共查询到20条相似文献,搜索用时 703 毫秒
1.
Electron-transfer dissociation (ETD) is a useful peptide fragmentation technique that can be applied to investigate post-translational
modifications (PTMs), the sequencing of highly hydrophilic peptides, and the identification of large peptides and even intact
proteins. In contrast to traditional fragmentation methods, such as collision-induced dissociation (CID), ETD produces c-
and z·-type product ions by randomly cleaving the N–Cα bonds. The disappointing fragmentation efficiency of ETD for doubly charged
peptides and phosphopeptide ions has been improved by ETcaD (supplemental activation). However, the ETD data derived from
most database search algorithms yield low confidence scores due to the presence of unreacted precursors and charge-reduced
ions within MS/MS spectra. In this work, we demonstrate that eight out of ten standard doubly charged peptides and phosphopeptides
can be effortlessly identified by electron-transfer coupled with collision-induced dissociation (ET/CID) using the SEQUEST
algorithm without further spectral processing. ET/CID was performed with the further dissociation of the charge-reduced ions
isolated from ETD ion/ion reactions. ET/CID had high fragmentation efficiency, which elevated the confidence scores of doubly
charged peptide and phosphospeptide sequencing. ET/CID was found to be an effective fragmentation strategy in “bottom-up”
proteomic analysis. 相似文献
2.
The aim of this study was to investigate the fragmentation behavior induced by low‐energy collision‐induced dissociation (LE‐CID) of four selected antioxidants applied in lubricants, by two different types of ion trap mass spectrometers: a three‐dimensional ion trap (3D‐IT) and a linear IT (LIT) Orbitrap MS. Two sterically hindered phenols and two aromatic amines were selected as model compounds representing different antioxidant classes and were characterized by positive‐ion electrospray ionization (ESI) and LE‐CID. Various types of molecular ions (e.g. [M]+?, [M + H]+, [M + NH4]+ or [M + Na]+) were used as precursor ions generating a significant number of structurally relevant product ions. Furthermore, the phenolic compounds were analyzed by negative‐ion ESI. For both IT types applied for fragmentation, the antioxidants exhibited the same unusual LE‐CID behavior: (1) they formed stable radical product ions and (2) C? C bond cleavages of aliphatic substituents were observed and their respective cleavage sites depended on the precursor ion selected. This fragmentation provided information on the type of structural isomer usually not obtainable for branched aliphatic substituents utilizing LE‐CID. Comparing the two instruments, the main benefit of applying the LIT‐Orbitrap was direct access to elemental composition of product ions enabling unambiguous interpretation of fragmentation trees not obtainable by the 3D‐IT device (e.g. loss of isobaric neutrals). It should be emphasized that the types of product ions formed do not depend on the type of IT analyzer applied. For characterizing degradation products of antioxidants, the LIT‐Orbitrap hybrid system, allowing the determination of accurate m/z values for product ions, is the method of choice. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
3.
Murrell J Despeyroux D Lammert SA Stephenson JL Goeringer DE 《Journal of the American Society for Mass Spectrometry》2003,14(7):785-789
Collision-induced dissociation (CID) in a quadrupole ion trap mass spectrometer is usually performed by applying a small amplitude excitation voltage at the same secular frequency as the ion of interest. Here we disclose studies examining the use of large amplitude voltage excitations (applied for short periods of time) to cause fragmentation of the ions of interest. This process has been examined using leucine enkephalin as the model compound and the motion of the ions within the ion trap simulated using ITSIM. The resulting fragmentation information obtained is identical with that observed by conventional resonance excitation CID. "Fast excitation" CID deposits (as determined by the intensity ratio of the a(4)/b(4) ion of leucine enkephalin) approximately the same amount of internal energy into an ion as conventional resonance excitation CID where the excitation signal is applied for much longer periods of time. The major difference between the two excitation techniques is the higher rate of excitation (gain in kinetic energy) between successive collisions with helium atoms with "fast excitation" CID as opposed to the conventional resonance excitation CID. With conventional resonance excitation CID ions fragment while the excitation voltage is still being applied whereas for "fast excitation" CID a higher proportion of the ions fragment in the ion cooling time following the excitation pulse. The fragmentation of the (M + 17H)(17+) of horse heart myoglobin is also shown to illustrate the application of "fast excitation" CID to proteins. 相似文献
4.
Andrew W. Jones Peter J. Winn Helen J. Cooper 《Journal of the American Society for Mass Spectrometry》2012,23(12):2063-2074
The radical ion chemistry of a suite of S-nitrosopeptides has been investigated. Doubly and triply-protonated ions of peptides NYCGLPGEYWLGNDK, NYCGLPGEYWLGNDR, NYCGLPGERWLGNDR, NACGAPGEKWAGNDK, NYCGLPGEKYLGNDK, NYGLPGCEKWYGNDK and NYGLPGEKWYGCNDK were subjected to electron capture dissociation (ECD), and collision-induced dissociation (CID). The peptide sequences were selected such that the effect of the site of S-nitrosylation, the nature and position of the basic amino acid residues, and the nature of the other amino acid side chains, could be interrogated. The ECD mass spectra were dominated by a peak corresponding to loss of ?NO from the charge-reduced precursor, which can be explained by a modified Utah-Washington mechanism. Some backbone fragmentation in which the nitrosyl modification was preserved was also observed in the ECD of some peptides. Molecular dynamics simulations of peptide ion structure suggest that the ECD behavior was dependent on the surface accessibility of the protonated residue. CID of the S-nitrosylated peptides resulted in homolysis of the S?CN bond to form a long-lived radical with loss of ?NO. The radical peptide ions were isolated and subjected to ECD and CID. ECD of the radical peptide ions provided an interesting comparison to ECD of the unmodified peptides. The dominant process was electron capture without further dissociation (ECnoD). CID of the radical peptide ions resulted in cysteine, leucine, and asparagine side chain losses, and radical-induced backbone fragmentation at tryptophan, tyrosine, and asparagine residues, in addition to charge-directed backbone fragmentation. 相似文献
5.
Diarmuid T. Kenny Samah M. A. Issa Niclas G. Karlsson 《Rapid communications in mass spectrometry : RCM》2011,25(18):2611-2618
Migration of sulfate groups between hydroxyl groups was identified after collision‐induced dissociation (CID) of sulfated oligosaccharides in an ion trap mass spectrometer in negative ion mode. Analysis of various sulfated oligosaccharides showed that this was a common phenomenon and was particularly prominent in sulfated oligosaccharides also containing sialic acid. It was also shown that the level of migration was increased when the sulfate was positioned on the flexible areas of the oligosaccharides not involved in the pyranose ring, such as the extra‐cyclic C‐6 carbon of hexoses or N‐acetylhexosamines, or on reduced oligosaccharide. This suggested that migration is dependent on the spatial availability of the sulfate in the ion trap during collision. It is proposed that the migration is initiated when the negatively charged ‐SO3– residue attached to the oligosaccharide precursor becomes protonated by a CID‐induced proton transfer. This is supported by the CID fragmentation of precursor ions depleted of acidic protons such as doubly charged [M – 2H]2– ions or the sodiated [M + Na – 2H]– ions of oligosaccharides containing one sulfate and one sialic acid in the same molecule. Compared to the CID fragmentation of their monocharged [M – H]– ions, no migration was observed in CID of proton depleted precursors. Alternative fragmentation parameters to suppress migration of sulfated oligosaccharides also showed that it was not present when sulfated oligosaccharides were fragmented by HCD (High‐Energy C‐trap Dissociation) in an Orbitrap mass spectrometer. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
6.
J. Larry Campbell James W. Hager J. C. Yves Le Blanc 《Journal of the American Society for Mass Spectrometry》2009,20(9):1672-1683
We propose a tandem mass spectrometry method that combines electron-transfer dissociation (ETD) with simultaneous collision-induced
dissociation (CID), termed ETD/CID. This technique can provide more complete sequence coverage of peptide ions, especially
those at lower charge states. A selected precursor ion is isolated and subjected to ETD. At the same time, a residual precursor
ion is subjected to activation via CID. The specific residual precursor ion selected for activation will depend upon the charge
state and m/z of the ETD precursor ion. Residual precursor ions, which include unreacted precursor ions and charge-reduced precursor ions
(either by electron-transfer or proton transfer), are often abundant remainders in ETD-only reactions. Preliminary results
demonstrate that during an ETD/CID experiment, b, y, c, and z-type ions can be produced in a single experiment and displayed
in a single mass spectrum. While some peptides, especially doubly protonated ones, do not fragment well by ETD, ETD/CID alleviates
this problem by acting in at least one of three ways: (1) the number of ETD fragment ions are enhanced by CID of residual
precursor ions, (2) both ETD and CID-derived fragments are produced, or (3) predominantly CID-derived fragments are produced
with little or no improvement in ETD-derived fragment ions. Two interesting scenarios are presented that display the flexibility
of the ETD/CID method. For example, smaller peptides that show little response to ETD are fragmented preferentially by CID
during the ETD/CID experiment. Conversely, larger peptides with higher charge states are fragmented primarily via ETD. Hence,
ETD/CID appears to rely upon the fundamental reactivity of the analyte cations to provide the best fragmentation without implementing
any additional logic or MS/MS experiments. In addition to the ETD/CID experiments, we describe a novel dual source interface
for providing front-end ETD capabilities on a linear ion trap mass spectrometer. 相似文献
7.
Ernst Pittenauer Günter Allmaier 《Journal of the American Society for Mass Spectrometry》2009,20(6):1037-1047
Triacylglycerols were analyzed as cationized species (Li+, Na+, K+) by high-energy CID at 20 keV collisions utilizing MALDI-TOF/RTOF mass spectrometry. Precursor ions, based on [M+Li]+-adduct ions exhibited incomplete fragmentation in the high and low m/z region whereas [M+K]+-adducts did not show useful fragmentation. Only sodiated precursor ions yielded product ion spectra with structurally diagnostic
product ions across the whole m/z range. The high m/z region of the CID spectra is dominated by abundant charge-remote fragmentation of the fatty acid substituents. In favorable
cases also positions of double bonds or of hydroxy groups of the fatty acid alkyl chains could be determined. A-type product
ions represent the end products of these charge-remote fragmentations. B- and C-type product ions yield the fatty acid composition
of individual triacylglycerol species based on loss of either one neutral fatty acid or one sodium carboxylate residue, respectively.
Product ions allowing fatty acid substituent positional determination were present in the low m/z range enabling identification of either the sn-1/sn-3 substituents (E-, F-, and G-type ions) or the sn-2 substituent (J-type ion). These findings were demonstrated with synthetic triacylglycerols and plant oils such as cocoa
butter, olive oil, and castor bean oil. Typical features of 20 keV CID spectra of sodiated triacylglycerols obtained by MALDI-TOF/RTOF
MS were an even distribution of product ions over the entire m/z range and a mass accuracy of ±0.1 to 0.2 u. One limitation of the application of this technique is mainly the insufficient
precursor ion gating after MS1 (gating window at 4 u) of species separated by 2 u. 相似文献
8.
Gas phase fragmentation of hydrogen deficient peptide radical cations continues to be an active area of research. While collision
induced dissociation (CID) of singly charged species is widely examined, dissociation channels of singly and multiply charged
radical cations in infrared multiphoton dissociation (IRMPD) and electron induced dissociation (EID) have not been, so far,
investigated. Here, we report on the gas phase dissociation of singly, doubly and triply charged hydrogen deficient peptide
radicals, [M + nH](n+1)+· (n = 0, 1, 2), in MS3 IRMPD and EID and compare the observed fragmentation pathways to those obtained in MS3 CID. Backbone fragmentation in MS3 IRMPD and EID was highly dependent on the charge state of the radical precursor ions, whereas amino acid side chain cleavages
were largely independent of the charge state selected for fragmentation. Cleavages at aromatic amino acids, either through
side chain loss or backbone fragmentation, were significantly enhanced over other dissociation channels. For singly charged
species, the MS3 IRMPD and EID spectra were mainly governed by radical-driven dissociation. Fragmentation of doubly and triply charged radical
cations proceeded through both radical- and charge-driven processes, resulting in the formation of a wide range of backbone
product ions including, a-, b-, c-, y-, x-, and z-type. While similarities existed between MS3 CID, IRMPD, and EID of the same species, several backbone product ions and side chain losses were unique for each activation
method. Furthermore, dominant dissociation pathways in each spectrum were dependent on ion activation method, amino acid composition,
and charge state selected for fragmentation. 相似文献
9.
Castro-Perez J Roddy TP Nibbering NM Shah V McLaren DG Previs S Attygalle AB Herath K Chen Z Wang SP Mitnaul L Hubbard BK Vreeken RJ Johns DG Hankemeier T 《Journal of the American Society for Mass Spectrometry》2011,22(9):1552-1567
A high content molecular fragmentation for the analysis of phosphatidylcholines (PC) was achieved utilizing a two-stage [trap (first generation fragmentation) and transfer (second generation fragmentation)] collision-induced dissociation (CID) in combination with travelling-wave ion mobility spectrometry (TWIMS). The novel aspects of this work reside in the fact that a TWIMS arrangement was used to obtain a high level structural information including location of fatty acyl substituents and double bonds for PCs in plasma, and the presence of alkali metal adduct ions such as [M?+?Li]+ was not required to obtain double bond positions. Elemental compositions for fragment ions were confirmed by accurate mass measurements. A very specific first generation fragment ion m/z 577 (M-phosphoryl choline) from the PC [16:0/18:1 (9Z)] was produced, which by further CID generated acylium ions containing either the fatty acyl 16:0 (C15H31CO+, m/z 239) or 18:1 (9Z) (C17H33CO+, m/z 265) substituent. Subsequent water loss from these acylium ions was key in producing hydrocarbon fragment ions mainly from the α-proximal position of the carbonyl group such as the hydrocarbon ion m/z 67 (+H2C-HC?=?CH-CH?=?CH2). Formation of these ions was of important significance for determining double bonds in the fatty acyl chains. In addition to this, and with the aid of 13C labeled lyso-phosphatidylcholine (LPC) 18:1 (9Z) in the ω-position (methyl) TAP fragmentation produced the ion at m/z 57. And was proven to be derived from the α-proximal (carboxylate) or distant ω-position (methyl) in the LPC. 相似文献
10.
Ma X Love CB Zhang X Xia Y 《Journal of the American Society for Mass Spectrometry》2011,22(5):922-930
In this study, we systematically investigated gas-phase fragmentation behavior of [M + nH + OH]n•+ ions formed from peptides containing intra-molecular disulfide bond. Backbone fragmentation and radical initiated neutral
losses were observed as the two competing processes upon low energy collision-induced dissociation (CID). Their relative contribution
was found to be affected by the charge state (n) of [M + nH + OH]n•+ ions and the means for activation, i.e., beam-type CID or ion trap CID. Radical initiated neutral losses were promoted in
ion-trap CID and for lower charge states where mobile protons were limited. Beam-type CID and dissociation of higher charge
states of [M + nH + OH]n•+ ions generally gave abundant backbone fragmentation, which was highly desirable for characterizing peptides containing disulfide
bonds. The amount of sequence information obtained from CID of [M + nH + OH]n•+ ions was compared with that from CID of disulfide bond reduced peptides. For the 11 peptides studied herein, similar extent
of sequence information was obtained from these two methods. 相似文献
11.
W E Steiner B H Clowers K Fuhrer M Gonin L M Matz W F Siems A J Schultz H H Hill 《Rapid communications in mass spectrometry : RCM》2001,15(23):2221-2226
Rapid screening and identification of drug and other mixtures are possible using a novel ambient pressure high-resolution ion mobility (APIMS) orthogonal reflector time-of-flight mass spectrometer (TOFMS). Departing ions from the APIMS drift tube traversed a pressure interface between the APIMS and TOFMS where they were subjected to numerous gas collisions that could produce selective fragmentation. By increasing the accelerating field in the pressure interface region, the ions generated using water-cooled electrospray ionization (ESI) underwent collision-induced dissociation (CID). Mixtures of ESI ions were separated by APIMS based on their respective size-to-charge (s/z) ratios while CID and analysis of mass-to-charge (m/z) ratios occurred in the pressure interface and TOFMS. Product ions that were formed in this pressure interface region could be readily assigned to precursor ions by matching the mobility drift times. This process was demonstrated by the examination of a mixture of amphetamines and the resulting fragmentation patterns of the mobility-separated precursor ion species [M + H](+). 相似文献
12.
Y. Yang W. J. Griffiths J. Sjövall J. -Å. Gustafsson J. Rafter 《Journal of the American Society for Mass Spectrometry》1997,8(1):50-61
Benzo[a]pyrene (BP) metabolites conjugated with glutathione, cysteine-glycine, cysteine, N-acetylcysteine, and sulfuric and glucuronic acids have been studied by microcolumn liquid chromatography-electrospray mass spectrometry with collision-induced dissociation (CID) on a hybrid double focusing magnetic sector-orthogonal time-of-flight tandem mass spectrometer equipped with a focal plane array detector. Negative-ion electrospray mass spectra of the conjugated BP metabolites showed strong [M – H]? ions. When the array detector was used, spectra were obtained from femtomoles of sample infused at mass resolutions of 5000 (full width at half maximum). Cone voltage fragmentation spectra show [M-H]? ions and fragment ions indicative of the BP moiety and/or the conjugating group. Linked scan CID spectra at constant B/E were found to contain structurally informative product ions from infusion of as little as 1 pmol of sample. CID spectra were also recorded by using the double focusing sectors for precursor ion selection and the orthogonal time-of-flight analyzer for product ion mass separation. The method was applied to the analysis of conjugated BP metabolites in the urine of germ-free rats given a single intraperitoneal dose of BP. 相似文献
13.
Collision-induced dissociation (CID) of deprotonated hexose-containing disaccharides (m/z 341) with 1–2, 1–4, and 1–6 linkages yields product ions at m/z 221, which have been identified as glycosyl-glycolaldehyde anions. From disaccharides with these linkages, CID of m/z 221 ions produces distinct fragmentation patterns that enable the stereochemistries and anomeric configurations of the non-reducing
sugar units to be determined. However, only trace quantities of m/z 221 ions can be generated for 1–3 linkages in Paul or linear ion traps, preventing further CID analysis. Here we demonstrate
that high intensities of m/z 221 ions can be built up in the linear ion trap (Q3) from beam-type CID of a series of 1–3 linked disaccharides conducted
on a triple quadrupole/linear ion trap mass spectrometer. 18O-labeling at the carbonyl position of the reducing sugar allowed mass-discrimination of the “sidedness” of dissociation events
to either side of the glycosidic linkage. Under relatively low energy beam-type CID and ion trap CID, an m/z 223 product ion containing 18O predominated. It was a structural isomer that fragmented quite differently than the glycosyl-glycolaldehydes and did not
provide structural information about the non-reducing sugar. Under higher collision energy beam-type CID conditions, the formation
of m/z 221 ions, which have the glycosyl-glycolaldehyde structures, were favored. Characteristic fragmentation patterns were observed
for each m/z 221 ion from higher energy beam-type CID of 1–3 linked disaccharides and the stereochemistry of the non-reducing sugar, together
with the anomeric configuration, were successfully identified both with and without 18O-labeling of the reducing sugar carbonyl group. 相似文献
14.
Farid Ichou Denis Lesage Xavier Machuron‐Mandard Christophe Junot Richard B. Cole Jean‐Claude Tabet 《Journal of mass spectrometry : JMS》2013,48(2):179-186
Control of the ion internal energy in mass spectrometry is needed to establish a workable mass spectral library. The purpose of this study is to understand and to compare the pressure effects on the collision‐induced dissociation (CID) spectrum pattern recorded using triple quadrupole instruments. The monoprotonated Leucine enkephalin [YGGFL, H+] was used as a thermometer molecule to calibrate the electrospray ionization (ESI) and the CID internal energies deposited on the molecular species and the time scale of ion decompositions. The survival yield and the ratio of a4/b4 fragment ions were mainly monitored. The energy uptake for the ESI source geometry used in our study has no impact on the CID spectrum fingerprint. The collision cell pressure for the [YGGFL, H+] has a major influence on the SY curves slope and on the experimental time scale. To demonstrate the pressure effect on internal energy distribution, three models (threshold, thermal and collisional) based on RRKM theory were built using the Masskinetics software. As a result, the limit of each model is discussed, and the investigation demonstrates that the thermal model, using truncated Maxwell‐Boltzmann internal energy distribution, is well‐suited for simulating the experimental data at high pressure widely used in the analytical conditions. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
15.
Sungho Ahn Joo Yeon Hong Moo Ki Hong Young Pyo Jang Myung Sook Oh Jee H. Jung Jongki Hong 《Rapid communications in mass spectrometry : RCM》2009,23(19):3158-3166
Sildenafil and its analogues, which are used as illegal additives in several dietary supplements, were isolated by liquid‐liquid extraction and column chromatography and analyzed by fast‐atom bombardment mass spectrometry (FAB‐MS). Structures of sildenafil and its derivatives were elucidated by FAB‐tandem mass spectrometry (MS/MS) with exact mass measurement in the positive‐ion mode. To find structurally diagnostic ions for the sildenafil analogues, authentic sildenafil was preferentially analyzed by high‐energy collision‐induced dissociation (CID)‐MS/MS. The CID‐MS/MS spectra of [M+H]+ precursor ions resulted in the formation of numerous characteristic ions via a series of dissociative processes. The product ions formed by CID provided important information on the modification of the piperazine ring, the phenylsulfonyl group and the pyrazolopyrimidine moiety of sildenafil. By interpreting their MS/MS spectra, the chemical structures of sildenafil analogues isolated from dietary supplements could be elucidated and fragmentation patterns were proposed. To clearly identify the sidenafil derivatives in dietary supplements, some of the derivatives such as acetildenafil, homosildenafil and hydroxyhomosildenafil which are not commercially available were synthesized and compared with their MS/MS spectra. In addition, high‐resolution mass measurements were conducted to obtain the elemental compositions of sildenafil and its analogues. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
16.
Ion activation methods for tandem mass spectrometry 总被引:7,自引:0,他引:7
This tutorial presents the most common ion activation techniques employed in tandem mass spectrometry. In-source fragmentation and metastable ion decompositions, as well as the general theory of unimolecular dissociations of ions, are initially discussed. This is followed by tandem mass spectrometry, which implies that the activation of ions is distinct from the ionization step, and that the precursor and product ions are both characterized independently by their mass/charge ratios. In collision-induced dissociation (CID), activation of the selected ions occurs by collision(s) with neutral gas molecules in a collision cell. This experiment can be done at high (keV) collision energies, using tandem sector and time-of-flight instruments, or at low (eV range) energies, in tandem quadrupole and ion trapping instruments. It can be performed using either single or multiple collisions with a selected gas and each of these factors influences the distribution of internal energy that the activated ion will possess. While CID remains the most common ion activation technique employed in analytical laboratories today, several new methods have become increasingly useful for specific applications. More recent techniques are examined and their differences, advantages and disadvantages are described in comparison with CID. Collisional activation upon impact of precursor ions on solid surfaces, surface-induced dissociation (SID), is gaining importance as an alternative to gas targets and has been implemented in several different types of mass spectrometers. Furthermore, unique fragmentation mechanisms of multiply-charged species can be studied by electron-capture dissociation (ECD). The ECD technique has been recognized as an efficient means to study non-covalent interactions and to gain sequence information in proteomics applications. Trapping instruments, such as quadrupole ion traps and Fourier transform ion cyclotron resonance instruments, are particularly useful for the photoactivation of ions, specifically for fragmentation of precursor ions by infrared multiphoton dissociation (IRMPD). IRMPD is a non-selective activation method and usually yields rich fragmentation spectra. Lastly, blackbody infrared radiative dissociation is presented with a focus on determining activation energies and other important parameters for the characterization of fragmentation pathways. The individual methods are presented so as to facilitate the understanding of each mechanism of activation and their particular advantages and representative applications. 相似文献
17.
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
18.
Teng-yi Huang Anastasia Kharlamova Scott A. McLuckey 《Journal of the American Society for Mass Spectrometry》2010,21(1):144-153
Gas-phase dissociation of model locked nucleic acid (LNA) oligonucleotides and functional LNA-DNA chimeras have been investigated
as a function of precursor ion charge state using ion trap collision-induced dissociation (CID). For the model LNA 5 and 8
mer, containing all four LNA monomers in the sequence, cleavage of all backbone bonds, generating a/w-, b/x-, c/y-, and d/z-ions,
was observed with no significant preference at lower charge states. Base loss ions, except loss of thymine, from the cleavage
of N-glycosidic bonds were also present. In general, complete sequence coverage was achieved in all charge states. For the
two LNA-DNA chimeras, however, dramatic differences in the relative contributions of the competing dissociation channels were
observed among different precursor ion charge states. At lower charge states, sequence information limited to the a-Base/w-fragment
ions from cleavage of the 3′C-O bond of DNA nucleotides, except thymidine (dT), was acquired from CID of both the LNA gapmer
and mixmer ions. On the other hand, extensive fragmentation from various dissociation channels was observed from post-ion/ion
ion trap CID of the higher charge state ions of both LNA-DNA chimeras. This report demonstrates that tandem mass spectrometry
is effective in the sequence characterization of LNA oligonucleotides and LNA-DNA chimeric therapeutics. 相似文献
19.
《Journal of mass spectrometry : JMS》2018,53(3):195-202
Over the years, with the instrumental analysis evolution, the relationships between the carried‐out results with the data of theoretical analysis in silico and the Hammett's parameters have been reported. They have been very useful for chemical characterization of small organic molecules. Thus, this work aims at showing the feasibility and limitations for Hammett's and density functional theory applications in electrospray ionization–collision‐induced dissociation (ESI‐CID) fragmentation provision. For this, 13 dihydropyrimidinones para, meta, and orto monosubstituted were studied using ESI and CID in positive mode. As a result, it was observed that the main fragmentation includes the isocyanate and ethanol loses at low energy. Nevertheless, at higher energies, radical ions formed by McLafferty rearrangement were observed. The Hammett plots were correlated fragmentation profiles, showing good linearity for the [M + H]+, which does not occur to radical ions and carbocation's. These tendencies had demonstrated that the stability of protonate and activation energy of secondary ions changes with the pKa. The density functional theory studies indicated that, both nitrogen atoms in the dihydropyrimidinone's prototypes are capable of being protonated. However, the activation energy of fragmentation products is not changed. Therefore, this work has shown information, which can be useful to understand tandem mass spectrometry in ESI‐CID conditions for small organic molecules series. This is the first step for normalization of fragmentation pathway. 相似文献
20.
Andreas Bertsch Andreas Leinenbach Anton Pervukhin Markus Lubeck Ralf Hartmer Carsten Baessmann Yasser Abbas Elnakady Rolf Müller Sebastian Böcker Christian G. Huber Oliver Kohlbacher 《Electrophoresis》2009,30(21):3736-3747
De novo sequencing of peptides using tandem MS is difficult due to missing fragment ions in the spectra commonly obtained after CID of peptide precursor ions. Complementing CID spectra with spectra obtained in an ion‐trap mass spectrometer upon electron transfer dissociation (ETD) significantly increases the sequence coverage with diagnostic ions. In the de novo sequencing algorithm CompNovo presented here, a divide‐and‐conquer approach was combined with an efficient mass decomposition algorithm to exploit the complementary information contained in CID and ETD spectra. After optimizing the parameters for the algorithm on a well‐defined training data set obtained for peptides from nine known proteins, the CompNovo algorithm was applied to the de novo sequencing of peptides derived from a whole protein extract of Sorangium cellulosum bacteria. To 2406 pairs of CID and ETD spectra contained in this data set, 675 fully correct sequences were assigned, which represent a success rate of 28.1%. It is shown that the CompNovo algorithm yields significantly improved sequencing accuracy as compared with published approaches using only CID spectra or combined CID and ETD spectra. 相似文献