镍系顺丁橡胶生产中不加终止剂技术

结合生产和科研实践,利用负离子配位聚合原理对镍催化体系丁二烯溶液聚合的聚合和行为进行了分析,结果表明,丁二烯转化率达到一定程度后,聚合将自动终止,顺丁橡胶生产中不必加终止剂,该技术应用后,对顺丁橡胶质量无影响,聚合更加平稳,催化剂用量下降。     

4种终止剂在悬浮法聚氯乙烯生产中的应用对比

从终止剂的物化性能、用量和使用成本,聚氯乙烯树脂的热稳定性,离心母液COD以及对聚合引发体系的影响等多个角度对4种终止剂(水溶型、油溶型、乳液型和悬浮型)进行了对比,以期为聚氯乙烯生产单位选择终止剂提供参考。     

The effect of moisture presoaking on graft copolymerization of methyl methacrylate in wood under mutual irradiation by electron beam accelerator

Polymerization of MMA was carried out in wood under mutual electron beam irradiation. The changes in molecular weight (M _n, M _m) and the number of polymer branches grafted to holocellulose and lignin were compared with the swelling degree (ΔL_H2O) of base veneers obtained by moisture presoaking before impregnation of the monomer. Increases in molecular weight as well as in the number of both grafted branches were observed with increase in ΔL_H2O up to ca. 4% in the lower range of ΔL_H2O. However, for the number of polymer branches grafted to holocellulose, the increse reached a peak at ΔL_H2O of ca. 4%, in contrast to the continuous increase of both molecular weights M _n and M _w. This is due to the bimolecular recombination-type termination of the propagating radicals mutually between those originating from the holocellulose and the irradiated MMA within the cellular parts or due to their termination onto lignin. The polymer branches grafted to lignin came from the latter termination, and it was found that the lower molecular weight branches grafted to lignin came from those propagating radicals which were produced from irradiated MMA in the void space and terminating onto lignin.     

FCC提升管反应器中终止剂注入对裂化反应的影响

通过对催化裂化提升管注入终止剂前后的工况进行数值模拟,研究了终止剂注入对提升管内速度分布、催化剂颗粒浓度分布、温度分布以及组分浓度分布的影响,考察了不同注入量以及注入高度的终止剂在提升管内的作用区域及其对裂化反应的影响。研究表明,终止剂的注入大幅提升了提升管内的油气速度,降低了催化剂浓度、油气和催化剂的温度,使得提升管内原料的裂化程度降低,二次反应减少。且不同注入量和注入高度的作用区域不同,对裂化反应的影响不同,应根据实际工况进行分析。     

A Fork Trap in the Chromosomal Termination Area Is Highly Conserved across All Escherichia coli Phylogenetic Groups

Termination of DNA replication, the final stage of genome duplication, is surprisingly complex, and failures to bring DNA synthesis to an accurate conclusion can impact genome stability and cell viability. In Escherichia coli, termination takes place in a specialised termination area opposite the origin. A ‘replication fork trap’ is formed by unidirectional fork barriers via the binding of Tus protein to genomic ter sites. Such a fork trap system is found in some bacterial species, but it appears not to be a general feature of bacterial chromosomes. The biochemical properties of fork trap systems have been extensively characterised, but little is known about their precise physiological roles. In this study, we compare locations and distributions of ter terminator sites in E. coli genomes across all phylogenetic groups, including Shigella. Our analysis shows that all ter sites are highly conserved in E. coli, with slightly more variability in the Shigella genomes. Our sequence analysis of ter sites and Tus proteins shows that the fork trap is likely to be active in all strains investigated. In addition, our analysis shows that the dif chromosome dimer resolution site is consistently located between the innermost ter sites, even if rearrangements have changed the location of the innermost termination area. Our data further support the idea that the replication fork trap has an important physiological role that provides an evolutionary advantage.     

镍系BR的聚合终止行为

利用丁二烯溶液聚合过程的粒子碰撞原理和聚合理论,研究了镍系顺丁橡胶（ＮｉＢＲ）的聚合终止行为。结果表明,聚合不加终止剂即可自动终止。自动终止技术应用于生产后,优化了工艺,提高了ＮｉＢＲ的生产能力。     

Synergy between Readthrough and Nonsense Mediated Decay Inhibition in a Murine Model of Cystic Fibrosis Nonsense Mutations

Many heritable genetic disorders arise from nonsense mutations, which generate premature termination codons (PTCs) in transcribed mRNA. PTCs ablate protein synthesis by prematurely terminating the translation of mutant mRNA, as well as reducing mutant mRNA quantity through targeted degradation by nonsense-mediated decay (NMD) mechanisms. Therapeutic strategies for nonsense mutations include facilitating ribosomal readthrough of the PTC and/or inhibiting NMD to restore protein function. However, the efficacy of combining readthrough agents and NMD inhibitors has not been thoroughly explored. In this study, we examined combinations of known NMD inhibitors and readthrough agents using functional analysis of the CFTR protein in primary cells from a mouse model carrying a G542X nonsense mutation in Cftr. We observed synergy between an inhibitor of the NMD component SMG-1 (SMG1i) and the readthrough agents G418, gentamicin, and paromomycin, but did not observe synergy with readthrough caused by amikacin, tobramycin, PTC124, escin, or amlexanox. These results indicate that treatment with NMD inhibitors can increase the quantity of functional protein following readthrough, and that combining NMD inhibitors and readthrough agents represents a potential therapeutic option for treating nonsense mutations.     

硅烷Y9669改性湿固化聚氨酯热熔胶的研制

以4,4′-二苯基甲烷二异氰酸酯(MDI)、聚醚多元醇(N-210)和聚己二酸己二醇酯(PHA)为主要原料,控制R=n(-NCO)/n(-OH)=2.0,制得PUR(湿固化聚氨酯热熔胶)的预聚体;然后以不同的硅烷偶联剂[如Y9669(N-苯基-γ-氨丙基三甲氧基硅烷)、KH-550和KH-560等]作为PUR中部分端-NCO基的封端剂,制备SPUR(硅烷化PUR)。结果表明:Y9669是较理想的封端剂,能使SPUR的剪切强度增加37.23%;SPUR的硬度、热稳定性能随Y9669封端率增加而增大;SPUR的剪切强度随Y9669封端率增加呈先升后降态势,并且在Y9669封端率为20%时相对最大(17.73 MPa)。     

脂联素对巨噬细胞ATP结合盒转运子A1表达及其功能的影响

目的探讨脂联素对巨噬细胞ATP结合盒转运子A1(ATP binding cassette transporter A1,ABCA1)及其上游调控因子肝脏X受体α(Liver X receptorα,LXRα)表达的影响及其在胆固醇逆转运(Reverse cholesterol transport,RCT)和抗动脉粥样硬化(Atherosclerosis,AS)中可能的作用机制。方法以不同浓度的脂联素(0、1、5、10μg/ml)体外培养巨噬细胞RAW264.7 24 h,RT-PCR法检测细胞中ABCA1和LXRα基因mRNA的转录水平,Western blot法检测细胞中ABCA1和LXRα蛋白的表达水平,闪烁计数法检测细胞内胆固醇的流出情况。结果脂联素能显著上调RAW264.7细胞中ABCA1和LXRα基因mRNA的转录水平及蛋白的表达水平(P<0.05),且呈浓度依赖性;脂联素能浓度依赖性地增加细胞内胆固醇的流出(P<0.05)。结论脂联素可通过LXRα途径上调巨噬细胞ABCA1基因的转录和翻译水平,促进胆固醇逆转运,延缓AS的发生、发展。     

一种乳腺特异性表达载体的构建

以兔乳清酸性蛋白基因启动子(rWAP,6.3 kb)、兔乳清酸性蛋白基因终止子(200 bp)和人瘦蛋白基因(cDNA,1.0 kb)经过一系列的亚克隆操作,构建了一种通用性的乳腺特异性表达载体,从而为通过转基因小鼠动物模型表达外源基因提供了极大的方便。     

黑曲霉纤维二糖酶基因的克隆及其在里氏木霉中的表达

里氏木霉(Trichodema reesei)是目前常用的纤维素酶生产菌种,其分泌的纤维素酶是一个多组分的复合体系,主要包括5种内切型-β-葡聚糖酶(endo-J3-glucanase,EG,EC3.2.1.4),两种外切型β-葡聚糖酶(exo-β-glucanase,EC3.2.1.91,也称纤维二糖水解酶cellobiohydrolase,CBH)和两种纤维二糖酶(cellobiase,EC3.2.1.21,也称β-葡萄糖苷酶β-glucosidase)[1-3].在里氏木霉的纤维素酶蛋白中,纤维二糖水解酶I(CBHI)受强启动子控制,其蛋白质比例最高,约占50%～60%[1],而纤维二糖酶(CB)的比例最低,只占1%左右[4].     

A Comprehensive Analysis of Codon Usage Patterns in Blunt Snout Bream (Megalobrama amblycephala) Based on RNA-Seq Data

Blunt snout bream (Megalobrama amblycephala) is an important fish species for its delicacy and high economic value in China. Codon usage analysis could be helpful to understand its codon biology, mRNA translation and vertebrate evolution. Based on RNA-Seq data for M. amblycephala, high-frequency codons (CUG, AGA, GUG, CAG and GAG), as well as low-frequency ones (NUA and NCG codons) were identified. A total of 724 high-frequency codon pairs were observed. Meanwhile, 14 preferred and 199 avoided neighboring codon pairs were also identified, but bias was almost not shown with one or more intervening codons inserted between the same pairs. Codon usage bias in the regions close to start and stop codons indicated apparent heterogeneity, which even occurs in the flanking nucleotide sequence. Codon usage bias (RSCU and SCUO) was related to GC₃ (GC content of 3rd nucleotide in codon) bias. Six GO (Gene ontology) categories and the number of methylation targets were influenced by GC₃. Codon usage patterns comparison among 23 vertebrates showed species specificities by using GC contents, codon usage and codon context analysis. This work provided new insights into fish biology and new information for breeding projects.     

Optimized Hemolysin Type 1 Secretion System in Escherichia coli by Directed Evolution of the Hly Enhancer Fragment and Including a Terminator Region

Type 1 secretion systems (T1SS) have a relatively simple architecture compared to other classes of secretion systems and therefore, are attractive to be optimized by protein engineering. Here, we report a KnowVolution campaign for the hemolysin (Hly) enhancer fragment, an untranslated region upstream of the hlyA gene, of the hemolysin T1SS of Escherichia coli to enhance its secretion efficiency. The best performing variant of the Hly enhancer fragment contained five nucleotide mutations at five positions (A30U, A36U, A54G, A81U, and A116U) resulted in a 2-fold increase in the secretion level of a model lipase fused to the secretion carrier HlyA1. Computational analysis suggested that altered affinity to the generated enhancer fragment towards the S1 ribosomal protein contributes to the enhanced secretion levels. Furthermore, we demonstrate that involving a native terminator region along with the generated Hly enhancer fragment increased the secretion levels of the Hly system up to 5-fold.