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991.
Yan-Fang Liu Rong-Zhen Liao Wan-Jian Ding Jian-Guo Yu Ruo-Zhuang Liu 《Journal of biological inorganic chemistry》2011,16(5):745-752
The reaction mechanism of the hydration of acetylene to acetaldehyde catalyzed by [WIVO(mnt)2]2− (where mnt2− is 1,2-dicyanoethylenedithiolate) is studied using density functional theory. Both the uncatalyzed and the catalyzed reaction
are considered to find out the origin of the catalysis. Three different models are investigated, in which an aquo, a hydroxo,
or an oxo coordinates to the tungsten center. A first-shell mechanism is suggested, similarly to recent calculations on tungsten-dependent
acetylene hydratase. The acetylene substrate first coordinates to the tungsten center in an η2 fashion. Then, the tungsten-bound hydroxide activates a water molecule to perform a nucleophilic attack on the acetylene,
resulting in the formation of a vinyl anion and a tungsten-bound water molecule. This is followed by proton transfer from
the tungsten-bound water molecule to the newly formed vinyl anion intermediate. Tungsten is directly involved in the reaction
by binding and activating acetylene and providing electrostatic stabilization to the transition states and intermediates.
Three other mechanisms are also considered, but the associated energetic barriers were found to be very high, ruling out those
possibilities. 相似文献
992.
Kamei H Ding Y Kajimura S Wells M Chiang P Duan C 《Development (Cambridge, England)》2011,138(4):777-786
Animals respond to adverse environments by slowing down or arresting growth and development. Upon returning to normal conditions, they often show compensatory acceleration in growth and developmental rate. This phenomenon, known as `catch-up' growth, is widely documented in the animal kingdom. The underlying molecular mechanisms, however, are poorly understood. Using the zebrafish embryo as an experimental model system, we tested the hypothesis that changes in IGF signaling activities play an important role in the accelerated growth and temporal development resulting from re-oxygenation following hypoxia. We show that chronic hypoxia reduced, and re-oxygenation accelerated, embryonic growth and developmental rate. Whereas hypoxia repressed the Igf1 receptor and its downstream Erk1/2 and Akt signaling activities, re-oxygenation restored their activities. Specific inhibition of Igf1 receptor signaling during re-oxygenation by genetic and pharmacological approaches attenuated catch-up growth. Further analysis showed that whereas PI3K-Akt is required in both normal and catch-up growth, Mek1/2-Erk1/2 activation induced by elevated IGF signaling during re-oxygenation is particularly crucial for catch-up growth. These results suggest that the evolutionarily conserved IGF signaling pathway coordinates growth and temporal development in zebrafish embryos in response to oxygen availability. 相似文献
993.
Ding Ding Huang Peng Pan Ying-Qiu Chen Shu-Qing 《World journal of microbiology & biotechnology》2011,27(12):2957-2967
In China, staphylococcin injection has been commonly used in the combined treatment of cancer to enhance the systemic immune
response and reduce the toxicities associated with chemotherapy and radiation therapy. It is claimed that the main active
component in the injection is staphylococcal enterotoxin C2 (SEC2). To determine whether other serological types of staphylococcal
enterotoxins (SEs) could also be present in the injection products, in this study, the distribution of se genes (from sea to see, from seg to seu) in the one and only production strain of Staphylococcus aureus from one manufacturing company was analyzed by PCR method. In addition, sek and seq genes were cloned from the strain and the corresponding recombinant proteins, rSEK and rSEQ, were expressed in Escherichia coli and purified by affinity chromatography and anion-exchange chromatography. The superantigenic properties of the two recombinant
proteins were then measured by MTT method. The PCR results showed that seven se genes are harbored by the production strain. However, sec2 gene was not detected. The results of MTT assay showed that rSEK and rSEQ could elicit strong stimulatory effects on proliferation
and cytotoxicity of murine splenocytes in vitro. Overall, the results in this study indicated that one or a plurality of the
seven SEs may be present in the related products, and that the two recombinant SEs are promising candidates as immunomodulatory
agents for cancer therapy. 相似文献
994.
Most of the DNA logic gates employ fluorescent or colorometric signals as their outputs, which were limited by the cumbersome handling procedures, lack of portability and lower sensitivity. To the best of our knowledge, the logic gates with electrochemiluminescent (ECL) signal as their outputs have not been reported. In response, we report here the construction of DNA molecular logic gates that produce ECL signals as their outputs, having the advantages of versatility, low background and simplified optical setup. The logic gates are based on the T-rich or C-rich oligonucleotides for the selective analysis of Hg(2+) and Ag(+) ions using energy or electron transfer-quenching path. Efficient and stable quenching of ECL of Ru bis(2,2'-bipyridine) (2,2'-bipyridine-4,4'-dicarboxylic acid) N-hydroxysuccinimide ester by oxidizing ferrocene at the Au electrode enabled us to use Hg(2+) and Ag(+) ions as inputs that activate logic gates, and to execute ECL of Ru(II) as readout signals for logic gate operations. 相似文献
995.
Wang Pin-Mei Wu Xue-Chang Chi Xiao-Qin Li Yu-Dong Zheng Dao-Qiong Ding Rui Min Hang 《World journal of microbiology & biotechnology》2011,27(1):185-188
To overcome the drawbacks of protoplast fusion in industrial breeding, strain-specific molecular markers were applied to select
hybrids of industrial Saccharomyces cerevisiae strains. Random Amplified Polymorphic DNA (RAPD) analysis was used to generate strain-specific RAPD markers for two industrial
yeast strains, Z8 and Z9. For industrial and technical controls, two RAPD markers with non-coding regions were converted into
stable Sequence Characterized Amplified Region (SCAR) markers. Hybrids of Z8 and Z9 were obtained by protoplast fusion in
combination with SCAR markers and were found to increase ethanol production by 4.3–8.1%. Results suggested that protoplast
fusion could be combined with RAPD-SCAR molecular markers and applied in industrial breeding instead of auxotrophic markers. 相似文献
996.
997.
Ding L Zhu J Zheng C Sheng C Qi J Liu X Han G Zhao J Lv J Zhou Y 《Bioorganic & medicinal chemistry letters》2011,21(22):6674-6677
A series of new substituted 4-amino-N-(diaminomethylene) benzenesulfonamides were synthesized and their in vitro acrosin inhibitory activities were evaluated. Most of the compounds showed potent acrosin inhibitory activities with compounds 4o and 4p being significantly more potent than the control compound N-alpha-tosyl-l-lysyl-chloromethyl-ketone (TLCK). The compounds provide a new scaffold for the development of acrosin inhibitory agents. 相似文献
998.
Efe JA Ding S 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2011,366(1575):2208-2221
Small molecules have been playing important roles in elucidating basic biology and treatment of a vast number of diseases for nearly a century, making their use in the field of stem cell biology a comparatively recent phenomenon. Nonetheless, the power of biology-oriented chemical design and synthesis, coupled with significant advances in screening technology, has enabled the discovery of a growing number of small molecules that have improved our understanding of stem cell biology and allowed us to manipulate stem cells in unprecedented ways. This review focuses on recent small molecule studies of (i) the key pathways governing stem cell homeostasis, (ii) the pluripotent stem cell niche, (iii) the directed differentiation of stem cells, (iv) the biology of adult stem cells, and (v) somatic cell reprogramming. In a very short period of time, small molecules have defined a perhaps universally attainable naive ground state of pluripotency, and are facilitating the precise, rapid and efficient differentiation of stem cells into somatic cell populations relevant to the clinic. Finally, following the publication of numerous groundbreaking studies at a pace and consistency unusual for a young field, we are closer than ever to completely eliminating the need for genetic modification in reprogramming. 相似文献
999.
三种接种物启动Anammox-EGSB反应器的性能 总被引:2,自引:0,他引:2
为了优选接种物和加速Anammox反应器启动,分别以厌氧产甲烷污泥 (Anaerobic methanogenic sludge,AMS)、新鲜厌氧氨氧化污泥 (Fresh Anammox sludge,FAS) 和储藏厌氧氨氧化污泥 (Stored Anammox sludge,SAS) 作为接种物,研究了厌氧氨氧化膨胀颗粒污泥床 (Anammox-EGSB) 反应器 (R1、R2和R3) 的启动性能。结果表明:3种接种物均能成功启动Anammox-EGSB反应器,启动性能的优劣次序为:R2 (接种物为 相似文献
1000.