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

Development and application of a capillary electrophoretic method for the composition analysis of a typical heteropolysaccharide from Codonopsis pilosula NANNF

A simple capillary electrophoretic method based on 1-phenyl-3-methyl-5-pyrazolon (PMP) derivatization has been developed for simultaneous separation and determination of nine aldoses (xylose, arabinose, glucose, rhamnose, fucose, galactose, mannose, glucuronic acid and galacturonic acid). The separation of PMP-labeled monosaccharide derivatives was carried out in uncoated capillary (48.5 cm x 75 microm i.d.) and under the selected optimum conditions of pH 11.0, 200 mM borate buffer at applied voltage 15 kV and capillary temperature 20 degrees C, the nine PMP-monosaccharides could be perfectly separated from each other within 40 min. Furthermore, the developed method was firstly applied to determine the sugar composition in the polysaccharide isolated from Chinese Codonopsis pilosula. The results showed that C. pilosula polysaccharide was a typically acidic heteropolysaccharide and was composed of arabinose, glucose, rhamnose, galactose, mannose, glucuronic acid and galacturonic acid in the molar contents of 48.1, 103.5, 16.1, 48.5, 7.5, 4.2 and 119.1 microM, respectively. The assay results were satisfactory.

Comparison of fluorescent labels for oligosaccharides and introduction of a new postlabeling purification method

Labeling of oligosaccharides with fluorescent dyes is the prerequisite for their sensitive analysis by high-performance liquid chromatography (HPLC). In this work, we present a fast new postlabeling cleanup procedure that requires no device other than the reaction vial itself. The procedure can be applied to essentially all labeling reagents. We also compare the performance of 15 different labels for N-glycan analysis in various analytical procedures. We took special care to prevent obscuring influences from incomplete derivatization and signal quenching by impurities. Procainamide emerged as more sensitive than anthranilic acid for normal-phase HPLC, but its chromatographic performance was not convincing. 2-aminopyridine was the label with the lowest retention on reversed-phase and graphitic carbon columns and, thus, appears to be most suitable for glycan fractionation by multidimensional HPLC. Most glycan derivatives performed better than native sugars in matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS) and electrospray ionization-MS (ESI-MS), but the gain was small and hardly sufficient to compensate for sample loss during preparation.

Lipidomics in diagnosis of lipidoses

A review is presented of the major clinical features of a number of glycolipidoses including Fabry, Gaucher, Tay-Sachs, metachromatic leukodystrophy as well as CeroidLipofucinosis and Sjogren-Larsson syndrome. The possibilities offered by lipidomics for diagnosis and follow-up after enzyme replacement therapy are presented from a practical perspective. The contribution of HPLC coupled with tandem mass spectrometry has considerably simplified the detection and assay of abnormal metabolites. Corresponding internal standards consisting of weighed mixtures of the stable-isotope labeled metabolites required to calibrate and quantitate lipid components of these orphan diseases standards have yet to become commercially available. A lipidomics approach has been found to compare favorably with DNA-sequence analysis for the rapid diagnosis of pre-birth syndromes resulting from these multiple gene defects. The method also seems to be suitable for screening applications in terms of a high throughput combined with a low rate of false diagnoses based on the wide differences in metabolite concentrations found in affected patients as compared with normal subjects. The practical advantages of handling samples for lipidomic diagnoses as compared to enzyme assay are presented for application to diagnosis during pregnancy.

Determination of triterpene glycosides in sea cucumber (Stichopus japonicus) and its related products by high-performance liquid chromatography

A creative and sensitive method has been developed for the determination of triterpene glycosides concentrations in sea cucumber ( Stichopus japonicus) and related products by using d-quinovose (6-deoxyglucose) as the measurement standard by reverse-phase high-performance liquid chromatography (HPLC) and variable-wavelength detection. d-quinovose, which is a unique monosaccharide in holostane triterpene glycosides, was liberated by acid hydrolysis and precolumn derivatized by 1-phenyl-3-methyl-5-pyrazolone (PMP). PMP-quinovose was analyzed by HPLC with 22% acetonitrile in 0.05 M KH2PO4 aquatic solution (pH 5.2) as mobile phase. The calibration curves of d-quinovose were linear within the range of 6.56-164 mg/L (r(2) > 0.995). The contents of triterpene glycosides in various S. japonicus products were determined after appropriate pretreatment methods. The concentration of triterpene glycosides was calculated by the formula C = C(qui) x alpha (alpha = 8.5). The result showed that this method was a simple, rapid, and stable method for the determination of triterpene glycosides in S. japonicus products.

Simultaneous analysis of FDG, ClDG and Kryptofix 2.2.2 in [18F]FDG preparation by high-performance liquid chromatography with UV detection

A practical, sensitive and rapid analytical method was established and validated for chemical impurity tests of 2-deoxy-2-fluoro-d-glucose (FDG), 2-deoxy-2-chloro-d-glucose (ClDG) and Kryptofix 2.2.2 (K-222) in [18F]FDG. This method was based on precolumn derivatization with ultraviolet (UV) detection. FDG and ClDG were rapidly derivatized with 1-phenyl-3-methyl-5-pyrazolone in the presence of borate buffer at 40 degrees C, and the labeled derivatives and K-222 were separated by reversed-phase high-performance liquid chromatography and monitored by UV absorbance at 210 nm. After optimization of the conditions, FDG, ClDG and K-222 could be determined within 15 min and showed good performance in terms of sensitivity, linearity and reproducibility. This method could be successfully applied to the quality control test of [18F]FDG produced by a commercially available apparatus.

Four acarviosin-containing oligosaccharides identified from Streptomyces coelicoflavus ZG0656 are potent inhibitors of alpha-amylase

Four aminooligosaccharides were isolated and purified from the culture filtrate of Streptomyces coelicoflavus ZG0656. Their chemical structures were determined by electrospray ionization tandem mass spectrometry (ESI-MS/MS) and two-dimensional nuclear magnetic resonance (NMR) spectroscopy. The names acarviostatins I03, II03, III03, and IV03 were given to the oligomers due to their acarviosin core structures. Acarviostatins III03 and IV03, which contain three and four acarviosin-glucose moieties, respectively, were identified as novel compounds. The four acarviostatins were all mixed noncompetitive inhibitors of porcine pancreatic alpha-amylase (PPA). The inhibition constants (K(i)) for acarviostatins III03 and IV03 were 0.008 and 0.033muM, respectively. Acarviostatin III03 is the most effective alpha-amylase inhibitor known to date, with a K(i) value 260 times more potent than acarbose.

Determination of galactose and mannose residues in natural galactomannans using a fast and efficient high-performance liquid chromatography/UV detection

The present work describes the validation of an easy, fast and efficient precolumn derivatization method for the quantification of oligosides, mannose and galactose obtained by degradation of galactomannans. This work combines an acid hydrolysis and an enzymatic degradation of natural galactomannans with the quantification of released residues by reversed-phase HPLC-UV, the most usual HPLC system in laboratories. In case of enzymatic degradation, mannotetraose has been detected and quantified for the first time, and an application to the evaluation of the galactosyl distribution in galactomannans is proposed. After an acidic hydrolysis, this method also allowed to obtain the mannose/galactose (M/G) ratio.

Detection of carbohydrates using new labeling reagent 1-(2-naphthyl)-3-methyl-5-pyrazolone by capillary zone electrophoresis with absorbance (UV)

A novel labeling reagent 1-(2-naphthyl)-3-methyl-5-pyrazolone (NMP) coupled with capillary electrophoresis (CE) with DAD detection for the determination of carbohydrates has been developed. The chromophore in the 1-phenyl-3-methyl-5-pyrazolone (PMP) reagent is replaced by naphthyl functional group, which results in a reagent with very high molar absorptivity (epsilon251 nm = 5.58 x 10(4) L mol(-1) cm(-1)). This permits NMP-labeled carbohydrates to be detected with UV absorbance in standard 50-mum-i.d. fused silica capillaries by zone electrophoresis. In this mode, nanomolar concentrations of detection limits are obtained. The method for the derivatization of carbohydrates with NMP is simplified. The derivatization reaction is rapid and mild in the presence of ammonia catalyst without further transfer steps. Nine monosaccharide derivatives such as mannose, galacturonic acid, glucuronic acid, rhamnose, glucose, galactose, xylose, arabinose and fucose can successfully be detected in CE mode. Good reproducibility can be obtained with relative standard deviation (R.S.D.) values of the migration times and peak area, respectively, from 0.44 to 0.48 and from 3.2 to 4.8. Furthermore, the developed method has been successfully applied to the analysis of carbohydrates in the hydrolyzed rape bee pollen samples.

Two novel aminooligosaccharides isolated from the culture of Streptomyces coelicoflavus ZG0656 as potent inhibitors of alpha-amylase

Two novel aminooligosaccharides were separated from the culture filtrate of Streptomyces coelicoflavus ZG0656. Their chemical structures were determined by electrospray ionization tandem mass spectrometry (ESI-MS/MS) and 2D nuclear magnetic resonance (NMR) spectroscopy. Because of their acarviosine core structures, the names acarviostatins II23 and II13 were given to the novel compounds. The two acarviostatins were both mixed noncompetitive inhibitors of porcine pancreatic alpha-amylase (PPA), with inhibition constants (K(i)) of 0.009 microM (acarviostatin II23) and 0.010 microM (acarviostatin II13). Therefore, acarviostatin II23 and acarviostatin II13 are, respectively, 231 and 208 times more potent than acarbose.

Determination of fluorescence-labeled asparaginyl-oligosaccharide in glycoprotein by reversed-phase ultraperformance liquid chromatography with electrospray ionization time-of-flight mass spectrometry

Eight fluorescence reagents, i.e., DBD-F, NBD-F, DNS-Cl, NDA, PSC, FITC, Fmoc-Cl, and DMEQ-COCl, which are reactive to an amino functional group, were tested for the labeling of asparaginyl-oligosaccharides in a glycoprotein. Although the optimal reaction conditions and the fluorescence maximal wavelengths were different for each reagent, the highly sensitive fluorescence detection at the femtomole level of Disialo-Asn (a representative asparaginyl-oligosaccharide) was obtained from the labeling utilizing these reagents. Among them, PSC was the most reliable reagent in terms of detection sensitivity (approximately 3 fmol, signal-to-noise ratio of 5 (S/N = 5) on the chromatogram). However, the structural information could not be obtained from the fluorescence detection. Thus, the on-line determination of a real sample was carried out by UPLC-ESI-TOF-MS. The detection limit of the PSC-labeled Disialo-Asn by selected-ion chromatography was 58 fmol (S/N = 5). When the proposed procedure was applied to the determination of oligosaccharides in ovalbumin, 15 species of PSC-labeled oligosaccharides possessing Man, GlcNAc, and Gal units were identified from the UPLC-ESI-TOF-MS. The number of identified oligosaccharides was relatively greater than the method using Fmoc-Cl. Based on the ovalbumin results, the proposed labeling with PSC followed by UPLC-ESI-TOF-MS detection seems to be useful for the on-line asparaginyl-oligosaccharide analysis.

Fully automated two-dimensional high-performance liquid chromatography with electrospray ionization time-of-flight mass spectrometry for the determination of oligosaccharides in glycopeptides after enzymic fluorescence labeling

Two-dimensional high-performance liquid chromatography using an electrospray ionization time-of-flight mass spectrometry (2D-HPLC-ESI-TOF-MS) system was established for the on-line determination of asparagine-linked oligosaccharides in glycopeptides. The analysis of the oligosaccharides started with the enzymic transglycosylation reaction utilizing Endo-beta-N-acetylglucosaminidase (Endo-M). The oligosaccharides were transferred to a fluorescent acceptor (NDA-Asn-GlcNAc) with Endo-M to produce the fluorescent oligosaccharides. The resulting fluorescent oligosaccharides were specifically isolated from the non-fluorescent oligosaccharides with fluorescence detection after separation by the 1st dimension Amide-80 column. The fraction of fluorescent oligosaccharides was effectively trapped in the anion exchange column. The trapped oligosaccharides were then separated by the 2nd dimension ODS column and sensitively determined by ESI-TOF-MS. Disialo-Asn (a model oligosaccharide) and several oligosaccharides liberated from ovalbumin could be efficiently separated by the 2D-HPLC and identified from the ESI-TOF-MS. Based on these results, the proposed 2D-HPLC-ESI-TOF-MS system may be useful for on-line oligosaccharide analyses. Although the analytical run time is still long, a high-throughput determination will be performed by optimization of the 2D-HPLC conditions.

Chemical composition and antioxidant activity of an acidic polysaccharide extracted from Cucurbita moschata Duchesne ex Poiret

A simple and sensitive high-performance capillary electrophoresis (HPCE) method was designed for quantitative analysis of the component monosaccharides of an acidic polysaccharide extracted from pumpkin. In this method, the polysaccharide was hydrolyzed into component monosaccharides with 2.0 M trifluoroacetic acid at 100 degrees C for 6 h and then labeled with 1-phenyl-3-methyl-5-pyrazolone, and subsequently the labeled monosaccharide derivatives were separated by HPCE. As a result, glucose (21.7%) and glucuronic acid (18.9%) were identified to be the main component monosaccharides, followed by galactose (11.5%), arabinose (9.8%), xylose (4.4%), and rhamnose (2.8%). Furthermore, the pumpkin polysaccharide was also demonstrated to effectively inhibit the H2O2-caused decrease of cell viability, lactate dehydrogenase leakage, and malondialdehyde formation, and also reduced the H2O2-caused decline of superoxide dismutase activity and glutathione depletion in cultured mouse peritoneal macrophages, indicating that pumpkin polysaccharide possessed significant cytoprotective effect and antioxidative activity.

Recent developments in sample preparation for chromatographic analysis of carbohydrates

Carbohydrates are a very important group of compounds due to their roles as structural materials, sources of energy, biological functions and environmental analytes; they are characterized by their structural diversity and the high number of isomers they present. While many advances have been made in carbohydrate analysis, the sample preparation remains difficult. This review aims to summarize the most important treatments which have been recently developed to be applied prior to the analysis of carbohydrates by chromatographic techniques. Due to the multiplicity of structures and matrices, many different techniques are required for clean-up, fractionation and derivatization. A number of new techniques which could be potentially adequate for carbohydrate characterization have also been revised.

Characterization of sulfated oligosaccharides in mucopolysaccharidosis type IIIA by electrospray ionization mass spectrometry

Heparan sulfate is a linear glycosaminoglycan with considerable structural diversity that binds a myriad of growth factors and proteins that play pivotal roles in a variety of biological processes. We have investigated the structural complexity of partially degraded fragments of heparan sulfate in mucopolysaccharidosis type IIIA in which there is a defect in heparan sulfate catabolism. Mono- to hexadecasaccharides were isolated from the urine of a mucopolysaccharidosis IIIA patient and shown to have non-reducing end glucosamine N-sulfate residues, reflecting the catabolic deficiency in heparan N-sulfatase (sulfamidase) activity. The use of nitrous acid digestion (pH 1.5) combined with separation by reverse-phase high-performance liquid chromatography and analysis by electrospray ionization-mass spectrometry identified multiple forms of these oligosaccharides with some N-acetylated glucosamine residues and one to three sulfates per disaccharide. Furthermore, we demonstrated that each oligosaccharide existed in multiple sulfated forms. Many structural isomers were present, suggesting a complex mixture of oligosaccharides present in the urine as a consequence of a defect in heparan sulfate degradation.

Variation of major neutral oligosaccharides levels in human colostrum

OBJECTIVES

Human colostrum is known to be important for the protection of infants against infection by pathogenic microorganisms. This protection is thought to be due, partially, to various neutral and acidic oligosaccharides that are present in colostrum and milk. However, the concentrations of each of the oligosaccharide of human colostrum have not yet been determined. The aim of this present study was to determine the concentration of each of the major neutral oligosaccharide for three consecutive days from the start of lactation.

METHOD

We analyzed the level of each neutral oligosaccharide in human colostrum, for three consecutive days from the start of lactation, obtained from 12 healthy Japanese women (ranging in age from 21 to 35 years; primipara 6 and multipara 6). The ABO blood groups of the donors were determined: A, three; B, three; O, five; AB, one. The determined human milk oligosaccharides were 2'-fucosyllactose (2'-FL), 3-fucosyllactose (3-FL), lactodifucotetraose (LDFT), lacto-N-tetraose (LNT), lacto-N-neotetraose (LNnT), three lacto-N-fucopentaose (LNFP I, II and III) and two lacto-N-difucohexaose (LNFDH I and II) using high-performance liquid chromatography (HPLC) with two derivatization techniques.

RESULTS

The concentrations of 2'-FL and LDFT in colostrum on day 1 were significantly higher than those on days 2 and 3 (P<0.05). An increase in LNT was observed on day 3 compared with day 1 (P<0.05).

CONCLUSION

These changes in concentrations of 2'-FL, LDFT and LNT may reflect the requirements for prebiotics and anti-infection agents by human infants during early lactation.

Application of a sensitive fluorometric HPLC assay to determine the sialic acid content of infant formulas

The developing human brain requires high amounts of sialic acids. While human milk is very rich in sialic acids, cow's milk based infant formulas provide lower amounts of sialic acids, and sialic acids are absent in soy milk based formulas. This has prompted interest in the supplementation of formulas with sialic acids, either free or bound to glycoconjugates. In order for fortification of infant formulas with sialic acids to be appropriate for the developmental needs of the infant, an accurate quantitation of sialic acid content of infant formulas through a reliable and easy-to-use method is, therefore, of great interest to industry. In the present method, we describe the application of one of the most widely used analytical techniques to the quantitation of sialic acids in infant formulas. Briefly, sialic acids are hydrolyzed from glycoconjugates, derivatized using 1,2-diamino-4,5-methylenedioxybenzene dihydrochloride (DMB), and separated using reversed-phase high-performance liquid chromatography. The method fulfilled the established criteria for validation, with an interassay standard deviation of less than 5%, accuracy greater than 97%, and surrogate recovery between 98 and 104%. An investigation of the ruggedness of the method identified two key criteria: both standards and samples must be subjected to the same temperature and pH conditions for an accurate quantitation; and prolonged storage (more than 2 days) of the DMB reagent and derivatives must be avoided. In conclusion, this method is specific, straightforward, and accurate and can be easily performed in a quality-assurance laboratory to track the level of sialic acid in formulas that contain both inherent and fortified amounts of sialic acids. Figure Infant formula and HPLC vials used for the sialic acid quantitation.

Resolution of oligosaccharides in glycopeptides using immobilized Endo-M and ultra-performance liquid chromatography with electrospray ionization time-of-flight mass spectrometry

The resolution of asparagine-linked oligosaccharides in glycopeptides was carried out by combination of the transglycosylation reaction and ultra-performance liquid chromatography with electrospray ionization time-of-flight mass spectrometry (UPLC-ESI-TOF-MS). The resolution of the oligosaccharides is based on the enzymic transglycosylation reaction with Endo-beta-N-acetylglucosaminidase (Endo-M) isolated from Mucor hiemalis. The oligosaccharides were transferred to a fluorescent acceptor (NDA-Asn-GlcNAc) with Endo-M to produce the fluorescent oligosaccharides. In the present research, the enzyme was also immobilized in the well of a microassay plate by the sol-gel technique. The transglycosylation reaction was easily managed due to the immobilization. Furthermore, multiple use was possible by the encapsulated Endo-M. The resulting fluorescent oligosaccharides were separated by UPLC and efficiently detected by ESI-TOF-MS. Several oligosaccharides in ovalbumin were successfully identified by the proposed procedure.

Chiral resolution of monosaccharides as 1-phenyl-3-methyl-5-pyrazolone derivatives by ligand-exchange CE using borate anion as a central ion of the chiral selector

Six reducing monosaccharides (mannose, galactose, fucose, glucose, xylose, and arabinose) were derivatized with 1-phenyl-3-methyl-5-pyrazolone (PMP) and chiral resolution of these racemic PMP-monosaccharides was studied by ligand-exchange CE using borate anion as a central ion of the chiral selector and (S)-3-amino-1,2-propanediol (SAP) as a chiral selector ligand. PMP-mannose, PMP-galactose and PMP-fucose were successfully enantioseparated. Lowering the capillary temperature increased the resolution of PMP-mannose system, but decreased that of PMP-galactose and PMP-fucose systems. Whereas the maximum resolution was obtained at pH 8.9 in the PMP-mannose system, resolution increased gradually with pH in the PMP-galactose and PMP-fucose systems. Expecting the formation of the ternary borate complexes with SAP and PMP-monosaccharide in the CE experiments, the optimized structures of the borate diastereomers were obtained by semiempirical molecular orbital calculations to discuss the structural difference of the diastereomers in connection with the enantioseparation behaviors.

Acrosome reaction is subfamily specific in sea star fertilization

In the fertilization process of sea stars, sperm is activated to go through the acrosome reaction before cell fusion. We focused on induction of the acrosome reaction as a key process in fertilization. Six species of sea stars were used in this study: Asterias amurensis, Asterias rubens, Asterias forbesi, Aphelasterias japonica, Distolasterias nipon, and Asterina pectinifera. Acrosome reaction assays indicate that the acrosome reaction can be induced across species within Asteriinae subfamily. However, cross-fertilization assays indicate that sea stars have species specificity in fertilization. Therefore, steps after the acrosome reaction are responsible for the species specificity. To explain acrosome reaction subfamily specificity at the molecular level, the sugar components of egg jelly were examined and analyzed by principal component analysis. A. amurensis and A. forbesi belong to the same induction group of the acrosome reaction. D. nipon and An. pectinifera are in a unique group. Enzyme-linked immunosorbent assays indicate that Asteriinae subfamily share a common glycan structure, the Fragment 1 of Acrosome Reaction-Inducing Substance from A. amurensis. Fragment 1 plays an important role in the subfamily specificity of acrosome reaction induction. In addition, A. amurensis sperm activating peptide was recognized by sperm from the same superorder. These results demonstrate that the specificity of acrosome reaction induction is present at the subfamily level in sea stars.

Recovery of free oligosaccharides from derivatives labeled by reductive amination

This study examined chemical regeneration of free oligosaccharides from their fluorescent derivatives prepared by reductive amination with various aromatic amines. Maltose derivatives of ethyl 4-aminobenzoate (p-ABEE), 2-aminobenzonitrile (o-ABN), 4-aminobenzonitrile (p-ABN), 7-amino-4-methylcoumarin (AMC), 2-aminobenzoic acid (o-ABA), 2-aminobenzamide (o-ABAD), 2-aminopyridine (AP), and 8-aminonaphthalene-1,3,6-trisulfonate (ANTS) were incubated at 30 degrees C with an aqueous solution of hydrogen peroxide/acetic acid. Recoveries of maltose from p-ABEE, p-ABN, and AMC derivatives were fairly good and gave approximately 90% of maltose. Recoveries of maltose from its o-substituted aniline (o-ABA, o-ABAD, and o-ABN) derivatives were 5-40%, but maltose was unrecoverable from AP and ANTS derivatives. Nevertheless, prior treatment of an AP derivative with cyanogen bromide enabled the regeneration of maltose in high yields. As an application, p-ABEE-labeled N-glycans from some glycoproteins separated on an amide column were identified by converting peak components to their AP derivatives via free saccharides and following mapping by reversed-phase chromatography.

Analysis of glycoprotein-derived oligosaccharides in glycoproteins detected on two-dimensional gel by capillary electrophoresis using on-line concentration method

Capillary electrophoresis (CE) is an effective tool to analyze carbohydrate mixture derived from glycoproteins with high resolution. However, CE has a disadvantage that a few nanoliters of a sample solution are injected to a narrow capillary. Therefore, we have to prepare a sample solution of high concentration for CE analysis. In the present study, we applied head column field-amplified sample stacking method to the analysis of N-linked oligosaccharides derived from glycoprotein separated by two-dimensional gel electrophoresis. Model studies demonstrated that we achieved 60-360 times concentration effect on the analysis of carbohydrate chains labeled with 3-aminobenzoic acid (3-AA). The method was applied to the analysis of N-linked oligosaccharides from glycoproteins separated and detected on PAGE gel. Heterogeneity of alpha1-acid glycoprotein (AGP), i.e. glycoforms, was examined by 2D-PAGE and N-linked oligosaccharides were released by in-gel digestion with PNGase F. The released oligosaccharides were derivatized with 3-AA and analyzed by CE. The results showed that glycoforms having lower pI values contained a larger amount of tetra- and tri-antennary oligosaccharides. In contrast, glycoforms having higher pI values contained bi-antennary oligosaccharides abundantly. The result clearly indicated that the spot of a glycoprotein glycoform detected by Coomassie brilliant blue staining on 2D-PAGE gel is sufficient for quantitative profiling of oligosaccharides.

Monitoring enzyme-catalyzed production of glucosamine-6P by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry: a new enzymatic assay for glucosamine-6P synthase

A matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) method for quantification of D-glucosamine-6P (GlcN-6P) that allows the kinetic study of glucosamine-6P synthase (Glms) is presented. The present report describes the optimization of the different steps of a new enzymatic assay for Glms based on in situ N-acetylation of GlcN-6P and MALDI-TOFMS analysis using N-(13C2)acetylglucosamine-6P as internal standard. Since no isotopically substituted GlcN-6P was available, the N-(13C2)acetyl derivative, easily obtained from (13C4)-acetic anhydride, was used as internal standard. Validation of the assay was achieved by measuring the fructose-6P Michaelis constant, in full agreement with reported values, and by studying the inhibition properties of arabinose-5P oxime.

Improved quality control of [18F]FDG by HPLC with UV detection

A conventional high-performance liquid chromatographic (HPLC) method for the analysis of 2-fluoro-2-deoxy-d-glucose (FDG) and 2-deoxy-2-chloro-d-glucose (ClDG) in [18F]FDG preparations is described. This method was based on a postcolumn derivatization with 2-cyanoacetamide (2-CA) and UV detection. FDG and ClDG were separated on a normal-phase column using acetonitrile/water as the mobile phase. The eluate was mixed with 2-CA in sodium borate buffer solution at the outlet of a PTFE coil (10 m x 0.5 mm id) from the column, and the reaction was carried out at 100 degrees C during the passage through the coil. The UV absorbance of the resultant product was monitored at 276 nm. Under optimum conditions, the detection limits [signal-to-noise (S/N) ratio=3] for FDG and ClDG were 0.31 and 0.17 microg/ml for a 20-microl injection volume, respectively, and the linearity ranges were 0.5-100 microg/ml for both compounds. The intra- and interday reproducibilities were better than 2.2% [relative standard deviation (R.S.D.)]. This HPLC separation procedure is also useful for determining the radiochemical purity of [18F]FDG preparations since it allows the analysis of 2-[18F]fluoro-1,3,4,6-tetra-O-acetyl-d-glucose ([18F]TAG), partially hydrolyzed [18F]TAG and [18F]F-. This method can be used at many positron emission tomography (PET) facilities since it does not require an expensive, sophisticated electrochemical detector.

Profiling oligosaccharidurias by electrospray tandem mass spectrometry: Quantifying reducing oligosaccharides

A method to semiquantify urinary oligosaccharides from patients suffering from oligosaccharidurias is presented. 1-Phenyl-3-methyl-5-pyrazolone has been used to derivatize urinary oligosaccharides prior to analysis by electrospray ionization-tandem mass spectrometry (ESI-MS/MS). Disease-specific oligosaccharides were identified for several oligosaccharidurias, including GM1 gangliosidosis, GM2 gangliosidosis, sialic acid storage disease, sialidase/neuraminidase deficiency, galactosialidosis, I-cell disease, fucosidosis, Pompe and Gaucher diseases, and alpha-mannosidosis. The oligosaccharides were referenced against the internal standard, methyl lactose, to produce ratios for comparison with control samples. Elevations in specific urinary oligosaccharides were indicative of lysosomal disease and the defective catabolic enzyme. This method has been adapted to enable assay of large sample numbers and could readily be extended to other oligosaccharidurias and to monitor oligosaccharide levels in patients receiving treatment. It also has immediate potential for incorporation into a newborn screening program.

Analysis of the monosaccharide components in Angelica polysaccharides by high performance liquid chromatography

An analytical method of on-line high performance liquid chromatography (HLPC) was developed to simultaneously separate and identify the monosaccharide composition of three Angelica polysaccharide fractions (APF), named APF1, APF2 and APF3. In this method, APF were hydrolyzed into component monosaccharides and subsequently labeled with 1-phenyl-3-methyl-5-pyrazolone (PMP), and then the labeled monosaccharide derivatives were separated by a reverse-phase C18 column and monitored by UV absorbance at 250 nm. The results showed that nine monosaccharide derivatives have been well separated by HPLC under optimized conditions and the composition analysis of monosaccharides from APF samples could be achieved using acid hydrolysis and a set of monosaccharide standards. With this method, the within-day and day to day precisions of the composition determinations were 3.41-4.87% and 3.12-4.93% (RSD), respectively. The method was successfully applied to the determination of the component monosaccharides of Angelica polysaccharides.

Resolution of N-linked oligosaccharides in glycoproteins based upon transglycosylation reaction by CE-TOF-MS

The resolution of asparagine-type oligosaccharides in glycoproteins was carried out by combination of the transglycosylation reaction and CE-TOF-MS. The oligosaccharides enzymatically transferred to a fluorescent acceptor (NDA-Asn-GlcNAc) with Endo-M. The resulting fluorescent-oligosaccharides were separated by CE and detected by TOF-MS. Disialo-Asn was successfully identified by the proposed procedure. Application to oligosaccharides in ovalbumin was also described in this communication.

High performance liquid chromatographic determination of N-butyryl glucosamine in rat plasma

PURPOSE

A high performance liquid chromatography (HPLC) method for determination in plasma of N-butyryl glucosamine (GLBU), a highly water-soluble compound with no chromophore was developed.

METHOD

To 100 muL of plasma containing GLBU was added fucose as internal standard. GLBU and fucose were derivatized using 1-phenyl-3-methyl-5-pyrazolone in the presence of sodium hydroxide at 70 degrees C for 30 min. The solution was neutralized with hydrochloric acid and the excess derivatizing reagent was extracted with chloroform. The aqueous layer was injected into an isocratic HPLC system consisting of an autoinjector, a single pump and a UV detector set at 245 nm. Two different 25 cm reversed phase columns were used, a 4 and a 10 microm C(18) columns. The mobile phase was a mixture of phosphate buffer (pH 7) and acetonitrile (80:20), which was run through a pump at a flow rate of 1.0 mL/min at ambient temperature.

RESULTS

Derivatized fucose and GLBU appeared 24 and 28 min, and at 34 and 37 min using 4 and 10 microm columns, respectively. The assay was linear over the range of 0.2-200 microg/mL with a limit of quantification of 0.2 and 1 microg/mL for the 4 and 10 microm columns, respectively. The method was applied to the determination of GLBU in rat plasma after oral administration of 233 mg/kg of GLBU.

CONCLUSION

The present assay is precise, and accurate with sufficient sensitivity for pharmacokinetic studies following therapeutically relevant doses.

Identification of a novel conjugate in human urine: bile acid acyl galactosides

We report a novel conjugate, bile acid acyl galactosides, which exist in the urine of healthy volunteers. To identify the two unknown peaks obtained in urine specimens from healthy subjects, the specimens were subjected to solid phase extraction and then to liquid chromatographic separation. The eluate corresponding to the unknown peaks on the chromatogram was collected. Following alkaline hydrolysis and liquid chromatography (LC)/electrospray ionization (ESI)-mass spectrometric (MS) analysis, cholic acid (CA) and deoxycholic acid (DCA) were identified as liberated bile acids. When a portion of the alkaline hydrolyzate was subjected to a derivatization reaction with 1-phenyl-3-methyl-5-pyrazolone, a derivative of galactose was detected by LC/ESI-MS. Finally, the liquid chromatographic and mass spectrometric properties of these unknown compounds in urine specimens were compared to those of authentic specimens and the structures were confirmed as CA 24-galactoside and DCA 24-galactoside. These results strongly imply that bile acid 24-galactosides, a novel conjugate, were synthesized in the human body.

Complete structure determination ofN-acetyl-D-galactosamine-binding mistletoe lectin-3 fromViscum album L. album

The primary structure of the B chain of the N-acetyl-D-galactosamine-recognizing mistletoe lectin-3 (ML-3B) has been deduced from proteolytic digest peptides of the purified glycoprotein, their HPLC-separation and Edman degradation and confirmation of the peptide sequences by MALDI-MS. ML-3B consists of 262 amino acid residues including 10 cysteine moieties. The structure and linkage of the carbohydrate side chains, connected to two N-glycosylation sites at positions Asn(95) and Asn(135) of the lectin, were determined by a combination of glycosidase treatment and MALDI-MS of corresponding glycopeptide fragments. The sequence alignment reveals a high homology with other B chains of type-II RIPs, although there are remarkable differences in the D-galactose-specific mistletoe lectin-1B chain. The recently published primary structure of the mistletoe lectin-3A chain1 and the now available primary sequence of the 3B chain allowed the construction of a preliminary homology model of ML-3. The model demonstrates, unequivocally, that ML-3 is a member of the type-II RIP family with rigid conservation of the enzymatic active site of the A chain and an identical overall protein fold. Specific amino acid residue exchanges and the different glycosylation pattern in comparison with ML-1 are discussed and related to the properties of the two glycoproteins. The knowledge of the complete primary structure of mistletoe lectin-3 is a major contribution towards more insight into the mechanism of the biological activity of commercial mistletoe preparations.

Rhodamine B amine as a highly sensitive fluorescence derivatization reagent for saccharides in reversed-phase liquid chromatography

6-Rhodamine B amine functions as a highly sensitive fluorescence derivatization reagent for mono- and oligosaccharides; it reacts with the reducing end of saccharides under acidic conditions. The fluorescent derivatives of five monosaccharides can be separated within 25 min by reversed-phase liquid chromatography with isocratic elution. The detection limits (S/N = 3) for mono-, di-, and oligosaccharides are 7-51, 13, and 9-35 fmol/20 microl injection, which correspond to analyte concentrations of 35-255, 65, 45-175 nM, respectively. We have applied this derivatization method successfully to the analysis of the components of oligosaccharides in glycoproteins (ribonuclease B and fetuin) following their acidic or enzymatic hydrolysis. The results from these analyses are in good agreements with the reported values established previously.

Mass spectrometry of oligosaccharides

Glycosylation is a common post-translational modification to cell surface and extracellular matrix (ECM) proteins as well as to lipids. As a result, cells carry a dense coat of carbohydrates on their surfaces that mediates a wide variety of cell-cell and cell-matrix interactions that are crucial to development and function. Because of the historical difficulties with the analysis of complex carbohydrate structures, a detailed understanding of their roles in biology has been slow to develop. Just as mass spectrometry has proven to be the core technology behind proteomics, it stands to play a similar role in the study of functional implications of carbohydrate expression, known as glycomics. This review summarizes the state of knowledge for the mass spectrometric analysis of oligosaccharides with regard to neutral, sialylated, and sulfated compound classes. Mass spectrometric techniques for the ionization and fragmentation of oligosaccharides are discussed so as to give the reader the background to make informed decisions to solve structure-activity relations in glycomics.

Surface glycans of Candida albicans and other pathogenic fungi: physiological roles, clinical uses, and experimental challenges

Although fungi have always been with us as commensals and pathogens, fungal infections have been increasing in frequency over the past few decades. There is a growing body of literature describing the involvement of carbohydrate groups in various aspects of fungal disease. Carbohydrates comprising the cell wall or capsule, or as a component of glycoproteins, are the fungal cell surface entities most likely to be exposed to the surrounding environment. Thus, the fungus-host interaction is likely to involve carbohydrates before DNA, RNA, or even protein. The interaction between fungal and host cells is also complex, and early studies using whole cells or crude cell fractions often produced seemingly conflicting results. What was needed, and what has been developing, is the ability to identify specific glycan structures and determine how they interact with immune system components. Carbohydrate analysis is complicated by the complexity of glycan structures and by the challenges of separating and detecting carbohydrates experimentally. Advances in carbohydrate chemistry have enabled us to move from the foundation of composition analysis to more rapid characterization of specific structures. This, in turn, will lead to a greater understanding of how fungi coexist with their hosts as commensals or exist in conflict as pathogens.

Structure of oligosaccharide side chains of an intestinal immune system modulating arabinogalactan isolated from rhizomes of Atractylodes lancea DC

An intestinal immune system modulating arabino-3,6-galactan (ALR-5IIa-1-1) has been found in rhizomes of Atractylodes lancea DC. [Planta Medica 1998, 64, 714-719; Carbohydr. Polyms. 2001, 46, 147-156], however other arabino-3,6-galactans from Larix and Acacia failed to express the modulating activity. Degradation of the galactosyl side chains in Araf-side chain-trimmed ALR-5IIa-1-1 (AF-ALR-5IIa-1-1) with an endo-beta-D-(1-->6)-galactanase remarkably decreased the activity of AF-ALR-5IIa-1-1. Structural analysis indicated that the major endo-beta-D-(1-->6)-galactanase-digestable side chains in ALR-5IIa-1-1 are composed of beta-D-(1-->6)-galactopyranosyl oligosaccharides having d.p. 1-8. Because degradation of the beta-D-(1-->3)-galactan backbone in AF-ALR-5IIa-1-1 also significantly reduced its activity, some of these galactosyl side chains attached to beta-D-(1-->3)-galactan backbone are suggested to be responsible for expression of the activity of ALR-5IIa-1-1.

Matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry. A comparison of fragmentation patterns of linear dextran obtained by in-source decay, post-source decay and collision-induced dissociation and the stability of linear and cyclic glucans studied by in-source decay

In the first part of this study fragmentation patterns from a range of dextran oligomers (containing 4-20 anhydroglucose units) were compared in three different methods of analysis coupled with matrix-assisted laser desorption/ionisation (MALDI) mass spectrometry. Collision-induced-dissociation (CID), prompt in-source decay (ISD) and post-source decay (PSD) all caused cleavage of the glycosidic bonds. Both CID and to a lesser extent ISD caused further cleavage of pyranose rings of the individual sugar residues. There was very little cleavage of pyranose rings detected in the PSD spectrum. Derivatisation of the reducing end-groups of the oligodextrans with 1-phenyl-3-methyl-5-pyrazolone (PMP) restricted cleavage in the MALDI mass spectrometer to the non-reducing end, and further it enabled the saccharides to be separated by HPLC so that a single chain length could be examined as a standard. Maltoheptaose was also used as a standard. In the second part of the study prompt ISD-MALDI mass spectrometry was used to compare the fragmentation of three oligoglucans, dextran, maltodextrin and gamma cyclodextrin, that have different linkages and different secondary structure. The results showed that the degree of fragmentation correlated with the degree of freedom in the saccharide chains in solution determined by NMR. Dextran the most random conformation was fragmented most whereas there was little evidence of any fragments, not even glycosidic bond breakage from cyclodextrin, even when the laser power was increased considerably. The fragmentation pattern of maltodextrin was intermediate. The patterns of fragmentation produced by MALDI mass spectrometry, particularly where standards are available to calibrate the spectrum and the energy of the laser is controlled, can be used to predict the type of linkage present.

Analysis of reducing carbohydrates by reductive tryptamine derivatization prior to micellar electrokinetic capillary chromatography

A micellar electrokinetic capillary chromatography method for determination of low molecular weight carbohydrates (dp 1-2) with an unbound carbonyl group as in aldoses or other reducing carbohydrates has been developed. Reductive amination of aldoses on the carbonyl group using tryptamine introduced a chromophor system to the carbohydrates enabling their sensitive UV detection at 220 nm and identification based on the indole group using diode array detection. Twelve carbohydrates including pentoses (d-ribose, l-arabinose, and d-xylose), hexoses (d-glucose, d-mannose, and d-galactose), deoxy sugars (l-rhamnose and l-fucose), uronic acids (d-glucuronic acid and d-galacturonic acid), and disaccharides (cellobiose and melibiose) are included in the study, using d-thyminose (2-deoxy-d-ribose) as the internal standard. Detection of all 12 carbohydrates is performed within 30 min. Linearity with correlation coefficients from 0.9864 to 0.9992 was found in the concentration range of 25-2500 micromol/L for all carbohydrates; the relative standard deviation on the migration times was between 0.27 and 0.80 min, and limits of quantification and limits of determination were in the picomole range.

GDP-mannose 3',5'-epimerase forms GDP-L-gulose, a putative intermediate for the de novo biosynthesis of vitamin C in plants

Despite its importance for agriculture, bioindustry, and nutrition, the fundamental process of L-ascorbic acid (vitamin C) biosynthesis in plants is not completely elucidated, and little is known about its regulation. The recently identified GDP-Man 3',5'-epimerase catalyzes a reversible epimerization of GDP-D-mannose that precedes the committed step in the biosynthesis of vitamin C, resulting in the hydrolysis of the highly energetic glycosyl-pyrophosphoryl linkage. Here, we characterize the native and recombinant GDP-Man 3',5'-epimerase of Arabidopsis thaliana. GDP and GDP-D-glucose are potent competitive inhibitors of the enzyme, whereas GDP-L-fucose gives a complex type of inhibition. The epimerase contains a modified version of the NAD binding motif and is inhibited by NAD(P)H and stimulated by NAD(P)+. A feedback inhibition of vitamin C biosynthesis is observed apparently at the level of GDP-Man 3',5'-epimerase. The epimerase catalyzes at least two distinct epimerization reactions and releases, besides the well known GDP-l-galactose, a novel intermediate: GDP-L-gulose. The yield of the epimerization varies and seems to depend on the molecular form of the enzyme. Both recombinant and native enzymes co-purified with a Hsp70 heat-shock protein (Escherichia coli DnaK and A. thaliana Hsc70.3, respectively). We speculate, therefore, that the Hsp70 molecular chaperones might be involved in folding and/or regulation of the epimerase. In summary, the plant epimerase undergoes a complex regulation and could control the carbon flux into the vitamin C pathway in response to the redox state of the cell, stress conditions, and GDP-sugar demand for the cell wall/glycoprotein biosynthesis. Exogenous L-gulose and L-gulono-1,4-lactone serve as direct precursors of l-ascorbic acid in plant cells. We propose an L-gulose pathway for the de novo biosynthesis of vitamin C in plants.

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.

Labelling saccharides with phenylhydrazine for electrospray and matrix-assisted laser desorption-ionization mass spectrometry

A well-known reaction of carbonyl compounds with phenylhydrazine has been applied to saccharides, providing increased sensitivity for mass spectrometric (MS) and ultraviolet (UV) detection during high-performance liquid chromatographic (HPLC) separations. After a simple derivatization procedure for 1 h at 70 degrees C and purification of the reaction mixture from excess reagent by extraction, the sugar derivatives were characterized by direct injection or on-line HPLC/electrospray ionization (ESI) and by matrix-assisted laser desorption/ionization (MALDI) MS. Because no salts are used or produced upon reaction, this procedure is very simple and suitable for the tagging of saccharides. The reaction allows for on-target derivatization and products are very stable. The derivatization procedure has been applied to commercially-obtained small saccharides and standard N-linked oligosaccharides. Lastly, hen ovalbumin N-glycans were detached enzymatically and characterized by MALDI-MS as their phenylhydrazone derivatives.

Determination of 1-phenyl-3-methyl-5-pyrazolone-labeled carbohydrates by liquid chromatography and micellar electrokinetic chromatography

In this paper, the method for the derivatization of carbohydrates with 1-phenyl-3-methyl-5-pyrazolone (PMP) was simplified. One-third of the derivatization time was saved. Five monosaccharide derivatives have been well separated by MEKC and HPLC under optimized conditions. Good reproducibility could be obtained with relative standard deviation (RSD) values of the migration times within 5.0 and 2.3%, respectively. Furthermore, the developed methods have been successfully applied to the analysis of carbohydrates in Aloe powder and food. These methods are quite useful for routine analysis of monosaccharides and oligosaccharides in real samples.

Improved capillary electrophoretic separation and mass spectrometric detection of oligosaccharides

We have developed a CE method for the separation of structural isomers of oligosaccharides labeled with N-quaternized benzylamine. Oligosaccharides with reducing ends were derivatized with benzylamine by reductive amination followed by quaternization to yield a fixed cation label. The benzylamine-derivatized oligosaccharides were analyzed by CE-UV in ammonium acetate buffer and off-line matrix-assisted laser desorption ionization (MALDI) MS. The method was applied to a 1 nmol sample of a model oligosaccharide (LNDFH 1). From this sample a 38 fmol diluted standard was detected. The quaternization of benzylamine-labeled products significantly improved CE separation of neutral oligosaccharides along with several structural isomers. Two hexasaccharide isomers (LNDFH I and LNDFH II) were baseline resolved using an ammonium acetate buffer. This method was also applied successfully to the profiling of oligosaccharides released from the glycoprotein RNase B. The release of 6 pmol of glycans followed by workup showed the detection of all components, with one component corresponding to 100 fmol. Micropreparative collection of CE enabled successful off-line CE-MALDI-MS without additional sample clean up. This report provides a simple and rapid method to separate and analyze oligosaccharides.

2-amino-3-phenylpyrazine, a sensitive fluorescence prelabeling reagent for the chromatographic or electrophoretic determination of saccharides

2-Amino-3-phenylpyrazine is found to be a sensitive fluorescence labeling reagent for saccharides with a reducing end. The labeled monosaccharides show strong fluorescence under various pH conditions, and could be analyzed by both HPLC and HPCE techniques. Laser induced fluorescence detection is also applicable. Following derivatization with 2-amino-3-phenylpyrazine, six monosaccharides are separated by an HPCE system within 23 min in the calibration range of 5 or 10 fmol to 5 pmol (injection amount). The within-day and day-to-day precisions of the monosaccharide determinations are 3.83-4.86% (RSD) and 3.37-4.56% (RSD), respectively. This method was successfully applied to the determination of component monosaccharides in a glycoprotein, bovine serum fetuin.