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1.
Hou-Jun Yang Mei-Yu He Yun-Hua Ye Yu-Fen Zhao 《Journal of mass spectrometry : JMS》1992,27(6):746-749
Positive ion fast atom bombardment mass spectrometry (FABMS) of in situ N-phosphorylated oligopeptides showed intense quasi-molecular ions together with the successive alkene loss fragment ions, which afford multiple checks of the unequivocal reality of the relative molecular mass of the tested samples. More interesting, in a novel cleavage pattern only the N-phosphoryl fragment ions gave intense peaks, the C-terminal series ions being suppressed. For each of the N-terminal ions, losses of alkenes also occur to provide multiple checks for the existence of these ions. The FABMS of the in situ N- phosphorylated oligopeptides might provide an easily accessible routine method for peptide sequencing. 相似文献
2.
Each amino acid in a peptide has a characteristic immonium ion (H2N+?CHR), the presence of which in a mass spectrum can indicate the presence of that amino acid. High-energy collision-induced decomposition studies on small peptide ions formed by fast atom bombardment showed the relative intensities of these immonium ions to be dependent on the relative positions of the amino acids in the peptide chain: C-terminal, N-terminal or in-chain. Evidence in favour of competition in the formation of immonium ions is presented. 相似文献
3.
The backbone cleavages of protonated tripeptide ions of the series Gly—Gly—Xxx, where Xxx ? Gly, Ala, Val, d-Leu, l-Leu, Ile, Phe, Tyr, Trp, Pro, Met and Glu, were studied in a hybrid tandem mass spectrometer. C-Terminal y-type ions and N-terminal a- and b-type ions were noted. A linear relationship between log (y1/b2) and the proton affinity of the C-terminal amino acid substituents was found: as the proton affinity of the C-terminal residue increases, the fraction of y1 ion formation increases. When the C-terminal substituent was more basic than Trp, the b2 ion was not observed. It is likely that the site of protonation changes from peptide bond to side-chain for just these residues, Lys, His and Arg. 相似文献
4.
R. E. Hamilton G. V. Patil K. Jayasimhulu R. A. Day 《Journal of mass spectrometry : JMS》1974,9(2):211-220
We have been able to extend the use of Schiff base derivatives in peptide sequencing to N-terminal prolyl peptides. Earlier studies from this laboratory revealed that certain aromatic Schiff bases of peptide esters gave electron-impact mass spectra with relatively intense molecular, sequence and internal fragment ions. We observed that the reaction of N-terminal prolyl peptide esters with 4-dimethylaminonaphthaldehyde, p-dimethylaminobenzaldehyde and 2-pyridinecarboxaldehyde gave cyclization products which were found to be 2-substituted-1-keto-3-aryl-5H-imidazo-[1,5-a]-pyrrole derivatives. The molecular ion and many of the expected cleavages were prominent in the mass spectra. Deuterium labeling at the α-carbon, amide nitrogen, or other exchangeable positions has been used in assigning the structure. It was also confirmed by the fragmentation pattern of the products derived by permethylation of the peptide derivative with tetramethylammonium hydroxide. Comparable cleavage patterns were seen among the N-terminal prolyl peptides examined. Proline amide gave the corresponding cyclized product. With the inclusion of N-terminal prolyl peptides in the list of peptides that we have examined, we may now prepare volatile derivatives of peptides containing any of the protein amino acids in two steps: esterification and treatment with the appropriate aromatic aldehyde. 相似文献
5.
Chin-Jen Wu Jue-Liang Hsu Sheng-Yu Huang Shu-Hui Chen 《Journal of the American Society for Mass Spectrometry》2010,21(3):460-471
We have previously coupled stable isotope dimethyl labeling with IMAC enrichment for quantifying the extent of protein phosphorylation
in vivo. The enhanced a1 signal of dimethylated peptides served as a unique mass tag for unequivocal identification of the N-terminal amino acids. In this study, we demonstrate that the a1 ion could further assist in mapping the precise phosphorylation site near the N-terminal region and allow the determination of the exact site and level of phosphorylation in one step by stable isotope
dimethyl labeling. We show that the a1 ion signal was suppressed for dimethylated peptides with a phosphorylation site at the N-terminus Ser/Thr residue (N-p*Ser/Thr) but was still enhanced for N-terminus Tyr residue (N-p*Tyr) or internal Ser/Thr residues (-p*Ser/Thr). Based on the dominant de-phosphorylated molecular ions and b-H3PO4 ions for N-p*Ser/Thr, we propose that dimethyl labeling increases the basicity of the N-terminus and accelerates the de-phosphorylation
for N-p*Ser/Thr precursors, which, however, suppresses the a1 ion enhancement due to the resulting unsaturated covalent bond on C
α
of the N-terminus amino acid. Using this method, we excluded three Ser/Thr phosphorylation sites in A431 cells, two of which, however,
were previously reported to be phosphorylation sites; we confirmed three known phosphorylation sites in A431 cells and quantified
their ratios upon EGF treatment. Notably, we identified a novel phosphorylation site on Ser43 residue at N-terminus of the tryptic peptide derived from SVH protein in pregnant rat uteri. SVH protein has not been reported or implied
with any phosphorylation event, and our data show that the Ser43 of SVH is an intrinsic phosphorylation site in pregnant rat
uteri and that its phosphorylation level was slightly decreased upon c-AMP treatment. 相似文献
6.
Fast atom bombardment mass spectrometry (FAB-MS) is applied to distinguish N-terminal series ions from C-terminal series ions of a peptide by on-probe acetylation, it providesvaluable information about the sequence of an unknown peptide. The FAB mass spectra containa number of characteristic ions at low-mass region in addition to the sequence ions at high-massregion. It was found that the ions below m/z 200 are characteristic of the amino acid composition ofthe peptide, from which the amino acid composition of the peptide could be estimated. Additionally,mixture analysis is also discussed. 相似文献
7.
Jinwei Yuan Liangru Yang Yongmei Xiao Lingbo Qu 《Phosphorus, sulfur, and silicon and the related elements》2016,191(10):1358-1361
Ten novel N-phosphoryl amino acids β-sitosterol esters were synthesized by coupling the N-phosphoryl amino acids with β-sitosterol under microwave irradiation, and their structures were elucidated by IR, NMR, and HR MS. Various reaction conditions including the catalyst, solvent, temperature and time were investigated. Under the optimal conditions, the reaction was finished in 20 min with 60–87% yields by employing DCC/DMAP as a catalyst system at room temperature. 相似文献
8.
Dr. Maria J. S. A. Silva Rafaela A. N. Cavadas Dr. Hélio Faustino Dr. Luís F. Veiros Dr. Pedro M. P. Gois 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(67):e202202377
N-terminal Cys modification has been intensively studied to produce homogeneous bioconjugates essentially through two modes of reaction: reversible modification with the equilibrium shifted towards the formation of the desired conjugate or stable and irreversible conjugates. Herein, we report a new method of N-terminal cysteine modification using O-salicylaldehyde esters (OSAEs) through fast conjugation and irreversible deconjugation. These reagents can rapidly react with N-terminal Cys at low-micromolar concentration to form thiazolidines with subsequent hydrolysis of the ester moiety to the phenolic derivative. These phenolic thiazolidines can be hydrolyzed at acidic pH (≈4.5) to recover the intact N-terminal Cys. Bioconjugation reactions using OSAEs offer controlled reversibility to as act as a protecting group for N-terminal cysteines, allowing the modification of in-chain residues without perturbing the N-terminal Cys, which can then be deprotected and used as a conjugation site. 相似文献
9.
Klyba L. V. Tarasova O. A. Shemetova M. A. Petrushenko K. B. Mikhaleva A. I. Trofimov B. A. 《Russian Journal of Organic Chemistry》2003,39(9):1325-1328
Fragmentation under electron impact of all N-isopropenylazoles, except for N-isopropenyl-2- phenylpyrrole, involves elimination of propyne or allene with formation of the corresponding NH azoles. N-Isopropenylpyrrole, N-isopropenyl-4,5,6,7-tetrahydroindole, and N-isopropenylindole give rise to rearrangement of the molecular ion into azepine structure, while the fragmentation of N-isopropenyl-2-phenylpyrrole is accompanied by transfromation into 5-methyl-5,6-dihydropyrrolo[2,1-a]isoquinoline. Retrodiene decom- position is the main fragmentation pathway of the molecular ions derived from N-isopropenyl-4,5,6,7-tetrahydroindole and its 2-methyl-substituted analog. In the decomposition of 2,3-di- and 2,3,5-trimethyl-N-isopropenylpyrrole, the major fragment ions are formed from the [M - H]+ ion having a pyridinium structure rather than from the molecular ion. N-Isopropenyldi- and -triazoles undergo fragmentation along competing pathways involving cleavage of the heteroring. 相似文献
10.
J. R. Cushnir S. Naylor J. H. Lamb P. B. Farmer 《Journal of mass spectrometry : JMS》1993,28(5):552-558
Human exposure to carcinogenic alkylating agents can lead to the formation of covalently bound adducts in DNA, some of which are excreted in urine as alkylated purines following DNA degradation and repair. Tandem mass spectrometric methods have been developed for the qualitative and quantitative determination of such alkylpurines in human urine. Short-chain alkyl- and hydroxyalkylguanines have been synthesized with the substituents at the N-7-, O6- and N2-positions of guanine. Examination of the product ion scans of their molecular ions (electron impact (EI) ionization) revealed that the ion at m/z 151, [guanine]+, was common to all of the alkylguanines studied, with the exception of the methylated analogues. Precursor ion scans of this ion on partially purified human urine extracts showed the presence of several ions (e.g. m/z 179, 195) which were consistent with molecular ions for alkylguanines. The presence of these and other constituents was confirmed by product ion spectra of molecular ions (EI and fast atom bombardment), and by high-performance liquid chromatographic separation prior to tandem mass spectrometry (MS/MS). Evidence was obtained for the presence of N-7-methyl-, N2-dimethyl-, N2-dimethyl-, N2-ethyl- and N-7-(2-hydroxyethyl)guanine. Quantitative methods were established for these five alkyl guanines using gas chromatography mass spectrometry (GC/MS) and GC/MS/MS. Deuterated internal standards were synthesized and added to the urine prior to extraction of alkylpurines by Sep-Pak cartridge chromatography. The products were converted into their tert-butyldimethylsilyl derivatives and analysed by selected ion monitoring (SIM) of [M – 57]+ or by multiple reaction monitoring (MRM) of the fragmentation M+˙ → [M – 57]+. The MRM method yielded values for N-7-methylguanine of 2.57 ± S.D. 1.32 mg day?1 (n = 6), N2-methylguanine of 0.31 ± 0.10 mg day?1 (n = 10) and N2-dimethylguanine of 0.21 ± 0.23 mg day?1 (n = 10). N2-Ethyl- and N-7-(2-hydroxyethyl)guanine could only be detected by SIM at levels of ~0.5 and 2 μg day?1, respectively. The MRM analyses, although inherently less sensitive than the SIM analyses, exhibit greater selectivity and consequently fewer contaminant ions. 相似文献
11.
Jason C. Rousecor Wen Yu Stephen A. Martin 《Journal of the American Society for Mass Spectrometry》1995,6(9):822-835
The types, extent, and overall distribution of peptide fragmentation produced by matrix-assisted laser desorption-ionization-postsource decay (MALDI-PSD) on a reflector time-of-flight mass spectrometer were compared with those obtained from high and low energy collision-induced dissociation (CID) on a four-sector mass spectrometer and from liquid secondary ion mass spectrometry (LSIMS) ion source fragmentation and LSIMS metastable ion (MI) decomposition on a two-sector mass spectrometer. The model peptides studied had sequences and compositions that yielded predominantly either N- or C-terminal fragmentation from CID. For des-Arg1 and des-Arg9 bradykinin (i.e., H-PPGFSPFR-OH and H-RP-PGFSPF-OH, respectively), the types of fragment ions and the extent to which each type is formed in both MALDI-PSD and low energy CID spectra are remarkably similar. This observation suggests that both methods deposit comparable internal energies (IE) into [M + H]+ precursor ions. The distribution of N-terminal, C-terminal, immonium, and internal fragmentation from MALDI-PSD spectra of des-Arg1 and des-Arg9 bradykinin did not change dramatically with respect to the terminal arginine position, contrary to those from LSIMS MI decomposition, high and low energy CID spectra. This observation in combination with the prominent immonium, internal, and minus 17 fragment ion types in PSD indicates that the imparted IE from MALDI and the 14 µs of flight time may promote steady-state decomposition kinetics. Fragmentation distributions of MALDI-PSD spectra are also similar to those in LSIMS spectra. This implies that the distribution of protonation sites in [M + H]+ is comparable for both techniques. 相似文献
12.
A. Peter Snyder Johannes H. Kremer Shirley A. Liebman Michael A. Schroeder Robert A. Fifer 《Journal of mass spectrometry : JMS》1989,24(1):15-21
Pyrolysis-atmospheric pressure chemical ionization was used to study the thermal decomposition of the energetic material cyclotrimethylenetrinitramine (RDX) and characterization of the individual molecular ion products was accomplished by tandem mass spectrometry. The analysis was aided with pyrolysis mass spectra of the (15N)- and perdeuterated RDX isotopes, and molecular formulae were derived for the m/z 46, 60, 74, 75, 85 and 98 molecular ions in the RDX pyrolysis mass spectrum. Equivalent fragments between the daughter ion mass spectra of the unlabeled and labeled RDX were determined in order to define a structure for each pyrolysis feature. Daughter ion mass spectra of pure reference compounds confirmed the identity of five of the six molecular ions. Perdeuterated RDX analyses provided evidence that m/z 74 and 75 are N,N-dimethylformamide and N-nitrosodimethylamine, respectively; m/z 46, 60 and 85 were identified as the protonated forms of formamide, N-methylformamide and dimethylaminoacetonitrile, respectively. 相似文献
13.
Chiral N-phosphoryl imines derived from (S)-BINOL have been designed and synthesized in good to excellent chemical yields. These N-phosphoryl imines were found to react with diketones smoothly without the use of any bases. They can also serve as electrophiles for the reaction with diethyl malonate in the presence of potassium carbonate. Good yields (62%—quant) and excellent diastereoselectivities (up to 99:1 dr) have been achieved for 10 examples. 相似文献
14.
Zirah S Afonso C Linne U Knappe TA Marahiel MA Rebuffat S Tabet JC 《Journal of the American Society for Mass Spectrometry》2011,22(3):467-479
Lasso peptides constitute a class of bioactive peptides sharing a knotted structure where the C-terminal tail of the peptide is threaded through and trapped within an N-terminal macrolactam ring. The structural characterization of lasso structures and differentiation from their unthreaded
topoisomers is not trivial and generally requires the use of complementary biochemical and spectroscopic methods. Here we
investigated two antimicrobial peptides belonging to the class II lasso peptide family and their corresponding unthreaded
topoisomers: microcin J25 (MccJ25), which is known to yield two-peptide product ions specific of the lasso structure under
collision-induced dissociation (CID), and capistruin, for which CID does not permit to unambiguously assign the lasso structure.
The two pairs of topoisomers were analyzed by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry
(ESI-FTICR MS) upon CID, infrared multiple photon dissociation (IRMPD), and electron capture dissociation (ECD). CID and ECD
spectra clearly permitted to differentiate MccJ25 from its non-lasso topoisomer MccJ25-Icm, while for capistruin, only ECD
was informative and showed different extent of hydrogen migration (formation of c•/z from c/z•) for the threaded and unthreaded topoisomers. The ECD spectra of the triply-charged MccJ25 and MccJ25-lcm showed a series
of radical b-type product ions ( b¢n · ) \left( {b{\prime}_n^{ \bullet }} \right) . We proposed that these ions are specific of cyclic-branched peptides and result from a dual c/z• and y/b dissociation, in
the ring and in the tail, respectively. This work shows the potentiality of ECD for structural characterization of peptide
topoisomers, as well as the effect of conformation on hydrogen migration subsequent to electron capture. 相似文献
15.
Ernst Pittenauer Anton Pachinger Günter Allmaier Erich R. Schmid 《Journal of mass spectrometry : JMS》1991,26(12):1065-1073
N-Acetylcysteine and nine N-acetylcysteine conjugates of synthetic origin were characterized by positive- and negative-ion plasma desorption mass Spectrometry. For sample preparation the electrospray technique and the nitrocellulose spin deposition technique were applied. The fragmentation of these compounds, which are best seen as S-substituted desaminoglycylcysteine dipeptides, shows a similar behaviour to that of linear peptides. In the positive-ion mass spectra intense protonated molecular ion peaks are observed. In addition, several sequence-specific fragment ions (A+, B+, [Y + 2H]+, Z+), immonium ions (I+) and a diagnostic fragment ion for mercap-turic acids (RM+) are detected. The negative-ion mass spectra exhibit deprotonated molecular ions and in contrast only one fragment ion corresponding to side-chain specific cleavage ([RXS]?) representing the xenobiotic moiety. In the case of a low alkali metal concentration on the target, cluster molecular ions of the [nM + H]+ or [nM - H]? ion type (n = 1-3) are observed. The analysis of an equimolar mixture of eight N-acetylcysteine conjugates shows different quasi-molecular ion yields for the positive- and negative-ion spectra. 相似文献
16.
Dunja Srzic Mladen
ini Zlatko Mei Gbor Czira Jzsef Tains 《Journal of mass spectrometry : JMS》1992,27(11):1305-1310
The electron impact-induced fragmentation of azobenzenes and its d1, d2, d5, d10, and 15N analogues was studied by mass Spectrometry and ion kinetic energy spectroscopy. The main fragment ions found in the mass spectrum of azobenzene are due to two parallel stepwise processes from the molecular ion: the expulsion of N2 and two hydrogen radicals producing an ion at m/z 152 having possibly a biphenylene radical cation structure and loss of C6H5? and N2. Except in the elimination of two hydrogen atoms from [M ? N2]+· ions, hydrogen scrambling between the phenyl rings does not feature in azobenzene upon electron impact. 相似文献
17.
Xiu-Sheng Miao Raymond E. March Chris D. Metcalfe 《International journal of mass spectrometry》2003,230(2-3):123
A mass spectrometric study of three N-oxides, quinoline N-oxide, and the synthetic antibiotics carbadox and olaquindox, was carried out with a hybrid quadrupole/time-of-flight (TOF) mass spectrometer coupled with electrospray (ES) and atmospheric pressure chemical ionization (APCI) sources. The full scan mass spectra of the N-oxides obtained with ES are similar to those obtained with APCI, and the characteristic fragment ions corresponding to [M+H−O]+√ were observed in the full scan mass spectrum of each N-oxide examined. The protonated molecule of each N-oxide was subjected to collision-induced dissociation (CID) and accurate mass measurements were made of each fragment ion so as to determine its elemental composition. Fragment ions generated at enhanced cone voltages upstream of the first mass-resolving element were subjected to CID so as to identify the direct product ion–precursor ion relationship. Plausible structures have been proposed for most of the fragment ions observed. Elimination of OH√ radicals generated from the N→O functional group is a characteristic fragmentation pathway of the N-oxides. The expulsion of radicals and small stable molecules is accompanied by formation and subsequent contraction of heterocyclic rings. 相似文献
18.
Lin Yan Jiarou Peng Xianyun Jiao Mengshen Cai 《Journal of mass spectrometry : JMS》1992,27(9):962-966
A series of new synthetic tetrabenzyl N-glucosidic, N-mannosidic and N-galactosidic isomers were investigated by fast atom bombardment (FAB)/mass-analysed ion kinetic energy (MIKE) spectrometry. The [M + H]+ ions were obtained with high abundance in the FAB spectra when using 3-nitrobenzyl alcohol as the matrix. The FAB/MIKE spectra provide characteristic daughter ions fragmented from selected molecular parent ions, allowing these isomers to be differentiated. In addition, an interesting rearrangement was found from the MIKE spectra, indicating that the benzyl (Bzl) group on the sugar ring is rearranged on to the N atom of the base (R) group to form [R + Bzl + H]+ and [R+ 2Bzl]+ ions. 相似文献
19.
Jona Merx Kas J. Houthuijs Dr. Hidde Elferink Eva Witlox Dr. Jasmin Mecinović Prof. Jos Oomens Dr. Jonathan Martens Dr. Thomas J. Boltje Prof. Floris P. J. T. Rutjes 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(9):e202104078
N-Acyliminium ions are highly reactive intermediates that are important for creating CC-bonds adjacent to nitrogen atoms. Here we report the characterization of cyclic N-acyliminium ions in the gas phase, generated by collision induced dissociation tandem mass spectrometry followed by infrared ion spectroscopy using the FELIX infrared free electron laser. Comparison of DFT calculated spectra with the experimentally observed IR spectra provided valuable insights in the conformations of the N-acyliminium ions. 相似文献
20.
The molecular ions of N,N-dimethylthiobenzamide and its ortho substituted derivatives (substituents CH3, Cl, Br, I) lose a hydrogen atom and/or the ortho substituent. The mechanism of this process has been studied by measurements of the ionization energies, appearance energies of the product ions m/z 164 and the kinetic energy release during this process. The structure of the product ions m/z 164 and relevant reference ions have been investigated by mass analysed ion kinetic energy spectra, B/E linked scan spectra and collision induced decompositions. The results show clearly the formation of two different kinds of product ions m/z 164 depending on the substituent lost. Type a ions are formed by loss of a H atom or the CH3 substituent and correspond to protonated 3,4-benzo-N-methylpyroline-2-thione. The formation of these ions occurs by a hydrogen rearrangement followed by an intramolecular substitution via a 5-membered cyclic intermediate and is associated with a large release of kinetic energy. In contrast, the loss of the halogeno substituents to give type b ions probably occurs via a direct displacement reaction by the sulfur atom of the thioamide group giving rise to Gaussian shaped peaks mass analysed ion kinetic energy spectra. 相似文献