Gang-Liang Huang

Fabrication and application of carbohydrate microarray for analyzing human serum antibody–carbohydrate interaction

We introduced a strategy for preparing a carbohydrate microarray and demonstrated its utility for characterizing carbohydrate binding and activities. We isolated the lipopolysaccharide (LPS) components from different bacteria and explored the possibility of immobilizing these glycoconjugates on a high-binding polystyrene plate. Carbohydrate-specific combination was examined by observing the binding of the blood group B analogic LPS O-polysaccharide from Escherichia coli on the high-binding polystyrene plate and anti-B from a broad spectra antibody of human blood serum. Strong binding of antibodies was screened, as it was evident that relative response value is two times higher than control. The hybridization results indicated that this method is a reliable technique for the detection of human intestinal bacteria and is expected to be applied in diagnostics and seroepidemiology.We introduced a strategy for preparing a carbohydrate microarray and demonstrated its utility for characterizing carbohydrate binding and activities. We isolated the lipopolysaccharide (LPS) components from different bacteria and explored the possibility of immobilizing these glycoconjugates on a high-binding polystyrene plate. Carbohydrate-specific combination was examined by observing the binding of the blood group B analogic LPS O-polysaccharide from Escherichia coli on the high-binding polystyrene plate and anti-B from a broad spectra antibody of human blood serum. Strong binding of antibodies was screened, as it was evident that relative response value is two times higher than control. The hybridization results indicated that this method is a reliable technique for the detection of human intestinal bacteria and is expected to be applied in diagnostics and seroepidemiology.

Hydrolysis characteristics of a β‐1,3‐d‐glucan elicitor from yeast

Fluorophore‐assisted carbohydrate electrophoresis (FACE) is a straightforward, sensitive method for determining the presence and relative abundance of individual (oligo)saccharides in a(n) (oligo)saccharide mixture. The single‐terminal aldehydes of oligoglucoside residues released by acid hydrolysis of β‐1,3‐d‐glucan from yeast were tagged with the charged fluorophore ANTS (8‐aminonaphthalene‐1,3,6‐trisulphonate), and separated with high resolution on the basis of size by PAGE. ANTS fluorescence labelling was not biased by oligoglucoside length; therefore band fluorescence intensity was directly related to the relative abundance of individual oligoglucoside moieties in a heterogeneous sample. FACE analysis revealed that the major oligoglucoside mixture released by acid hydrolysis from β‐1,3‐d‐glucan was composed of monosaccharide, disaccharide, trisaccharide, tetrasaccharide, pentasaccharide, hexasaccharide, heptasaccharide and octasaccharide, and the order of abundance from high to low was trisaccharide, monosaccharide, disaccharide, tetrasaccharide, pentasaccharide, hexasaccharide, heptasaccharide and octasaccharide respectively. In conclusion, FACE represents an accessible, sensitive and quantitative analytical tool enabling the characterization of a(n) (oligo)saccharide mixture.

Fluorophore-assisted carbohydrate electrophoresis as detection method for carbohydrate-protein interactions.

Fluorophore-assisted carbohydrate electrophoresis (FACE) is a straight-forward, sensitive method for determining the presence and relative abundance of individual (oligo) saccharide in a(n) (oligo) saccharide mixture. The single terminal aldehydes of (oligo) saccharides were tagged with the charged fluorophore 8-aminonaphthalene-1,3,6-trisulfonate (ANTS), and separated with high resolution on the basis of size by polyacrylamide gel electrophoresis. ANTS fluorescence labeling is not biased by (oligo) saccharide length. Therefore, band fluorescence intensity is directly related to the relative abundance of individual (oligo) saccharide moieties in heterogeneous sample. In the same time, it also indicates that FACE can be used to investigate the interactions of carbohydrates and proteins.

Immobilization of UDP-galactose 4-epimerase from Escherichia coli on the yeast cell surface.

UDP-galactose 4-epimerase (EC 5.1.3.2, Gal E) from Escherichia coli catalyzes the reversible reaction between UDP-galactose and UDP-glucose. In this study, the Gal E gene from E. coli, coding UDP-galactose 4-epimerase, was cloned into pYD1 plasmid and then transformed into Saccharomyces cerevisiae EBY100 for expression of Gal E on the cell surface. Enzyme activity analyses with EBY100 cells showed that the enzyme displayed on the yeast cell surface was very active in the conversion between UDP-Glc and UDP-Gal. It took about 3 min to reach equilibrium from UDP-galactose to UDP-glucose.

Production and chitinase-binding ability of lipo-chitopentaose nodulation factor

The penta-N-acetyl-chitopentaose 2 has been prepared by using recombinant E. coli strains harboring the nodC gene (encoding chitooligosaccharide synthase) from Azorhizobium caulinodans. Then, the deacetylase NodB removed the N-acetyl moiety from the nonreducing terminus of 2 to give tetra-N-acetyl-chitopentaose 3. N-Acylation of 3 with stearyl chloride was performed in DMF containing water and provided the corresponding lipo-chitopentaose nodulation factor 4. A binding chitinase assay indicated that 4 was much more stable than 3.

A new fermentation process allows large-scale production of tetra-N-acetyl-chitotetraosyl allosamizoline

A new compound 2, possessing a tetra-N-acetyl-chitotetraosyl moiety as a constituent, was synthesized by bacterial fermentation, which used allosamizoline 1 as the initial acceptor. A 2-binding chitinase assay, indicated that the chitinase was inactivated by 2 with IC50 = 0.03 μg/mL.

Structure-function relations of carbohydrates by neoglycolipid arrays

The work presented herein is a new noncovalent glycoarray assembly method for microplates created by simply mixing together a carbohydrate and a teradecylamine. α-d-Mannopyranoside, α-d-glucopyranoside, and α-d-galactopyranoside were utilized in model studies and product formations were detected by lectin binding. The method can be extended to study the steric hindrance effect of carbohydrate-protein interactions, namely the structure-function relations of carbohydrates.

Interactions of carbohydrates and proteins by fluorophore-assisted carbohydrate electrophoresis.

A sensitive, specific, and rapid method for the detection of carbohydrate-protein interactions is demonstrated by fluorophore-assisted carbohydrate electrophoresis (FACE). The procedure is simple and the cost is low. The advantage of this method is that carbohydrate-protein interactions can be easily displayed by FACE, and the carbohydrates do not need to be purified.

Chemo-enzymatic synthesis of hexakis(6-O-allyl)cyclomaltohexaose

Cyclodextrins [1] (CDs) and their synthetic derivatives [2] attract much attention due to their complexation abilities. CDs consist of six, seven, or eight units of α-1,4-linked D-glucopyranose (named α-, β-, and γ-CD, respectively) and have the shape of truncated cones with secondary hydroxy groups at the 2 and 3 positions of glucose units arranged at the wider rim and primary hydroxy groups at the 6 position at the narrower rim. Hydroxy groups provide the resulting complex with hydrophilic character and also allow further synthetic transform ations. In such studies, regioselectively monosubs tit ted CDs play an important role, but their utility is limited by complicated preparation methods. Cyclomaltodextrin glucanotransferases (CGTase; EC 2.4.1.19) are able to convert starch into CDs, closed-ring structures in which six or more glucose units are joined by means of α-1,4 glucosidic bonds [3]. Depending on the type of CD (with six, seven, or eight glucopyranose residues: α-, β-, or γ-CD, respectively) initially formed, the CD-forming enzymes are classified as α-, β-, or γ-CGTases [4]. In this study, we present a simple method for the synthesis of hexakis(6O-allyl)cyclomaltohexaose. It will indicate that CD derivatives also can be directly synthesized by the thermostable CGTase catalyzing starch derivatives. We took advantage of the fact that in excess base the preferred outcome of the reaction of amylose with allyl bromide will be substitution in the O-6 position (Scheme 1). The crude product was isolated via precipitation with EtOH and subsequent freeze-drying. The per-6O-allyl amylose 2 was obtained in 78% yield. The extremely thermophilic anaerobic archaeon strain B1001 producing CGTase was isolated from a hot-spring environment [5]. The temperatures for per-6O-allyl amylose-degrading activity and cyclodextrin synthesis activity were 110 and 90 to 100°C, respectively. The hexakis(6O-allyl)cyclomaltohexaose 3 was obtained in 62% yield.