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RISS 인기검색어
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- 저자 : Kenichi Komura (검색결과 5 건)
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Development of Ganglioside Probes for Live Imaging of Lipid Rafts
Naoko Komura,Hiromune Ando,Kenichi Suzuki,Rahul Chadda,Yasuhiro Ikeda,Hideharu Ishida,Akihiro Kusumi,Makoto Kiso 한국당과학회 2012 한국당과학회 학술대회 Vol.2012 No.1
Lipid rafts have been assumed to work as a platform where protein receptors, cholesterols and gangliosides (representatively GM3 and GM1) assemble and interact for efficient signal transduction. According to the observation of these raft molecules by single molecule tracking technique, raft components were frequently but very transiently recruited to the cluster of GPI-anchored proteins formed upon binding of extracellular signaling molecules [1]. However, behaviors and functions of gangliosides in living cell membranes have never been extensively investigated because of the lack of their fluorescent probes that behave as equivalents of native gangliosides. To address this issue, we intend to develope novel fluorescent GM3 and GM1 probes for single molecule tracking, in which glycan parts are site-specifically labeled with various fluorescent dyes and evaluate the functionality of the fluorescent gangliosides. We designed the replacement of the C9 hydroxyl groups of sialic acid of GM3 and GM1 with amino groups to introduce fluorescent dyes. The synthesis of glycan parts of GM3 and GM1 were successfully achieved by using a Neu-Gal unit having a trifluoroacetamide at the C9 position. Next, the glycan parts were glycosidated with the Glc-Cer acceptor developed by our research group [2], yielding the skeletons of GM3 and GM1, respectively, which was followed by the conversion of trifluoroacetamide groups into amino groups. Finally the amino GM3 and GM1 were conjugated with fluorescent dyes through amide linkages, producing the targeted fluorescent gangliosides GM3 and GM1. The synthesized gangliosides were subjected to biophysical evaluations; DRM analysis and single molecule observation of colocalization with raft molecules (GPI-anchored protein, CD59 and epidermal growth factor receptor). Results obtained in these evaluations demonstrated great influence of the loaded position and polarity of fluorescent dye on the raftphilicity of gangliosides. Furthermore, the Kd value of the fluorescent GM1 probe for cholera toxin B subunit (CTXB) was comparable to that of native GM1, indicating that dye did not interfere the binding to CTXB. These results strongly suggest that the fluorescent gangliosides can be used to identify behaviors and functions of gangliosides in raft domains.
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The isopropylation of biphenyl over H-mordenite - Roles of 3- and 4-isopropylbiphenyls
Yoshihiro Sugi,Chokkalingam Anand,Tomonori Sugimura,Kenichi Komura,Yoshihiro Kubota,Jong Ho Kim,Gon Seo,Ajayan Vinu 한국화학공학회 2013 Korean Journal of Chemical Engineering Vol.30 No.5
The isopropylation of biphenyl (BP) and 3- and 4-isopropylbiphenyls (3- and 4-IPBPs) was examined over H-mordenites (MOR) to elucidate the mechanism of shape-selective formation of 4,4'-diisopropylbiphenyl (4,4'-DIPB). The isopropylation of BP occurred predominantly to form 4-isopropylbiphenyl (4-IPBP) from BP and 4,4'-DIPB from 4-IPBP. However, 3-IPBP, a minor isomer from BP, cannot participate effectively in the formation of 3,4'-DIPB due to steric restriction of its isopropyl moiety with MOR channels. Selective formation of 4,4'-DIPB was observed at low to moderate temperatures: 225-275 oC. However, the selectivities for 4,4'-DIPB were decreased at high temperatures,300-350 oC under propene pressure, 0.8MPa, by the isomerization of 4,4'-DIPB at external acid sites. The isomerization of 4,4'-DIPB occurred under low propene pressure even at 250 oC. The roles of 3- and 4-IPBPs in the formation of DIPB isomers were examined in the isopropylation of their mixtures. 4-IPBP was consumed much faster than 3-IPBP in all cases examined. 4-IPBP was an exclusive precursor to DIPB isomers, particularly 4,4'-DIPB. 4,4'-DIPB was also found as a predominant isomer in encapsulated products at all conditions examined. These results show that 4-IPBP can preferentially establish active transition state with propene and acid site in MOR channels, resulting in selective formation of 4,4'-DIPB. It is concluded that the isopropylation of BP over MOR occurs through reactant selectivity mechanism and restricted transition state mechanism, but not through product selectivity mechanism.
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Yoshihiro Sugi,Yukio Hasegawa,Hiroshi Tamada,Kenichi Komura,Yoshihiro Kubota,김종호 한국화학공학회 2011 Korean Journal of Chemical Engineering Vol.28 No.2
Isopropylation of naphthalene (NP) was examined over H-mordenite (MOR), H-Y zeolite (FAU), and HBeta zeolite (BEA) in order to elucidate roles of isopropylnaphthalene (IPN) isomers during the catalysis. 2-IPN was the predominant isomer over MOR and works as a precursor for the selective formation of β,β-DIPN, particularly, 2,6-DIPN. In contrast, 1-IPN was predominant (with 2-IPN as a minor isomer) over FAU and BEA at low temperatures;dialkylation accompanied by the consumption of 1- and 2-IPN led to predominant formation of α,α- and α,β-DIPN. The formation of β,β-DIPN from 2-IPN was enhanced at higher temperatures. Bulky transition states of 1-IPN in IPN isomers and α,α- and α,β-DIPN among DIPN isomers were hindered by the interaction with MOR channels, resulting in the selective formation of β,β-DIPN, particularly 2,6-DIPN through the less bulky 2-IPN. FAU and BEA allow the formation of α,α- and α,β-DIPN from both of 1- and 2-IPN isomers because their channels are too large to exclude bulky transition states. The catalysis over FAU and BEA occurred under kinetic control at lower temperatures, and thermodynamic control also participates at higher temperatures.
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Vapor-Phase Ethylation of Biphenyl over MTW Zeolites
Mulla, Shafeek Abdul Rashid,Waghmode, Suresh B.,Watanabe, Seiji,Maekawa, Hiroyoshi,Komura, Kenichi,Kubota, Yoshihiro,Sugi, Yoshihiro,Kim, Jong-Ho,Seo, Gon The Chemical Society of Japan 2006 Bulletin of the Chemical Society of Japan Vol.79 No.9
<P>Vapor-phase ethylation of biphenyl (BP) with ethanol over the MTW zeolites was examined by using a fixed-bed flow reactor, and compared to the catalyses over MOR and MFI zeolites. Two types of MTW zeolites: MTW-S (small crystal) and MTW-L (large crystal) were synthesized under hydrothermal conditions. The selectivity for 4,4′-diethylbiphenyl (4,4′-DEBP) over the MTW zeolites was the highest among the other zeolites, such as MOR and MFI. The catalytic activity of MTW-S was higher than MTW-L. The selectivities for 4,4′-DEBP at 300 °C were ca. 30% for MTW-S and ca. 22% for MTW-L among the DEBP isomers. The dealumination of the MTW zeolites enhanced the selectivity for 4,4′-DEBP although the catalytic activity was slightly decreased. In particular, the selectivity for 4,4′-DEBP over dealuminated MTW-L by steaming and subsequent refluxing in hydrochloric acid increased from 22 to 42% at 300 °C. The enhancement of the selectivity for 4,4′-DEBP is due to the decrease in non-selective reactions at external acid sites because these sites are removed by the dealumination. The selectivities are higher than those of equilibrium mixtures, and the slimmest isomer. 4,4′-DEBP is preferentially formed due to the steric interaction of reactants and products with acidic sites in the MTW channels. Molecular modeling on the diffusion of products in the MTW channel suggests that 4,4′-DEBP isomer can diffuse most easily among DEBP isomers. 4,4′-DEBP and other isomers easily diffuse inside MOR channel; however, they cannot in the MFI channels. These results show that the formation of 4,4′-DEBP is the most favorable due to the diffusion and the restriction of transition state in the MTW channels.</P>
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