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N-linked glycosylation (N-glycosylation) is a common protein post-translational modification, occurring on more than half of mammalian proteins; in striking contract with small molecule modifications (such as methylation, phosphorylation) with only single structures, N-glycosylation has multiple dimensional structural features (monosaccharide composition, sequence, linkage, anomer), which generates enormous N-glycan structures; and these structures widely regulate protein structure and functions. For the modification site, N-glycosylation occurs on the Asn residue among the consensus N-X-S/T/C (X≠P) motif; mutation-originated amino acid change may lead to loss of such an original motif and thus loss-of-glycosylation (LoG) or gain of such a new motif and thus gain-of-glycosylation (GoG). Both LoG and GoG generates new structures and functions of glycoproteins, which has been observed in the S protein of SARS-Cov-2 as well as malignant diseases. Here we report our glycoproteome-wide qualitative N-glycoproteomics characterization of GoGs in breast cancer Adriamycin drug resistance (ADR) cells (MCF-7/ADR) and cancer stem cells (MCF-7/ADR CSCs); comprehensive N-glycosite and N-glycan structure information at the intact N-glycopeptide level were reported. [Display omitted] • The method of building the putative gain-of-glycosylation (GoG) protein database is established • The glycoproteome level characterization of GoGs is benchmarked with two cell lines • GoGs from common mutations including MUTAGEN, VARIANT and VAR_SEQ are demonstrated. [ABSTRACT FROM AUTHOR]

For top-down protein database search and identification from tandem mass spectra, our isotopic envelope fingerprinting search algorithm and ProteinGoggle search engine have demonstrated their strength of efficiently resolving heavily overlapping data as well separating non-ideal data with non-ideal isotopic envelopes from ideal ones with ideal isotopic envelopes. Here we report our updated ProteinGoggle 2.0 for intact protein database search with full-capacity. The indispensable updates include users' optional definition of dynamic post-translational modifications and static chemical labeling during database creation, comprehensive dissociation methods and ion series, as well as a Proteoform Score for each proteoform. ProteinGoggle has previously been benchmarked with both collision-based dissociation (CID, HCD) and electron-based dissociation (ETD) data of either intact proteins or intact proteomes. Here we report our further benchmarking of the new version of ProteinGoggle with publically available photon-based dissociation (UVPD) data ( http://hdl.handle.net/2022/17316 ) of intact E. coli ribosomal proteins. Biological significance Protein species (aka proteoforms) function at their molecular level, and diverse structures and biological roles of every proteoform come from often co-occurring proteolysis, amino acid variation and post-translational modifications. Complete and high-throughput capture of this combinatorial information of proteoforms has become possible in evolving top-down proteomics; yet, various methods and technologies, especially database search and bioinformatics identification tools, in the top-down pipeline are still in their infancy stages and demand intensive research and development. [ABSTRACT FROM AUTHOR]

N-glycosylation is a common post-translational modification (PTM) in plants that possesses important biological functions including protein folding, protein quality control, protein stability and protein-protein interactions. Nowadays, the interest in analysis of glycoproteins using mass spectrometry is increasing because of advances in instrumentation and automatic data analysis tools. Here, we describe the progresses in mass spectrometry-based N-glycomics and N-glycoproteomics in plants. We also provide a comprehensive summary of N-glycan structures in plants according to the biosynthetic rules and up-to-date reports, which serves as a theoretical database for all N-glycan-related search engines. [Display omitted] • Methods and application progresses in mass spectrometry-based N-glycomics was comprehensively reviewed. • Methods and application progresses in mass spectrometry-based N-glycoproteomics was comprehensively reviewed. • Structural characteristics and core structures of plant N-glycans were summarized as a theoretical reference database. [ABSTRACT FROM AUTHOR]

N-glycosylation is one of the most frequently occurring protein post-translational modifications (PTMs) with broad cellular, physiological and pathological relevance. Mass spectrometry-based N-glycomics has become the state-of-the-art instrumental analytical pipeline for sensitive, high-throughput and comprehensive characterization of N-glycans and N-glycomes. Improvement and new development of methods in N-glycan release, enrichment, derivatization, isotopic labeling, separation, ionization, MS, tandem MS and informatics accompany side-by-side wider and deeper application. This review provides a comprehensive update of mass spectrometry-based qualitative and quantitative N-glycomics in the years of 2017–2018. Image 1 • MS-based N-glycomics is the best tool for high-throughput profiling of N-glycans. • Qualitative information of N-glycans at multi-level are readily available. • Updated progresses in frontier methods and applications in 2017–2018 are reviewed. [ABSTRACT FROM AUTHOR]

Phosphorylation is one of the most important and widely studied protein post-translational modifications. Tandem mass spectrometry using higher-energy collisional dissociation has evolved into a state-of-the-art analytical platform for both phosphorylation identification and site localization. Tens of thousands of phosphopeptides can now be routinely identified from a single shotgun proteomics study; site localization, however, is much more complicated and many challenges still exist. Here, we report our development of P-bracket using direct experimental evidence of phospho-containing site-determining product ions for accurate site localization without the need for additional FLR control. A P-bracket is defined as a complementary product ion pair that forms a bracket to confine a phosphorylation event to a unique site. P-bracket has been successfully benchmarked with a set of six synthetic phosphopeptides with a single phosphorylation event, a set of 96 synthetic peptides and phosphopeptide reference libraries, and two HeLa phosphopeptide LC-MS/MS (HCD) datasets; Accurate phosphosite localization by P-bracket will greatly enhance identification confidence of phosphopeptides and contribute to structural and functional studies of phosphoproteins. [ABSTRACT FROM AUTHOR]

Neutral loss and internal product ions have been found to be significant in both peptide and protein tandem mass spectra and they have been proposed to be included in database search and for protein identification. In addition to common canonical b/y ions in collision-based dissociation or c/z ions in electron-based dissociation, inclusion of neutral loss and internal product ions would certainly make better use of tandem mass spectra data; however, their ultimate utility for protein identification with false discovery rate control remains unclear. Here we report our proteome-level utility benchmarking of neutral loss and internal product ions with tandem mass spectra of intact E. coli proteome. Utility of internal product ions was further evaluated at the protein level using selected tandem mass spectra of individual E. coli proteins. We found that both neutral loss and internal products ions do not have direct utility for protein identification when they were used for scoring of P Score; but they do have indirect utility for provision of more canonical b/y ions when they are included in the database search and overlapping ions between different ion types are resolved. Biological significance Tandem mass spectrometry has evolved to be a state-of-the-art method for characterization of protein primary structures (including amino acid sequence, post-translational modifications (PTMs) as well as their site location), where full study and utilization tandem mass spectra and product ions are indispensable. This primary structure information is essential for higher order structure and eventual function study of proteins. [ABSTRACT FROM AUTHOR]