Mass spectrometry-based analyses showing the effects of secretor and blood group status on salivary N-glycosylation

ANALYSIS OF CARBOHYDRATES AND GLYCOCONJUGATES BY MATRIX-ASSISTED LASER DESORPTION/IONIZATION MASS SPECTROMETRY: AN UPDATE FOR 2015-2016

This review is the ninth update of the original article published in 1999 on the application of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2016. Also included are papers that describe methods appropriate to analysis by MALDI, such as sample preparation techniques, even though the ionization method is not MALDI. Topics covered in the first part of the review include general aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, fragmentation and arrays. The second part of the review is devoted to applications to various structural types such as oligo- and poly-saccharides, glycoproteins, glycolipids, glycosides and biopharmaceuticals. Much of this material is presented in tabular form. The third part of the review covers medical and industrial applications of the technique, studies of enzyme reactions and applications to chemical synthesis. The reported work shows increasing use of combined new techniques such as ion mobility and the enormous impact that MALDI imaging is having. MALDI, although invented over 30 years ago is still an ideal technique for carbohydrate analysis and advancements in the technique and range of applications show no sign of deminishing. © 2020 Wiley Periodicals, Inc.

NEGATIVE ION MASS SPECTROMETRY FOR THE ANALYSIS OF N-LINKED GLYCANS

N-glycans from glycoproteins are complex, branched structures whose structural determination presents many analytical problems. Mass spectrometry, usually conducted in positive ion mode, often requires extensive sample manipulation, usually by derivatization such as permethylation, to provide the necessary structure-revealing fragment ions. The newer but, so far, lesser used negative ion techniques, on the contrary, provide a wealth of structural information not present in positive ion spectra that greatly simplify the analysis of these compounds and can usually be conducted without the need for derivatization. This review describes the use of negative ion mass spectrometry for the structural analysis of N-linked glycans and emphasises the many advantages that can be gained by this mode of operation. Biosynthesis and structures of the compounds are described followed by methods for release of the glycans from the protein. Methods for ionization are discussed with emphasis on matrix-assisted laser desorption/ionization (MALDI) and methods for producing negative ions from neutral compounds. Acidic glycans naturally give deprotonated species under most ionization conditions. Fragmentation of negative ions is discussed next with particular reference to those ions that are diagnostic for specific features such as the branching topology of the glycans and substitution positions of moieties such as fucose and sulfate, features that are often difficult to identify easily by conventional techniques such as positive ion fragmentation and exoglycosidase digestions. The advantages of negative over positive ions for this structural work are emphasised with an example of a series of glycans where all other methods failed to produce a structure. Fragmentation of derivatized glycans is discussed next, both with respect to derivatives at the reducing terminus of the molecules, and to methods for neutralization of the acidic groups on sialic acids to both stabilize them for MALDI analysis and to produce the diagnostic fragments seen with the neutral glycans. The use of ion mobility, combined with conventional mass spectrometry is described with emphasis on its use to extract clean glycan spectra both before and after fragmentation, to separate isomers and its use to extract additional information from separated fragment ions. A section on applications follows with examples of the identification of novel structures from lower organisms and tables listing the use of negative ions for structural identification of specific glycoproteins, glycans from viruses and uses in the biopharmaceutical industry and in medicine. The review concludes with a summary of the advantages and disadvantages of the technique. © 2020 John Wiley & Sons Ltd. Mass Spec Rev.

The Effect of Time on Blood Types of ABO Systems on Saliva Spots of Cigarette Butts for Forensic Identification

The identification process is not only carried out on the body of a victim of a crime, but identification can also be carried out on the evidence evidence found at the crime scene. The timing of a crime case and the time interval for collecting evidence of a crime is an obstacle in the process of identifying blood saliva on cigarette butts. Saliva will dry within an hour and forty minutes at room temperature and with the influence of various other factors saliva will dry in less than three hours. The purpose of this study was to determine the effect of the duration of temperature exposure on the protein levels of cigarette saliva in order to help the identification process of forensic blood groups. The time series design was used in this study where 18 filter cigarette butts were collected from 6 individuals who were subjected to research with blood types A, B and AB then incubated 1.3 and 6 hours. Examination of protein content was carried out using trizol reagent with UV spectrophotometer reading. The data was processed using non-parametric T-test statistics. There was a decrease in salivary levels in a predetermined time of 1, 3 and 6 hours. Cigarette butt saliva protein levels can still be detected within 1, 3 and 6 hours so that they can be used to help identify the forensic blood group from cigarette butt saliva.

Glycan recognition at the saliva - oral microbiome interface

The mouth is a first critical interface where most potentially harmful substances or pathogens contact the host environment. Adaptive and innate immune defense mechanisms are established there to inactivate or eliminate pathogenic microbes that traverse the oral environment on the way to their target organs and tissues. Protein and glycoprotein components of saliva play a particularly important role in modulating the oral microbiota and helping with the clearance of pathogens. It has long been acknowledged that glycobiological and glycoimmunological aspects play a pivotal role in oral host-microbe, microbe-host, and microbe-microbe interactions in the mouth. In this review, we aim to delineate how glycan-mediated host defense mechanisms in the oral cavity support human health. We will describe the role of glycans attached to large molecular size salivary glycoproteins which act as a first line of primordial host defense in the human mouth. We will further discuss how glycan recognition contributes to both colonization and clearance of oral microbes.

N-glycan microheterogeneity regulates interactions of plasma proteins

Glycosylation is one of the most common and complex posttranslation modifications that significantly influences protein structure and function. However, linking individual glycan structures to protein interactions remains challenging and typically requires multiple techniques. Here, we establish a mass-spectrometric approach to systematically dissect the microheterogeneity of two important serum proteins, α1-acid glycoprotein and haptoglobin, and relate glycan features to drug and protein-binding interaction kinetics. We found that the degree of N-glycan branching and extent of terminal fucosylation can attenuate or enhance these interactions, providing important insight into drug transport in plasma. Our study demonstrates an approach capable of investigating how protein glycosylation fine-tunes protein–drug interactions at the glycan-specific level and will prove universally useful for studying glycoprotein interactions.

Altered glycosylation patterns of plasma proteins are associated with autoimmune disorders and pathogenesis of various cancers. Elucidating glycoprotein microheterogeneity and relating subtle changes in the glycan structural repertoire to changes in protein–protein, or protein–small molecule interactions, remains a significant challenge in glycobiology. Here, we apply mass spectrometry-based approaches to elucidate the global and site-specific microheterogeneity of two plasma proteins: α1-acid glycoprotein (AGP) and haptoglobin (Hp). We then determine the dissociation constants of the anticoagulant warfarin to different AGP glycoforms and reveal how subtle N-glycan differences, namely, increased antennae branching and terminal fucosylation, reduce drug-binding affinity. Conversely, similar analysis of the haptoglobin–hemoglobin (Hp–Hb) complex reveals the contrary effects of fucosylation and N-glycan branching on Hp–Hb interactions. Taken together, our results not only elucidate how glycoprotein microheterogeneity regulates protein–drug/protein interactions but also inform the pharmacokinetics of plasma proteins, many of which are drug targets, and whose glycosylation status changes in various disease states.

Structural Studies of Fucosylated N-Glycans by Ion Mobility Mass Spectrometry and Collision-Induced Fragmentation of Negative Ions

There is considerable potential for the use of ion mobility mass spectrometry in structural glycobiology due in large part to the gas-phase separation attributes not typically observed by orthogonal methods. Here, we evaluate the capability of traveling wave ion mobility combined with negative ion collision-induced dissociation to provide structural information on N-linked glycans containing multiple fucose residues forming the Lewisx and Lewisy epitopes. These epitopes are involved in processes such as cell-cell recognition and are important as cancer biomarkers. Specific information that could be obtained from the intact N-glycans by negative ion CID included the general topology of the glycan such as the presence or absence of a bisecting GlcNAc residue and the branching pattern of the triantennary glycans. Information on the location of the fucose residues was also readily obtainable from ions specific to each antenna. Some isobaric fragment ions produced prior to ion mobility could subsequently be separated and, in some cases, provided additional valuable structural information that was missing from the CID spectra alone. Graphical abstract ᅟ.

Identification of Lewis and Blood Group Carbohydrate Epitopes by Ion Mobility-Tandem-Mass Spectrometry Fingerprinting

Glycans have several elements that contribute to their structural complexity, involving a range of monosaccharide building blocks, configuration of linkages between residues and various degrees of branching on a given structure. Their analysis remains challenging and resolving minor isomeric variants can be difficult, in particular terminal fucosylated Lewis and blood group antigens present on N- and O-glycans. Accurately characterizing these isomeric structures by current techniques is not straightforward and typically requires a combination of methods and/or sample derivatization. Yet the ability to monitor the occurrence of these epitopes is important as structural changes are associated with several human diseases. The use of ion mobility-mass spectrometry (IM-MS), which separates ions in the gas phase based on their size, charge and shape, offers a new potential tool for glycan analysis and recent reports have demonstrated its potential for glycomics. Here we show that Lewis and blood group isomers, which have identical fragmentation spectra, exhibit very distinctive IM drift times and collision cross sections (CCS). We show that IM-MS/MS analysis can rapidly and accurately differentiate epitopes from parotid gland N-glycans and milk oligosaccharides based on fucosylated fragment ions with characteristic CCSs.