Problems Inherent in Physico-chemical Studies of Polysaccharides

Problems Inherent in Physico-chemical Studies of Polysaccharides 

In addition to the types of information mentioned in the Introduction, the complete characterization of a polysaccharide requires a knowledge of (1) the general structure of the molecules, (2) the different molecular weight-averages and the molecular weight-distribution, and (3) the shape of the molecules. 

Organic-chemical studies cannot determine completely the structure of polysaccharides, as such methods can only account for about 95% of the linkages present. In many instances there is evidence that labile bonds exist, and the presence of these can only be determined from kinetic studies of the rates of hydrolysis of the polysaccharide under different conditions. The establishment of the presence or absence of such labile linkages should form an important preliminary in the study of the polysaccharides, especially as the breakdown occurring during isolation may be of this nature. 

As the unsubstituted polysaccharides are rarely stable in solution, soluble derivatives must almost invariably be used, and a study of the unavoidable degradation accompanying the preparation of such derivatives is also essential. The use of soluble derivatives may not be entirely satisfactory as there is the possibility that linear natural polymers might aggregate in solution (compare the behavior of certain synthetic polymers, e.g., polyvinyl chloride24). A similar effect may occur in the presence of 

---

IV. Problems Inherent in Physico-chemical Studies of Polysaccharides. 298... 

---