Fast Atom Bombardment Mass Spectra Research Articles

Fast atom bombardment and secondary ion mass spectra of thiamine hydrochloride

AbstractThe ratio of the fragment ions at m/z 122 and m/z 123 in the positive ion fast atom bombardment or secondary ion mass spectra of thiamine hydrochloride varies with sample preparation and experimental conditions. For all mass spectra that contained significant abundances of matrix (S) ions [S + H]+, the fragment at m/z 123 is the more abundant of the two ions. If [S + H]+ ions are not observed in the mass spectrum under the conditions selected, the ion at m/z 122 is more abundant. This correlation suggests that hydrogen transfer to the fragment ion occurs in the gas phase, with the composition of the ion‐solvent cluster ions in the selvedge region being the key factor. The ratio of the fragment ions at m/z 123 and m/z 122 is thus an indicator of the extent of protonation in the selvedge, the region immediately above the solvent surface created by primary particle bombardment.

Synthesis and fast atom bombardment mass spectrometry of the coordination complexes of the ligand 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane

Metal complexes containing the ligand 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazatetradecane were synthesized and characterized using electron impact (EI) and fast atom bombardment (FAB). The FAB mass spectra were obtained in positive and negative ion mode. FAB in the positive ion mode proved to be the most successful technique for the identification of these compounds. The majority of the FAB spectra obtained were structurally informative, although not all showed molecular (M+) or quasimolecular ([M + H]+) ions. The fragmentations observed were characteristic of the ligands and the metal, and were interpreted based on the chemical and spectroscopic properties of these compounds. Keywords: FAB mass spectroscopy, tetraazacyclotetradecane complexes.

Fast atom bombardment mass spectra of 5‐substituted‐4‐hydroperoxy‐cyclophosphamides

Organic Mass SpectrometryVolume 24, Issue 5 p. 347-349 New Mass Spectra Fast atom bombardment mass spectra of 5-substituted-4-hydroperoxy-cyclophosphamides Lawrence R. Phillips, Corresponding Author Lawrence R. Phillips Division of Biochemistry and Biophysics, Center for Biologics Evaluation and Research, Food and Drug Administration, 8800 Rockville Pike, Bethesda, Maryland 20892, USADivision of Biochemistry and Biophysics, Center for Biologics Evaluation and Research, Food and Drug Administration, 8800 Rockville Pike, Bethesda, Maryland 20892, USASearch for more papers by this authorGerald Zon, Gerald Zon Division of Biochemistry and Biophysics, Center for Biologics Evaluation and Research, Food and Drug Administration, 8800 Rockville Pike, Bethesda, Maryland 20892, USASearch for more papers by this authorWilliam M. Bone, William M. Bone Division of Biochemistry, Walter Reed Army Institute of Research, Walter Reed Army Medical Center, Washington, D.C. 20307-5100, USASearch for more papers by this authorVictoria L. Boyd, Victoria L. Boyd Division of Biochemistry, Walter Reed Army Institute of Research, Walter Reed Army Medical Center, Washington, D.C. 20307-5100, USASearch for more papers by this authorSusan M. Ludeman, Susan M. Ludeman The Department of Chemistry, The Catholic University of America, Washington, D.C. 20064, USASearch for more papers by this author Lawrence R. Phillips, Corresponding Author Lawrence R. Phillips Division of Biochemistry and Biophysics, Center for Biologics Evaluation and Research, Food and Drug Administration, 8800 Rockville Pike, Bethesda, Maryland 20892, USADivision of Biochemistry and Biophysics, Center for Biologics Evaluation and Research, Food and Drug Administration, 8800 Rockville Pike, Bethesda, Maryland 20892, USASearch for more papers by this authorGerald Zon, Gerald Zon Division of Biochemistry and Biophysics, Center for Biologics Evaluation and Research, Food and Drug Administration, 8800 Rockville Pike, Bethesda, Maryland 20892, USASearch for more papers by this authorWilliam M. Bone, William M. Bone Division of Biochemistry, Walter Reed Army Institute of Research, Walter Reed Army Medical Center, Washington, D.C. 20307-5100, USASearch for more papers by this authorVictoria L. Boyd, Victoria L. Boyd Division of Biochemistry, Walter Reed Army Institute of Research, Walter Reed Army Medical Center, Washington, D.C. 20307-5100, USASearch for more papers by this authorSusan M. Ludeman, Susan M. Ludeman The Department of Chemistry, The Catholic University of America, Washington, D.C. 20064, USASearch for more papers by this author First published: May 1989 https://doi.org/10.1002/oms.1210240511Citations: 2AboutPDF 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 Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume24, Issue5May 1989Pages 347-349 RelatedInformation

Fast atom bombardment mass spectra of peptides. Dimer ion studies. Part VI

Positive ion fast atom bombardment mass spectra of the opioid pentapeptides leucine enkephalin (1) (H-Tyr-Gly-Gly-Phe-Leu-OH or YGGFL), methionine enkephalin (2) (H-Tyr-Gly-Gly-Phe-Met-OH or YGGFM) and leucine enkephalin-2H2 (3) (H-Tyr-2Gly-2H2-Gly-Phe-Leu-OH or YGGFL-2H2) have been recorded in glycerol. The following experiments have been carried out: (i) dimer studies [2M + 1]+; (ii) decompositions of dimers: daughter ions from (YGGFL)2, (YGGFL-YGGFL-2H2) and (YGGFL-2H2)2 as well as (YGGFM–YGGFL) and (YGGFM)2 dimers; (iii) solvation site and pyridine collision-activated dissociation studies for dimer ions; (iv) mechanism of formation of [(2M + 1) – Gly4]+ ions.

ChemInform Abstract: Stepwise Ligand Dissociation and Multiple Changes in Oxidation State in the Fast Atom Bombardment Mass Spectra of Cyanometalate Complexes of Transition Metals

Both positive- and negative-ion fast atom bombardment (f.a.b.) mass spectra of cyanometalate complexes (metal = Fe, Cr, Mn, Ni, Mo, or W in various oxidation states) show considerable fragmentation, especially when the counter ion is an alkali metal. Analysis of the spectra reveals the existence of several families of ions from each complex, each family being characterised by the number of cations associated with the complex ion. Each family of ions give long sequences of peaks which indicate the sequential loss of neutral CN and possibly (CN)2 fragments, a conclusion confirmed by searching for the precursors of a given daughter ion. As each CN fragments is lost, the oxidation state of the metal decreases by one, leading eventually to very low oxidation states and co-ordination numbers. These sequential processes have implications for the mechanism of f.a.b., which is viewed as a gas-phase rather than a matrix process.

N‐phosphoryl amino acids and peptides. Part II: Fast atom bombardment mass spectrometry of N‐di‐isopropyloxyphosphoryl and N‐dibutyloxyphosphoryl amino acids

AbstractThe positive ion fast atom bombardment mass spectra of N‐di‐isopropyloxyphosphoryl (Dipp) and N‐dibutyloxyphosphoryl (Dbp) amino acids or amino acid methyl esters are presented; and according to the observation of the metastable ions and the high‐resolution accurate mass measurement their fragmentation patterns are postulated. Both types of compounds were found to undergo similar fragmentations to produce (HO)2P(O)NCHR + H+, in most cases as the most abundant fragment ion of structural significance. An intrinsical difference between the two types of compounds is that N‐Dippamino acids appear to favour the successive losses of two molecules of propylene, while the loss of HCOOH seems to be preferred by the Dbp amino acids. For those compounds containing an extra functional group on the side chain of amino acids such as serine or glutamic acid some other type of fragmentation was observed besides the normal phenomenon.

NMR studies of some η 4-diene-rhodium(I) and main group metal derivatives of funtionally substituted cyclopentadienes

The carbon-13 NMR spectra of twenty four acyclic and cyclic η 4-1,3-, 1,4- and 1,5-diene-rhodium(I) complexes of type η 5-C 5H 4XRh (η 4-diene), (X =H, Cl, Ph, CO 2CH 3 or CHO) are described. Each diene type can be easily distinguished from the values of its 103Rh 13C coupling constants and olefincarbon coordination shifts. The effects of methyl substituents on the relative chemical shifts of the acyclic η 4-1,3-diene carbon atom are broadly similar to that in analogous η 4-dienetricarbonyliron systems, but the metalcarbon coupling constants imply a greater degree of retrodative bonding in the case of the rhodium complexes. The largest coordination shifts are found for the β olefin carbons of the 1,4-diene complexes. The unusual metalcarbon coupling in these complexes are a reflection of the strained conformation adopted on bonding to rhodium, and do not suggest conjugative interaction between the two alkene functions. The spectra of the 1,5-diene complexes show the expected trend resulting from a reduction in strain energy relative to that for the previous case. The spectra of the η 5-cyclopentadienyl groups in these complexes as discussed in terms of a small contribution from either an η 3-allyl-η 2-ene or a η 4-diolefin-η 1-alkyl rotamer to the metalring bonding scheme; the rotamer type is governed by the cyclopentadienyl ring substituent and counter diene ligand. Several functionally-substituted cyclopentadienide salts have been examined by variable temperature hydrogen-1 and carbon-13 NMR spectroscopy. The fluxional behaviour of Tl 1(C 5H 4NO 2 and K(C 5H 4CHO) demonstrate how the Lewis acid character of the metal ion and the electron-accepting nature of the ring substituent control the structural preference for a form in which the substituent is either co-planar or orthogonal with respect to the cyclopentadienide group. Two dimensional 1H 13C NMR spectra and simulation techniques peritted unambiguous assignment of ring nuclei. The chemical ionisation and fast atom bombardment mass spectra of several of the thallium(I) complexes reveal considerable association in the vapour state.

Fast atom bombardment mass spectrometry of carbobenzyloxy‐protected amino acids and peptides

AbstractThe positive fast atom bombardment (FAB) mass spectra of 15 N‐carbobenzyloxy derivatives of α‐amino acids are presented together with those of some synthetic peptides containing other widely employed protecting groups. The data obtained allow a fragmentation pattern to be established for the N‐carbobenzyloxy moiety and to obtain detailed structural information on the main fragment ions. A study of the ion current ratio vs. time pattern shows that important fragments derive from the parent protonated molecule through FAB‐induced condensed‐phase reactions.

Cluster formation in the fast atom bombardment (FAB) mass spectra of dioxouranium(VI) dinitrate and diacetate

Cluster formation in the fast atom bombardment (FAB) mass spectra of dioxouranium(VI) dinitrate and diacetate

Fast atom bombardment of metal-pyochelin complexes: Metastable analysis at constantB/E of zinc-pyochelin

Fast atom bombardment (FAB) mass spectrometry was used to characterize the pyochelin complexes of iron and zinc. Ferripyochelin readily forms the [M + H]+ and [2M + H]+ ions in a glycerol matrix. The molecular ion was 2.5 fold more abundant when acetic acid was present. Iron was shown to be present in the iron-pyochelin complex as the ferric ion by wet chemical methods. Differentiation between ferric and ferrous ions by FAB was not successful owing to the FAB reducing environment. Ferric ions were reduced by FAB to ferrous ions in the following model salts—ferric chloride, ferric nitrate and ferric sulfate—when dissolved in either glycerol, thioglycerol or the magic bullet matrix. Ferric and ferrous chloride salts gave virtually identical spectra with a glycerol/acetic acid matrix. Zinc-pyochelin readily forms the [M + H]+ and [2M + H]+ ions, but only when acetic acid was present in the glycerol matrix. The FAB mass spectrum of zinc-pyochelin exhibited various fragmentations which can be used in structural analysis. Linked-scan at constant B/E and accurate mass data were used to characterize the fragmentations of the zinc-pyochelin complex. Metastable analysis allowed the fragmentation pathway of zinc-pyochelin to be determined.

Reduction processes in the fast atom bombardment mass spectra of pyridinium salts. The effect of reduction potential and concentration

The enhancement of the (C + 1)/C ratio in the fast atom bombardment mass spectra of seven pyridinium cations has been measured. No dependence of the enhancement on the cation reduction potential could be identified. The N-methyl pyridinium cation, which showed no enchancement under matrix-free conditions, exhibited an increase in the (C + 1)/C ratio with decreasing concentration. This concentration dependence was eliminated when the bombardment energy was reduced from 9 to 5 keV. Possible mechanisms for the concentration dependence and the variation with bombardment energy are proposed. Keywords: fast atom bombardment, reduction, pyridinium salts.

Studies on fast atom bombardment (FAB), electron ionization (EI) and chemical ionization (CI) mass spectra of prenylated flavonoids.

Positive ion FAB mass spectra of prenylated flavonoids were compared with the corresponding EI and CI mass spectra, and some fragment ions similar to those in the EI mass spectra and CI-like intense protonated molecules (M+H)+ were recognized. Major fragmentations in the EI and FAB mass spectra were discussed. It was concluded that FAB ionization possesses both features, EI-like hard ionization and CI-like soft ionization.

Studies on spiroborate complexes. Part III. Fast atom bombardment mass spectrometry of bis-catechol spiroborate and its analogues

Nagative-ion fast atom bombardment mass spectra of spiroborate complexes are simple and highly diagnostic of the structures of the borate anions. In hydroxylic liquid matrices, exchange of the spiroborate ligand and solvent molecules occurs slowly on the probe tip. This interference is particularly noticeable with glycerol as solvent. The repercussions of in situ ligand exchange for studies of other anions are discussed. Positive-ion fast atom bombardment mass spectra can be used to identify readily the counter-cations in the spiroborate complexes.

Tandem mass spectrometric study on fragmentation in fast atom bombardment mass spectra of prenylated flavonoids.

It was directly proved that the molecular ion M+ produced under FAB condition results in an EI-like fragmentation, and the protonated molecule (M+H)+ a CI-like fragmentation, by using a four-sector tandem mass spectrometer. The result was confirmed by comparing the B2/E2 linked scan FAB (B2/E2 tandem FAB) mass spectra of three prenylated flavonoids with the corresponding B/E linked scan EI (B/E-EI) and B/E-CI mass spectra.

An unexpected intramolecular cyclization of isothiouronium teicoplanins. II Reaction mechanism and biological activity.

N15-Isothiouronium derivatives of teicoplanin and its aglycone submitted to alkaline condition give rise to an intramolecular cyclization. The structures of the new gamma-lactam derivatives were determined by using 1H NMR, IR and fast atom bombardment mass spectra. The cyclization mechanism was interpreted on the basis of the identification of the intermediate structure. The poor in vitro antibacterial activity of the new cyclic compounds and the negligible affinity for the synthetic peptidoglycan model Ac2-L-Lys-D-Ala-D-Ala is probably due to the lack of the N-17 amidic proton and to the lack of the basic character of the nitrogen in position 15.

Structural Determination of a Cyclic Metabolite of NAD+ with Intracellular Ca2+-mobilizing Activity

Incubation of NAD+ with extracts from sea urchin eggs resulted in production of a metabolite which could mobilize intracellular Ca2+ stores of the eggs. In this study we present structural evidence indicating that the metabolite is a cyclized ADP-ribose having an N-glycosyl linkage between the anomeric carbon of the terminal ribose unit and the N6-amino group of the adenine moiety. In view of this structure we propose cyclic ADP-ribose as the common name for the metabolite. The purification procedure for the metabolite consisted of deproteinizing the incubated egg extracts and sequentially chromatographing the extracts through three different high pressure liquid chromatography (HPLC) columns. The homogeneity of the purified metabolite was further verified by HPLC on a Partisil 5 SAX column. Using radioactive precursor NAD+ with label at various positions it was demonstrated that the metabolite was indeed derived from NAD+ and that the adenine ring as well as the adenylate alpha-phosphate were retained in the metabolite whereas the nicotinamide group was removed. This was confirmed by 1H NMR and two-dimensional COSY experiments, which also allowed the identification of all 12 protons on the two ribosyl units as well as the two protons on the adenine ring. From the chemical shifts of the two anomeric protons it was concluded that the C-1 carbons of both ribosyl units were still bonded to nitrogen. The positive and negative ion fast atom bombardment mass spectra showed (M + Na)+, (M - H + 2Na)+, (M - H)-, and (M - 2H + Na)- peaks at m/z 564, 586, 540, and 562, respectively. Exact mass measurements indicated a molecular weight of 540.0526 for (M - H)-. This together with the constraints imposed by the results from NMR, radioactive labeling, and total phosphate determination uniquely specified a molecular composition of C15H21N5O13P2. Analysis by 1H NMR and mass spectroscopy of the only major breakdown product of the metabolite after prolonged incubation at room temperature established that it was ADP-ribose, thus providing strong support for the cyclic structure.

Fast Atom Bombardment Mass Spectra of Disulphonated Cyanine Dyestuffs

Fast Atom Bombardment Mass Spectra of Disulphonated Cyanine Dyestuffs

Fast atom bombardment and collisional activation mass spectrometry of oligosaccharides related to xylans

The positive ion fast atom bombardment (FAB) mass spectra of oligosaccharides related to D-xylan and D-glucurono-D-xylans were investigated. Although the mass spectra of the underivatized oligosaccharides are relatively weak, they still offer reliable information on the molecular weight of these compounds from their [M + H]+ and [M + H + glycerol]+ ions. Esterification, glycosidation and/or partial methylation improve the relative abundances of the molecular and fragment ions with respect to those of the glycerol matrix. The mass spectra of these derivatized compounds also allow the determination of the mass of the monosaccharide units by the occurrence of more abundant and characteristic fragment ions. The differently linked D-xylobioses of the (1 → 2), (1 → 3) and (1 → 4) type cannot be distinguished on the basis of their mass spectra alone. The collisional activation (CA) spectra of the [M + H + glycerol]+ adduct ions, however, revealed that an unequivocal determination of the type of linkage in these isomers is possible. The small values of the discrepancy factors in the FAB CA spectra prove that CA mass spectrometry is, also in combination with FAB ionization, the most precise of the current mass spectrometric techniques.

Hydrophobic effects in the fast atom bombardment mass spectra of proteins and large peptides

The positive ion fast atom bombardment (FAB) mass spectra of a number of large peptides and small proteins are presented. The relationship between the hydrophobic character of such molecules (based on the primary amino acid sequence) and signal ion abundance observed in FAB mass spectrometry is examined, as well as the phenomenon of molecular ion suppression of large peptides by the presence of other more hydrophobic peptides in the matrix. It is concluded that the signal ion abundance of large peptides/small proteins is related to hydrophobic character and the consequences of such an observation are discussed with regard to obtaining FAB mass spectra of large peptides and proteins.

Comparative electron impact, chemical ionization and fast atom bombardment mass spectra of Nα ‐(t‐butyloxycarbonyl)–O–(di–t–butylphosphoro)–L–serine

Comparative electron impact, chemical ionization and fast atom bombardment mass spectra of N_α ‐(t‐butyloxycarbonyl)–O–(di–t–butylphosphoro)–L–serine