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Crescimento, esporulação e virulência do inóculo de Cercospora piaropi, agente de biocontrole do aguapé

Ávila,Zilá R. de; Pitelli,Robinson A.
Fonte: Sociedade Brasileira de Fitopatologia Publicador: Sociedade Brasileira de Fitopatologia
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2004 Português
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O presente ensaio foi realizado com o objetivo de avaliar a produção de biomassa micelial bem como a esporulação de Cercospora piaropi, nos meios líquidos V8, ETD (Extrato de Tomate Diluído) e BD (Batata - Dextrose), em períodos de cultivo de 96, 120, 144 e 168 h, sob agitação constante. Adicionalmente foi avaliado o efeito de períodos de desidratação da biomassa micelial (24, 48, 72, 96 e 120 h) sobre a esporulação. Os inóculos obtidos foram avaliados quanto à severidade da doença em plantas de aguapé (Eichhornia crassipes). De acordo com os resultados, o meio ETD proporcionou maior crescimento micelial em relação aos meios BD e V8, destacando-se o período de 144 h de agitação. Entretanto, o meio V8 induziu esporulação superior do patógeno, quando cultivado por 120 h. Os inóculos obtidos nos meios V8 e ETD causaram maiores valores de severidade da doença. O período de desidratação da biomassa micelial a partir de 72 h favoreceu maior produção de conídios. Não houve efeito do período de desidratação sobre a severidade da doença.

Revealing the Dynamics of the 20 S Proteasome Phosphoproteome : A Combined CID and Electron Transfer Dissociation Approach*S⃞

Lu, Haojie; Zong, Chenggong; Wang, Yueju; Young, Glen W.; Deng, Ning; Souda, Pete; Li, Xiaohai; Whitelegge, Julian; Drews, Oliver; Yang, Peng-Yuan; Ping, Peipei
Fonte: American Society for Biochemistry and Molecular Biology Publicador: American Society for Biochemistry and Molecular Biology
Tipo: Artigo de Revista Científica
Publicado em /11/2008 Português
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The 20 S proteasomes play a critical role in intracellular homeostasis and stress response. Their function is tuned by covalent modifications, such as phosphorylation. In this study, we performed a comprehensive characterization of the phosphoproteome for the 20 S proteasome complexes in both the murine heart and liver. A platform combining parallel approaches in differential sample fractionation (SDS-PAGE, IEF, and two-dimensional electrophoresis), enzymatic digestion (trypsin and chymotrypsin), phosphopeptide enrichment (TiO2), and peptide fragmentation (CID and electron transfer dissociation (ETD)) has proven to be essential for identifying low abundance phosphopeptides. As a result, a total of 52 phosphorylation identifications were made in mammalian tissues; 44 of them were novel. These identifications include single (serine, threonine, and tyrosine) and dual phosphorylation peptides. 34 phosphopeptides were identified by CID; 10 phosphopeptides, including a key modification on the catalytically essential β5 subunit, were identified only by ETD; eight phosphopeptides were shared identifications by both CID and ETD. Besides the commonly shared phosphorylation sites, unique sites were detected in the murine heart and liver, documenting variances in phosphorylation between tissues within the proteasome populations. Furthermore the biological significance of these 20 S phosphoproteomes was evaluated. The role of cAMP-dependent protein kinase A (PKA) to modulate these phosphoproteomes was examined. Using a proteomics approach...

Enrichment and Analysis of Non-enzymatically Glycated Peptides: Boronate Affinity Chromatography Coupled with Electron Transfer Dissociation Mass Spectrometry

Zhang, Qibin; Tang, Ning; Brock, Jonathan W. C.; Mottaz, Heather M.; Ames, Jennifer M.; Baynes, John W.; Smith, Richard D.; Metz, Thomas O.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
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Non-enzymatic glycation of peptides and proteins by D-glucose has important implications in the pathogenesis of diabetes mellitus, particularly in the development of diabetic complications. However, no effective high-throughput methods exist for identifying proteins containing this low abundance post-translational modification in bottom-up proteomic studies. In this report, phenylboronate affinity chromatography was used in a two-step enrichment scheme to selectively isolate first glycated proteins and then glycated, tryptic peptides from human serum glycated in vitro. Enriched peptides were subsequently analyzed by alternating electron transfer dissociation (ETD) and collision induced dissociation (CID) tandem mass spectrometry. ETD fragmentation mode permitted identification of a significantly higher number of glycated peptides (87.6% of all identified peptides) versus CID mode (17.0% of all identified peptides), when utilizing enrichment on first the protein and then the peptide level. This study illustrates that phenylboronate affinity chromatography coupled with LC-MS/MS and using ETD as the fragmentation mode is an efficient approach for analysis of glycated proteins and may have broad application in studies of diabetes mellitus.

Decision Tree-Driven Tandem Mass Spectrometry for Shotgun Proteomics

Swaney, Danielle L.; McAlister, Graeme C.; Coon, Joshua J.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
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Mass spectrometry (MS) has become a key technology for modern large-scale protein sequencing. Tandem MS (MS/MS) — the process of peptide ion dissociation followed by mass-to-charge (m/z) analysis — is the critical component of MS approaches. Recent advances in mass spectrometry now permit two discrete, and complementary, types of peptide ion fragmentation — collision-activated dissociation (CAD) and electron transfer dissociation (ETD) on a single instrument. To exploit this complementarity and increase sequencing success rates, we designed and embedded a data dependent-decision tree algorithm (DT) to make unsupervised, real-time decisions of which fragmentation method to employ based on precursor charge (z) and m/z. Large-scale proteome analysis of Saccharomyces cerevisiae and human embryonic stem cells (hES) with the DT algorithm netted 53,055 peptide identifications — besting either CAD (38,293) or ETD (39,507) alone. That trend was maintained upon application of the DT method to phosphoproteomics, yielding 7,422 vs. either 2,801 (CAD) or 5,874 (ETD) phosphopeptides.

Implementation of Electron-Transfer Dissociation on a Hybrid Linear Ion Trap–Orbitrap Mass Spectrometer

McAlister, Graeme C.; Phanstiel, Doug; Good, David M.; Berggren, W. Travis; Coon, Joshua J.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
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We describe the adaptation of a hybrid quadrupole linear ion trap–orbitrap mass spectrometer to accommodate electron-transfer ion/ion reactions (ETD) for peptide and protein characterization. The method utilizes pulsed, dual electrospray ion sources and requires minimal instrument modification. Switching between cation and reagent anion injection schemes is automated and accomplished within a few hundred milliseconds. Ion/ion reactions are conducted within the linear ion trap, after which the c- and z-type product ions are passed to the orbitrap for high-resolution m/z analysis. With this arrangement, mass accuracies are typically measured to within 2 ppm at a resolving power of ~60 000. Using large peptides and intact proteins, we demonstrate such capabilities will accelerate our ability to interrogate high-mass species. To illustrate compatibility with automated data-dependent analysis and subsequent data processing, we couple the technique with an online chromatographic separation of a yeast whole-cell lysate followed by peptide identification using ProSight PC. Fairly long pulsing times and relatively low ET efficiency, as compared to conventional ETD instrumentation, are the main drawbacks of this approach. Still, our results suggest that the implementation of ETD on sensitive...

Dual Electrospray Ion Source for Electron-Transfer Dissociation on a Hybrid Linear Ion Trap–Orbitrap Mass Spectrometer

Williams, D. Keith; McAlister, Graeme C.; Good, David M.; Coon, Joshua J.; Muddiman, David C.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
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A dual electrospray ionization source (ESI) has been modified to simultaneously produce cations and anions, one from each emitter, for performing rapid electron-transfer dissociation (ETD) ion/ion reactions on a hybrid linear ion trap–orbitrap mass spectrometer. Unlike the pulsed dual ESI sources that were used to generate ETD reagent ions, this source separates the emitters in space, rather than time, by physically switching which one is in front of the atmospheric inlet. The new arrangement allows for substantially enhanced spray stability and decreased switching times (≤30 ms), allowing for more tandem-MS spectra per unit time. Herein, we demonstrate the stability of the ETD anion population and the ability to identify several c- and z-type product ions from multiply protonated peptide cations.

Analysis of non-enzymatically glycated peptides: neutral-loss-triggered MS3 versus multi-stage activation tandem mass spectrometry

Zhang, Qibin; Petyuk, Vladislav A.; Schepmoes, Athena A.; Orton, Daniel J.; Monroe, Matthew E.; Yang, Feng; Smith, Richard D.; Metz, Thomas O.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /10/2008 Português
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Non-enzymatic glycation of tissue proteins has important implications in the development of complications of diabetes mellitus. While electron transfer dissociation (ETD) has been shown to outperform collision-induced dissociation (CID) in sequencing glycated peptides by tandem mass spectrometry, ETD instrumentation is not yet widely available and often suffers from significantly lower sensitivity than CID. In this study, we evaluated different advanced CID techniques (i.e., neutral-loss-triggered MS3 and multi-stage activation) during liquid chromatography/multi-stage mass spectrometric (LC/MSn) analyses of Amadori-modified peptides enriched from human serum glycated in vitro. During neutral-loss-triggered MS3 experiments, MS3 scans triggered by neutral losses of 3 H2O or 3 H2O + HCHO produced similar results in terms of glycated peptide identifications. However, neutral losses of 3 H2O resulted in significantly more glycated peptide identifications during multi-stage activation experiments. Overall, the multi-stage activation approach produced more glycated peptide identifications, while the neutral-loss-triggered MS3 approach resulted in much higher specificity. Both techniques are viable alternatives to ETD for identifying glycated peptides.

Probing the Mechanism of Electron Capture and Electron Transfer Dissociation Using Tags with Variable Electron Affinity

Sohn, Chang Ho; Chung, Cheol K.; Yin, Sheng; Ramachandran, Prasanna; Loo, Joseph A.; Beauchamp, J. L.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 22/04/2009 Português
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Electron capture dissociation (ECD) and electron transfer dissociation (ETD) of doubly protonated electron affinity (EA)-tuned peptides were studied to further illuminate the mechanism of these processes. The model peptide FQpSEEQQQTEDELQDK, containing a phosphoserine residue, was converted to EA-tuned peptides via β-elimination and Michael addition of various thiol compounds. These include propanyl, benzyl, 4-cyanobenzyl, perfluorobenzyl, 3,5-dicyanobenzyl, 3-nitrobenzyl and 3,5-dinitrobenzyl structural moieties, having a range of EA from -1.15 to 1.65 eV, excluding the propanyl group. Typical ECD or ETD backbone fragmentations are completely inhibited in peptides with substituent tags having EA over 1.00 eV, which are referred to as electron predators in this work. Nearly identical rates of electron capture by the dications substituted by the benzyl (EA = -1.15 eV) and 3-nitrobenzyl (EA = 1.00 eV) moieties are observed, which indicates the similarity of electron capture cross sections for the two derivatized peptides. This observation leads to the inference that electron capture kinetics are governed by the long range electron-dication interaction and are not affected by side chain derivatives with positive EA. Once an electron is captured to high-n Rydberg states...

Affinity Enrichment and Characterization of Mucin Core-1 Type Glycopeptides from Bovine Serum*

Darula, Zsuzsanna; Medzihradszky, Katalin F.
Fonte: The American Society for Biochemistry and Molecular Biology Publicador: The American Society for Biochemistry and Molecular Biology
Tipo: Artigo de Revista Científica
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The lack of consensus sequence, common core structure, and universal endoglycosidase for the release of O-linked oligosaccharides makes O-glycosylation more difficult to tackle than N-glycosylation. Structural elucidation by mass spectrometry is usually inconclusive as the CID spectra of most glycopeptides are dominated by carbohydrate-related fragments, preventing peptide identification. In addition, O-linked structures also undergo a gas-phase rearrangement reaction, which eliminates the sugar without leaving a telltale sign at its former attachment site. In the present study we report the enrichment and mass spectrometric analysis of proteins from bovine serum bearing Galβ1–3GalNAcα (mucin core-1 type) structures and the analysis of O-linked glycopeptides utilizing electron transfer dissociation and high resolution, high mass accuracy precursor ion measurements. Electron transfer dissociation (ETD) analysis of intact glycopeptides provided sufficient information for the identification of several glycosylation sites. However, glycopeptides frequently feature precursor ions of low charge density (m/z > ∼850) that will not undergo efficient ETD fragmentation. Exoglycosidase digestion was utilized to reduce the mass of the molecules while retaining their charge. ETD analysis of species modified by a single GalNAc at each site was significantly more successful in the characterization of multiply modified molecules. We report the unambiguous identification of 21 novel glycosylation sites. We also detail the limitations of the enrichment method as well as the ETD analysis.

Charge Prediction Machine: A tool for inferring precursor charge states of Electron Transfer Dissociation tandem mass spectra

Carvalho, Paulo C; Cociorva, Daniel; Wong, Catherine; Carvalho, Maria da Gloria da C; Barbosa, Valmir C; Yates, John R
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 01/03/2009 Português
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Electron Transfer Dissociation (ETD) can dissociate highly charged ions. Efficient analysis of ions dissociated with ETD requires accurate determination of charge states for calculation of molecular weight. We created an algorithm to assign the charge state of ions often used for ETD. The program, Charge Prediction Machine (CPM), uses Bayesian decision theory to account for different charge reduction processes encountered in ETD, and can also handle multiplex spectra. CPM correctly assigned charge states to 98% of the 13,097 MS2 spectra from a combined dataset of four experiments. In a comparison between CPM and a competing program, Charger (ThermoFisher), CPM produced half the mistakes.

Precursor charge state prediction for electron transfer dissociation tandem mass spectra

Sharma, Vagisha; Eng, Jimmy K.; Feldman, Sergey; von Haller, Priska D.; MacCoss, Michael J.; Noble, William S.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 01/10/2010 Português
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Electron-transfer dissociation (ETD) induces fragmentation along the peptide backbone by transferring an electron from a radical anion to a protonated peptide. In contrast with collision induced dissociation, side chains and modifications such as phosphorylation are left intact through the ETD process. Because the precursor charge state is an important input to MS/MS sequence database search tools, the ability to accurately determine the precursor charge is helpful for the identification process. Furthermore, because ETD can be applied to large, highly charged peptides, the need for accurate precursor charge state determination is magnified. Otherwise, each spectrum must be searched repeatedly using a large range of possible precursor charge states. To address this problem, we have developed an ETD charge state prediction tool based on support vector machine classifiers that is demonstrated to exhibit superior classification accuracy while minimizing the overall number of predicted charge states. The tool is freely available, open source, cross platform compatible, and demonstrated to perform well when compared with an existing charge state prediction tool. The program is available from http://code.google.com/p/etdz/.

Simultaneous Glycan-Peptide Characterization Using Hydrophilic Interaction Chromatography and Parallel Fragmentation by CID, Higher Energy Collisional Dissociation, and Electron Transfer Dissociation MS Applied to the N-Linked Glycoproteome of Campylobacter jejuni*

Scott, Nichollas E.; Parker, Benjamin L.; Connolly, Angela M.; Paulech, Jana; Edwards, Alistair V. G.; Crossett, Ben; Falconer, Linda; Kolarich, Daniel; Djordjevic, Steven P.; Højrup, Peter; Packer, Nicolle H.; Larsen, Martin R.; Cordwell, Stuart J.
Fonte: The American Society for Biochemistry and Molecular Biology Publicador: The American Society for Biochemistry and Molecular Biology
Tipo: Artigo de Revista Científica
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Campylobacter jejuni is a gastrointestinal pathogen that is able to modify membrane and periplasmic proteins by the N-linked addition of a 7-residue glycan at the strict attachment motif (D/E)XNX(S/T). Strategies for a comprehensive analysis of the targets of glycosylation, however, are hampered by the resistance of the glycan-peptide bond to enzymatic digestion or β-elimination and have previously concentrated on soluble glycoproteins compatible with lectin affinity and gel-based approaches. We developed strategies for enriching C. jejuni HB93-13 glycopeptides using zwitterionic hydrophilic interaction chromatography and examined novel fragmentation, including collision-induced dissociation (CID) and higher energy collisional (C-trap) dissociation (HCD) as well as CID/electron transfer dissociation (ETD) mass spectrometry. CID/HCD enabled the identification of glycan structure and peptide backbone, allowing glycopeptide identification, whereas CID/ETD enabled the elucidation of glycosylation sites by maintaining the glycan-peptide linkage. A total of 130 glycopeptides, representing 75 glycosylation sites, were identified from LC-MS/MS using zwitterionic hydrophilic interaction chromatography coupled to CID/HCD and CID/ETD. CID/HCD provided the majority of the identifications (73 sites) compared with ETD (26 sites). We also examined soluble glycoproteins by soybean agglutinin affinity and two-dimensional electrophoresis and identified a further six glycosylation sites. This study more than doubles the number of confirmed N-linked glycosylation sites in C. jejuni and is the first to utilize HCD fragmentation for glycopeptide identification with intact glycan. We also show that hydrophobic integral membrane proteins are significant targets of glycosylation in this organism. Our data demonstrate that peptide-centric approaches coupled to novel mass spectrometric fragmentation techniques may be suitable for application to eukaryotic glycoproteins for simultaneous elucidation of glycan structures and peptide sequence.

Analysis of Intact Monoclonal Antibody IgG1 by Electron Transfer Dissociation Orbitrap FTMS*

Fornelli, Luca; Damoc, Eugen; Thomas, Paul M.; Kelleher, Neil L.; Aizikov, Konstantin; Denisov, Eduard; Makarov, Alexander; Tsybin, Yury O.
Fonte: The American Society for Biochemistry and Molecular Biology Publicador: The American Society for Biochemistry and Molecular Biology
Tipo: Artigo de Revista Científica
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The primary structural information of proteins employed as biotherapeutics is essential if one wishes to understand their structure–function relationship, as well as in the rational design of new therapeutics and for quality control. Given both the large size (around 150 kDa) and the structural complexity of intact immunoglobulin G (IgG), which includes a variable number of disulfide bridges, its extensive fragmentation and subsequent sequence determination by means of tandem mass spectrometry (MS) are challenging. Here, we applied electron transfer dissociation (ETD), implemented on a hybrid Orbitrap Fourier transform mass spectrometer (FTMS), to analyze a commercial recombinant IgG in a liquid chromatography (LC)-tandem mass spectrometry (MS/MS) top-down experiment. The lack of sensitivity typically observed during the top-down MS of large proteins was addressed by averaging time-domain transients recorded in different LC-MS/MS experiments before performing Fourier transform signal processing. The results demonstrate that an improved signal-to-noise ratio, along with the higher resolution and mass accuracy provided by Orbitrap FTMS (relative to previous applications of top-down ETD-based proteomics on IgG), is essential for comprehensive analysis. Specifically...

Electron Transfer Dissociation: Effects of Cation Charge State on Product Partitioning in Ion/Ion Electron Transfer to Multiply Protonated Polypeptides

Liu, Jian; McLuckey, Scott A.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 15/12/2012 Português
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The effect of cation charge state on product partitioning in the gas-phase ion/ion electron transfer reactions of multiply protonated tryptic peptides, model peptides, and relatively large peptides with singly charged radical anions has been examined. In particular, partitioning into various competing channels, such as proton transfer (PT) versus electron transfer (ET), electron transfer with subsequent dissociation (ETD) versus electron transfer with no dissociation (ET,noD), and fragmentation of backbone bonds versus fragmentation of side chains, was measured quantitatively as a function of peptide charge state to allow insights to be drawn about the fundamental aspects of ion/ion reactions that lead to ETD. The ET channel increases relative to the PT channel, ETD increases relative to ET,noD, and fragmentation at backbone bonds increases relative to side-chain cleavages as cation charge state increases. The increase in ET versus PT with charge state is consistent with a Landau-Zener based curve-crossing model. An optimum charge state for ET is predicted by the model for the ground state-to-ground state reaction. However, when the population of excited product ion states is considered, it is possible that a decrease in ET efficiency as charge state increases will not be observed due to the possibility of the population of excited electronic states of the products. Several factors can contribute to the increase in ETD versus ET...

Comparison of Proteome Discoverer and PEAKS Studio for Phosphoproteome Analysis

Wojtkiewicz, Melinda; Wiederin, Jayme; Ciborowski, Pawel; Olszowy, Pawel
Fonte: Association of Biomolecular Resource Facilities Publicador: Association of Biomolecular Resource Facilities
Tipo: Artigo de Revista Científica
Publicado em /05/2013 Português
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Phosphorylation of proteins is a reversible post-translational modification that is fundamental in the regulation of cellular processes, such as protein function, cellular signaling and protein-complex formation. The ability to perform a global analysis of phosphoproteome will give us insight as to how mechanisms of proteins and pathways might become altered due to changing experimental conditions. Because only a fraction of proteins or any given protein is phosphorylated, enrichment of sample for phosphoproteins or phosphopeptides is essential to the success of identification. Briefly, 100 ug of mouse whole cell lysate was digested in-solution with trypsin overnight. Samples were cleaned-up using PepClean columns, and then processed using TiO2 Phosphopeptide Enrichment and Clean-up Kit (Pierce, Inc.). The enriched samples were injected onto nano-LC-LTQ Orbitrap with ETD in configuration of HCD and ETD as two microscans complementing information from MS/MS spectra. The acquisition method was created in data-dependent mode with one precursor scan in the Orbitrap, followed by fragmentation of the 4 most abundant peaks in both ETD detected in the LTQ, and in HCD detected in the Orbitrap. Tolerances were set to 10 ppm for the Orbitrap precursors and fragments while 0.8 Da for the ETD fragments. The following dynamic modifications were applied: Phospho/+79.966 Da (S...

SEQUENCE ANALYSIS OF PEPTIDE:OLIGONUCLEOTIDE HETEROCONJUGATES BY ELECTRON CAPTURE DISSOCIATION AND ELECTRON TRANSFER DISSOCIATION

Krivos, Kady L.; Limbach, Patrick A.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
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Mass spectrometry analysis of protein-nucleic acid cross-links is challenging due to the dramatically different chemical properties of the two components. Identifying specific sites of attachment between proteins and nucleic acids requires methods that enable sequencing of both the peptide and oligonucleotide component of the heteroconjugate cross-link. While collision-induced dissociation (CID) has previously been used for sequencing such heteroconjugates, CID generates fragmentation along the phosphodiester backbone of the oligonucleotide preferentially. The result is a reduction in peptide fragmentation within the heteroconjugate. In this work, we have examined the effectiveness of electron capture dissociation (ECD) and electron transfer dissociation (ETD) for sequencing heteroconjugates. Both methods were found to yield preferential fragmentation of the peptide component of a peptide:oligonucleotide heteroconjugate, with minimal differences in sequence coverage between these two electron-induced dissociation methods. Sequence coverage was found to increase with increasing charge state of the heteroconjugate, but decreases with increasing size of the oligonucleotide component. To overcome potential intermolecular interactions between the two components of the heteroconjugate...

Improved Identification and Relative Quantification of Sites of Peptide and Protein Oxidation for Hydroxyl Radical Footprinting

Li, Xiaoyan; Li, Zixuan; Xie, Boer; Sharp, Joshua S.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
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Protein oxidation is typically associated with oxidative stress and aging and affects protein function in normal and pathological processes. Additionally, deliberate oxidative labeling is used to probe protein structure and protein-ligand interactions in hydroxyl radical protein footprinting (HRPF). Oxidation often occurs at multiple sites, leading to mixtures of oxidation isomers that differ only by the site of modification. We utilized sets of synthetic, isomeric “oxidized” peptides to test and compare the ability of electron-transfer dissociation (ETD) and collision-induced dissociation (CID), as well as nano-ultra high performance liquid chromatography (nanoUPLC) separation, to quantitate oxidation isomers with one oxidation at multiple adjacent sites in mixtures of peptides. Tandem mass spectrometry by ETD generates fragment ion ratios that accurately report on relative oxidative modification extent on specific sites, regardless of the charge state of the precursor ion. Conversely, CID was found to generate quantitative MS/MS product ions only at the higher precursor charge state. Oxidized isomers having multiple sites of oxidation in each of two peptide sequences in HRPF product of protein Robo-1 Ig1-2, a protein involved in nervous system axon guidance...

Transfer of planar orders onto a sphere: formation and properties of complex topological defects

Roshal, D. S.; Petrov, C. Yu.; Myasnikova, A. E.; Rochal, S. B.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 30/09/2013 Português
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General topological principles how to transfer the planar orders onto a sphere are considered. Formation of extended topological defects (ETDs), which have a reconstructed inner structure surrounded by perfect initial order, is discussed. Topological charge of the ETD can be determined from the shape of a characteristic polygon bounding the defect. Relation between the total topological charge of all defects in the spherical structure and the type of initial planar order is found. It is also demonstrated that in the spherical hexagonal crystal a dislocation located in the ETD area is actually absorbed by it, because the order outside the defect doesn't display existence of dislocation in any way. For the case of singly connected spherical hexagonal order arising from mutual repulsion of N particles (N < 1000) only triangulation of the order inside the ETD regions recovers the linear scars which represent a narrow parts of wider ETD areas.; Comment: 11 pictures, 6 figures

Probing the mechanism of electron capture and electron transfer dissociation using tags with variable electron affinity

Sohn, Chang Ho; Chung, Cheol K.; Yin, Sheng; Ramachandran, Prasanna; Loo, Joseph A.; Beauchamp, J. L.
Fonte: American Chemical Society Publicador: American Chemical Society
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em 22/04/2009 Português
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Electron capture dissociation (ECD) and electron transfer dissociation (ETD) of doubly protonated electron affinity (EA)-tuned peptides were studied to further illuminate the mechanism of these processes. The model peptide FQpSEEQQQTEDELQDK, containing a phosphoserine residue, was converted to EA-tuned peptides via β-elimination and Michael addition of various thiol compounds. These include propanyl, benzyl, 4-cyanobenzyl, perfluorobenzyl, 3,5-dicyanobenzyl, 3-nitrobenzyl, and 3,5-dinitrobenzyl structural moieties, having a range of EA from −1.15 to +1.65 eV, excluding the propanyl group. Typical ECD or ETD backbone fragmentations are completely inhibited in peptides with substituent tags having EA over 1.00 eV, which are referred to as electron predators in this work. Nearly identical rates of electron capture by the dications substituted by the benzyl (EA = −1.15 eV) and 3-nitrobenzyl (EA = 1.00 eV) moieties are observed, which indicates the similarity of electron capture cross sections for the two derivatized peptides. This observation leads to the inference that electron capture kinetics are governed by the long-range electron−dication interaction and are not affected by side chain derivatives with positive EA. Once an electron is captured to high-n Rydberg states...

Electronic Theses and Dissertations in Current Research Information Systems

Schöpfel, Joachim; Zendulková, Danica; Fatemi, Omid
Fonte: euroCRIS Publicador: euroCRIS
Tipo: Conference Paper
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Delivered at the CRIS2014 Conference in Rome; published in Procedia Computer Science 33 (Jul 2014).; Contains conference paper (8 pages) and presentations by Joachim Schöpfel (12 slides) and Omar Fatemi (14 slides).; Electronic theses and dissertations (ETD) represent a significant part of academic publications. They contain valuable information about academic research, in particular on research projects, institutions and experts. This information can be useful for the management of expertise and skills of persons and organisations in the current research information systems (CRIS). The paper provides an overview on projects and initiatives linking ETD and CRIS infrastructures, with empirical insight from existing systems in Slovakia, Iran and France. The paper reviews also the way the Common European Research Information Format (CERIF) integrates the specific information related to ETD (results, links, second level elements, semantics…). The discussion puts the focus on metadata, interoperability and complementary material (data). The findings allow for the framing of some recommendations on the integration of ETD in CRIS.