Sugar Clusters Research Articles

Synthetic assembly of α-O-linked-type GlcNAc using polymer chemistry affords sugar clusters, which effectively bind to lectins

Fischer’s glycoside synthesis was applied to linker precursor alcohols of two different lengths having appropriate alkane chains to obtain the corresponding α-glycoside and it was found to be applicable with moderate yields. Water-soluble glycomonomers were systematically prepared from N-acetyl-d-glucosamine (GlcNAc) by introducing two kinds of alcohols having different methylene lengths. Typical radical polymerizations of the glycomonomers with acrylamide as a modulator for control of the distance between carbohydrate residues in water in the presence of ammonium persulfate (APS)-N,N,N’,N’-tetramethylethylenediamine (TEMED) gave a series of glycopolymers with various α-glycoside-type GlcNAc residue densities. Fluorometric analysis of the interaction of wheat germ agglutinin (WGA) with the glycopolymers was performed and the results showed unique binding specificities based on structural differences.

Potensi Karbon Pada Tegakan Hutan Adat Imbo Putui Desa Petapahan Kabupaten Kampar

Abstract
 Forests are one of the natural resources that can absorb carbon dioxide in the atmosphere in the process of photosynthesis, carbon dioxide (CO2) in the atmosphere is bound and converted into a form of energy (sugar clusters) that is beneficial for life. Forests are able to reduce carbon emissions and store them in various compartments such as plants, litter, and soil organic matter. Plants as carbon storage causes the concentration of carbon dioxide in the atmosphere to decrease. This study aims to calculate the potential for carbon stored and absorbed in the form of CO2 in the Imbo Putui customary forest, Petapahan Village, Kampar District. The study used a systematic sampling method with random start by making plots measuring 20 m x 20 m for poles and trees and 50 cm x 50 cm for litter sampling, the number of plots was 63 with a distance between plots of 100 meters. The research results show that the potential value of carbon stored in the 251 h-1 Imbo Putui customary forest reaches748,406.70tons of CO2 that consists of a tree level of 745,008.16 tons pole level of 3117.42 tons and litter of 281.12 tones

CuAAC synthesis of resorcin[4]arene-based glycoclusters as multivalent ligands of lectins

Synthetic multivalent glycoclusters show promise as anti-adhesives for the treatment of bacterial infections. Here we report the synthesis of a family of tetravalent galactose and lactose functionalised macrocycles based on the resorcin[4]arene core. The development of diastereoselective synthetic routes for the formation of lower-rim propargylated resorcin[4]arenes and their functionalistion via Cu-catalyzed azide-alkyne click chemistry is described. ELLA binding studies confirm that galactose sugar clusters are effective ligands for the PA-IL bacterial lectin of Pseudomonas aeruginosa while poor binding for the lactose-based monovalent probe and no binding could be measured for the multivalent glycoclusters was observed for the human galectin-1.

Universal patterns of equilibrium cluster growth in aqueous sugars observed by dynamic light scattering.

Dynamic light scattering performed on aqueous solutions of three sugars (glucose, maltose and sucrose) reveal a common pattern of sugar cluster formation with a narrow cluster size distribution. In each case, equilibrium clusters form whose size increases with increasing sugar content in an identical power law manner in advance of a common, critical-like, percolation threshold near 83 wt % sugar. The critical exponent of the power law divergence of the cluster size varies with temperature, increasing with decreasing temperature, due to changes in the strength of the intermolecular hydrogen bond and appears to vanish for temperatures in excess of 90 °C. Detailed analysis of the cluster growth process suggests a two-stage process: an initial cluster phase formed at low volume fractions, ϕ, consisting of noninteracting, monodisperse sugar clusters whose size increases ϕ(1/3) followed by an aggregation stage, active at concentrations above about ϕ=40%, where cluster-cluster contact first occurs.

Universal Patterns of Equilibrium Cluster Growth in Aqueous Sugars Observed by Dynamic Light Scattering.

Dynamic light scattering performed on aqueous solutions of three sugars (glucose, maltose and sucrose) reveal a common pattern of sugar cluster formation with a narrow cluster size distribution. In each case, equilibrium clusters form whose size increases with increasing sugar content in an identical power law manner in advance of a common, critical-like, percolation threshold near 83 wt% sugar. The critical exponent of the power law divergence of the cluster size varies with temperature, increasing with decreasing temperature, due to changes in the strength of the intermolecular hydrogen bond and appears to vanish for temperatures in excess of 90 °C. Detailed analysis of the cluster growth process suggests a two-stage process: an initial cluster phase formed at low volume fractions, φ, consisting of non-interacting, monodisperse sugar clusters whose size increases φ(1/3) followed by an aggregation stage, active at concentrations above about φ = 40%, where cluster-cluster contact first occurs.

Preparation, characterization and immunogenicity of HIV-1 related high-mannose oligosaccharides-CRM197 glycoconjugates

The dense glycan shield on the surface of human immunodeficiency virus type 1 (HIV-1) gp120 masks conserved protein epitopes and facilitates virus entry via interaction to glycan binding proteins on susceptible host cells. The broadly neutralizing monoclonal antibody 2G12 binds a cluster of high-mannose oligosaccharides on the gp120 subunit of HIV-1 Env protein. This oligomannose epitope is currently being considered for the design of a synthetic vaccine. The cluster nature of the 2G12 epitope suggests that a multivalent antigen presentation is important to develop a carbohydrate-based vaccine candidate. In this work we describe the development of neoglycoconjugates displaying clustered HIV-1 related oligomannose carbohydrates. We exploited flexible polyamidoamine (PAMAM) scaffold to generate four- and eight-valent sugar clusters of HIV-1-related oligomannose antigens Man(4), Man(6) and Man(9). The multivalent presentation of oligomannoses increased the avidity of Man(4) and Man(9) to 2G12. The synthetic glycodendrons were then covalently coupled to the protein carrier CRM(197), formulated with the adjuvant MF59, and used to immunize two animal species. Oligomannose-specific IgG antibodies were generated; however, the antisera failed to recognize recombinant HIV-1 gp120 proteins. We conclude that further structural vaccinology work is needed to identify an antigen presentation that closely matches in vivo the structure of the epitope mapped by 2G12.

Anomalous Dynamics of Hydration Water in Carbohydrate Solutions

Molecular dynamics simulations have been carried out to investigate the dynamics of fructose aqueous solutions up to 70 wt % concentration. We find that the hydrogen (H)-bonded network of fructose molecules extends with increasing sugar content and forms a structurally heterogeneous system around and above 45 wt % concentration, characterized as a percolated-like solute domain permeated by patchy regions of solvent. The presence of such aggregates in concentrated solutions promotes the slowing down of water translational, reorientational, and H-bonding dynamics, typical of many biomolecular environments. Analysis of the effects of the topological and energetic disorder of the sugar aggregates on vicinal water dynamics, similar to that recently carried out for the hydration layer of proteins by Pizzitutti et al. (J. Phys. Chem. B 2007, 111, 7584), reveals many similarities between the dynamical anomaly of the hydration layers of both systems. Like a protein surface, topological and energetic disorders of the sugar aggregates both contribute to the translational diffusion anomaly. However, unlike in the vicinity of a protein surface, the rotational relaxation is also hindered by the topological disorder created by the intertwined, percolating sugar clusters in concentrated solutions.

How Homogeneous Are the Trehalose, Maltose, and Sucrose Water Solutions? An Insight from Molecular Dynamics Simulations

The structural properties resulting from the reciprocal influence between water and three well-known homologous disaccharides, namely, trehalose, maltose, and sucrose, in aqueous solutions have been investigated in the 4-66 wt % concentration range by means of molecular dynamics computer simulations. Hydration numbers clearly show that trehalose binds to a larger number of water molecules than do maltose or sucrose, thus affecting the water structure to a deeper extent. Two-dimensional radial distribution functions of trehalose solutions definitely reveal that water is preferentially localized at the hydration sites found in the trehalose dihydrate crystal, this tendency being enhanced when increasing trehalose concentration. Over a rather wide concentration range (4-49 wt %), the fluctuations of the radius of gyration and of the glycosidic dihedral angles of trehalose indicate a higher flexibility with respect to maltose and sucrose. At sugar concentrations between 33 and 66 wt %, the mean sugar cluster size and the number of sugar-sugar hydrogen bonds formed within sugar clusters reveal that trehalose is able to form larger clusters than sucrose but smaller than maltose. These features suggest that trehalose-water mixtures would be more homogeneous than the two others, thus reducing both desiccation stresses and ice formation.

Photoswitchable cluster glycosides as tools to probe carbohydrate–protein interactions: synthesis and lectin-binding studies of azobenzene containing multivalent sugar ligands

Synthetic cluster glycosides have often been used to unravel mechanisms of carbohydrate-protein interactions. Although synthetic cluster glycosides are constituted on scaffolds to achieve high avidities in lectin binding, there have been no known attempts to modulate the orientations of the sugar clusters with the aid of a functional scaffold onto which the sugar units are linked. Herein, we describe synthesis, physical, and lectin-binding studies of a series of alpha-D-mannopyranoside and beta-D-galactopyranosyl-(1-->4)-beta-D-glucopyranoside glycoclusters that are attached to a photoswitchable azobenzenoid core. These glycoclusters were synthesized by the amidation of amine-tethered glycopyranosides with azobenzene carbonyl chlorides. From kinetic studies, the cis forms of the azobenzene-glycopyranoside derivative were found to be more stable in aqueous solutions than in organic solvents. Molecular modeling studies were performed to estimate the relative geometries of the photoswitchable glycoclusters in the trans- and cis-isomeric forms. Isothermal titration calorimetry (ITC) was employed to assess the binding of these glycoclusters to lectins peanut agglutinin (PNA) and concanavalin A (Con A). Although binding affinities were enhanced several orders higher as the valency of the sugar was increased, a biphasic-binding profile in ITC plots was observed during few glycoclusters lectin-binding processes. The biphasic-binding profile indicates a "cooperativity" in the binding process. An important outcome of this study is that in addition to inherent clustering of the sugar units as a molecular feature, an induced clustering emanates because of the isomerization of the trans form of the azobenzene scaffold to the cis-isomeric form.

Oligolysine-based saccharide clusters: synthesis and specificity.

In search of specific and highly selective sugar clusters for cell receptors, such as membrane lectins, various disaccharides were coupled to small peptide cores through an amide bond. In a first step, the reducing disaccharides, i.e. lactose and three different dimannoses, were converted into glycosyl-pyroglutamyl-beta-alanine derivatives. The free carboxylic group of these conjugates was then coupled to the alpha and epsilon amino groups of the core peptide (Lys( n )-Ala-Cys-NH2) with n =1 to 5, with complete substitution leading to homogeneous glycoclusters. The thiol group of the cysteine residue was used to tag the glycosylated oligolysines upon reaction with fluorescein iodoacetamide. The affinity of these glycoclusters towards two plant lectins was assessed by surface plasmon resonance. The selectivity of their cell uptake was investigated by flow cytometry using two types of cells: a human hepatoma cell line (HepG2 cells) expressing the plasma membrane galactose-specific lectin, and monocyte-derived dendritic cells expressing the plasma membrane mannose-specific lectin. The glycoclusters containing four or five disaccharides were shown to bind plant lectins and cell surface membrane lectins with a narrow selectivity and with a high affinity.

ChemInform Abstract: Sugar—Lectin Interactions: Sugar Clusters, Lectin Multivalency and Avidity

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.

Peroxo-Bridged Dinuclear Cobalt(III) Complexes Containing N-Glycoside Ligands from Tris(2-aminoethyl)amine and d-Glucose or Maltose

Peroxo-bridged dinuclear cobalt(III) complexes, [{Co((d-Glc)2-tren)}2(μ-O2)]X3·5H2O (X = Cl (2·5H2O), Br (3·5H2O)) and [{Co((Mal)2-tren)}2(μ-O2)]Cl3·6H2O (4·6H2O), were prepared from CoX2·6H2O, tris(2-aminoethyl)amine, and d-glucose (d-Glc) or maltose (α-d-glucopyranosyl-(1→4)-d-glucose; Mal), and were characterized by elemental analysis, UV−vis absorption, circular dichroism, 1H and 13C NMR spectroscopic techniques, and X-ray absorption and crystallographic analyses, where (aldose)2-tren is bis(N-aldosyl-2-aminoethyl)(2-aminoethyl)amine (aldose = d-Glc, Mal). The structure of 2 and 4 were determined by X-ray crystallography to consist of two Co(III) ions bridged by a peroxo unit: 2·4H2O·CH3OH, orthorhombic, P212121 (No. 19), a = 19.384(8) Å, b = 23.468(5) Å, c = 13.195(5) Å, V = 6002(2) Å3, Z = 4, Dcalcd = 1.440 g cm-3, T = −99 °C, R = 0.078, Rw = 0.085 for 4961 reflections with I > 3σ(I); 4·2.25H2O·3.75CH3OH, monoclinic, P21 (No. 4), a = 12.819(7) Å, b = 49.168(18) Å, c = 14.973(6) Å, β = 104.59(4)°, V = 9130(7) Å3, Z = 4, Dcalcd = 1.459 gcm-3, T = −136 °C, R = 0.101 for 6837 reflections with I > 2σ(I). The hydrogen bondings between the sugar moieties deviates the Co−O−O−Co torsional angle from planarity to 100.4(6)° (2) and av 102(1)° (4). The electronic structures of the twisted Co2(μ-O)2 core were discussed on the basis of extended Hückel MO calculations. The present discrete complexes have a tetravalent sugar domain around the dinuclear center and clearly demonstrated distinct sugar−sugar interactions which could be a minimal model for so-called sugar clusters of glycoproteins on cell surfaces.

Preparation and host-guest interactions of novel macrocyclic sugar clusters having mono- and oligosaccharides

Novel macrocyclic sugar clusters, which are constructed with a macrocyclic skeleton and four carbohydrate branches composed of glucose, maltose, or maltotriose derivatives individually, were prepared. Host-guest interactions between the hosts and a fluorescent guest, 8-anilinonaphthalene-1-sulphonate, were examined in aqueous media. The sugar clusters having maltose, or maltotriose residues strongly bind concanavaline A, but never peanut lectin. Novel macrocyclic sugar clusters having glucose, maltose, and maltotriose derivatives individually were prepared. The guest-binding behavior of the sugar clusters toward hydrophobic guest was examined by fluorescence spectroscopy in aqueous media. [Display omitted]

Molecular delivery systems using macrocyclic sugar clusters

Abstract

Surface Plasmon Resonance Study on the Interaction of Immobilized Macrocyclic Sugar Clusters with Lectins and Water-soluble Polymers

Abstract A surface plasmon resonance study indicates that an amphiphilic calix[4] resorcarene derivative having eight polar side chains with terminal galactose or glucose residues and four long alkyl chains are immobilized on a hydrophobic sensor chip; the resulting monolayer of the sugar moieties, exposed to the bulk aqueous phase, binds lectin polysaccharides, and ploy(vinylalcohol) in water.

有機合成化学の挑戦‐２１世紀に向けて 生体機能関連 人工超分子：多点相互作用の展開

Multiple interaction plays important roles in molecular recognition. In the present article are described recent advances in the supramolecular multiple interactions. It is composed of three parts. The first one deals with a strategic switch from convergent multiple interaction sites to divergent ones. The latter is suited not for host-guest complexation but for intermolecular network formation and hence allows molecular alignment control in crystals. In the second part is shown the use of templates to induce biologically-significant supramolecular structures such as α-helical folding of peptides and sugar clusters. The last part is concerned with how multiple hydrogen bonding interaction can become effective in aqueous media. Examples include a membrane-forming cooperation of hydrogen bonding and hydrophobic effect, a very strong adsorption of a macrocyclic sugar cluster on polar solid surfaces, and guest-binding supramolecular cavities in microporous crystals maintained by hydrogen-bonds.