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With implications in several medical conditions, N‐linked glycosylation is one of the most important posttranslation modifications present in all living organisms. Due to their nontemplate synthesis, glycan structures are extraordinarily complex and require multiple analytical techniques for complete structural elucidation. Mass spectrometry is the most common way to investigate N‐linked glycans; however, with techniques such as liquid‐chromatography mass spectrometry, there is complete loss of spatial information. Mass spectrometry imaging is a transformative analytical technique that can visualize the spatial distribution of ions within a biological sample and has been shown to be a powerful tool to investigate N‐linked glycosylation. This review covers the fundamentals of mass spectrometry imaging and N‐linked glycosylation and highlights important findings of recent key studies aimed at expanding and improving the glycomics imaging field. [ABSTRACT FROM AUTHOR]

Glycans are complex structures that require MS/MS for detailed structural elucidation. Incorporating metals can provide more structural information by inhibiting glycosidic cleavage and enhancing cross-ring fragmentation. A direct analysis was performed using lithium doping and IR-MALDESI to induce cross-ring fragmentation of glycans. The protonated and lithiated versions of the two glycans were isolated and subjected to HCD. For protonated glycans, only glycosidic cleavages were observed. Using lithium doping, MS/MS consisted of abundant cross-ring fragments. Seventeen cross-ring fragments were detected across both glycans using lithium-doped ESI. This is the first incorporation of metal doping in IR-MALDESI to achieve cross-ring fragments in MS/MS analysis. [ABSTRACT FROM AUTHOR]

Metallothioneins (MTs) are a ubiquitous class of small cysteine-rich metal-binding proteins involved in metal homeostasis and detoxification with highly versatile metal binding properties. Despite the long-standing association of MT with M 3 S 3 and M 4 S 5 metal clusters, synthetic complexes with these core architectures are exceptionally rare. Here, we demonstrate an approach to synthesizing and characterizing aggregates of group 12 metal ions with monocyclic M 3 S 3 cores in acetonitrile solution without the protection of a protein. Multidentate monothiol ligand N , N -bis(2-pyridylmethyl)-2-aminoethanethiol ( L1H ) provided [Cd 3 ( L1 ) 3 ](ClO 4 ) 3 ( 1 ), the first structurally characterized nonproteinaceous aggregate with a metallothionein-like monocyclic Cd 3 S 3 core. In addition, [Zn 3 ( L1 ) 3 ](ClO 4 ) 3 ·4CH 3 CN ( 2 ·4CH 3 CN) was characterized by X-ray crystallography. The complex cations of 1 and 2 had comparable structures despite being nonisomorphic. Variable temperature and concentration 1 H NMR were used to investigate aggregation equilibria of 1 , 2 , and a precipitate with composition "Hg( L1 )(ClO 4 )" ( 3 ). Cryogenic 1 H NMR studies of 3 revealed a J ( 199 Hg 1 H) coupling constant pattern consistent with an aggregate possessing a cyclic core. ESI-MS was used for gas-phase characterization of 1 - 3 , as well as mixed-metal [M 2 M'( L1 ) 3 (ClO 4 ) 2 ] + ions prepared in situ by pairwise acetonitrile solution combinations of the group 12 complexes of L1 . Access to synthetic variants of metallothionein-like group 12 aggregates provides an additional approach to understanding their behavior.