BioFiles Volume 5, Number 1 — Glycobiology

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Introduction


Vicki Caligur

This issue of BioFiles examines topics of interest in glycobiology. While carbohydrate biology may be thought to be of lesser interest than high visibility research areas such as genomics, epigenetics, and metabolomics, consider the extent to which the non-scientific community recognizes the abbreviation "H1N1" as a strain of influenza ("flu") virus. The abbreviation refers to the specific type of carbohydrate binding (hemagglutinin, "H") and cleavage (neuraminidase, "N") intrinsic to the virus. These binding and cleavage activities are specifically directed toward sialic acids present on the surface of mammalian cells, demonstrating a direct connection between human health and carbohydrate biology.

Sialic acids and sialylation of glycoproteins and glycosphingolipids have been associated with normal development and immunity, intracellular signaling by sialic acid-binding proteins, and bacterial and viral pathogens. Sialic acids work in conjunction with sialic acid binding proteins as active components of the innate immune system in vertebrates, in order to prevent infection by viruses and bacteria that can also bind to sialic acid residues. Changes in sialic acids and sialic acid binding proteins in the innate immune system are important to the evolutionary race to prevent infection by pathogenic prokaryotes and viruses able to mutate more rapidly. Even though changes in sialic acid expression have also been found in many human pathogenic diseases including cancer and diabetes, little is known of the reasons and causes.

Mass spectrometry (MS) is a critical technique used in glycoprotein analysis for the investigation of intact proteins, digested glycopeptides, or liberated glycans. Because of the complexity of glycoproteins and glycan structures, no single technique is optimal for all studies. A comparison of three methods is presented, along with recommended matrices for MS analysis and deglycosylation kits for the release of oligosaccharides from glycoproteins.

Lectins are a historically recognized group of non-immunogenic proteins that have preferential binding for specific carbohydrate ligands. Lectin conjugates can be used to probe tissues in a technique similar to immunohistochemistry, using the carbohydrate-binding property of the lectin to attach to cell surface oligosaccharides. By attaching a sensitive fluorescent dye to a lectin that binds to chitotrose, a fungal disaccharide not found in animals, it is possible to detect fungi in diseased human tissue samples.

Hyaluronan (hyaluronic acid) is a glycosaminoglycan involved in cellular development and signaling, and the variations in its biological function appear to be dependant on polymer size. Research on hyaluronan has been limited by the lack of availability of hyaluronan of defined mass and low polydispersity. Select-HA™, now available through Sigma-Aldrich, was developed to support hyaluronan research needs. Select-HA is a monodisperse hyaluronan prepared via enzymatic synthesis from a Generally Regarded as Safe (GRAS) bacterial source. The patented synthesis method makes a high level of size control possible. Each Select-HA has a narrow-size distribution with an average molecular mass within a defined range, making it possible to design experiments with reduced polymer variability or that incorporate molecular mass comparisons.

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