A wide variety of complex oligosaccharides has now been made accessible as a result of methodological improvements in the sphere of chemical synthesis, which can be used for the study of conformations and interactions with protein-receptor molecules. Such work is of particular importance because the oligosaccharide chains of glycoproteins and glycolipids anchored to the plasma membrane are important in cell-cell interactions and are receptors for enzymes, hormones, proteins, and viruses; furthermore, they determine the antigen properties of cells. The methods of synthesis available for the production of selective linkages in oligosaccharides are dealt with, particular attention being paid to conversion of saccharides into oligosaccharides, which are important from the biological point of view.

Advances in Selective Chemical Syntheses of Complex Oligosaccharides

13C nmr study of α- and β-anomeric pairs of d-mannopyranosides and l-rhamnopyranosides

CE has been alive for over two decades now, yet its sensitivity is still regarded as being inferior to that of more traditional methods of separation such as HPLC. As such, it is unsurprising that overcoming this issue still generates much scientific interest. This review continues to update this series of reviews, first published in Electrophoresis in 2007, with updates published in 2009 and 2011 and covers material published through to June 2012. It includes developments in the field of stacking, covering all methods from field amplified sample stacking and large volume sample stacking, through to isotachophoresis, dynamic pH junction and sweeping. Attention is also given to online or inline extraction methods that have been used for electrophoresis.

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Recent advances in enhancing the sensitivity of electrophoresis and electrochromatography in capillaries and microchips (2016–2018)

Specificity in the interaction of direct dyes with polysaccharides

Publisher Summary This chapter focuses on the hemicelluloses of the Gramineae (grasses and cereals). The term “hemicelluloses” is also often extended to include certain carbohydrates in cereal endosperms—namely, non-starch polysaccharides. Hemicellulose refers to all of the types of polysaccharide in the Gramineae, other than celluloses, starches, and fructans. Hemicellulose chemistry has a vocabulary lacking invariant definitions, and insight into the nature of hemicelluloses has been gained by the work not only of chemists and biochemists but of applied scientists having research interests in animal nutrition, brewing, cereals, paper manufacture, and starch production. The chapter also discusses species and various tribes of Gramineae, isolation of hemicellulosimca materials and of pure hemicelluloses, and structural feature in hemicelluloses. The importance of knowledge about the hemicelluloses may be gauged by looking at the abundance of photosynthetically renewable grasses and bearing in mind that, apart from the materials in the seed, one third of their composition is hemicellulose.

The Hemicelluloses of Grasses and Cereals

Velocity-difference induced focusing (V-DIF) of nucleotides was achieved by using a dynamic pH junction in capillary electrophoresis (CE) with UV detection. The influence of specific analyte properties, such as nucleotide base structure, sugar structure, and degree of phosphorylation, is examined. The pKa values and borate complexation with vicinal diols are important factors that caused the focusing. Therefore, the pH and borate content in the sample and background electrolyte can be adjusted to optimize the focusing effect. This method allows the injection of large volumes of sample (∼300 nL), resulting in at least 50-fold improvement in concentration sensitivity. The detection limit of 4.0 × 10-8 M for nucleotides can be achieved in favorable conditions. V-DIF can be also applied to nucleotide pool analysis from cell extracts to improve the concentration sensitivity of CE and to reduce the time-consuming steps of desalting and off-line preconcentration that are often required for assays of nucleotides ...

Velocity-difference induced focusing of nucleotides in capillary electrophoresis with a dynamic pH junction.

A comprehensive theory is proposed to describe the migration behavior of analytes in capillary electrophoresis (CE) when one or more additives are present in the buffer solution. This theory amalgamates and extends the previous work done by others. The capacity factor (k') in this theory is defined as the product of the equilibrium constant and the additive concentration, thus, k' changes linearly with additive concentration. The net electrophoretic mobility of an analyte is a function of k', therefore, it can be changed by varying the additive concentration. Three parameters are needed to predict the mobility of an analyte in a one-additive CE system: the mobility of the free analyte, the mobility of the complex, and the equilibrium constant for the analyte-additive interaction (which determines the fraction of the free analyte at different additive concentrations). When additives are used, the change in viscosity obscures this relationship, therefore, a viscosity correction factor is required to convert all mobilities to an ideal state where the viscosity remains constant. The migration behavior of an analyte in a solution with multiple additives can be predicted and controlled, once the equilibrium constants of the interactions between the analyte and each of the additives are obtained separately. beta-Cyclodextrin and hydroxypropyl-beta-cyclodextrin are used as additives and the migration behavior of phenol, p-nitrophenol, and benzoic acid are studied as a model system to verify this theory. When the necessary viscosity correction factor is included, the net electrophoretic mobilities of the analytes obtained from experimental results agree with the values predicted by the theory based on dynamic complexation. Although only experiments with one and two additives were carried out to verify the theory, the equations apply to situations when more than two additives are used. The relationship between the theories of electrophoresis and chromatography is clarified.

Quantitative description of analyte migration behavior based on dynamic complexation in capillary electrophoresis with one or more additives.

Synthesis of 4-O-β-D-mannopyranosyl-L-rhamnopyranose

The presence of acetate and pyruvate groups in Klebsiella capsular polysaccharides may be demonstrated and estimated quantitatively by running the proton magnetic resonance spectrum of the polysaccharide (as sodium salt) in deuterium oxide at 95 C. Such spectra also permit an assessment to be made of the number of alpha- and beta-linkages in the repeat unit of the polysaccharide structure.

Proton Magnetic Resonance Spectroscopy of Klebsiella Capsular Polysaccharides

The configuration (D or L) of a sugar may be determined conveniently by circular dichroism measurements at 213 nm on alditol acetates, or their methylated derivatives, where the acetoxy group acts as a chromophore. Only milligram quantities of material are required and the method is well suited to analyzing fractions obtained by gas–liquid chromatography. Structural information which may be derived from the c.d. spectra is briefly discussed.

Gwendolyn M. Bebault

Papers

Velocity-difference induced focusing of nucleotides in capillary electrophoresis with a dynamic pH junction.

Quantitative description of analyte migration behavior based on dynamic complexation in capillary electrophoresis with one or more additives.

Synthesis of 4-O-β-D-mannopyranosyl-L-rhamnopyranose

Proton Magnetic Resonance Spectroscopy of Klebsiella Capsular Polysaccharides

Semimicro Determination of Sugar Configuration by Measurement of Circular Dichroism of Alditol Acetates