Biomedical Engineering Reference
In-Depth Information
glycosidic linkage
base
O
P
O
OH
R
H
O
O
O
O
H
C
O
HO
OH
(OH)
O
Proteins
Polysaccharides
Nucleic acids
Figure 1.1
Typical unit structures of polysaccharides, proteins, and
nucleic acids.
polysaccharide compounds has attracted much attention because of
their potential to apply as practical materials in the field of medicine,
pharmaceutics, cosmetics, and food industries.
Cellulose, starch, and chitin are the most representative
polysaccharides in nature (Fig. 1.2). Cellulose is the most abundant
organic substance on the earth, which is composed of
4)-linked
glucose residues [7]. It has been a symbolic molecule in polymers
and macromolecules, and so far, various fundamental and practical
studies on cellulose have been carried out, which concern its structure,
chemical and physical properties, biosynthesis, and morphology.
Starch is composed of both amylose with a linear structure and
amylopectin with a branched structure [8]. The former consists
of glucose residues linked through
β
-(1
4)-glycosidic linkages
and the latter is composed of a linear chain of
α
-(1
α
-(1
4)-glycosidic
α
linkages, interlinked by
6)-glycosidic linkages. Chitin is the
second most abundant biological macromolecule on the earth after
cellulose, which is found as a skeletal component of invertebrates.
Chitin is composed of
-(1
N
-acetyl-d-glucosamine (GlcNAc) residues
β
linked through
4)-glycosidic linkages [9,10].
Chemical synthesis of the polysaccharide was first performed by
an attempt of cellulose synthesis in 1941 [11]. Then, attempts have
been made to produce cellulose-type polysaccharides by traditional
polymerization of glucose derivatives. For example, polycondensation
of a glucose monomer, where hydroxy groups of 2-, 3-, and 6- positions
were protected, was performed in the presence of P
-(1
to give the
glucose polymer [12]. Although the authors claimed that the product
had cellulose structure, definite evidence of the stereochemistry of
glycosidic linkages, i.e.,
O
2
10
4)-fashion, in the product was not
sufficiently obtained. Since then, many efforts on polymerization
had been devoted to chemical synthesis of polysaccharides with
β
-(1
