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31.
Iori Era Yasutaka Kitagawa Natsumi Yasuda Taigo Kamimura Naoka Amamizu Hiromasa Sato Keigo Cho Mitsutaka Okumura Masayoshi Nakano 《Molecules (Basel, Switzerland)》2021,26(20)
The effect of hydrogen bonds around the active site of Anabaena [2Fe-2S] ferredoxin (Fd) on a vertical ionization potential of the reduced state (IP(red)) is examined based on the density functional theory (DFT) calculations. The results indicate that a single hydrogen bond increases the relative stability of the reduced state, and shifts IP(red) to a reductive side by 0.31–0.33 eV, regardless of the attached sulfur atoms. In addition, the IP(red) value can be changed by the number of hydrogen bonds around the active site. The results also suggest that the redox potential of [2Fe-2S] Fd is controlled by the number of hydrogen bonds because IP(red) is considered to be a major factor in the redox potential. Furthermore, there is a possibility that the redox potentials of artificial iron-sulfur clusters can be finely controlled by the number of the hydrogen bonds attached to the sulfur atoms of the cluster. 相似文献
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The enantioselective Diels-Alder reactions of 1-phenoxycarbonyl-1,2-dihydropyridine with 1-alkylated acryloyl-pyrazolidin-3-ones using chiral cationic palladium-phosphinooxazolidine (Pd-POZ) catalyst afforded chiral isoquinuclidines with excellent enantioselectivity (up to 97% ee). 相似文献
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Masami Kuriyama Natsumi Hanazawa Yusuke Abe Kotone Katagiri Shimpei Ono Kosuke Yamamoto Osamu Onomura 《Chemical science》2020,11(31):8295
Metal-free N- and O-arylation reactions of pyridin-2-ones as ambident nucleophiles have been achieved with diaryliodonium salts on the basis of base-dependent chemoselectivity. In the presence of N,N-diethylaniline in fluorobenzene, pyridin-2-ones were very selectively converted to N-arylated products in high yields. On the other hand, the O-arylation reactions smoothly proceeded with the use of quinoline in chlorobenzene, leading to high yields and selectivities. In these methods, a variety of pyridin-2-ones in addition to pyridin-4-one and a set of diaryliodonium salts were accepted as suitable reaction partners.The metal-free N- and O-arylation reactions of pyridin-2-ones with diaryliodonium salts were achieved on the basis of base-dependent chemoselectivity. 相似文献
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We describe the synthesis of novel C4-linked imidazole ribonucleoside phosphoramidite (PA) 1a by which the imidazole moiety is incorporated into VS ribozyme to study its role in general acid and base catalysis. Investigation of protecting groups for the imidazole-N first indicated that pivaloyloxymethyl (POM) was adequate as an N-protecting group for the imidazole nucleoside, which could be readily removed under mild basic conditions. Further, the synthetic method was extended to synthesis of 2′-deoxy- and 2′-O-allyl nucleoside PAs 1b and 1c. 相似文献
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Potent Th2 Cytokine Bias of Natural Killer T Cell by CD1d Glycolipid Ligands: Anchoring Effect of Polar Groups in the Lipid Component 下载免费PDF全文
Dr. Shinsuke Inuki Emi Kashiwabara Natsumi Hirata Junichiro Kishi Etsuko Nabika Prof. Dr. Yukari Fujimoto 《Angewandte Chemie (International ed. in English)》2018,57(31):9655-9659
Th2‐biasing CD1d ligands are attractive potential candidates for adjuvants and therapeutic drugs. However, the number of potent ligands is limited, and their biasing mechanism remain unclear. Herein, a series of novel Th2‐biasing CD1d glycolipid ligands, based on modification of their lipid part, have been identified. These have shown high binding affinities and efficient Th2 cytokine production. Importantly, the truncated acyl chain containing variants still retain their binding affinities and agonistic activities, which can be associated with an “anchoring effect,” that is, formation of a buried hydrogen bond between a polar group on the acyl chain and the CD1d lipid‐binding pocket. The analysis indicated that the appearance rates of ligand–CD1d complexes on the cell surface were involved in Th2‐biasing responses. The designed ligands, having the anchor in the shorter lipid part, are one of the most potent Th2‐biasing ligands among the known ligands. 相似文献
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Iwasaki Y Mochizuki K Nakano Y Maruya N Goto M Maruyama Y Ito R Saito K Nakazawa H 《Biomedical chromatography : BMC》2012,26(1):41-50
Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are well-known and important contributors to oxidative and nitrosative stress in several diseases. Hydroxylated phenylalanine and nitrated tyrosine products appear to be particularly susceptible targets of oxidative and nitrosative stress. We compared fluorescence reagents for their potential use in the analysis of hydroxylated phenylalanine and nitrated tyrosine products with a high-sensitivity and high-specificity HPLC-UV-FL technique. The analytes were extracted from serum via solid-phase extraction on Waters Oasis MCX cartridges. Chromatographic separation was achieved on an ODS column (Capcell Pak MG II; 150 × 2.0 mm) using a gradient mobile phase consisting of 20 mm sodium phosphate buffer (adjusted to pH 3.0) and acetonitrile. The method quantification limit for 4-nitrophenylalanine, m-tyrosine, and 3-nitrotyrosine was 0.1 μm. The relative standard deviation of the precision and accuracy was acceptable at the spiked concentration of 0.1 μm for 4-nitrophenylalanine, m-tyrosine and 3-nitrotyrosine. The method could be used for the in vitro analysis of serum samples. 相似文献
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The asymmetric synthesis of an acyclic anti-β-alkoxy ether was achieved by the Ireland-Claisen rearrangement of Z-3-alkoxy-2-propenyl glycolate ester, prepared from Garner’s aldehyde, a glycolic acid derivative, and ethynyl N,N-diisopropylcarbamate. The resulting acyclic ether was facilely converted to seven- and eight-membered cyclic ethers via processes involving ring-closing olefin metatheses. 相似文献
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[Structure: see text] The 2-bromobenzylidene group, designed as a novel protecting/radical-translocating (PRT) group, proved to be effective for an unusual 1,6-hydrogen transfer reaction. Using this PRT group, 4-branched ribose derivatives were stereoselectively prepared. 相似文献