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1.
Cole SR Ma X Zhang X Xia Y 《Journal of the American Society for Mass Spectrometry》2012,23(2):310-320
The fragmentation chemistry of peptides containing intrachain disulfide bonds was investigated under electron transfer dissociation
(ETD) conditions. Fragments within the cyclic region of the peptide backbone due to intrachain disulfide bond formation were
observed, including: c (odd electron), z (even electron), c-33 Da, z + 33 Da, c + 32 Da, and z–32 Da types of ions. The presence
of these ions indicated cleavages both at the disulfide bond and the N–Cα backbone from a single electron transfer event.
Mechanistic studies supported a mechanism whereby the N–Cα bond was cleaved first, and radical-driven reactions caused cleavage
at either an S–S bond or an S–C bond within cysteinyl residues. Direct ETD at the disulfide linkage was also observed, correlating
with signature loss of 33 Da (SH) from the charge-reduced peptide ions. Initial ETD cleavage at the disulfide bond was found
to be promoted amongst peptides ions of lower charge states, while backbone fragmentation was more abundant for higher charge
states. The capability of inducing both backbone and disulfide bond cleavages from ETD could be particularly useful for sequencing
peptides containing intact intrachain disulfide bonds. ETD of the 13 peptides studied herein all showed substantial sequence
coverage, accounting for 75%–100% of possible backbone fragmentation. 相似文献
2.
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
3.
Wang Z Zhang Y Zhang H Harrington PB Chen H 《Journal of the American Society for Mass Spectrometry》2012,23(3):520-529
We previously reported that selenamide reagents such as ebselen and N-(phenylseleno)phthalimide (NPSP) can be used to selectively derivatize thiols for mass spectrometric analysis, and the introduced
selenium tags are useful as they could survive or removed with collision-induced dissociation (CID). Described herein is the
further study of the reactivity of various protein/peptide thiols toward NPSP and its application to derivatize thiol peptides
in protein digests. With a modified protocol (i.e., dissolving NPSP in acetonitrile instead of aqueous solvent), we found
that quantitative conversion of thiols can be obtained in seconds, using NPSP in a slight excess amount (NPSP:thiol of 1.1–2:1).
Further investigation shows that the thiol reactivity toward NPSP reflects its chemical environment and accessibility in proteins/peptides.
For instance, adjacent basic amino acid residues increase the thiol reactivity, probably because they could stabilize the
thiolate form to facilitate the nucleophilic attack of thiol on NPSP. In the case of creatine phosphokinase, the native protein
predominately has one thiol reacted with NPSP while all of four thiol groups of the denatured protein can be derivatized,
in accordance with the corresponding protein conformation. In addition, thiol peptides in protein/peptide enzymatic digests
can be quickly and effectively tagged by NPSP following tri-n-butylphosphine (TBP) reduction. Notably, all three thiols of the peptide QCCASVCSL in the insulin peptic digest can be modified
simultaneously by NPSP. These results suggest a novel and selective method for protecting thiols in the bottom-up approach
for protein structure analysis. 相似文献
4.
Marija Mentinova Hongling Han Scott A. McLuckey 《Rapid communications in mass spectrometry : RCM》2009,23(17):2647-2655
The dissociation chemistry of somatostatin‐14 was examined using various tandem mass spectrometry techniques including low‐energy beam‐type and ion trap collision‐induced dissociation (CID) of protonated and deprotonated forms of the peptide, CID of peptide‐gold complexes, and electron transfer dissociation (ETD) of cations. Most of the sequence of somatostatin‐14 is present within a loop defined by the disulfide linkage between Cys‐3 and Cys‐14. The generation of readily interpretable sequence‐related ions from within the loop requires the cleavage of at least one of the bonds of the disulfide linkage and the cleavage of one polypeptide backbone bond. CID of the protonated forms of somatostatin did not appear to give rise to an appreciable degree of dissociation of the disulfide linkage. Sequential fragmentation via multiple alternative pathways tended to generate very complex spectra. CID of the anions proceeded through CH2? S cleavages extensively but relatively few structurally diagnostic ions were generated. The incorporation of Au(I) into the molecule via ion/ion reactions followed by CID gave rise to many structurally relevant dissociation products, particularly for the [M+Au+H]2+ species. The products were generated by a combination of S? S bond cleavage and amide bond cleavage. ETD of the [M+3H]3+ ion generated rich sequence information, as did CID of the electron transfer products that did not fragment directly upon electron transfer. The electron transfer results suggest that both the S? S bond and an N? Cα bond can be cleaved following a single electron transfer reaction. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
5.
The dissociation behavior of phosphorylated and sulfonated peptide anions was explored using metastable atom-activated dissociation
mass spectrometry (MAD-MS) and collision-induced dissociation (CID). A beam of high kinetic energy helium (He) metastable
atoms was exposed to isolated phosphorylated and sulfonated peptides in the 3– and 2– charge states. Unlike CID, where phosphate
losses are dominant, the major dissociation channels observed using MAD were Cα – C peptide backbone cleavages and neutral losses of CO2, H2O, and [CO2 + H2O] from the charge reduced (oxidized) product ion, consistent with an electron detachment dissociation (EDD) mechanism such
as Penning ionization. Regardless of charge state or modification, MAD provides ample backbone cleavages with little modification
loss, which allows for unambiguous PTM site determination. The relative abundance of certain fragment ions in MAD is also
demonstrated to be somewhat sensitive to the number and location of deprotonation sites, with backbone cleavage somewhat favored
adjacent to deprotonated sites like aspartic acid residues. MAD provides a complementary dissociation technique to CID, ECD,
ETD, and EDD for peptide sequencing and modification identification. MAD offers the unique ability to analyze highly acidic
peptides that contain few to no basic amino acids in either negative or positive ion mode. 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.
Phanstiel D Zhang Y Marto JA Coon JJ 《Journal of the American Society for Mass Spectrometry》2008,19(9):1255-1262
Electron transfer dissociation (ETD) has become increasingly used in proteomic analyses due to its complementarity to collision-activated dissociation (CAD) and its ability to sequence peptides with post-translation modifications (PTMs). It was previously unknown, however, whether ETD would be compatible with a commonly employed quantification technique, isobaric tags for relative and absolute quantification (iTRAQ), since the fragmentation mechanisms and pathways of ETD differ significantly from CAD. We demonstrate here that ETD of iTRAQ labeled peptides produces c- and z -type fragment ions as well as reporter ions that are unique from those produced by CAD. Exact molecular formulas of product ions were determined by ETD fragmentation of iTRAQ-labeled synthetic peptides followed by high mass accuracy orbitrap mass analysis. These experiments revealed that ETD cleavage of the N-C(alpha) bond of the iTRAQ tag results in fragment ions that could be used for quantification. Synthetic peptide work demonstrates that these fragment ions provide up to three channels of quantification and that the quality is similar to that provided by beam-type CAD. Protein standards were used to evaluate peptide and protein quantification of iTRAQ labeling in conjunction with ETD, beam-type CAD, and pulsed Q dissociation (PQD) on a hybrid ion trap-orbitrap mass spectrometer. For reporter ion intensities above a certain threshold all three strategies provided reliable peptide quantification (average error < 10%). Approximately 36%, 8%, and 16% of scans identified fall below this threshold for ETD, HCD, and PQD, respectively. At the protein level, average errors were 2.3%, 1.7%, and 3.6% for ETD, HCD, and PQD, respectively. 相似文献
8.
Guan F Uboh CE Soma LR Rudy J 《Journal of the American Society for Mass Spectrometry》2011,22(4):718-730
Identification of an unknown substance without any information remains a daunting challenge despite advances in chemistry
and mass spectrometry. However, an unknown cyclic peptide in a sample with very limited volume seized at a Pennsylvania racetrack
has been successfully identified. The unknown sample was determined by accurate mass measurements to contain a small unknown
peptide as the major component. Collision-induced dissociation (CID) of the unknown peptide revealed the presence of Lys (not
Gln, by accurate mass), Phe, and Arg residues, and absence of any y-type product ion. The latter, together with the tryptic
digestion results of the unusual deamidation and absence of any tryptic cleavage, suggests a cyclic structure for the peptide.
Electron-transfer dissociation (ETD) of the unknown peptide indicated the presence of Gln (not Lys, by the unusual deamidation),
Phe, and Arg residues and their connectivity. After all the results were pieced together, a cyclic tetrapeptide, cyclo[Arg-Lys-N(C6H9)Gln-Phe], is proposed for the unknown peptide. Observations of different amino acid residues from CID and ETD experiments
for the peptide were interpreted by a fragmentation pathway proposed, as was preferential CID loss of a Lys residue from the
peptide. ETD was used for the first time in sequencing of a cyclic peptide; product ions resulting from ETD of the peptide
identified were categorized into two types and named pseudo-b and pseudo-z ions that are important for sequencing of cyclic
peptides. The ETD product ions were interpreted by fragmentation pathways proposed. Additionally, multi-stage CID mass spectrometry
cannot provide complete sequence information for cyclic peptides containing adjacent Arg and Lys residues. The identified
cyclic peptide has not been documented in the literature, its pharmacological effects are unknown, but it might be a “designer”
drug with athletic performance-enhancing effects. 相似文献
9.
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
10.
This tutorial provides an overview of the evolution of some of the key concepts in the gas-phase fragmentation of different classes of peptide ions under various conditions [e.g. collision-induced dissociation (CID) and electron transfer dissociation (ETD)], and then demonstrates how these concepts can be used to develop new methods. For example, an understanding of the role of the mobile proton and neighboring group interactions in the fragmentation reactions of protonated peptides has led to the design of the 'SELECT' method. For ETD, a model based on the Landau-Zener theory reveals the role of both thermodynamic and geometric effects in the electron transfer from polyatomic reagent anions to multiply protonated peptides, and this predictive model has facilitated the design of a new strategy to form ETD reagent anions from precursors generated via ESI. Finally, two promising, emerging areas of gas-phase ion chemistry of peptides are also described: (1) the design of new gas-phase radical chemistry to probe peptide structure, and (2) selective cleavage of disulfide bonds of peptides in the gas phase via various physicochemical approaches. 相似文献
11.
Collision Induced Dissociation Products of Disulfide-Bonded Peptides: Ions Result from the Cleavage of More Than One Bond 总被引:2,自引:0,他引:2
Clark DF Go EP Toumi ML Desaire H 《Journal of the American Society for Mass Spectrometry》2011,22(3):492-498
Disulfide bonds are a post-translational modification (PTM) that can be scrambled or shuffled to non-native bonds during recombinant
expression, sample handling, or sample purification. Currently, mapping of disulfide bonds is not easy because of various
sample requirements and data analysis difficulties. One step towards facilitating this difficult work is developing a better
understanding of how disulfide-bonded peptides fragment during collision induced dissociation (CID). Most automated analysis
algorithms function based on the assumption that the preponderance of product ions observed during the dissociation of disulfide-bonded
peptides result from the cleavage of just one peptide bond, and in this report we tested that assumption by extensively analyzing
the product ions generated when several disulfide-bonded peptides are subjected to CID on a quadrupole time of flight (QTOF)
instrument. We found that one of the most common types of product ions generated resulted from two peptide bond cleavages,
or a double cleavage. We found that for several of the disulfide-bonded peptides analyzed, the number of double cleavage product
ions outnumbered those of single cleavages. The influence of charge state and precursor ion size was investigated, to determine
if those parameters dictated the amount of double cleavage product ions formed. It was found in this sample set that no strong
correlation existed between the charge state or peptide size and the portion of product ions assigned as double cleavages.
These data show that these ions could account for many of the product ions detected in CID data of disulfide bonded peptides.
We also showed the utility of double cleavage product ions on a peptide with multiple cysteines present. Double cleavage products
were able to fully characterize the bonding pattern of each cysteine where typical single b/y cleavage products could not. 相似文献
12.
The fragmentation behavior of nitrated and S-nitrosylated peptides were studied using collision induced dissociation (CID)
and metastable atom-activated dissociation mass spectrometry (MAD-MS). Various charge states, such as 1+, 2+, 3+, 2–, of modified
and unmodified peptides were exposed to a beam of high kinetic energy helium (He) metastable atoms resulting in extensive
backbone fragmentation with significant retention of the post-translation modifications (PTMs). Whereas the high electron
affinity of the nitrotyrosine moiety quenches radical chemistry and fragmentation in electron capture dissociation (ECD) and
electron transfer dissociation (ETD), MAD does produce numerous backbone cleavages in the vicinity of the modification. Fragment
ions of nitrosylated cysteine modifications typically exhibit more abundant neutral losses than nitrated tyrosine modifications
because of the extremely labile nature of the nitrosylated cysteine residues. However, compared with CID, MAD produced between
66% and 86% more fragment ions, which preserved the labile –NO modification. MAD was also able to differentiate I/L residues
in the modified peptides. MAD is able to induce radical ion chemistry even in the presence of strong radical traps and therefore
offers unique advantages to ECD, ETD, and CID for determination of PTMs such as nitrated and S-nitrosylated peptides. 相似文献
13.
Hao Wang Robert M. Straubinger John M. Aletta Jin Cao Xiaotao Duan Haoying Yu Jun Qu 《Journal of the American Society for Mass Spectrometry》2009,20(3):507-519
Protein arginine (Arg) methylation serves an important functional role in eucaryotic cells, and typically occurs in domains
consisting of multiple Arg in close proximity. Localization of methylarginine (MA) within Arg-rich domains poses a challenge
for mass spectrometry (MS)-based methods; the peptides are highly charged under electrospray ionization (ESI), which limits
the number of sequence-informative products produced by collision induced dissociation (CID), and loss of the labile methylation
moieties during CID precludes effective fragmentation of the peptide backbone. Here the fragmentation behavior of Arg-rich
peptides was investigated comprehensively using electron-transfer dissociation (ETD) and CID for both methylated and unmodified
glycine-/Arg-rich peptides (GAR), derived from residues 679–695 of human nucleolin, which contains methylation motifs that
are widely-represented in biological systems. ETD produced abundant information for sequencing and MA localization, whereas
CID failed to provide credible identification for any available charge state (z=2–4). Nevertheless, CID produced characteristic
neutral losses that can be employed to distinguish among different types of MA, as suggested by previous works and confirmed
here with product ion scans of high accuracy/resolution by an LTQ/Orbitrap. To analyze MA-peptides in relatively complex mixtures,
a method was developed that employs nano-LC coupled to alternating CID/ETD for peptide sequencing and MA localization/characterization,
and an Orbitrap for accurate precursor measurement and relative quantification of MA-peptide stoichiometries. As proof of
concept, GAR-peptides methylated in vitro by protein arginine N-methyltransferases PRMT1 and PRMT7 were analyzed. It was observed that PRMT1 generated a number of monomethylated (MMA) and
asymmetric-dimethylated peptides, while PRMT7 produced predominantly MMA peptides and some symmetric-dimethylated peptides.
This approach and the results may advance understanding of the actions of PRMTs and the functional significance of Arg methylation
patterns. 相似文献
14.
Zhang Q Frolov A Tang N Hoffmann R van de Goor T Metz TO Smith RD 《Rapid communications in mass spectrometry : RCM》2007,21(5):661-666
Non-enzymatic glycation of peptides and proteins by D-glucose has important implications in the pathogenesis of diabetes mellitus, particularly in the context of development of diabetic complications. The fragmentation behavior of glycated peptides produced from reaction of D-glucose with lysine residues was investigated by electron transfer dissociation (ETD) and collision-induced dissociation (CID) tandem mass spectrometry. It was found that high abundance ions corresponding to various degrees of neutral water losses, as well as furylium ion production, dominate the CID spectra, and that the sequence-informative b and y ions were rarely observed when Amadori-modified peptides were fragmented. Contrary to what was observed under CID conditions, ions corresponding to neutral losses of water or furylium ion production were not observed in the ETD spectra. Instead, abundant and almost complete series of c- and z-type ions were observed regardless of whether the modification site was located in the middle of the sequence or close to the N-terminus, greatly facilitating the peptide sequencing. This study strongly suggests that ETD is a better technique for proteomic studies of non-enzymatically glycated peptides and proteins. 相似文献
15.
Shannon L. Cook Carolyn M. Zimmermann David Singer Maria Fedorova Ralf Hoffmann Glen P. Jackson 《Journal of mass spectrometry : JMS》2012,47(6):786-794
The fragmentation behavior of the 2+ and 3+ charge states of eleven different phosphorylated tau peptides was studied using collision‐induced dissociation (CID), electron transfer dissociation (ETD) and metastable atom‐activated dissociation (MAD). The synthetic peptides studied contain up to two known phosphorylation sites on serine or threonine residues, at least two basic residues, and between four and eight potential sites of phosphorylation. CID produced mainly b‐/y‐type ions with abundant neutral losses of the phosphorylation modification. ETD produced c‐/z‐type ions in highest abundance but also showed numerous y‐type ions at a frequency about 50% that of the z‐type ions. The major peaks observed in the ETD spectra correspond to the charge‐reduced product ions and small neutral losses from the charge‐reduced peaks. ETD of the 2+ charge state of each peptide generally produced fewer backbone cleavages than the 3+ charge state, consistent with previous reports. Regardless of charge state, MAD achieved more extensive backbone cleavage than CID or ETD, while retaining the modification(s) in most cases. In all but one case, unambiguous modification site determination was achieved with MAD. MAD produced 15–20% better sequence coverage than CID and ETD for both the 2+ and 3+ charge states and very different fragmentation products indicating that the mechanism of fragmentation in MAD is unique and complementary to CID and ETD. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
16.
Hayakawa S Hashimoto M Nagao H Awazu K Toyoda M Ichihara T Shigeri Y 《Rapid communications in mass spectrometry : RCM》2008,22(4):567-572
Doubly protonated phosphopeptide (YGGMHRQET(p)VDC) ions obtained by electrospray ionization were collided with Xe and Cs targets to give singly and doubly charged positive ions via collision-induced dissociation (CID). The resulting ions were analyzed and detected by using an electrostatic analyzer (ESA). Whereas doubly charged fragment ions resulting from collisionally activated dissociation (CAD) were dominant in the CID spectrum with the Xe target, singly charged fragment ions resulting from electron transfer dissociation (ETD) were dominant in the CID spectrum with the Cs target. The most intense peak resulting from ETD was estimated to be associated with the charge-reduced ion with H2 lost from the precursor. Five c-type fragment ions with amino acid residues detached consecutively from the C-terminal were clearly observed without a loss of the phosphate group. These ions must be formed by N--Calpha bond cleavage, in a manner similar to the cases of electron capture dissociation (ECD) and ETD from negative ions. Although the accuracy in m/z of the CID spectra was about +/-1 Th because of the mass analysis using the ESA, it is supposed from the m/z values of the c-type ions that these ions were accompanied by the loss of a hydrogen atom. Four z-type (or y--NH3, or y--H2O) ions analogously detached consecutively from the N-terminal were also observed. The fragmentation processes took place within the time scale of 4.5 micros in the high-energy collision. The present results demonstrated that high-energy ETD with the alkali metal target allowed determination of the position of phosphorylation and the amino acid sequence of post-translational peptides. 相似文献
17.
Wu WW Wang G Insel PA Hsiao CT Zou S Maudsley S Martin B Shen RF 《Journal of the American Society for Mass Spectrometry》2011,22(10):1753-1762
Pulsed Q collision induced dissociation (PQD) was developed to facilitate detection of low-mass reporter ions from labeling
reagents (e.g., iTRΑQ) in peptide quantification using an LTQ mass spectrometer (MS). Despite the large number of linear ion
traps worldwide, the use and optimization of PQD for protein identification have been limited, in part due to less effective
ion fragmentation relative to the collision induced dissociation (CID). PQD expands the m/z coverage of fragment ions to the lower m/z range by circumventing the typical low mass cut-off of an ion trap MS. Since database searching relies on the matching between
theoretical and observed spectra, it is not clear how ion intensity and peak number might affect the outcomes of a database
search. In this report, we systematically evaluated the attributes of PQD mass spectra, performed intensity optimization,
and assessed the benefits of using PQD on the identification of peptides and phosphopeptides from an LTQ. Based on head-to-head
comparisons between CID (higher intensity) and PQD (better m/z coverage), peptides identified using PQD generally have Xcorr scores lower than those using CID. Such score differences were
considerably diminished by the use of 0.1% m-nitrobenzyl alcohol (m-NBA) in mobile phases. The ion intensities of both CID
and PQD were adversely affected by increasing m/z of the precursor, with PQD more sensitive than CID. In addition to negating the 1/3 rule, PQD enhances direct bond cleavage
and generates patterns of fragment ions different from those of CID, particularly for peptides with a labile functional group
(e.g., phosphopeptides). The higher energy fragmentation pathway of PQD on peptide fragmentation was further compared to those
of CID and the quadrupole-type activation in parallel experiments. 相似文献
18.
Xiaojuan Li Cheng Lin Liang Han Catherine E. Costello Peter B. O’Connor 《Journal of the American Society for Mass Spectrometry》2010,21(4):646-656
Secondary fragmentations of three synthetic peptides (human αA crystallin peptide 1-11, the deamidated form of human βB2 crystallin peptide 4-14, and amyloid β peptide 25-35) were studied in both electron capture dissociation (ECD) and electron-transfer dissociation (ETD) mode. In
ECD, in addition to c and z· ion formations, charge remote fragmentations (CRF) of z· ions were abundant, resulting in internal
fragment formation or partial/entire side-chain losses from amino acids, sometimes several residues away from the backbone
cleavage site, and to some extent multiple side-chain losses. The internal fragments were observed in peptides with basic
residues located in the middle of the sequences, which was different from most tryptic peptides with basic residues located
at the C-terminus. These secondary cleavages were initiated by hydrogen abstraction at the α-, β-, or γ-position of the amino acid side chain. In comparison, ETD generates fewer CRF fragments than ECD. This secondary cleavage
study will facilitate ECD/ETD spectra interpretation, and help de novo sequencing and database searching. 相似文献
19.
In contrast to previous electron capture dissociation (ECD) studies, we find that electron transfer dissociation (ETD) of
Cu(II)–peptide complexes can generate c- and z-type product ions when the peptide has a sufficient number of strongly coordinating
residues. Double-resonance experiments, ion-molecule reactions, and collision-induced dissociation (CID) prove that the c
and z product ions are formed via typical radical pathways without the associated reduction of Cu(II), despite the high second
ionization energy of Cu. A positive correlation between the number of Cu(II) binding groups in the peptide sequence and the
extent of c and z ion formation was also observed. This trend is rationalized by considering that the recombination energy
of Cu(II) can be lowered by strong binding ligands to an extent that enables electron transfer to non-Cu sites (e.g., protonation
sites) to compete with Cu(II) reduction, thereby generating c/z ions in a manner similar to that observed for protonated (i.e.,
nonmetalated) peptides. 相似文献
20.
Liang X Liu J LeBlanc Y Covey T Ptak AC Brenna JT McLuckey SA 《Journal of the American Society for Mass Spectrometry》2007,18(10):1783-1788
The ability to generate gaseous doubly charged cations of glycerophosphocholine (GPC) lipids via electrospray ionization has made possible the evaluation of electron-transfer dissociation (ETD) for their structural characterization. Doubly sodiated GPC cations have been reacted with azobenzene radical anions in a linear ion trap mass spectrometer. The ion/ion reactions proceed through sodium transfer, electron-transfer, and complex formation. Electron-transfer reactions are shown to give rise to cleavage at each ester linkage with the subsequent loss of a neutral quaternary nitrogen moiety. Electron-transfer without dissociation produces [M + 2Na](+.) radical cations, which undergo collision-induced dissociation (CID) to give products that arise from bond cleavage of each fatty acid chain. The CID of the complex ions yields products similar to those produced directly from the electron-transfer reactions of doubly sodiated GPC, although with different relative abundances. These findings indicate that the analysis of GPC lipids by ETD in conjunction with CID can provide some structural information, such as the number of carbons, degree of unsaturation for each fatty acid substituent, and the positions of the fatty acid substituents; some information about the location of the double bonds may be present in low intensity CID product ions. 相似文献