Trisaccharide Side Chains Research Articles

A Comprehensive Review of Xanthan Gum-Based Oral Drug Delivery Systems.

Xanthan gum (XG) is an exopolysaccharide synthesized by the aerobic fermentation of simple sugars using Xanthomonas bacteria. It comprises a cellulosic backbone with a trisaccharide side chain connected to alternative glucose residues in the main backbone through α (1→3) linkage. XG dissolves readily in cold and hot water to produce a viscous solution that behaves like a pseudoplastic fluid. It shows excellent resistance to enzymatic degradation and great stability throughout a broad temperature, pH, or salt concentration range. Additionally, XG is nontoxic, biocompatible, and biodegradable, making it a suitable carrier for drug delivery. Furthermore, the carboxylic functions of pyruvate and glucuronic acid offer a considerable opportunity for chemical modification to meet the desired criteria for a specific application. Therefore, XG or its derivatives in conjunction with other polymers have frequently been studied as matrices for tablets, nanoparticles, microparticles, and hydrogels. This review primarily focuses on the applications of XG in various oral delivery systems over the past decade, including sustained-release formulations, gastroretentive dosage forms, and colon-targeted drug delivery. Source, production methods, and physicochemical properties relevant to drug delivery applications of XG have also been discussed.

Structural elucidation of hemicelluloses from oil-tea camellia fruit shell

Oil-tea camellia fruit shell (CFS) is a very abundant waste lignocellulosic resource. The current treatments of CFS, i.e. composting and burning, pose a severe threat on environment. Up to 50 % of the dry mass of CFS is composed of hemicelluloses. However, chemical structures of the hemicelluloses in CFS have not been extensively studied, which limits their high-value utilization. In this study, different types of hemicelluloses were isolated from CFS through alkali fractionation with the assistance of Ba(OH)2 and H3BO3. Xylan, galacto-glucomannan and xyloglucan were found to be the major hemicelluloses in CFS. Through methylation, HSQC and HMBC analyses, we have found that the xylan in CFS is composed of →4)-β-D-Xylp-(1→ and →3,4)-β-D-Xylp-(1→ linked by (1→4)-β glycosidic bond as the main chain; the side chains are α-L-Fucp-(1→, →5)-α-L-Araf-(1→, β-D-Xylp-(1→, α-L-Rhap-(1→ and 4-O-Me-α-D-GlcpA-(1→, connected to the main chain through (1→3) glycosidic bond. The main chain of galacto-glucomannan in CFS consists of →6)-β-D-Glcp-(1→, →4)-β-D-Glcp-(1→, →4,6)-β-D-Glcp-(1→ and →4)-β-D-Manp-(1→; the side chains are β-D-Glcp-(1→, →2)-β-D-Galp-(1→, β-D-Manp-(1→ and →6)-β-D-Galp-(1→ connected to the main chain through (1→6) glycosidic bonds. Moreover, galactose residues are connected by α-L-Fucp-(1→. The main chain of xyloglucan is composed of →4)-β-D-Glcp-(1→, →4,6)-β-D-Glcp-(1→ and →6)-β-D-Glcp-(1→; the side groups, i.e. β-D-Xylp-(1→ and →4)-β-D-Xylp-(1→, are connected to the main chain by (1→6) glycosidic bond; →2)-β-D-Galp-(1→ and α-L-Fucp-(1→ can also connect to →4)-β-D-Xylp-(1→ forming di- or trisaccharide side chains.

Dual-network polyvinyl alcohol/polyacrylamide/xanthan gum ionic conductive hydrogels for flexible electronic devices

Ionic conductive hydrogels (ICHs) have received widespread attention as an ideal candidate for flexible electronic devices. However, conventional ICHs failed in widespread applications due to their inability to simultaneously possess high toughness, high ionic conductivity, and anti-freezing properties. Here, polyvinyl alcohol (PVA) and polyacrylamide (PAAm) were first dissolved in the zinc chloride solution, in which zinc ions (Zn2+) act as ionic cross-linkers and conducting ions, followed by the introduction of xanthan gum (XG) with a unique structure of trisaccharide side chains into the PVA/PAAm semi-interpenetrating network to prepare a dual-network ICHs (refers as PPXZ). Enabled by the synergistic effect of intermolecular chemical covalent cross-linking and physical cross-linking, PPXZ hydrogels exhibit significantly improved mechanical properties without sacrificing electrical conductivity. Furthermore, PPXZ hydrogels are successfully applied to flexible electronic devices, such as strain sensors and zinc ion hybrid supercapacitors, exhibiting satisfactory sensing sensitivity and cycling stability at a wide temperature range, respectively. Even at a high current density (10 A g−1), the capacity of the supercapacitor retains 88.24 % after 10,000 cycles. This strategy provides new insight for ICHs in wide temperature-applied flexible electronic devices.

Proteomic Analysis of the Xanthan-Degrading Pathway of Microbacterium sp. XT11.

Xanthan, a highly stable polysaccharide which is not easily degraded by most microorganisms, contains a cellulosic backbone with trisaccharide side chains composed of mannosyl-glucuronyl-mannose attached α-1,3 to alternating glucosyl residues. Different digestion strategies were first applied to demonstrate the complexity about the proteomes of Microbacterium sp. XT11 in xanthan medium and glucose medium. Significantly up-regulated proteins induced by xanthan were screened out by the label-free quantitation of the proteomes of Microbacterium sp. XT11 in xanthan medium and glucose medium. Consequently, 2746 and 2878 proteins were identified in proteomes of Microbacterium sp. XT11 in xanthan medium and glucose medium individually, which represent 80.6 and 84.4% of total protein dataset predicted to be expressed by the gene. In the list of 430 induced proteins containing the proteins specifically expressed or up-regulated in xanthan medium, 19 proteins involved in carbohydrate-active enzymes database and 38 proteins annotated with transporter activity were critical in the degrading pathway of xanthan. Four CAZymes (GH3, GH38, GH9, and PL8) and one ABC transporter (LX1-1GL001097) were verified with quantitative real-time polymerase chain reaction. Four CAZymes (GH3, GH38, GH9, and PL8) were further verified with the enzyme assay. This study suggests a xanthan-degrading pathway in Microbacterium sp. XT11, and other potential xanthan degradation-related proteins still need further investigation.

Bacterial cyclic β-(1,2)-glucans sequester iron to protect against iron-induced toxicity.

Cellular iron homeostasis is critical for survival and growth. Bacteria employ a variety of strategies to sequester iron from the environment and to store intracellular iron surplus that can be utilized in iron-restricted conditions while also limiting the potential for the production of iron-induced reactive oxygen species (ROS). Here, we report that membrane-derived oligosaccharide (mdo) glucan, an intrinsic component of Gram-negative bacteria, sequesters the ferrous form of iron. Iron-binding, uptake, and localization experiments indicated that both secreted and periplasmic β-(1,2)-glucans bind iron specifically and promote growth under iron-restricted conditions. Xanthomonas campestris and Escherichia coli mutants blocked in the production of β-(1,2)-glucan accumulate low amounts of intracellular iron under iron-restricted conditions, whereas they exhibit elevated ROS production and sensitivity under iron-replete conditions. Our results reveal a critical role of glucan in intracellular iron homeostasis conserved in Gram-negative bacteria.

Anticoagulant Activity of Rhamnan Sulfate Isolated from Commercially Cultured <i>Monostroma nitidum</i>

The green seaweed, <i>Monostroma nitidum</i>, is widespread in Japan. In Okinawa Prefecture, the production of seaweed is performed using culture-nets that are seeded artificially. Algae contain a soluble polysaccharide, rhamnan sulfate. To estimate its applicability, the anticoagulant activity of rhamnan sulfate was investigated. Rhamanan sulfate was fractionated by ion-exchange chromatography on a DEAE-sepharose column, and two fractions (A and B) were obtained. Partially hydrolyzed rhamnan sulfates with different molecular mass (C1, C2 and C3) were also prepared. The activated partial thromboplastin time (APTT) test, prothrombin time (PT) and thrombin time (TT) were applied using human plasma and compared with standard heparin (174 units/mg). The native rhamnan sulfate (molecular mass, 630 kDa; sulfuric acid content, 22.7%), fraction A (12.4%) and fraction B (27.8%) showed approximately 73% APTT activity in comparison with that of standard heparin, but fraction C2 (molecular mass, 450 kDa) had a higher activity than that of the standard (107%). On the other hand, in the PT assay, all fractions except fraction C2 and C3 (370 kDa) showed higher activity approximately 120-155% greater than that of standard heparin. The TT activity of rhamnan sulfate depended on the sulfate content, and that of fraction B, which has high sulfuric acid content (27.8%), was 135-173% greater than that of heparin. The sulfate groups of L-rhamnosyl residues and carboxyl group of D-glucuronosyl residue on the trisaccharide side chains of the rhamnan sulfate might interact strongly with the active site of thrombin molecules. The results and discussion suggested that rhamnan sulfate from commercially cultured <i>Monostroma nitidum</i> could be a potential anticoagulant polysaccharide.

Structural features of soluble cereal arabinoxylan fibers associated with a slow rate of in vitro fermentation by human fecal microbiota

Most soluble dietary fibers ferment rapidly in the proximal colon, potentially causing discomfort and poor tolerability. Alkali-extracted arabinoxylan isolates from corn, wheat, rice and sorghum brans were prepared, through hydrolysis (except sorghum) and ethanol fractionation, to have a broad range of initial fermentation rates, and their linkage patterns were determined to understand structural aspects related to slow fermentation rate. They were all highly branched polymers with degree of substitution greater than 64%. There was no relationship of molecular mass, arabinose:xylose ratio, or degree of substitution to fermentation rate patterns. Slow fermenting wheat and corn arabinoxylans had much higher amount of terminal xylose in branches than fast fermenting rice and sorghum arabinoxylans. The slowest fermenting wheat arabinoxylan additionally contained a complex trisaccharide side chain with two arabinoses linked at the O-2 and O-3 positions of an arabinose that is O-2 linked to the xylan backbone. Structural features were proposed for tolerable slowly fermentable arabinoxylan with possible beneficial fermentation function into the distal colon.

Xanthan Gum and Its Derivatives as a Potential Bio-polymeric Carrier for Drug Delivery System

Xanthan gum is a high molecular weight natural polysaccharide produced by fermentation process. It consists of 1, 4-linked β-D-glucose residues, having a trisaccharide side chain attached to alternate D-glucosyl residues. Although the gum has many properties desirable for drug delivery, its practical use is mainly confined to the unmodified forms due to slow dissolution and substantial swelling in biological fluids. Xanthan gum has been chemically modified by conventional chemical methods like carboxymethylation, and grafting such as free radical, microwave-assisted, chemoenzymatic and plasma assisted chemical grafting to alter physicochemical properties for a wide spectrum of biological applications. This article reviews various techniques utilized for modification of xanthan gum and its applications in a range of drug delivery systems.

Characterization of the Enzymes Encoded by the Anthrose Biosynthetic Operon of Bacillus anthracis

Bacillus anthracis spores, the etiological agents of anthrax, possess a loosely fitting outer layer called the exosporium that is composed of a basal layer and an external hairlike nap. The filaments of the nap are formed by trimers of the collagenlike glycoprotein BclA. Multiple pentasaccharide and trisaccharide side chains are O linked to BclA. The nonreducing terminal residue of the pentasaccharide side chain is the unusual sugar anthrose. A plausible biosynthetic pathway for anthrose biosynthesis has been proposed, and an antABCD operon encoding four putative anthrose biosynthetic enzymes has been identified. In this study, we genetically and biochemically characterized the activities of these enzymes. We also used mutant B. anthracis strains to determine the effects on BclA glycosylation of individually inactivating the genes of the anthrose operon. The inactivation of antA resulted in the appearance of BclA pentasaccharides containing anthrose analogs possessing shorter side chains linked to the amino group of the sugar. The inactivation of antB resulted in BclA being replaced with only trisaccharides, suggesting that the enzyme encoded by the gene is a dTDP-β-L-rhamnose α-1,3-L-rhamnosyl transferase that attaches the fourth residue of the pentasaccharide side chain. The inactivation of antC and antD resulted in the disappearance of BclA pentasaccharides and the appearance of a tetrasaccharide lacking anthrose. These phenotypes are entirely consistent with the proposed roles for the antABCD-encoded enzymes in anthrose biosynthesis. Purified AntA was then shown to exhibit β-methylcrotonyl-coenzyme A (CoA) hydratase activity, as we predicted. Similarly, we confirmed that purified AntC had aminotransferase activity and that purified AntD displayed N-acyltransferase activity.

多糖類のゲル化機構とフコイダンの利用開発に関する研究

The structure-function relationship of the polysaccharides from the view point of the rheological characteristics in aqueous solutions has been insighted into when I was listening to the first movement of the piano sonata No. 14, Op. 27-2, entitled Moon-light which was composed by Ludwig van Beethoven on July in 1973. At that time, I was a doctoral student at the Department of Food Science and Technology, Kyushu University. After getting job at the University of the Ryukyus in 1982, it has been investigated. Gelation mechanism for κ-carrageenan, ι-carrageenan, agarose (agar), gellan gum, alginic acid, curdlan and amylose has been analyzed, respectively, at the molecular level where sulfate oxygen, ring oxygen, hemiacetal oxygen, cations, hydroxyl groups oriented at axial, and methyl groups take part in the intra- and intermolecular associations with ionic bonding, electrostatic forces of attraction, hydrogen bonding and van der Waals forces of attraction. Co-gelation mechanism of xanthan with galactomannan (locust bean gum, tara bean gum, guar gum and Leucaena galactomannan), and with konjac glucomannan, where trisaccharide side-chains of the former molecules contribute with hydrogen bonding has also been analyzed, respectively. The structure-function relationship for non-gelling welan, rhamsan, S-657, S-88, S-198, shizophyllan and amylopectins (rice, potato and wheat), the structure of which is similar to that of gelling gellan, curdlan and amylose has been analyzed. The gellan family of the polysaccharides, as metioned above, have given a good opportunity to investigate the molecular origin for their rheological characteristics. Recently, we have analyzed a gelatinization and retrogradation mechanisms of rice, potato and wheat starches. From the results and discussions, the principles of the polysaccharide gels have been established. Though many investigations concerning the gelling properties of the polysaccharides have been done to discuss structure-function relationship, no one has established gelation mechanisms at the molecular level except the author. There is reasonable consistency in our investigations. Thus, rheological analysis is one of the most significant methods to realize the structure-function relationships of polysaccharides in aqueous solutions. We have isolated a novel fucoidan, which substituted an acetyl group, from commercially cultured Cladosiphon okamuranus in Okinawa, Japan and has been covered by a patent. The fucoidan has an excellent flow characteristics and immunological activity. The fucoidan has now been used in food and cosmetic industries, production of which increases year by year.

Effect of calcium ions on the gelling and drug release characteristics of xanthan matrix tablets

Xanthan is a well-known biopolymer. It is an anionic polysaccharide, whose primary structure depends on the bacterial strain and fermentation conditions. Xanthan was extensively studied in combination with galactomannans, and over 90 patents cover the technology of this preparation. Our aim was to investigate the relation between the physical properties of a xanthan matrix in the absence or presence of calcium ions and its influence on the release of pentoxifylline. The release of pentoxifylline from xanthan tablets in purified water was shown to be very slow and governed by the process of polymer relaxation. The presence of calcium ions significantly increased the drug release, changing the release mechanism into a more diffusion controlled one. Xanthan matrices showed substantially faster and more extensive swelling in water than in the presence of Ca 2+ ions. Surprisingly, negative correlation between drug release and degree of swelling was obtained for xanthan: the higher the swelling, the slower the drug release. Higher ionic strength led to lower erosion of xanthan tablets, and the gel layers formed were more rigid and of firmer texture, as shown by rheological experiments and textural profiling. The results indicate that the presence of Ca 2+ ions in the solution or in matrices does not cause crosslinking of xanthan polymers, but causes charge screening of ionized groups on the trisaccharide side chains of xanthan, leading to lower inter-molecular repulsion and changing water arrangement. The understanding of the parameters influencing drug release leads to the conclusion that xanthan is suitable for controlled release formulations, especially with the incorporation of certain small counterions.

Structure of a colitose-containing O-polysaccharide from the lipopolysaccharide of Providencia alcalifaciens O6

The O-polysaccharide was isolated by mild acid degradation of the lipopolysaccharide of Providencia alcalifaciens O6 and studied by sugar and methylation analysis, selective hydrolytic removal of 3,6-dideoxy- l- xylo-hexose (colitose, Col), 1H and 13C NMR spectroscopy, including 2D 1H, 1H COSY, TOCSY, ROESY and H-detected 1H, 13C HSQC and HMBC experiments. The polysaccharide was found to have a branched pentasaccharide repeating unit with the following structure: [Display omitted] Remarkably, the trisaccharide side chain of the O6-polysaccharide represents a colitose (‘3-deoxy- l-fucose’) analogue of the H type 1 (precursor) antigenic determinant.

Function of lanGT3, a Glycosyltransferase Gene Involved in Landomycin A Biosynthesis

The glycosyltransferase gene lanGT3, involved in the biosynthesis of the angucyclic antibiotic landomycin A, has been characterised by targeted gene deletion. A lanGT3 mutant was shown to produce landomycin E, which consists of a trisaccharide side chain attached to the polyketide moiety. Expression of lanGT3 in the mutant restored landomycin A production. Our results indicate that LanGT3 is responsible for the transfer of the fourth sugar during landomycin A biosynthesis.

Control of Pierce's Disease through Degradation of Xanthan Gum

The diseases caused by Xylella fastidiosa are associated with aggregation of the bacteria m xylem vessels, formation of a gummy matrix and subsequent blockage of water uptake. In the closely related pathogen, Xanthomonas campestris, xanthan gum is known to be an important virulence factor, probably contributing to bacterial adhesion, aggregation and plugging of xylem. Xanthan gum, produced by X. campestris, is an extra-cellular polysaccharide consisting of a cellulose backbone (<TEX>$\bate$</TEX>-1,4-linked D-glucose) with trisaccharide side chains composed of mannose, glucuronic acid and mannose attached to alternate glucose residues in the backbone. We had constructed a mutant of X. campestris lacking gumI gene that is responsible for adding the terminal mannose for producing modified xanthan gum which is similar to xanthan gum fromX. fastidiosa. The modified xanthan gum degrading endgphytic bacterium Acineto-bacter johnsonii GX123 isolated from the oleander infected with leaf scorch disease.

Structural determination of the phytotoxic mannan exopolysaccharide from Pseudomonas syringae pv. ciccaronei

The structural determination was performed of a mannan exopolysaccharide from the Gram negative bacterium Pseudomonas syringae pv. ciccaronei, which is the pathogenic agent responsible for the leaf spots of carob plants. The structure, obtained by chemical, enzymatic and spectroscopic methods, consisted of a backbone of α-(1→6)-linked mannopyranose units with 80% substituted at C-2 by mono-, di- and trisaccharide side chains. In addition, terminal glucose units and phosphate groups were found to be present. This is, to the best of our knowledge, the first report of a mannan exopolysaccharide structure from a phytopathogenic bacterium. The pure polysaccharide showed phytotoxic effects, i.e., chlorosis and necrosis on tobacco leaves.

The three-dimensional structure of the 4:1 mithramycin:d(ACCCGGGT)(2) complex: evidence for an interaction between the E saccharides.

Mithramycin and chromomycin, two antitumor drugs, each having an identical aglycone and nearly identical disaccharide and trisaccharide side chains, have differing binding properties to a small oligonucleotide, d(ACCCGGGT)(2) (M. A. Keniry et al., Journal of Molecular Biology, 1993, Vol. 231, pp. 753-767). In order to understand the forces that induce four mithramycin molecules to bind to d(ACCCGGGT)(2) instead of two drug molecules in the case of chromomycin, the structure of the 4:2:1 mithramycin: Mg(2+):d(ACCCGGGT)(2) complex was investigated by (1)H-nmr and restrained molecular dynamics. The resulting three-dimensional model showed that in order to accommodate the close approach of one neighboring mithramycin dimer, the inwardly directed CDE saccharide chain of the neighboring mithramycin dimer undergoes a conformational change such that the E saccharide no longer spans the minor groove but reorients so that the hydrophilic face of the E saccharides from the two dimers oppose each other. Two hydrogen bonds are formed between the hydroxyl groups of the two opposing E saccharide groups. The results are interpreted in terms of the differences in stereochemistry and functional group substitutions between mithramycin and chromomycin. A mithramycin dimer is able to self-associate on an oligonucleotide template because it has two hydroxyl groups on the same face of its terminal E saccharide. A chromomycin dimer is unable to self-associate because one of these hydroxyl groups is acetylated and the neighboring hydroxyl group has a stereochemistry that cannot permit close contact of the hydroxyl group with a neighbouring chromomycin dimer.

Structural Principles of Polysaccharide Gels.

The author and colleagues have proposed a gelation mechanism for K -carrageenan, c -car-rageenan, agarose (agar), gellan gum, curdlan, amylose, and alginic acid at the molecular level in aqueous solutions in preceding papers. The synergistic gelation mechanism between xanthan gum and galactomannans (locust-bean, tara-bean and guar gum), and konjac glucomannan, where trisac-charide side-chains of the former molecule take part in the interaction, have been proposed. The synergistic gelation mechanism between K -carrageenan and galactomannan (locust-bean gum) has also been proposed. Recently, we have proposed gelatinization and retrogradation mechanisms of rice starch. The polysaccharides in water changed into an ice-like structure with hydrogen bonding between polymer and water molecules, and between water molecules even at a concentration range of 0.1-1.0% (w/v) at room temperature, resulting in gelation. Such dramatic changes from liquid into gels have not yet generally been understood at the molecular level. The research conducted by the author now makes it possible to discuss, in principle, because structure-function relationships from the viewpoint of rheology not only of the gelling polysaccharides mentioned above, but also of non-gelling welan, rhamsan, S-657 gum, schizophyllan, and amylopectins (rice and potato), the structure of which is similar to that of gelling gellan gum, curdlan and amylose, have also been analyzed at the molecular level in our preceding papers.

Solid-phase synthesis of the B-chain of human α2HS glycoprotein

The B-chain of human α2HS glycoprotein 1, a heptacosapeptide carrying a trisaccharide (sialyl T) side chain, was synthesized. Prior to the Fmoc-based solid-phase synthesis of the glycopeptide, the benzyl-protected glycosyl serine building block 6 was prepared via β-stereoselective glycosylation of the 2-azido-2-deoxygalactosyl serine 11 with the sialyl galactosyl trichloroacetimidate 9. An automated peptide synthesizer was efficiently used for the elongation of the entire peptide chain except for the coupling with 6. The synthesized glycopeptide was cleaved from the resin by the TFA method. The resultant mixture of the benzylated glycopeptides was treated with TMSOTf–thioanisole in TFA and then with aq NaHCO 3 and 1,4-dithiothreitol to give 1.

Total synthesis of B-chain of human α2HS glycoprotein

B-chain of human α2HS glycoprotein 1, a cystein-containing heptacosapeptide carrying a trisaccharide (sialyl T) side chain, was synthesized for the first time by the solid-phase method utilizing a glycosyl serine building block 11 with benzyl protecting groups.

Xyloglucan sidechains modulate binding to cellulose during in vitro binding assays as predicted by conformational dynamics simulations.

Cross-links between cellulose microfibrils and xyloglucan (XG) molecules play a major role in defining the structural properties of plant cell walls and the regulation of growth and development of dicotyledonous plants. How these cross-links are established and how they are regulated has yet to be determined. In a previous study, preliminary data were presented which suggested that the different sidechains of XG may play a role in controlling cellulose microfibril-XG interactions. In this study, this question is addressed directly by analyzing to what extent the different sidechains of pea cell wall XG and nasturtium seed storage XG affect their binding to cellulose microfibrils. Of particular importance to this study are the chemical data indicating that pea XG possesses a trisaccharide sidechain, which is not found in nasturtium XG. To this end, conformational dynamic simulations have been used to predict whether oligosaccharides representative of pea and nasturtium XG can adopt a hypothesized cellulose-binding conformation and which of these XGs exhibits a preferential ability to bind cellulose. Extensive analysis of the conformational forms populated during 300 K and high-temperature Monte Carlo simulations established that a planar, sterically accessible, glucan backbone is essential for optimal cellulose-binding. For the trisaccharide sidechain-containing oligosaccharide as found in pea XG, sidechain orientation appeared to regulate the gradual acquisition of this hypothesized cellulose binding conformation. Thus, conformational forms were identified that included the twisted backbone (non-planar) putative solution form of XG, forms in which the trisaccharide sidechain orientation enables increased backbone planarity and steric accessibility, and finally a planar, sterically accessible, backbone. By applying these conformational requirements for cellulose binding, it has been determined that pea XG possesses a two- to threefold occurrence of the cellulose binding conformation than nasturtium XG. Based on this finding, it was predicted that pea XG would bind to cellulose at a higher rate than nasturtium XG. In vitro binding assays showed that pea XG-avicel binding does indeed occur at a twofold higher rate than nasturtium XG-avicel binding. The enhanced ability of pea cell wall XG over nasturtium seed storage XG to associate with cellulose is consistent with a structural role of the former during epicotyl growth where efficient association with cellulose is a requirement. In contrast, the relatively low ability of nasturtium XG to bind cellulose is consistent with the need to enhance the accessibility of this polymer to glycanases during germination. These findings suggest potential roles for XG sidechain substitution, enabling XG to function in a variety of different biological contexts.