Disaccharides properties

Kovacs H, Bagley S and Kowalewski J 1989 Motional properties of two disaccharides in solutions as studied by carbon-13 relaxation and NOE outside of the extreme narrowing region J. Magn. Reson. 85 530 1... 

Several new exopolysaccharides such as welan and rhamsan produced by Alcaltngettes spp may supercede xanthan for some industrial applications. These are based on the same repeat tetrasaccharide backbone of glucose, glucuronic acid, glucose and rhamnose but differ in the substituents rhamsan has a disaccharide side chain and welan a monosaccharide. Both are stable at high temperature and have excellent pseudoplastic properties. 

Disaccharides like maltose, lactose, and trehalose are used for their similarity to sucrose, but with differences in some properties, such as sweetness, melting point, or hygroscopicity. 

The side chains in the latter are flexible disaccharides on account of poor-quality diffraction patterns, their tentative molecular structures are known only from computer modeling.1" On the other hand, well-defined crystal structures are available for gellan and welan, and they can be correlated with the physical properties of the polysaccharides the details are presented here. Their conformation angles are listed in Table VI. 

The conformational analysis was developped recently by different authors first on the disaccharide units to investigate the role of the charge on C-6 position on the conformation [29-32]. From this study, the 2i or right-handed 3i helices were described as most problable conformations [30,31]. These conformations were also demonstrated from x-ray diffraction [33] or on the basis of circular dichroTsm [34], From these data, the repeat unit in the axial-axial conformation has a 4.3 A° length which will be used to characterize the electrostatic properties. 

We used this procedure in estimating the chain properties of hyaluronic acid 16). Hyaluronic acid is a regular polysaccharide with a disaccharide repeat unit. The two units are glucuronic acid (Figure 1) and N-acetyl glucosamine (Figure 2). 

Alekhine had mentioned that turanose reacts with phenylhydrazine. Maquenne prepared the phenylosazone and described its precipitation from water in the flocculent or gel condition that is so very characteristic of the substance, but he did not report an analysis. A year after Ma-quenne s publication, Emil Fischer16 examined a small sample of amorphous turanose which had been sent by Dr. Konowaloff of Moscow. Its phenylosazone was prepared in good crystalline form by several recrystallizations from aqueous alcohol the analysis of these crystals proved conclusively the disaccharide formula for turanose which Alekhine had proposed from the analysis of amorphous substances. The writer had occasion recently to prepare turanose phenylosazone in considerable quantity its very characteristic properties and those of the derived phenylosotriazole are described on pages 27 and 28. 

K. Marotte, C. Preville, C. Sabin, M. Moume-Pymbock, A. Imberty, and R. Roy, Synthesis and binding properties of divalent and trivalent clusters of the Lewis a disaccharide moiety to Pseudomonas aeruginosa lectin PA-IEL, Org. Biomol. Chem., 5 (2007) 2953-2961. 

Lactose is a disaccharide reducing sugar. Unlike the other sugars mentioned, lactose is not particularly soluble. A property that has some use in yeast-containing products is that lactose is not fermented by baker s yeast. 

The answer is d, (Hardman, p 9L3.) Sucralfate is a sulfated disaccharide that contains poly aluminum hydroxide. It has primarily protective properties and attaches firmly to ulcer craters. It has no significant acid-neutralizing properties. 

The structure of the leaving group is a decisive factor for donor properties. Natural substrates for glycosidases are polysaccharidic chains and the corresponding disaccharides are still used in transglycosylation reactions as... 

The conformational properties of a glyconucleoside containing an. S -glycosidic linkage have been also studied and compared to those of the corresponding O-disaccharide. A / and NOE data examination allowed a full pseudorotational analysis, showing a switch in the conformational preferences between the two molecules, the natural and the mimetic one.59... 

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