Separation of disaccharides by affinity capillary electrophoresis in lectin-containing electrophoretic solutions

A method for detecting tumor cells derived from colorectal cancer by targeting cell surface glycosylation with affinity capillary electrophoresis

Circulating tumor cells (CTCs) are involved in metastasis; thus, one of the most important approaches for identifying metastatic cancer is to detect CTCs in blood. In the present study, we examined whether directly analyzing cells with capillary electrophoresis (CE) could distinguish cancer cells from normal cells, based on differences in cell surface glycosylation. We compared human colorectal cancer (CRC) cell lines to a normal colon epithelium cell line. Our results demonstrated that direct CE analysis could successfully distinguish between CRC and normal cells with high reproducibility, based on migration times. We found that the weighted-average migration time was significantly shorter for CRC cells than for normal cells. Next, we observed changes in the electrophoretic behaviors of CRC cells by adding five different types of lectins. When Aleuria aurantia lectin was added, migration delays were observed in CRC cells, but not in normal colon cells. Therefore, by focusing on shifts in migration time after adding specific lectins, we could distinguish cancer cells from normal cells. These findings suggested that this diagnostic method of directly analyzing cells with CE after adding specific lectin(s) could be useful for detecting the difference in the sugar moieties on a surface of normal and cancer cells.

Derivatization of carbohydrates for chromatographic, electrophoretic and mass spectrometric structure analysis

Carbohydrates, either alone or as constituents of glycoproteins, proteoglycans and glycolipids, are mediators of several cellular events and (patho)physiological processes. Progress in the "glycome" project is closely related to the analytical tools used to define carbohydrate structure and correlate structure with function. Chromatography, electrophoresis and mass spectrometry are the indispensable analytical tools of the on-going research. Carbohydrate derivatization is required for most of these analytical procedures. This review article gives an overview of derivatization methods of carbohydrates for their liquid chromatographic and electrophoretic separation, as well as the mass spectrometric characterization. Pre-column and on-capillary derivatization methods are presented with special emphasis on the derivatization of large carbohydrates.

Analysis of carbohydrates as 1-phenyl-3-methyl-5-pyrazolone derivatives by capillary/microchip electrophoresis and capillary electrochromatography

The 1-phenyl-3-methyl-5-pyrazolone (PMP) method has many advantages over hitherto reported methods based on reductive amination and hydrazone formation. This short review summarizes the various aspects of the PMP method, including the principle of derivatization, the simplicity of derivatization procedure, the high sensitivities to UV monitoring and ESI-MS, and the diversity of separation modes in capillary electrophoresis, and presents a number of application data for carbohydrate analysis in biological samples by this method. It also describes successful automation of carbohydrate analysis by in-capillary derivatization with PMP and miniaturization to microchip electrophoresis with whole channel UV detection allowing rapid (within 1 min) analysis of small amounts of PMP derivatives of carbohydrates. Furthermore, it discusses the possibility of capillary electrochromatography in carbohydrate analysis as PMP derivatives, and proposes an in-capillary modification strategy for improving column efficiency and elution time reproducibility.

Simultaneous estimation of the association constants of glycoprotein glycoforms to a common protein by capillary electrophoresis

The efficacy of our capillary electrophoresis method for simultaneous estimation of the association constants of glycoprotein glycoforms to a common target protein was demonstrated using ribonuclease and ovalbumin glycoforms as glycoform models and Lens culinaris agglutinin (LCA) as a protein model. The ribonuclease glycoforms were fairly well separated in the absence of LCA at pH 5.8, but the peaks were retarded without any change of separation profile in the presence of LCA, the retardation becoming greater as LCA concentration increased. The estimated values of apparent association constant (K(a)) were at the 10(6)M(-1) level for all the ribonuclease glycoforms, and there was no significant difference among glycoforms. The high-mannose-type N-glycans released from a mixture of ribonuclease glycoforms gave lower values of K(a) at the 10(4)-10(5)M(-1) level to the same protein, and the glycans having a larger number of the mannose residue gave larger K(a) values. These results imply that the glycan moiety in this glycoprotein might contribute to its binding to the protein, but the polypeptide core played the major role. In contrast, ovalbumin glycoforms gave poorly resolved peaks in the absence of LCA, but they were separated into several peaks in the presence of LCA, which were tentatively assigned based on the knowledge of affinity to this lectin, and K(a) values were estimated simultaneously. The estimated K(a) values were smaller than those of the ribonuclease glycoforms, suggesting the major role of the N-glycan moiety. Thus, capillary electrophoresis allowed simultaneous estimation of K(a) values under common conditions using small amounts of glycoform mixtures and proteins without prior isolation and purification. Comparison of the obtained values will provide useful information on the glycan structure-affinity correlation.

Improved high-performance liquid chromatographic method to estimate aminosugars and its application to glycosaminoglycan determination in plasma and serum

An improved isocratic high-performance liquid chromatography (HPLC) method for the analysis of L-(-)-fucose. D-(+)-galactosamine, D-(+)-glucosamine, D-(+)-galactose, obtained by hydrolysis of glycosaminoglycans (GAGs) and D-(+)-glucose and D-(+)-mannose is described. The presence in circulation of GAGs, acid polysaccharide sequences of alternate monosaccharide units, aminosugar and uronic acid (galactose in keratan sulfate), has been measured in terms of their sugar components. To evaluate concentration of these circulating sugars we considered blood samples obtained from healthy humans. Plasma or serum was filtered through weak anion-exchange Ecteola-cellulose either untreated or after mild alkaline treatment. GAGs adhering to resin were recovered by salt elution, and desalted on Bio-Gel P-2 resin. GAG fractionation by charge was carried out on a strong anion exchanger. GAG composition was evaluated in terms of galactose and aminosugars, measured in HPLC by the proposed procedure using anion-exchange resin and pulsed amperometric detection. The mobile phase consisted of 0.02 M NaOH and elution was carried out at flow-rate of 1.0 ml/min. The amperometric detector was set as follows: t1 (0.5 s), E1 (+0.1 V); t2 (0.09 s), E2 (+0.6 V); t3 (0.05 s), E3 (-0.6 V). The analysis required 14 min. Calibration standard curves for the six analytes were linear from 0.25 to 40 microM. RSD values for intra- and inter-day variabilities were < or = 5.3% at concentrations between 0.25 and 40 microM. Accuracy, expressed as percentage error, ranged from - 16 to 14%. The method was specific and sensitive with quantitation limits of 1 pmol for L-(-)-fucose, D-galactosamine and D-glucosamine, 3 pmol for D-(+)-galactose and D-(+)-glucose and 5 pmol for D-(+)-mannose. The results of the assay showed higher GAG concentrations in serum than in plasma.

Capillary electrophoretic analysis of carbohydrates derivatized by in-capillary condensation with 1-phenyl-3-methyl-5-pyrazolone

Our previous papers on capillary electrophoresis (CE) have shown that samples can be derivatized in a capillary and the derivatives can be analyzed immediately after derivatization, provided that the derivatization reaction is so rapid as to complete in seconds. The present paper presents extended application of in-capillary derivatization to a much slower reaction such as the condensation of reducing carbohydrates with 1-phenyl-3-methyl-5-pyrazolone (PMP) which requires 30 min at 70 degrees C in pre-column derivatization by manual operation. It was necessary to first drive the introduced plugs of sample and reagent solutions to put them together at the entrance of the heated portion of a capillary, then to allow the superimposed plugs to react for a relevant period. We showed how to determine the introduction times of the sample and the reagent solutions as well as intermediate running buffer, the voltages to be applied for plug driving and product analysis, and the duration of voltage application, all of which are important for effective in-capillary derivatization. An example of the analysis of maltooligosaccharides by this technique is presented. It was shown that maltooligosaccharides were quantitatively derivatized with PMP in 35 min at 57 degrees C, and the derivatives could be analyzed in ca. 15 min by CE immediately after derivatization. Separation was satisfactory in 200 mM borate buffer, pH 8.2 containing sodium dodecyl sulfate to a concentration of 200 mM. Although the theoretical plate number, and accordingly the resolution, were significantly lower than the corresponding values in pre-capillary derivatization, reasonable reproducibility was ensured for both migration time (RSD 3.5% on average) and peak area (RSD less than 3%) under the optimized conditions. It is notable that sample amount could be lowered to the 10 fmol level, in contrast to the 10 pmol level in pre-capillary derivatization. In addition, since the technique employed here (the modified at-inlet technique of in-capillary derivatization) is easily automated, the established system will be highly beneficial for routine analysis of carbohydrates. Analysis by this technique was also shown to be useful for kinetic study of the derivatization reaction.

Recent advances in affinity capillary electrophoresis

Use of the specificity of (bio)interactions can effectively overcome the selectivity limitation faced in capillary electrophoresis (CE), and the resulting technique usually is referred to as affinity capillary electrophoresis (ACE). Despite the high selectivity of ACE, several important problems still need to be addressed. A major issue in all CE separations, including ACE, is the concentration detection limit. Using UV detection, this is usually in the order of 10(-6) M whereas laser-induced fluorescence (LIF) detection can provide detection limits down to the sub-10(-10) M range. However, a marked disadvantage of LIF is that labeling of the analytes is usually required, which might change the interaction behavior of the solutes under investigation. Additionally, labeling reactions at sub-10(-10) M concentration levels are certainly not trivial and often difficult to perform quantitatively. Alternative and universal detection approaches, particularly mass spectrometric (MS) detection, look very promising but (A) CE-MS techniques are still far from routine application. Important future progress in sensitive detection strategies is likely to increase the use of ACE in the future.

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.

Recent developments in capillary electrophoresis and capillary electrochromatography of carbohydrate species

This review article is concerned with the recent developments in capillary electrophoresis (CE) and capillary electrochromatography (CEC) of carbohydrates. The literature shows that CE possesses impressive potential in the analysis of carbohydrates. On the other hand, CEC has just started to show promise in the analysis of carbohydrates. Advances in separation and detection approaches of derivatized and underivatized carbohydrates are discussed based on the available literature. In addition, important applications are illustrated.