A-L-Fucose

In der Lacto-AT-fucopentaose II ist die a-L-Fucose mit dem IV-Acetyl-glucosamin-Rest in 4-Stellung verkniipft 143a). 

The surface in Figure 19 thus clearly represents half the total energy of an interior a-L-fucose residue embedded in a long a-(1 2)-L-fucan helix due to its interactions with the other residues of the chain. 

A new method of stereoselective synthesis of thiodisaccharides by conjugate addition of 1-thio- D-glucose (8a) or 1-thio-a-L-fucose (30b) to an imsatura-ted carbohydrate molecule was also used for the preparation of o-glucopyrano-syl- and of L-fiicopyranosyl-thiodisaccharides [56]. 

There are no striking differences in interatomic distances apparent from crystal analyses of /3-D-galactose and a-L-fucose, and the C-5 to C-6 distances are essentially the same.36... 

Other syrupy, benzylated bromides bearing O-acetyl or O-p-nitro-benzoyl groups were also prepared and characterized,86-84 as well as a partially benzylated chloride.85 Acid hydrolysis of 22 gave crystalline 2-O-benzyl-a-L-fucose, which was acylated with p-nitrobenzoyl chloride-pyridine. Treatment84 of the resulting tris(p-nitrobenzoate) with hydrogen bromide-dichloromethane led to precipitation of p-nitrobenzoic acid and formation of syrupy 2-0-benzyl-3,4-di-0-(p-nitro-benzoyl)-a-L-fucopyranosyl bromide (33). 

It is well known that intestinal M cells have the ability to efficiently transcytose macromolecules and inert particles, which has stimulated researchers to target M cells for oral delivery of macromolecular drugs and particles.26,52 For example, Ulex europaeus 1 (UEAl), a lectin specific for a-L-fucose residues, selectively binds to mouse Peyer s patch M cells.56 It has become apparent that UEAl can be used to target macromolecules to mouse Peyer s patch M cells and to enhance macromolecular... 

Structurally, the O-polysaccharide chains of H. pylori clinical isolates have a poly-A-acetyl-lactosamine (-LacNAc) chain decorated with multiple lateral a-L-fucose residues forming internal Lex determinants with terminal Lex or Ley units (Fig. 10.4) or, in some strains with additional, D-glucose or D-galactose residues (Moran 2001 a,b, 2008 Monteiro, 2001). Moreover, Lea, Leb, sialyl-Lex, and H-1 antigens have been structurally described in other strains, as well as the related blood groups A and B (Fig. 10.4), but occur in association with Lex and LacNAc chains (Monteiro et al., 2000a,b Heneghan et al., 2000). 

The glycoconjugate a-L-fucose-BSA was used to immunize rabbits. The immunization was performed interdermally at multisites on the back of the neck and repeated weekly for 10 weeks. Blood samples were collected weekly and immune sera samples were prepared. It was found in later experiments that on immunization by this glycoconjugate two types of antibodies were produced. One type was specific only for a-L-fucose and the other for BSA and the conjugate with a BSA moiety, Fig (40). 

Fig. (40). Two column affinity chromatography of immune serum from rabbits immunized with a-L-fucose-BSA (see the text).

Experiment 3. Role of a-L-fucose in the Stability of Lectin-Glycoproteins Complexes... 

Figure 9.7 Structures of some sugars. (A) L-Fucose (pyranose form). Note that the -CH3 group points downward this indicates l series in the Haworth structural convention. (B) Maltose (a-D-glucopyranosyl-l,4-D-glucopyranose) (C) cellobiose (/3-D-glucopyranosyl-1,4-D-glycopyranose) and (D) sucrose (a-D-glucopyranosyl-l,2-/3-D-fructofuranoside). (Reproduced by permission from Diem K, Lentner C. Scientific Tables. Basel Ciba-Geigy, 1971.)...

The reaction mixture for /3-galactosidase contained in a final volume of 0.5 mL 50 mM sodium citrate buffer (pH 3.5), 0.1 U/mL of /3-galactosidase, 1 mg/mL of bovine serum albumin, 0.02% sodium azide, 1 mM a-L-fucose (internal standard), and lactose (5-40 mM). The assay was conducted at 30°C. Aliquots of 20 fiL were removed at 8-minute intervals up to 48 minutes and added to 1 mL of distilled water at 4°C. The hydrolysis of substrate did not exceed 5%. Samples were desalted by passage through a column containing 0.2 mL each of Dowex AG50W-X12 (H+ form) and Dowex AG3-X4 (OH-form). The column was washed with 2 mL of distilled water and the eluate evaporated to dryness and taken up in water to give a lactose concentration of 0.2 mM. A 175 fiL aliquot was used for HPLC analysis. 

Galactosyltransferase (0.05-0.25 mU) was assayed in 50 /u.L of 50 mM cacodylate-HCl buffer (pH 7.4) containing 0.4 mM UDP-galactose, 25 mM glucose, 30 mM MnCl2,0.2 mg/mL of a-lactalbumin, 1.0 mg/mL bovine serum albumin, and 0.1 mM a-L-fucose (internal standard). The reaction was stopped by the addition of 1 mL of cold distilled water. Samples were processed as described above. The mobile phase for HPLC was 100 mM NaOH, and a detector setting of 0 to 3.0 fiA was used. 

---