Fast Atom Bombardment Mass Spectra Research Articles

Evidence for a lysine-specific fragmentation in fast-atom bombardment mass spectra of peptides.

A fragmentation process observed for peptides that contain lysine, or other amino acids which possess a free amino group on their sidechain, is reported. The ions generated by this process are found 16 Da below the acylium-type B ions that result from fragmentation at the C-terminal side of lysine or other amine-containing residues in fast-atom bombardment (FAB) mass spectra. These ions, which are referred to as (B-16) ions, permit differentiation between the isobaric amino acids lysine and glutamine in peptide mass spectra. High resolution measurements indicate that (B-16) ions differ in composition from the corresponding B ions by the removal of one oxygen atom. Formation is believed to occur through a cyclization process initiated by nucleophilic attack by the free amino group of the lysine sidechain at the carbon of the acylium ion (B ion). A similar process initiated directly from the protonated peptide may also occur. Analogous cyclization processes are restricted for glutamine because this residue is comparatively less nucleophilic than lysine (i.e., amide vs amine). Although (B-16) ions have been detected under high energy collisionally induced dissociation, they are formed less readily than by FAB mass spectrometry. A mechanism consistent with this observation as well as other experimental evidence is presented to account for the formation of (B-16) ions.

Mass spectrometric studies of phosphodiesters linked to oxysterols and nucleosides, a family of biologically potent oxygenated sterols

AbstractNegative‐ion fast atom bombardment mass spectra of five compounds resulting from combinations between oxysterols and nucleoside analogues linked by phosphodiester bonds are presented and interpreted. This method seems to be the most appropriate for elucidating the structure of these complex, labile and non‐volatile phosphate‐containing molecules which exhibit important antitumour and/or immunosuppressive activities.

Fast Atom Bombardment Mass Spectrometry of Arene-Chromium Complexes: Cr(η6-C6-Ph6)2, Cr{η6-PhPh[Cr(CO)3]}2 and Fe(η-C5H4-η6-PhCr(CO)3)n(η-C5H4Ph)2-n (N = 0-2)

The fast atom bombardment mass spectra of several high molecular weight η- arene -chromium complexes have been measured and analysed. Interesting features include the observation of loss of C2Ph2 from [Cr(C6Ph6)2]+ to give [Cr(C10Ph10)]+ as the base peak, which appears to be derived from pentaphenylcyclopentadiene; the ready loss of Cr(CO)3 moieties from complexes containing this group; and the formation of ions containing CrFe groups in the spectra of the ferrocene derivatives.

Synthesis of 1,10,19,28-tetraoxa-4,7,13,16,22,25,31,34-octaazacyclohexatriacontane (L) and its complex [Cu4L(OH)4][ClO4]4·2H2O

A 36-membered macrocycle with four ethylenediamine entities, 1,10,19,28-tetraoxa-4,7,13,16,22,25,31,34-octaazacyclohexatriacontane (L), has been synthesized and characterized by 1H and 13C NMR and fast atom bombardment (FAB) mass spectra. Its complexing behaviour toward copper(II) ion was investigated spectroscopically and the macrocycle shown to incorporate four copper(II) ions in the range pH 6–9. A tetranuclear complex [Cu4L(OH)4][ClO4]4·2H2O was obtained and characterized to be of a cubane-type Cu4(OH)4 core surrounded by the macrocycle, according to IR, visible, FAB and ESR spectra, cyclic voltammetry, and cryomagnetic susceptibility.

Characterization of a New Insecticide, Clavamine, from the Venom of a Spider, Nephila clavata by Use of a Synthetic Compound.

In this paper, we compared the chemical and biological activities of natural and synthetic clavamines, N-[2, 4-dihydroxyphenylacetyl-4-L-asparaginyl)-N'-[N-(L-arginyl-glycyl-L-alanyl)-8-amino-4-azaoctanoyl]-1, 5-pentane-diamine (DPA→Asn→Cad←Ptr←Ala←Gly←Arg)[DPA, 2, 4-dihydroxyphenylacetic acid; Cad, 1.5-pentanediamine (cadaverine); Ptr, 8-amino-4-azaoctanoic acid (putreanine, or carboxyethylputrescine)], and found that both were identical. Both compounds showed the same Rf value in thin-layer chromatography and the same retention time in high performance liquid chromatography (HPLC). Both hydrolyzates consisted of the same components, such as Gly, DPA, Ala, Asp, Arg and Ptr in gas chromatography. The Edman degradation of both compounds also gave exactly the same sequence. The 1H-NMR spectrum and fast atom bombardment (FAB) mass spectrum of the synthetic compound coincided with those of the natural one. Both were active on the insects used. Clavamine was the main component of the insecticidal activity in the crude venom. By this synthetic study, the structure of a new venom insecticide was thus established. The synthetic compound in abundant quantity will be advantageous for practical use as an insecticide over natural ones, because the latter is available only in small amounts. Also, it will be useful for the exploitation of a new field of biochemistry for polyamines.

Fast-atom bombardment mass spectrometry of oligomeric dicyanobis(polypyridine) ruthenium (II) complexes

The positive-ion fast-atom bombardment (FAB) mass spectra of the biniclear [CNRu(L2)CNRu(L'2)CN]+ and trinuclear [CNRu(L2)CNRu(L2CNRu(L2)CN]2+ complexes (L=2,2′-bipyridine; L' = 2,2′-bipyridine or 1,10-phenanthroline) have been investigated and compared with those of the mononuclear NCRu(L'2CN species. The FAB fragmentation patterns of the mononuclear species are interpreted by a combination of simple losses of neutral polypyridine ligands andHCN molecules and provide useful information for the understanding of the gas-phase decomposition of the oligimeric species.

Retrosynthetic fragmentation in the fast atom bombardment mass spectra of eserine and some related compounds

AbstractThe positive‐ion fast atom bombardment (FAB) mass spectra of eserine and some carbamate analogues were recorded and showed a partially different fragmentation process, with respect to that of the corresponding chemical ionization (Cl) fragmentation. This unexpected behaviour could be explained by taking into account the known solution chemical behaviour of the protonated species, and assigning to the molecular species observed under FAB a different–yet related–molecular connectivity. This may be considered as evidence that the sputtered species under FAB closely reflect the chemical behaviour of the analysed molecule in the solution environment.

The electron impact, chemical ionization and fast atom bombardment positive ion mass spectra of 1,2-bis(sulfonyl)methylhydrazines

A series of bis(sulfonyl)-1-methylhydrazines were analyzed by positive ion electron impact (EI), chemical ionization (CI) and fast atom bombardment (FAB) mass spectrometry. Since these compounds showed activity against the L1210 leukemia, an understanding of their mass spectral behavior is important should the structural characterization of metabolites be required. FAB proved to be the most useful technique, generally providing abundant protonated molecule ion peaks, in contrast to the weak peaks observed with CI (ammonia or isobutane) and the total absence of molecular ion peaks in the EI mass spectra. In addition, utilizing FAB eliminated the problem of thermal decomposition, which was very difficult to control under EI and CI experimental conditions. Fragments observed in FAB and CI mass spectra were consistent with protonation at the methyl-bearing nitrogen. One can locate the R1 and R2 moieties relative to the methyl-bearing nitrogen in FAB and CI by assigning that nitrogen as the site of protonation, with subsequent elimination of R2SO2H.

Isolation and identification of bile salts conjugated with cysteinolic acid from bile of the red seabream, Pagrosomus major.

Bile salts present in gallbladder of wild and cultured red seabream, Pagrosomus major, a marine teleost were analyzed. The bile from wild red seabream was found to contain two previously unknown bile salts along with two known bile salts, taurocholate and taurochenodeoxycholate. Isolation of each bile salt was performed by column chromatography. Fast atom bombardment mass spectra of the unknown bile salts showed the molecular ions (M-H)- of m/z 544 and 528 which are shifted 30 mass units upfield compared to those (m/z 514 and 498) of taurocholate and taurochendeoxycholate, respectively; this is consistent with the presence of cysteinolic acid (mol wt 155) instead of taurine (mol wt 125). Enzymatic hydrolysis of the bile salts released cholic acid and chenodeoxycholic acid, respectively, and an amino acid that was identified as D-cysteinolic acid by direct comparison with an authentic sample. From these results, the bile salts in the bile of wild red seabream were identified as the conjugates of cholic acid and chenodeoxycholic acid with cysteinolic acid. 1H- and 13C-magnetic resonance spectra of the bile salts were also consistent with the proposed structure. The cysteinolic acid conjugates were found only in wild and not in cultured red seabream; this distinction seems to result from differences in dietary cysteinolic acid.

Isolation, amino acid sequence and synthesis of dermaseptin, a novel antimicrobial peptide of amphibian skin

A 34-residue antimicrobial peptide named dermaseptin was purified to homogeneity from amphibian skin by a 3-step protocol involving molecular sieve filtration, ion-exchange chromatography, and reversed-phase high-performance liquid chromatography. The complete amino acid sequence of dermaseptin, ALWKTMLKKLGTMALHAGKAALGAAADTISQGTQ, was determined by automated Edman degradation of the peptide and of fragments generated by trypsin. Fast atom bombardment mass spectra of dermaseptin gave a protonated molecular ion m/z 3455.4 which matched the theoretical molecular weight predicted from the amino acid sequence. Dermaseptin was synthesized by the solid-phase method. The synthetic replicate was shown to be indistinguishable from natural dermaseptin with respect to chromatographic properties, amino acid sequence determination, and mass spectrometry analysis. Dermaseptin is a water-soluble, thermostable, and nonhemolytic peptide endowed with highly potent antimicrobial activity against pathogenic fungi at micromolar concentration. Circular dichroism spectra of dermaseptin in hydrophobic media indicated 80% alpha-helical conformation, and predictions of secondary structure suggested that dermaseptin can be configured as an amphiphatic alpha-helix spanning over residues 1-27, a structure that perturbs membrane functions regulating water flux.

A reliable method for the amino acid sequence determination in tetrapeptides: A study on the positive and negative ion tandem mass spectra of tetrapeptides

An unambiguous method for sequencing tetrapeptides based upon the combined use of fast atom bombardment mass, MI and collisional activation (CA) spectra of protonated and sodium-cationized peptide molecules is proposed. The positions in the peptide of non-C-terminal Ile/Leu are determined by 'Wn + Na ions in the CA spectra of [M + Na]+. The second part of the paper is an evaluation of the fragmentations in the negative ion MI and CA spectra of deprotonated tetrapeptides.

Application of microcolumn liquid chromatography-continuous-flow fast atom bombardment mass spectrometry in environmental studies of sulfonylurea herbicides

The use of 0.25-mm I.D. packed capillary liquid chromatography columns coupled with continuous-flow fast atom bombardment (FAB) mass spectrometry has proven to be a very valuable technique, especially for the identification of unknown sulfonylurea herbicide metabolites. Several new and unusual heterocycle ring-opened metabolites and hydrolysis products were identified, and metabolic pathways were proposed. Typical column flow-rates are 1–2 μl/min, which allows direct coupling with no sample splitting. This is important in our metabolite identification work, since we are usuallly sample-limited. Techniques for increasing injection volume to allow analyses of dilute solutions and the use of polymeric packing for separation of polar metabolites are discussed. The FAB mass spectra usually provide unequivocal molecular weights and structurally useful fragments ions, which often allows structure assignments on exceedingly small quantities of isolated metabolites.

Formation and fragmentation of the [M + Na]+ ion of glycosides in fast atom bombardment mass spectrometry

AbstractPositive‐ion fast atom bombardment (FAB) mass spectra of flavonol and steroid glycosides with sodium chloride added showed well known characteristic features; of the appearance of [M + Na]+ peaks, disappearance of [M + H]+ peaks and a significant decrease in the peak heights of fragment ions. Compared with the features in the FAB mass spectra of crown ethers with addition of salt, and above features suggest a complexation between Na+ and the glycosides in matrix solution. The B/E‐constant linked scanning technique was used to obtain structural information of the [M + Na]+ ion of the glycosides. The B/E spectra gave the daughter‐ion peaks, suggesting that coordination of Na+ with the biosides and triosides occurs at the sugar moiety, whereas the coordination with the monoglycosides occurs at the aglycone moiety, except for monoglycosides in which the aglycone moiety does not contain significant oxygen functional groups such as OH and CO.

Fast atom bombardment mass spectra of thiotepa

Organic Mass SpectrometryVolume 26, Issue 6 p. 619-620 Oms Letter Fast atom bombardment mass spectra of thiotepa M. V. Kosevich, M. V. Kosevich Institute for Low Temperature Physics and Engineering, Ukr. SSR Academy fo Sciences, 47, Lenin Avenue, Kharkov, 310164, USSRSearch for more papers by this authorV. S. Shelkovsky, V. S. Shelkovsky Institute for Low Temperature Physics and Engineering, Ukr. SSR Academy fo Sciences, 47, Lenin Avenue, Kharkov, 310164, USSRSearch for more papers by this authorO. A. Boryak, O. A. Boryak Institute for Low Temperature Physics and Engineering, Ukr. SSR Academy fo Sciences, 47, Lenin Avenue, Kharkov, 310164, USSRSearch for more papers by this authorO. I. Stepanov, O. I. Stepanov Institute for Low Temperature Physics and Engineering, Ukr. SSR Academy fo Sciences, 47, Lenin Avenue, Kharkov, 310164, USSRSearch for more papers by this author M. V. Kosevich, M. V. Kosevich Institute for Low Temperature Physics and Engineering, Ukr. SSR Academy fo Sciences, 47, Lenin Avenue, Kharkov, 310164, USSRSearch for more papers by this authorV. S. Shelkovsky, V. S. Shelkovsky Institute for Low Temperature Physics and Engineering, Ukr. SSR Academy fo Sciences, 47, Lenin Avenue, Kharkov, 310164, USSRSearch for more papers by this authorO. A. Boryak, O. A. Boryak Institute for Low Temperature Physics and Engineering, Ukr. SSR Academy fo Sciences, 47, Lenin Avenue, Kharkov, 310164, USSRSearch for more papers by this authorO. I. Stepanov, O. I. Stepanov Institute for Low Temperature Physics and Engineering, Ukr. SSR Academy fo Sciences, 47, Lenin Avenue, Kharkov, 310164, USSRSearch for more papers by this author First published: June 1991 https://doi.org/10.1002/oms.1210260615Citations: 3AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL No abstract is available for this article.Citing Literature Volume26, Issue6June 1991Pages 619-620 RelatedInformation

Technetium(II) complexes of potentially heptadentate Schiff base ligands: synthesis and characterization. X-ray crystal structure of [Tc(tren-py 3)](PF 6) 2

The synthesis and characterization of structural isomers of tris[4-(2-pyridyl)-3-aza-3-butenyl] aminetechnetium(II) tetraphenylborate are described. Two other structural isomers, tris[4-(2-(6-methyl- pyridyl))-3-aza-3-butenyl]aminetechnetium(II) tetraphenylborate and tris[4-(2-pyridyl)3-aza-3-pentenyl]aminetechnetium(II) tetraphenylborate, are also reported. Fast atom bombardment mass spectra, electron spin resonance spectra, cyclic voltammetry and conductivity studies of the new, Tc(II) complexes of potentially heptadentate ligands are discussed. The X-ray crystallographic structure of the PF 6 − salt of the major isomer of tris[4-(2-pyridyl)-3-aza-3-butenyl]aminetechnetium(II) shows a pseudo seven coordinate capped octahedral geometry. The mean Tc-imine nitrogen distance is 2.071 Å, and the mean Tc-pyridine nitrogen distance is 2.109 Å. The Tc-tertiary amine nitrogen distance is 2.933(7) Å, but this nitrogen's lone pair is directed toward the Tc atom (the average Tc-NC angle is 102°). Crystal data for C 24H 27F 12N 7P 2Tc: monoclinic space group P2 1/ c, a=15.082(1), b=10.7455(8), c=19.777(1) Å, β=110.29(1)°, V=3006.2(8) Å 3 to give Z=4 and R=0.061.

Mass spectral characteristics of okadaic acid and simple derivatives

Electron ionization (EI), chemical ionization (CI) and fast-atom bombardment (FAB) mass spectra of the marine toxin okadaic acid and its synthetic methyl, pentafluorobenzyl, and trimethylsilyl ester and ether derivatives were generated. Several ionization conditions and ion-processing methods were used to obtain positive- and negative-ion conventional spectra and tandem (MS/MS) spectra. The EI and the positive-ion CI spectra provided fragment ions characteristic of the structure, and the negative-ion CI and FAB spectra provided molecular ions. The addition of alkali salts to the FAB matrix resulted in reduced fragmentation and the formation of intense alkali-metal-cationized molecules. Pentafluorobenzyl ester derivatives provided intense carboxylate ions under electron-capture ionization. Analytically useful MS/MS spectra were obtained by low-energy collision-induced decomposition of the carboxylate anion produced from the tetrasilylated pentafluorobenzylokadaate.

Utilization of the chemical properties of liquid matrices to investigate reductive processes in fast atom bombardment mass spectra

The choice of liquid matrix for fast atom bombardment (FAB) mass spectrometry is important not only for optimizing spectral appearance in terms of the physical properties of the sample molecule (e.g. hydrophobicity) but also in terms of chemical reactivity. The suppression of physicochemical phenomena occurring in the FAB source and hence of chemical reactions of the sample can lead to much improved spectra. In this way, peaks resulting from specific processes can be targeted and their intensity optimized. In addition, the technique may be used to investigate the physicochemical phenomena themselves, which, despite the enormous usage of FAB mass spectrometry are still poorly understood in terms of mechanism and origin.

Determination of enzyme kinetic parameters of cyclic CMP‐specific phosphodiesterase by quantitative fast atom bombardment tandem mass spectrometry

AbstractThe determination of cytidine 3′,5′‐cyclic monophosphate‐specific phosphodiesterase activity by means of fast‐atom bombardment (FAB) mass Spectrometry with mass‐analysed ion kinetic energy (MIKE) spectrum scanning is described. Initial efforts to determine the activity of the enzyme by this method were unsuccessful owing to the obfuscation of sample‐related peaks by peaks emanating from the incubation buffer and cation adducts; dilution of buffer and a desalting procedure overcame these difficulties. In the resulting positive‐ion FAB mass spectra, characteristic peaks of the enzyme substrate and product could be readily identified and the protonated molecular ions selected for MIKE scanning. By spiking enzyme incubates with known amounts of substrate and product, and measuring peak heights in the MIKE spectra of both spiked and unspiked samples, the substrate/product ratio at the end of a series of phosphodiesterase incubations was determined. From the data obtained, the Km and Vmax of the phosphodiesterase were calculated as 6.08 mM and 11 μmol min−1 mg−1, respectively, showing good agreement with the analogous values of 8.06 mM and 5.8 μmol−1 min−1 mg−1 obtained by radioactive assay.

Direct evidence for degradation of esperamicin A1 with thiol confirmed by fast‐atom bombardment mass spectrometry

A degradation of esperamicin A1, which is a potent antitumor antibiotic having DNA-cleaving activity, was studied by fast-atom bombardment (FAB) mass spectrometry. It was proved that the degradation easily occurs via the thiol group(s) in the matrix solution and not by a FAB-induced reaction. It was concluded that from the FAB mass spectra of all non-volatile compounds, the molecular weight should be determined by using at least two chemically different matrices.

Biosynthesis of isochorismate in Klebsiella pneumoniae: origin of O-2

The shikimate metabolites are key precursors to a large number of natural products, including aromatic amino acids. Chorismic acid is an important branch point in the biosynthetic pathway to aromatic amino acids. Chorismic acid is also unique among natural products since it is the only compound known to undergo an enzymatic Claisen rearrangement. A metabolite of chorismic acid, isochorismic acid, first observed in Aerobacter aerogenes differs in its chemical structure by the location of the hydroxyl group and the double bonds. Isochorismic acid is a precursor to a growing number of shikimate-derived metabolites. Isochorismic acid has also been postulated to be an intermediate of m-carboxyaromatic amino acids, implying another enzymatic Claisen rearrangement. In this publication, we have isolated isochorismate synthase and found that on lyophilization the enzyme is stable for at least 6 months at -20 degrees C. Incubation of chorismate with this preparation in water enriched with 18O led to incorporation of one atom of 18O as proven from the fast atom bombardment mass spectra of the HPLC purified derived isochorismate.