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排序方式: 共有269条查询结果,搜索用时 31 毫秒
31.
Bang JK Naka H Teruya K Aimoto S Konno H Nosaka K Tatsumi T Akaji K 《The Journal of organic chemistry》2005,70(25):10596-10599
[reaction: see text] The solid-phase Horner-Emmons reaction was successfully applied for the convenient syntheses of olefin-containing protease inhibitors. The isomerization during the solid-phase Horner-Emmons reaction can be minimized simply by the use of an appropriate amount of the base. The synthesized olefin peptides, which have an olefin gamma-amino acid at the scissile site, were found to act as effective inhibitors for the HTLV-1 protease for the first time. 相似文献
32.
33.
Tolerance, bioaccumulation, biotransformation and excretion of arsenic compounds by the fresh–water shrimp (Neocaridina denticulata) and the killifish (Oryzias latipes) (collected from the natural environment) were investigated. Tolerances (LC50) of the shrimp against disodium arsenate [abbreviated as As(V)], methylarsonic acid (MAA), dimethylarsinic acid (DMAA), and arsenobetaine (AB) were 1.5, 10, 40, and 150μg As ml?1, respectively. N. denticulata accumulated arsenic from an aqueous phase containing 1 μg As ml?1 of As(V), 10 μg As ml?1 of MAA, 30 μg As ml?1 of DMAA or 150 μg As ml?1 of AB, and biotransformed and excreted part of these species. Both methylation and demethylation of the arsenicals were observed in vivo. When living N. denticulata accumulating arsenic was transferred into an arsenic–free medium, a part of the accumulated arsenic was excreted. The concentration of methylated arsenicals relative to total arsenic was higher in the excrement than in the organism. Total arsenic accumulation in each species via food in the food chain Green algae (Chlorella vulgaris) → shrimp (N. denticulata) → killifish (O. latipes) decreased by one order of magnitude or more, and the concentration of methylated arsenic relative to total arsenic accumulated increased successively with elevation in the trophic level. Only trace amounts of monomethylarsenic species were detected in the shrimp and fish tested. Dimethylarsenic species in alga and shrimp, and trimethylarsenic species in killifish, were the predominant methylated arsenic species, respectively. 相似文献
34.
Ichikawa A Sugimoto Y Tanaka S 《Proceedings of the Japan Academy. Series B, Physical and biological sciences》2010,86(8):848-866
Histamine and prostaglandins (PGs) play a variety of physiological roles as autacoids, which function in the vicinity of their sources and maintain local homeostasis in the body. They stimulate target cells by acting on their specific receptors, which are coupled to trimeric G proteins. For the precise understanding of the physiological roles of histamine and PGs, it is necessary to clarify the molecular mechanisms involved in their synthesis as well as their receptor-mediated responses. We cloned the cDNAs for mouse L-histidine decarboxylase (HDC) and 6 mouse prostanoid receptors (4 PGE(2) receptors, PGF receptor, and PGI receptor). We then characterized the expression patterns and functions of these genes. Furthermore, we established gene-targeted mouse strains for HDC and PG receptors to explore the novel pathophysiological roles of histamine and PGs. We have here summarized our research, which should contribute to progress in the molecular biology of HDC and PG receptors. 相似文献
35.
Zhaokui Wang Shigeki Naka Hiroyuki Okada 《Applied Physics A: Materials Science & Processing》2010,100(4):1103-1108
We have investigated the performance of organic light-emitting devices (OLEDs) with a rubrene-doped mixed single layer by
using 4,4′-bis[N-(1-napthyl)-N-phenyl- amion] biphenyl (α-NPD) as hole transport layer. Comparing to a conventional heterostructure OLED, equal luminance vs. current density characteristics
were obtained. In addition, maximum power efficiency was threefold improved, and the achieved value was 5.90 lm/W by optimizing
a mixing ratio of hole and electron transport materials. By evaluating the temperature dependence of the
J
–
V
characteristics for electron-injection dominated device, the electron injection from Al/LiF to mixed organic layer is attributed to Schottky thermal emission model. And the barrier height of the electron injection from Al/LiF into mixed single layer was obtained to be 0.62 eV, which is lower
than Al/Alq3 interface. Meanwhile, the mixed single-layer device exhibited superior operational durability at a half-luminance of 2,250 h
under a constant current operation mode. The reliability was improved with a factor of two compared to the heterostructure
device due to the improvement of stability in mixed organic molecules and removal of the heterojunction interface in the mixed
single-layer device. 相似文献
36.
Yukihiko Nakata Toshikazu Kuniya 《Journal of Mathematical Analysis and Applications》2010,363(1):230-9
In this paper, we study a class of periodic SEIRS epidemic models and it is shown that the global dynamics is determined by the basic reproduction number R0 which is defined through the spectral radius of a linear integral operator. If R0<1, then the disease free periodic solution is globally asymptotically stable and if R0>1, then the disease persists. Our results really improve the results in [T. Zhang, Z. Teng, On a nonautonomous SEIRS model in epidemiology Bull. Math. Biol. 69 (8) (2007) 2537-2559] for the periodic case. Moreover, from our results, we see that the eradication policy on the basis of the basic reproduction number of the time-averaged system may overestimate the infectious risk of the periodic disease. Numerical simulations which support our theoretical analysis are also given. 相似文献
37.
Ikuo Kawashima Hiroaki Imoto Masatoshi Ishida Hiroyuki Furuta Shunsuke Yamamoto Masaya Mitsuishi Susumu Tanaka Toshiki Fujii Kensuke Naka 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(34):11812-11816
Dibenzo[b,f]arsepins possessing severely distorted cores compared to those of other heteropins were synthesized. These derivatives exhibited dual photoluminescence in the green‐to‐red region (500–700 nm) and the near‐ultraviolet region (<380 nm), which could be attributed to the planarization of the arsepin core in the lowest singlet excited (S1) state. The computational approach for the assessment of the aromatic indices revealed that the dibenzoarsepins studied show aromaticity (8π system) in the S1 states in line with Baird's rule. The lone pair electrons of the arsenic atoms play a crucial role in the aromaticity in the S1 states. 相似文献
38.
M. Naka 《Journal of Non》1980,41(1):71-77
The crystallization temperature of Fe80?XMXP13C7 and Fe80?XNXP13C7 alloys has been investigated, where M is Zr, Nb, Mo, Ru, Rh or Pd, and N is B, C, Si, P, As, Sn or Sb. Zr and Mo effectively increase TX and Pd decreases it. The increase in crystallization temperature TX with the concentration of elements M, is larger for the second group of periodic elements, except for the case of Pd, compared with the first group of periodic elements. The crystallization temperature is related to the average electron concentration, the atomic size and the atomic cohesive energy of the additive metal.The metalloidal elements N, except for Sn and Sb, increase the TX of Fe80?XNXP13C7 alloys. In particular, the addition of B, C, Si of P definitely increases TX and small amounts of Sn or Sb markedly decrease it. Contrary to the effects of metallic elements, the effects of metalloidal elements do not show the general trend. However, in the same group of the periodic system TX decrease with increasing the atomic size and decreasing cohesive energies for metalloidal elements. 相似文献
39.
Kondo Y Morey JV Morgan JC Naka H Nobuto D Raithby PR Uchiyama M Wheatley AE 《Journal of the American Chemical Society》2007,129(42):12734-12738
Sequential reaction of HTMP (= 2,2,6,6-tetramethylpiperidine) with nBuLi and Et2Zn affords unsolvated polymer chains of EtZn(micro-Et)(micro-TMP)Li 6. The scope of this reagent in directed ortho metalation (DoM) chemistry has been tested by its reaction with N,N-diisopropylnaphthamide in THF to give EtZn(micro-C10H6C(O)NiPr2-2)2Li.2THF 7. Data reveal that 6 has undergone reaction with 2 equiv of aromatic tertiary amide and imply that it exhibits dual alkyl/amido basicity. DFT calculations reveal that direct alkyl basicity is kinetically disfavored and instead point to a stepwise mechanism whereby 6 acts as an amido base, liberating HTMP during the first DoM event. Re-coordination of the amine at lithium then incurs the elimination of EtH. Reaction of the resulting alkyl(amido)(arylamido)zincate with a second equivalent of N,N-diisopropylnaphthamide eliminates HTMP and affords 7. Both DoM steps involve the exhibition of amido basicity and each reveals a low kinetic barrier to reaction. Understanding of this reaction sequence is tested by treating 6 with N,N-diisopropylbenzamide in THF. On the basis of theory and experiment, the presence of THF solvent (in place of stronger Lewis bases) combined with the use of a sterically less congested aromatic amide is expected to encourage threefold, stepwise reaction. Isolation and characterization of the resulting tripodal zincate Zn(micro-C6H4C(O)NiPr2-2)3Li.THF 8 bears this out and suggests a significant new level of control in zincate-induced DoM chemistry through the combination of experiment and DFT studies. 相似文献
40.
Ueno M Yonemoto M Hashimoto M Wheatley AE Naka H Kondo Y 《Chemical communications (Cambridge, England)》2007,(22):2264-2266
A novel type of deprotonative arylation of nucleophiles was conducted using Et(3)SiH/cat. t-Bu-P4 and the powerful S(N)Ar reactions of aryl fluorides were accomplished using alcohols and malonates as nucleophiles. 相似文献