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.     

Characterization and Antioxidant Activity of Mannans from Saccharomyces cerevisiae with Different Molecular Weight

Polysaccharides were extracted from natural sources with various biological activities, which are strongly influenced by their chemical structure and molecular weight. In this research, mannans polysaccharides were obtained from Saccharomyces cerevisiae by ethanol precipitation. The molecular weight of YM50, YM70, and YM90 mannans was 172.90 kDa, 87.09 kDa, and 54.05 kDa, respectively. Scanning electron microscopy of YM 90 mannans showed a rough surface with numerous cavities, while the surfaces of YM50 and YM70 were relatively smooth. Sepharose CL-6B and FTIR indicated that mannans had the characteristic bands of polysaccharides. The antioxidant activities of polysaccharides were evaluated in vitro using various assays. Mannans showed a good scavenging activity of DPPH radicals which depend on the molecular weight and concentration, and a higher scavenging activity of hydroxyl radical than ferric-reducing power activities. For the three types of mannans, cytotoxicity and hemolytic activity were rarely detected in mice erythrocytes and Caco-2 cells. Those results could contribute to the further application of mannans from Saccharomyces cerevisiae in the food and medicine industry.     

Application of chromatography in purification and structural analysis of natural polysaccharides: A review

Polysaccharides are widely distributed in natural sources from monocytic microorganisms to higher animals, and are found in a variety of biological activities in recent decades. Natural polysaccharides have the characteristics of large molecular weight, diverse composition, and complex structure, so their purification and structural analysis are difficult issues in research. Chromatography as a powerful separation technique, plays an irreplaceable role in the separation and structural analysis of natural polysaccharides, especially in the purification of polysaccharides, the separation of hydrolysates, and the analysis of monosaccharide composition. The separation mechanisms and application of different chromatographic methods in the studies of polysaccharides were summarized in this review. Moreover, the advantages and drawbacks of various chromatography methods were discussed as well.     

中药多糖成分前处理及检测方法研究进展

多糖是中药的重要活性成分之一,具有降血脂、降血糖、增强免疫、抗肿瘤、抗氧化、抗凝血、抗炎症、抗衰老等活性。该类物质具有极性强、分子量大、结构难确证等特点,成为中药多糖新药开发的瓶颈。该文综述了近10年关于中药多糖成分的前处理及检测方法,以期为中药多糖定性定量分析,质量控制的提高,多糖药物深度开发和中药物质基础的全面研究提供参考。     

Polysaccharides from Medicine and Food Homology Materials: A Review on Their Extraction,Purification, Structure,and Biological Activities

Medicine and food homology (MFH) materials are rich in polysaccharides, proteins, fats, vitamins, and other components. Hence, they have good medical and nutritional values. Polysaccharides are identified as one of the pivotal bioactive constituents of MFH materials. Accumulating evidence has revealed that MFH polysaccharides (MFHPs) have a variety of biological activities, such as antioxidant, immunomodulatory, anti-tumor, hepatoprotective, anti-aging, anti-inflammatory, and radioprotective activities. Consequently, the research progress and future prospects of MFHPs must be systematically reviewed to promote their better understanding. This paper reviewed the extraction and purification methods, structure, biological activities, and potential molecular mechanisms of MFHPs. This review may provide some valuable insights for further research regarding MFHPs.     

Natural and edible biopolymer poly-gamma-glutamic acid: synthesis, production, and applications

Poly-gamma-glutamic acid (gamma-PGA) is a very promising biodegradable polymer that is produced by Bacillus subtilis. Gamma-PGA is water-soluble, anionic, biodegradable, and edible. This paper reviews the production of a strain of gamma-PGA and recent developments with respect to applications in terms of Ca absorption, moisturizing properties, gamma-PGA conjugation, super absorbent polymer, and so on. Our recent research shows that gamma-PGA can be used as an immune-stimulating and anti-tumor agent, especially at high molecular weight.     

影响离子导电高分子材料性能的内因与外因

材料分子设计离不开结构与性能的关系。分析内因与外因两方面影响因素对材料功能特性的影响有助于优化功能材料的结构。本文以离子型导电功能高分子材料为例,详细分析了各种因素对材料电导率的影响,为离子型导电功能高分子材料的结构设计提供依据。     

MALDI-TOF MS analysis of native and permethylated or benzimidazole-derivatized polysaccharides

MALDI-TOF MS provides rapid and sensitive analyses of larger biomolecules. However, MS analyses of polysaccharide have been reported to have lower sensitivity compared to peptides and proteins. Here, we investigated some polysaccharides chemically derivatized by permethylation and ortho-phenylene diamine (OPD) tagging. Methylated glycan is obviously able to improve the sensitivity for mass spectrometry detection. Oxidative condensation by UV-activation tagging to saccharides by OPD and peptide-OPD also improve the sensitivity of MALDI-TOF MS analyses. Polysaccharides including dextran, glucomannan, arabinoxylan, arabinogalactan and beta-1,3-glucan, isolated from nutritional supplements of Ganoderma lucidum and Saccharomyces pastorianus were measured using MALDI-TOF MS with 2,5-dihydroxybenzoic acid (2,5-DHB) as the matrix. These glycans were also derivatized to methylated and benzimidazole-tagged glycans by chemical transformation for molecular weight analysis. The derivatized polysaccharides showed excellent MALDI-TOF MS signal enhancement in the molecular weight range from 1 to 5 kDa. Here, we demonstrate an efficient method to give glycan-benzimidazole (glycan-BIM) derivatives for polysaccharide determination in MALDI-TOF MS. Therefore, permethylated or benzimidazole-derivatized polysaccharides provide a new option for polysaccharide analysis using MALDI-TOF MS.     

杏鲍菇多糖WPP2的结构表征及抗肿瘤活性

采用热水浸提法从杏鲍菇中提取粗多糖, 经纯化得到一种新的多糖WPP2.通过紫外光谱、色谱、质谱、核磁共振、红外光谱、环境扫描电子显微镜(ESEM)和原子力显微镜(AFM)等技术相结合的方法, 对WPP2结构进行了表征, 并对其体外抗氧化和抗肿瘤活性进行了初步探讨.结果表明, WPP2的平均分子量为4.499×10⁵, 主要由Glc组成, 每个重复单元存在2条支链,→1,2,3)-β-D-Manp和→1,2,6)-β-D-Manp位于支链位点, 支链由→1,6)-β-D-Glcp和→1,6)-β-D-Galp构成, 非还原末端基为→1)-β-D-Glcp, 主链主要由→1,3)-β-D-Glcp,→1,6)-β-D-Galp和→1,3)-β-D-Manp糖残基组成.刚果红实验结果表明其具有三螺旋结构; 用ESEM和AFM首次在纳米尺度观察到WPP2具有多分枝结构; 活性实验结果表明WPP2具有一定的抗氧化和抗肿瘤活性.     

Studies on Sulfation of Lycium barbarum Polysaccharides

Polysaccharides can anti-virus, such as human immunodeficiency virus (HIV-1),[1] herpes simplex virus (HSV-1,HSV-2) and cytomegalovirus. Some of them are sulfates, e.g. dextran sulfate, heparin, sulfonation of chitosan and sulfated derivatives of Lentinan. Our results showed that sulfated derivatives of Lycium barbarum polysaccharides (LBP)have anti-HIV activity. Because the anti-HIV activity of LBP was deeply dependent on the molecular weight, the sulfation pattern and glycosidic branches besides degree of sulfation (DS), so we emphasized our work on the factors of DS.     

Isolation and characterization of antigens fromPseudomonas aeruginosa in exhaustively cultivated biomass

Biotechnology for producing biomass and controlling biosynthetic processes of desired complex polysaccharides is developed. The isolated polysaccharides exhibit protective activity in a test for active protection. Various polysaccharide fractions induced the production of antibodies with different degrees of passive protection. The most active antibodies are obtained from the blood of animals immunized with the first fraction of polysaccharides from biomass strain 263. Polysaccharides of the first fraction are analyzed by HPLC. The amount of nucleic acids and proteins in the preparation is quantitatively estimated. Presented at the Third International Symposium on Natural Product Chemistry, Bukhara, 1998. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 658–660, September–October, 1999.     

Polysaccharide Chemistry in Drug Delivery,Endocrinology, and Vaccines

Polysaccharides, due to their outstanding properties, have attracted the attention of researchers, working in the biomedical field and especially of those working in drug delivery. Modified/functionalized polysaccharides further increase the importance for various applications. Delivery of therapeutics for diverse ailments in different endocrine glands and hormones safely, is a focal point of researchers working in the field. Among the routes followed, the transdermal route is preferred due to non-exposure of active moieties to the harsh gastric environment and first-pass metabolism. This review starts with the overview of polysaccharides used for the delivery of various therapeutic agents. Advantages of polysaccharides used in the transdermal route are addressed in detail. Types of polysaccharides will be elaborated through examples, and in this context, special emphasis will be on the polysaccharides being used for synthesis of the membranes/films. Techniques employed for their modification to design novel carriers for therapeutics delivery will also be discussed. The review will end with a brief discussion on recent developments and future perspectives for delivery of therapeutic agents, and vaccine development.     

The significance of complex polysaccharides in personal care formulations

Complex polysaccharides have numerous pharmacological activities, such as antioxidant, antibacterial, antiviral, immunomodulating, anticoagulant and anticancer effects. In personal care products, these biopolymers are used as thickener and stabilizing agents or as moisturizing ingredients that could be beneficial to the skin. Various polysaccharides, such as glycosaminoglycans (GAGs), hyaluronic acid (HA), carrageenan, fucose, fucoidan, chitin, chitosan, etc., have applications in cosmeceutical industries. GAGs and HA incorporated in moisturizing creams strengthen the skin barrier by forming a protective layer which prevents transdermal water loss. Therefore, these polysaccharides have been formulated into potential cosmeceuticals and biopharmaceuticals.     

Comparisons of Isolation Methods,Structural Features,and Bioactivities of the Polysaccharides from Three Common Panax Species: A Review of Recent Progress

Panax spp. (Araliaceae family) are widely used medicinal plants and they mainly include Panax ginseng C.A. Meyer, Panax quinquefolium L. (American ginseng), and Panax notoginseng (notoginseng). Polysaccharides are the main active ingredients in these plants and have demonstrated diverse pharmacological functions, but comparisons of isolation methods, structural features, and bioactivities of these polysaccharides have not yet been reported. This review summarizes recent advances associated with 112 polysaccharides from ginseng, 25 polysaccharides from American ginseng, and 36 polysaccharides from notoginseng and it compares the differences in extraction, purification, structural features, and bioactivities. Most studies focus on ginseng polysaccharides and comparisons are typically made with the polysaccharides from American ginseng and notoginseng. For the extraction, purification, and structural analysis, the processes are similar for the polysaccharides from the three Panax species. Previous studies determined that 55 polysaccharides from ginseng, 18 polysaccharides from American ginseng, and 9 polysaccharides from notoginseng exhibited anti-tumor activity, immunoregulatory effects, anti-oxidant activity, and other pharmacological functions, which are mediated by multiple signaling pathways, including mitogen-activated protein kinase, nuclear factor kappa B, or redox balance pathways. This review can provide new insights into the similarities and differences among the polysaccharides from the three Panax species, which can facilitate and guide further studies to explore the medicinal properties of the Araliaceae family used in traditional Chinese medicine.     

Comparative Analysis of Polysaccharides from Two Ecological Types of Leymus chinensis

Leymus chinensis(Trin.) Tzvel., widely distributed at eastern Eurasian steppe and divided into gray-green type and yellow-green type, has different stress resistance to environment. In the present study, the water-soluble polysaccharides from two ecotypes of L. chinensis were analyzed in detail, and the differences between polysaccharides from the two ecotypes of L. chinensis in the yield, monosaccharide composition, molecular weight and structure were clarified. The polysaccharides of L. chinensis were composed of both neutral and acidic polysaccharides. The neutral polysaccharides contained mannose, glucose, galactose, xylose and arabinose, and mainly consisted of β-1,4-Glcp, α-1,3-Galp and α-1,2-Xylp residues. The acidic polysaccharides contained mannose, rhamnose, glucuronic acid, galacturonic acid, glucose, galactose, xylose and arabinose. However, the yields, monosaccharides contents and the molecular weights of the polysaccharides from the two ecotypes of L. chinensis were different. Moreover, the resistance type(gray-green type) of L. chinensis contained a number of α-1,3-Manp and reducing end of β-Glcp residues, and much more O-methyl groups than normal type(yellow-green type) of L. chinensis. The differences of the polysaccharides of the two ecotypes of L. chinensis might be due to the long-term environmental adaptability of plant, and the differences of the polysaccharides might influence the stress resistance of L. chinensis.     

Characteristics of polysaccharides and protein associated with them from dried and freshly collected red alga <Emphasis Type="Italic">Tichocarpus crinitus</Emphasis>

Polysaccharides isolated by successive extraction with water at 20 and 80°C from freshly collected and dried alga T. crinitus were compared. It was shown that the yield of polysaccharides from freshly collected alga was 40–44%; from dried material, less than 25%. It was found that the amount of extracted polysaccharides and their molecular weights decreased upon storage of dried alga for three years. Polysaccharides isolated from freshly collected and dried alga had identical structures and were a mixture of κ/β- and a new X-type of carrageenan. It was shown that protein, the amount of which reached 24% in the extracts obtained at 20°C, was strongly bound to the carrageenan. The amino-acid compositions of the proteins associated with the polysaccharides isolated at 20 and 80°C were identical and had an elevated content of serine, glutamic acid, glycine, and alanine.     

Conformation of poly(methacrylic acid) in alcohol–water mixtures. III. Dependence on molecular weight

Poly(methacrylic acid) has been studied in 0.002N HCl–ethanol mixtures as a function of molecular weight. A different dependence on molecular weight is noted at different alcohol concentrations. Since the intrinsic viscosity passes through a series of extrema with changes in alcohol concentration, the dependence on molecular weight has been considered in two regions of alcohol concentration in particular. The region of the first minimum and the region of the second minimum (or overall maximum). In the region of the first minimum, intrinsic viscosity is proportional to M^½, just as in 0.002N HCl. The Huggins coefficient k′ is large (ca. 60) but drops to about 10 when the molecular weight exceeds 320,000. In the region of the second minimum the dependence on molecular weight is complex. Intrinsic viscosity is proportional to molecular weight both at low and at high molecular weight and thus indicates freely draining structures. There is a conformational contraction, however, at molecular weight about 320,000 leading from one type of structure to the other. The structure at higher molecular weight may involve a specially strong bond between specifically grouped segments in the chain. The positions of the extrema along the alcohol concentration axis are not molecular weight dependent, particularly above 320,000. Results available for molecular weight dependence in methanol agree well with this picture. The present results confirm prediction inherent in the model of Silberberg and Priel and Silberberg.     

Rheologically interesting polysaccharides from yeasts

We have examined the relationships between primary, secondary, and tertiary structures of polysaccharides exhibiting the rheological property of friction (drag) reduction in turbulent flows. We found an example of an exopolysaccharide from the yeastCryptococcus laurentii that possessed high molecular weight but exhibited lower than expected drag reducing activity. Earlier correlations by Hoyt (8,10) showing that β1 → 3, β→4, and αl → 3 linkages in polysaccharides favored drag reduction were expanded to include correlations to secondary structure. The effect of sidechains in a series of gellan gums was shown to be related to sidechain length and position. Disruption of secondary structure in drag reducing polysaccharides reduced drag reducing activity for some but not all exopolysaccharides. The polymer fromC. laurentii was shown to be more stable than xanthan gum and other exopolysaccharides under the most vigorous of denaturing conditions. We also showed a direct relationship between extensional viscosity measurements and the drag reducing coefficient for four exopolysaccharides.

     

Supported molecular catalysts for the heterogeneous CO2 electroreduction

The thorough understanding of homogeneous catalysis has triggered intense research activities on the immobilization of molecular catalysts for the heterogeneous CO₂ electroreduction. Herein, we discuss recent advances in the heterogeneous field with focus on the intrinsic effect coming from the catalyst structure and the extrinsic effect exerted by the catalyst immobilization strategy and support material on the catalytic performance.     

甘草多糖螺旋结构的原子力显微镜研究

用原子力显微镜(AFM)对甘草多糖的微观结构进行观察, 实验结果表明, 甘草多糖主要由葡萄糖、阿拉伯糖和半乳糖组成. 甘草多糖分子的稀溶液铺展在Ni^2＋处理的云母片上, 经干燥, 乙醇固定后, 获得稳定、重复的图像. 甘草多糖分子具有高度分枝的结构, 并且糖链间形成环状、柱状或近似于螺旋状的结构. 甘草多糖链呈多股紧密的螺旋结构, 这种现象可能与该多糖中分子间的Van der Waals相互作用以及糖链间氢键缔合有关.