小球藻吸附水中Pb2+影响因素的初步研究

对小球藻生物吸附水中Pb2 + 的影响因素作了初步研究。实验表明 :在小球藻处于指数生长期和静止期时加入Pb2 + ,去除率达 6 0 %以上 ;当藻细胞密度一定时 ,随着Pb2 + 浓度的增加 ,Pb2 + 的去除率增大 ;当Pb2 + 浓度一定时 ,随着藻细胞密度的增加 ,小球藻对Pb2 + 的去除率增大 ,藻细胞密度为 1 2 9× 10 8个 /ml时 ,去除率可达 92 82 % ;加强光照可以促进小球藻对Pb2 + 的吸附 ;在pH值为 5～ 10的范围内 ,pH对Pb2 + 吸附影响不大 ,较佳的pH值在 7左右。实验最佳条件的去除率在 90 %以上 ,去除效果较好。     

新月藻生物吸附Pb2+影响因素的研究

对新月藻生物吸附Pb^2 的影响因素作了初步研究,实验表明,在新月藻的指数生长期和静止期加入Pb^2 时,Pb^2 的去除率较高;当藻细胞密度一定时,随着Pb^2 浓度的增加,其去除率增大,当Pb^2 浓度一定时,随着藻细胞密度的增加,新月藻对Pb^2 的去除率增大;pH对Pb^2 吸附影响不大,在pH5-9的范围内,Pb^2 去除率在60%以上。     

小球藻对镉离子的吸附速率方程

研究了小球藻对Cd^2 的吸附动力学。研究表明,小球藻对Cd^2 有一定的吸附作用,在吸附的起始阶段,吸附速率较快,且随温度的升高吸附速率增大,吸附过程在20min内达到平衡。结果还表明,该吸附是简单的一级反应,并由此建立了吸附反应的速率方程,推算出吸附反应的活化能Ea=31．42kl／mol。     

固定化海洋微藻对污水中Ni2+的吸附

采用海藻酸钠包埋小球藻和叉鞭金藻,制得含藻细胞的固定化胶球,用其对Ni^2 进行生物吸附,研究了固定化小球藻和固定化叉鞭金藻对污水中Ni^2 的吸附率。结果表明：对于同一种固定化微藻,处于对数生长中期时对Ni^2 吸附效果较好,且吸附过程主要在前4h完成;Ni^2 浓度越大,吸附率越高;固定化微藻比悬浮态微藻吸附率高;在相同的实验条件下,固定化小球藻比固定化叉鞭金藻吸附率高。     

粘盖牛肝菌不同菌株对Zn2+、Cd2+的吸附及其对油松Zn2+、Cd2+的耐受性

为了探讨同一菌根真菌不同菌株对重金属的耐受性,选用采集于内蒙古阴山山脉不同地区的粘盖牛肝菌(Suillus bovinus)的不同菌株进行研究。首先,在不同浓度Zn^2 、Cd^2 液体培养基中培养菌丝体,以了解各菌株菌丝体对重金属的耐受性及吸附能力,采用烘干法和原予吸收法分别测定菌丝体的生物量和菌丝体、培养液中Zn^2 、Cd^2 含量,结果表明：劈柴沟粘盖牛肝菌在Zn^2 、Cd^2 胁迫条件下,生物量、吸附能力约为其余各菌株的1．5～2倍。其次,为了探明油松(Pinus tabulaeformis)形成菌根后对Zn^2 、Cd^2 胁迫的耐受性及其耐受机理,采用一次性定量浇灌不同浓度Zn^2 、Cd^2 溶液的方法,测定了菌根化油松苗地上、地下生物量及Zn^2 、Cd^2 含量的分配,结果表明：菌根形成后能显著促进油松的生长及对Zn^2 、Cd^2 胁迫的耐受性,并且菌根能够帮助油松吸收基质中大量的Zn^2 、Cd^2 ,根中重金属的含量是茎叶中的2～3倍以上,非菌根苗在重金属浓度稍高(Zn^2 400mg／kg;Cd^2 40mg／kg)时就会死亡。经方差分析及多重比较证实,劈柴沟粘盖牛肝菌对Zn^2 、Cd^2 的耐受性及对油松的促生效果与其它各菌株存在显著的差异,这可能是它通过把吸收的Zn^2 、Cd^2 最大限度地输送到根中的同时,也输送到了茎叶中,使重金属在体内得到一定程度的稀释,使自身免受毒害。     

小球藻生物富集锌、镉机制的研究

藻类对许多重金属具有较强的生物富集能力,小球藻（Chlorella spp.)分别在不同系列Zn^2 ,Cd^2 浓度下培养8d间隔2d,测定小球藻的生物量及Zn和Cd的含量。结果表明,小球藻随水体中Zn^2 和Cd^2 的浓度不同,在重重金属水体中暴露时间不同,具有不同的富集速率和能力。     

高岭土对Fe~(2+)的吸附及其对高岭土中Fe~(3+)生物还原的影响研究

利用异化铁还原微生物可将高岭土中不溶性的Fe3+还原成可溶性的Fe2+,但是此过程中产生的Fe2+能够被高岭土以及异化铁还原微生物吸附,从而影响高岭土中铁的异化还原。本文研究了pH、高岭土量、Fe2+浓度、温度4个因素对高岭土吸附Fe2+的影响;并采用Logistic方程拟合,研究Fe2+及温度对高岭土中Fe3+的生物还原特征。结果表明:pH、高岭土量、浓度、温度4个因素均会影响高岭土吸附Fe2+,当Fe2+吸附在高岭土和微生物菌体表面时,微生物的活性下降,同时高岭土表面Fe3+的生物可利用性也降低,Fe3+生物还原的最大速率减小。     

石油焦基高比表面积活性炭对水中Pb2+离子吸附性能的研究

以石油焦基为原料,采用KOH活化法制取高比表面积活性炭。考察了高比表面积活性炭吸附水中Pb^2 时,pH值、Pb^2 浓度、吸附时间和活性炭用量等因素对Pb^2 吸附量和水中Pb^2 残余浓度的影响。实验结果表明：高比表面积活性炭在适宜条件下对Pb^2 具有较大的吸附量和良好的再生效果。为高比表面积活性炭在废水中的实际应用提供了理论依据。     

啤酒酵母生物吸附镉的研究

研究了啤酒酵母在游离与固定化条件下对重金属离子Cd^2 的生物吸附特性。灭活的啤酒酵母在适当条件下对Cd^2 有较强的吸附作用,它的吸附能力受到酵母浓度、Cd^2 浓度、pH值和固定化方法等的影响。结果显示：实验条件下,啤酒酵母的最高吸附率达93％,此时的吸附能力为46．5mg Cd^2 ／g干酵母。吸附后用1mol／L的HC1解吸,解吸率达84％。用海藻酸钙凝胶包埋法对啤酒酵母细胞进行固定化,固定化细胞对Cd^2 的吸附主要受到海藻酸钠浓度和Cal2浓度的影响,且凝胶本身对Cd^2 的吸附能力不能忽略。     

Hg^2＋和Cd^2＋胁迫对满江红生理和细胞超微结构的影响

研究了在梯度浓度Hg^2 和Cd^2 胁迫下,满江红（Azolla imbricata(Roxb.)Nakai)的叶绿素含量,叶绿素a/b比值,光合放氧速率,呼吸速率,抗氧化酶系（超氧化物歧化酶（SOD）,过氧化氢酶（CAT）,过氧化物酶（POD）和细胞超微结构受He^2 和Cd^2 的毒害影响。结果显示：随着胁迫程度的增大,叶绿素含量,叶绿素a/b比值,光合放氧速率明显下降,呼吸速率均在2mg/L浓度下达到峰值,尔后下降;SOD,CAT,POD的活性均出现不同程度的应激性升高（除POD在Cd^2 处理时下降）,尔后下降,电镜观察发现,随着污染物浓度的增加和胁迫时间的延长,叶绿体出现膨大,破损和解体;线粒体嵴突膨胀和线粒体变形及空泡化;核染色质凝集,核仁消失。核膜破裂,实验结果表明：Hg^2 和Cd^2 污染不仅损害植物的生理活性,而且也破坏细胞的超微结构,最终导致植物死亡,随着Hg^2 和Cd^2 为3.0-3.5mg/L。对满江红鱼腥藻（Anabaena azollae Strasburger)细胞的超微结构变化观察表明,满江红鱼腥藻对Hg^2 和Cd^2 的耐受性明显高于满江红。     

Inhibition of thymidylate synthase by 2′,2′-difluoro-2′-deoxycytidine (Gemcitabine) and its metabolite 2′,2′-difluoro-2′-deoxyuridine

2′,2′-Difluoro-2′-deoxycytidine (dFdC, gemcitabine) is a cytidine analogue active against several solid tumor types, such as ovarian, pancreatic and non-small cell lung cancer. The compound has a complex mechanism of action. Because of the structural similarity of one metabolite of dFdC, dFdUMP, with the natural substrate for thymidylate synthase (TS) dUMP, we investigated whether dFdC and its deamination product 2′,2′-difluoro-2′-deoxyuridine (dFdU) would inhibit TS. This study was performed using two solid tumor cell lines: the human ovarian carcinoma cell line A2780 and its dFdC-resistant variant AG6000. The specific TS inhibitor Raltitrexed (RTX) was included as a positive control. Using the in situ TS activity assay measuring the intracellular conversion of [5-³H]-2′-deoxyuridine or [5-³H]-2′-deoxycytidine to dTMP and tritiated water, it was observed that dFdC and dFdU inhibited TS. In A2780 cells after a 4 h exposure to 1 μM dFdC tritium release was inhibited by 50% but did not increase after 24 h, Inhibition was also observed following dFdU at 100 μM. No effect was observed in the dFdC-resistant cell line AG6000; in this cell line only RTX had an inhibitory effect on TS activity. In the A2780 cell line RTX inhibited TS in a time dependent manner. In addition, DNA specific compounds such as 2′-C-cyano-2′-deoxy-1-beta-D-arabino-pentafuranosylcytosine and aphidicoline were utilized to exclude DNA inhibition mediated down regulation of the thymidine kinase.Inhibition of the enzyme resulted in a relative increase of mis-incorporation of [5-³H]-2′-deoxyuridine into DNA. In an attempt to elucidate the mechanism of in situ TS inhibition the ternary complex formation and possible inhibition in cellular extracts of A2780 cells, before and after exposure to dFdC, were determined. With the applied methods no proof for formation of a stable complex was found. In simultaneously performed experiments with 5FU such a complex formation could be demonstrated. However, using purified TS it was demonstrated that dFdUMP and not dFdCMP competitively inhibited TS with a Ki of 130 μM, without ternary complex formation. In conclusion, in this paper we reveal a new target of dFdC: thymidylate synthase.     

A concise synthesis of 4-nitrophenyl 2-azido-2-deoxy- and 2-acetamido-2-deoxy-D-mannopyranosides

4-nitrophenyl 3,4,6-tri-O-acetyl-2-azido-2-deoxy-alpha- and beta-D-mannopyranosides were prepared from methyl 4,6-O-benzylidene-alpha-D-glucopyranoside and 1,3,4,6-tetra-O-acetyl-alpha-D-glucopyranose, respectively. Chemoselective reduction of both azides with hydrogen sulfide readily afforded 4-nitrophenyl 2-acetamido-4,6-di-O-acetyl-2-deoxy-alpha-D- and -beta-D-mannopyranosides in higher yields than reduction with triphenylphosphine or a polymer-supported triarylphosphine. Subsequent de-O-acetylation yielded 4-nitrophenyl 2-acetamido-2-deoxy-alpha-D-mannopyranoside and 4-nitrophenyl 2-acetamido-2-deoxy-beta-D-mannopyranoside in 20% and 44% overall yields, respectively.     

Ca2+位于H2O2上游参与H2S诱导的拟南芥气孔关闭过程

以拟南芥为材料,利用药理学实验,结合分光光度法和激光共聚焦显微技术,研究了Ca2+在硫化氢(H2S)诱导拟南芥气孔关闭过程中的作用及其与过氧化氢(H2O2)的关系。结果表明： H2S诱导气孔关闭, Ca2+螯合剂EGTA和质膜Ca2+通道阻断剂硝苯地平(Nif)能不同程度抑制H2S诱导的气孔关闭,而内质网钙泵阻断剂毒胡萝卜素(Thaps)对H2S的作用无显著影响。由此推测, Ca2+参与调节H2S诱导的拟南芥气孔关闭过程,且胞质中Ca2+来源于胞外Ca2+的内流。另外, H2S诱导拟南芥叶片NADPH氧化酶基因AtRBOHD和AtRBOHF以及细胞壁过氧化物酶基因AtPRX34表达增强,促进叶片和保卫细胞中H2O2积累, EGTA对此起抑制作用,而外源CaCl2处理上调AtRBOHD、AtRBOHF和AtPRX34的表达。表明Ca2+可能位于H2O2上游参与H2S诱导的拟南芥气孔关闭过程。     

Smurf2 is a TRAF2 binding protein that triggers TNF-R2 ubiquitination and TNF-R2-induced JNK activation

TRAF2 plays a central role in TNF-induced signalling to NF-κB and JNK/p38 MAPK. To better understand the molecular mechanisms that mediate this dual function of TRAF2, we performed a yeast two-hybrid screening for TRAF2 interacting proteins using the Sos recruitment system. This resulted in the identification of the E3 ubiquitin ligase Smurf2 as a TRAF2 binding protein. TRAF2 overexpression was shown to trigger Smurf2 ubiquitination and the formation of a TNF-R2/Smurf2 complex. Smurf2 on its turn promoted TNF-R2 ubiquitination and the relocalization of TNF-R2 as well as TRAF2 to a detergent-insoluble cell fraction. This was associated with enhanced TNF-R2-induced JNK activation, whereas TNF-R2-induced NF-κB activation remained unaffected. These results suggest an important role for Smurf2 binding to TRAF2 in determining specific signalling outputs of TNF-R2.     

Synthesis of [2S-2-H]- and [2R-2-H]hexadecanoic acids

[2S-2-²H]- and [2R-2-²H]hexadecanoic acids were synthesized in overall yields of 59–67%. Methyl(2R)-2-hydroxyhexadecanoate, from the acid produced by Hansenula sydowiorum, was converted to the p-toluenesulphonate, reduced to trideutero alcohol with lithium aluminium deuteride and oxidized to [2S-2-²H]hexadecanoic acid. Methyl (2S)-2-chlorohexadecanoate, which was a by-product of tosylation and was also prepared by chlorinatioon of the hydroxy ester with thionyl chloride, on reduction and oxidation as before gave [2R-2-²H]-hexadecanoic acid. Intermediates were fully characterized, isotopic purity was 97% and optical purity was maintained throughout the syntheses. Attempts to reduce the tosyl or chloro groups, only, with sodium borodeuteride gave low yields probably due to preferential reduction of the ester group; 1,2-epoxyhexadecane was obtained from the tosylate and 2-chlorohexadecan-1-ol from the chloro ester.     

植物细胞的氧化猝发和H2O2的信号转导

概述了植物细胞氧化猝发的特性、产生机理、生理作用以及Ｈ２Ｏ２信号转导途径及其对基因表达的调控等的研究进展。     

拟南芥血红蛋白1(AtGLB1)与过氧化氢的相互作用

拟南芥的血红蛋白1(AtGLB1)属于非共生的血红蛋白。在低氧胁迫中对植物细胞中过氧化氢(H2O2)内稳态的维持起了很重要的作用。为了检测AtGLB1与H2O2能否直接相互作用,我们扩增了拟南芥的AtGLB1基因,并将其克隆到原核表达质粒pET32a中,测序鉴定正确后转化大肠杆菌BL21。IPTG诱导目的蛋白表达后,镍离子亲和层析柱(Ni2+-NTA)纯化了靶蛋白。体外表达的氧合的AtGLB1能与H2O2直接相互作用。因此,与H2O2反应可能是AtGLB1清除低氧胁迫下产生的H2O2的一种方式。     

PPP2R2A在乳腺癌细胞中结合GFPT2并导致其去磷酸化

PPP2R2A是PP2A磷酸酶的调控亚基之一,以往的研究报道显示,PPP2R2A可促进肿瘤细胞生存和生长。本研究通过串联亲和纯化联合HPLC-Chip-ESI/MS/MS筛选PPP2R2A的相互作用蛋白质,分析结果显示,L-谷氨酰胺-D-果糖-6-磷酸转氨酶1(Glutamine-fructose-6-phosphate transaminase 1,GFPT1)和L-谷氨酰胺-D-果糖-6-磷酸转氨酶2(Glutamine-fructose-6-phosphate transaminase 2,GFPT2)是PPP2R2A可能的结合蛋白。通过免疫荧光共定位、GST Pull-down和免疫共沉淀等方法,进一步确认了PPP2R2A和GFPT1及GFPT2的相互结合。通过shRNA下调PPP2R2A后,GFPT2的磷酸化水平显著增加,但GFPT1的磷酸化水平改变不明显。GFPT2是O-GlcNAC糖基化修饰通路中的一个限速酶,在乳腺癌细胞MDA-MB-231中下调PPP2R2A后,蛋白质O-GlcNAC糖基化修饰水平增加。这些结果表明,PPP2R2A可直接结合GFPT2,并导致其去磷酸化,进而影响细胞内O-GlcNAC糖基化修饰。