Homoglycanes

Polysaccharides composed of only one kind of monosaccharide are described as homopolysaccharides (homoglycans). Similarly, if two or more different kinds of monomeric unit are present, the class name heteropolysaccharide (heteroglycan) may be used. (See 2-Carb-39.)... 

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Cellulose, a linear homoglycan of pi 4-linked glucose residues, is the most abundant organic substance in nature. Almost half of the total biomass consists of cellulose. Some 40-50% of plant cell walls are formed by cellulose. The proportion of cellulose in cotton fibers, an important raw material, is 98%. Cellulose molecules can contain more than 10" glucose residues (mass 1-2 10 Da) and can reach lengths of 6-8 pm. 

Nutritionally, carbohydrates may generally be classified as simple sugars (e.g. glucose or fructose), polysaccharides (e.g. homoglycans such as starch or beta-glucans) or complex carbohydrates (e.g. glycoproteins). 

Classified into homoglycans and heteroglycans depending upon the kind of monosaccharides present. Depending upon the function, they are classified as storage and structural polysaccharides. 

Cellulose differs from most other polysaccharides in being a homoglycan with a single type of linkage and in occurring naturally as a partially crystalline, high-molecular-weight poly-... 

Several Py-MS studies were done on homoglycans. A Py-FI MS study on a (1- 4)-p-xylan [2] showed several characteristic ions such as m/z = 132 (associated with the monomer unit C5H8O4), the ion m/z = 96 (associated with furfural, C5H4O2), and the ion m/z = 114 (probably associated with 3-hydroxy-2-penteno-1,5-lactone, CsHsOs). The study showed that retro-aldolization between C-1 and C-2 atoms does not take place. Smaller ions seen in the spectrum were probably generated from further pyrolysis of the initially formed fragments. 

Hydrogen bonding is clearly ubiquitous in stabilising protein secondary structures and nucleic acid double helices (by Watson-Crick base pairing between anti-parallel phosphodiester chains), and in the wide range of homoglycan secondary to quaternary structures. 

Homopolysaccharide (homoglycan) a general term for a polysaccharide composed of a single type of monosaccharide residue is obtained by replacing the ending -ose by -an, such as (1—>4)-a-D-glucan. 

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