Project description:We developed TMMF strategy (Targeted MS strategy combined with Multi-Fragmentation) which provided plenty information of targeted glycopeptides based on complementary MS2 spectra from HCD, ETD and CID in a single MS run.
Project description:In this study we compared three different fragmentation techniques and two combined fragmentation schemes available on a novel tribrid mass spectrometer (Orbitrap Fusion Lumos, Themro Fisher Scientific) CID, HCD, ETD, ETD with supplemental CID (ETciD) and ETD with supplemental HCD (EThcD) on cross-linked peptides obtained by tryptic cleavage of SDA-cross-linked Human Serum Albumin (HSA). The three-dimensional structure of HSA has been resolved by X-ray crystallography [35] and is used as ground-truth to evaluate the identification results. Right choice of the fragmentation method allows increasing the number of identified linkage sites, increasing the sequence coverage of both linked peptides thereby reducing the second peptide problem, and increasing the precision of cross-link site calling.
Project description:Site-specific N-glycosylation characterization requires intact N-glycopeptide analysis based on suitable tandem mass spectrometry (MS/MS) method. Electron-transfer/higher-energy collisional dissociation (EThcD), stepped collision energy/higher-energy collisional dissociation (sceHCD), and higher-energy collision dissociation-product-dependent electron-transfer dissociation (HCD-pd-ETD) have emerged as valuable approaches for clinical glycoproteomics. However, each of them incurs some compromise, necessitating the performance comparisons when applied to the analysis of complex clinical samples (e.g., plasma, urine, cells, and tissue). Herein, we developed a hybrid mass spectrometry fragmentation method, EThcD-sceHCD, by combining EThcD and sceHCD. Moreover, we compared the performance of this method with those previous approaches (EThcD, sceHCD, HCD-pd-ETD, and sceHCD-pd-ETD) in the intact N-glycopeptide analysis, and determined its applicability for clinical N-glycoproteomic study.
Project description:IgG was collected from virgin and pregnant listeria challenged mouse plasma. Polyclonal IgG was analyzed by reduction, alkylation, and LC-MS with top-down MS/MS (HCD and ETD)to look for glycosylation PTMs
Project description:A key step in proteomics is the digestion of proteins into peptides, so far largely done by using trypsin. Tryptic digestion leads to peptides that in ESI-MS attain predominantly two charges, via protonation at the free N-terminus and at the C-terminal basic residue Arginine or Lysine. These peptides can be readily sequenced and identified by collision-induced dissociation (CID) or higher-energy collisional dissociation (HCD), as the fragmentation rules are well understood. Here we explore the trypsin mirror protease, LysargiNase, which cleaves equally specifically at Arg and Lys, albeit at the N-terminal end. The resulting peptides are therefore practically tryptic-alike in length and sequence, except that the two charges are now both positioned at the N-terminus. We compare the chromatographic separation properties, gas phase fragmentation behavior and (phospho)proteome sequence coverage of tryptic and LysargiNase peptides using electron-transfer dissociation (ETD), and for comparison HCD. We find that tryptic and LysargiNase peptides fragment nearly as mirror images. For LysargiNase predominantly N-terminal peptide ions (c-ions/ETD, b-ions/HCD) are formed, whereas for trypsin C-terminal fragment ions dominate (z-ions/ETD, y-ions/HCD). Especially during ETD LysargiNase peptides fragment into low-complexity, but information rich sequence ladders. We observe that trypsin and LysargiNase chart distinct parts of the (phospho)proteome. Therefore, we conclude that the collective use LysargiNase and Trypsin will benefit a more in-depth and reliable analysis of (phospho)proteomes.
Project description:Glycosylation is among the most abundant and diverse protein post-translational modifications (PTMs) identified to date. The structural analysis of this PTM is challenging due to the diverse monosaccharides which are not conserved among organisms, the branched nature of glycans, their isomeric structures, and heterogeneity in the glycan distribution at a given site. Glycoproteomics experiments have adopted the traditional high-throughput LC-MSn proteomics workflow to analyze site-specific glycosylation. However, comprehensive computational platforms for data analyses are scarce. To address this limitation, we present a comprehensive, open-source, modular software for glycoproteomics data analysis called GlycoPAT (GlycoProteomics Analysis Toolbox). The program introduces ‘SmallGlyPep’ as a minimal linear representation of glycopeptides for MSn data analysis. It enables MS/MS analysis of N- and O-linked glycosylation using a novel scoring scheme to rank the hits based on cross-correlation and probability based analysis. False discovery calculations, parallel computing facilities and user-friendly GUIs (Graphical User Interfaces) are also provided. GlycoPAT is used to analyze site-specific glycosylation on simple glycoproteins, protein mixtures and human plasma cryoprecipitate. The results show that the simultaneous consideration of peptide and glycan fragmentation enables high quality MS spectrum annotation in three common MS/MS fragmentation modes: CID, HCD and ETD.
Project description:Site-specific characterization of glycosylation requires intact glycopeptide analysis, and recent efforts have focused on how to best interrogate glycopeptides using tandem mass spectrometry (MS/MS). Beam-type collisional activation, i.e., higher-energy collisional dissociation (HCD), has been a valuable approach, but stepped collision energy HCD (sceHCD) and electron transfer dissociation with HCD supplemental activation (EThcD) have emerged as potentially more suitable alternatives. Both sceHCD and EThcD have been used with success in large-scale glycoproteomic experiments, but they each incur some degree of compromise. Furthermore, N-glycoproteomics has made significant progress in the last few years, and there is growing interest in extending this progress to O-glycoproteomics, which necessitates comparisons of method performance for the two classes of glycopeptides. Here, we systematically explore the advantages and disadvantages of conventional HCD, sceHCD, ETD, and EThcD for intact glycopeptide analysis and comment on their suitability for both N- and O-glycoproteomic applications. For N-glycopeptides, HCD and sceHCD generate similar numbers of identifications, although sceHCD generally provides higher quality spectra. Both significantly outperform EThcD methods, indicating that ETD-based methods are not required for routine N-glycoproteomics. Conversely, ETD-based methods, especially EThcD, are indispensable for site-specific analyses of O-glycopeptides. Our data show that O-glycopeptides cannot be robustly characterized with HCD-centric methods that are sufficient for N-glycopeptides, and glycoproteomic methods aiming to characterize O-glycopeptides must be constructed accordingly.
Project description:ADP-ribosylation is a posttranslational modification whose HCD products are dominated by complete or partial modification losses, complicating peptide sequencing and acceptor site localization efforts. We tested whether in-source CID performed on a quadrupole Orbitrap could convert ADPr to the smaller phosphoribose-H2O derivative to facilitate HCD-dependent peptide sequencing. Human macrophage like cell line THP-1-derived ADP-ribosyl (ADPr) peptides were analyzed on a quadrupole Orbitrap. We monitored the interconversion of ADPr (+541.061 Da) to phosphoribosyl-H2O (+193.997 Da) peptides while varying the source and high-field asymmetric waveform ion mobility mass spectrometry (FAIMS) compensation voltages. Xcorr and ptmRS were used to evaluate peptide sequencing and acceptor site confidence, respectively. In-source CID-HCD-derived phosphoribosyl-H2O acceptor sites were compared to those determined by EThcD, performed on a quadrupole ion trap Orbitrap. Interconversion of ADPr peptides to their phosphoribosyl-H2O derivatives increased with increasing source voltage (up to 50V), as judged by monitoring the corresponding modification loss ([adenosine monophosphate/AMP]+) and the number of identified phosphoribosyl-H2O peptide identifications. The average Xcorr increased from 1.36 (ADPr) to 2.26 (phosphoribosyl-H2O), similar to that achieved with EThcD for ADPr peptides (2.29). The number of high-confidence acceptor sites (>95%) also increased, from 31% (ADPr) to 70% (phosphoribosyl-H2O), which was comparable to EThcD (70%). In-source CID converts ADP-ribosyl to phosphoribosyl-H2O peptides that are more amenable to HCD-dependent peptide sequencing, providing an alternative method for acceptor site determination when ETD-based methods are not available.
Project description:Gaining a complete and unbiased understanding of the non-tryptic peptide repertoire presented by HLA-I complexes by LC-MS/MS is indispensable for therapy design for cancer, autoimmunity and infectious diseases. A serious concern in HLA peptide analysis is that the routinely used, collision-based fragmentation methods (CID/HCD) do not always render sufficiently informative MS2 spectra, whereby gaps in the fragmentation sequence coverage prevent unambiguous assignments. EThcD can be utilized to generate complementary ion series, i.e. b/y ions and c/z ions, resulting in richer, more informative MS2 spectra, thereby filling in the gaps. Here, we present data generated on a novel hybrid Orbitrap mass spectrometer, facilitating fast and efficient hybrid fragmentation due to the implementation of EThcD in the ion routing multipole. We hypothesized that this would enable more comprehensive and less error-prone analysis of immunopeptidomes at minimal costs in duty-cycle. First, we optimized ETD/EThcD methods using an elastase-digested cell lysate, as this contains peptides of similar length and charge distributions to immunopeptides. Next, we compared HCD and EThcD on immunopeptidomes originating from three cell lines with distinct HLA-I complexes that present peptides with varying physicochemical properties. We demonstrate that the new instrument not only enables efficient and fast ETD reactions, but when combined with collision-based supplemental activation, i.e. EThcD, also consistently increases the sequence coverage and identification of peptide sequences, otherwise missed by using solely HCD. We reveal several of the biochemical properties that make HLA peptides preferably identifiable by EThcD, with internal Arg residues being one of the most dominant determinants. Finally, we demonstrate the power of EThcD for the identification and localization of HLA peptides harboring post-translational modifications, focusing here on HLA Arg mono-/di-methylation. We foresee that this new instrument with efficient EThcD capabilities enhances not only immunopeptidomics analysis, but also analysis of peptides harboring post-translational modifications and de novo sequencing.