The regression model for octanol/water partition coefficients ( K ow ), is founded with only two molecular descriptors available through quantum chemical calculations: solvation free energy (Δ G S ), and so...The regression model for octanol/water partition coefficients ( K ow ), is founded with only two molecular descriptors available through quantum chemical calculations: solvation free energy (Δ G S ), and solvent accessible surface area (SASA). For the properties of 47 organic compounds from 17 types, the model gives a correction coefficient (adjusted for degrees of freedom) of 0 959 and a standard error of 0 277 log unit. It is a suitable way to predict the partition properties that are related to solute solvent interactions in the water phase.展开更多
Adsorption properties of brick for the removal of divalent cations increased significantly after this material were pre-activated by HCl and subsequently impregnated with ferrihydrite. Scanning electron microscopy (SE...Adsorption properties of brick for the removal of divalent cations increased significantly after this material were pre-activated by HCl and subsequently impregnated with ferrihydrite. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) analysis demonstrated that ferrihydrite was preferentially attached to clays (mainly to metakaolinite) and possessed Na atoms at levels higher than those observed in iron-poor aggregates. Sodium is bound to hydroxyl groups which have a function as reactive sites and give rise to surface charge. Zeta potential measurements were conducted to determine the isoelectric point (IEP) and salt-addition method was used to assess the point of zero charge (PZC) of this brick. Modified brick has a positive charge in water up to pH ≈ 3.2 and negative charge above this pH. Moreover, pH was found to be the most important factor affecting the adsorption process, suggesting the possible implication of electrostatic forces at the brick-water interface. The complexation model proposed by James and Healy was applied to our system: theoretical data on free-energy changes due to effects associated both with electrostatic attraction and solvation, were found to be in agreement with those determined from kinetic experiments. Column experiments permitted further to show that adsorption reactions were strongly inhibited by addition of an inert electrolyte (like NaNO3). Under this condition, ionic strength increased and most surface sites of the brick would be occupied by Na+ ions, leading to a charge neutralization and thereby a depletion of electrostatic forces.展开更多
膜蛋白在细胞生命活动中扮演着重要的角色。目前,有很多方法用来预测和分类膜转运蛋白。然而,预测膜蛋白功能的工作并不多。为了解决这个问题,基于蛋白质序列信息结合快速傅里叶变换利用支持向量机的方法预测来自TCDB数据库中的channels...膜蛋白在细胞生命活动中扮演着重要的角色。目前,有很多方法用来预测和分类膜转运蛋白。然而,预测膜蛋白功能的工作并不多。为了解决这个问题,基于蛋白质序列信息结合快速傅里叶变换利用支持向量机的方法预测来自TCDB数据库中的channels/pores,electrochemical potential-driven transporters和primary active transporters三类膜转运蛋白共1817条蛋白质的功能。模型使用20种氨基酸的分布,残基的疏水性、平均极性和溶剂化自由能为原始的特征数据,利用快速傅里叶变换将其转化为频域上的信息作为机器学习的特征输入。通过五倍交叉检验预测准确率达到了72.1%,而先前的文献报道的准确率为68.1%。论文的研究证明该方法可以有效地对channels/pores,electrochemical potential-driven transporters和primary active transporters三种不同功能的膜转运蛋白进行功能分类。展开更多
基金TheNationalNaturalScienceFoundationofChina (No .2 9837180 )andtheResearchFoundationfortheDoctoralProgramofHigherEducationofChi
文摘The regression model for octanol/water partition coefficients ( K ow ), is founded with only two molecular descriptors available through quantum chemical calculations: solvation free energy (Δ G S ), and solvent accessible surface area (SASA). For the properties of 47 organic compounds from 17 types, the model gives a correction coefficient (adjusted for degrees of freedom) of 0 959 and a standard error of 0 277 log unit. It is a suitable way to predict the partition properties that are related to solute solvent interactions in the water phase.
文摘Adsorption properties of brick for the removal of divalent cations increased significantly after this material were pre-activated by HCl and subsequently impregnated with ferrihydrite. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) analysis demonstrated that ferrihydrite was preferentially attached to clays (mainly to metakaolinite) and possessed Na atoms at levels higher than those observed in iron-poor aggregates. Sodium is bound to hydroxyl groups which have a function as reactive sites and give rise to surface charge. Zeta potential measurements were conducted to determine the isoelectric point (IEP) and salt-addition method was used to assess the point of zero charge (PZC) of this brick. Modified brick has a positive charge in water up to pH ≈ 3.2 and negative charge above this pH. Moreover, pH was found to be the most important factor affecting the adsorption process, suggesting the possible implication of electrostatic forces at the brick-water interface. The complexation model proposed by James and Healy was applied to our system: theoretical data on free-energy changes due to effects associated both with electrostatic attraction and solvation, were found to be in agreement with those determined from kinetic experiments. Column experiments permitted further to show that adsorption reactions were strongly inhibited by addition of an inert electrolyte (like NaNO3). Under this condition, ionic strength increased and most surface sites of the brick would be occupied by Na+ ions, leading to a charge neutralization and thereby a depletion of electrostatic forces.
文摘膜蛋白在细胞生命活动中扮演着重要的角色。目前,有很多方法用来预测和分类膜转运蛋白。然而,预测膜蛋白功能的工作并不多。为了解决这个问题,基于蛋白质序列信息结合快速傅里叶变换利用支持向量机的方法预测来自TCDB数据库中的channels/pores,electrochemical potential-driven transporters和primary active transporters三类膜转运蛋白共1817条蛋白质的功能。模型使用20种氨基酸的分布,残基的疏水性、平均极性和溶剂化自由能为原始的特征数据,利用快速傅里叶变换将其转化为频域上的信息作为机器学习的特征输入。通过五倍交叉检验预测准确率达到了72.1%,而先前的文献报道的准确率为68.1%。论文的研究证明该方法可以有效地对channels/pores,electrochemical potential-driven transporters和primary active transporters三种不同功能的膜转运蛋白进行功能分类。
