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

Abstract

Although matrix-assisted laser desorption/ionization (MALDI) mass spectrometry is one of the most widely used so ionization methods for biomolecules, the lack of detailed understanding of ionization mechanisms restricts its application in the analysis of carbohydrates. Structural identi cation 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.

Desorption ionization using through‐hole alumina membrane offers higher reproducibility than 2,5‐dihydroxybenzoic acid, a widely used matrix in Fourier transform ion cyclotron resonance mass spectrometry imaging analysis

“…14 The results often differ from person to person, even from experiment to experiment, due to the difficulty in maintaining identical conditions for matrix application. 15,16 Homogenous spraying has been achieved by the emergence of automatic matrix sprayers, such as the TM-Sprayer™ (HTX Technologies, Carrboro, NC, USA) or the iMLayer™ (Shimadzu Co. Ltd, Kyoto, Japan), although these are costly and the procedure is time-consuming. 13 To combat matrix crystal heterogeneity, ionic liquid matrices (ILMs) have been reported to offer higher signal intensity, enhanced spot homogeneity, increased signal reproducibility, and similar or better detection limits compared with the widely used crystalline matrix 2,5-dihydroxybenzoic acid (DHB).…”

“…However, the quality and the reproducibility of MALDI data are directly affected by the sample preparation method 14 . The results often differ from person to person, even from experiment to experiment, due to the difficulty in maintaining identical conditions for matrix application 15,16 . Homogenous spraying has been achieved by the emergence of automatic matrix sprayers, such as the TM‐Sprayer™ (HTX Technologies, Carrboro, NC, USA) or the iMLayer™ (Shimadzu Co. Ltd, Kyoto, Japan), although these are costly and the procedure is time‐consuming 13 .…”

An optimized method for the detection and spatial distribution of aminoglycoside and vancomycin antibiotics in tissue sections by mass spectrometry imaging

“…The penetration of these drugs at the site of infection using MSI for lesion PK has never been ascertained before. This is primarily due to the poor ionization efficiency of aminoglycosides and ion suppression effects caused by more abundant and readily ionizable endogenous lipids 44,45 . Aminoglycosides are particularly problematic and are commonly derivatized to improve their ionization efficiency prior to quantification by mass spectrometry 46 .…”

Proteomic fingerprinting of Neotropical hard tick species (Acari: Ixodidae) using a self-curated mass spectra reference library

“…Matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometry is an analytical technique that allows for sensitive and accurate detection of complex molecules such as proteins, peptides, lipids and nucleic acids [13][14][15]. The conventional MALDI approach has been used successfully for proteomic fingerprinting through pattern recognition for the identification of microorganisms such as pathogenic bacteria and fungi, which can be cultured in the laboratory and form discrete colonies with very consistent mass spectra that facilitates the development of reference libraries for identification of unknown samples [16,17]. In fact, a commercial program offered by the manufacturers of the MALDI technology is PLOS NEGLECTED TROPICAL DISEASES capable of determining statistical similarities between the spectra of unknown samples and a well-curated, proprietary reference library of bacteria and fungi to identify the species of the unknown specimen.…”

“…This is analogous to the process of matching fingerprints, and offers a simplified comparison score that ranges from 0.0 to 3.0. Scores above or equal to 2.3 represent a confident match at the genus rank, and high probability at the species level, while values below 1.7 are considered as non-reliable identifications [16][17][18].…”