Atom Bombardment Tandem Mass Spectrometry Research Articles

Structural determination of cerebrosides isolated from Asterias amurensis starfish eggs using high‐energy collision‐induced dissociation of sodium‐adducted molecules

Six cerebrosides were isolated from the eggs of the starfish Asterias amurensis using solvent extraction, silica gel column chromatography, and reversed-phase high-performance liquid chromatography. This study demonstrated that the structures of cerebrosides could be completely characterized, based on their sodium-adducted molecules, using fast atom bombardment (FAB) tandem mass spectrometry. The high-energy collision-induced dissociation of the sodium-adducted molecule, [M + Na](+), of each cerebroside molecular species generated abundant ions, providing information on the compositions of the 2-hydroxy fatty acids and long-chain sphingoid bases, as well as the sugar moiety polar head group. Each homologous ion series along the fatty acid and aliphatic chain of the sphingoid base was useful for locating the double-bond positions of both chains and the methyl branching position of the long-chain base. The N-fatty acyl portions were primarily long-chain saturated or monoenoic acids (C16 to C24) with an α-hydroxy group. The sphingoid long-chain base portions were aliphatic chains (C18 or C22) with two or three degrees of unsaturation and with or without methyl branching.

ChemInform Abstract: Synthesis and Characterization of Dimetallacalix(8)arene Complexes.

The one-pot synthesis of a variety of [4-tert-butylcalix [8] arene (MOR) 2 ] − [M' or R'NH 3 ] + (M=Ti, Zr, V, Sn; M'=Li, Na, K) complexes is described. The 1 H NMR spectra of these compounds possess several interesting features, including upfield shifts of α or β protons on the alkoxide ligand and a phenol hydroxyl resonance. The upfield shift is due to shielding of the alkoxide ligand by the aryl rings of the calixarene macrocycle. The ligands are located in cavities, made up of three aryl rings of the macrocycle. Fast atom bombardment mass spectrometry (FABMS) and tandem mass spectrometry have been used to obtain molecular ion information as well as identify fragment ions from these complexes

Structural determination of monoacylglycerols extracted from marine sponge by fast atom bombardment tandem mass spectrometry

Five new monoacylglycerols (MAGs) were isolated from the marine sponge Stelletta sp. by reversed-phase high-performance liquid chromatography and analyzed by positive ion fast atom bombardment mass spectrometry (FAB-MS). FAB mass spectra of these compounds produced abundant sodium-adducted molecules [M+Na]+ from a mixture of 3-nitrobenzyl alcohol and sodium iodide. The structural elucidation of these sponge MAGs was carried out by FAB tandem mass spectrometry (MS/MS). To find diagnostic ions for the characterization of the MAGs, authentic MAGs were initially analyzed by collision-induced dissociation (CID) MS/MS. The CID MS/MS of [M+Na]+ precursor ions resulted in the formation of numerous characteristic product ions via a series of dissociative processes. The product ions formed by charge-remote fragmentation (CRF) provided important information for the characterization of acyl chains substituted at the glycerol backbone, and product ions at m/z 84, 97, 113 and 139 were diagnostic for the sodiated glycerol backbone. On the basis of these fragmentation patterns, the structures of five MAGs extracted from marine sponge were elucidated. In addition, high-resolution mass measurement was performed to obtain the elemental compositions of the MAGs.

Structural determination of hexadecanoic lysophosphatidylcholine regioisomers by fast atom bombardment tandem mass spectrometry.

The structural determination of sn-1 and sn-2 hexadecanoic lysophosphatidylcholine (LPC) regioisomers was carried out using fast atom bombardment tandem mass spectrometry (FAB-MS/MS). The collision-induced dissociation (CID) of protonated and sodiated molecules produced diverse product ions due mainly to charge remote fragmentations. Based on the information obtained from the CID spectra of protonated and sodiated molecules, sn-1 and sn-2 hexadecanoic LPC isomers could be discriminated. Especially, the abundance ratio of the diagnostic ion pair [m/z 224/226] in the CID spectra of [M + H](+) ions was shown to be greatly different. Moreover, the CID-MS/MS spectra of sodium-adducted molecules for hexadecanoic LPC isomers showed characteristic product ions such as [M + Na - 103](+), [M + Na - 85](+), and [M + Na - 59](+), by which their regio-specificity can be differentiated.

Study of structural characteristic features of phenanthriondolizidine alkaloids by fast atom bombardment with tandem mass spectrometry

The mass spectrometric behavior of phenanthroindolizidine alkaloids has been investigated in detail by positive ion fast atom bombardment tandem mass spectrometry (FAB-MS/MS) combined with collision-induced dissociation (CID). The fragmentation has been correlated with the skeleton structure and positions of substituents. The product ions arising from retro-Diels-Alder cleavages differ clearly for compounds with different skeletons. The substituents at C-14 were observed to markedly influence the fragmentation pathway of [M + H](+) ions. A diversity of dissociation behavior initiated by the variation of substituents on the aromatic ring was also observed in the CID spectra. Product ions resulting from loss of CH(4) were obtained for compounds in which both C-6 and C-7 are occupied by methoxy groups. FAB-MS/MS spectra can reflect the connection between the fragmentation behavior and structural features of these phenanthroindolizidine alkaloids rapidly and effectively, and should prove to be a powerful method to determine the structures of related compounds.

Identification of fonofos metabolites in Latuca sativa, Beta vulgaris, and Triticum aestivum by packed capillary flow fast atom bombardment tandem mass spectrometry.

The metabolism of fonofos, a thiophosphonate insecticide, was investigated in mature lettuce (Latuca sativa), beet (Beta vulgaris), and wheat (Triticum aestivum). Six new metabolites were identified by LC-MS and LC-MS-MS analysis using fast atom bombardment (FAB) and packed capillary LC columns with application of the on-column focusing technique. These methods provided the sensitivity required to identify unknown metabolites that were present in the mature plants at only 20-230 ppb. Structural elucidation was facilitated by use of fonofos labeled with both carbon-14 and carbon-13 in the phenyl ring. In all three plants fonofos was converted to a glucose conjugate of thiophenoxylactic acid. Oxidation of the glucose conjugate gave isomeric sulfoxides in all species examined. Thiophenoxylactic acid was found esterified to malonic acid in lettuce. In beets, S-phenylcysteine was found as its malonic acid amide. A second metabolite unique to beets was N-(malonyl)-[2[(ethoxyethylphosphinothionyl)oxy]phenyl]cysteine. This novel structure was confirmed by synthesis.

Biomarker techniques to screen for bacteria that produce polyunsaturated fatty acids

The production of polyunsaturated fatty acids (PUFA) by bacteria has been firmly established for over two decades although it is still commonly ignored. Investigations of Antarctic sea ice have revealed a high diversity of novel bacterial taxa with the ability to produce PUFA. The majority are psychrophilic (requiring low temperatures for growth) and halophilic (requiring the presence of salts for growth), in contrast to the bacterial community present in the underlying water column. Specific fatty acids may be used as indicators of PUFA-producing bacteria in environmental samples. Structural studies of bacterial phospholipids have been particularly revealing in suggesting biomarkers specific for prokaryotic PUFA input. The use of negative ion fast atom bombardment tandem mass spectrometry for the analysis of bacterial phospholipids has identified species specific for certain groups of bacterial PUFA producers. The phylogeny of PUFA production in the γ- Proteobacteria also suggests the future use of PUFA genes for the assessment of marine bacterial biodiversity.

Structural characterization of isoxazolidinyl nucleosides by fast atom bombardment tandem mass spectrometry.

4'-Aza-2',3'-dideoxyerythrofuranosyl derivatives of thymine (AdT, 1) and uracil (AdU, 2) are analogues of 2',3'-dideoxyribofuranosyl thymine (ddT, 3) and uracyl (ddU, 4). Compounds 1 and 2 are representative of a new class of antiviral agents where the sugar moiety is replaced by an isoxazolidine ring. The increasing importance of isoxazolidinyl nucleosides has encouraged the exploitation of simple mass spectrometric rules for unambiguously assigning their structure. The species 1, 2, 5 and 6 were therefore synthesized in order to evaluate the role of the basic centre of the modified sugar moiety in their gas-phase chemistry. The tandem mass spectra of these compounds are similar to those of the wild-type nucleosides and display fragment ions corresponding to [B + 2H](+),[M - BH](+) and [B + 27](+) species, where B is the nucleobase. The last species derives from a retrocycloaddition process which is less evident in 2'-deoxyribosides. This behaviour is consistent with protonation of the analytes at the pyrimidine rings. Model isoxazolidines, in which the nucleobase was replaced by a phenyl or a naphthyl moiety, displayed the expected behaviour of species with a localized charge on the N-O moiety of the isoxazolidine ring.

Structural determination of lysophosphatidylcholines extracted from marine sponges by fast atom bombardment tandem mass spectrometry.

A series of lysophosphatidylcholines were isolated from the marine sponge Spirastrella abata by reversed-phase high performance liquid chromatography (HPLC) and analyzed by fast atom bombardment mass spectrometry (FAB-MS). Their structural elucidation was carried out with fast atom bombardment tandem mass spectrometry (FAB-MS/MS). The collision-induced dissociation (CID) of protonated and sodiated molecular ions produced diverse product ions via a series of dissociative processes. Because of the positive charge of the amine group at the end of the molecules, charge-remote fragmentation patterns of specific ions, [M + H](+) or [M + Na](+), were very helpful for the identification of product ions which are characteristic for choline and long hydrocarbon chains substituted at the glycerol back bone. Moreover, the CID-MS/MS spectra of sodium adducted molecular ions for lysophosphatidylcholines yielded common characteristic fragment ions for the choline moiety and characteristic ions [M + Na-103](+), [M + Na-85](+) and [M + Na-59](+) in the higher mass region.

The early glycation products of the Maillard reaction: mass spectrometric characterization of novel imidazolidinones derived from an opioid pentapeptide and glucose

Glucose-substituted imidazolidinones related to the endogenous opioid peptide leucine-enkephalin have been investigated using fast atom bombardment tandem mass spectrometry (FAB-MS/MS) and electrospray ionization tandem mass spectrometry (ESI-MS/MS). In addition to Amadori compounds, the studied imidazolidinones represent a novel type of the early glycation products formed in the Maillard reaction. To obtain insight into the fragmentation behavior of these carbohydrate-peptide adducts, we also studied synthetic precursors of the glucose-substituted imidazolidinones as well as the corresponding isopropylidene derivatives. The collision-induced dissociation (CID) spectra of [M + H](+) ions of all these imidazolidinones have been compared. Detailed analysis showed that fragmentation of each compound generates two ions at m/z 566 and m/z 598 which are characteristic and undoubtedly confirm the imidazolidinone-type structure. These two significant ions were identified as the M + 10 and M + 42 modifications of the N-terminus of the parent opioid pentapeptide effected by the carbohydrate moiety. Furthermore, the ion at m/z 178 is identified as the M + 42 modification of the immonium ion of the N-terminal amino acid (tyrosine) also effected by the carbohydrate moiety. They can be used as diagnostic ions for imidazolidinone-type compounds in studying the Maillard reaction. Thus, we have demonstrated the utility of FAB-MS/MS and ESI-MS/MS in the structural determination and identification of such novel peptide-carbohydrate adducts, useful in understanding the details of the mechanism of non-enzymatic glycation in vivo.

Identification of triacylglycerols containing two short‐chain fatty acids at sn‐2 and sn‐3 positions from bovine udder by fast atom bombardment tandem mass spectrometry

Identification of triacylglycerols containing two short‐chain fatty acids at sn‐2 and sn‐3 positions from bovine udder by fast atom bombardment tandem mass spectrometry

Squid nerve sphingomyelin containing an unusual sphingoid base

A new methodology has been developed to determine sphingolipid structures by positive-ion fast atom bombardment tandem mass spectrometry (FAB-MS/MS). The method was verified by application to a structurally known glycosphingolipid, and then used in the structural study of an unusual sphingomyelin isolated from squid (Loligo pealei) nerve. Our previous study of this squid sphingomyelin indicated that the major base had a branched C19 alkyl chain with three double bonds, two of which were conjugated. The positions of the branching as well as the double bonds of this base were unambiguously determined by directly comparing the product ion spectra of the long-chain base ion (LCB+) of two ceramides, one derived from squid nerve sphingomyelin and another, glucosylceramide, obtained from starfish spermatozoa. The latter served as the standard because the structure had already been determined by nuclear magnetic resonance (NMR). The precursor ion here was LCB+, that is, [CH2 − C(NH2) = CHR]+, rather than [M + H]+, where R represents the backbone hydrocarbon chain counting from C-4. The results clearly showed that the squid nerve base is identical to the base derived from starfish (Asterias amurensis), that is, 2-amino-9-methyl-4,8,10-octadecatriene-1,3-diol.This is the first report in which the detailed structure of a branched polyunsaturated sphingoid base was studied by tandem mass spectrometry without derivatization or the aid of NMR. The occurrence of such an unusual sphingoid base in various phyla and tissues suggests the conjugated polyunsaturated branched sphingoid base plays a significant role in animals.

Identification of triacylglycerols containing two short-chain fatty acids at sn-2 and sn-3 positions from bovine udder by fast atom bombardment tandem mass spectrometry.

Several triacylglycerol (TAG) molecular species, that contain two short-chain fatty acids (C4 to C8) at the sn-2 and sn-3 positions of the glycerol backbone, were isolated from bovine udder by using solvent extraction and silica gel column chromatography. Their structures were identified by fast atom bombardment (FAB) tandem mass spectrometry (MS/MS), based on the information obtained from collision-induced dissociation (CID) spectra of sodium-adducted molecules ([M + Na](+)) of model TAG compounds which had been synthesized from glycerol and appropriate fatty acids. For each species, the relative positions of the three fatty acids on the glycerol backbone, as well as fatty acid composition and double-bond position in the fatty acyl group, were determined. A majority of sodium-adducted molecules observed in the FAB mass spectrum were mixtures of at least two components that have different fatty acid composition but the same molecular mass. In addition, all the components present in mixtures of all the species contain a long-chain fatty acid (C12 to C18) at the sn-1 position, a short-chain fatty acid (C4 to C8) at the sn-2 position, and a butyric acid uniquely at the sn-3 position.

Structures of the O-specific polysaccharides from Yokenella regensburgei (Koserella trabulsii) strains PCM 2476, 2477, 2478, and 2494: high-resolution magic-angle spinning NMR investigation of the O-specific polysaccharides in native lipopolysaccharides and directly on the surface of living bacteria.

The structures of the carbohydrate O-specific side-chain moiety of the lipopolysaccharides (LPS) of Yokenella regensburgei, strains PCM 2476, 2477, 2478, and 2494, have been investigated by (1)H and (13)C NMR, fast atom bombardment tandem mass spectrometry (FAB-MSMS), matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry, methylation analysis, partial acid hydrolysis, and immunological methods. It was concluded that the O-specific polysaccharides of strains 2476, 2477, 2478, and 2494 are composed of the same basic trisaccharide repeating unit having the structure -->3)-alpha-D-FucpNAc-(1-->2)-L-alpha-D-Hepp-(1-->3)-6-deoxy -alpha-L- Talp-(1-->, in which L-alpha-D-Hepp is L-glycero-alpha-D-manno-heptopyranose. The detailed analysis revealed, however, differences in O-acetylation patterns of the 6-deoxy-L-talose residue, with 2- and 4-O-acetyl disubstituted -->3)-6-deoxy-alpha-L-Talp-(1--> in strain PCM 2476 and a 2-O-acetylated residue in strains 2477, 2478, and 2494. These structures represent novel, trisaccharide repeating units of bacterial O-antigens that are characteristic and unique to the Y. regensburgeispecies. By use of the high-resolution magic-angle spinning (HR-MAS) technique, (1)H NMR spectra of the O-polysaccharides directly in isolated LPS were obtained. This allowed for almost full assignment and structural determination of the polysaccharide. By this technique the O-polysaccharide components were also observed in their original form directly on the surface of living bacterial cells.

Liquid chromatography–electrospray mass spectrometry as a tool for the analysis of sulfated oligosaccharides from mucin glycoproteins

An approach for analyzing sulfated oligosaccharide alditol mixtures by liquid chromatography–electrospray mass spectrometry (LC–ESI-MS) is described. Two columns, an amino-bonded column and a porous graphitized carbon column (PGC) were used. Oligosaccharides were eluted with linear gradients of acetonitrile and water, with 5 mM ammonium hydrogencarbonate or formate buffers at a basic pH. The methods were evaluated on a mixture of sulfated oligosaccharide alditols prepared from mucin glycoproteins from pig stomach. Results from LC–ESI-MS of the mixture were compared with the structural information obtained by high energy collision fragmentation using fast atom bombardment tandem mass spectrometry (FAB-MS–MS). The separation ability of the two columns was also tested using a more complex mixture of sulfated oligosaccharides from pig colon, where several isomers were detected. The potential use of in-source collision-induced dissociation (CID) to gain sequence information of sulfated oligosaccharides was also evaluated. The major fragment ions obtained by in-source CID of the trisaccharide Hex-3HexNAcol6-HexNAc6-SO3− were sufficient for assigning the oligosaccharide sequence and the position of the sulfate group within the monosaccharide moiety. The LC–ESI-MS approach should be a valuable tool for characterization of mucin glycosylation and alterations during pathological conditions.

Analysis of saponins from black bean by electrospray ionization and fast atom bombardment tandem mass spectrometry

Analysis of saponins from black bean by electrospray ionization and fast atom bombardment tandem mass spectrometry

Analysis of saponins from black bean by electrospray ionization and fast atom bombardment tandem mass spectrometry

Analysis of saponins from black bean by electrospray ionization and fast atom bombardment tandem mass spectrometry

Analysis of saponins from black bean by electrospray ionization and fast atom bombardment tandem mass spectrometry.

Saponins from black bean (Vigna mungo L. Hepper) were analyzed using positive and negative ion fast atom bombardment mass spectrometry (FAB-MS) and liquid chromatography/mass spectrometry. Methanol was used to extract the saponins from defatted black bean, which was partially purified by extraction with n-butanol, and the extract was dialyzed with 3000 M(r) cut-off tubing. The dialyzate was analyzed using mass spectrometry. According to FAB-MS/MS, mixtures from black bean contain soyasaponin I as the predominant saponin. In addition, MS/MS analysis was performed in which the structures of saponins of black bean cotyledon were determined to be soyasaponin I, soyasaponin II, soyasaponin V, 3-O-[alpha-L-rhamnopyranosyl-(1 --> 2)-beta-D-galactopyranosyl-(1 --> 2)-beta-D-glucuronopyranosyl]complogenin (saponin A) and 3-O-[alpha-L-rhamnopyranosyl-(1 --> 2)-beta-D-glucopyranosyl-(1 --> 2)-beta-D-glucopyranosyl]oleanolic acid (saponin B). For the black bean shell and the root of black bean sprout, analysis confirmed the saponins of soyasaponin I, soyasaponin II, soyasaponin V, saponin A, saponin B, acetylsoyasaponin A(4) and soyasaponin beta(g). Moreover, all the studied saponins were found in the stem and leaves of the black bean sprouts, except soyasaponin beta(g) and acetylsoyasaponin A(4), respectively.

Structural characterization of lichenysin A components by fast atom bombardment tandem mass spectrometry

The structural characterization of the cyclic lipoheptapeptide surfactant lichenysin A components, produced by Bacillus licheniformis strains via the non-ribosomal pathway on a corresponding peptide synthetase, was carried out using a tandem mass spectrometry (MS/MS) under fast atom bombardment (FAB) conditions. Based on the analysis of the collision-induced fragment-ion spectrum of the single charged molecular ions of both native and partially hydrolyzed forms of lipopeptide, a new general structure of lichenysin A components was elucidated. It varies from previously proposed structure by having in the peptide portion of lipopeptide the l-Gln-1 and l-Asp-5 residues instead of l-Glu-1 and l-Asn-5. The verified chemical structure of lichenysin A was found to be reflected in the structural organization of the corresponding lichenysin A synthetase, LchA, described recently.

Structural Identification of Glycerolipid Molecular Species Isolated from CyanobacteriumSynechocystissp. PCC 6803 Using Fast Atom Bombardment Tandem Mass Spectrometry

Our previous works have demonstrated that fast atom bombardment tandem mass spectrometry can be a valuable tool in determining the complete structure of glycoglycerolipids and glycerophospholipids. Collision-induced dissociation of sodium-adducted molecular ions ([M + Na]+or [M − H + 2Na]+) generates diverse product ions informative on the double-bond position in fatty acyl groups as well as the polar head group and fatty acid composition. Here we report that this direct and rapid method can be applied to the structural determination of individual molecular species of each glycerolipid class purified from the total lipid extract of cyanobacteriumSynechocystissp. PCC 6803. Especially, based on the preference for the loss of the fatty acyl group positioned at thesn-2, it was proved that all of the molecular species of diacylglycerolipids contained a palmitoyl group exclusively at thesn-2 position. Additionally, lysoglycerolipids, monoacyl forms of four major membrane diacylglycerolipids, were first isolated together from a fresh extract. Using fast atom bombardment mass spectrometry and tandem mass spectrometry, it was found that each lysoglycerolipid had a molecular species with only palmitic acid as a fatty acyl group. Thus, these compounds could be synthesized by specific enzyme-catalyzed hydrolysis of thesn-1 fatty acyl group of the corresponding diacylglycerolipids.