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Ion mobility measurements of product ions has been used characterize the collisional cross-section (CCS) of various complex lipid [M-H](−) ions using traveling wave ion mobility mass spectrometry (TWIMS). TWIMS analysis of various product ion derived after collisional activation of mono-and di-hydroxy arachidonate metabolites was found to be more complex than the analysis of intact molecular ions and provided some insight into molecular mechanisms involved in product ion formation. The CCS observed for the molecular ion [M-H](−) and certain product ions were consistent with a folded ion structure, the latter predicted by the proposed mechanisms of product ion formation. Unexpectedly, product ions from [M-H-H(2)O - CO(2)](−) and [M-H-H(2)O](−) displayed complex ion mobility profiles suggesting multiple mechanisms of ion formation. The [M-H-H(2)O](−) ion from LTB(4) was studied in more detail using both nitrogen and helium as the drift gas in the ion mobility cell. One population of [M-H-H(2)O](−) product ions from LTB(4) was consistent with formation of covalent ring structures, while the ions displaying a higher CCS were consistent with a more open-chain structure. Using molecular dynamics and theoretical CCS calculations, energy minimized structures of those product ions with the open-chain structures were found to have a higher CCS than a folded molecular ion structure. The measurement of product ion mobility can be an additional and unique signature of eicosanoids measured by LC-MS/MS techniques.

Mass spectrometry has played a critical role in the identification and quantitation of lipids present in biological extracts. Various strategies have emerged in order to carry out lipidomic studies. These include both shotgun approaches as well as those engaging liquid chromatographic separation of lipid species prior to mass spectrometric analysis. Nonetheless challenges remain at every level of the lipidomic experiment, including extraction of lipids, identification of specific species, and quantitation of the vast array of lipids present in the sample extract. New strategies have emerged to address some of these issues; however, precise quantitation remains a significant challenge. The use of the ratio of the abundance of the molecular ion species to that of an internal standard enables quite accurate assessment of fold changes within complex lipid species without the need for exact quantitation. Challenges continue to remain in terms of availability of reference standard material as well as relevant internal standards.

Mass spectrometry has played a critical role in the identification and quantitation of lipids present in biological extracts. Various strategies have emerged in order to carry out lipidomic studies. These include both shotgun approaches as well as those engaging liquid chromatographic separation of lipid species prior to mass spectrometric analysis. Nonetheless challenges remain at every level of the lipidomic experiment, including extraction of lipids, identification of specific species, and quantitation of the vast array of lipids present in the sample extract. New strategies have emerged to address some of these issues; however, precise quantitation remains a significant challenge. The use of the ratio of the abundance of the molecular ion species to that of an internal standard enables quite accurate assessment of fold changes within complex lipid species without the need for exact quantitation. Challenges continue to remain in terms of availability of reference standard material as well as relevant internal standards.

Echium oil (EO), which is enriched in 18:4 n-3, the immediate product of fatty acid desaturase 2 (FADS2) desaturation of 18:3 n-3, is as atheroprotective as fish oil (FO). The objective of this study was to determine whether botanical oils enriched in the FADS2 products 18:3 n-6 versus 18:4 n-3 are equally atheroprotective. LDL receptor KO mice were fed one of four atherogenic diets containing 0.2% cholesterol and 10% calories as palm oil (PO) plus 10% calories as: 1) PO; 2) borage oil (BO; 18:3 n-6 enriched); 3) EO (18:4 n-3 enriched); or 4) FO for 16 weeks. Mice fed BO, EO, and FO versus PO had significantly lower plasma total and VLDL cholesterol concentrations; hepatic neutral lipid content and inflammation, aortic CE content, aortic root intimal area and macrophage content; and peritoneal macrophage inflammation, CE content, and ex vivo chemotaxis. Atheromas lacked oxidized CEs despite abundant generation of macrophage 12/15 lipooxygenase-derived metabolites. We conclude that botanical oils enriched in 18:3 n-6 and 18:4 n-3 PUFAs beyond the rate-limiting FADS2 enzyme are equally effective in preventing atherosclerosis and hepatosteatosis compared with saturated/monounsaturated fat due to cellular enrichment of ≥20 PUFAs, reduced plasma VLDL, and attenuated macrophage inflammation.

The tandem mass spectrometry, ion mobility, and normal phase HPLC of isomeric phosphatidylglycerol (PG) and bis(monoacylglycerol)phosphate (BMP) have been investigated in this study with the objective of differentiating these unique classes of lipids. Measurement of ion mobility using the traveling wave method for negative molecular and product ions from isomeric PG and BMP yielded identical results, but different ion mobilities were observed for positive product ions arising from collision-induced dissociation (CID). The fastest moving positive product ions from the ion mobility analysis of BMP(18:1/18:1) were monoglyceride-like, and the slowest moving product ions from this BMP corresponded to [M+H-2H2O]+, which were readily observed for BMP but were only at very low abundance in the CID spectra of PG. The major product ions observed from the sodium adduct of PG(18:1/18:1) were consistent with diglyceride-like ion formation, but for BMP(18:1/18:1) only monoglyceride-like product ions were formed. The usefulness of ion mobility separation was tested with the selection of positive product ions derived from the isomeric PG and BMP molecular species in the lipid extract of RAW 264.7 cells. The ion mobility spectra of monoglyceride-like ions derived from BMP species with various esterified fatty acyl groups displayed some separation in ion mobility based on fatty acyl chain length and presence of a double bond in the acyl chain. The mechanism of ion formation of the diglyceride- and monoglyceride-like ions from PG and BMP respectively was examined using deuterium-labeled species including PG(D3116:0/18:1) and PG and BMP labeled by deuterium exchange.

The positions of double bonds along the carbon chain of methylene interrupted polyunsaturated fatty acids are unique identifiers of specific fatty acids derived from biochemical reactions that occur in cells. It is possible to obtain direct structural information as to these double bond positions using tandem mass spectrometry after collisional activation of the carboxylate anions of an acetone adduct at each of the double bond positions formed by the photochemical Paterno-Buchi reaction with acetone. This reaction can be carried out by exposing a small portion of an inline fused silica capillary to UV photons from a mercury vapor lamp as the sample is infused into the electrospray ion source of a mass spectrometer. Collisional activation of [M – H]− yields a series of reverse Paterno-Buchi reaction product ions that essentially are derived from cleavage of the original carbon–carbon double bonds that yield an isopropenyl carboxylate anion corresponding to each double bond location. Aldehydic reverse Pate...

A novel method for lipid analysis called CTS (collisional activation and traveling wave mass spectrometry), involving tandem mass spectrometry of all precursor ions with ion mobility determinations of all product ions, was applied to a sample of human serum. The resulting four-dimensional data set (precursor ion, product ion, ion mobility value, and intensity) was found to be useful for characterization of lipids as classes as well as for identification of specific species. Utilization of ion mobility measurements of the product ions is a novel approach for lipid analysis. The trends and patterns of product mobility values when visually displayed yield information on lipid classes and specific species independent of mass determination. Collection of a comprehensive set of data that incorporates all precursor-product relationships, combined with ion mobility measurements of all products, enables data analysis where different molecular properties can be juxtaposed and analyzed to assist with class and species identification. Overall, CTS is a powerful, specific, and comprehensive method for lipid analysis.

Neutral lipids are a diverse family of hydrophobic biomolecules that have important roles in cellular biochemistry of all living species but have in common the property of charge neutrality. A large component of neutral lipids is the glycerolipids composed of triacylglycerols, diacylglycerols, and monoacylglycerols that can serve as cellular energy stores as well as signaling molecules. Another abundant lipid class in many cells is the cholesterol esters that are on one hand sterols and the other fatty acyl lipids, but in either case are neutral lipids involved in cholesterol homeostasis and transport in the blood. The analysis of these molecules in the context of lipidomics remains challenging because of their charge neutrality and the complex mixtures of molecular species present in cells. Various techniques have been used to ionize these neutral lipids prior to mass spectrometric analysis including electron ionization, atmospheric chemical ionization, electrospray ionization and matrix assisted laser desorption/ionization. Various approaches to deal with the complex mixture of molecular species have been developed including shotgun lipidomics and chromatographic-based separations such as gas chromatography, reversed phase liquid chromatography, and normal phase liquid chromatography. Several applications of these approaches are discussed. .

As a result of recent advances, remarkable images revealing the distribution of complex lipids in tissues are now generated by matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI IMS). Lipids are amphipathic biomolecules with hydrophobic structural characteristics made by either an initial anion thioester condensation reaction (fatty acid synthase) or by carbocation condensation of branched chain pyrophosphate intermediates (isoprene pathway).1 Lipids play essential roles in cellular function including the self-assembly of phospholipids to form the constitutive outer and inner membrane bilayer of every living cell. Specific components of these membrane phospholipids include species that contain esterified arachidonate that can be enzymatically released to a free acid and transformed to potent signaling molecules (prostaglandins, leukotrienes) with myriad biological effects. The lipid cholesterol is an essential component of bilayer membranes that has a complicated, yet highly regulated biosynthesis. Elevation of cholesterol levels (predominantly as cholesteryl esters) in blood has been implicated in heart disease and is commonly monitored in consideration of human health. Some lipid molecules play the central role in biochemical energy storage in the form of triacylglycerol molecules stored in lipid bodies within most all cells. Mass spectrometry has historically been a tool of choice in biochemical studies of lipids. The sensitivity and specificity of mass spectral data are useful to sort out the complexity of lipid structures to begin to follow biological changes. While techniques such as fluorescence confocal microscopy or ability to engineer proteins that can be expressed in cells with fluorescent tags have become the mainstream of modern biochemical research, such techniques are not amenable to most lipids due to the relatively small size of the lipid molecules and the dynamic nature of their structure in the cell. Recent developments in MALDI IMS have merged specificity of lipid identification with two-dimensional molecular mapping to enable biochemical studies of lipids across regions of a biological tissue. Several significant reasons for the success of MALDI IMS applied to lipid imaging have emerged. The first is the high abundance of various lipids in biological tissues because these hydrophobic molecules constitute the external and internal defining membranes of each cell. These membranes are almost exclusively bilayers composed of phospholipids, sphingolipids, and cholesterol that are closely packed in high local concentrations to render the membrane only semipermeable to water. A second reason is that many lipids, e.g. phospholipids, are already ionized as either phosphate anions or nitrogen centered cations and generate abundant positive or negative ions during the MALDI process. An equally important factor in the success of MALDI IMS of lipids is that the molecular weight of these biomolecules is generally below 1,000 Da, which is an optimal mass range for the most sensitive operation of modern mass spectrometers. Additionally this low molecular weight facilitates diffusion of lipids into a matrix crystal driven by the high concentration of the lipid within the microstructure of the tissue. Because of these fundamental factors coupled with the exciting potential of MALDI IMS, lipid molecules have been frequently used as substrates for the advancement of IMS methodology and instrumentation. Research groups that utilize secondary ion mass spectrometry (SIMS) imaging have embraced lipid biochemistry by moving from inorganic to biological applications, development of larger particle size beams and demonstrations of sub-micron lateral resolution.2,3 Similar development and implementation of instrumentation for MALDI IMS has leveraged lipid diversity, abundance and contrast in rodent brain samples to achieve advancements in technology.4-8 The development of different matrices useful for MALDI IMS,9-16 different methods of matrix application17-23 and different matrix modifiers24,25 have been employed in MALDI IMS experiments to establish the value and parameters of these method modifications for lipid analysis. Advances in biology have been a direct result of our ability to observe biochemical events at the micron and submicron regimes within a tissue. Having a sensitive technique that reveals molecular structure information about specific lipids in a tissue with 10-50 μm resolution and provides information relative to concentration of that lipid, has already provided insight into lipid biochemistry at the tissue level. Since lipids are products of complex, intertwined enzymatic processes, MALDI IMS data reveals the integrated solution to complex reaction pathways that define the living cell in terms of lipid biochemistry. It has become apparent to a host of scientists converging into the use of MALDI IMS from fields as diverse as neuroscience, chemistry, and instrument development that there is a richness and complexity of lipid biochemistry suggested by the exquisite, molecule specific MALDI images created in the course of developing this technology. Many reviews have focused on the technological developments of MALDI IMS of lipids with respect to the issues mentioned above.2,26,27 This review focuses on the lipid biochemistry revealed by MALDI IMS.

Lipid mediators are important in lung biochemistry and are derived from the enzymatic oxidation of arachidonic and docosahexaenoic acids, which are PUFAs that are present in phospholipids in cell membranes. In this study, MALDI imaging MS was used to determine the localization of arachidonate- and docosahexaenoate-containing phospholipids in mouse lung. These PUFA-containing phospholipids were determined to be uniquely abundant at the lining of small and large airways, which were unequivocally identified by immunohistochemistry. In addition, it was found that the blood vessels present in the lung were characterized by sphingomyelin molecular species, and lung surfactant phospholipids appeared evenly distributed throughout the lung parenchyma, indicating alveolar localization. This technique revealed unexpected high concentrations of arachidonate- and docosahexaenoate-containing phospholipids lining the airways in pulmonary tissue, which could serve as precursors of lipid mediators affecting airways biology.

Background Omega‐3 polyunsaturated fatty acids (ω3 PUFA s) suppress inflammation through activation of free fatty acid receptor 4 ( FFAR 4), but this pathway has not been explored in the context of cardiovascular disease. We aimed to elucidate the involvement of FFAR 4 activation by ω3 PUFA s in the process of vascular inflammation and neointimal hyperplasia in mice. Methods and Results We used mice with disruption of FFAR 4 ( Ffar4 −/− ), along with a strain that synthesizes high levels of ω3 PUFA s ( fat‐1 ) and a group of crossed mice ( Ffar4 −/− / fat‐1 ), to elucidate the role of FFAR 4 in vascular dysfunction using acute and chronic thrombosis/vascular remodeling models. The presence of FFAR 4 in vascular‐associated cells including perivascular adipocytes and macrophages, but not platelets, was demonstrated. ω3 PUFA s endogenously generated in fat‐1 mice (n=9), but not in compound Ffar4 −/− / fat‐1 mice (n=9), attenuated femoral arterial thrombosis induced by FeCl 3 . Neointimal hyperplasia and vascular inflammation in the common carotid artery were significantly curtailed 4 weeks after FeCl 3 injury in fat‐1 mice (n=6). This included greater luminal diameter and enhanced blood flow, reduced intima:media ratio, and diminished macrophage infiltration in the vasculature and perivascular adipose tissue compared with control mice. These effects were attenuated in the Ffar4 −/− / fat‐1 mice. Conclusions These results indicate that ω3 PUFA s mitigate vascular inflammation, arterial thrombus formation, and neointimal hyperplasia by interaction with FFAR 4 in mice. Moreover, the ω3 PUFA – FFAR 4 pathway decreases inflammatory responses with dampened macrophage transmigration and infiltration.

The spectrum of nonalcoholic fatty liver disease (NAFLD) includes steatosis, nonalcoholic steatohepatitis (NASH), and cirrhosis. Recognition and timely diagnosis of these different stages, particularly NASH, is important for both potential reversibility and limitation of complications. Liver biopsy remains the clinical standard for definitive diagnosis. Diagnostic tools minimizing the need for invasive procedures or that add information to histologic data are important in novel management strategies for the growing epidemic of NAFLD. We describe an "omics" approach to detecting a reproducible signature of lipid metabolites, aqueous intracellular metabolites, SNPs, and mRNA transcripts in a double-blinded study of patients with different stages of NAFLD that involves profiling liver biopsies, plasma, and urine samples. Using linear discriminant analysis, a panel of 20 plasma metabolites that includes glycerophospholipids, sphingolipids, sterols, and various aqueous small molecular weight components involved in cellular metabolic pathways, can be used to differentiate between NASH and steatosis. This identification of differential biomolecular signatures has the potential to improve clinical diagnosis and facilitate therapeutic intervention of NAFLD.

In mammalian cells, the main stored neutral lipids are triacylglycerol and cholesteryl esters, which are produced by two related enzymes, acyl-CoA:diacylglycerol acyltransferase (DGAT) and acyl-CoA:cholesterol acyltransferase (ACAT), respectively. Very little is known about the metabolism, intracellular storage and function of neutral lipids in many pathogenic lower eukaryotes. In this paper, we have characterized the activity of an important triacylglycerol synthetic enzyme in the protozoan Toxoplasma gondii. A full-length cDNA and gene encoding a T. gondii DGAT1-related enzyme were identified and designated TgDGAT1. The gene is composed of 15 exons and 14 introns, and encodes a protein with a predicted M(r) 63.5kDa, containing signature motifs characteristic of the DGAT1 family. The native protein migrates at 44kDa under reducing conditions. TgDGAT1 is an integral membrane protein localized to the parasite cortical and perinuclear endoplasmic reticulum, with the C-terminus oriented to the lumen of the organelle. When a Saccharomyces cerevisiae mutant strain lacking neutral lipid production is transformed with TgDGAT1 cDNA, a significant DGAT activity is reconstituted, resulting in triacylglycerol synthesis and biogenesis of cytosolic lipid inclusions, resembling lipid bodies in T. gondii. No production of steryl esters is observed upon TgDGAT1 expression in yeast. In contrast to human DGAT1 lacking fatty acid specificity, TgDGAT1 preferentially incorporates palmitate. Our results indicate that parasitic protozoa are also neutral lipid accumulators and illustrate the first example of the existence of a functional DGAT gene in an ancient eukaryote, demonstrating that diacylglycerol esterification is evolutionarily conserved.

The importance of the mass spectral product ion structure is highlighted in quantitative assays, which typically use multiple reaction monitoring (MRM), and in the discovery of novel metabolites. Estradiol is an important sex steroid whose quantitation and metabolite identification using tandem mass spectrometry has been widely employed in numerous clinical studies. Negative electrospray ionization tandem mass spectrometry of estradiol (E2) results in several product ions, including the abundant m/z 183 and 169. Although m/z 183 is one of the most abundant product ions used in many quantitative assays, the structure of m/z 183 has not been rigorously examined. We suggest a structure for m/z 183 and a mechanism of formation consistent with collision induced dissociation (CID) of E2 and several stable isotopes ([D4]-E2, [(13)C6]-E2, and [D1]-E2). An additional product ion from E2, namely m/z 169, has also been examined. MS(3) experiments indicated that both m/z 183 and m/z 169 originate from only E2 [M - H](-) m/z 271. These ions, m/z 183 and m/z 169, were also present in the collision induced decomposition mass spectra of other prominent estrogens, estrone (E1) and estriol (E3), indicating that these two product ions could be used to elucidate the estrogenic origin of novel metabolites. We propose two fragmentation schemes to explain the CID data and suggest a structure of m/z 183 and m/z 169 consistent with several isotopic variants and high resolution mass spectrometric measurements.

The organic constituents of atmospheric aerosols collected at Niwot Ridge, Colorado, along with various physical and meteorological data, were measured during a collaborative field study. Temporal changes in the composition of samples collected during summertime at Niwot Ridge, a rural site in the Rocky Mountains west of Denver, were studied. Volatile organic compounds were thermally desorbed from aerosol particles, separated by gas chromatography, and identified by mass spectrometry. For each of 48 2- to 5-hour samples, 18 organic compounds in aerosol particles, 11 organic and inorganic compounds in the vapor phase, wind direction, and time of day were measured. Relationships among the variables were analyzed by principal component analysis in order to examine the covariations within the data set. The 31 variables are grouped into seven factors, and individual compounds, as well as the factors, serve as molecular markers for biologic and anthropogenic emission sources. Elucidation of several distinct associations within both rural and urban air masses was possible because of the high time resolution achieved in the collection and analysis of aerosols. In addition, factor scores were used to illustrate how several organic compounds vary with respect to local atmospheric dynamics.

A series of [Pd(triphosphine)(CH3CN)](BF4)2 complexes has been prepared with different chelate bites. Stoichiometric reactions of these complexes with triethylphosphine, NaBH4, and H2 have been studied, as well as the catalytic electrochemical reduction of CO2. All of these reactions show significant chelate effects. [Pd(ttpE)(CH3CN)](BF4)2 (where ttpE is bis(3-(diethylphosphino)propyl)phenylphosphine) catalyzes the electrochemical reduction of CO2 to CO in acidic dimethylformamide solutions and reacts with NaBH4 or H2 to form [Pd(ttpE)(H)](BF4). The latter complex is the decomposition product formed under catalytic conditions. X-ray diffraction studies of [Pd(ttpE)(CH3CN)](BF4)2 and [Pd(ttpE)(H)](BF4) provide insight into possible steric origins of reactivity differences between the last two complexes and analogous complexes with smaller chelate bites. [Pd(ttpE)(CH3CN)](BF4)2 has a square-planar structure with one methylene group of the ethyl substituents making a close contact with the nitrogen atom of ...

Various organic compounds in aerosol particles in ambient air near a coniferous forest fire in Boulder, Colorado were identified as molecular markers of wood burning and forest fires. Particle samples were collected by filtering small volumes of air. The samples were analysed using thermal desorption followed by gas chromatographic separation and detection, a highly sensitive analytical method. Several compounds unique to softwood combustion were identified in the samples. Additionally, a predominance of odd-carbon-numbered n-alkanes over the corresponding even-carbon-numbered n-alkanes was observed. This predominance is a well-documented molecular pattern indicative of epicutical waxes in plants.

4-chlorobenzoyl CoA dehalogenase catalyzes the replacement of the chlorine substituent on 4-chlorobenzoyl CoA with a hydroxyl group. We have explored alternative mechanisms for the enzymic dehalogenation reaction. The dehalogenation reaction appears to occur via an S{sub N}Ar mechanism. Further investigations suggested that the reaction proceeds by displacement of chloride by an enzymic carboxylate, followed by hydrolysis of an aryl-enzyme intermediate. When an alternative nucleophile hydroxylamine was included in reaction mixtures, no product derived from direct attack of hydroxylamine upon 4-chlorobenzoyl CoA could be detected. However inclusion of higher concentrations of hydroxylamine (100 mM) resulted in inactivation of the enzyme. These data are consistent with the formation of an aryl-enzyme intermediate that is converted to a hydroxamic acid upon attack by hydroxylamine. 26 refs., 2 figs., 2 tabs.

An improved method of flow injection analysis for aqueous nitrite ion exploits the sensitivity and selectivity of the nitric oxide (NO) chemilluminescence detector. Trace analysis of nitrite ion in a small sample (5-160 microL) is accomplished by conversion of nitrite ion to NO by aqueous iodide in acid. The resulting NO is transported to the gas phase through a semipermeable membrane and subsequently detected by monitoring the photoemission of the reaction between NO and ozone (O3). Chemiluminescence detection is selective for measurement of NO, and, since the detection occurs in the gas-phase, neither sample coloration nor turbidity interfere. The detection limit for a 100-microL sample is 0.04 ppb of nitrite ion. The precision at the 10 ppb level is 2% relative standard deviation, and 60-180 samples can be analyzed per hour. Samples of human saliva and food extracts were analyzed; the results from a standard colorimetric measurement are compared with those from the new chemiluminescence method in order to further validate the latter method. A high degree of selectivity is obtained due to the three discriminating steps in the process: (1) the nitrite ion to NO conversion conditions are virtually specific for nitrite ion, (2) only volatile products of the conversion will be swept to the gas phase (avoiding turbidity or color in spectrophotometric methods), and (3) the NO chemiluminescence detector selectively detects the emission from the NO + O3 reaction. The method is free of interferences, offers detection limits of low parts per billion of nitrite ion, and allows the analysis of up to 180 microL-sized samples per hour, with little sample preparation and no chromatographic separation. Much smaller samples can be analyzed by this method than in previously reported batch analysis methods, which typically require 5 mL or more of sample and often need chromatographic separations as well.

The sequential addition of diethyl vinylphosphonate to primary phosphines followed by reduction with lithium aluminum hydride can be used to synthesize small dendrimers containing up to 15 phosphorus atoms. A second approach uses the addition of bis((diethylphosphino)ethyl)phosphine to tetravinylsilane to produce a dendrimer containing 12 phosphorus atoms. The connectivities of these ligands are established unambiguously by {sup 31}P NMR spectroscopy. These dendrimers react with [Pd(CH{sub 3}CN){sub 4}](BF{sub 4}){sub 2} to produce metalated dendrimers which catalyze the electrochemical reduction of CO{sub 2} to CO. Relationships between catalytic properties and dendrimer structure are discussed.

A new sulfur and nitrogen—phosphorus detector for gas chromatography is described. The detector is an integrated thermionic ionization— chemiluminescence device permitting simultaneous detection of sulfur-containing and nitrogen- or phosphorus-containing compounds. This new flameless detector utilizes a heated rubidium-doped ceramic bead in a thermionic ionization chamber to produce sulfur monoxide from sulfur compounds. The SO is mixed with O 3 and the resulting chemiluminescence is monitored with a photomultiplier tube, providing sulfur-selective detection. The thermionic ionization detector signal serves as an independent second response channel, affording simultaneous selective and sensitive nitrogen—phosphorus detection. Two chromatograms are obtained, one in which selectivity is exhibited for nitrogen and phosphorus compounds, and the other for sulfur compounds present in the sample.

The structures of two Ba(II) chelates of β-diketonates have been determined; one is mononuclear and the other is multinuclear. The Ba(II) chelate of the anion of 2,2,6,6-tetramethyl-3,5-heptanedione (thd) recrystallized from pentane formed monoclinic crystals, space group I2/a, with dimensions a=24.365(9) A, b=21.174(10) A, c=48.486(16) A, β=100.98(3) o , and Z=8. This structure was determined to be a β-diketonate deficient pentanuclear complex with the formula Ba 5 (thd) 9 (HrO) 3 (OH). Both β-diketonate and water ligands act as bridges between barium ions in this structure, resulting in a thermally unstable compound

The quantitative determination of 48 molecular species of regioisomeric diacylglycerols has been made in a single analysis of an extract of bone marrow derived macrophages. The analytical procedure involves solvent extraction of neutral lipids, including diacylglycerols, derivatization of free hydroxyl moieties as 2,4-difluorophenyl urethane, and analysis by normal phase liquid chromatography-tandem mass spectrometry. The derivatization step not only prevents fatty acyl group migration, thus allowing determination of both 1,2- and 1,3-diacylglycerols, but also yields species that are sensitively and uniquely determined by constant neutral loss mass spectrometry. The method also detected monoacylglycerols, which were characterized by unique retention time and collisional spectra, and were present in mouse bone marrow derived macrophage extracts.

Mass spectrometric techniques have been developed to record mass spectra of biomolecules including lipids as they naturally exist within tissues and thereby permit the generation of images displaying the distribution of specific lipids in tissues, organs, and intact animals. These techniques are based on matrix-assisted laser desorption/ionization (MALDI) that requires matrix application onto the tissue surface prior to analysis. One technique of application that has recently shown significant advantages for lipid analysis is sublimation of matrix followed by vapor deposition directly onto the tissue. Explanations for enhanced sensitivity realized by sublimation/deposition related to sample temperature after a laser pulse and matrix crystal size are presented. Specific examples of sublimation/deposition in lipid imaging of various organs including brain, ocular tissue, and kidney are presented.

The focus of the present study was to define the human plasma lipidome and to establish novel analytical methodologies to quantify the large spectrum of plasma lipids. Partial lipid analysis is now a regular part of every patient's blood test and physicians readily and regularly prescribe drugs that alter the levels of major plasma lipids such as cholesterol and triglycerides. Plasma contains many thousands of distinct lipid molecular species that fall into six main categories including fatty acyls, glycerolipids, glycerophospholipids, sphingolipids, sterols, and prenols. The physiological contributions of these diverse lipids and how their levels change in response to therapy remain largely unknown. As a first step toward answering these questions, we provide herein an in-depth lipidomics analysis of a pooled human plasma obtained from healthy individuals after overnight fasting and with a gender balance and an ethnic distribution that is representative of the US population. In total, we quantitatively assessed the levels of over 500 distinct molecular species distributed among the main lipid categories. As more information is obtained regarding the roles of individual lipids in health and disease, it seems likely that future blood tests will include an ever increasing number of these lipid molecules.

We report the isolation of C60 and C70 from combustion soot that is produced in high-temperature, low-pressure premixed flat flames. A critical parameter for high fullerene yields in combustion appears to be a very high flame temperature. Equilibrium calculations indicate that low pressures are important, but the experimental evidence is not clear at this time. Combustion synthesis yields fullerenes with a C70/C60 ratio of about 40%, as compared with the 12% reported for electric-arc-generated fullerenes. The overall yields from carbon are very low (ca. 0.03%) but the soot studied had been produced in flames that were in no way optimized for fullerene production.

Trace-level vapor-phase organic components in tropospheric samples have been identified using combined glass capillary gas chromatography-mass spectrometry. Samples were collected on Tenax-GC sorbent from an aircraft sampling port at various locations over North America and the Atlantic and Pacific Oceans. The compounds found in these samples include n-alkanes (hexane to pentadecane), alkenes, benzene and alkylbenzenes, styrene, tetrachloroethylene, dichlorobenzenes, dimethyldisulfide, and benzaldehyde. The concentrations of benzene and toluene were determined to be in the range of

Palladium was pyrolytically deposited by a supercritical fluid transport-chemical deposition method using the metal β-diketonate complex bis-(2,2,7-trimethyl-3,5-octanedionato)palladium(II). Deposition at a rate of 95 nm/min occurred at a substrate temperature of 740 °C. X-ray diffraction and electron microprobe analyses of the reflective films that were deposited on fused silica substrates showed that they contained polycrystalline palladium. The films were electrically conductive, but conductivity was substantially lower than that for bulk palladium. X-ray diffraction of the films deposited on (100) Si substrates showed that palladium silicide was formed.

Nitrogen dioxide was used to oxidize nonsuperconducting, powdered YBa2Cu3O6.0 to form a material that exhibits the Meissner effect at liquid nitrogen temperature. Nitrogen dioxide treatment at 200 °C for 70 h results in a mixed-phase material containing superconducting YBa2Cu3O6.9 that exhibits onset of superconductivity at 91.5 K and a midpoint at 88 K. During a 70-h exposure of YBa2Cu3O6 to NO2 at 200 °C, a mixture of oxidation and degradation products is formed, including YBa2Cu3O6.9 (61% by weight) and Ba(NO3)2 (23% by weight). Heating the NO2-treated product to 900 °C results in the evolution of NO, NO2, and O2; cooling the sample and annealing at 400 °C in an O2 stream generates the superconducting oxide.

Several of the {beta}-diketonate metal complexes used for metal organic chemical vapor deposition (MOCVD) of thin-film superconductors have been characterized by thermogravimetric analysis, mass spectrometry, and gas chromatography/mass spectrometry. The volatility of the alkaline-earth-metal chelates has been studied, and it has been determined that one reason the alkaline-earth-metal chelates are less volatile than other metal {beta}-diketonates is that they exist as oligomers. For example, one barium {beta}-diketonate chelate consists of a cluster of five metal ions bridged by {beta}-diketonate carbonyl oxygens and water molecules. It has also been found that the addition of uncomplexed (protonated) {beta}-keto enolate ligand to the carrier gas stream greatly improves the gas chromatographic behavior of these alkaline-earth-metal chelates, probably owing to adduct formation accompanying the dissociation of the oligomers. The results of these studies, as well as the implications for using these chelates together with auxiliary ligands for MOCVD, will be discussed. 3 tables, 5 figs., 26 refs.

Reported here is the mass spectral identification of sorbitol-based nuclear clarifying agents (NCAs) and the quantitative description of their extractability from common laboratory and household plasticware made of polypropylene. NCAs are frequently added to polypropylene to improve optical clarity, increase performance properties, and aid in the manufacturing process of this plastic. NCA addition makes polypropylene plasticware more aesthetically pleasing to the user and makes the product competitive with other plastic formulations. We show here that several NCAs are readily extracted with either ethanol or water from plastic labware during typical laboratory procedures. Observed levels ranged from a nanogram to micrograms of NCA. NCAs were also detected in extracts from plastic food storage containers; levels ranged from 1 to 10 microg in two of the three brands tested. The electron ionization mass spectra for three sorbitol-based nuclear clarifying agents (1,3:2,4-bis-O-(benzylidene)sorbitol, 1,3:2,4-bis-O-(p-methylbenzylidene)sorbitol, 1,3:2,4-bis-O-(3,4-dimethylbenzylidene)sorbitol) are presented for the native and trimethylsilyl-derivatized compounds together with the collision-induced dissociation mass spectra; gas and liquid chromatographic data are also reported. These NCAs now join other well-known plasticizers such as phthalate esters and bisphenol A as common laboratory contaminants. While the potential toxicity of NCAs in mammalian systems is unknown, the current data provide scientists and consumers the opportunity to make more informed decisions regarding the use of polypropylene plastics.

There are a host of hydrophobic compounds present within cells that can be termed neutral lipids. In large part, this designation recognizes lack of ionic charge on these molecules in aqueous solution as well as biosynthetic pathways based on carbocation and carbanion condensations that assemble lip...

Triacylglycerols (TAGs) and diacylglycerols (DAGs) are present in cells as a complex mixture of molecular species that differ in the nature of the fatty acyl groups esterified to the glycerol backbone. In some cases, the molecular weights of these species are identical, confounding assignments of identity and quantity by molecular weight. Electrospray ionization results in the formation of [M+NH4]+ ions that can be collisionally activated to yield an abundant product ion corresponding to the loss of ammonia plus one of the fatty acyl groups as a free carboxylic acid. A method was developed using tandem mass spectrometry (MS) and neutral loss scanning to analyze the complex mixture of TAGs and DAGs present in cells and to quantitatively determine changes in TAGs and DAGs molecular species containing identical fatty acyl groups in an experimental series. Eighteen different deuterium-labeled internal standards were synthesized to serve to normalize the ion signal for each neutral loss scan. An example of the application of this method was in the quantitative analysis of TAG and DAG molecular species present in RAW 264.7 cells treated with a Toll-4 receptor ligand, Kdo2-lipid A, in a time course study.

Common organic matrix-assisted laser desorption/ionization (MALDI) matrices, 2,5-dihydroxybenzoic acid, 3,5-dimethoxy-4-hydroxycinnamic acid, and alpha-cyano-4-hydroxycinnamic acid, were found to undergo sublimation without decomposition under conditions of reduced pressure and elevated temperature. This solid to vapor-phase transition was exploited to apply MALDI matrix onto tissue samples over a broad surface in a solvent-free application for mass spectrometric imaging. Sublimation of matrix produced an even layer of small crystals across the sample plate. The deposition was readily controlled with time, temperature, and pressure settings and was highly reproducible from one sample to the next. Mass spectrometric images acquired from phospholipid standards robotically spotted onto a MALDI plate yielded a more intense, even signal with fewer sodium adducts when matrix was applied by sublimation relative to samples where matrix was deposited by an electrospray technique. MALDI matrix could be readily applied to tissue sections on glass slides and stainless steel MALDI plate inserts as long as good thermal contact was made with the condenser of the sublimation device. Sections of mouse brain were coated with matrix applied by sublimation and were imaged using a Q-q-TOF mass spectrometer to yield mass spectral images of very high quality. Image quality is likely enhanced by several features of this technique including the microcrystalline morphology of the deposited matrix, increased purity of deposited matrix, and evenness of deposition. This inexpensive method was reproducible and eliminated the potential for spreading of analytes arising from solvent deposition during matrix application.

Triacylglycerols (TAGs) and diacylglycerols (DAGs) are present in cells as a complex mixture of molecular species that differ in the nature of the fatty acyl groups esterified to the glycerol backbone. In some cases, the molecular weights of these species are identical, confounding assignments of identity and quantity by molecular weight. Electrospray ionization results in the formation of [M+NH4]+ ions that can be collisionally activated to yield an abundant product ion corresponding to the loss of ammonia plus one of the fatty acyl groups as a free carboxylic acid. A method was developed using tandem mass spectrometry (MS) and neutral loss scanning to analyze the complex mixture of TAGs and DAGs present in cells and to quantitatively determine changes in TAGs and DAGs molecular species containing identical fatty acyl groups in an experimental series. Eighteen different deuterium-labeled internal standards were synthesized to serve to normalize the ion signal for each neutral loss scan. An example of the application of this method was in the quantitative analysis of TAG and DAG molecular species present in RAW 264.7 cells treated with a Toll-4 receptor ligand, Kdo2-lipid A, in a time course study.

Mass spectrometry has made significant advances in the analysis of lipid substances, both simple and complex present in extracts of eukaryotic and prokaryotic cells. The development of the ionization techniques of electrospray ionization and matrix-assisted laser desorption ionization (MALDI) have both been applied to the analysis of lipids. The example of the types of structural information that can be obtained from MALDI-TOF tandem mass spectrometry is exemplified by the analysis of Kdo 2 –lipid A, a complex lipopolysaccharide known to activate toll-like 4 receptors on mammalian cells. Analysis of Kdo 2 –lipid A obtained from an Escherichia coli WBB06 was found to generate an abundant [ M − H] − ion at m / z 2236.4 and a more abundant carbon-13 isotope at m / z 2237.4. Furthermore, collisional activation of the lipid A portion of the molecule at m / z 1796.3 resulted in a series of ions corresponding to the loss of all four fatty acyl groups as neutral carboxylic acids. An altogether different challenge of mass spectrometry applied to the area of lipid analysis is that of quantitative analysis. Two rather different requirements have emerged. One with high precision and accuracy for the measurement of relatively few lipid species that are produced at very low concentrations and typically interact with specific receptor proteins. A rather different challenge is that for the analysis of abundant lipid classes, which are composed of multiple molecular species that can approach several hundred under certain circumstances.