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Chemistry - Student Works

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Browsing Chemistry - Student Works by Author "Manary, Brandon"

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    Designing a model for the enzyme–substrate complex to investigate the detailed catalytic mechanism of lactoperoxidase by quantum chemical methods
    (2015) Manary, Brandon; Llano, Jorge
    Lactoperoxidase (LPO) is a heme enzyme found in exocrine secretions such as milk, saliva and endodermal mucus. LPO catalyzes the formation of oxidizing oxoanions that act as natural antibiotics in those body fluids. LPO is a versatile enzyme that converts thiocyanate ions (SCN−) to hypothiocyanite ions (OSCN−), as well as halide ions (i.e., Cl−, Br− and I−) to hypohalite ions (i.e., ClO−, BrO− and IO−). By means of quantum-mechanical–molecular-mechanical (QM–MM) calculations, this investigation aims to find the sequence of bond-breaking and bond forming steps by which LPO converts the anions into the oxoanions in its active-site. In this particular study, we present a molecular model for the LPO active-site, which was generated from a detailed analysis and comparison of the available crystallographic structures of LPO deposited in the Protein Data Bank. We also propose a chemical model for the enzyme–substrate complex, which will be used as the starting structure in the QM–MM computation of the LPO catalytic mechanism.
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    Molecular modelling and kinase assay for CePNKP binding to DNA
    (2017) Manary, Brandon; Bernstein, Nina; Llano, Jorge
    Computational techniques of homology modelling, enzyme–substrate docking, and molecular dynamics were applied to elucidate the structure and substrate binding properties of the DNA repair enzyme polynucleotide kinase/phosphatase from the nematode C. elegans (CePNKP). PNKP is involved in the repair of DNA strand breaks, a form of DNA damage caused by reactive oxygen species, ionizing radiation and certain chemical mutagens. Mutations in human PNKP have been associated with the neurological disorders Microcephaly with Intractable Seizures (MCSZ) and Ataxia Oculomotor Apraxia 4 (AOA4). In addition, human PNKP has been identified as a potential drug target for the development of chemo- and radiosensitizing agents for cancer treatment. CePNKP is a useful model system for studying the human enzyme. The substrate preference for both human and C. elegans PNKP has been investigated, and found to be similar, with higher selectivity for recessed over blunt DNA ends. However, CePNKP exhibits a more exclusive preference for recessed DNA ends than human PNKP. To elucidate the reason for the unique substrate specificity of CePNKP, the structure of CePNKP in complex with its DNA substrate must be determined in atomistic detail by molecular modelling. The generated structural model is compared with our experimental results of kinase activity assays of wild-type CePNKP.