Towards PNA Directed Chemical Total Protein Synthesis

This thesis is concerned wi.th the development of a novel methodology for the chemical synthesis of proteins. The methodology is expected to overcome limitations of current techniques for chemical synthesis of proteins that restrict the size of the target molecule to less than 150 amino acids. It is intended that the use of a DNA analogue, PNA, as a directing group will allow different short polypeptides to self-assemble into a desired target protein. The first chapter is an overview of literature concerning templated synthesis and the applications of PNA. Examples of simple mctal-templated synthesis are discussed however there is a particular focus on the work of David Liu and his DNA-templated synthesis. The uses of PNA in a number of diverse applications are presented along with brief comparative descriptions of PNA and DNA. A brief discussion of current methodologies for protein synthesis is then used to set the context for the project aims and a description of the proposed methodology. The second chapter details the effort made in modifying literature procedures to successfully develop the robust and reproduCible cqemistry required for multi-gram synthesis ofPNA monomers. The third chapter briefly discusses the computer-aided design of a pair of linker molecules that act as a bridge between polypeptides and their PNA directing groups. The challenging synthesis of these linker molecules is detailed and synthetic routes for the multi-gram synthesis of both are given. The fourth chapter charts the development of the solid-supported chemistry used to construct PNA-peptide chimeras with close attention to the challenges encountered with incorporating the linker molecules. Of the two chimera targets required. to examine PNA-directcd ligation, a multi-gram preparative synthetic route is presented for one chimera. A route that provides analytical quantities of the complementary chimera is also discussed. The fifth chapter presents the experimental procedures used for the synthesis of the compounds involved in this project. Analytical data and the characterisation of compounds are detailed for each compound where possible.