非病毒基因载体材料聚谷氨酸-聚丙烯亚胺的合成及与DNA的结合稳定性

目的合成非病毒基因载体材料聚谷氨酸-聚丙烯亚胺,并考查其与DNA的结合能力及稳定性。方法以G2.0聚丙烯亚胺(PPI)为引发剂,通过开环聚合的方法,合成了聚丙烯亚胺-聚谷氨酸苄脂多臂接枝聚合物,再以G1.0聚丙烯亚胺或G2.0聚丙烯亚胺作为氨解试剂进行氨解合成了新型树枝状的聚谷氨酸-聚丙烯亚胺聚合物(MP-g-PPI)。采用红外光谱(IR)、1HNMR对聚合产物进行结构表征,通过琼脂糖凝胶电泳实验考察聚合物与DNA的结合能力,通过离心法考察了聚合物与DNA形成复合物的沉淀稳定性,通过MTT法考察聚合物在Hela细胞中的毒性,并通过测定发荧光细胞百分数获得复合物在Hek-293细胞中的转染率。结果成功合成了聚谷氨酸-聚丙烯亚胺聚合物,此聚合物可有效的与DNA结合成纳米复合物,可通过一定的空间斥力阻止复合物的聚集,且毒性较PEI 25K低,可有效介导基因的转染。结论聚谷氨酸-聚丙烯亚胺聚合物可与DNA形成稳定的复合物,此聚合物有望成为新型的非病毒基因载体材料。

聚羟肟酸捕集剂处理含铜废水的研究

研究了聚羟肟酸捕集剂对水中Cu^(2+)的螯合去除功能,考察了pH值、捕集剂加入量、处理时间对去除率的影响.结果表明:在pH=5.5～6,聚羟肟酸用量为Cu^(2+)质量的3.4倍,处理时间为50min时,Cu^(2+)的去除率达99.73%,处理后的废水达到了国家《污水综合排放标准》.该法与碱中和法所得Cu^(2+)沉淀相比,其铜离子的浸出量仅为后者的1/315.故聚羟肟酸处理含Cu^(2+)废水具有更好的环境安全性.对聚羟肟酸捕集剂与Cu^(2+)的螫合去除机理进行了初步探讨.

压力作用后的蓝藻在太湖中的生长控制机理

为了探明原位加压控制太湖蓝藻的效果和机理,实验研究了加压蓝藻在太湖中的垂直分布规律、生长衰亡趋势及沉淀稳定性。结果表明,0.7 MPa加压处理可使一定范围内的水体表面不再有蓝藻聚集,水体藻类叶绿素a平均浓度降低98%以上,加压后的蓝藻数量呈上少下多的竖向分布,且处于较低水平;经加压后的蓝藻沉淀至湖底无光区,无法进行光合作用生长繁殖,也无法大量生成新气囊而上浮至水体上层接受光照而繁殖,经过120 h左右失去活性而彻底衰亡。

Microstructure stability of Ti_2Al N/Ti-48Al-2Cr-2Nb composite at 900 °C

Microstructure stability of in situ synthesized Ti2AlN/Ti-48Al-2Cr-2Nb composite during aging at 900 ℃ was investigated by XRD, OM and TEM, and the unreinforced Ti-48Al-2Cr-2Nb alloy was also examined for comparison. The result showed that in the TiAl alloy,α2 lamellae thinned and were broken down, and became discontinuous with increasing aging time. The decomposition ofα2 lamella toγ which was characterized by parallel decomposition and breakdown ofα2 lamellae led to the degradation of the lamellar structure. While in the composite, lamellar structure remained relatively stable even after aging at 900 ℃ for 100 h. No breakdown ofα2 lamellae except parallel decomposition and precipitation of fine nitride particles was observed. The better microstructural stability of the composite was mainly attributed to the precipitation of Ti2AlN particles at theα2/γ interface which played an important role in retarding the coarsening of lamellar microstructure in the matrix of composite.

Effects of co-precipitation temperature on structure and properties of La and Y doped cerium zirconium mixed oxides

Due to the oxygen storage and release properties,cerium zirconium mixed oxides are recognized as the key material in automotive three-way catalysts.To reveal the effects of co-precipitation temperature on structure,physical and chemical properties of multi-doped cerium zirconium mixed oxides,a series of La and Y doped cerium zirconium mixed oxides(CZLYs)were synthesized via a co-precipitation method,and the physical and chemical properties of CZLYs were systemically characterized by XRD,N_(2) adsorption−desorption,TEM,XPS,oxygen storage capacity(OSC)and hydrogen temperature programmed reduction(H_(2)-TPR).The results show that co-precipitation temperature is an important parameter to influence the crystal size,oxygen storage capacity and thermal stability of CZLYs.When the co-precipitation temperature was 60℃,the best redox properties and thermal stability of CZLYs were obtained.After thermal treatment at 1100℃for 10 h,the specific surface area and oxygen storage capacity of the corresponding aged sample were 15.42 m^(2)/g and 497.7μmol/g,respectively.In addition,a mechanism was proposed to reveal the effects of co-precipitation temperature on the structure and properties of CZLYs.

Inhibition of SIRT1 Increases EZH2 Protein Level and Enhances the Repression of EZH2 on Target Gene Expression

Objective To study the regulatory roles of SIRT1 on EZH2 expression and the further ef-fects on EZH2's repression of target gene expression. Methods The stable SIRT1 RNAi and Control RNAi HeLa cells were established by in-fection with retroviruses expressing shSIRT1 and shLuc respectively followed by puromycin selection. EZH2 protein level was detected by Western blot in either whole cell lysate or the fractional cell extract. Reverse transcription-polymerase chain reaction was performed to detect the mRNA level of EZH2. Cycloheximide was used to treat SIRT1 RNAi and Control RNAi cells for protein stability assay. Chromatin immunoprecipitation (ChIP) assay was applied to measure enrichment of SIRT1, EZH2, and trimethylated H3K27 (H3K27me3) at SATB1 promoter in SIRT1 RNAi and Control RNAi cells. Results Western blot results showed that EZH2 protein level increased upon SIRT1 de-pletion. Fractional extraction results showed unchanged cytoplasmic fraction and increased chromatin fraction of EZH2 protein in SIRT1 RNAi cells. The mRNA level of EZH2 was not affected by knockdown of SIRT1. SIRT1 recruitment was not detected at the promoter region of EZH2 gene locus. The protein stability assay showed that the protein stability of EZH2 increases upon SIRT1 knockdown. Upon SIRT1 depletion, EZH2 and H3K27me3 recruitment at SATB1 promoter increases and the mRNA level of SATB1 decreases. Conclusions Depletion of SIRT1 increases the protein stability of EZH2. The regulation of EZH2 protein level by SIRT1 affects the repressive effects of EZH2 on the target gene expres-sion.

Investigation of the thermal stability of Mn ferrite particles synthesized by a modified co-precipitation method

Manganese ferrite particles with spinel structure were synthesized by a modified co-precipitation method,and then the thermal stability on their structural and magnetic properties was investigated by thermal annealing at different gas ambients.Experimental results showed that decomposition of metal oxides occurred when Mn ferrite particles with spinel structure were annealed under air ambient,while samples annealed in vacuum or argon remained in the spinel structural form.The highest saturation magnetization value of 58 emu/g was obtained when the sample was annealed at 400℃ in argon.The result showed that the thermal stability of MnFe2O4 was better under Ar ambient conditions or in vacuum.