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排序方式: 共有175条查询结果,搜索用时 15 毫秒
1.
Translation elongation factor 1 alpha (EF-1 alpha) catalyzes the GTP-dependent binding of amino-acyl-tRNA to the ribosome. Previously, Tetrahymena 14-nm filament-associated protein was identified as EF-1 alpha [Kurasawa et al. (1992) Exp. Cell Res. 203, 251-258]. This and several other studies suggest that EF-1 alpha functions not only in translation but also in regulation of some part of the cytoskeleton. Tetrahymena EF-1 alpha bound to F-actin and induced bundling of F-actin. We investigated the effects of GTP/GDP and Ca2+/calmodulin on F-actin bundling activity of EF-1alpha. The presence of GTP, GDP, or guanylyl-imidodiphosphate (GMP-PNP) slightly decreased the amount of EF-1 alpha which bound to F-actin, but each had virtually no effect on the F-actin bundling activity. The formation of F-actin bundles by EF-1 alpha was Ca(2+)-insensitive. In the absence of Ca2+, calmodulin did not bind to EF-1 alpha and F-actin. On the other hand, in the presence of Ca2+, calmodulin directly bound to EF-1 alpha but did not have any serious influence on EF-1 alpha/F-actin binding. Under the conditions, electron microscopy demonstrated that Ca2+/calmodulin completely inhibited the F-actin bundling by EF-1 alpha. These results indicate that CA2+/calmodulin regulates the F-actin bundling activity of EF-1 alpha without inhibition of the binding between Ef-1 alpha and F-actin. 相似文献
2.
Abstract— We have developed a process to fabricate optical components, such as a lens, prism, or diffuser, directly on to a glass substrate. Processes include precision mastering by diamond cutting and multi‐layer photopolymer (2P) molding to realize flat surfaces and the integration of multiple components with an alignment within a few micrometers. 相似文献
3.
Shun'ichi Numata Shuuichi Oohara Koji Fujisaki Jun'Ichi Imaizumi Noriyuki Kinjo 《应用聚合物科学杂志》1986,31(1):101-110
The thermal expansion behavior for various aromatic polymides was investigated. Usally polymers, including polyimides, have high thermal expansion coefficients (3–6 × 10?5 K?1), compared with metals and ceramics. However, there are some polyimides which have very low thermal expansion coefficients below 1 × 10?5 K?1. This property was observed for the polymides obtained from pyromellitic dianhydride or 3,3′ 4,4′-biphenyltetracarboxylic dianhydride and aromatic diamines which were constituted of only benzene rings fused at para positions. It was proposed that their low thermal expansion coefficient related to the linearity in their polymer molecular skeltons. 相似文献
4.
5.
Tetsuya Ōgushi Gopal N. Suresha Yutaka Honjo Yoshihisa Ōzono Iwazo Kawano Tadashi Numata Yoshinori Hakuraku 《Journal of Low Temperature Physics》1987,69(5-6):451-457
We prepared La-Sr-Nb-O system samples both in bulk form and as a film, with sharp resistive transitions at temperatures of 228–323 K, depending on the annealing conditions. The sharp resistive transitions might be attributable to superconductivity. Magnetic ordering was observed over a narrow temperature range around 40 K for some of the samples. 相似文献
6.
For the elucidation of the crystal structures of the two crystalline allomorphs of cellulose triacetate (CTA), namely CTA I and CTA II, two-dimensional (2D) solid-state through-bond 13C-13C and 1H-13C correlations NMR techniques applied to the two crystalline allomorphs of CTA. As a result, the 13C and 1H chemical shifts of the glucopyranose ring of CTA I and CTA II were completely assigned by the 2D NMR spectra of these allomorphs. On the 2D 13C-13C correlation spectrum of CTA II, two sets of the 13C-13C correlations from C1 to C6 were observed. This indicated that the CP/MAS 13C NMR spectrum of CTA II can be characterized by its overlapping of the 13C subspectra of two kinds of 2,3,6-triacetyl-anhydroglucopyranose units and that there are two magnetically non-equivalent sites in the unit cell of CTA II. In the case of CTA I, the numbers of respective 13C and 1H shifts of CTA I agreed with the those of the glucopyranose residue in the allomorph, strongly suggesting that the asymmetric unit of CTA I is only one glucose residue. In addition, conformational differences in the exocyclic C5-C6 bonds between CTA I and CTA II were strongly suggested by the notable differences in the 1H and 13C chemical shifts at the C6 sites of these allomorphs. 相似文献
7.
Dynamics of learning near singularities in layered networks 总被引:1,自引:0,他引:1
We explicitly analyze the trajectories of learning near singularities in hierarchical networks, such as multilayer perceptrons and radial basis function networks, which include permutation symmetry of hidden nodes, and show their general properties. Such symmetry induces singularities in their parameter space, where the Fisher information matrix degenerates and odd learning behaviors, especially the existence of plateaus in gradient descent learning, arise due to the geometric structure of singularity. We plot dynamic vector fields to demonstrate the universal trajectories of learning near singularities. The singularity induces two types of plateaus, the on-singularity plateau and the near-singularity plateau, depending on the stability of the singularity and the initial parameters of learning. The results presented in this letter are universally applicable to a wide class of hierarchical models. Detailed stability analysis of the dynamics of learning in radial basis function networks and multilayer perceptrons will be presented in separate work. 相似文献
8.
9.
Magdoom KN Subramanian D Chakravarthy VS Ravindran B Amari S Meenakshisundaram N 《Neural computation》2011,23(2):477-516
We present a computational model that highlights the role of basal ganglia (BG) in generating simple reaching movements. The model is cast within the reinforcement learning (RL) framework with correspondence between RL components and neuroanatomy as follows: dopamine signal of substantia nigra pars compacta as the temporal difference error, striatum as the substrate for the critic, and the motor cortex as the actor. A key feature of this neurobiological interpretation is our hypothesis that the indirect pathway is the explorer. Chaotic activity, originating from the indirect pathway part of the model, drives the wandering, exploratory movements of the arm. Thus, the direct pathway subserves exploitation, while the indirect pathway subserves exploration. The motor cortex becomes more and more independent of the corrective influence of BG as training progresses. Reaching trajectories show diminishing variability with training. Reaching movements associated with Parkinson's disease (PD) are simulated by reducing dopamine and degrading the complexity of indirect pathway dynamics by switching it from chaotic to periodic behavior. Under the simulated PD conditions, the arm exhibits PD motor symptoms like tremor, bradykinesia and undershooting. The model echoes the notion that PD is a dynamical disease. 相似文献
10.
This paper presents a new method of partition, named-splitting, of a point set ind-dimensional space. Given a pointG in ad-dimensional simplexT, T(G;i) is the subsimplex spanned by G and the ith facet ofT. LetS be a set ofn points inT, and let be a sequence of nonnegative integers 1, ..., nd+1 satisfying
i=1
d+1
1=n The-splitter of (T, S) is a pointG inT such thatT(G;i) contains at least
i
points ofS in its closure for everyi=1, 2, ...,d + 1. The associated dissection is the re-splitting.The existence of a-splitting is shown for any (T, S) and, and two efficient algorithms for finding such a splitting are given. One runs inO(d2n logn + d3n) time, and the other runs inO(n) time if the dimensiond can be considered as a constant. Applications of re-splitting to mesh generation, polygonal-tour generation, and a combinatorial assignment problem are given. 相似文献