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191.
192.
Aetheramides A and B are very potent anti-HIV agents. An enantioselective synthesis of a MEM-protected aetheramide A derivative is described. The synthesis was accomplished in a convergent and stereoselective manner. The key reactions involved asymmetric dihydroxylation, asymmetric allylation, asymmetric syn-aldol reactions, and asymmetric hydrogenation. 相似文献
193.
A fast, simple, and efficient protocol for the direct conversion of alcohols and aldehydes to methyl ester has been developed using TsNBr2 without any catalyst. The one pot reaction proceeds in the presence of a base at room temperature in methanol, to produce the corresponding methyl ester in high yield within a short time. 相似文献
194.
Saraca asoca is an IUCN red-listed tree species that extensively famous in the Ayurvedic medicine field. Saraca asoca (Roxb.) de Wilde belongs to the family Fabaceae, has been used to treat various gynecological disorders, bacterial infections, worm infestations, haemmorhagic dysentery, uterine pain, skin diseases, cancer, circulatory, cardiovascular disorders, and many others. All parts of the Saraca asoca have medicinal values. Numerous antioxidant compounds like flavonoids, catechin, beta-sitosterol, lignin glycosides are present in the bark, leaf, and flower of Saraca asoca plant, which help to stabilize free radicals molecules that are associated with the development of cancer conditions. Currently in the cancer research study field new and more effective modes of natural therapies are recently being analyzed. Traditional medicines have been used for their preventative role against various diseases in the human population. Plant based therapy for cancer prevention is becoming more demanding due to its various unique properties such as natural chemical composition, less expensiveness, naturally available., easily orally administrable, significant chemo-protective activities, nontoxic to normal cells in the body, less side effects compared to other synthetic chemotherapeutic drugs. The chemotherapeutic drugs will be harmful to both cancer and normal cells. Additionally, some common side effects or health consequences like vomiting, nausea, bleeding, hair fall, alopecia, hyperuricemia, thrombocytopenia, bone marrow depression, mucositis are very common after chemotherapeutic drug treatment in cancer. This review paper summarizes the evidences which agree with the fact that flavonoids and other phenolic compounds in Saraca asoca plant possess significant antioxidant activity and an efficient chemopreventive characteristic against different types of cancer. This paper reviews the anticancer activities of Saraca asoca bark and flower and discusses the potential preventive roles of phenolic and flavonoids compounds, present in bark and flower of Saraca asoca in the cancer treatment process. 相似文献
195.
Arya Ghosh Subash C.B. Gopinath Sayeed Mohammad Firdous Santheraleka Ramanathan 《印度化学会志》2022,99(8):100604
Human Mammary Tumor Virus (HMTV) or Mouse Mammary Tumor Virus holds similarity as an endogenous onco-retrovirus belongs to retroviridae family, predominantly infects the epithelial cell of human as well as mouse. With the recognition of nano-biosensor in nanotechnology, ideal interdigitated electrode (IDE) was genuinely performed for HMTV detection. Aluminium enriched IDE (AlIDE) was fabricated for high performance detection with a cost-effective photolithography technique. In this research, (3-glycidyloxypropyl) trimethoxysilane refined platform was selected to detect the conductivity with HMTV target DNA interaction on the designed AlIDE. Strong binding affinity of streptavidin-biotin with target DNA enhanced the sensitivity by empowering higher number of HMTV probe and target complementation on sensing surface. Furthermore, the target DNA was immobilized on probe modified AlIDE and a quantitative value of 100 aM attained as a lowest detection. A linear with dose-dependent duplex formation was shown with the regression coefficient value of 0.964. Negative control has shown insignificant detection at 10 pM, which justifies the higher fold discrimination with specificity. The excellence of AlIDE performance in detection of HMTV may pave the way for more verification on other diseases. 相似文献
196.
197.
Sushant G. Ghosh Muhammed Amir 《The European Physical Journal C - Particles and Fields》2015,75(11):553
We investigate the horizon structure and ergosphere in a rotating Bardeen regular black hole, which has an additional parameter (g) due to the magnetic charge, apart from the mass (M) and the rotation parameter (a). Interestingly, for each value of the parameter g, there exists a critical rotation parameter (\(a=a_{E}\)), which corresponds to an extremal black hole with degenerate horizons, while for \(a<a_{E}\) it describes a non-extremal black hole with two horizons, and no black hole for \(a>a_{E}\). We find that the extremal value \(a_E\) is also influenced by the parameter g, and so is the ergosphere. While the value of \(a_E\) remarkably decreases when compared with the Kerr black hole, the ergosphere becomes thicker with the increase in g. We also study the collision of two equal mass particles near the horizon of this black hole, and explicitly show the effect of the parameter g. The center-of-mass energy (\(E_\mathrm{CM}\)) not only depend on the rotation parameter a, but also on the parameter g. It is demonstrated that the \(E_\mathrm{CM}\) could be arbitrarily high in the extremal cases when one of the colliding particles has a critical angular momentum, thereby suggesting that the rotating Bardeen regular black hole can act as a particle accelerator. 相似文献
198.
S. Nagaraj C. V. Vishnuvardhan Sajal Ghosh R. Sridharan 《Journal of Thermal Analysis and Calorimetry》2014,115(2):1835-1839
The phase diagram of binary LiBr–CaBr2 system was investigated using differential thermal analysis (DTA) between room temperature and 800 °C. From the DTA results obtained over the entire range of composition from pure LiBr to pure CaBr2 in steps of ~5 mol%, the phase diagram was constructed and is reported here. The results indicated the possible existence of a compound at 50 mol% LiBr, namely, LiCaBr3. The compound undergoes peritectic decomposition at 552 °C. The system shows a eutectic reaction at 532 °C between this compound and LiBr phase, and the eutectic composition is close to 80 mol% LiBr. The compound LiCaBr3 decomposes into CaBr2 and LiBr phases below 272 °C. Co-existing phases in different phase fields are characterized by X-ray diffraction analysis. 相似文献
199.
Spectroscopic and Computational Study of a Nonheme Iron Nitrosyl Center in a Biosynthetic Model of Nitric Oxide Reductase
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Dr. Saumen Chakraborty Julian Reed Matthew Ross Dr. Mark J. Nilges Igor D. Petrik Dr. Soumya Ghosh Prof. Dr. Sharon Hammes‐Schiffer Prof. Dr. J. Timothy Sage Prof. Dr. Yong Zhang Prof. Dr. Charles E. Schulz Prof. Dr. Yi Lu 《Angewandte Chemie (International ed. in English)》2014,53(9):2417-2421
A major barrier to understanding the mechanism of nitric oxide reductases (NORs) is the lack of a selective probe of NO binding to the nonheme FeB center. By replacing the heme in a biosynthetic model of NORs, which structurally and functionally mimics NORs, with isostructural ZnPP, the electronic structure and functional properties of the FeB nitrosyl complex was probed. This approach allowed observation of the first S=3/2 nonheme {FeNO}7 complex in a protein‐based model system of NOR. Detailed spectroscopic and computational studies show that the electronic state of the {FeNO}7 complex is best described as a high spin ferrous iron (S=2) antiferromagnetically coupled to an NO radical (S= 1/2) [Fe2+‐NO.]. The radical nature of the FeB‐bound NO would facilitate N? N bond formation by radical coupling with the heme‐bound NO. This finding, therefore, supports the proposed trans mechanism of NO reduction by NORs. 相似文献
200.
The weakly ionic amphiphilic diblock copolymer polystyrene-b-poly(acrylic acid) was synthesized by nitroxy radical-mediated living radical polymerization with precise control of block length, block ratio, and polydispersity. Systematical surface tension experiments and foam formation observations revealed that this polymer was non-surface active under neutral and alkaline (pH 10) conditions, while it was surface active under an acidic condition (pH 3). This result supports our proposed origin of non-surface activity; the image charge repulsion at the air/water interface is essential in addition to very stable micelle formation in the bulk solution. At a higher pH (pH 12), the polymer showed slight surface activity since the added NaOH played a role as an added salt. The critical micelle concentration (cmc) was estimated by static light scattering. Cmc increased with increasing added salt (NaCl) concentration as was observed for other strongly ionic non-surface-active polymers. Hence, this trend is characteristic for non-surface-active polymers. The pH dependence of cmc was minimum at pH 8–10. Since the acrylic acid block is fully ionized under this condition, the strong image charge repulsion at this condition accelerated micelle formation at a low polymer concentration, which consequently decreased cmc. Micelles in bulk solution were confirmed by dynamic light scattering, and the salt concentration and pH dependencies of the hydrodynamic radius of the micelles were also estimated. The pH-responsive non-surface-active/surface-active transition observed in this study strongly supports the fact that the image charge repulsion is an essential factor for non-surface activity in addition to stable micelle formation in solution. 相似文献