Significant Fragment Ions Research Articles

A shadow of ink: Test papers soaked in 4:7-diphenyl-1:10-phenanthroline as a carrier of elemental information for spectrochemical investigations of manuscripts by XRF, LA-ICP-MS and SIMS

In this study, X-Ray Fluorescence Spectrometry (XRF), Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) and Secondary Ion Mass Spectrometry (SIMS) have been used to assess the transfer of ions between iron-gall inks and indicator papers soaked in 4:7-diphenyl-1:10-phenanthroline. Such indicators are commonly used in the conservation practice to detect Fe(II) ions and diagnose a presence of ink corrosion phenomena in historical manuscripts. For this purpose four different model inks with variable Fe:Cu proportions were prepared on the basis of gall nuts extract mixed with FeSO4.7H2O, CuSO4.5H2O and Gum Arabic. Obtained results indicate that apart from the main components of inks (S, Fe and Cu) also other elements can migrate to indicator test papers. Collected XRF and LA-ICP-MS data were consistent in their potential for reconstructing major elemental composition of model inks on the basis of indirect analysis with indicator test papers. LA-ICP-MS extended the range of learning into the trace elemental composition, while SIMS allowed observations of structurally significant fragment ions (ML2+, ML+, M+) where L = 4:7-diphenyl-1:10-phenanthroline and M = Fe or Cu ions.

Diagnostic Fragmentation Pathways for Identification of Phthalate Metabolites in Nontargeted Analysis Studies.

Phthalates have been studied due to their linkages with adverse developmental effects; however, metabolites of this class of compounds are undercharacterized and are poorly captured by traditional targeted analysis. In this study, we developed a nontargeted analysis approach for identifying and classifying phthalate metabolites based on a comprehensive study of their fragmentation pathways in electrospray ionization (ESI) quadrupole-time-of-flight mass spectrometry (QTOF-MS). This approach identifies molecular features in the data as phthalate metabolites via the detection of three structurally significant fragment ions. Then phthalate metabolites are classified into four types based on the presence of additional fragment ions specific to each type. Cleavage mechanisms for each class of phthalate metabolite are proposed based on fragmentation patterns generated at various collision energies (CE). All of the tested phthalate metabolites including oxidative and nonoxidative metabolites produced a fragment ion at m/z 121.0295, representing the deprotonated benzoate ion [C6H5COO]-. Most tested phthalate metabolites can produce a specific ion at m/z 147.0088, the deprotonated o-phthalic anhydride ion. However, phthalate carboxylate metabolites can only produce the [M-H-R]- ion at m/z 165.0193 and do not produce the fragment at m/z 147.0088. Other phthalate oxidative metabolites (hydroxyl- and oxo-) follow a different fragmentation pathway than nonoxidative metabolites. With this workflow, eight unknown phthalate metabolites were putatively identified in pooled urine, with one identified as a previously unreported metabolite by a combination of the MS/MS spectrum and the predicted retention time. Method detection limits for phthalate metabolites in urine were also estimated.

Direct determination of nosiheptide residue in animal tissues by liquid chromatography-tandem mass spectrometry

Because only very weak signals of fragment ions of nosiheptide can be obtained, nosiheptide is usually detected by liquid chromatography-tandem mass spectrometry (LC-MS/MS) via the determination of its hydrolyzed degradation product named HMIA in previous studies. The indirect method suffers from several problems, such as complicated samplepreparation, unavailable commercial HMIA, and the risk of the false-positive result by HMIA. However, we found that nosiheptide could produce several significant fragment ions under high collision energy (CE). Therefore, we developed a method for the direct determination of nosiheptide by LC-MS/MS in animal tissues. The sample was extracted with ACN, then degreased with n-hexane, and purified by an HLB solid-phase extraction (SPE) cartridge. After being filtered through the PTFE filter, it was analyzed by LC-MS/MS in selected reaction monitoring (SRM) mode. The influencing factors, such as mobile phase, SPE cartridge, filter material, and matrix effect, were investigated. Nosiheptide showed a good linear relationship (R2 ≥ 0.999) within the concentration range from 0.3 μg/L to 20 μg/L under optimized conditions. The limit of detection (LOD) was 0.3 μg/kg, while the limit of quantification (LOQ) was 1.0 μg/kg in chicken, bovine muscle, swine muscle, and swine liver. The average recoveries at spiked levels of 1.0, 2.0, and 10 μg/kg ranged from 83% to 101%, with the relative standard deviations (RSDs) <12%. Compared with the methods previously reported, our newly developed method was more simple, convenient, and sensitive. Moreover, it was successfully applied for the determination of nosiheptide residue in medicated chicken samples.

Differentiation of methylated indole ring regioisomers of JWH-007: GC–MS and GC–IR studies

The five regioisomeric methylated indole ring analogues of JWH-018 can be prepared directly from a common set of precursor materials. These five isomers include 2-methyl-1-n-pentyl-3-(1-naphthoyl)-indole (JWH-007) and its four regioisomeric analogues, 4-, 5-, 6- and 7-methyl substituted indoles. The EI-MS spectra show equivalent regioisomeric major fragments resulting from cleavage of the groups attached to the central indole nucleus. The characteristic [M−17]+ fragment ion at m/z 338 resulting from the loss of OH group is significant in the mass spectra of all the studied compounds except Compound 2 (JWH-007) which has two significant fragment ions at m/z 340 and m/z 270. Cations at m/z 298, 284, 228 and 200 result from fragmentation of the naphthoyl and/or n-pentyl groups. GC separations on a trifluoropropylmethyl polysiloxane (Rtx-200) provided excellent resolution of these compounds. The elution order appears to be related to the degree of crowding of indole ring substituents. The vapor phase infrared spectra in the range of 1700–700 cm−1 showed unique and characteristic absorption patterns for each of the five regioisomeric compounds which allowed for discrimination among the isomers in this set of cannabinoid compounds.

Gas chromatographic mass spectrometric detection of dihydroxy fatty acids preserved in the ‘bound’ phase of organic residues of archaeological pottery vessels

A methodology is presented for the determination of dihydroxy fatty acids preserved in the 'bound' phase of organic residues preserved in archaeological potsherds. The method comprises saponification, esterification, silica gel column chromatographic fractionation, and analysis by gas chromatography/mass spectrometry. The electron ionisation mass spectra of the trimethylsilyl ether methyl ester derivatives are characterised by fragment ions arising from cleavage of the bond between the two vicinal trimethylsiloxy groups. Other significant fragment ions are [M-15](+.), [M-31](+.), m/z 147 and ions characteristic of vicinal disubstituted (trimethylsiloxy) TMSO- groups (Δ(7,8), Δ(9,10), Δ(11,12) and Δ(13,14): m/z 304, 332, 360 and 388, respectively). The dihydroxy fatty acids identified in archaeological extracts exhibited carbon numbers ranging from C(16) to C(22) and concentrations varying from 0.05 to 14.05 µg g(-1) . The wide range of dihydroxy fatty acids observed indicates that this approach may be applied confidently in screening archaeological potsherds for the degradation products of monounsaturated fatty acids derived from commodities processed in archaeological pottery vessels.

Liquid chromatography–mass spectrometric determination of plasmalogens in human plasma

A new liquid chromatography-mass spectrometry (LC/MS) method has been developed for the quantitative analysis of plasmalogens in human plasma using a nonendogenous plasmalogen (1-O-1'-(Z)-tricosenyl-2-oleoyl-rac-glycero-3-phosphocholine, PLS 23:0/18:1) as an internal standard. 1-O-1'-(Z)-Tricosenyl glyceryl ether was prepared by reacting lithioalkoxyallyl with 1-iodoeicosane as the key intermediate in the formation of PLS 23:0/18:1. In LC/MS analyses, PLS 23:0/18:1 generated significant fragment ions in positive and negative modes. In positive ion mode, the [M+H](+) of PLS 23:0/18:1 yielded unique fragments with cleavages at the sn-1 and sn-2 positions of the glycerol backbone. In negative ion mode, the [M+CH(3)COO](-) of PLS 23:0/18:1 resulted in characteristic fragmentation at the sn-2 and sn-3 positions. 1-O-1'-(Z)-Hexadecenyl-2-linoleoyl-rac-glycero-3-phosphocholine (PLS 16:0/18:2) and 2-arachidonoyl-O-1'-(Z)-hexadecenyl-rac-glycero-3-phosphocholine (PLS 16:0/20:4) were chemically synthesized as PLS 23:0/18:1. The calibration curves obtained for PLS 16:0/18:2 and PLS 16:0/20:4 were linear throughout the calibration range (0.04-1.60 pmol). The LOD (S/N = 5:1) was 0.008 pmol and the LOQ (S/N = 6:1) was 0.01 pmol for both PLS 16:0/18:2 and PLS 16:0/20:4. Plasma concentrations of PLS 16:0/18:2 and PLS 16:0/20:4 were 4.0 ± 1.3 μM and 3.5 ± 1.2 μM (mean ± SD), respectively, in five healthy volunteers.

Trends in the reactions of gaseous phenyl pnictogen radical cations C6H5EH2˙+ (E = N, P, As)

In context of an analysis of the effect of the central atom E of gaseous radical cations of phenyl pnictogens C(6)H(5)EH(2), E = N (1), P (2), and As (3), the mass spectrometric reactions of phenyl phosphane 2 have been re-investigated by D-labeling and by using methods of tandem mass spectrometry. The 70 eV mass spectrum of 2 shows the base peak for ion [M-2H](*+) and significant peaks for ions [M-H](+), [M-(2C,3H)](+), [M-PH] (*+), and [M-(C,P,2H)](+). Metastable 2(*+) fragments exclusively by loss of H(2), and the investigation of deuterated 2-d(2) shows that excessive H/D migrations occur before fragmentation. Other significant fragment ions in the mass spectrum of 2 arise by losses of C(2)H(2,) P, or HCP from the ion [M-H](+). This mass spectrometric behavior puts the radical cation 2(*+) in between the fragmentation reactions of aniline radical cation 1(*+) (loss of H and subsequent losses of C(2)H(2,) or HCN) and phenyl arsane radical cation 3(*+) (elimination of H(2) and loss of As from ion [M-H](+)). The fragmentation mechanisms of the radical cations 1(*+) -3(*+) and of related ions were analyzed by calculations of the enthalpy of relevant species at the stationary points of the minimum enthalpy reaction pathways using the DFT hybrid functionals UBHLYP/6-311+G(2d,p)//UBHLYP/6-311+G(d). The results show that, in contrast to ionized aniline 1(*+), the reactions of the derivatives 2(*+) and 3(*+) of the heavier main group elements P and As are characterized by an easy elimination of H(2)via a reductive elimination of group C(6)H(5)-E (E = P, As) and by a special stability of bicyclic isomers of 2(*+) and 3(*+). Thus, while 1(*+) rearranges by ring expansion and formation an 7-aza-tropylium cation by loss of H., the increased stability of bicyclic intermediates in the rearrangement of 2(*+) and in particular of 3(*+) results in separate rearrangement pathways. The origin of these effects is the more extended and diffuse nature of the 3p and 4p AO of P and As.

GC/MS on an LC/MS instrument using atmospheric pressure photoionization

Atmospheric pressure (AP) GC/MS was first introduced by Horning et al. [E.C. Horning, M.G. Horning, D.I. Carroll, I. Dzidic, R.N. Stillwell, Anal. Chem. 45 (1973) 936] using 63Ni as a beta-emitter for ionization. Because, at the time special instrumentation was required, the technique was only applied with consistency to negative ion environmental studies where high sensitivity was required [T. Kinouchi, A.T.L. Miranda, L.G. Rushing, F.A. Beland, W.A. Korfmacher, J. High Resolut. Chromatogr., Chromatogr. Commun. 13 (1990) 281]. Currently, AP ion sources are commonly available on LC/MS instruments and recently a method was reported for converting an AP-LC/MS ion source to a combination AP-LC/MS:GC/MS source [C.N. McEwen, R.G. McKay, J. Am. Soc. Mass Spectrom. 16 (2005) 1730]. Here, we report the use of atmospheric pressure photoionization (APPI) with GC/MS and compare this to AP chemical ionization (APCI) GC/MS and electron ionization (EI) GC/MS. Using a nitrogen purge gas, we observe excellent chromatographic resolution and abundant molecular M + and MH + ions as well as structurally significant fragment ions. Comparison of a 9.8 eV UV lamp with a 10.6 eV lamp, as expected, shows that the higher energy lamp gives more universal ionization and more fragment ions than the lower energy lamp. While there are clear differences in the fragment ions observed by APPI-MS versus EI-MS, there are also similarities. As might be expected from the ionization mechanism, APPI ionization is similar to low energy EI. These odd electron fragment ions are useful in identifying unknown compounds by comparison to mass spectra in computer libraries.

GC‐MS analysis of amino acid enantiomers as their N(O,S)‐perfluoroacyl perfluoroalkyl esters: Application to space analysis

The target of the in-situ research of optical activity in extraterrestrial samples stimulated an extended investigation of a GC-MS method based on the derivatization of amino acids by using a mixture of perfluorinated alcohols and perfluorinated anhydrides. Amino acids are converted to their N(O,S)-perfluoroacyl perfluoroalkyl esters in a single-step procedure, using different combinations of the derivatization reagents trifluoroacetic anhydride (TFAA)-2,2,2-trifluoro-1-ethanol (TFE), TFAA-2,2,3,3,4,4,4-heptafluoro-1-butanol (HFB), and heptafluorobutyric anhydride (HFBA)-HFB. The derivatives obtained are analyzed using two different chiral columns: Chirasil-L-Val and gamma-cyclodextrin (Rt-gamma-DEXsa) stationary phases which show different and complementary enantiomeric selectivity. The mass spectra of the derivatives are studied, and mass fragmentation patterns are proposed: significant fragment ions can be identified to detect amino acid derivatives. The obtained results are compared in terms of the enantiomeric separation achieved and mass spectrometric response. Linearity studies and the measurement of the limit of detection (LOD) show that the proposed method is suitable for a quantitative determination of enantiomers of several amino acids. The use of the programmed temperature vaporiser (PTV) technique for the injection of the untreated reaction mixture is a promising method for avoiding manual treatment of the sample and decreasing the LOD.

Analysis of undeclared synthetic phosphodiesterase-5 inhibitors in dietary supplements and herbal matrices by LC–ESI–MS and LC–UV

A liquid chromatography–electrospray ionisation–mass spectrometry (LC–ESI–MS) method was developed to screen for the presence of synthetic phosphodiesterase type 5 (PDE-5) inhibitors including sildenafil, tadalafil and vardenafil. The method was applied to the analysis of dietary supplements and bulk herbal materials. Bulk powders or composites of tablets, capsules or liquids were prepared and an extraction of PDE-5 inhibitors was performed using a mixture of acetonitrile and water with sonication. Identification of sildenafil, vardenafil or tadalafil was accomplished using a single quadrupole mass spectrometer coupled to a liquid chromatograph with an electrospray interface. Positive ion detection in the full scan mode was used while in-source collision induced dissociation (CID) provided several structurally significant fragment ions to aid in the mass spectral identification. Approximately half of the 40 botanical products analyzed were found to contain undeclared synthetic PDE-5 inhibitors. For products found to contain one of these three compounds by LC–MS, HPLC with UV detection was used for quantitation.

Structural study of spirolide marine toxins by mass spectrometry. Part II. Mass spectrometric characterization of unknown spirolides and related compounds in a cultured phytoplankton extract.

The spirolides are a family of marine biotoxins derived from the dinoflagellate Alexandrium ostenfeldii, recently isolated from contaminated shellfish and characterized. A crude phytoplankton extract has been extensively studied for mass spectrometric determination and characterization of several known spirolides and previously unreported compounds. The complex sample was initially analyzed by full-scan mass spectrometry in an ion-trap instrument, enabling identification of several components. Subsequent analysis by selected-ion monitoring in a triple-quadrupole instrument resulted in the confirmation of the identities of the compounds detected in the ion trap. Purification of the crude extract was performed using an automated mass-based fractionation system, yielding several fractions with different relative contributions of the spirolide components. Collision-induced dissociation (CID) in the triple-quadrupole instrument produced significant fragment ions for all identified species. Selective enrichment of some minor compounds in certain fractions enabled excellent CID spectra to be generated; this had previously been impossible, because of interferences from the major toxins present. Fourier-transform ion cyclotron resonance (FTICR) mass spectrometry was then performed for accurate determination of the masses of MH+ ions of all the species present in the sample. Additionally, infrared multiphoton dissociation in the FTICR instrument generated elemental formulae for product ions, including those formed in the previous collisional activation experiments. Collection of these results and the fragmentation scheme proposed for the main component of the extract, 13-desmethyl spirolide C, from part I of this study, enabled elucidation of the structures of some uncharacterized spirolides and some biogenetically related compounds present at previously unreported masses.

Electrospray ionization tandem mass spectrometric characteristics and fragmentation mechanisms of distamycin analogues.

The electrospray ionization tandem mass spectrometric (ESI-MS/MS) characteristics and fragmentation mechanisms of eight distamycin analogues containing N-methylpyrrole and N-methylimidazole were investigated. The members of two isomeric groups of distamycin analogues with the same elemental composition can be distinguished by MS/MS spectra of protonated molecules and of significant fragment ions.

Separation of cyclosporins by high-performance liquid chromatography and mass spectrometric study of cyclosporin metabolites.

A semi-preparative (high-performance liquid chromatography) method for separation of cyclosporin metabolites in a fungal fermentation sample was developed. By using the optimized chromatographic separation, 20 cyclosporin metabolites in a process sample were isolated, and their molecular masses measured by double focusing sector mass spectrometry. The structures of some of the cyclosporin congeners were investigated by tandem sector mass spectrometry using fast atom bombardment ionization. The isobaric cyclosporins D ([Val2] CS) and G ([Nva2] CS) were differentiated by significantly different relative intensities of a fragment ion at m/z 30 [CH4N]+ from a precursor ion at m/z 72 [C4H10N]+. Otherwise the tandem mass spectrometry (MS/MS) spectra of the fragment ions of the two isomers are very similar. Cyclosporin A and iso-cyclosporin A were also analysed by high energy MS/MS. No significant fragment ions were found to provide distinctions between them. Relatively good overviews of process samples containing very similar structures were achieved by combining LC separation, molecular ion recognition and MS/MS characterization.

Study of sinapinyl but-3-enylglucosinolate (boreavan A) and related compounds by mass spectrometry

Electron impact (EI), positive and negative ion fast atom bombardment (FAB) combined with tandem mass spectrometry was used for the structural elucidation of sinapinyl but-3-enylglucosinolate (boreavan A). The EI mass spectra showed the presence of ions due to the sinapic acid moiety. Protonated and deprotonated quasi-molecules and some structurally significant fragment ions due to sulphate were observed in the FAB mass spectra. The tandem mass spectra gave information for the identification of the main building blocks and the sequence ions of the sinapinium cation in boreavan A, and also showed that the number of side chains present in the glucosinolate moiety has a potential influence on the location of the anion part of boreavan A. © 1997 John Wiley & Sons, Ltd.

MALDI-TOF and electrospray tandem mass spectrometric analysis of fatty acyl-CoA esters

Coenzyme A (CoA) thioesters play a central role in many biochemical reactions, and methods for sensitive identification of these compounds are important for studies of cellular processes. The direct analysis of intact long-chain fatty acyl CoA esters was investigated using matrix assisted laser desorption time-of-flight and electrospray ionization mass spectrometry. Both techniques resulted in the formation of abundant positive and negative ions indicative of the molecular weight of the fatty acyl CoA molecular species. Several structurally significant fragment ions, in particular positive ions indicative of the fatty acyl portion of the molecule, were formed during ionization processes. Metastable (MALDI-TOF) and collision-induced decomposition (quadrupole tandem mass spectrometry) of these molecular ion species resulted in the formation of similar product ions independent of the mode of ionization. Abundant product ions, corresponding to the fatty acyl portion as well as the pantetheine-ADP portion of the molecule, were observed with both ionization techniques. Decomposition of the [M + H] + ion of hexadecyl coenzyme A (C16:0 CoA) at m / z 1006 yielded a prominent product ion at m / z 499 which was characteristic of the fatty acyl portion of the molecule. Similar fatty acyl product ion fragments corresponding to a neutral loss of 609 were found for the [M + H] + species of all the fatty acyl CoA esters investigated. This prominent and diagnostic fragment could be used to detect molecular species of CoA esters present in complex biological mixtures.

Electron ionization mass spectrometric analysis of 5-nitro octaethylprophyrin: evidence for scission of the porphyrin macrocycle

Analysis of the electron ionization mass spectrum (EIMS) of 5-nitro octaethylporphyrin reveals that the molecular ion m/z 579 undergoes novel fragmentations. The typical fragmentation pathway of β-cleavage of peripheral substituents is suppressed. Furthermore, the presence of the fragment ion m/z 375 provides strong evidence for a fragmentation pathway that involves cleavage of the porphyrin macrocycle. Such a fragmentation pathway has not been reported previously for porphyrins bearing β-pyrrolic substituents. Subsequent EIMS and electron ionization tandem mass spectrometric analyses, both of the 5-nitro octaethylporphyrin and of its analogs isotopically labeled at the meso (bridge) position ( 13 C) or at the pyrrolic nitrogens ( 15 N) or at the nitro group ( 15 N), confirmed the ring scission process. The elemental composition of the significant fragment ions was confirmed by high-resolution EIMS. The anomalous behavior may be attributed to macrocyclic distortion and/or the electron-withdrawing effect of the nitro group.

Attomole Biomolecule Mass Analysis by Matrix-Assisted Laser Desorption/Ionization Fourier Transform Ion Cyclotron Resonance

Significantly improved sensitivity for analysis of biomolecules by MALDI FT-ICR mass spectrometry is achieved by (i) microscope-monitored sample deposition onto a small indentation on the probe tip and (ii) multiple remeasurement of ions from a single laser shot. A simple modification to the solids probe tip allows for microdeposition of a few amols of analyte onto small indentation spots previously aligned with the laser beam. Ion multiple remeasurement of the same ion packet enhances the signal-to-noise ratio and thus extends the achievable FT-ICR MS detection limit. We demonstrate that FT-ICR can be used to detect parent and structurally significant fragment ions of peptides and phospholipids at low amol amounts. Positive ion mass spectra for approximately 90 amol of a mixture of angiotensin II and bradykinin, approximately 40 amol of dipalmitoylglycerophosphatidylcholine, and approximately 8 amol of substance P constitute the lowest reported detection limits to date for FT-ICR mass analysis of MALDI-generated ions.

Analysis of modified oligonucleotides by matrix-assisted laser desorption/ionization Fourier transform mass spectrometry.

Matrix-assisted laser desorption/ionization (MALDI) Fourier transform ion cyclotron resonance mass spectrometry (FTMS) has been applied to the structural characterization of modified oligodeoxyribonucleotide 4-, 6-, and 11-mers. Each oligonucleotide contained one modified base, either an O6-methyl-substituted guanine, an N6-(10R)-trans-opened benzo[a]pyrenediol epoxide adduct of adenine, or an N2-(R)-styrene oxide adduct of guanine. 3-Hydroxypicolinic acid was used as the MALDI matrix for molecular weight and purity determinations, while either 2,5-dihydroxybenzoic acid (DHBA) or an anthranilic/nicotinic acid (AA/NA) mixture was used to induce fragmentation for the production of structurally significant fragment ions. For the 4- and 6-mers, the oligonucleotide sequence could be obtained from the direct AA/NA or DHBA spectra. Sequence information was also obtained by inserting a time delay between the laser desorption event and ion detection to permit metastable decomposition. For the 11-mers, high-mass sequence ions were not detected. Although similar sequence ions were observed in both the positive and the negative ion mass spectra, more fragmentation was generally observed in the positive ion mode. In the positive ion mode, modified base fragment ions were observed when DHBA was used, and these fragments were examined using accurate mass measurements, collisionally induced dissociations, and ion-molecule reactions to characterize the modified base. MALDI-FTMS signals from one sample application can be used for the measurement of hundreds of spectra. The direct MALDI-FT mass spectra show matrix-dependent, structurally informative fragments, and CID experiments can be implemented using low-picomole sample quantities.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry of paclitaxel and related taxanes.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry has been demonstrated for the analysis of Taxus brevifolia extracts. The detection limit for the taxanes contained therein is estimated at 1 pmol using the matrix 4-nitroaniline at a matrix-to-analyte molar ratio of 100:1. Acquisition and calibration of the mass spectral data requires less than 5 min. The [M+H]+, [M+Na]+, and [M+K]+ ions provide mol wt confirmation and structurally significant fragment ions indicative of the various substituent groups located on the diterpene skeleton are formed.

Structural Elucidation by Fast Atom Bombardment Mass Spectrometry of Multisulfated Oligosaccharides Isolated from Human Respiratory Mucous Glycoproteins

Abstract Underivatized mono- and multisulfated oligosaccharides obtained by the alkalineborohydride treatment of human respiratory mucous glycoproteins were analyzed by positive ion fast atom bombardment mass spectrometry (FAB MS). Employing three unique and structurally homologous groups, the FAB mass spectra of a mono- and a disulfated tri- and tetrasaccharide and a mono-, di- and trisulfated branched hexasaccharide were compared. Each produced mass spectra displaying molecular weight-related and structurally significant fragment ions including fragments differing in mass by multiples of 102 amu reflecting the loss of one or more sulfate esters. From these data, combined with monosaccharide composition, the carbohydrate sequence and number and location of sulfate esters can readily be determined. These findings, with other chemical and enzymatic analyses, make FAB MS a valuable tool applicable to the unambiguous structural elucidation of underivatized reduced, linear and branched, mucous glycoprotein ol...