New recombinant DNA methodology for protein engineering.

Over the past year considerable progress has been made in the application of recombinant DNA technology to protein engineering. A number of new methods for gene synthesis and mutagenesis have been reported that simplify the construction of novel coding sequences. The polymerase chain reaction plays an increasingly important role in these methods. Amino acid diversity has been extended by the incorporation of unnatural amino acids via coupled in vitro transcription-translation methods. Novel random mutagenesis strategies have been developed that substitute amino acids with a desired chemical character at a given position, thereby generating a sophisticated library of protein variants.