The molecular electronegativity-distance vector (MEDV) is employed to describe the chemical structure of bisphenol A analogs and their correlated estrogen activities. The result shows that the constructed models have good predictability and indicates substructures that may influence estrogen activities of chemicals.
CUI ShihaiLIU ShushenYANG JingWANG XiaodongWANG Liansheng
The structural and thermodynamic （PCTAs） in the ideal gas state at 298.15 K and 1.013 properties of 75 polychlorinated thianthrenes ×10^5 Pa have been calculated at the B3LYP/6- 31G＊ level using Gaussian 98 program. Based on the output data of Gaussian, the isodesmic reactions were designed to calculate standard enthalpy of formation （△fH^θ） and standard free energy of formation （△fH^θ） of PCTAs congeners. The relations of these thermodynamic parameters with the number and position of C1 atom substitution （Npcs） were discussed, and it was found that there exists high correlation between thermodynamic parameters （total energy （TE）, zero-point vibrational energy （ZPE）, thermal correction to energy （Eth）, heat capacity at constant volume （Cv^θ）, entropy （S^θ）, enthalpy （H^θ）, free energy （G^θ）, standard enthalpies of formation （△fH^θ） and standard Gibbs energies of formation （△fG^θ）） and Npcs. On the basis of the relative magnitude of their △fG^θ, the order of relative stability of PCTA congeners was theoretically proposed. In addition, the correlations between structural parameters and Npcs were also discussed. The good correlations were found between molecular average polarizability （α）, energy of the highest occupied molecular orbital （EHOMO）, molecular volume （Vm） and Npcs, and all R^2 values are larger than 0.95. Moreover, it was supposed that the isomer groups with higher toxicity should be Tri-CTA and TCTA.
A new molecular representation, molecular hologram, is employed to investigate the quantitative rela- tionships between gas chromatographic retention indices (GC-RI) and molecular structures of polychlorinated diben- zofurans (PCDFs). Together with application of partial least squares (PLS) regression, the quantitative structure-reten- tion relationship (QSRR) model is constructed for GC-RI of 135 PCDFs. This new QSRR model presents high statistical quality and predictive value with crossvalidation correlation coefficient q2LOO values of 0.998, and non-crossvalidation correlation coefficient r2 of 0.998. 100 PCDFs are selected randomly as training set and the rest as testing set. The re- sult of PLS regressive analysis of training set yields r2 of 0.998 and q2LOO of 0.997. The GC-RIs of testing set are pre- dicted, and the correlation equation indicates that the model based on training set has excellent ability to predict the GC-RIs of PCDFs in testing set.
