Title:
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The chemical synthesis of proteins
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The viability of extending the present methodology designed for the solid phase synthesis of peptides has been investigated. Using the catalytic domain of stromelysin (SCD. 173 residues) as the model system, a number of different factors affecting the preparation and purification of chemically synthesised proteins are examined. The purification SCD, prepared using stepwise solid phase synthesis is described. Following characterisation, it is evident that protein of the correct primary sequence has been prepared, furthermore, preliminary studies centred on the enzymatic activity of SCD indicate that active protease has been isolated. However, comparison of the conformational and biophysical properties of chemically synthesised SCD with the recombinant counterpart, suggests that there are problems associated with the folding of the synthetic SCD. The construction of chemically synthesised SCD via convergent protein synthesis is also described. Two different coupling strategies involving classical and azide fragment condensation are examined where it has been highlighted that the overall success of each fragment coupling is greatly dependent on the peptide length and sequence. As well as comparing methods for the preparation and coupling of fully and minimally protected peptides, general procedures for both solution and solid phase fragment coupling are discussed. A novel strategy for the convergent synthesis of peptides and proteins has been investigated. In this total chemical synthesis, two minimally protected peptides are joined through unique, mutually reactive functional groups, yielding a peptide analogue with a thioether replacement for the native peptide bond at the site of ligation. A general route to C-terminal sulfhydryl and N-terminal haloacetylated peptides is presented, accompanied with results of the preliminary ligation studies.
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