Separation of negatively charged carbohydrates by capillary electrophoresis

Clinical presentation and diagnosis of mucopolysaccharidoses

Mucopolysaccharidoses (MPS) are estimated to affect1 in 25,000 live births although specific rates vary between the ethnic origin and country. MPS are a group of lysosomal storage disorders, which cause the buildup of GAG(s) due to insufficient or absent GAG-degrading enzymes. With seven types of MPS disorders and eleven subtypes, the MPS family presents unique challenges for early clinical diagnosis due to the molecular and clinical heterogeneity between groups and patients. Novel methods of early identification, particularly newborn screening through mass spectrometry, can change the flow of diagnosis, allowing enzyme and GAG quantification before the presentation of clinical symptoms improving outcomes. Genetic testing of patients and their families can also be conducted preemptively. This testing enables families to make informed decisions about family planning, leading to prenatal diagnosis. In this review, we discuss the clinical symptoms of each MPS type as they initially appear in patients, biochemical and molecular diagnostic methods, and the future of newborn screening for this group of disorders.

Glycosaminoglycans detection methods: Applications of mass spectrometry

Glycosaminoglycans (GAGs) are long blocks of negatively charged polysaccharides. They are one of the major components of the extracellular matrix and play multiple roles in different tissues and organs. The accumulation of undegraded GAGs causes mucopolysaccharidoses (MPS). GAGs are associated with other pathological conditions such as osteoarthritis, inflammation, diabetes mellitus, spinal cord injury, and cancer. The need for further understanding of GAG functions and mechanisms of action boosted the development of qualitative and quantitative (alcian blue, toluidine blue, paper and thin layer chromatography, gas chromatography, high pressure liquid chromatography, capillary electrophoresis, 1,9-dimethylmethylene blue, enzyme linked-immunosorbent assay, mass spectrometry) techniques. The availability of quantitative techniques has facilitated translational research on GAGs into the medical field for: 1) diagnosis, monitoring, and screening for MPS; 2) analysis of GAG synthetic and degradation pathways; and 3) determination of physiological and pathological roles of GAGs. This review provides a history of development of GAG assays and insights about the use of tandem mass spectrometry and its applications for GAG analysis.

Recent advances on separation and characterization of human milk oligosaccharides

Free human milk oligosaccharides (HMOs) are unique due to their highly complex nature and important emerging biological and protective functions during early life such as prebiotic activity, pathogen deflection, and epithelial and immune cell modulation. Moreover, four genetically determined heterogeneous HMO secretory groups are known to be based on their structure and composition. Over the years, several analytical techniques have been applied to characterize and quantitate HMOs, including nuclear magnetic resonance spectroscopy, high-performance liquid chromatography (HPLC), high pH anion-exchange chromatography, off-line and on-line mass spectrometry (MS), and capillary electrophoresis (CE). Even if these techniques have proven to be efficient and simple, most glycans have no significant UV absorption and derivatization with fluorophore groups prior to separation usually results in higher sensitivity and an improved chromatographic/electrophoretic profile. Consequently, the analysis by HPLC/CE of derivatized milk oligosaccharides with different chromophoric active tags has been developed. However, UV or fluorescence detection does not provide specific structural information and this is a key point in particular related to the highly complex nature of the milk glycan mixtures. As a consequence, for a specific determination of complex mixtures of oligomers, analytical separation is usually required with evaluation by means of MS, which has been successfully applied to HMOs, resulting in efficient compositional analysis and profiling in various milk samples. This review aims to give an overview of the current state-of-the-art techniques used in HMO analysis.

Capillary Electrophoresis of Mono- and Oligosaccharides

This chapter reports an overview of the recent advances in the analysis of mono- and oligosaccharides by capillary electrophoresis (CE); furthermore, relevant reviews and research articles recently published in the field are tabulated. Additionally, pretreatments and procedures applied to uncharged and acidic carbohydrates (i.e., monosaccharides and lower oligosaccharides carrying carboxylate, sulfate, or phosphate groups) are described.Representative examples of such procedures are reported in detail, upon describing robust methodologies for the study of (1) neutral oligosaccharides derivatized by reductive amination and by formation of glycosylamines; (2) sialic acid derivatized with 2-aminoacridone, released from human serum immunoglobulin G; (3) anomeric couples of neutral glycosides separated using borate-based buffers; (4) unsaturated, underivatized oligosaccharides from lyase-treated alginate.

High-performance CE of Escherichia coli K4 cell surface polysaccharides

A high-performance CE application for a quick, reproducible, highly precise and sensitive determination of the lipopolysaccharide produced by Escherichia coli K4 (O5:K4:H4) and of its de-lipid A form is described. The two species were separated within 30 min on an uncoated fused-silica capillary, in normal polarity mode at 20 kV, using an SDS buffer. Detected at 190 nm, the de-lipid A and the LPS species showed two peaks at distinctive migration times (10.45 and 16.10 min, respectively) and were quantified with high reproducibility and linearity (the correlation factors were 0.99 and 0.98, respectively) over the ranges from 60 to 600 ng (1-10 ng/nL) for de-lipid A lipopolysaccharide and from 150 to 600 ng (2.5-10 ng/nL) for the LPS. The described method was also employed in the contemporary analysis and the determination of the two E. coli K4 cell surface polysaccharides, the LPS and the K4, and of their defructosylated and de-lipid A species, respectively. The four molecules were detected and precisely quantified in complex matrices as fermentation broth supernatant or in samples withdrawn throughout the purification process, thus demonstrating the possibility to apply high-performance CE as a reliable analytical tool in biotechnological processes.

Improved workup for glycosaminoglycan disaccharide analysis using CE with LIF detection

This work describes improved workup and instrumental conditions to enable robust, sensitive glycosaminoglycan (GAG) disaccharide analysis from complex biological samples. In the process of applying CE with LIF to GAG disaccharide analysis in biological samples, we have made improvements to existing methods. These include (i) optimization of reductive amination conditions, (ii) improvement in sensitivity through the use of a cellulose cleanup procedure for the derivatization, and (iii) optimization of separation conditions for robustness and reproducibility. The improved method enables analysis of disaccharide quantities as low as 1 pmol prior to derivatization. Biological GAG samples were exhaustively digested using lyase enzymes, the disaccharide products and standards were derivatized with the fluorophore 2-aminoacridone and subjected to reversed polarity CE-LIF detection. These conditions resolved all known chondroitin sulfate (CS) disaccharides or 11 of 12 standard heparin/heparan sulfate disaccharides, using 50 mM phosphate buffer, pH 3.5, and reversed polarity at 30 kV with 0.3 psi pressure. Relative standard deviation in migration times of CS ranged from 0.1 to 2.0% over 60 days, and the relative standard deviations of peak areas were less than 3.2%, suggesting that the method is reproducible and precise. The CS disaccharide compositions are similar to those obtained by our group using tandem MS. The reversed polarity CE-LIF disaccharide analysis protocol yields baseline resolution and quantification of heparin/heparan sulfate and CS/dermatan sulfate disaccharides from both standard preparations and biologically relevant proteoglycan samples. The improved CE-LIF method enables disaccharide quantification of biologically relevant proteoglycans from small samples of intact tissue.

Capillary electrophoresis of acidic oligosaccharides from human milk

Interest in defining the array of oligosaccharides of human milk has been increasing. Pathogens that bind glycans on their host mucosal surfaces may be inhibited by human milk oligosaccharides. It has been postulated that acidic oligosaccharides in human milk may inhibit binding by pathogens that bind acidic glycans in the gut, but testing this hypothesis requires their reliable quantification in milk. Sialyloligosaccharides of human milk have been quantified by HPLC and CE. A recent CE technique uses the MEKC mode with direct detection at 205 nm to resolve and quantify, in the native form, the 12 most dominant sialyloligosaccharides of human milk in a single 35-min run. The method gives a linear response from 39 to 2500 microg/mL with a coefficient of variation between 2 to 9% and accuracy from 93 to 109%. This was used to detect variation in expression of specific sialyloligosaccharides in milk. Individual sialyloligosaccharide concentrations in milk differ among individual donors and between less and more mature milk. Thus, CE can be used to measure variation in sialyloligosaccharide expression in milk, and thereby test the relationship of this variation-to-variation in risk of specific diseases in breastfed infants.

Capillary electrophoresis of sugar acids

This chapter illustrates the usefulness of capillary electrophoresis (CE) for the analysis of sugar acids, that is, monosaccharides and lower oligosaccharides carrying carboxylate, sulphate or phosphate groups. In order to provide a general description of the main results and challenges in the field, some relevant applications and reviews on CE of such saccharidic compounds are tabulated. Furthermore, some detailed experimental procedures are shown, regarding the CE analysis of sugar acids released upon hydrolysis of acidic polysaccharides and of glycans linked to glycoproteins. In particular, the protocols will deal with the following compounds: (i) unsaturated, underivatized oligosaccharides from lyase-treated alginate; (ii) oligosaccharides derivatized with 4-aminobenzonitrile, arising from chemical hydrolysis of alginate; (iii) sialic acid derivatized with 2-aminoacridone, released from human serum immunoglobulin G.

A simple capillary electrophoresis method for the rapid separation and determination of intact low molecular weight and unfractionated heparins

A simple, selective and accurate capillary electrophoresis (CE) method has been developed for the rapid separation and identification of various low molecular weight heparins (LMWHs) and unfractionated heparin. Separation and operational parameters were investigated using dalteparin sodium as the test LMWH. The developed method used a 70 cm fused silica capillary (50 microm i.d.) with a detection window 8.5 cm from the distal end. Phosphate electrolyte (pH 3.5; 50 mM), an applied voltage of -30 k V, UV detection at 230 nm and sample injection at 20 mbar for 5s were used. The method performance was assessed in terms of linearity, selectivity, intra- and inter-day precision and accuracy. The method was successfully applied to the European Pharmacopeia LMWH standard, dalteparin sodium, enoxaparin sodium and heparin sodium with a significant reduction in the run time and increased resolution compared with previously reported CE methods. Different CE separation profiles were obtained for various LMWHs and unfractionated heparin showing significant structural diversity. The current methodology was sensitive enough to reveal minor constituent differences between two different batches of enoxaparin sodium. This CE method also clearly showed chemical changes that occurred to LMWHs under different stress conditions. The sensitivity, selectivity and simplicity of the developed method allow its application in research or manufacturing for the identification, stability analysis, characterization and monitoring of batch-to-batch consistency of different low molecular weight and unfractionated heparins.

Enhanced electrophoretic resolution of monosulfate glycosaminoglycan disaccharide isomers on poly(methyl methacrylate) chips

To improve the separation of monosulfate glycosaminoglycan disaccharide isomers by microchip electrophoresis, we found that addition of 1,4-dioxane (DO) dramatically improved analyte resolution, probably due to solvation effects. Methylcellulose (MC) was tested for the ability to suppress EOF and analyte adsorption to the chip. To improve analyte resolution, buffer pH, beta-CD, and DO were systematically investigated. Fast separation was achieved by increasing the electric field strength, and field-amplified sample stacking occurred with increasing buffer concentrations. Therefore, based on our findings, we describe an efficient method for the separation of monosulfate and trisulfate unsaturated disaccharides (DeltaDi-UA2S, DeltaDi-4S, DeltaDi-6S, and DeltaDi-triS) derivatized with 2-aminoacridone hydrochloride. A mixture of monosulfate disaccharide isomers (DeltaDi-UA2S, DeltaDi-4S, and DeltaDi-6S) was baseline-separated within 75 s on a poly(methyl methacrylate) chip using a mixed buffer (DO/running buffer 57:43 v:v), 0.5% MC, pH 6.81, with an E(sep) of 558 V/cm. The theoretical plate was in the range of 5 x 10(5) to 1 x 10(6) m-1.

Development of a novel analytical method for determination of chondroitin sulfate using an in-capillary enzyme reaction

A novel analytical method for determination of total amount of chondroitin sulfate (CS) based on its conversion to desulfated chondro-disaccharide via an enzyme-catalyzed reaction, was developed. Using the in-capillary enzyme reaction, the method was also applied to the successful construction of an on-line analytical system. Within this system, electrophoretic migration was used to mix zones containing the enzyme mixture (chondroitinase ABC, chondro-4-sulfatase, chondro-6-sulfatase and 2-o-sulfatase) and the substrate (CS). The reaction was then allowed to proceed in the presence of a weak electric field and, finally, the product (desulfated chondro-disaccharide) of enzyme reaction migrated to the detector under the influence of an applied electric field. A polyvinyl alcohol-coated capillary was used to reduce protein adsorption. Desulfated chondro-disaccharide was successfully migrated toward the anode in 10 mM Tris-acetate buffer (pH 7.0) under reversed polarity and detected at 232 nm. The established method was validated and demonstrated to be applicable in the determination of total amount of CS in a commercial ophthalmic solution. No interference from the formulation excipients was observed. Good linearity was obtained, with correlation coefficients above 0.999. Recoveries and precisions ranged from 100.0 to 100.5%, and from 0.2 to 0.6% of the relative standard deviation, respectively. Good agreement was obtained between the established method and traditional photometric method based on carbazole reaction. In this study, application of the method to disaccharide compositional analysis was also performed.

Reversed-phase ion-pairing liquid chromatography/ion trap mass spectrometry for the analysis of negatively charged, derivatized glycans

The significant complexity, similar polarity and lack of ionizable sites make the analysis of glycans an analytical challenge. These compounds are often derivatized and separated by normal-phase high-performance liquid chromatography (HPLC) or capillary electrophoresis (CE) followed by UV or fluorescence detection. Due to widespread use of reversed-phase chromatography coupled to electrospray mass spectrometry as an analytical tool, our laboratory has developed this methodology for the analysis of glycans derivatized with a negatively charged tag, 8-aminonaphthalene-1,3,6-trisulfonic acid (ANTS). It is possible to exploit the ability of this negatively charged tag to interact with a mobile phase ion-pairing reagent, allowing retention on a reversed-phase C(18) column for subsequent on-line UV or MS analysis. ANTS-derivatized samples, including a maltooligosaccharide ladder and glycans released from bovine ribonuclease B, bovine fetuin, and chicken ovalbumin, were analyzed using this method. In addition to reversed-phase retention, ribonuclease B and ovalbumin derivatives displayed highly desirable isomeric separation. With the use of mass spectrometric detection for glycan identity, this allowed relative quantitation of individual components.

Advances in analysis of glycosaminoglycans: its application for the assessment of physiological and pathological states of connective tissues

Glycosaminoglycans are a class of biological macromolecules found mainly in connective tissues as constituents of proteoglycans, covalently linked to their core protein. Hyaluronan is the only glycosaminoglycan present under its single form and possesses the ability to aggregate with the class of proteoglycans termed hyalectans. Proteoglycans are localised both at the extracellular and cellular (cell-surface and intracellular) levels and, via either their glycosaminoglycan chains or their core proteins participate in and regulate several cellular events and (patho)physiological processes. Advances in analytical separational techniques, including high-performance liquid chromatography, capillary electrophoresis and fluorophore assisted carbohydrate electrophoresis, make possible to examine alterations of glycosaminoglycans with respect to their amounts and fine structural features in various pathological conditions, thus becoming applicable for diagnosis. In this review we present the chromatographic and electromigration procedures developed to analyse and characterise glycosaminoglycans. Moreover, a critical evaluation of the biological relevance of the results obtained by the developed methodology is discussed.

Capillary electrophoresis for the analysis of glycosaminoglycans and glycosaminoglycan-derived oligosaccharides

Glycosaminoglycans are a family of polydisperse, highly sulfated complex mixtures of linear polysaccharides that are involved in many life processes. Defining the structure of glycosaminoglycans is an important factor in elucidating their structure-activity relationship. Capillary electrophoresis has emerged as a highly promising technique consuming an extremely small amount of sample and capable of rapid, high-resolution separation, characterization and quantitation of analytes. Numerous capillary electrophoresis methods for analysis of intact glycosaminoglycans and glycosaminoglycan-derived oligosaccharides have been developed. These methods allow for both qualitative and quantitative analysis with a high level of sensitivity. This review is concerned with separation methods of capillary electrophoresis, detection methods and applications to several aspects of research into glycosaminoglycans and glycosaminoglycan-derived oligosaccharides. The importance of capillary electrophoresis in biological and pharmaceutical samples in glycobiology and carbohydrate biochemistry and its possible applications in disease diagnosis and monitoring chemical synthesis are described.

Analysis of intact heparin by capillary electrophoresis using short end injection configuration

A capillary electrophoresis method for the analysis of intact heparin was developed using a phosphate buffer and a fused silica capillary. Operational parameters such as pH and concentration of the running buffer were investigated. The short end injection configuration permitted a gain on peak efficiency, on the analysis time and on the repeatability of both migration times and peak areas, through a reduction of the migration distance. Moreover, the beneficial effect of the presence of sodium chloride in the heparin sample on the peak efficiency was demonstrated and the influence of the salts on the conformation of the heparin was discussed. The optimized method (short end injection configuration, 50mM phosphate buffer pH 3, heparin sample prepared in 10 g/L NaCl solution) was validated in terms of linearity, reproducibility and specificity according to ICH requirements.

Analysis of glycosaminoglycan-derived disaccharides in biologic samples by capillary electrophoresis and protocol for sequencing glycosaminoglycans

Glycosaminoglycans are biologically significant carbohydrates which either as free chains (hyaluronan) or constituents of proteoglycans (chondroitin/dermatan sulfates, heparin, heparan sulfate and keratan sulfate) participate and regulate several cellular events and (patho)physiological processes. Capillary electrophoresis, due to its high resolving power and sensitivity, has been successfully used for the analysis of glycosaminoglycans. Determination of compositional characteristics, such as disaccharide sulfation pattern, is a useful prerequisite for elucidating the interactions of glycosaminoglycans with matrix effective molecules and, therefore, essential in understanding the biological functions of proteoglycans. The interest in the field of characterization of such biologically important carbohydrates is soaring and advances in this field will signal a new revolution in the area of glycomics equivalent to that of genomics and proteomics. This review focuses on the capillary electrophoresis methods used to determine the disaccharide pattern of glycosaminoglycans in various biologic samples as well as advances in the sequence analysis of glycosaminoglycans using both chromatographic and electrophoretic techniques.

Structure analysis of lipoglycans and lipoglycan-derived carbohydrates by capillary electrophoresis and mass spectrometry

Lipoglycans (lipopolysaccharides, lipoarabinomannans and glycolipids) are unique components of the cell membrane of all cells and the envelope of many bacteria. They play important roles in determining cell-environment interactions, which, however, are only partly understood due to incomplete description of their structural components, lipids and glycans. Capillary electrophoresis is an analytical technique of high separation efficiency and minimum sample requirements and has successfully been used for the analysis of several molecules of biological importance: proteins, nucleic acids and glycoconjugates. In the last years, a few applications of capillary electrophoresis to the analysis of lipoglycans have been reported. Analysis of lipoglycans involves the study of two parameters: intact molecules and carbohydrate parts. The conjunction of capillary electrophoresis and mass spectroscopy not only enhances the detection sensitivity, but also provides structural information on these structurally complex molecules. The interest in the field is rising and the results from the exact determination on the lipoglycan structure are expected to improve our understanding of the molecular mechanism of lipoglycan binding to proteins and cells of host organisms as well as their relationship to the virulence and pathogenesis of bacteria. In this report, an overview of the capillary electrophoresis methods used to analyze and characterize the intact lipoglycans as well as their carbohydrate parts is presented.

A capillary zone electrophoresis method for determining N-acetylneuraminic acid in glycoproteins and blood sera

A simple capillary zone electrophoresis (CZE) method for the determination of the content of the major sialic acid form N-acetylneuraminic acid (Neu5Ac) in glycoproteins was established. The present method utilizes a simplified hydrolysis-purification procedure consisting of mild acid hydrolysis (25 mM trifluoroacetic acid for 2h at 80 degrees C) to release Neu5Ac and ultrafiltration on Centricon-3 membrane to remove the obtained asialoglycoproteins and other macromolecules present in biologic samples. Derivatization with benzoic anhydride at 80 degrees C for 20 min resulted in complete conversion of Neu5Ac to per-O-benzoylated Neu5Ac. CZE analysis was performed using the operating buffer 25mM phosphate, pH 3.5, containing 50% (v/v) acetonitrile as organic modifier at 30 kV, and detection of the per-O-benzoylated Neu5Ac at 231 nm. The method showed excellent repeatability (RDS<1.98%) and a linearity range from 5 microg/mL to 5mg/mL with a detection limit of 2 microM. Application of the method to microanalysis of human alpha(1)-acid glycoprotein and blood serum samples showed excellent agreement with previously published values, suggesting a high precision for the developed CZE method.

Ultramicroanalysis of reducing carbohydrates by capillary electrophoresis with laser-induced fluorescence detection as 7-nitro-2,1,3-benzoxadiazole-tagged N-methylglycamine derivatives

A method for ultramicroanalysis of carbohydrates using capillary electrophoresis with laser-induced fluorescence detection was developed, based on precapillary conversion to 7-nitro-2,1, 3-benzoxadiazole (NBD)-tagged N-methylglycamines. Although the derivatization involves two-step reactions, i.e., reductive N-methylamination followed by condensation with NBD-F, they can be carried out in a one-pot fashion and proceed quantitatively within ca. 50 min in total. Since the reaction conditions are mild, it does not cause desialylation. The derivatives can be well separated by capillary electrophoresis and sensitively detected by argon laser-induced fluorescence. It allowed detection of monosaccharides of down to nanomolar concentrations for analytical sample solution, which correspond to the attomole injected amounts, and good linearity was observed over a wide range. It was also successfully applied to analysis of N-glycans in a microgram quantity of a glycoprotein. Studies on the cleanup of derivatized product are also described in relation to N-glycan analysis.

Effects of amine modifiers on the separation of tetramethylrhodamine-labeled mono- and oligosaccharides by capillary zone electrophoresis

In this work, nine tetramethylrhodamine (TMR) labeled isomeric oligosaccharide derivatives of betaGal(1 --> 4) betaGlcNAc-O-TMR were separated by capillary zone electrophoresis coupled with laser-induced fluorescence detection. Charged species were created in situ by complexation with borate and phenylborate. Micellar separation was achieved by addition of 10 mM sodium dodecylsulfate to the running buffer. We have investigated the effects of adding a homologous series of monoamine modifiers on the separation efficiency of these oligosaccharides. The separation was significantly improved in the presence of the organic modifiers methyl- and ethylamines, but worsened in the presence of propyl- and butylamines. Possible mechanisms of the amine additives are discussed.

State-of-the-art of capillary electrophoresis with application to the area of glycoconjugates

Glycoconjugates constitute a major group of biomolecules, which participate in several biological functions and processes. Their carbohydrate components play key roles in determining the properties of glycoconjugates and, therefore, analysis and structural characterization of carbohydrates are essential. Capillary electrophoresis, due to its high resolving power and sensitivity, has been successfully used for the analysis of carbohydrates. In this review the principles of high-performance capillary electrophoresis; mechanisms employed for glycoconjugate analysis as well as the various detection techniques used are summarized.

3-Aminobenzamide and 3-aminobenzoic acid, tags for capillary electrophoresis of complex carbohydrates with laser-induced fluorescent detection

The efficiencies in derivatization of reducing carbohydrates were compared by capillary electrophoresis using maltose as a model with nine monoaminobenzene derivatives by reductive amination in the presence of sodium cyanoborohydride. We found that aminobenzene derivatives substituted at the 3-position showed good reactivity with reducing carbohydrates as expected from the reaction mechanism, although the fluorescence intensities and molar absorptivities of these derivatives were not as high as those of 2- and 4-aminobenzene derivatives. The reagents, 3-aminobenzamide and 3-aminobenzoic acid, which showed the highest reactivity, were applied to the labeling of carbohydrate chains obtained from some sialic acid-containing glycoprotein samples, and also high-mannose and hybrid-type oligosaccharides. Capillary electrophoresis of these labeled carbohydrate chains in an inner surface-modified capillary with (50% phenyl)methylpolysiloxane allowed excellent separation of sialic acid-containing carbohydrate chains derived from fetuin and thyroglobulin as well as high mannose-type and hybrid-type carbohydrates derived from bovine pancreas ribonuclease B, soybean agglutinin and hen ovalbumin. The lower limit of calibration was as low as the 10(-16) mol (injected amount) with helium-cadmium laser induced detection.

The development and application of capillary electrophoresis methods for food analysis

Capillary electrophoresis (CE) offers the analyst a number of key advantages for the analysis of the components of foods. CE offers better resolution than, say, high-performance liquid chromatography (HPLC), and is more adept at the simultaneous separation of a number of components of different chemistries within a single matrix. In addition, CE requires less rigorous sample cleanup procedures than HPLC, while offering the same degree of automation. However, despite these advantages, CE remains under-utilized by food analysts. Therefore, this review consolidates and discusses the currently reported applications of CE that are relevant to the analysis of foods. Some discussion is also devoted to the development of these reported methods and to the advantages/disadvantages compared with the more usual methods for each particular analysis. It is the aim of this review to give practicing food analysts an overview of the current scope of CE.

A tabulated review of capillary electrophoresis of carbohydrates

This review summarizes publications on capillary electrophoresis (CE) of carbohydrates, covering almost all hitherto published papers on this topic. It is designed to be a convenient tool for the literature search by providing a comprehensive table. Since CE analysis of carbohydrates is generally complicated due to the structural diversity of carbohydrate species, an attempt is made in this table to supply detailed information on the analyzed form (underivatized or derivatized, type of derivative) and analytical conditions (capillary size, state of the inner wall, composition of the electrophoretic solution, applied voltage, detection method, etc.), for each combination of carbohydrate species to be analyzed. In addition, a brief overview is presented to help in the literature search.

Strategies for capillary electrophoresis: method development and validation for pharmaceutical and biological applications

This review is in support of the development of selective, reproducible and validated capillary electrophoretis (CE) methods. Focusing on pharmaceutical and biological applications, the successful use of CE is demonstrated by more than 800 references, mainly from 1994 until 1998. Approximately 80 recent reviews have been catalogued. These articles sum up the existing strategies for method development in CE, especially in the search for generally accepted concepts, but also looking for new, promising reagents and ideas. General strategies for method development were derived not only with regard to selectivity and efficiency, but also with regard to precision, short analysis time, limit of detection, sample pretreatment requirements and validation. Standard buffer recipes, surfactants used in micellar electrokinetic capillary chromatography (MEKC), chiral selectors, useful buffer additives, polymeric separation media, electroosmotic flow (EOF) modifiers, dynamic and permanent coatings, actions to deal with complex matrices and aspects of validation are collected in 20 tables. Detailed schemes for the development of MEKC methods and chiral separations, for optimizing separation efficiency, means of troubleshooting, and other important information for key decisions during method development are given in 19 diagrams. Method development for peptide and protein separations, possibilities to influence the EOF and how to stabilize it, as well as indirect detection are considered in special sections.

A survey of methodological challenges for glycosaminoglycan/proteoglycan analysis and structural characterization by capillary electrophoresis

Proteoglycans participate and regulate several physiological processes via their glycosaminoglycan constituents. For a deeper understanding of how they interact with extracellular ligands as well as with cell bound effector molecules, the fine chemical structures of their glycosaminoglycan chains must be elucidated. Lately developed capillary electrophoretic techniques is a powerful analytical tool for the analysis of glycosaminoglycans, combining a high resolving power with sensitive detection. In this review we describe how depolymerized and intact glycosaminoglycans/proteoglycans can be characterized by capillary electrophoresis, relating these analyses to their possible biological significance. Conditions for running these separations and the detection systems for particular applications are also summarized.

Enzymatic assay of galactosyltransferase by capillary electrophoresis

The kinetic parameters of a galactosyltransferase-catalyzed reaction were determined for the first time using capillary zone electrophoresis (CZE) using the methylumbelliferyl (MU) glycoside of N-acetylglucosamine as the acceptor molecule. The CZE was performed using borate buffer and the enzymatic transformations were monitored at 214 nm. The kinetic parameters obtained for MU-GlcNAc were Km = 35.9 microM and Vmax = 7.5 micromol/min/mg, and those for UDP-Gal were Km = 115.3 microM and Vmax = 12.4 micromol/min/mg. A representative inhibition assay was also carried out using UDP as an inhibitor to give the Ki value of 83.9 microM against MU-GlcNAc. The structure of the synthetic product was also confirmed using 1H NMR spectroscopies after isolation by simple chromatography.

Quality control of pentosane polysulfate by capillary zone electrophoresis using indirect detection

Pentosane polysulfate sodium salt (PPS) is a mixture of multiply charged anionic polysaccharides, used for urological treatment. Several constituents of the polysaccharide can be characterized by a highly reproducible fingerprint. In comparison with earlier approaches the separation efficiency has been further improved using an anionic benzene-1,2,4-tricarboxylic acid buffer (8.7 mmol l-1, pH = 4.9) with indirect UV detection (lambda = 217 nm) and a special capillary pretreatment (1 M NaOH for 10 h at 25 degrees C applying -20 kV). The method has been optimized with regard to buffer concentration and pH. The robustness was tested on several capillaries. PPS was separated from all major synthetic impurities such a sulfate, chloride and acetate. Twelve PPS batches from two manufactures were measured and compared.

Detection of glycosaminoglycans as a copper(II) complex in high-performance liquid chromatography

Glycosaminoglycans including heparin, heparan sulfate, chondroitin sulfate, dermatan sulfate and hyaluronan were analyzed by high-performance gel filtration chromatography. Detection was achieved at 240 nm based on the formation of copper(II) complex in copper sulfate solution at low pH. Detection of the copper(II)-heparin complex is sensitive, permitting the analysis of as little as 10(-7) g. This method was also successfully applied to the analysis of the chemically derivatized glycosaminoglycans (de-N-acetylated and/or oversulfated chondroitin sulfate) that cannot be depolymerized by enzymes such as heparin and chondroitin lyases.

Use of a binary mixture of quaternary ammonium salts in fluorometric determination of glycosaminoglycans

The concentration of glycosaminoglycans, in an aqueous solution was determined by observing the fluorescent intensity of the ion of 2-hexadecyl-9H-pyrido[4,3b]indole at 450 nm by irradiating 253-nm light after dissolution of the insoluble salt in ethanol, which was formed by the reaction between a solution of a sample of glycosaminoglycan and an aqueous solution of the binary mixture of fluorescent 2-hexadecyl-9H-pyrido[4,3b]indolium bromide and hexadecyl pyridinium chloride. The fluorescent quaternary ammonium salt, which was slightly soluble in water, was solubilized in water by forming mixed micelles with a nonfluorescent soluble quaternary ammonium salt. The present method showed good linearity for the calibration curves between 5 and 1000 micrograms/ml in all samples of glycosaminoglycan except keratan sulfate. The relative standard deviation in determination was less than 3% for the whole calibration range.

Analysis of endotoxins by capillary electrophoresis

Endotoxins are part of the outer membrane of gram-negative bacteria such as E. coli. Upon entering the blood stream, they cause a violent, sometimes life-threatening, response of the immune system. Endotoxins are lipopolysaccharides (LPS), lacking optically active groups, and their detection in the underivatized state can be difficult. In this paper the potential of capillary electrophoresis (CE) for LPS analysis is investigated. By using a standard phosphate buffer method, concentrations down to 100 micrograms/mL can be detected within 6 min. The detection limit can be lowered by one order of magnitude by using a sodium dodecyl sulfate (SDS)/borate buffer, pH 9.2. In this buffer, the SDS serves to homogenize the size of the LPS aggregates, while the borate forms complexes with the diol groups of the molecule, thereby enhancing its optical activity. The formation of LPS-affinity complexes with the UV-active polymyxin B or labeling of the LPS with a fluorophore (fluorescein isothiocyanate) was unsuccessful. Best results, in terms of detection limit and speed, were obtained with an indirect UV-detection CE method. By using a strongly UV-active electrophoresis buffer, endotoxins could be detected as "negative" peaks. In this case, a detection limit of 3 micrograms/mL (35 pM) was determined. Proteins and other UV-active substances did not disturb the assay, since they generated no detectable signals. The indirect UV detection was used to quantify the residual LPS content of a DNA preparation from E. coli.

Fast separation of underivatized carbohydrates by coelectroosmotic capillary electrophoresis

A method for the rapid quantitative analysis of underivatized acidic sugars, monosaccharides and disaccharides using coelectroosmotic capillary electrophoresis was developed. Indirect UV detection at 254 nm using sorbate as background electrolyte was employed for monitoring the analytes. A highly alkaline pH value of the electrolyte system was chosen in order to achieve an electrophoretic mobility of the saccharides towards the anode. A dynamic reversal of the electroosmotic flow and, by this means, a codirectional movement of the negatively charged analytes and the electroosmotic flow is accomplished by employing a polycationic surfactant (hexadimethrine bromide), which is added to the background electrolyte. To further improve the resolution of specific carbohydrates, acetone is used as organic modifier. A practical application of the developed method for the fast determination of fructose, glucose, and sucrose in various soft drinks is provided.

Exploration of the action pattern of Streptomyces hyaluronate lyase using high-resolution capillary electrophoresis

Hyaluronic acid was treated exhaustively with a hyaluronate lyase (hyaluronidase, EC 4.2.2.1) from Streptomyces hyalurolyticus to obtain a tetrasaccharide and a hexasaccharide product in a molar ratio of 1 to 1.2. The tetrasaccharide product was fluorescently labeled at the reducing end by reductive amination with 7-amino 1,3-naphthalene disulfonic acid (AGA) and the structure of the conjugate was determined spectroscopically. Partial treatments of hyaluronic acid with hyaluronate lyase afforded complex mixtures of oligosaccharides that were similarly fluorescently labeled. These labeled oligosaccharide mixtures were analyzed using high-resolution capillary electrophoresis. The resulting electropherograms showed the content of each hyaluronic acid derived oligosaccharide, having a degree of polymerization (dp) from 4 to 50, throughout the enzymatic reaction. Computer simulation studies gave comparable kinetic profiles suggesting that hyaluronate lyase exhibits a random endolytic action pattern. Interestingly, oligosaccharides of certain size (dp) were under-represented in these oligosaccharide mixtures suggesting that linkages at spacings of 10 to 12 saccharide units are somewhat resistant to this enzyme. The cause of this resistance might be the result of secondary or higher order structural features present in the hyaluronic acid polymer.

Analysis of glycoproteins, glycopeptides and glycoprotein-derived oligosaccharides by high-performance capillary electrophoresis

Recent developments in the analysis of glycoproteins by high-performance capillary electrophoresis are reviewed, with emphasis on their carbohydrate chains. Glycoforms of glycoproteins were directly separated from each other by careful optimization of the analytical conditions. Glycopeptides in tyrptic digests were separated and the peptides carrying glycosylation sites were differentiated from others. Released oligosaccharide chains were separated from each other by direct or modified zone electrophoresis and directly detected by measuring the UV absorption at a low wavelength. Precolumn derivatization by various methods extended the utility of both the separation mode and detection technique. Dual mode analysis after derivatization permitted reliable identification and quantification without references.