Carboxyl and Amide Transitions in the Circular Dichroism of Glycosaminoglycans

Glycosaminoglycans (GAG), a group of acidic polysaccharides, is a coined word from glycosamine (amino sugar) and glycans (polysaccharides). These polysaccharides are of animal origin. With the possible exception of hyaluronic acid, they are present in tissues as segments of larger macromolecules, the proteoglycans, which consist of carbohydrate chains (the glycosaminoglycans) covalently linked to protein. The structure, occurrence, physicochemical properties, and physiological function of glycosaminoglycans have been described in some recent articles (1,2,3). The conformation of hexose polysaccharides in solution including the earlier chiroptical studies of glycosaminoglycans was reviewed by Stone (4) and very recently by Chakrabarti and Park (5) who described in detail the structure and interaction properties of these macromolecules. Glycosaminoglycans are linear polyelectrolytes with a repeating disaccharide unit consisting of a N-acetylglycosamine, and, with the exception of keratan sulfate, a uronic acid. They differ in parent monosaccharides, molecular weight, degree of sulfation, and homogeneity of these characteristics, and