Side-reactions often occur during peptide synthesis resulting in modified amino acid moieties. To identify these residues, liquid secondary ion/collision-induced dissociation mass spectra were recorded. The main fragments are generated by cleavage of the peptide bond. To facilitate interpretation of the spectra and assignment of the structure, a simple, but flexible and efficient, computer program is presented. The program allows the verification of the correct structure of the synthesized peptides and the deduction of the type of side-products formed, such as alkylation of tryptophan residues.
Organic Mass SpectrometryVolume 29, Issue 4 p. 210-210 Book Review J. R. chapman. Practical organic mass spectrometry. A guide of chemical and biochemical analysis. Wiley, chichester, 2nd edn, 1993, 330 pp. Price: £ 39.95 Peter J. Derrick, Peter J. DerrickSearch for more papers by this author Peter J. Derrick, Peter J. DerrickSearch for more papers by this author First published: April 1994 https://doi.org/10.1002/oms.1210290411AboutPDF 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 onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume29, Issue4April 1994Pages 210-210 RelatedInformation
Organic Mass SpectrometryVolume 29, Issue 9 p. 455-457 Accounts The bigglesworth factor Trevor McAllister, Trevor McAllister CSIRO, Melbourne, Australia Trevor McAllister was born in Belfast in 1941 and took all three of his degrees in chemistry there, at Queen's University, Belfast. From there he went to Fred Lossing's laboratoryu at NRC in Ottawa, where he first became acquainted with mass spectrometers (in their Bigglesworth era). After two years is Canada (1966-68) he went to the mass spectrometry laboratory at the CSIRO Division of Chemical Physics in Melbourne where his first instrument was an old Consolidated 21-102, which had been the first mass spectrometer in Australia when it was bought in 1948. He began to leave the Bigglesworth era behind during the 1970s when he spent many years in the field of ion-molecule reaction studies, using ICR and quadrupole instruments, and applying the results to problems in ionospheres and atmospheric diffusion flames. In the mid 1980s research priorities changed so much in CSIRO that he found himself calculating equilibriums for ceramicists and MOCVD deposition of tellurides for electronic engineers. Just as he thought that he would never operate a mass spectrometer again, he was shifted onto a project to destroy CFCs using argon arc plasmas, which involved analysis by means of a Varian Saturn GC/MS. It was the cultural shock of finding that there were no valves or potentiometers to turn or twiddle, but only a computer keyboard for control, which inspired ‘The Bigglesworth Factor’.Search for more papers by this author Trevor McAllister, Trevor McAllister CSIRO, Melbourne, Australia Trevor McAllister was born in Belfast in 1941 and took all three of his degrees in chemistry there, at Queen's University, Belfast. From there he went to Fred Lossing's laboratoryu at NRC in Ottawa, where he first became acquainted with mass spectrometers (in their Bigglesworth era). After two years is Canada (1966-68) he went to the mass spectrometry laboratory at the CSIRO Division of Chemical Physics in Melbourne where his first instrument was an old Consolidated 21-102, which had been the first mass spectrometer in Australia when it was bought in 1948. He began to leave the Bigglesworth era behind during the 1970s when he spent many years in the field of ion-molecule reaction studies, using ICR and quadrupole instruments, and applying the results to problems in ionospheres and atmospheric diffusion flames. In the mid 1980s research priorities changed so much in CSIRO that he found himself calculating equilibriums for ceramicists and MOCVD deposition of tellurides for electronic engineers. Just as he thought that he would never operate a mass spectrometer again, he was shifted onto a project to destroy CFCs using argon arc plasmas, which involved analysis by means of a Varian Saturn GC/MS. It was the cultural shock of finding that there were no valves or potentiometers to turn or twiddle, but only a computer keyboard for control, which inspired ‘The Bigglesworth Factor’.Search for more papers by this author First published: September 1994 https://doi.org/10.1002/oms.1210290902 AboutPDF 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 onEmailFacebookTwitterLinkedInRedditWechat Volume29, Issue9September 1994Pages 455-457 RelatedInformation
Amides of lithocholic acid (3alpha-hydroxy-5beta-cholan-24-oic acid) with 6-aminocaproic acid and 4-aminobutyric acid were prepared and examined by electron impact ionization mass spectrometry. Both these compounds gave an unusual [M - 57]+ fragment. Since the product-ion analysis of [M - 57]+ revealed the presence of fragments corresponding to the intact steroid nucleus in addition to that of the original amino acid (6-aminocaproic acid or 4-aminobutyric acid), we concluded that the integrity of the steroid amide had been retained in this fragment. The absence of this fragment from the product-ion spectrum of [M - CH3]+ rules out the sequential loss from the molecular ion of 15 + 42 u as the origin of this signal. Mass spectrometry of the 24-C-13-labelled lithocholykaproylamide showed the retention of the label in the [M - 57]+ fragment. In contrast, the corresponding compound labelled with deuterium at C(23) showed a significant loss of the label during the formation of this product ion at [M - 58]+. In addition, through a combination of derivatization and tandem mass spectrometry, it was demonstrated that this loss of 57 u represented a rearrangement with the expulsion of a C4H9 radical from the side-chain spanning C(20) to C(23) resulting in a truncated steroid-amide fragment. This fragmentation pattern has not been observed in bile acid conjugates with N-alpha-amino acids.
To evaluate the necessity for cooling laser-desorbed molecules to obtain molecular ions and minimal fragmentation, mass spectra of a series of methoxybenzenes were measured in two different experimental configurations. In one geometry, laser-desorbed molecules were entrained in a pulsed supersonic jet before ionization. In the other, the molecules were ionized directly after laser desorption. The samples were ionized with laser-generated vacuum ultraviolet radiation in a single-photon process or ultraviolet radiation in a multi-photon process.
The El mass spectra of six n-butylboronate ester derivatives of the major metabolite of prostaglandins F1alpha and F2alpha (PGF-M) are presented and discussed. Proposed ion assignments and fragmentation pathways are based on substituent shifts, on data from a deuterium-labeled methoxime derivative and on the analysis of collision-induced dissociation spectra of selected ions. Fragment ions suitable for identification and quantification of PGF-M in a biological matrix and diagnostically valuable ions for structure recognition are proposed.
Several proteins in the relative molecular mass (RMM) range 1150-29 000 are examined by means of both positive electrospray and matrix-assisted laser desorption/ionization mass spectrometry. Accuracy of the measured RMMs, resolution and overall sensitivity are discussed. Tbe presence of more than one component in a number of the investigated compounds permitted the assessment of both desorption methods for the analysis of mixtures. Solvent-induced conformational changes are linked to charge-state distribution shifts observed in some positive electrospray mass spectre.
The positive-ion mass spectra of twelve organic dyes used as molecular probes were measured using liquid secondary ion mass spectrometry (LSIMS). Nine of the twelve dyes were singly charged cations and the other three were doubly charged cations. The mass spectra of each of the dyes in m-nitrobenzyl alcohol contain abundant signals for the intact cation, C+ (singly charged cation dyes), or for singly-charged forms of the doubly charged cation formed by proton loss, [C2+-H+](+), or halogen counter ion attachment, [C2++X(-)](+). Fragmentation is usually minimal under the conditions used. However, the cations of five of the singly charged compounds appear to undergo charge-remote fragmentation. Collision-induced dissociation experiments on a hybrid mass spectrometer of EBqQ geometry at collision energies up to 300 eV failed to access this fragmentation pathway. In contrast to the LSIMS of many other doubly charged organic compounds, two of the dicationic dyes produced a doubly charged ion of reasonable abundance (2-20%) in the mass spectrum. When glycerol was used as a matrix solvent, the addition of the matrix modifier trifluoroacetic acid increased the abundance of C2+.
The electron impact ionization mass spectra of 4,5-bis(alkylthio)-1,3-dithiole-2-thiones and their 1,2-dithiole-3-thione isomers were studied by accurate mass measurements and linked scans. The relative abundance of ions formed following the extrusion of S2, CS or CS2 allows an unambiguous isomer differentiation. Isomerization of molecular ions was studied by means of metastable ion analysis and collision-induced dissociation. Tle order of reactivity was analogous to that observed in isomerization under photochemical conditions.
The stereochemistry of six pairs of diastereomeric chlorin derivatives was investigated by electron impact (EI), fast atom bombardment (FAB) and direct chemical ionization DCI mass spectrometry. It was demonstrated that FAB and EI mass spectrometry are convenient and rapid methods for distinguishing between diastereomeric chlorin derivatives due to their different fragmentation patterns.
The nature and location of modifications of fatty acids are determined by resonance electron capture (REC) ionization of free acids and their methyl esters and pyrrolidides. The molecular negative ions (MNI) formed in the high resonance region undergo both charge-remote and charge-driven decomposition. The spectra of fragments arising from dissociation of these high-energy MNI contain decisive information on the original structure of the neutrals. The pyrrolidides of fatty acids result in simpler spectra on the one hand, and on the other hand these spectra give complete structure information.
Mass spectral fragmentations of two cyclopentane, eight cyclohexane and four norbornane/ene 1,3-amino alcohols were studied under electron ionization (EI) by low-resolution, high-resolution, metastable ion analysis and collision-induced dissociation (CID) techniques. All stereoisomeric compounds gave rise to identical 70 eV EI mass spectra. However, the spectra of positional isomers clearly differed. The main fragmentation pathway for the saturated compounds began as an alpha-cleavage reaction with respect to the nitrogen atom. For the norbornene compounds a retro-Diels-Alder reaction was favoured. Relative to the aminomethyl-substituted compounds the fragmentation patterns for the compounds having the amino group connected directly to the ring were more complicated. The chemical ionization (CI) mass spectra were recorded using ammonia, isobutane, methane, dichloromethane and acetone as reagent gas. From the norbornanelene compounds the di-exo isomers decomposed more easily than the di-endo isomers with most of the reagent gases used. Differences between stereoisomers were observed directly only under methane CI. The decomposition products of the [M + H]+ ions generated under ammonis and isobutane CI were studies by recording their CID mass spectra. These spectra allowed the differentiation of the stereoisomers, at least to some extent.
Post-source decay matrix-assisted laser desorption ionization (PSD-MALDI) of sodium ion-attached branched oligosaccharides derived from glycoproteins was demonstrated as a method of structure analysis by reflectron time-of-flight (TOF) mass spectrometry. Mono-, di- and triantennary structures were investigated. The fragmentation patterns of these (structurally related) substances as obtained in the positive-ion mode showed characteristic differences correlated with branching sites and linkage positions. Two-bond ring cleavages as known from fast atom bombardment/collision-induced dissociation and IR laser desorption mass spectrometry were also observed. Internal fragment ions formed by up to four consecutive cleavages were obtained with high intensity, allowing the branching structure of complex carbohydrates to be identified. PSD-MALDI of oligosaccharides is characterized by high sensitivity, very good signal-to-noise ratios and high reproducibility of fragmentation patterns and signal intensities.
Permethylated, peracetylated and perbenzoylated derivatives of glycosphingolipids (GSLs) were prepared to compare their liquid secondary ionization mass spectrometric (LSIMS) and collision-induced dissociation tandem mass spectrometric (CID/MS/MS) fragmentation patterns and also to determine sensitivity improvement in LSIMS and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) relative to the native species. Permethylation was carried out in the liquid phase, whereas peracetylation and perbenzoylation could be effected using either liquid (bulk)-phase or gas-phase procedures. Lower amounts of starting material were required for the gas-phase derivatization (less than or equal to 100 pmol) compared with the bulk phase (less than or equal to 1 nmol), because the former method permits more efficient sample handling. All three types of derivatives yielded sensitivity improvements of at least two orders of magnitude over the native species in both LSIMS and MALDI-TOFMS. The behavior of the permethylated compounds was used as the benchmark for GSL structural information content in normal and tandem mass spectra. Fragments present in spectra of the three types of derivatives generated complementary information. Permethylated GSLs favored the formation of ions related to the ceramide moieties, whereas peracetylation enhanced the production of carbohydrate-related ions. The LSI mass spectra of perbenzoylated GSLs contained information on both ceramide and sugar portions of the molecules. Each of the LSIMS, MS/MS and MALDI-TOFMS techniques proved to be complementary to the others in this study; the use of all three is recommended for the generation of complete structural information.
The mass spectral behaviour of nine 1,3-dioxolanes, seven 1,3-dithiolanes and seven 1,3-oxathiolanes was studied under chemical ionization conditions with ammonia, isobutane, methane, acetone, acetone-d6 or pentan-3-one as reagent gas. The proton affinity of the first members in each series was not large enough for ammonia to protonate them; instead, the ionization took place through unstable [M + NH4]+ ions. Isobutane, which gave rise to abundant [M + H]+ ions in all cases, was the best reagent gas for the determination of the molecular mass. Methane chemical ionization caused extensive fragmentations either through ring cleavage or through the elimination of the largest substituent from ring positions 2 as a neutral hydrocarbon. The ketones used as reagent gas reacted to form adduct ions. In the case of dioxolanes and oxathiolanes, the [M + RCO]+ adduct ion decomposed through ring opening and then, as a consequence of intramolecular nucleophilic substitution, through the elimination of a neutral carbonyl compound. Resonance-stabilized dioxolanylium and oxathiolanylium ions were obtained for dioxolanes and oxathiolanes, respectively. This reaction was almost non-existent for the dithiolanes.
The electrospray mass spectra of gramicidin S cations that originated from 0.2 M solutions of 18 nitrogen-containing bases were examined. The relative abundances of the [M + 2H](2+) to the [M + H](+) ion were found to correlate not with the solution pH but with the proton affinities of the bases. It is postulated that some of the [M + 2H](2+) and the [M + H](+) ions exist as adducts with the nitrogen bases in solution, these adducts being desorbed into the gas phase during electrospray and dissociated in the lens region via collision-induced dissociations to yield apparent proton attachment spectra. Some of these adducts were observed under nominally zero collision energy conditions.
Survivor-ion mass spectrometry is used to distinguish stereoisomeric cis- and trans-4-methylcyclohexanol. The method involves producing ions by electron impact ionization and submitting them without mass selection to collisional neutralization and reionization, followed by selective monitoring of non-dissociating ions. The differences in the electron impact mass spectra of the stereoisomers, due to the different fragment ion elemental compositions and structures, are highlighted by collisional neutralization with Xe, NO and CH3SSCH3, followed by reionization with oxygen. The differences in the survivor-ion spectra are due to different neutralization efficiencies of the isobaric and isomeric ions produced by electron impact ionization, different stabilities of the intermediate neutral species, different reionization efficiencies and reionized ion stabilities. Neutralization-reionization spectra of the C7H12+., C6H9+ C3H6O+. and C3H5O+ ions from stereoisomeric 4-methylcyclohexanols are also reported.
Chlorins in a sedimentary mixture were characterized, without prior isolation of individual components, using electrospray ionization combined with ion trap mass spectrometry. Collision-induced dissociation in the atmospheric sampling interface and multi-step mass spectrometry (i.e. MS(n) where n greater than or equal to 2) were used in order to obtain structural information about the macrocycle. Fragmentation pathways are proposed for different macrocycle types based on data from model chlorins. Three unknown chlorins (RMM = 888, 844 and 790) are assigned as having bacteriochlorophyll macrocycle types esterified to unusual side-chains (i.e, dihydrophytol for the unknown with a bacteriopheophorbide a structure, phytol and an alcohol with a molecular mass of 242 u for the two unknowns with a proposed bacteriopyropheophorbide d structure).
Organic Mass SpectrometryVolume 29, Issue 1 p. 57-59 Oms Letters Gas-phase ion chemistry of carbon suboxide L. Pandolfo, L. Pandolfo Dipartimento di Chimica Inorganica, Metallorganica e Analit ca, Università di Padova, Via Marzolo 1, 35132 Padova, ItalySearch for more papers by this authorG. Paiaro, G. Paiaro Dipartimento di Chimica Inorganica, Metallorganica e Analit ca, Università di Padova, Via Marzolo 1, 35132 Padova, ItalySearch for more papers by this authorS. Catinella, Corresponding Author S. Catinella CNR Area di Ricerca, Corso Stati Uniti 4, 35020 Padova, ItalyCNR Area di Ricerca, Corso Stati Uniti 4, 35020 Padova, ItalySearch for more papers by this authorP. Traldi, P. Traldi CNR Area di Ricerca, Corso Stati Uniti 4, 35020 Padova, ItalySearch for more papers by this author L. Pandolfo, L. Pandolfo Dipartimento di Chimica Inorganica, Metallorganica e Analit ca, Università di Padova, Via Marzolo 1, 35132 Padova, ItalySearch for more papers by this authorG. Paiaro, G. Paiaro Dipartimento di Chimica Inorganica, Metallorganica e Analit ca, Università di Padova, Via Marzolo 1, 35132 Padova, ItalySearch for more papers by this authorS. Catinella, Corresponding Author S. Catinella CNR Area di Ricerca, Corso Stati Uniti 4, 35020 Padova, ItalyCNR Area di Ricerca, Corso Stati Uniti 4, 35020 Padova, ItalySearch for more papers by this authorP. Traldi, P. Traldi CNR Area di Ricerca, Corso Stati Uniti 4, 35020 Padova, ItalySearch for more papers by this author First published: January 1994 https://doi.org/10.1002/oms.1210290111Citations: 4AboutPDF 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 onEmailFacebookTwitterLinkedInRedditWechat References 1 P. S. Skell, J. J. Havel and M. J. McGlinchey, Acc. Chem. Res. 6, 97 (1973). 2(a) F. Diederich and R. L. Whetten, Acc. Chem. Res. 25, 119 (1992); (b) A. L. Zhang, S. C. O'Brien, S. R. Heat, Y. Liu, R. D. Curl, H. W. Kroto and R. F. Smalley, J. Phys. Chem. 90, 525 (1986); (c) J. M. Hawkins, Acc. Chem. Res. 25, 150 (1992). 3 R. E. Smalley, Acc. Chem. Res. 25, 25 (1992). 4 O. Diels and B. Wolf, Chem. Ber. 39, 689 (1906). 5(a) J. R. Sabin and H. Kim, J. Chem. Phys. 56, 2195 (1971); (b) U. Gelius, C. J. Allan, D. A. Allison, H. Siegbahn and K. Siegbahn, Chem. Phys. Lett. 11, 224 (1971); (c) W. J. Lafferty, A. G. Maki and E. K. Plyer, J. Chem. Phys. 40, 224 (1964); (d) G. Trinquier and J. P. Malrieu, J. Am. Chem. Soc. 109, 5303 (1987). 6(a) L. B. Dashkevich and V. G. Beilin, Russ. Chem. Rev. 36, 391 (1967); (b) T. Kappe and E. Ziegler, Angew. Chem., Int. Ed. Engl. 13, 491 (1974); (c) G. Paiaro and L. Pandolfo, Comments Inorg. Chem. 12, 213 (1991). 7(a) E. B. Jenkins, D. C. Morton and A. W. Sweigart, Astrophys. J. 157 (P1), 913 (1969); (b) M. Shimizu, In Proceedings of Symposium on Planetary Atmospheres, ed. by J. A. Vallance, p. 67. Royal Society of Canada, Ottawa (1977); (c) M. Shimizu, ISAS Res. Note No. 45, Institute of Space and Aeronautical Sciences, University of Tokyo, Tokyo (1977); (d) M. Shimizu, Astropnys. Space Sci. 62, 509 (1979); (e) H. Yanagawa and F. Egami, Precambrian Res. 14, 75 (1981). 8(a) V. I. Oyama, B. J. Berdahl and F. Woeller, Life Sci. Space Res. 17, 47 (1979); (b) V. I. Oyama and B. J. Berhahl, J. Mol. Evol. 14, 199 (1979). 9 W. T. Huntress, Jr, M. Allen and M. Delitsky, Nature (London) 352, 316 (1912). 10(a) H. B. Palmer and T. J. Hirt, J. Am. Chem. Soc. 84, 113 (1962); (b) A. Wehrer, P. Wehrer and X. Duval, Bull. Soc. Chim. Fr. 11–12, 434 (1980). 11(a) F. F. Martinotti, M. J. Welch and A. P. Wolf, Chem Commun. 115 (1968); (b) E. Y. Lam, P. Gaspar and A. P. Wolf, J. Phys. Chem. 75, 445 (1971). 12(a) S. M. Schildcrout and J. L. Franklin, J. Am. Chem. Soc. 92, 251 (1970); (b) C. H. Roberts and C. H. DePuy, Zh. Obshch. Khim. 59, 1931 (1989). 13 R. E. March and R. J. Hughes, Quadrupole Storage Mass Spectrometry. Wiley-Interscience, New York (1989). 14 C. E. Ardanaz, J. Kavka, F. Guidugli, P. Traldi and U. Vettori Rapid Commun. Mass Spectrom. 5, 5 (1991). 15 O. Curcuruto, S. Fontana and P. Traldi, Rapid Commun. Mass Spectrom. 6, 322 (1992). 16 S. Catinella, P. Traldi and E. Celon, Rapid Commun. Mass Spectrom. 7, 315 (1993), and references cited therein. Citing Literature Volume29, Issue1January 1994Pages 57-59 ReferencesRelatedInformation
The electron impact-induced fragmentation of 2,2-dimethyl- and 2-ethyl-1,3-indandione, 1 and 2, and their isomers, 3-isopropylidene- and 3-propylidenephthalide, 3 and 4, respectively, was studied in detail by mass-analysed ion kinetic energy (MIKE) and collision-induced dissociation (CID-MIKE) spectrometry, including H-2 and C-13-labelled analogues of 1 and 2. In all regimes of internal energy, the molecular ions 1+. - 4+. interconvert by up to seven consecutive, reversible isomerization steps prior to the main fragmentation processes, viz. loss of CH3. and C2H4 . 1,3-Indandione and 3-methylenephthalide ions with identical alkylidene moieties (i.e. 1+. half arrow right over half arrow left 3+. and 2+. half arrow right over half arrow left 4+.) equilibrate rapidly and completely prior to fragmentation, whereas these pairs of isomers interconvert only slowly via a five-step rearrangement of the indandione ions 1+. half arrow right half arrow left 2+.. Distinct from the behaviour of simpler ionized carbonyl species, a 1,2-C shift of a (formally) neutral carbonyl group is found to occur along with that of a protonated one. Also distinct from simpler cases, methyl loss does not take place from the ionized enol intermediates formed within the interconversion 1+. half arrow right over half arrow left 2+. of the diketone ions but rather from the n-propylidenephthalide ions 4+.. This follows from CID-MIKE spectrometry of the [M - CH3]+ ions of 1-4 and two reference C10H7O2+ (m/z 159) ions of authentic structures (protonated 2-methylene-1,3-indandione and protonated 1,4-naphthoquinone). The characteristic CID fragmentation of the C10H7O2+ ions is rationalized. Finally, the multistep isomerization of ionized 1,3-indandiones apparently also extends to higher homologues [eg. 5+. from 2-ethyl-2-methyl-1,3-indandione (5) and 6+. from 2,2-diethyl-1,3-indandione (6)]: the ionized phthaloyl group of 1,3-indandione radical cations 1+., 2+., 5+. and 6+., originally attached with its two acyl functionalities to the same carbon of the aliphatic chain, performs, in fact, a 'multi-step migration'.
