斜顶菌(Clitopiluscaespitosuspk.)多糖构象的比较研究——分子量大小,支链长短对构象的影响

川刚果红复合物法及旋光法,比较分析了五种一级结构有所差异的斜项菌多糖水溶液中的构象情况。结果表明,溶液中构象特征及构象稳定性与其一级结构主要有三方面的依赖关系:一是分枝结构(分枝率、分枝长短、分枝点比例等)的比例高、则形成三股螺旋的能力与稳定性较低;二是在基本结构相同时,随主链的增长(分子量增加)形成三股螺旋的能力增加,三股螺旋的稳定性亦增加。分子量小到一定程度(w～0.9万)亦即糖链残基数少于60,即不能形成三股螺旋。三是主链中糖苷键连接方式的影响。生物大分子,如蛋白质、核酸等都有复杂的空间结构,而且这些空间结构是建立在一级结构的基础上的。对于多糖这种生物大分子化合物空间结构及其与一级结构的关系,国内外研究尚不多。近年来关于β1→3萄聚糖的空间结构已有不少报道,如 Lintain Sohizophyllan Sclorogluoan Diotyophora indusiata萄聚糖斜顶菌多糖等,这些多糖无论线性还是具有分枝的结构,都具有三股螺旋的空间结构,且其与刚果红所成复合物,及其旋光特征均有些特殊规律,这些规律可做为评价这类多糖构象特征的指标。我们以斜顶菌中提取、分离、制备的五种多糖为材料,试以刚果红与多糖形成复合物为指标,结合旋光性变化等较简单方法,进行了比较分析,从其一级结构与空间结构的关系上得到一些结果。     

白术多糖的溶液构象及其变化

采用刚果红实验判断白术多糖WAM在溶液中的构象特征,通过测定不同溶液体系中多糖分子的黏度、比旋度、紫外吸收光谱和圆二色谱的变化来研究多糖构象及其变化规律.实验结果表明:WAM不具有螺旋结构,温度、金属离子、变性剂均可以使WAM构象发生改变.WAM在溶液中以无规则线团形式存在.     

多糖化学结构解析研究进展

多糖作为自然界中含量丰富的生物大分子,其不同的化学结构会影响其生物学活性.由于多糖结构复杂使其解析起来十分繁琐和困难,多糖的深入研究受到限制.因此,文中介绍了天然产物多糖初级结构和高级结构的研究方法,同时对毛细管电泳-质谱联用技术(CEMS)、基质辅助激光解吸电离飞行时间质谱联用技术(MALDI-TOF-MS)、二维核磁共振技术(~1H-~1H COSY、HSQC、HMBC)、分子模拟技术等最新检测手段在多糖化学结构解析中的应用进行综述.这些技术可以方便快捷的提供多糖组成、链接顺序等一级结构信息,同时也可以表征多糖的空间构象,成为解析多糖结构、探究多糖结构-功能关系不可或缺的工具.     

茯苓多糖与羧甲基茯苓多糖的结构表征

用高压液相色谱，红外光谱，核磁共振谱，Ｘ－射线衍射谱，热分析，可见光分光光度法等现代物理方法研究了具有抗肿瘤活性的茯苓多糖与羧甲基茯苓多糖的结构，结果表明，茯苓多糖是不含有β－（１→６）葡聚糖支链的β－（１→３）－Ｄ－葡聚糖，羧甲基茯苓多为 的羧甲基呈－ＣＨ２ＣＯＯ状态，茯苓多糖在中性或微碱性溶液中呈三股螺旋构象。     

正壬烷构象的振动光谱研究

对于含有一个gauche构象的正壬烷,包括全反式构象在内主要有四种稳定构象。为了得到各种构象与特征频率之间的对应关系,运用从头计算方法分别计算出了这四种构象的红外振动频率以及相应强度。根据其振动强度以及振动特征,特别是振动发生在gauche位置的振动模式,得到了各种构象在整个范围内的红外光谱特征峰以及相同振动模式随构象变化的规律。这不但弥补了正壬烷链构象实验研究的不足,而且还起到一定的理论指导作用。     

三级相互作用下Ploy（trimethylene oxide）链的构象性质

基于旋转异构态近似模型,用半经验势函数计算了Ｐｌｏ６链在三级相互作用下构象能,并用三级相互作用近似下的统计权重矩阵方法计算了该链的特征比、偶极矩比等构象性质。结果表明,由三级相互作用近似得到的特征比,偶极矩比比由二级相互作用近似得到的结果有较大的改善,且和实验值较为一致。     

神奇的多糖家族

多糖是一类天然高分子化合物,它是由醛糖或酮糖通过糖苷键连接在一起的多聚物。多糖在自然界分布极广,对动植物的生命极为重要,是构成生命的四大基本物质之一。而且具有多种生理活性。活性多糖专指具有某种特殊生理活性的多糖化合物。活性多糖包括真菌多糖,主要有灵芝多糖、猪苓多糖、香菇多糖、云芝多糖、茯苓多糖等:植物多糖,主要有人参多糖、枸杞多糖、黄芪多糖、板蓝根多糖等;动物多糖,主要指来源于许多低等动物特别是节肢动物如虾、蟹、昆虫等外壳的甲壳素和存在于高等动物体内的粘多糖等。活性多糖作为生物效应调节剂。主要作用于机体的免疫系统。具有抗肿瘤、抗炎、抗凝血、抗病毒、降血脂、降血糖等活性。     

神奇的多糖家族连载②

多糖是一类天然高分子化合物,它是由醛糖或酮糖通过糖苷键连接在一起的多聚物。多糖在自然界分布极广。对动植物的生命极为重要,是构成生命的四大基本物质之一,而且具有多种生理活性。活性多糖专指具有某种特殊生理活性的多糖化合物。活性多糖包括真菌多糖。主要有灵芝多糖、猪苓多糖、香菇多糖、云芝多糖、茯苓多糖等;植物多糖,主要有人参多糖、枸杞多糖、黄芪多糖、板蓝根多糖等;动物多糖,主要指来源于许多低等动物特别是节肢动物如虾、蟹、昆虫等外壳的甲壳素和存在于高等动物体内的粘多糖等。活性多糖作为生物效应调节剂,主要作用于机体的免疫系统,具有抗肿瘤、抗炎、抗凝血、抗病毒、降血脂、降血糖等活性。     

植物多糖与保健

文章介绍了植物多糖的多种生物活性,如提高机体免疫力、抗肿瘤、抗辐射、抗衰老、降血脂、降血糖、抗病毒等。讨论了植物多糖的开发利用及深入研究。     

多糖定量检测的研究进展

本文综述了多种多糖定量检测的方法,可分为两大类：一类是直接测定多糖本身,如高效液相色谱法、高效毛细管电泳法、凝胶渗透色谱法等;另一类间接测定法,是利用测定组成多糖的单糖来完成定量。     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the     

An affordable accurate evaluation of the binding conformations predicted by molecular docking studies in bio-system

Franck-Condon factors bridge the gap between theoretical modeling and experimental observations for molecular electronic spectroscopy and electron transfer.Under the displaced harmonic oscillator approximation,multidimensional Franck-Condon factors are decomposed into a product of many one-dimensional(1D)Franck-Condon(FC)factors,and each 1D-FC factor is associated with one Huang-Rhys factor that determines the leading contribution of     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with