Sequence analysis of alginate-derived oligosaccharides by negative-ion electrospray tandem mass spectrometry

Disaggregation and fibrillation during sol-gel transition of alginate hydrogels

The rheological and morphological characteristics of Ca-crosslinked alginate hydrogels with two different M/G ratios, α-L-guluronate (G)-rich and β-D-mannuronate (M)-rich, each with one alginic acid concentration, were investigated. It was found that the stiffness and elasticity of alginate hydrogels are derived from the thickness and density of the fibril network structures. In aqueous alginate solution, ball-like aggregates of alginates are present. Time-resolved small-angle X-ray scattering and time-domain nuclear magnetic resonance measurements suggest that the disaggregation of alginate aggregates and loose fibrillation occur in the early stage of the sol-gel transition. After these induction stage, direct gelation is finally caused by the formation of the egg-box junction. G-rich alginate hydrogel has a higher stiffness and a thicker and denser fibril network structure than M-rich alginate hydrogel. The former also exhibits faster and more significant changes in physical properties during the sol-gel transition.

Synthesis and characterization of silk-poly(guluronate) hybrid polymers for the fabrication of dual crosslinked, mechanically dynamic hydrogels

The rapid ionic crosslinking of alginate has been actively studied for biomedical applications including hydrogel scaffolds for tissue engineering, injectable gels, and 3D bioprinting. However, the poor structural stability of ionic crosslinks under physiological conditions limits the widespread applications of these hydrogels. Moreover, the lack of cell adhesion to the material combined with the inability of proteases to degrade alginate further restrict utility as hydrogel scaffolds. Blends of alginate with silk fibroin have been proposed for improved structural and mechanical properties, but potential phase separation between the hydrophobic protein and the hydrophilic polysaccharide remains an issue. In this study, we demonstrated the synthesis of a hybrid biopolymer composed of a silk backbone with side chains of poly(guluronate) isolated from alginate to introduce rapid ionic crosslinking on enzymatically crosslinked silk-based hydrogels for on-demand and reversible stiffening and softening properties. Dual crosslinked macro- and microgels of silk fibroin-poly(guluronate) (SF-PG) hybrid polymers displayed dynamic morphology with reversible shrinking and swelling behavior. SF-PG hydrogel discs demonstrated dynamic mechanics with compressive moduli ranging from less than 5 kPa to over 80 kPa and underwent proteolytic degradation unlike covalently crosslinked alginate controls. SF-PG gels supplemented with gelatin substituted with tyramine or both tyramine and PG also supported the attachment and survival of murine fibroblasts, suggesting potential uses of these new hydrogels in mammalian cell culture to investigate cellular responses to dynamic mechanics or modeling of diseases defined by matrix mechanics, such as fibrosis and cancer.

Process and applications of alginate oligosaccharides with emphasis on health beneficial perspectives

Alginates are linear polymers comprising 40% of the dry weight of algae possess various applications in food and biomedical industries. Alginate oligosaccharides (AOS), a degradation product of alginate, is now gaining much attention for their beneficial role in food, pharmaceutical and agricultural industries. Hence this review was aimed to compile the information on alginate and AOS (prepared from seaweeds) during 1994-2020. As per our knowledge, this is the first review on the potential use of alginate oligosaccharides in different fields. The alginate derivatives are grouped according to their applications. They are involved in the isolation process and show antimicrobial, antioxidant, anti-inflammatory, antihypertension, anticancer, and immunostimulatory properties. AOS also have significant applications in prebiotics, nutritional supplements, plant growth development and others products.

Production and Characterization of Durvillaea antarctica Enzyme Extract for Antioxidant and Anti-Metabolic Syndrome Effects

In this study, three enzyme hydrolysate termed Dur-A, Dur-B, and Dur-C, were produced from Durvillaea antarctica biomass using viscozyme, cellulase, and α-amylase, respectively. Dur-A, Dur-B, and Dur-C, exhibited fucose-containing sulfated polysaccharide from chemical composition determination and characterization by FTIR analyses. In addition, Dur-A, Dur-B, and Dur-C, had high extraction yields and low molecular weights. All extracts determined to have antioxidant activities by DPPH (2,2-diphenyl-1-picrylhydrazyl), ABTS (2,20-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt), and ferrous ion-chelating methods. All extracts were also able to positively suppress the activities of key enzymes involved in metabolic syndrome: angiotensin I-converting enzyme (ACE), α-amylase, α-glucosidase, and pancreatic lipase. In general, Dur-B exhibited higher antioxidant and higher anti-metabolic syndrome effects as compared to the other two extracts. Based on the above health promoting properties, these extracts (especially Dur-B) can be used as potential natural antioxidants and natural anti-metabolic syndrome agents in a variety of food, cosmetic, and nutraceutical products for health applications.

Digestion characteristics of polysaccharides from Gracilaria lemaneiformis and its interaction with the human gut microbiota

The health effects of polysaccharides have attracted lots of attention, but the exact mechanism remains unclear. This study indicated that polysaccharides from Gracilaria lemaneiformis (GLPs) tolerated the conditions of mouth, stomach, and small intestine, and it reached the colon integrally, where it increased the production of short chain fatty acids, altered the gut microbiota, and especially increased the level of Bacteroides. To explore the underlying mechanism, hundreds of Bacteroides strains were isolated from the human feces and identified by MALDI-TOF/MS. It showed that Bacteroides species profile was different between individuals, revealing an inherent difference in the human gut microbiota. The use of Bacteroides on GLPs was species-dependent, and various small molecular GLPs fragments can be liberated from growth of Bacteroides species. On the other hand, Bacteroides species that unable to grow with GLPs can live in GLPs-derived fragments, forming a GLPs utilization network. It should be noted that small molecular GLPs fragments can be easier to be metabolized by intestinal microbes and have better effect on cellular response. It suggested that the effect of polysaccharides cannot only be attributed to modulation of the gut microbiota, but also associated with the effect of microbial degradation on GLPs own activities.

Alginate oligosaccharides: The structure-function relationships and the directional preparation for application

Alginate oligosaccharides (AOS) are degradation products of alginate extracted from brown algae. With low molecular weight, high water solubility, and good biological activity, AOS present anti-inflammatory, antimicrobial, antioxidant, and antitumor properties. They also exert growth-promoting effects in animals and plants. Three types of AOS, mannuronate oligosaccharides (MAOS), guluronate oligosaccharides (GAOS), and heterozygous mannuronate and guluronate oligosaccharides (HAOS), can be produced from alginate by enzymatic hydrolysis. Thus far, most studies on the applications and biological activities of AOS have been based mainly on a hybrid form of HAOS. To improve the directional production of AOS for practical applications, systematic studies on the structures and related biological activities of AOS are needed. This review provides a summary of current understanding of structure-function relationships and advances in the production of AOS. The current challenges and opportunities in the application of AOS is suggested to guide the precise application of AOS in practice.

Preparation and potential applications of alginate oligosaccharides

Alginate, a linear polymer consisting of β-D-mannuronic acid (M) and α-L-guluronic acid (G) with 1,4-glycosidic linkages and comprising 40% of the dry weight of algae, possesses various applications in the food and nutraceutical industries. However, the potential applications of alginate are restricted in some fields because of its low water solubility and high solution viscosity. Alginate oligosaccharides (AOS) on the other hand, have low molecular weight which result in better water solubility. Hence, it becomes a more popular target to be researched in recent years for its use in foods and nutraceuticals. AOS can be obtained by multiple degradation methods, including enzymatic degradation, from alginate or alginate-derived poly G and poly M. AOS have unique bioactivity and can bring human health benefits, which render them potentials to be developed/incorporated into functional food. This review comprehensively covers methods of the preparation and analysis of AOS, and discussed the potential applications of AOS in foods and nutraceuticals.

Utilizing heterologously overexpressed endo-1,3-fucanase to investigate the structure of sulfated fucan from sea cucumber (Holothuria hilla)

Sea cucumber sulfated fucan (SC-FUC) attracted increasing interests in the recent decades. Endo-1,3-fucanase has been employed in the structural clarification and structure-function relationship investigations of SC-FUC. Nevertheless, the preparation of wild-type endo-1,3-fucanase is costly and time-consuming, which hinders its further utilization. In this study, a heterologously overexpressed endo-1,3-fucanase (FunA) was introduced into structural identification of SC-FUC. FunA was efficiently prepared within one day and utilized in the investigation of sulfated fucan from sea cucumber Holothuria hilla (Hh-FUC). By using enzymatic degradation, glycomics and NMR analysis, the major structure of Hh-FUC was identified to be composed of a tetrasaccharide repeating unit →3-α-l-Fucp-1 → 3-α-l-Fucp2,4(OSO3-)-1 → 3-α-l-Fucp2(OSO3-)-1 → 3-α-l-Fucp2(OSO3-)-1→. Due to the efficient acquisition of enzyme and the superior oligosaccharide recovery, 0.6 mL of E. coli broth and 10 mg of Hh-FUC were sufficient for the structural identification. The results demonstrated the superiority of heterologously overexpressed fucanase over its wild-type enzyme in structural investigation of sulfated fucan.

Cloning, Heterologous Expression, and Characterization of a βκ-Carrageenase From Marine Bacterium Wenyingzhuangia funcanilytica: A Specific Enzyme for the Hybrid Carrageenan-Furcellaran

Carrageenan is a group of important food polysaccharides with high structural heterogeneity. Furcellaran is a typical hybrid carrageenan, which contains the structure consisted of alternative β-carrageenan and κ-carrageenan motifs. Although several furcellaran-hydrolyzing enzymes have been characterized, their specificity for the glycosidic linkage was still unclear. In this study, we cloned, expressed, and characterized a novel GH16_13 furcellaran-hydrolyzing enzyme Cgbk16A_Wf from the marine bacterium Wenyingzhuangia fucanilytica CZ1127. Cgbk16A_Wf exhibited its maximum activity at 50°C and pH 6.0 and showed high thermal stability. The oligosaccharides in enzymatic products were identified by liquid chromatography coupled with high-resolution mass spectrometry (LC-HRMS) and nuclear magnetic resonance (NMR) spectroscopy. It was confirmed that Cgbk16A_Wf specifically cleaves the β-1,4 linkages between β-carrageenan and κ-carrageenan motifs from non-reducing end to reducing end. Considering the structural heterogeneity of carrageenan and for the unambiguous indication of the specificity, we recommended to name the furcellaran-hydrolyzing activity represented by Cgbk16A as “βκ-carrageenase” instead of “furcellaranase”.

Potential applications of alginate oligosaccharides for biomedicine - A mini review

Extensive research on marine algae, especially on their health-promoting properties, has been conducted. Various ingredients with potential biomedical applications have been discovered and extracted from marine algae. Alginate oligosaccharides are low molecular weight alginate polysaccharides present in cell walls of brown algae. They exhibit various health benefits such as anti-inflammatory, anti-microbial, anti-oxidant, anti-tumor and immunomodulation. Their low-toxicity, non-immunogenicity, and biodegradability make them an excellent material in biomedicine. Alginate oligosaccharides can be chemically or biochemically modified to enhance their biological activity and potential in pharmaceutical applications. This paper provides a brief overview on alginate oligosaccharides characteristics, modification patterns and highlights their vital health promoting properties.

Alginate derived functional oligosaccharides: Recent developments, barriers, and future outlooks

Alginate is a biopolymer used extensively in the food, pharmaceutical, and chemical industries. Alginate oligosaccharides (AOS) derived from alginate exhibit superior biological activities and therapeutic potential. Alginate lyases with characteristic substrate specificity can facilitate the production of a broad array of AOS with precise structure and functionality. By adopting innovative analytical tools in conjunction with focused clinical studies, the structure-bioactivity relationship of a number of AOS has been brought to light. This review covers fundamental aspects and recent developments in AOS research. Enzymatic and microbial processes involved in AOS production from brown algae and sequential steps involved in AOS structure elucidation are outlined. Biological mechanisms underlying the health benefits of AOS and their potential industrial and therapeutic applications are elaborated. Withal, various challenges in AOS research are traced out, and future directions, specifically on recombinant systems for AOS preparation, are delineated to further widen the horizon of these exceptional oligosaccharides.

Preparation of alginate oligosaccharides and their biological activities in plants: A review

Alginate oligosaccharide (AOS) is the degradation product of alginates extracted from brown algae. As a multifunctional oligomer, it has attracted widespread attention in plant research. Different methods of preparation generate AOS possessing diverse structural properties, and result in differences in AOS activity. In this review, the methods of preparation and characterization of AOS are briefly summarized, followed by a systematic introduction to the activity and mechanisms of AOS in plants. AOS can act as a growth promoter at different growth stages of plants. AOS also enhances resistance to pathogens, drought, salt, heavy metals and other stressors by triggering plant immunity, exerting bioactivity just like a pathogen-associated molecular pattern. In addition, AOS can regulate ABA biosynthesis and metabolite to preserve fruit quality and enhance shelf life. This review provides a comprehensive summary of the biological activity of AOS in plants, which will support research and the application of AOS treatments for plants in the future.

Elucidation of a Unique Pattern and the Role of Carbohydrate Binding Module of an Alginate Lyase

Alginate oligosaccharides with different degrees of polymerization (DPs) possess diverse physiological activities. Therefore, in recent years, increasing attention has been drawn to the use of enzymes for the preparation of alginate oligosaccharides for food and industrial applications. Previously, we identified and characterized a novel bifunctional alginate lyase Aly7A, which can specifically release trisaccharide from three different substrate types with a unique degradation pattern. Herein, we investigated its degradation pattern by modular truncation and molecular docking. The results suggested that Aly7A adopted a unique action mode towards different substrates with the substrate chain sliding into the binding pocket of the catalytic domain to position the next trisaccharide for cleavage. Deletion of the Aly7A carbohydrate binding module (CBM) domain resulted in a complex distribution of degradation products and no preference for trisaccharide formation, indicating that the CBM may act as a “controller” during the trisaccharide release process. This study further testifies CBM as a regulator of product distribution and provides new insights into well-defined generation of alginate oligosaccharides with associated CBMs.

Electrospray ionization mass spectrometry characterization of ubiquitous minor lipids and oligosaccharides in milk of the camel (Camelus dromedarius) and their inhibition of oxidative stress in human plasma

The aim of this study was to characterize minor lipids in methanol fraction extracted from raw camel milk after loading it on a water-preconditioned short C18 open column and fractionating with a gradient of methanol/water. The C18 column showed high fractionation efficiency of minor lipids, such as glycosphingolipids, lipopolysaccharides, or oligosaccharides, when compared with other constituents, in particular polysaccharides, proteins, and free fatty acids. Liquid chromatography electrospray ionization tandem mass spectrometry in negative ion mode was used to identify 21 new glycosphingolipids, lipopolysaccharides, and oligosaccharides. Electrospray ionization tandem mass spectrometry was qualified to provide relevant data for recognizing the molecular mass, glycosylation sequences, and structure of saccharide moieties for the revealed compounds. The sequence of combinations of one selected lipopolysaccharide, which was considered the backbone of the remaining lipopolysaccharides, was confirmed in a density functional theory study. The obtained results showed that the tested fraction is a rich source of glycosphingolipids, lipopolysaccharides, and oligosaccharides with antioxidant activity.

A simple method to calculate the degree of polymerization of alginate oligosaccharides and low molecular weight alginates

This study presents a quick, simple and accurate method to calculate the degree of polymerization (DP) of alginate oligosaccharides (AOS) and low molecular weight alginates from the concentration of reducing sugar determined by 3,5-dinitrosalicylic acid (DNS) assay. ¹H NMR spectroscopy, mass spectroscopy (MS) and certified standards were used to verify the accuracy of this method, and the results showed DP calculated from DNS assay agreed with the actual DP. This method has great potential to simplify the process of measuring DP of alginate in lab and thus could be incorporated into various researches on alginates in the future. Moreover, similar method could be applied when studying the DP of other oligosaccharides.

Effects of alginate oligosaccharides with different molecular weights and guluronic to mannuronic acid ratios on glyceollin induction and accumulation in soybeans

Alginate oligosaccharides (AOs) are linear oligosaccharides with alternating sequences of mannuronic acid (M) and guluronic acid (G) residues. AOs can be used as a safe elicitor to induce glyceollins, which have many human health benefits, in soybean seeds. In this research, four AO fractions with different chemical structures and molecular weights were separated, purified, and then characterized by NMR spectroscopy and ESI-MS. With a 4,5-unsaturated hexuronic acid residue (△) at the non-reducing terminus, the structures of these four AO fractions were △G, △MG, △GMG and △MGGG, which exhibited glyceollin-inducing activities of 1.2339, 0.3472, 0.6494 and 1.0611 (mg/g dry weight) in soybean seeds, respectively. The results demonstrated that a larger molecular weight or a higher G/M ratio might correlate with a higher glyceollin-inducing activity. Moreover, the alginate disaccharide △G could be introduced as relatively safe and efficient elicitor of high glyceollin content in soybeans.

A novel polysaccharide derived from algae extract inhibits cancer progression via JNK, not via the p38 MAPK signaling pathway

Cancer has long been one of the most malignant diseases worldwide. Processes in cancer cells are often mediated by Jun N-terminal kinase (JNK), p38 mitogen-activated protein kinase (p38 MAPK) and other signaling pathways. Traditional therapies are often problematic. Recently, a novel polysaccharide derived from algae extract was investigated due to the increasing interest in biological activities of compounds from marine organisms. The effect of this novel polysaccharide on human MKN45 gastric carcinoma cells was determined previously. The current aimed to determine whether the polysaccharide affects other types of cancer, and the deeper mechanisms involved in the process. Human MCF-7 breast cancer cells were used to investigate the novel polysaccharide for its role in the cell growth and migration, and determine the mechanisms affected. MTT assay, nuclear staining and fluorescence activated cell sorting analysis demonstrated that the novel polysaccharide reduced the viability of MCF-7 cells by inducing cell apoptosis and arresting the cells at G2/M phase. Results of western blot analysis demonstrated that phosphorylation of JNK and expression of p53, caspase-9 and caspase-3 were upregulated in the polysaccharide-treated MCF-7 cells. SP600125, an inhibitor of JNK, maintained MCF-7 cell viability, prevented cell apoptosis and cycle arrest, and downregulated the polysaccharide-induced protein phosphorylation/expression. However, a migration assay demonstrated that the novel polysaccharide did not change the migration of MCF-7 cells, as well as the expression of p38 MAPK, and matrix metalloproteinase-9 and -2. Taken together, the current study demonstrated that the novel polysaccharide suppressed cancer cell growth, induced cancer cell apoptosis and cell cycle arrest via JNK signaling, but had no effect on cancer cell migration and p38 MAPK signaling.

A Novel Bifunctional Endolytic Alginate Lyase with Variable Alginate-Degrading Modes and Versatile Monosaccharide-Producing Properties

Endo-type alginate lyases usually degrade alginate completely into various size-defined unsaturated oligosaccharide products (≥disaccharides), while exoenzymes primarily produce monosaccharide products including saturated mannuronate (M) and guluronate (G) units and particularly unsaturated Δ units. Recently, two bifunctional alginate lyases have been identified as endolytic but M- and G-producing with variable action modes. However, endolytic Δ-producing alginate lyases remain undiscovered. Herein, a new Flammeovirga protein, Aly2, was classified into the polysaccharide lyase 7 superfamily. The recombinant enzyme and its truncated protein showed similar stable biochemical characteristics. Using different sugar chains as testing substrates, we demonstrated that the two enzymes are bifunctional while G-preferring, endolytic whereas monosaccharide-producing. Furthermore, the catalytic module of Aly2 can vary the action modes depending on the terminus type, molecular size, and M/G content of the substrate, thereby yielding different levels of M, G, and Δ units. Notably, the enzymes preferentially produce Δ units when digesting small size-defined oligosaccharide substrates, particularly the smallest substrate (unsaturated tetrasaccharide fractions). Deletion of the non-catalytic region of Aly2 caused weak changes in the action modes and biochemical characteristics. This study provided extended insights into alginate lyase groups with variable action modes for accurate enzyme use.

Protection of color and chemical degradation of anthocyanin from purple corn (Zea mays L.) by zinc ions and alginate through chemical interaction in a beverage model

Anthocyanin-rich purple corn pericarp water extract (PCW) has the potential to be used as a natural pigment in beverages. However, it has a limited shelf-life in aqueous solutions. The aim was to evaluate the effect of zinc ion (Zn²⁺) and alginate on color and chemical stability of anthocyanins from colored corn (PCW) in a beverage model for 12weeks. PCW was incorporated to Kool-Aid® Invisible™ along with ZnCl₂ and/or alginate. Individual ANC were quantified through HPLC, and color stability was evaluated through the CIE-L*a*b* color system. Complexation between PCW and Zn/alginate was evaluated with fluorescence spectroscopy. The combination of Zn and alginate was the most effective treatment improving the half-life of total ANC concentration (10.4weeks), cyanidin-3-O-glucoside (7.5weeks) and chroma (18.4weeks), compared to only PCW (6.6, 4.5 and 12.7weeks, respectively). Zn and alginate had bimolecular quenching constants (Zn k_q: 3.4×10¹¹ M^-1S^-1 and AA k_q: 1.0×10¹² M^-1S^-1) suggesting that fluorescence quenching was binding rather than collisional. Results suggested that Zn/alginate interacted with ANC from purple corn slowing its chemical degradation.

A rhamnan-type sulfated polysaccharide with novel structure from Monostroma angicava Kjellm (Chlorophyta) and its bioactivity

A homogeneous polysaccharide was obtained from Monostroma angicava Kjellm by water extraction, preparative anion-exchange and size-exclusion chromatography. Results of chemical and spectroscopic analyses showed that the polysaccharide was a glucuronic acid-containing rhamnan-type sulfated polysaccharide. The backbone mainly consisted of →3)-α-l-Rhap-(1→ and →2)-α-l-Rhap-(1→ residues, partially sulfated at C-2 of →3)-α-l-Rhap-(1→ and C-3/C-4 of →2)-α-l-Rhap-(1→. The branching contained unsulfated or monosulfated 3-linked, 2-linked, 4-linked α-l-rhamnose and terminal β-d-glucuronic acid residues. The polysaccharide had strong antidiabetic activity assessed by glucose consumption, total cholesterol and triglyceride levels using human hepatocellular carcinoma (HepG2) and insulin-resistant HepG2 cells. The polysaccharide exhibited high anticoagulant property by activated partial thromboplastin time and thrombin time assays, and possessed high fibrin(ogen)olytic activity evaluated by plasminogen activator inhibitior-1, fibrin(ogen) degradation products and D-dimer levels using rats plasma. The investigation demonstrated that the polysaccharide from Monostroma angicava Kjellm was a novel sulfated rhamnan and could be a potential antidiabetic and anticoagulant polysaccharide.

Degradation of Marine Algae-Derived Carbohydrates by Bacteroidetes Isolated from Human Gut Microbiota

Carrageenan, agarose, and alginate are algae-derived undigested polysaccharides that have been used as food additives for hundreds of years. Fermentation of dietary carbohydrates of our food in the lower gut of humans is a critical process for the function and integrity of both the bacterial community and host cells. However, little is known about the fermentation of these three kinds of seaweed carbohydrates by human gut microbiota. Here, the degradation characteristics of carrageenan, agarose, alginate, and their oligosaccharides, by Bacteroides xylanisolvens, Bacteroides ovatus, and Bacteroides uniforms, isolated from human gut microbiota, are studied.

In vitro fermentation of alginate and its derivatives by human gut microbiota

Alginate (Alg) has a long history as a food ingredient in East Asia. However, the human gut microbes responsible for the degradation of alginate and its derivatives have not been fully understood yet. Here, we report that alginate and the low molecular polymer derivatives of mannuronic acid oligosaccharides (MO) and guluronic acid oligosaccharides (GO) can be completely degraded and utilized at various rates by fecal microbiota obtained from six Chinese individuals. However, the derivative of propylene glycol alginate sodium sulfate (PSS) was not hydrolyzed. The bacteria having a pronounced ability to degrade Alg, MO and GO were isolated from human fecal samples and were identified as Bacteroides ovatus, Bacteroides xylanisolvens, and Bacteroides thetaiotaomicron. Alg, MO and GO can increase the production level of short chain fatty acids (SCFA), but GO generates the highest level of SCFA. Our data suggest that alginate and its derivatives could be degraded by specific bacteria in the human gut, providing the basis for the impacts of alginate and its derivates as special food additives on human health.

Negative-Ion Electrospray Tandem Mass Spectrometry and Microarray Analyses of Developmentally Regulated Antigens Based on Type 1 and Type 2 Backbone Sequences

Type 1 (Galβ1-3GlcNAc) and type 2 (Galβ1-4GlcNAc) sequences are constituents of the backbones of a large family of glycans of glycoproteins and glycolipids whose branching and peripheral substitutions are developmentally regulated. It is highly desirable to have microsequencing methods that can be used to precisely identify and monitor these oligosaccharide sequences with high sensitivity. Negative-ion electrospray tandem mass spectrometry with collision-induced dissociation has been used for characterization of branching points, peripheral substitutions, and partial assignment of linkages in reducing oligosaccharides. We now extend this method to characterizing entire sequences of linear type 1 and type 2 chain-based glycans, focusing on the type 1 and type 2 units in the internal regions including the linkages connecting type 1 and type 2 disaccharide units. We apply the principles to sequence analysis of closely related isomeric oligosaccharides and demonstrate by microarray analyses distinct binding activities of antibodies and a lectin toward various combinations of type 1 and 2 units joined by 1,3- and 1,6-linkages. These sequence-specific carbohydrate-binding proteins are in turn valuable tools for detecting and distinguishing the type 1 and type 2-based developmentally regulated glycan sequences.

Extraction, Isolation, Structural Characterization and Anti-Tumor Properties of an Apigalacturonan-Rich Polysaccharide from the Sea Grass Zostera caespitosa Miki

An apigalacturonan (AGA)-rich polysaccharide, ZCMP, was isolated from the sea grass Zostera caespitosa Miki. The depolymerized fragments derived from ZCMP were obtained by either acidic degradation or pectinase degradation, and their structures were characterized by electrospray ionization collision-induced-dissociation mass spectrometry (ESI-CID-MS2) and nuclear magnetic resonance (NMR) spectroscopy. The average molecular weight of ZCMP was 77.2 kD and it consisted of galacturonic acid (GalA), apiosefuranose (Api), galactose (Gal), rhamnose (Rha), arabinose (Ara), xylose (Xyl), and mannose (Man), at a molar ratio of 51.4꞉15.5꞉6.0꞉11.8꞉4.2꞉4.4꞉4.2. There were two regions of AGA (70%) and rhamnogalacturonan-I (RG-Ι, 30%) in ZCMP. AGA was composed of an α-1,4-D-galactopyranosyluronan backbone mainly substituted at the O-3 position by single Api residues. RG-Ι possessed a backbone of repeating disaccharide units of →4GalAα1,2Rhaα1→, with a few α-L-arabinose and β-D-galactose residues as side chains. The anti-angiogenesis assay showed that ZCMP inhibited the migratory activity of human umbilical vein endothelial cell (HUVECs), with no influence on endothelial cells growth. ZCMP also promoted macrophage phagocytosis. These findings of the present study demonstrated the potential anti-tumor activity of ZCMP through anti-angiogenic and immunoregulatory pathways.

Novel vanadyl complexes of alginate saccharides: synthesis, characterization, and biological activities

Vanadium compounds present many physiological functions. However, vanadium(IV) and (V) salts are difficult for gastrointestinal absorption and have strong side effects. Therefore organic oxovanadium compounds gain more attention. Vanadyl alginate polysaccharides (VAPS) and vanadyl alginate oligosaccharides (VAOS) were obtained from aqueous solutions of VOSO4 at pH 12. They were characterized by infrared spectroscopy, UV-vis spectroscopy and inductively coupled plasma-mass spectrometry (ICP-MS). The antioxidant activity of oxovanadium(IV) complexes was investigated in hydroxyl and DPPH radical scavenging systems in vitro. The results reveal that activities of VAPS and VAOS in the two systems were stronger than those of alginate polysaccharides (APS) and alginate oligosaccharides (AOS), respectively. In addition, VAPS and VAOS promoted significantly the antiproliferation of ligands of human hepatoma cell line BEL-7402. Oxovanadium(IV) complexes were potent inhibitors of protein tyrosine phosphatase 1B (PTP1B) with IC50 values in the range of 6.4-18.7μg/mL, indicated in biochemical assays. In addition, Vanadyl-alginate had no significant side effects on proliferation and viability of HL-7702 hepatic cells. In the future, they can be added to medicines and ease the growing threat that cancer and diabetes mellitus cause to human health.

Applications of mass spectrometry to structural analysis of marine oligosaccharides

Marine oligosaccharides have attracted increasing attention recently in developing potential drugs and biomaterials for their particular physical and chemical properties. However, the composition and sequence analysis of marine oligosaccharides are very challenging for their structural complexity and heterogeneity. Mass spectrometry (MS) has become an important technique for carbohydrate analysis by providing more detailed structural information, including molecular mass, sugar constituent, sequence, inter-residue linkage position and substitution pattern. This paper provides an overview of the structural analysis based on MS approaches in marine oligosaccharides, which are derived from some biologically important marine polysaccharides, including agaran, carrageenan, alginate, sulfated fucan, chitosan, glycosaminoglycan (GAG) and GAG-like polysaccharides. Applications of electrospray ionization mass spectrometry (ESI-MS) are mainly presented and the general applications of matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) are also outlined. Some technical challenges in the structural analysis of marine oligosaccharides by MS have also been pointed out.

Typing of blood-group antigens on neutral oligosaccharides by negative-ion electrospray ionization tandem mass spectrometry

Blood-group antigens, such as those containing fucose and bearing the ABO(H)- and Lewis-type determinants expressed on the carbohydrate chains of glycoproteins and glycolipids, and also on unconjugated free oligosaccharides in human milk and other secretions, are associated with various biological functions. We have previously shown the utility of negative-ion electrospay ionization tandem mass spectrometry with collision-induced dissociation (ESI-CID-MS/MS) for typing of Lewis (Le) determinants, for example, Le(a), Le(x), Le(b), and Le(y) on neutral and sialylated oligosaccharide chains. In the present report, we extended the strategy to characterization of blood-group A-, B-, and H-determinants on type 1 and type 2 and also on type 4 globoside chains to provide a high sensitivity method for typing of all the major blood-group antigens, including the A, B, H, Le(a), Le(x), Le(b), and Le(y) determinants, present in oligosaccharides. Using the principles established, we identified two minor unknown oligosaccharide components present in the products of enzymatic synthesis by bacterial fermentation. We also demonstrated that the unique fragmentations derived from the D- and (0,2)A-type cleavages observed in ESI-CID-MS/MS, which are important for assigning blood-group and chain types, only occur under the negative-ion conditions for reducing sugars but not for reduced alditols or under positive-ion conditions.

Separation and identification of individual alginate oligosaccharides in the feces of alginate-fed pigs

This research aimed to develop a method for analyzing specific alginate oligosaccharides (AOS) in a complex matrix such as pig feces. The data obtained were used to study alginate degradation by the microbiota in the large intestine during adaptation, including the individual variation between pigs. A method using an UHPLC system with an ethylene bridged hybrid (BEH) amide column coupled with MS(n) detection was able to distinguish saturated and unsaturated AOS with DP 2-10. Isomers of unsaturated trimer and tetramer could be separated and annotated. In the feces, saturated and unsaturated AOS were present. The presence of unsaturated AOS indicates that the microbiota produced alginate lyase. The microbiota utilized unsaturated AOS more than saturated AOS. The results also suggested that guluronic acid at the reducing end of AOS inhibits the utilization by microbiota during the first weeks of adaptation. After adaptation, the microbiota was able to utilize a broader range of AOS.

ESIMS analysis of fucoidan preparations from Costaria costata, extracted from alga at different life-stages

Four fucoidan fractions from brown alga Costaria costata, collected at different life-stages: vegetative, May (5F2 and 5F3) and generative, July (7F1 and 7F2) collections were characterized. It was found that seaweed synthesizes different set of fucoidans - one with high fucose content and substantial percentage of hexoses and uronic acid and lower sulfate content (7F1, 5F2 and 5F3) and other - highly sulfated galactofucan (7F2). Structural features of fractions 7F2 and 5F3 were predominantly determined by mass spectrometric analysis of low-molecular-weight (LMW) oligosaccharide fragments, obtained by autohydrolysis of 7F2 and mild acid hydrolysis of 5F3 fucoidans. It was found that oligosaccharides from 7F2 fractions were mainly built up of sulfated at C-2 and/or at C-2/C-4 (1→3)-linked α-l-fucopyranose residues. d-Galactose residues, sulfated either at C-2 or C-6, were found as parts of mixed di- and trisaccharides at both termini and, probably, internal. Fucose residues in 5F3 fucoidan fragments were sulfated at C-2 and sometimes at C-4. Galactose residues were sulfated at C-4 and less frequently at C-2. Resistant to hydrolysis fraction was probably a core, built up with fucose, mannose and glucuronic acid. Presumably, oligosaccharide fragments were branches at C-4 of GlcA. They were sulfated at C-2 and sometimes at C-4 (1→3)- and/or (1→4)-linked fucooligosaccharides (sometimes terminated with (1→3)-linked galactose) and sulfated at C-4 or C-2 (1→4)- or, probably, (1→6)-linked galactooligosaccharides, probably, with own branches, formed by (1→2)-linked galactose residues. Unsulfated xylose residues were probably terminal in chains built up of fucose. It was confirmed, that monosaccharide content and structure of fucoidans of vegetative algae changed following its life stage. Generative alga in general produced highly sulfated galactofucan having lower MW along with less sulfated mannoglucuronofucan with higher MW, which was extensively synthesized by vegetative algae.

Sequence analysis of the sulfated rhamno-oligosaccharides derived from a sulfated rhamnan

Three sulfated rhamno-oligosaccharides, designated O1, O2 and O3, were obtained by mild acid hydrolysis of the sulfated rhamnan and purified by gel-permeation chromatography. On the basis of one- and two-dimensional nuclear magnetic resonance (1D, 2D NMR) spectroscopic analyses, the oligosaccharide O1 was characterized to be α-L-Rhap-(2SO4)-(1→3)-α-L-Rhap. The fragmentation pattern of the homogeneous disaccharide in the product ion spectra was recognized by negative-ion electrospray tandem mass spectrometry with collision-induced dissociation (ES-CID MS/MS). With the principles established, the sequences of the oligosaccharides O2 and O3 were deduced to be α-L-Rhap-(2SO4)-(1→3)-α-L-Rhap-(1→3)-α-L-Rhap, and α-L-Rhap-(2SO4)-(1→3)-α-L-Rhap-(1→3)-α-L-Rhap-(1→3)-α-L-Rhap (2SO(4)), respectively. The investigation demonstrated that the sulfated rhamnan-derived oligosaccharides were novel sulfated oligosaccharides different from those of other polysaccharides-degraded from algae, and it could be possible to determine the sequence of the sulfated rhamno-oligosaccharides directly from the glycosidic cleavage fragmentation in the product ion spectra.

Analysis of extracellular alginate lyase and its gene from a marine bacterial strain, Pseudoalteromonas atlantica AR06

Pseudoalteromonas atlantica AR06 is a marine bacterial strain that can utilize alginate as a sole source of carbon and energy. The extracellular protein fraction prepared from the AR06 cultivation media exhibited alginate lyase activity to depolymerize the alginate molecules having homopolymeric and heteropolymeric forms of mannuronate and guluronate so as to mainly convert into the dimer to tetramer. A DNA fragment encoding a portion of alginate lyase was amplified from AR06 genomic DNA by PCR using a set of degenerated primers, and then the whole alginate lyase gene, named alyA, and its flanking regions were obtained from a cosmid library of AR06 genomic DNA. The alyA mutant of AR06 showed (1) the loss of alginate depolymerization activity on alginate agar plate and (2) significant growth defects in alginate minimal medium; these defects were complemented by the introduction of the alyA gene. Furthermore, zymography and biochemical analyses revealed that three extracellular protein bands of AR06 had alginate lyase activities and that all three protein bands were derived from the nascent alyA gene product. These results clearly indicated that the alyA gene greatly contributes to the assimilation of alginate in AR06. The transcription of the alyA gene was induced by the presence of alginate in minimal medium, but its obvious induction was not observed in rich medium even in the presence of alginate.

Sequence Analysis of Native Oligosaccharides Using Negative ESI Tandem MS

Carbohydrates exhibit many physiologically and pharmacologically important activities, yet their complicated structure and sequence pose major analytical challenges. Although their structural complexity makes analysis of carbohydrate difficult, mass spectrometry (MS) with high sensitivity, resolution and accuracy has become a vital tool in many applications related to analysis of carbohydrates or oligosaccharides. This application is essentially based on soft ionization technique which facilitates the ionization and vaporization of large, polar and thermally labile biomolecules. Electrospray-ionization (ESI), one of the soft ionization technique, tandem MS has been used in the sequencing of peptides, proteins, lipids, nucleic acids and more recently carbohydrates. The development of the ESI and tandem MS has begun to make carbohydrate analysis more routine. This review will focus on the application of the ESI tandem MS for the sequence analysis of native oligosaccharides, including neutral saccharides with multiple linkages, and the uronic acid polymers, alginate and glycosaminoglycans structures containing epimers.

Structural analysis of a fucoidan from the brown alga Fucus evanescens by MALDI-TOF and tandem ESI mass spectrometry

A fucoidan, a heterogeneous sulfated polysaccharide from the brown alga Fucus evanescens, was depolymerized under solvolytic conditions, and its ethanol-extracted low-molecular-weight fraction was analyzed by MALDI-TOFMS and ESIMS/MS. It was found that the mixture contained unsulfated oligosaccharides including some monosulfated components, which were shown to consist of mainly (1-->3)-linked 2-O-sulfonated fucose residues (from 1 to 4). Minor components of the mixture were shown to contain 2-O- and 4-O-sulfonated xylose and galactose residues. Among them, mixed monosulfonated fucooligosaccharides were detected and characterized: Xyl-(1-->4)-Fuc, Gal-(1-->4)-Fuc, Gal-(1-->4)-Gal-(1-->4)-Fuc, Gal-(1-->4)-Gal. Fucose, galactose, and xylose residues were shown to be mainly 2-O-sulfonated with traces of 4-O-sulfonation. Glucuronic acid was also found as a part of non-sulfated fucooligosaccharides: Fuc-(1-->3)-GlcA, Fuc-(1-->4)-Fuc-(1-->3)-GlcA, Fuc-(1-->3)-Fuc-(1-->4)-Fuc-(1-->3)-GlcA.