Disaccharides


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Disaccharides

 

bioses, carbohydrates whose molecules consist of two monosaccharide groups. All disaccharides have a glycoside type of structure in which the hydrogen atom of a glycoside hydroxyl of one monosaccharide molecule is replaced by a group from another monosaccharide molecule bonded by a hemiacetal or alcohol hydroxyl. In the former case the disaccharides that form lack reducing properties, but in the second case they have them (I). The group of irreducible disaccharides includes trehalose (mycose, or fungus sugar), which consists of two glucose groups (II), and saccharose, which consists of glucose and fructose groups (III). The group of reducible disaccharides includes maltose (IV), cellobiose (V), and lactose (VI).

Disaccharides may contain the five- or six-membered rings of the monosaccharides (pentoses and hexoses) and may differ with respect to the configuration of the glycoside bond (α- or β-glycosides). The spatial forms (conformations) of the rings of the monosaccharide groups in the various disaccharides can vary. Thus, cellobiose and maltose differ not only in the configuration of the glycoside bond (α in maltose and β in cellobiose) but also in the fact that in cellobiose both groups have the same conformation, whereas in maltose they are different.

Disaccharides crystallize well, are readily soluble in water and 45-48-percent alcohol, only slightly soluble in 96-percent alcohol, optically active, and sweet to the taste. They are hydrolyzed by acids (in the case of saccharose it is called inversion); if the monosaccharide group has a five-membered ring the rate of acid hydrolysis of the disaccharide is increased. Disaccharides are also hydrolyzed by enzymes (carbohydrases), such as α- and β-glucosidases (depending on the type of glycoside bond in the disaccharide). Hydrolysis produces monosaccharides.

Disaccharides are widespread in animals and plants. They occur in the free state (as products of biosynthesis or of partial hydrolysis of polysaccharides) and in the form of structural components of glycosides and other compounds. Disaccharides are usually produced from natural sources— for example, saccharose from the sugar beet or from sugar-cane, and lactose from milk. Many disaccharides can be synthesized by chemical and biochemical means.

Saccharose, lactose, and maltose are valuable food and flavoring substances. The sugar industry produces saccharose.

REFERENCES

Khimiia uglevodov. Moscow, 1967.
Stepanenko, B. N. Uglevody: Uspekhi v izuchenii stroeniia i metabolizma. Moscow, 1968.
Stanèk, J., J. Černý, and J. Pacák. The Oligosaccharides. Prague, 1965.

B. N. STEPANENKO

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The results show that chloroform fractions can inhibit starch breakdown to disaccharides in the stomach.
LMU chemist Professor Ivan Huc, who heads a research group devoted to the study of Biomimetic Supramolecular Chemistry, has designed and synthesized a molecular structure which features a helical binding pocket that is made-to-measure for the recognition and capture of xylobiose, a member of the disaccharide class of carbohydrates to which sugar (sucrose) also belongs.
LpxB is the glycosyltransferase that forms the base glucosamine disaccharide of lipid A, catalyzing the formation of the glycosidic bond between the anomeric carbon of the UDP-DAG glucosamine and the 6-hydroxyl of lipid X to form lipid A disaccharide [56].
Besides, a lower sulphation degree of CS chains, expressed as ratio between [DELTA]di-mono 4S and total disaccharides ([DELTA]di-mono 4S +[DELTA]di-non S), was observed in both classes of patients compared to controls (p = 0.046 and p = 0.021 for T1DM and T2DM, resp.), while no differences were found between T1DM and T2DM patients (p = 0.873).
After clinical improvement occurs, gradual reintroduction of disaccharides might help the patient determine which disaccharides they can tolerate and at what level of intake.
In the meat industry, the sugars added to meat products include sucrose and lactose (disaccharides) [4, 5], honey and rice syrup [1], and glycerol and sorbitol [16].
Serum Levels of glycosaminoglycans and chondroitin sulfate/hyaluronic acid disaccharides as diagnostic markers for liver diseases.
(1980) Facile synthesis of [alpha]- and [beta]-O-glycosyl imidates; preparation of glycosides and disaccharides. Angew.
The filtrate containing monosaccharide and disaccharides was put in an oven until complete dryness then dissolved in 20 mL of distilled water.
Free sugars include monosaccharides, such as glucose and fructose, and disaccharides, such as sucrose or table sugar, that have been added to foods and drinks.
Whilst high glycaemic ingredients, such as maltodextrin, help to reduce the sugar because they are oligo- or polysaccharides (and not mono- or disaccharides), they nevertheless have a significant impact on a persons metabolism.
SAN DIEGO--For patients with diarrhea-predominant irritable bowel syndrome (IBS), avoiding FODMAPs (fermentable oligosaccharides, disaccharides, Improvement with naldemedine was seen early and was durable, abdominal pain and bloating significantly more than following standard advice to eat smaller meals and limit caffeine and alcohol, researchers reported.