Synthesis of nucleoside analogues and peptides for nanoore analysis and controlled bioactivity

Abstract

This research describes the synthesis of nucleoside analogues and peptides, and their application to nanopore technology and cell biology. Nanopore technology is a technique in which analytes are detected by disturbances in ionic current caused as they traverse a pore, at a fixed applied potential. Here potential applications of the technology are explored. A nanopore-based method to detect enzymatic activity was investigated. The technique involved the detection of peptide fragments proteolytically released from a solid-support. The released fragments gave rise to distinct electrical signals which facilitated their identification and characterisation. The frequency with which they traversed the pore was indicative of enzyme activity. The technique was successfully applied to the detection of the protease enzyme, renin, in the presence of human serum. An approach to count nucleotide repeat sequences, which are the basis of forensic DNA fingerprinting, was also investigated. It was hypothesised that chemically modified copies of the repeat regions could be generated using primer extension and nucleoside analogues. The copying could be performed such that a single analogue was incorporated per repeat. Ensuing nanopore analysis would then give rise to electrical signals in which the analogues could be identified from unique signals. The number of repeat sequences could simply be determined by counting the number of signals. It was envisaged that this could be achieved using adamantane-modified nucleosides. However, these did not give rise to the expected result. Inspired by the adamantane project, analogues of the drug, azacytidine were synthesised. Azacytidine is used to treat cancers that arise due to epigenetic modifications of DNA. It was hypothesised that its side-effects could be mitigated using photocaged-derivatives of the nucleoside, as these would enable greater temporal and spatial control of drug release. Analogues of azacytidine were successfully synthesised and shown to be uncaged back to the parent nucleoside

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