Pendant Carbohydrate Research Articles

Selective and Tunable Galectin Binding of Glycopolymers Synthesized by a Generalizable Conjugation Method.

Glycopolymers, conjugates of synthetic polymers with pendant carbohydrates, are becoming increasingly important to probe the role of carbohydrates in cellular processes and for applications like biosensors and drug delivery. A library of glycopolymers bearing different sugar moieties was synthesized by grafting amino-functionalized sugars to poly(acrylic acid) via DMTMM coupling. Primary amines were introduced at the anomeric (C-1) position to a number of unprotected mono-, di-, and trisaccharides using ammonium carbamate and conjugated to poly(acrylic acid) of different molecular weights, synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. This approach provides a simple and efficient route for the preparation of glycopolymers that differ only in the identity or degree of substitution of the sugar moiety on the polymer. The binding parameters (ka, kd, and KD) of these new glycopolymers to galectins-1 and -3 were quantified using surface plasmon resonance. The galectins selectively bound only to lactose-containing polymers, and the binding affinity was dependent on the galectin type, degree of sugar substitution and the molecular weight of polymer chains. Binding to both galectin-1 and -3 increased with a higher degree of sugar substitution, and higher molecular weight of the polymer backbone, reaching KD values on the order of 10-11 M.

Copolymers containing carbohydrates and other biomolecules: design, synthesis and applications.

Glycopolymers are synthetic polymers containing pendant carbohydrate groups. Other biological compounds can be incorporated into glycopolymers to prepare both random and block copolymers aimed at bio-related applications: boronic acid can be introduced as a functional group to obtain crosslinked hydrogels; cholesterol and bile acids can be introduced to render the polymers more hydrophobic for the formation of micelles. Sugar-containing block copolymers with biocompatible blocks such as polypeptides, poly(ethylene glycol), poly(lactic acid) and poly(ε-caprolactone) were also prepared for potential application in drug carriers. These glycopolymers interact with lectins or lectin-containing surfaces as natural carbohydrate mimics. This review highlights the recent progress in the synthesis of random or block glycopolymers. Examples of the applications of glycopolymers in the separation and removal of toxins and bacteria, tumor cell recognition and glucose-responsive insulin delivery are presented and discussed.

Versatile Methodology for Glycosurfaces: Direct Ligation of Nonderivatized Reducing Saccharides to Poly(pentafluorophenyl acrylate) Grafted Surfaces via Hydrazide Conjugation

In this work, we report a convenient and versatile strategy for surface-grafted glycopolymer constructs with the goal of surface modification that controls the chemical presentation and grafting density of carbohydrate side chains. This approach employs a difunctional hydrazine linker, chemically modified to an active ester containing poly(pentafluorophenyl acrylate) grafted scaffold, to conjugate a variety of saccharides through the reducing end. The successive conjugation steps are carried out under mild conditions and yield high surface densities of sugars, as high as 4.8 nmol·cm-2, capable of multivalency, with an intact structure and retained bioactivity. We also demonstrate that this glycosylated surface can bind specific lectins according to the structure of its pendant carbohydrate. To demonstrate bioactivity, this surface platform is used to study the binding events of a human respiratory tract pathogen, Mycoplasma pneumoniae, on surfaces conjugated with sialylated sugars.

Evaluation of cytotoxic activity of titanocene difluorides and determination of their mechanism of action in ovarian cancer cells.

Ovarian cancer is the seventh-most common cancer amongst women and the most deadly gynecologic cancer. Cisplatin based drugs are used in first line therapy, but resistance represents a major obstacle for successful treatment. In this study, we investigated the anticancer effects and mechanism of action of three titanocene difluorides, two bearing a pendant carbohydrate moiety (α-D-ribofuranos-5-yl) on their periphery and one without any substitution. The efficacy of these compounds on ovarian cancer cell lines was evaluated in relation to their particular chemical structure and compared with cisplatin as the most common treatment modality for this type of cancer. The typical mechanism of cisplatin action involves DNA damage, activation of p53 protein and induction of cell death, as previously described for titanium ions. Nevertheless, our data indicate that the effect of titanocene difluoride derivatives is mediated via the endoplasmic reticulum stress pathway and autophagy. We anticipate that the presence of substituents on cyclopentadienyl ring(s) might play an important role in modulation of the activity of particular compounds. Titanocene difluorides exert comparable cytotoxic activity as cisplatin and are more efficient in cisplatin-resistant cell lines. Our results suggest potential utilization of these compounds especially in the treatment of cisplatin-resistant tumor cells.

Cationic charged helical glycopolypeptide using ring opening polymerization of 6-deoxy-6-azido-glyco-N-carboxyanhydride.

Glycopolypeptides with a defined secondary structure are of significance in understanding biological phenomena. Synthetic glycopolypeptides, or polypeptides featuring pendant carbohydrate moieties, have been of particular interest in the field of tissue engineering and drug delivery. In this work, we have synthesized charged water-soluble glycopolypeptides that adopt a helical conformation in water. This was carried out by the synthesis of a glyco-N-carboxyanhydride (glyco-NCA) containing an azide group at the sixth position of the carbohydrate ring. Subsequently, the NCA was polymerized to obtain azide-containing glycopolypeptides having good control over molecular weight and polydispersity index (PDI) in high yields. We were also able to control the incorporation of the azide group by synthesizing random co-glycopolypeptide containing 6-deoxy-6-azido and regular 6-OAc functionalized glucose. This azide functionality allows for the easy attachment of a bioactive group, which could potentially enhance the biological activity of the glycopolypeptide. We were able to obtain water-soluble charged glycopolypeptides by both reducing the azide groups into amines and using CuAAC with propargylamine. These charged glycopolypeptides were shown to have a helical conformation in water. Preliminary studies showed that these charged glycopolypeptides showed good biocompatibility and were efficiently taken up by HepG2 cells.

ChemInform Abstract: Glycopolymer Probes of Signal Transduction

AbstractReview: 212 refs.

Glycopolymer probes of signal transduction.

Glycans are key participants in biological processes ranging from reproduction to cellular communication to infection. Revealing glycan roles and the underlying molecular mechanisms by which glycans manifest their function requires access to glycan derivatives that vary systematically. To this end, glycopolymers (polymers bearing pendant carbohydrates) have emerged as valuable glycan analogs. Because glycopolymers can readily be synthesized, their overall shape can be varied, and they can be altered systematically to dissect the structural features that underpin their activities. This review provides examples in which glycopolymers have been used to effect carbohydrate-mediated signal transduction. Our objective is to illustrate how these powerful tools can reveal the molecular mechanisms that underlie carbohydrate-mediated signal transduction.

Nanoscale Clustering of Carbohydrate Thiols in Mixed Self-Assembled Monolayers on Gold

Self-assembled monolayers (SAMs) bearing pendant carbohydrate functionality are frequently employed to tailor glycan-specific bioactivity onto gold substrates. The resulting glycoSAMs are valuable for interrogating glycan-mediated biological interactions via surface analytical techniques, microarrays, and label-free biosensors. GlycoSAM composition can be readily modified during assembly by using mixed solutions containing thiolated species, including carbohydrates, oligo(ethylene glycol) (OEG), and other inert moieties. This intrinsic tunability of the self-assembled system is frequently used to optimize bioavailability and antibiofouling properties of the resulting SAM. However, until now, our nanoscale understanding of the behavior of these mixed glycoSAMs has lacked detail. In this study, we examined the time-dependent clustering of mixed sugar + OEG glycoSAMs on ultraflat gold substrates. Composition and surface morphologic changes in the monolayers were analyzed by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), respectively. We provide evidence that the observed clustering is consistent with a phase separation process in which surface-bound glycans self-associate to form dense glycoclusters within the monolayer. These observations have significant implications for the construction of mixed glycoSAMs for use in biosensing and glycomics applications.

Synthesis of Rhenium(I) Tricarbonyl Complexes with Carbohydrate‐Pendant Tridentate Ligands and Their Cellular Uptake

AbstractTwelve [ReIL(CO)3]n+ complexes with various carbohydrate‐pendant ligands L have been prepared and their uptake into HeLa S3 cells were investigated. The ligand library includes: (i) glucose/galactose as the carbohydrate group; (ii) bis(2‐pyridylmethyl)amine (DPA), bis(2‐quinolylmethyl)amine (DQA), or N‐(2‐pyridylmethyl)glycine (NPG) as the metal binding component; and (iii) an ethylene chain as a linker between the metal binding site and the O/C‐glycosides. Microwave induced plasma mass spectroscopy (MIP‐MS) measurements revealed that all complexes were extensively incorporated into the HeLa cells over a 24 h period, and the DQA complexes showed the highest uptake of all the complexes in the series. However, in comparison to the corresponding Re complexes without the pendant carbohydrate functions (prepared with the related ligands LDPA, LDQA, and LNPG), only the NPG complexes exhibited carbohydrate enhanced cellular uptake. Considering their water solubility and cellular uptake properties, the NPG complexes containing an O‐glycoside group (L1 and L′1) are the best candidates for enhancing cellular uptake of metal ions. Microscopic analysis with PC‐12 cells in the presence of thefluorescent complex [Re(L′7)(CO)3]Cl, revealed that the complex stays in the cell cytosol and cannot penetrate into the nucleus.

Synthesis and ring-opening polymerizations of novel S-glycooxazolines

A new 2-oxazolines containing S-galactosyl substituents linked to alkyl chains of different lengths; (S-glycooxazoline) were prepared relatively in high yields. By using a 1:1 adduct of 2-methyl-2-oxazoline and methyl triflate, as the initiator, the monomer was polymerized via ring-opening polymerization (ROP) to give products with relatively narrow molecular weight distributions. Homo- and copolymerization were performed, and the kinetics of these new S-glycooxazolines in the ROP are investigated. After a quantitative deprotection, poly(2-oxazoline)s having pendant carbohydrate were obtained. The interaction of the poly(S-glycooxazoline) with RCA120 lectin was investigated, the binding constant between glycopolymer and lectin was increased by 102 times compared with that of the monosaccharide (D-galactose). The in vivo expression of green fluorescent protein using the synthesized poly(S-glycooxazoline)s as polymeric inducers in Escherichia coli host were performed. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010

Synthesis of a family of amphiphilic glycopolymers via controlled ring-opening polymerization of functionalized cyclic carbonates and their application in drug delivery

Polymers bearing pendant carbohydrates have a variety of biomedical applications especially in the area of targeted drug delivery. Here we report the synthesis of a family of amphiphilic block glycopolymers containing d glucose, d galactose and d mannose via metal-free organocatalyzed ring-opening polymerization of functional cyclic carbonates generating narrowly dispersed products of controlled molecular weight and end-group fidelity, and their application in drug delivery. These glycopolymers self-assemble into micelles having a high density of sugar molecules in the shell, a size less than 100 nm with narrow size distribution even after drug loading, and little cytotoxicity, which are important for drug delivery. Using galactose-containing micelles as an example, we demonstrate their strong targeting ability towards ASGP-R positive HepG2 liver cancer cells in comparison with ASGP-R negative HEK293 cells although the galactose is attached to the carbonate monomer at 6-position. The enhanced uptake of DOX-loaded galactose-containing micelles by HepG2 cells significantly increases cytotoxicity of DOX as compared to HEK293. This new family of amphiphilic block glycopolymers has great potential as carriers for targeted drug delivery.

55Cobalt complexes with pendant carbohydrates as potential PET imaging agents

Bis-ligand cobalt(II) complexes of four 3-hydroxy-4-pyridinone ligands with pendant carbohydrates were synthesized and examined for their potential as radiopharmaceuticals. Non-radioactive complexes were prepared on the macroscopic scale and characterized by elemental analysis, mass spectrometry, IR and UV/visible spectroscopy. Facile radiolabeling produced the 55Co complexes in high radiochemical yields (>95%). Identification of the radiolabeled compounds was accomplished by HPLC comparison with the corresponding non-radioactive complexes.

Effects of Polymer Structure on the Inhibition of Cholera Toxin by Linear Polypeptide-Based Glycopolymers

A variety of important biological events are mediated by the multivalent interaction between relevant oligosaccharides and multiple saccharide receptors on lectins, toxins, and cell surfaces; a variety of glycopolymeric materials have therefore been investigated in studies aimed at manipulating these events. The synthesis of protein- and polypeptide-based glycopolymers via protein engineering and other methods offers opportunities to control both the number and the spacing of saccharides on a scaffold, as well as the conformation of the polymer backbone, and will therefore facilitate the structure-based design of polymers for inhibition of multivalent binding events. In initial studies, we have synthesized a family of galactose-functionalized glycopolymers with a poly(L-glutamic acid) backbone, in which the density and linker length of the pendant carbohydrate moiety were varied. The composition of the glycopolymers was determined via (1)H NMR spectroscopy, and the impact of saccharide density and linker length, as well as the potential for these polypeptide-based glycopolymers to act as high-affinity inhibitors of the cholera toxin, has been indicated via competitive enzyme-linked immunosorbent assay and fluorescence titration experiments. The results of these studies suggest strategies for optimizing the binding of linear glycopolymers to bacterial toxins and will aid in the design of additional protein-based materials for studying the impact of multivalency, spacing, and backbone rigidity in a variety of biologically relevant binding events.

One-Pot Glyco-Affinity Precipitation Purification for Enhanced Proteomics: The Flexible Alignment of Solution-Phase Capture/Release and Solid-Phase Separation

A one-pot affinity precipitation purification of carbohydrate-binding protein was demonstrated by designing thermally responsive glyco-polypeptide polymers, which were synthesized by selective coupling of pendant carbohydrate groups to a recombinant elastin-like triblock protein copolymer (ELP). The thermally driven inverse transition temperature of the ELP-based triblock polymer is maintained upon incorporation of carbohydrate ligands, which was confirmed by differential scanning calorimetry and (1)H NMR spectroscopy experiments. As a test system, lactose derivatized ELP was used to selectively purify a galactose-specific binding lectin through simple temperature-triggered precipitation in a high level of efficiency. Potential opportunities might be provided for enhanced proteomic, cell isolation as well as pathogen detection applications.

Carbohydrate-Bearing 3-Hydroxy-4-pyridinonato Complexes of Gallium(III) and Indium(III)

Gallium and indium complexes with pendant carbohydrates have been prepared and examined for their potential as radiopharmaceuticals. Carbohydrate-bearing 3-hydroxy-4-pyridinone ligand precursors and their tris(ligand)gallium(III) and -indium(III) complexes were synthesized and characterized by mass spectrometry, elemental analysis, and (1)H and (13)C NMR spectroscopy, and in the case of one intermediate, by X-ray crystallography. With three equivalents of ligand, neutral complexes formed with the bidentate hydroxypyridinone moiety complexing the gallium(III) and indium(III) metal centers.

Asymmetric Epoxidation of α-Olefins Having Neighboring Sugar Chiral Templates and Alternating Copolymerization with Dicarboxylic Anhydrides

Sugar-substituted epoxides 5-8 were synthesized by asymmetric epoxidation (in CH(2)Cl(2)/water) of alpha-olefins having neighboring sugars (1-4) by use of an achiral oxidant (MCPBA), in which the sugar moiety acted as a chiral template. The diastereoselectivities depend on the methylene spacer between vinyl group and carbohydrate derivatives. The methylene spacer between sugar and vinyl groups influenced the diastereoselectvity. In the case of epoxidation of 4 at 27 degrees C for 24 h, the diastereoselectivity was the highest (99/1). Copolymerizations of 5-8 with succinic anhydride were attained at 100 degrees C for 72 h to give poly(ethylene succinate) having pendant carbohydrate [poly(SAn-alt-5), M(n) = 1.4 x 10(3); poly(SAn-alt-6), M(n) = 2.2 x10(3); poly(SAn-alt-7), M(n) = 2.9 x 10(3); poly(SAn-alt-8), M(n) = 1.8 x 10(3)]. The methylene spacer between sugar and epoxide has an effect on the reactivity of epoxide in copolymerization as well as the diastereoselectivity. Alternating copolymerization of 7 and glutaric anhydride gave a polyester of M(n) 4.2 x10(3).

Electrochemical detection of Arachis hypogaea(peanut) agglutinin binding to monovalent and clustered lactosyl motifs immobilized on a polypyrrole film

Direct detection of peanut agglutinin/lactose interactions was realized by an electrochemical approach based on a polypyrrole coated electrode displaying pendant carbohydrates.

STUDY OF MECHANISM OF ENANTIOSEPARATION. III. THE INFLUENCE OF CARBOHYDRATE MOIETIES OF TEICOPLANIN-BONDED CHIRAL STATIONARY PHASE ON THE SEPARATION OF SOME DERIVATES OF PHENYLCARBAMIC ACID

ABSTRACT Enantiomeric separation of alkoxysubstituted esters of phenylcarbamic acid (local anesthetic drugs) is carried out using high performance liquid chromatography (HPLC) with two chiral stationary phases. The teicoplanin chiral stationary phase—chirobiotic T and the teicoplanin chiral stationary phase without the pendant carbohydrate moieties—chirobiotic teicoplanin aglycone (TAG) were used. The influence of the sugar units, the concentration of the ionic modifiers (diethylamine), the influence of the position and of number of carbon atoms in the analytic alkoxychain substituent, and the composition of the mobile phase; on retention factors and resolution of enantiomers were investigated. By comparison of chromatographic parameters obtained by using both chiral stationary phases, the influence of carbohydrate moieties on the mechanism of chiral separation could be evaluated. The interaction mechanism of the enantiomeric separations is discussed. Better separation, in terms of—greater values of R ij of enantiomers—was achieved with the chirobiotic TAG column.

Synthesis and Polymerization of a New Class of Oligosaccharide-and Polyamide-Macromers Having a Styrene End-Group

Abstract As an approach to synthesis of oligo- and polysaccharide-containing polymers, two types of polystyrenes having pendant carbohydrate groups were prepared. Their functions, especially amphiphilic behaviors in water, were revealed. A new polyamide macromer having a vinylbenzyl group (Mn 3000-3800) was prepared by the anionic polymerization of bicyclic oxalactam followed by the reaction with p-vinylbenzylamine. Another polyamide macromer telechelated with amino groups (Mn, 1400 and 4100) was also prepared by the similar method.

糖質高分子

Research on syntheses and functions of polymers consisting of carbohydrate and noncarbohydrate moieties is now expanding rapidly. An advance in the field is attributable to discoveries of important biological roles of carbohydrates, developments of chemical and physical methods and techniques for separation, analysis, and synthesis, as well as demand for effective utilization of renewable resources. The present review deals with three different types of the polymers : (1) Modified polysaccharides. Discussion is focused on regioselectivities of chemical modifications.(2) Polymers containing carbohydrates in the main chain. Recently developed routes for condensation polymers and block copolymers are described.(3) Polymers having pendant carbohydrates. Polymer-supported carbohydrates are used as intermediates in the syntheses of carbohydrates and as potential chiral templates. Linear, soluble polymers are also of interest as amphiphilic polymers capable of binding organic solutes in water and as tools for examination of bioorganic mechanisms and for pharmacological applications. Oligosaccharide-containing polymers are expected to play a role in recognition, acting as receptors for lectins, enzymes, proteins, hormones, and viruses.