菌类多糖链构象及其表征方法研究进展

概述了菌类多糖在溶液中链构象及其表征方法的研究进展.主要报道从各种真菌(香菇、茯苓、灵芝、木耳、黄单胞菌、裂褶菌等)中提取的多糖在溶液中的分子量、分子形态和尺寸,即链构象.同时介绍多糖链构象对生物活性的影响,并且指出多糖刚性链带电基团及适量分子量有利于促进它与免疫细胞上受体结合,从而抑制肿瘤细胞增殖.由此表明,多糖链构象的研究对弄清其生物功能和推动生命科学发展十分重要.多糖在溶液中主要以无规线团、双螺旋、三螺旋、蠕虫状、棒状链以及聚集体构象存在,它取决于单糖组成、糖苷键、支链结构以及分子内和分子间作用力.测定链构象的方法主要包括光散射、黏度、显微技术(透射电镜,扫描电镜以及原子力显微镜)、微量热法和小角X-射线散射等.此外,介绍了多糖溶液理论以及计算链构象参数的表达式.     

菌类多糖链构象及其表征方法研究进展 （专题报道）

 概述了菌类多糖在溶液中链构象及其表征方法的研究进展.主要报道从各种真菌（香菇、茯苓、灵芝、木耳、黄单胞菌、裂褶菌等）中提取的多糖在溶液中的分子量、分子形态和尺寸,即链构象.同时介绍多糖链构象对生物活性的影响,并且指出多糖刚性链带电基团及适量分子量有利于促进它与免疫细胞上受体结合,从而抑制肿瘤细胞增殖.由此表明,多糖链构象的研究对弄清其生物功能和推动生命科学发展十分重要.多糖在溶液中主要以无规线团、双螺旋、三螺旋、蠕虫状、棒状链以及聚集体构象存在,它取决于单糖组成、糖苷键、支链结构以及分子内和分子间作用力.测定链构象的方法主要包括光散射、黏度、显微技术（透射电镜,扫描电镜以及原子力显微镜）、微量热法和小角X-射线散射等.此外,介绍了多糖溶液理论以及计算链构象参数的表达式.     

凝胶色谱与多角激光光散射联用研究聚氧化乙烯的扩展效应和链构象

采用凝胶色谱与多角激光光散射联用的方法,测定了一系列不同分子量的聚乙二醇(PEG)和聚氧化乙烯(PEO)在色谱柱中的扩展效应.扩展因子随PEG/PEO分子量的增加而增大,经扩展效应改正后得到了样品的准确分子量和分子量分布.同时建立了PEO的Z均回转半径Rgz与重均分子量Mw之间的单分散标度关系:Rgz=0.0272 Mw0.56,结果表明,长链PEO在水溶液中由于排除体积效应采取溶胀的无规线团构象.     

基于高效阴离子色谱-脉冲安培法优化阿拉伯木聚精单精组成分析

以大粒车前子来源阿拉伯木聚糖为研究对象,采用完全酸水解结合高效阴离子色谱-脉冲安培法测定单糖组成,系统优化酸的种类和浓度、水解温度和时间、水解后样品放置时间等水解条件.结果表明,将车前子多糖置于2 mol/L H2 SO4、120℃常压油浴条件下水解2 h时,效果较好,但水解后稀释液放置时间不宜超过6 h.大粒车前子多糖主要由阿拉伯糖(8.89%)和木糖(41.52%)组成,同时检测出半乳糖醛酸(0.73%)、葡萄糖醛酸(3.44%)和微量的半乳糖、葡萄糖,结果重现性良好.利用上述最优条件水解黍子壳、燕麦麸皮和青稞来源阿拉伯木聚糖并分析单糖组成,均获得较好结果.本研究为分析各种来源阿拉伯木聚糖的单糖组成提供了参考.     

乌龙茶多糖OTPS 2-1的光谱特性、形貌特征及热特性研究

采用纤维素和葡聚糖凝胶柱层析法分离纯化,获得乌龙茶多糖主要组分OTPS2-1.经GC,HPLC,UV,IR和GPC-LLS证实OTPS2-1是富含糖醛酸和少量蛋白质的三元糖复合物,相对重均分子量为8.877×10⁴,糖基由半乳糖、葡萄糖、阿拉伯糖、岩藻糖和鼠李糖组成,其摩尔比为7.58:2.14:7.05:1.76:1.02.利用AFM,QELS及LSCM观察OTPS2-1在溶液中的形貌特征,结果表明,OTSP2-1在溶液中呈直径0.2～0.5μm、高度0.3～0.6μm的短棒形不均一聚集体,并具有强烈的荧光,溶液的pH值显著影响其聚集行为.pH值、离子强度和络合物等环境因素的改变,均导致多糖立体构象和非对称性的变化.OTPS2-1在SEM低倍镜下呈折叠卷曲形貌,在高倍镜下呈现平整的图像.综合热分析结果表明,在加热过程中,多糖有3次大的质量损失过程,出现3次吸热峰和放热峰.提示茶叶经过半发酵处理后,多糖组成、分子质量分布以及分子间相互作用可引起微观形貌、链构象和聚集行为的变化,有利于提高生物活性.     

一种手性甲壳型液晶高分子的稀溶液行为及链刚性

用激光光散射和粘度法研究了一系列窄分子量分布的新的手性甲壳型液晶聚合物P1～P6的溶液行为及其链刚性.研究发现四氢呋喃是聚合物P1～P6的良溶剂.在四氢呋喃溶液中,聚合物P1～P6的特性粘数[η]和均方根旋转半径z12对重均分子量Mw的依赖关系分别是[η]=(2.75±0.05)×10-3Mw0.78±0.02和z12=(1.53±0.04)×10-2Mw0.60±0.01.按照YamakawaFujiiYoshizaki蠕虫状圆筒模型的粘度理论和BohdaneckyBushin表达式,求得聚合物的单位围长摩尔质量ML=(29.8±1.0)×102nm,构象保持长度q=(15.4±3.0)nm.q和MHS方程指数α的值说明这类在结构上属于侧链型液晶高分子的聚合物在良溶剂四氢呋喃中呈现比较伸展的刚性链构象,其链刚性与半刚性主链液晶高分子的相似.     

木质素基高效减水剂GCL1-JB的分子量测定

分别采用静态光散射法(SLS)和凝胶渗透色谱法(GPC)测定了木质素基高效减水剂GCL1-JB的分子量(Mw).由于GCL1-JB直接溶于水中存在聚电解质效应和聚集现象,SLS法测得的分子量(Mw,SLS)远大于GPC测得的分子量(Mw,GPC).为了通过SLS测得GCL1-JB的真实Mw,在GCL1-JB溶液中加入NaCl来屏蔽GCL1-JB的聚电解质效应,并采用0.45μm的微孔滤膜滤除GCL1-JB聚集体.GCL1-JB的动态光散射测试中存在2个扩散峰:快模式峰和慢模式峰.快模式峰对应GCL1-JB的单分子行为,而慢模式峰对应GCL1-JB的聚电解质效应和GCL1-JB聚集体.GCL1-JB动态光散射的慢模式峰随着NaCl的不断加入和进一步的过滤处理而逐渐减弱.当NaCl在溶液中的浓度达到0.1 mol/L,动态光散射的慢模式峰完全消失.在没有慢模式峰存在的条件下利用SLS测得GCL1-JB的绝对分子量为121300,这个分子量被认为是GCL1-JB单分子的真实分子量.然而该条件下SLS法测得的Mw,SLS仍然比GPC法测得的Mw,GPC大,这是由于GCL1-JB与GPC标样NaPSS的构象差异引起的.GCL1-JB的分子构象比NaPSS的更卷曲,所以用NaPSS作为GPC标样得到Mw,GPC比GCL1-JB的真实分子量小.本研究提出了一种利用SLS准确测量GCL1-JB的Mw的方法,对存在聚电解质效应和聚集现象的木质素及其衍生产物的绝对分子量测定具有普遍的借鉴意义.     

热水提取与超声提取的麦冬多糖结构与构象特征的比较研究

利用热水与超声提取麦冬粗多糖,DEAE-cellulose52纤维素与Sephacryl S-300凝胶柱层析对其进行分离纯化,得到热水提取的麦冬多糖均一组分WPOJ-DS与超声提取的麦冬多糖均一组分UPOJ-DS。采用高效液相色谱法、气相色谱法、红外光谱法、部分酸水解、甲基化分析及核磁共振对WPOJ-DS与UPOJDS的结构进行表征;利用刚果红实验、圆二色谱实验及原子力显微镜对其溶液构象进行了比较研究。结果表明,超声提取对麦冬多糖的分子量、单糖组成摩尔比及构型会产生影响,WPOJ-DS与UPOJ-DS的主链均主要由→6)-D-Glcp(1→和→3,6)-D-Glcf(1→组成,但WPOJ-DS中存在→6)-β-D-Glcp(1→,而UPOJDS中没有;刚果红实验、圆二色谱实验与原子力显微镜结果显示UPOJ-DS存在螺旋结构,而WPOJ-DS没有;且在不同溶液环境中,WPOJ-DS与UPOJ-DS的溶液构象不同。     

白芷多糖的分析

研究了白芷多糖的结构和单糖组成。采用紫外光谱和红外光谱法对白芷多糖进行定性分析。结果表明,白芷多糖具有多糖特征性的紫外和红外吸收峰,其分子中存在酰胺结构;凝胶渗透色谱法测定结果表明,白芷多糖的峰值分子量为88538;采用气相色谱法测定白芷多糖中单糖的种类和构成比例,结果表明,白芷多糖由鼠李糖、阿拉伯糖、木糖、甘露糖、葡萄糖和半乳糖等7种单糖组成,并计算出其中6种单糖的摩尔组成比例。     

三螺旋多糖的链结构与功能研究进展

三螺旋多糖是自然界中存在的具有特殊链结构的一类生物大分子,它不仅具有较高的生物活性,而且具有特殊的分子识别能力以及其他多糖无法比拟的功能特性。本文主要概述三螺旋多糖的链结构及其构象转变,分析其变性和复性过程中分子链间的相互作用,阐明三螺旋结构形成和形态变化的科学规律。同时,综述了三螺旋多糖的链构象与其生物活性之间的构效关系,以及基于螺旋构象转变构建的多糖基功能材料的最新研究进展。     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.     

Synthesis of pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles by Curtius reaction in Morita-Baylis-Hillman derivatives

Synthesis of substituted pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles from the Morita-Baylis-Hillman derivatives of acrylates via saponification followed by Curtius reaction is described.     

正丁胺对激光染料荧光谱影响的研究

用正丁胺作为碳源,采用射频辉光放电制备碳膜,选用激光染料R6G和聚乙二醇混合液作为蒸气源,采用单源热蒸发,在蒸发室与染料同时沉积得到混合膜,用拉曼光谱和红外光谱分析了碳膜的结构和键合方式,分析表明:碳膜中存在胺基团和氢原子.混合膜的荧光谱测量结果表明,认为正丁胺对染料荧光谱的影响是因为胺基和氢原子的存在.     

Cu0-catalysed 1,3-dipolar cycloadditions of α-amino acid derived N,N-cyclic azomethine imines to ynones

A series of 20 CuAIAC reactions between eight 4-acylamino substituted pyrazolidine-3-one-1-azomethine imines and four terminal ynones were performed using Cu⁰ as catalyst. The corresponding fluorescent cycloadducts were obtained in very high yields upon simple workup. Thus, Cu-metal turned out to be a better catalyst than Cu^I in terms of yield and ease of isolation. Availability of azomethine imines, mild reaction conditions, and simple workup enable a “click” access to libraries of densely substituted 2,3-dihydro-1H,5H-pyrazolo[1,2-a]pyrazol-1-ones. Reactivity of differently substituted dipoles was evaluated experimentally and by quantum chemical methods (DFT).     

Synthesis and antioxidative/anti-inflammatory activity of novel fullerene–polyamine conjugates

(E)-4-(Fullerenopyrrolidin-1-yl)-3-methylbut-2-enoic acid and its corresponding succinimidyl ester, readily obtained through Prato-type modification of C₆₀, were used for the selective N-acylation of polyamines. The thus obtained conjugates were evaluated for their antioxidative and anti-inflammatory activity and their cytotoxicity was determined. Members of this family of compounds showed interesting anti-lipid peroxidation, anti-lipoxygenase and anti-inflammatory activity and comparable cytocompatibility to spermidine.