All cells in nature are covered with a dense and complex array of glycans, which reflect cell properties and lineages, and are thus often utilized as cellular markers for identification of particular cell types. Stage-specific embryonic antigens (SSEA-3, SSEA-4) and tumor-rejection antigens (Tra-1–60 and Tra-1–81), which have been used to identify human induced pluripotent stem cells (hiPSCs), are also glycans. However, very little is known about a whole picture of cell surface glycans, the glycome, of hiPSCs. We performed comprehensive glycome analysis of a large set of hiPSCs using high-density lectin microarray and identified three characteristic features of cell surface glycans of hiPSCs: α2→6Sia, α1→2Fuc, type-1 LacNAc. These features were also confirmed by DNA microarray and glycosidase-assisted MALDI-TOF mass spectrometry (MS)/HPLC mapping. Furthermore, we found a novel lectin probe, rBC2LCN, which is highly specific to human hiPSCs. In this review, our recent findings concerning hiPSCs surface glycans and this novel hiPSC-specific probe are described and discussed.
The glycosylation reaction, which makes glycosidic linkages to develop a sugar chain, is one of the essential reactions in the realms of glycoscience. An understanding of mechanistic details of this key reaction will not only give researchers deeper insights on the nature of biochemical glycosylation reactions but will further the development of synthetic strategies in a rational way. In the present article we will overview the studies on mechanisms of glycosylation reactions, focusing on those using computational approaches. We review theoretical studies on general mechanistic issues, extensively discussing them in conjunction with the influence of neighboring groups and solvents, as well as stereoelectronic effect. The influence of a glycosyl donor’s conformational flexibility on its reactivity/stereoselectivity and the debate about exocyclic or endocyclic cleavage of pyranoside rings are also described.