Disaccharides hydration

In the eight disaccharide hydrates, six water molecules are four-coordinated and three are three-coordinated. In the four trisaccharide hydrates, the ratio is reversed with eight three-coordinated and three four-coordinated. This suggests that the more complex the molecules, the greater trend toward three-coordination, but the sampling is too small for a definitive conclusion. 

Various fully-acetylated monosaccharides and disaccharides or sugar alcohols are readily separable by chromatographic adsorption on Mag-nesol (a hydrated magnesium acid silicate)111 and the unacetylated substances may be separated on clay columns.112... 

Carbohydrates are literally hydrates of carbon, containing only the elements carbon, oxygen, and hydrogen. In the human diet, they are considered macronutrients, along with proteins and fats (triacylglycerols). The three types of carbohydrates are monosaccharides, disaccharides, and polysaccharides. 

Finally, Fig. 6.32 compares the internal dynamics of hydrated C-phycocyanin with that of the same system plus trehalose, a well known cryoprotecting disaccharide. Fig. 6.32 shows that the dynamics is slowed down by about 1.5 decades. The observation is interpreted as a slowing down of the protein dynamics due to the viscosity increase of the water shell by the added trehalose molecules. This finding is corrobated by the changes of the mean-squared-dis-... 

Fig. 8. Solid-phase synthesis sequence to fully protected blood group determinant tetrasaccharide 17 starting from disaccharide acceptor resin 13. Reagents and conditions (a) 7b, DMTST, DCM, MS 4 A (b) NaOMe, MeOH, THF (c) 12, DMTST, DCM, MS 4 A (d) (i) 5% hydrazine hydrate, DMF, (ii) Ac20, Py (e) NaOMe/MeOH.

Disaccharides can have similar utility to monosaccharides in DNA delivery polymers. Trehalose, a disaccharide composed of two glucose units linked via an a-(l—>1) glycosidic bond, has been shown to have cryo- and lyo-protective properties, attributed to an unusually large hydration volume [152]. As a function of these properties, trehalose has been shown to prevent aggregation and fusion of proteins and lipids [153]. Logically, incorporation of these features into a polymer backbone could afford similar characteristics to a DNA delivery system and may prevent aggregation of polyplexes in physiological serum concentrations and ionic... 

Table 12.1. Comparison of various hydration properties of disaccharides...

It is noticeable that the monosaccharides, which are oblate molecules able to pack efficiently, form significantly less hydrates than do the disaccharides or nucleosides, which are more awkward-shaped molecules from the packing point of view. 

The structure of the laminarabiose hemihydrate [LAMBIO] is particularly interesting in this respect because it involves the co-crystallization in equal proportions of an anhydrous and monohydrate disaccharide. This structure is really a 1 1 complex between an anhydrous and monohydrate structure with different, but separate, hydrogen-bonding schemes for the anhydrous and hydrated molecules (see Fig. 13.51). 

The fact that hydrates are more common in the disaccharides provides an opportunity to study the way in which the inclusion of water molecules may influence the hydrogen-bonding patterns of oligo- and polysaccharides. The crystal structures of several compounds have been studied in both the anhydrous and hydrated forms. 

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