Glycopolymers carrying sulfated saccharides with modest sugar contents (11% and 28%) were found to suppress the formation of amyloid fibrils by amyloid beta peptides (Abeta(1-42), Abeta(1-40), and Abeta(25-35)), as evaluated by thioflavin T assays and atomic force microscopy observation. Circular dichroism spectra showed that the conformation of amyloid beta peptides depended on the glycopolymer additives, and that the glycopolymer additives reduced the beta-sheet contents. Neutralization activity was confirmed by in vitro assay with HeLa cells.
View Article and Find Full Text PDFShiga toxin (Stx) is one of the most critical factors in the development of hemolytic uremic syndrome and other systemic complications following enterohemorrhagic Escherichia coli (EHEC) infection. Substances neutralizing Stx by interfering with toxin-receptor binding have been explored as therapeutic candidates for EHEC infection. In this study, we examined globotriaosyl (Gb3), galabiosyl (Gb2) and galacto-trehalose, each of which was synthetically conjugated with a polyacrylamide backbone, for Stxneutralizing activity.
View Article and Find Full Text PDFThe bis(alpha-D-mannopyranosyl)-[60]fullerene conjugate 3 was prepared by thermal coupling of C60 and either 2-azidoethyl 2,3,4,6-tetra-O-acetyl- or 2,3;4,6-di-O-isopropylidene-alpha-D-mannopyranoside (Scheme). Compound 3 was found to readily self-assemble. Dynamic-light-scattering (DLS) and atomic-force microscopy (AFM) experiments supported that the amphiphilic compound gives rise to nano-sized supramolecular structures during sugar deprotection (Ac-group removal) performed in MeOH/CH2Cl2 solution.
View Article and Find Full Text PDFThe 5-6- and 6-6-junction isomers of alpha-D-mannopyranosyl [60]fullerene were studied by means of circular dichroism (CD), deuterium labeling, 1H-NMR, molecular-dynamics (MD) calculations, and a lectin-binding assay. The CD spectra of the O-acetylated derivatives allowed clear discrimination of the isomers, while the 1H-NMR spectra, with assistance from deuterium labeling and MD calculations, served to disclose the unique conformation and molecular geometry of each acetylated isomer in chloroform solution. The deprotected 5-6- and 6-6-isomers, which gave colloidal suspensions in aqueous mixtures, displayed marked activity in blocking lectin-induced hemagglutination by concanavalin A.
View Article and Find Full Text PDFMoraxella catarrhalis is one of the major pathogens of respiratory and middle ear infections. Attachment of this bacterium to the surface of human pharyngeal epithelial cells is the first step in the pathogenesis of infections. This study revealed that sulfatide might act as a binding molecule for the attachment of M.
View Article and Find Full Text PDFA Gb3-trisaccharide mimic peptide was selected with biopanning from a phage display library against anti-Gb3 antibody to neutralize Shiga toxins (Stxs). Biopanning was carried out on a microplate immobilized with a Fab fragment of anti-Gb3 antibody and a subtraction procedure screening was applied to enhance specificity. The selected phage clones showed strong affinity to anti-Gb3 antibody and to Stxs.
View Article and Find Full Text PDFWe have designed novel short peptides expressing both antimicrobial and Shiga-toxin (Stx) neutralization activities by combining nuclear localization signal (NLS) peptides (RIRKKLR, PKKKRKV, and PRRRK) tandemly with globotriaoside (Gb3) mimic peptide (WHWTWL). These fusion peptides exhibited excellent antimicrobial activity against both gram-positive and gram-negative bacteria. A peptide WHWTWLRIRKKLR (Trp-His-Trp-Thr-Trp-Leu-Arg-Ile-Arg-Lys-Lys-Leu-Arg), especially, exhibited about 100 times higher activity than the original NLS peptide.
View Article and Find Full Text PDFBiomacromolecules
December 2005
A novel strategy for artificial regulation system of gene expression applying the specific molecular recognition between carbohydrate and lectin is proposed. Plasmid-lactose conjugates (pActin-lactose and pGFP-lactose) prepared via diazocoupling maintained the transcription activity with T7 RNA polymerase. Gel-shift assay showed that the pActin-lactose conjugates were specifically complexed with galactose-specific lectin RCA(120) with a strong binding affinity (K(a) = 7.
View Article and Find Full Text PDFDivergent pathways are disclosed in the activation of 2-O-benzyl-1-hydroxy sugars by a reagent combination of CBr4 and Ph3P, all of which afford one-pot alpha-glycosylation methods. When this reagent is used in CH2Cl2, the 1-hydroxy sugar is converted to the alpha-glycosyl bromide in a conventional way and leads to the one-pot alpha-glycosylation method based on a halide ion-catalytic mechanism. In either DMF or a mixture of DMF and CHCl3, however, alternative alpha-glycosyl species are generated.
View Article and Find Full Text PDFAn oligomaltose-carrying polystyrene "glycoconjugate polystyrene" was synthesized by the homopolymerization of 4-vinylbenzylamine oligomaltonic amides, derived from maltose, maltotriose, maltopentaose, and maltoheptaose. The resultant amphiphilic glycoconjugate polystyrenes were dissolved in 0.1 M aqueous urea, and their structures characterized by small-angle X-ray scattering and molecular modeling.
View Article and Find Full Text PDFWe describe herein the construction of periodically, spatially controlled glycoclusters along DNA duplexes and their cooperative lectin recognition. Site-specifically alpha-mannosylated oligodeoxynucleotide 20-mer (Man-ODN20) was synthesized via the phosphoramidite solid-phase synthesis. Alternate hybridization of the Man-ODN20 with the half-sliding complementary ODN 20-mer (hscODN20) gave an alternately prolonged Man-cluster Man-ODN20/hscODN20.
View Article and Find Full Text PDFCarbohydrate-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.
View Article and Find Full Text PDFWe 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.
View Article and Find Full Text PDFPeptides binding to a Gb3 mimic were selected from 12-mer peptide library. The self-assembled monolayer (SAM) of a Gb3 mimic was formed on the gold surface, and biopanning was carried out with the phage display peptide library. After three rounds of biopanning, four individual sequences were obtained from 10 phage clones, and the selected peptides having the specific 7-mer sequence (FHENWPS) showed affinities to the Gb3 mimic as strong as to RCA120.
View Article and Find Full Text PDFA chemoenzymic methodology is extended to the library synthesis of regioselectively O-sulfonated pNP D-gluco and D-mannopyranosides. The method involves the sequential reactions of chemical O-sulfonation and sulfatase-catalyzed O-desulfonation. pNP 2,6-di-O-sulfo-alpha-D-glucopyranoside and pNP 3,6-di-O-sulfo-alpha-D-mannopyranoside were obtained as sodium salts using chemical methods by way of dibutylstannylene acetals or tributylstannyl ethers.
View Article and Find Full Text PDFCarbohydrate-carbohydrate interactions between Gg3 trisaccharide-carrying polystyrene (PN(Gg3)) and monolayers of several glycosphingolipids (GSLs) were quantitatively investigated by surface plasmon resonance techniques. PN(Gg3) was adsorbed onto a GM3 monolayer strongly and specifically with an apparent affinity constant of K(a) = 2.5 x 10(6) M(-1), and the apparent affinity constants onto GSLs decreased in the following order: GM3 > LacCer > (KDN)GM3 approximately GlcCer > GM2 approximately GD3 approximately GM4 > GM1 approximately 2,6-isoGM3 > ceramide.
View Article and Find Full Text PDFBiological activity of N-acetyl-6-sulfo-beta-d-glucosaminides (6-sulfo-GlcNAc 1) having a structural homology to N-acetylneuraminic acid (Neu5Ac 2) and 2-deoxy-2,3-dehydro-N-acetylneuraminic acid (Neu5Ac2en 3) was examined in terms of inhibitory activity against influenza virus sialidase (influenza, A/Memphis/1/71 H3N2). pNP 6-Sulfo-GlcNAc 1a was proved to show substantial activity to inhibit the virus sialidase (IC(50)=2.8 mM), though p-nitrophenyl (pNP) GlcNAc without 6-sulfo group and pNP 6-sulfo-GlcNH(3)(+) 1b without 2-NHAc showed little activity (IC(50) >50 mM).
View Article and Find Full Text PDFWe describe herein the relationship between the spatial arrangement of self-organized galactose clusters and lectin recognition. beta-Galactose-modified deoxyuridine phosphoramidite was synthesized and applied to solid-phase synthesis to provide 18-, 20-, and 22-mers of site-specifically galactosylated oligodeoxynucleotides (Gal-ODNs). These Gal-ODNs were self-organized through hybridization with the corresponding 18-, 20-, and 22-mers of half-sliding complementary ODNs (hsc-ODNs) to give periodic galactoside clusters.
View Article and Find Full Text PDFBioorg Med Chem Lett
September 2003
6-Sulfo-D-GlcNAc with a molecular geometry close to that of N-acetylneuraminic acid (Neu5Ac) was hypothesized to serve as a simple Neu5Ac mimic possessing high potential in biochemical and medicinal applications. The hypothesis was evidenced with a neuraminidase inhibition assay using p-nitrophenyl (pNP) 3-, 4-, and 6-sulfo-beta-D-GlcNAc (4, 5 and 2a) and 6-sulfo-beta-D-Glc 6, in which only pNP 6-sulfo-beta-D-GlcNAc 2a was found to show substantial activity.
View Article and Find Full Text PDF[structure: see text] C(3)-Symmetric glycoconjugates carrying three equivalent Lewis(X) antigens or beta-lactosides were synthesized from p-nitrophenyl glycosides and trimesic acid via regio- and stereocontrolled glycosylation reactions. An (1)H NMR study has shown that the C(3)-symmetric glycoconjugates soluble in water provide useful probes to investigate the Ca(2+)-dependent Lewis(X)-Lewis(X) association.
View Article and Find Full Text PDFThe reaction of a 2-O-benzyl-1-hydroxy sugar with CBr4 and Ph3P generates a glycosyl bromide in situ, which is coupled with an acceptor alcohol in the presence of N,N-tetramethylurea to afford an alpha-glycosyl product virtually quantitatively. In a proposed pathway, the reagent combination plays multiple roles such as the generation of a glycosyl donor, the activation of glycosylation, and the dehydration of the reaction system. These roles allow a simple alpha-glycosylation to be performed without special attention to dehydration.
View Article and Find Full Text PDFTris-bipyridine ferrous and ruthenium complexes carrying various saccharide appendages have been investigated to develop sensory systems for monitoring saccharide-binding phenomena. Ferrous O-glycoclusters having spacer moieties inserted between saccharide appendages and the complex core showed enhanced affinities to lectins, but ferrous N-glycoclusters, in which the saccharide-appendages are directly linked to the complex core via amide linkage, had low lectin-affinities. Molecular dynamics calculation indicated that the O-glycoclusters have flexible and densely packed saccharide clusters, in contrast to the octahedrally fixed saccharide arrays of N-glycoclusters.
View Article and Find Full Text PDFThe substrate specificities of three molluscan sulfatases (E.C. 3.
View Article and Find Full Text PDF[reaction: see text] A concept for the development of practical glycosylation is presented and demonstrated by one-pot alpha-glycosylation applying Appel agents for 2-O-benzyl-1-OH hexoses in DMF. The reaction, in situ giving the equilibrium of glycosyl bromides and more reactive O-glycoside intermediates, accomplishes a near-quantitative alpha-glycosylation removing the water molecules.
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