Disaccharide stability

A computer-built model, having an axial rise per disaccharide of 0.84 nm and possible stabilization by an 0-3-H 0-5, intramolecular hydrogen-bond from a hexosamine to a uronic acid residue, is a rather extended, two-fold helix (see Fig. 8),346 with each fold approximately corresponding341,346 to the disaccharide repeat in Fig. 7a. A substantially similar model was obtained by use of calculations also taking into consid-... 

Summarizing the results of many investigations, monosaccharides and such derivatives as D-mannitol and D-glucitol are rather weak acceptors. Disaccharides, including such acceptor products as isomaltose, are much better acceptors, except for certain molecules, for instance leucrose, which is not an acceptor.29,46,47 The decrease of enzyme activity with time has been described in terms of a first-order reaction. The inactivation parameters have been calculated for the immobilized enzyme. The inactivation constants kd were 0.0135 (1/d) when maltose was the acceptor (stabilizing), and 0.029 (1/d) when fructose was the acceptor.38... 

The hydroxyproline residues stabilize the triple helix by forming hydrogen bonds between the a-chains, while the hydroxyl groups of hydroxylysine are partly glycosylated with a disaccharide (-Glc-Gal). 

Mithramycin (24) bears the terminal sugar unit -mycarose. By a similar preparation as for the methyl-branched glycals and the -enantiomer of namely the labile g-mycaral 40 w s obtained ( ). Its NIS condensation with the 3, 4 -Saol disaccharide proceeds smoothly, but the reaction turned out to be rather slow with respect to the stability of the g-mycaral. This results in only a modest yield (12%) of the trisaccharide which was hydrogenolyzed to compound 4. This in turn constitutes an isomer of the trisaccharide sequence in... 

Species III-V in Scheme 6 are also formed when Cr(V) is generated by reaction of Cr(VI) with GSH (1 1 ratio) at pH 5.0 and stabilized by the presence of a 10-fold excess of the disaccharide over Cr(VI).70 This result provides evidence that the Cr(V) species observed at this pH correspond effectively to Cr(V) chelates formed with the disaccharide and not with the oxidized product (the aldobionic acid). 

Upon acetylation and subsequent O-deacetylation in alkaline media, both the mono- and bis-(amido) derivatives of mono- and disaccharides always showed great stability, with high recoveries of the original amido sugar. 

D-galactose, methyl a- and 0-D-glucopyranosides, and a number of disaccharides, thus demonstrating that mass spectrometry is useful in the field of carbohydrate chemistry. In this study, the appearance potentials of CjHnOs ions were measured, and the results interpreted in terms of greater stability of the /9-(d or l) (equatorial) anomer with respect to the o-(d or l) (axial) one in the CA conformation. 

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