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排序方式: 共有415条查询结果,搜索用时 15 毫秒
91.
92.
SS Narula RW Yuan SE Adams OM Green J Green TB Philips LD Zydowsky MC Botfield M Hatada ER Laird 《Canadian Metallurgical Quarterly》1995,3(10):1061-1073
BACKGROUND: Recruitment of the intracellular tyrosine kinase Syk to activated immune-response receptors is a critical early step in intracellular signaling. In mast cells, Syk specifically associates with doubly phosphorylated immunoreceptor tyrosine-based activation motifs (ITAMs) that are found within the IgE receptor. The mechanism by which Syk recognizes these motifs is not fully understood. Both Syk SH2 (Src homology 2) domains are required for high-affinity binding to these motifs, but the C-terminal SH2 domain (Syk-C) can function independently and can bind, in isolation, to the tyrosine-phosphorylated IgE receptor in vitro. In order to improve understanding of the cellular function of Syk, we have determined the solution structure of Syk-C complexed with a phosphotyrosine peptide derived from the gamma subunit of the IgE receptor. RESULTS: The Syk-C:peptide structure is compared with liganded structures of both the SH2 domain of Src and the C-terminal SH2 domain of ZAP-70 (the 70 kDa zeta-associated protein). The topologies of these domains are similar, although significant differences occur in the loop regions. In the Syk-C structure, the phosphotyrosine and leucine residues of the peptide ligand interact with pockets on the protein, and the intervening residues are extended. CONCLUSIONS: Syk-C resembles other SH2 domains in its peptide-binding interactions and overall topology, a result that is consistent with its ability to function as an independent SH2 domain in vitro. This result suggests that Syk-C plays a unique role in the intact Syk protein. The determinants of the binding affinity and selectivity of Syk-C may reside in the least-conserved structural elements that comprise the phosphotyrosine- and leucine-binding sites. These structural features can be exploited for the design of Syk-selective SH2 antagonists for the treatment of allergic disorders and asthma. 相似文献
93.
We cloned a new imprinted gene by searching for parental-origin-specific CpG methylations using methylation-sensitive two-dimensional genome scanning method. This gene encodes a putative 51 kDa protein with significant similarity to U2 small nuclear ribonucleoprotein auxiliary factor small subunits, an essential mammalian splicing factor, and is located on mouse chromosome 11, of which maternal duplication/paternal deficiency results in a small body. 相似文献
94.
Preparation of hydrophilic polyethylene foam of open cell type by radiation grafting of acrylic acid
Kanako Kaji Motoyoshi Hatada Iwao Yoshizawa Choji Kohara Kuniaki Komai 《应用聚合物科学杂志》1989,37(8):2153-2164
Hydrophilic polyethylene foam was synthesized by radiation grafting of acrylic acid onto polyethylene foam of open cell type using monomer solution containing Mohr's salt which inhibits homopolymerization of the monomer. The graft foam was easily dyed by cationic dyes and showed excellent moisture regain. The wicking properties were also excellent and were almost the same as those of commercially available PVA foam. The surface resistivity of 1016 ohm of the original foam decreased to 106 ohm and half decay time of surface charge decreased from 8000 s to 1 s by the grafting, indicating that the grafted foam has excellent antistatic properties. 相似文献
95.
Kohji Yoshinaga Takafumi Yokoyama Yutaka Sugawa Hiroyuki Karakawa Naoyuki Enomoto Hiroyasu Nishida Michio Komatsu 《Polymer Bulletin》1992,28(6):663-668
Summary Radical polymerizations of vinyl monomers using a initiator of 2,2-azobis(2-amidinopropane) dihydrochloride on monodispersed silica colloid led to formation of spherical polymer/SiO2 composites, retained particle size. Addition of hydroxypropyl cellulose to the reaction system resulted in yielding excellent dispersible composites into ethanol by short period ultrasonic irradiation. The polymerization of styrene in the presence of mercapto-amine or carboxylic acid derivatives could successfully introduce amino or carboxyl group on the Poly(styrene)/SiO2 composite. 相似文献
96.
97.
Through thickness reinforced stitched laminates with different stitch densities (0.11 and 0.028?mm?2) were studied in order to analyse effects on laminate behaviour, under in-plane tensile loading based on continuum mechanics. Multi-layered stitched laminates with the stacking sequence [+45/90/?45/02/+45/902/?45/0]s were modelled on a lamina-wise basis to analyse the macroscopic damage and local stress–strain constitutive behaviour. Interfaces between lamina and stitch yarns were assumed to be perfectly glued and were modelled by the contact capability. Discretisation procedures using the principle of virtual work were applied in addition to discretisation of the contact traction. Progressive failure analysis with Puck’s failure criteria was conducted to characterise the failure behaviour of the laminate. This analysis showed that reinforcement density is one of the key factors affecting strength, stiffness and crack propagation in composite laminates. By suppressing the damage initiation, densely stitched laminates showed 15.2% higher in-plane stiffness than moderately stitched laminates. The results obtained by the finite element technique are consistent with the experimental results. 相似文献
98.
Osamu Nakagawa Nobutaka Fujimoto Takafumi Nishiura Tatsuki Kitayama Koichi Hatada 《Polymer Bulletin》1992,29(5):579-586
Summary Highly syndiotactic diblock and triblock copolymers comprising lauryl methacrylate (LMA) and methyl methacrylate (MMA) with narrow molecular weight distributions were prepared by the living anionic polymerization with t-C4H9Li/(C2H5)3Al in toluene at low temperature. The block copolymers were soluble in acetone which is a non-solvent for poly(lauryl methacrylate) (PLMA). 1HNMR and vapor pressure osmometric analyses of the block copolymers indicated the aggregation of the copolymer in acetone through the interaction between PLMA blocks. Stereocomplex formation between the triblock copolymer and isotactic poly(methyl methacrylate) (PMMA) took place more effectively in solution than in the solid state. 相似文献
99.
Koichi Hatada Koichi Ute Tohru Nishimura Masaharu Kashiyama Toshinori Saito Makoto Takeuchi 《Polymer Bulletin》1990,23(2):157-162
Summary Packed column SFC has been found suitable for the rapid and detailed analysis of the isotactic and syndiotactic oligomers
of MMA, when the temperature gradient technique was applied and the modifier was employed. Oligomer components from trimer
to 20-mer separated completely. The heptamer fraction collected three times by SFC gave the 1H NMR spectrum of satisfactorily high S/N ratio; the spectrum agreed well with that of the standard sample. Separation by
tacticity as well as by molecular weight was observed for the SFC of a mixture of the isotactic and syndiotactic oligomers.
The isotactic oligomers had longer retention time than the syndiotactic oligomers of the corresponding degree of polymerization.
Part 3: cf. Ute K. Nishimura T, Hatada K, Polym J (1989) 21: 1027 相似文献
100.
Machiko Shimada Yoshio Nakamura Yasuo Kusama Osamu Matsuda Naoyuki Tamura Eiichi Kageyama 《应用聚合物科学杂志》1974,18(11):3387-3396
The types of free radicals produced in the water-accessible regions of cellulose I and cellulose II fibers by γ-irradiation in nitrogen atmosphere at room temperature were studied by ESR spectroscopy. The ESR spectra of the irradiated cellulose I and II change by contacting the fibers with water, and after immersion in water the spectral shape depends on the orientation of the fiber axes to the magnetic field. These spectra are probably related to the free radicals generated in the highly ordered regions inaccessible to water in irradiated cellulosic fibers. The ESR spectrum of free radicals generated in decrystallized cellulose after irradiation consists of a singlet and a doublet. When the ESR spectra of free radicals formed in the highly ordered regions of cellulose I and II and the singlet and the doublet are combined in adequate ratio, the constructed spectra are similar to those of the radicals scavenged by water in the irradiated cellulose I and II fibers. From these facts, the spectra due to the free radicals in the water-accessible regions in irradiated cellulose I and II are considered to consist of the singlet and the doublet formed by free radicals in the typical amorphous regions and the spectra of other types of radicals generated in the semicrystalline regions. 相似文献