Chemical and biochemical characterization of multistranded guanine-rich DNA supramolecules

An alternative platform technology for modifying nucleic acid structure without changing its original chemical DNA structure is examined. In this platform, multiple DNA strands interact by non-covalent bonding to form a new structure of DNA supramolecule.; This thesis focuses on the study of multistranded guanine-rich DNA supramolecules that are stabilized by guanine-guanine interactions. Structural variations are observed among DNA supramolecules formed by different guanine-rich oligonucleotides. The guanine-guanine interactions in DNA complexes formed by telomere-like sequences, for example d(T15G4T2G4), are different from that in the complex formed by d(T15G15 ) called frayed wires.; A new type of intermolecular Multistrand Guanine-Guanine interaction (MGG) is found to exist contributing to the stabilization of frayed wires. This MGG interaction can be differentiated from the canonical guanine tetrad through both strand association stoichiometry and chemical reactivity of dimethyl sulphate at the N7 site of guanine. The MGG interaction observed in frayed wires does not require the N7 sites of the guanine bases to form stable complexes; therefore, methylation by dimethyl sulphate at N7 sites does not hinder the formation of frayed wires. This phenomenon does not occur in complexes stabilized by guanine tetrads.; The manifestation of different guanine-guanine interactions arises from two factors: the number of contiguous guanines and the availability of the N7 sites in the guanine base in the sequence. The thermal stability of the d(T15Gn) DNA complexes is determined by various factors. These factors include the nature of guanine-guanine interaction, the number and arrangement of the contiguous guanines within the DNA sequences, and the balance between the stabilization force of the guanine bases versus the unfavorable contribution of the non-guanine portion within the oligonucleotide sequences.; Our data indicate that frayed wires are resistant to enzymatic degradation by common nucleases. Ligands bound to frayed wires are also protected from degradation.; Frayed wires stabilized by MGG interaction may be used as a carrier for biologically active molecules.