纳米二氧化锡电极的制备及其用于水体中大肠杆菌的快速计数研究

制备了新型纳米二氧化锡电极, 将此电极用于水体中大肠杆菌的快速计数研究. 实验结果表明, 用该电极为工作电极, 采用计时电流法能简便、快速、灵敏地对水体中的大肠杆菌进行计数. 通过大肠杆菌脂质过氧化后丙二醛含量的检测, 对大肠杆菌在纳米二氧化锡电极上的电化学响应机理进行了初步的探讨.     

季铵盐型金属卟啉的合成及其对大肠杆菌生长代谢的抑制作用

以5,10,15,20-四(4′-吡啶基)卟啉为原料,合成了一系列季铵盐型金属卟啉1a,1b和2a～2c.使用LKB2277热活性监测器测定了大肠杆菌在不同浓度的金属卟啉1a,1b和2a～2c作用下的产热曲线,得到了大肠杆菌生长速率常数k,最大发热功率P_max和最大发热功率的出现时间t_p,发现季铵盐型金属卟啉2c对大肠杆菌生长代谢的抑制活性明显大于其它季铵盐型金属卟啉.     

基于纳米MnO2的免标记型DNA电化学生物传感器用于大肠杆菌的测定

以室温固相合成法制备纳米MnO2,通过壳聚糖（CHIT）的成膜效应将纳米MnO2固定在玻碳电极表面。DNA在MnO2/CHIT膜上的固定和杂交通过循环伏安和电化学交流阻抗进行表征。以电化学阻抗免标记法检测目标DNA,固定于电极表面的DNA探针与目标DNA杂交后使电极表面的电子传递电阻增大,以此作为检测信号可以高灵敏度地测定目标DNA。电化学阻抗谱检测大肠杆菌基因片段的线性范围为2.0×10^-11 ～2.0×10^-6mol/L,检出限为1.0×10^-12mol/L。     

Straightforward Approach for Preparing Durable Antibacterial ZnO Nanoparticle Coatings on Flexible Substrates

Flexible antibacterial materials have gained utmost importance in protection from the distribution of bacteria and viruses due to the exceptional variety of applications. Herein, we demonstrate a readily scalable and rapid single-step approach for producing durable ZnO nanoparticle antibacterial coating on flexible polymer substrates at room temperature. Substrates used are polystyrene, poly(ethylene-co-vinyl acetate) copolymer, poly(methyl methacrylate), polypropylene, high density polyethylene and a commercial acrylate type adhesive tape. The deposition was achieved by a spin-coating process using a slurry of ZnO nanoparticles in toluene. A stable modification layer was obtained when toluene was a solvent for the polymer substrates, namely polystyrene and poly(ethylene-co-vinyl acetate). These coatings show high antibacterial efficiency causing >5 log decrease in the viable counts of Gram-negative bacteria Escherichia. coli and Gram-positive bacteria Staphylococcus aureus in 120 min. Even after tapping these coated surfaces 500 times, the antibacterial properties remained unchanged, showing that the coating obtained by the presented method is very robust. In contrast to the above findings, the coatings are unstable when toluene is not a solvent for the substrate.     

Threonine Facilitates Cd Excretion by Increasing the Abundance of Gut Escherichia coli in Cd-Exposed Mice

Cadmium (Cd) can easily enter the body through the food chain and threaten health since Cd pollution is prevalent in the environment. Gut microbiota is necessary for the reduction of metal ions. To reduce Cd-induced harmful impacts and Cd accumulation in the body, we investigated the effect of amino acids on gut microbiota and Cd excretion in (fecal Cd) Cd-exposed mice. The screening of 20 amino acids showed that threonine (Thr) effectively increased fecal Cd, and reduced Cd-induced intestinal structural damage. The abundance of Escherichia-Shigella genus and KF843036_g significantly increased after the oral administration of Thr. As the type species of the Escherichia-Shigella genus, Escherichia coli exhibited high similarity to KF843036_g species and significantly decreased Cd-induced gut damage. Cd contents in the liver, kidney, and gut of Cd-exposed mice were also significantly (p < 0.05) decreased after E. coli treatment, while the contents in the feces were increased. The results demonstrated the potential roles that gut E. coli might play in Thr-mediated Cd excretion in Cd-exposed mice. The findings may provide important data for better understanding the molecular biological mechanism of Thr in reducing Cd accumulation in the body.     

Fabrication and Excellent Antibacterial Activity of Well-defined CuO/Graphdiyne Nanostructure

Copper oxide(CuO),due to its low cost,good chemical and physical stability,has recently been given special attention as a potential candidate for antibacterial agents.However,developing novel CuO nanocomposites with improved antibacterial property and unraveling the interface promotion mechanism has been a fundamental challenge for decades.Herein,well-defined CuO/graphdiyne(CuO/GDY)nanostructures with uniformly anchored CuO nanoparticles(ca.4.5 nm)have been fabricated.The CuO/GDY nanostructure exhibited superior E.coli inactivation efficiency,which is nearly 19 times and 7.9 times higher than the bare GDY and commercial CuO,respectively.The improved E.coli inactivation performance was mainly due to the increased reactive O2-species generated by the activation of molecular O2 over CuO/GDY surface.These findings demonstrate the efficient antibacterial activity of well-defined CuO/GDY nanostructures and provide insights on the development of efficient GDY-based antibacterial materials.     

大肠杆菌密码子与蛋白质二级结构的关系

通过对大肠杆菌(E．coli)的蛋白质二级结构α螺旋、β折叠和无规卷曲的片段分别进行分析。发现有些蛋白质二级结构所对应氨基酸的密码子在结构片段的不同位置上具有明显的分布偏向性．有些密码子偏向于出现在结构片段的头部。有些则偏向于出现在结构片段的中部或尾部．同时还发现α螺旋片段中具有位置偏向性的密码子较多。而β折叠和无规卷曲片段中具有偏向性的密码子则较少．对人类蛋白质二级结构的片段进行统计分析，发现密码子也具有类似的偏向性，但是与大肠杆菌相比。又具有自己的特征．     

负载型TiO2／玻璃弹簧的光催化杀菌作用

 研究了自主开发的负载型TiO2／玻璃弹簧光催化剂对大肠杆菌的光催化杀菌作用．结果表明，光催化杀菌效果明显好于单独紫外光的杀菌效果．光催化杀菌过程存在一个诱导期．用扫描电镜和透射电镜观察经不同时间杀菌处理的菌液，结果显示光催化作用于细菌的细胞壁和细胞膜，使其破裂并导致细胞死亡．探讨了光催化剂的制备条件（如浸涂浆料浓度、浸涂次数、热处理条件等）对光催化杀菌效率的影响．     

提高微生物酶传感器选择性的研究

微生物酶传感器是将微生物固定于化学电极上,直接利用微生物体内的酶分解底物而测定的一类生物传感器。同酶传感器相比,它有使用寿命长、制作简便、酶源易获得等优点。自1977年首篇报道以来,测定不同氨基酸和其它有机物的微生物传感器相继问世。但由于微生物通常是一个混合酶体系,使得微生物酶传感器选择性较差。文献曾报道用酶抑制剂进行预处理的办法来降低干扰物响应。本文则利用不同酶耐热性的差异进行温度预处理,以及在培养微生物时,使用不同培养基来改善微生物产酶的特性,从而提高微生物酶传感器的选择性。原大肠杆菌膜电极对L-天冬酰胺、L-谷氨酰胺和L-天冬氨酸均有响应,经升温处理后,对L-天冬氨酸的响应消除,即测定L-天冬酰胺或L-谷氨酰胺时,L-天冬氨酸不再产生干扰,再经改变培养基后,L-谷氨酰胺的响应明显减小,而L-天冬酰胺的响应保持不变。 1 实验部分 PXS-215型离子活度计(上海分析仪器厂);501型氨气敏电极(江苏电分析仪器厂);3086-XY函数记录仪;812型控温磁力搅拌器(上海司乐仪器厂);THZ-82型恒温振荡器(上海跃进医疗器械一厂);电热手提高压蒸汽消毒器(上海医用核子仪器厂);LD4-2A离心机(北京医用离心机厂)。 主要试剂为0.100mol/L的L-天冬酰胺、L-谷氨酰胺和L-天冬氨酸,均用生化纯固     

两种稀土卟啉配合物与大肠杆菌作用的微量热研究

用LKB-2277生物活性检测系统测定了新合成的阳离子型稀土卟啉配合物{[Re(TMP)(H2O)3]Cl, Re=Y、Yb, TMP=5, 10, 15, 20-四(4’-甲氧基苯基)卟啉}在37 ℃时对大肠杆菌作用的产热曲线,根据产热曲线求算了在稀土卟啉配合物作用下,大肠杆菌生长代谢的速率常数k,抑制率I,传代时间tG和半抑制浓度cI,50等热动力学参数.结果表明,稀土卟啉配合物在低浓度下对大肠杆菌有刺激作用,高浓度下为抑制作用,[Yb(TMP)(H2O)3]Cl的半抑制浓度cI,50为143 mg•L-1,其对大肠杆菌的抑制作用优于[Y(TMP)(H2O)3]Cl.