Analysis and purification of oligosaccharides by high-performance liquid affinity chromatography

Analysis of biomolecular interactions using affinity microcolumns: a review

Affinity chromatography has become an important tool for characterizing biomolecular interactions. The use of affinity microcolumns, which contain immobilized binding agents and have volumes in the mid-to-low microliter range, has received particular attention in recent years. Potential advantages of affinity microcolumns include the many analysis and detection formats that can be used with these columns, as well as the need for only small amounts of supports and immobilized binding agents. This review examines how affinity microcolumns have been used to examine biomolecular interactions. Both capillary-based microcolumns and short microcolumns are considered. The use of affinity microcolumns with zonal elution and frontal analysis methods are discussed. The techniques of peak decay analysis, ultrafast affinity extraction, split-peak analysis, and band-broadening studies are also explored. The principles of these methods are examined and various applications are provided to illustrate the use of these methods with affinity microcolumns. It is shown how these techniques can be utilized to provide information on the binding strength and kinetics of an interaction, as well as on the number and types of binding sites. It is further demonstrated how information on competition or displacement effects can be obtained by these methods.

Immunoaffinity chromatography: an introduction to applications and recent developments

Immunoaffinity chromatography (IAC) combines the use of LC with the specific binding of antibodies or related agents. The resulting method can be used in assays for a particular target or for purification and concentration of analytes prior to further examination by another technique. This review discusses the history and principles of IAC and the various formats that can be used with this method. An overview is given of the general properties of antibodies and of antibody-production methods. The supports and immobilization methods used with antibodies in IAC and the selection of application and elution conditions for IAC are also discussed. Several applications of IAC are considered, including its use in purification, immunodepletion, direct sample analysis, chromatographic immunoassays and combined analysis methods. Recent developments include the use of IAC with CE or MS, ultrafast immunoextraction methods and the use of immunoaffinity columns in microanalytical systems.

Applications of silica supports in affinity chromatography

The combined use of silica-based chromatographic supports with immobilized affinity ligands can be used in many preparative and analytical applications. One example is the use of silica-based affinity columns in HPLC, giving rise to a method known as high-performance affinity chromatography (HPAC). This review discusses the role that silica has played in the development of affinity chromatography and HPAC and the applications of silica in these methods. This includes a discussion of the types of ligands that have been employed with silica and the methods by which these ligands have been immobilized. Various formats have also been presented for the use of silica in affinity chromatographic methods, including assays involving direct or indirect analyte detection, on-line or off-line affinity extraction, and chiral separations. The use of silica-based affinity columns in studies of biological systems based on zonal elution and frontal analysis methods will also be considered.

Application of cereals and cereal components in functional foods: a review

The food industry is directing new product development towards the area of functional foods and functional food ingredients due to consumers' demand for healthier foods. In this respect, probiotic dairy foods containing human-derived Lactobacillus and Bifidobacterium species and prebiotic food formulations containing ingredients that cannot be digested by the human host in the upper gastrointestinal tract and can selectively stimulate the growth of one or a limited number of colonic bacteria have been recently introduced into the market. The aim of these products is to affect beneficially the gut microbial composition and activities. Cereals offer another alternative for the production of functional foods. The multiple beneficial effects of cereals can be exploited in different ways leading to the design of novel cereal foods or cereal ingredients that can target specific populations. Cereals can be used as fermentable substrates for the growth of probiotic microorganisms. The main parameters that have to be considered are the composition and processing of the cereal grains, the substrate formulation, the growth capability and productivity of the starter culture, the stability of the probiotic strain during storage, the organoleptic properties and the nutritional value of the final product. Additionally, cereals can be used as sources of nondigestible carbohydrates that besides promoting several beneficial physiological effects can also selectively stimulate the growth of lactobacilli and bifidobacteria present in the colon and act as prebiotics. Cereals contain water-soluble fibre, such as beta-glucan and arabinoxylan, oilgosaccharides, such as galacto- and fructo-oligosaccharides and resistant starch, which have been suggested to fulfil the prebiotic concept. Separation of specific fractions of fibre from different cereal varieties or cereal by-products, according to the knowledge of fibre distribution in cereal grains, could be achieved through processing technologies, such as milling, sieving, and debranning or pearling. Finally, cereal constituents, such as starch, can be used as encapsulation materials for probiotics in order to improve their stability during storage and enhance their viability during their passage through the adverse conditions of the gastrointestinal tract. It could be concluded that functional foods based on cereals is a challenging perspective, however, the development of new technologies of cereal processing that enhance their health potential and the acceptability of the food product are of primary importance.

Affinity Chromatography: A Review of Clinical Applications

Affinity chromatography is a type of liquid chromatography that makes use of biological-like interactions for the separation and specific analysis of sample components. This review describes the basic principles of affinity chromatography and examines its use in the testing of clinical samples, with an emphasis on HPLC-based methods. Some traditional applications of this approach include the use of boronate, lectin, protein A or protein G, and immunoaffinity supports for the direct quantification of solutes. Newer techniques that use antibody-based columns for on- or off-line sample extraction are examined in detail, as are methods that use affinity chromatography in combination with other analytical methods, such as reversed-phase liquid chromatography, gas chromatography, and capillary electrophoresis. Indirect analyte detection methods are also described in which immunoaffinity chromatography is used to perform flow-based immunoassays. Other applications that are reviewed include affinity-based chiral separations and the use of affinity chromatography for the study of drug or hormone interactions with binding proteins. Some areas of possible future developments are then considered, such as tandem affinity methods and the use of synthetic dyes, immobilized metal ions, molecular imprints, or aptamers as affinity ligands for clinical analytes.

Survey of recent advances in analytical applications of immunoaffinity chromatography

Methods that use immunoaffinity chromatography (IAC) for sample preparation or detection are becoming increasingly popular as tools in the analysis of biological and nonbiological compounds. This paper presents an overview of immunoaffinity chromatography and examines some recent developments of this technique in analytical applications. The emphasis is placed on HPLC-based IAC methods or those that combine IAC with other instrumental techniques; however, novel approaches that employ low-performance IAC columns for chemical quantitation are also considered. Particular applications that are examined include (1) the use of IAC in the direct detection of analytes, (2) the extraction of samples by IAC prior to on- or off-line detection by other methods, (3) the use of IAC in chromatographic-based immunoassays, and (4) the development of postcolumn reactors based on IAC for the detection of analytes as they elute from other types of chromatographic columns. The advantages and limitations for each approach are considered. In addition, a summary is provided of reports in the literature that have used IAC for these various formats.

The analysis of fluorophore-labeled carbohydrates by polyacrylamide gel electrophoresis

The glycans of glycoconjugates mediate numerous important biological processes. Their separation and structural determination present considerable difficulties because of the small quantities that are available from biological sources and the inherent difficulty of analyzing the wide variety of complex structures that exist. A method for the analysis of reducing saccharides by PAGE that uses specific fluorophore labeling and is simple, rapid, sensitive, and readily available to biological researchers, has been developed. This method is known acronimically either as PAGEFS (PAGE of Fluorophore-labeled Saccharides) or in one commercial format as FACE (Fluorophore-Assisted Carbohydrate Electrophoresis). In the PAGEFS method, saccharides having an aldehydic reducing end group are labeled quantitatively with a fluorophore and then separated with high resolution by PAGE. Two fluorophores, 8-aminonaphthalene-1,3,6-trisulfonic acid (ANTS) and 2-aminoacridone (AMAC), have been used to enable the separation of a variety of saccharide positional isomers, anomers, and epimers. Subpicomolar quantities of individual saccharides can be detected using a sensitive imaging system. Mixtures of oligosaccharides obtained by enzymatic cleavage from glycoproteins can be labeled and electrophoresed to yield an oligosaccharide profile of each protein. AMAC can be used to distinguish unequivocally between acidic and neutral oligosaccharides. Methods of obtaining saccharide sequence information from purified oligosaccharides have been developed using enzymatic degradation. Other applications and the potential of the system are described.

Detection of fungal carbohydrate antigens by high-performance immunoaffinity chromatography using a protein A column with covalently linked immunoglobulin G

Fungal carbohydrate antigens were analysed by high-performance immunoaffinity chromatography (HPIAC) with immunoglobulin G (IgG) antibodies raised against extracellular polysaccharides of Mucor racemosus. The protein A-IgG complex was covalently bound with dimethyl pimelimidate, which enabled the use of strong acidic buffers to release the tightly bound antigens from the column. Prior to pulsed-amperometric detection, an anion-micromembrane suppressor was used to raise the pH of the effluent to above 12 without dilution. The HPIAC system provides a sophisticated method for the rapid and sensitive detection of antigenic oligomeric carbohydrates in biological samples and is proposed as an alternative to quantitative enzyme-linked immunosorbent assay techniques.

The selectin GMP-140 binds to sialylated, fucosylated lactosaminoglycans on both myeloid and nonmyeloid cells

Granule membrane protein-140 (GMP-140) is an inducible receptor for myeloid leukocytes on activated platelets and endothelium. Like other selectins, GMP-140 recognizes specific oligosaccharide ligands. However, prior data on the nature of these ligands are contradictory. We investigated the structural features required for ligand interaction with GMP-140 using purified GMP-140, cells naturally expressing specific oligosaccharides, and cells expressing cloned glycosyltransferases. Like the related selectin endothelial leukocyte adhesion molecule-1 (ELAM-1), GMP-140 recognizes alpha(2-3)sialylated, alpha(1-3)fucosylated lactosaminoglycans on both myeloid and nonmyeloid cells, including the sequence Neu5Ac alpha 2-3Gal beta 1-4(Fuc alpha 1-3)GlcNac beta-R (sialyl Lewis x). Recognition requires sialic acid, because cells expressing large amounts of Lewis x, but not sialyl Lewis x, do not interact with GMP-140. Although sialyl Lewis x is expressed by both myeloid HL-60 cells and CHO cells transfected with an alpha 1-3/4 fucosyltransferase, GMP-140 binds with significantly higher affinity to HL-60 cells. Thus, the sialyl Lewis x tetrasaccharide may require additional structural modifications or specific presentations in order for leukocytes in flowing blood to interact rapidly and with high affinity to GMP-140 on activated platelets or endothelium.