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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Design, synthesis, and evaluation of fluorescent sensors for intracellular imaging of monovalent copper

Yang, Liuchun 21 July 2005 (has links)
The main theme of this thesis is to develop a fluorescent probe for imaging the subcellular distribution of kinetically labile copper pools that might play a critical role in copper homeostasis. Various copper-selective sensors were designed by combining 1,3,5-triaryl-2-pyrazoline fluorophores with polythioethers as receptor moieties. A series of donor-substituted 1,3,5-triaryl-2-pyrazoline fluorophores were synthesized and characterized in terms of their photophysical and electrochemical properties. Interestingly, the aryl substituents attached to the 1- and 3-position of the pyrazoline ring influence the photophysical properties of the fluorophore in distinctly different ways. The excited-state equilibrium energy is primarily influenced by changes of the substituent in the 1-position, whereas the reduction potential of the fluorophore is determined by the 3-aryl group. Results from computational analyses agree well with the experimental data. A pyrazoline fluorophore library was synthesized, and their photophysical and electrochemical properties were studied. The compounds cover a broad range of excited state energies and reduction potentials, and allow for selective and differential tuning of these two parameters. A series of thiazacrownethers and tripodal aniline copper(I) receptors were synthesized and their copper binding stoichiometries, stability constants, and copper-self-exchange kinetics were investigated. The measured self-exchange activation parameters revealed for all studied ligands a negative activation entropy, suggesting a predominant associative exchange mechanism. With detailed knowledge of the fluorophore platform and copper receptors, sensor CTAP-1 was designed, synthesized and characterized. The probe shows a 4.6-fold emission enhancement and reaches a quantum yield of 14% upon saturation with Cu(I). The sensor exhibits excellent selectivity towards Cu(I) and is insensitive towards millimolar concentrations of Mg(II) or Ca(II). Mouse fibroblast cells (3T3) incubated with the sensor produced a copper-dependent perinuclear staining pattern, which colocalizes with the subcellular location of the mitochondria and the Golgi apparatus. The subcellular topography of copper was further determined by synchrotron-based x-ray fluorescence (SXRF) microscopy. Furthermore, microprobe x-ray absorption measurements at various subcellular locations showed a near-edge feature that is characteristic for low-coordinate monovalent copper. The data provide a coherent picture with evidence for a kinetically labile copper pool, which is predominantly localized in the mitochondria and the Golgi apparatus.

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