Fast Atom Bombardment Mass Spectra Research Articles

Differentiation of Diastereomeric Tertiarybutoxycarbonylprolylproline Ethyl Esters by Collision-Induced Dissociation of Sodium Adduct Ions in Fast Atom Bombardment Mass Spectrometry.

The formation and the fragmentation of the sodium adduct ions for tertiarybutoxycarbonyl-L-prolyl-L-proline ethyl ester (Boc-L-Pro-L-Pro-OEt) were compared with those for Boc-D-Pro-L-Pro-OEt on the addition of sodium chloride in positive-ion fast atom bombardment (FAB) mass spectrometry. The abundance of the [M+Na]+ ion was about 2 times lower than that of the [M+H]′ ion on the addition of sodium chloride in FAB mass spectrum for Boc-L-Pro-L-Pro-OEt, while the former was almost same as the latter in the spectrum for Boc-D-Pro-L-Pro-OEt, suggesting that Boc-D-Pro-L-Pro-OEt has a stronger Na′ ion affinity than Boc-L-Pro-L-Pro-OEt. On the other hand, in the collision-induced dissociation (CID) mass spectra of the [M+Na]′ ions, the abundance of the [M+Na-C(CH3)3+ H]+ ion, which is due to the loss of a tertiarybutyl group from the [M+Na]+ ion for Boc-D-Pro-L-Pro-OEt, was higher than that for Boc-L-Pro-L-Pro-OEt. These results indicate that Boc-L-Pro-L-Pro-OEt was distinguished from Boc-D-Pro-L-Pro-OEt by the CID mass spectra of the [M+Na]+ ions, and the difference of the cleavage patterns between Boc-L-Pro-L-Pro-OEt and Boc-D-Pro-L-Pro-OEt when the carboxyl-terminals were protected with ethyl ester, was smaller than that between tertiarybutoxycarbonyl-L-prolyl-L-proline (Boc-L-Pro-L-Pro) and Boc-D-Pro-L-Pro when they were free reported previously.1)

Potentiometric evaluation of solvent polymeric carbonate-selective membranes based on molecular tweezer-type neutral carriers

Potentiometric properties of the ion-selective electrodes) based on highly plasticized PVC membranes doped with the carbonate-selective cholic acid (CA) derivatives have been measured. The carbonate-selective neutral carriers have been prepared by coupling one to three trifluoroacetobenzoyl (TFAB) groups to a cholic acid derivative which has three hydroxyl linkers lining on the C3, C7, and C12 positions of its rigid steroidal ring structure. The membranes based on cholic acid derivatives with two TFABs [3,7-bis(TFAB)CA, 3,12-bis(TFAB)CA, and 7,12-bis(T-FAB)CA] exhibited remarkably improved carbonate selectivity, indicating that the bis(FAB)CAs behave like molecular tweezers for the carbonate ion. For example, 3,12-bis(TFAB)CA resulted in 10-300-fold-enhanced carbonate selectivity over other anions (e.g., salicylate, ClO4-, SCN-, (HPO4)2-, NO3-, NO2-, Br-, and Cl-) compared to that of the neutral carriers with a single TFAB group. The distances between the carbonate binding centers of bis(TFAB)CAs, i.e., the carbonyl carbons of the two TFAB groups, are in the 7.3-7.9-A range at the AM1 level semiempirical calculation, which is too far for the carbonate ion to form direct covalent bonding. The fast atom bombardment mass spectra of bis(TFAB)CAs show that significant fractions of the compounds are either mono- or dihydrated before complexing the carbonate ion. These findings seem to suggest that bis(TFAB)CAs recognize the incoming carbonate ion by forming both covalent and hydrogen bonding between the hydrated and unhydrated TFAB groups. The analytical utility of the carbonate-selective electrode based on 3,12-bis(TFAB)-CA has been demonstrated by measuring the total carbon dioxide in human serum in the presence of lipophilic anion interferents, e.g., salicylate.

Mass Spectrometry of Oligosaccharides(I)—Formation of the [M+Nh4]+ Ion of Oligosaccharides in Fast Atom Bombardment Mass Spectrometry

In positive-ion fast atom bombardment (FAB) mass spectrometry, when oligosaccharides are mixed with an appropriate amount of NH4Cl, a highly abundant [M+NH4]+ peak appears in FAB mass spectra. From the adduct ion [M+NH4]+, the molecular weights of oligosaccharides can be determined definitively. This technique may especially be applied to analyze the mixture of oligosaccharides.

Negative fast atom bombardment ionization of aromatic sulfonic acids: unusual sample-matrix interaction.

The most intense ion(s) in negative ion fast atom bombardment (FAB) mass spectra of 2- and 4-benzaldehyde sulfonic acid (BSA) in glycerol or 3-nitrobenzyl alcohol matrix corresponds to a covalent association of the analyte with one or two matrix molecules accompanied by the elimination of a molecule of water. The molecular ion [M - H](-), however, is of low abundance. The identity of the resulting ions [M + nA - H(2)O - H](-) (where M is the analyte and A is the matrix) was confirmed by exact mass measurement using the peak matching technique. These covalent matrix-analyte complexes were not observed when the sulfonic acid functionality in BSA was substituted with COOH, NO(2), and OH or when the sulfonic acid was in salt form. These observations indicate that the free sulfonic acid group in BSA is responsible for the covalent adduct formation. To our knowledge, analyte-matrix covalent association in negative ion FAB spectra of BSA has not been reported previously.

Mass spectrometric study of tricarbonyl (eta(6)-phenyl methanols) of chromium(0).

A mass spectrometric study of several tricarbonyl (eta(6)-phenyl methanols) of chromium(0) was performed. Electron ionization (EI), chemical ionization (CI) and fast atom bombardment (FAB) mass spectra were acquired for each molecule, and compared in order to establish a general fragmentation pattern. The suggested pathways were investigated and confirmed by means of constant b/e linked scans and high resolution data. In addition a Hammett-McLafferty correlation for some peaks derived from the molecular ions was accomplished.

Characterization of iridoids by fast atom bombardment mass spectrometry followed by collision-induced dissociation of

Fast atom bombardment mass spectra of a series of naturally occurring and synthetically modified iridoid glycosides were studied using lithium cationization and collision-induced dissociation of the resulting [M+Li]+ ions. Lithium cationization leads to the unambiguous determination of the molecular masses of these compounds. Collision-induced dissociation of the lithiated molecular ions give valuable structural information regarding the nature of the substituent on both the aglycone and the sugar moieties. The characteristic fragmentation pathways identified are (1) elimination of neutral molecules comprising the substituents on either the aglycone or sugar moieties, (2) formation of lithiated aglycone and their fragment ions, (3) formation of lithiated sugar and their fragment ions, (4) fragmentation corresponding to the cleavage of the aglycone or sugar ring and (5) fragmentation characteristic of the substituents present in either the aglycone or sugar parts of the molecule. Elimination of two acyloxy radicals from the lithiated molecular ion is a characteristic fragmentation in the case of acyloxy derivatives.

Synthesis and Characterization of Novel Self-Generating Liquid MOCVD Precursors for Thin Films of Zinc Oxide

Three novel Zn(hfa)2·2H2O·polyether adducts have been prepared through simple procedures with stoichiometric quantities of zinc hydroxide, Hhfa, and polyether. The products have been characterized by elemental analysis, X-ray single-crystal analysis, fast atom bombardment mass spectra, 1H and 19F NMR spectra, thermogravimetric (TG)−differential TG−differential scanning calorimetry (DSC) thermal measurements, and infrared transmittance spectroscopy. An attempt to obtain water-free adduct was unsuccessful even using excess polyethers. X-ray single-crystal data of the Zn(hfa)2·2H2O·diglyme adduct show that the polyether does not coordinate to the metal center. Nevertheless, metrical data are indicative of bridging interactions involving the oxygen of one coordinated H2O molecule and the three oxygens of the diglyme. Very mild heating (37−51 °C) results in liquid compounds that, in turn, can easily be evaporated. Preliminary gas-phase Fourier transform-IR measurements in vacuo suggest that the anhydrous Zn(hf...

Identification of triacylglycerols containing two short-chain fatty acids at sn-2 and sn-3 positions from bovine udder by fast atom bombardment tandem mass spectrometry.

Several triacylglycerol (TAG) molecular species, that contain two short-chain fatty acids (C4 to C8) at the sn-2 and sn-3 positions of the glycerol backbone, were isolated from bovine udder by using solvent extraction and silica gel column chromatography. Their structures were identified by fast atom bombardment (FAB) tandem mass spectrometry (MS/MS), based on the information obtained from collision-induced dissociation (CID) spectra of sodium-adducted molecules ([M + Na](+)) of model TAG compounds which had been synthesized from glycerol and appropriate fatty acids. For each species, the relative positions of the three fatty acids on the glycerol backbone, as well as fatty acid composition and double-bond position in the fatty acyl group, were determined. A majority of sodium-adducted molecules observed in the FAB mass spectrum were mixtures of at least two components that have different fatty acid composition but the same molecular mass. In addition, all the components present in mixtures of all the species contain a long-chain fatty acid (C12 to C18) at the sn-1 position, a short-chain fatty acid (C4 to C8) at the sn-2 position, and a butyric acid uniquely at the sn-3 position.

Preparation, spectroscopic investigation and antibacterial activity of some organomercury(II) and organotin(IV) dithio complexes

Phenylmercuric acetate, triphenyltin chloride and dibutyltin chloride react with alkali-metal or ammonium salts of some 1,1- and 1,2-dithio ligands in appropriate molar ratios to yield a series of organometallic dithio complexes of the type [PhHgX] (X = butylxanthate (Buxant−), cyclohexylxanthate (Cyxant−), benzylxanthate (Bzxant−) or pyrrolidin-1-yldithiocarbamate (Pdtc−); [(PhHg)2X] (X = isomaleonitriledithiolate (i-MNT2−) or 1-ethoxycarbonyl-1-cyanoethylene-2,2-dithiolate (ecda2−); Ph3SnX (X = Buxant− or Pdtc−); [(Ph3Sn)2(i-MNT)] and [Bu2SnMNT] (MNT2− = maleonitriledithiolate). These complexes have been characterized by elemental analysis, molar conductance measurements, IR, FT-Raman, 1H and 13C NMR and fast atom bombardment (FAB) mass spectra. Cyclic dimeric structures for phenylmercuryxanthates and monomeric structures for the remaining complexes are suggested. Antibacterial activities of the complexes and parent ligands have been screened against some well-known pathogenic bacteria. Organomercury dithiolates have been found to be more potential antibacterial than organotin complexes. Copyright © 2000 John Wiley & Sons, Ltd.

有機分子のフラグメンテーションに関する基礎的研究 有機分子へのプロトン付加および生成プロトン化分子のフラグメンテーション

Protonation of organic compounds and fragmentations of resulting protonated molecules are reviewed. In chemical ionization (CI) mass spectrometry, the amount of protonation and the extent of bond cleavages of typical functional groups are evaluated by using appropriate test compounds. A new parameter, protonation susceptibility (PS), is introduced, which is not directly related to the ordinary proton affinity (PA) of organic compounds. CI mass spectra of a series of compounds are quantitatively analyzed, and prediction of an unknown spectrum is shown to be successful. The principal modes of bond cleavages in even-electron ions are also formulated. These results are compared to the protonation in fast atom bombardment (FAB) and electrospray ionization (ESI) mass spectra, where the protonation takes place in condensed phase-like environment and in solution, respectively.

Low-temperature fast atom bombardment mass spectra of frozen nitric acid-water solution

Positive ion low-temperature fast atom bombardment mass spectra of the frozen nitric acid-water system with an initial components ratio which provides preferential formation of the crystalline hydrate of the nitric acid trihydrate, HNO(3).3H(2)O, are reported. A complicated spectral pattern is created by a number of cluster sets which, on the basis of discussion, were attributed to (H(2)O)(n). NO(+) (n = 1-3), (H(2)O)(n).NO(2)(+) (n = 1, 2), (HNO(3))(m). (H(2)O)(n).H(+) (m = 1-5 and n variable) and (H(2)O)(n).H(+) (n = 1-9). Similarities between the size-dependent behavior of hydrate clusters of nitrogen oxides and nitric acid obtained with sputtering from the solid in the present low-temperature experiments and under gas-phase conditions (reported earlier in the literature) were revealed. A suggestion as to possibility of the yield of the cluster ions sputtered due to energetic particle collision with the frozen grains of water ice and nitric acid trihydrate, present in the atmosphere, to the total ionic population of the atmosphere is discussed. Copyright 1999 John Wiley & Sons, Ltd.

Low temperature fast atom bombardment mass spectra of HCl water solution

Low temperature fast atom bombardment mass spectra of the frozen water solution of HCl contain a set of clusters (H 2O) n · H +, which is an order of magnitude more abundant and differs in intensity distribution from a simlar cluster set usually produced from pure water ice. The cluster pattern is discussed in the light of formation of phases of crystalline hydrates in the frozen solution.

Applicability of fast-atom bombardment mass spectrometry to the characterization of fulvic acid

A variety of experimental parameters have been evaluated for their effect on the fast-atom bombardment (FAB) mass spectrum of five fulvic acids. Eleven common FAB matrices were evaluated. Only glycerol gave any indication of a fulvic acid spectrum, and this was a very weak signal increase superimposed onto the glycerol spectrum. Continuous-flow FAB was also evaluated using a glycerol matrix and no significant signal was observed in the FAB mass spectrum. Five techniques used to modify the matrix or the sample to enhance a spectrum's signal-to-noise ratio were also studied. Surfactants were added to modify the matrix surface tension, removal of sodium from the fulvic acid samples (to minimize the formation of ([M + Na] +) was accomplished using complexation and ultra-centrifugation, fulvic acid `ions' were preformed in the matrix by the addition of acid or base, and fulvic acid was methylated to increase its hydrophobicity. None of these techniques enhanced the FAB mass spectrum of fulvic acid. The lack of a significant ion intensity attributable to fulvic acid is probably due to its heterogeneous, multi-component nature. Despite some reports in the literature to the contrary, it does not appear that it is possible to characterize fulvic acid by FAB mass spectrometry.

Macrocycles, 6. MALDI-TOF mass spectrometry of tin-initiated macrocyclic polylactones in comparison to classical mass-spectroscopic methods

2,2-Dibutyl-2-stanna-1,3-dioxepane (1) was used as cyclic initiator for the (ring expansion) polymerization of L-lactide, ε-caprolactone, β-D,L-butyrolactone and 1,4-dioxane-2-one. The polymerizations were conducted in bulk at 80 and 120°C with monomer/initiator mole ratios of 6, 10, and 20. When the resulting macrocyclic oligolactones (DP-6) were subjected to mass spectroscopy total thermal degradation via transesterification took place and the original molecule peak was not detectable. In the case of fast atom bombardment (FAB) and matrix-assisted laser desorption ionization/time of flight (MALDI-TOF) measurements the alcohols or phenols used as matrix materials cleave the Sn—O bonds of the macrocycles and the MALDI-TOF mass spectra showed the molecule peaks of OH-terminated telechelic polylactones. Stoichiometric insertion of γ-thiobutyrolactone into the Sn—O bonds yielded stabilized macrocyclic polylactones containing the less reactive Sn—S bonds, which allowed the recording of FAB and MALDI-TOF mass spectra showing the molecule peaks of intact tin-containing cyclic oligo- and polylactones.

Fast-atom bombardment mass spectra of isopropylidene derivatives of glucose and mannose

Abundant [M + H]+, [M-H]+ and [M-CH3]+ ions are observed in the fast-atom bombardment mass spectra of isopropylidene derivatives of glucose and mannose. Formation of abundant [M-H]+ is attributed to beam-induced processes. The collision-induced dissociation spectra of the [M + H]+ ions of the α- and β- anomers of the glucose derivatives differ in the abundances of the fragment ions. As expected, marked differences are noticed in the fragmentations of the [M + H]+ and the corresponding [M + Li]+ ions. Lithium cationization induces cleavage of the isopropylidene ring. Copyright © 1999 John Wiley & Sons, Ltd.

Chemical synthesis of d-ribo-phytosphingosine-1-phosphate, a potential modulator of cellular processes

d-erythro -Sphingosine-1-phosphate (2), an intermediate in sphingosine metabolism, shows a diversity of biological activities. Comparable roles might be anticipated for d-ribo -phytosphingosine-1-phosphate (1). We describe an efficient three-step chemical synthesis of 1 from d-ribo -phytosphingosine. Our approach is based on standard phosphoramidite methodology and on the finding of Boumendjel and Miller ( J. Lipid Res. 1994. 35: 2305-2311) that sphingosine can be monophosphorylated at the 1-hydroxyl without protection of the 3-hydroxyl. However, we were unable to duplicate their reported synthesis of 2 without important modifications in reagents and reaction conditions. Under the reported conditions for preparing 2, we obtained a cyclic carbamate (14), which we have isolated and identified. The structures of 1 and the cyclic carbamate 14 were elucidated by a combination of mass spectrometry and 1D and 2D nuclear magnetic resonance spectroscopy.

HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY-TANDEM MASS SPECTROMETRY OF CARDIAC STEROIDS

High performance liquid chromatography-tandem mass spectrometry (LS/MSn) utilizing an ion trap mass spectrometer has been used for the analyses of representative cardiac steroids. In the case of bufotoxin having a polar residue (suberoylarginine), the positive-electrospray ionization (ESI) was 50 times more sensitive than the atmospheric pressure chemical ionization (APCI) and provided information concerning the molecular weight as well as the structures of both aglycone and suberoylarginine. The corresponding bufogenin showed 2 times better sensitivity in the positive-APCI than ESI. The mass spectrum of digoxin with the positive-APCI showed fragment ions not only derived from aglycone but also formed by losses of sugars. The cleavage of the dioxane ring has been observed on the cardiac glycoside having an unusual sugar linkage. Fast atom bombardment mass spectra of these compounds were examined and compared with the data obtained from LC/MSn.

Synthesis, characterization and DNA-binding properties of novel dipyridophenazine complex of ruthenium (II) : [Ru(IP) 2(DPPZ)] 2+

A novel ruthenium(II) complex of dipyridophenazine (DPPZ) with the ancillary ligand imidazole[4,5- f] [1,10]phenanthroline (IP), [Ru(IP) 2(DPPZ)] (PF 6) 2, has been synthesized and characterized by elemental analysis, 1D and 2D 1H NMR, fast-atom bombardment mass spectra (FABMS), electronic spectroscopy and cyclic voltammetry. The DNA-binding properties of the complex were studied by spectroscopic methods. The intrinsic binding constant, K =2.1 × 10 7M −1, of the complex to calf thymus DNA has been determined by absorption titration in 5 mmol dm −3 Tris-HCl, 50 mmol dm −3 NaCl buffer (pH 7.0). The excited state lifetimes and luminescence quenching with [Fe(CN) 6] 4− as the quencher in the presence of DNA were also tested and mono-exponentiality was observed for the emission decay curves. Viscosity measurements together with the optical titrations unambiguously proved that the complex bound with DNA intercalatively and that the binding affinity to DNA was several times larger than that of the parent complex [Ru(bpy) 2(DPPZ)] 2+.

Reductive degradation of O-acyl oximes under fast-atom bombardment conditions

A degradation phenomenon of O-acyl oximes under fast-atom bombardment (FAB) conditions is described from the point of view of reactivity with the liquid matrix and irradiation time with the xenon neutral beam. Mass spectra of O-acyl oximes were compared with those of the free oxime and hydroxylamine as model compounds, by using two different matrices, m-nitrobenzyl alcohol and DTT/TG12 (a 1 : 2 mixture of dithiothreitol and thioglycerol). A characteristic fragment ion was observed in the FAB mass spectra of O-acyl oximes and a free oxime only when DTT/TG12 was used. Collision-activated dissociation (CAD) was used to search for the origin and to confirm the structure of the characteristic fragment ion. The CAD spectra of the molecular-related ions, [M – H] + ,M +• and [M + H] + , demonstrated that this characteristic fragment ion was not derived from any of these precursor ions. The CAD spectra of the characteristic fragment ion, which originated from O-acyl oximes, were very similar to those from free oximes and these results indicated that the fragment ion had the same structure. It was concluded that the degradation, under FAB conditions, was caused by a reductive reaction of the oxime moiety (–O–N=C<) in O-acyl oximes regardless of its acyl moiety and that the degradation was initiated by the thiol group(s) in the matrix. The abundance of the ion originating from reductive degradation increased with increasing irradiation time with the xenon neutral beam.

Partially selective methanolysis of sebacic units in biodegradable multicomponent copolyesters

The composition and molar masses of equimolar multicomponent copolyesters, obtained from 1,4-butandiol and mixtures of succinic, adipic, sebacic, and terephthalic acids were characterized by 13C NMR, size exclusion chromatography (SEC), matrix assisted laser desorption ionization-time of flight mass spectroscopy (MALDI-TOF-MS), and viscosimetry. These copolyesters were subjected to partial methanolysis, and the composition and sequence of the oligomers obtained in the methanolysis were determined by the analysis of their fast atom bombardment (FAB-MS) mass spectra. The comparison of the composition data obtained by FAB-MS and 13C NMR indicates that for copolymers containing sebacic units the methanolysis is a partially selective process, and that oligomers containing sebacic units accumulate in the residue.