Synthesis and properties of nucleic acid duplexes and quadruplexes containing 3'-S-phosphorothiolate linkages

Matthew Piperakis, Michael (2012) Synthesis and properties of nucleic acid duplexes and quadruplexes containing 3'-S-phosphorothiolate linkages PhD thesis, University of Liverpool.

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Abstract

3'-Thiopurine 2'-deoxynucleosides have been incorporated into model oligodeoxynucleotides (DONs) thus giving rise to ODNs that consist of the 3- S-phosporothiolate (3'-sp) linkage. Due to the complex chemical manipulations implicated, the preparation of such analogues has been scarcely explored to date. The 3'-thiopurine nucleosides were prepared prior to incorporation into the desired DON sequences by traditional automated 3'---+5' solid-phase phosporamidite chemistry. Two different strategies, one involving neighbouring group participation and the other an in situ oxidation-reduction, were successfully applied for the key C3' epimerisation in deoxyadenosine and deoxyguanosine, respectively. Subsequent UV denaturation studies revealed that the destabilisation effect recorded in DNA/DNA duplexes consisting of a single 3'-sp modified residue on one strand was diminished when more 3'-sp modified residues were incorporated. The destabilisation is expected on the basis that the sugars on the 3'-sp modified and neighbouring residues predominantly adopt the RNA-like North conformation. A surprising stabilisation effect was, moreover, observed for DNA/RNA hybrids containing 3'-sp modifications in the RNA strand. Additionally, when 3'-sp modifications were incorporated into both strands of the homo- or hetero-duplexes, an additive effect was generally exhibited. UV denaturation studies revealed a significant position specific 3'-sp substitution effect when incorporated into G-quadruplexes; the thermal stability of the tetramolecular complex was significantly increased when either of the two central guanines in the G-tract of the sequence was modified. A clear position-dependent substitution effect on the rate of association of the quadruplex was also observed, however, no correlation between the kinetics of association and the recorded thermal stability was realised.

Item Type:	Thesis (PhD)
Depositing User:	Symplectic Admin
Date Deposited:	19 Oct 2023 17:54
Last Modified:	19 Oct 2023 17:56
DOI:	10.17638/03174332
Copyright Statement:	Copyright © and Moral Rights for this thesis and any accompanying data (where applicable) are retained by the author and/or other copyright owners. A copy can be downloaded for personal non-commercial research or study, without prior permission or charge
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3174332
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