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91.
Fluorescence spectroscopic studies of acenaphthylene dimers in saturated hydrocarbon solution have revealed that the dimer (A2) photodissociates to 相似文献
92.
Crystal growth processes of low-density framework forms of crystalline silicon, named Si clathrates ( Si34 and Si46), during solid phase epitaxy (SPE) have been successfully observed in molecular-dynamics simulations using the Tersoff potential. The activation energy of SPE for Si34 has been found to correspond with the experimental value ( approximately 2.7 eV) for the cubic diamond phase, while the SPE rates of Si46 are much lower than that of Si34. The structural transition from Si46 to Si34 can be also observed during the Si46-[001] SPE. The present results suggest that new wide-gap Si semiconductors with clathrate structures can be prepared using epitaxial growth techniques. 相似文献
93.
Moriguchi T Yanagi T Kunimori M Wada T Sekine M 《The Journal of organic chemistry》2000,65(24):8229-8238
This paper describes the design and synthesis of a new type of aminoacyl-adenylate analogue (aa-AMPN) having an N-acyl phosphoramidate linkage where the oxygen atom of the mixed anhydride bond of aminoacyl-adenylate (aa-AMP) is replaced by an amino group. This new type of aa-AMP analogue is expected to be useful as material for studies on the recognition mechanism of the aminoacylation of tRNA and other biochemical reactions. The condensation of phosphoramidite derivatives of carboxamides with nucleoside derivatives failed, because the activated phosphoramidite derivatives reacted with not only the hydroxyl groups but also another reactive species. An alternative approach was examined by the reaction of 5'-O-phosphoramidite adenosine derivatives with carboxamide derivatives. The TBTr and TSE groups were chosen for protection of the amino group of amino acid amides and the phosphate group, respectively. Detailed studies revealed that the use of 5-(3,5-dinitrophenyl)-1H-tetrazole as an activating catalyst of phosphoramidites resulted in rapid condensation within 10 min to give fully protected aa-AMPN derivatives. No side reaction occurred. Deprotection of these products via a two-step procedure gave aa-AMPN derivatives in good yields. It also turned out that aa-AMPNs thus obtained are stable under both acidic and basic conditions, such as 0.1 M HCl (pH 1.0) and 0.1 M NaOH (pH 13.0). 相似文献
94.
Sadaaki Iwanaga 《Proceedings of the Japan Academy. Series B, Physical and biological sciences》2007,83(4):110-119
A hemocyte lysate from horseshoe crab (Limulus) produced a gel, when exposed to Gram-negative bacterial endotoxins, lipopolysaccharides (LPS). This gelation reaction of the lysate, so-called Limulus test, has been widely employed as a simple and very sensitive assay method for endotoxins. Recent biochemical studies on the principle of Limulus test indicate that the hemocytes contain several serine protease zymogens, which constitute a coagulation cascade triggered by endotoxins, and that there is a (1,3)-β-D-glucan-mediated coagulation pathway which also results in the formation of gel. Up to now, six protein components, designated coagulogen, proclotting enzyme, factor B, factor C, and factor G, all of which are closely associated with the endotoxin-mediated coagulation pathway, have been purified and biochemically characterized. The molecular structures of these proteins have also been elucidated. Moreover, the reconstitution experiments using the isolated clotting factors, factor C, factor B, proclotting enzyme and coagulogen in the presence of endotoxin, leads to the formation of coagulin gel. Here, I will focus on the biochemical principle of Limulus test for detecting bacterial endotoxins, and its activation and regulation mechanism on the LPS-mediated coagulation cascade. 相似文献
95.
Ma YuGang Fang DeQing Sun XiaoYan Zhou Pei Cai XiangZhou Chen JinGen Guo Wei Tian WenDong Wang HongWei Zhang GuoQiang Cao XiGuang Fu Yao Hu ZhengGuo Wang JianSong Wang Meng Togano Y. Aoi N. Baba H. Honda T. Okada K. Hara Y. Ieki K. Ishibashi Y. Itou Y. Iwasa N. Kanno S. Kawabata T. Kimura H. Kondo Y. Kurita K. Kurokawa M. Moriguchi T. Murakami H. Oishi H. Ota S. Ozawa A. Sakurai H. Shimoura S. Shioda R. Takeshita E. Takeuchi S. Yamada K. Yamada Y. Yasuda Y. Yoneda K. Motobayashi T. 《中国科学:物理学 力学 天文学(英文版)》2011,54(1):18-23
Two-proton relative momentum distributions from the break-up channels 23Al→p+p+21Na and 22Mg→p+p+20Ne at an energy of 60–70 A MeV have been measured together with two-proton opening angles at the projectile fragment separator beamline (RIPS) in the RIKEN Ring Cyclotron Facility. The results demonstrate the existence of diproton emission component from single-step 2He for highly excited 23Al and 22Mg. 相似文献
96.
Dr. Shinsuke Nishida Dr. Junya Kawai Miki Moriguchi Tomohiro Ohba Naoki Haneda Dr. Kozo Fukui Prof. Akira Fuyuhiro Prof. Daisuke Shiomi Prof. Kazunobu Sato Prof. Takeji Takui Prof. Kazuhiro Nakasuji Prof. Yasushi Morita 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(36):11904-11915
The tri‐tert‐butylphenalenyl (TBPLY) radical exists as a π dimer in the crystal form with perfect overlapping of the singly occupied molecular orbitals (SOMOs) causing strong antiferromagnetic exchange interactions. 2,5‐Di‐tert‐butyl‐6‐oxophenalenoxyl (6OPO) is a phenalenyl‐based air‐stable neutral π radical with extensive spin delocalization and is a counter analogue of phenalenyl in terms of the topological symmetry of the spin density distribution. X‐ray crystal structure analyses showed that 8‐tert‐butyl‐ and 8‐(p‐XC6H4)‐6OPOs (X=I, Br) also form π dimers in the crystalline state. The π‐dimeric structure of 8‐tert‐butyl‐6OPO is seemingly similar to that of TBPLY even though its SOMO–SOMO overlap is small compared with that of TBPLY. The 8‐(p‐XC6H4) derivatives form slipped stacking π dimers in which the SOMO–SOMO overlaps are greater than in 8‐tert‐butyl‐6OPO, but still smaller than in TBPLY. The solid‐state electronic spectra of the 6OPO derivatives show much weaker intradimer charge‐transfer bands, and SQUID measurements for 8‐(p‐BrC6H4)‐6OPO show a weak antiferromagnetic exchange interaction in the π dimer. These results demonstrate that the control of the spin distribution patterns of the phenalenyl skeleton switches the mode of exchange interaction within the phenalenyl‐based π dimer. The formation of the relevant multicenter–two‐electron bonds is discussed. 相似文献
97.
The polymerization of vinyl monomer initiated with poly-2-hydroxyethylmethacrylate (PHEMA) in water was carried out at 85°C. Cu(II) ion was not necessary for this polymerization. Methacrylate monomers were polymerized, while styrene and acrylonitrile were not. The polymerization was found to proceed through a radical mechanism in the interior of PHEMA which was swelled in water. The grafting efficiency of MMA polymer obtained was about 90%. The overall activation energy was estimated to be 32.9 kJ/mol. 相似文献
98.
Sasaki K Kogure K Chaki S Nakamura Y Moriguchi R Hamada H Danev R Nagayama K Futaki S Harashima H 《Analytical and bioanalytical chemistry》2008,391(8):2717-2727
We previously reported that transferrin (Tf)-modified liposomes (Tf-L) additionally modified with a cholesterylated pH-sensitive
fusogenic peptide (Chol-GALA) can release an encapsulated aqueous phase marker to cytosol via endosomal membrane fusion. However,
further obstacles need to be overcome to bring the Tf-L to the level of a viral-like gene delivery system. In this study,
we developed a novel packaging method to encapsulate condensed plasmid DNA into PEgylated Tf-L (Tf-PEG-L) to form a core–shell-type
nanoparticle. The most difficult challenge was to provide a mechanism of escape for the condensed core from endosome to cytosol
in the presence of polyethylene glycol (PEG). We hypothesized that a membrane-introduced Chol-GALA and a PEgylated GALA would
interact synergistically to induce membrane fusion between liposome and endosome. By simultaneously incorporating Chol-GALA
into the membrane of Tf-PEG-L and GALA at tips of PEG chains, a condensed core was released into cytosol, and transfection
acitivty increased 100-fold. We concluded that topological control was responsible for the synergistic effect of GALA derivatives
introduced on Tf-PEG-L.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Kentaro Sasaki and Kentaro Kogure contributed equally to this work. 相似文献
99.
Asakawa D Moriguchi S Takayama M 《Journal of the American Society for Mass Spectrometry》2012,23(1):108-115
The influence of arginine (Arg), lysine (Lys), and phenylalanine (Phe) residues and phosphorylation on the molecular ion yields
of model peptides have been quantitatively studied using matrix-assisted laser desorption/ionization (MALDI) mass spectrometry
in both positive- and negative-ion mode. The results obtained from these experiments have been interpreted from the standpoint
of two different components, namely, desorption and ionization, on the basis of the physicochemical properties of constituent
amino acids of the model peptides. The presence of basic residues such as Arg and Lys enhanced the ion yields of protonated
molecules [M + H]+. An N-terminal rather than a C-terminal Arg residue was advantageous for the formation of both [M + H]+ and [M – H]–. The presence of the Phe residue resulted in the increase of the ion yields of both [M + H]+ and [M – H]–. In contrast, the presence of phosphate group(s) contributed to the suppression of the yields of both [M + H]+ and [M – H]– due to the loss of phosphate group. The detection limits for both [M + H]+ and [M – H]– of model peptides have been evaluated. 相似文献
100.
A new quassinoid, ailantinol H, was isolated from the aerial parts of Ailanthus altissima. The structure was elucidated based on spectral evidence. 相似文献