Quantum chemical parameters of 10 amino acids with D- and L-configurations were firstly calculated with semi-empirical AM1 method. Furthermore, the relationship between molecular structures of D-, L-amino acids and t...Quantum chemical parameters of 10 amino acids with D- and L-configurations were firstly calculated with semi-empirical AM1 method. Furthermore, the relationship between molecular structures of D-, L-amino acids and their sweetness were observed. The results show that upon different configurations of amino acids, the sweetness is relative with their formation heat, dipole moment, energy gap of frontier orbital and other parameters. The formation heats of the same amino acids possessing D- and L-configurations are different except glycine. The algebraic value of D-amino acid is generally larger than that of corresponding L-configuration with only one except of tyrosine. The dipole moment of D-amino acid is generally larger than that of corresponding L-amino acid except tyrosine and lysine. The lowest unoccupied orbital energy （ELUMO） of D-amino acid is higher than that of corresponding L-configuration except phenylalanine. △E of D-amino acid is larger than that of L-amino acid except histidine, phenylalanine and lysine. The larger gap will have advantage for its matching with frontier orbital energy of human protein acceptor, which strengthens the interaction between D-amino acid and sweet taste acceptor. Besides, the changing rules of these parameters are generally identical.展开更多
The structural characteristics of different alkoxides of Y. Ba and Cu are studied with quantum chemi-cal CNDO /2 calculations. The relative hydrolysis rate coefficients k_M of them are obtained according tothe relati...The structural characteristics of different alkoxides of Y. Ba and Cu are studied with quantum chemi-cal CNDO /2 calculations. The relative hydrolysis rate coefficients k_M of them are obtained according tothe relationship between frontier orbitals and organic chemical reactions. Based on the above results. properexperimental conditions for the preparation of homogeneous ultra-purity. submicro high-T_cYBa_2Cu_3O_(7-δ) superconducting powders are proposed.展开更多
In this paper, we evaluate semiempirical methods (AM1, PM3, and ZINDO), HF and DFT (B3LYP) in different basis sets to determine which method best describes the sign and magnitude of the geometrical parameters of artem...In this paper, we evaluate semiempirical methods (AM1, PM3, and ZINDO), HF and DFT (B3LYP) in different basis sets to determine which method best describes the sign and magnitude of the geometrical parameters of artemisinin in the region of the endoperoxide ring compared to crystallographic data. We also classify these methods using statistical analysis. The results of PCA were based on three main components, explaining 98.0539% of the total variance, for the geometrical parameters C3O13, O1O2C3, O13C12C12a, and O2C3O13C12. The DFT method (B3LYP) corresponded well with the experimental data in the hierarchical cluster analysis (HCA). The experimental and theoretical angles were analyzed by simple linear regression, and statistical parameters (correlation coefficients, significance, and predictability) were evaluated to determine the accuracy of the calculations. The statistical analysis exhibited a good correlation and high predictive power for the DFT (B3LYP) method in the 6-31G** basis set.展开更多
The title compound was synthesized by the base catalyzed reaction of 5-（（quinolin- 8-yloxy）methyl）-1,3,4-oxadiazole-2（3H）-thione with methyl chloroacetate. The structure was supported by the spectroscopic data a...The title compound was synthesized by the base catalyzed reaction of 5-（（quinolin- 8-yloxy）methyl）-1,3,4-oxadiazole-2（3H）-thione with methyl chloroacetate. The structure was supported by the spectroscopic data and unambiguously confirmed by single-crystal X-ray diffraction studies. It crystallizes from a methanol solution in the triclinic space group Pi with unit cell dimensions a = 7.4509（9）, b = 10.2389（12）, c = 12.2299（15）A, a = 74.771（2）, β = 77.956（2）, 7 = 69.263（2）°, V = 834.98（17） A3 and Z = 2. In order to gain some valuable insights into the molecular structure, the quantum mechanical calculations were performed using both HF and time-dependent density functional theory at the B3LYP/6-31G（d,p） level. The molecular geometry from X-ray determination of the title compound in the ground state has been compared using the Hartree-Fock （HF） and density functional theory （DFT） with the 6-31G（d） basis set. The calculated results show that the DFT and HF can well reproduce the structure of the title compound. The energetic behavior of the title compound was examined using the B3LYP method with the 6-31G（d） basis set. The harmonic vibrational frequencies calculated have been compared with the experimental FTIR and FT-Raman spectra. The restricted Hartree-Fock and density functional theory-based nuclear magnetic resonance （NMR） calculation procedure was also performed, and it was used for assigning the 13C and 1H NMR chemical shifts of the title compound. Moreover, molecular electrostatic potential and thermodynamic parameters of the title compound were investigated by theoretical calculations.展开更多
The criterion of orientating group of electrophilic aromatic nitration was discussed by means of pattern recognition method with quantum-chemical parameters as features, and the product ratios of the reactions were qu...The criterion of orientating group of electrophilic aromatic nitration was discussed by means of pattern recognition method with quantum-chemical parameters as features, and the product ratios of the reactions were quantitatively calculated using artificial neural network (ANN) method with the same parameters as inputs, based on the ab initio calculation of quantum chemistry, The quantum-chemical parameters involved orbital energy, orbital electron population, atomic total electron density and atomic net charge. The predicted values are in agreement with experimental results and the predicted error of the ANN with quantum-chemical parameters for the reaction is the smallest among the all methods.展开更多
利用量子化学程序计算了23个2-羟基-3-烷基-1,4-萘醌化合物的量子化学参数(如:最高占据轨道能级、最低空轨道能级、极化率、氧原子静电荷、偶极矩、生成热、水化能、脂水分配系数),并对化合物对光系统Ⅱ(PSⅡ)的抑制活性进行了定量结构...利用量子化学程序计算了23个2-羟基-3-烷基-1,4-萘醌化合物的量子化学参数(如:最高占据轨道能级、最低空轨道能级、极化率、氧原子静电荷、偶极矩、生成热、水化能、脂水分配系数),并对化合物对光系统Ⅱ(PSⅡ)的抑制活性进行了定量结构-活性相关(Q SAR s)分析,其中生成热、水化能、脂水分配系数、极化度四个参数共同构建的多元二阶模型准确性最高(R=0.897,F=11.026).通过该模型可推测活性大小主要取决于它们从水相迁移到生物相的难易程度以及与生物体靶位发生色散作用(疏水作用)的能力.展开更多
The two-dimensional Quantitative Structure-Activity Relationship （2D-QSAR） models have been developed to estimate and predict the inhibitory activities of a series of HEPT analogues against HIV-1 by using quantum ch...The two-dimensional Quantitative Structure-Activity Relationship （2D-QSAR） models have been developed to estimate and predict the inhibitory activities of a series of HEPT analogues against HIV-1 by using quantum chemical parameters and physicochemical parameters. The best model of three parameters yields r = 0.908, r^2A = 0.800 and s = 0.467 based on stepwise multiple regression （SMR） method. The stability of the model has been verified by t-test, and the results show that the model has perfect robustness. The predictive power of QSAR models has been tested by Leave-One-Out （LOO） and Leave-Group（regularly random set）-Out（LGO） procedure Cross-Validation methodology. The r^2cv of 0.755 and r^2pred of 0.759 were obtained, respectively.展开更多
Density function theory and discrete variation method (DFT-DVM) were used to study the adsorption of [Au(AsS 3)] 2- on the surface of kaolinite.The correlation among structure,chemical bond and stability was discuss...Density function theory and discrete variation method (DFT-DVM) were used to study the adsorption of [Au(AsS 3)] 2- on the surface of kaolinite.The correlation among structure,chemical bond and stability was discussed.Several models were selected with [Au(AsS 3)] 2- in different directions and sites.The results show that the models with gold on the edge of kaolinite basal layer contain pincerlike bond among gold and several oxygen atoms and form strong Au-O covalent bond,so these models are more stable than those with gold above or under the layer.The models with gold near to [AlO 2(OH) 4] octahedra are more stable than those with gold near to the vacancy without aluminium.These two stable tendencies in kaolinite-[Au(AsS 3)] 2- are stronger than that in kaolinite-Au systems.The interaction between [Au(AsS 3)] 2- and kaolinite is stronger than that between gold and kaolinite,and this interaction is strong enough to form the surface complexes.展开更多
Sodium 3,5-bis(hydroxyimino)-1-methyl-2,4,6-trioxocyclohexanide C7H5N2NaO5 (I) has been isolated as the only product of the reaction of nitrosation of methylphloroglucinol. The structure of the titled compound has bee...Sodium 3,5-bis(hydroxyimino)-1-methyl-2,4,6-trioxocyclohexanide C7H5N2NaO5 (I) has been isolated as the only product of the reaction of nitrosation of methylphloroglucinol. The structure of the titled compound has been determined from single crystal X-ray diffraction data. The hydrated C7H5N2NaO52.5H2O crystallizes in the monoclinic space group C2/c, with a(?) 16.408(3);b(?) 12.446(3);c(?) 13.716(3);(o) 126.34(3). The planar organic anion exists in a triketo-dihydroxyimino form with the C–O and C–N distances from 1.220(2) to 1.271(2)?? and from 1.292(2) to 1.293?? respectively. In the IR spectrum of I, the sharp absorption band occurred at 1681 cm-1 due to C=O stretching indicating the strong H-interactions. The correlations of theoretical (DFT-B3LYP/aug-cc-pVDZ) and experimental UV-vis absorption spectra in neutral and alkaline ethanolic solutions showed the existence of hydroxyimino-nitroso tautomerism while ionization of I.展开更多
文摘Quantum chemical parameters of 10 amino acids with D- and L-configurations were firstly calculated with semi-empirical AM1 method. Furthermore, the relationship between molecular structures of D-, L-amino acids and their sweetness were observed. The results show that upon different configurations of amino acids, the sweetness is relative with their formation heat, dipole moment, energy gap of frontier orbital and other parameters. The formation heats of the same amino acids possessing D- and L-configurations are different except glycine. The algebraic value of D-amino acid is generally larger than that of corresponding L-configuration with only one except of tyrosine. The dipole moment of D-amino acid is generally larger than that of corresponding L-amino acid except tyrosine and lysine. The lowest unoccupied orbital energy （ELUMO） of D-amino acid is higher than that of corresponding L-configuration except phenylalanine. △E of D-amino acid is larger than that of L-amino acid except histidine, phenylalanine and lysine. The larger gap will have advantage for its matching with frontier orbital energy of human protein acceptor, which strengthens the interaction between D-amino acid and sweet taste acceptor. Besides, the changing rules of these parameters are generally identical.
文摘The structural characteristics of different alkoxides of Y. Ba and Cu are studied with quantum chemi-cal CNDO /2 calculations. The relative hydrolysis rate coefficients k_M of them are obtained according tothe relationship between frontier orbitals and organic chemical reactions. Based on the above results. properexperimental conditions for the preparation of homogeneous ultra-purity. submicro high-T_cYBa_2Cu_3O_(7-δ) superconducting powders are proposed.
文摘In this paper, we evaluate semiempirical methods (AM1, PM3, and ZINDO), HF and DFT (B3LYP) in different basis sets to determine which method best describes the sign and magnitude of the geometrical parameters of artemisinin in the region of the endoperoxide ring compared to crystallographic data. We also classify these methods using statistical analysis. The results of PCA were based on three main components, explaining 98.0539% of the total variance, for the geometrical parameters C3O13, O1O2C3, O13C12C12a, and O2C3O13C12. The DFT method (B3LYP) corresponded well with the experimental data in the hierarchical cluster analysis (HCA). The experimental and theoretical angles were analyzed by simple linear regression, and statistical parameters (correlation coefficients, significance, and predictability) were evaluated to determine the accuracy of the calculations. The statistical analysis exhibited a good correlation and high predictive power for the DFT (B3LYP) method in the 6-31G** basis set.
文摘The title compound was synthesized by the base catalyzed reaction of 5-（（quinolin- 8-yloxy）methyl）-1,3,4-oxadiazole-2（3H）-thione with methyl chloroacetate. The structure was supported by the spectroscopic data and unambiguously confirmed by single-crystal X-ray diffraction studies. It crystallizes from a methanol solution in the triclinic space group Pi with unit cell dimensions a = 7.4509（9）, b = 10.2389（12）, c = 12.2299（15）A, a = 74.771（2）, β = 77.956（2）, 7 = 69.263（2）°, V = 834.98（17） A3 and Z = 2. In order to gain some valuable insights into the molecular structure, the quantum mechanical calculations were performed using both HF and time-dependent density functional theory at the B3LYP/6-31G（d,p） level. The molecular geometry from X-ray determination of the title compound in the ground state has been compared using the Hartree-Fock （HF） and density functional theory （DFT） with the 6-31G（d） basis set. The calculated results show that the DFT and HF can well reproduce the structure of the title compound. The energetic behavior of the title compound was examined using the B3LYP method with the 6-31G（d） basis set. The harmonic vibrational frequencies calculated have been compared with the experimental FTIR and FT-Raman spectra. The restricted Hartree-Fock and density functional theory-based nuclear magnetic resonance （NMR） calculation procedure was also performed, and it was used for assigning the 13C and 1H NMR chemical shifts of the title compound. Moreover, molecular electrostatic potential and thermodynamic parameters of the title compound were investigated by theoretical calculations.
基金Project (NO. 99C113) supported by the Eduction Commission of Hunan Province.
文摘The criterion of orientating group of electrophilic aromatic nitration was discussed by means of pattern recognition method with quantum-chemical parameters as features, and the product ratios of the reactions were quantitatively calculated using artificial neural network (ANN) method with the same parameters as inputs, based on the ab initio calculation of quantum chemistry, The quantum-chemical parameters involved orbital energy, orbital electron population, atomic total electron density and atomic net charge. The predicted values are in agreement with experimental results and the predicted error of the ANN with quantum-chemical parameters for the reaction is the smallest among the all methods.
文摘利用量子化学程序计算了23个2-羟基-3-烷基-1,4-萘醌化合物的量子化学参数(如:最高占据轨道能级、最低空轨道能级、极化率、氧原子静电荷、偶极矩、生成热、水化能、脂水分配系数),并对化合物对光系统Ⅱ(PSⅡ)的抑制活性进行了定量结构-活性相关(Q SAR s)分析,其中生成热、水化能、脂水分配系数、极化度四个参数共同构建的多元二阶模型准确性最高(R=0.897,F=11.026).通过该模型可推测活性大小主要取决于它们从水相迁移到生物相的难易程度以及与生物体靶位发生色散作用(疏水作用)的能力.
文摘The two-dimensional Quantitative Structure-Activity Relationship （2D-QSAR） models have been developed to estimate and predict the inhibitory activities of a series of HEPT analogues against HIV-1 by using quantum chemical parameters and physicochemical parameters. The best model of three parameters yields r = 0.908, r^2A = 0.800 and s = 0.467 based on stepwise multiple regression （SMR） method. The stability of the model has been verified by t-test, and the results show that the model has perfect robustness. The predictive power of QSAR models has been tested by Leave-One-Out （LOO） and Leave-Group（regularly random set）-Out（LGO） procedure Cross-Validation methodology. The r^2cv of 0.755 and r^2pred of 0.759 were obtained, respectively.
基金FundedbytheNationalNaturalScienceFoundationofChi na (No .4 0 172 0 17)
文摘Density function theory and discrete variation method (DFT-DVM) were used to study the adsorption of [Au(AsS 3)] 2- on the surface of kaolinite.The correlation among structure,chemical bond and stability was discussed.Several models were selected with [Au(AsS 3)] 2- in different directions and sites.The results show that the models with gold on the edge of kaolinite basal layer contain pincerlike bond among gold and several oxygen atoms and form strong Au-O covalent bond,so these models are more stable than those with gold above or under the layer.The models with gold near to [AlO 2(OH) 4] octahedra are more stable than those with gold near to the vacancy without aluminium.These two stable tendencies in kaolinite-[Au(AsS 3)] 2- are stronger than that in kaolinite-Au systems.The interaction between [Au(AsS 3)] 2- and kaolinite is stronger than that between gold and kaolinite,and this interaction is strong enough to form the surface complexes.
文摘Sodium 3,5-bis(hydroxyimino)-1-methyl-2,4,6-trioxocyclohexanide C7H5N2NaO5 (I) has been isolated as the only product of the reaction of nitrosation of methylphloroglucinol. The structure of the titled compound has been determined from single crystal X-ray diffraction data. The hydrated C7H5N2NaO52.5H2O crystallizes in the monoclinic space group C2/c, with a(?) 16.408(3);b(?) 12.446(3);c(?) 13.716(3);(o) 126.34(3). The planar organic anion exists in a triketo-dihydroxyimino form with the C–O and C–N distances from 1.220(2) to 1.271(2)?? and from 1.292(2) to 1.293?? respectively. In the IR spectrum of I, the sharp absorption band occurred at 1681 cm-1 due to C=O stretching indicating the strong H-interactions. The correlations of theoretical (DFT-B3LYP/aug-cc-pVDZ) and experimental UV-vis absorption spectra in neutral and alkaline ethanolic solutions showed the existence of hydroxyimino-nitroso tautomerism while ionization of I.
