurts), the GC separation was combined with a "fast extraction" under acidic conditions. For fat-based foods (margarines), online coupled LC-GC offered an elegant and efficient way to avoid time-consuming sample preparation steps. The robust and rapid methods allow conclusions on both, the stanol profiles and the fatty acid moieties, and thus provide a basis for the authentication of this type of functional food ingredients.

Genetic, hormonal, and metabolomic influences on social behavior and sex preference of XXY mice

XXY men (Klinefelter syndrome) are testosterone deficient, socially isolated, exhibit impaired gender identity, and may experience more homosexual behaviors. Here, we characterize social behaviors in a validated XXY mouse model to understand mechanisms. Sociability and gender preference were assessed by three-chambered choice tasks before and after castration and after testosterone replacement. Metabolomic activities of brain and blood were quantified through fractional synthesis rates of palmitate and ribose (GC-MS). XXY mice exhibit greater sociability than XY littermates, particularly for male mice. The differences in sociability disappear after matching androgen exposure. Intact XXY, compared with XY, mice prefer male mice odors when the alternatives are ovariectomized female mice odors, but they prefer estrous over male mice odors, suggesting that preference for male mice may be due to social, not sexual, cues. Castration followed by testosterone treatment essentially remove these preferences. Fractional synthesis rates of palmitate are higher in the hypothalamus, amygdala, and hippocampus of XXY compared with XY mice but not with ribose in these brain regions or palmitate in blood. Androgen ablation in XY mice increases fractional synthesis rates of fatty acids in the brain to levels indistinguishable from those in XXY mice. We conclude that intact XXY mice exhibit increased sociability, differences in gender preference for mice and their odors are due to social rather than sexual cues and, these differences are mostly related to androgen deficiency rather than genetics. Specific metabolic changes in brain lipids, which are also regulated by androgens, are observed in brain regions that are involved in these behaviors.

Unique lipid a modifications in Pseudomonas aeruginosa isolated from the airways of patients with cystic fibrosis

Three structural features of lipid A (addition of palmitate [C16 fatty acid], addition of aminoarabinose [positively charged amino sugar residue], and retention of 3-hydroxydecanoate [3-OH C10 fatty acid]) were determined for Pseudomonas aeruginosa isolates from patients with cystic fibrosis (CF; n=86), from the environment (n=13), and from patients with other conditions (n=14). Among P. aeruginosa CF isolates, 100% had lipid A with palmitate, 24.6% with aminoarabinose, and 33.3% retained 3-hydroxydecanoate. None of the isolates from the environment or from patients with other conditions displayed these modifications. These results indicate that unique lipid A modifications occur in clinical P. aeruginosa CF isolates.

A novel functional assay for simultaneous determination of total fatty acid beta-oxidation flux and acylcarnitine profiling in human skin fibroblasts using (2)H(31)-palmitate by isotope ratio mass spectrometry and electrospray tandem mass spectrometry

BACKGROUND

Two separate and complementary assays, total mitochondrial fatty acid beta-oxidation (FAO) flux rate and acylcarnitine profiling, have been used to establish a definitive diagnosis of FAO defects (FAOD) in cultured cells. We developed a novel functional assay for total FAO rate assay by measurement of deuterated water enrichment and to combine it with the conventional acylcarnitine profiling method into a single tracer incubation experiment.

METHODS

Skin fibroblasts were incubated in a medium containing universal deuterium-labeled palmitate ((2)H(31)-palmitate) and l-carnitine without glucose supplementation for 96 h. The culture medium was assayed for deuterated water enrichment using isotope ratio mass spectrometry (IRMS) and acylcarnitine profiling by electrospray-ionization tandem mass spectrometry (ESI/MS/MS).

RESULTS

The medians of (2)H(2)O enrichment after 96 h of incubation of (2)H(31)-palmitate of the control, other inherited metabolic diseases and FAOD cell lines were 109.9, 102 and 23.1 ppm/mg protein/96 h, respectively. All fibroblasts with FAOD except carnitine uptake defective, multiple acyl-CoA dehydrogenase and short-chain 3-hydroxyacyl-CoA dehydrogenase deficient cells were well separated from the control (<60% control median, p<0.05) and could be identified by IRMS assay. Accumulations of disease-specific acylcarnitines due to blockage in the carnitine cycle and FAO spiral were also demonstrated by acylcarnitine profiling.

CONCLUSIONS

This novel functional assay is less time consuming and relatively simple by comparison to other published methods and can be used to investigate patients suspected to have FAO defects.

Fatty acid composition of Abies pindrow (West Himalayan fir)

The leaves of Abies pindrow, collected from Murree Hills, Punjab (Pakistan) revealed the presence of eleven fatty acids including eight saturated and three unsaturated fatty acids. They ranged from C(14) to C(24) and were detected as methyl esters by GC-MS technique. The saturated fatty acids were present in much greater proportion than unsaturated ones. Isopalmatic acid was found to be major saturated fatty acid and the oleic acid as predominant unsaturated acid. (+)-14-Methyl palmatic acid and (+)-Isosteric acid were the next higher saturated and unsaturated fatty acids respectively.

HPLC quantification of sphingolipids in soybeans with modified palmitate content

Efficient separation and accurate quantification of sphingolipids (SL) are important for studying SL concentrations and biological functions. The objectives of this study were to develop effective methods for the separation and quantification of SL and to determine the relationship between palmitate and SL contents of mature soybean seeds. Methods using column chromatography and high-performance liquid chromatography-evaporative light scattering detector (HPLC-ELSD) were developed to separate and quantify glucosylceramide (GlcCer) and ceramide (Cer) in 15 soybeans lines in which palmitate content ranged from 3.7 to 40.7%. There were significant differences among the lines for GlcCer (83.4-397.6 nmol/g) and major Cer contents (8.4-20.7 nmol/g) on a dry weight basis. The correlations of palmitate content with GlcCer and Cer concentrations were not significant. The results indicated that the palmitate content of soybean seed did not affect their GlcCer and Cer contents. Genetic factors other than those that control palmitate content seemed to be responsible for the variation among soybean lines for GlcCer and Cer contents.

Sample preparation methods for beeswax characterization by gas chromatography with flame ionization detection

New and simpler methods of sample preparation to determine several families of compounds in beeswax by conventional and high temperature gas chromatography are proposed. To analyze hydrocarbons and palmitates, a dilution of sample is enough whereas for the total acid content, a hydrolysis and simultaneous methylation with BF3-methanol results more effective than the usual methods; for the total content of alcohols, a further acetylation with acetic anhydride is necessary. Free alcohols are directly acetylated in a sample dissolution but for free acids and monoesterified 1,2,3-propanetriols analysis, a previous extraction with acetonitrile is required. The concentrations of all the compounds studied are expressed in weight percentage referred only to one standard: octadecyl octadecanoate. The precision of the analytical methods has been evaluated showing its importance in the analysis of beeswaxes used in apiculture.

Characterization of microemulsion structures in the pseudoternary phase diagram of isopropyl palmitate/water/Brij 97:1-butanol

This research was aimed to characterize microemulsion systems of isopropyl palmitate (IPP), water, and 2:1 Brij 97 and 1-butanol by different experimental techniques. A pseudoternary phase diagram was constructed using water titration method. At 45% wt/wt surfactant system, microemulsions containing various ratios of water and IPP were prepared and identified by electrical conductivity, viscosity, differential scanning calorimetry (DSC), cryo-field emission scanning electron microscopy (cryo-FESEM) and nuclear magnetic resonance (NMR). The results from conductivity and viscosity suggested a percolation transition from water-in-oil (water/oil) to oil-in-water (oil/water) microemulsions at 30% wt/wt water. From DSC results, the exothermic peak of water and the endothermic peak of IPP indicated that the transition of water/oil to oil/water microemulsions occurred at 30% wt/wt water. Cryo-FESEM photomicrographs revealed globular structures of microemulsions at higher than 15% wt/wt water. In addition, self-diffusion coefficients determined by NMR reflected that the diffusability of water increased at higher than 35% wt/wt water, while that of IPP was in reverse. Therefore, the results from all techniques are in good agreement and indicate that the water/oil and oil/water transition point occurred in the range of 30% to 35% wt/wt water.

Determination of magnesium stearate in capsule- or tablet-type supplements

A simple method for the determination of magnesium stearate in capsule- or tablet-type supplements was developed. Free stearic acid in the sample was removed by extraction with tetrahydrofuran. The remaining stearate was converted to stearic acid by reaction with a cation-exchange resin. The resulting stearic acid was determined by gas chromatography with a polar column. Esters of stearic acid were not converted to stearic acid and would not cause a positive error in the amount of stearate. The amount of magnesium stearate was calculated based on the stearic acid concentration thus obtained. Magnesium stearate levels in 5 out of 25 supplements exceeded 2500 microg/g, which indicated the possible admixture of magnesium stearate.

[Analysis of constituents of essential oil from the skin of water caltrop]

OBJECTIVE

To analyze the constituents of essential oil from the skin of water caltrop.

METHOD

Water steam distillation and GC-MS were used.

RESULT

58 componds were separated respectively. 56 componds being identified which were 96. 5% of the totle essential oil.

CONCLUSION

Diethyl phthalate, acetamide, N-acetyl-N, N'-1,2-ethanediylbis-, isopropyl palmitate, hexadecanoic acid, Z-11 and octadecanoic acid are the main component of essential oil from the skin of water caltrop.

Quantification of zeaxanthin dipalmitate and total carotenoids in Lycium fruits (Fructus Lycii)

An HPLC-DAD method has been developed to quantitatively analyze for the content of zeaxanthin dipalmitate, a major carotenoid in Fructus Lycii, in different species of the genus Lycium. Determination was performed using an Alltima C18 column with the mobile phase consisting of acetonitrile and dichloromethane (42:58). The total contents of carotenoids in these samples were also determined by using UV spectrophotometric assay. Total carotenoid concentrations of different Fructus Lycii are within the range of 0.03-0.5%. Zeaxanthin dipalmitate is a predominant carotenoid, comprising 31-56% of the total carotenoids in Fructus Lycii. This study is the first systematic quantification of the carotenoids in the fruits of different Lycium species. The results demonstrated that these methods are reliable and facile techniques for rapid analysis of carotenoids for crude drug and plant-derived food supplements.

An infrared spectroscopic method for quantitative analysis of fatty alcohols and fatty acid esters in machinery oils

A new infrared spectroscopic method suitable for determining total fatty alcohol and fatty acid ester concentrations in industrial oils has been developed. Oil samples were diluted with toluene (1:3 w/w), the toxicity and volatility of which are relatively low compared with more commonly used IR solvents, like carbon tetrachloride or carbon disulfide. Mixture standards were prepared from dodecanol, tetradecanol, octadecanol, methyl stearate and methyl palmitate. Some analytical and statistical tests were performed on the developed method. The recoveries and the repeatability of the method proved to be sufficient for the quantitative determination of fatty alcohol and fatty acid ester additives in industrial oils. Reproducibility testing in another laboratory also produced satisfactory results. The developed method also proved to be relatively quick and simple. This method was developed to satisfy industry's need to determine the concentrations of these oil additives, and it has already been applied successfully in machinery oil analysis.

Labeling and quantifying sites of protein palmitoylation

As a reversible posttranslational modification, protein palmitoylation has the potential to regulate the trafficking and function of a variety of proteins. However, the extent, function, and dynamic nature of palmitoylation are poorly resolved because of limitations in assay methods. Here, we introduce methods where hydroxylamine-mediated cleavage of the palmitoyl-thioester bond generates a free sulfhydryl, which can then be specifically labeled with sulfhydryl-reactive reagents. This methodology is more sensitive and allows for quantitative estimates of palmitoylation. Unlike other techniques used to assay posttranslational modifications, the techniques we have developed can label all sites of modification with a variety of probes, radiolabeled or nonradioactive, and can be used to assay the palmitoylation of proteins expressed in vivo in brain or other tissues.

Normal mode analyses of methyl palmitate all-trans and disordered forms in wagging progressive region

Normal mode analyses are made for methyl palmitate molecule having all-trans or conformational disorders around the ester head group, in order to explain characteristic observed frequency shifts in the wagging progressive region between all-trans and disorder chains in triglyceride molecules. It was found that one gauche conformation at C(alpha)-C(beta) position and 90 degrees rotation of the ester head group in an alkyl chain produce frequency shifts for twisting mode as observed. For wagging modes, contamination of the disorders around the head group makes assignments change and apparent frequency shifts occur.

Bioassays of APONIN-3 and -4 with rabbit erythrocytes

Rabbit erythrocytes in methanolic phosphate medium were used to bioassay the activity of authentic samples of methyl stearate and methyl palmitate (in 10% methanol:90% water, v/v), which had been identified as apparent oceanic naturally occurring cytolins (APONIN-3 and -4) produced by Nannochloris oculata. The two natural products are notable for cytolytic activity toward the unarmoured dinoflagellate, Gymnodinium breve Davis, an organism responsible for red tides consisting of harmful algal blooms in the Gulf of Mexico and along the eastern coast of the United States. Bioassays were done with heparinized rabbit blood. The absorbance at 540 nm was observed for 15 min in comparison with a sample treated with haemolysing agent. The results indicated that at reasonable concentrations of 1-10 ppm, neither was a haemolysin, although such concentrations caused cytolysis of G. breve cultures.

Specific lipopolysaccharide found in cystic fibrosis airway Pseudomonas aeruginosa

Cystic fibrosis (CF) patients develop chronic airway infections with Pseudomonas aeruginosa (PA). Pseudomonas aeruginosa synthesized lipopolysaccharide (LPS) with a variety of penta- and hexa-acylated lipid A structures under different environmental conditions. CF patient PA synthesized LPS with specific lipid A structures indicating unique recognition of the CF airway environment. CF-specific lipid A forms containing palmitate and aminoarabinose were associated with resistance to cationic antimicrobial peptides and increased inflammatory responses, indicating that they are likely to be involved in airway disease.

Lipid A modifications characteristic of Salmonella typhimurium are induced by NH4VO3 in Escherichia coli K12. Detection of 4-amino-4-deoxy-L-arabinose, phosphoethanolamine and palmitate

Two-thirds of the lipid A in wild-type Escherichia coli K12 is a hexa-acylated disaccharide of glucosamine in which monophosphate groups are attached at positions 1 and 4'. The remaining lipid A contains a monophosphate substituent at position 4' and a pyrophosphate moiety at position 1. The biosynthesis of the 1-pyrophosphate unit is unknown. Its presence is associated with lipid A translocation to the outer membrane (Zhou, Z., White, K. A., Polissi, A., Georgopoulos, C., and Raetz, C. R. H. (1998) J. Biol. Chem. 273, 12466-12475). To determine if a phosphatase regulates the amount of the lipid A 1-pyrophosphate, we grew cells in broth containing nonspecific phosphatase inhibitors. Na2WO4 and sodium fluoride increased the relative amount of the 1-pyrophosphate slightly. Remarkably, NH4VO3-treated cells generated almost no 1-pyrophosphate, but made six major new lipid A derivatives (EV1 to EV6). Matrix-assisted laser desorption ionization/time of flight mass spectrometry of purified EV1 to EV6 indicated that these compounds were lipid A species substituted singly or in combination with palmitoyl, phosphoethanolamine, and/or aminodeoxypentose residues. The aminodeoxypentose residue was released by incubation in chloroform/methanol (4:1, v/v) at 25 degrees C, and was characterized by 1H NMR spectroscopy. The chemical shifts and vicinal coupling constants of the two anomers of the aminodeoxypentose released from EV3 closely resembled those of synthetic 4-amino-4-deoxy-L-arabinose. NH4VO3-induced lipid A modification did not require the PhoP/PhoQ two-component regulatory system, and also occurred in E. coli msbB or htrB mutants. The lipid A variants that accumulate in NH4VO3-treated E. coli K12 are the same as many of those normally found in untreated Salmonella typhimurium and Salmonella minnesota, demonstrating that E. coli K12 has latent enzyme systems for synthesizing these important derivatives.

Effect of dietary lipid on gamma-glutamyl transferase-positive foci during hepatocarcinogenesis in rats

The effect of dietary lipid on gamma-glutamyl transferase-positive (GGT-positive) foci was investigated. Female Sprague-Dawley rats were dosed with diethylnitrosamine (15 mg/kg) at 24 h of age. After weaning, they were fed nutritionally complete semipurified diets for 3 months. Rats fed 15% corn oil had significantly lower hepatic phospholipid eicosapentaenoate and docosahexaenoate than rats fed 7.5% corn oil plus 7.5% fish oil, 5% corn oil plus 10% fish oil (P < 0.05). However, rats fed 15% corn oil had significantly greater hepatic phospholipid arachidonate than rats fed the other two diets (P < 0.05), suggesting that n-3 polyunsaturated fatty acids were incorporated into hepatic phospholipid at the expense of n-6 polyunsaturated fatty acids. Hepatic PGF2alpha content was significantly greater in rats fed 15% corn oil than in rats fed the other two diets (P < 0.05). Rats fed fish oil had significantly lower hepatic vitamin E content than rats fed corn oil (P < 0.05). Hepatic lipid peroxidation (TBARS) tended to increase with increased dietary fish oil (P < 0.05). Dietary lipid did not influence GGT-positive foci area or number. In conclusion, dietary lipid affected hepatic PGF2alpha production, however, showed no effect on GGT-positive foci area and number. This may suggest that PGF2alpha is not the underlying mechanism for GGT-positive foci during hepatocarcinogenesis.

Cardioprotective profile of MET-88, an inhibitor of carnitine synthesis, and insulin during hypoxia in isolated perfused rat hearts

3-(2,2,2-trimethylhydrazinium) propionate (MET-88) is an inhibitor of carnitine synthesis. This study was carried out to investigate whether or not reduction of carnitine content could attenuate hypoxic damage in isolated perfused rat hearts. Rats were divided into four groups: 1) vehicle control; 2) pretreatment with MET-88 (MET-88); 3) application of insulin (500 muU/mL) in the perfusate (insulin); and 4) pretreatment with MET-88 and application of insulin (MET-88 + insulin). MET-88 (100 mg/kg) was orally administered once a day for 10 days until the day before the experiments. Hearts were initially perfused for a 10 min period under normoxia, followed by a 30 min period under hypoxia. Hearts were frozen at the end of hypoxia for the measurement of high-energy phosphates, carnitine derivatives, and glycolysis intermediates. In a separate series of untreated and MET-88 treated hearts, exogenous glucose and palmitate oxidation was measured. MET-88 decreased the extent of the depression of cardiac contractility (+dP/dt), and aortic flow during the hypoxic state. Insulin also improved cardiac function, and co-treatment of MET-88 and insulin additionally improved cardiac function during hypoxia. MET-88 prevented the decrease of high-energy phosphate and the increase of long-chain acylcarnitine after 30 min of hypoxic perfusion. In addition, MET-88 increased the steady state of glucose oxidation in hypoxic perfused rat hearts. These results indicate that MET-88 has cardioprotective effects on contractile function and energy metabolism of isolated perfused rat hearts in a hypoxic condition. Preventing the accumulation of long-chain acylcarnitine may serve to protect hypoxic hearts.

Triglyceride disposition in isolated hepatocytes after treatment with hydrazine

Treatment of animals with hydrazine causes the accumulation of triglycerides in the liver but the mechanism remains unclear. Therefore, the effect of hydrazine on hepatic triglyceride synthesis and subsequent transport was studied in a hepatocyte model, in vitro in order to isolate liver cells from extrahepatic influences. Hepatocytes were isolated and either incubated in suspension with [14C]palmitate in the presence of hydrazine (2-12 mM) or pre-incubated with [14C]palmitate, washed free of the fatty acid and then incubated with hydrazine (2-12 mM). Hydrazine resulted in a significant reduction in the incorporation of [14C]palmitate into triglycerides and reduction in the transportation of triglycerides out of cells. When [14C]palmitate was in the incubation medium, ATP levels were reduced by lower concentrations of hydrazine than have previously been reported. None of the concentrations of hydrazine used affected cell membrane integrity (viability) as measured by LDH leakage. The 14CO2 produced by the beta-oxidation of [14C]palmitate was also measured in short term incubations (30 min) carried out in sealed vessels. There was a dose dependent increase in 14CO2 produced by very low concentrations of hydrazine (0.01-0.1 mM) after which the effect was maximal and concentrations above 8 mM hydrazine decreased 14CO2 production. The data suggest that the inhibition of transportation of triglycerides out of cells by hydrazine may have a more important role in the accumulation of triglycerides in the liver than has been previously recognised. However, the model was not able to mimic the accumulation of triglycerides in hepatocytes seen in vivo.

Lipid composition of hepatic and adipose tissues from normal cats and from cats with idiopathic hepatic lipidosis

The purpose of this study was to characterize the lipid classes in hepatic and adipose tissues from cats with idiopathic hepatic lipidosis (IHL). Concentrations of triglyceride, phospholipid phosphorus, and free and total cholesterol were determined in lipid extracts of liver homogenates from 5 cats with IHL and 5 healthy control cats. Total fatty acid composition of liver and adipose tissue was also compared. Triglyceride accounted for 34% of liver by weight in cats with IHL (338 +/- 38 mg/g wet liver) versus 1% in control cats (9.9 +/- 1.0 mg/g wet liver, P < .001). The mass of cholesterol ester was significantly higher in triglyceride-free (TG-free) liver from cats with IHL (741 +/- 340 micrograms/g TG-free wet liver) compared to healthy cats (31 +/- 11 micrograms/g TG-free wet liver, P < .05). Total fatty acid composition of hepatic tissue in the 2 groups differed; palmitate was higher (19.5 +/- 1.1% of total fatty acids in cats with IHL versus 9.2 +/- 2.7% in controls, P < .05), stearate was lower (8.5 +/- 0.8% versus 16.8 +/- 1.1%, P < .05), oleate was higher (41.2 +/- 1.6% versus 31.1 +/- 1.8%, P < .05), and arachidonate was lower (1.2 +/- 0.2% versus 6.0 +/- 0.9%, P < .05). The total fatty acid composition of adipose tissue also differed between the 2 groups; palmitate was higher (26.2 +/- 1.2% in cats with IHL versus 21.3 +/- 0.6% in controls, P < .05), total monounsaturated fatty acids were higher (48.4 +/- 1.0% versus 45.0 +/- 0.8%, P < .05), linolenate was lower (13.3 +/- 1.6% versus 17.5 +/- 0.9%, P < .05), total (n-6) fatty acids were lower (13.8 +/- 1.38% versus 18.4 +/- 0.83%, P < .05), linolenate was lower (0.2 +/- 0.04% versus 0.7 +/- 0.06%, P < .06), and total (n-3) fatty acids were lower (0.3 +/- 0.02% versus 1.3 +/- 0.32%, P < .05). The fatty acid composition of both liver and adipose tissue was similar for stearate, oleate, linoleate, and linolenate in cats with IHL. These results support the hypothesis that the origin of hepatic triglyceride in cats with IHL is the mobilization of fatty acids from adipose tissue.

Quantitative evaluation of carbon isotopic fractionation during reversed-phase high-performance liquid chromatography

The fractionation of 13C during low-performance preparative LC and high-performance LC is reported quantitatively for methyl palmitate and using high-precision isotope ratio mass spectrometry (IR-MS). For both preparative and high-performance analytical columns, 13C enrichment is about 7% greater than the parent starting material, drops sharply in the first section of the peak and then settles to a value about 1% below that of the starting material. Recycling over a single HPLC column did not induce greater fractionation. These results emphasize the importance of quantitative peak collection for high-precision IR-MS studies, particularly the first part of the peak where the isotope ratio changes rapidly.

The composition of individual molecular species of plasma phosphatidylcholine in human pregnancy

The molecular species composition of plasma phosphatidylcholine (PC) was measured in sequential blood samples from 13 pregnant women from 16 weeks of gestation to delivery at term. The increased total plasma PC concentration at term was due solely to increased concentrations of individual species containing palmitate (16:0) rather than stearate (18:0) at the sn-1 position. The specific increase of PC16:0/22:6 concentration in mid-gestation suggests that adaptations to maternal hepatic PC metabolism may provide a mechanism to ensure adequate supply of 22:6(n-3) to the fetus. While cord plasma PC was comparable to liver PC composition from three stillborn term infants, the compositions of these tissues differed from maternal plasma PC, which contained significantly more PC16:0/18:2 and PC18:0/18:2. These results suggest that, although fetal acquisition of polyunsaturated fatty acids (PUFA) is dependent on the maternal lipid supply, the detailed composition of fetal plasma PC may be regulated largely by intrinsic fetal mechanisms such as placental and liver PC metabolism. Similarly, the specific alterations to maternal plasma PC composition in pregnancy, which we postulate are associated with the supply of PUFA to the fetus, were substantially independent of variations in maternal dietary lipid nutrition.

Thermotropic behavior of stratum corneum lipids containing a pseudo-ceramide

The mechanism of the self-assembly of the lamellar structure of natural stratum corneum lipids (SCL) has been a subject of considerable interest. We have examined this question by using a synthetic pseudo-ceramide (sphingolipid E, SLE) which was analogous to the naturally occurring ceramide type 2. The thermotropic properties and the structural characteristics of SLE, together with other main components of SCL, fatty acids, and cholesterol, were investigated by differential scanning calorimetry and X-ray analysis. A mixture of SLE and stearic acid was in a stable alpha-form having a lamellar structure, which is very similar to that of natural SCL. However, lipid mixtures in which stearic acid were replaced by oleic acid did not form lamellar structures, and existed in the crystalline states. This indicates that the stable bilayer formation of the natural SCL is strongly dependent on the molecular fatty acid structure. Moreover, incorporation of cholesterol (0-50%) into equimolar mixtures of SLE/stearic acid and of SLE/oleic acid caused a marked decrease of melting entropies, while the aggregation states of both systems were not changed. This effect of cholesterol can be attributed to the disorder of the molecular packing. These results suggest that the hydrophobic interactions between the SCL are important for bilayer formation as are the hydrophilic interactions between the polar groups.

Characterization of the lipid moiety of the glycosylphosphatidylinositol anchor of Trypanosoma cruzi 1G7-antigen

The 90-kDa stage-specific 1G7-antigen has been implicated in the invasion of host cells by the metacyclic forms of Trypanosoma cruzi. The antigen is attached to the plasma membrane via glycosylphosphatidylinositol, the partial structure of which was the first to be determined for a protein of this parasite. In this study, the complete structure of the lipid component of the anchor was determined by electrospray mass spectrometry, gas chromatography mass spectrometry, phospholipase sensitivity and high-performance thin-layer chromatography of the diaradylglycerol components after benzoylation. These analyses showed that the lipid moiety of 1G7-antigen is composed essentially of 1-O-hexadecyl-2-O-hexadecanoyl-phosphatidylinositol and 1-O-hexadecyl-2-O-octadecanoyl-phosphatidylinositol. The high sensitivity of the electrospray mass spectrometric analysis unexpectedly revealed the presence of a small proportion of putative inositol-phosphoceramide structures, and confirmed the absence of inositol-acylated species. An interesting finding was that the biosynthetic incorporation of [3H]palmitate labelled solely the acyl position, and not the 1-O-alkyl chain in the 1G7-antigen anchor.

Phosphorylation and palmitoylation of the human D2L dopamine receptor in Sf9 cells

We have expressed and biochemically characterized the human D2long (D2L) dopamine receptor isoform using the baculovirus/Sf9 cell system. The expressed receptor bound ligands with a pharmacological profile similar to that reported for neuronal and cloned D2L receptors expressed in mammalian cell lines. Dopamine binding to D2L receptor was sensitive to guanine nucleotides, indicating receptor coupling to endogenous G proteins. A D2L receptor-specific antibody identified two major protein species at approximately 44 kDa and at approximately 93 kDa in immunoblots, suggesting the presence of D2L receptor monomers and dimers. Both species were purified by immunoprecipitation from digitonin-solubilized preparation of cells expressing D2L receptor prelabeled with 32P(i) or [3H]-palmitate. These results constitute the first direct evidence for D2L receptor phosphorylation and palmitoylation.

Biosynthesis of a novel 3-oxo-2-tetradecyloctadecanoate-containing phospholipid by a cell-free extract of Corynebacterium diphtheriae

We have isolated, purified, and identified by chemical analyses and mass spectrometry, a novel 3-oxo-2-tetradecyloctadecanoate (dehydrocorynomycolate)-containing phospholipid (PL-1) from the chloroform-methanol extract of Corynebacterium diphtheriae. This phospholipid was separated from all of the other known dehydrocorynomycolate and 3-hydroxy-2-tetradecyloctadecanoate (corynomycolate)-containing lipids and found to be unstable even at -20 degrees C. It was present in trace amounts as a homologous series (molecular weights of 1400 and 1404 as the methyl esters) and composed of a dehydrocorynomycolate, a phosphate group, a diacylglycerol, and an unidentified amine-containing component. Because of the complexity of these phospholipids, their complete structural determination is yet to be completed. A cell-free extract of C. diphtheriae catalyzed the incorporation of radiolabel from [14C]palmitic acid into PL-1. This incorporation was ATP-dependent, and the rate was linear with respect to both time and protein concentration. The radiolabel was incorporated primarily into the dehydrocorynomycoloyl moiety of PL-1. While avidin did not show any significant effect, cerulenin showed a marked inhibition of this reaction. Based on these results, we suggest that this dehydrocorynomycolate-containing PL-1 may be the long-sought acyl carrier-containing product of a Claisen-type condensation.

Effect of palmitate concentration on the relative contributions of the beta-oxidation pathway and citric acid cycle to total O2 consumption of isolated rat hepatocytes

The relative contributions of beta-oxidation and citric acid cycle activity to total O2 consumption during fatty acid oxidation were examined in isolated hepatocytes. When hepatocytes were incubated with palmitate alone, a rise in fatty acid concentration induced an increase in O2 uptake that reflected a large stimulation of beta-oxidation and an accompanying smaller inhibition of citric acid cycle oxidation. In the presence of lactate, successive increments in palmitate concentration over the range from 0 to 1.0 mM stimulated glucose synthesis and brought about a concomitant incremental stimulation of both beta-oxidation and citric acid cycle flux. However, above 1.5 mM palmitate, additional increments in fatty acid concentration depressed gluconeogenesis and citric acid cycle activity but induced a further stimulation of beta-oxidation. These findings demonstrate that, during fatty acid oxidation, the rate of citric acid cycle turnover is more closely linked to the rate of glucose synthesis than is the rate of beta-oxidation. This may be relevant to observations that the stimulation of hepatic O2 consumption, induced by fatty acid oxidation, is much greater than can be explained in terms of the ATP-demand arising from exposure of hepatocytes to fatty acid.

Quantitative studies on fatty acid metabolism in isolated parenchymal cells from normal and cirrhotic livers in rats

Parenchymal cells isolated from normal and thioacetamide-induced micronodular cirrhotic rat livers were used to evaluate changes in hepatocellular fatty acid (FA) metabolism in cirrhosis. Exogenous free FA (FFA) are rapidly taken up by hepatocytes obtained either from normal or cirrhotic livers. They are predominantly esterified to triglycerides and accumulate intracytoplasmatically as lipid droplets with increasing cellular FFA uptake. In the parenchymal cells of cirrhotic livers, however, the following changes were observed when compared with controls: (i) decreased cellular output of esterified FA derived both from exogenous sources and from de novo FA synthesis; (ii) increased total ketone body production, mainly as beta-hydroxybutyrate; (iii) decreased cholesterol synthesis; and (iv) enhanced incorporation of newly synthesized FA into phospholipids in spite of an unaffected rate of FA synthesis. In summary, the data provide evidence for intrinsic alterations in the lipid metabolism in the parenchymal cells of cirrhotic livers which are preserved in the isolated hepatocytes under optimum incubation conditions for oxygen and substrate supply.

Nondenaturing protein electrotransfer of the esterase activity of lipolytic preparations

Lipolytic enzymes subjected to nondenaturing polyacrylamide gel electrophoresis were electrophoretically transferred under nondenaturing conditions onto a solid-state matrix. Electrotransfer permitted the visualization of hydrolytic activity to the long-chain water insoluble substrate alpha-naphthyl palmitate. Four commercial preparations: a lipase from Candida cylindracea, an esterase from porcine liver, a lipase from Pseudomonas sp., and a cholesterol esterase from Pseudomonas fluorescens were examined.

Two-dimensional electrophoresis of the fatty acid binding protein from human heart: evidence for a thiol group which can form an intermolecular disulfide bond

A 100,000 g supernatant from human heart muscle, containing cytosolic proteins with some contaminating plasma proteins, was analyzed for fatty acid binding protein (FABP) by two-dimensional electrophoresis (2-DE) using isoelectric focusing under nondenaturing conditions in the first dimension. FABP purified from human heart muscle was found to comigrate with a major spot in 2-DE gels of the supernatant. This spot was comparable with those of the myoglobins in staining intensity. When purified FABP was charged with [3H]palmitate and subjected to nondenaturing 2-DE, radioactivity always comigrated with this protein. Under denaturing and reducing conditions in the second dimension, FABP was found to have a pI of 5.3 and an apparent molecular weight of 15,000. Isoforms of FABP, reported here for the first time to occur in human heart muscle, were observed as minor spots focusing at pH 5.1 and 5.7. When electrophoresis in the second dimension was carried out under denaturing but nonreducing conditions, an additional protein appeared at pH 5.3 with an apparent molecular weight of about 30,000. This protein was identified as a dimer of FABP and evidence for the involvement of an intermolecular disulfide bond in this dimerization is presented.

Cell mass of Mycobacterium bovis BCG estimated by gas chromatography

The presence of additives and large cellular aggregates in freeze-dried BCG vaccines precludes accurate measurement of total cell content by traditional methods. The possibility that extraction and quantitation of a cell membrane fatty acid may provide a suitable means of cell mass determination was tested. The palmitic acid methyl ester peak area determined by gas chromatography was directly proportional to the wet weight of freshly grown Tice-, Pasteur-, and Glaxo-substrain BCG, as well as the dry weight of the ampoule contents after removal of soluble material. Extraction of palmitic acid from Tice BCG vaccine was not appreciably affected by lyophilization and the calculated dry cell mass values of freeze-dried vaccine samples correlated well with particle number. This method, therefore, may be useful in measuring BCG cell mass during all stages of vaccine manufacture and storage.

Serum albumin binding of palmitate and stearate. Multiple binding theory for insoluble ligands

In usual studies of ligand binding to a carrier, free and bound ligand concentrations are measured in equilibrium mixtures with varying carrier and ligand concentrations. The observed data are then analyzed by a binding equation such as Scatchard's or the general binding equation. With palmitic, stearic and oleic acids as ligands we found that the aqueous solubility is too low to allow this procedure. We have consequently transformed the general binding equation so that it does not contain parameters related to aqueous solutions of the ligand. While the classical binding equations describe affinities of transfer of a ligand from an aqueous solution to the carrier, the new equation is valid for transfer of a ligand from one bound state to another, i.e. for relative binding description. The relative binding constants, L1, L2, L3 ... Li, in the new equation thus define the transfer affinity for the ligand from a 1:1 complex with a standard carrier to an i:1 complex of the ligand with the carrier investigated. Binding of palmitate and stearate to human serum albumin was studied by determination of dialytic exchange rates between identical fatty acid/albumin solutions. The results were analyzed by the new equation without reference to ligands in aqueous solution.

Negative ion ammonia chemical ionization and electron impact ionization mass spectrometric analysis of steryl fatty acyl esters

Synthesis of steryl palmitates, varied in the nature of the steryl moiety, provided model compounds for investigation of the mass spectrometric behavior of steryl long-chain fatty acyl esters. The structure of the steryl moiety was varied according to: (i) position and degree of unsaturation in the steroid nucleus and C-17 side-chain, (ii) position and degree of methylation, (iii) presence or absence of a 9 beta, 19-cyclopropane ring. Compounds were chosen so as to be representative of biochemically important steryl esters. Electron impact (EI) behavior of steryl palmitate esters closely resembles that of their short-chain (e.g. acetate) counterparts. M+.ions were generally weak or absent and the major high mass ions arose from characteristic fragmentations of the steroid nucleus following loss of the acyl moiety ([M-RCO2H]+.). Fragment ions characteristic of the acyl moiety were lacking. Negative ion chemical ionization (NICI) using ammonia as reagent gas, on the other hand, afforded spectra containing characteristic fragment ions [RCO2]-, [RCO2-18]-, and [RCO2-19]- from which the nature of the fatty acyl moiety can be readily deduced. Hence, NICI and EI provide complementary means of ionization for the mass spectrometric determination of structures of steryl esters.

Phosphatidylethanolamine of lung surfactant: proportion and fatty acid patterns of the alkylacyl, alkenylacyl and diacyl subclasses

The phosphatidylethanolamine fraction isolated from lung surfactant consisted of 33% of the alkylacyl, 39% of the alkenylacyl and 25% of the diacyl subclass. Palmitic acid was the major fatty acid of the alkyl acyl and alkenylacyl subclasses. In diacylphosphatidylethanolamine, saturated and unsaturated fatty acids revealed a ratio of nearly 1.

Human tissue factor contains thioester-linked palmitate and stearate on the cytoplasmic half-cystine

The state of the five half-cystine residues in human tissue factor (TF) has been characterized. The results indicate that the four half-cystines in the extracellular domain of TF form two disulfide bonds and the half-cystine in the cytoplasmic region is acylated by palmitic acid and stearic acid. The extracellular disulfide cross-links, Cys49-Cys57 and Cys186-Cys209, were deduced from the analysis of tryptic peptides. Acylation of the cytoplasmic half-cystine was demonstrated by purifying and characterizing fibroblast TF from cells labeled with [3H]palmitic acid. Radiolabeled fibroblast TF was observed by autoradiography following sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The tritiated material covalently bound to the protein was identified as [3H]palmitate and [3H]stearate by reverse-phase high-pressure liquid chromatography. Deacylation of TF with hydroxylamine resulted in the spontaneous generation of disulfide-linked TF dimers. This result suggests that the disulfide-linked TF dimer, a minor component of most TF preparations, and the recently described heterodimeric form of TF are artifacts produced by deacylation of Cys245 and subsequent interchain disulfide bond formation.