Multiple-reaction monitoring liquid chromatography mass spectrometry for monosaccharide compositional analysis of glycoproteins

Acid hydrolysis conditions for quantification of meningococcal X polysaccharide in a pentavalent vaccine using HPAEC-PAD/ESI-MS

A selective and sensitive method was evaluated for quantitation of meningococcal X (Men X) polysaccharide in pentavalent meningococcal A, C, W, Y and X conjugate vaccine using different acid hydrolysis conditions like HCl, TFA, HF, HF-TFA, and HF-HCl. High-performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD) using CarboPac PA10 column was used to identify the hydrolyzed products based on retention time and its comparison with monosaccharide standards. Complete release of glucosamine (GlcN) from Men X in monovalent bulk and pentavalent vaccine samples was achieved using HF hydrolysis at 80 °C for 2 h. The Men X HF-hydrolyzed polysaccharide to glucosamine along with the reference standard was identified using collision-induced dissociation (CID) electrospray mass spectroscopy and the MS/MS fragments of m/z 162, m/z 144 and m/z 84. Meningococcal polysaccharide concentration was determined with a correlation coefficient r2 >0.99 using polysaccharide reference standard. The serogroups A, W, and Y were converted to their monosaccharides units and quantified using this method however, milder acid hydrolysis 0.1 M HCl 80 °C 2 h for release of sialic acid for Men C polysaccharide was found to be more suitable. These methods will provide necessary tools and prove to be beneficial to laboratories developing new saccharide-based vaccine combinations.

Common Post-translational Modifications (PTMs) of Proteins: Analysis by Up-to-Date Analytical Techniques with an Emphasis on Barley

Post-translational modifications (PTMs) of biomacromolecules can be useful for understanding the processes by which a relatively small number of individual genes in a particular genome can generate enormous biological complexity in different organisms. The proteomes of barley and the brewing process were investigated by different techniques. However, their diverse and complex PTMs remain understudied. As standard analytical approaches have limitations, innovative analytical approaches need to be developed and applied in PTM studies. To make further progress in this field, it is necessary to specify the sites of modification, as well as to characterize individual isoforms with increased selectivity and sensitivity. This review summarizes advances in the PTM analysis of barley proteins, particularly those involving mass spectrometric detection. Our focus is on monitoring phosphorylation, glycation, and glycosylation, which critically influence functional behavior in metabolism and regulation in organisms.

Metabolomic Profiling of Malaysian and New Zealand Honey Using Concatenated NMR and HRMS Datasets

This study aims to compare the metabolomic profiles of Malaysian and New Zealand honey while determining their anti-oncogenic activity for potential prophylactic functions. Metabolomics tools including multivariate analysis were applied on concatenated LC-HRMS and NMR datasets to afford an intensive chemical profile of honey samples and have a snapshot of the bioactive metabolites in the respective collections. Malaysian samples were found to have higher sugar and polyphenolic content, while New Zealand samples afforded higher concentration of low molecular weight (MW) lipids. However, New Zealand honey collected from the northern islands had higher concentration of acetylated saccharides, while those from the southern islands yielded higher low MW phenolic metabolites that were comparable to Malaysian honey. Mild anti-oncogenic compounds against breast cancer cell line ZR75 were putatively identified in Malaysian honey that included earlier described antioxidants such as gingerdiol, 2-hexylphenol-O-β-D-xylopyranoside, plastoquinone, tropine isovalerate, plumerinine, and 3,5-(12-phenyl-8-dodecenyl)resorcinol, along with several phenolic esters and lignans.

In-depth characterization of non-human sialic acid (Neu5Gc) in human serum using label-free ZIC-HILIC/MRM-MS

Sialic acid Neu5Gc, a non-human glycan, is recognized as a new harmful substance that can cause vascular disease and cancer. Humans are unable to synthesize Neu5Gc due to a genetic defect that converts Neu5Ac to Neu5Gc, but Neu5Gc is often observed in human biological samples. Therefore, the demand for accurately measuring the amount of Neu5Gc present in human blood or tissues is rapidly increasing, but there is still no method to reliably quantify trace amounts of a non-human sugar. In particular, selective isolation and detection of Neu5Gc from human serum is analytically challenging due to the presence of excess sialic acid Neu5Ac, which has physicochemical properties very similar to Neu5Gc. Herein, we developed the label-free approach based on ZIC-HILIC/MRM-MS that can enrich sialic acids released from human serum and simultaneously monitor Neu5Ac and Neu5Gc. The combination of complete separation of Neu5Gc from abundant Neu5Ac by hydrophilic and electrostatic interactions with selective monitoring of structure-specific cross-ring cleavage ions generated by negative CID-MS/MS was remarkably effective for quantification of Neu5Ac and Neu5Gc at the femtomole level. Indeed, we were able to successfully determine the absolute quantitation of Neu5Gc from 30 healthy donors in the range of 3.336 ± 1.252 pg/μL (mean ± SD), 10,000 times lower than Neu5Ac. In particular, analysis of sialic acids in protein-free serum revealed that both Neu5Ac and Neu5G are mostly bound to proteins and/or lipids, but not in free form. In addition, the correlation between expression level of Neu5Gc and biological factors such as BMI, age, and sex was investigated. This method can be widely used in studies requiring sialic acid-related measurements such as disease diagnosis or prediction of immunogenicity in biopharmaceuticals as it is both fast and highly sensitive.

Glycoengineering of Aspergillus nidulans to produce precursors for humanized N-glycan structures

Filamentous fungi secrete protein with a very high efficiency, and this potential can be exploited advantageously to produce therapeutic proteins at low costs. A significant barrier to this goal is posed by the fact that fungal N-glycosylation varies substantially from that of humans. Inappropriate N-glycosylation of therapeutics results in reduced product quality, including poor efficacy, decreased serum half-life, and undesirable immune reactions. One solution to this problem is to reprogram the glycosylation pathway of filamentous fungi to decorate proteins with glycans that match, or can be remodeled into, those that are accepted by humans. In yeast, deletion of ALG3 leads to the accumulation of Man₅GlcNAc₂ glycan structures that can act as a precursor for remodeling. However, in Aspergilli, deletion of the ALG3 homolog algC leads to an N-glycan pool where the majority of the structures contain more hexose residues than the Man_3-5GlcNAc₂ species that can serve as substrates for humanized glycan structures. Hence, additional strain optimization is required. In this report, we have used gene deletions in combination with enzymatic and chemical glycan treatments to investigate N-glycosylation in the model fungus Aspergillus nidulans. In vitro analyses showed that only some of the N-glycan structures produced by a mutant A. nidulans strain, which is devoid of any of the known ER mannose transferases, can be trimmed into desirable Man₃GlcNAc₂ glycan structures, as substantial amounts of glycan structures appear to be capped by glucose residues. In agreement with this view, deletion of the ALG6 homolog algF, which encodes the putative α-1,3- glucosyltransferase that adds the first glucose residue to the growing ER glycan structure, dramatically reduces the amounts of Hex_6-7HexNAc₂ structures. Similarly, these structures are also sensitive to overexpression of the genes encoding the heterodimeric α-glucosidase II complex. Without the glucose caps, a new set of large N-glycan structures was formed. Formation of this set is mostly, perhaps entirely, due to mannosylation, as overexpression of the gene encoding mannosidase activity led to their elimination. Based on our new insights into the N-glycan processing in A. nidulans, an A. nidulans mutant strain was constructed in which more than 70% of the glycoforms appear to be Man_3-5GlcNAc₂ species, which may serve as precursors for further engineering in order to create more complex human-like N-glycan structures.

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.

Identification of compounds from terrestrial dissolved organic matter toxic to cyanobacteria

There is emerging evidence for the phytotoxicity of terrestrial dissolved organic matter (DOM), however its sources, transformations and ecological effects in aquatic ecosystems are poorly understood. DOM characterization by Nuclear Magnetic Resonance (NMR) spectroscopy has typically involved solid-state techniques, but poor resolution has often precluded identification of individual components. This study is the first to directly identify individual phytotoxic components using a novel combined approach of preparative HPLC fractionation of DOM (obtained from leaves of two common riparian trees, Casuarina cunninghamiana and Eucalyptus tereticornis). This was followed by chemical characterization of fractions, using one-dimensional (1D) and two-dimensional (2D) solution-state ¹H NMR analyses. Additionally, the phytotoxic effect of the fractions was determined using cultures of the cyanobacteria Raphidiopsis (Cylindrospermopsis) raciborskii. The amino acid, proline, from Casuarina leachate was identified as phytotoxic, while for Eucalyptus leachate, it was gallic acid and polyphenols. These phytotoxicants remained in the leachates when they were incubated in sunlight or the dark conditions over 5 days. Our study identifies phytotoxic compounds with the potential to affect algal species composition, and potentially control nuisance R. raciborskii blooms.

Simultaneous analysis of monosaccharides using ultra high performance liquid chromatography-high resolution mass spectrometry without derivatization for validation of certified reference materials

Monosaccharide composition of biological samples can reflect an individual's health status. Monitoring the concentration of individual monosaccharides in human serum requires a technique for the simultaneous analysis of multiple monosaccharide molecules. Furthermore, certified reference materials (CRMs) for overall monosaccharide composition of human serum are required in order to validate the performance of clinical laboratory instruments. In the present study, we present a novel method for the simultaneous analysis of numerous monosaccharide molecules without the need for derivatization or post-column treatment. We utilized ultra-high-performance liquid chromatography (UHPLC)-quadrupole/orbitrap mass spectrometry incorporating a hydrophilic interaction chromatography (HILIC) column. We optimized the precursor ions, product ions, mobile phase composition and gradient program, flow rate, and column temperature. Seven monosaccharides (D-Ribose, L-Arabinose, D-Xylose, D-Fructose, D-Mannose, D-Galactose and D-Glucose) were able to be separated and quantified. We validated the method and the seven molecules showed favorable limits of detection and quantification, recovery rates, carry-over effects, intra- and inter-day accuracy and precision, resolution, and measurement uncertainty. We analyzed human serum samples using the method. To avoid ion suppression and D-d₂-Glucose peak interference, compounds present at concentrations outside of the calibration range were analyzed from diluted samples. Quantification of serum samples corroborated some previous clinical research, in that increased D-Glucose concentration was associated with increased concentrations of D-Mannose and D-Ribose. We also validated the CRMs, and expect these to have utility as standards for serum monosaccharide profiling, thus contributing to public health.

Multiple Reaction Monitoring Mass Spectrometry for the Drug Monitoring of Ivacaftor, Tezacaftor, and Elexacaftor Treatment Response in Cystic Fibrosis: A High-Throughput Method

Ivacaftor-tezacaftor and ivacaftor-tezacaftor-elexacaftor are new breakthrough cystic fibrosis (CF) drug combinations that directly modulate the activity and trafficking of the defective CF transmembrane conductance regulator protein (CFTR) underlying the CF disease state. Currently, in the hospital setting, there are no therapeutic drug monitoring assays for these very expensive, albeit, life-saving drugs. A rapid and precise novel method for the quantification of ivacaftor, its metabolites, tezacaftor, and elexacaftor, in human plasma was developed and validated using multiple reaction monitoring mass spectrometry (MRM/MS). The MRM/MS analytical method was validated at a concentration range of 0.0025-1 μg/mL for ivacaftor, ivacaftor-M1, ivacaftor-M6, tezacaftor, and elexacaftor in human plasma. The method displayed good accuracy (90.62-94.51%) and reproducibility (99.91-100%) including at low concentrations 0.01 μg/mL. With a mobile phase consisting of [acetonitrile/water]/0.1% formic acid (70:30 v/v) at a flow rate of 0.5 mL/min, a linear correlation was observed over a concentration range of 0.0025-1 μg/mL in human plasma for ivacaftor (R ² = 0.9865105), ivacaftor-M1 (R ² = 0.9852684), ivacaftor-M6 (R ² = 0.9911764), tezacaftor (R ² = 0.98742470), and elexacaftor (R ² = 0.9897608). The reported method can accurately quantify ivacaftor, ivacaftor-M1, ivacaftor-M6, tezacaftor, and elexacaftor at low concentrations in human plasma. We have established a cost-efficient and timely method for measuring ivacaftor, its metabolites, and tezacaftor with or without elexacaftor in human plasma suitable for high-throughput applications in the hospital settings or clinical trials.

NEGATIVE ION MASS SPECTROMETRY FOR THE ANALYSIS OF N-LINKED GLYCANS

N-glycans from glycoproteins are complex, branched structures whose structural determination presents many analytical problems. Mass spectrometry, usually conducted in positive ion mode, often requires extensive sample manipulation, usually by derivatization such as permethylation, to provide the necessary structure-revealing fragment ions. The newer but, so far, lesser used negative ion techniques, on the contrary, provide a wealth of structural information not present in positive ion spectra that greatly simplify the analysis of these compounds and can usually be conducted without the need for derivatization. This review describes the use of negative ion mass spectrometry for the structural analysis of N-linked glycans and emphasises the many advantages that can be gained by this mode of operation. Biosynthesis and structures of the compounds are described followed by methods for release of the glycans from the protein. Methods for ionization are discussed with emphasis on matrix-assisted laser desorption/ionization (MALDI) and methods for producing negative ions from neutral compounds. Acidic glycans naturally give deprotonated species under most ionization conditions. Fragmentation of negative ions is discussed next with particular reference to those ions that are diagnostic for specific features such as the branching topology of the glycans and substitution positions of moieties such as fucose and sulfate, features that are often difficult to identify easily by conventional techniques such as positive ion fragmentation and exoglycosidase digestions. The advantages of negative over positive ions for this structural work are emphasised with an example of a series of glycans where all other methods failed to produce a structure. Fragmentation of derivatized glycans is discussed next, both with respect to derivatives at the reducing terminus of the molecules, and to methods for neutralization of the acidic groups on sialic acids to both stabilize them for MALDI analysis and to produce the diagnostic fragments seen with the neutral glycans. The use of ion mobility, combined with conventional mass spectrometry is described with emphasis on its use to extract clean glycan spectra both before and after fragmentation, to separate isomers and its use to extract additional information from separated fragment ions. A section on applications follows with examples of the identification of novel structures from lower organisms and tables listing the use of negative ions for structural identification of specific glycoproteins, glycans from viruses and uses in the biopharmaceutical industry and in medicine. The review concludes with a summary of the advantages and disadvantages of the technique. © 2020 John Wiley & Sons Ltd. Mass Spec Rev.

Protein Glycosylation Investigated by Mass Spectrometry: An Overview

The protein glycosylation is a post-translational modification of crucial importance for its involvement in molecular recognition, protein trafficking, regulation, and inflammation. Indeed, abnormalities in protein glycosylation are correlated with several disease states such as cancer, inflammatory diseases, and congenial disorders. The understanding of cellular mechanisms through the elucidation of glycan composition encourages researchers to find analytical solutions for their detection. Actually, the multiplicity and diversity of glycan structures bond to the proteins, the variations in polarity of the individual saccharide residues, and the poor ionization efficiencies make their detection much trickier than other kinds of biopolymers. An overview of the most prominent techniques based on mass spectrometry (MS) for protein glycosylation (glycoproteomics) studies is here presented. The tricks and pre-treatments of samples are discussed as a crucial step prodromal to the MS analysis to improve the glycan ionization efficiency. Therefore, the different instrumental MS mode is also explored for the qualitative and quantitative analysis of glycopeptides and the glycans structural composition, thus contributing to the elucidation of biological mechanisms.

Determination of Soluble Mono, Di, and Oligosaccharide Content in 23 Dry Beans (Phaseolus vulgaris L.)

Beans provide a rich source of plant-based proteins and carbohydrates. It is well documented in the literature that the raffinose family of oligosaccharides (RFOs: raffinose, stachyose, and verbascose) is linked with flatulence issues. In this study, the soluble sugar content of 23 dry beans was investigated using a newly developed and validated analytical method with high-performance anion-exchange chromatography coupled to an amperometric pulse detection. All seven sugars (galactose, glucose, fructose, sucrose, raffinose, stachyose, and verbascose) showed good linearity (r² ≥ 0.99) between 0.156 and 20 μg/mL. The limit of detection and quantification were determined as 0.01-0.11 μg/mL and 0.04-0.32 μg/mL, respectively. Significant variations in the profiles and concentrations of individual and total sugars were observed in 23 dry beans. Sucrose and stachyose were the two prominent soluble sugars combinedly representing an average of 86% of the total soluble sugars. Yellow split beans, large lima, and black eyed peas contained higher amounts of total soluble sugars (79.8-83.6 mg/g), whereas lower amounts were observed in speckled butter peas and lentils (53.6-56.6 mg/g). Garbanzo beans contained maximum levels of mono and disaccharides (MD), and yellow split beans showed the highest levels of RFOs. Based on the hierarchical cluster analysis of the total soluble sugars (TS), MD, RFOs, and MD/RFOs ratio, 23 beans can be classified into five groups. The average TS content and the MD/RFOs ratios of the five groups were determined as group 1 (TS = 55.1 mg/g and MD/RFOs = 0.30), group 2 (TS = 77.6 mg/g and MD/RFOs = 0.31), group 3 (TS = 78.3 mg/g and MD/RFOs = 0.51), group 4 (TS = 59.1 mg/g and MD/RFOs = 1.06), and group 5 (TS = 68.5 mg/g and MD/RFOs = 0.62). This information is useful for researchers, food industries, and consumers that are looking for plant-based protein source as an alternative to animal proteins with reduced flatulence problems.

Effects of photochemical and microbiological changes in terrestrial dissolved organic matter on its chemical characteristics and phytotoxicity towards cyanobacteria

Previous studies have shown that under laboratory conditions, dissolved organic matter (DOM) leached from plants can be differentially more phytotoxic to cyanobacteria, compared to green algae. This study examined how DOM source and transformation processes (microbial and photochemical) affect its chemical composition and phytotoxicity towards a cultured species of cyanobacteria (Raphidiopsis raciborskii) using a factorial experimental design. To complement cyanobacterial bioassays, the chemical composition and associated changes in DOM were determined using spectroscopic (nuclear magnetic resonance (NMR) and absorbance) and elemental analyses. Sunlight exposed DOM from leaves of the terrestrial plants, Casuarina cunninghamiana and Eucalyptus tereticornis had the most phytotoxic effect compared to DOM not exposed to sunlight. This phytotoxic DOM was characterised by relatively low nitrogen content, containing highly coloured and relatively high molecular mass constituents. Both mixed effect model and PCA approaches to predict inhibition of photosynthetic yield indicated phytotoxicity could be predicted (P < 0.001) based upon the following parameters: C: N ratio; gilvin, and lignin-derived phenol content of DOM. Parallel proton-detected 1D and 2D NMR techniques showed that glucose anomers were the major constituents of fresh leachate. With ageing, glucose anomers disappeared and products of microbial transformation appeared, but there was no indication of the appearance of additional phytotoxic compounds. This suggests that reactive oxygen species may be responsible, at least partially, for DOM phytotoxicity. This study provides important new information highlighting the characteristics of DOM that link with phytotoxic effects.

Standardized protocols and procedures can precisely and accurately quantify non-structural carbohydrates

Non-structural carbohydrates (NSCs), the stored products of photosynthesis, building blocks for growth and fuel for respiration, are central to plant metabolism, but their measurement is challenging. Differences in methods and procedures among laboratories can cause results to vary widely, limiting our ability to integrate and generalize patterns in plant carbon balance among studies. A recent assessment found that NSC concentrations measured for a common set of samples can vary by an order of magnitude, but sources for this variability were unclear. We measured a common set of nine plant material types, and two synthetic samples with known NSC concentrations, using a common protocol for sugar extraction and starch digestion, and three different sugar quantification methods (ion chromatography, enzyme, acid) in six laboratories. We also tested how sample handling, extraction solvent and centralizing parts of the procedure in one laboratory affected results. Non-structural carbohydrate concentrations measured for synthetic samples were within about 11.5% of known values for all three methods. However, differences among quantification methods were the largest source of variation in NSC measurements for natural plant samples because the three methods quantify different NSCs. The enzyme method quantified only glucose, fructose and sucrose, with ion chromatography we additionally quantified galactose, while the acid method quantified a large range of mono- and oligosaccharides. For some natural samples, sugars quantified with the acid method were two to five times higher than with other methods, demonstrating that trees allocate carbon to a range of sugar molecules. Sample handling had little effect on measurements, while ethanol sugar extraction improved accuracy over water extraction. Our results demonstrate that reasonable accuracy of NSC measurements can be achieved when different methods are used, as long as protocols are robust and standardized. Thus, we provide detailed protocols for the extraction, digestion and quantification of NSCs in plant samples, which should improve the comparability of NSC measurements among laboratories.

Liquid Chromatography-Tandem Mass Spectrometry Approach for Determining Glycosidic Linkages

The structural analysis of carbohydrates remains challenging mainly due to the lack of rapid analytical methods able to determine and quantitate glycosidic linkages between the diverse monosaccharides found in natural oligosaccharides and polysaccharides. In this research, we present the first liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based method for the rapid and simultaneous relative quantitation of glycosidic linkages for oligosaccharide and polysaccharide characterization. The method developed employs ultrahigh-performance liquid chromatography coupled with triple quadrupole mass spectrometry (UHPLC/QqQ-MS) analysis performed in multiple reaction monitoring (MRM) mode. A library of 22 glycosidic linkages was built using commercial oligosaccharide standards. Permethylation and hydrolysis conditions along with LC-MS/MS parameters were optimized resulting in a workflow requiring only 50 μg of substrate for the analysis. Samples were homogenized, permethylated, hydrolyzed, and then derivatized with 1-phenyl-3-methyl-5-pyrazolone (PMP) prior to analysis by UHPLC/MRM-MS. Separation by C18 reversed-phase UHPLC along with the simultaneous monitoring of derivatized terminal, linear, bisecting, and trisecting monosaccharide linkages by mass spectrometry is achieved within a 15 min run time. Reproducibility, efficacy, and robustness of the method was demonstrated with galactan ( Lupin) and polysaccharides within food such as whole carrots. The speed and specificity of the method enables its application toward the rapid glycosidic linkage analysis of oligosaccharides and polysaccharides.

Accurate Quantification of N-Glycolylneuraminic Acid in Therapeutic Proteins Using Supramolecular Mass Spectrometry

Practical applications of innovative host-guest systems are challenging because of unexpected guest competitors and/or subtle environmental differences. Herein, a supramolecular mass spectrometry (MS)-based method using a synthetic host, cucurbit[7]uril (CB[7]), was developed for identifying and quantifying N-glycolylneuraminic acid (Neu5Gc) in therapeutic glycoproteins, which critically reduces drug efficacy. The development of a reliable derivatization-free analytical method for Neu5Gc is highly challenging because of the interference by the abundant N-acetylneuraminic acid (Neu5Ac). CB[7] recognized the subtle structural differences between Neu5Gc and Neu5Ac. Distinct host-guest interactions between CB[7] and the two sialic acids produced a highly linear relationship between the complexation and concentration proportions of the two sialic acids in MS. Furthermore, the developed method had sub-picomolar quantification limits and a wide range of applicability for diverse glycoproteins, demonstrating the potential utility of this method as a reliable assay of Neu5Gc in therapeutic glycoproteins.

Natural organic matter contained in clay rock pore water: Direct quantification at the molecular level using electrospray ionization mass spectrometry

RATIONALE

Natural organic matter (NOM) is present in the environment and could influence the migration of heavy metals/radionuclides. The dissolved fraction of NOM (DOM) is usually quantified using total organic carbon analysis or UV-visible spectrometry. Nonetheless, analysis using pattern recognition cannot provide the full spectrum of organic molecules contained in waters, especially low-molecular-weight compounds. In the context of nuclear performance assessment studies, ground waters may contain DOM and a key aspect is to quantify different categories of NOM types in order to further evaluate the transport and fate of radionuclides in the environment.

METHODS

Thus, a method for the quantification of DOM at the molecular level was developed, based on electrospray ionization mass spectrometry (ESI-MS). This method simultaneously gives structural information on DOM and the individual concentrations of these low-molecular-weight compounds without pretreatment and/or preconcentration of the samples.

RESULTS

Several methods of quantification (internal calibration, calibrated addition of external standard, sequential tandem mass spectrometry) have been optimized and successfully applied to real natural samples. They are discussed in this paper with a focus on acidic compounds, which are the compounds that most probably could influence the migration of heavy metals and radionuclides in the clay rock pore water from the French Callovo-Oxfordian (COx) nuclear repository site.

CONCLUSIONS

Quantification of in situ dissolved NOM from the COx has been performed using ESI-MS. For the first time to our knowledge, it was possible to give a quite exhaustive and quantitative inventory of the small organic compounds present without proceeding to any chemical treatment or sample crushing and for naturally occurring concentrations.

Revisiting monosaccharide analysis - quantitation of a comprehensive set of monosaccharides using dynamic multiple reaction monitoring

A rapid method for the quantitation of sixteen neutral and acidic monosaccharides, from both animal and plant sources was developed using ultra-high performance liquid chromatography triple quadrupole mass spectrometry (UHPLC/QqQ-MS) in dynamic multiple reaction monitoring (dMRM) mode. Monosaccharides including three pentoses (ribose, xylose, arabinose), two deoxyhexoses (rhamnose, fucose), five hexoses (fructose, mannose, allose, glucose, galactose), two hexuronic acids (glucuronic acid, galacturonic acid), and two N-acetyl-hexosamines (GlcNAc, GalNAc), were derivatized with 1-phenyl-3-methyl-5-pyrazolone (PMP), while underivatized sialic acids, Neu5Ac and Neu5Gc, were simultaneously analyzed with a 10-minute run. With the optimized UHPLC conditions, baseline separations of the isomers were achieved. The sensitivity and calibration ranges of this method were determined. The limits of detection were between femtomoles and attomoles with linear ranges spanning four to six orders of magnitude and coefficients of variation (CVs) ≤7.2%. Spiking experiments performed on a pooled fecal sample demonstrated the high accuracy of this method even when applied to samples with complicated matrices. The validated method was applied to fecal samples from an infant transitioning from breast milk to weaning foods. Major milk monosaccharides including galactose, fucose, glucose, GlcNAc, and Neu5Ac were found to be the most abundant components in the feces of milk-fed infants. PMP-derivatives of nine other monosaccharides including apiose, lyxose, altrose, talose, gulose, glucosamine, galactosamine, mannosamine, and N-acetylmannosamine (ManNAc) were also tested and could be added to the quantitation method depending on the need. The speed and sensitivity of the method makes it readily adaptable to rapid throughput analysis of monosaccharides in biological samples.

Identification of a novel component leading to anti-tumor activity besides the major ingredient cordycepin in Cordyceps militaris extract

In accordance with our previous study that was carried out to identify novel anti-tumor ingredients, chromatographic separation in combination with an anti-tumor activity assay was used for analysis of Cordyceps militaris extract in this study. Various modes of chromatography including reversed-phase, cation-exchange and anion-exchange were used to separate components of Cordyceps militaris, which showed various chemical properties. Anti-tumor activity of each fraction was assessed by a Hoechst staining-based apoptosis assay using malignant melanoma MeWo cells. By these repeated approaches through chromatographic segregation and cell biological assay, we finally succeeded in identifying the target substance from a certain fraction that included neutral hydrophilic components using a pre-column and post-column chlorine adduct ionization LC-APCI-MS method. The target substance was a mono-carbohydrate, xylitol, that induced apoptotic cell death in MeWo cells but not in normal human OUMS-24 fibroblasts. This is the first study showing that Cordyceps militaris extract contains a large amount of xylitol. Thus, our results will contribute greatly to uncovering the mysterious multifunctional herbal drug Cordyceps militaris as an anti-tumor agent.

"Hypermethylation" of anthranilic acid-labeled sugars confers the selectivity required for liquid chromatography-mass spectrometry

Analysis of the monosaccharides of complex carbohydrates is often performed by liquid chromatography with fluorescence detection. Unfortunately, methylated sugars, unusual amino- or deoxysugars and incomplete hydrolysis can lead to erroneous assignments of peaks. Here, we demonstrate that a volatile buffer system is suitable for the separation of anthranilic acid labeled sugars. It allows off-line examination of peaks by electrospray mass spectrometry. Approaches towards on-line mass spectrometric detection using reversed-phase or porous graphitic carbon columns fell short of achieving sufficient separation of the relevant isobaric sugars. Adequate chromatographic performance for isomeric sugars was achieved with reversed-phase chromatography of "hyper"-methylated anthranilic acid-labeled monosaccharides. Deuteromethyl iodide facilitates the discovery of naturally methylated sugars and identification of their parent monosaccharide as demonstrated with N-glycans of the snail Achatina fulica, where two thirds of the galactoses and a quarter of the mannoses were methylated.

Simultaneous determination of rhamnose, xylitol, arabitol, fructose, glucose, inositol, sucrose, maltose in jujube (Zizyphus jujube Mill.) extract: comparison of HPLC-ELSD, LC-ESI-MS/MS and GC-MS

Background

Jujube extract is commonly used as a food additive and flavoring. The sensory properties of the extract, especially sweetness, are a critical factor determining the product quality and therefore affecting consumer acceptability. Small molecular carbohydrates make major contribution to the sweetness of the jujube extract, and their types and contents in the extract have direct influence on quality of the product. So, an appropriate qualitative and quantitative method for determination of the carbohydrates is vitally important for quality control of the product.

Results

High performance liquid chromatography-evaporative light scattering detection (HPLC-ELSD), liquid chromatography-electronic spay ionization tandem mass spectrometry (LC-ESI-MS/MS), and gas chromatography–mass spectrometry (GC–MS) methods have been developed and applied to determining small molecular carbohydrates in jujube extract, respectively. Eight sugars and alditols were identified from the extract, including rhamnose, xylitol, arabitol, fructose, glucose, inositol, sucrose, and maltose. Comparisons were carried out to investigate the performance of the methods. Although the methods have been found to perform satisfactorily, only three sugars (fructose, glucose and inositol) could be detected by all these methods. Meanwhile, a similar quantitative result for the three sugars can be obtained by the methods.

Conclusions

Eight sugars and alditols in the jujube extract were determined by HPLC-ELSD, LC-ESI-MS/MS and GC–MS, respectively. The LC-ELSD method and the LC-ESI-MS/MS method with good precision and accuracy were suitable for quantitative analysis of carbohydrates in jujube extract; although the performance of the GC–MS method for quantitative analysis was inferior to the other methods, it has a wider scope in qualitative analysis. A multi-analysis technique should be adopted in order to obtain complete constituents of about the carbohydrates in jujube extract, and the methods should be employed according to the purpose of analysis.

Electronic supplementary material

The online version of this article (doi:10.1186/s13065-016-0171-2) contains supplementary material, which is available to authorized users.

An optimized capillary electrophoresis method for the simultaneous analysis of biomass degradation products in ionic liquid containing samples

An indirect capillary electrophoresis method for a quantitative determination of mono-, di- and oligosaccharides was developed to investigate biomass degradation, the isomerization of glucose into fructose and conversion of fructose to 5-hydroxymethylfurfural (5-HMF) in ionic liquids (ILs). Three chromophores, namely 2,6-pyridinedicarboxylic acid (PDC), maleic acid and phthalic acid, were used to perform indirect detection. The electroosmotic flow (EOF) was reversed to reduce analysis time, using 1-tetradecyl-3-methylimidazolium chloride (C14MImCl). The simultaneous separation of the underivatized mono-, di- and oligosaccharides was performed using four cellodextrin oligomers (cellotriose, cellotetraose, cellopentaose, cellohexaose), eight carbohydrates (xylose, fructose, glucose, galactose, lactose, cellobiose, raffinose, sucrose), two organic acids (acetic acid, levulinic acid) and 5-HMF. The best performance was obtained using background electrolyte (BGE) composed of 138.2mM NaOH, 40mM maleic acid and 5mMC14MImCl, the applied voltage was -21.7kV. The linear ranges for analyzed compounds were following: organic acids, raffinose and sucrose from 0.20 to 7mM, cellodextrin oligomers from 0.25 to 5mM, other analyzed carbohydrates from 0.25 to 7mM and 5-HMF from 0.05 to 7mM. The relative standard deviations (RSD) of peak areas varied from 3.47 to 9.62% during a 5-day analysis period and 0.58-5.29% during one day.

Separation of monosaccharides hydrolyzed from glycoproteins without the need for derivatization

Chromatographic separation of monosaccharides hydrolyzed from glycoconjugates or complex, aggregate biomaterials, can be achieved by classic analytical methods without a need for derivatizing the monosaccharide subunits. A simple and sensitive method is presented for characterizing underivatized monosaccharides following hydrolysis from N- and O-linked glycoproteins using high-performance liquid chromatography separation with mass spectrometry detection (LC-MS). This method is adaptable for characterizing anything from purified glycoproteins to mixtures of glycoforms, for relative or absolute quantification applications, and even for the analysis of complex biomaterials. Use of an amide stationary phase with HILIC chromatography is demonstrated to retain the highly polar, underivatized monosaccharides and to resolve stereoisomers and potentially interfering contaminants. This work illustrates an original approach for characterization of N- and O-linked glycoprotein standards, mixtures, and for complex biological materials such as a total yeast extract.

Identification of edible Bird’s nest with amino acid and monosaccharide analysis

This study describes the approach of amino acid and monosaccharide combined with Hotelling T2 range plot to identify edible bird nests (EBN) and non-EBN. Prior to the approach, an analytical method was developed and validated to quantify monosaccharides in EBN. Hotelling T2 range plots of both compounds were successful in predicting the different types of EBN and differentiating EBN and non-EBN. This outcome suggests EBN contains a group of glycoproteins which is not affected by the EBN’s coloration, country of origin, and/or the processing method of the food item. In addition, the glycoproteins were shown to be unique to EBN. EBN were revealed to be rich in protein and essential amino acids as well as contain a wider variety of monosaccharides than most food items. The overall findings suggest that amino acid and monosaccharide provide information not only on the detected compounds and also insights into the glycoproteins of EBN.

Monitoring Organic Reactions by Micellar Electrokinetic Chromatography

A method was established to monitor organic reactions by micellar capillary electrokinetic chromatography (MEKC). After optimizing conditions such as the composition of the solvents, the surfactant, and the apparent pH (pH*) of the system, the method was utilized to analyze the reaction of glycidyl methacrylate (GMA) and allyl amine. The main products were identified in the electropherograms. The reaction procedure was monitored in real time. This method was found to have common applicability, being able to separate and detect nonaqueous soluble, nonionic, and low-UV-Vis absorbance compounds. It provides a rapid and low-cost way to understand organic reactions and to direct synthesis works.

Extracted Fragment Ion Mobility Distributions: A New Method for Complex Mixture Analysis

A new method is presented for constructing ion mobility distributions of precursor ions based upon the extraction of drift time distributions that are monitored for selected fragment ions. The approach is demonstrated with a recently designed instrument that combines ion mobility spectrometry (IMS) with ion trap mass spectrometry (MS) and ion fragmentation, as shown in a recent publication [J. Am. Soc. Mass Spectrom. 22 (2011) 1477-1485]. Here, we illustrate the method by examining selected charge states of electrosprayed ubiquitin ions, an extract from diesel fuel, and a mixture of phosphorylated peptide isomers. For ubiquitin ions, extraction of all drift times over small mass-to-charge (m/z) ranges corresponding to unique fragments of a given charge state allows the determination of precursor ion mobility distributions. A second example of the utility of the approach includes the distinguishing of precursor ion mobility distributions for isobaric, basic components from commercially available diesel fuel. Extraction of data for a single fragment ion is sufficient to distinguish the precursor ion mobility distribution of cycloalkyl-pyridine derivatives from pyrindan derivatives. Finally, the method is applied for the analysis of phosphopeptide isomers (LFpTGHPESLER and LFTGHPEpSLER) in a mixture. The approach alleviates several analytical challenges that include separation and characterization of species having similar (or identical) m/z values within complex mixtures.

Targeted proteomics by selected reaction monitoring mass spectrometry: applications to systems biology and biomarker discovery

Mass Spectrometry-based proteomics is now considered a relatively established strategy for protein analysis, ranging from global expression profiling to the identification of protein complexes and specific post-translational modifications. Recently, Selected Reaction Monitoring Mass Spectrometry (SRM-MS) has become increasingly popular in proteome research for the targeted quantification of proteins and post-translational modifications. Using triple quadrupole instrumentation (QqQ), specific analyte molecules are targeted in a data-directed mode. Used routinely for the quantitative analysis of small molecular compounds for at least three decades, the technology is now experiencing broadened application in the proteomics community. In the current review, we will provide a detailed summary of current developments in targeted proteomics, including some of the recent applications to biological research and biomarker discovery.

Sialic acid-focused quantitative mouse serum glycoproteomics by multiple reaction monitoring assay

Despite increasing importance of protein glycosylation, most of the large-scale glycoproteomics have been limited to profiling the sites of N-glycosylation. However, in-depth knowledge of protein glycosylation to uncover functions and their clinical applications requires quantitative glycoproteomics eliciting both peptide and glycan sequences concurrently. Here we describe a novel strategy for the multiplexed quantitative mouse serum glycoproteomics based on a specific chemical ligation, namely, reverse glycoblotting technique, focusing sialic acids and multiple reaction monitoring (MRM). LC-MS/MS analysis of de-glycosylated peptides identified 270 mouse serum peptides (95 glycoproteins) as sialylated glycopeptides, of which 67 glycopeptides were fully characterized by MS/MS analyses in a straightforward manner. We revealed the importance of a fragment ion containing innermost N-acetylglucosamine (GlcNAc) residue as MRM transitions regardless the sequence of the peptides. Versatility of the reverse glycoblotting-assisted MRM assays was demonstrated by quantitative comparison of 25 targeted glycopeptides from 16 proteins between mice with homo and hetero types of diabetes disease model.

Quantification of monosaccharides through multiple-reaction monitoring liquid chromatography/mass spectrometry using an aminopropyl column

A simple, sensitive, and reproducible quantitative liquid chromatography/tandem mass spectrometry (LC/MS/MS) method was designed for the simultaneous quantification of monosaccharides derived from glycoprotein and blood serum using a multiple-reaction monitoring (MRM) approach. Sialic acids and neutral monosaccharides were efficiently separated using an amino-bonded silica phase column. Neutral monosaccharide molecules were detected as their aldol acetate anion adducts [M + CH(3)CO(2)](-) using electrospray ionization in negative ion MRM mode, while sialic acids were detected as deprotonated ions [M-H](-). The new method did not require a reduction step, and exhibited very high sensitivity to carbohydrates with limits of detection of 1 pg for the sugars studied. The linearity of the described approach spanned over three orders of magnitude (pg to ng). The method was validated for monosaccharides originating from N-linked glycans attached to glycoproteins and glycoproteins found in human blood serum. The method effectively quantified monosaccharides originating from as little as 1 microg of glycoprotein and 5 microL of blood serum. The method was robust, reproducible, and highly sensitive. It did not require reduction, derivatization or postcolumn addition of reagents.