Chondroitin, chemical structure

The final Klebsiella polysaccharide that will be mentioned specifically is KZS, whose chemical structure was determined by Niemann et al (24) (Figure 30). This polysaccharide is of particular interesT because its backbone consists of a similar alternating 1, 3 diequatorial, 1, 4 diequatorial glycosidic linkage geometry to that found in the connective tissue polysaccharides, hyaluronic acid, chondroitin sulphate and dermatan sulphate (25). All these three polysaccharides have exhibited 3-fold helical conformations with axially projected chemical repeats in the range 0.95 - 0.97 nm which is comparable to 0.97 nm found in K25 which also forms a 3-fold helix (14). Further, left-handed helices were found to be more favourable in K25 as has previously been observed in the connective tissue polysaccharides. The similarities between these various different structures is apparent in Figure 31 which shows projections down the axis of K25 and several of the connective tissue polysaccharides. 

In order to shed more light on the Interaction of water with these mucopolysaccharides, we employ the DSC method to follow the melting behavior of aqueous solutions of the polysaccharides cooled to -50 C. The polymers chosen here are chondroitin sulfate A (Chn S-A), chondroitin sulfate C (Chn S-C), chondroitin (Chn), heparin (Hpn), and hyaluronic acid (HyA). Their chemical structures are shown in Figure 1. The DSC curves allow us to determine the amount of the non-freezing water In highly concentrated solutions, since any endothermic peak Is not observed for such solutions over a wide temperature range (17. 18). This paper will also describe the presence of more than one endothermic peak In the DSC curves for solutions of relatively low polymer concentrations. 

In all, eight glycosaminoglycans of essentially diflFerent chemical structures have been identified. Through the times, these glycosaminoglycans have been individually named in a number of ways, as shown in Table 1. Most of these names are used currently, and so the reader will find it useful to have this table available when consulting the primary literature. Where the term chondroitin sulfate appears in the more recent literature, this can mean chondroitin 4-sulfate or chondroitin 6-sulfate or a mixture of the two. The terms keratan sulfate I and keratan sulfate II are sometimes used to denote keratan sulfates of comeal and skeletal origin, respectively, there being some differences between the two. 

Chondroitin sulphate fractions in human plasma and urine have similar chemical structures, including low levels of sulphate, and similar molecular weights (8 x 10 ), making it likely that the plasma low-sulphate content chondroitin sulphate is a precursor of the urinary product in aged subjects. ... 

The chemical structure of teichan seems to be very similar to the structure of chondroitin, but with a-glycosidic linkages. The identification of the position of the glucuronosyl residue needs further confirmation, whereas the position of the galactosaminidic linkage is stUl unknown. 

The first and still only clue for a difference between the chemical structure of chondroitin 4-sulfate and chondroitin 6-sulfate was supplied by studies of the infrared spectra. An adsorption band corresponding to an axial sulfate group was observed in the 840 to 850 wave number region for chondroitin 4-sulfate, whereas this band shifted to the 815 to 825 wave number region for the 6-isomer, corresponding to an equatorial position. Since the only hydroxyl group, in equatorial position and available for... 

Heparin/heparan, hyaluronan, and chondroitin are three prevalent glycosaminoglycans. Vertebrates use glycosaminoglycans in structural, recognition, adhesion, and signaling roles. Chemical synthesis of naturally occurring polysaccharides is considered to be impractical. Most polysaccharides, especially those from bacteria origins, are obtained by purification from natural sources or from cell culture, enzymatic approaches have been increasingly applied to obtain some structures. 

Heparin may be classified as a mucopolysaccharide on the basis that it contains glucosamine, but it has very distinctive properties, and it is better to recognize a separate class of natural compounds, the heparins or hepar-inoids. In this review, the term mucopolysaccharide is limited to the substances in Table 3.1, as distinct from the heparins and heparinoids, listed in Table 3.2. Sulphation of mucopolysaccharides results in heparinoids when the product resembles heparins in the chemical and biological properties included under definitions. An important biological difference is that the typical mucopolysaccharides, such as the chondroitin sulphuric acids, are the important structural materials of connective tissue, while the naturally... 

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