木犀草素对金黄色葡萄球菌的抑菌活性及其机制

【目的】研究木犀草素对金黄色葡萄球菌的抑制活性及其机制。【方法】利用2,3,5-氯化三苯基四氮唑(TTC)染色,细胞膜渗透性测定,SDS-PAGE蛋白谱变化,4′,6-二脒基-2-苯基吲哚(DAPI)荧光染色法等对木犀草素的抑菌活性及其机制进行研究。【结果】木犀草素能影响金黄色葡萄球菌细胞膜的通透性,木犀草素作用16h,菌体可溶性蛋白总量减少64.54%,DNA含量减少48.44%,RNA含量减少39.35%,木犀草素的浓度为1.6mg/mL时,拓扑异构酶I和II的活性可完全被抑制。【结论】木犀草素有明显的抑菌活性,其抑菌机制主要是通过抑制DNA拓扑异构酶的活性,进而影响菌体核酸及蛋白质的合成来实现的。     

拓扑异构酶Ⅱ的结构、功能及作用机制研究进展

拓扑异构酶是存在于细胞核内的一类酶,它们能够催化DNA链的断裂和结合,从而调控DNA的拓扑状态,在基因复制、转录、重组、修复和染色体重塑过程中参与了DNA超螺旋结构模板的调节。拓扑异构酶通过催化切断DNA链的磷酸二酯键,产生DNA缺口而发挥作用,这种缺口可以改变DNA分子的拓扑结构,从而解决DNA缠结状态这一问题。在哺乳动物中,主要存在I型和II型两种拓扑异构酶。拓扑异构酶I(type I topoisomerase,Top1)催化产生DNA分子上的单链缺口,而拓扑异构酶II(type II topoisomerase,Top2)则催化产生DNA分子上的双链缺口。Top2在哺乳动物中又分为α亚型和β亚型。其中,Top2α的功能主要与细胞的增殖和多潜能性相关,而Top2β在神经发育中具有重要作用。本文就Top2的结构、功能和作用机制的相关研究进展作一综述。     

拓扑异构酶Ⅱ的结构、功能及作用机制研究进展北大核心CSCD

拓扑异构酶是存在于细胞核内的一类酶,它们能够催化DNA链的断裂和结合,从而调控DNA的拓扑状态,在基因复制、转录、重组、修复和染色体重塑过程中参与了DNA超螺旋结构模板的调节。拓扑异构酶通过催化切断DNA链的磷酸二酯键,产生DNA缺口而发挥作用,这种缺口可以改变DNA分子的拓扑结构,从而解决DNA缠结状态这一问题。在哺乳动物中,主要存在I型和II型两种拓扑异构酶。拓扑异构酶I(type I topoisomerase,Top1)催化产生DNA分子上的单链缺口,而拓扑异构酶II(type II topoisomerase,Top2)则催化产生DNA分子上的双链缺口。Top2在哺乳动物中又分为α亚型和β亚型。其中,Top2α的功能主要与细胞的增殖和多潜能性相关,而Top2β在神经发育中具有重要作用。本文就Top2的结构、功能和作用机制的相关研究进展作一综述。     

两株高DNA拓扑异构酶Ⅰ抑制活性的药用植物内生真菌筛选

从7种中国南方药用植物中分离了278株内生真菌,分析了其发酵液甲醇提取物对人DNA拓扑异构酶Ⅰ(hTo-poI)松驰活性的抑制能力。对2株具有高hTopoI抑制力的内生真菌(LF4-7L和LF6-1)进行了深入研究。通过发酵物对hTo-poI抑制能力的时间变化曲线,表明2株内生真菌的hTopoI抑制物质在其生长停滞阶段才大量产生和积累。经分子鉴定,LF4-7L可能是阴炭团菌(Hypoxylon stygium),而与LF6-1L最相近的是毛竹基腐病菌(Arthrinium phaeospermum)。     

耻垢分枝杆菌宿主整合因子(IHF)对DNA拓扑结构的影响

结核分枝杆菌(Mycobaterium tuberculosis)是结核病的病原菌,每年导致数百万人死亡.对于分枝杆菌基本生物学特性的研究有助于新的药物及治疗手段的研发.耻垢分枝杆菌(M.smegmatis)是分枝杆菌属中的一种非致病菌,与结核分枝杆菌亲缘关系较近,是实验室常用的研究分枝杆菌的模式菌种.分枝杆菌主要编码三种染色质蛋白,类组蛋白HU、Lsr2和宿主整合因子IHF.为研究IHF在染色体包装中的作用,我们在大肠杆菌中表达、纯化了耻垢分枝杆菌IHF蛋白(MsIHF),并对其影响DNA拓扑结构的性质进行了系统分析.体外研究的结果表明,MsIHF以同二聚体的形式存在,其对负超螺旋DNA具有一定的结合偏好性,同时,该蛋白可以有效地固定DNA负超螺旋.进一步的研究表明,MsIHF可以调控拓扑异构酶的活性.MsIHF的结合明显地抑制拓扑异构酶Ⅰ的松弛活性,而与此相反,该蛋白可以轻微地促进旋转酶引入DNA负超螺旋的能力.以上结果提示,MsIHF可能通过调控拓扑异构酶的活性影响染色体DNA的结构,进而调控其包装.     

苦楝化学成分及抗糖尿病活性研究

为研究苦楝皮的化学成分及其抗糖尿病活性,采用正相、反相及Sephadex LH-20凝胶柱色谱等方法分离纯化化合物,通过波谱数据和理化性质分别鉴定为12β,20(S)-dihydroxydammar-24-en-3-one(1),dammarendiol II 3-O-caffeate(2),24-methylenecycloartenone(3),meliavolin(4),3,20-diacetyl-11-methoxy-1-tigloylmeliacarpinin(5),methyl 3-formyl-2,4-dihydroxy-6-methyl benzoate(6),usnic acid(7),epi-catechin(8)。其中化合物1~3,6,7均为首次从该植物中分离得到。采用酶偶联、液闪接近测定等技术测试化合物2~5体外抗糖尿病活性。研究结果表明,受试化合物2~5均未表现出GK、SIRT1体外激动活性和DPPIV抑制活性,但化合物2对人11β-HSD1具有显著的抑制作用(IC50=94.15 nmol/L)。     

蛋白质磷酸化和脱磷酸化对DNA拓扑异构酶Ⅰ活力调节的研究

本文以小鼠正常肝和H_(22a)腹水型肝癌细胞为材料,从中分离出纯度较高的拓扑异构酶Ⅰ和细胞质酪氨酸蛋白激酶(TPK)来研究磷酸化和脱磷酸化对拓扑异构酶Ⅰ活力的调节。结果表明TPK能活化拓扑异构酶Ⅰ。另外还发现PKA和碱性磷酸酶(CIP)能分别活化和抑制拓扑异构酶Ⅰ。     

芫花花蕾中一个新的瑞香烷二萜类化合物CSCD

为了研究中药芫花(Daphne genkwa)的干燥花蕾化学成分及其抑制皮肤病原真菌活性,采用正相硅胶及半制备HPLC等多种色谱技术对芫花花蕾95%乙醇提取物进行分离纯化得到2个瑞香烷型二萜类化合物,并通过MS、NMR和ECD等波谱技术和文献数据比对鉴定化合物结构,分别为daphgenin A(1)和yuanhuakine B(2),其中化合物1为新的瑞香烷型二萜类化合物。同时,结合MIC法测定该化合物对皮肤真菌犬小孢子菌、红色毛癣菌、须癣毛癣菌和马拉色菌的抑制活性,结果表明化合物1和2对皮肤病原真菌有一定的抑制活性,化合物1对红色毛癣菌和须癣毛癣菌的抑制活性与阳性对照组相当(MIC值4.0μg/mL),化合物2对红色毛癣菌显示显著的抑制活性,其MIC值为2.0μg/mL。     

木麻黄凋落物化学成分及其生物活性的研究

利用多种柱色谱和高效液相色谱相结合的方法从木麻黄(Casuarina equisetifolia)凋落物的乙酸乙酯提取物中分离得到7个单体化合物,通过波谱分析结合理化性质鉴定化合物结构分别为:3β-(p-hydroxy-trans-cinnamoyloxy)olean-12-en-28-oicacid(1),3-O-(E)-coumaroylerythrodiol(2),casuarmondtol(3),alnusdiol(4),山柰酚-3-O-α-L-鼠李糖苷(5),4″-反-香豆酰基-山柰酚-3-O-α-L-鼠李糖苷(6),山柰酚(7),其中化合物3、4、6和7为首次从该植物中分离得到。分别采用MTT法、Ellman法和PNPG法对单体化合物的体外细胞毒活性、乙酰胆碱酯酶抑制活性和α-糖苷酶抑制活性进行测试,测试结果表明,化合物1和6具有细胞毒活性,化合物1~4和6具有乙酰胆碱酯酶抑制活性,化合物1和3~5具有α-糖苷酶抑制活性。     

新型喜树碱类抗癌药物的研究进展

喜树碱是1966年由喜树中分离而来的一种五环结构的生物碱,早期对其抗肿瘤活性的发现更是引发了科学家们对此类化合物极大的研究兴趣,现在已经证实喜树碱类化合物主要是通过抑制在DNA代谢过程中发挥重要作用的I型拓扑异构酶。但其自身因水溶性差、毒副作用强,在临床应用上易出现不良反应。半个世纪以来,国内外研究者在对其作用机制及构效关系的研究基础上,开发出了数以百计的喜树碱类衍生物,很多已经进入临床或临床前研究。但目前仅有两种喜树碱类的化合物拓扑替康和依立替康被美国FDA批准应用于临床上肿瘤的治疗。本文就已上市的喜树碱类化合物以及喜树碱类抗肿瘤药物开发的挑战进行了综述。     

On the origin of the Hirudinea and the demise of the Oligochaeta

The phylogenetic relationships of the Clitellata were investigated with a data set of published and new complete 18S rRNA gene sequences of 51 species representing 41 families. Sequences were aligned on the basis of a secondary structure model and analysed with maximum parsimony and maximum likelihood. In contrast to the latter method, parsimony did not recover the monophyly of Clitellata. However, a close scrutiny of the data suggested a spurious attraction between some polychaetes and clitellates. As a rule, molecular trees are closely aligned with morphology-based phylogenies. Acanthobdellida and Euhirudinea were reconciled in their traditional Hirudinea clade and were included in the Oligochaeta with the Branchiobdellida via the Lumbriculidae as a possible link between the two assemblages. While the 18S gene yielded a meaningful historical signal for determining relationships within clitellates, the exact position of Hirudinea and Branchiobdellida within oligochaetes remained unresolved. The lack of phylogenetic signal is interpreted as evidence for a rapid radiation of these taxa. The placement of Clitellata within the Polychaeta remained unresolved. The biological reality of polytomies within annelids is suggested and supports the hypothesis of an extremely ancient radiation of polychaetes and emergence of clitellates.     

On the ontogeny of the haptor and the evolution of the Monogenea

Data on the ontogeny of the posterior haptor of monogeneans were obtained from more than 150 publications and summarised. These data were plotted into diagrams showing evolutionary capacity levels based on the theory of a progressive evolution of marginal hooks, anchors and other attachment components of the posterior haptor in the Monogenea (Malmberg, 1986). 5 + 5 unhinged marginal hooks are assumed to be the most primitive monogenean haptoral condition. Thus the diagrams were founded on a 5 + 5 unhinged marginal hook evolutionary capacity level, and the evolutionary capacity levels of anchors and other haptoral attachement components were arranged according to haptoral ontogenetical sequences. In the final plotting diagram data on hosts, type of spermatozoa, oncomiracidial ciliation, sensilla pattern and protonephridial systems were also included. In this way a number of correlations were revealed. Thus, for example, the number of 5 + 5 marginal hooks correlates with the most primitive monogenean type of spermatozoon and with few sensillae, many ciliated cells and a simple protonephridial system in the oncomiracidium. On the basis of the reviewed data it is concluded that the ancient monogeneans with 5 + 5 unhinged marginal hooks were divided into two main lines, one retaining unhinged marginal hooks and the other evolving hinged marginal hooks. Both main lines have recent representatives at different marginal hook evolutionary capacity levels, i.e. monogeneans retaining a haptor with only marginal hooks. For the main line with hinged marginal hooks the name Articulon-choinea n. subclass is proposed. Members with 8 + 8 hinged marginal hooks only are here called Proanchorea n. superord. Monogeneans with unhinged marginal hooks only are here called Ananchorea n. superord. and three new families are erected for its recent members: Anonchohapteridae n. fam., Acolpentronidae n. fam. and Anacanthoridae n. fam. (with 7 + 7, 8 + 8 and 9 + 9 unhinged marginal hooks, respectively). Except for the families of Articulonchoinea (e.g. Acanthocotylidae, Gyrodactylidae, Tetraonchoididae) Bychowsky's (1957) division of the Monogenea into the Oligonchoinea and Polyonchoinea fits the proposed scheme, i.e. monogeneans with unhinged marginal hooks form one old group, the Oligonchoinea, which have 5 + 5 unhinged marginal hooks, and the other group form the Polyonchoinea, which (with the exception of the Hexabothriidae) has a greater number (7 + 7, 8 + 8 or 9 + 9) of unhinged marginal hooks. It is proposed that both these names, Oligonchoinea (sensu mihi) and Polyonchoinea (sensu mihi), will be retained on one side and Articulonchoinea placed on the other side, which reflects the early monogenean evolution. Except for the members of Ananchorea [Polyonchoinea], all members of the Oligonchoinea and Polyonchoinea have anchors, which imply that they are further evolved, i.e. have passed the 5 + 5 marginal hook evolutionary capacity level (Malmberg, 1986). There are two main types of anchors in the Monogenea: haptoral anchors, with anlages appearing in the haptor, and peduncular anchors, with anlages in the peduncle. There are two types of haptoral anchors: peripheral haptoral anchors, ontogenetically the oldest, and central haptoral anchors. Peduncular anchors, in turn, are ontogenetically younger than peripheral haptoral anchors. There may be two pairs of peduncular anchors: medial peduncular anchors, ontogentically the oldest, and lateral peduncular anchors. Only peduncular (not haptoral) anchors have anchor bars. Monogeneans with haptoral anchors are here called Mediohaptanchorea n. superord. and Laterohaptanchorea n. superord. or haptanchoreans. All oligonchoineans and the oldest polyonchoineans are haptanchoreans. Certain members of Calceostomatidae [Polyonchoinea] are the only monogeneans with both (peripheral) haptoral and peduncular anchors (one pair). These monogeneans are here called Mixanchorea n. superord. Polyonchoineans with peduncular anchors and unhinged marginal hooks are here called the Pedunculanchorea n. superord. The most primitive pedunculanchoreans have only one pair of peduncular anchors with an anchor bar, while the most advanced have both medial and lateral peduncular anchors; each pair having an anchor bar. Certain families of the Articulonchoinea, the Anchorea n. superord., also have peduncular anchors (parallel evolution): only one family, the Sundanonchidae n. fam., has both medial and lateral peduncular anchors, each anchor pair with an anchor bar. Evolutionary lines from different monogenean evolutionary capacity levels are discussed and a new system of classification for the Monogenea is proposed.In agreeing to publish this article, I recognise that its contents are controversial and contrary to generally accepted views on monogenean systematics and evolution. I have anticipated a reaction to the article by inviting senior workers in the field to comment upon it: their views will be reported in a future issue of this journal. EditorIn agreeing to publish this article, I recognise that its contents are controversial and contrary to generally accepted views on monogenean systematics and evolution. I have anticipated a reaction to the article by inviting senior workers in the field to comment upon it: their views will be reported in a future issue of this journal. Editor