Glycoconjugate Polymers Research Articles

Design and synthesis of trivalent Tn glycoconjugate polymers by nitroxide-mediated polymerization

A new synthetic method for preparing Tn glycoconjugate polymers, containing tumor-associated carbohydrate antigens, by controlled living radical polymerization is reported. To mimic the authentic structures of Tn glycopeptide antigens and to explore the controlled living radical polymerization, three tumor-associated carbohydrate antigens (GalNAc, GalNAcα1-O-Ser, and GalNAcα1-O-Thr) were attached to a styrene-type monomer through a diethylene glycol spacer. Under nitroxide-mediated polymerization, controlled living radical polymerization proceeded to afford defined glycopeptide polymers with different Tn densities and compositions. The polydispersity index (PDI) and molecular weights were increased and conversions were decreased upon increasing the concentration of Tn glycoconjugate monomers. The resulting Tn glycoconjugate polymers were characterized by NMR and IR. The spectral data indicate that the Tn glycoconjugate moiety did attach to the polymer chain and Tn glycoconjugate density could be adjusted through the nitroxide-mediated polymerization conditions. The number of Tn units containing in the polymer chains could be estimated by NMR integration. This synthetic approach provides a new and efficient tool for constructing novel Tn glycoconjugate polymers.

Elimination Filter for Verotoxins —Highly Adsorbing by Glycoconjugate Polymer—

Abstract Glycoconjugate polymer having globotriose, which is a ligand for Verotoxins (VTs: VT1 and VT2), was immobilized to the filter paper. By flowing VTs solution through the filter paper, the elimination ability of the filter paper for VT1 and VT2 was evaluated. The globotriose-immobilizing filter effectively diluted the starting concentration of VT1 (1 μg/mL) and VT2 (1 μg/mL) to about one hundred thousandth and about one thousandth parts of the starting concentration, respectively.

Synthesis and spectroscopic characterization of single-wall carbon nanotubes wrapped by glycoconjugate polymer with bioactive sugars

A novel multivalent carbohydrate-CNT hybrid has been synthesized from SWNT and glycoconjugate polymer, carrying carbohydrate as pendant groups at side chain. Dispersion of SWNT in aqueous solution by using glycoconjugate polymer is achieved by sonication and ultracentrifugation. The multivalent carbohydrate-CNT hybrid is revealed to be photoluminescence active by near-infrared fluorescence spectroscopy. AFM measurements of the hybrid support not only the wrapping of SWNT by glycoconjugate polymer but also successful carbohydrate attachment of individual SWNT.

Development of dialyzer with immobilized glycoconjugate polymers for removal of Shiga-toxin

The dialyzer for Shiga-toxin elimination was developed and its performance was established. The dialyzer was prepared by immobilization of multivalent ligands. Glycoconjugate polymers having oligosaccharides and amino groups were synthesized to function as Shiga-toxin adsorbents. The amino group was utilized to immobilize the polymer inside the cellulose hollow fiber of the dialyzer. Cellulose hollow fibers packed in the dialyzer were carboxymethylated under moderate conditions. The glycoconjugate polymers were bound covalently to the hollow fibers of the dialyzer by condensation reaction between the amino group of the polymer and the carboxyl group of the cellulose hollow fiber. Shiga-toxin eliminabilities of the prepared dialyzers were evaluated at various conditions. Even at high concentration of protein such as FCS, the dialyzer showed an excellent performance for Shiga-toxin adsorption.

Immobilization of Glycoconjugate Polymers on Cellulose Membrane for Affinity Separation

Membranes with immobilized glycoconjugate polymers were prepared and lectin adsorption was evaluated. Glycoconjugate polymers having the carbohydrates, lactose, and mannose, the amino groups of the...

The Role of Anti-non-Gal Antibodies in the Development of Acute Humoral Xenograft Rejection of hDAF Transgenic Porcine Kidneys in Baboons Receiving Anti-Gal Antibody Neutralization Therapy

The present study was undertaken to determine the role of preformed and induced anti-non-Gal antibodies in the rejection of hDAF pig-to-baboon kidney xenotransplants after anti-Gal antibody neutralization therapy. Seven baboons received life-supporting kidney transplants from hDAF transgenic pigs. Anti-Gal antibodies were neutralized by GAS914 or TPC (a Gal PEG glycoconjugate polymer). Group 1 (n=5) underwent a conventional immunosuppressive therapy with FK506, rabbit anti-thymocyte serum/immunoglobulin, mycophenolate mofetil, and steroids. Group 2 (n=2) received an anti-humoral immunity regimen with LF15-0195, Rituxan and cobra venom factor in addition to ATG, FK506 and steroids. Levels of anti-non-Gal antibodies and their mediated complement-dependent cytotoxic activities (CDC) were detected by flow cytometry using Gal knockout (k/o) pig lymphocytes (LC) or endothelial cells (EC) as targets. Continuous infusion of GAS914/TPC significantly reduced anti-Gal antibodies. In Group 1, four of five baboons developed severe acute humoral xenograft rejection (AHXR) and the rejection was associated with either a high level of preformed anti-non-Gal IgG or a marked elevation in induced anti-non-Gal IgG and IgM. Sera collected at the time of AHXR had a high level of CDC to porcine LC/EC from Gal k/o animals. The intensive anti-humoral therapy in Group 2 completely inhibited both anti-Gal and non-Gal antibody production and prevented AHXR. However, this therapy was not well tolerated by the baboons. In a pig-to-baboon kidney transplant model, both preformed and induced anti-non-Gal antibodies are strongly associated with the pathogenesis of AHXR when anti-Gal antibodies are neutralized.

Chemo-enzymatic synthesis of disaccharide-branched copolymers with high molecular weight

Glycoconjugate polymers containing lactose or sucrose branches with high molecular weight were synthesized by radical polymerization from enzymatically prepared monomers, 6 II- O-vinylhexanedioyl-lactose (VHL) and 1 Fru- O-vinylhexanedioyl-sucrose (VHS). Lactose and sucrose were submitted to transesterification with divinyl hexanedioate in anhydrous pyridine catalyzed by an alkaline protease from Bacillus subtilis at 50 °C. VHL and VHS were obtained respectively without any blocking/deblocking steps. Homopolymer of vinyl sugar esters and copolymers of acrylic acid or acrylamide were prepared with Fe 2+/K 2S 2O 8/H 2O 2 as initiator. The resultant polymer was characterized by FTIR, NMR spectroscopy and GPC. The biodegradation of the glycoconjugate polymer was investigated using enzymatic method in aqueous buffer, and results showed that the polymers were biodegradable.

Chemoenzymatic synthesis of glycoconjugate polymers starting from nonreducing disaccharides

AbstractHere we report the chemoenzymatic synthesis and recognition function of glycoconjugate polymers carrying nonreducing disaccharides [α‐D‐glucopyranosyl‐(1‐1)‐α‐D‐glucopyranoside (trehalose) and α‐D‐galactopyranosyl‐(1‐1)‐α‐D‐glucopyranoside (Gal‐type trehalose)]. The lipase‐catalyzed esterification of the disaccharides with divinyl sebacate is completely selective at the primary Glc 6‐OH position of trehalose and at the Gal 6‐OH position of Gal‐type trehalose. The resultant vinyl esters can be polymerized to yield glycoconjugate polymers with poly(vinyl alcohol) backbones. The interactions of the glycoconjugate polymers with lectins (concanavalin A and Bandeiraera simplicifolia) are amplified because of the glycocluster effect. The polymer carrying pendant α‐D‐galactopyranosyl‐(1‐1)‐α‐D‐glucopyranoside shows inhibition activity against Shiga toxin‐1 based on a stereochemical structure similar to that of globosyl Gb2 disaccharide. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4598–4606, 2004

Micropatterned carbohydrate displays by self-assembly of glycoconjugate polymers on hydrophobic templates on silicon.

We report a novel strategy for micropatterned carbohydrate displays on Si substrates. This method exploited the hydrophobic-hydrophilic microfabrication by photolithography of ODS-SAM on Si substrates and the subsequent selective self-assembly of glycoconjugate polymers onto the hydrophobic regions. Protein micropatterning by molecular recognition on the carbohydrate substrates was also successful.

Synthesis of glycoconjugate polymer carrying globotriaose as artificial multivalent ligand for Shiga toxin-producing Escherichia coli O157: H7

As an artificial ligand, a glycoconjugate polymer carrying carbohydrate moiety of lactosyl ceramide or globotriaosyl ceramide (Gb 3) was synthesized. Gb 3 is known as the receptor of Shiga toxin-producing Escherichia coli O157: H7. The preparation of the glycoconjugate polymer initially involves the construction of the carbohydrate moiety of Gb 3 derivative which has n-pentenyl group as polymerizable group. In addition, the n-pentenyl group of the Gb 3 derivative was modified and different polymerizable groups such as acrylamide group were introduced at ω-position of the aglycon. Radical polymerization of the synthesized glycosyl monomers with or without acrylamide proceeded smoothly in water using ammonium persulfate and N, N, N′, N′-tetramethylethylenediamine as usual initiator system and gave water-soluble glycoconjugate polymers having various polymer compositions. These polymers have the potential to neutralize Shiga toxin by reason of cluster effect and multivalency.

Analysis of GM3-Gg3 interaction using clustered gycoconjugate models constructed from glycolipid monolayers and artificial glycoconjugate polymers.

Carbohydrate-carbohydrate interactions between clustered GM3 on the Langmuir monolayer and clustered Gg3 trisaccharide along a polystyrene chain were investigated using surface pressure-area (pi-A) isotherms and surface plasmon resonance (SPR). The pi-A isotherm of the GM3 monolayer was expanded substantially and specifically by the Gg3-trisaccharide-bearing glycoconjugate polystyrene [PN(Gg3)] even at 10(-12) M. The PN(Gg3)-induced expansion of the GM3 monolayer required no calcium ion, and the expansion was strongly inhibited in the presence of urea and acetamido sugars. SPR studies of the GM3-Gg3 interaction were carried out to estimate the affinity constant and specificity of the interaction quantitatively. PN(Gg3) was adsorbed onto the GM3 monolayer strongly and specifically with an apparent affinity constant of Ka = 2.5 x 10(6) M(-1). The mechanism of the GM3-Gg3 interaction was discussed on the basis of the relationship between affinity and structure. We found that the NHAc groups of N -acetylneuraminic acid in GM3 and of GalNAc in Gg3 play an important role in the GM3-Gg3 interaction and that PN(Gg3) recognizes not only some specified portions of GM3 but also the trisaccharide as a whole. Published in 2003.

Chemoenzymatically synthesized glycoconjugate polymers.

Glycoconjugate polymers with poly(vinyl alcohol) (PVA) backbone were synthesized via a chemoenzymatic method. The sugar alcohols of maltose and lactose were submitted to transesterification in the presence of lipases. The esterification was achieved with high selectivity and yield, and the resulting maltitol and lactitol 6-vinyl sebacates were polymerized by a conventional radical initiator with hydrogen peroxide and ascorbic acid. The glycoconjugate polymers carrying alpha-glucose and beta-galactose as recognition signals showed the biological activity such as lectin recognition abilities and hepatocyte adhension. The biodegradability of these polymers was modest but higher than PVA.

Chemoenzymatic synthesis of glycoconjugate polymers: greening the synthesis of biomaterials

Glycoconjugate polymers with biodegradable poly(vinyl alcohol) (PVA) were synthesized via lipase-catalyzed transesterification of sugar alcohols (maltitol and lactitol) with divinyl dicarboxylates and subsequent radical polymerization. The conversion and chemoselectivity in transesterification were dependent on the lipases, the sugar alcohols, and the alkyl chain length of the dicarboxylates. Chemoselective esterification was attained in the presence of lipase from Candida antarctica (lipase CA) to give maltitol 6-vinyl sebacate, lactitol 6-vinyl sebacate, and lactitol 6-vinyl adipate in high yields. Polymerization of these vinyl esters with hydrogen peroxide/ascorbic acid as initiator gave glycoconjugate polymers. These polymers were suggested to take micellar conformations in water and to bind strongly to specific lectins (concanavalin A or RCA120). The biodegradabilities of these polymers were modest but higher than PVA. This simple synthesis will be useful to develop various glycoconjugate polymers with high biological activities due to the multivalent glyco-cluster effect and biodegradability due to their PVA backbone and ester linkage.

Self-assembled monolayers of globotriaosylceramide (Gb3) mimics: surface-specific affinity with shiga toxins

Self-assembled monolayers (SAMs) of Gb3 mimics having different lengths of alkyl chains were prepared on gold surfaces, and their interactions with galactose-specific lectin (RCA 120) and Shiga toxins (Stxs) were investigated by a quartz crystal microbalance (QCM) in aqueous solutions. Their interaction with RCA 120 was enhanced owing to the “cluster effect,” regardless of the alkyl chain length of the SAMs. The interaction with Stxs was dependent on the alkyl chain length of Gb3 mimics. Stx-1 and Stx-2 showed a stronger affinity to the Gb3C2 SAM with ethyl disulfide and to the Gb3C10 with decyl disulfide, respectively. Gb3 glycoconjugate polymer with no alkyl spacer inhibited the adsorption of Stx-1 to Gb3C10 SAM but did not inhibit the adsorption of Stx-2 to Gb3C10 SAM. The results suggest that the alkyl chain of the glycolipid takes part in the binding to Stx-2 but not to Stx-1, which is also supported by the computer simulation of Stx-1 with a Gb3 model substance.

Galactosylated N-vinylpyrrolidone-maleic acid copolymers: synthesis, characterization, and interaction with lectins.

Water-soluble artificial glycoconjugate polymers were synthesized from poly(N-vinylpyrrolidone-co-maleic anhydride) by amidation with an amine-containing galactose derivative. The glycopolymers having different galactose contents were fully characterized in terms of chemical structure by NMR and potentiometric titrations, and their aqueous behavior was studied by viscometric measurements. Their specific binding properties were examined by enzyme-linked lectin assays using RCA(120) lectin. Whatever the glycopolymer, the grafted galactoses were shown to behave similarly to free galactose.

Convenient use of non-malodorous thioglycosyl donors for the assembly of multivalent globo- and isoglobosyl trisaccharides

New thioglycosyl donors ( o-methoxycarbonylphenyl 2,3,4,6-tetra- O-benzyl-1-thio-β- d-galactopyranoside and its 6- O-acetyl analogue) were designed and used for the synthesis of glycoconjugate polymers carrying Gb 3 [Gal(α1→4)Gal(β1→4)Glc] and isoGb 3 [Gal(α1→3)Gal(β1→4)Glc] clusters as side chains. These donors scarcely evolved the unpleasant odor of thiophenols and showed a high α-anomeric selectivity in the galactosylation of p-nitrophenyl β-lactoside derivatives, although in moderate yields. The derived trisaccharides were converted to multivalent carbohydrate ligands and were subjected to a biological assay with Shiga toxins. The multivalent Gb 3 ligand was highly active in inhibiting the toxicity, while the isoGb 3 ligand showed no activity, indicating that Stx-I discriminates between the carbohydrate structures.

A Quartz-crystal microbalance study of adsorption behaviors of artificial glycoconjugate polymers with different saccharide chain lengths and with different backbone structures

Adsorption of glycopolymers is essential for the development of biologically active surfaces employing oligosaccharides as recognition signals. The adsorption behavior has been investigated by quartz-crystal microbalances (QCMs) with use of two different series of glycopolymers: (1) polystyrenes carrying maltooligosaccharides with different saccharide lengths and (2) lactose-carrying polymers with polystyrene and polyphenylacrylamide main chain structures. These glycopolymers were adsorbed on the hydrophobic surfaces of self-assembled monolayers (SAM) of 1-octadecanethiol and cast films of polystyrene from their aqueous solutions, but not on hydrophilic surfaces of SAM of cystamine hydrochloride. The apparent association constants (K a = 10 4 ∼ 10 6 M -1 in molarity of the monomeric unit) and maximum adsorption amounts (Δm max ) on 1-octadecanethiol SAMs and polystyrene cast films were estimated from the Langmuir adsorption isotherms. These values depended on the side-chain oligosaceharide lengths and the main chain chemical structures of these glycopolymers. The adsorption behavior has been discussed in correlation with the desorption of the adsorbed polymer in an aqueous surfactant solution, the partition of the glycopolymer in a water/1-octanol system, and the adsorption amont of bovine serum albumin (BSA) onto the glycopolymer-adsorbed surface. We propose that these polymers are adsorbed in loop-train-tail conformations in which the ratio of the loop-tail portion to the train portion depends on the hydrophilic-hydrophobic property of the polymers.

Synthesis of an artificial glycoconjugate polymer carrying Pk-antigenic trisaccharide and its potent neutralization activity against Shiga-like toxin

Fluorescence-labeled glycoconjugate polymers carrying carbohydrate segments of a globotriaosyl ceramide (Gb3) were synthesized and subjected to biological assays using Escherichia coli O-157 strains and Shiga-like toxins (Stx-I and Stx-II). For the fluorescence labeling, a new polymerizable fluorescent monomer with a TBMB carbonyl chromophore (Ex. 325 nm, Em. 410 nm) was designed. A glycosyl monomer of the trisaccharide segment of Gb3 was prepared from p-nitrophenyl β-lactoside and copolymerized with acrylamide and the fluorescent monomer to prepare a fluorescence-labeled glycoconjugate copolymer carrying [α-d-galactopyranosyl-(1→)-β-d-galactopyranosyl]-(1→)-β-d-glucopyranoside. The polymer showed potent neutralization activity against Stx-I and also binding activity onto E. coli O-157 strains.

ChemInform Abstract: Synthesis of Artificial Glycoconjugate Polymers Carrying Biologically Active Trisaccharides with α‐D‐Galactopyranosyl (1→3) and (1→4)‐Linkage.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Synthesis of Artificial Glycoconjugate Polymers Carrying 6-O-Phosphocholine α-D-Glucopyranoside, Biologically Active Segment of Main Cell Membrane Glycolipids of Mycoplasma Fermentas

ABSTRACT As carbohydrate probes to investigate the biological activity of novel phosphocholine-containing glycoglycerolipids of M. fermentans, artificial glycoconjugate polymers carrying 6-O-phosphocholine α-D-glucopyranoside were synthesized. The synthesis involved α-selective 1-O-p-nitrophenylation (pNP) of 1,6-di-O-acetyl-2,3,4-tri-O-benzyl-D-glucopyranose in the presence of a Lewis acid followed by the introduction of a phosphocholine group at position O-6 by an amidite method. The pNP group was converted into a p-N-methacrylamidophenyl group for subsequent radical polymerization.