Disaccharides crystalline conformations

Crystalline Conformations of Disaccharide Moieties 973 Table 2. Standard molecular dimensions for pyranosides. Distances are given in A and angles in... 

Rotation around a linkage between two sugars may take place. This influences the shape of the disaccharide, and affects the conformation that the polysaccharide will adopt. When a carbohydrate polymer is obtained in crystalline form, characterization of its shape is possible by using X-ray diffraction. However, it is not at all certain that this X-ray conformation will be that of the active form in the biological environment. Nevertheless, it constitutes a basis for formulating hypotheses concerning the shape in a biological environment. 

In crystalline or solvated phases, the situation is quite different fi om the gas phase several studies have established that both lactose and cellobiose adopt a trans conformation about their glycosidic linkages [88-92]. Despite this, single hydration of the disaccharides (in the gas phase) does not affect their preference for... 

Table 3. Details of the conformations at the glycosidic linkages for disaccharides and oligosaccharides in crystalline state. 

Figure 6. Iso-energy contours of three-disaccharides as calculated with the MM3 program, along with the glycosidic conformations observed in crystalline complexes with lectins.

---