Positive Fast Atom Bombardment Research Articles

Fast Atom Bombardment Mass Spectrometry of Coumaric Acids

Abstract The technique of positive fast atom bombardment mass spectrometry combined with collisional activation and metastable ion data has been shown to provide molecular mass and useful fragmentation information for discrimination between the coumaric acid isomers. In addition to the occurrence of an ortho-effect, also para and meta positions could be distinguished.

Monophosphoryl lipid A obtained from lipopolysaccharides of Salmonella minnesota R595. Purification of the dimethyl derivative by high performance liquid chromatography and complete structural determination.

The monophosphoryl lipid A (MLA) obtained from the lipopolysaccharides of Salmonella minnesota R595 was fractionated on a silicic acid column to yield the heptaacyl, hexaacyl, and pentaacyl MLA. Each of these MLAs was methylated with diazomethane to yield the dimethyl derivative and purified to homogeneity by reverse-phase high performance liquid chromatography. The molecular ions obtained by positive ion fast atom bombardment mass spectrometry of purified dimethyl heptaacyl MLA allowed us to establish the molecular formula and Mr of C112H211N2O23P and 1983.3, respectively. Cleavage at the glycosidic linkage yielded an oxonium ion of mass 1115, which showed that the distal sugar unit contained one phosphate (dimethyl), two hydroxymyristates, one laurate, and one myristate, while the reducing sugar unit contained two hydroxymyristates and one palmitate. By utilizing two-dimensional NMR spectroscopy, we were able to assign all of the protons of dimethyl heptaacyl MLA. This assignment included the beta protons of the three acyloxyacyl groups. A substantial downfield shift of the protons at the 3- and 3' -carbons was observed, which indicated that these two positions are occupied by ester groups. Fast atom bombardment mass spectral analysis of the hexaacyl and pentaacyl MLAs showed that these structures were identical to the previously designated TLC-3 and TLC-5 fractions, respectively, from Salmonella typhimurium. From this study, the complete structures of the MLA series found in the LPS of S. minnesota can now be described.

Fast atom bombardment and collisional activation mass spectrometry of retinyl phosphate mannose synthesized by liver membranes.

Fast atom bombardment (FAB) and collisional activation dissociation (CAD) mass-analysed ion kinetic energy (MIKE) spectra have confirmed the structures of retinyl phosphate (Ret-P), retinyl phosphate mannose (Ret-P-Man) and guanosine 5'-diphospho-D-mannose (GDP-Man). Ret-P-Man was made in vitro while Ret-P and GDP-Man were chemically synthesized. Positive ion FAB mass spectrometry of Ret-P showed an observable short-lived spectrum with a mass ion at m/z 367 [M + H]+, and a major fragment ion at m/z 269 [M + H - H3PO4]+. Negative ion FAB mass spectrometry of Ret-P showed a strong stable spectrum with a parent ion at m/z 365 [M - H]-, a glycerol (G) adduct ion at m/z 457 [M - H + G]- and a dimer ion at m/z 731 [2M - H]-. GDP-Man showed an intense spectrum with parent ion at m/z 604 [M - H]- and cationized species at m/z 626 [M + Na - 2H]- and 648 [M + 2Na - 3H]-. Negative ion FAB mass spectrometry of Ret-P-Man showed a parent ion at m/z 527 [M - H]- and a fragment ion at m/z 259 [C6H12PO9]-. The CAD-MIKE spectra showed structurally significant fragment ions at m/z 442 and 361 for the [M - H]- ion of GDP-Man, and at m/z 509, 406, 364 and 241 for the [M - H]- ion of Ret-P-Man. FAB and CAD-MIKE spectra have been applied successfully to confirm the structure of Ret-P-Man made in vitro from Ret-P and GDP-Man.

Fast atom bombardment mass spectrometry of salts of substituted methylene bisphosphonic acids and other analogues of pyrophosphoric acid

AbstractFast atom bombardment mass spectra have been obtained of salts of analogues of inorganic pyrophosphoric acid, e.g. substituted methylene bisphonates, and positive ion fast atom bombardment mass spectrometry (FABMS) has proved to be more successful than negative ion FABMS for the analysis of these salts. Owing to the low molecular weight of these analogues, FAMBS of the free acids and the sodium salts does not always give results which are easy to interpret as interference by peaks from the matrix can occur. However, the potassium salts in a 60% glycerol matrix, when bombarded by argon atoms, give good FAB spectra which are relatively free of interfering peaks.

Fast atom bombardment mass spectrometry ofSolanum glycoalkaloids and its potential for mixture analysis

The positive ion fast atom bombardment mass spectra of ten glycoalkaloids and five related alkaloids are reported. The spectra of the glycoalkaloids are characterized by abundant [M + H]+ species and fragment ions, resulting from cleavage of the individual carbohydrate groups. Several of these ions have been observed to be diagnostic for individual glycoalkaloids and have allowed the analysis of mixtures of standards as well as crude extracts of potato peel and sprout.

Fast atom bombardment mass spectrometry and tandem mass spectrometry in antibiotics: identification of nucleoside antitumor antibiotic toyocamycin in fermentation broth.

The presence of the nucleoside antitumor antibiotic toyocamycin in the fermentation broth was determined by a combination of negative and positive ion fast atom bombardment (FAB) mass spectrometry, high resolution FAB mass spectrometry and mass-analysed ion kinetic energy spectrometry (MIKES). A reasonable limit of detection for toyocamycin in the whole broth was obtained by combining the specificity of mass spectrometry/mass spectrometry (also called tandem mass spectrometry) to FAB. The role played by the fermentation matrix upon the production and the observation of characteristic ions by FAB using xenon atoms was examined. High-performance liquid chromatography (HPLC) and FAB mass spectrometry were used to monitor toyocamycin at all stages of strain development, fermentation and recovery.

Elucidation of structure and microheterogeneity of the polypeptide antibiotics paracelsin and trichotoxin A-50 by fast atom bombardment mass spectrometry in combination with selectivein situ hydrolysis

Specific and sensitive procedures have been developed which enabled the structure elucidation of the polypeptide antibiotics (peptaibols), paracelsin isolated from Trichoderma reesei, and of trichotoxin A-50 from Trichoderma viride, by fast atom bombardment and field desorption mass spectrometry. Both peptides were found to exhibit a pronounced microheterogeneity by single and multiple exchange of amino acids. Separation by analytical and semipreparative high-performance liquid chromatography (HPLC) on octadecylsilyl-bonded, reversed-phase columns afforded a series of sequence analogues for each polypeptide. Unequivocal molecular weight and sequence identifications were obtained by positive and negative ion fast atom bombardment (FAB), and field desorption (FD) mass spectrometry, in combination with a single, selective acidolytic cleavage step. Most important for the FAB mass spectral analysis of the extremely hydrophobic polypeptides was the development of oligoethylene-glycols and -glycol ethers as suitable liquid matrix systems, yielding high sensitivity and structurally significant fragment ions of high abundance. At these conditions, the positive ion FAB mass spectra exhibit regular abundant sequence ions with acylium end groups by peptide bond cleavage from the N-terminus, which provided direct sequence determinations for 13 of 20 residues of paracelsin, and for 12 of 18 residues of trichotoxin A-50. The sequence-specific fragmentation precisely continues up to, and ends at the preferential acidolytic cleavage sites (Pro residues). The remaining C-terminal sequence data was obtained by FD and FAB mass spectra of prolyl-hexa- and -heptapeptaibols produced by acidolytic cleavage in situ with aqueous trifluoroacetic acid. In contrast to the original polypeptides, glycerol as a polar matrix was most suitable for the analysis of prolylpeptaibol fragments in the hyrolysis mixture. By contrast, treatment of paracelsins and trichotoxins A-50 with trifluororacetic acid under anhydrous conditions yielded the corresponding trifluoroacetylated polypeptide derivatives which served to ascertain the position of the C-terminal amino alcohol residues. With this procedure, the structures of 14 closely related, partially isobaric sequence analogues of trichotoxin A-50, and of four sequence analogues of paracelsin were determined with amounts of material in the low nanomole range, which provide an exact pattern of the variable and the conservative sequence areas for these polypeptides.

Fast atom bombardment mass spectrometry of glycosphingolipids. Glycosphingolipids containing neutral sugars.

Natural and synthetic glycosphingolipids containing neutral sugars have been analyzed by positive and negative ion fast atom bombardment mass spectrometry. Basic structural characterization including saccharide size and sequence and ceramide composition is possible on the basis of the fragment ions observed. The degree of fragmentation could be increased by using higher sample concentrations and lower fast atom beam energies. Commercially available synthetic compounds that had been presumed to be pure were shown to contain homologous fatty acids. Mixtures of glycosphingolipids such as those obtained from Gaucher's spleen and from human erythrocytes can be characterized and quantitated.

Fast atom bombardment mass spectrometry of cyanogenic glycosides

The potential of positive and negative Ion fast atom bombardment mass spectrometry in the examination of cyanogenic glycosides has been demonstrated by the analysis of linamarin, prunasin, neolinustatin and amygdalin.

Separation and characterization of toxic and nontoxic forms of lipid A.

Highly purified and well-characterized samples of precursors and derivatives of bacterial lipopolysaccharides (LPS) were used to study the relationship between the chemical structure of lipid A and its toxicity. These samples included lipids X and Y (monosaccharide precursors of lipid A) from Escherchia coli MN7; incomplete lipid A (a disaccharide precursor of lipid A) from Salmonella typhimurium i50; and monophosphoryl lipid A, TLC-3 (a derivative of LPS), from S. typhimurium G30/C21. In addition, a diphosphoryl lipid A, TLC-3, was prepared from LPS of S. typhimurium G30/C21 and characterized by positive fast atom bombardment mass spectrometry. The diphosphoryl lipid A, TLC-3 fraction, was determined to be very toxic by the chick embryo lethal-dose test (CELD50 = 0.0064 microgram). Lipids X and Y, incomplete lipid A, and monophosphoryl lipid A (TLC-3), were all nontoxic (CELD50 greater than 10 micrograms). These results suggest a multiple structural requirement for toxicity of lipid A. Toxic lipid A must contain all of the following components: a glucosamine disaccharide, a sugar-1-phosphate, and normal fatty acid(s).

Fast atom bombardment combined with tandem mass spectrometry for the determination of nucleosides

The positive and negative ion fast atom bombardment (FAB) mass spectra and fast atom bombardment collisionally activated decomposition (CAD) spectra of a series of nucleosides and two dinucleotides are reported. The nucleosides studied are substituted forms of guanosine, adenosine, nebularine, tubercidin, uridine, and related pyrimidines. The FAB and CAD data both contain similar information. The CAD spectra are found to provide some structural information not found in the FAB mass spectra. Tandem mass spectrometry also allows emphasis to be put on weak fragments which are either not observed in the FAB mass spectrum or are lost in the matrix ion signals.

Analysis of peptides with unusual structural features by fast atom bombardment mass spectrometry: Protease inhibitors

Positive ion and negative ion fast atom bombardment mass spectra of several natural and synthetic enzyme inhibitors are presented. It is shown that the fast atom bombardment method is well suited to the analysis of these unusual peptides. Complete amino acid sequences can be deduced from the mass spectra in most cases. Structural features typical of the inhibitors include (a) C-terminal aldehyde groups (e.g. leupeptin), (b) urea linkages in the peptide backbone (e.g. antipain, chymostatin), (c) prevalence of arginyl or α-(2-iminohexahydropyrimidyl)glycl residues, and (d) presence of an N-(glycosylphosphoryl) group (e.g. phosphoramidon). Several examples of synthetic peptides with common protecting groups are also presented. It is concluded that positive ion and negative ion fast atom bombardment mass spectra provide complementary information, the two techniques being sensitive to entirely different structural aspects of the inhibitors.

A fast atom bombardment and field ionization/field desorption study of some isomeric unsaturated dicarboxylic acids

AbstractGeometrically isomeric dicarboxylic acids, such as maleic and fumaric acid and their methyl homologues, and the isomeric phthalic acids, have been investigated using fast atom bombardment, field ionization and field desorption mass spectrometry. The most intense peak in the positive ion fast atom bombardment spectra corresponds with the [M + H]+ ion. This ion, when derived from the E‐acids, tragments either by successive loss of water and carbon monoxide or by elimination of carbon dioxide. In the case of the Z‐acids only elimination of water from the [M + H]+ ions is observed to occur to a significant extent. The same is true for the [M + H]+ ions of the isomeric phthalic acids, that is the [M + H] ions derived from iso‐ and terephthalic acid exhibit more fragmentation than those of phthalic acid. All these acids undergo much less fragmentation upon field ionization, where not only abundant [M + H]+ ions, but also abundant [M]+· ions, are observed. Upon field desorption only the [M + H]+ and [M + Na]+ ions are observed under the measuring conditions. Negative ion fast atom bombardment spectra of the acids mentioned have also been recorded. In addition to the most abundant [MH]− ions relatively intense peaks are observed, which correspond with the [M]−˙ ions. The fragmentations observed for these ions appear to be quite different from those reported in an earlier electron impact study and in a recent atmospheric pressure ionization investigation.

Positive and negative ion fast atom bombardment mass spectra of some penicilloic acids.

The technique of fast atom bombardment mass spectrometry has been shown to be capable of producing molecular weight and useful fragmentation information from a selection of penicilloic acids. In addition, the technique has been shown to give similar information on alkali metal salts of penicilloic acids.

Field desorption mass spectrometry of anthracyclines comparison with other soft ionization techniques

Field desorption mass spectral data relative to 38 anthracycline derivatives are presented. A molecular ion, or [MH]+ ion is always present; in most cases it is the base peak in the spectrum at the best anode temperature. Increase in the emitter temperature promotes fragmentation which gives useful structural information. A comparison has been made between field desorption and other soft ionization techniques such as fast atom bombardment, desorption chemical ionization and a liquid chromatographic mass spectrometric interface with direct liquid introduction into a chemical ionization ion source. The most significant results were obtained by using positive and negative ion fast atom bombardment and direct liquid introduction with negative ion detection.

Structural Characterization of Sulfated Glycosaminoglycans by Fast Atom Bombardment Mass Spectrometry: Application to Chondroitin Sulfate

Abstract Polysulfated oligosaccharides obtained from enzymatic digests of chondroitin sulfate have been successfully analyzed by positive and negative ion fast atom bombardment mass spectrometry. The spectra show intense cationized molecular ions and fragment ions from which sugar sequence and sites of sulfation can be readily determined. In addition, polymers of 4-O-sulfate and 6-O-sulfate positional isomers may be distinguished by fast atom bombardment mass spectrometry. The mass spectra also indicate the presence of structural homologs of chondroitin sulfate that contain more than one covalently bound sulfate moiety per two sugar residues. The effects of salt concentration, liquid matrix composition and ionization mode (negative versus positive ion abstraction) on the quality and information content of the mass spectra are discussed in detail.

Analysis of steroid and vitamin D glucuronides and sulfates by fast atom bombardment mass spectrometry

The direct analysis of underivatized steroid and vitamin D glucuronide and sulfate conjugates by positive and negative ion fast atom bombardment mass spectrometry has been demonstrated. The technique allows unambiguous molecular weight determination of these conjugates and provides useful fragmentation information in many cases. Analysis of low microgram amounts of such conjugates purified from biological sources has been carried out.

Fast atom bombardment mass spectrometry of nucleosides and nucleotides

The positive and negative fast atom bombardment spectra of two nucleosides, 10 mononucleotides, two derivatized mononucleotides and 11 dinucleoside monophosphates have been recorded. Molecular ions (protonated or deprotonated) and some structurally significant fragments, sometimes involving cationization, were obtained. The spectra were compared with field desorption and thermospray ionization spectra whenever possible.

A 15N labelling, FD and FAB study of ammonia loss from protonated arginine molecules

AbstractThe positive ion field desorption (FD) spectrum of arginine taken at the best anode temperature only contains a peak due to [M+H]+ ions. At higher emitter temperatures a considerable amount of fragmentation is induced and the [M+HNH3]+ ions become most abundant. Specific 15N labelling reveals that the eliminated ammonia molecule, exclusively, contains one of the terminal nitrogen atoms of the guanidyl group. This also applies to the ammonia loss from metastably decomposing [M+H]+ ions. The positive ion fast atom bombardment (FAB) spectrum shows more fragmentation than the FD spectrum. In contrast with the FD results, the [M+H]+ ions generated upon FAB with ion lifetimes <10−6 s eliminate both ammonia containing one of the terminal nitrogen atoms of the guanidyl group and ammonia containing the α‐amino group in the ratio of 1.35, as found by 15N labelling. The metastably decomposing [M+H]+ ions, however, eliminate only the former ammonia molecule. In the negative ion FD and FAB spectra no other peak than that corresponding to the [MH]− ion is observed. Some attention has been paid to the thermal degradation of arginine on the basis of a few Curie‐point pyrolysis experiments.

Complete structure of lipid A obtained from the lipopolysaccharides of the heptoseless mutant of Salmonella typhimurium.

A highly purified monophosphoryl lipid A, TLC-3 fraction obtained from the lipopolysaccharides of the heptoseless mutant Salmonella typhimurium G30/C21 was converted to the dimethyl pentatrimethylsilyl derivative and analyzed by proton NMR spectroscopy at 400 MHz. Substantial downfield shifts of the resonances for protons at the 3- and 3'-carbons of the glucosamine disaccharide to 5.06 and 5.15 ppm, respectively, occurred from the normal range of 3.5-4.1 ppm, indicating that these two positions on the sugar rings were acylated. Significant downfield shift of the resonances for protons at the 4- and 6'-carbons did not occur, indicating the absence of acyl groups at these two positions. Since positive ion fast atom bombardment mass spectrometry previously established the presence of hydroxymyristoyl and myristoxymyristoyl esters at the reducing end and distal subunits, respectively, these acyl groups must be attached to the oxygen of the corresponding 3- and 3'-carbons of lipid A. With these results, we can now describe the complete structure of the monophosphoryl lipid A, TLC-3 from S. typhimurium.