Search results for "Saccharide"

1994

The synthesis of linear carbohydrate modified polysiloxanes has been successfully performed by hydrosilation of functionalized and protected carbohydrate derivates. The functionalization (allyl glycosilation) may be applied to a wide variety of reducing carbohydrates. In this study, mono-, di- and oligosaccharides were converted by a simple two-step reaction (β-acetylation and allyl glycosilation) into active compounds, allowing the polymer analogous addition to random poly[dimethyl-co-hydromethyl]siloxanes (hydrosilation). By variation of the Si–H amount in the starting polymers, polysiloxanes with 1.5% to 56% (by weight) carbohydrate content were prepared. At small degrees of substitution…

Water-soluble polysaccharides from Opuntia stricta Haw. fruit peels: Recovery, identification and evaluation of their antioxidant activities

2015

Abstract Opuntia stricta Haw. is considered as one of the most common cactus plant growing in Tunisia. Extracting valuable compounds from its fruit peel, considered as by-product, is drawing more and more attention, making it on the verge of commercialization. Water-soluble polysaccharides were extracted from Opuntia stricta Haw. peels, and their chemical composition assessed using thin layer chromatography. The antioxidant activities of the extracted polysaccharides were assessed using 2,2-diphenyl-1-picrylhydrazyl free radical scavenging activity, total antioxidant activity and reducing power capacity. The extraction yield of water-soluble polysaccharides was 7.53±0.86%. The chemical comp…

Effect of chelatants on gellan gel rheological properties and setting temperature for immobilization of living bifidobacteria.

1993

The effect of various concentrations of sequestrants (sodium citrate, sodium metaphosphate, and EDTA) was studied on gellan gel (1.5-2.5% (w/v)) setting temperature and rheological properties. Addition of EDTA between 0 and 0.8% (w/v) led to a progressive decrease of setting temperature. Citrate and metaphosphate decreased this parameter when added up to 0.4 or 0.6%, depending on gellan gum concentration, eventually resulting in the absence of gel formation at room temperature for the 1.5% gellan solution containing 0.4% citrate. This effect was accompanied by a significant decrease of gel strength and stiffness and might be attributed to the binding of the divalent cations required for cha…

Patterns of wall synthesis inSaccharomyces cerevisiae

1979

Wall formation inSaccharomyces cerevisiae seems to be the result of two main patterns of wall material deposition: (i) around the whole periphery of the cell in nonbudding ones, and (ii) mainly at the tip of the daughter cell or at the cross wall that separates dividing cells. This interpretation has been obtained following experiments in which RNA or protein synthesis has been inhibited. Under these conditions, glucan formation takes place, and wall thickening is probably due to the accumulation of this polysaccharide. Furthermore, once a pattern of wall deposition has been established, it is not modified by inhibition of RNA or protein synthesis.

Relationships Between Dimorphism, Cell Wall Structure, and Surface Activities in Candida albicans

1991

Most cells are covered with a complex network of interacting molecules that form the extracellular matrix. These molecules (proteins and polysaccharides) are secreted locally and interact among themselves to form an organized structure outside the cell plasma membrane. In unicellular eukaryotic organisms and plant cells, this structure is reinforced to withstand osmotic changes in the external environment, giving rise to the so-called cell wall.

A strategy for chromatographic and structural analysis of monosaccharide species from glycoproteins.

1996

A general strategy for the chromatographic and structural analysis of the monosaccharide species fucose (Fuc), N-acetylgalactosamine (GalNAc), N-acetylglucosamine (GlcNAc), galactose (Gal), glucose (Glc), mannose (Man), N-acetylneuraminic acid (NANA) present in glycoproteins is described. Qualitative and quantitative aspects for the separation of these glycoprotein monosaccharides (monosaccharide species) using ligand-exchange chromatography (LEC) and high pH anion-exchange chromatography (HPAEC) in combination with pulsed-amperometric detection (PAD), refractive index (RI) and ultraviolet (UV) monitoring are discussed in detail. The conditions for the acidic hydrolysis of glycoproteins and…

Oligosaccharide recognition by selectins: Synthesis and biological activity of multivalent sialyl lewis-X ligands

1995

Abstract Trivalent sialyl Lewis-X ligands 6–8 anchored onto flexible templates have been synthesized and evaluated as inhibitors of E-selectin and P-selectin mediated cell adhesion in cell culture assays and in vivo. Biological activities in vitro correlated with spacer length and lead to ligands with 3-fold (E-selectin) and 5-fold (P-selectin) improved receptor binding avidity per single tetrasaccharide moiety.

Direct acid-catalysed mechanical depolymerisation of fibre sludge to reducing sugars using planetary milling

2016

Abstract This study performed a direct solvent-free acid-catalysed mechanical depolymerisation of fibre sludge to reducing sugars which involves one step of acid milling in a planetary mill. The common reported ‘solvent-free’ mechanocatalytic depolymerisation of lignocellulose which includes 1) acid impregnation, 2) vacuum evaporation and 3) mechanocatalytic depolymerisation was also performed as a reference. The major converted monosaccharides were determined by capillary electrophoresis and the results of total reducing sugar (TRS) yields were carried out based on the 3,5-dinitrosalicylic acid (DNS) method. The results showed that the TRS conversion of direct acid-catalysed mechanical dep…

Characterization of totally chlorine-free effluents from Kraft pulp bleaching

1999

A capillary zone electrophoresis (CZE) method for analyzing the total acid hydrolysis products (monosaccharides and their derivatives) of the dissolved carbohydrates from a totally chlorine-free bleaching plant was developed. Several borate buffer concentrations and other running conditions were tested. Neutral monosaccharides (arabinose, galactose, glucose, mannose, rhamnose and xylose) in hydrolysates were derivatized by means of 4-aminobenzonitrile and resolved by 500 mM borate buffer (pH 9.5, 16.0 kV). The detection level was less than 10 fmol. In addition, the separation of some uronic acids and oligosaccharides was studied.

Historical and current progress in understanding the origin and structure of humic substances

2010

Research into humic substances (HS) has focused selectively on the search for aromatic structures. All aromatic compounds are regarded as eligible HS constituents, whereas aliphatic, polysaccharide structural constituents are considered non-HS. Wet chemical methods for analysing HS produce 2–5% aromatic compounds from the original starting material. Only those compounds in the hydrophobic extraction phases are studied carefully. Compounds in the hydrophilic extraction phases, containing mainly aliphatics, are discarded. Solid-state NMR spectra from HS show 30–40% of carbon–carbon unsaturation, which is selectively interpreted as ‘aromatic’. No recognition is given to the fact that NMR spect…