Matrix-assisted laser desorption/ionization (MALDI) is one of the soft ionization methods in mass spectrometry (MS). Its analyte compatibility with a matrix can improve analyte-selective ionization efficiency and control the fragmentation properties of the product ions. 2,5-dihydroxybenzoic acid (DHB) is a versatile matrix that can be used for various molecular species. Although DHB is commonly used as the matrix of first choice for MALDI MS of glycans, many attempts to optimize DHB for glycan analysis using additives have also been reported. This mini-review will present additives of the DHB-based matrix that promote direct analysis of carbohydrates and glycoconjugates by MALDI MS.

Protein C-mannosylation is a unique type of protein glycosylation in which a single α-mannose is attached to the indole C2 of tryptophan (Trp) through a C–C bond. The Trp-x-x-Trp (WxxW) sequences, whose first Trp residue may be C-mannosylated, constitute the consensus motifs of this rare glycosylation modification. Dpy-19 was recognized as a gene encoding C-mannosyltransferase in Caenorhabditis elegans. DPY19L1 and DPY19L3 were later confirmed as mammalian C-mannosyltransferases. The consensus motif can be found in the thrombospondin type 1 repeat and cytokine receptor type I families as well as in many other proteins, and recent studies suggest critical roles of C-mannosylation in the folding, sorting, and/or secretion of the substrate proteins. We successfully synthesized C-mannosylated Trp-containing Trp-Ser-Pro-Trp (WSPW) peptides. As a result of using these peptides in our investigations, we proposed that C-mannosylation may have biological functions in addition to contributing to the folding and stability of the substrate proteins. In this mini-review, we discuss the biological roles of C-mannosylation in physiology and pathology as based on our recent findings.

Matrix-assisted laser desorption/ionization (MALDI) is one of the soft ionization methods in mass spectrometry (MS). Its analyte compatibility with a matrix can improve analyte-selective ionization efficiency and control the fragmentation properties of the product ions. 2,5-dihydroxybenzoic acid (DHB) is a versatile matrix that can be used for various molecular species. Although DHB is commonly used as the matrix of first choice for MALDI MS of glycans, many attempts to optimize DHB for glycan analysis using additives have also been reported. This mini-review will present additives of the DHB-based matrix that promote direct analysis of carbohydrates and glycoconjugates by MALDI MS.

Protein C-mannosylation is a unique type of protein glycosylation in which a single α-mannose is attached to the indole C2 of tryptophan (Trp) through a C–C bond. The Trp-x-x-Trp (WxxW) sequences, whose first Trp residue may be C-mannosylated, constitute the consensus motifs of this rare glycosylation modification. Dpy-19 was recognized as a gene encoding C-mannosyltransferase in Caenorhabditis elegans. DPY19L1 and DPY19L3 were later confirmed as mammalian C-mannosyltransferases. The consensus motif can be found in the thrombospondin type 1 repeat and cytokine receptor type I families as well as in many other proteins, and recent studies suggest critical roles of C-mannosylation in the folding, sorting, and/or secretion of the substrate proteins. We successfully synthesized C-mannosylated Trp-containing Trp-Ser-Pro-Trp (WSPW) peptides. As a result of using these peptides in our investigations, we proposed that C-mannosylation may have biological functions in addition to contributing to the folding and stability of the substrate proteins. In this mini-review, we discuss the biological roles of C-mannosylation in physiology and pathology as based on our recent findings.