The influence of buffer composition on separation efficiency and resolution in capillary electrophoresis of 8-aminonaphthalene-1,3,6-trisulfonic acid labeled monosaccharides and complex carbohydrates

LC-MS/MS-based non-isotopically paired labeling (NIPL) strategy for the qualification and quantification of monosaccharides

Investigation into monosaccharides is critical for studies of oligosaccharides structure and function in biological processes. However, monosaccharides quantification is still challenge due to their isomeric structure and high hydrophilic properties. Besides, it was difficult to obtain isotopic internal standards (IS) of each monosaccharide in complex matrixes. Herein, we developed a novel strategy for the qualification and quantification of monosaccharides in urine using two structure analogs 1-(4-methylphenyl)-3-methyl-5-pyrazolone (MPMP) and1-phenyl-3-methyl-5-pyrazolone (PMP) as non-isotopically paired labeling (NIPL) reagents by liquid chromatograph-tandem mass spectrometry (LC-MS/MS). The derivatized monosaccharides by NIPL method not only had sufficient retention time differences on reversed-phase column, but also exhibited predominant product ion pairs (m/z 189 & m/z 175) in the multiple reaction monitoring (MRM) mode. In this method, PMP labeled standards were adopted as one-to-one internal standards (ISs). 12 urinary monosaccharides were successfully determined and the linear ranges expanded five orders of magnitude with limit of quantification (LOQ) varied from 0.09 ng mL^-1 to 0.36 ng mL^-1 as well as the accuracy higher than 98.15% and the relative standard derivation (RSD) lower than 7.92%. With assistance of multivariate analysis, the targeted monosaccharide biomarkers were firstly obtained for the diagnosis of bladder cancer. By the inexpensive NIPL reagents-MPMP/PMP, the developed strategy possessed the specific advantages of low cost, simple operation, high sensitivity and high accuracy for the qualification and quantitation of monosaccharides. As expected, this method will provide an alternative application potential for targeted metabolomics analysis.

Current landscape of protein glycosylation analysis and recent progress toward a novel paradigm of glycoscience research

This review covers the basics and some applications of methodologies for the analysis of glycoprotein glycans. Analytical techniques used for glycoprotein glycans, including liquid chromatography (LC), capillary electrophoresis (CE), mass spectrometry (MS), and high-throughput analytical methods based on microfluidics, were described to supply the essentials about biopharmaceutical and biomarker glycoproteins. We will also describe the MS analysis of glycoproteins and glycopeptides as well as the chemical and enzymatic releasing methods of glycans from glycoproteins and the chemical reactions used for the derivatization of glycans. We hope the techniques have accommodated most of the requests from glycoproteomics researchers.

Identification of Low Abundant Isomeric N-Glycan Structures in Biological Therapeutics by LC/MS

An effective LC-MS based method for online characterization of low abundant structural isomers of N-linked glycans in biological therapeutics was developed. N-linked glycans of a recombinant monoclonal antibody were released by PNGase F and labeled with 2-aminobenzamide (2-AB) fluorescent tag. The labeled glycans were analyzed by online ultraperformance liquid chromatography-hydrophilic interaction liquid chromatography (UPLC-HILIC) coupled with mass spectrometry (MS). The glycan structure was characterized by MS(n) fragmentation in negative ion mode followed by identification of the signature D ions. The assignment included monosaccharide sequence and linkage information. The developed method successfully characterized structural isomers of A1G1F (assigned as terminal sialic acid attached in the 1,6 branch at 2,3 position), and A1G1F' (assigned as terminal sialic acid attached in the 1,3 branch at 2,3 position). Moreover, using the same approach, previously unknown low abundant species were identified unambiguously. One such structural isomer at low level, terminal GlcNAc of G1F+GlcNAc, was identified to be linked at the 1,6 branch. Additionally, another low level structural isomer, previously assigned as Man8 glycan, was found to be Man7+Glc glycan as its 1,3 branch containing three mannoses and one terminal glucose. The identification was further confirmed by a purified α-1,2-endomannosidase enzyme to generate the cleavage of α-1,3 linked terminal disaccharides (Man+glucose). Using this approach, different lots or different CHO produced mAbs was thoroughly examined and found that the newly identified "Man8" (Man7+Glc) was also present in different batches and in some commercially available therapeutic mAbs.

Analysis of glycans derived from glycoconjugates by capillary electrophoresis-mass spectrometry

The high structural variation of glycan derived from glycoconjugates, which substantially increases with the molecular size of a protein, contributes to the complexity of glycosylation patterns commonly associated with glycoconjugates. In the case of glycoproteins, such variation originates from the multiple glycosylation sites of proteins and the number of glycan structures associated with each site (microheterogeneity). The ability to comprehensively characterize highly complex mixture of glycans has been analytically stimulating and challenging. Although the most powerful MS and MS/MS techniques are capable of providing a wealth of structural information, they are still not able to readily identify isomeric glycan structures without high-order MS/MS (MS(n) ). The analysis of isomeric glycan structures has been attained using several separation methods, including high-pH anion-exchange chromatography, hydrophilic interaction chromatography and GC. However, CE and microfluidics CE (MCE) offer high separation efficiency and resolutions, allowing the separation of closely related glycan structures. Therefore, interfacing CE and MCE to MS is a powerful analytical approach, allowing potentially comprehensive and sensitive analysis of complex glycan samples. This review describes and discusses the utility of different CE and MCE approaches in the structural characterization of glycoproteins and the feasibility of interfacing these approaches to MS.

Multiplexed analytical glycomics: rapid and confident IgG N-glycan structural elucidation

N-glycans attached to the C(H)2 domains of the Fc or the antigen binding regions of IgG play an important role in stabilizing and modulating antibody activity. Exhaustive elucidation of 32 IgG N-glycans using a combination of weak anion exchange enrichment and exoglycosidase array digestion with subsequent profiling exceeded 48 h. Pursuing increased throughput and associated structural annotation confidence, we compared the 1.7 μm hydrophilic interaction phase for UPLC with CE-LIF for the rapid and comprehensive characterization of N-glycans released from healthy human serum polyclonal IgG. Combination of the data individually generated using each technique demonstrated that complete structural annotation was possible within a total analysis time of 20 min due to the advantageous orthogonality of the separation mechanisms. The parallel use of both analytical techniques provides a powerful platform for rapid and comprehensive analysis of IgG N-glycosylation present on therapeutic antibodies or on antibodies of biomedical or pathological significance.

Separation of 2-aminobenzamide labeled glycans using hydrophilic interaction chromatography columns packed with 1.7 microm sorbent

Separation by hydrophilic interaction chromatography (HILIC) with fluorescence detection utilizing a sub-2 microm glycan column for the separation of 2-aminobenzamide (2-AB) labeled N-linked glycans is described. The HILIC column packed with a 1.7 microm amide sorbent improves the peak capacity compared to a 3.0 microm HILIC column by a similar degree as observed in reversed-phase ultra-performance liquid chromatography (RP-UPLC). The results indicated that the optimal peak capacity was achieved at flow rate 0.2-0.5 mL/min. HILIC method transfer guidelines were shown to further enhance the resolution of glycans by changing initial gradient conditions, flow rate, column temperature, and different column lengths. Additionally, excellent resolution can be achieved in the separation of 2-AB labeled glycans released from fetuin, RNase B, and human IgG with a rapid analysis time.

Glycomic analysis by capillary electrophoresis-mass spectrometry

The occurrence of multiple glycosylation sites on a protein, together with the number of glycan structures which could potentially be associated with each site (microheterogeneity) often leads to a large number of structural combinations. These structural variations increase with the molecular size of a protein, thus contributing to the complexity of glycosylation patterns. Resolving such fine structural differences has been instrumentally difficult. The degree of glycoprotein microheterogeneity has been analytically challenging in the identification of unique glycan structures that can be crucial to a distinct biological function. Despite the wealth of information provided by the most powerful mass spectrometric (MS) and tandem MS techniques, they are not able to readily identify isomeric structures. Although various separation methods provide alternatives for the analysis of glycan pools containing isomeric structures, capillary electrophoresis (CE) is often the method of choice for resolving closely related glycan structures because of its unmatched separation efficiency. It is thus natural to consider combining CE with the MS-based technologies. This review describes the utility of different CE approaches in the structural characterization of glycoproteins, and discusses the feasibility of their interface to mass spectrometry.

Capillary electrophoresis for the analysis of glycoprotein pharmaceuticals

Carbohydrate chains in glycoprotein pharmaceuticals play important roles for the expression of their biological activities, but the structure and compositions of carbohydrate chains are dependent on the conditions for their production. Therefore, evaluation of the carbohydrate chains is quite important for productive process development, characterization of product for approval application, and routine quality control. The oligosaccharides themselves have complex structure including blanching and various glycosidic linkages, and oligosaccharides in one glycoprotein pharmaceutical generally have high heterogeneity, and characterization of oligosaccharide moiety in glycoprotein has been a challenging target. In these situations, CE has been realized as a powerful tool for oligosaccharide analysis due to its high resolution and automatic operating system. This review focuses on the application of CE to the glycoform analysis of glycoproteins and profiling of the N-linked glycans released from glycoprotein pharmaceuticals. Current applications for structure analysis using CE-MS(n) technique and glycan profiling method for therapeutic antibody are also described.

Miniaturized separation techniques in glycomic investigations

High-sensitivity glycomic analyses are becoming of a great interest in modern biomedical and clinical research, as well as in the development of recombinant protein products. The evolution of separation techniques for glycomic analysis at high sensitivity is highlighted in this review. These methodologies include capillary liquid chromatography, capillary electrophoresis (CE) and capillary electrochromatography (CEC). The potential of such methodologies in glycomic analysis is demonstrated for model glycoproteins as well as total glycomes derived from biological samples.

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.

Capillary electrophoresis/electrospray ion trap mass spectrometry for the analysis of negatively charged derivatized and underivatized glycans

The increasing interest in the development of glycoproteins for therapeutic purposes has created a greater demand for methods to characterize the sugar moieties bound to them. Traditionally, released carbohydrates are derivatized using such methods as permethylation or fluorescent tagging prior to analysis by high performance liquid chromatography (HPLC), capillary electrophoresis (CE), or direct infusion mass spectrometry. However, little research has been performed using CE with on-line mass spectrometry (MS) detection. The CE separation of neutral oligosaccharides requires the covalent attachment of a charged species for electrophoretic migration. Among charged labels which have shown promise in assisting CE and HPLC separation is the fluorophore 8-aminonaphthalene-1,3,6-trisulfonic acid (ANTS). This report describes the qualitative profiling of charged ANTS-derivatized and underivatized complex glycans by CE with on-line electrospray ion trap mass spectrometry. Several neutral standard glycans including a maltooligosaccharide ladder were derivatized with ANTS and subjected to CE/UV and CE/MS using low pH buffers consisting of citric and 6-aminocaproic acid salts. The ANTS-derivatized species were detected as negative ions, and multiple stage MS analysis provided valuable structural information. Fragment ions were easily identified, showing promise for the identification of unknowns. N-Linked glycans released from bovine fetuin were used to demonstrate the applicability of ANTS derivatization followed by CE/MS for the analysis of negatively charged glycans. Analyses were performed on both underivatized and ANTS-derivatized species, and sialylated glycans were separated and detected in both forms. The ability of the ion trap mass spectrometer to perform multiple stage analysis was exploited, with MS5 information obtained on selected glycans. This technique presents a complementary method to existing methodologies for the profiling of glycan mixtures.

Systematic analysis of oxidative degradation of polysaccharides using PAGE and HPLC--MS

Oxidation of polysaccharides yields hydroxyaldehydes and hydroxycarboxylic acids. Aldehydes and carboxylic acids were separately conjugated to 8-aminonaphthalene-1,3,6-trisulfonic acid (ANTS) or tyrosine t-butyl ester (TBT). The ANTS-labeled derivatives were separated by molecular size on PAGE gels and detected by fluorescence. TBT-labeled derivatives were separated by reverse phase chromatography on a C18-HPLC column and analyzed by positive ion electrospray mass spectroscopy (HPLC--MS). This combination of procedures allowed a systematic analysis of carbohydrate oxidation products.

DNA and buffers: the hidden danger of complex formation

The free solution electrophoretic mobility of DNA differs significantly in different buffers, suggesting that DNA-buffer interactions are present in certain buffer systems. Here, capillary and gel electrophoresis data are combined to show that the Tris ions in Tris-acetate-EDTA (TAE) buffers are associated with the DNA helix to approximately the same extent as sodium ions. The borate ions in Tris-borate-EDTA (TBE) buffers interact with DNA to form highly charged DNA-borate complexes, which are stable both in free solution and in polyacrylamide gels. DNA-borate complexes are not observed in agarose gels, because of the competition of the agarose gel fibers for the borate residues. The resulting agarose-borate complexes increase the negative charge of the agarose gel fibers, leading to an increased electroendosmotic flow of the solvent in agarose-TBE gels. The combined results indicate that the buffers in which DNA is studied cannot automatically be assumed to be innocuous.

Analysis of glycosaminoglycan monosaccharides by capillary electrophoresis using indirect laser-induced fluorescence detection

Two methods for monosaccharide analysis by capillary electrophoresis (CE) using counterelectroosmotic and coelectroosmotic modes with indirect laser-induced fluorescence detection were optimised and compared. A mixture of seven glycosaminoglycan-derived hexoses was separated in alkaline fluorescein-based electrolytes and detected in both counterelectroosmotic and coelectroosmotic conditions. The fluorescein concentration and pH of the background electrolyte, and the influence of the reversal of electroosmotic flow by addition of hexadimethrine bromide on the separation were studied. Coelectroosmotic CE conditions provided better resolution and limits of detection. A 10(-6) M fluorescein solution at pH 12.25 containing 0.0005% (w/v) hexadimethrine bromide was used as background electrolyte. Quality parameters such as run-to-run, day-to-day precision and limits of detection were calculated, and better figures of merit were obtained for the coelectrooosmotic conditions than for the counterelectroosmotic mode. The coelectroosmotic method was applied to the quantitation of the hexosamine contents in glycosaminoglycans after acid hydrolysis. The method proved to be suitable for the determination of dermatan sulfate in heparin down to 2% (w/w).

High-resolution polyacrylamide gel electrophoresis of carbohydrates derivatized with a visible dye

A technique for carbohydrate analysis that is both inexpensive and easily performed is currently unavailable. In this communication we address the problem and have outlined a method for labeling saccharides with a visible dye, 4-amino-1,1'-azobenzene-3, 4'-disulfonic acid, which has an absorption maximum of 489 nm and an extinction coefficient of 37,615, to facilitate visible detection at low levels. The visible dye was coupled by a reductive amination to different sugars. The sugar-dye adducts were then separated by electrophoresis on alkaline polyacrylamide gels. The gels were scanned with a densitometer, and visible sugar-dye adducts were qualitatively analyzed by identifying them according to their mobilities. The sugar-dye adducts were quantified by determining their densitometric volume. The kinetics of the reductive amination reactions, performed at 37 degrees C, were different for each of three saccharides tested. The rate constants for glucose and fucose were 1.31 times greater and 1.8 times greater, respectively, than that of maltotriose. The reductive amination reactions were essentially complete after approximately 16 h under the given experimental conditions. A linear dose-response relationship was observed between the amount of sugar (monosaccharide, trisaccharide, or heptasaccharide) in the reductive amination reaction. The quantity of saccharide-dye adduct that could be visually detected for glucose, maltotriose, and maltoheptaose, was 25, 25, and 50 nmol, respectively. Sugar-dye adducts were separated from one another by varying the acrylamide concentration in the polyacrylamide gels. Sugar-dye adducts of monosaccharides, disaccharides, trisaccharides, and heptasaccharides were separated on alkaline 30% polyacrylamide gels with mobilities of 0.778, 0.667, 0.639, and 0.375. Adducts of glucose, fucose, galactose, and mannose were separated with mobilities of 0.844, 0.833, 0.820, and 0.810, respectively, on a 30 to 40% gradient polyacrylamide gel. Adducts of glucose and glucose derivatives were separated on a 35% polyacrylamide gel. This technique provides an inexpensive and easily performed method of carbohydrate analysis to laboratories that do not have the highly trained personnel nor the expensive equipment needed for other methods of carbohydrate analysis. The method is most applicable to research problems where sensitivity (20 pmol) is not a problem. The simplicity of the method also makes it easily incorporated into teaching laboratories.

A tabulated review of capillary electrophoresis of carbohydrates

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

Electrophoretic behavior and size distribution of the acidic polysaccharides produced by the bacteria Bradyrhizobium (Chamaecytisus) strain BGA-1 and Bradyrhizobium japonicum USDA 110

The electrophoretic behavior in polyacrylamide gels of the acidic polysaccharides produced by the soil bacteria Bradyrhizobium (Chamaecytisus) strain BGA1 and Bradyrhizobiumjaponicum USDA1 10 has been studied. Both polysaccharides were polydisperse, producing a ladder-like pattern after fixation with Alcian Blue and silver staining of the gel. The polysaccharide molecules were separated according to their size, and they behaved as a collection of flexible random coils of different size and similar charge/mass ratio. The electrophoretic behavior was not affected by the presence of acetyl groups in the polysaccharide. The range of molecular weights of the exopolysaccharide produced by B. japonicum USDA110 was wider and with larger molecules than that of the polysaccharide produced by strain BGA1. The resolution was dependent on the electrophoresis buffer; the best results were achieved with Tris-borate; in Tris-glycine buffer, the resolution was worse, and it was not improved by the addition of sodium dodecyl sulfate (SDS).

Recent developments in capillary electrophoresis of carbohydrate species

Carbohydrates are ubiquitous species involved in many life processes. Because of the multilateral roles of carbohydrates, their analysis has come to have increasing importance. As shown in this review, capillary electrophoresis in its various modes of operation has proved very useful in the analysis of carbohydrate species including mono- and oligosaccharides, glycoproteins, glycopeptides and glycosaminoglycans. Advances in separation approaches and applications as well as advances in detection including sensitive and selective pre-column derivatization are described. In summary, this comprehensive review is a supplement to previous reviews and covers the published work in 1996 and the first half of 1997.

The free solution mobility of DNA

The free solution mobility of DNA has been measured by capillary electrophoresis in the two buffers most commonly used for DNA gel electrophoresis, Tris-borate-EDTA (TBE) and Tris-acetate-EDTA (TAE). The capillaries were coated with polymers of either of two novel acrylamide monomers, N-acryloylaminoethoxyethanol or N-acryloylaminopropanol, both of which are stable at basic pH and effectively eliminate the electroendosmotic mobility due to the capillary walls. The free solution mobility of DNA in TAE buffer was found to be (3.75 +/- 0.04) x 10(-4) cm2 V-1 s-1 at 25 degrees C, independent of DNA concentration, sample size, electric field strength, and capillary coating, and in good agreement with other values in the literature. The free solution mobility was independent of DNA molecular weight from approximately 400 base pairs to 48.5 kilobase pairs, but decreased monotonically with decreasing molecular weight for smaller fragments. Surprisingly, the free solution mobility of DNA in TBE buffer was found to be (4.5 +/- 0.1) x 10(-4) cm2 V-1 s-1, about 20% larger than observed in TAE buffer, presumably because of the formation of nonspecific borate-deoxyribose complexes.