Fluorophore-assisted carbohydrate electrophoresis: a new technology for the analysis of glycans

At the present time there is considerable interest in the elucidation of the structures of naturally occurring oligosaccharides. Commonly, these carbohydrates occur linked covalently to other biomolecules, as in the case of glycoproteins, proteoglycans and glycolipids, although they are also found unbound in various biological fluids such as milk and urine. They are known to be of singular importance in a wide variety of biological processes [ 1-1 11. For instance, in the case of glycoproteins, they can be involved in protein folding, in the increased solubility and stability of secreted proteins, in the regulation of the uptake of glycoproteins by cells, as messenger moieties which control intracellular protein movements and secretion, and in processes involved in intercellular recognition such as the binding of platelets and leucocytes to vascular endothelial cells. They are known also to be markers for tumour cells and for cellular differentiation, and they can be ligands for pathogens and targets for anti-receptor autoantibodies. Interest in the chemical structure of these carbohydrates is not only academic but also has commercial implications. For instance, the precise definition of the structure of glycoproteins produced by recombinant gene technology will require analysis of the glycans of the various glycoforms which can be produced in different cell lines [7, 121. There is also much interest in the possibility of producing pharmaceuticals based on specific oligosaccharides [7, 131. Generally, glycans are constituted by relatively few types of monosaccharide. For instance, the asparagine-linked glycans (N-glycans) of mammalian glycoproteins consist mostly of only galactose, mannose, fucose, N-acetylgalactosamine and N-acetylglucosamine. However, they can be linked in several different ways so as to give many complex chemical structures which are often branched and sometimes substituted by inorganic groups such as sulphate and phosphate. In the case of glycosaminoglycans (GAGS), substitution by sulphate is a common and integral part of the structure