The Experts below are selected from a list of 288 Experts worldwide ranked by ideXlab platform
Patrice Courvalin - One of the best experts on this subject based on the ideXlab platform.
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Evolution of glycopeptide resistance.
Evolutionary Biology of Bacterial and Fungal Pathogens, 2008Co-Authors: Patrice CourvalinAbstract:This chapter briefly reviews the mode of action and the mechanism of bacterial resistance to Glycopeptides, as exemplified by the VanB type, and discusses its diversity, regulation, evolution, origin, and recent dissemination to methicillin-resistant Staphylococcus aureus. Classification of glycopeptide resistance is based on the primary sequence of the structural genes for the resistance ligases. Although the six types of resistance involve related enzymic functions, they can be distinguished by the location of the corresponding genes and by the mode of regulation of gene expression. An interesting phenomenon that has developed in some VanB- and VanA-type enterococci is vancomycin dependence. These glycopeptide-dependent strains are also able to grow in the absence of Glycopeptides if supplied with the dipeptide D-Ala-D-Ala, confirming that they are unable to produce the ligase encoded by the chromosomal ddl gene. The vanF operon is composed of five genes (vanYF, vanZF, vanHF, vanF, and vanXF) encoding homologues of VanY, VanZ, VanH, VanA, and VanX, and the genes essential for resistance (vanHF, vanF, and vanXF) are organized and oriented as in VanA-type strains. The evolutionary lineage of these groups of homologous genes is not clear, but they may have a common ancestor, or Paenibacillus could be a progenitor of the resistance operons acquired by enterococci. Conjugal transfer of plasmids that have acquired Tn1546-like elements by transposition appears to be responsible for the spread of glycopeptide resistance in enterococci.
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Resistance to Glycopeptides in gram-positive pathogens.
Gram-Positive Pathogens Second Edition, 2006Co-Authors: Henry S. Fraimow, Patrice CourvalinAbstract:Glycopeptide antimicrobials are natural products that are produced by various soil-dwelling species of the order Actinomycetales such as Amycolatopsis orientalis and Amycolatopsis coloradensis. With the recent emergence of glycopeptide-resistant enterococci and staphylococci, there has been renewed interest by the pharmaceutical industry in the development of modified semisynthetic Glycopeptides with enhanced activity against resistant gram-positive pathogens including glycopeptide-resistant organisms. Due to Glycopeptides' unique mechanism of action and ability to interfere with multiple critical reactions in peptidoglycan synthesis, acquired resistance to Glycopeptides was deemed unlikely. The mechanisms of acquired resistance to Glycopeptides in enterococci have been well characterized and reflect changes in target analogous to those in intrinsically resistant organisms. The newer, semisynthetic Glycopeptides oritavancin and telavancin have enhanced activity against some strains of enterococci with acquired glycopeptide resistance. The basis of both intrinsic and acquired glycopeptide resistance in enterococci involves alteration of the composition of the terminal dipeptide in muramyl pentapeptide cell wall precursors, resulting in a structure with decreased binding affinity for Glycopeptides. Two additional enterococcal resistance genotypes, vanE and vanG, have also recently been described. Both are characterized by low-level vancomycin resistance mediated through the synthesis of precursors terminating in D-Ala-DSer analogous to the mechanism of VanC-type resistance. The chromosomally located five-gene vanE resistance cluster from Enterococcus faecalis BM4405 is organized very similarly to the vanC operon and includes genes encoding the VanE ligase, the VanXYE D,D-dipeptidase-D,D-carboxypeptidase, and the VanTE serine racemase, as well as the VanRESE two-component regulator.
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Acquired and intrinsic glycopeptide resistance in enterococci
International Journal of Antimicrobial Agents, 2000Co-Authors: Y Gholizadeh, Patrice CourvalinAbstract:Enterococci are Gram-positive cocci responsible for severe human infections, such as endocarditis, meningitis, and septicemia and constitute an increasingly frequent cause of nosocomial infections. Enterococci are resistant to nearly all classes of drugs including, since 1986, Glycopeptides. Vancomycin and teicoplanin act by blocking cell wall formation and resistance is due to synthesis of modified late peptidoglycan precursors. Glycopeptide resistance can be intrinsic or acquired and strains may be resistant to vancomycin and teicoplanin, or to vancomycin only. Five types of glycopeptide resistance and their biochemical mechanisms have been described in enterococci. Clinical isolates that are dependent on vancomycin for growth have been isolated. Data suggest a dual origin for resistance: glycopeptide-producing organisms or enterococcal species intrinsically resistant to these drugs.
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Update on vancomycin resistance
Int.J.Clin.Pract., 2000Co-Authors: B Perichon, Patrice CourvalinAbstract:Enterococci can be responsible for severe infections such as endocarditis, meningitis and septicaemia and are one of the most important causes of nosocomial infections. Resistance in enterococci concerns many classes of antibiotics including, since 1986, Glycopeptides. These antibiotics act by blocking cell wall formation, and resistance is due to synthesis of modified peptidoglycan precursors. Resistance can be acquired or intrinsic and strains may be resistant to vancomycin and teicoplanin, or to vancomycin only. Five types of glycopeptide resistance and their biochemical mechanisms have been described. Furthermore, strains that are dependent on vancomycin for growth have been isolated from clinical samples. Data suggest that resistance could originate in glycopeptide-producing organisms or in enterococcal species intrinsically resistant to these antibiotics
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Mechanisms and implications of glycopeptide resistance in enterococci
The American Journal of Medicine, 1991Co-Authors: Eliane Derlot, Patrice CourvalinAbstract:Abstract Glycopeptide resistance is recent in enterococci and its expression is inducible by Glycopeptides. Two phenotypes can be distinguished: (a) resistance to high levels of vancomycin and teicoplanin, and (b) resistance to low levels of vancomycin only. There is no cross-resistance between Glycopeptides, glycolipodepsipeptides (ramoplanin), and lipopeptides (daptomycin). The determinants conferring low-level resistance are nontransferable and presumably chromosomal. High-level resistance is plasmid-mediated and the plasmids range from 34 to 40 kb, are self-transferable, and encode various resistance combinations. All plasmids share the same glycopeptide resistance determinant, which is distinct from that conferring low-level resistance. Induction of resistance is associated with induction of about a 40 kDa protein. We have determined the sequence of the vanA gene encoding one such resistance protein designated VANA. Amino acid sequence similarity was detected between VANA and d-Ala: d-Ala ligases from Enterobacteriaceae. Complementation analysis in Escherichia coli indicated that VANA possesses d-Ala: d-Ala ligase activity and is therefore related to enzymes that catalyze synthesis of glycopeptide target, i.e., terminal d-Ala-d-Ala of peptidoglycan precursors. The contribution of VANA to synthesis of peptidoglycan in the presence of Glycopeptides is unknown: VANA could bind to d-Ala-d-Ala, preventing the binding of the drugs; could modify the target of the drug; and could be a ligase with novel specificity.
Manfred Wuhrer - One of the best experts on this subject based on the ideXlab platform.
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Linkage-specific sialic acid derivatization for MALDI-TOF-MS profiling of IgG Glycopeptides.
Analytical Chemistry, 2015Co-Authors: Noortje De Haan, Karli R. Reiding, Markus Haberger, Dietmar Reusch, David Falck, Manfred WuhrerAbstract:Glycosylation is a common co- and post-translational protein modification, having a large influence on protein properties like conformation and solubility. Furthermore, glycosylation is an important determinant of efficacy and clearance of biopharmaceuticals such as immunoglobulin G (IgG). Matrix-assisted laser desorption/ionization (MALDI)-time-of-flight (TOF)-mass spectrometry (MS) shows potential for the site-specific glycosylation analysis of IgG at the glycopeptide level. With this approach, however, important information about glycopeptide sialylation is not duly covered because of in-source and metastable decay of the sialylated species. Here, we present a highly repeatable sialic acid derivatization method to allow subclass-specific MALDI-TOF-MS analysis of tryptic IgG Glycopeptides. The method, employing dimethylamidation with the carboxylic acid activator 1-ethyl-3-(3-dimethylamino)propyl)carbodiimide (EDC) and the catalyst 1-hydroxybenzotriazole (HOBt), results in different masses for the funct...
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Recent advances in hydrophilic interaction liquid chromatography (HILIC) for structural glycomics
Electrophoresis, 2011Co-Authors: Gerhild Zauner, André M Deelder, Manfred WuhrerAbstract:This review presents recent progress in employing hydrophilic interaction liquid chromatography (HILIC) for glycan and Glycopeptides analysis. After an introduction of this technique, the following themes are addressed: (i) implementation of HILIC in large-scale studies for analyzing the human plasma N-glycome; (ii) the use of HILIC UPLC (ultrahigh pressure liquid chromatography) for fast high-resolution runs and its successful application with online MS for glycan and glycopeptide analysis; (iii) high-throughput profiling using HILIC solid-phase extraction in combination with MS detection; (iv) HILIC sample preparation for CE and CGE; (v) the latest glycoproteomic approaches implementing HILIC separation; (vi) future perspectives of HILIC including its use in large-scale glycoproteomics studies such as the analysis of entire glycoproteomes at the glycopeptide level.
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protein glycosylation analysis by hilic lc ms of proteinase k generated n and o Glycopeptides
Journal of Separation Science, 2010Co-Authors: Gerhild Zauner, André M Deelder, Carolien A M Koeleman, Manfred WuhrerAbstract:Analysis of protein glycosylation is essential in order to correlate certain disease types with oligosaccharide structures on proteins. Here, a method for the MS characterization of site-specific protein glycosylation is presented. Using asialofetuin and fetuin as model substances, a protocol for glycopeptide dissection was developed based on unspecific proteolysis by Proteinase K. The resulting Glycopeptides were then resolved by nanoscale hydrophilic interaction liquid chromatography-electrospray multistage MS. The early elution range of O-Glycopeptides was clearly separated from the late elution range of N-Glycopeptides. Glycopeptides were analyzed by ion trap-MS/MS, which revealed fragmentations of glycosidic linkages and some peptide backbone cleavages; MS3 spectra predominantly exhibited cleavages of the peptide backbone and provided essential information on the peptide sequence. The previously reported N- and O-glycan attachment sites of fetuin could be confirmed; moreover using our method, the occupation of a new, additional O-glycosylation site serine 296 was found. In conclusion, this approach appears to be a valuable technique for in-depth analysis of the site-specific N-glycosylation and O-glycosylation of individual glycoproteins.
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glycoproteomics based on tandem mass spectrometry of Glycopeptides
Journal of Chromatography B, 2007Co-Authors: Manfred Wuhrer, André M Deelder, Isabel M Catalina, Cornelis H HokkeAbstract:Next to the identification of proteins and the determination of their expression levels, the analysis of post-translational modifications (PTM) is becoming an increasingly important aspect in proteomics. Here, we review mass spectrometric (MS) techniques for the study of protein glycosylation at the glycopeptide level. Enrichment and separation techniques for glycoproteins and Glycopeptides from complex (glyco-)protein mixtures and digests are summarized. Various tandem MS (MS/MS) techniques for the analysis of Glycopeptides are described and compared with respect to the information they provide on peptide sequence, glycan attachment site and glycan structure. Approaches using electrospray ionization and matrix-assisted laser desorption/ionization (MALDI) of Glycopeptides are presented and the following fragmentation techniques in glycopeptide analysis are compared: collision-induced fragmentation on different types of instruments, metastable fragmentation after MALDI ionization, infrared multi-photon dissociation, electron-capture dissociation and electron-transfer dissociation. This review discusses the potential and limitations of tandem mass spectrometry of Glycopeptides as a tool in structural glycoproteomics.
Ulla Mandel - One of the best experts on this subject based on the ideXlab platform.
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Characterization of an immunodominant cancer-specific O-glycopeptide epitope in murine podoplanin (OTS8)
Glycoconjugate Journal, 2010Co-Authors: Catharina Steentoft, Katrine T.-b. G. Schjoldager, Emiliano Cló, Johannes W. Pedersen, Knud Jensen, Ola Blixt, Ulla Mandel, Steven B. Levery, Henrik ClausenAbstract:Auto-antibodies induced by cancer represent promising sensitive biomarkers and probes to identify immunotherapeutic targets without immunological tolerance. Surprisingly few epitopes for such auto-antibodies have been identified to date. Recently, a cancer-specific syngeneic murine monoclonal antibody 237, developed to a spontaneous murine fibrosarcoma, was shown to be directed to murine podoplanin (OTS8) with truncated Tn O-glycans. Our understanding of such cancer-specific auto-antibodies to truncated glycoforms of glycoproteins is limited. Here we have investigated immunogenicity of a chemoenzymatically produced Tn-glycopeptide derived from the putative murine podoplanin O-glycopeptide epitope. We found that the Tn O-glycopeptide was highly immunogenic in mice and produced a Tn-glycoform specific response with no reactivity against unglycosylated peptides or the O-glycopeptide with extended O-glycan (STn and T glycoforms). The immunodominant epitope was strictly dependent on the peptide sequence, required Tn at a specific single Thr residue (Thr^77), and antibodies to the epitope were not found in naive mice. We further tested a Tn O-glycopeptide library derived from human podoplanin by microarray analysis and demonstrated that the epitope was not conserved in man. We also tested human cancer sera for potential auto-antibodies to similar epitopes, but did not detect such antibodies to the Tn-library of podoplanin. The reagents and methods developed will be valuable for further studies of the nature and timing of induction of auto-antibodies to distinct O-glycopeptide epitopes induced by cancer. The results demonstrate that truncated O-Glycopeptides constitute highly distinct antibody epitopes with great potential as targets for biomarkers and immunotherapeutics.
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Cancer biomarkers defined by autoantibody signatures to aberrant O-glycopeptide epitopes
Cancer Research, 2010Co-Authors: Hans H. Wandall, Govind Ragupathi, Phil O. Livingston, Michael A. Hollingsworth, Johannes W. Pedersen, Ola Blixt, Mads Agervig Tarp, Ulla Mandel, Eric P. Bennett, Joyce Taylor-papadimitriouAbstract:Autoantibodies to cancer antigens hold promise as biomarkers for early detection of cancer. Proteins that are aberrantly processed in cancer cells are likely to present autoantibody targets. The extracellular mucin MUC1 is overexpressed and aberrantly glycosylated in many cancers; thus, we evaluated whether autoantibodies generated to aberrant O-glycoforms of MUC1 might serve as sensitive diagnostic biomarkers for cancer. Using an antibody-based glycoprofiling ELISA assay, we documented that aberrant truncated glycoforms were not detected in sera of cancer patients. An O-glycopeptide microarray was developed that detected IgG antibodies to aberrant O-glycopeptide epitopes in patients vaccinated with a keyhole limpet hemocyanin-conjugated truncated MUC1 peptide. We detected cancer-associated IgG autoantibodies in sera from breast, ovarian, and prostate cancer patients against different aberrent O-glycopeptide epitopes derived from MUC1. These autoantibodies represent a previously unaddressed source of sensitive biomarkers for early detection of cancer. The methods we have developed for chemoenzymatic synthesis of O-Glycopeptides on microarrays may allow for broader mining of the entire cancer O-glycopeptidome. ©2010 AACR.
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chemoenzymatically synthesized multimeric tn stn muc1 Glycopeptides elicit cancer specific anti muc1 antibody responses and override tolerance
Glycobiology, 2006Co-Authors: Anne Louise Sorensen, Mads Agervig Tarp, Ulla Mandel, Celso A. Reis, Kavitha Ramachandran, Vasanthi Sankaranarayanan, Tilo Schwientek, Ros Graham, Joyce TaylorpapadimitriouAbstract:The MUC1 mucin represents a prime target antigen for cancer immunotherapy because it is abundantly expressed and aberrantly glycosylated in carcinomas. Attempts to generate strong humoral immunity to MUC1 by immunization with peptides have generally failed partly because of tolerance. In this study, we have developed chemoenzymatic synthesis of extended MUC1 TR Glycopeptides with cancer-associated O-glycosylation using a panel of recombinant human glycosyltransferases. MUC1 Glycopeptides with different densities of Tn and STn glycoforms conjugated to KLH were used as immunogens to evaluate an optimal vaccine design. Glycopeptides with complete 0-glycan occupancy (five sites per repeat) elicited the strongest antibody response reacting with MUC1 expressed in breast cancer cell lines in both Balb/c and MUC1.Tg mice. The elicited humoral immune response showed remarkable specificity for cancer cells suggesting that the glycopeptide design holds promise as a cancer vaccine. The elicited immune responses were directed to combined glycopeptide epitopes, and both peptide sequence and carbohydrate structures were important for the antigen. A MAb (5E5) with similar specificity as the elicited immune response was generated and shown to have the same remarkable cancer specificity. This antibody may hold promise in diagnostic and immuno-preventive measures.
Heather Desaire - One of the best experts on this subject based on the ideXlab platform.
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Dissecting the dissociation patterns of fucosylated Glycopeptides undergoing CID: a case study in improving automated glycopeptide analysis scoring algorithms
Analytical Methods, 2017Co-Authors: Jude C. Lakbub, Xiaomeng Su, Eden P. Go, Heather DesaireAbstract:The need to investigate the fragmentation of fucosylated Glycopeptides is driven by recent work showing that at least one, and perhaps many, glycopeptide analysis scoring algorithms are less effective at identifying fucosylated Glycopeptides than non-fucosylated Glycopeptides. Herein, we study the CID fragmentation characteristics of fucosylated Glycopeptides and the scoring rules of the glycopeptide analysis software, GlycoPep Grader, in an effort to improve automated assignments of these important Glycopeptides. We identified some prominent product ions from a common fragmentation pathway of fucosylated Glycopeptides that were not accounted for in the scoring rules. Based on this finding, we propose new scoring rules for fucosylated Glycopeptides that can be incorporated into GlycoPep Grader and other similar analysis software tools to more accurately identify these species. The approach used here, to improve one particular scoring algorithm, could henceforth be used to improve any other algorithm that assigns Glycopeptides based on their MS/MS data.
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Two New Tools for Glycopeptide Analysis Researchers: A Glycopeptide Decoy Generator and a Large Data Set of Assigned CID Spectra of Glycopeptides
Journal of Proteome Research, 2017Co-Authors: Jude C. Lakbub, Xiaomeng Su, Eden P. Go, Milani Wijeweera Patabandige, Heather DesaireAbstract:The glycopeptide analysis field is tightly constrained by a lack of effective tools that translate mass spectrometry data into meaningful chemical information, and perhaps the most challenging aspect of building effective glycopeptide analysis software is designing an accurate scoring algorithm for MS/MS data. We provide the glycoproteomics community with two tools to address this challenge. The first tool, a curated set of 100 expert-assigned CID spectra of Glycopeptides, contains a diverse set of spectra from a variety of glycan types; the second tool, Glycopeptide Decoy Generator, is a new software application that generates glycopeptide decoys de novo. We developed these tools so that emerging methods of assigning Glycopeptides’ CID spectra could be rigorously tested. Software developers or those interested in developing skills in expert (manual) analysis can use these tools to facilitate their work. We demonstrate the tools’ utility in assessing the quality of one particular glycopeptide software pac...
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glycopep detector a tool for assigning mass spectrometry data of n linked Glycopeptides on the basis of their electron transfer dissociation spectra
Analytical Chemistry, 2013Co-Authors: Daniel F Clark, Eden P. Go, Heather DesaireAbstract:Electron transfer dissociation (ETD) is commonly used in fragmenting N-linked Glycopeptides in their mass spectral analyses to complement collision-induced dissociation (CID) experiments. The glycan remains intact through ETD, while the peptide backbone is cleaved, providing the sequence of amino acids for a glycopeptide. Nonetheless, data analysis is a major bottleneck to high-throughput glycopeptide identification based on ETD data, due to the complexity and diversity of ETD mass spectra compared to CID counterparts. GlycoPep Detector (GPD) is a web-based tool to address this challenge. It filters out noise peaks that interfere with glycopeptide sequencing, correlates input glycopeptide compositions with the ETD spectra, and assigns a score for each candidate. By considering multiple ion series (c-, z-, and y-ions) and scoring them separately, the software gives more weighting to the ion series that matches peaks of high intensity in the spectra. This feature enables the correct glycopeptide to receive ...
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Glycopeptide analysis: recent developments and applications
Molecular & Cellular Proteomics, 2013Co-Authors: Heather DesaireAbstract:Glycopeptide-based analysis is used to inform researchers about the glycans on one or more proteins. The method's key attractive feature is its ability to link glycosylation information to exact locations (glycosylation sites) on proteins. Numerous applications for glycopeptide analysis are known, and several examples are described herein. The techniques used to characterize Glycopeptides are still emerging, and recently, research focused on facilitating aspects of glycopeptide analysis has advanced significantly in the areas of sample preparation, MS fragmentation, and automation of data analysis. These recent developments, described herein, provide the foundation for the growth of glycopeptide analysis as a blossoming field.
Ola Blixt - One of the best experts on this subject based on the ideXlab platform.
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Synthesis of O-Glycopeptides and construction of glycopeptide microarrays.
Methods of Molecular Biology, 2020Co-Authors: Ola BlixtAbstract:O-glycosylation of proteins is an important modification which affects biological function and immunity. In this chapter, we provide protocols for efficient solid-phase O-glycopeptide synthesis (SPGPS) and protocols for the construction of glycopeptide microarray chips for screening applications. This will be exemplified for mucin-type Glycopeptides and the construction of glycopeptide microarrays. To this end, the protocols provided are particularly suited for small-scale robotic parallel synthesis. N-Terminal amine capping of deletion peptides during synthesis stands out as vital to this strategy. It allows for direct on-slide enrichment of the full-length target product and thereby bypasses tedious isolation and purification procedures.
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Characterization of an immunodominant cancer-specific O-glycopeptide epitope in murine podoplanin (OTS8)
Glycoconjugate Journal, 2010Co-Authors: Catharina Steentoft, Katrine T.-b. G. Schjoldager, Emiliano Cló, Johannes W. Pedersen, Knud Jensen, Ola Blixt, Ulla Mandel, Steven B. Levery, Henrik ClausenAbstract:Auto-antibodies induced by cancer represent promising sensitive biomarkers and probes to identify immunotherapeutic targets without immunological tolerance. Surprisingly few epitopes for such auto-antibodies have been identified to date. Recently, a cancer-specific syngeneic murine monoclonal antibody 237, developed to a spontaneous murine fibrosarcoma, was shown to be directed to murine podoplanin (OTS8) with truncated Tn O-glycans. Our understanding of such cancer-specific auto-antibodies to truncated glycoforms of glycoproteins is limited. Here we have investigated immunogenicity of a chemoenzymatically produced Tn-glycopeptide derived from the putative murine podoplanin O-glycopeptide epitope. We found that the Tn O-glycopeptide was highly immunogenic in mice and produced a Tn-glycoform specific response with no reactivity against unglycosylated peptides or the O-glycopeptide with extended O-glycan (STn and T glycoforms). The immunodominant epitope was strictly dependent on the peptide sequence, required Tn at a specific single Thr residue (Thr^77), and antibodies to the epitope were not found in naive mice. We further tested a Tn O-glycopeptide library derived from human podoplanin by microarray analysis and demonstrated that the epitope was not conserved in man. We also tested human cancer sera for potential auto-antibodies to similar epitopes, but did not detect such antibodies to the Tn-library of podoplanin. The reagents and methods developed will be valuable for further studies of the nature and timing of induction of auto-antibodies to distinct O-glycopeptide epitopes induced by cancer. The results demonstrate that truncated O-Glycopeptides constitute highly distinct antibody epitopes with great potential as targets for biomarkers and immunotherapeutics.
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Cancer biomarkers defined by autoantibody signatures to aberrant O-glycopeptide epitopes
Cancer Research, 2010Co-Authors: Hans H. Wandall, Govind Ragupathi, Phil O. Livingston, Michael A. Hollingsworth, Johannes W. Pedersen, Ola Blixt, Mads Agervig Tarp, Ulla Mandel, Eric P. Bennett, Joyce Taylor-papadimitriouAbstract:Autoantibodies to cancer antigens hold promise as biomarkers for early detection of cancer. Proteins that are aberrantly processed in cancer cells are likely to present autoantibody targets. The extracellular mucin MUC1 is overexpressed and aberrantly glycosylated in many cancers; thus, we evaluated whether autoantibodies generated to aberrant O-glycoforms of MUC1 might serve as sensitive diagnostic biomarkers for cancer. Using an antibody-based glycoprofiling ELISA assay, we documented that aberrant truncated glycoforms were not detected in sera of cancer patients. An O-glycopeptide microarray was developed that detected IgG antibodies to aberrant O-glycopeptide epitopes in patients vaccinated with a keyhole limpet hemocyanin-conjugated truncated MUC1 peptide. We detected cancer-associated IgG autoantibodies in sera from breast, ovarian, and prostate cancer patients against different aberrent O-glycopeptide epitopes derived from MUC1. These autoantibodies represent a previously unaddressed source of sensitive biomarkers for early detection of cancer. The methods we have developed for chemoenzymatic synthesis of O-Glycopeptides on microarrays may allow for broader mining of the entire cancer O-glycopeptidome. ©2010 AACR.