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171.
172.
The molecular anvil model of an enzyme taking into consideration the flexibility of enzyme molecules
Kazuo Amaya 《Journal of inclusion phenomena and macrocyclic chemistry》1987,5(4):535-544
The concept of a molecular anvil model of an enzyme, assuming a rigid enzyme molecule, is introduced. Two distinct features of enzymes, high catalytic power and high specificity, are reasonably and consistently explained. The dynamic nature of molecular anvil action is stressed. The origin of the high catalytic power is the spontaneous creation of a high energy state at the anvil site. The origin of the high specificity is a high sensitivity of the maximum accessible potential energy to the relatively extruded distance of the molecular anvil. The flexible model is developed by assuming a flexible enzyme molecule. It is deduced from this flexible model that enzyme activity shows a maximum with a wide range of monotonous change of the configuration of the enzyme molecule. This is the origin of the general property of enzymes that enzyme activity shows a maximum with monotonous variation of environmental parameters such as pH, temperature, pressure or some times concentration of chemical substances. The induced fit theory of Koshland is reasonably explained. The relation and differences between individual theories of enzymes are discussed. The enzymological basis of the complex regulation of biological organisms is discussed. The inversion of the sign of control of effectors is predicted when environmental parameters are varied. This concept may be useful in designing artificial enzymes or high specificity catalysts.Presented at the Fourth International Symposium on Inclusion Phenomena and the Third International Symposium on Cyclodextrins, Lancaster, U.K., 20–25 July 1986. 相似文献
173.
非恒温CO表面催化氧化体系双随机共振 总被引:1,自引:0,他引:1
当考虑化学反应热、热传导和热辐射的影响时, Pt(110)/CO+O2表面催化氧化体系温度出现时空变化. 以衬底温度为控制参数, 通过计算机模拟, 研究了衬底温度噪声对该非恒温表面反应体系振荡动力学行为的影响. 研究发现, 温度噪声可以诱导体系双随机共振现象, 而且增大衬底温度可以使体系共振行为由双随机共振变为单随机共振. 这表明体系可以利用温度噪声加强其反应振荡, 并对其具有双重选择性, 人们可以通过改变衬底温度大小来控制体系的共振行为. 相似文献
174.
Penna Thereza Christina Vessoni Chiarini Eb Machoshvili Irene Alexeevna Ishii Marina Pessoa Adalberto 《Applied biochemistry and biotechnology》2002,98(1-9):791-802
The recombinant green fluorescent protein (gfp
uv
) was expressed by Escherichia coli DH5-α cells transformed with the plasmid pGFPuv. The gfp
uv
was selectively permeabilized from the cells in buffer solution (25 mM Tris-HCl, pH 8.0), after freezing (−70°C for 15 h), by four freeze (−20°C)/thaw cycles interlaid by sonication. The average
content of released gfp
uv
(experiment 2) was 7.76, 34.58, 39.38, 12.90, and 5.38%, for the initial freezing (−70°C) and the first, second, third and
fourth freeze/thaw cycles, respectively. Superfusion on freezing was observed between −11°C and −14°C, after which it reached
−20°C at 0.83°C/min. 相似文献
175.
In this paper, we present rational approximations based on Fourier series representation. For periodic piecewise analytic functions, the well-known Gibbs phenomenon hampers the convergence of the standard Fourier method. Here, for a given set of the Fourier coefficients from a periodic piecewise analytic function, we define Fourier-Padé-Galerkin and Fourier-Padé collocation methods by expressing the coefficients for the rational approximations using the Fourier data. We show that those methods converge exponentially in the smooth region and successfully reduce the Gibbs oscillations as the degrees of the denominators and the numerators of the Padé approximants increase.
Numerical results are demonstrated in several examples. The collocation method is applied as a postprocessing step to the standard pseudospectral simulations for the one-dimensional inviscid Burgers' equation and the two-dimensional incompressible inviscid Boussinesq convection flow.
176.
本文研究了一类多进小波展开的Gibbs函数的渐近性质,特别地,包括了多进Daubechies型小波. 相似文献
177.
178.
Gitta Kutyniok 《Constructive Approximation》2007,25(3):239-253
For a large class of irregular wavelet frames we derive a fundamental relationship between the affine density of the set of
indices, the frame bounds, and the admissibility constant of the wavelet. Several implications of this theorem are studied.
For instance, this result reveals one reason why wavelet systems do not display a Nyquist phenomenon analogous to Gabor systems,
a question asked in Daubechies' Ten Lectures book. It also implies that the affine density of the set of indices associated
with a tight wavelet frame has to be uniform. Finally, we show that affine density conditions can even be used to characterize
the existence of wavelet frames, thus serving, in particular, as sufficient conditions. 相似文献
179.
180.
Assembled complex, Fe(bpa)2(NCX)2 (bpa=1,2-bis(4-pyridyl)ethane; X=S, Se, BH3) enclathrated diphenylmethane. The skeletons were interpenetrating structures for NCS and NCSe complexes, while 2D grid structure
was obtained for NCBH3 complex. The assembled iron complexes showed spin-crossover phenomena by enclathrating diphenylmethane. The ratio of spin
transition and the transition temperature depended on the assembled structure. 相似文献