Fatty acids ofLactobacillus bulgaricus determined by gas chromatography — Mass spectrometry

Fatty acids (in the form of pyrrolidinides) ofLactobacillus bulgaricus were identified by gas chromatography—mass spectrometry using two columns differing in the polarity of the stationary phase. In addition to the described fatty acids (primarily the most abundant vaccenic acid), we detected nine fatty acids that have not yet been described in the genusLactobacillus (all of them minority compounds) and in four of them we determined the position of the double bond. The occurrence of vaccenic acid was related to other sources of positional isomers of octadecenoic acids (parsley seed - petroselmic acid; olive oil — oleic acid).     

Characterization of astaxanthin esters in Haematococcus pluvialis by liquid chromatography-atmospheric pressure chemical ionization mass spectrometry

After first being analyzed by HPLC, 4 free carotenoids, 15 astaxanthin monoesters, 12 astaxanthin diesters, and 3 astacin monoesters in Haematococcus pluvialis were identified by liquid chromatography-atmospheric pressure chemical ionization mass spectrometry (LC-(APCI)MS). Identification of each compound was based on the characteristic fragment ions of the positive ion mode, negative ion mode, and MS(2). Astaxanthin esters were identified based on the loss of one or two fatty acids. In a positive ion mode, astaxanthin monoesters had characteristic fragment ions at m/z 597 [M+H-fatty acid](+) and m/z 579 and 561 that resulted from a continuous loss of water. The relative intensity of m/z 579 in MS(2) amounted to more than 80% of that of the molecular ion. In astaxanthin diesters, the intensity of m/z 561 occasionally was equal to that of m/z 579, but in general the former, amounting to 50 to 60% or more of the molecular ion, was stronger than the latter, which decreased to 20 to 30% of the molecular ion. In addition, a set of compounds with maximum absorbance at 400 nm, detected by high-performance liquid chromatography-diode array detector (HPLC-DAD), had strong characteristic fragment ions at m/z 871 and 593 in the positive ion mode MS(2). They were presumed to be linolenic acid or an isomer of omega-6-gamma-linolenic acid esters of astacin.     

Fatty acids ofSerratia determined by gas chromatography

The fatty acids in whole-cell methanolysates of 19Serratia strains were identified and quantitated by gas liquid chromatography. The major fatty acid components were 3-OH-C14∶0, C16∶0, C16∶1, and C18∶1+2. They contributed 50–80% of the components in each strain. Significant quantities were also contributed by C14∶0. The other components tended to contribute less than 3% each. Principal component analysis of the fatty acid composition data yielded a three-dimensional ordination of strains that roughly reflected the present taxonomic knowledge on the genusSerratia.     

Liquid chromatography/mass spectrometry of fatty acids as their anthrylmethyl esters

The mass spectra of a series of saturated and unsaturated fatty acids have been recorded as their anthrylmethyl esters using a liquid chromatographic mass spectrometric interface. The spectra show an intense peak for the aromatic nucleus, and a molecular ion. The liquid chromatographic/mass spectrometric separation was performed on a reverse phase column using a solvent system of acetone + acetonitrile. While a complete separation of the fatty acids known to occur in man was not achieved, the recognition of all of these acids is possible using a scanning mode or by ion monitoring.     

Molecular weight determination of methyl esters of mycolic acids using thermospray mass spectrometry.

Methyl esters of normal fatty acids, corynomycolate and corynomycolenate were used as model compounds for thermospray mass spectrometric procedures for molecular weight determination of the related nocardial mycolic acids. By using ammonium acetate at the positive ion generator, in both cases, a family of ions was produced. The following members were found and corresponded to the adducts: (1) M + H; M + NH4 and M + H + NH4 for methyl esters of normal fatty acids, whereas M + H, M + 2H and M + H + NH4 were the adducts most frequently observed with methyl corynomycolates. The methyl esters of C40-C48 mycolic acids from Rhodococcus rhodochrous exhibited prominent peaks corresponding to adducts M + H + NH4 whereas those corresponding to M + 2H showed slightly lower intensities. The structure M + H had no significant representatives with this subclass of mycolic acids. A similar pattern was observed with methyl esters of C50-C54 mycolic acids from Nocardia asteroides GUH-2. Ion peaks C50-C54 representing adducts M + 2H and M + H + NH4 prevailed in the mass spectrum. In this case, the intensities of peaks corresponding to M + 2H were slightly higher than those of the M + H + NH4. Essentially three main species of nocardomycolic acids were detected: (1) monounsaturated C50:1, C52:1 and C54:1; (2) diunsaturated C50:2, C52:2 and C54:2 and (3) triunsaturated C52:3 and C54:3 mycolic acids. The most abundant mycolic acid was C52:2 followed in decreasing abundance by C52:1, C54:2, C50:2, C52:3 and C54:3 mycolic acids.     

Analysis of nucleic acids by ion-spray mass spectrometry

We analyzed various synthetic oligonucleotides with the use of ion-spray mass spectrometer. The most suitable conditions were investigated for analyzing oligonucleotides with molecular weights ranging from 3000 to 15000. We have found that the pH of the solvent was critical to reduce the formation of adduct ions in the mass spectra. Tandem mass spectrometry was also used to study the sequences.     

Structural characterization of wax esters by electron ionization mass spectrometry

The interpretation of the electron ionization mass spectra of straight-chain and methyl-branched saturated and unsaturated wax esters (WEs) is discussed in this study based on the spectra of 154 standards. The most important fragments indicative of the structure of the acid and alcohol chains are identified and summarized for WEs with various number of double bonds in the chains. Briefly, most WEs provide acylium ions allowing structural characterization of the acid part, whereas the alcohol part gives corresponding alkyl radical cations. The elemental composition of selected important fragments is established from a high-resolution accurate mass analysis. The ion abundances are discussed with respect to the length and unsaturation of the aliphatic chains. The interpretation of the spectra of branched or unsaturated WEs requires the recognition of small but important peaks that are difficult to discern among the other fragments. We demonstrate that such fragments are easily detected in differential mass spectra. This approach requires spectra of WE standards (e.g., straight-chain analogs in the case of branched WEs) recorded under the same experimental conditions. The WEs mass spectral database provided in the supplemental data can be used as a reference for the analysis of the GC/EI-MS data.     

Fatty acids and esters from Panax pseudo-ginseng rhizomes

In addition to methyl palmitate, palmitic acid, stearic acid, eicosanoic acid, triacontanoic acid, hexatriacontanoic acid, pentatriacontane, sitosterol and sitosterol-β-D-glucoside, two new compounds isolated from the rhizomes of Panax pseudo-ginseng have been characterized as 14-hydroxyheneicosanoic acid and dotriacontanyl palmitate, respectively, by physico-chemical studies.     

Identification and quantitation of urinary dicarboxylic acids as their dicyclohexyl esters in disease states by gas chromatography mass spectrometry

Clinical studies were conducted by gas chromatography mass spectrometry selected ion monitoring of urinary dicarboxylic acids as dicyclohexyl esters. The dicyclohexyl esters of the dicarboxylic acids give characteristic electron impact mass spectra suitable for selected ion monitoring. The mass spectra exhibit a prominent acid + 1H ion and an (acid + 1H)-H2O ion for use as quantitating and confirming ions. The cyclohexyl esters are stable for days at room temperature and have excellent chromatographic properties. Dicarboxylic acid quantitation is performed within one hour using only 50 microliter of unpurified urine. A rapid method specifically for methylmalonic acid quantitation is described which has assisted physicians in the diagnosis of pernicious anemia and methylmalonic aciduria. This procedure is applicable for screening urinary organic acids for detection of inborn errors of metabolism. The detection of a child with elevated medium length dicarboxylic acids in the terminal urine specimen is reported. This condition, previously described as an inborn error, is attributed to a terminal event. Finally, an increase in urinary succinic acid paralleling putrescine levels is described during a response to cancer chemotherapy.     

Histone H4 acetylation dynamics determined by stable isotope labeling with amino acids in cell culture and mass spectrometry

This paper describes an integrated approach that couples stable isotope labeling with amino acids in cell culture to acetic acid-urea polyacrylamide gel electrophoresis (AU-PAGE) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) for the quantitation and dynamics of histone H4 acetylation. The 697 acute lymphoblastic cell lines were grown in regular medium and in medium in which lysine was substituted with deuterium-labeled lysine. Histone deacetylase (HDAC) activity was inhibited by addition of the HDAC inhibitor depsipeptide to the culture medium for different exposure times. Histones were extracted from cells pooled from unlabeled, untreated cells and from labeled, treated cells, followed by AU-PAGE separation. Gel bands corresponding to different acetylation states of H4 were excised, in-gel digested with trypsin, and analyzed by MALDI-TOF MS. Detailed information was obtained for both the change of histone H4 acetylation specific to the N terminus and the global transformation of H4 from one acetylation state to another following treatment with the HDAC inhibitor depsipeptide. The kinetics of H4 acetylation was also assessed. This study provides a quantitative basis for developing potential therapies by using epigenetic regulation and the developed methodology can be applied to quantitation of change for other histone modifications induced by external stimuli.     

Improved detection of polyunsaturated fatty acids as phenacyl esters using liquid chromatography-ion trap mass spectrometry

The fatty acid composition of Shewanella pealeana was determined by the analysis of fatty acid methyl esters via gas chromatography-mass spectrometry (GC-MS) and fatty acid 2-oxo-phenylethyl esters via high-performance liquid chromatography-mass spectrometry (LC-MS) combined with ultra violet (UV) detection. There was good agreement between the percentage composition of components determined by GC-MS and LC-UV analyses. However, LC-MS analysis using Atmospheric Pressure Chemical Ionization (APCI) demonstrated dramatically enhanced detection of unsaturated fatty acid 2-oxo-phenylethyl esters. The degree of enhancement was proportional to the degree of unsaturation. Tests with a pure polyunsaturated fatty acid (PUFA) standard gave an absolute detection limit in full scan mode of 200 pg. In samples, the selectivity of MS over UV gave a significantly lower detection limit due to lack of chemical interferences. In 'Selected Reaction Monitoring' (SRM) mode, the detection limit was 5 pg. This was essentially independent of whether the sample is a standard or complex mixture of fatty acids. Tandem mass spectrometry was used to support structural information and to enhance the ability to target specific fatty acids. Several PUFAs which were not evident from GC-MS analysis were detected and identified by APCI LC-MS, including some rare or novel PUFAs from S. pealeana and a menhaden oil standard. Detailed analysis of bacterial fatty acid composition by either GC-MS or APCI LC-MS is highly preferable to analysis systems based solely on retention time identification.     

Enantiodiscrimination of chiral alpha-aminophosphonic acids by mass spectrometry.

Diastereomeric clusters between first-group metal ions (M(+)) and chiral alpha-aminophosphonic acids (A and B) have been readily generated in the gas phase by electrospray ionization (ESI) and their fragmentation investigated by mass spectrometry. The complexes studied had the general formula [MA(S)B(2)](+) and [MA(R)B(2)](+), where M = H, Li, Na, or K, A(S) and A(R) are the two enantiomers of a given acid A, and B is a reference alpha-aminophosphonic acid of defined configuration. Collision-induced decomposition (CID) of [MA(S)B(2)](+) and [MA(R)B(2)](+) leads to fragmentation patterns characterized by [MAB](+)/[MB(2)] abundance ratios which depend on the configuration of ligand A. These different spectral features were correlated to the different stability of the diastereomeric [MA(S)B(2)](+) and [MA(R)B(2)](+) complexes in the gas phase. The results have been discussed in the light of MM2 Molecular Mechanics Force Field calculations.     

Electrospray mass spectrometry of human hair wax esters

Wax esters extracted from human hair have been examined by capillary GC-MS and by nano electrospray ionization (ESI) mass spectrometry using a tandem quadrupole mass spectrometer. Initially, the wax esters were examined by capillary GC-MS using conventional means, thus revealing an incomplete chromatographic resolution of the complex array of >200 wax esters ranging from 28 to 40 carbons in length, including saturated/straight-chained, unsaturated/straight-chained, saturated/branched, and unsaturated/branched molecular species. ESI of wax esters produced ammonium adduct ions [M+NH4]+, and collisional activation of these ions formed abundant [RCO2H2]+ product ions. Wax esters containing a double bond in the fatty acyl or fatty alcohol portion of the molecule revealed identical behavior, suggesting little influence of the double bond on the ionization process or subsequent decomposition. The wax ester mixture was analyzed by ESI and tandem mass spectrometry using multiple reaction monitoring and neutral loss scanning. The neutral loss experiment [loss of NH3 and CH2=CH-(CH2)nCH3] was particularly effective at rapidly surveying the complex biological mixture, identifying>160 different wax esters that range from 24 to 42 total carbons.     

Posttranslational modifications to human bone sialoprotein determined by mass spectrometry.

Bone sialoprotein (BSP) is an acidic 301 amino acid protein expressed by osteoblasts and at a low level by hypertrophic chondrocytes. Its expression is highest during early stages of bone formation, and it is particularly abundant in the cells lining the surface of newly formed trabeculae. BSP contains numerous substituents which are anionic in nature and apparently essential for the function of the protein. Thus, the proposed role of BSP in hydroxyapatite nucleation and growth may depend on such modifying groups. The posttranslational modifications include several acidic oligosaccharides as well as phosphate and sulfate groups. This work combines matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry with selective enzyme treatment of BSP to provide new information on the precise distribution and structure of oligosaccharides, sulfate, and phosphate groups in BSP isolated from human bone. The results provide a high level of detail in the location of these modifying groups toward the end of providing a basis for further understanding the function of BSP in bone nucleation.     

Fatty acids of leaf wax esters in Coincya Rouy (Brassicaceae)

A total of 46 populations belonging to the genus Coincya Ruoy (Brassicaceae) from the Iberian Peninsula was examined for their wax ester fatty acids composition. Size of ester fatty acids in the genus Coincya varies between 14 and 28 carbon atoms. This series is dominated by acids with an even number of carbon atoms. The most abundant acids are Ojg, C^y, C^^o and C₂₆ among evens and C₁₇ and C₂₁ among odds. A positive correlation was observed between chemical composition and environmental adaptation, and also with certain morphological characters. Changes relate to low temperatures or to high relative humidity, and there is a positive correlation between chemical composition and leaf glaucousness.