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排序方式: 共有146条查询结果,搜索用时 15 毫秒
121.
Steven C. Howell Xiangyun Qiu Joseph E. Curtis 《Journal of computational chemistry》2016,37(29):2553-2563
Understanding the structure–function relationship of biomolecules containing DNA has motivated experiments aimed at determining molecular structure using methods such as small‐angle X‐ray and neutron scattering (SAXS and SANS). SAXS and SANS are useful for determining macromolecular shape in solution, a process which benefits by using atomistic models that reproduce the scattering data. The variety of algorithms available for creating and modifying model DNA structures lack the ability to rapidly modify all‐atom models to generate structure ensembles. This article describes a Monte Carlo algorithm for simulating DNA, not with the goal of predicting an equilibrium structure, but rather to generate an ensemble of plausible structures which can be filtered using experimental results to identify a sub‐ensemble of conformations that reproduce the solution scattering of DNA macromolecules. The algorithm generates an ensemble of atomic structures through an iterative cycle in which B‐DNA is represented using a wormlike bead–rod model, new configurations are generated by sampling bend and twist moves, then atomic detail is recovered by back mapping from the final coarse‐grained configuration. Using this algorithm on commodity computing hardware, one can rapidly generate an ensemble of atomic level models, each model representing a physically realistic configuration that could be further studied using molecular dynamics. © 2016 Wiley Periodicals, Inc. 相似文献
122.
Xiaoyun He Xuezhu Du Xiangyun Zang Lili Dong Zijian Gu Liping Cao 《Natural product research》2016,30(8):941-947
A furanone (1), (S)-methyl 2-(2-hydroxy-3,4-dimethyl-5-oxo-2,5-dihydrofuran-2-yl)acetate, was isolated from the edible mushroom Grifola frondosa. Mass spectrometry and NMR analyses were used to elucidate the structure of this compound, and its absolute configuration was determined using circular dichroism spectroscopy. Compound 1 exhibited specific antifungal activity against the plant pathogens, Fusarium oxysporum, Gibberella zeae and Piricularia oryzae and the opportunistic human pathogen, Pseudallescheria boydii, resulting in minimum inhibitory concentration values of 2.5, 2.5, 1.25 and 0.15 μg/mL, respectively. In contrast, the furanone showed only weak activity towards Aspergillus spp., Candida albicans and several other fungal strains tested as well as no appreciable antibacterial activity. 相似文献
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124.
水合锑酸钠中微量Sb(Ⅲ)的测定 总被引:5,自引:0,他引:5
以甲基橙为指示剂,在4mol.L^-3HCl中用硫酸测水合锑酸钠中微量Sb(Ⅲ),研究了溶样方法,介质酸度、等影响。结果表明,该法准确度较高,分析手续简便。 相似文献
125.
In this paper,we propose a Rayleigh quotient iteration method (RQI)to calculate the Z-eigenpairs of the symmetric tensor,which can be viewed as a generalization of shifted symmetric higher-order power method (SS-HOPM).The convergence analysis and the fixed-point analysis of this algorithm are given.Nu-merical examples show that RQI needs fewer iterations than SS-HOPM while keep the amount of computation per iteration. 相似文献
126.
In this study, the authors have investigated the structural and optical properties of ZnO layer grown by pulsed laser deposition on GaN/r-plane sapphire. X-ray diffraction results demonstrate the ZnO film to be highly preferentially deposited at a-axis orientation; the different rocking curve values along the two orthogonal directions indicate the low C2v symmetry in the growth a-plane ZnO. From free stress to large tensile stress (about 1.34 × 109 Pa) distribution along the growth direction of ZnO is revealed by visible Raman mapping spectra. The enhanced significantly high-order longitudinal-optical (LO) phonon modes up to 4th and no TO phonons have been observed in Raman spectrum under UV 325 nm by resonance conditions; an intense and broad disorder activated surface phonon mode is also observed, resulting from the increased disorder on the film surface with stripe-like growth features. Low-temperature photoluminescence measurements reveal that the band-edge emission of ZnO is dominated by neutral donor-bound exciton and free electrons to neutral acceptor emissions. Interfacial microstructure of ZnO/GaN has been examined by transmission electron microscopy, with the epitaxial relationship () ZnO//() GaN. All these results indicated that GaN template played an important role in the growth of ZnO film, with full advantage of small lattice mismatch. 相似文献
127.
Xiangyun Shi Xueyong Zhou Xinyu Song 《Nonlinear Analysis: Real World Applications》2010,11(3):1795-1809
In this paper, the dynamical behavior of a virus dynamics model with CTL immune response and time delay is studied. Time delay is used to describe the time between the infected cell and the emission of viral particles on a cellular level. The effect of time delay on stability of the equilibria of the CTL immune response model has been studied and sufficient criteria for local asymptotic stability of the disease-free equilibrium, immune-free equilibrium and endemic equilibrium and global asymptotic stability of the disease-free equilibrium are given. Some conditions for Hopf bifurcation around immune-free equilibrium and endemic equilibrium to occur are also obtained by using the time delay as a bifurcation parameter. Numerical simulation with some hypothetical sets of data has been done to support the analytical findings. 相似文献
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129.
本文用恢复电位法、荧光分光光度法及粘度法研究了镉(Ⅱ)与牛血清白蛋白(BSA)的配位平衡和pH的影响。结果表明BSA有两类镉结合部位(2个强结合和10个弱结合部位)。Cd—BSA配位反应受pH影响,在近中性pH范围Cd(Ⅱ)与BSA结合未接近饱和时,以CURFIT程序对结合曲线拟合发现,每摩尔BSA平均结合Cd(Ⅱ)摩尔数的对数值与游离镉浓度的对数间成线性关系,进一步用Marguardt法处理得到Cd(Ⅱ)与BSA结合平衡方程式:N
=K[Cd2+]m,K和m均为pH函数。构象研究表明H+和Cd(Ⅱ)的结合都能引起BSA构象改变。用凝胶色谱法测定了Zn(Ⅱ)、Ca(Ⅱ)、吐温—80和十二烷基硫酸钠(SDS)对Cd—BSA结合的影响。Zn(Ⅱ)可以竞争Cd(Ⅱ)在BSA上结合部位使Cd(Ⅱ)活动化。SDS能够有效抑制Cd(Ⅱ)与BSA结合,这种作用可能与SDS引起BSA构象改变有关。 相似文献
130.
N2O分解反应的蒙特卡罗模拟 总被引:2,自引:2,他引:2
N2O作为大气污染物之一早已受到人们的注意,许多人研究了N2O在金属氧化物上的分解反应得到了一些基本的实验事实[1]:(1)反应速率与原料气中N2O的分压近似成比例.(2)在反应初期,N2的生成速率由大变小,O2的生成速率由小变大,达到平衡时,N2生成速率是O2生成速率的二倍.(3)过渡应答法研究表明,把原料气由N2O和He的混合气体切换成纯He后,N2立即停止发生,而O2的生成仍能维持一段时间.基于上述实验事实,人们对Nzo的催化分解反应提出了一些可能的机理,主要有下面两种看法:另一方面,人们还发现几O的催化分解反应是一个振荡… 相似文献