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。     

高分子量褐藻多酚抗氧化性质研究

采用DPPH体系、羟基自由基体系、烷基自由基引发的亚油酸氧化体系、超氧阴离子自由基体系对海黍子高分子量褐藻多酚抗氧化性质进行了研究,发现其清除DPPH活性、清除羟基自由基活性、抑制烷基自由基引发的亚油酸氧化的活性分别为77％、27％和21％,但它不具有清除超氧阴离子自由基的能力。褐藻多酚具有供氢能力,其连三羟基的供氢能力大于间三羟基,清除羟基自由基与其苯环提供的羟基自由基加成位点的数量有关。     

海洋褐藻多糖的复杂结构、降解酶系以及生物学功能

海洋大型藻类(包括褐藻、红藻和绿藻)具有生物质资源产量高、生长过程中不占用耕地和淡水资源等优点,是未来生物炼制的优良原料。2021年,中国褐藻产量为190万吨,远高于其他经济藻类。但是与绿藻相比,褐藻所含的褐藻酸盐和红藻所含的3,6-脱水-L-半乳糖等多糖组分不容易发酵,极大地限制了其高值转化的进程。本文针对褐藻多糖的高效降解与高值转化这一研究热点,总结了褐藻的系统发育与褐藻多糖(褐藻胶、岩藻多糖以及昆布多糖)的复杂结构组成,分析了3类海洋多糖降解酶系的家族、空间结构及其特异性识别专一底物的活性架构等特征,并对褐藻多糖降解产物及其衍生寡糖的生物学功能进行了构效分析,以期揭示海洋多糖降解酶系的高效催化机制和特异性识别机理,推动褐藻的高效生物降解转化,为精准定制生物活性寡糖,构建绿色低碳工业化生产工艺提供参考。     

苏云金杆菌酪氨酸酶基因转化子黑色素的研究

苏云金杆菌(Bacillusthuringiensis,Bt)是使用广泛的杀虫细菌。将构建的含有嗜麦芽假单胞菌酪氨酸酶基因的重组质粒导入苏云金杆菌体内,使后者获得了稳定产生黑色素的能力。所产黑色素是无定形物质,在大多数有机和无机溶剂中溶解度低或不溶解,在碱性溶液中有较好的溶解性,在中性及弱酸性溶液中溶解度低,pH<4时沉淀;可用过氧化氢或次氯酸钠氧化,也能被银离子或硫化氢还原;含有天然物质中少见的自由基,并能清除由紫外线诱导产生的自由基;能吸收所有波长的光线,在紫外波长下吸收值最大,能有效地保护紫外辐射对蛋白质及DNA等生物大分子物质的损害,具有很强的抗辐射作用。使转化子抗辐射能力显著增强,杀虫活性稳定保持;能抵抗病毒的侵袭,生长旺盛;对畜禽安全。     

植物性食材的酚类化合物及其对机体的抗氧化保护

抗氧化剂已经被广泛用作食品或医药添加剂,从而抑制食品的氧化降解或保护人体细胞免受自由基的攻击.酚类化舍物因具有强大的抗氧化活性和清除自由基的能力而备受瞩目.在寻找天然抗氧化剂以替代有致癌性的合成抗氧化剂,或研究对人体健康有益的功能性成分过程中,人们对食品酚类的兴趣逐渐浓厚.本文对来自于陆地(水果、蔬菜及其他)和海洋食材(红藻、褐藻和绿藻等)中之主要酚类化合物的种类、含量、清除自由基以及对机体的抗氧化保护等功效进行了综述.陆生植物主要包括水果、蔬菜和其他食材,海洋植物包括红藻、褐藻和绿藻等.另外,本文还对酚类化合物的抗氧化机理和在开发食品添加剂或功能性膳食成分中的应用前景进行了讨论.     

五种昆虫多糖的体外抗氧化活性

采用邻苯三酚自氧化法、DPPH法、Fenton反应体系、FRAP分析法及对过氧化氢损伤细胞保护作用方法对白蜡虫Ericerus pela Cavannes雌成虫多糖、蝗虫多糖、喙尾琵甲多糖、美洲大蠊多糖及家蚕蛹多糖进行体外抗氧化研究,评价昆虫多糖总还原能力,对超氧阴离子自由基(O2-·)、DPPH·、羟自由基(·OH)的清除作用及损伤细胞存活率影响。试验结果表明,5种多糖对几种自由基均有不同程度的清除作用,且均呈现一定的量效关系;但对不同的氧化体系呈现不同的清除活性,白蜡虫多糖的总还原能力最强;白蜡虫、喙尾琵甲、美洲大蠊及蝗虫多糖对DPPH的清除率相对较明显;在羟自由基的清除能力上蚕蛹、喙尾琵甲及美洲大蠊多糖相对较强;各昆虫多糖对超氧阴离子清除能力不明显。5种多糖对过氧化氢损伤细胞有一定保护作用,在不同浓度范围内能增加细胞存活率。研究表明昆虫多糖具有一定抗氧化活性,可成为天然抗氧化物的来源。     

甘油葡萄糖苷αGG抗氧化性能及其对UV致细胞损伤保护修复的研究

笔者探讨了酶法制得的甘油葡萄糖苷(αGG)的抗氧化性能及其对紫外辐射致细胞损伤保护修复的促进作用.通过测定对DPPH自由基(DPPH·)、羟基自由基(·OH)和超氧阴离子自由基(·O2)的清除能力来研究αGG的抗氧化活性.结果表明:αGG对3种自由基均存在不同程度的清除能力,且抗氧化性与其质量浓度呈正相关;当αGG为2...     

半枝莲、白花蛇舌草及其药对提取物抗氧化及清除自由基活性

采用几种化学及生物学模型考察了半枝莲、白花蛇舌草及其药对提取物抗氧化及清除自由基活性.研究结果表明三种提取物中,半枝莲提取物还原能力、清除DPPH及·OH自由基能力最强,药对提取物螯合Fe2 能力以及保护DNA免受自由基损伤能力最强.提示提取物抗氧化及清除自由基活性可能与其黄酮组成及含量相关.推测药对的抗癌作用机理可能与金属离子的螯合能力和对DNA损伤的保护作用等有关.     

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。     

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。     

海洋寡糖及其衍生物活性的研究进展

海洋寡糖由海洋多糖经弱酸或糖苷酶等方法降解制备,具有来源丰富、结构新颖、分子量小、类型多样等特点,表现出抗肿瘤、抗氧化、免疫调节、抗病毒等多种生物活性,在食品、医药、保健品及化妆品等领域有着广泛的应用,具有巨大的开发潜力。为了及时了解海洋寡糖的研究进展,促进海洋寡糖的应用与开发,就海洋寡糖及其衍生物的免疫调节、抗肿瘤、抑菌、抗病毒、抗氧化、抗辐射、抗凝血、抗糖尿病以及调节肠道微生物等方面的活性研究进展进行了简要总结,以期为海洋寡糖及其衍生物的深入研究和深度开发提供参考。     

短波紫外线对日本三角涡虫的损伤及六种酶活力的影响

用短波紫外线(UV-C)照射处理日本三角涡虫,观察了涡虫的损伤状况,探讨了紫外线辐射对涡虫乳酸脱氢酶(LDH)、Na -K -ATP酶、Ca2 -Mg2 -ATP酶、超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和谷胱甘肽过氧比物酶(GSH-PX)活力的影响。结果表明,短波紫外线辐射对涡虫的损伤明显,照射的时间越长,涡虫在照射后出现死亡解体现象的时间就越短。随着紫外线照射时间的延长,LDH活力呈下降趋势;Na -K -ATP酶活力呈上升趋势而Ca2 -Mg2 -ATP酶活力呈下降趋势;SOD活力有明显的增加;CAT活力有增加趋势;GSH-PX活力波动较大,但总体仍呈增加趋势。不论是从紫外线对日本三角涡虫的损伤情况、还是对其六种酶活力的影响来看,日本三角涡虫是一种对紫外线辐射非常敏感的动物,在检测紫外线辐射及筛选抗紫外线辐射防护剂等方面具有潜在价值和应用前景。     

A test of the "flexible stem" model of evolution: ancestral plasticity, genetic accommodation, and morphological divergence in the threespine stickleback radiation

If an ancestral stem group repeatedly colonizes similar environments, developmental plasticity specific to that group should consistently give rise to similar phenotypes. Parallel selection on those similar phenotypes could lead to the repeated evolution of characteristic ecotypes, a property common to many adaptive radiations. A key prediction of this "flexible stem" model of adaptive radiation is that patterns of phenotypic divergence in derived groups should mirror patterns of developmental plasticity in their common ancestor. The threespine stickleback radiation provides an excellent opportunity to test this prediction because the marine form is representative of the ancestral stem group, which has repeatedly given rise to several characteristic ecotypes. We examined plasticity of several aspects of shape and trophic morphology in response to diets characteristic of either the derived benthic ecotype or the limnetic ecotype. When marine fish were reared on alternative diets, plasticity of head and mouth shape paralleled phenotypic divergence between the derived ecotypes, supporting the flexible stem model. Benthic and limnetic fish exhibited patterns of plasticity similar to those of the marine population; however, some differences in population means were present, as well as subtle differences in shape plasticity in the benthic population, indicating a role for genetic accommodation in this system.     

Hemocyanin from the keyhole limpet Megathura crenulata (KLH) carries a novel type of N-glycans with Gal(beta1-6)Man-motifs.

Keyhole limpet (Megathura crenulata) hemocyanin (KLH), an extracellular respiratory protein, is widely used as hapten carrier and immune stimulant. Although it is generally accepted that the sugar constituents of this glycoprotein are likely to be implicated in the antigenicity and biomedical properties of KLH, knowledge of its carbohydrate structure is still limited. Therefore, we have investigated the N-linked oligosaccharides of KLH. Glycan chains were enzymatically liberated from tryptic glycopeptides, pyridylaminated and separated by two-dimensional HPLC. Only neutral oligosaccharides were obtained and characterized by carbohydrate constituent and methylation analyses, MALDI-TOF-MS, ESI-ion trap-MS and sequential exoglycosidase digestion. The results revealed that KLH is carrying high mannose-type glycans and truncated sugar chains derived thereof. As a characteristic feature, a number of the studied N-glycans contained a Gal(beta1-6)Man-unit which has not been found in glycoprotein-N-glycans so far. Hence, our studies demonstrate that this marine mollusk glycoprotein is characterized by a unique oligosaccharide pattern comprising, in part, novel structural elements.     

Characterization of mucin-type oligosaccharides with the sialyl-Le(a) structure from human colorectal adenocarcinoma cells

Oligosaccharides with the sialyl-Le(a) structure have been isolated on an affinity column of a monoclonal antibody, MSW 113, from mucin-type glycoproteins derived from the surfaces of SW 1116 and LS 180 cells, and their secretions. The oligosaccharides were polydisperse with respect to molecular size, the oligosaccharides derived from glycoproteins in culture media being larger than those in cell lysates, as assessed by gel filtration. Some of the oligosaccharides were susceptible to degradation by endo-beta-galactosidase (E. freundii), as judged from the change in the gel filtration pattern. These results indicate that oligosaccharides with the sialyl-Le(a) structure derived from mucin-type glycoproteins produced by human colonic cancer cells are extremely large in size and complex in structure, and that some of them contain the poly-N-acetyllactosamine structure.     

Seaweed Oligosaccharides Stimulate Plant Growth by Enhancing Carbon and Nitrogen Assimilation, Basal Metabolism, and Cell Division

It is now well established that plant cell wall oligosaccharides can stimulate or inhibit growth and development in plants. In addition, it has been determined that seaweed (marine algae) cell wall polysaccharides and derived oligosaccharides can enhance growth in plants. In particular, oligo-alginates obtained by depolymerization of alginates from brown seaweeds increase growth of different plants by enhancing nitrogen assimilation and basal metabolism. Interestingly, oligo-alginates also stimulate growth of marine and fresh water green microalgae, increasing the content of fatty acids. On the other hand, oligo-carrageenans obtained by depolymerization of carrageenans from red seaweeds increase growth of tobacco plants by enhancing photosynthesis, nitrogen assimilation, basal metabolism, and cell division. In addition, oligo-carrageenans increase protection against viral, fungal, and bacterial infections in tobacco plants, which is determined, at least in part, by the accumulation of several phenylpropanoid compounds (PPCs) with antimicrobial activity. Moreover, oligo-carrageenans stimulate growth of 3-year-old Eucalyptus globulus trees by increasing photosynthesis, nitrogen assimilation, and basal metabolism. Furthermore, oligo-carrageenans induce an increase in cellulose content and in the level of essential oil and some PPCs with antimicrobial activities, suggesting that defense against pathogens may be also enhanced. Thus, seaweed oligosaccharides induce a dual beneficial effect in plants and trees, enhancing growth, which is determined by the increase in carbon and nitrogen assimilation, basal metabolism, and cell division, and defense against pathogens, which is determined by the accumulation of compounds with antimicrobial activities. In this sense, molecular mechanisms that potentially interconnect activation of plant growth and defense responses are discussed.     

The role of variation and plasticity in parental care during the adaptive radiation of three‐spine sticklebacks

Phenotypic plasticity might influence evolutionary processes such as adaptive radiations. Plasticity in parental care might be especially effective in facilitating adaptive radiations if it allows populations to persist in novel environments. Here, we test the hypothesis that behavioral plasticity by parents in response to predation risk facilitated the adaptive radiation of three‐spine sticklebacks. We compared the behavior of fathers across multiple ancestral (marine) and derived (freshwater) stickleback populations that differ in time since establishment. We measured behavioral plasticity in fathers in response to a predator found only in freshwater environments, simulating conditions marine males experience when colonizing freshwater. The antipredator behavior of males from newly established freshwater populations was intermediate between marine populations and well‐established freshwater populations. In contrast to our predictions, on average, there was greater behavioral plasticity in derived freshwater populations than in ancestral marine populations. However, we found greater individual variation in behavioral reaction norms in marine populations compared to well‐established freshwater populations, with newly established freshwater populations intermediate. This suggests that standing variation in behavioral reaction norms within ancestral populations might provide different evolutionary trajectories, and illustrates how plasticity can contribute to adaptive radiations.     

The occurrence of mouse-type oligosaccharides in mouse-human chimeric immunoglobulin G

The asparagine-linked sugar chains of mouse-human chimeric IgG which is composed of the variable regions derived from mouse and the constant regions derived from human and produced in mouse cells were quantitatively released as tritium-labelled oligosaccharides by hydrazinolysis followed by N-acetylation and NaB3H4-reduction. Paper electrophoresis in combination with sialidase digestion indicated that more than 70% of the oligosaccharides were neutral and the rest was sialylated oligosaccharides. Their structures were determined by sequential exoglycosidase digestions. The mouse-human chimeric IgG was shown to have same sugar chains as those of mouse IgG.     

Structures of the oligosaccharide chains in swine trachea mucin glycoproteins

The structures of large O-glycosidically linked oligosaccharides derived from swine trachea mucin glycoprotein were established. Reduced oligosaccharides released by treatment with alkaline borohydride were separated by gel filtration on Bio-Gel P-6 and the neutral oligosaccharides were isolated by chromatography on DEAE-cellulose. Eight oligosaccharides (DIa to BII), ranging in length from 8 to 15 sugar units, were isolated. On the basis of carbohydrate composition and analytical data from sequential treatment with exoglycosidases and permethylation analysis, the following structures were assigned to these oligosaccharides: (Formula: see text).     

Abnormal lipid-linked oligosaccharides in class E Thy-1-negative mutant lymphomas.

The glycosylation defect of Thy-1-mutant lymphomas of the class E complementation group has been identified as a block in the synthesis of the lipid-linked oligosaccharide precursor of the asparagine-linked oligosaccharides of glycoproteins. Two major lipid-linked oligosaccharides were isolated from the mutant cells. Both oligosaccharides were smaller than the lipid-linkid oligosaccharides of wild-type lymphomas and, in contrast to the lipid-linked oligosaccharides isolated from wild-type cells, both were resistant to digestion with endoglycosidase H. The oligosaccharides of newly synthesized polypeptides in class E Thy-1-cells were also resistant to endoglycosidase H digestion, providing strong evidence that they are derived from the abnormal lipid-linked oligosaccharides.