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1.
We present a new size-modified Poisson–Boltzmann ion channel (SMPBIC) model and use it to calculate the electrostatic potential, ionic concentrations, and electrostatic solvation free energy for a voltage-dependent anion channel (VDAC) on a biological membrane in a solution mixture of multiple ionic species. In particular, the new SMPBIC model adopts a membrane surface charge density and a natural Neumann boundary condition to reflect the charge effect of the membrane on the electrostatics of VDAC. To avoid the singularity difficulties caused by the atomic charges of VDAC, the new SMPBIC model is split into three submodels such that the solution of one of the submodels is obtained analytically and contains all the singularity points of the SMPBIC model. The other two submodels are then solved numerically much more efficiently than the original SMPBIC model. As an application of this SMPBIC submodel partitioning scheme, we derive a new formula for computing the electrostatic solvation free energy. Numerical results for a human VDAC isoform 1 (hVDAC1) in three different salt solutions, each with up to five different ionic species, confirm the significant effects of membrane surface charges on both the electrostatics and ionic concentrations. The results also show that the new SMPBIC model can describe well the anion selectivity property of hVDAC1, and that the new electrostatic solvation free energy formula can significantly improve the accuracy of the currently used formula. © 2019 Wiley Periodicals, Inc. 相似文献
2.
The immobilized metal complexes with the Schiff’s base of salen have shown high catalytic activity in oxidation of alkenes, cycloalkenes, and alcohols as compared with their unsupported analogs. Due to the heterogeneous nature of such catalysts, their separation and recycling is rather simple. 相似文献
3.
This paper proposes and analyzes a class of multigrid smoothers called the parallel multiplicative (PM) smoother by subspace decomposition techniques. It shows that the well known additive and multiplicative smoothers and the JSOR smoother are special cases of the PM smoother, and their smoothing properties can be obtained directly from the PM analysis. Moreover, numerical results are presented in this paper to show that the JSOR smoother is more robust and effective than the damped Jacobi smoother on current MIMD parallel computers.
AMS subject classification (2000) 65N55, 65Y05.Received May 2004. Revised September 2004. Communicated by Per Lötstedt.Dexuan Xie: This work was partially supported by the National Science Foundation through grant DMS-0241236. 相似文献
4.
In this paper, a new integral equation of electrostatics is proposed as an integral form of a basic dielectric continuum model,
which is traditionally represented in a form of Poisson differential equation. As an application in protein simulations, the
new integral equation is reduced to a second kind Fredholm boundary integral equation on the interface between the solute
and solvent regions for a piecewise constant permittivity function, together with two new integral expressions for the electrostatics
within the solute and solvent regions. The new integral equation and expressions work for any charge problem over the whole
space (including the one with charges on the interface). This valuable feature is verified numerically for a dielectric sphere
model with a point charge inside, outside, or on the sphere in this paper. 相似文献
5.
Dexuan Xie Suresh B. Singh Eugene M. Fluder Tamar Schlick 《Mathematical Programming》2003,95(1):161-185
The similarity and diversity sampling problems are two challenging optimization tasks that arise in the analysis of chemical
databases. As a first step to their solution, we propose an efficient projection/ refinement protocol based on the principal
component analysis (PCA) and the truncated-Newton minimization method implemented by our package TNPACK (PCA/TNPACK). We show
that PCA can provide the same initial guess as the singular value decomposition (SVD) for the optimization task of solving
the distance-geometry optimization problem if each column of a database matrix has a mean of zero. Hence, our PCA/TNPACK approach
is analogous to the SVD/TNPACK projection/refinement protocol that we developed recently for visualizing large chemical databases.
Using PCA/TNPACK and the Merck MDDR database (MDL Drug Data Report), we further investigate the projection/refinement procedure
with regards to the preservation of the original clusters of chemical compounds, the accuracy of similarity and diversity
sampling of chemical compounds, and the potential application in the study of structure activity relationships. We also explore
by simple experiments accuracy and efficiency aspects of the PCA/TNPACK procedure compared to those of a global optimization
algorithm (simulated annealing, as implemented by the program package SIMANN) in terms of producing the projection mapping
of a database. Numerical results show that the 2D PCA/TNPACK mapping can preserve the distance relationships of the original
database and is thus valuable as a first step in similarity and diversity applications. Of course, the generation of a global
rather than local minimizer and its interpretation in terms of pharameceutical applications remains a challenge. Since all
numerical tests are performed on the Merck MDDR database, results are representative of realistic cases encountered in the
field of drug design, and may help analyze properties of medicinal compounds.
Received: December 21, 2000 / Accepted: August 19, 2002 Published online: September 27, 2002
Mathematics Subject Classification (2000): 65K10, 62H25, 92C50 相似文献
6.
Yingzi Peng Dexuan Huo Liang Zheng Zhenghong Qian 《Particle & Particle Systems Characterization》2012,29(1):3-7
ZnO microstructures have been grown from zinc chloride (ZnCl2) and ammonia solution at 100 °C for 1 – 24 hours. X‐ray diffraction, scanning electron microscope and field‐emission scanning microscope were utilized to investigate the structural properties and morphology of the ZnO crystals. Structural investigations show that phase‐pure hexagonal structure ZnO has been successfully synthesized, and the hexagonal structure ZnO can be achieved in solutions with an appropriate range of concentrations. Under our experimental conditions, several different morphologies of ZnO structures were obtained, including flower‐like and bar flower‐like. The relationship between the morphology and experimental conditions are discussed. 相似文献
7.
The nonlinear Poisson–Boltzmann equation (PBE) is a widely-used implicit solvent model in biomolecular simulations. This paper
formulates a new PBE nonlinear algebraic system from a mortar finite element approximation, and proposes a new minimization
protocol to solve it efficiently. In particular, the PBE mortar nonlinear algebraic system is proved to have a unique solution,
and is equivalent to a unconstrained minimization problem. It is then solved as the unconstrained minimization problem by
the subspace trust region Newton method. Numerical results show that the new minimization protocol is more efficient than
the traditional merit least squares approach in solving the nonlinear system. At least 80 percent of the total CPU time was
saved for a PBE model problem.
AMS subject classification (2000) 65N30, 65H10, 65K10, 92-08 相似文献
8.
Chen Shifeng Wei Xuebin Liu Jinhui Sun Zhanxue Chen Gongxin Yang Mei Liu Yuanyuan Wang Duo Ma Chengcui Kong Dexuan 《Journal of Radioanalytical and Nuclear Chemistry》2022,331(6):2583-2596
Journal of Radioanalytical and Nuclear Chemistry - Mineralogical study showed that the Yuejin uranium ore is from a low grade, high carbonate and high pyrite sandstone type uranium deposit. Uranium... 相似文献
9.
原子吸收法测定人精子中锌和铜含量的研究 总被引:1,自引:0,他引:1
本文采用石墨炉原子吸收法,以NH4NO3和Mg(NO3)2混合剂作基体改进剂,测定了人精子中微量元素铜和锌。基方法的特征质量分别为10.00pgCu/0.0044A.S.,9.80PgZ/0.004A.S;平均加收率为97.42%,锌为101.91%,铜和锌的精密度分别是4.1%和4.03%。 相似文献
10.
Efficient and divergent one-pot synthesis of fully substituted 1H-pyrazoles and isoxazoles from cyclopropyl oximes based on reaction conditions selection is reported. Under Vilsmeier conditions (POCl3/DMF), substituted 1 H-pyrazoles were synthesized from 1-carbamoyl, 1-oximyl cyclopropanes via sequential ring-opening, chlorovinylation, and intramolecular aza-cyclization. In the presence of POCl3/CH2Cl2, substituted isoxazoles were obtained from the cyclopropyl oximes via ring-opening and intramolecular nucleophilic vinylic substitution (SNV) reactions. 相似文献