Field desorption and fast atom bombardment mass spectrometry of bleomycins and their derivatives

Accurate and rapid modeling of iron-bleomycin-induced DNA damage using tethered duplex oligonucleotides and electrospray ionization ion trap mass spectrometric analysis

Bleomycin B(2)(BLM) in the presence of iron [Fe(II)] and O(2)catalyzes single-stranded (ss) and double-stranded (ds) cleavage of DNA. Electrospray ionization ion trap mass spectrometry was used to monitor these cleavage processes. Two duplex oligonucleotides containing an ethylene oxide tether between both strands were used in this investigation, allowing facile monitoring of all ss and ds cleavage events. A sequence for site-specific binding and cleavage by Fe-BLM was incorporated into each analyte. One of these core sequences, GTAC, is a known hot-spot for ds cleavage, while the other sequence, GGCC, is a hot-spot for ss cleavage. Incubation of each oligo-nucleotide under anaerobic conditions with Fe(II)-BLM allowed detection of the non-covalent ternary Fe-BLM/oligonucleotide complex in the gas phase. Cleavage studies were then performed utilizing O(2)-activated Fe(II)-BLM. No work-up or separation steps were required and direct MS and MS/MS analyses of the crude reaction mixtures confirmed sequence-specific Fe-BLM-induced cleavage. Comparison of the cleavage patterns for both oligonucleotides revealed sequence-dependent preferences for ss and ds cleavages in accordance with previously established gel electrophoresis analysis of hairpin oligonucleotides. This novel methodology allowed direct, rapid and accurate determination of cleavage profiles of model duplex oligonucleotides after exposure to activated Fe-BLM.

Fast atom bombardment mass spectrometry in the pharmaceutical analysis of drugs

The principles, techniques and value of fast atom bombardment mass spectrometry are summarized in this revïew. Applications of the method in such areas as molecular weight determination, standard and metabolic studies, and peptide sequencing, as well as direct quantitative analysis, are surveyed, with examples from several classes of compounds with pharmacological activity.

Desorption ionization mass spectrometry of synthetic porphyrins

The desorption ionization mass spectra are reported for two classes of synthetic porphyrins--'tailed' derivatives of deuteroporphyrin IX and meso-substituted derivatized tetraphenylporphines. The mass spectra were obtained by three desorption ionization techniques--fast atom bombardment (FAB), desorption chemical ionization (DCI) and 'in-beam' or desorption electron ionization (DEI). The emphasis of this study is to determine the usefulness of the three desorption ionization methods for the molecular weight and side-chain structure determinations of synthetic porphyrins. The molecular parent ions and the major fragmentation pathways are discussed in detail. The DEI method yielded the fewest mass spectra showing molecular parent ions from the compounds studied, whereas FAB gave the most. The major fragmentation pathways were compound dependent and similar for all three ionization methods; generally, those cleavages alpha and beta to carbonyl groups predominated. The FAB spectra showed strong molecular adduct ions in several spectra that could be attributed to an in situ coordination of iron-containing porphyrins with the thio-containing liquid matrix molecules.

Peptide studies using a fast atom bombardment high field mass spectrometer and data system. 1--Sample introduction, data acquisition and mass calibration

Conditions were established for analyzing as little as 5 pmol of an underivatized peptide delivered in a glycerol sample matrix as a thin film onto a gold-plated copper sample stage and then bombarded with xenon fast atoms. Calibration of the fast atom bombardment high field mass spectrometer and data system was achieved using cesium iodide/glycerol as a reference. Calibration at several accelerating potentials permitted a mass range from 393 to 5941 u. Several factors were examined that contribute to the quality of the mass spectrum: components within the glycerol such as other peptides, alkali salts, acid and reducing agents; the nature of the fast atom gas; concentration of the peptide delivered to the sample stage; and the effect of the sample stage and sample matrix on sensitivity.

Fast Atom Bombardment Mass Spectrometry

Fast atom bombardment mass spectrometry has become a powerful structural tool since the first reports of its use in 1981. Samples are ionized in the condensed state, usually in a glycerol matrix, by bombarding the matrix with xenon or argon atoms with energies of 5000 to 10,000 electron volts. This yields both positive and negative secondary ions, which are sputtered from the surface. The technique has been used to detect inorganic ion clusters to mass 25,800 and biologically active peptides to mass 5700, and it gives molecular ions of such highly polar or labile organic compounds as glycosphingolipids and polyene antibiotics. It can be especially valuable in determining the sequences of amino acids in polypeptides.

Advances in methods and techniques for the identification of xenobiotic conjugates

This review discusses recent advances in methods and instrumentation that are potentially useful for the characterization of polar xenobiotic conjugates. Topics that are discussed include: fast atom bombardment, secondary ion, 252Cf-plasma desorption, field desorption and direct chemical ionization mass spectrometry and, proton and carbon-13 nuclear magnetic resonance spectrometry.