Separation and identification of O-acetyl-O-methyl-galactononitriles by gas-liquid chromatography and mass spectrometry

The gas-liquid-chromatographic retention-times and the mass-spectral features of partially methylated d-galactononitrile acetates are reported. Distinctive fragmentation of each of the mono-O-methyl derivatives allows their identification, and the results are applicable to the same substituted derivatives of the other aldohexoses. A new fragmentation-pathway, typical of the acetylated and the O-acetyl-O-methylaldononitriles, is proposed in order to justify previously unexplained fragments. This fragmentation competes with the known ones in derivatives that do not carry vicinal methoxyl groups.     

Compositional and molecular species analysis of phospholipids by high performance liquid chromatography coupled with chemical ionization mass spectrometry

High performance liquid chromatography (HPLC) was combined with chemical ionization mass spectrometry (CIMS) by the use of a moving-belt interface. The technique was employed for the analysis of naturally occurring phospholipids. Positive and negative ion mass spectra of various phospholipids such as phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol, phosphatidylglycerol, and sphingomyelin were obtained in the chemical ionization mode with ammonia or methane as the reagent gas. Specific ions for individual phospholipid "bases" were identified. These ions were used in specific ion monitoring of the phospholipids during HPLC-CIMS. CIMS of each phospholipid also provided extensive information on the molecular species of the individual class of phospholipids. Relative abundance of different molecular species of each phospholipid as determined by CIMS agreed well with the results obtained by gas-liquid chromatography. Rat brain phospholipids were analyzed by HPLC-CIMS in about 15 minutes. Routinely, about 5 micrograms of individual phospholipid was analyzed by HPLC-CIMS, however, with specific ion monitoring the method provides a detection capability at the subnanogram level.     

Bacteriocin detection by liquid chromatography/mass spectrometry for rapid identification

Aims: To establish a new system to detect and identify bacteriocins in the early stage of screening for novel bacteriocins. Methods and Results: Liquid chromatography/mass spectrometry (LC/MS) was employed for development of a new system for rapid detection and identification of bacteriocins. The system detected and identified bacteriocins such as nisin and lacticin 481 from 25 μl of culture supernatants of their producing strains by accurate mass determination coupled with simultaneous impurity removal within 40 min. Especially, the system clearly distinguished three nisin variants (A, Z, Q) in culture supernatants of their producing strains, although they have similar structures and molecular masses. Each one‐step pretreatment by cell adsorption–desorption or acetone precipitation improved bacteriocin detection dramatically, especially for mundticin KS. This system could be applied for detection and molecular mass determination of novel bacteriocins by extracting bacteriocin‐related ions. Conclusions: The developed system could detect and identify some kinds of bacteriocin from culture supernatants or pretreated samples. Significance and Impact of the Study: The developed system helps us to identify bacteriocins in the early stage of screening without any or with one‐step pretreatment. This system is effective on not only detection of known bacteriocins but also identification of novel bacteriocins. Consequently, this system will accelerate discovery of novel bacteriocins.     

Identification of pyruvated monosaccharides in polysaccharides by gas-liquid chromatography mass spectrometry

Twelve bacterial polysaccharides of known structure containing a representative range of pyruvated monosaccharides, were methanolysed, trimethylsilylated, and analysed by g.l.c. and g.l.c.-m.s. Except for 3,4-O-(1-carboxyethylidene)-L-rhamnose, which was unusually labile, the pyruvic acid substituents were largely retained during methanolysis and the Me3Si derivatives of the resulting pyruvated methyl glycosides gave distinctive g.l.c. peaks with characteristic mass spectra. The pyranose rings of 4,6-O-(1-carboxyethylidene)-D-glucose, 4,6-O-(1-carboxyethylidene)-D-mannose, 4,6-O-(1-carboxyethylidene)-D-galactose, and 3,4-O-(1-carboxyethylidene)-D-galactose survived the methanolysis, but that of 2,3-O-(1-carboxyethylidene)-D-glucuronic acid was cleaved to give the methyl ester of 2,3-O-(1-carboxyethylidene)-aldehydo-D-glucuronic acid dimethyl acetal. In the case of 2,3-O-(1-carboxyethylidene)-D-galactose, cleavage of the pyranose ring was less complete; under the conditions used in these experiments two-thirds of the pyranose rings were intact while one-third were cleaved to give the methyl ester of 2,3-O-(1-carboxyethylidene)-aldehydo-D-galactose dimethyl acetal. A very small amount of 3,4-O-(1-carboxyethylidene)-L-rhamnose from one polysaccharide retained its pyruvic acid substituent after gentle methanolysis to give the methyl ester of 3,4-O-(1-carboxyethylidene)-aldehydo-L-rhamnose dimethyl acetal. Susceptibility to cleavage of the pyranose ring during methanolysis appears to be a property of pyruvated monosaccharides with trans-fused 1,3-dioxolane rings.     

Studies on trimethylsilyl derivatives of 1,2-dialkylglycerols by gas-liquid chromatography mass spectrometry

Trimethylsilyl derivatives of 1,2-dihexadecyl- and 1,2-dioctadecyl-glycerols were subjected to analysis by a gas chromatograph mass spectrometer system. The mass chromatographic identification of four kinds of glycerophospholipids, 1,2-dihexadecyl, 1-hexadec-1-enyl-2-hexadecanoyl, 1-hexadecyl-2-hexadecanoyl- and 1,2-dihexadecanoyl-glycerol is also described.     

The gas-liquid cromatography with mass spectrometry for the identification of yeasts

Methods based on gas chromatography, have been used for identification of the yeasts. In order to know the value of the patterns obtained by this method, we have used this technique and mass spectrometry on 44 strains belonging to 16 genus and 21 species of collection yeasts, identifying the corresponding peaks to 22 fatty acids methyl esters by means of the reaction times of the corresponding standards and the confirmation of molecular weigh by mass spectrometry. The correlation coefficient was of 0.848965. The chromatographic technique seems of great utility for the determination of lipidotypes.     

Analysis of polyunsaturated aminophospholipid molecular species using isotope-tagged derivatives and tandem mass spectrometry/mass spectrometry/mass spectrometry

When aminophospholipids with only saturated and monounsaturated fatty acids esterified to the glycerol backbone were labeled with isotopically enriched N-methylpiperazine acetic acid N-hydroxysuccinimide ester reagents, it was found that they could be readily detected as N-methylpiperazine-amide-tagged aminophospholipids using a precursor scan of the stable isotope reporter ion (m/z 114-117) formed by tandem mass spectrometry/mass spectrometry. However, it was found in the current study that these precursor ion scans are not useful in determining the changes of aminophospholipids with polyunsaturated fatty acids (PUFAs) esterified to the glycerol backbone due to the presence of interfering ions in the reporter ion region. Therefore, a method was developed using tandem mass spectrometry/mass spectrometry/mass spectrometry (MS(3)) to obtain reporter ion ratios that were not distorted by interfering ions present in the collision-induced dissociation spectra of nontagged aminophospholipids with PUFAs. This new MS(3) method for N-methylpiperazine- amide-tagged aminophospholipids was used to examine the fate of diacyl, ether, or plasmalogen glycerophosphoethanolamine (GPEtn) species after exposure of human polymorphonuclear leukocytes to A23187 and granulocyte macrophage-colony-stimulating factor/formyl-methionyl-leucyl-phenylalanine stimuli, which can induce eicosanoid biosynthesis, to follow those GPEtn molecular species which were the source of arachidonic acid released. Upon stimulation of the human polymorphonuclear leukocyte, it was found that the abundant arachidonoyl GPEtn plasmalogen molecular species were uniquely reduced in relative content compared to ether or diacyl species and this subclass of GPEtn may be a source of the arachidonic acid converted to leukotrienes by the 5-lipoxygenase pathway activated in this cell.     

The analysis of 2-acetamido-2-deoxyaldose derivatives by gas-liquid chromatography and mass spectrometry

Syntheses are reported of 4-substituted, 4-deoxy analogs of methyl β-D-galactopyranoside (the 4-amino-4-deoxy, 4-azido-4-deoxy, 4-bromo-4-deoxy, 4-chloro-4-deoxy, 4-deoxy-4-fluoro, 4-deoxy-4-iodo, and 4-thio derivatives) as potential substrates of D-galactose oxidase. These syntheses involved nucleophilic displacement of the 4-(p-bromophenylsulfonyl)oxy group of appropriate D-glucose derivatives, although the more reactive (trifluoromethylsulfonyl)oxy group was also utilized as a novel leaving-group. Formation of the bromo and iodo derivatives was accompanied by appreciable halogen exchange and a resulting overall retention of configuration, and formation of the thio compound was attended by competing reactions. Optical rotatory characteristics of the halogeno compounds, their triacetates, and tribenzoates are described, and “anomalous” behavior of the last group is noted.     

Shotgun analysis of phospholipids from mouse liver and brain by nanoflow liquid chromatography/tandem mass spectrometry

It was demonstrated that a shotgun approach can be utilized for the characterization of phospholipids (PLs) extracted from mouse liver and brain by using nanoflow reversed phase liquid chromatography/electrospray ionization tandem mass spectrometry (LC-ESI-MS-MS). In this study, a dual scan method was introduced for the high throughput analysis of complex PL mixtures. Two consecutive LC-ESI-MS-MS runs were made in positive ion mode (for phosphatidylcholines (PCs) and phosphatidylethanolamines (PEs)) first followed by analysis in negative ion mode (for phosphatidylserine (PSs) and phosphatidylinositol (PIs)) using the same binary gradient elution with and without adding formic acid, respectively. The separation of the PLs was carried out using a home made pull tip capillary column (C18) with an end frit. The MS analysis of the eluted PL molecules was performed with a precursor scan followed by a data dependent MS-MS scan. The developed dual scan method was tested with the extracts of PCs and PIs mixtures from soybean, PEs from Escherichia coli, and PSs from bovine brain. It was further applied for the characterization of intact PL samples that were extracted from both mouse liver and mouse brain in the laboratory, and resulted in the identification of 90 and 80 PL species, respectively.     

O-methyl oximes of sugars. Analysis as O-trimethylsilyl derivatives by gas-liquid chromatography and mass spectrometry

The mass spectra of aldoses, partially methylated aldoses, deoxyaldoses, and ketoses containing 3–7 carbons, were recorded on the ethers of the trimethylsilyl O-methyl oxime derivatives. Each compound gave a distinctive spectrum indicating the carbon-chain length and the location of substituents. The gas-liquid chromatographic properties of most compounds in this study were also examined.     

Metabolite identification of missile fuel JP-10 by gas chromatography mass spectrometry

The identification of the metabolites of the Air Force missile fuel JP-10 was accomplished. 5-Hydroxy-JP-10 was identified as the urinary metabolite of rats, mice and hamsters exposed to JP-10. 5-Keto-JP-10 was a major metabolite found in kidney extracts of male rats exposed to JP-10 but not found in kidney extracts from female rats or from other species. Sex-related differences in the formation of 5-keto-JP-10 in rats were studied.