共查询到20条相似文献,搜索用时 15 毫秒
1.
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
2.
Mikhail M. Savitski Frank Fischer Toby Mathieson Gavain Sweetman Manja Lang Marcus Bantscheff 《Journal of the American Society for Mass Spectrometry》2010,21(10):1668-1679
Quantitative mass spectrometry-based proteomic assays often suffer from a lack of robustness and reproducibility. We here
describe a targeted mass spectrometric data acquisition strategy for affinity enriched subproteomes—in our case the kinome—that
enables a substantially improved reproducibility of detection, and improved quantification via isobaric tags. Inclusion mass
lists containing m/z, charge state, and retention time were created based on a set of 80 shotgun-type experiments performed under identical experimental
conditions. For each target protein, peptides were selected according to their frequency of observation and isobaric tag for
relative and absolute quantitation (iTRAQ) reporter ion quality. Retention times of selected peptides were aligned using similarity
driven pairwise alignment strategy yielding <1 min standard deviation for 4 h gradients. Multiple fragmentation of the same
peptides resulted in better statistics and more precise reporter ion based quantification without any loss in coverage. Overall,
24% more target proteins were quantified using the targeted data acquisition approach, and precision of quantification improved
by >1.5-fold. We also show that a combination of higher energy collisional dissociation (HCD) with collisional induced dissociation
(CID) outperformed pulsed-Q-dissociation (PQD) on the OrbitrapXL. With the CID/ HCD based targeted data acquisition approach
10% more quantifiable target proteins were identified and a 2-fold increase in quantification precision was achieved. We have
observed excellent reproducibility between different instruments, underlining the robustness of the approach. 相似文献
3.
Christian J. Koehler Magnus ?. Arntzen Achim Treumann Bernd Thiede 《Analytical and bioanalytical chemistry》2012,404(4):1103-1114
Isobaric peptide termini labeling (IPTL) is a quantification method which permits relative quantification using quantification points distributed throughout the whole tandem mass spectrometry (MS/MS) spectrum. It is based on the complementary derivatization of peptide termini with different isotopes resulting in isobaric peptides. Here, we use our recently developed software package IsobariQ to investigate how processing and data analysis parameters can improve IPTL data. Deisotoping provided cleaner MS/MS spectra and improved protein identification and quantification. Denoising should be used with caution because it may remove highly regulated ion pairs. An outlier detection algorithm on the ratios within every individual MS/MS spectrum was beneficial in removing false-positive quantification points. MS/MS spectra using IPTL typically contain two peptide series with complementary labels resulting in lower Mascot ion scores than non-labeled equivalent peptides. To avoid this penalty, the two chemical modifications for IPTL were specified as variables including satellite neutral losses of tetradeuterium with positive loss for the heavy isotopes and negative loss for the light isotopes. Thus, the less dominant complementary ion series were not considered for the scoring, which improved the ion scores significantly. In addition, we showed that IPTL was suitable for fragmentation by electron transfer dissociation (ETD) and higher energy collisionally activated dissociation (HCD) besides the already reported collision-induced dissociation (CID). Notably, ETD and HCD data can be identified and quantified using IsobariQ. ETD outperformed CID and HCD only for charge states ≥4+ but yielded in total fewer protein identifications and quantifications. In contrast, the high-resolution information of HCD fragmented peptides provided most identification and quantification results using the same scan speed. 相似文献
4.
Yi Zhang Scott B. Ficarro Shaojuan Li Jarrod A. Marto 《Journal of the American Society for Mass Spectrometry》2009,20(8):1425-1434
Despite the tremendous commercial success of radio frequency quadrupole ion traps for bottom-up proteomics studies, there
is growing evidence that peptides decorated with labile post-translational modifications are less amenable to low-energy,
resonate excitation MS/MS analysis. Moreover, multiplexed stable isotope reagents designed for MS/MS-based quantification
of peptides rely on accurate and robust detection of low-mass fragments for all precursors. Collectively these observations
suggest that beam-type or tandem in-space MS/MS measurements, such as that available on traditional triple quadrupole mass
spectrometers, may provide beneficial figures of merit for quantitative proteomics analyses. The recent introduction of a
multipole collision cell adjacent to an Orbitrap mass analyzer provides for higher energy collisionally activated dissociation
(HCD) with efficient capture of fragment ions over a wide mass range. Here we describe optimization of various instrument
and post-acquisition parameters that collectively provide for quantification of iTRAQ-labeled phosphorylated peptides isolated
from complex cell lysates. Peptides spanning a concentration dynamic range of 100:1 are readily quantified. Our results indicate
that appropriate parameterization of collision energy as a function of precursor m/z and z provides for optimal performance in terms of peptide identification and relative quantification by iTRAQ. Using this approach,
we readily identify activated signaling pathways downstream of oncogenic mutants of Flt-3 kinase in a model system of human
myeloid leukemia. 相似文献
5.
Doubly protonated peptides that undergo an electron transfer reaction without dissociation in a linear ion trap can be subjected to beam-type collisional activation upon transfer from the linear ion trap into an adjacent mass analyzer, as demonstrated here with a hybrid triple quadrupole/linear ion trap system. The activation can be promoted by use of a DC offset difference between the ion trap used for reaction and the ion trap into which the products are injected of 12-16 V, which gives rise to energetic collisions between the transferred ions and the collision/bath gas employed in the linear ion trap used for ion/ion reactions. Such a process can be executed routinely on hybrid linear ion trap/triple quadrupole tandem mass spectrometers and is demonstrated here with several model peptides as well as a few dozen tryptic peptides. Collisional activation of the peptide precursor ions that survive electron transfer frequently provides structural information that is absent from the precursor ions that fragment spontaneously upon electron transfer. The degree to which additional structural information is obtained by collisional activation of the surviving singly charged peptide ions depends upon peptide size. Little or no additional structural information is obtained from small peptides (<8 residues) due to the high electron transfer dissociation (ETD) efficiencies noted for these peptides as well as the extensive sequence information that tends to be forthcoming from ETD of such species. Collisional activation of the surviving electron transfer products provided greatest benefit for peptides of 8-15 residues. 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.
The modification of serine and threonine residues in proteins by a single N-acetylglucosamine (O-GlcNAc) residue is an emerging
post-translational modification (PTM) with broad biological implications. However, the systematic or large-scale analysis
of this PTM is hampered by several factors, including low stoichiometry and the lability of the O-glycosidic bond during tandem
mass spectrometry. Using a library of 72 synthetic glycopeptides, we developed a two-stage tandem MS approach consisting of
pulsed Q dissociation (PQD) for O-GlcNAc peptide detection and electron transfer dissociation (ETD) for identification and
site localization. Based on a set of O-GlcNAc specific fragment ions, we further developed a score (OScore) that discriminates
O-GlcNAc peptide spectra from spectra of unmodified peptides with 95% sensitivity and >99% specificity. Integrating the OScore
into the two-stage LC-MS/MS approach detected O-GlcNAc peptides in the low fmol range and at 10-fold better sensitivity than
a single data-dependent ETD tandem MS experiment. 相似文献
8.
Hart SR Lau KW Hao Z Broadhead R Portman N Hühmer A Gull K McKean PG Hubbard SJ Gaskell SJ 《Journal of the American Society for Mass Spectrometry》2009,20(2):167-175
The use of electron-transfer dissociation as an alternative peptide ion activation method for generation of protein sequence
information is examined here in comparison with the conventional method of choice, collisionally activated dissociation, using
a linear ion trapping instrument. Direct comparability between collisionally and electron-transfer-activated product ion data
were ensured by employing an activation-switching method during acquisition, sequentially activating precisely the same precursor
ion species with each fragmentation method in turn. Sequest (Thermo Fisher Scientific, San Jose, CA) searching of product
ion data generated an overlapping yet distinct pool of polypeptide identifications from the products of collisional and electron-transfer-mediated
activation products. To provide a highly confident set of protein recognitions, identification data were filtered using parameters
that achieved a peptide false discovery rate of 1%, with two or more independent peptide assignments required for each protein.
The use of electron transfer dissociation (ETD) has allowed us to identify additional peptides where the quality of product
ion data generated by collisionally activated dissociation (CAD) was insufficient to infer peptide sequence. Thus, a combined
ETD/CAD approach leads to the recognition of more peptides and proteins than are achieved using peptide analysis by CAD- or
ETD-based tandem mass spectrometry alone. 相似文献
9.
Comparison of the activation time effects and the internal energy distributions for the CID,PQD and HCD excitation modes
下载免费PDF全文
![点击此处可从《Journal of mass spectrometry : JMS》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Farid Ichou Adrian Schwarzenberg Denis Lesage Sandra Alves Christophe Junot Xavier Machuron‐Mandard Jean‐Claude Tabet 《Journal of mass spectrometry : JMS》2014,49(6):498-508
Reproducibility among different types of excitation modes is a major bottleneck in the field of tandem mass spectrometry library development in metabolomics. In this study, we specifically evaluated the influence of collision voltage and activation time parameters on tandem mass spectrometry spectra for various excitation modes [collision‐induced dissociation (CID), pulsed Q dissociation (PQD) and higher‐energy collision dissociation (HCD)] of Orbitrap‐based instruments. For this purpose, internal energy deposition was probed using an approach based on Rice–Rampserger–Kassel–Marcus modeling with three thermometer compounds of different degree of freedom (69, 228 and 420) and a thermal model. This model treats consecutively the activation and decomposition steps, and the survival precursor ion populations are characterized by truncated Maxwell–Boltzmann internal energy distributions. This study demonstrates that the activation time has a significant impact on MS/MS spectra using the CID and PQD modes. The proposed model seems suitable to describe the multiple collision regime in the PQD and HCD modes. Linear relationships between mean internal energy and collision voltage are shown for the latter modes and the three thermometer molecules. These results suggest that a calibration based on the collision voltage should provide reproducible for PQD, HCD to be compared with CID in tandem in space instruments. However, an important signal loss is observed in PQD excitation mode whatever the mass of the studied compounds, which may affect not only parent ions but also fragment ions depending on the fragmentation parameters. A calibration approach for the CID mode based on the variation of activation time parameter is more appropriate than one based on collision voltage. In fact, the activation time parameter in CID induces a modification of the collisional regime and thus helps control the orientation of the fragmentation pathways (competitive or consecutive dissociations). Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
10.
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
11.
Shannon L. Cook Olivier L. Collin Glen P. Jackson 《Journal of mass spectrometry : JMS》2009,44(8):1211-1223
Extensive backbone fragmentation resulting in a‐, b‐, c‐, x‐, y‐ and z‐type ions is observed of singly and doubly charged peptide ions through their interaction with a high kinetic energy beam of argon or helium metastable atoms in a modified quadrupole ion trap mass spectrometer. The ability to determine phosphorylation‐sites confirms the observation with previous reports and we report the new ability to distinguish between leucine and isoleucine residues and the ability to cleave two covalent bonds of the proline ring resulting in a‐, b‐, x‐, y‐, z‐ and w‐type ions. The fragmentation spectra indicate that fragmentation occurs through nonergodic radical ion chemistry akin to electron capture dissociation (ECD), electron transfer dissociation (ETD) and electron ionization dissociation mechanisms. However, metastable atom‐activated dissociation mass spectrometry demonstrates three apparent benefits to ECD and ETD: (1) the ability to fragment singly charged precursor ions, (2) the ability to fragment negatively charged ions and (3) the ability to cleave the proline ring that requires the cleavage of two covalent bonds. Helium metastable atoms generated more fragment ions than argon metastable atoms for both substance P and bradykinin regardless of the precursor ion charge state. Reaction times less than 250 ms and efficiencies approaching 5% are compatible with on‐line fragmentation, as would be desirable for bottom‐up proteomics applications. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
12.
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
13.
Samgina TY Vorontsov EA Gorshkov VA Artemenko KA Nifant'ev IE Kanawati B Schmitt-Kopplin P Zubarev RA Lebedev AT 《Journal of the American Society for Mass Spectrometry》2011,22(12):2246-2255
Mass spectrometry faces considerable difficulties in de novo sequencing of long non-tryptic peptides with S–S bonds. Long
disulfide-containing peptides brevinins 1E and 2Ec from frog Rana ridibunda were reduced and alkylated with nine novel and three known derivatizing agents. Eight of the novel reagents are maleimide
derivatives. Modified samples were subjected to MS/MS studies on FT-ICR and Orbitrap mass spectrometers using CAD/HCD or ECD/ETD
techniques. Procedures, fragmentation patterns, and sequence coverage for two peptides modified with 12 tags are described.
ECD/ETD and CAD fragmentation revealed complementary sequence information. Higher-energy collisionally activated dissociation
(HCD) sufficiently enhanced y-ions formation for brevinin 1E, but not for brevinin 2Ec. Some novel tags [N-benzylmaleimide, N-(2,6-dimethylphenyl)maleimide] along with known N-phenylmaleimide and iodoacetic acid showed high total sequence coverage taking into account combined ETD and HCD fragmentation.
Moreover, modification of long (34 residues) brevinin 2Ec with N-benzylmaleimide or N-(2,6-dimethylphenyl)maleimide yielded high sequence coverage and full C-terminal sequence determination with ECD alone. 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.
Lössner C Blackstock W Gunaratne J 《Journal of the American Society for Mass Spectrometry》2012,23(1):186-189
Pulsed Q collision induced dissociation (PQD) was introduced for isobaric tag quantification on linear ion traps to circumvent
the problem of the low-mass cut-off for collision induced dissociation (CID). Unfortunately, fragmentation efficiency is compromised
and PQD has found limited use for identification as well as quantification. We demonstrate that PQD has a comparable peptide
identification performance to CID on dual-pressure linear ion traps, opening the potential for wider use of isobaric tag quantification
on this new generation of linear ion traps. 相似文献
16.
Andrey N. Vilkov Victor V. Laiko Vladimir M. Doroshenko 《Journal of mass spectrometry : JMS》2009,44(4):477-484
A novel ion dissociation technique, which is capable of providing an efficient fragmentation of peptides at essential atmospheric pressure conditions, is developed. The fragmentation patterns observed often contain c‐type fragments that are specific to electron capture dissociation/electron transfer dissociation (ECD/ETD), along with the y‐/b‐type fragments that are specific to collision‐activated dissociation (CAD). In the presented experimental setup, ion fragmentation takes place within a flow reactor located in the atmospheric pressure region between the ion source and the mass spectrometer. According to a proposed mechanism, the fragmentation results from the interaction of ESI‐generated analyte ions with the gas‐phase radical species produced by a corona discharge source. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
17.
《Journal of mass spectrometry : JMS》2017,52(8):543-549
1,4,7,10‐Tetraazacyclododecane‐1,4,7,10‐tetraacetic acid (DOTA) derivatives are applied in quantitative proteomics owing to their ability to react with different functional groups, to harbor lanthanoides and hence their compatibility with molecular and elemental mass spectrometry. The new DOTA derivatives, namely Ln‐MeCAT‐Click and Ln‐DOTA‐Dimedone, allow efficient thiol labeling and targeting sulfenation as an important post‐translational modification, respectively. Quantitative applications require the investigation of fragmentation behavior of these reagents. Therefore, the fragmentation behavior of Ln‐MeCAT‐Click and Ln‐DOTA‐Dimedone was studied using collision‐induced dissociation (CID), infrared multiphoton dissociation (IRMPD) and higher‐energy collision dissociation (HCD) using different energy levels, and the efficiency of reporter ion production was estimated. The efficiency of characteristic fragment formation was in the order IRMPD > HCD (normal energy level) > CID. On the other hand, the application of HCD at high energy levels (HCD@HE; NCE > 250%) resulted in a significant increase in reporter ion production (33–54%). This new strategy was successfully applied to generate label‐specific reporter ions for DOTA amino labeling at the N‐termini and in a quantitative fashion for the estimation of amino:thiol ratio in peptides. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
18.
Christian K. Frese Dirk Nolting A. F. Maarten Altelaar Jens Griep-Raming Shabaz Mohammed Albert J. R. Heck 《Journal of the American Society for Mass Spectrometry》2013,24(11):1663-1670
Electron transfer dissociation (ETD) is commonly employed in ion traps utilizing rf fields that facilitate efficient electron transfer reactions. Here, we explore performing ETD in the HCD collision cell on an Orbitrap Velos instrument by applying a static DC gradient axially to the rods. This gradient enables simultaneous three dimensional, charge sign independent, trapping of cations and anions, initiating electron transfer reactions in the center of the HCD cell where oppositely charged ions clouds overlap. Here, we evaluate this mode of operation for a number of tryptic peptide populations and the top-down sequence analysis of ubiquitin. Our preliminary data show that performing ETD in the HCD cell provides similar fragmentation as ion trap-ETD but requires further optimization to match performance of ion trap-ETD. 相似文献
19.
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
20.
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