Supramolecular helical arrangement of porphyrins along DNA : a thesis submitted in the partial fulfilment of the requirements for the degree of Doctor of Philosophy in Chemistry, Massey University, Palmerston North, New Zealand
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Date
2010
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Massey University
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Abstract
Porphyrins are useful chromophores and have been used in numerous biological
applications including light harvesting, oxygen transport and energy transfer. DNA is a
perfect template for the controlled assembly of organic chromophores. By combining
DNA and porphyrins in a controlled manner we have developed a novel range of
porphyrin-DNA supramolecular constructs for future applications in
nanobiotechnology.
A number of β-pyrrolic functionalised porphyrin precursors were synthesised to be used
as building blocks in the construction of both covalently and non-covalently modified
DNAs. Using these porphyrins we have created several lipophilic porphyrin-DNA
complexes through non-covalent attachment methods. Using a CuI catalysed azide
alkyne cycloaddition (CuAAC) reaction of azido functionalised porphyrins we have
developed a versatile approach for the covalent, site specific internal porphyrin insertion
into oligonucleotides in a post-synthetic manner. We have investigated a number of
duplex structures where porphyrins were located in the major or minor grooves of the
duplex. Additionally, porphyrins were studied as intercalating moieties when they were
inserted as a bulge in the middle of the duplexes or parallel triplexes. Additionally,
when porphyrins were placed in both strands of the duplex they formed a zipper type
structure in the minor groove. This resulted in a significant increase in the duplex
thermal stability due to the formation of porphyrin H-aggregates. UV-Vis and CD
spectroscopy as well as molecular modelling were used to help understand the
interactions between porphyrins in the duplex.
These findings lay the foundation for the future design of artificial DNA-chromophore
supramolecular architectures and for their applications in material science and
nanotechnology.
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Keywords
Chromophores, Nanobiotechnology, DNA modification, Porphyrin interactions