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971.
Piao LZ Park HR Park YK Lee SK Park JH Park MK 《Chemical & pharmaceutical bulletin》2002,50(3):309-311
Currently, aloesin is used in the cosmetic industry as a whitening agent because it inhibits tyrosinase activity. Aloesin is a C-glycosylated chromone compound isolated from aloe, and it is difficult to synthesize because of C-glycosyl moiety in the molecule. The purpose of this study is to search for a new chromone compound which is easy to synthesize and which posesses stronger tyrosinase inhibitory activity than aloesin. Fourteen chromone derivatives were synthesized and screened for their mushroom-tyrosinase inhibitory activity. 5-Methyl-7-methoxy-2-(2'-benzyl-3'-oxobutyl)chromone (15) showed the strongest activity among tested compounds. Its activity was not only stronger than aloesin, but also stronger than arbutin and kojic acid. The kinetic analysis revealed a competitive inhibition of 15 with tyrosinase for the L-tyrosine binding site. 相似文献
972.
Yong ZHANG Ke Li ZHANG* Man Ke JIA Hao TANG Ju Tang SUN Liang Jie YUAN College of Chemistry Molecular science Department of Chemistry Wuhan University Wuhan 《中国化学快报》2002,13(6):587-588
In recent years, the research on rare earth became a focus, and a lot of rare earth complex compounds with AB2O4 stoichiometry were prepared1-3. The compound SnDy2O4 is expected to spinel-type phase while it exhibits a new structure type. SnDy2O4 was prepared by the thermal decomposition of the oxalate precursor that was prepared by rheological phase reaction method. SnO(AR), Dy2O3(99.9%) and H2C2O4·2H2O are ground in molar ratio 1:1:4.1, and placed into the reaction apparatus. … 相似文献
973.
Lunn MR Root DE Martino AM Flaherty SP Kelley BP Coovert DD Burghes AH Man NT Morris GE Zhou J Androphy EJ Sumner CJ Stockwell BR 《Chemistry & biology》2004,11(11):1489-1493
Most patients with the pediatric neurodegenerative disease spinal muscular atrophy have a homozygous deletion of the survival motor neuron 1 (SMN1) gene, but retain one or more copies of the closely related SMN2 gene. The SMN2 gene encodes the same protein (SMN) but produces it at a low efficiency compared with the SMN1 gene. We performed a high-throughput screen of approximately 47,000 compounds to identify those that increase production of an SMN2-luciferase reporter protein, but not an SMN1-luciferase reporter protein. Indoprofen, a nonsteroidal anti-inflammatory drug (NSAID) and cyclooxygenase (COX) inhibitor, selectively increased SMN2-luciferase reporter protein and endogenous SMN protein and caused a 5-fold increase in the number of nuclear gems in fibroblasts from SMA patients. No other NSAIDs or COX inhibitors tested exhibited this activity. 相似文献
974.
Organic-inorganic hybrid composites were prepared by the sol-gel method for the hard coating agent of transparent plastic, and their abrasion resistance, optical and surface characteristics were evaluated. Methyltriethoxy-silane (MTES) and colloidal silica were used as starting materials. The addition of MTES to colloidal silica enabled the formation of dense thin films with very smooth surface on the substrates. The thin films were strongly adhered to the substrates without primer treatment. The abrasion resistance increased with the increase in the ratio of MTES to the colloidal silica. Optimal amount of MTES for the hard coating agent was 100 wt% to the colloidal silica. The addition of curing catalyst, tetramethylammonium formate was found to be very effective to enhance the adhesion strength of coating agent to the substrates and reduced curing time. 相似文献
975.
Four-carbon-tethered pyridones undergo photocycloaddition to give exclusively trans-[4 + 4] products. The presence of a tether alcohol engenders a solvent-dependent diastereoselectivity for the cycloaddition by intramolecular hydrogen bonding to the adjacent pyridone. Following cycloaddition, the alcohol can deliver a carbonyl group to the proximal, hindered amide nitrogen, leading to a very facile amide hydrolysis. 相似文献
976.
Lee HI Pak C Shin CH Chang H Seung D Yie JE Kim JM 《Chemical communications (Cambridge, England)》2005,(48):6035-6037
Combining both nano-replication and nano-imprinting techniques using dual silica templates provides a simple way to synthesize ordered mesoporous carbons with bimodal pore size distributions ( approximately 1.5 nm and approximately 3.5 nm). 相似文献
977.
Li Li Zheng Lv Zhongwei Man Zhenzhen Xu YuLing Wei Hua Geng Hongbing Fu 《Chemical science》2021,12(9):3308
Amyloid fibrils are associated with many neurodegenerative diseases. In situ and in vivo visualization of amyloid fibrils is important for medical diagnostics and requires fluorescent probes with both excitation and emission wavelengths in the far-red and NIR region, and simultaneously with high binding-affinity to amyloid fibrils and the ability to cross the blood–brain barrier, which, however, remain a challenge. Here, we rationally design and synthesize an excellent polarity-sensitive two-photon excited NIR fluorophore (TZPI) based on a donor (D)–acceptor (A)-ion compound. The electron-rich carbazole group and the ionic pyridinium bromide group, linked by an electron-poor π-conjugated benzothiadiazole group, ensure strong near infrared (NIR) emission. Furthermore, the lipophilic carbazole together with the benzothiadiazole group facilitates docking of the probe in the hydrophobic domains of amyloid aggregates with the dissociation constant Kd = 20 nM and 13.5-fold higher binding affinity to insulin fibrils than the commercial probe ThT. On association with the amyloid fibrils, the tiny decrease in polarity leads to a large increase in its NIR emission intensity with an on–off ratio > 10; meanwhile, the TZPI probe exhibits a quantum yield of up to 30% and two-photon absorption cross-section values of up to 467.6 GM at 890 nm. Moreover, the application of TZPI in two-photon imaging is investigated. The ultrahigh binding affinity, the strong NIR emission, the good two-photon absorption properties, the high photo-stability, the appropriate molecular mass of 569 Da and the lipophilicity with log P = 1.66 ± 0.1 to cross the BBB make TZPI promising as an ideal candidate for detecting amyloid plaques in vivo.A polarity-active NIR probe based on the transformation from the CT state to the LE state for two-photon imaging of amyloid fibrils. 相似文献
978.
Tetra-oligophenylene substituted calix[4]arene assemblies containing up to three phenylene units have been synthesized by a convergent approach using Suzuki cross-coupling and their optical properties were investigated and compared with the corresponding monomer. 相似文献
979.
Fung WK Huang X Man ML Ng SM Hung MY Lin Z Lau CP 《Journal of the American Chemical Society》2003,125(38):11539-11544
The indenylruthenium hydride complex (eta(5)-C(9)H(7))Ru(dppm)H was found to be active in catalyzing the hydration of nitriles to amides. The chloro analogue (eta(5)-C(9)H(7))Ru(dppm)Cl was, however, found to be inactive. Density functional theory calculations at the B3LYP level provide explanations for the effectiveness of the hydride complex and the ineffectiveness of the chloro complex in the catalysis. It is learned that the presence of a Ru-H.H-OH dihydrogen-bonding interaction in the transition state lowers the reaction barrier in the case of (eta(5)-C(9)H(7))Ru(dppm)H, but in the chloro system, the corresponding transition state does not contain this type of interaction and the reaction barrier is much higher. A similar dihydrogen-bond-promoting effect is believed to be responsible for the catalytic activity of the hydrotris(pyrazolyl)borato (Tp) ruthenium complex TpRu(PPh(3))(CH(3)CN)H in CH(3)CN hydration. The chloro analogue TpRu(PPh(3))(CH(3)CN)Cl shows no catalytic activity. 相似文献
980.
Kwang Seok Oh Byung Gwon Lee Man Seok Han Yong Gun Shul 《Reaction Kinetics and Catalysis Letters》2002,77(1):51-58
The effect of calcination conditions on MoO3/SiO2 catalysts for the synthesis of methylphenyl carbonate was investigated in terms of catalytic activities and surface properties. The calcination temperature was varied in the range of 300 to 800oC. These calcination conditions have shown a close relationship with the catalyst activities. The optimal calcination temperature of MoO3/SiO2was found to be around 550-600oC. The catalysts were characterized by XRD, SEM, FT-IR and XPS analysis. 相似文献