褐藻多糖的分离提取及生理活性研究进展

褐藻多糖是海藻胶、褐藻糖胶和褐藻淀粉的统称,主要存在于褐藻中。褐藻糖胶作为其主要的生理活性物质,主要由L-岩藻糖和硫酸酯基组成,具有抗氧化、抗凝血、防癌抗肿瘤、抗病毒和消炎等活性。综述了褐藻多糖的提取分离方法和褐藻糖胶的生理活性研究进展,以期为褐藻多糖的应用提供参考。     

HILIC-ESI-HCD-MS/MS寡糖图谱分析用于海参褐藻糖胶的结构鉴定

褐藻糖胶也称为岩藻黄质、岩藻多糖、褐藻多糖,是一种硫化的多糖,常见于海参、海藻等褐藻纲及海藻类的植物中。研究发现,具有特定硫酸化结构的糖类结构域在生物功能中起着至关重要的作用。因此,对褐藻糖胶寡糖进行精细的结构表征,尤其是确定其硫酸化结构,对于理解褐藻糖胶的结构-功能关系至关重要。     

褐藻多糖

褐藻多糖主要包括褐藻胶、褐藻糖胶和褐藻淀粉。近年来研究表明,褐藻多糖有一定的抗癌、抗HIV-1作用。详细介绍了褐藻多糖的来源、类型、结构及性质;分离、提纯方法以及它们的生理活性和相关的构效关系研究。     

褐藻糖胶的化学组成及生物活性的研究

褐藻糖胶是一种从褐藻中提取的硫酸多糖,是一种天然活性物质,具有许多药用功能。近年来有关褐藻糖胶在医药方面的应用受到越来越多研究人员的关注。就其组成分析及其生物活性的研究作一综述。     

羊栖菜褐藻糖胶抗凝血活性的研究

本文研究了羊栖菜褐藻糖胶的化学组成和抗凝血活性之间的关系。采用热水提取得羊栖菜粗多糖,CaCl2纯化得褐藻糖胶,DEAE Sepharose CL-6B柱层析与Sepharose CL-6B柱层析对褐藻糖胶进行分级,得到F1、F2、F31、F32和F33五个级分,均为岩藻糖、半乳糖和甘露糖等糖基组成的杂多糖,并含有硫酸酯和糖醛酸以及少量的蛋白质,相对分子质量范围2．5万～95万。采用活化部分凝血活酶时间(APTT)和凝血酶时间(TT)检测了这5个级分的抗凝血活性,结果显示,羊栖菜褐藻糖胶能显著延长APTT的凝血时间,而对TT的影响不明显。F1、F31和F32对APTT的影响比较显著,而F2、F33和羊栖菜粗多糖的影响较小。研究表明,羊栖菜褐藻糖胶主要是通过抑制内源凝血途径而达到抗凝血的效果,其抗凝血活性与褐藻糖胶的硫酸基含量成正相关,而与相对分子质量和糖醛酸含量无关。     

褐藻多糖及其衍生物的抗肿瘤作用

海洋植物作为一类有益健康的天然产品受到诸多关注。其中,褐藻科植物和褐藻的粗提取物在抗肿瘤活性方面显示出极大优势。鉴于此,褐藻粗提取物的活性成分褐藻多糖的抗肿瘤作用引起制药领域的极大兴趣。褐藻多糖包括褐藻胶、岩藻聚糖和褐藻淀粉等,主要来自海带、巨藻、泡叶藻、墨角藻等海藻植物。研究发现,褐藻糖胶的衍生物及海藻酸钠的衍生物具有降血压、调节免疫、抗炎抗病毒、抗氧化以及抗肿瘤的作用。本文介绍了褐藻多糖及其衍生物在抗肿瘤活性方面的研究现状。     

日粮添加褐藻糖胶对断奶仔猪抗炎能力和肠道微生物多样性的影响

【目的】本试验旨在研究日粮添加海带提取物褐藻糖胶对断奶仔猪生长性能、营养物质消化率、机体免疫力和肠道微生物多样性的影响。【方法】试验选用36头初始体重为(7.43±0.12) kg的健康仔猪,按照随机区组设计分为3组,每组12头。日粮处理组分别为不含抗生素的基础日粮组、抗生素组和褐藻糖胶组;试验期为28d。评价褐藻糖胶对仔猪生长性能和营养物质消化率的影响;通过比色法和酶联免疫吸附法检测血清中与免疫相关的指标;通过16S rRNA扩增子高通量测序检测试验第0、14和28天肠道微生物多样性。【结果】日粮添加褐藻糖胶可降低试验0–14 d仔猪耗料增重比(P0.05),但对试验全期仔猪平均日增重和平均日采量无显著影响(P0.05)。与对照组相比,饲喂褐藻糖胶日粮后,仔猪的中性洗涤纤维和酸性洗涤纤维表观消化率显著提高(P0.05);仔猪饲喂抗生素和褐藻糖胶日粮后,血清IL-22含量显著降低。试验第14天,抗生素组和褐藻糖胶处理组中Bacteroidetes数量呈上升趋势(P=0.07);试验第28天,抗生素组和褐藻糖胶处理组Actinobacteria丰度显著高于对照组(P0.05),且褐藻糖胶处理组Bacteroides属的菌群丰度显著高于对照组和抗生素组。【结论】日粮添加褐藻糖胶提高了断奶仔猪纤维养分消化率和拟杆菌属的丰富度和多样性,并且降低了促炎性细胞因子IL-22含量,这有助于缓解仔猪的断奶应激反应,建立稳定健康肠道菌群。     

羊栖菜中褐藻糖胶的组分分离及分析

为了确定羊栖菜褐藻糖胶中的活性组分 ,用分子量结合硫酸化程度的分级方法将其分成不同组分。经热水抽提的羊栖菜多糖 ,将去除褐藻胶、海带淀粉后剩余的褐藻糖胶经过DEAE—Sepharose离子交换色谱柱和Sepharose 4B凝胶层析柱被分成 5个褐藻糖胶组分。 5个组分中硫酸基和岩藻糖近似的分子数量之比分别为 1.863、0 .0 68、1.2 2 9、1.62 9,1.0 10 ;平均分子量分别为 2 .0× 10 4 、2 .2× 10 4 、8.2× 10 4 、2 1.4× 10 4 、32 .0× 10 4 ;百分含量分别为 8.6%、2 2 .9%、4 8.5 %、5 .7%、14.3%。     

几种天然产物对高尿酸血症大鼠血清尿酸水平的影响初探

目的:探讨几种天然产物对高尿酸血症大鼠血清尿酸水平及尿酸排泄的影响.方法:对wistar大鼠灌胃氧嗪酸钾和酵母膏,制作高尿酸血症大鼠动物模型.灌胃给药褐藻糖胶、柠檬酸钾和东哥阿里提取物,2周后采血并进行代谢实验,检测血清尿酸、尿素氮,24小时尿液体积、pH值、尿酸浓度及总量,分析三种活性物质对机体尿酸水平、尿酸排泄、肾脏功能的影响.结果:三种物质均可显著降低高尿酸血症模型大鼠的血清尿酸水平,其中东哥阿里提取物组的24小时排泄尿酸总量较模型组显著降低,褐藻糖胶对实验大鼠的血清尿素氮水平升高有抑制作用.结论:三种活性物质对高尿酸血症大鼠血清尿酸浓度有降低作用,其中褐藻糖胶对肾脏功能有保护作用,从而保证尿酸的顺利排泄,而东哥阿里在降低血尿酸水平的同时,24小时尿液中排泄的尿酸总量也显著低于模型对照组,其机制可能与抑制尿酸生成有关.     

裙带菜假根中褐藻糖胶的提取

研究了温度、pH值、提取时间和水藻比及添加果胶酶和纤维素酶对采用乙醇沉淀法提取裙带菜假根中褐藻糖胶的影响。单因素和正交实验结果表明,80℃p、H 5、提取时间5 h下的褐藻糖胶得率最高,水藻比影响不明显。添加500 u/g果胶酶和纤维素酶可分别增加57%和46%。     

蛋白质结构与功能中的结构域

结构域是蛋白质亚基结构中的紧密球状区域.结构域作为蛋白质结构中介于二级与三级结构之间的又一结构层次,在蛋白质中起着独立的结构单位、功能单位与折叠单位的作用.在复杂蛋白质中,结构域具有结构与功能组件与遗传单位的作用.结构域层次的研究将会促进蛋白质结构与功能关系、蛋白质折叠机制以及蛋白质设计的研究.     

蛋白质结构研究现状与展望

本文综述了近年来蛋白质结构的确定、预测、比较、分类和功能五个问题的研究概况,并分析了解决每个问题的方法,最后指出蛋白质结构研究的发展前景。     

Structure evolution and incomplete induction

Evolutionary strategies such as the evolution strategy (Rechenberg 1965, 1973; Schwefel 1977) or genetic algorithms (Holland 1975; Goldberg 1989) have been widely applied to systems where parameters have to be determined according to a particular objective function. A necessary demand in all these experiments is that the structures of the objects to be optimised are well defined, because these structures are part of the objective function. With structure evolution the range of applications of evolutionary algorithms can now be expanded to tasks which are less accurately described, i.e. where the structures of the objects are fairly unknown. Heuristical effort is reduced first to defining structure components by combinations of which the structure space is generated. The structure space can be nearly infinitely large. Furthermore, the mutation procedures for structures have to be determined, complying with the demand for strong causality. In its computer model the algorithm of structure evolution involves the phenomenon of isolation, a feature of biological evolution additional to replication, mutation, and selection, which have already been implemented in other strategies. The idea of structure evolution is to let different but some what similar structures of an object compete in temporarily isolated populations where the respective parameter evolution is carried out. Thus structure evolution can perform a most effective search, both in structure and parameter space. The algorithm is demonstrated with two examples: a neural filter in a visual system and the topologies of frameworks. The first of the examples touches the problem of incompletely described tasks, and this paper will show that the effect of overlearning can be avoided by a learning procedure called incomplete induction, which fits best with the algorithm of structure evolution.     

Underlying and Superficial Critical Structure

The superficial structure of Maddocks oritique of Shapiro (1979) consists of trivial complaints, misreadings of Shapiro's arguments, and flawed analysis of ethnographic materials. The chief generative element in this structure is Maddock's pose as Defender of the Faith for LBvi-Straussian scholasticism.     

Solvent Structure and Enzyme Activity

Abstract

Enzymes are fluctuating particles in thermal equilibrium with their solvent environment. A variety of models of enzyme action have postulated selective excitation of enzyme vibrational modes or triggering of correlated motion of catalytic groups through collisions with solvent particles as the basis of catalytic activity. Solvent composition and structure are expected to influence such interactions. Solutes such as p-dioxane, t-butanol, and tetraalkylammonium chlorides are known to be strong perturbants of the structure of water. However, when the kinetic parameters of two enzymes, carboxypeptidase A and α-chymotrypsin, were examined carefully in aqueous mixtures containing these solutes, no significant influence of solvent structure or mass composition on the catalytic rate constant was found. The results indicate, furthermore, that, within the low viscosity limit, fluctuations in enzyme structure that are responsible for activated processes in the catalytically rate limiting step appear not to be significantly influenced by dynamic processes in the bulk solvent.     

肝素结构与功能的研究进展

肝素是一类结构异常复杂的糖胺聚糖,与此相对应的是其多种生物学功能。除了经典的抗凝血及其相关的抗血拴生成以外,肝素还具有抗平滑肌细胞增殖、抗炎症、抗肿瘤及抗病毒等,并且这些生物活性同抗凝活性无关,而同肝素的特异结构密切相关。本文综述了肝素的多种生物学功能、作用机制及结构与功能的关系。     

昆虫受精囊的结构与功能

昆虫受精囊是在雌雄交配之后,作为雌性贮存、释放精子和使卵受精的器官,其结构、功能及活动调节对保持精子活性和卵子受精有重要的影响。该文对昆虫受精囊结构、功能及其活动调节的研究进展做一介绍,以期为相关研究提供有益的资料。     

子宫珠蛋白的结构与功能

子宫珠蛋白(UG)是类固醇激素诱导的、进化保守的多功能蛋白,从其基因结构、蛋白质结构、分布调节、合成的机制及其功能等方面来看,UG通过其假定受体介导自分泌和旁分泌途径发挥作用,它可能属于细胞因子/趋化因子家族,关于UG结构、调节和功能的阐明将为揭示人类一般疾病、探索胚胎植入奥秘以及研究肿瘤发生机制提供新的认识.     

Reconstruction and Stability of Secondary Structure Elements in the Context of Protein Structure Prediction

Efficient and accurate reconstruction of secondary structure elements in the context of protein structure prediction is the major focus of this work. We present a novel approach capable of reconstructing α-helices and β-sheets in atomic detail. The method is based on Metropolis Monte Carlo simulations in a force field of empirical potentials that are designed to stabilize secondary structure elements in room-temperature simulations. Particular attention is paid to lateral side-chain interactions in β-sheets and between the turns of α-helices, as well as backbone hydrogen bonding. The force constants are optimized using contrastive divergence, a novel machine learning technique, from a data set of known structures. Using this approach, we demonstrate the applicability of the framework to the problem of reconstructing the overall protein fold for a number of commonly studied small proteins, based on only predicted secondary structure and contact map. For protein G and chymotrypsin inhibitor 2, we are able to reconstruct the secondary structure elements in atomic detail and the overall protein folds with a root mean-square deviation of <10 Å. For cold-shock protein and the SH3 domain, we accurately reproduce the secondary structure elements and the topology of the 5-stranded β-sheets, but not the barrel structure. The importance of high-quality secondary structure and contact map prediction is discussed.     

Structure and mechanism of proton-translocating transhydrogenase

Recent developments have led to advances in our understanding of the structure and mechanism of action of proton-translocating (or AB) transhydrogenase. There is (a) a high-resolution crystal structure, and an NMR structure, of the NADP(H)-binding component (dIII), (b) a homology-based model of the NAD(H)-binding component (dI) and (c) an emerging consensus on the position of the transmembrane helices (in dII). The crystal structure of dIII, in particular, provides new insights into the mechanism by which the energy released in proton translocation across the membrane is coupled to changes in the binding affinities of NADP(+) and NADPH that drive the chemical reaction.