Identification of glycoconjugates in the urine of a patient with congenital disorder of glycosylation by high-resolution mass spectrometry

Life sciences and mass spectrometry: some personal reflections

Molecular analysis of biological systems by mass spectrometry was in focus of technological developments in the second half of the 20th century, in which the issues of chemical identification of high molecular diversity by biophysical instrumental methods appeared as a mission impossible. By developing dialogs between researchers dealing with life sciences and medicine on one side and technology developers on the other, new horizons toward deciphering, identifying and quantifying of complex systems became a reality. Contributions toward this goal can be today considered as pioneering efforts delivered by a number of researchers, including generations of motivated students and associates.

Glutathione-functionalized two-dimensional cobalt sulfide nanosheets for rapid and highly efficient enrichment of N-glycopeptides

Protein glycosylation plays pivotal role in a variety of biological processes and has association with many diseases. The highly efficient glycopeptide enrichment is essential for the mass spectrometry-based glycoproteome research to reduce interference from non-glycopeptides. In this study, novel glutathione-functionalized two-dimensional cobalt sulfide nanosheets (Co-S@Au-GSH) were synthesized for rapid and highly effective enrichment of glycopeptides. By using this nanomaterial, 34 and 21 N-glycopeptides were effectively captured from human serum immunoglobulin G (IgG) and horseradish peroxidase (HRP) digests, respectively. In addition, the Co-S@Au-GSH showed remarkable performance in N-glycopeptide extraction with high selectivity (HRP: BSA = 1:500), low limit of detection (0.5 fmol/μL), high binding capacity (150 mg/g), good reusability, and great robustness. Moreover, it was successfully applied in complex serum samples, demonstrating its excellent enrichment performance. These results indicated that this nanomaterial has great potential in complicated practice samples in glycoproteome determination.

Identification and structural characterization of novel O- and N-glycoforms in the urine of a Schindler disease patient by Orbitrap mass spectrometry

Schindler disease is an inherited metabolic disorder caused by the deficient activity of α-N-acetylgalactosaminidase enzyme. An accurate diagnosis requires, besides clinical examination, complex and costly biochemical and molecular genetic tests. In the last years, mass spectrometry (MS) based on nanofluidics and high-resolution instruments has become a successful alternative for disease diagnosis based on the investigation of O-glycopeptides in patient urine. A complex mixture of glycoforms extracted from the urine of a 3-year-old patient was investigated by Orbitrap MS equipped with Nanospray Flex Ion Source in the negative ion mode. For structural characterization of several molecular species, collision-induced dissociation MS² -MS³ was carried out using collision energy values within 20-60 eV range. By our approach, 39 novel species associated to this condition were identified, among which O-glycopeptides, free O-glycans and one structure corresponding to an N-glycan never characterized in the context of Schindler disease. The experiments conducted at a resolution of 60 000 allowed the discrimination and identification of a total number of 69 different species with an average mass accuracy of 9.87 ppm, an in-run reproducibility of almost 100%, an experiment-to-experiment and day-to-day reproducibility of about 95%. This study brings contributions in the diagnosis of Schindler disease through the elucidation of potential biomarker species in urine. Our multistage MS results completed with 39 new glycoforms the inventory of potential biomarker structures associated to Schindler disease. For the first time, an N-glycan was identified and structurally characterized in Schindler patient urine, which opens new research directions in the field. Copyright © 2015 John Wiley & Sons, Ltd.

Glycoproteomics-based identification of cancer biomarkers

Protein glycosylation is one of the most common posttranslational modifications in mammalian cells. It is involved in many biological pathways and molecular functions and is well suited for proteomics-based disease investigations. Aberrant protein glycosylation may be associated with disease processes. Specific glycoforms of glycoproteins may serve as potential biomarkers for the early detection of disease or as biomarkers for the evaluation of therapeutic efficacy for treatment of cancer, diabetes, and other diseases. Recent technological developments, including lectin affinity chromatography and mass spectrometry, have provided researchers the ability to obtain detailed information concerning protein glycosylation. These in-depth investigations, including profiling and quantifying glycoprotein expression, as well as comprehensive glycan structural analyses may provide important information leading to the development of disease-related biomarkers. This paper describes methodologies for the detection of cancer-related glycoprotein and glycan structural alterations and briefly summarizes several current cancer-related findings.

The impact of mass spectrometry in the diagnosis of congenital disorders of glycosylation

Contribution of mass spectrometry (MS) in the diagnosis and characterization of congenital disorders of glycosylation (CDG) has long been known. CDG type I diseases are characterized by the under-occupancy of protein N-glycosylation sites. Electrospray (ESI) MS and matrix assisted laser desorption ionization (MALDI) MS are effective for underglycosylation analyses of intact serum Transferrin (Tf) in CDG-I patients by mass determination of individual component glycoforms. Thus, high-throughput methods developed to speed-up analytical times found increasing application in clinical testing for CDG detection. ESI MS recognizable glycoform profiles of serum Tf have been reported in CDG-I different from PMM2-CDG and in individual CDG-II defects. MALDI MS analysis of acidic and neutral N-linked glycans released from total plasma or targeted glycoproteins, is the mainstream tool to explore abnormal oligosaccharide structure and changes in the relative amount of individual oligosaccharides in CDG-II patients. Here we briefly review state-of-the-art and updates of MS-based applications for the diagnosis of CDG with special emphasis to detectable glycosylation profiles reported in different CDG types.

Mass Spectrometry for the Analysis of Milk Oligosaccharides

Mass Spectrometry (MS) has emerged as an indispensable tool for the analysis of biomolecules due to its sensitivity, versatility and ease of applicability to complex samples. Nevertheless, the analysis of free oligosaccharides and protein bound sugars in secretions such as milk poses certain challenges. In this review, the benefits and limitations of different sample preparation approaches for the mass spectrometric analysis of free oligosaccharides and glycoproteins are discussed. Appropriate sample preparation is the first crucial step for successful mass spectrometric analysis. Different MS techniques and instrument combinations already successfully applied to the analysis of milk oligosaccharides are also introduced. Available tandem and MSn applications for the differentiation of structural isomers are described and their limitations discussed. This review is intended to give an overview on the available MS methodology and technology available for analysing various kinds of oligosaccharides in milk.

Chip-mass spectrometry for glycomic studies

The introduction of micro- and nanochip front end technologies for electrospray mass spectrometry addressed a major challenge in carbohydrate analysis: high sensitivity structural determination and heterogeneity assessment in high dynamic range mixtures of biological origin. Chip-enhanced electrospray ionization was demonstrated to provide reproducible performance irrespective of the type of carbohydrate, while the amenability of chip systems for coupling with different mass spectrometers greatly advance the chip/MS technique as a versatile key tool in glycomic studies. A more accurate representation of the glycan repertoire to include novel biologically-relevant information was achieved in different biological sources, asserting this technique as a valuable tool in glycan biomarker discovery and monitoring. Additionally, the integration of various analytical functions onto chip devices and direct hyphenation to MS proved its potential for glycan analysis during the recent years, whereby a new analytical tool is on the verge of maturation: lab-on-chip MS glycomics. The achievements until early beginning of 2007 on the implementation of chip- and functional integrated chip/MS in systems glycobiology studies are reviewed here.

Identification of Monosialylated N-glycoforms in the CDG Urinome by Ion Mobility Tandem Mass Spectrometry: The Potential for Clinical Applications

Introduction

A novel approach of ion mobility tandem mass spectrometry (IMS-MS/MS) is applied to analysis of human glycourinome to obtain carbohydrate pattern data of congenital disorders of glycosylation patient. Overlapping of the complex carbohydrate mass range landscape has been highly reduced upon IMS-MS procedure, allowing more efficient identification by mapping and sequencing of glycan precursor ions, following their separation by mobility, according to difference in drift time through the traveling wave IMS cell. Intact and truncated N- and O-glycan structures modified by sialylation and fucosylation were identified according to their drift time separated molecular ions and submitted to fragmentation in a narrow mass window.

IMS CID MS/MS Analysis

The fragmentation spectra generated from the IMS separated precursor ions contain series of fragment ions maintaining the same mobility as their parent ions, and the assignment accuracy can be significantly enhanced.

Conclusion

According to the specific fragment ion patterns, carbohydrate epitopes described to be involved in pathological processes were assigned. A high potential of this glycomics-based strategy for clinical applications can be presented.

Ion mobility mass spectrometry analysis of human glycourinome

Complex carbohydrates are macromolecules biosynthesized in nontemplate-type processes, bearing specific glycoepitopes involved in crucial recognition processes such as cell differentiation and cell-cell interactions. Chemical structure of single components in complex mixtures can be analyzed by mass spectrometry for determination of the size and sequence of monosaccharides involved, branching patterns, and substitution by fucose and sialic acids. For de novo identification of glycoforms in human urinome containing N- and O-free and amino acid-linked oligosaccharides, a novel method of ion mobility tandem mass spectrometry followed by computer-assisted assignment is described. Distinct patterns of ions nested specifically by their m/z values and their drift time are observed by IMS-MS. An additional peak capacity for identification of time-separated m/z values in the IMS TOF MS mode for differentiation of singly, doubly, and triply charged molecular ion species by ion mobility separation contributes to significant reduction of carbohydrate complexity in a given mass window. Profiling of glycoforms from human urinome represents a highly efficient approach for biomarker discovery and differential glycotarget identification, demonstrating potential for diagnosis of human diseases, as for congenital disorders of glycosylation.

MALDI-QTOFMS/MS identification of glycoforms from the urine of a CDG patient

Identification of single glycoconjugate components in a complex mixture from the urine of a patient suffering from a congenital disorder of glycosylation was probed by MALDIMS analysis on a hybrid quadrupole time-of-flight instrument. In negative ion mode, complex maps containing more than 50 ionic species were obtained and a number of molecular ions directly as-signed using a previously developed computer-assisted algorithm. To confirm the data and determine the carbohydrate sequence, single molecular ions were selected and submitted to fragmentation experiments. Interpretation of fragmentation spectra was also assisted by the soft-ware using alignment with spectra generated in silico. According to fragmentation data, the majority of glycoconjugate ionic species could be assigned to free oligosaccharides along with ten species tentatively assigned to glycopeptides. Following this approach for glycan identification by a combination of MALDI-QTOFMS and MS/MS experiments, computer-assisted assignment and fragment analysis, data for a potential glycan data base are produced. Of high benefit for this approach are two main factors: low sample consumption due to the high sensitivity of ion formation, and generation of only singly charged species in MALDIMS allowing interpretation with-out any deconvolution. In this experimental set-up, sequencing of single components from the MALDI maps by low energy CID followed by computer-assisted assignment and data base search is proposed as a most efficient strategy for the rapid identification of complex carbohydrate structures in clinical glycomics.

Sequencing of O-glycopeptides derived from an S-layer glycoprotein of Geobacillus stearothermophilus NRS 2004/3a containing up to 51 monosaccharide residues at a single glycosylation site by fourier transform ion cyclotron resonance infrared multiphoton dissociation mass spectrometry

The microheterogeneity of large sugar chains in glycopeptides from S-layer glycoproteins containing up to 51 monosaccharide residues at a single O-attachment site on a 12 amino acid peptide backbone was investigated by Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS). Structural elucidation of glycopeptides with the same amino acid sequence and different glycoforms, having such a high saccharide-to-peptide ratio, was achieved by applying infrared multiphoton dissociation (IRMPD) MS/MS for the first time. A 100% sequence coverage of the glycan chain and a 50% coverage of the peptide backbone fragmentation were obtained. The microheterogeneity of carbohydrate chains at the same glycosylation site, containing largely rhamnose, could have been reliably assessed.

Analysis of oversulfation in a chondroitin sulfate oligosaccharide fraction from bovine aorta by nanoelectrospray ionization quadrupole time-of-flight and Fourier-transform ion cyclotron resonance mass spectrometry

A combination of negative ion nano-electrospray ionization Fourier-transform ion cyclotron resonance and quadrupole time-of-flight mass spectrometry was applied to analysis of oversulfation in glycosaminoglycan oligosaccharides of the chondroitin sulfate type from bovine aorta. Taking advantage of the high-resolution and high mass accuracy provided by the FT-ICR instrument, a direct compositional assignment of all species present in the mixture can be obtained. An oligosaccharide fraction containing mainly hexasaccharides exhibited different levels of sulfation, indicated by the presence of species with regular sulfation pattern as well as oversulfated oligosaccharides with one additional sulfate group. Oversulfation can be directly identified from the high-resolution/high mass accuracy FT-ICR mass spectra according to their specific isotopic fine structure. Location of sulfate groups was analyzed by Q-TOF MS and low-energy CID MS/MS. Tetrasulfated hexasaccharides were analyzed by use of collision-induced dissociation at variable collision energy for an unambiguous assignment of the attachment site of the sulfate groups by minimizing unspecific neutral losses. Cleavage of glycosidic bonds gave rise to B- and C-type ions and their respective complementary Y- and Z-type fragment ions.

The use of mass spectrometry for the proteomic analysis of glycosylation

Of all protein PTMs, glycosylation is by far the most common, and is a target for proteomic research. Glycosylation plays key roles in controlling various cellular processes and the modifications of the glycan structures in diseases highlight the clinical importance of this PTM. Glycosylation analysis remains a difficult task. MS, in combination with modern separation methodologies, is one of the most powerful and versatile techniques for the structural analysis of glycoconjugates. This review describes methodologies based on MS for detailed characterization of glycoconjugates in complex biological samples at the sensitivity required for proteomic work.