灵芝孢子粉水溶性多糖的分离、纯化及结构研究

灵芝孢子粉的热水提取液经醇析,脱脂,去单寡糖后由SepharoseCL 6B柱层析纯化,所得多糖SGL Ⅱ2经高效液相方法鉴定纯度为单一级分,相对分子质量为5 .37×10 4。再经部分酸水解、高碘酸氧化、Smith降解、甲基化分析及IR、GC、GC MS和13 CNMR等方法确定其结构。结果表明多糖SGL Ⅱ 2由葡萄糖和半乳糖组成,为少分支结构,由1→3连接和1→6连接的葡萄糖构成主链,部分1→6连接葡萄糖在3位或4位有分支,侧链为1→4连接的半乳糖,分支末端残基为葡萄糖。     

具有抗氧化活性的酸性菟丝子多糖H2的研究

从药用植物菟丝子 (CuscutachinensisLam .)的种子中经碱液提取所得的粗多糖CHC ,经进一步分离纯化得一酸性纯多糖H2 ,其分子量大于 1.0× 10 6,利用化学方法和光谱分析方法对其结构进行了研究。多糖H2由 1,6_linked_β_DGalp、1,4_linked_β_DGalp、1,4_linked_β_DGalA和 1,2or 4_linked_β_L_Rhap构成主链 ,并在部分1,6_linked_β_DGalp残基的O_3位和 1,2or 4_linked_β_L_Rhap残基的O_4或O_2形成分枝点 ,以末端半乳糖构成末端。侧链由末端半乳糖 ,1,6_linked_β_DGalp、1,4_linked_β_DGalp和 1,3,6_linked_β_DGalp残基构成 ,连接于主链的1,6_linked_β_DGalp残基的O_3位。阿拉伯糖残基 1,5_linkedAra、1,3,5_linkedAra、末端Ara以及末端鼠李糖残基存在于多糖分子H2的外周 ,连接于侧链和主链的 1,6_linked_β_DGalp残基的O_3位。此外 ,药理研究结果显示 ,H2能减少自由基引起的对大鼠成嗜铬细胞瘤PC12神经细胞系的损伤 ,明显提高细胞的存活率     

赤芝孢子粉中一个葡聚糖的分离纯化与结构鉴定

从破壁的赤芝 (Ganodermalucidum (Fr.)Karst)孢子粉中分离纯化到一个水溶性的、以 1,4连接的D_葡萄糖为主链、在 6位接 1,6连接葡萄糖的α_D 葡聚糖。高效分子排阻色谱测定 ,重均分子量为 9.3× 10 3 ,[α]2 1D = 174.2° (c 0 .87,H2 O)。通过糖组成分析 ,甲基化反应 ,乙酰解及一维和二维核磁等光谱解析 ,确定其结构如下 :　　　　　　　　　　　　　　　　α_D_Glcp_(1→ 6 )_α_D_Glcp_(1→ 6 )_α_D_Glcp　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　 1　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　↓　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　 6　　　　　　　〔→ 4)_α_D_Glcp_(1→ 4)_α_D_Glcp_(1→ 4)_α_D_Glcp_(1→ 4)_α_D_Glcp_(1→ 4_)_α_D_Glcp_(1→〕n     

猴头菌水溶性多糖的分离纯化与结构表征

从猴头菌子实体中分离得到一种新型的水溶性杂多糖HEPF2,分子量大小为1.66′104Da,该多糖由岩藻糖、半乳糖和葡萄糖以1.00:3.69:5.42比例构成,同时也含有微量的3-O-甲基鼠李糖。进一步利用傅立叶变换红外光谱法、糖组成分析、甲基化分析、部分酸水解法和核磁共振法等方法进行结构鉴定,检测结果表明,该杂多糖中包含1→4、1→6结合的葡萄糖和1→6结合的半乳糖残基,连接于主链的侧链残基,包括岩藻糖残基、少数的端基葡萄糖和半乳糖残基。核磁共振法检测结果还表明,1→4结合葡萄糖为β构型,(1→6)结合半乳糖、(1→2,6)结合半乳糖和端基葡萄糖均为α构型。     

两种灵芝孢子粉多糖的分离纯化和结构

本文采用水提醇沉法从灵芝孢子粉中提取其粗多糖,经Sepharose CL-6B凝胶柱层析分离得两种主要成分LBPI和LBPII,经高效液相色谱鉴定,均为高均一性成分,分子量分别为9.17×10 ⁴和1.86×10 ⁴;经酸水解、乙酰化和气相色谱分析,确定LBPI的单糖组成为甘露糖、半乳糖和葡萄糖,LBPII的单糖组成为鼠李糖、甘露糖、半乳糖和葡萄糖;通过高碘酸氧化、甲基化和GC-MS进行结构分析,确定LBPI中葡萄糖残基连接方式为1→、1→4,6和1→3,6连接,半乳糖残基为1→6连接,甘露糖残基为1→3,6连接,LBPII中鼠李糖残基连接方式为1→连接,葡萄糖残基为1→、1→4、1→6、1→4,6和1→3,6连接,半乳糖残基为1→6连接,甘露糖残基为1→2,3,6连接。综上,两种多糖LBPI和LBPII均为多分支的中型杂多糖,但两者的单糖组成和连接方式存在差异,这两种多糖成分均为首次报道,可望为灵芝孢子粉的成分、活性研究和资源开发提供理论依据。     

胚乳中淀粉的合成

禾本科植物胚乳内所含有的淀粉根据其结构、组成可以分为两类：直链淀粉（由α-1,4糖苷键连接的多聚D-葡萄糖）和支链淀粉（在以α-1,4糖苷键连接的主链上通过形成α-1,6糖苷键引入支链的多聚D-葡萄糖）。前者是以一种线性无序状态存在,而支链淀粉则是构成淀粉半晶体结构的主要成分。其中,除了负责合成作为糖基直接供体的ADP—Glc的酶AGPase外,直链淀粉中链的延伸反应由GBSSI完成,而支链淀粉的合成则相对复杂,需要SS、SBE、DBE、SP等一些酶的协同调控来共同完成。本文综述了胚乳中淀粉合成过程中所涉及的一些关键酶的研究进展,并对此研究领域进行了展望。     

两个赤芝子实体多糖的理化特性分析及结构鉴定

赤芝子实体多糖P32A分子量为506,322,P32B分子量为287,389,两种多糖均以己糖为主构成。P32A由鼠李糖、木糖、甘露糖和葡萄糖组成,四种单糖的摩尔比为：4．3：2．6：6．3：11．4;P32B亦由鼠李糖、木糖、甘露糖和葡萄糖组成,摩尔比为：1．2：1．0：2．1：9．2。该结果显示,P32A与P32B具有较类似的糖组成,且都以葡萄糖和甘露糖为主要单糖组分。根据^13C NMR和甲基化的结果分析知P32A可能含有l→4连接的葡萄糖构成的主链,非还原末端均由葡萄糖构成,此外P32A中还有l,4-连接的甘露糖和l,3—连接的鼠李糖。P32B可能以l→3连接形成主链,部分l,3-连接葡萄糖的6位有分支,该多糖也含有由葡萄糖构成的非还原末端,与P32A类似,P32B中还含有l,4-连接的甘露糖,不同的是不含l,3—连接的鼠李糖。     

放射形土壤杆菌生物变型Is－123l产丁二酸型多糖的研究

从北京地区土样中分离到一株革兰氏阴性、无芽胞、稀周毛及运动的菌株S－1231。它能以糖类为底物产丁二酸型胞外多糖,不能利用淀粉和纤维素。该菌发酵葡萄糖产酸,生长12－24小时．细胞杆状O．7一O．8×1．3—1．5μm,圆端,单个或成对。在营养洋菜平板上菌落圆形、低凸、表面光滑、润泽、边缘整齐。该菌产生3－酮基乳糖,接种向日葵不致瘤,DNA中G十c含量62．8 －63.4免分子％。该菌氧化酶阳性,接触酶阳性,产生H2s,35℃生长,2％NaCl生长,及石蕊牛奶产碱,该菌定为放射形土壤杆菌生物变型Ⅰ。组分分析表明．该菌株产生的胞外多糖(简称Agran－s)由D－葡萄糖(69．1％),D－半乳糖(8.6％),丙酮酸(9．5％)和丁二酸(10．8%)组成。甲基化分析表明,多糖Agran－s含有下列主要结构单位(均为β－糖苷键)：(1→3)一连接的D－葡萄糖(21 2％);(1→3)－连接的D－半乳糖(11．4％);(1－6)－连接的D葡萄糖(10．5％);(1→4)－连接的D－葡萄耱(30．4％)。(1→4,1→6)连接的D－葡萄糖(22．2％)和末端D－葡萄糖(4．3％)。     

根瘤菌TISTR 386胞外酸性多糖的结构研究

根瘤菌TISTR 386胞外酸性多糖有二种九糖的重复单位构成。重复单位主要成份是D一葡萄糖,D一半乳糖和D一葡萄糖醛酸,它们的克分子比例分别是6：l：2和5：2：2。另外还含有一些丙酮酸和醋酸。甲基化分析表明,这个多糖由一个(1→3)键,一个(1→6)键,三个(1→4)键,一个(1→4,1→6)键连结的葡萄糖残基,一个(1→3)键连结的D-半乳糖残基,以及一个(1→3)键,一个(1→4)键连结的D-葡萄糖醛酸残基所组成。非还原末端糖残基是D葡萄糖或是带有丙酮酸的D一半乳糖,这也是二种九糖重复单位区别所在。     

紫芝细胞壁大分子量葡聚糖的纯化及结构鉴定

采用超微粉碎、热水浸提法从紫芝子实体水提残渣中获得细胞壁粗多糖,通过30%乙醇沉淀、20%醇洗的方法纯化出大分子量均一多糖GSCW30E-20E。苯酚硫酸法检测其多糖含量为98.03%,单糖组成分析显示其仅由葡萄糖组成,高效凝胶尺寸排阻色谱-多角度激光散射仪-示差折光检测技术测定其重均分子量为1.552×10 ⁶g/mol。通过红外光谱、甲基化及核磁共振分析对其结构进行解析,结果表明,GSCW30E-20E是一种β-D-葡聚糖,该多糖主链由β-(1,3)-糖苷键连接而成,每3个糖残基主链上通过β-(1,6)-糖苷键连有一个葡萄糖残基为支链。     

A Unique Protease Cleavage Site Predicted in the Spike Protein of the Novel Pneumonia Coronavirus (2019-nCoV) Potentially Related to Viral Transmissibility

正Dear Editor,In December 2019, a novel human coronavirus caused an epidemic of severe pneumonia(Coronavirus Disease 2019,COVID-19) in Wuhan, Hubei, China(Wu et al. 2020; Zhu et al. 2020). So far, this virus has spread to all areas of China and even to other countries. The epidemic has caused 67,102 confirmed infections with 1526 fatal cases     

Curcuminoids as inhibitors of thioredoxin reductase: A receptor based pharmacophore study with distance mapping of the active site

Curcumin is the yellow pigment of turmeric that interacts irreversibly forming an adduct with thioredoxin reductase (TrxR), an enzyme responsible for redox control of cell and defence against oxidative stress. Docking at both the active sites of TrxR was performed to compare the potency of three naturally occurring curcuminoids, namely curcumin, demethoxy curcumin and bis-demethoxy curcumin. Results show that active sites of TrxR occur at the junction of E and F chains. Volume and area of both cavities is predicted. It has been concluded by distance mapping of the most active conformations that Se atom of catalytic residue SeCYS498, is at a distance of 3.56 from C13 of demethoxy curcumin at the E chain active site, whereas C13 carbon atom forms adduct with Se atom of SeCys 498. We report that at least one methoxy group in curcuminoids is necessary for interation with catalytic residues of thioredoxin. Pharmacophore of both active sites of the TrxR receptor for curcumin and demethoxy curcumin molecules has been drawn and proposed for design and synthesis of most probable potent antiproliferative synthetic drugs.     

Comparative morphology of the carpel in the Liliaceae: Hewardieae, Petrosavieae, and Tricyrteae

The young pistils in the melanthioid tribes, Hewardieae, Petrosavieae and Tricyrteae, are uniformly tricarpellate and syncarpous. They lack raphide idioblasts. All are multiovulate, with bitegmic ovules. The Petrosavieae are marked by the presence of septal glands and incomplete syncarpy. Tepals and stamens adhere to the ovary in the Hewardieae and the Petrosavieae but not in the Tricyrteae. Two vascular bundles occur in the stamens of the Hewartlieae and Tricyrtis latifolia. Ventral bundles in the upper part of the ovary of the Hewardieae are continuous with compound septal bundles and placental bundles in the lower part. Putative ventral bundles occur in the alternate position in the Tricyrteae and putative placental bundles in the opposite. position in the Petrosavieae. The dichtomously branched stigma in each carpel of the Tricyrteae is supplied by a bifurcated dorsal bundle.     

Selection with two alleles and complete dominance

For a plant selection model with frequency-independent viabilities, fertilities and selfing rates, it is shown that apart from global fixation, for certain parameter combinations a protected polymorphism and facultative fixation (either allele may become fixed according to initial frequencies) may both occur. Facultative fixation requires different selling rates for the dominant and recessive type. Protection of the polymorphism requires resource allocation for male and female function. In this connection the problem of purely genetically caused population extinction is discussed.
For general frequency dependence and regular segregation, the chances for establishment of a completely recessive gene are compared to those of a completely dominant gene. It is proven that the process of establishment of the recessive gene, despite a fitness advantage, may be considerably endangered by drift effects if random mating prevails. The recessive gene may reach the same effectivity in establishment as a dominant gene, only if the recessive homozygote mates exclusively with its own type during the period of establishment.     

Composition and diversity of bird communities in Swedish farmland–forest mosaic landscapes

CapsuleThe amount of forest (at local and landscape scales) and occurrence of residual habitats at the local scale are shown to be the major factors influencing bird community composition in farmland–forest landscapes in central Sweden.

Aims To investigate the importance of local habitat and landscape structure for breeding birds in farmland–forest landscapes in central Sweden.

Methods Breeding birds were censused at 292 points. A detailed habitat mapping was made within 300 m of the points. Within a 300–600 m radius only two major habitats (forests and arable fields) were identified.

Results Cluster analyses of bird communities identified three site types that also differed in habitat composition: (i) partially forested sites in forested landscapes; (ii) heterogeneous sites with residual habitats in mosaic landscapes; and (iii) field-dominated farmland sites in open landscapes. A total of 19 of 25 farmland bird species (restricted to farmland or using both farmland and forest) had the highest abundance in farmland sites with mosaics of forest and farmland, while only six farmland species had the highest abundance in field-dominated sites. The bird community changed from being dominated by farmland species to being dominated by forest species (common in forest landscapes without farmland) at small proportions (10–20%) of forest at the local scale. A major difference in habitat composition between heterogeneous and field-dominated sites was the occurrence of different residual habitats (e.g. shrubby areas and seminatural grasslands). These habitats seemed to influence bird community composition more than land-use, despite covering <10% of the area. Seminatural grasslands were important for bird community composition and species-richness, but grazing seemed to be less important. Among different land-use types, cereal crops were the least preferred fields. Set-asides with tall vegetation and short rotation coppices were positively associated with species-richness of farmland birds.

Conclusion In general, the composition of the landscape was important for bird community composition, although amount and distribution of forests, occurrence of residual habitats and land-use of fields at the local scale had the strongest influence on bird community composition. The possible implications of these patterns for managing farmland–forest landscapes are discussed.     

Chemical constituents from the fruits of Rhus typhina L. and their chemotaxonomic significance

This work describes the isolation and characterization of twenty-nine compounds from the fruits of Rhus typhina L., including eleven flavonoids (1–11), eleven phenols (12–22), two pentacyclic triterpenes (23–24), two organic acids (25–26), one lumichrome (27), one courmarin (28) and one pyrimidine (29) on the basis of their spectroscopic data. Compounds apigenin (1), daidzein (4), orobol (5), 3′, 5, 5′, 7-tetrahydroxyflavanone (6), naringenin (7), butein (8), (-)-catechin (9), quercetin-3-O-α-L-(3″-O-galloyl)-rhamnoside (11), 2-hydroxybenzoic acid (13), 4-hydroxybenzaldehyde (14), vanillin (15), methyl 3,4-dihydroxybenzoate (16), 3,5-dihydroxybenzamide (18), tyrosol (19), caffeic acid (20), 3-(2,4,6-trihydroxyphenyl)-1-(4-hydroxyphenyl)-propan-1-one (21), phlorizin (22), friedelin (23), oleanolic acid (24), 4,4-dimethyl-heptanedioic acid (25), anthranilic acid (26), lumichrome (27), scoparone (28) and uracil (29) have not been recorded before in this plant. This is the first report on the occurrence of compounds 4–7, 9, 11, 13–14, 16, 18–21, 25–29 from the genus Rhus. Moreover, the chemotaxonomic significance of these isolated compounds was also summarized.