Functionalized HgTe nanoparticles promote laser-induced solid phase ionization/dissociation for comprehensive glycan sequencing

Structural identification of carbohydrate isomers using ambient infrared-assisted dissociation

Informative dissociation of carbohydrates using an infrared (IR) irradiation system is demonstrated under ambient conditions without the instrumentation of a mass spectrometer. Structural identification of carbohydrates and associated conjugates is essential for understanding their biological functions, but identification remains challenging. Herein, an easy and rugged method is reported for the structural identification of model carbohydrates, including Globo-H, three trisaccharide isomers (nigerotriose/laminaritriose/cellotriose), and two hexasaccharide isomers (laminarihexaose/isomaltohexaose). For Globo-H, the numbers of cross-ring cleavages increased by factors of 4.4 and 3.4 upon ambient IR exposure, compared to an untreated control and a collision-induced dissociation (CID) sample. Moreover, 25-82% enhancement in the numbers of glycosidic bond cleavages upon ambient IR exposure was also obtained compared to untreated and CID samples. Unique features of first-generation fragments produced by ambient IR facilitated the differentiation of three trisaccharide isomers. Semi-quantitative analysis was achieved (coefficient of determination (R²) of 0.982) in a mixture of two hexasaccharide isomers via unique features generated upon ambient IR. Photothermal and radical migration effects induced by ambient IR were postulated as responsible for promoting carbohydrate fragmentation. This easy and rugged method could be a universally applicable protocol and complementary to other techniques for detailed structural characterization of carbohydrates.

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.

MALDI Matrices for the Analysis of Low Molecular Weight Compounds: Rational Design, Challenges and Perspectives

The analysis of low molecular weight (LMW) compounds is of great interest to detect small pharmaceutical drugs rapidly and sensitively, or to trace and understand metabolic pathways. Matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) plays a central role in the analysis of high molecular weight (bio)molecules. However, its application for LMW compounds is restricted by spectral interferences in the low m/z region, which are produced by conventional organic matrices. Several strategies regarding sample preparation have been investigated to overcome this problem. A different rationale is centred on developing new matrices which not only meet the fundamental requirements of good absorption and high ionization efficiency, but are also vacuum stable and "MALDI silent", i. e., do not give matrix-related signals in the LMW area. This review gives an overview on the rational design strategies used to develop matrix systems for the analysis of LMW compounds, focusing on (i) the modification of well-known matrices, (ii) the search for high molecular weight matrices, (iii) the development of binary, hybrid and nanomaterial-based matrices, (iv) the advance of reactive matrices and (v) the progress made regarding matrices for negative or dual polarity mode.

Rapid detection of perfluorinated sulfonic acids through preconcentration by bubble bursting and surface-assisted laser desorption/ionization

We developed a preconcentration method in which aerosol droplets containing enriched perfluorinated sulfonic acids (PFSs) are generated through bubble bursting and collected. The droplets were subjected to PFS analysis of perfluorohexane sulfonic acid (PFHxS) and perfluorooctanesulfonic acid (PFOS) through surface-assisted laser desorption/ionization-time-of-flight mass spectrometry; silver nanoplates (AgNPts) were assisting materials. The method was highly efficient, with an approximately three-order magnitude enhancement (5 × 10-13 to 1 × 10-11 M). Ultralow PFS concentrations (0.5 ng/L of PFOS; 0.4 ng/L of PFHxS) were detected in preconcentrated tap water containing PFSs. Our method has potential for rapid real-world PFS detection in water.

Glycoproteomic Alterations in Drug-Resistant Nonsmall Cell Lung Cancer Cells Revealed by Lectin Magnetic Nanoprobe-Based Mass Spectrometry

Understanding the functional role of glycosylation-mediated pathogenesis requires deep characterization of glycoproteome, which remains extremely challenging due to the inherently complex nature of glycoproteins. We demonstrate the utility of lectin-magnetic nanoprobe (MNP@lectin) coupled to Orbitrap HCD-CID-MS/MS for complementary glycotope-specific enrichment and site-specific glycosylation analysis of the glycoproteome. By three nanoprobes, MNP@ConA, MNP@AAL, and MNP@SNA, our results revealed the first large-scale glycoproteome of nonsmall cell lung cancer (NSCLC) with 2290 and 2767 nonredundant glycopeptides confidently identified (Byonic score ≥100) in EGFR-TKI-sensitive PC9 and -resistant PC9-IR cells, respectively, especially with more fucosylated and sialylated glycopeptides in PC9-IR cells. The complementary enrichment was demonstrated with only five glycopeptides commonly enriched in three MNP@lectins. Glycotope specificity of 79 and 62% for enrichment was achieved using MNP@AAL and MNP@SNA, respectively. Label-free quantitation revealed predominant fucosylation in PC9-IR cells, suggesting its potential role associated with NSCLC resistance. Moreover, without immunoprecipitation, this multilectin nanoprobe allows the sensitive identification of 51 glycopeptides from 10 of 12 reported sites from onco-protein EGFR. Our results not only demonstrated a sensitive approach to study the vastly under-represented N-glycoprotome but also may pave the way for a glycoproteomic atlas to further explore the site-specific function of glycoproteins associated with drug resistance in NSCLC.

Mass spectrometry for protein sialoglycosylation

Sialic acids are a family of structurally unique and negatively charged nine-carbon sugars, normally found at the terminal positions of glycan chains on glycoproteins and glycolipids. The glycosylation of proteins is a universal post-translational modification in eukaryotic species and regulates essential biological functions, in which the most common sialic acid is N-acetyl-neuraminic acid (2-keto-5-acetamido-3,5-dideoxy-D-glycero-D-galactononulopyranos-1-onic acid) (Neu5NAc). Because of the properties of sialic acids under general mass spectrometry (MS) conditions, such as instability, ionization discrimination, and mixed adducts, the use of MS in the analysis of protein sialoglycosylation is still challenging. The present review is focused on the application of MS related methodologies to the study of both N- and O-linked sialoglycans. We reviewed MS-based strategies for characterizing sialylation by analyzing intact glycoproteins, proteolytic digested glycopeptides, and released glycans. The review concludes with future perspectives in the field.

Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry: Mechanistic Studies and Methods for Improving the Structural Identification of Carbohydrates

Although matrix-assisted laser desorption/ionization (MALDI) mass spectrometry is one of the most widely used soft ionization methods for biomolecules, the lack of detailed understanding of ionization mechanisms restricts its application in the analysis of carbohydrates. Structural identification of carbohydrates achieved by MALDI mass spectrometry helps us to gain insights into biological functions and pathogenesis of disease. In this review, we highlight mechanistic details of MALDI, including both ionization and desorption. Strategies to improve the ion yield of carbohydrates are also reviewed. Furthermore, commonly used fragmentation methods to identify the structure are discussed.

Nanomaterials as Assisted Matrix of Laser Desorption/Ionization Time-of-Flight Mass Spectrometry for the Analysis of Small Molecules

Matrix-assisted laser desorption/ionization (MALDI), a soft ionization method, coupling with time-of-flight mass spectrometry (TOF MS) has become an indispensible tool for analyzing macromolecules, such as peptides, proteins, nucleic acids and polymers. However, the application of MALDI for the analysis of small molecules (<700 Da) has become the great challenge because of the interference from the conventional matrix in low mass region. To overcome this drawback, more attention has been paid to explore interference-free methods in the past decade. The technique of applying nanomaterials as matrix of laser desorption/ionization (LDI), also called nanomaterial-assisted laser desorption/ionization (nanomaterial-assisted LDI), has attracted considerable attention in the analysis of low-molecular weight compounds in TOF MS. This review mainly summarized the applications of different types of nanomaterials including carbon-based, metal-based and metal-organic frameworks as assisted matrices for LDI in the analysis of small biological molecules, environmental pollutants and other low-molecular weight compounds.