On-line HPLC/ESI-MS separation and characterization of hyaluronan oligosaccharides from 2-mers to 40-mers

Quantitative determination of chondroitin sulfate with various molecular weights in raw materials by pre-column derivatization with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate

A simple and reliable HPLC method was developed for quantification of chondroitin sulfate (CS). The procedure is based on precolumn hydrolysis of CS to liberate galactosamine and subsequent derivatization with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate. Hydrolysis and derivatization conditions were optimized. A linear correlation coefficient of 0.9999 was calculated within the range of 10-1500 μg/mL from the standard curve. The method produces good precision and good accuracy (100.75 % recovery). An advantage over other common methods is its ability to quantify CS of all molecular weights and structures, as evidenced by the determination of CS fractions with narrow molecular weight distributions obtained through depolymerization by different methods, while enzymatic HPLC was proven to be infeasible. Extraction recoveries of CS from monosaccharide mixed samples were > 93 %. The reliability was also validated by a small difference (-1.95 % to 4.12 %) relative to enzymatic HPLC results in analysing representative CS samples of different animal origins and suppliers.

Preparation and antibacterial effect of chitooligosaccharides monomers with different polymerization degrees from crab shell chitosan by enzymatic hydrolysis

This study aimed to explore the structure and antibacterial properties of chitooligosaccharide monomers with different polymerization degrees and to provide a theoretical basis for inhibiting Salmonella infection. Chitosan was used as a raw material to prepare and separate low-molecular-weight chitooligosaccharides. Chitobiose, chitotriose, and chitotetraose were obtained by gradient elution with cation exchange resin. The molecular weights and acetyl groups of the three monomers were determined by matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) and nuclear magnetic resonance (NMR), respectively. Three chitooligosaccharide monomers were used to explore the antibacterial effect on Salmonella. The results showed that the degree of deacetylation of chitosan was 92.6%, and the enzyme activity of chitosanase was 102.53 U/g. Within 18 h, chitosan was enzymatically hydrolyzed to chitooligosaccharides containing chitobiose, chitotriose, and chitotetraose, which were analyzed by thin-layer chromatography (TLC) and MALDI-TOF. MALD-TOF and TLC showed that the separation of monomers with ion exchange resins was effective, and NMR showed that there was no acetyl group. Chitobiose had a poor inhibitory effect on Salmonella, and chitotriose and chitotetraose had equivalent antibacterial effects.

Molecular weight determination of low molecular weight hyaluronic acid and chondroitin sulfate by gel permeation chromatography

Low molecular weight (LWM) hyaluronic acid (HA) and chondroitin sulfate (CS) have a wide range of applications. To determine their molecular weight (MW), we developed a gel permeation chromatography (GPC) method, which is calibrated based on serrated peaks in the chromatograms. MW calibrants were obtained from the enzymolysis of HA and CS using hyaluronidase. The identical structure of calibrants and samples ensured the soundness of the method. The highest confidence MWs were up to 14,454 and 14,605 for HA and CS, respectively, and the standard curves showed very high correlation coefficients. Thanks to the changeless relationship between MW and its contribution to the GPC integral, the second calibration curves could be derived via one GPC column, also embodied correlation coefficients of >0.9999. The discrepancies of MW values were minuscule, and the measurement of a sample could be conducted in <30 min. The accuracy of the method was verified using LWM heparins, and the measured Mw values showed a 1.2 %-2.0 % error relative to pharmacopeia results. The MW results obtained for LWM-HA and LWM-CS samples were also consistent with the results obtained by multiangle laser light scattering. The method was also verified be able to measure the very low MWs.

Methods for isolating and analyzing physiological hyaluronan: a review

The carbohydrate hyaluronan (or hyaluronic acid, HA) is found in all human tissues and biofluids where it has wide-ranging functions in health and disease that are dictated by both its abundance and size. Consequently, hyaluronan evaluation in physiological samples has significant translational potential. Although the analytical tools and techniques for probing other biomolecules such as proteins and nucleic acids have become standard approaches in biochemistry, those available for investigating hyaluronan are less well established. In this review, we survey methods related to the assessment of native hyaluronan in biological specimens, including protocols for separating it from biological matrices and technologies for determining its concentration and molecular weight.

A guide to hyaluronan and related enzymes in breast cancer: biological significance and diagnostic value

Hyaluronan (HA) is a unique nonsulfated glycosaminoglycan that contributes to breast cancer cells growth and functional properties, including cell migration, invasion, adhesion, as well as tumor-associated angiogenesis in different stages of breast cancer progression and especially metastasis. Latest data show that the levels of HA and/or low molecular mass HA in blood serum and plasma of breast cancer patients may be a useful biomarker for breast cancer prognosis, differential diagnosis, and patients' treatment monitoring. Therefore, the qualitative and quantitative determination of HA in biological samples is an emerging area of research. This review gathers, categorizes, and sums up all the currently used methodologies to analyze HA and HA-related enzymes. The advantages, disadvantages, limitations in use, and the information they provide, are critically considered and discussed. Moreover, emphasis is given to the significance of HA determination in breast cancer, as well as of its related enzymes, for diagnosis and prognosis of this type of cancer.

A facile quantification of hyaluronic acid and its crosslinking using gas-phase electrophoresis

We report a facile, high-resolution approach to quantitatively characterize hyaluronic acid (HA) and study its crosslinking reaction using electrospray-differential mobility analysis (ES-DMA). Mobility size distributions, number concentrations, molecular mass distributions, and polydispersity index of HAs were obtained successfully via a rapid analysis by ES-DMA (< 30 min). The limit of detection, the limit of quantification, and the precision of the mobility size measurement achieve 2.5 nm, 4.0 nm, and 0.3 nm, respectively. Size exclusion chromatography (SEC) was employed as an orthogonal approach, showing that the averaged molecular mass and polydispersity index of HA measured by ES-DMA were close to the results of SEC on a semi-quantitative basis. The 1,4-butanediol diglycidyl ether (BDDE)-induced crosslinking of HA was also able to be successfully characterized through a time-dependent study using ES-DMA, which has shown the promise of direct analysis of solution-based reactions. Both the extent and the rate of HA crosslinking (induced by BDDE) were proportional to reaction temperature and concentration ratio of HA to BDDE. The activation energy of the reaction-limited BDDE-induced crosslinking of HA was found to be ≈ 21 kJ/mol. The prototype study demonstrates ES-DMA as a new method for a rapid quantitative characterization of HA and its derivative product and providing a capability of real-time monitoring of the HA crosslinking during formulation process. Graphical abstract.

A Review of the Preparation, Analysis and Biological Functions of Chitooligosaccharide

Chitooligosaccharide (COS), which is acknowledged for possessing multiple functions, is a kind of low-molecular-weight polymer prepared by degrading chitosan via enzymatic, chemical methods, etc. COS has comprehensive applications in various fields including food, agriculture, pharmacy, clinical therapy, and environmental industries. Besides having excellent properties such as biodegradability, biocompatibility, adsorptive abilities and non-toxicity like chitin and chitosan, COS has better solubility. In addition, COS has strong biological functions including anti-inflammatory, antitumor, immunomodulatory, neuroprotective effects, etc. The present paper has summarized the preparation methods, analytical techniques and biological functions to provide an overall understanding of the application of COS.

Label-free analysis of physiological hyaluronan size distribution with a solid-state nanopore sensor

Hyaluronan (or hyaluronic acid, HA) is a ubiquitous molecule that plays critical roles in numerous physiological functions in vivo, including tissue hydration, inflammation, and joint lubrication. Both the abundance and size distribution of HA in biological fluids are recognized as robust indicators of various pathologies and disease progressions. However, such analyses remain challenging because conventional methods are not sufficiently sensitive, have limited dynamic range, and/or are only semi-quantitative. Here we demonstrate label-free detection and molecular weight discrimination of HA with a solid-state nanopore sensor. We first employ synthetic HA polymers to validate the measurement approach and then use the platform to determine the size distribution of as little as 10 ng of HA extracted directly from synovial fluid in an equine model of osteoarthritis. Our results establish a quantitative method for assessment of a significant molecular biomarker that bridges a gap in the current state of the art.

Characterisation of separated end hyaluronan oligosaccharides from leech hyaluronidase and evaluation of angiogenesis

Hyaluronan oligosaccharides (o-HAs), especially saturated o-HAs, have attracted intensive attention due to their potential applications in medical treatments. In this study, the hydrolysis process of leech hyaluronidase (LHase) towards the hyaluronan was investigated by HPLC and HPLC/ESI-MS. The proportions of hyaluronan tetrasaccharide (HA4) with hexasaccharide (HA6), end products, were illustrated to have a relationship with the amount of LHase. Higher yield of HA4 was achieved with higher activity of LHase. After optimisation of the packing resin and operation parameters (balanced pH, elution concentration, elution volume and elution flow rate), the highly pure HA4 and HA6 were efficiently separated and prepared by combining ion exchange Q-Sepharose Fast Flow and size exclusion column chromatography. Compared with o-HAs (average Mr of 4000 Da), HA4 and HA6 were demonstrated to show higher activity for promoting angiogenesis, which was similar with the corresponding HA4 and HA6 produced by bovine testicular hyaluronidase. The pure HA4 and HA6 that prepared from LHase will attract intensive studies and be used in potential applications in near future.

The Content and Size of Hyaluronan in Biological Fluids and Tissues

Hyaluronan is a simple repeating disaccharide polymer, synthesized at the cell surface by integral membrane synthases. The repeating sequence is perfectly homogeneous, and is the same in all vertebrate tissues and fluids. The polymer molecular mass is more variable. Most commonly, hyaluronan is synthesized as a high-molecular mass polymer, with an average molecular mass of approximately 1000–8000 kDa. There are a number of studies showing increased hyaluronan content, but reduced average molecular mass with a broader range of sizes present, in tissues or fluids when inflammatory or tissue-remodeling processes occur. In parallel studies, exogenous hyaluronan fragments of low-molecular mass (generally, <200 kDa) have been shown to affect cell behavior through binding to receptor proteins such as CD44 and RHAMM (gene name HMMR), and to signal either directly or indirectly through toll-like receptors. These data suggest that receptor sensitivity to hyaluronan size provides a biosensor of the state of the microenvironment surrounding the cell. Sensitive methods for isolation and characterization of hyaluronan and its fragments have been developed and continue to improve. This review provides an overview of the methods and our current state of knowledge of hyaluronan content and size distribution in biological fluids and tissues.

Determination of hyaluronan molecular mass distribution in human breast milk

Hyaluronan (HA) in human milk mediates host responses to microbial infection via TLR4- and CD44-dependent signaling. Signaling by HA is generally size specific. Because pure HA with average molecular mass (M) of 35 kDa can elicit a protective response in intestinal epithelial cells, it has been proposed that human milk HA may have a bioactive low-M component. Here we report the size distribution of HA in human milk samples from 20 unique donors. A new method for HA analysis, employing ion exchange (IEX) chromatography to fractionate HA by size and specific quantification of each size fraction by competitive enzyme-linked sorbent assay (ELSA), was developed. When separated into four fractions, milk HA with M⩽20 kDa, M∼20 to 60 kDa, and M∼60 to 110 kDa comprised averages of 1.5, 1.4, and 2.0% of the total HA, respectively. The remaining 95% was HA with M⩾110 kDa. Electrophoretic analysis of the higher M HA from 13 samples showed nearly identical M distributions, with an average M of approximately 440 kDa. This higher M HA component in human milk is proposed to bind to CD44 and to enhance human beta defensin 2 (HBD2) induction by the low-M HA components.

Determination of sodium hyaluronate in pharmaceutical formulations by HPLC-UV

A liquid chromatography (HPLC) method with UV detection was developed for determination of sodium hyaluronate in pharmaceutical formulation. Sodium hyaluronate is a polymer of disaccharides, composed of d-glucuronic acid and d-N-acetylglucosamine, linked via alternating β-1, 4 and β-1, 3 glycosidic bonds. Being a polymer compound it lacks a UV absorbing chromophore. In the absence of a UV absorbing chromophore and highly polar nature of compound, the analysis becomes a major challenge. To overcome these problems a novel method for the determination of sodium hyaluronate was developed and validated based on size exclusion liquid chromatography (SEC) with UV detection. An isocratic mobile phase consisting of buffer 0.05 M potassium dihydrogen phosphate, pH adjusted to 7.0 using potassium hydroxide (10%) was used. Chromatography was carried out at 25 °C on a BioSep SEC S2000, 300 mm×7.8 mm column. The detection was carried out using variable wavelength UV-vis detector set at 205 nm. The compounds were eluted isocratically at a steady flow rate of 1.0 mL/min. Sodium hyaluronate retention time was about 4.9 min with an asymmetry factor of 1.93. A calibration curve was obtained from 1 to 38 g/mL (r>0.9998). Within-day % RSD was 1.0 and between-day % RSD was 1.10. Specificity/selectivity experiments revealed the absence of interference from excipients, recovery from spiked samples for sodium hyaluronate was 99-102. The developed method was applied to the determination of sodium hyaluronate in pharmaceutical drug substance and product.

On-line separation and characterization of hyaluronan oligosaccharides derived from radical depolymerization

Hydroxyl radicals are widely implicated in the oxidation of carbohydrates in biological and industrial processes and are often responsible for their structural modification resulting in functional damage. In this study, the radical depolymerization of the polysaccharide hyaluronan was studied in a reaction with hydroxyl radicals generated by Fenton Chemistry. A simple method for isolation and identification of the resulting non-sulfated oligosaccharide products of oxidative depolymerization was established. Hyaluronan oligosaccharides were analyzed using ion-pairing reversed phase high performance liquid chromatography coupled with tandem electrospray mass spectrometry. The sequence of saturated hyaluronan oligosaccharides having even- and odd-numbers of saccharide units, afforded through oxidative depolymerization, were identified. This study represents a simple, effective 'fingerprinting' protocol for detecting the damage done to hyaluronan by oxidative radicals. This study should help reveal the potential biological outcome of reactive-oxygen radical-mediated depolymerization of hyaluronan.

High-resolution separation of homogeneous chitooligomers series from 2-mers to 7-mers by ion-exchange chromatography

Highly purified chitooligomers with single degree of polymerization are of significance for studying bioactivity of chitooligomers. However, there are few reports on high-resolution preparative separation of chitooligomers, especially for those oligomers with degree of polymerization higher than 4. This study developed a high-resolution chromatography for the preparative separation of a pure fully deacetylated chitooligomer series. A glucosamine oligomer mixture with low degree of polymerization was prepared by acid hydrolysis of a highly deacetylated chitosan. Then, six fractions were separated from the prepared oligomer mixture by ion-exchange chromatography and analyzed by HPLC and ESI/MS, which primarily contained glucosamine dimers, trimers, tetramers, pentamers, hexamers, and heptamers, respectively, with chromatographic purities over 98% for dimers to hexamers and a purity of 93% for heptamers. The yields of a single round of separation were 75, 60, 60, 55, 35, and 20 mg for glucosamine dimers, trimers, tetramers, pentamers, hexamers, and heptamers, respectively. Furthermore, a chromatographic separation model for GlcN homomers was established. The capacity factor (k) of glucosamine oligomers and their degrees of polymerization (DPs) exhibited a good correlation, lnk = 0.786 + 0.846 lnDP, (R(2) = 0.997). Based on this equation, glucosamine octamers are expected to be separated by this system.

Identification, characterization, and molecular cloning of a novel hyaluronidase, a member of glycosyl hydrolase family 16, from Penicillium spp

Hyaluronidase (HAase) activity was detected in the culture supernatants of Penicillium purpurogenum and Penicillium funiculosum. The HAase from Penicillium spp. (HAase-P) was a hyaluronate 4-glycanohydrolase, which catalyzed the endolytic hydrolysis of the β-1,4 glycosidic linkage, as do vertebrate HAases. The gene encoding HAase-P was cloned and expressed in Escherichia coli. According to homology analyses of the deduced amino acid sequences, HAase-P is not classified into any of the known HAase groups, but belongs to glycoside hydrolase family 16, which includes endo-β-1,3(4)-glucanase. Regarding the substrate specificities, no chondroitinase and glucanase activities were detected. Judging from homology analyses and enzymatic properties, HAase-P seems to be a new type of HAase.

High-performance liquid chromatography-mass spectrometry for mapping and sequencing glycosaminoglycan-derived oligosaccharides

Glycosaminoglycans (GAGs) have proven to be very difficult to analyze and characterize because of their high negative charge density, polydispersity and sequence heterogeneity. As the specificity of the interactions between GAGs and proteins results from the structure of these polysaccharides, an understanding of GAG structure is essential for developing a structure-activity relationship. Electrospray ionization (ESI) mass spectrometry (MS) is particularly promising for the analysis of oligosaccharides chemically or enzymatically generated by GAGs because of its relatively soft ionization capacity. Furthermore, on-line high-performance liquid chromatography (HPLC)-MS greatly enhances the characterization of complex mixtures of GAG-derived oligosaccharides, providing important structural information and affording their disaccharide composition. A detailed protocol for producing oligosaccharides from various GAGs, using controlled, specific enzymatic or chemical depolymerization, is presented, together with their HPLC separation, using volatile reversed-phase ion-pairing reagents and on-line ESI-MS structural identification. This analysis provides an oligosaccharide map together with sequence information from a reading frame beginning at the nonreducing end of the GAG chains. The preparation of oligosaccharides can be carried out in 10 h, with subsequent HPLC analysis in 1-2 h and HPLC-MS analysis taking another 2 h.

Improved separation and characterization of lipopolysaccharide related compounds by reverse phase ion pairing-HPLC/electrospray ionization-quadrupole-mass spectrometry (RPIP-HPLC/ESI-Q-MS)

A new approach for the separation and inline characterization of lipopolysaccharide (LPS) related compounds has been developed. The separation was based on the difference in the number of charged phosphate and ethanolamine groups, as non-stoichiometric substituents, on the polysaccharide backbone, and was achieved with reverse phase ion-pairing chromatography (RPIP-HPLC). Tributylamine was used as an ion-pair reagent. In the conditions used in this study, tributylammonium then binds to the LPS related compounds through the negatively charged phosphate groups. This changes the hydrophobicity of the analytes at different positions and allows for separation based on both the number and position of the substituents on the analyte. The RPIP-HPLC was found to be effective for the separation of the O,N-deacylated derivative (deON) and polysaccharide portion (PS) from the LPS of Escherichia coli C strain. Post-column fluorescence derivatization (FLD), using sodium periodate and taurine, was used to detect the separated LPS related species. On the other hand, the separated species were also detected by direct infusion into the ESI-Q-MS using a volatile ammonium acetate buffer rather than the more traditional potassium phosphate buffer. The signal to noise ratio (S/N ratio) was low for the total ion chromatogram, however, high S/N ratios as well as good resolution were attained by selected ion monitoring (SIM) using m/z numbers corresponding to species with different numbers of non-stoichiometric substituents. Five species for deON and ten species for PS were clearly identified on the SIM chromatogram on the RPIP-HPLC/ESI-Q-MS. Accordingly, the present method allows for the effective separation and inline identification of the species corresponding to the diverse non-stoichiometric substitutions in LPS related compounds.

Structural analysis of chondroitin sulfate from Scyliorhinus canicula: a useful source of this polysaccharide

Chondroitin sulfate (CS), a constituent of proteoglycans, is a key component of the connective tissues and it is widely used as a precautionary drug for joint diseases; for this reason, the increased demand of this polysaccharide has posed the problem to identify new and secure sources of this product. In this context, CS from the cartilage of the lesser spotted dogfish (Scyliorhinus canicula, a cartilaginous fish) was isolated and investigated through chemical and spectroscopical techniques. The structural elucidation was performed on the entire polysaccharide and confirmed analyzing the products obtained via ABC lyase treatment. As a result, its compositional analysis disclosed the occurrence of CS-A, CS-C, CS-D, and CS-0S motifs in the ratio of 41, 32, 19.8, and 8.2%, respectively. Additionally, two different glycopeptides were isolated and characterized via NMR, providing information on the linkage oligosaccharide region joining the glycosaminoglycan chain to the core protein. Therefore, chondroitin sulfate from Scyliorhinus canicula appears very similar to that isolated from shark, a cartilaginous and taxonomically related fish, with the main difference residing in the major percentage of the CS-A motif. In the light of the results obtained, Scyliorhinus canicula chondroitin sulfate possesses a chemical structure compatible for the formulation of commercial and pharmaceutical products.

Mass spectrometry for the characterization of unsulfated chondroitin oligosaccharides from 2-mers to 16-mers. Comparison with hyaluronic acid oligomers

This study reports for the first time the complete liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS) and tandem mass spectrometry (MS/MS) analyses performed in negative ion mode of saturated unsulfated chondroitin oligosaccharides up to 16-mers and comparison with hyaluronic acid (HA) oligomers differing only in the nature of the hexosamine residue. MS/MS of the chondroitin disaccharide on the singly charged precursor at m/z 396.1 afforded a glycosidic cleavage C1 product ion at m/z 192.9. In the tetrasaccharide, C2 (m/z 396.0) and C3 (m/z 572.0) product anions were generated by glycosidic cleavage. A C5 [M-2H]2- product ion at m/z 475.1 was generated by the glycosidic cleavage of the hexasaccharide, and a C7 ion (m/z 664.6, charge state of -2) was produced from the octasaccharide. The same fragmentation pattern of deprotonated oligomers was observed for the largest oligosaccharides, from 10- to 16-mers. There has been no previous report of MS/MS spectra for unsulfated chondroitin oligomers of these sizes. Unsulfated saturated chondroitin oligosaccharides with x-mer units and larger than a tetrasaccharide dissociate to almost exclusively form CX-1-type ions. Saturated HA oligomers also afforded the same fragmentation pattern as deprotonated oligomers by ESI-MS and MS/MS analyses. Thus, under the experimental conditions used in the current study, we were unable to distinguish between unsulfated chondroitin and HA.

Capillary electrophoresis of complex natural polysaccharides

Complex natural polysaccharides, glycosaminoglycans (GAGs), are a class of ubiquitous macromolecules that exhibit a wide range of biological functions and participate and regulate multiple cellular events and (patho)physiological processes. They are generally present either as free chains (hyaluronic acid and bacterial acidic polysaccharides) or as side chains of proteoglycans (PGs; chondroitin/dermatan sulfate, heparin/heparan sulfate, and keratan sulfate) and are most often found in cell membranes and in the extracellular matrix. The recent emergence of modern analytical tools for their study has produced a virtual explosion in the field of glycomics. CE, due to its high resolving power and sensitivity, has been useful in the analysis of intact GAGs and GAG-derived oligosaccharides and disaccharides affording concentration and structural characterization data essential for understanding the biological functions of GAGs. In this review, novel off-line and on-line CE-MS and MS/MS methods for screening of GAG-derived oligosaccharides and disaccharides will be discussed.

Chondroitin C lyase [4.2.2.] is unable to cleave fructosylated sequences inside the partially fructosylated Escherichia coli K4 polymer

Chondroitin C lyase was demonstrated to be unable to act on fructosylated sequences inside a partially fructosylated polysaccharide having the chondroitin backbone structure, the Escherichia coli K4 polymer, using different analytical approaches. Chondroitin C lyase produced various unsaturated oligosaccharides by acting on an approximately 27%-fructosylated K4 polymer. The online HPLC-ESI-MS approach showed the disaccharide nature of the main species produced by chondroitinase C as DeltaHexA-GalNAc. Furthermore, the non-digested sequences inside the K4 polymer were demonstrated to be oligosaccharides bearing a fructose for each glucuronic acid unit. In fact, unsaturated fully fructosylated oligomers, from tetrasaccharide to decasaccharide (DeltaHexA(Fru)-GalNAc-[GlcA(Fru)-GalNAc](n) with n between 1 and 4), at decreasing percentages, were produced by the enzyme. These results clearly indicate that chondroitinase C cleaved the innermost glucuronic acid-N-acetylgalactosamine linkage without affecting the 1,4 glycosidic linkage between fructosylated glucuronic acid and N-acetylgalactosamine residues, confirming that the 3-O-fructosylation of the GlcA residue renders the polysaccharide resistant to the enzyme action. This novel specific activity of chondroitinase C was also useful for the production of discrete microgram amounts of fully fructosylated oligomers, from 4- to 10-mers, from E. coli K4 for possible further studies and applications.

Mass spectrometry characterization of Escherichia coli K4 oligosaccharides from 2-mers to more than 20-mers

The separation and characterization of oligosaccharides obtained by hyaluronidase [E.C. 3.2.1.35] digestion of Escherichia coli K4 polysaccharide using online high-performance liquid chromatography/electrospray ionization mass spectrometry (HPLC/ESI-MS) are presented. Complete identification and structural information for oligosaccharides containing 2-24 monomers (from 2- to 24-mers) were obtained. In particular, smaller K4 species, from 2-mers to 4-mers, exhibited mainly [M-H](-1) anions, whereas the 6- to 8-mers existed predominantly at the charge state of -2. The K4 oligomers from 10-mers to 14-mers were mainly represented by [M-3H](-3) anions while species from 16- to 20-mers were characterized by a charge state of -4. K4 oligosaccharides from 22- to 24-mers existed as [M-4H](-4) and [M-5H](-5) anions and, for this latter species, ions having a charge state of -6 appeared. For smaller K4 species, in particular from 6-mers to 10-mers, ESI-MS revealed anions related to the loss of one monosaccharide unit from the oligomers due to apparent collisional activation and ion source fragmentation. However, no odd-numbered anions were produced for K4 2/4-mer species or for oligosaccharides greater than 12-mers, while for K4 species 8/10-mer, ESI-MS revealed odd-numbered anions generally in low relative abundance making the interpretation of the spectra easier. The ESI-MS spectra of oligosaccharides separated by online HPLC were applied to the evaluation of the K4 polymerization process, confirming that the addition of fructose units is not critical for chain elongation as variously fructosylated oligomer species were detected directly on the K4 carbohydrate backbone.