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61.
Trifluoroacetonitrile was condensed with diethyl malonate to give a novel ethyl 2,6-bis(trifluoromethyl)-4-hydroxypyrimidine-5-carboxylate ( 2 ) in 88% yield. Derivations of 2 are also described. 相似文献
62.
Show-An Chen Hsiou-Jeng Shy 《Journal of polymer science. Part A, Polymer chemistry》1985,23(9):2441-2446
Polyacetylene (PA) deposited on a platinum surface is synthesized by electrochemical polymerization of acetylene in a cell with platinum strip as cathode, nickel strip as anode, and nickel bromide in acetonitrile as electrolyte. The electrolytic solution is presaturated with acetylene. The PA so produced has a granular morphology and high surface area (79 m2/g), and is insoluble. Polymerization at lower temperature gives higher content in cis units. It has the same chemical structure as that produced using the Shirakawa method as examined by elemental analysis, infrared spectroscopy, x-ray diffraction, and differential scanning calorimetry. 相似文献
63.
Yamada Ji Satoki S Mishima S Akashi N Takahashi K Masuda N Nishimoto Y Takasaki S Anzai H 《The Journal of organic chemistry》1996,61(12):3987-3995
Efficient synthetic methods for the construction of a wide variety of unsymmetrical tetrathiafulvalenes (TTFs) via the Me(3)Al-promoted reactions of organotin thiolates or selenolates with esters are described. Reaction of tin thiolates (3a-c and 10) and selenolates (3d, 5, and 7) with esters (11a,b) in the presence of Me(3)Al as a Lewis acid gave dihydrotetrathiafulvalene derivatives (12, 14, 15, and 17-20) and 1,3-dithiane derivatives (13 and 16). In addition, the synthesis of diselenadithiafulvalene derivatives (25-28) could be accomplished by Me(3)Al-mediated reaction of tin thiolate (2a) or selenolates (3d and 5) with esters (22a, 22d, and 24). Furthermore, the application of the Me(3)Al-promoted reaction of tin thiolate (34) with esters (11a-b, 22a-d, and 35a-b) for the synthesis of unsymmetrical TTFs-fused donors enabled us to obtain various TTFs-fused systems (29-33) in short steps. 相似文献
64.
HIV-1 cell entry is mediated by sequential interactions of the envelope protein gp120 with the receptor CD4 and a coreceptor, usually CCR5 or CXCR4, depending on the individual virion. Considerable efforts on exploiting the HIV coreceptors as drug targets have led to the new class of coreceptor antagonists. While these antiretroviral drugs aim at preventing virus/coreceptor interaction by binding to host proteins, neutralizing antibodies directed against the coreceptor-binding sites on gp120 have attracted attention as possible vaccine candidates. However, both approaches are complicated by the multiple protective mechanisms of gp120 which allow for rapid escape from selective pressures exerted by drugs or antibodies. Thus, advances in rational drug and vaccine design rely heavily on improved insights into the relation between genotype and phenotype, the evolution of coreceptor usage, and, ultimately the structural biology of coreceptor usage and inhibition. The third variable (V3) loop of gp120, crucially involved in all these aspects, will be a major focus of this review. 相似文献
65.
A. Hamzah C. W. Beh S. B. Sarmani J. Y. Liow L. Abugassa 《Journal of Radioanalytical and Nuclear Chemistry》2004,259(3):499-503
Chinese herbs are accepted as an alternative medicine for specific treatment of illness. It is important to know the contents
of these herbs that might cause gene mutation. Ten most popular herbs used in Malaysia were analyzed by instrumental neutron
activation analysis. A total of 16 trace and major elements were determined and the concentration of elements varied depending
on the origin of the herb. The study showed that the toxic elements found in the samples were below the levels prescribed
by health regulations. The mutagenicity test showed that there was no toxic effect due to the heavy metals present in the
herbs.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
66.
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68.
Hari M. Srivastava Kun‐Jen Chung Jui‐Jung Liao Shy‐Der Lin Sheng‐Tu Chuang 《Mathematical Methods in the Applied Sciences》2019,42(11):3967-3977
Several recent studies in supply chain system and related areas explored various economic order quantity (EOQ) models for noninstantaneous deteriorating items with imperfect quality and trade credit financing. In particular, in the year 2007, Teng et al investigated an EOQ model in which the supplier offers the retailer the permissible delay period M and the retailer, in turn, provides the trade credit period N (with ) to his/her customers. The main purpose of this article is twofold: (a) It modifies the annual total relevant cost TVC(T) in the study of Teng et al and presents the correct derivations of TVC(T) by applying mathematical analytic tools and techniques. (b) It exposes some logical and mathematical problems in the proof of Theorem 1 in Teng et al. It also corrects and overcomes all of the errors and shortcomings by systematically presenting the complete and mathematical solution procedures in order to locate all optimal solutions for the model in Teng et al. 相似文献
69.
Yuning Hong Hao Xiong Jacky Wing Yip Lam Dr. Matthias Häußler Dr. Jianzhao Liu Yong Yu Yongchun Zhong Dr. Herman H. Y. Sung Dr. Ian D. Williams Prof. Kam Sing Wong Prof. Ben Zhong Tang Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(4):1232-1245
Whereas most conventional DNA probes are flat disklike aromatic molecules, we explored the possibility of developing quadruplex sensors with nonplanar conformations, in particular, the propeller‐shaped tetraphenylethene (TPE) salts with aggregation‐induced emission (AIE) characteristics. 1,1,2,2‐Tetrakis[4‐(2‐triethylammonioethoxy)phenyl]ethene tetrabromide (TPE‐ 1 ) was found to show a specific affinity to a particular quadruplex structure formed by a human telomeric DNA strand in the presence of K+ ions, as indicated by the enhanced and bathochromically shifted emission of the AIE fluorogen. Steady‐state and time‐resolved spectral analyses revealed that the specific binding stems from a structural matching between the AIE fluorogen and the DNA strand in the folding process. Computational modeling suggests that the AIE molecule docks on the grooves of the quadruplex surface with the aid of electrostatic attraction. The binding preference of TPE‐ 1 enables it to serve as a bioprobe for direct monitoring of cation‐driven conformational transitions between the quadruplexes of various conformations, a job unachievable by the traditional G‐quadruplex biosensors. Methyl thiazolyl tetrazolium (MTT) assays reveal that TPE‐ 1 is cytocompatible, posing no toxicity to living cells. 相似文献
70.
Li Z Dong Y Mi B Tang Y Häussler M Tong H Dong Y Lam JW Ren Y Sung HH Wong KS Gao P Williams ID Kwok HS Tang BZ 《The journal of physical chemistry. B》2005,109(20):10061-10066
We synthesized a group of silole regioisomers 1(x,y), whose photoluminescence varied dramatically with its regiostructure. By internally hindering the intramolecular rotation, we succeeded in creating a novel silole (1(3,4)) that is strongly luminescent in solutions and whose fluorescence quantum yield in acetone is as high as 83%. We revealed that 1(3,4) was a sensitive chemosensor capable of optically discriminating nitroaromatic regioisomers of p-, o-, and m-nitroanilines. Against general belief, crystal formation of 1(2,4) blue-shifted its emission color and boosted its emission efficiency. The light-emitting diode based on the crystal of 1(2,4) emitted a strong blue light (464 nm) in a high current efficiency (5.86 cd/A). 相似文献