Coded addition

A 22nd natural genetically coded amino acid was discovered by US researchers two years ago. Now, they have taken the next logical step in amino acid chemistry and successfully synthesized the compound, L-pyrrolysine, and demonstrated that the microbe Escherichia coli can incorporate it into its proteins. Scientists assumed until 1986 that there were only 20 "canonical" amino acids, but the discovery of selenocysteine changed the received wisdom. Then in 2002, microbiologist Joe Krzycki and biochemist Michael Chan of Ohio State University added a 22nd amino acid to the list. Krzycki suggests that future work may lead to artificial proteins with unusual chemical properties for use in medicine or industry.