Affinity of Hemicellulose for Cellulose Produced by Acetobacter Xylinum

Cellulose composites were produced by culturing Acetobacter aceti subsp. xylinum (ATCC 53524, agitation tolerant strain) under shaking and agitating conditions in the presence of 2% pine or beech Björkman lignin-carbohydrate complexes (LCCs) or six different types of hemicellulosic polysaccharides including glucuronoxylan, glucomannan, O-acetyl-glucuronoxylan, arabinoglucuronoxylan, arabinogalactan and xyloglucan. Hemicellulosic polysaccharide contents in cellulose composites were similar in spite of the differences in culture, shaking and agitating conditions. On the basis of hemicellulosic polysaccharide contents and X-ray diffraction patterns after extraction by dilute NaOH solution, glucomannan family polysaccharides were found to have the highest affinity to bacterial cellulose. Composites with neutral and acidic LCCs were resistant against alkali while high lability of their delignified carbohydrates against alkali indicates the importance of lignin for formation of cellulose-hemicellulose-lignin framework of plant secondary cell-walls.     

Neutron scattering from PEEK

An alkali‐soluble polysaccharide, GM5‐1, from the mycelium of Ganoderma tsugae, was fractionated by the nonsolvent addition method. The weight‐average molecular mass (M _w) and intrinsic viscosity ([η]) of fractions were studied by laser light scattering and viscometry with dimethylsulfoxide (DMSO) containing 0.25M LiCl (0.25M LiCl/DMSO) as the solvent at 30°C. The dependences of [η] and the radius of gyration (?S ²?_z ^1/2) on M _w were found to be [η]=9.8×10^?2 M _w ^0.57 (cm³g^?1) and ?S ²?_z ^1/2=1.65×10^?2 M _w ^0.58 (nm) in the M _w range from 8.6×10⁵ to 2.6×10⁶. The analysis based on current theories for a wormlike chain showed that the chain conformational parameters of GM5‐1 were 4.2 nm for persistence length (q) and 833 nm^?1 for linear mass density (M_L) with an obvious excluded volume effect. The results suggested the alkali‐soluble polysaccharide behaves like a semiflexible chain in 0.25M LiCl/DMSO at 30°C.     

多糖化学合成研究进展

多糖是一类结构复杂的生物大分子,广泛分布于微生物、植物、动物等生物体中,参与众多重要的生命过程.然而,多糖研究一直受限于难以获得足量结构均一的多糖物质,这使得多糖的结构和功能研究及其相关的应用研究进展缓慢.近几十年来,随着糖合成技术的进步,糖的化学合成效率不断提高,人们开始关注复杂多糖的化学合成,并取得了一些进展.本文主要对多糖化学合成所涉及的糖基化方法、糖组装策略和代表性的合成工作进行综述,并对研究前景进行展望.     

Determination of Polysaccharide Hydrolyzates in Chinese Herbal Medicine by UltraHigh-Performance Liquid Chromatography-Quadrupole Time-of-Flight Mass Spectrometry and Evaporative Light Scattering Detection

Ultrahigh-performance liquid chromatography coupled with evaporative light scattering detector was used to optimize acid hydrolysis conditions of polysaccharides from Dendrobium candidum. The optimized conditions were the concentration of H₂SO₄, 0.4?M, hydrolysis temperature, 90°C, and hydrolysis time, 1?h. Ultrahigh-performance liquid chromatography-quadrupole time-of-flight mass spectrometry was used to obtain the total ion current chromatograms and determine the hydrolyzates of polysaccharides, such as monosaccharides, oligosaccharides, and some low-molecular weight polysaccharides from D. candidum, Cordyceps sinensis, and Ganoderma atrum. The accurate mass data were analyzed by chemometric tools, including an unsupervised analytical method, principal component analysis (one-way ANOVA, p?D. candidum polysaccharides from different locations and grades can be discriminated effectively by the principal component analysis scores. The quality predictive models showed a high value with a low prediction error calculated from both validation and training sets.     

Determination of Polysaccharides in Undaria pinnatifida by Ionic Liquid-Modified Silica Gel Size Exclusion Chromatography

Ionic liquid-modified silica particles with a large pore size were synthesized and used as the stationary phase for size exclusion chromatography coupled with a refractive index detector for the determination of polysaccharides, such as fucoidan, alginic acid, and laminarin from Undaria pinnatifida (seaweed). The molecular weight of polysaccharide was determined by a dextran standard curve (5–1100?kDa). The ionic liquid-modified silica column exhibited excellent size exclusion properties in separating laminarin from other components. The 1-butyl-3-methyl-imidazolium bis-(trifluoromethylsulfonyl)-amino silica column has superior resolution in laminarin separation than the other columns because the amino-group in ionic liquid provide π–π interactions due to aromaticity of the ring structure, which enhances the effect of the hydroxyl group in the target compound separation. The concentrations of polysaccharides were calculated using a standard linear equation to be 0.332–0.484?mg/g of fucoidan, 0.207–0.301?mg/g of alginic acid, and 0.154–0.297?mg/g of laminarin.     

Structural characterisation of a water-soluble polysaccharide from tissue-cultured Dendrobium huoshanense C.Z. Tang et S.J. Cheng

A water-soluble polysaccharide TC-DHPA4 with a molecular weight of 8.0 × 10⁵ Da was isolated from tissue-cultured Dendrobium huoshanense by anion exchange and gel permeation chromatography. Monosaccharide analysis revealed that the homogeneous polysaccharide was made up of rhamnose, arabinose, mannose, glucose, galactose and glucuronic acid with a molar ratio of 1.28:1:1.67:4.71:10.43:1.42. The sugar residue sequence analysis based on the GC-MS files and NMR spectra indicated that the backbone of TC-DHPA4 consisted of the repeated units:→6)-β-Galp-(1→6)-β-Galp-(1→4)-β-GlcpA-(1→6)-β-Glcp-(1→6)-β-Glcp-(→. The sugar residue sequences β-Glcp-(1→)-α-Rhap-(1→3)-β-Galp-(1→, β-Glcp-(1→4)-α-Rhap-(1→3)-β-Galp-(1→, β-Galp-(1→6)-β-Manp-(1→3)-β-Galp-(1→, and α-l-Araf-(1→2)-β-Manp-(1→3)-β-Galp-(1→ were identified as the branches attached to the C-3 position of (1→6)-linked galactose in the backbone.     

GC-MS analysis of the bioactive phytoconstituents of various organic crude extracts from the seed kernels of Manilkara bidentata (balata) collected in Trinidad,W.I.

The present study reports the first phytochemical investigation of the seed kernels of Manilkara bidentata (Balata) harvested in Trinidad, W.I. Gas chromatography–mass spectrometry (GC-MS) analysis of the n-hexane, chloroform, ethyl acetate, ethanol and methanol extracts showed a total of 39 components. 2,6,10,14,18-pentamethyl-2,6,10,14,18-eicosapentaene (74.93%), 9-octadecenoic acid, (Z)- 2,3-dihydroxypropyl ester (79.98%), (Z)-ethyl oleate (92.75%), Z,E-2-methyl-3,13-octadecadien-1-ol (80.51%) and 5-(hydroxymethyl)-2-furancarboxyaldehyde (50.32%) were the major constituents identified in the n-hexane, chloroform, ethyl acetate, ethanol and methanol extracts, respectively. The extracts showed the presence of several bioactive components and provides reference data for further research of its active constituents.     

Efficient synthesis and characterization of new photoactive dextran esters showing nanosphere formation

Different types of photoactive dextran derivatives with high degree of substitution were prepared by an efficient and mild esterification of the biopolymer with 2-methoxycinnamic acid, [(4-methyl-2-oxo-2H-chromen-7-yl)oxy]acetic acid, and azobenzene-4-carboxylic acid via in situ activation of the carboxylic acid groups with N,N'-carbonyldiimidazole. The structures of the novel dextran esters were evaluated by means of NMR spectroscopy applying the perpropionylated samples. Perpropionylation yields samples soluble in chloroform and acetonitrile that are very useful solvents not only for NMR but also for UV-vis spectroscopic studies. The photochemistry was studied by NMR and UV-vis spectroscopy in the dissolved state and the changes observed may be used to control the properties. The photoactive dextran esters form spherical nanoparticles of a size below 200 nm that are of interest in the design of smart materials.     

NOVEL pH-SENSITIVE DRUG DELIVERY SYSTEM BASED ON NATURAL POLYSACCHARIDE FOR DOXORUBICIN RELEASE

A novel pH-sensitive nanoparticle drug delivery system (DDS) derived fl'om natural polysaccharide pullulan for doxorubicin (DOX) release was prepared.Pullulan was functionalized by successive carboxymethylization and amidation to introduce hydrazide groups.DOX was then grafted onto pullulan backbone through the pH-sensitive hydrazone bond to form a pullulan/DOX conjugate.This conjugate self-assembled to form nano-sized particles in aqueous solution as a result of the hydrophobic interaction of the DOX.Tr...