QSAR MODELING OF BIOCONCENTRATION FACTORS IN FISH BASED ON FRAGMENT CONSTANTS AND STRUCTURAL CORRECTION FACTORS

The quantitative structure-activity relationship between the BCF and fragment constant of organic chemicals was studied using a database containing 337 experimental BCF values. The database covered a large variety of chemicals ranging from the very hydrophobic to the very hydrophilic with logKow values between 0.39 and 8.60. The structural features affecting the BCFs were identified and evaluated during a preliminary modeling. A final linear multivariate regression model was derived that was able to account for as much as 98.0% of the variation in the experimental BCF values. The mean absolute error for the final model was 0.315 log-units. In addition, the predictability and robustness of the model was also evaluated.     

Three-dimensional quantitative structure activity relationships of quorum-sensing and biofilm inhibitors in gram-negative bacteria

Thirty N-acyl homoserine lactone (AHL) analogs with variable antibacterial activity and displaying inhibition of biofilm formation were selected to develop models for establishing three-dimensional quantitative structure-activity relationships (3D-QSAR). Comparative molecular field analysis (CoMFA) and comparative similarity indices analysis (CoMSIA) were carried out to determine the optimum structural requirements for selectivity and potency of quorum-sensing and bacterial biofilm inhibition. The best CoMFA model predicted a q² value of 0.519 and an r² value of 0.984 and revealed that electrostatic and steric properties play a significant role in potency and selectivity. The CoMSIA model predicted a q² value of 0.411 and an r² value of 0.938 based on a combination of steric, electrostatic, and hydrophobic effects. The analysis of the contour maps from each model provide insight into the structural requirements for increasing the activity of a compound. Consequently, manipulating the chemical and physical properties of substituted acyl groups on the homoserine lactone moiety can provide important information toward enhancing the antibacterial properties of the target chemical compound.     

Occurrence and ecological hazard assessment of selected veterinary medicines in livestock wastewater treatment plants

The occurrence of some veterinary medicines in the livestock wastewater plants (WWTPs) was investigated. This investigation represented the occurrence of veterinary medicines to treat in the livestock WWTPs or be discharged into the water system in Korea since the sampling sites were widely distributed across the nation and samples were collected from the 11 livestock WWTPs. Nine antibiotics, two analgesics, and two disinfectants occurred in the livestock wastewater plants (WWTPs). From 11 livestock WWTP influents, chlortetracycline, oxytetracycline, acetylsalicylic acid, and disinfectants frequently occurred with the high concentrations. Meanwhile, sulfamethoxazole, erythromycin-H₂O, and trimethoprim did not occur during sampling periods. The values for log Kow of each chemical showed a high correlation with the number of hydrogen bonding acceptors and were important parameters to estimate and understand the biodegradability and toxicity of a compound in the environment. The biodegradability of each compound was proportional to the hydrophilicity of each compound and the toxicity was proportional to the number of hydrogen bonding acceptors of each compound. The expected introductory concentration (EIC), predicted exposure concentration (PEC), and hazard quotient showed that the livestock WWTP effluents were hazardous to ecosystems.     

Optimal descriptor as a translator of eclectic information into the prediction of membrane damage by means of various TiO2 nanoparticles

The increasing use of nanomaterials incorporated into consumer products leads to the need for developing approaches to establish “quantitative structure–activity relationships” (QSARs) for various nanomaterials. However, the molecular structure as rule is not available for nanomaterials at least in its classic meaning. An possible alternative of classic QSAR (based on the molecular structure) is the using of data on physicochemical features of TiO₂ nanoparticles. The damage to cellular membranes (units L⁻¹) by means of various TiO₂ nanoparticles is examined as the endpoint.     

连接性指数对脂肪醇的QSPR/QSAR研究

用碳原子取代醇中的氧,构造出极性很小、结构和原化合物相似的分子.定义原子特征值f_i=1 sum h_(ij),并在邻接矩阵的基础上,建立该化合物的连接性指数~mG,~mG=sum(f_i·f_i·f_k…)~0.5,其中,~0C=sum(f_i)~0.5.G=sum(f_i·f_i)~0.5.~mG对脂肪醇异构体具有很强的区分能力,且~0G与醇的-lgS_w,lgK_ow均有良好的相关性,复相关系数均在0.99以上.~0G具有物理意义明确,计算简单等优点.     

麻痹性贝毒素生物毒性的量子化学研究

运用密度泛函(DFT)理论在B3LYP/6-31G(d)水平下计算了17种麻痹性贝毒素的量子化学结构描述符,采用修正Cp统计量为目标函数的改进蚁群算法进行变量选择,建立了麻痹性贝毒素的半数致死浓度与其量化参数之间的QSAR模型;模型的决定系数R2为0.968,交叉验证系数q2为0.858,表明模型具备良好的拟合效果和较...     

有机物的结构——活性/性质定量关系及其在环境化学和环境毒理学中的应用

有机物结构-活性定量关系研究(QSAR,Quantitative Structure-Activity Relationship)用于环境化学和环境毒理学领域取得了引人注目的成功。有机污染物在环境中的行为,尤其在生物体内的富集和致毒是环境化学和环境毒理学的主要研究方向之一。QSAR法可以从已有的大量情报中最大量地提取有关环境污染物结构—活性关系进行深入的研究。     

根据片段常数法估算有机化合物对虹鳟的LC50值

根据258种有机物对虹鳟的96h半数致死浓度(LC₅₀)实测值建立了预测有机物对虹鳟LC₅₀的片段常数估算模型.讨论了模型的误差和稳健性.结果表明,有机物的片段常数及结构因子与虹鳟log1/LC₅₀之间具有很好的定量关系.可以根据化合物片段估算其对虹鳟的半数致死浓度.最终模型的可决系数为0.9495,平均误差0.42个对数单位.无论就单一化合物或化合物类别而言,模型均具有较高的稳健性.     

利用神经网络法对胺类有机物急性毒性的分类及定量预测

运用三层误差反向传播网络对５１种胺类有机物进行了结构－毒性关系的研究,进入的结构参数为分子连接性指数信息理论指及分子量等６种均可通过分子拓扑图直接计算获得的指标。毒性参数选用大鼠经口ＬＤ５０,根据其大小将样本分为３类：高毒,中毒,低毒,在神经网络模型上作出差别归类,并分别对每类进行定量预测。