Mannose disaccharide

Systematic investigations of mannose-binding proteins with clustered mannosides other than natural multiantennary oligosaccharides have been rather scarce until recently. However, using 6 -0-phosphorylated mannose disaccharide scaffolded on peptide templates using combinatorial glycopeptide libraries. 

It will be noted that the snowdrop lectin (GNA) is specific for Man(al-3)Man linkages and exhibits high affinity for the branched trisaccharide Man(al-3)[Man(al-6)]Man [104,110] the daffodil lectin (NPA) for a-1,3- and a-l,6-linked mannose disaccharides [105] the amaryllis lectin (HHA) for a-l,6-linked mannose oligosaecharides [105] and the garlic (ASA) and ramsons (AUA) lectins for Man(al-3)Man units [106]. Similar to the snowdrop lectin, the orchid lectin Listera ovata) is highly specific for a-1,3-mannose oligomers [109]. 

M. K. Christensen, M. Meldal, K. Bock, H. Cordes, S. Mouritsen, H. Eisner. Synthesis of glycosylated peptide templates containing 6 -0- phosphorylaled mannose disaccharides and their binding to the mannose-6-phosphate receptor. J. Chem. Soc., Perkin Trans. 1 1994, 1299-1310. 

In efforts to shift the equilibrium toward product, the addition of water-miscible organic cosolvents was investigated, but this usually results in enzyme inactivation and a decrease in Km for the glycoside acceptor(254). The use of high substrate concentrations and elevated reaction temperatures have also been explored. Johansson et al.12551 reported the synthesis of mannose disaccharides with jack bean a-mannosidase, while Ajisaka et al.[2561 utilized almond (3-glucosidase with glucose... 

Tetra-0-benzyl-Z)-glucose l-O-a or p-trichloroacetimidate with alcohols in nitrile solvents with TMS triflate as catalyst react at -40° to give 70-90% yields of disaccharides (from primary or secondary alchols) with p a ratios of 8-24 1 by way, it is proposed, of intermediate ions which involve strong association with the solvent. With mannose disaccharides ratios are about 1 1. ... 

The weights of other monosaccharides and reducing disaccharides which will reduce i ml. of this standard Fehling s solution are galactose, 0 00511 g- fructose. 0 00514 g.. mannose, 0 00431 g. lactose, 0 00678 g. maltose, 0 00807 g. 

D (+) Galactose is a constituent of numerous polysaccharides It is best obtained by acid hydrolysis of lactose (milk sugar) a disaccharide of d glucose and d galactose L (—) Galactose also occurs naturally and can be prepared by hydrolysis of flaxseed gum and agar The principal source of d (+) mannose is hydrolysis of the polysaccharide of the ivory nut a large nut like seed obtained from a South American palm... 

Draw the structure of the disaccharide formed by two moles of a-mannose (see Question 19). 

The Enzymes II (E-IIs) of the phosphoenolpyruvate (P-enolpyruvate)-dependent phosphotransferase system (PTS) are carbohydrate transporters found only in prokaryotes. They not only transport hexoses and hexitols, but also pentitols and disaccharides. The PTS substrates are listed in Table I. The abbreviations used (as superscripts) throughout the text for these substrates are as follows Bgl, jS-gluco-side Cel, cellobiose Fru, fructose Glc, glucose Gut, glucitol Lac, lactose Man, mannose Mtl, mannitol Nag, iV-acetylglucosamine Scr, sucrose Sor, sorbose Xtl, xylitol. 

From pig mucosa. Notations as for Scheme 1. Major products (yield 40-80% of original heparin). Major disaccharide fraction (50-80%). From heparin chains terminating with a D-glucuronic acid residue at the reducing end. Minor products (yield <3% of original heparin). From the active site for antithrombin (asterisk denotes 3-C-sulfation of the amino sugar or anhydro-D-mannose). 

A new NMR method for the determination of the anomeric configuration in mono- and disaccharides has been described.18 The protocol is based on the different cross-correlated relaxation between proton chemical shift anisotropy (CSA) and dipolar relaxation for the a and (3 anomers of sugars. Only the ot-anomers show the presence of CSA (HI or Hl )-proton dipole (H1-H2 or Hl -H2 ) in the longitudinal relaxation of the anomeric protons. The method is of special interest for cases in which vicinal coupling constants between HI and H2 in both anomers a and (3 are similar and small, such as D-mannose, and the non-ambiguous description of the anomeric configuration needs additional measurements. 

Figure 14.7 Models of phosphorylated high-mannose M7 and a glycopeptide mimic obtained by MD calculation showing similar conformations. They are seen from the point of interaction with the mannose-6-phosphate receptor. Disaccharide phosphates are emphasized as spheres.76...

Carbohydrates are diverse with respect to occurrence and size. Familiar mono and disaccharides include glucose, fructose, sucrose (table sugar), cellobiose, and mannose. Familiar polysaccharides are listed in Table 9.1 along with their source, purity, and molecular weight range. 

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