High-performance liquid chromatography of reducing carbohydrates as strongly ultraviolet-absorbing and electrochemically sensitive 1-phenyl-3-methyl-5-pyrazolone derivatives

Disaccharide analysis of glycosaminoglycans synthesized by cardiac myxoma cells in tumor tissues and in cell culture

We analyzed the main disaccharide units of glycosaminoglycans synthesized by cardiac myxoma cells in vivo and in cell culture using high-performance liquid chromatography after 1-phenyl-3-methyl-5-pyrasolone labeling. Cardiac myxoma tissues contained large amounts of chondroitin-6-sulfate (46%) and hyaluronic acid (32%), along with some chondroitin-4-sulfate (13%), chondroitin (6%), and much less dermatan sulfate (3%). Cultured cardiac myxoma cells synthesized mainly chondroitin-6-sulfate. The abundant glycosaminoglycans in myxoma tissues may make up the characteristic friable gelatinous matrix which is favorable for embolism and tumor cell growth.

Determination of mono- and disaccharides by capillary electrophoresis with contactless conductivity detection

The separation and detection of common mono- and disaccharides by capillary electrophoresis (CE) with contactless conductivity detection (CCD) is presented. At high values of pH, the sugars are converted to anionic species that can be separated by CE and indirectly detected by CCD. The main anionic species present in the running electrolytes are hydroxide and phosphate, which have greater mobility than the ionized sugars, and, thus, the indirect detection is possible. The method was applied to analysis of glucose, fructose, and sucrose in soft drinks, isotonic beverages, fruit juice, and sugarcane spirits. Galactose was used as internal standard in all cases. Plate numbers range from ca. 70,700 to 168,200 and the limits of detection from 13 to 31 microM.

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.

Application of the StrOligo algorithm for the automated structure assignment of complex N-linked glycans from glycoproteins using tandem mass spectrometry

Oligosaccharides associated with proteins are known to give these molecules specific conformations and functions. Analysis of proteins would not be complete without studying the glycans. However, high-throughput techniques in proteomics will soon overwhelm the current capacity of methods if no automation is incorporated into glycomics. New capabilities of the StrOligo algorithm introduced for this purpose (Ethier et al., Rapid Commun. Mass Spectrom., 2002; 16: 1743) will be discussed here. Experimental tandem mass spectra were acquired to test the algorithm using a hybrid quadrupole-time-of-flight (QqTOF) instrument with a matrix-assisted laser desorption/ionization (MALDI) source. The samples were N-linked oligosaccharides from monoclonal antibody IgG, beta interferon and fetuin, detached by enzymatic deglycosylation and labeled at the reducing end. Improvements to the program were made in order to reduce the need for user intervention. StrOligo strips the spectra down to monoisotopic peaks only. The algorithm first builds a relationship tree, accounting for each observed loss of a monosaccharide moiety, and then analyzes the tree and proposes possible structures from combinations of adducts and fragment ion types. A score, which reflects agreement with experimental results, is then given to each proposed structure. The program then decides which combination is the best one and labels relevant peaks in the experimental mass spectrum using a modified nomenclature. The usefulness of the algorithm has been demonstrated by assigning structures to several glycans released from glycoproteins. The analysis was completed in less than 2 minutes for any glycan, which is a substantial improvement over manual interpretation.

Separation methods for sialic acids and critical evaluation of their biologic relevance

Sialic acids are biosynthesized by almost all organisms as a 9-carbon carboxylated monosaccharide and are integral components of glycoconjugates. More than 40 naturally occurring sialic acid derivatives of the three main forms of sialic acids, the N-acetyl- and N-glycolylneuraminic acid and 2-keto-3-deoxy-nonulosonic acid have been identified. Due to the great importance of sialic acids as key mediators in a plethora of cellular events, including cell-cell recognition and cell-matrix interactions, their analysis in biologic samples is useful for a deeper understanding of the various (patho)physiological processes and of value in disease diagnosis and monitoring. In this review we summarize the methodology developed to isolate and liberate sialic acids from biologic samples as well as the chromatographic, electromigration and hyphenated techniques available for their separation and analysis. A critical evaluation of the biological relevance of the results obtained by analyzing sialic acids in biologic samples is also presented.

A study of immunoglobulin G glycosylation in monoclonal and polyclonal species by electrospray and matrix-assisted laser desorption/ionization mass spectrometry

N-linked oligosaccharides were released from human and bovine polyclonal immunoglobulin G (IgG) obtained from commercial sources and also from a monoclonal IgG(1) secreted by murine B-lymphocyte hybridoma cells (CC9C10) grown under different serum-free conditions. These conditions differed according to their steady-state dissolved oxygen concentrations. This work is based on a previous quantitative study where released glycans were characterized by fluorophore-assisted carbohydrate electrophoresis (FACE) and high-pH anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD) (J. P. Kunkel, D. C. H. Jan, J. C. Jamieson, and M. Butler, 1998, J. Biotechnol. 62, 55-71). In the present article, peptide-N-glycosidase F-released glycans from different species of polyclonal IgG and murine monoclonal IgG were characterized qualitatively by high-performance liquid chromatography (HPLC) coupled to electrospray ionization mass spectrometry (ESI-MS). The glycans were also analyzed by matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS). The MALDI mass spectrometer used allowed acquisition of MS and tandem MS data, which were useful in structural investigations at a more detailed level than allowed by FACE and HPAEC-PAD. Predominant N-linked structures, as determined by all techniques, were core-fucosyl asialyl biantennary chains with varying galactosylation. Minor amounts of afucosyl, bisected, and monosialyl oligosaccharides were also detected. In contrast to FACE and HPAEC-PAD, MALDI-double quadrupole/time-of-flight MS and HPLC/ESI-MS also detected low-abundance high-mannose and hybrid structures in some of the species under investigation.

Paclitaxel delivery systems: the use of amino acid linkers in the conjugation of paclitaxel with carboxymethyldextran to create prodrugs

Paclitaxel was bound via its hydroxyl group to carboxymethyldextran (CMDex, 150 kDa) by means of an amino acid linker; the linker was introduced into the 2'- or 7-hydroxyl group of the paclitaxel through an ester bond. These conjugates--CMDex-2'-paclitaxel and CMDex-7-paclitaxel--were designed to be water-soluble with a paclitaxel content between 6-8% (w/w) with a degree of subsititution (DS) of the CM groups at 0.6 per sugar residue. The release of the paclitaxel from the conjugates was influenced by the hydroxyl group (2'- or 7-) of paclitaxel to which the amino acid linker was introduced, and by what amino acid was used as the linker. In mouse plasma incubated at 37 degrees C for 72 h, the most paclitaxel was released using CMDex-paclitaxel conjugate with 2'gly followed by, in descending order, 2'-ala, 2'-leu, 2'-ile, and 7-gly as the amino linkers. Colon 26, a Taxol resistant cancer, was introduced into mice and the conjugates were intravenously administered by bolus injection for a tumor distribution study, and intermittently intravenously administered for a tumor growth regression study. In both studies the highest amount of paclitaxel release was found in the CMDex-2'-gly-paclitaxel followed by CMDex-2'-ala-paclitaxel, CMDex-2'-leu-paclitaxel and paclitaxel. There was a direct correlation between the amount of paclitaxel released and the observed efficacy. CMDex-2'-ile-paclitaxel and CMDex-7-gly-paclitaxel did not show any anti-tumor activity. These results clearly demonstrate that a CMDex-paclitaxel with an appropriate amino acid linker has significant anti-tumor activity against colon 26, and that these anti-tumor effects appear to correlate with the amounts of paclitaxel released in the tumor.

Analysis of glycoproteins and the oligosaccharides thereof by high-performance capillary electrophoresis-significance in regulatory studies on biopharmaceutical products

This review describes the recent development in the analysis of glycoproteins using capillary electrophoresis with various separation techniques, and focuses especially on the analysis of recombinant glycoprotein pharmaceuticals. We include the analysis of glycoprotein multiforms (ie glycoform) as well as glycan analysis. The relationship between glycoprotein multiforms and oligosaccharide distributions in a glycoprotein sample is also discussed. Further, recent development in capillary electrophoresis-mass spectrometry is described.

Automated structural assignment of derivatized complex N-linked oligosaccharides from tandem mass spectra

Glycoprotein function is controlled by several biological factors, one of them being the structure of carbohydrate chains (glycans) attached to specific amino acids of the protein backbone. Changes in glycan structures have been shown to modify the secondary and tertiary conformation of glycoproteins, thus their function. Powerful analytical tools are available for the characterization of sugar structures, and recently mass spectrometry (MS) has been increasingly useful for this purpose. Manual interpretation of tandem mass spectrum is possible but tedious. Automated interpretation should speed the analysis and enhance the results obtained. A new computer program for automated interpretation of tandem MS spectra of complex N-linked glycans oligosaccharides from mammals will be described. N-Linked oligosaccharides standards were derivatized with 1-phenyl-3-methyl-5-pyrazolone (PMP) and analyzed by matrix-assisted laser desorption/ionization (MALDI)-tandem MS. Simulated tandem mass spectra of other common glycans were also generated to test the algorithm. The MALDI-MS/MS spectra featured resolved isotopic distributions for the [M + H](+) and fragment ions of oligosaccharides. These isotopic distributions complicated the automated analysis of the spectra and were removed to leave only monoisotopic peaks. An algorithm was written for this purpose, yielding simplified tandem mass spectra. Another algorithm is then used to determine the structure of the oligosaccharide. A score is then given to each structure, depending on agreement with experimental results. The program successfully assigned the true structure in 24 out of the 28 cases (86%) and the true structure was among the three top scoring structures in all cases.

Determination of Oligosaccharides in Pompe Disease by Electrospray Ionization Tandem Mass Spectrometry

Background: The development of therapies for lysosomal storage disorders has created a need for biochemical markers to monitor the efficacy of therapy and methods to quantify these markers in biologic samples. In Pompe disease, the concentration of a tetrasaccharide, consisting of four glucose residues, is reputedly increased in urine and plasma, but faster and more sensitive methods are required for the analysis of this, and other oligosaccharides, from biologic fluids.

Methods: We optimized the derivatization of storage oligosaccharides with 1-phenyl-3-methyl-5-pyrazolone for the measurement, by electrospray ionization tandem mass spectrometry, of oligosaccharide concentrations in urine (n = 6), plasma (n = 11), and dried-blood spots (n = 17) from Pompe-affected individuals. Age-matched control samples of urine (n = 10), plasma (n = 28), and blood spots (n = 369) were also analyzed.

Results: The mean tetrasaccharide concentration was increased in urine from infantile-onset (0.69–12 mmol/mol of creatinine) and adult-onset (0.22–3.0 mmol/mol of creatinine) Pompe individuals compared with age-matched controls. In plasma samples, an increased tetrasaccharide concentration was observed in some infantile patients (up to 22 μmol/L) compared with age-matched controls (mean, 2.2 μmol/L). The method developed was sensitive enough to determine oligosaccharide concentrations in a single 3-mm blood spot, but no differences were observed between blood spots from control and Pompe-affected individuals.

Conclusions: Measurements of oligosaccharide concentrations in urine by this new method have potential application for the diagnosis and monitoring of patients with Pompe disease. Plasma analysis may have limited application for infantile patients, but analysis of blood spots does not discriminate between controls and affected individuals.

Rapid analysis of amino sugars by microchip electrophoresis with laser-induced fluorescence detection

Microchip electrophoresis for the short-time analysis of amino sugars is described. D-Glucosamine, D-galactosamine and their reduced forms were labeled with 4-nitro-2,1,3-benzoxadiazole 7-fluoride (NBD-F) at pH 6.0 and the fluorescent derivatives were purified on an octadecyl silica (ODS) gel plate. The derivatives were analyzed by electrophoresis on a microfabricated chip with a 33 mm long separation channel with argon laser-induced fluorescence detection. Under the established conditions, these amino sugarderivatives were well separated from each other within 60 s. Amino sugars of as small an amount as 0.5 fmol could be detected with a signal-to-noise (S/N) ratio of 3, and peak response showed good linearity between at least 0.8 and 8 fmol of samples with a relative standard deviation (RSD) of ca. 4%. This method was also applied to the analysis of amino sugar composition of O-linked glycans released from bovine submaxillary mucin with alkali in the presence of borohydride. The result of amino sugar composition analysis for individual O-glycans fractionated by high-performance liquid chromatography was quite useful for their identification.

Capillary electrophoresis method for the analysis of inorganic anions, organic acids, amino acids, nucleotides, carbohydrates and other anionic compounds

A previously developed capillary zone electrophoresis (CZE) method with indirect UV detection for the simultaneous determination of inorganic and organic anions, amino acids and carbohydrates using 20 mM 2,6-pyridinedicarboxylic acid (PDC) as the background electrolyte was extended to allow determination of 206 anions including those above--mentioned and physiological amino acids, nucleotides, aromatic acids, haloacetic acids, alcohols, phosphorylated saccharides, oxyhalides, metal oxoacids, metal-ethylenediaminetetraacetic acid (EDTA) complexes, forensic anions, Good's buffers and herbicides. Every compound could be analyzed and their electrophoretic mobility determined simply by selecting detection wavelength. This method is simple and universal for anion analysis, and could be readily applied to the simultaneous determination of anionic compounds. In this work, it was used to identify and quantify important anions in sea urchin and sake.

Knockout of an azorhizobial dTDP-L-rhamnose synthase affects lipopolysaccharide and extracellular polysaccharide production and disables symbiosis with Sesbania rostrata

A nonpolar mutation was made in the oac2 gene of Azorhizobium caulinodans. oac2 is an ortholog of the Salmonella typhimurium rfbD gene that encodes a dTDP-L-rhamnose synthase. The knockout of oac2 changed the lipopolysaccharide (LPS) pattern and affected the extracellular polysaccharide production but had no effect on bacterial hydrophobicity. Upon hot phenol extraction, the wild-type LPS partitioned in the phenol phase. The LPS fraction of ORS571-oac2 partitioned in the water phase and had a reduced rhamnose content and truncated LPS molecules on the basis of faster migration in detergent gel electrophoresis. Strain ORS571-oac2 induced ineffective nodule-like structures on Sesbania rostrata. There was no clear demarcation between central and peripheral tissues, and neither leghemoglobin nor bacteroids were present. Light and electron microscopy revealed that the mutant bacteria were retained in enlarged, thick-walled infection threads. Infection centers emitted a blue autofluorescence under UV light. The data indicate that rhamnose synthesis is important for the production of surface carbohydrates that are required to sustain the compatible interaction between A. caulinodans and S. rostrata.

Investigation of different combinations of derivatization, separation methods and electrospray ionization mass spectrometry for standard oligosaccharides and glycans from ovalbumin

Derivatization procedures using 1-phenyl-3-methyl-5-pyrazolone (PMP) and 2-aminonaphthalene trisulfone (ANTS) were selected among a number of well known methods for labelling carbohydrates. PMP derivatives were selected owing to our laboratory's previous high-performance liquid chromatography/electrospray ionization mass spectrometry (HPLC/ESI-MS) experience with these, whereas the ANTS-labelled compounds were prepared for fluorophore-assisted carbohydrate electrophoresis (FACE) separation. ANTS-oligosaccharide standards were characterized to study their ionization patterns. Reversed-phase and normal-phase HPLC systems were coupled on-line with ESI-MS. Each necessitated its own mobile phase system which, in turn, imposed some important changes in the ionization conditions used and/or on the ionization patterns and spectra obtained. Following characterization of the intact glycoprotein ovalbumin with ESI-MS, its glycans were detached using the enzyme PNGase-F. The glycans were subjected to PMP and ANTS derivatization. It was very difficult to separate ANTS derivatives by reversed-phase HPLC owing to lack of retention, and normal-phase HPLC offered reasonable retention with limited separation. PMP compounds overall yielded better normal- and reversed-phase separations and improved sensitivity over the ANTS-labelled sugars, for which negative mode ESI had to be used. The combination of ESI of intact ovalbumin and ESI of PMP-glycans gave rise to the detection of over 20 different glycoforms, excluding the possible presence of structural isomers for each sugar composition detected.

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.

Analysis of sialo-N-glycans in glycoproteins as 1-phenyl-3-methyl-5-pyrazolone derivatives by capillary electrophoresis

A method for the analysis of the sialo-N-glycans in glycoproteins was established by the electrokinetic chromatography mode of capillary electrophoresis (CE) in sodium dodecyl sulfate (SDS) micelles as 1-phenyl-3-methyl-5-pyrazolone (PMP) derivatives, using sialo-N-glycans in fetuin as a model. Six major and some minor peaks were observed for the N-glycans in fetuin, which were well separated from each other using 50 mM phosphate buffer, pH 6.0, containing SDS to a concentration of 30 mM in an uncoated fused-silica capillary, and these peaks were assigned to sialo-N-glycans having either of the biantennary or beta1-3/beta1-4 linked galactose-containing complex type triantennary N-glycans as the basic structures, by an indirect method based on the assignment of the peaks in high-performance liquid chromatography separated in parallel with CE and peak collation between these two separation methods. The attaching position of the sialic acid residue was determined using the linkage preference of neuraminidase isozymes. The established system is considered to be useful for routine analysis of microheterogeneity of the carbohydrate moiety of this model glycoprotein from the following reasons: (1) the derivatization with PMP proceeds quantitatively under mild conditions without causing release of the sialic acid residue, (2) the derivatives can be sensitively detected by UV absorption, (3) the procedure is simple, rapid and reproducible. Preliminary results of N-glycan analysis for several other glycoproteins under these conditions are also presented.

Direct determination of amino acids and carbohydrates by high-performance capillary electrophoresis with refractometric detection

This is an initial report to propose a novel approach in high-performance capillary electrophoresis (HPCE) for the direct detection of compounds without natural absorbance in the UV and visible spectral range, such as amino acids and carbohydrates. A refractometry detector with the 2 nl cell (Applied Systems, Minsk, Belarus) was employed to identify amino acids and carbohydrates without derivatization. The first results are provided on separation of seven free amino acids in the phosphate running buffer and three free carbohydrates in the borate-sodium dodecyl sulfate running buffer and detection by refractometer. Fused capillaries of 50 or 75 microm internal diameter and separation voltage (10-23 kV) were applied. Detection limits ranged typically from 10 to 100 fmol and the response was linear over two orders of magnitude for most of the amino acids and carbohydrates. The HPCE system demonstrated good long-term stability and reproducibility with a relative standard deviation, less than 5% for the migration time (n=10).

Fluorometric determination of mucin-type glycoproteins by the galactose oxidase-peroxidase method

We developed a convenient and specific method for the determination of mucin-type glycoproteins using galactose oxidase and horseradish peroxidase on the basis of the contents of galactosyl and N-acetylgalactosaminyl residues in glycoproteins. Galactose and galactosamine residues released from glycoproteins after hydrolysis were oxidized with galactose oxidase and subsequently the resultant hydrogen peroxide was determined by a combination of horseradish peroxidase and 3-(p-hydroxyphenyl) propionic acid as a fluorogenic substrate. The contents of galactose/galactosamine residues in N- and O-glycans, as determined by the galactose oxidase-peroxidase method, were in good agreement with those described in the previous reports. We applied the present method to determine mucin-type glycoproteins secreted from rat gastric mucosa by stimulation with misoprostol, a prostaglandin E(1) analogue in vivo. Thus, the galactose oxidase-peroxidase method is useful for the determination of mucin-type glycoproteins in biological materials.

Monosaccharide composition of sweetpotato fiber and cell wall polysaccharides from sweetpotato, cassava, and potato analyzed by the high-performance anion exchange chromatography with pulsed amperometric detection method

The cell wall materials (CWMs) from sweetpotato (Ipomoea batatas cv. Kokei 14), cassava (Manihot esculenta), and potato (Solanum tuberosum cv. Danshaku) and commercial sweetpotato fiber as well as their polysaccharide fractions were analyzed for sugar composition by the high-performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD) method. The separation of arabinose and rhamnose, and xylose and mannose, by this method has been improved using a CarboPac PA 10 column. Pretreatment of the CWMs and cellulose fractions with 12 M H(2)SO(4) was required for complete hydrolysis to occur. Commercial sweetpotato fiber was found to be mainly composed of glucose (88.4%), but small amounts of other sugars were also detected. Among the root crops, sweetpotato CWM had the highest amount of pectin and galacturonic acid. Fucose was detected only in cassava CWM and its hemicellulose fraction, while galactose was present in the highest amount in potato CWM. Among the polysaccharide fractions, it was only in the hemicellulose fraction where significant differences in the sugar composition, especially in the galactose content, were observed among the root crops.

Regiospecific transglycolytic synthesis and structural characterization of 6-O-alpha-glucopyranosyl-glucopyranose (isomaltose)

The enzymatic synthesis of 6-O-alpha-glucopyranosyl-glucopyranose (isomaltose) was achieved. The regiospecific transglycosylation reaction was catalyzed by a crude preparation of alpha-D-glucosidase from Aspergillus niger, using p-nitrophenyl alpha-D-glucopyranose as the donor and glucopyranose as the acceptor. The yield of the reaction was 59% on a molar basis with respect to the donor. The structural identity of the product was fully determined by HPLC, HPAEC-PAD, ionspray mass spectrometry and (13)C NMR.

Disaccharide analysis of skin glycosaminoglycans in atrophoderma of Pasini and Pierini

There are divergent opinions as to whether atrophoderma of Pasini and Pierini (APP) is a nosologic entity or a primary atrophic morphoea. In this study, we used high performance liquid chromatography to analyse the skin disaccharide contents of glycosaminoglycan (GAG) in two patients with APP and compared the results with those from a typical atrophic morphoea patient. Perilesional uninvolved skin was used as a control in each patient. In the atrophic phase morphoea, both the total amount of disaccharide per skin punch-biopsy and the amount of DeltaDi-4S(DS) - the main disaccharide unit of dermatan sulphate - per mg dry weight were increased. These changes were consistent with sclerotic phase morphoea. In contrast, the total amount of disaccharide per skin punch-biopsy was decreased and the amount of DeltaDi-4S(DS) per mg dry weight was decreased or unchanged in APP. Our results suggest that GAG metabolism in APP may be unique and quite different from that in morphoea.

Preparation of various silica-based columns for capillary electrochromatography by in-column derivatization

Chemically bonded silica gels were prepared in a capillary by pumping an ethanolic solution of a silylating reagent, such as octadecyltrimethoxysilane, 3-aminopropyltrimethoxysilane and dimethyloctadecyltrimethoxysilylpropylammonium chloride into a heated capillary packed with bare silica particles. The silylation reactions were completed in a short time and thus-prepared columns showed high column efficiency and high reproducibility. Examples are shown for the separation of 1-phenyl-3-methyl-5-pyrazolone (PMP) derivatives of aldopentoses on a 3-aminopropylated silica column and benzoate homologues as well as PMP derivatives of the component monosaccharides of glycoproteins on an octadecylammonium column. Since the presence of frit filters hampers high efficiency separation, an attempt was made to fix the bed of modified silica gel particles to the capillary inner wall by a cross-linking technique. The results indicated that this technique is promising.

Regiospecific glycosidase-assisted synthesis of lacto-N-biose I (Galbeta1-3GlcNAc) and 3'-sialyl-lacto-N-biose I (NeuAcalpha2-3Galbeta1-3GlcNAc)

The all-transglycolytic synthesis of lacto-N-biose I (Galbeta1-3GlcNAc) and 3'-sialyl-lacto-N-biose I (NeuAcalpha2-3Galbeta1-3GlcNAc) was performed. The disaccharide lacto-N-biose I was obtained by use of p-nitrophenyl beta-D-galactopyranoside as the donor, 2-acetamido-2-deoxy-D-glucopyranose as the acceptor and Xanthomonas manihotis beta-D-galactosidase as the catalyst. The reaction was shown to be regiospecific, with a high molar yield (about 55%) with respect to the donor. Lacto-N-biose I obtained by this method was used as the acceptor for a subsequent enzymatic reaction catalyzed by Trypanosoma cruzi trans-sialidase in which 2'-(4-methylumbellyferyl)-alpha-D-N-acetylneuraminic was used as the donor of the N-acetylneuraminil moiety. The reaction generated the product, 3'-sialyl-lacto-N-biose I, regiospecifically and with a molar yield of about 35%.

Matrix-assisted laser desorption/ionization mass spectrometry of carbohydrates

This review describes the application of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry to carbohydrate analysis and covers the period 1991-1998. The technique is particularly valuable for carbohydrates because it enables underivatised, as well as derivatised compounds to be examined. The various MALDI matrices that have been used for carbohydrate analysis are described, and the use of derivatization for improving mass spectral detection limits is also discussed. Methods for sample preparation and for extracting carbohydrates from biological media prior to mass spectrometric analysis are compared with emphasis on highly sensitive mass spectrometric methods. Quantitative aspects of MALDI are covered with respect to the relationship between signal strength and both mass and compound structure. The value of mass measurements by MALDI to provide a carbohydrate composition is stressed, together with the ability of the technique to provide fragmentation spectra. The use of in-source and post-source decay and collision-induced fragmentation in this context is described with emphasis on ions that provide information on the linkage and branching patterns of carbohydrates. The use of MALDI mass spectrometry, linked with exoglycosidase sequencing, is described for N-linked glycans derived from glycoproteins, and methods for the analysis of O-linked glycans are also covered. The review ends with a description of various applications of the technique to carbohydrates found as constituents of glycoproteins, bacterial glycolipids, sphingolipids, and glycolipid anchors.

Monosaccharide compositions of Danaus plexippus (monarch butterfly) and Trichoplusia ni (cabbage looper) egg glycoproteins

Monosaccharide compositions of eggs from Danaus plexippus (monarch butterfly) and Trichoplusia ni (cabbage looper) were analyzed. Analyses were performed mainly with high performance anion exchange chromatography (HPAEC) using crude extracts of eggs or SDS-PAGE separated and PVDF-blotted protein bands. Man and GlcN were the major components in all cases, but low levels of Gal and Fuc were possibly present in some samples. Some T. ni egg glycoproteins even contained GalN. Although a peak comigrating with Neu5Ac could be detected with HPAEC-PAD or RP-HPLC (fluorometry) after derivatization with 1,2-diamino-4,5-methylenedioxy-benzene, the quantities were too small to be significant as an integral part of the analyzed glycoproteins. These data suggests that most of glycans on the glycoproteins are pauci-Man type N-glycans, but a small portion of N-glycan may be either hybrid type or complex type.

Analysis of carbohydrate heterogeneity in a glycoprotein using liquid chromatography/mass spectrometry and liquid chromatography with tandem mass spectrometry

High-performance liquid chromatography with on-line electrospray ionization mass spectrometry (ESI-LC/MS) was investigated for the analysis of carbohydrate heterogeneity using RNase B as a model glycoprotein. Oligosaccharides released from RNase B with endoglycosidase H were reduced and separated on a graphitized carbon column (GCC). GCC-HPLC/MS in the positive-ion mode was successful in the identification of one Man5GlcNAc, three Man6GlcNAc, three Man7GlcNAc, three Man8GlcNAc, one Man9GlcNAc, and an oligosaccharide having six hexose units (Hex) and two N-acetylhexosamine units (HexNAc). The branch structures of the three Man7GlcNAc isomers were determined by liquid chromatography with tandem mass spectrometry (LC/MS/MS). LC/MS/MS analysis was shown to be useful for the detection and identification of a trace amount of Hex6HexNAc2 alditol as a hybrid-type oligosaccharide. Its structure was confirmed by the combination of LC/MS with enzymatic digestion using beta-galactosidase and N-acetyl-beta-glucosaminidase. The relative quantities of high-mannose-type oligosaccharides in RNase B detected by ESI-LC/MS are in reasonable agreement with those by UV, high-pH anion-exchange chromatography with pulsed amperometric detection, fluorophore-assisted carbohydrate electrophoresis. Our results indicate that LC/MS and LC/MS/MS can be utilized to elucidate the distribution of oligosaccharides and their structures, which differ in molecular weight, sugar sequence, and branch structure.

Electrospray ionization mass spectrometry of 1-phenyl-3-methyl-5-pyrazolone derivatives of neutral and N-acetylated oligosaccharides

Derivatization using 1-phenyl-3-methyl-5-pyrazolone (PMP) was selected among a number of reported methods for labeling carbohydrates, since it gives a quantitative yield, proceeds through a rapid reaction and involves a simple clean-up procedure. Moreover, PMP derivatives provide an increase in sensitivity with ultraviolet and mass spectrometric detection relative to native neutral sugars. Sensitivity studies were carried out using a standard oligosaccharide, tetraglucose. One of the aims of these studies was to determine the minimum amounts of PMP-tetraglucose necessary to generate informative full-scan electrospray ionization (ESI) mass spectra and collision-induced dissociation tandem mass spectra. Another aim was to characterize the fragmentation pattern of PMP derivatives. Quantitative and qualitative studies were also carried out with a typical N-linked oligosaccharide obtained commercially. The PMP-labeled compound underwent directed cleavages which produced fragments containing the reducing end. The native N-linked sugar yielded fragments corresponding to cleavages from both ends of the molecule. Under the same ESI conditions, the N-linked oligosaccharide exhibited more lability, or tendency to fragment, than neutral tetraglucose, in both the derivatized and native forms. Also, PMP labeling was shown to enhance sensitivity in the case of a neutral oligosaccharide, i.e. tetraglucose, whereas the labeling of an N-acetylated oligosaccharide, NGA3, did not yield a noticeable improvement in sensitivity.

Mode of action of chitin deacetylase from Mucor rouxii on N-acetylchitooligosaccharides

The mode of action of chitin deacetylase from the fungus Mucor rouxii on N-acetylchitooligosaccharides with a degree of polymerization 1-7 has been elucidated. Identification of the sequence of chitin oligomers following enzymatic deacetylation was verified by the alternative use of two specific exo-glycosidases in conjunction with HPLC. The results were further verified by 1H-NMR spectroscopy. It was observed that the length of the oligomer is important for enzyme action. The enzyme cannot effectively deacetylate chitin oligomers with a degree of polymerization lower than three. Tetra-N-acetylchitotetraose and penta-N-acetylchitopentaose are fully deacetylated by the enzyme, while in the case of tri-N-acetylchitotriose, hexa-N-acetylchitohexaose and hepta-N-acetylchitoheptaose the reducing-end residue always remains intact. Furthermore, the enzyme initially removes an acetyl group from the nonreducing-end residue of all chitin oligomers with a degree of polymerization higher than 2, and further catalyses the hydrolysis of the following acetamido groups in a processive fashion. The results are in agreement with the mode of action that the same enzyme exhibits on partially deacetylated water soluble chitosan polymers.

Analysis of sialyllactoses in blood and urine by high-performance liquid chromatography

A sensitive and highly selective high-performance liquid chromatography (HPLC)-based method has been developed for the analysis of oligosaccharides in biological fluids. In this method, a sample of biological fluid, such as blood serum or urine, is filtered through a 10,000 molecular weight cutoff filter cartridge to remove large molecules such as proteins and lipids. The carbohydrates in the filtrate are then derivatized with 1-phenyl-3-methyl-5-pyrazolone (PMP) as described previously [Anal. Biochem. 180, 351-357, (1989)]. The derivatized carbohydrates are separated by reverse-phase HPLC and monitored by UV absorbance at 245 nm. Quantitative analysis of the carbohydrates can be achieved based on their integration values relative to a standard calibration curve. Since neutral and acidic carbohydrates can be separated by using Dowex 1-X8 anion exchange resin, this method can be used specifically to analyze neutral, acidic, and total carbohydrates in the biological fluids. Because PMP specifically reacts with reducing aldoses, interference from noncarbohydrate components present in the biological fluids is essentially eliminated. This method has proven to be highly sensitive, requiring as little as 5 pmol of analyte for reliable analysis. It has also been used successfully for pharmacokinetic analysis of carbohydrate drugs in human blood and urine samples.

Effect of 1-phenyl-3-methyl-5-pyrazolone labeling on the fragmentation behavior of asialo and sialylated N-linked glycans under electrospray ionization conditions

The advantages of labeling free N-linked oligosaccharides with 1-phenyl-3-methyl-5-pyrazolone (PMP), for high performance liquid chromatography (HPLC) and electrospray ionization mass spectrometry (ESI-MS) are discussed. The study focuses on some asialo and sialylated sugars, and compares the HPLC and ESI-MS behaviors of the PMP-labeled substances vs. the native compounds. It is pointed out that native free N-linked carbohydrates have very low affinities for the C18 reversed phases commonly used in HPLC. Native asialo oligosaccharides yield good ESI-MS sensitivity, although they are very susceptible to in-source collision-induced dissociation (CID), and the fragments are produced from any of the branches of the molecules, i.e. do not give specific structural information. Native N-linked standards bearing one sialic acid residue yield a 10-fold loss of ESI-MS sensitivity vs. asialo compounds, and native sugars with two sialic acid moieties were not detectable. The PMP labeling of asialo and sialylated sugars yielded higher affinities for HPLC C18 columns and, even at the early stages of method development, it was possible to separate three PMP-labeled standards to a useful extent. In ESI-MS, PMP-asialo sugars did not yield a significant increase in sensitivity vs. the native species; however, fragmentation produced by in-source CID was more directed as all predominant fragment ions contained the bis-PMP label. This feature is particularly useful when structural determination of an unknown sugar is required. PMP-sialylated sugars gave rise to very clean and informative ESI mass spectra. The monosialo sugar yielded a 100-fold sensitivity improvement vs. its native analog and, in the case of the disialylated compound, a 100% improvement was obtained in the positive mode. Most fragment ions were informative and contained the reducing end on the molecules, thus facilitating spectral interpretation. The combination of PMP derivatization with on-line HPLC/ESI-MS is a promising method for the analysis of asialo and sialylated carbohydrate mixtures.

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

Separation of the 1-phenyl-3-methyl-5-pyrazolone (PMP) derivatives of simple disaccharides (maltose, cellobiose, gentiobiose, lactose, and melibiose) by affinity capillary electrophoresis was investigated using lectin-containing neutral phosphate buffers, filled in a linear polyacrylamide-coated capillary. When Lens culinaris agglutinin (LCA) was added, the derivatives of glucobioses were retarded with varying magnitudes depending on the amount of LCA and were well separated from each other and from galactosyl glucose under optimized conditions. Addition of Ricinus communis 60 kDa agglutinin (RCA60) to the phosphate buffer gave a different migration profile, in which the derivatives of galactosyl glucoses were more retarded than those of glucobioses. However, addition of either lectin did not accomplish complete separation of the derivatives of all these disaccharides even under optimum conditions. The addition of two kinds of lectins in appropriate proportions improved separation. Thus, the binary system composed of LCA and RCA60, as well as LCA and soybean agglutinin from Glycine max (SBA), gave better separation of these derivatives, giving peak tops for all derivatives.

Separation of 1-phenyl-3-methyl-5-pyrazolone derivatives of monosaccharides by capillary electrochromatography

1-Phenyl-3-methyl-5-pyrazolone (PMP) derivatives of component monosaccharides in glycoproteins (fucose, galactose, mannose, N-acetylgalactosamine and N-acetylglucosamine) and epimeric aldopentoses (arabinose, lyxose, ribose and xylose) were well separated from each other by capillary electrochromatography on a Hypersil ODS column with a mixture of 50 mM N-(2-hydroxyethyl)piperazine-2'-(2-ethanesulfonic acid) buffer, pH 6.0 to approximately 6.3, and acetonitrile (2.2:1 v/v) as eluent. The elution of these compounds showed relatively strong dependence on the pH and concentration of the buffer salts contained in the eluent, as compared to the elution by pressure-driven high-performance liquid chromatography (HPLC) on the same stationary phase, but separation of PMP-monosaccharides was better than that by HPLC. Retention times of PMP-monosaccharides were highly reproducible with a relative standard deviation (RSD) of approximately 0.6%, and quantification with an RSD less than 5% could be achieved using 3-O-methylglucose as an internal standard.

Simultaneous determination of monosaccharides in glycoproteins by capillary electrophoresis

A rapid, easy, and reproducible capillary electrophoretic method for the simultaneous determination of acidic, neutral, and amino sugars and sugar alcohols was developed. Underivatized mannuronic acid, glucuronic acid, galacturonic acid, N-glycolylneuraminic acid, N-acetylneuraminic acid, glucosamine, galactosamine, mannose, xylose, glucose, galactose, fucose, ribose, mannitol, sorbitol, xylitol, and inositol were simultaneously determined with indirect UV detection using 2,6-pyridinedicarboxylic acid as a background electrolyte. A highly alkaline pH condition was used in order to charge carbohydrates negatively and to promote migration toward the anode. Electroosmotic flow was reversed to the direction of the anode by adding cetyltrimethylammonium bromide to the electrolyte. The separation of the carbohydrates was investigated by optimizing the operating pH value and satisfactory resolution was obtained at pH 12.1. The relative standard deviations of the method for carbohydrates were between 0.02 and 0.33% for migration times and were greater than 2.7% for peak areas (n = 6). The minimum detectable level ranged from 23 to 71 microM with a 6-nl injection at a signal-to-noise ratio of 3. This method was applied to the composition analysis of monosaccharides in glycoprotein. After acid hydrolysis of fetuin under each optimum condition, sialo, neutral, and amino sugars were quantified under the same electrophoretic condition.

Characterization of carbohydrates using a combination of derivatization, high-performance liquid chromatography and mass spectrometry

A combination of derivatization methods, chromatographic techniques and mass spectrometric ionization modes have been explored for the characterization of small sugars and medium-size oligosaccharides. Derivatization using 1-phenyl-3-methyl-5-pyrazolone (PMP) was preferred over pyridylamination (PA) owing to the simplicity of the reaction method, and also to enhanced ionization efficiency of the PMP derivatives relative to aminopyridyl sugars. The good quality and ease of separation of PMP derivatives by high-performance liquid chromatography were also advantages of using PMP derivatization rather than pyridylamination. PMP- and PA-monosaccharides produced abundant ions by either fast atom bombardment (FAB), electrospray ionization (ESI) or matrix-assisted laser desorption/ionization (MALDI). The PA and PMP derivatives of lactose, fucosyllactose and sialyllactose yielded FAB spectra with low S/N ratios, whereas ESI and MALDI produced better spectra with a hundredth of the material used for FAB. In general, PMP derivatives of these di- and trisaccharides gave rise to stronger signals than PA analogs. For Oligosaccharides containing more than three sugar rings, only PMP was used for derivatization, FAB was dropped and only ESI and MALDI were utilized.