Mass spectrometry is the most widely used analytical technique for glycans. Mass spectrometry (MS) can be used to determine molecular weight, monosaccharide composition, anomeric configuration, sugar sequence, linkage, and branch positions. Different types of MS can be used for glycans including one-dimensional mass analysis which determines molecular weight, tandem mass spectrometry which fragments ions to provide structural information, and ion mobility mass spectrometry which separates ions in the gas phase. These approaches combine orthogonal methods to tackle the structural complexity of glycans with high sensitivity and specificity for carbohydrate analysis.
Mass spectrometry plays a role in profiling glycans due to its ability to obtain unequivocal molecular information that is impossible to obtain through other techniques. This includes accurate mass measurements that determine elemental composition and fragmentation methods that can be used to determine structural connectivity. Methods such as chromatography or electrophoresis separate glycans according to their physiochemical properties; however, they do not identify the glycans after separation. MS detection provides ions that generate m/z values characteristic of particular carbohydrates. Glycans also lack strong chromophores for sensitive optical detection and generally lack volatility for vaporization without ionization into the gas phase. Coupling soft ionization methods with high resolution MS instruments allows for the characterization of native glycans.
Fig. 1 Schematic illustration of the experimental workflow for isomer-specific monitoring.1,5
Isomers have the same mass but differ in position of linkage, anomeric configurations and branching of saccharide units. Chromatographic separation does not usually separate all isomers so there may be more than one glycan eluting from the chromatography system at any one time giving rise to complex spectra. Furthermore, mass spectrometry cannot tell how many possible structures are made up of the same elements (isobars), based purely on their m/z value. Ion mobility separation or tandem fragmentation methods may be used to produce product ions that help differentiate structures.
Advantages of mass spectrometry include high sensitivity (allowing detection of low abundant glycans), high throughput, detailed structural information, and compatibility with many ionization techniques (such as electrospray ionization which can be coupled with liquid chromatography or matrix-assisted laser desorption which is useful for analyzing dried samples). Soft ionization methods allow labile glycosidic bonds to survive the ionization process to the gas phase, so that glycan structures do not need to be chemically released from the protein or other molecules they are bound to prior to analysis. Mass spectrometry allows analysis of both native glycans and permethylated glycans.
Simple mass spectrometry lacks resolving power for several reasons. Ionization suppression can occur, such that high abundance molecules will mask analytes of interest. Additionally, MS is unable to distinguish isomers. MS analysis of glycan mixtures by direct infusion produces a spectrum that is difficult to deconvolute due to these factors as well as coelution of glycans that have the same mass. Also there is often bias introduced by ionization efficiencies of different classes of glycans. Differences in ionization efficiencies often lead to an inability to determine relative abundances. Glycans should therefore be separated before MS analysis. Separation before MS allows for better assignment of structure due to association of chromatographic characteristics with MS data. It also simplifies the MS spectrum by separating compounds.
Table 1 Limitations of Mass Spectrometry and Mitigation Strategies
| MS Limitation | Manifestation | Complementary Solution |
| Ionization suppression | Signal dominance by abundant species | Chromatographic separation before MS |
| Isomeric ambiguity | Identical masses for different structures | Ion mobility or LC separation |
| Quantitative bias | Variable ionization efficiency | Internal standard normalization |
| Spectral complexity | Overlapping peaks in mixtures | Pre-fractionation by chromatography |
Four distinct dimensions of mass spectrometry exist for the analysis of glycans. The first dimension involves measuring molecular weight. The second dimension separates glycans by tandemly fragmenting them in the mass spectrometer. Glycan fragments can provide details on glycan connectivity and sequence. Thirdly, glycans can be separated in the gas phase by their shape (structural isomers) using ion mobility technology. Ultimately, each dimension measures a different aspect of glycan structure. While mass gives information on glycan composition, fragmentation sequences and ion mobility data gives information on structure. Selecting the correct MS dimension will depend on the goals of the study.
Mass information obtained from single-stage analysis can provide the molecular weight of intact glycans. From accurate mass measurement, monosaccharide composition can be deduced by exploiting known mass differences between hexoses, N-acetylhexosamines, deoxyhexoses, and sialic acids. High-resolution instruments allow separation of isobaric compositions that vary slightly in elemental composition. Isotopic envelope can determine number of carbons and can provide further structural information. It should be noted that mass analysis cannot differentiate structural isomers nor determine linkage position. Chromatographic retention correlations or additional fragmentation experiments are needed to make confident structural assignments.
Structural characterization of glycans by tandem mass spectrometry (MS/MS) is accomplished by fragmenting the selected precursor ions to generate structural data. Fragment ions observed in the product ion spectrum provide sequence information, branching information, and sugar connectivity. Glycosidic bond cleavages, produced during collision-induced dissociation (CID), show sequence information of monosaccharide residues. Cross-ring cleavages produced during higher-energy collisional dissociation (HCD) or electron-based dissociation (ECD) methods provide linkage position information. Either fragmentation technique can be used depending on whether sequence or linkage information is desired. Using both fragmentation techniques can be complimentary for structure elucidation of complex glycans.
Ion mobility MS separates ions in a drift cell based on their collision cross-section (CCS). The separation provides another dimension that can differentiate isomeric glycans (those that have the same mass but different structures) because of their different shapes in the gas phase. Collision cross-section may allow differentiation between linkage isomers, anomers and other conformational isomers that cannot be separated chromatographically or do ambigious mass spectra. Structures that pack together tightly will travel through the drift tube faster than more expanded ion shapes. Combining ion mobility with retention time and mass information allows for greater structural fidelity.
The three MS dimensions serve different purposes but together provide all necessary information for glycan characterization that is superior to each method used individually. The accurate mass obtained from intact mass analysis is used to determine composition and to filter candidate structures by database search. Isomeric structures filtered by IMS that have the same mass are distinguished from each other using tandem fragmentation. Tandem MS can also provide structural characteristics such as sequence and connectivity of glycans. By combining all three MS dimensions (sequentially or on a single instrument), structural information can be obtained with reduced ambiguity to allow confident glycan identification.
Ionization methods are the methods used to transfer ions from the condensed phase to the gaseous phase in mass spectrometry. The ionization method can have a large effect on how many ions get transferred into the gas phase as well as the charge state distribution of the ions and the structural integrity of those ions. Electrospray ionization or MALDI are often used with glycan analysis. The difference between these two types of ionization will determine what type of separation technique can be used with the mass spectrometry, how complex the spectrum will be, and what types of glycans can be analyzed. Differences between electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI).
Direct analysis of glycans from solution is possible with electrospray ionization, which tends to produce multiply charged ions allowing detection of higher-mass glycans and compatibility with online liquid chromatography separation techniques. Multiplying the charge state of the ions (typically with solution-phase aerosol charging) allows for lower m/z to be detected which corresponds to higher oligosaccharide masses. Electrospray ionization is considered to be a soft ionization technique; however, labile sialic acid residues can fragment in-source under typical electrospray ionization operating conditions. Careful tuning of the source parameters can minimize this in-source fragmentation.
MALDI-MS involves irradiation with pulsed laser light of glycan and matrix co-crystallized mixtures to produce ions, mainly singly charged ions, that are typically easier to interpret and allows for high-throughput analysis. MALDI is a solid phase technique which traps analytes in matrices that crystallize and absorb UV radiation used to cause ionization while minimizing glycosidic bond cleavage. Since MALDI transfers more internal energy during desorption, there is increased potential for metastable decay as well as loss of acid labile groups from the source compared to electrospray ionization typically requiring derivatization of these labile groups before analysis.
Detection sensitivity and quantitation are strongly dependent on the ionization technique used since different glycans ionize with different efficiencies and ionization suppression may occur. Response factors vary with electrospray ionization depending on whether the glycan is acidic or neutral and ion suppression may occur in samples with more complex matrices, obscuring less abundant components. Matrix-assisted laser desorption ionization sensitivity relies on uniform crystal formation of the matrix and analyte mixture, leading to signal variability across the surface.
Mass analyzers are the detection and measurement devices that make up glycan profiling platforms. These separate ions of different mass-to-charge ratios so glycans can be identified and characterized based on their carbohydrates' masses. Mass analyzers provide resolution, mass accuracy and sensitivity limits that are determined by the analyzer technology. These factors dictate what glycans (small oligosaccharides, highly charged glycans or complex multi-antennary glycans) can be routinely profiled or structurally elucidated. Time-of-flight, orbital trapping and ion cyclotron resonance mass analyzers are just some platforms with differing sensitivities and specificities.
Fig. 2 Sample preparation workflow.2,5
TOF analyzers determine ion masses by measuring the time required for ions to travel through field-free regions; ions with greater velocity reach the detector first. Ions of lower mass attain higher velocities than heavier ions. Quadrupole TOF instruments allow precursor ion selection (usually a quadrupole mass analyzer with a TOF mass analyzer) for selective analysis of specific analytes in complex mixtures with high sensitivity and resolution appropriate for glycan analysis. They are very fast and can be used to analyze native glycans as well as derivatized glycans. Resolution is high enough to separate glycans with isobaric compositions. Structures can be elucidated by tandem fragmentation (MS/MS). Acquisition speed permits coupling with liquid chromatography separation techniques or high-throughput screening methods.
Orbitrap mass analyzers operate by trapping ions in an electrostatic field. Their m/z is determined by measuring the frequency of oscillations. Ions with higher m/z ratios oscillate slower. Orbitraps can achieve high resolution by observing oscillations for longer periods of time. Fourier transform ion cyclotron resonance (FTICR) mass spectrometers contain magnets that force ions into cyclotron motion. This allows for the highest possible mass resolution commercially available. Orbitraps and FTICRs detect image current and perform a Fourier transform to produce a mass spectrum. Their high resolution allows for very high accuracy mass measurements. This allows one to make confident assignments of elemental composition and differentiate between isobaric species that have slight differences in exact mass. Applications of these types of analyzers include analysis of glycoproteins as well as when structural characterization requires high resolution mass measurements.
Resolution refers to the ability to separate peaks that are close in mass. The higher the resolution the easier it is to resolve isobaric glycans, as well as assigning the correct charge state. Mass accuracy refers to how close the observed mass is to the theoretical mass. With high mass accuracy (below parts-per-million, or ppm), elemental composition of glycans can be determined with high confidence, as well as analysis of isotopic fine structure. Dynamic range refers to the range between the largest signal and the smallest signal that can be detected. With good dynamic range, rare glycoforms can be quantified in the presence of highly abundant glycoforms. Trade-offs are sometimes necessary between these performance measures. For example, extremely high resolution may come at the cost of scan speed or sensitivity. This could decrease dynamic range when analyzing biological samples with a large mass range.
Mass spectrometry interpretation is the cognitive task of assigning biological significance to masses and fragmentation spectra. It involves matching measured accurate mass with predicted composition, analyzing fragmentation spectra to determine sequence/connectivity and to gain confidence in a structural assignment, and reporting structural assignments with their corresponding confidence level. Interpretation can be complicated by non-unique masses that match multiple possible structures and by fragmentation spectra that are consistent with multiple structures.
Glycan composition assignment requires comparing experimental m/z values to predicted values based on the known composition of monosaccharide subunits such as hexose, N-acetylhexosamine, fucose, and sialic acid. Instruments capable of providing exact mass can distinguish between different compositions that have the same nominal mass (isobaric compositions), by determining their elemental composition (number of each type of residue). Glycan composition assignment reduces the possible structures to those that fit a particular molecular formula. This formula is then treated as a hypothesis to be tested either by MS/MS fragmentation or orthogonal separation methods.
Limitations of composition-only assignments are introduced by the fact that different glycans may have the same composition but differ in linkage positions, anomeric states and branching patterns. Elemental compositions are indistinguishable by mass spectrometry. Composition assignments are therefore not specific enough to assign activity or functionality. In addition, pairs of monosaccharides can have the same mass. For example fucose+N-glycolylneuraminic acid and hexose+N-acetylneuraminic acid share the same mass. Accurate mass can not distinguish between these examples either. This limitation can be overcome using tandem MS or chromatographic separation techniques for confident structural assignments beyond elemental composition.
Annotation errors can occur because of incorrect choice of monoisotopic peak (the software assigns the wrong isotope peak as the monoisotopic peak mass assignment), causing systematic errors in mass and incorrect elemental composition assignment, assigning of sodium, potassium or ammonium adducts as protonated species (shift in mass leading to wrong elemental formula assignment), false positive hits generated by software algorithm searching large glycan databases against noisy spectra when allowing too many unrealistic modifications per monosaccharide or wrong assignment of peak charge state(s). Spectra containing in-source fragments (which appear as artificial peaks in the spectrum) may lead to assignment of these fragments as species that were not present. It can also occur due to failure to account for biosynthetic rules which may eliminate chemically impossible structures.
MS/MS analysis of glycans using tandem mass spectrometry offers an unambiguous method for glycan sequencing, branching and connectivity information via gas phase fragmentation of selected precursor ions. Product ion spectra obtained from tandem MS experiments will reveal diagnostic fragments which indicate the structural relationships of carbohydrates that are not determined by intact mass. Selective isolation of glycans and dissociation of the ions allows tandem mass spectrometry to determine structure.
Fragmentation of glycans can happen either by glycosidic cleavages or cross-ring cleavages. Glycosidic cleavages cleave the linkage between two monosaccharides leaving the rings intact, and can produce either B-type (fragmentation at non-reducing end) or Y-type fragments (fragmentation at reducing end). Cross-ring cleavages on the other hand, break within the ring and can result in either A-type or X-type fragments which tell you about the linkage based on which ring was cleaved. Branching points and unique linkages are determining factors in fragment abundance.
Collision-induced dissociation relies on low energy collisions of precursor ions with neutral gas molecules to produce activation energy. Collision-induced dissociation tends to produce cleavages of the glycosidic bonds which can be helpful in sequencing glycans, but rarely produces cross-ring fragments needed for linkage analysis. Higher-energy collisional dissociation (HCD) involves higher collision energies which leads to further fragmentation including cross-ring cleavages. However, labile glycans such as sialic acids may be lost during this process. Electron-transfer dissociation causes fragmentation through radical based mechanisms. This helps maintain glycan modifications and produces fragments that can provide orthogonal information to fragmentation caused by collision.
Diagnostic ions have unique structures that allow certain glycan features to be identified with certainty. For example, B ions that contain non-reducing terminal fragments can tell you whether a terminal epitope, such as a sialic acid or fucose residue, is present. Y ions that contain the reducing end can indicate what monosaccharide residues are present and their sequence along with branching pattern. Diagnostic information about linkage can be obtained by examining cross-ring A ions. Mass differences between cross-ring ions are diagnostic of the linkage position (how sugars are attached to each other). These observations must be pieced together by correlating multiple fragment ions.
Assignment of tandem MS spectra is challenging because many cleavages can occur, leading to a family of related fragment ions. Glycans with different linkages may produce indistinguishable fragments and therefore cannot be distinguished based on fragmentation alone. This may occur with glycosidic bond position isomers, or anomeric mixtures. Furthermore, there are currently no exhaustive lists of fragment ions that take glycans into account. Fragmentation efficiencies can also vary depending on the glycan structure, and noise peaks can further compolicy correctly between sequences. All of these factors make expert review and interpretation necessary.
Table 2 Challenges in Glycan MS/MS Interpretation
| Challenge Category | Specific Issue | Impact on Analysis | Mitigation Approach |
| Spectral complexity | Overlapping fragment series | Ambiguous peak assignment | High-resolution instruments and careful validation |
| Isomeric ambiguity | Similar fragmentation patterns | Uncertain structural differentiation | Multiple fragmentation methods or orthogonal separation |
| Database limitations | Incomplete fragment libraries | Reduced automated identification | Expert manual interpretation and method standardization |
Ion mobility mass spectrometry (IMS-MS) is another dimension that can be added to obtain structural information about glycans. It separates ions in the gas phase according to their collisional cross-section. This adds shape-selective separation to mass-selective identification. This orthogonal separation adds confidence to glycan identification. Ion mobility helps resolve isomeric glycans that have the same mass but may have different structures.
Ion mobility separation forces ions through a buffer gas within a drift region using an electric field. Mobility is influenced by the frequency of collision with neutral gas molecules in the drift region. The smaller or more compact an ion is, the fewer number of collisions it experiences with neutral gas molecules resulting in a faster drift through the drift region than larger or more elongated structures. Drift tube ion mobility spectrometry uses electric fields to measure drift times that are linearly related to collision cross-section using the Mason-Schamp equation. Traveling wave ion mobility uses voltage waves moving through the separation region to accelerate ions. Arrival times can then be calibrated using standards of known mobility to give collision cross-section values.
Collision cross sections (CCS) values are intrinsic molecular properties that reflect differences in the 3-dimensional structures of glycan isomers in the gas phase. Glycan isomers that differ by α vs β anomeric configuration or position isomers (e.g. 1→3 vs 1→4 linkage) will have different CCS values. This difference arises from the extended conformation of β anomers which results in larger CCS values compared to α anomers and the different folded structures that glycans adopt depending on linkage position. These differences in CCS can be leveraged to confidently identify glycan isomers without extensive fragmentation.
Ion mobility MS strengths include fast separation times in the millisecond range, ease of integration with current mass spectrometric technologies and providing resolution of chromatographic co-eluting isomers. Reducing spectral complexity by resolving precursor ions before dissociation allows cleaner MS/MS spectra to be used for structural characterization. Limitations include unresolved isomeric glycans with similar gas phase conformations, challenges in predicting CCS values for certain structures, and mobility region ion losses. Conformational flexibility in larger glycans can also lead to wide at distribution that are difficult to interpret without chromatographic separation.
Quantitation using mass spectrometry-based glycan analysis is complicated due to differences in ionization efficiency, loss on fragmentation, and detector response for each glycan. Therefore normalization during ionization techniques, the use of internal standards, and validation of methods must be considered when quantitating glycans using MS in order to obtain comparable results between samples. Reproducibility must be validated for each run to account for changes between batches of samples. Biologically relevant abundance of analytes determined by MS signals is necessary for comparative purposes as well as for meeting regulatory guidelines.
Signal strengths can differ greatly throughout the glycome. This means that some classes of glycans may generate stronger or weaker signals than expected based on their actual abundance. This quantitative bias can occur if, for example, sialylated glycans respond differently under electrospray ionization conditions than neutral glycans due to differences in charge states or if ionization efficiency decreases with increasing molecular size or susceptibility to in-source fragmentation. These biases are problematic when trying to quantitate relative abundance of glycoforms between samples and standards should be carefully optimized. Response factor corrections may need to be applied.
Isotopic labelling allows for differential analysis of multiple samples as the isotopic labels add or subtract mass to differentiate between multiple samples measured in the same experiment, thus removing any run-to-run differences. Absolute quantitation can be achieved by spiking-in stable isotope-labeled internal standards (SILIS), which can be isotopically labeled glycans themselves, heavy-isotope derivatization reagents or isotopically labeled synthetic bionic glycome libraries. These standards correct for sample loss during preparation and changing degrees of ionization as well as instrument response fluctuations. Full-glycome SILIS that mimic the glycome distribution of the natural sample provide an internal standard that represents the entire structure space, thus allowing more accurate quantitation, especially for low abundant structures that are affected by noise.
Variability at several levels (sample preparation, machine, data processing) needs to be carefully monitored in order to achieve reproducible MS-based glycan quantitation. Samples processed on different MS instrument runs may suffer from batch effects which make comparisons difficult due to global shift in signal intensities or mass calibration. Using QC pools, standards that span batches and randomizing sample injection order allows statistical assessment of batch drift and correction for any systematic errors.
Liquid chromatography–mass spectrometry (LC/MS) takes advantage of both technologies. Liquid chromatography resolves co-eluting isomeric glycans that cannot be distinguished by MS alone. Mass spectrometry identifies specific glycans (where chromatography only gives retention time) and can provide structural information on glycans. Linkages cannot be determined easily but the order of elution of linkage isomers can be determined by LC/MS if they can be chromatographically resolved. In practice, different modes of liquid chromatography can be interfaced to many varieties of mass spectrometry to achieve full structural characterization of glycans.
LC–MS coupling considerations include compatibility of the interface with mobile phase composition and compatibility of the separation conditions with the ionization efficiency. An electrospray interface will tolerate the aqueous-organic gradient that is used for HILIC and PGC separations. Ionization efficiency may benefit from post-column addition of makeup flows on HILIC due to the higher organic content. Due to reversed-phase separations relying on volatile mobile phases for MS detection in general, labeled glycans may be analyzed sensitively following RP separations. Matrix assisted laser desorption interfaces do not require liquid flow through the interface permitting offline coupling of fractions collected from the chromatography onto target plates for analysis.
Separation of isomers prior to MS analysis allows more confident assignment of glycan structures. This is because without chromatographic separation complex MS spectra can result from co-eluting isomeric glycans. Correlation of retention time with that of a known standard or number of Glucose residues is another orthogonal method for identifying glycans. By adding this separation technique fewer interfering isobaric species are present during MS analysis. Glycan ionization can also be improved through separation, as it can decrease ion suppression allowing less abundant glycans to be detected. MS/MS spectra will also be cleaner and contain fragment ions specific to a single glycan structure.
The orthogonal deployment of several LC modes along with MS allows the acquisition of maximal structural information, since different separation mechanisms interrogate glycans based on their physicochemical properties. Thus, while HILIC separations followed by MS can be used to rapidly attain general glycome coverage with available standardized retention databases enabling automation of identification, RP-LC-MS can be employed for more in-depth characterization of labeled glycan isomers due to separation on hydrophobic interactions. Full isomeric characterization, including linkage-specific and anomeric separation can be achieved through coupling with PGC-MS. Utilizing the complementary nature of these platforms, consensus structural assignments with higher confidence can be achieved by integrating data obtained from each platform to allow complete glycan profiling.
Incomplete structural information / identification is one of the major drawbacks of MS-based glycan profiling methods. Some structures can not be fully resolved (eg isomers). Spectra of heterogeneous mixtures can be difficult to interpret. Identification from fragmentation alone can be ambiguous. These are all important considerations when selecting a method that is right for your needs and knowing the limitations of the results.
MS cannot resolve certain glycan structural isomers including stereoisomers, anomers, and linkage position isomers. Structures that have the same mass and break in similar ways upon fragmentation will still be indistinguishable. Although higher resolving power mass analyzers such as high-field trapping instruments can sometimes resolve these structures, as well as ion mobility techniques, there will still be instances where isomers cannot be confidently distinguished. This is especially true for isomers with complex branching or glycans with small conformational differences. Due to this ambiguity one must be careful to present findings with some uncertainty and restrict claims to known structure only when the stereochemistry cannot be determined.
Complex data is produced from MS-based glycan profiling experiments. Glycan signals can have large overlapping isotopes, multiple charge states, and complex fragmentation patterns which cannot easily be interpreted manually. Algorithms are not yet sophisticated enough to handle glycan structure combinations easily. As such results tend to generate possible identifications that have scoring or confidence metrics that need to be verified by researchers. A spectral library for glycans covering all possible glycans does not exist which makes database searching difficult. Glycan structures also often have in-source fragments, adducts and noise peaks which create false positives during data analysis.
Orthogonal confirmation can include retention time correlation with chromatography, binding to glycan-specific antibodies (lectins), cleavage with linkage specific exoglycosidases to confirm expected mass shifts and/or NMR spectroscopy. The former methods can provide strong support for assignments made by mass spectrometry. NMR provides unequivocal assignment of structure including stereochemistry, however due to sensitivity limitations it typically can only be done on purified glycans. Combining orthogonal data can allow high confidence structure assignment suitable for publications and regulatory filings.
Table 3 Orthogonal Validation Strategies
| Validation Technique | Information Provided | Complementary Role | Integration Benefit |
| Chromatography | Retention behavior | Separation-based confirmation | Reduced isomeric ambiguity |
| Lectin binding | Epitope recognition | Biological specificity validation | Functional relevance confirmation |
| Enzymatic digestion | Mass shift patterns | Linkage position verification | Structural corroboration |
| NMR spectroscopy | Complete 3D structure | Definitive stereochemistry | Gold standard confirmation |
MS has been established as one of the key enabling technologies for glycan structural characterization because of its sensitivity, specificity, and ability to convey structural information content. Indeed, for many carbohydrate analysis needs spanning clinical to biopharmaceutical workflows, MS analysis alone is often sufficient for glycan characterization. The combination of MS/MS, and orthogonal separation approaches such as ion mobility constitutes a powerful tool set that can tackle glycan analysis challenges at each level of structural complexity beginning with composition assignments, sequencing information, and isomeric differentiation. Although MS by itself cannot always unambiguously define structures within complex carbohydrate mixtures, techniques such as chromatographic separation, use of exoglycosidase digestion, or ion mobility can increase confidence in glycan identification when coupled with MS analysis. Additionally, ongoing development of ionization methods, mass analyzers, and software for data interpretation will continue to expand the range of carbohydrates that can be readily studied by MS. For these reasons, MS has become more than just a detection platform for glycan analysis, it is now the workhorse for glycan structural characterization. When applied strategically based on experimental goals and in combination with orthogonal confirming methods, MS, MS/MS, and ion-mobility can shift glycan analysis from simple observation to understanding of mechanism.
Mass spectrometry (MS) is central to advanced glycan profiling, enabling high-resolution composition analysis, structural elucidation, and confident differentiation of complex glycan species. However, generating high-quality MS data is only part of the solution. Accurate glycomics analysis requires optimized ionization conditions, appropriate fragmentation strategies, and rigorous data interpretation. Our mass spectrometry-based glycan profiling services integrate MS, MS/MS, and ion mobility technologies to deliver reliable structural and quantitative insight for research, biopharmaceutical development, and quality control applications.
We design tailored MS workflows based on analytical objectives, sample type, and required structural depth. Our capabilities include:
For complex samples—such as monoclonal antibodies, biosimilars, serum glycoproteins, or cell culture supernatants—we optimize:
This integrated approach ensures that glycan MS data reflects true structural diversity rather than analytical artifacts.
Interpreting glycan MS and MS/MS spectra requires expertise in fragmentation pathways, isomer ambiguity, and potential analytical bias. Composition-based assignments alone are insufficient when structural isomers share identical masses. Our data interpretation services include:
For biopharmaceutical applications, we support interpretation of glycosylation as a critical quality attribute (CQA), including comparability assessments and structural confirmation. For research studies, we assist in linking MS-derived glycan patterns to biological function and mechanistic hypotheses. Our goal is to deliver MS-based glycan analysis that is structurally rigorous, reproducible, and aligned with scientific and regulatory expectations.
If you require advanced mass spectrometry-based glycan profiling, LC-MS integration, or expert interpretation of complex MS data, our team provides customized, quality-controlled analytical solutions. Contact us to discuss your sample type, structural resolution requirements, and timeline for comprehensive glycan characterization.
References
