Chemical synthesis and genetic engineering

Techniques to introduce post-translational modifications into proteins assembled by genetic engineering methodology are just being developed. In contrast, such structural changes are usually easily introduced by chemical synthesis. 

The various techniques are complementary, but it is likely that they will be increasingly used in concert. Parts of a protein may be produced by genetic engineering, chemical synthesis, enzymic synthesis or semi-synthesis and any of the last three methods could be used to link the fragments. 

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