New Structure-function Relationships of Carbohydrates

Biochimica et Biophysica Acta (BBA) - General Subjects, 2006

Recently, microarray technology has increasingly been widely applied in glycobiology. This technology has rather evident potential advantages: unlimited number of carbohydrate ligands coated onto one small sized chip, enormously low consumption of both carbohydrate ligands and carbohydrate-binding proteins to be tested, etc. Literature data demonstrate that three approaches are used for glycoarray design. The first one is based on the physical adsorption of glycomolecules on a surface (as in a common ELISA), the second one-on covalent immobilization, and the third one-on a streptavidin-biotin system. In all of the described methods, carbohydrate ligands were placed on chips as a 2D monolayer and high sensitivity was achieved due to fluorescent detection. Notably, a tendency of stepping from model chips toward real multiarrays, where the number of carbohydrate ligands can be up to two hundred, has been observed the last 2 years, this already producing a number of interesting findings when studying carbohydrate-binding proteins. In 2005 new construction, 3D glycochip was described, where 150 μm diameter polyacrylamide gel elements serve as microreactors instead of 2D dots. As a result of the 3D placement of a ligand, two orders of magnitude increase of its density is possible, this providing principal signal improvement during fluorescent detection and increasing method sensitivity. At the same time, carbohydrate consumption is low, i.e., ∼1 pmol per gel element. Copolymerization chemistry enables the immobilization of several glycomolecule classes to the gel, in particular, aminospacered oligosaccharides, polyacrylamide conjugates, and even 2-aminopyridine derivatives of oligosaccharides, which are widely used in the structural analysis of glycoprotein N-chains.

Science, 2007

Carbohydrate recognition is biologically important but intrinsically challenging, for both nature and host-guest chemists. Saccharides are complex, subtly variable, and camouflaged by hydroxyl groups that hinder discrimination between substrate and water. We have developed a rational strategy for the biomimetic recognition of carbohydrates with all-equatorial stereochemistry (β-glucose, analogs, and homologs) and have now applied it to disaccharides such as cellobiose. Our synthetic receptor showed good affinities, not unlike those of some lectins (carbohydrate-binding proteins). Binding was demonstrated by nuclear magnetic resonance, induced circular dichroism, fluorescence spectroscopy, and calorimetry, all methods giving self-consistent results. Selectivity for the target substrates was exceptional; minor changes to disaccharide structure (for instance, cellobiose to lactose) caused almost complete suppression of complex formation.

Carbohydrates - Comprehensive Studies on Glycobiology and Glycotechnology, 2012

Organic & Biomolecular Chemistry

Density depended binding and selectivity is studied on glycodendron microarray with defined valency, which were prepared by on-chip synthesis and analysed by in situ MALDI-TOF MS.

Glycobiology, 2004

To facilitate deciphering the information content in the glycome, thin film-coated photoactivatable surfaces were applied for covalent immobilization of glycans, glycoconjugates, or lectins in microarray formats. Light-induced immobilization of a series of bacterial exopolysaccharides on photoactivatable dextran-coated analytical platforms allowed covalent binding of the exopolysaccharides. Their specific galactose decoration was detected with fluorescence-labeled lectins. Similarly, glycoconjugates were covalently immobilized and displayed glycans were profiled for fucose, sialic acid, galactose, and lactosamine epitopes. The applicability of such platforms for glycan profiling was further tested with extracts of Caco2 epithelial cells. Following spontaneous differentiation or on pretreatment with sialyllactose, Caco2 cells showed a reduction of specific glycan epitopes. The changed glycosylation phenotypes coincided with altered enteropathogenic E. coli adhesion to the cells. This microarray strategy was also suitable for the immobilization of lectins through biotin-neutravidin-biotin bridging on platforms functionalized with a biotin derivatized photoactivatable dextran. All immobilized glycans were specifically and differentially detected either on glycoconjugate or lectin arrays. The results demonstrate the feasibility and versatility of the novel platforms for glycan profiling.

2012

In 1954 Boyd and Shapleigh proposed the term lectin, from the Latin verb legere (which means "to select"). This term was based on the fact that these proteins have the ability to distinguish between erythrocytes of different blood types [9]. Lectins were early defined as carbohydrate-binding proteins of nonimmune origin that agglutinate cells or as carbohydrate-binding proteins other than antibodies or enzymes. However, these definitions were updated, since some plant enzymes are fusion proteins composed of a carbohydrate-binding and a catalytic domain, for instance, type 2 RIPs, such as ricin and abrin, are fusion products of a catalytically active A-chain (which has the Nglycosidase activity) and a carbohydrate-binding B-chain, both linked by a disulfide bond [10]. Furthermore, there is in nature carbohydrate-binding proteins possessing only one binding site and, therefore, are not capable of precipitating glycoconjugates or agglutinating cells [11]. Thus, in 1995 Peumans and Van Damme proposed the most suitable definition for lectins. According to the "new" definition, all plant proteins that possess at least one noncatalytic domain that binds reversibly to a specific mono-or oligosaccharide are considered as lectins [12,13]. 2.1. Plant lectins Lectins are proteins widely distributed in nature such in microorganisms, plants, animals and humans, acting as mediators of a wide range of biological events that involve the crucial step of protein-carbohydrate recognition, such as cell communication, host defense, fertilization, cell development, parasitic infection, tumor metastasis, inflammation, etc [14-15]. Peumans and Van Damme classified the plant lectins according to their overall structure. Merolectins consist exclusively of a single carbohydrate-binding domain (e.g. hevein, a

Chemical Communications, 2008

Carbohydrate arrays (glycoarrays) have recently emerged as a high-throughput tool for studying carbohydrate-binding proteins and carbohydrate-processing enzymes. A number of sophisticated array platforms that allow for qualitative and quantitative analysis of carbohydrate binding and modification on the array surface have been developed, including analysis by fluorescence spectroscopy, mass spectrometry and surface plasmon resonance spectroscopy. These platforms, together with examples of biologically-relevant applications are reviewed in this Feature Article.

Chembiochem, 2004

Bioconjugate Chemistry, 2009

Carbohydrate microarrays have received great attention as high-throughput analytic tools in studies of carbohydratemediated biological processes. Most of the methods employed to fabricate glycan microarrays rely on the immobilization of modified glycans on the properly derivatized surfaces. This immobilization strategy requires the availability of modified glycans whose syntheses in many cases are time-consuming and difficult. We have developed a simple and direct immobilization technique that involves a one-step, site-specific attachment of diverse unmodified glycans to the hydrazide-derivatized glass surface. To demonstrate the generality of this direct immobilization method, we examined its use for the construction of carbohydrate microarrays containing a variety of glycans. The results of protein and cell-binding experiments indicate that the glycan microarrays, prepared by using this methodology, are applicable to the rapid evaluation of glycan-mediated biomolecular interactions and the determination of quantitative binding affinities between carbohydrates and proteins.

Natural Product Communications

A simple method to immobilize carbohydrates on a glass surface to obtain a carbohydrate microarray is described. The array was used to study carbohydrate-lectin interactions. The glass surface was modified with aldehyde terminated linker groups of various chain lengths. Coupling of carbohydrates with an amino terminated alkyl spacer to the aldehyde terminated glass followed by reductive amination resulted in carbohydrate microarrays. Fluorescently labeled (FI-TC) lectins (concanavalin A and Arachis hypogaea) were used to study specific carbohydrate-lectin interactions. contact angle, atomic force microscopy (AFM) and confocal laser fluorescence microscopy (CLFM) techniques were used in this study to monitor the modification of the glass and the successful selective binding of lectins to the carbohydrate microarray.