Disaccharides relationship

In 1896, Fischer developed the phenylhydrazine test" for the detection of hydrolytic scission of disaccharides, especially by enzymes this depends on the fact that the phenylosazones of disaccharides are soluble in hot water, whereas those of the monosaccharides are not. Lactose is hydrolyzed by emulsin (1894) and by lactase it is not fermentable by yeast, and is unaffected by invertase (1894). An extract of the small intestine of horses and cattle, especially from young animals, hydrolyzes lactose (1896). The action of enzymes on lactose allowed it to be classified, along with cellobiose and maltose, with the normal (and not the y-type of) methyl glucoside (1914). In the discussion of maltose, the relationship of lactose to the /9-series will be mentioned later. 

To be consistent with the relationship between a mono- and a disaccharide, some authorities do not term a tetrose or a pentose a monosaccharide. By combining the aid- and ket- prefixes, certain compounds then may be called aldohcxoses. such as glucose and galactose, or ketohexoses. such as fructose and sorbose. 

It was shown that, in the maturing seeds, while the synthesis of reserve hemicellulose progresses in the endosperm, a large amount of a trehalose is formed, in addition to sucrose and umbelliferose.92 This trehalose disappears rapidly during the progress of the ripening process, and umbelliferose accumulates continuously. It was predicted that the trehalose may be present in most umbellifers however, the relationship of this disaccharide to the biosynthesis of umbelliferose, and the mechanism involved therein, are not known. 

Correlations between chemical structure and mobility of the sugars were noted by these workers. The 1,4-linked disaccharides and a-D-gly-cosidically linked disaccharides move faster than do the corresponding 1,6-linked disaccharides and /3-D-glycosides, respectively. The / -value relationship between two sugars is maintained when the sugars are converted to glycosides. This bears out Martin s prediction that formation of derivatives will not swamp differences between a pair of solutes being separated. 

Before we leave the sugars we should say a little about the compounds formed when sugars combine together. These are the saccharides and they have the same relationship to sugars as peptides and proteins have to amino acids. We have met one simple disaccharide, sucrose, but we need to meet some more important molecules. 

Fig. 4. Variation of trans-O-glycoside 3/hcoc values (corrected) with dihedral angle. .. computed by DFT for four / -[ 1 —>4]-linked disaccharide mimics. The dashed line is a plot of the Karplus equation (Eq. (36)) defined experimentally by Tvaroska et al.,sl and the solid line is the computed relationship (Eq. (39)), where represents 3/h-4, c-i data, and O is 3/h-i,c-4 data.84...

As outlined in Section VI, tliis greatly simphfied picture has been confirmed by an extensive series of binding studies with sialyl-Lewis derivatives that had been synthesized as candidate phannaceutical agents. In accordance with the incremental refinement of structure-activity relationships over time, the design of inhibitoiy structures followed a series of models decreasing in complexity. These have been designated the tetrasaccharide, trisaccharide, disaccharide, and monosaccharide... 

---