Estudo do coeficiente de partição octanol-água de bifenilas policloradas (PCBs) utilizando parâmetros topológicos

Abstract

A STUDY OF OCTANOL/WATER PARTITION COEFFICIENT OF POLYCHLORINATED BIPHENYLS (PCBs) USING TOPOLOGICAL INDICES. A model based on chemical structure was developed for the accurate prediction of octanol/water partition coefficient (K OW ) of polychlorinated biphenyls (PCBs), which are molecules of environmental interest. Partial least squares (PLS) was used to build the regression model. Topological indices were used as molecular descriptors. Variable selection was performed by Hierarchical Cluster Analysis (HCA). In the modeling process, the experimental K OW measured for 30 PCBs by thin-layer chromatography -retention time (TLC-RT) has been used. The developed model (Q 2 = 0,990 and r 2 = 0,994) was used to estimate the log K OW values for the 179 PCB congeners whose K OW data have not yet been measured by TLC-RT method. The results showed that topological indices can be very useful to predict the K OW.

Análise Citotóxica E Mutagênica Do Extrato Aquoso De Maytenus Guyanensis Klotzsch Ex Reissek (Celastraceae) Chichuá (Xixuá) Amazônico

“…O extrato aquoso da entrecasca M. guyanensis nas concentrações de 3,85 e 38,5 mg/mL não apresenta ação citotóxica e mutagênica, e ainda atuam como anticitotóxi-co e antimutagênico, porém mesmo nessas concentrações é indicado estudos de biacumulação, para um melhor entendimento dos efeitos da utilização desses extratos vegetais a longo prazo (SILVA; FERREIRA, 2003).…”

A Protocol for Fish Lipid Analysis Using Nuclear Magnetic Resonance Spectroscopy

“…In relation to phospholipids and glycolipids classes, lipids with structural function that are components of the plasma membrane, which mostly act as a barrier to the passage of polar molecules and ions, 51 was observed a minimal variation in the glycolipids content, and significant variation in phospholipids levels. In addition, we have observed that glycolipids were the class which has presented the lowest contribution in the total lipid values.…”

“…The Blight and Dyer 31 method is a fast and efficient method and a great reference for the extraction and purification of total lipids from biological samples. 33,[49][50][51] A mixture of chloroform, methanol, and water must be able to extract neutral and polar lipids. This mixture is sufficiently nonpolar to break the associations with the cell membrane and/or lipoproteins.…”

“…Furthermore, the mixture also must be sufficiently polar to release electrostatic forces and hydrogen interactions. 31,33,50,51 Fish lipids are strongly related to the availability of food and energy storage. In a period in which there is a high availability of food, fish tend to store more lipids than in decreased food availability where the fish energy storage decreases because of lipid use for the maintenance of vital functions.…”

Determinação de ascarel em óleo isolante de transformadores

“…Outros tipos também são conhecidos como ascarel do tipo A, 60% da espécie 1260 e 40% de triclorobenzeno; e ascarel do tipo B, 70% da espécie 1254 e 30% de triclorobenzeno 4 . Devido à sua alta toxicidade e risco ao meio ambiente o uso dos PCBs foi proibido no Brasil a partir de 1981, através da Portaria Interministerial n o 19, de 2 de Janeiro de 1981 [1][2][3][4][5] . A substituição do ascarel na indústria de transformadores foi feita preferencialmente pelo líquido de silicone ou "óleo silicone".…”