噬菌体AB3裂解酶的抗菌谱及其抗菌机制

目的明确噬茵体AB3裂解酶LysAB3的抗茵谱及其抗菌机制。方法利用扩散法检测裂解酶LysAB3的抗茵谱;扩增裂解酶LysAB3基因序列前端的354 bp以pET28a(+)为载体构建重组质粒,在大肠杆菌BL21(DE3)中表达,Ni~(2+)-NTA亲和层析柱纯化重组蛋白,得到删除了两性多肽结构的裂解酶LysAB3-D,并测定其抗茵率。结果裂解酶LysAB3可以裂解全部40株鲍曼不动杆菌菌株;删除了两性多肽结构后,裂解酶LysAB3-D的抗菌率由95.8%下降至33.3%。结论裂解酶LysAB3的抗茵谱较宽;其杀菌机制可能是通过其两性多肽结构增加细菌外膜通透性,辅助酶解催化域进入其中降解肽聚糖。     

粉煤灰混凝剂与传统混凝剂对乳品废水中COD和SS去除效果的比较研究

以乳品废水为处理对象,自制粉煤灰混凝剂、硫酸铝、聚合氯化铝(PAC)为实验药剂,研究了不同pH值、温度和投加量下,COD和SS的去除效果.结果 表明:在弱酸性和中性pH值下,各混凝剂的处理效果较好,且粉煤灰混凝剂的处理效果最好;水温在12～29℃时,PAC和粉煤灰混凝剂受温度影响很小,其中对粉煤灰的影响最小;各混凝剂均存在最佳投加量(1×10-3mol/L),在相同投量下,自制粉煤灰的混凝效果好于传统混凝剂.因此,粉煤灰混凝剂可以替代传统混凝剂来处理乳品废水.     

噬菌体D29的免疫原性及安全性评价

目的对噬菌体D29的免疫原性及安全性进行评价。方法将BALB／C小鼠随机分为噬菌体D29滴鼻暴露组（剂量9×10^8PFU）、噬菌体D29皮下注射组（剂量9×10^8PFU）,phagebuffer滴鼻组、phagebuffer皮下注射组、生理盐水滴鼻组、生理盐水皮下注射组、空白对照组,每组动物第一周第一天、第三天暴露一次,以后每周第一天暴露一次,共暴露6周。观察暴露期间噬菌体中和抗体的动态变化、暴露6周后血清中IL-2、IL-4、IL-12、IFN-1、TNF-α和NO的含量及CD4／CD8比例变化,小鼠碳粒廓清率变化、在饲养过程中各组动物的进食量以及活动、体重、生存情况,以及暴露结束后解剖取得脏器作病理学比较。结果D29滴鼻暴露组在第7天即产生低效价的中和抗体,第14天抗体效价下降,第28天之后不能检测到中和抗体,D29皮下注射组中和抗体从第7天开始产生,第21天上升,之后趋于稳定,其余组均无中和抗体产生。各组小鼠血清中细胞因子、CIM／CD8比例、碳粒廓清率以及饲养过程中各组动物的进食量以及活动、体重、生存情况均无明显差异。病理学上各实验组脏器除脾脏外均有轻微充血、水肿表现。结论D29具有抗原特性,可刺激机体产生中和抗体,但不会对机体的安全产生威胁。     

纳米TiO2/ZnO光催化降解氯胺磷的研究

采用溶胶-凝胶法制备了几种不同比例的纳米TiO2/ZnO复合半导体光催化剂及纯TiO2、ZnO单组分催化剂,并利用XRD,FE-SEM等手段对样品的结构和形貌进行表征.选用有机磷药氯胺磷为光催化降解对象,利用钼锑抗分光光度法测量并计算降解率,研究了溶液初始浓度、催化剂用量、催化剂的不同配比、热处理温度及溶液的pH值等因素对光催化降解效果的影响.实验结果表明:对于初始浓度4.5mg/L的氯胺磷溶液,催化剂用量为0.6 g·L<'-1>时,TiO2与ZnO的最佳比例为10:1,最佳热处理温度为500℃.反应进行5 h后,最大降解率可达到44.1%.在酸性及碱性介质中均有利于氯胺磷的降解,降解后溶液pH值都向中性趋近     

TiO2薄膜的光电催化性能及电化学阻抗谱研究

用直流磁控溅射法在钛网上制备了TiO2薄膜催化剂,采用电化学阻抗谱（EIS）对其阻抗谱特征进行了表征.同时以偶氮酸性红溶液为模型污染物,验证了此工作电极在不同条件下的光电催化活性与阻抗谱之间的关系.研究表明：光电催化实验中TiO2薄膜在同时有紫外光和外加阳极偏压的情况下,有效实现电子-空穴分离,具有最好的催化活性;最佳的外加阳极偏压值为0.3V;其EIS Nyquist图上阻抗环半径也在此时最小,最容易发生反应,与光电催化实验结果一致.     

盐酸小檗碱结肠定位包衣片的制备工艺和体外释放研究

目的 用丙烯酸树脂水分散体包衣技术制备pH敏感-时间控释型盐酸小檗碱结肠定位包衣片,评价其体外释药特性.方法 采用滚转包衣机多层薄膜包衣技术制备结肠定位包衣片,以羟丙甲纤维素HPMC作为隔离层,pH敏感型丙烯酸树脂Eudragit L30D-55与Eudragit S100混合包衣液作为肠溶层,渗透型丙烯酸树脂Eudragit RL30D和Eudragit RS30D混合液作为缓释层,以柠檬酸三乙酯作为增塑剂,滑石粉作为抗粘剂,通过正交实验进行处方优化,研究包衣片在模拟人体胃肠道环境中的释药速率.结果 最佳包衣处方:隔离层增重1.2%;肠溶层组成Eudragit L30D-55:S100(1:5),包衣增重4%;缓释层组成(1:1),包衣增重2%.包衣片在0.1moL·L-1盐酸溶液中2h无药物释放,在pH6.8的磷酸盐缓冲液中3h药物释放低于10%,在pH7.8的磷酸盐缓冲液中呈缓慢释放,12h内药物释放量在70%左右,累积释药百分率高于标示量的80%.结论 水分散体包衣技术制备结肠定位包衣片工艺合理可行,有良好的开发和应用前景.     

复合吸剂液相同时脱硫脱硝特性研究

以NaClO2和NaClO溶液为复合吸收剂,在制鼓泡反应上对SO2和NOx吸收特性进行了实验研究.考察了复合吸收剂溶液中NaClO2和NaClO浓度、溶液pH值、反应温度等主要参数对SO2和NOx脱除效率影响,获最佳实验条件为：NaClO2和NaClO摩尔比1：1,溶液pH值5.5,反应温度为50℃.在最佳实验条件下,同时脱硫脱硝效率可分别达100%和89.2%.通过产物分析和相关物种电极电位分析,揭示了复合吸收剂同时脱硫脱硝机理,即复合吸收剂中亚氯酸根离、次氯酸、二氧化氯及氯共同与SO2和NOx发生了氧化吸收反应.热力学研究表明,脱硫脱硝反应均可以发进行,且为放热反应.动力学研究证实,同时脱硫脱硝过程中,SO2反应分级数为1,反应平均活化能为21.6kJmol-1;NO反应分级数为1,反应平均活化能为8.2kJmol-1.     

胃癌侧群细胞耐药性研究及干细胞相关基因检测

目的研究胃癌侧群（Side Population,sP）细胞对化疗药物5-Fu（氟尿嘧啶）的耐药性及可能机制,并检测干细胞相关基因Nanog、Musashi-1及cD44的表达情况。方法选择人胃癌细胞株sGc-7901,以荧光染料H0echst 33342染色,维拉帕米桔抗对照,应用流式细胞仪分选sP细胞和nonsP细胞。细胞耐药实验比较sP细胞与nonsP细胞对化疗药物5．Fu的耐药性差异;westem_h10t检测ABcG2和bcl-2蛋白表达情况;流式细胞仪分析细胞周期;荧光定量PcR检测两组细胞中干细胞相关基因Nanog、Musashi-1及cD44mRNA的表达差异。结果胃癌细胞株sGc．790l中sP细胞的比例为2．8％,sP细胞对5-Fu的耐药存活率明显高于non-sP细胞（P〈0．05）,与nonsP细胞相比,sP细胞高表达耐药蛋白ABcG2和抗凋亡蛋白bcl-2,有更多的细胞处于c0／G1期（P〈0．05）,并高表达干细胞相关基因Musashi-1和cD44。结论胃癌sGC_7901细胞株中sP细胞对化疗药物5．Fu的耐药性明显高于nonsP细胞,其耐药机制可能与sP细胞高表达耐药蛋白ABcG2和抗凋亡蛋白bcl-2,有更多细胞处于G0／Gl期有关;Musashi-1和cD44可能是相对特异性的胃癌干细胞标志物。     

立方烷电子结构和光学性质的研究

为了全面了解立方烷的性质,本文利用CASTEP程序包基于密度泛函理论的交换关联函数（GGA）方法对立方烷的电子结构和光学性质进行研究。在计算的过程中首先优化立方烷的晶体结构并与实验值进行对比,结果符合很好。立方烷的能带带隙为5．453CV,吸收系数最大峰值为2．509&#215;10^5cm^-1.然后又研究光学性质的吸收谱,反射谱和能量损失函数。     

葛根素通过ERK1/2信号通路调控成骨细胞增殖的实验研究

目的研究中草药葛根素对小鼠MC3T3-E1成骨细胞增值的影响以及ERK1/2信号通路在其中的作用,为葛根素治疗骨质疏松症的临床应用提供科学指导和理论依据。方法取购自中国医学科学院细胞中心的小鼠MC3T3-E1成骨细胞系体外培养并进行传代。分别用不同浓度的葛根素作用于成骨细胞,在成骨细胞生长成熟后,运用四甲基偶氮唑盐法(MTT法)和台盼蓝染色检测各组干预后成骨细胞的活性。检测出最适宜的干预时间作用于细胞活性最高的组别后,1)流式细胞仪检测葛根素影响成骨细胞增殖周期的最佳浓度;2)提取出成骨细胞内蛋白质,通过Western Bloting法检测最佳浓度的葛根素对成骨细胞内增殖相关蛋白cyclin D1和CDK4以及ERK1/2信号通路的影响,并使用ERK1/2通路阻断剂PD0089,观察对细胞增殖蛋白的影响。结果细胞MTT和台盼蓝染色实验结果显示,1 umol/L葛根素是促进成骨细胞增殖生长的最佳浓度。流式细胞仪检测发现1 umol/L葛根素能够促进成骨细胞G1向S期转变。Western Bloting结果均显示1 umol/L葛根素能明显促进成骨细胞增殖蛋白cyclin D1和CDK4以及ERK1/2信号通路蛋白的表达。使用ERK1/2信号通路阻断剂PD98059后,cyclin D1和CDK4蛋白的表达量下降,差异具有统计学意义。结论葛根素对小鼠成骨细胞表现出明显的增殖作用,可以通过ERK1/2信号通路调控成骨细胞增值周期蛋白表达,这可能是葛根素防治绝经后骨质疏松症的作用机制,为葛根素的应用提供了实验依据,也为发掘新的抗骨质疏松药物提供了线索。     

Molecular mechanisms of CRISPR-mediated microbial immunity

Bacteriophages (phages) infect bacteria in order to replicate and burst out of the host, killing the cell, when reproduction is completed. Thus, from a bacterial perspective, phages pose a persistent lethal threat to bacterial populations. Not surprisingly, bacteria evolved multiple defense barriers to interfere with nearly every step of phage life cycles. Phages respond to this selection pressure by counter-evolving their genomes to evade bacterial resistance. The antagonistic interaction between bacteria and rapidly diversifying viruses promotes the evolution and dissemination of bacteriophage-resistance mechanisms in bacteria. Recently, an adaptive microbial immune system, named clustered regularly interspaced short palindromic repeats (CRISPR) and which provides acquired immunity against viruses and plasmids, has been identified. Unlike the restriction–modification anti-phage barrier that subjects to cleavage any foreign DNA lacking a protective methyl-tag in the target site, the CRISPR–Cas systems are invader-specific, adaptive, and heritable. In this review, we focus on the molecular mechanisms of interference/immunity provided by different CRISPR–Cas systems.     

Herbicide resistance and supersensitivity in photosystem II

Resistance to triazine herbicides in higher plants was first observed in 1970. A mutation in the photosystem II reaction center D1 protein at position Ser264 --> Gly is responsible for this resistance. So far, 37 single mutants, 16 double mutants, 5 triple mutants and 5 deletion/insertion mutants in the D1 protein have been obtained by randomly induced and site-directed mutagenesis in cyanobacteria and algae. The influence of these mutations on the binding affinities of different classes of herbicides will be discussed. Because a sufficiently high resolution X-ray structure of photosystem II does not yet exist, the reaction center of purple photosynthetic bacteria, which is homologous to photosystem II, served as a model. In the bacterial reaction center a total of 25 single and 3 double herbicide-resistant mutants have been generated.     

Effect of Tween 80 on lipids ofMycobacterium phlei ATCC 354

Summary Addition of Tween 80 to the growth medium brings about qualitative and quantitative changes in the lipids ofMycobacterium phlei ATCC 354. The results suggest that Tween 80 itself may be a variant in the system.Acknowledgments. K. R. D. is grateful to the Indian Council of Agricultural Research, New Delhi, for the award of Senior Research Fellowship. This study was supported in part by funds from Indian Council of Medical Research, New Delhi, and University Grants Commision, New Delhi.     

Pili in Gram-negative and Gram-positive bacteria — structure, assembly and their role in disease

Many bacterial species possess long filamentous structures known as pili or fimbriae extending from their surfaces. Despite the diversity in pilus structure and biogenesis, pili in Gram-negative bacteria are typically formed by non-covalent homopolymerization of major pilus subunit proteins (pilins), which generates the pilus shaft. Additional pilins may be added to the fiber and often function as host cell adhesins. Some pili are also involved in biofilm formation, phage transduction, DNA uptake and a special form of bacterial cell movement, known as ‘twitching motility’ In contrast, the more recently discovered pili in Gram-positive bacteria are formed by covalent polymerization of pilin subunits in a process that requires a dedicated sortase enzyme. Minor pilins are added to the fiber and play a major role in host cell colonization. This review gives an overview of the structure, assembly and function of the best-characterized pili of both Gram-negative and Gram-positive bacteria. Received 08 August 2008; received after revision 24 September 2008; accepted 01 October 2008     

Ligase activity of lig- bacteria infected with mu bacteriophage at non-permissive temperatures]

Infection of bacteria E. coli lig ts7, which contain a thermosensitive ligase by phage Mu results in a decrease in the sensitivity to the lethal action of ultraviolet irradiation and stimulation of lysogenization among the surviving cells. These observations suggest the existence of a phage coded ligase which has the character of an integrase.     

Infection of frog tadpoles (Amphibia) by insect parasitic nematodes (Rhabditida)

Summary Infective stage juveniles ofNeoaplectana carpocapsae (Steinernematidae) andHeterohabditis heliothidis (Heterorhabditidae) were able to penetrate through the alimentary tract of young tadpoles ofHyla regilla (Hylidae) andXenopus laevis (Pipidae) and enter the body cavity. Some infectives ofN. carpocapsae were able to release their symbiotic bacterium,Xenorhabdus nematophilus inside the host and in two cases, the nematodes developed into adult females before they perished. Tadpole mortality was associated with foreign bacteria entering the penetration holes made by the invading nematodes. The infective stage juveniles of both nematodes frequently encountered a host defense reaction upon reaching the tadpole's infective stage juveniles of both nematodes frequently encountered a host defense reaction upon reaching the tadpole's coelom.     

Inhibitory effect of halocyamine,an antimicrobial substance from ascidian hemocytes,on the growth of fish viruses and marine bacteria

Summary Halocyamine A, an antimicrobial substance isolated from hemocytes of the solitary ascidianHalocynthia roretzi, inhibited in vitro the growth of fish RNA viruses (infectious hematopoietic necrosis virus and infectious pancreatic necrosis virus). Pretreatment of RNA virus with halocyamine A reduced the infectivity of the virus toward host cells. The growth of marine bacteria,Achromobacter aquamarinus andPseudomonas perfectomarinus, was also inhibited by halocyamine A but that ofAlteromonas putrefaciens andVibrio anguillarum was not. These results suggest that halocyamine may have a role in the defense mechanisms ofH. roretzi against marine viruses and bacteria.     

Effect of Tween 80 on lipids of Mycobacterium phlei ATCC 354

Addition of Tween 80 to the growth medium brings about qualitative and quantitative changes in the lipids of Mycobacterium phlei ATCC 354. The results suggest that Tween 80 itself may be a variant in the system.