金顶侧耳酸提水溶性多糖的研究——PC-3的分离、纯化与结构确定

金顶侧耳(Pleurotus citrinopileatus)子实体的3%三氯乙酸提取液经甲醇分级,十六烷基三甲基溴化铵等进一步提纯得到水溶性多糖PC-3。经Sepharose CL-4B柱层析,醋酸纤维素薄膜电泳、聚丙烯酰胺凝胶电泳鉴定,PC-3为均一级份。G.C.与P.C.分析表明,Gal、Man为该多糖的组份,其单糖摩尔比为2.5∶1.0。PC-3的分子量约为67000,比旋光度[α]_D~(18°)=+28°。经核磁共振谱等分析,PC-3不含β型糖苷键。部份酸水解、高碘酸氧化、Smith降解、完全甲基化、G.C.及G.C.-M.S.的分析表明,PC-3是由α(1→6)糖苷键相连的半乳糖构成分子的主链,部分残基C_2上带有分支,每5个Gal残基带有1个侧链,侧链为α(1-2)Man-α(1-2)Man。     

当归水溶性多糖级分As-Ⅲa和As-Ⅲb的纯化鉴定与结构研究

当归热水抽提得到的粗多糖,经乙醇分级沉淀,ＤＥＡＥ纤维素分离和ＳｅｐｈａｄｅｘＧ１５０柱层析纯化,得到水洗脱级分Ａｓ—Ⅲａ和碱洗脱级分Ａｓ—Ⅲｂ两个多糖级分。经测定这两级分为均一组分。红外光谱呈现出典型的多糖吸收峰。气相色谱分析表明Ａｓ—Ⅲａ由葡萄糖组成,Ａｓ—Ⅲｂ由葡萄糖、甘露糖和阿拉伯糖组成。高碘酸氧化及Ｓｍｉｔｈ降解分析表明Ａｓ—Ⅲａ的单体通过α（１→３）糖苷键相连,Ａｓ—Ⅲｂ主要通过（１→４）和（１→６）糖苷键相连。     

高相对分子质量裂褶多糖的制备与结构鉴定

以裂褶菌（Schizophyllum commune）发酵生产的培养物为研究对象,经过活性炭脱色、Sevag法脱杂蛋白、乙醇沉淀得粗多糖,再经Sephadex G-200柱层析分离纯化得裂褶多糖纯品.通过Sephadex G-200凝胶层析法测得其平均分子质量为436kDa;由气相色谱、红外光谱、高碘酸氧化、Smith降解、^13C核磁共振等方法表征其化学结构,推测其结构为具有（1→6）分支的β-〔1-3）-D-葡聚糖：其组成重复单元应该含有3个主链糖基和一个单糖分支,主链的取代发生在C-1和C-3之间,即为1→3糖苷键;分支发生在C-1和C-6之间,即为1→6糖苷键,其中分支点在主链糖基的C-6上.     

小刺猴头菌丝体多糖的结构研究

对小刺猴头过滤掉发酵液的发酵菌丝体,水提和碱提后获得的均一组分多糖HMP-w1.1和HMP-a1.1进行结构性质的研究。结果表明:HMP-w1.1是分子量为36.3 kD的α型吡喃糖,单糖组成为甘露糖(Man),葡萄糖(Glc),半乳糖(Gal),岩藻糖(Fuc);HMP-a1.1是分子量为42.8 kD的β型吡喃糖,单糖组成为甘露糖(Man),半乳糖醛酸(GalUA),葡萄糖(Glc),半乳糖(Gal),岩藻糖(Fuc)。综合高碘酸氧化和Smith降解的试验结果,推断HMP-w1.1的糖苷键构型可能为1→、1→4、1→4,6、1→6、1→2、1→2,6;HMP-a1.1的糖苷键构型可能为1→6、1→2、1→2,6。     

安络小皮伞中水溶性多糖的研究——Ⅰ.甘露聚糖 FP_1 的纯化与结构研究

从安络小皮伞水溶性多糖中分离纯化得一甘露聚糖 FP_1。分子量约为24万。经红外光谱、~+H-NMR 谱和亲和层析指明为β-甘露聚糖。结构分析采用高碘酸氧化、Smith 降解、完全甲基化 GC、GC-MS 与~(13)C-NMR 分析,分子的主链是β-D-(1→6)连接的甘露糖,支链为β-(1→3),β(1→2)甘露糖,分别连接在主链的 O-3和 O-2上。     

玉米花粉多糖PMAⅠ的结构解析

从玉米花粉中分离得到一种多糖PMA I,经鉴定为单一纯多糖,通过IR、NMR、高碘酸氧化、Smith降解等手段对其结构进行了研究,确定PMA I主要以Rha,Xyl和GlcOMe组成,分子摩尔比Rha:Xyl:GlcOMe=12.7:2.1:1,以α(1→3)键为主链,以α(1→6)键构成分支结构。     

大马勃水溶性多糖的结构研究

采用热水浸提,乙醇沉淀的方法得到大马勃粗多糖,经Sevag法脱蛋白,DEAE—sepharose fast flow离子交换层析及sephacrylS-300HR凝胶过滤法得大马勃多糖（CGPI-1）。气相色谱研究表明,其单糖组成为：Gal,Glc,Man等四种单糖,其中Gal,Glc,Man,摩尔比为3．92：11．28：1．22。经部分酸水解,红外光谱及核磁共振光谱,高碘酸氧化,Smith降解等分析,CGPI-1的主链由Man和Glc构成,存在β型和α型两种糖苷键构型,支链或主链的末端残基由β-Gal（1→4）,β-Glc（1→6）,α—Glc（1→4）构成,其分子中存在酰胺结构。原子力显微镜观察发现CGPI-1呈分支的线性分子,在水溶液中容易互相缠绕形成强大的网络结构。     

玉米花粉多糖PMA Ⅰ的结构解析

从玉米花粉中分离得到一种多糖PMAⅠ,经鉴定为单一纯多糖,通过IR、NMR、高碘酸氧化、Smith降解等手段对其结构进行了研究,确定PMAⅠ主要以Rha,Xyl和GlcOMe组成,分子摩尔比RhaXylGlcOMe=12.72.11,以α(1→3)键为主链,以α(1→6)键构成分支结构.     

刺五加果水溶性多糖的研究——AS-2的分离纯化与结构探讨

从刺五加果中抽提出水溶性粗多糖。经酸性乙醇分级及反复冻融得到多糖AS-2。AS-2经Sepharose CL-4B柱层析为单一对称峰,经醋酸纤维素膜电泳为一条带,冻融后高速离心无沉淀可证明其为均一级分。G.C分析表明,AS-2由Ara、Xyl、Rha、Gal、Glc组成,其单糖摩尔比为1.6:1.2:1.8:1.0:3.6。AS-2的分子量约为78kD,比旋光度[α]_D~(25)=+17°,特性粘度[η]=0.068。红外光谱分析含β型糖苷键。部分酸水解、酶解、高碘酸酸化、Smith降解、完全甲基化、G.C,G.C-M.S的分析结果表明,以β(1→3)Glc及β(1→4)Glc构成分子的主链。Glc的C_3上带有分支,约每4个己糖残基带有1个侧链。侧链上,Rha多以1→4苷键相连,部分残基C_2上有分支。Gal存在(1→6)及(1→3)连接方式,多数Glc以(1→6)苷键连结,少数Glc出现在分子非还原末端。位于分子末端的还有Ara与Xyl。     

铁皮石斛原球茎多糖DCPP1a-1的理化性质及抗肿瘤活性

铁皮石斛原球茎粗多糖(DCPP)经阴离子交换纤维素柱(DEAE-52)和凝胶柱(Sephadex G-200)色谱分离纯化,得灰色粉末状多糖DCPP1 a-1。采用薄层层析、高效液相色谱、紫外光谱、红外光谱和高碘酸钠氧化等方法进行组成结构分析;并研究了DCPP1 a-1的体内抗肿瘤作用。结果表明,DCPP1 a-1为均一组分,具有α-吡喃糖苷键,分子中1→6键、1→2/1→4键、1→3键所占的比例分别为4.0%,52.1%和44.9%,平均分子量为189kD,由甘露糖和葡萄糖按7.015∶1的摩尔比组成,是首次从原球茎中分离出的新型多糖。多糖DCPP1 a-1的三个剂量组50、150、250 mg/kg对H22肝癌小鼠有不同程度的抑瘤作用,抑瘤率分别为28.6%、19.3%和15.7%。其中以低剂量组的抑瘤效果最好(P<0.05),并显著提高了胸腺和脾指数(P<0.05)。     

紫球藻多糖化学结构解析

为明确紫球藻多糖的化学结构,本文采用化学分析和光谱分析方法对紫球藻多糖的一级糖链结构进行了分析。GC分析表明该多糖由木糖、葡萄糖和半乳糖组成,为一种杂多糖,其摩尔比为:2.96∶1.25∶3.06;红外光谱分析结果显示紫球藻多糖为硫酸化多糖,糖苷键类型为β构型;化学分析结果推断紫球藻多糖糖链连接方式以1→3为主,存在少量1→2,1→4,1→6键型,且半乳糖在支链或主链末端有较大量的存在,木糖和葡萄糖在主链或靠近主链区域有特定分布;NMR分析显示紫球藻多糖的硫酸酯基连在C-6上,且多糖的糖苷键为β型;GC-MS联机分析进一步确定紫球藻多糖为一种主要含有1→3糖苷键,并含有1→4,1→6糖苷键的杂多糖。综合上述分析,推断出紫球藻多糖的糖链主链的重复单元结构。     

Prediction of the anomeric configuration, type of linkage, and residues in disaccharides from 1D (13)C NMR data

A machine learning approach was explored for the prediction of the anomeric configuration, residues, and type of linkages of disaccharides using (13)C NMR chemical shifts. For this study, 154 pyranosyl disaccharides were used that are dimers of the α or β anomers of d-glucose, d-galactose or d-mannose residues bonded through α or β glycosidic linkages of types 1→2, 1→3, 1→4, or 1→6, as well as methoxylated disaccharides. The (13)C NMR chemical shifts of the training set were calculated using the casper (Computer Assisted SPectrum Evaluation of Regular polysaccharides) program, and chemical shifts of the test set were experimental values obtained from the literature. Experiments were performed for (1) classification of the anomeric configuration, (2) classification of the type of linkage, and (3) classification of the residues. Classification trees could correctly classify 67%, 74%, and 38% of the test set for the three tasks, respectively, on the basis of unassigned chemical shifts. The results for the same experiments using Random Forests were 93%, 90%, and 68%, respectively.     

东北红豆杉多糖的化学研究

利用水提醇沉提取东北红豆杉多糖TP,经超滤得到超滤外液TP-1和内液TP-2。TP-2进行部分酸水解和凝胶柱层析分离纯化,得到TP-2-1a。通过对理化性质、分子量、单糖组成和甲基化测定结果分析,确定其分子量分布在7.0 kDa左右,糖组成由Rha、Man、Gal、Glu、GalA和GlcA构成,摩尔比为:16.9∶1.0∶15.5∶1.3∶9.9∶2.5,中性糖以Gal的1→3、1→4连接为主,在1→3连接的O-6位上有分支;Rha以1→2连接为主,在O-4位上有分支;Man以1→4、1→6连接为主;Glu以1→3、1→4连接为主;非还原末端主要是Gal及少量的Man、Glu和Rha。酸性糖以1→4连接GalA为主,无分支。该多糖为首次从东北红豆杉中分离得到。     

31P- and 13C-N.M.R.-spectral and chemical characterization of the end-group and repeating-unit components of oligosaccharides derived by acid hydrolysis of haemophilus influenzae type b capsular polysaccharide

Haemophilus influenzae type b capsular polysaccharide [repeating unit, →3)-β- d-Ribf-(1 → 1)- d-Ribol-5-(PO ₂H→] was partially hydrolyzed with HCl to give oligosaccharides that were isolated by size-exclusion chromatography, and then characterized by ³¹P- and ¹³C-n.m.r.-spectral and chemical methods, in order to determine the end-group composition and, hence, the number-average chain-length がL. The ratio (～17:8) of monophosphate end-groups to d-ribofuranose end-groups revealed the relative rates of hydrolysis of the phosphoric diester linkage and the glycosidic linkage in the repeating-unit structure. Cleavage of the phosphoric diester linkage was ～92% regioselective, as indicated by the ～ 12:1 ratio of d-ribofuranose monophosphate end-groups to d-ribitol monophosphate end-groups. The n.m.r. spectra of the oligosaccharide repeating-unit provided evidence for partial stereomutation (～3–8%) that involved rearrangement of the d-ribofuranose phosphoric diester linkage and anomerization at C-1 of d-ribofuranose. Variously sized oligosaccharides (がL = 4, 7, and 12) that had d-ribofuranose end-groups reacted with bovine serum albumin that had an average of ～9 adipyl hydrazide functionalities, to give, within experimental error, quantitative yields of the corresponding, hydrazone-linked, oligosaccharide-protein conjugates.     

Oligomannoside biosynthesis in Mycobacterium smegmatis

A cell-free particulate enzyme system of Mycobacterium smegmatis ATCC 607 was shown to catalyze the incorporation of labeled mannose from GDP-[¹⁴C]mannose into endogenous acceptors to form a series of labeled neutral oligomannosides. These oligomannosides were devoid of amino sugar. The major oligomannoside product was characterized to be a trimannoside, O-α-d-mannopyranosyl-(1 → 2)-O-α-d-mannopyranosyl(1 → 2)-d-mannose and represented 46% of the total labeled oligomannoside product. The higher oligomannosides were shown to have either/or both α(1 → 2) and α(1 → 6) glycosidic linkages. A series of unlabeled endogenous oligosaccharides was isolated from the 105,000g supernatant fractions of the cell-free extracts of M. smegmatis and found to be chromatographically similar to the labeled oligomannosides synthesized by the cell-free system. The nature of the endogenous acceptor was not determined.     

A molecular dynamics study of the effect of glycosidic linkage type in the hemicellulose backbone on the molecular chain flexibility

The macromolecular conformation of the constituent polysaccharides in lignocellulosic biomass influences their supramolecular interactions, and therefore their function in plants and their performance in technical products. The flexibility of glycosidic linkages from the backbone of hemicelluloses was studied by evaluating the conformational freedom of the φ and ψ dihedral angles using molecular dynamic simulations, additionally selected molecules were correlated with experimental data by nuclear magnetic resonance spectroscopy. Three types of β‐(1→4) glycosidic linkages involving the monosaccharides (Glcp, Xylp and Manp) present in the backbone of hemicelluloses were defined. Different di‐ and tetrasaccharides with combinations of such sugar monomers from hemicelluloses were simulated, and free energy maps of the φ – ψ space and hydrogen‐bonding patterns were obtained. The glycosidic linkage between Glc‐Glc or Glc‐Man (C‐type) was the stiffest with mainly one probable conformation; the linkage from Man‐Man or Man‐Glc (M‐type) was similar but with an increased probability for an alternative conformation making it more flexible, and the linkage between two Xyl‐units (X‐type) was the most flexible with two almost equally populated conformations. Glycosidic linkages of the same type showed essentially the same conformational space in both disaccharides and in the central region of tetrasaccharides. Different probabilities of glycosidic linkage conformations in the backbone of hemicelluloses can be directly estimated from the free energy maps, which to a large degree affect the overall macromolecular conformations of these polymers. The information gained contributes to an increased understanding of the function of hemicelluloses both in the cell wall and in technical products.     

Arabinogalactans in a purified allergen preparation from pollen of timothy (Phleum pratense)

The purified allergen preparation representing a certain fraction of an aqueous timothy pollen extractcontained ca. 20% carbohydrate, mainly as arabinose (7%) and galactose (13%). The protein content was 63%. Fractionation on DEAE-Sephadex and Sephadex G-100 gave one neutral and two acidic fractions, all containing protein, arabinose and galactose. The structure of the carbohydrate moiety was investigated by methylation analysis, periodate oxidation and enzyme incubation. The acidic fraction contained (1→6)-linked galactose residues, some being substituted on O-3 with arabinose. The neutral fraction consisted of a more extensively branched arabinogalactan with longer side chains of (1→3)- and (1→5)-linked arabinose. The arabinose was present mainly as α-l-arabinofuranosyl residues. Alkaline degradation and subsequent fractionation indicated the presence of a covalent linkage between hydroxyproline and arabinose. Periodate oxidation or incubation with α-l-arabinofuranosidase did not affect the allergenic activity of the extract.     

Solution conformation of a pectic acid fragment by 1H-nmr and molecular dynamics

¹H-NMR and molecular dynamics simulations in vacuo and in water of (1 → 4)-α-D -galacturono-disaccharide were performed. The results of the molecular dynamics simulations showed that the molecule fluctuates between two conformations characterized by different values of torsion angles around the glycosidic linkage and two different intramolecular hydrogen bonds. When these conformations are extrapolated to a regular polymeric structure, they generate pectic acid compatible with a 2₁- or a right-handed 3₁-helix. © 1994 John Wiley & Sons, Inc.     

Water-soluble glycoproteins from Cannabis sativa (Thailand)

Glycoproteins were extracted with water from leaves of Cannabis sativa grown from seeds of Thailand origin. By ion exchange chromatography the material was separated into a neutral and an acidic fraction. Both glycoprotein fractions contained arabinose, galactose, glucose, mannose and xylose, and in addition rhamnose and galacturonic acid were present in the acidic fraction. The carbohydrate moieties were investigated by methylation analysis and Smith-degradation, whereas the glycopeptide linkage was studied by alkaline hydrolysis in the presence of NaBH₄ and Na₂SO₃, respectively. This linkage was shown to be of the serine-O-galactoside type. The carbohydrate structure is highly branched, the majority of branches terminating in arabinofuranose end groups. Arabinose is also present in the chain, predominantly (1 → 4)- and/or (1 → 5)-linked. Galactose makes up most of the main chain as (1 → 3)-linked residues but also constitutes end groups and branch points, as do mannose and/or glucose. Xylose and rhamnose are present as (1 → 4)- and (1 → 2)-linked units, respectively. Galacturonic acid is assumed to be (1 → 4)- linked with some branching at 3 position. The amino acid hydroxyproline, present in the glycoprotein of South African Cannabis leaves, was absent in the corresponding Thailand material.     

X-ray crystal structure of galabiose, O-alpha-D-galactopyranosyl-(1---4)-D-galactopyranose

O-alpha-D-Galactopyranosyl-(1---4)-D-galactopyranose, C12H22O11, Mr = 342.30, crystallises in the orthorhombic space group P2(1)2(1)2(1), and has alpha = 5.826(1), b = 13.904(3), c = 17.772(4) A, Z = 4, and Dx = 1.579 g.cm-3. Intensity data were collected with a CAD4 diffractometer. The structure was solved by direct methods and refined to R = 0.063 and Rw = 0.084 for 2758 independent reflections. The glycosidic linkage is of the type 1-axial-4-axial with torsion angles phi O-5' (O-5'-C-1'-O-1'-C-4) = 98.1(2) degrees, psi C-3 (C-3-C-4-O-1'-C-1') = -81.9(3) degrees, phi H (H-1'-C-1'-O-1'-C-4) = -18 degrees, and psi H (H-4-C-4-O-1'-C-1') = 35 degrees. The conformation is stabilised by an O-3 . . . O-5' intramolecular hydrogen-bond with length 2.787(3) A and O-3-H . . . O-5' = 162 degrees. The glycosidic linkage causes a folding of the molecule with an angle of 117 degrees between the least-square planes through the pyranosidic rings. The crystal investigated contained 56(1)% of alpha- and 44(1)% of beta-galabiose as well as approximately 70% of the gauche-trans and approximately 30% of the trans-gauche conformers about the exocyclic C-5'-C-6' and C-5-C-6 bonds. The crystal packing is governed by hydrogen bonding that engages all oxygen atoms except the intramolecular acceptor O-5' and the glycosidic O-1' oxygen atoms.