Capillary zone electrophoresis for the quantitation of oligosaccharides formed through the action of chitinase

Modeling the Isoelectric Focusing of Peptides in an OFFGEL Multicompartment Cell

In proteomic analysis of complex samples at the peptide level (termed shotgun proteomics), an effective prefractionation is crucial to decrease the complexity of the peptide mixture for further analysis. In this perspective, the high-resolving power of the IEF fractionation step is a determining parameter, in order to obtain well-defined fractions and correct information on peptide isoelectric points, to provide an additional filter for protein identification. Here, we explore the resolving power of OFFGEL IEF as a prefractionation tool to separate peptides. By modeling the peak width evolution versus the peptide charge gradient at pI, we demonstrate that for the three proteomes considered in silico (Deinococcus radiodurans, Saccharomyces cerevisiae, and Homo sapiens), 90% of the peptides should be correctly focused and recovered in two wells at most. This result strongly suggests OFFGEL to be used as a powerful fractionation tool in shotgun proteomics. The influence of the height and shape of the compartments is also investigated, to give the optimal cell dimensions for an enhanced peptide recovery and fast focusing time.

Synthesis and enzymatic evaluation of five-membered iminocyclitols and a pseudodisaccharide

Described here are the synthesis of five-membered iminocyclitols with galacto-configuration and a pseudodisaccharide, and their inhibitory activities against beta-galactosyltransferase, beta-galactosidase and alpha-mannosidase.

Analysis of 8-aminonaphthalene-1,3,6-trisulfonate-derivatized oligosaccharides by capillary electrophoresis-electrospray ionization quadrupole ion trap mass spectrometry

Dextran was partially hydrolyzed with 0.1 mol/l HCl and the hydrolysate was derivatized with 8-aminonaphthalene-1,3,6-trisulfonate (ANTS) by reductive amination. The derivatized-oligosaccharide mixture was separated by capillary electrophoresis (CE) in a buffer of 1% HAc-NH4OH, pH 3.4, and the separated components were detected on-line by electrospray ionization quadrupole ion trap mass spectrometry (ESI-QIT-MS) in the negative ion mode. A mass accuracy lower than 0.01% could be achieved and as low as 1.6 pmol of detxran octaose could be detected. ANTS-derivatized dextran oligosaccharide with a degree of polymerization (DP) lower than 6 produced both [M-H]- and [M-2H]2- ions, whereas those with a DP of 6 or higher than 6 produced only [M-2H]2- ion. As 1< or =DP< or =6, the percentage of [M-2H]2- ion in the total ions of [M-H]- and [M-2H]2- was found to be a linear function of the logarithmic DP. Molecular mass determination with ESI-QIT-MS strengthens the power of CE analysis of oligosaccharides.

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.

Analysis of glycosaminoglycans and their oligosaccharide fragments by capillary electrophoresis

Glycosaminoglycans are high molecular mass polymers found in living tissues. They are degraded by site specific enzymes to oligosaccharide fragments. Polymers and oligomers all carry negative charge and are found as salts soluble in water. Consequently, capillary electrophoresis has come to the fore as an analytical technique in this field. This review discusses application of the technique to the chondroitin-dermatan, heparin and hyaluronan groups of polymer and the derived oligosaccharides. Direct and indirect UV detection are discussed as well as detection methods involving precolumn derivatization. Capillary electrophoresis has found use in the characterisation of heparin and in following the changes in chondroitin and hyaluronan during the onset of arthritic disease in humans. Some glycosaminoglycans have been used as asymmetric anions in the separation of enantiomers of low molecular mass compounds by capillary electrophoresis.

Determination of minute enzymatic activities by means of capillary electrophoretic techniques

Capillary electrophoretic analysis of enzymes, co-enzymes, substrates and other chemical species that can be linked to an enzymatic reaction is reviewed with 80 references. Both off-line and on-line assays of minute enzymatic activities are discussed. In addition to heterogeneous on-line enzyme assays, a special emphasis is given to a newly established on-line technique called electrophoretically mediated microanalysis (EMMA). The basic principle, procedure, and various detection modes of EMMA are discussed. The recent developments in on-line determination of various enzyme substrates as well as on-line enzyme kinetic studies are also summarized. Some potential future developments in the determination of enzymatic activities by means of CE are also presented.

Beta-N-acetylhexosaminidase: a target for the design of antifungal agents

This review provides biochemical, analytical, and biological background information relating to beta-N-acetylhexosaminidase (HexNAc'ase; EC 3.2.1.52) as an emerging target for the design of low-molecular-weight antifungals. The article includes the following: (1) a biochemical description of HexNAc'ase (reaction catalyzed, nomenclature, and mechanism of action) that sets it apart from other, similar enzymes; (2) an overview and a critical evaluation of methods to assay the enzyme, including in crude extracts (photo- and fluorometric procedures with model substrates; HPLC/pulsed amperometric detection of N-acetylglucosamine and chito-oligomers; end-point vs. rate measurements); (3) a summary of some general characteristics of HexNAc'ases from fungi and organisms of other types (Km values, substrate preference, and glycoconjugation); (4) an hypothesis of a specific target function of wall-associated HexNAc'ase (a component of the assembly of surface-located enzymes effecting a continuous turnover and remodelling of the wall fabric through its combined hydrolytic and transglycosylating activities, and a mediator enzyme acting in concert with chitinase and chitin synthase to provide for the controlled lysis and synthesis of chitin during growth); (5) a tabulation of the structural formulae of reaction-based HexNAc'ase inhibitors with Ki values < or = 100 microM (some of them representing transition state mimics that could serve as leads for the development of new antifungals); and (6) an outline of approaches towards the establishment of a three-dimensional model of HexNAc'ase suitable for a truly rational design of antimycotics as well as agricultural fungicides.

Detection and differentiation of pectic enzyme activity in vitro and in vivo by capillary electrophoresis of products from fluorescent-labeled substrate

A sensitive assay is described for the detection of pectate-depolymerizing enzymes using capillary electrophoresis of a fluorescent end-labeled pectate oligomer. The labeled oligomer is allowed to react with the enzyme either in vitro or in vivo, such as inside the intercellular spaces of a cotton cotyledon, and after an appropriate incubation time the products are analyzed by capillary electrophoresis. The site and mode of action of the pectate-depolymerizing activity can be inferred from the products. Both endo- and exopolygalacturonase activity, and lyase activity, were distinguished. Since only the fluorescent oligomer and products from its labeled reducing end are detected, there is no interference from other compounds; only pectic enzyme activity is detected. By this type of analysis we can show that there is considerable endo- and exo-polygalacturonase activity in the intercellular spaces of cotton cotyledons.

Fingerprinting of glycans as their 2-aminoacridone derivatives by capillary electrophoresis and laser-induced fluorescence

Capillary electrophoresis and laser-induced fluorescence detection have been used to fingerprint the 2-aminoacridone derivatives of complex glycans released from bovine fetuin and human IgG monoclonal antibodies. The utility of this method in distinguishing between N- and O-linked oligosaccharides and in determining the presence of sialic acid residues in glycan mixtures at an early stage of analysis has been demonstrated.

Separation of negatively charged carbohydrates by capillary electrophoresis

Capillary electrophoresis (CE) has recently emerged as a highly promising technique consuming an extremely small amount of sample and capable of the rapid, high-resolution separation, characterization, and quantitation of analytes. CE has been used for the separation of biopolymers, including acidic carbohydrates. Since CE is basically an analytical method for ions, acidic carbohydrates that give anions in weakly acid, neutral, or alkaline media are often the direct objects of this method. The scope of this review is limited to the use of CE for the analysis of carbohydrates containing carboxylate, sulfate, and phosphate groups as well as neutral carbohydrates that have been derivatized to incorporate strongly acidic functionality, such as sulfonate groups.

Separation of 8-aminonaphthalene-1,3,6-trisulfonic acid-labelled neutral and sialylated N-linked complex oligosaccharides by capillary electrophoresis

Complex oligosaccharides, both neutral and sialylated, were derivatized with 8-aminonaphthalene-1,3,6-trisulfonic acid (ANTS) and separated by capillary electrophoresis. The derivatization reaction was carried out in a total reaction volume of 2 microliters. The separated peaks were detected by laser-induced fluorescence detection using the 325-nm line of a He-Cd laser. Concentration and mass detection limits of 5 x 10(-8) M and 500 amol, respectively, could be achieved. The limiting step for higher sensitivity is not the detector performance, however, but the chemistry with a derivatization limit of 2.5 x 10(-6) M. Two labelling protocols were established, one with overnight reaction at 40 degrees C and the other with a 2.5-h derivatization time at 80 degrees C. Neutral oligosaccharides could be labelled with either protocol. However, sialylated oligosaccharides hydrolysed when labeled at 80 degrees C. Low nanomole to picomole amounts of oligomannose-type and complex-type oligosaccharide mixtures were derivatized and separated in less than 8 min with excellent resolution using a phosphate background electrolyte at pH 2.5. The linear relationship between the electrophoretic mobility and the charge-to-mass ratios of the ANTS conjugates was used for peak assignment. Further, the influence of the three-dimensional structure of the complex oligosaccharides on their migration behaviour is discussed. The suitability of the ANTS derivatization and the subsequent separation for the analysis of complex oligosaccharide patterns is demonstrated with oligosaccharide libraries derived from ovalbumin and bovine fetuin. For peak assignment the patterns are compared with those of the oligomannose and the complex-type oligosaccharide mixtures.(ABSTRACT TRUNCATED AT 250 WORDS)

Capillary electrophoresis of carboxylated carbohydrates. I. Selective precolumn derivatization of gangliosides with UV absorbing and fluorescent tags

We demonstrate that the precolumn derivatization reaction, recently introduced by our laboratory for the selective labeling of carboxylated monosaccharides, can be readily transposed to other glycoconjugates containing carboxylated sugar residues, namely sialogangliosides. The selective derivatization reaction described here involved the attachment of sulfanilic acid (a UV-absorbing tag) or 7-aminonaphthalene-1,3-disulfonic acid (a UV-absorbing and also fluorescing tag) to the sialic acid moiety of the gangliosides via the carboxylic group in the presence of water-soluble carbodiimide. This labeling of the sialic acid moiety of the gangliosides with a chromophore and/or fluorophore leads to the formation of an amide bond between the carboxylic group of the sugar residue and the amino group of the derivatizing agent, thus replacing the weak carboxylic acid group of the carbohydrate species by the stronger sulfonic acid group which is ionized over the entire pH range. Furthermore, novel electrolyte systems were introduced and evaluated for the separation of the derivatized and underivatized gangliosides. The addition of acetonitrile or alpha-cyclodextrin (alpha-CD) to the running electrolyte was necessary to break-up the aggregation of amphiphilic gangliosides and allowed for their efficient separation as monomers in aqueous media using capillary electrophoresis. Several operating parameters were investigated with these electrolyte systems including the additive concentration as well as the ionic strength, pH and nature of the running electrolyte. Acetonitrile at 50% (v/v) in 5 mM sodium phosphate at high and low pH or 15 mM alpha-CD in 100 mM sodium borate, pH 10.0, proved ideal, in terms of resolution and separation efficiency, for the group separation of mono-, di- and trisialogangliosides. On the other hand, the complete resolution of disialoganglioside isomers (e.g., GD1a and GD1b) necessitated the superimposition of a chromatographic component on the electrophoretic process. This was achieved by adding either a hydrophobic (e.g., decanoyl-N-methylglucamide-borate surfactant complex) or hydrophilic [e.g., poly(vinyl alcohol) or hydroxypropyl cellulose] selectors to the running electrolyte.

Capillary zone electrophoresis of oligosaccharides derivatized with various aminonaphthalene sulfonic acids

Malto-oligosaccharides were derivatized via their reducing ends with different aminoaphthalene mono-, di- and trisulfonic acids by reductive amination. The derivatives were then separated by capillary zone electrophoresis in uncoated fused silica capillaries, using 50 mM triethylammonium phosphate buffer, pH 2.5, as running electrolyte. The effect of degree of charge on speed of analysis and resolution was studied for different aminonaphthalene mono-, di- and trisulfonic acids. Under the conditions used, a higher degree of charge on the derivatives provided both faster analyses and higher resolution. Investigation of the electrophoretic behavior of derivatized oligosaccharides obtained from bovine pancreatic ribonuclease B gave insight into the possibility of applying such electrophoretic systems to the analysis of more complex carbohydrates. The resolution of positional isomers under the conditions described indicated that the high resolving power of this technique allows separations not strictly based on the effects of charge and mass of the analytes, but on structural characteristics as well. The relationship between electrophoretic mobility and molecular structure was investigated for the different derivatives.

Capillary zone electrophoresis of derivatized acidic monosaccharides

A new and specific precolumn derivatization reaction for acidic monosaccharides was introduced and evaluated in the separation and sensitive detection of carbohydrates by capillary electrophoresis. The derivatization reaction involved the attachment of sulfanilic acid (a UV absorbing tag) or 7-amino-naphthalene-1,3-disulfonic acid (a UV absorbing and fluorescing tag) via a condensation reaction between the amino group of the derivatizing agent and the carboxyl group of the sugar in the presence of a water-soluble carbodiimide. The derivatization reaction replaced the weak carboxylic acid of the sugar by a strong sulfonic acid, which is fully ionized at all pH. This allowed the electrophoresis of the sugar derivatives over a wide pH range and permitted the determination of acidic carbohydrates at very low femtomole levels by UV and fluorescence detection.

The mapping by high-pH anion-exchange chromatography with pulsed amperometric detection and capillary electrophoresis of the carbohydrate moieties of human plasma alpha 1-acid glycoprotein

The reducing oligosaccharides released from alpha 1-acid glycoprotein (AGP) by conventional hydrazinolysis have been analyzed by two different mapping techniques, using high-pH anion-exchange chromatography with pulsed amperometric detection (HPAE-PAD) and capillary electrophoresis (CE) with uv detection at 190 nm. The CE measurements proved about 4000 times more sensitive than the measurements by HPAE-PAD. The N-glycan pool was fractionated by Mono Q anion-exchange chromatography, and individual fractions so obtained were desialylated using Vibrio cholerae neuraminidase. The resulting asialo-N-glycans were further analyzed by HPAE-PAD, revealing 2 major, 4 intermediate, and 4 small peaks and at least 3 spikes, which counted for at least 13 different asialo-N-glycans. The carbohydrate structures were tentatively assigned by comparison of the Mono Q-separated N-glycans with the known AGP carbohydrate structures and known structures contained in a mapping database that allows structural assignment of N-glycans by mere comparison of retention times. In addition to the hitherto known AGP carbohydrate structures, we have tentatively identified a number of sulfated N-glycans that are currently being analyzed in more detail. We have also compared the glycan pools recovered from AGP using hydrazinolysis and glycopeptidase F (PNGase F). Approximately 40 distinct peaks could be detected in the hydrazinolysis-derived N-glycan pool by either technique (HPAE-PAD and CE), while about 30 distinct peaks were detected in the N-glycan pool derived by PNGase F digestion of the tryptic AGP digest of the same batch of AGP. These differences were attributed to an increased desialylation (approximately 3 mol%) during hydrazinolysis, based on the detection by HPAE-PAD and CE of free sialic acid and monosialylated oligosaccharides in the glycan pool derived by conventional hydrazinolysis. The integrity of the N-glycans' chitobiose core was examined by 500-MHz 1H NMR spectoscopy. The hydrazinolysis procedure could be optimized such that the hydrazinolysis-derived N-glycan pool was chromatographically essentially identical to the PNGase F-derived N-glycan pool. Hydrazinolysis proved best, with practically no loss of N-acetlylneuraminic acid and the closest resemblance to the PNGase F-derived N-glycan pool, using an automated apparatus. Notably, it was recognized that, in our hands, PNGase F digestion in the presence of sodium dodecyl sulfate resulted in partial desialylation of the liberated N-glycans.

An electrophoresis-based assay for glycosyltransferase activity

Polyacrylamide gel electrophoresis (PAGE) and capillary zone electrophoresis (CZE) were used to measure the activity of glycosyltransferases. Acceptor molecules were prepared by reductive amination of the monopotassium 7-amino-1,3-naphthalenedisulfonic acid (AGA) Schiff base with sugars. The resulting sugar conjugates were purified by gradient PAGE and recovered using semidry electrotransfer into a positively charged nylon membrane. The beta(1----4)galactosyltransferase was shown, by PAGE analysis, to transfer a beta-galactosyl residue to the AGA conjugate of beta-D-GlcNAc-(1----4)-beta-D-GlcNAc-(1----4)-D-GlcNAc (compound 4). Similarly, alpha(1----2)fucosyltransferase isolated from porcine submaxillary glands was shown to transfer fucose from GDP-fucose to the AGA conjugate of beta-D-Gal-(1----4)-beta-D-GlcNAc-(1----6)-D-Gal (compound 5). This conjugate (compound 5) was also an acceptor for the alpha(1----3/4)fucosyltransferase partially purified from human milk. The latter reaction was followed by both gradient PAGE and CZE, having sensitivities of 200 pmol and 80 fmol, respectively.

Lectin affinity electrophoresis for the separation of fluorescently labeled sugar derivatives

Lectin affinity electrophoresis was applied to the separation of charged, fluorescent conjugates of disaccharides. Four fluorescent conjugates were prepared by reductive amination of alpha-D-Man-(1----3)-D-Man, alpha-D-Gal-(1----4)-D-Glc, alpha-D-Gal-(1----6)-D-Glc, and beta-D-Gal-(1----4)-D-Glc in the presence of 7-amino-1,3-naphthalenedisulfonic acid. These charged fluorescent-disaccharide conjugates all have identical molecular weight and in the absence of conconavalin A lectin failed to separate either by agarose or by polyacrylamide gel electrophoresis. In the presence of either free or immobilized concanavalin A, agarose gel electrophoresis and polyacrylamide gel electrophoresis could separate the fluorescent conjugate of alpha-D-Man-(1----3)-D-Man from that of alpha-D-Gal-(1----4)-D-Gal, alpha-D-Gal-(1----6)-D-Glc, and beta-D-Gal-(1----4)-D-Glc.