Fast atom bombardment mass spectrometry of bleomycin A2 and B2 and their metal complexes

The new mass spectrometric technique of fast atom bombardment is applied to the analysis of bleomycins either separately or in mixtures. The spectra are reproducible and afford valuable analytical data and structurally significant fragmentation patterns on these important antibiotics. The procedures outlined have also enabled the characterisation of various metal complexes.     

Fast atom bombardment mass spectrometry of bovine proinsulin

The application of Fast Atom Bombardment Mass Spectrometry to the measurement of small differences in molecular weight is discussed in relation to the spectra of bovine proinsulin and a genetic variant.     

Fast atom bombardment mass spectrometry of human proinsulin

The observation of protonated molecular species from human proinsulin obtained by fast atom bombardment mass spectrometry is reported.     

Fast atom bombardment mass spectrometry of estrogen glucuronides and sulfates

Fast atom bombardment (FAB) mass spectra of 13 intact, underivatized glucuronides and/or sulfate salts are reported. Spectra are characterized by abundant ions formed by attachment of a proton, [M+H]+, or of an alkali ion, [M+alkali]+, to the glucuronide or sulfate salt. Fragment ions were of low intensity. FAB spectra can be used to obtain the molecular weight of a sample, to assess its purity and to identify the nature of the alkali of the glucuronide or sulfate salt.     

Fast atom bombardment mass spectrometry of bouvardin and selected analogs

The fast atom bombardment (FAB) mass spectra of bouvardin (1) 6-O-methylbouvardin (2), deoxybouvardin (3) and a synthetic analog (4) have been examined. The spectra of the bicyclic compounds 1-3 display site-directed fragmentations resulting from the presence of a phenolic bridged tyrosine moiety unique to this class of compounds. Comparison of the spectrum of 4, which lacks the rigid 14-membered ring, with the spectra of 1-3 shows some similarities, but clearly does not cleave in a site-directed manner as the other bouvardin analogs. Fragmentation pathways are postulated which account for most of the major ions observed in the FAB mass spectra of these potentially useful antitumor agents. Metastable ion analysis confirms the operation of the proposed pathways.     

Fast atom bombardment mass spectrometry of the anthocyanins violanin and platyconin

Fast atom bombardment mass spectrometry (FABMS) of the acylated anthocyanin violanin confirmed its molecular mass (919) and gave a fragmentation pattern in agreement with its known structure. FABMS of the more complex flower pigment platyconin gave its accurate molecular mass as 1421.3740 and a fragmentation pattern suggesting that platyconin is delphinidin 3-rutinoside-5-glucoside with two mols of glucosylcaffeic acid attached to the glucose moiety of rutinose in a branched-chain arrangement.     

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 in the study of dopamine melanogenesis intermediates

Fast atom bombardment was applied to the study of the intermediates of the reaction dopamine-tyrosinase after treatment with diazomethane. The identification of trimethoxyindoline, dopamine-o-quinone and dimethoxyindole was easily achieved by this ionization method, together with accurate mass measurements and collision experiments. The structures of these compounds are in agreement with those already hypothesized in studies on melanogenesis.     

Fast atom bombardment mass spectrometry and tandem mass spectrometry of biologically active peptidoglycan monomers from Neisseria gonorrhoeae

Fast atom bombardment mass spectrometry (FABMS) and tandem mass spectrometry (MS/MS) were employed to define the structures of Neisseria gonorrhoeae peptidoglycan monomers that were of interest because of their abilities to mediate diverse biological reactions ranging from arthritogenicity to somogenicity. FABMS-determined molecular weights of individual components present in several different enzymatically derived classes of gonococcal monomers revealed that each of these classes was a complex mixture of up to 13 distinct peptidoglycan fragments. These ranged from the predominant disaccharide tetrapeptides possessing reducing or nonreducing 1,6-anhydro-N-acetylmuramic acid ends to relatively minor constituents containing glycine or asparagine in addition to traditional peptidoglycan amino acids, i.e. alanine, glutamic acid, and diaminopimelic acid. FABMS of high performance liquid chromatography-purified monomers yielded some sequence information; however, analysis even of unfractionated peptidoglycan mixtures using a JEOL HX110/HX110 tandem mass spectrometer operating at 10 kV provided unambiguous primary sequence data for the peptidoglycan monomers and defined the position of glycine in four compounds as well as the location of O-acetyl substituents (present on some compounds) on C-6 of the N-acetylmuramic acid residue.     

Fast atom bombardment mass spectrometry of steroid sulphates: qualitative and quantitative analyses

Negative ion mass spectra obtained by fast atom bombardment of glycerol solutions of steroid sulphates include the steroid sulphate anion as the single prominent feature. High sensitivity is achieved, with full spectra obtained for samples of less than 15 ng. Differentiation of the isomeric steroids, dehydroepiandrosterone sulphate and testosterone sulphate, is made by comparison of the products of fragmentation of metastable ions. Analyses of biological extracts suffer from poorly-understood matrix effects which may cause partial or complete suppression of the signal attributable to steroid sulphates. Use of an immunoadsorption extraction technique, however, has permitted the detection and approximate quantification (using a (2H2) analogue as internal standard) of dehydroepiandrosterone sulphate in blood plasma. Interference from glycerol background is avoided by preparation of the pentafluorobenzyloxime derivatives.     

Fast atom bombardment mass spectrometric characterization of peptides

Structural characterization of peptides in the range of 500–5000 Da, using fast atom bombardment (FAB) and Cs⁺ ion liquid secondary ion mass spectrometry (SIMS), is reviewed. These include syntheitc peptides Kemptamide (mol wt 1516); GIF-C15 (mol wt 1875), an isolated natural product as an acylated pentapeptide; and polypeptides generated from enzymatic digests of proteins. MS data is shown to reveal molecular weight and sequence information as well as determine disulfide bonds between cysteine residues and glycosylation sites in the case of a glycopeptide. The complementarity of MS technique to classical biochemical methods for peptide characterization is highlighted. The reader is briefly acquainted with two newer ionization techniques namely, electrospray ionization (ESI) and matrix-assisted laser desorption ionization (MALDI). Synthetic chemists and biochemists can refer to the in-depth review articles that are cited throughout this article.     

Fast atom bombardment mass spectrometry and chemical analysis in determinations of acyl-blocked protein structures

Peptide generation and fast atom bombardment mass spectrometry in combination with conventional chemical analysis was used to identify the blocking group and establish the N-terminal structure of six different proteins at the nanomole level. In this manner, the first terminal structures of three non-mammalian alcohol dehydrogenases were determined, demonstrating the presence of N-terminal acetylation in these piscine, amphibian, and avian enzymes. Similarly, two different yeast glucose-6-phosphate dehydrogenases and a minor variant of a human alcohol dehydrogenase were found to be acetylated. The exact end location of C-terminal structures was also established. Together, the analyses permit the definition of terminal regions and blocking groups, thus facilitating the delineation of remaining structures.     

Analysis of gangliosides using fast atom bombardment mass spectrometry

The native gangliosides GM3, GM1, Fuc-GM1, GD1a, GD1b, Fuc-GD1b, GT1b and GQ1b were analysed by fast atom bombardment mass spectrometry (FAB-MS) in the negative ion mode in a matrix of thioglycerol. After permethylation the same gangliosides were analysed by electron impact (EI) and FAB-MS in the positive ion mode. The negative ion mass spectra furnished information on the molecular weight, the ceramide moiety and the sequence of carbohydrate residues. The sites of attachment and the number of sialic acids present could be deduced directly from the pattern of sequence ions. After addition of sodium acetate positive ion FAB-spectra of the permethylated samples show intense pseudomolecular ions M + Na, that provide evidence on the homogeneity of the samples. In addition, the ceramide part, the oligosaccharide moiety obtained after cleavage of the glycosidic bond of the hexosamine residue, the whole carbohydrate chain and the sialic acids are represented by specific fragment ions. With EI-MS further information can be obtained on the sphingosine and fatty acid components of the ceramide residue. The data show, that the combination of soft ionization mass spectrometry with classical EI-MS gives valuable information on the structure and homogeneity of gangliosides. The method is also applicable to the structural elucidation or quantitation of more complex gangliosides or glycolipid mixtures using only micrograms of material.     

Derivatization of ketosteroids for fast atom bombardment mass spectrometry

Girard's reagents were used to derivatize ketosteroids and conjugates for analysis by positive ion fast atom bombardment mass spectrometry. Spectra contain an abundant ion corresponding to the cation (C+) of the newly formed ionic derivative (C+A-) and relatively little fragmentation. With derivatization, detection of ketosteroids at a concentration of 1 microgram microliter-1 in glycerol was straightforward. Such derivatization schemes may prove useful in the analysis of ketosteroids in complex biological mixtures.     

Fast atom bombardment (FAB) mass spectrometry: a mass spectral investigation of some of the insulins

Mass measurements of the protonated molecules [M + H]+ of four insulins are presented. In addition, structurally significant fragment ions are observed in the mass spectrum and metastable scanning has been used to link these ions to the protonated molecule.     

Protein N-terminal analysis using fast atom bombardment mass spectrometry

An immunoassay is described that discriminates between monomers and oligomers of human leukocyte interferon. The assay in principle can be used to distinguish between monomers and oligomers of any substance.     

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.     

Fast atom bombardment mass spectrometry of insulin, insulin A-chain, insulin B-chain, and glucagon

Fast atom bombardment mass spectral data are presented for the polypeptides insulin, oxidized insulin A-chain, carboxymethylated insulin B-chain, and glucagon. The doubly-charged molecular ion of the intact insulin molecule produced with fast atom bombardment with xenon atoms is observed at a reduced accelerating voltage (4 kV).