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      Application of x-ray spectroscopy and density functional theory to toxicology of polychlorinated biphenyls

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      FORREST-THESIS.pdf (6.627Mb)
      Date
      2014-06-20
      Author
      Forrest, Jay
      Type
      Thesis
      Degree Level
      Masters
      Metadata
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      Abstract
      While much is known about the toxicity of polychlorinated biphenyls (PCBs), there are tens of thousands of natural and synthetic chemicals in the environment that can activate the aryl hydrocarbon receptor (AhR) and thus cause toxicity. Since it would be difficult to conduct studies of the toxicity of each and every compound, here is presented a new model based on first-principles taking into account the basic electronic and electron trans- fer characteristics of PCBs, but can be used to predict the toxicities of other AhR-active compounds. The predictive model is based on Density Functional Theory. The model predicts that the energy gap between highest occupied (HOMO) and lowest unoccupied (LUMO) molecular orbitals is the overarching indicator of toxicity of PCBs, but not the only factor. The model explains why chlorination of both para-positions is required for maximum toxic potency. To rank potency of PCBs, the dipole moment in relation to the most chemically active chlorine-sites is critical. The theory is consistent with the accepted toxic equivalency factor (TEF) model for these molecules and is also able to improve on ranking toxic potency of PCBs with similar TEFs. This new model also includes a 13th dioxin-like PCB, PCB 74, not considered in the current TEF model developed by the World Health Organization (WHO). The model was applied to HOMO-LUMO gap mea- surements of a set of PCBs and the measurements are consistent with the model. Values of HOMO-LUMO gap can also be used to predict bio-accumulation of PCBs. The model provides an in silico method to screen a wide range of chemicals to predict their ability to act as an AhR agonist.
      Degree
      Master of Science (M.Sc.)
      Department
      Physics and Engineering Physics
      Program
      Physics
      Supervisor
      Chang, Gap Soo
      Committee
      Johanson, Robert; Bradley, Micheal; Tanaka, Kaori
      Copyright Date
      September 2012
      URI
      http://hdl.handle.net/10388/ETD-2012-09-907
      Subject
      Polychlorinated biphenyls, DFT, x-ray spectroscopy, toxicology
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